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Sample records for surface treated montmorillonite

  1. Interactions of aminomethylphosphonic acid and sarcosine with montmorillonite interlayer surfaces

    NASA Astrophysics Data System (ADS)

    Rennig, Amanda; Slutter, Annette; Tribe, Lorena

    The smectite clay, montmorillonite, can be found in many soils throughout the world. In addition to its importance in agriculture and soil remediation, montmorillonite has extensive applications in industry both in its natural form and as a component of composite materials. The adsorptive properties of montmorillonite have been explored in relation to its interactions with the common herbicide glyphosate. This herbicide, when exposed to microorganisms in the soil is degraded, forming two products: aminomethylphosphonic acid (AMPA) and sarcosine. The atomic-level interactions of these compounds with the montmorillonite interlayer surfaces are studied here using molecular mechanics. The final outcomes of these calculations are analyzed in terms of the proximity of the montmorillonite surface to the moieties of the degradation products. The phosphonate moiety was found to be the most important source of interactions for AMPA, while for sarcosine there was an even distribution between the amino and carboxylic moieties, and Na+ ion mediated surface complexes.0

  2. Monomers of cutin biopolymer: sorption and esterification on montmorillonite surfaces

    NASA Astrophysics Data System (ADS)

    Olshansky, Yaniv; Polubesova, Tamara; Chefetz, Benny

    2013-04-01

    One of the important precursors for soil organic matter is plant cuticle, a thin layer of predominantly lipids that cover all primary aerial surfaces of vascular plants. In most plant species cutin biopolymer is the major component of the cuticle (30-85% weight). Therefore cutin is the third most abundant plant biopolymer (after lignin and cellulose). Cutin is an insoluble, high molecular weight bio-polyester, which is constructed of inter-esterified cross linked hydroxy-fatty acids and hydroxyepoxy-fatty acids. The most common building blocks of the cutin are derivatives of palmitic acid, among them 9(10),16 dihydroxy palmitic acid (diHPA) is the main component. These fatty acids and their esters are commonly found in major organo-mineral soil fraction-humin. Hence, the complexes of cutin monomers with minerals may serve as model of humin. Both cutin and humin act as adsorption efficient domains for organic contaminants. However, only scarce information is available about the interactions of cutin with soil mineral surfaces, in particular with common soil mineral montmorillonite. The main hypothesize of the study is that adsorbed cutin monomers will be reconstituted on montmorillonite surface due to esterification and oligomerization, and that interactions of cutin monomers with montmorillonite will be affected by the type of exchangeable cation. Cutin monomers were obtained from the fruits of tomato (Lycopersicon esculentum). Adsorption of monomers was measured for crude Wyoming montmorillonites and montmorillonites saturated with Fe3+ and Ca2+. To understand the mechanism of monomer-clay interactions and to evaluate esterification on the clay surface, XRD and FTIR analyses of the montmorillonite-monomers complexes were performed. Our results demonstrated that the interactions of cutin monomers with montmorillonite are affected by the type of exchangeable cation. Isotherms of adsorption of cutin monomers on montmorillonites were fitted by a dual mode model of sorption, which combines site specific adsorption mechanism (Langmuir) and partitioning mechanism. Adsorption of monomers by Fe3+-montmorillonite was higher than for Ca2+ and crude -montmorillonites. XRD measurements showed expansion of d-spacing of montmorillonite samples with the increase in diHPA loading from 12.32, 12.66 and 12.17 Å for Fe3+- Ca2+- and crude-montmorillonite up to 16.84, 16.62 and 16.79 Å for organo-clay complexes of Fe3+-, Ca2+- and crude-montmorillonites respectively. This significant expansion of d-spacing suggests interlayer, and probably, multilayer diHPA adsorption by montmorillonite. Based on FTIR data we suggest that diHPA forms inner-sphere complexes with Fe3+-montmorillonite surface but not with Ca2+ and crude-montmorillonites. However all montmorillonite samples induce esterification and oligomerization of the monomers, which was demonstrated by FTIR spectra of the organo-montmorillonite complexes and by LC-MS analysis of the organic material extracted from organo-clay complexes. These results confirmed our hypothesis about oligomerization of cuticular monomers on mineral surfaces. We assume that esterification and oligomerization of monomers on montmorillonite surfaces simulate similar soil processes, which result in the formation of soil organo-mineral complexes and humin.

  3. Adsorption of Crystal violet on raw and acid-treated montmorillonite, K10, in aqueous suspension.

    PubMed

    Sarma, Gautam Kumar; Sen Gupta, Susmita; Bhattacharyya, Krishna G

    2016-04-15

    Crystal violet is used as a dye in cotton and silk textiles, paints and printing ink. The dye is hazardous and exposure to it may cause permanent injury to the cornea and conjunctiva including permanent blindness, and in severe cases, may lead to respiratory and kidney failure. The present work describes removal of Crystal violet from aqueous solution by adsorption on raw and acid-treated montmorillonite, K10. The clay mineral was treated with 0.25 and 0.50 M sulfuric acid and the resulting materials were characterized by XRD, zeta potential, SEM, FTIR, cation exchange capacity, BET surface area and pore volume measurements. The influences of pH, interaction time, adsorbent amount, and temperature on adsorption were monitored and explained on the basis of physico-chemical characteristics of the materials. Basic pH generally favors adsorption but considerable removal was possible even under neutral conditions. Adsorption was very rapid and equilibrium could be attained in 180 min. The kinetics conformed to second order model. Langmuir monolayer adsorption capacity of raw montmorillonite K10 was 370.37 mg g(-1) whereas 0.25 M and 0.50 M acid treated montmorillonite K10 had capacities of 384.62 and 400.0 mg g(-1) respectively at 303 K. Adsorption was exothermic and decreased in the temperature range of 293-323 K. Thermodynamically, the process was spontaneous with Gibbs energy decreasing with rise in temperature. The results suggest that montmorillonite K10 and its acid treated forms would be suitable for removing Crystal violet from aqueous solution. PMID:26866669

  4. Characterization of montmorillonite surfaces after modification by organosilane.

    SciTech Connect

    Song, K.; Sandi, G.; Chemistry

    2001-04-01

    X-ray powder diffraction (XRD), thermal gravimetric analysis (TGA), surface area measurements, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy were used to examine the surface properties of organosilane-modified smectite-type aluminosilicate clays. Organic modified clays derived from the reactions of montmorillonite (containing 93-95% montmorillonite from a bentonite, <1% quartz, and 4-6% opal CT) with octadecyltrichlorosilane (C{sub 18}H{sub 37}SiCl{sub 3}) and octadecyltrimethoxysilane [C{sub 18}H{sub 37}Si(OMe){sub 3}] are highly hydrophobic. Surface loadings of the modified clays depend on the organosilane and the solvent, and they range from 10 to 25 wt. %. The organic species are probably adsorbed to the outer surfaces and bound to the edges of the clay via condensation with edge-OH groups. Encapsulation of montmorillonite with C{sub 18}H{sub 37}SiCl{sub 3} and C{sub 18}H{sub 37}Si(OMe){sub 3} resulted in hydrophobic coating that acts like a 'cage' around the clay particles to limit diffusion. Basal spacings of the organic modified clays remain at {approx}15 {angstrom} upon heating to 400{sup o}C in N{sub 2}, whereas those of unmodified clays collapse to {approx}10 {angstrom}. A considerable reduction in surface area (by 75-90%) for organic modified clays is observed, which is consistent with the existence of a surface coating. The solvent used can affect the amount of organic silane coated on the clay particles, whereas the difference between the products prepared using C{sub 18}H{sub 37}SiCl{sub 3} and C{sub 18}H{sub 37}Si(OMe){sub 3} in the same solvent is relatively small. The carbon and oxygen K-edge NEXAFS spectroscopy of the modified montmorillonite surfaces showed that surface coatings on the outside of the clay particles exist. The encapsulating system may allow for economical remediation and storage of hazardous materials.

  5. Theoretical characterization of formamide on the inner surface of montmorillonite

    NASA Astrophysics Data System (ADS)

    Shi, Jing; Lou, Zhaoyang; Yang, Mingli; Zhang, Yao; Liu, Houbin; Meng, Yingfeng

    2014-06-01

    Density functional theory calculations were performed to characterize the low-lying structures of formamide (FA) and protonated formamide (FAH) in the interlayer space of montmorillonite (MMT). The interactions among FA/FAH, H2O, Na+, and the inner surface of MMT were systematically analyzed. The carbonyl-O of FA/FAH has strong coulomb interaction with Na+, while its amide-H forms hydrogen bonds (HBs) with water and MMT surface. The adsorption of FA is promoted by H2O, which exhibits a cooperative adsorption effect by enhancing the FA-Na+ coulomb interaction and by forming HBs with FA. Our study reveals the structural basis of FA/FAH as an intercalator for MMT splitting.

  6. First-principles study of water desorption from montmorillonite surface.

    PubMed

    Zhang, Yao; Meng, Yingfeng; Liu, Houbin; Yang, Mingli

    2016-05-01

    Knowledge about water desorption is important to give a full picture of water diffusion in montmorillonites (MMT), which is a driving factor in MMT swelling. The desorption paths and energetics of water molecules from the surface of MMT with trapped Li(+), Na(+) or K(+) counterions were studied using periodic density functional theory calculations. Two paths-surface and vacuum desorption-were designed for water desorption starting from a stationary structure in which water bonds with both the counterion and the MMT surface. Surface desorption is energetically more favorable than vacuum desorption due to water-surface hydrogen bonds that help stabilize the intermediate structure of water released from the counterion. The energy barriers of water desorption are in the order of Li(+) > Na(+) > K(+), which can be attributed to the short ionic radius of Li(+), which favors strong binding with the water molecule. The temperature dependence of water adsorption and desorption rates were compared based on the computed activation energies. Our calculations reveal that the water desorption on the MMT surface has a different mechanism from water adsorption, which results from surface effects favoring stabilization of water conformers during the desorption process. PMID:27083565

  7. Surface area of montmorillonite from the dynamic sorption of nitrogen and carbon dioxide

    USGS Publications Warehouse

    Thomas, J., Jr.; Bohor, B.F.

    1968-01-01

    Surface area determinations were made on a montmorillonite with various cations emplaced on the exchangeable sites, utilizing nitrogen and carbon dioxide as adsorbates at 77 ??K and 195 ??K, respectively, in a dynamic system. From the fraction of a Mississippi montmorillonite less than about 1 ?? in size, samples were prepared by replacing the original exchangeable cations with Li+, Na+, K+, Rb+, Cs+, Mg++, Ca++, Ba++, and NH4+, forming a series of homoionic montmorillonite species. Surface areas from 3-point B.E.T. plots (half-hour adsorption points), with nitrogen as the adsorbate, ranged from 61 m2/g for Li-montmorillonite to 138 m2/g for Cs-montmorillonite, thus reflecting a certain degree of nitrogen penetration between layers. Complete penetration should theoretically result in a surface area of over 300 m2/g for this clay with a nitrogen monolayer between each pair of platelets. The experimental data indicate that the extent of penetration is time-dependent and is also a function of the interlayer forces as governed by the size and charge of the replaceable cation. This finding negates the generally accepted concept that nitrogen at 77 ??K does not penetrate the layers and provides a measure only of the external surface of expandable clay minerals. A further measure of the variation of interlayer forces is provided by the adsorption of carbon dioxide at 195 ??K. Surface area values ranged from 99 m2/g for Li-montmorillonite to 315 m2/g for Csmontmorillonite. Although the carbon dioxide molecule is larger than the nitrogen molecule, its greater penetration apparently is a result of its being kinetically more energetic (with a larger diffusion coefficient) at its higher adsorption temperature. Similar differences have been found with both adsorbates in the study of microporous substances, such as coal, where activated diffusion is of considerable significance. ?? 1968.

  8. Influence of the intercalated cations on the surface energy of montmorillonites: consequences for the morphology and gas barrier properties of polyethylene/montmorillonites nanocomposites.

    PubMed

    Picard, E; Gauthier, H; Gérard, J-F; Espuche, E

    2007-03-15

    Organically modified montmorillonites obtained by cation exchange from the same natural layered silicate were studied. The surface properties of the pristine and a series of organically modified clays were determined by inverse gas chromatography and the water adsorption mechanisms were studied by a gravimetric technique coupled with a microcalorimeter. A significant increase of the specific surface area, a decrease of the water adsorption, and a decrease of the dispersive component of the surface energy were observed when the sodium cations of the natural montmorillonite were exchanged for a quaternary ammonium. Slighter differences in surface properties were observed, on the other hand, between the different types of organically modified montmorillonites. Indeed, similar dispersive components of the surface energy were determined on the organoclays. Nevertheless, the specific surface area increased in the range 48-80 m(2)/g with increasing d-spacing values and the presence of specific groups attached to the quaternary ammonium, such as phenyl rings or hydroxyl groups, led to some specific behaviors, i.e., a more pronounced base character and a higher water adsorption at high activity, respectively. Differences in interlayer cation chain organization, denoted as crystallinity, were also observed as a function of the nature of the chains borne by the quaternary ammonium. In a later step, polyethylene-based nanocomposites were prepared with those organically modified montmorillonites. The clay dispersion and the barrier properties of the nanocomposites were discussed as a function of the montmorillonite characteristics and of the matrix/montmorillonite interactions expected from surface energy characterization. PMID:17222420

  9. Reflectance spectroscopy of palagonite and iron-rich montmorillonite clay mixtures - Implications for the surface composition of Mars

    NASA Technical Reports Server (NTRS)

    Orenberg, James; Handy, Jonathan

    1992-01-01

    The diffuse reflectance spectra of Hawaiian palagonite mixtures with an Fe-rich montmorillonite have prompted their present use as spectral analogs of the Martian surface. Like the Mars spectrum and unlike clays, the 2.2-micron reflectance spectrum absorption band is not present in the palagonite sample; neither is the 2.2-micron Al-OH clay lattice band seen in palagonite-montmorillonite mixtures, where the latter component remains below 15 wt pct. Fe-rich montmorillonite clay may therefore be present in Mars, in combination with palagonite, while remaining undetected in remotely sensed spectra.

  10. Solid surface photochemistry of montmorillonite: mechanisms for the arsenite oxidation under UV-A irradiation.

    PubMed

    Yuan, Yanan; Wang, Yajie; Ding, Wei; Li, Jinjun; Wu, Feng

    2016-01-01

    Transformation of inorganic arsenic species has drawn great concern in recent decades because of worldwide and speciation-dependent pollution and the hazards that they pose to the environment and to human health. As(III) photooxidation in aquatic systems has received much attention, but little is known about photochemical transformation of arsenic species on top soil. As(III) photooxidation on natural montmorillonite under UV-A radiation was investigated by using a moisture- and temperature-controlled photochemical chamber with two black-light lamps. Initial As(III) concentration, pH, layer thickness, humic acid (HA) concentration, the presence of additional iron ions, and the contribution of reactive oxygen species (ROS) were examined. The results show that pH values of the clay layers greatly influenced As(III) photooxidation on montmorillonite. As(III) photooxidation followed the Langmuir-Hinshelwood model. HA and additional iron ions greatly promoted photooxidation, but excess Fe(II) competed with As(III) for oxidation by ROS. Scavenging experiments revealed that natural montmorillonite induced the conversion of As(III) to As(V) by generating ROS (mainly HO(•) and HO2(•)/O2(•-)) and that HO(•) radical was the predominant oxidant in this system. Our work demonstrates that photooxidation on the surface of natural clay minerals in top soil can be important to As(III) transformation. This allows understanding and predicting the speciation and behavior of arsenic on the soil surface. PMID:26194238

  11. Brnsted sites on acid-treated montmorillonite: a theoretical study with probe molecules.

    PubMed

    Briones-Jurado, Claudia; Agacino-Valds, Esther

    2009-08-01

    The effect of isomorphic substitution on Brnsted acid sites, generated during acid treatment of montmorillonite, was studied using the density functional theory (DFT) and the cluster model method. Cluster models describing acid montmorillonite were constructed and used as a matrix for the protonation of several test molecules under different types of isomorphic substitution. Our results concerning geometries, energies, and infrared vibrational frequencies indicate that isomorphic substitution of aluminum with magnesium in the octahedral sheet leads to stronger acid sites and more effective protonation of test molecules than those produced by substitution of silicon with aluminum in the tetrahedral sheet. PMID:19591477

  12. Reflectance Spectroscopy of Palagonite and Iron-Rich Montmorillonite Clay Mixtures: Implications for the Surface Composition of Mars

    NASA Technical Reports Server (NTRS)

    Orenberg, James; Handy, Jonathan

    1992-01-01

    Mixtures of a Hawaiian palagonite and an iron-rich, montmorillonite clay (15.8 +/- 0.4 wt% Fe as Fe2O3) were evaluated as Mars surface spectral analogs from their diffuse reflectance spectra. The presence of the 2.2 microns absorption band in the reflectance spectrum of clays and its absence in the Mars spectrum have been interpreted as indicating that highly crystalline aluminous hydroxylated clays cannot be a major mineral component of the soil on Mars. The palagonite sample used in this study does not show this absorption feature in its spectrum. In mixtures of palagonite and iron-rich montmorillonite, the 2.2 microns Al-OH clay lattice band is not seen below 15 wt% montmorillonite. This suggests the possibility that iron-rich montmorillonite clay may be present in the soil of Mars at up to 15 wt% in combination with palagonite, and remain undetected in remotely sensed spectra of Mars.

  13. Adsorption and characterization of MCPA on DDTMA- and raw-montmorillonite: Surface sites involved.

    PubMed

    Santiago, Cintia C; Fernández, Mariela A; Torres Sánchez, Rosa M

    2016-01-01

    The 4-chloro-2-methylphenoxy acid (MCPA) is an herbicide widely used in agriculture, which generates a great concern about contamination of surface water and serious consequences for human health and the environment. In this work, the adsorption of MCPA on an Argentine montmorillonite (MMT) and its organo-montmorillonite product (OMMT) with different dodecyl trimethyl ammonium loading was investigated. MCPA adsorption on OMMT increases at least 3 times, with respect to the amount determined for MMT. X-ray diffraction and zeta potential analyses indicated the inner (interlayer) and outer surface participate as adsorption sites. Changes in surface electric charge and also interlayer expansion suggest that dimethyl amine (MCPA counterion) was also surface-adsorbed. The larger aggregates of OMMT, without and with MCPA, obtained compared to those of MMT samples, generate an improvement in the coagulation efficiency. This property, particularly after MCPA retention, allows an easier separation of the solids from the solution and enables a simple technological process application. PMID:26786275

  14. Sol-gel network silica/modified montmorillonite clay hybrid nanocomposites for hydrophobic surface coatings.

    PubMed

    Meera, Kamal Mohamed Seeni; Sankar, Rajavelu Murali; Murali, Adhigan; Jaisankar, Sellamuthu N; Mandal, Asit Baran

    2012-02-01

    Sol-gel silica/nanoclay composites were prepared through sol-gel polymerization technique using tetraethylorthosilicate precursor and montmorillonite (MMT) clay in aqueous media. In this study, both montmorillonite-K(+) and organically modified MMT (OMMT) clays were used. The prepared composites were coated on glass substrate by making 1 wt% solution in ethyltrichlorosilane. The incorporation of nanoclay does not alter the intensity of characteristic Si-O-Si peak of silica network. Thermogravimetric studies show that increasing clay content increased the degradation temperature of the composites. Differential scanning calorimetry (DSC) results of organically modified MMT nanoclay incorporated composite show a shift in the melting behavior up to 38°C. From DSC thermograms, we observed that the ΔH value decreased with increasing clay loading. X-ray diffraction patterns prove the presence of nanoclay in the composite and increase in the concentration of organically modified nanoclay from 3 to 5 wt% increases the intensity of the peak at 2θ=8° corresponds to OMMT. Morphology of the control silica gel composite was greatly influenced by the incorporation of OMMT. The presence of nanoclay changed the surface of control silica gel composite into cleaved surface with brittle in nature. Contact angle measurements were done for the coatings to study their surface behavior. These hybrid coatings on glass substrate may have applications for hydrophobic coatings on leather substrate. PMID:22056084

  15. Reflectance spectroscopy of palagonite and iron-rich montmorillonite clay mixtures: Implications for the surface composition of Mars

    NASA Technical Reports Server (NTRS)

    Orenberg, J. B.; Handy, J.

    1991-01-01

    Because of the power of remote sensing reflectance spectroscopy in determining mineralogy, it was used as the major method of identifying possible mineral analogs of the Martian surface. A summary of proposed Martian surface compositions from reflectance spectroscopy before 1979 was presented. Since that time, iron-rich montmorillonite clay, nanocrystalline or nanophase hematite, and palagonite were suggested as Mars soil analog materials.

  16. Preparation and characterization of montmorillonite silica nanocomposites: A sol gel approach to modifying clay surfaces

    NASA Astrophysics Data System (ADS)

    Qian, Zhongzhong; Hu, Guangjun; Zhang, Shimin; Yang, Mingshu

    2008-09-01

    Montmorillonite-silica nanocomposites were prepared by a sol-gel approach involving hydrolysis reaction of alkoxysilanes (TEOS) and subsequent condensation reaction with hydroxyl groups of the clay, resulting in the formation of the mesoporous silica network and silica nanoparticles covered or attached on the clay surfaces. According to X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and nitrogen adsorption isotherms, the structure and surface properties of the sol-gel-modified clay can be controlled by varying the TEOS/clay mass ratio and/or adding trace amounts of acid as catalyst. In the case of acid-catalyzed procedures, large continuous mesoporous silica was covered on the clay surfaces, resulting in delamination of clay platelets in silica matrix at higher TEOS/clay ratio, and attaching of isolated mesoporous silica on the clay surface at lower TEOS/clay ratio, respectively. In the case of non-catalyzed procedures, silica nanoparticles were attached on the two-dimensional (2D) clay platelets, while the stack order of the clay was maintained regardless of the TEOS/clay ratios. This sol-gel modification approach combines the surface properties of mesoporous silica and nanoparticles with layered clay, while inheriting the structural properties of the pristine clay such as further intercalation with organic compounds and polymers.

  17. Sonogashira couplings on the surface of montmorillonite-supported Pd/Cu nanoalloys.

    PubMed

    Xu, Wei; Sun, Huaming; Yu, Bo; Zhang, Guofang; Zhang, Weiqiang; Gao, Ziwei

    2014-11-26

    To explore the true identity of palladium-catalyzed Sonogashira coupling reaction, montmorillonite (MMT)-supported transition metal nanoparticles (MMT@M, M=Pd, Cu, Fe, and Ni) were prepared, characterized, and evaluated systematically. Among all MMT@M catalysts, MMT@Pd/Cu showed the highest activity, and it was successfully extended to 20 examples with 57%-97% yields. The morphology characterization of MMT@Pd/Cu revealed that the crystalline bimetallic particles were dispersed on a MMT layer as nanoalloy with diameters ranged from 10 to 11 nm. In situ IR analysis using CO as molecular probe and XPS characterization found that the surface of Pd/Cu particles consisted of both catalytic active sites of Pd(0) and Cu(I). The experiments on the catalytic activities of MMT@M found that Pd/Cu catalyst system exhibited high activity only in nanoalloy form. Therefore, the Pd/Cu nanoalloy was identified as catalyst, on which the interatom Pd/Cu transmetalation between surfaces was proposed to be responsible for its synergistic activity. PMID:25315209

  18. Structure modification of montmorillonite nanoclay by surface coating with soy protein.

    PubMed

    Jin, Minfeng; Zhong, Qixin

    2012-12-01

    To achieve exfoliated and/or intercalated structures, montmorillonite (MMT) was surface-coated by soy protein at 60 °C, at MMT/soy protein powder mass ratios of 49:1, 9:1, 4:1, and 2:1 and pH 2.0-10.0. The protein-coated MMT was triple-washed and lyophilized for characterization. Protein coating was observed at all pH conditions, based on data from X-ray diffraction, Fourier transform infrared spectroscopy, zeta potential, and quantification of protein remaining in the continuous phase and present in the triple-washed MMT. At a mass ratio of 4:1, >90% protein bound with MMT, with the largest d-spacing at pH 9.0. When the mass ratio was increased to 2:1, protein-coated MMT at pH 9.0 demonstrated the highest degree of intercalation/exfoliation, corresponding to disappearance of the diffraction peak characteristic of pristine MMT. This study thus demonstrated that intercalation/exfoliation of MMT can be easily achieved by coating with low-cost soy protein for manufacturing nanocomposite materials. PMID:23163488

  19. VERUCLAY – a new type of photo-adsorbent active in the visible light range: modification of montmorillonite surface with organic surfactant

    EPA Science Inventory

    Montmorillonite K10 was treated with VeruSOL-3, a biodegradable and food-grade surfactant mixture of coconut oil, castor oil and citrus extracts, to manufacture a benign catalytic adsorbent that is active in the visible light. Veruclay was characterized by SEM, XRD, TGA, UVDRS, a...

  20. VERUCLAY a new type of photo-adsorbent active in the visible light range: modification of montmorillonite surface with organic surfactant

    EPA Science Inventory

    Montmorillonite K10 was treated with VeruSOL-3, a biodegradable and food-grade surfactant mixture of coconut oil, castor oil and citrus extracts, to manufacture a benign catalytic adsorbent that is active in the visible light. Veruclay was characterized by SEM, XRD, TGA, UVDRS, a...

  1. Reflectance spectroscopy and GEX simulation of palagonite and iron-rich montmorillonite clay mixtures: Implications for the surface composition of Mars

    NASA Technical Reports Server (NTRS)

    Orenberg, J. B.; Handy, J.; Quinn, R.

    1992-01-01

    Because of the power of remote sensing reflectance spectroscopy in determining mineralogy, it has been used as the major method of identifying a possible mineral analogue of the martian surface. A summary of proposed martian surface compositions from reflectance spectroscopy before 1979 was presented by Singer et al. Since that time, iron-rich montmorillonite clay, nanocrystalline or nanophase hematite, and palagonite have been suggested as Mars soil analogue materials. Palagonite in petrological terms is best described as an amorphous, hydrated, ferric iron, silica gel. Montmorillonite is a member of the smectite clay group, and its structure is characterized by an octahedral sheet in coordination with two tetrahedral sheets in which oxygen atoms are shared. The crystal unity of montmorillonite is well defined in contrast to palagonite where it is considered amorphous or poorly crystalline at best. Because of the absence of the diagnostic strong 2.2-micron reflectance band characteristic of clays in the near-infrared (NIR) spectrum of Mars and palagonite and based upon a consideration of wide wavelength coverage (0.3-50 microns), Roush et al. concluded that palagonite is a more likely Mars surface analogue. In spite of the spectral agreement of palagonite and the Mars reflectance spectrum in the 2.2-micron region, palagonite shows poor correspondence with the results of the Viking LR experiment. In contrast, iron-rich montmorillonite clays show relatively good agreement with the results of the Viking LR experiment. This spectral study was undertaken to evaluate the spectral properties of mixtures of palagonite and Mars analogue iron-rich montmorillonite clay (16-18 wt. percent Fe as Fe2O3) as a Mars surface mineralogical model. Mixtures of minerals as Mars surface analogue materials have been studied before, but the mixtures were restricted to crystalline clays and iron oxides.

  2. Cadmium ion adsorption controls the growth of CdS nanoparticles on layered montmorillonite and calumit surfaces

    SciTech Connect

    Dekany, I.; Turi, L.; Galbacs, G.; Fendler, J.H.

    1999-05-15

    Adsorption isotherms have been determined for the intercalation of cadmium ions (Cd{sup 2+}) into layered hydrophobized montmorillonite (HDP-M) and calumit (DBS-C) sheets dispersed in ethanol (1)-cyclohexane (2) mixtures. The amount of Cd{sup 2+} adsorbed depended strongly on the composition of the binary liquid; at an ethanol mole fraction of 0.05 (x{sub 1} = 0.05), 95% of the added Cd{sup 2+} is located in the ethanolic nanoreactor at the HDP-M (or DBS-C) surface. CdS nanoparticles have been generated in situ in ethanolic nanoreactors at the HDP-M and DBS-C surfaces. Absorption spectrophotometric measurements provided information on the number of CdS nanoparticles formed and on their absorption edges, bandgaps, and mean diameters. Good correlations have been obtained between the adsorption isotherms and the size (and the amount) of the CdS formed. X-ray diffractometry established that CdS nanoparticles stretched the HDP-M and DBS-C lamellas unevenly upon intercalation.

  3. Np(V) and Pu(v) ion exchange and surface-mediated reduction mechanisms on montmorillonite.

    PubMed

    Zavarin, Mavrik; Powell, Brian A; Bourbin, Mathilde; Zhao, Pihong; Kersting, Annie B

    2012-03-01

    Due to their ubiquity and chemical reactivity, aluminosilicate clays play an important role in actinide retardation and colloid-facilitated transport in the environment. In this work, Pu(V) and Np(V) sorption to Na-montmorillonite was examined as a function of ionic strength, pH, and time. Np(V) sorption equilibrium was reached within 2 h. Sorption was relatively weak and showed a pH and ionic strength dependence. An approximate NpO(2)(+) → Na(+) Vanselow ion exchange coefficient (Kv) was determined on the basis of Np(V) sorption in 0.01 and 1.0 M NaCl solutions at pH < 5 (Kv ~ 0.3). In contrast to Np(V), Pu(V) sorption equilibrium was not achieved on the time-scale of weeks. Pu(V) sorption was much stronger than Np(V), and sorption rates exhibited both a pH and ionic strength dependence. Differences in Np(V) and Pu(V) sorption behavior are indicative of surface-mediated transformation of Pu(V) to Pu(IV) which has been reported for a number of redox-active and redox-inactive minerals. A model of the pH and ionic strength dependence of Pu(V) sorption rates suggests that H(+) exchangeable cations facilitate Pu(V) reduction. While surface complexation may play a dominant role in Pu sorption and colloid-facilitated transport under alkaline conditions, results from this study suggest that Pu(V) ion exchange and surface-mediated reduction to Pu(IV) can immobilize Pu or enhance its colloid-facilitated transport in the environment at neutral to mildly acidic pHs. PMID:22296270

  4. Adsorption of low molecular weight halocarbons by montmorillonite

    SciTech Connect

    Estes, T.J.; Shah, R.V.; Vilker, V.L. )

    1988-04-01

    Montmorillonite clay from Clay Spur, WY, was found to adsorb several low molecular weight, hydrophobic halocarbons from aqueous solution at sub-parts-per-million levels. The halocarbons studied were trichloroethylene, tetrachloroethylene, hexachloroethane, and dibromochloropropane. When the montmorillonite was treated with sodium citrate-bicarbonate-dithionite (CBD), it adsorbed higher levels of halocarbons than the untreated clay. In addition, the CBD-treated clay exhibited a maximum in halocarbon adsorption around pH 4, while untreated clay showed little variation in adsorption over the pH range 2-10. Adsorption of trichloroethylene was inhibited by low concentrations of sodium chloride (0.01 M or greater) in solution. Aging the CBD-treated clay in water decreased its capacity to adsorb trichloroethylene. Desorption studies showed that the sorption of tetrachloroethylene to CBD-treated clay is an irreversible process when compared to sorption by fumed silica. The ability of montmorillonite to adsorb halocarbons and the instability of the clay in water are postulated to involve changes in the oxide surface coating on the clay.

  5. Surface properties of in situ organo-montmorillonite modified wood flour and the influence on mechanical properties of composites with polypropylene

    NASA Astrophysics Data System (ADS)

    Liu, Ru; Sun, Wenjing; Cao, Jinzhen; Wang, Jiamin

    2016-01-01

    In this study, wood flours (WFs) were modified by sodium-montmorillonite (Na-MMT) and didecyl dimethyl ammonium chloride (DDAC) in two steps to form organo-montmorillonite (OMMT) inside WFs at different OMMT concentrations (0.25, 0.5, 0.75 and 1%, respectively). The surface properties of WFs were investigated as an approach to understand the compatibility of WF/polypropylene (PP) composites. The mechanical properties of the composites were also tested. The results showed that: (1) OMMT modification did not influence the surface morphologies of WFs; (2) owing to the covering of OMMT on WF surface, with increasing OMMT concentration, the surface free energies of WFs increased with both increases of dispersive and polar components, and the surface hydroxyl groups of WF decreased, suggesting good compatibility with non-polar PP; (3) the flexural and tensile strength were correlated with the dispersive component fraction. Significant improvements in flexural and tensile strength were found at OMMT concentration of 0.5%. With increase of OMMT concentration, the flexural and Young's modulus increased. However, the impact strength decreased.

  6. NANOFILTRATION FOULANTS FROM A TREATED SURFACE WATER

    EPA Science Inventory

    The foulant from pilot nanofiltration membrane elements fed conventionally-treated surface water for 15 months was analyzed for organic, inorganic, and biological parameters. The foulant responsible for flux loss was shown to be a film layer 20 to 80 um thick with the greatest de...

  7. Perovskite LaFeO3/montmorillonite nanocomposites: synthesis, interface characteristics and enhanced photocatalytic activity

    PubMed Central

    Peng, Kang; Fu, Liangjie; Yang, Huaming; Ouyang, Jing

    2016-01-01

    Perovskite LaFeO3/montmorillonite nanocomposites (LaFeO3/MMT) have been successfully prepared via assembling LaFeO3 nanoparticles on the surface of montmorillonite with citric acid assisted sol-gel method. The results indicated that the uniform LaFeO3 nanoparticles were densely deposited onto the surface of montmorillonite, mainly ranging in diameter from 10 nm to 15 nm. The photocatalytic activity of LaFeO3/MMT was evaluated by the degradation of Rhodamine B (RhB) under visible light irradiation, indicating that LaFeO3/MMT exhibited remarkable adsorption efficiency and excellent photocatalytic activity with the overall removal rate of RhB up to 99.34% after visible light irradiation lasting for 90 min. The interface characteristic and possible degradation mechanism were explored. The interface characterization of LaFeO3/MMT suggested that LaFeO3 nanoparticles could be immobilized on the surface of montmorillonite with the Si-O-Fe bonds. The abundant hydroxyl groups of montmorillonite, semiconductor photocatalysis of LaFeO3 and Fenton-like reaction could enhance the photocatalytic degradation through a synergistic effect. Therefore, the LaFeO3/MMT is a very promising photocatalyst in future industrial application to treat effectively wastewater of dyes. PMID:26778180

  8. Perovskite LaFeO3/montmorillonite nanocomposites: synthesis, interface characteristics and enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Peng, Kang; Fu, Liangjie; Yang, Huaming; Ouyang, Jing

    2016-01-01

    Perovskite LaFeO3/montmorillonite nanocomposites (LaFeO3/MMT) have been successfully prepared via assembling LaFeO3 nanoparticles on the surface of montmorillonite with citric acid assisted sol-gel method. The results indicated that the uniform LaFeO3 nanoparticles were densely deposited onto the surface of montmorillonite, mainly ranging in diameter from 10 nm to 15 nm. The photocatalytic activity of LaFeO3/MMT was evaluated by the degradation of Rhodamine B (RhB) under visible light irradiation, indicating that LaFeO3/MMT exhibited remarkable adsorption efficiency and excellent photocatalytic activity with the overall removal rate of RhB up to 99.34% after visible light irradiation lasting for 90 min. The interface characteristic and possible degradation mechanism were explored. The interface characterization of LaFeO3/MMT suggested that LaFeO3 nanoparticles could be immobilized on the surface of montmorillonite with the Si-O-Fe bonds. The abundant hydroxyl groups of montmorillonite, semiconductor photocatalysis of LaFeO3 and Fenton-like reaction could enhance the photocatalytic degradation through a synergistic effect. Therefore, the LaFeO3/MMT is a very promising photocatalyst in future industrial application to treat effectively wastewater of dyes.

  9. Perovskite LaFeO3/montmorillonite nanocomposites: synthesis, interface characteristics and enhanced photocatalytic activity.

    PubMed

    Peng, Kang; Fu, Liangjie; Yang, Huaming; Ouyang, Jing

    2016-01-01

    Perovskite LaFeO3/montmorillonite nanocomposites (LaFeO3/MMT) have been successfully prepared via assembling LaFeO3 nanoparticles on the surface of montmorillonite with citric acid assisted sol-gel method. The results indicated that the uniform LaFeO3 nanoparticles were densely deposited onto the surface of montmorillonite, mainly ranging in diameter from 10 nm to 15 nm. The photocatalytic activity of LaFeO3/MMT was evaluated by the degradation of Rhodamine B (RhB) under visible light irradiation, indicating that LaFeO3/MMT exhibited remarkable adsorption efficiency and excellent photocatalytic activity with the overall removal rate of RhB up to 99.34% after visible light irradiation lasting for 90 min. The interface characteristic and possible degradation mechanism were explored. The interface characterization of LaFeO3/MMT suggested that LaFeO3 nanoparticles could be immobilized on the surface of montmorillonite with the Si-O-Fe bonds. The abundant hydroxyl groups of montmorillonite, semiconductor photocatalysis of LaFeO3 and Fenton-like reaction could enhance the photocatalytic degradation through a synergistic effect. Therefore, the LaFeO3/MMT is a very promising photocatalyst in future industrial application to treat effectively wastewater of dyes. PMID:26778180

  10. Elaboration et caracterisation de nanocomposites polyethylene/montmorillonite

    NASA Astrophysics Data System (ADS)

    Stoeffler, Karen

    This research project consists in preparing polyethylene/montmorillonite nanocomposites for film packaging applications. Montmorillonite is a natural clay with an exceptional aspect ratio. In recent years, its incorporation in polymer matrices has attracted great interest. The pioneer work from Toyota on polyamide-6/montmorillonite composites has shown that it was possible to disperse the clay at a nanometric scale. Such a structure, so-called exfoliated, leads to a significant increase in mechanical, barrier and fire retardant properties, even at low volumetric fractions of clay. This allows a valorization of the polymeric material at moderate cost. Due to its high polarity, montmorilloite exfoliation in polymeric matrices is problematic. In the particular case of polyolefin matrices, the platelets dispersion remains limited: most frequently, the composites obtained exhibit conventional structures (microcomposites) or intercalated structures. To solve this problem, two techniques are commonly employed: the surface treatment of the clay, which allows the expansion of the interfoliar gallery while increasing the affinity between the clay and the polymer, and the use of a polar compatibilizing agent (grafted polyolefin). The first part of this thesis deals with the preparation and the characterization of highly thermally stable organophilic montmorillonites. Commercial organophilic montmorillonites are treated with quaternary ammonium intercalating agents. However, those intercalating agents present a poor thermal stability and are susceptible to decompose upon processing, thus affecting the clay dispersion and the final properties of the nanocomposites. In this work, it was proposed to modify the clay with alkyl pyridinium, alkyl imidazolium and alkyl phosphonium intercalating agents, which are more stable than ammonium based cations. Organophilic montmorillonites with enhanced thermal stabilites compared to commercial organoclays (+20°C to +70°C) were prepared. The effect of the chemical structure of the intercalating agent on the capacity of the organoclay to be dispersed in polyethylene matrices was analyzed. In addition, the influence of the dispersion on the thermal stability of the nanocomposites prepared is discussed. In a second part, the effect of the compatibilizing agent characteristics on the quality of the clay dispersion in polyethylene/montmorillonite nanocomposites was analyzed. The mechanical properties and the oxygen permeability of the nanocomposites were evaluated and related to the level of clay delamination and to the strength of the polymer/clay interface, which was evaluated through surface tension measurements.

  11. Reflectance spectroscopy of ferric sulfate-bearing montmorillonites as Mars soil analog materials

    NASA Technical Reports Server (NTRS)

    Bishop, J. L.; Pieters, C. M.; Burns, R. G.; Edwards, J. O.; Mancinelli, R. L.; Froschl, H.

    1995-01-01

    Spectroscopic analyses have shown that smectites enhanced in the laboratory with additional ferric species exhibit important similarities to those of the soils on Mars. Ferrihydrite in these chemically treated smectites has features in the visible to near-infrared region that resemble the energies and band strengths of features in reflectance spectra observed for several bright regions on Mars. New samples have been prepared with sulfate as well, because S was found by Viking to be a major component in the surface material on Mars. A suite of ferrihydrite-bearing and ferric sulfate-bearing montmorillonites, prepared with variable Fe3+ and S concentrations and variable pH conditions, has been analyzed using reflectance spectroscopy in the visible and infrared regions, Mossbauer spectroscopy at room temperature and 4 K, differential thermal analysis, and X-ray diffraction. These analyses support the formation of ferrihydrite of variable crystallinity in the ferrihydrite-bearing montmorillonites and a combination of schwertmannite and ferrihydrite in the ferric sulfate-bearing montmorillonites. Small quantities of poorly crystalline or nanophase forms of other ferric materials may also be present in these samples. The chemical formation conditions of the ferrihydrite-bearing and ferric sulfate-bearing montmorillonites influence the character of the low temperature Mossbauer sextets and the visible reflectance spectra. An absorption minimum is observed at 0.88-0.89 micrometers in spectra of the ferric sulfate-bearing samples, and at 0.89-0.92 micrometers in spectra of the ferrihydrate-bearing montmorillonites. Mossbauer spectra of the ferric sulfate-bearing montmorillonites indicate variable concentrations of ferrihydrite and schwertmannite in the interlaminar spaces and along grain surfaces. Dehydration under reduced atmospheric pressure conditions induces a greater effect on the adsorbed and interlayer water in ferrihydrite-bearing montmorillonite than on the water in ferric sulfate-bearing montmorillonite. Reflectance spectra of ferric sulfate-bearing montmorillonite include a strong 3-micrometers band that is more resistant to dry atmospheric conditions than the 3-micrometers band in spectra of similarly prepared ferrihydrite-bearing montmorillonites.

  12. Ferric sulfate montmorillonites as Mars soil analogs

    NASA Technical Reports Server (NTRS)

    Bishop, J. L.; Pieters, C. M.; Burns, R. G.

    1993-01-01

    Spectroscopic analyses have shown that Fe(3+)-doped smectites prepared in the laboratory exhibit important similarities to the soils on Mars. Ferrihydrite in these smectites has features in the visible to near-infrared region that resemble the energies and band-strengths of features in reflectance spectra observed for several bright regions on Mars. Ferric - sulfate - montmorillonite samples have been prepared more recently because they are a good compositional match with the surface material on Mars as measured by Viking. Reflectance spectra of montmorillonite doped with ferric sulfate in the interlayer regions include a strong 3 micron band that persists under dry conditions. This is in contrast to spectra of similarly prepared ferric-doped montmorillonites, which exhibit a relatively weaker 3 micron band under comparable dry environmental conditions. Presented here are reflectance spectra of a suite of ferric-sulfate exchanged montmorillonites prepared with variable ferric sulfate concentrations and variable pH conditions.

  13. Dispersibility of Amphibious Montmorillonite

    NASA Astrophysics Data System (ADS)

    Yeh, Meng-Heng; Hwang, Weng-Sing; Kuo, Wuei-Jueng

    2005-09-01

    The objective of this study is to develop a suitable method to convert hydrophilic montmorillonite into amphibious montmorillonite by replacing the sodium ions normally found in clay with poly(oxyethylene) (POE)-amide chlorite cations. Amphibious montmorillonite has a high d-spacing and good dispersion characteristics in many different types of solutions, including those having an intermediate hydrophilic lipophilic balance (HLB) value. Four different modifying cations are tested and X-ray diffraction analysis is performed to measure the resulting changes in the d-spacing of the MMT. Scanning electron microscopy is employed to investigate the morphology of the modified clays. A laser-doppler particle analyzer is used to measure the particle size of the clays in various solutions. Dobrat’s method is applied to calculate the dispersibility of each clay and Stoke’s law is used to evaluate the settling rate. The results indicate that the d-spacing of the POE-amide chlorite cation modified montmorillonite increases from 1.28 to 3.51 nm. The amphibious montmorillonite demonstrates good dispersion characteristics in eight commonly employed coating solutions with intermediate HLB values.

  14. Methane aqueous fluids in montmorillonite clay interlayer under near-surface geological conditions: a grand canonical Monte Carlo and molecular dynamics simulation study.

    PubMed

    Rao, Qi; Leng, Yongsheng

    2014-09-18

    The grand-canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations are performed to investigate the methane aqueous fluids in Na-montmorillonite clay interlayer under near-surface geological temperature and pressure conditions (T = 300 K and P = 20-50 bar). The chemical potentials of water and methane under these T/P conditions are calculated using the Widom's insertion method. These chemical potentials are used in the GCMC simulations to determine the contents of different species in the clay interlayer, especially in those that correspond to the equilibrium stable spacing distances. Simulation results show that initial clay swelling is dominated by water adsorption into the clay interlayer, followed by the intercalation of methane as the basal spacing increases. However, it is found that this methane intercalation process is strongly influenced by the relative humidity and the total gas pressure of the system. High relative humidity may facilitate water molecules entering the clay interlayer region and inhibit the intercalation of methane molecules. MD simulations show that sodium ions are fully hydrated by water molecules and clay surface oxygen atoms, while methane molecules are not fully coordinated. This situation is attributed to the less water content in clay interlayer and the subsequent formation of methane dimer or trimer clusters due to the hydrophobic nature of small hydrocarbon molecules. PMID:25167085

  15. Peptide Therapeutics for Treating Ocular Surface Infections

    PubMed Central

    2014-01-01

    Abstract Microbial pathogens—bacteria, viruses, fungi, and parasites—are significant causes of blindness, particularly in developing countries. For bacterial and some viral infections a number of antimicrobial drugs are available for therapy but there are fewer available for use in treating fungal and parasitic keratitis. There are also problems with current antimicrobials, such as limited efficacy and the presence of drug-resistant microbes. Thus, there is a need to develop additional drugs. Nature has given us an example of 1 potential source of new antimicrobials: antimicrobial peptides and proteins that are either present in bodily fluids and tissues constitutively or are induced upon infection. Given the nature of peptides, topical applications are the most likely use to be successful and this is ideal for treating keratitis. Such peptides would also be active against drug-resistant pathogens and might act synergistically if used in combination therapy. Hundreds of peptides with antimicrobial properties have been isolated or synthesized but only a handful have been tested against ocular pathogens and even fewer have been tested in animal models. This review summarizes the currently available information on the use of peptides to treat keratitis, outlines some of the problems that have been identified, and discusses future studies that will be needed. Most of the peptides that have been tested have shown activity at concentrations that do not warrant further development, but 1 or 2 have promising activity raising the possibility that peptides can be developed to treat keratitis. PMID:25250986

  16. The adsorption of nucleotides and polynucleotides on montmorillonite clay

    NASA Astrophysics Data System (ADS)

    Ferris, James P.; Ertem, Gözen; Agarwal, Vipin K.

    1989-03-01

    The binding of adenine derivatives to Na+-montmorillonite increases in the order 5'-AMP, 3'-AMP, 5'-ADPmontmorillonite surface and binding is a consequence of the electrostatic interaction between the protonated base and the negative charges on the surface of the montmorillonite. Different binding trends were observed with Cu2+-montmorillonite with AMP binding more strongly than adenosine and UMP binding more strongly than uridine. It is concluded that ligation to the Cu2+ is a major force in the binding of nucleotides to Cu2+-montmorillonite. RNA homopolymers exhibit strong adsorption to Na+- and Cu2+-montmorillonite and are not readily washed from the clay. Factors contributing to the binding are discussed. Watson-Crick hydrogen bonding of 5'-AMP to poly(U) and 5'-GMP to poly(C) was observed when the homopolymers are bound to the surface of the clay. No association of 5'-UMP to poly(U) bound to clay was detected. The possible role of montmorillonite clays in the prebiotic formation of RNA is discussed.

  17. Modeling the Adsorption of Oxalate onto Montmorillonite.

    PubMed

    Ramos, M Elena; Emiroglu, Caglayan; García, David; Sainz-Díaz, C Ignacio; Huertas, F Javier

    2015-11-01

    In this work, a multiscale modeling of the interaction of oxalate with clay mineral surfaces from macroscale thermodynamic equilibria simulations to atomistic calculations is presented. Previous results from macroscopic adsorption data of oxalate on montmorillonite in 0.01 M KNO3 media at 25 °C within the pH range from 2.5 to 9 have been used to develop a surface complexation model. The experimental adsorption edge data were fitted using the triple-layer model (TLM) with the aid of the FITEQL 4.0 computer program. Surface complexation of oxalate is described by two reactions: >AlOH + Ox(2-) + 2H(+) = >AlOxH + H2O (log K = 14.39) and >AlOH + Ox(2-) + H(+) = >AlOx(-) + H2O (log K = 10.39). The monodentate complex >AlOxH dominated adsorption below pH 4, and the bidentate complex >AlOx(-) was predominant at higher pH values. Both of the proposed inner-sphere oxalate species are qualitatively consistent with previously published diffuse reflectance FTIR spectroscopic results for oxalate on montmorillonite edge surface (Chem. Geol. 2014, 363, 283-292). Atomistic computational studies have been performed to understand the interactions at the molecular level between adsorbates and mineral surface, showing the atomic structures and IR frequency shifts of the adsorption complexes of oxalate with the edge surface of a periodic montmorillonite model. PMID:26444928

  18. Effect of modified montmorillonites on the biodegradation and adsorption of biomarkers such as hopanes, steranes and diasteranes.

    PubMed

    Ugochukwu, Uzochukwu C; Head, Ian M; Manning, David A C

    2013-12-01

    The effect of modified montmorillonites on the biodegradation and adsorption of selected steranes, diasteranes and hopanes was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The unmodified montmorillonite was treated with didecyldimethylammonium bromide, hydrochloric acid and the relevant metallic chloride to produce organomontmorillonite, acid activated montmorillonite and homoionic montmorillonite respectively which were used in this study. The study indicated that organomontmorillonite, acid activated montmorillonite and potassium montmorillonite did not support the biodegradation of the selected steranes, diasteranes and hopanes as alteration of the biomarkers via biodegradation varied from a paltry 2-6 %. The adsorption of the selected biomarkers on acid activated montmorillonite and organomontmorillonite was also poor. However, adsorption of the biomarkers on potassium montmorillonite was relatively high. Sodium montmorillonite and unmodified montmorillonite appear to stimulate the biodegradation of the selected biomarkers moderately (30-35 %) with adsorption occurring at low level. Calcium montmorillonite and ferric montmorillonite effected significant biodegradation (51-60 %) of the selected biomarkers. PMID:23749373

  19. Montmorillonite Dissolution in Simulated Lung Fluids

    NASA Astrophysics Data System (ADS)

    Schmidt, M.; Wendlandt, R. F.

    2008-12-01

    Because lung fluids" first interaction is with the surface of inhaled grains, the surface properties of inhaled mineral dusts may have a generally mitigating effect on cytotoxicity and carcinogenicity. Wendlandt et al. (Appl. Geochem. 22, 2007) investigated the surface properties of respirable-sized quartz grains in bentonites and recognized pervasive montmorillonite surface coatings on silica grains. The purpose of this study was to determine the dissolution rate and biodurability of montmorillonite in simulated lung fluids and to assess its potential to mitigate silica cytotoxicity. Modified batch reaction experiments were conducted on purified and size fractionated calcic (SAz-2; 0.4-5 μm) and sodic (DC-2; 0.4-2 μm) montmorillonites for 120 to 160 days of reaction time at 37°C in both simulated extracellular lung fluid (Lu) and simulated lysosomal fluid (Ly). Modified batch experiments simulated a flow-through setup and minimized sample handling difficulties. Reacted Lu and Ly fluid was analyzed for Mg, Al, and Si on an ICP-OE spectrometer. Steady state dissolution was reached 90-100 days after the start of the experiment and maintained for 40-60 days. Measured montmorillonite dissolution rates based on BET surface areas and Si steady state release range from 4.1x10-15 mol/m2/s at the slowest to 1.0x10-14 mol/m2/s at the fastest with relative uncertainties of less than 10%. Samples reacting in Ly (pH = 4.55) dissolved faster than those in Lu (pH = 7.40), and DC-2 dissolved faster than SAz-2. The measured range of biodurabilities was 1,300 to 3,400 years for a 1 μm grain assuming a spherical volume and a molar volume equal to that of illite. The difference in salinities of the two fluids was too slight to draw conclusions about the relationship of ionic strength to dissolution rate. Results indicate that montmorillonite dissolution is incongruent and edge controlled. Dissolution rates for DC- 2 and SAz-2 clays were comparable to those reported in the literature. Biodurability results fall well beyond the lifespan of humans confirming montmorillonite's potential to mitigate silica cytotoxicity.

  20. Material, Mechanical, and Tribological Characterization of Laser-Treated Surfaces

    NASA Astrophysics Data System (ADS)

    Yilbas, Bekir Sami; Kumar, Aditya; Bhushan, Bharat; Aleem, B. J. Abdul

    2014-10-01

    Laser treatment under nitrogen assisting gas environment of cobalt-nickel-chromium-tungsten-based superalloy and high-velocity oxygen-fuel thermal spray coating of nickel-chromium-based superalloy on carbon steel was carried out to improve mechanical and tribological properties. Superalloy surface was preprepared to include B4C particles at the surface prior to the laser treatment process. Material and morphological changes in the laser-treated samples were examined using scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction (XRD) analysis. Residual stresses present at the surface region of the laser-treated layer were determined from the XRD data. The microhardness of the laser-treated surface was measured by indentation tests. Fracture toughness of the coating surfaces before and after laser treatment were also measured using overload indentation tests. Macrowear and macrofriction characterization were carried out using pin-on-disk tests.

  1. Immobilization of zinc and cadmium by montmorillonite compounds: Effects of aging and subsequent acidification

    SciTech Connect

    Lothenbach, B.; Furrer, G.; Schaerli, H.; Schulin, R.

    1999-09-01

    The addition of aluminum treated montmorillonites as binding agents that immobilize heavy metals is an innovative approach for the remediation of arable soils polluted with heavy metals. The authors investigated the influence of aging and subsequent sudden acidification on the binding of zinc and cadmium by montmorillonite, Al-montmorillonite and Al{sub 13}-montmorillonite increased, probably due to a partial incorporation in the aluminum hydroxide lattice. Sorption and desorption were hysteretic with respect to pH, i.e., desorption required lower pH values that adsorption to reach the same state of metal partitioning between solid phase and solution. In addition, these minerals enhance the pH buffer capacity of the soil. The results suggest that Al-montmorillonite and Al{sub 13}-montmorillonite are suitable minerals to be used as binding agents for the gentle immobilization of heavy metals in polluted soils.

  2. Sol-gel hybrid films based on organosilane and montmorillonite for corrosion inhibition of AA2024.

    PubMed

    Dalmoro, V; dos Santos, J H Z; Armelin, E; Alemán, C; Azambuja, D S

    2014-07-15

    The present work reports the production of films on AA2024-T3 composed of vinyltrimethoxysilane (VTMS)/tetraethylorthosilicate (TEOS) with incorporation of montmorillonite (sodium montmorillonite and montmorillonite modified with quaternary ammonium salt, abbreviated Na and 30B, respectively), generated by the sol-gel process. According to FT-IR analyses the incorporation of montmorillonite does not affect silica network. Electrochemical characterization was performed by electrochemical impedance spectroscopy measurement in 0.05 mol L(-1) NaCl solution. Results indicate that montmorillonite incorporation improves the corrosion protection compared to the non-modified system. Scanning electron microscopy micrographs reveal that high concentrations of montmorillonite provide agglomerations on the metallic surface, which is in detriment of the anticorrosive performance. The VTMS/TEOS/30B films with the lowest concentration (22 mg L(-1)) of embedded clay provide the highest corrosion protection. PMID:24863798

  3. Molecular dynamics simulation of TCDD adsorption on organo-montmorillonite.

    PubMed

    Zhu, Runliang; Hu, Wenhao; You, Zhimin; Ge, Fei; Tian, Kaixun

    2012-07-01

    In this work, molecular dynamics simulation was applied to investigate the adsorption of Tetrachlorodibenzo-p-Dioxin (TCDD) on tetramethylammonium (TMA) and tetrapropylammonium (TPA) modified montmorillonite, with the aim of providing novel information for understanding the adsorptive characteristics of organo-montmorillonite toward organic contaminants. The simulation results showed that on both outer surface and interlayer space of TPA modified montmorillonite (TPA-mont), TCDD was adsorbed between the TPA cations with the molecular edge facing siloxane surface. Similar result was observed for the adsorption on the outer surface of TMA modified montmorillonite (TMA-mont). These results indicated that TCDD had stronger interaction with organic cation than with siloxane surface. While in the interlayer space of TMA-mont, TCDD showed a coplanar orientation with the siloxane surfaces, which could be ascribed to the limited gallery height within TMA-mont interlayer. Comparing with TMA-mont, TPA-mont had larger adsorption energy toward TCDD but smaller interlayer space to accommodate TCDD. Our results indicated that molecular dynamics simulation can be a powerful tool in characterizing the adsorptive characteristics of organoclays and provided additional proof that for the organo-montmorillonite synthesized with small organic cations, the available interlayer space rather than the attractive force plays the dominant role for their adsorption capacity toward HOCs. PMID:22487236

  4. Surface treated polypropylene (PP) fibres for reinforced concrete

    SciTech Connect

    López-Buendía, Angel M.; Romero-Sánchez, María Dolores; Climent, Verónica

    2013-12-15

    Surface treatments on a polypropylene (PP) fibre have contributed to the improvement of fibre/concrete adhesion in fibre-reinforced concrete. The treatments to the PP fibre were characterized by contact angle measurements, ATR-IR and XPS to analyse chemical alterations. The surface topography and fibre/concrete interaction were analysed by several microscopic techniques, namely optical petrographic, and scanning electron microscopy. Treatment modified the surface chemistry and topography of the fibre by introducing sodium moieties and created additional fibre surface roughness. Modifications in the fibre surface led to an increase in the adhesion properties between the treated fibres and concrete and an improvement in the mechanical properties of the fibre-reinforced concrete composite as compared to the concrete containing untreated PP fibres. Compatibility with the concrete and increased roughness and mineral surface was also improved by nucleated portlandite and ettringite mineral association anchored on the alkaline PP fibre surface, which is induced during treatment.

  5. Peptide Formation Mechanism on Montmorillonite Under Thermal Conditions

    NASA Astrophysics Data System (ADS)

    Fuchida, Shigeshi; Masuda, Harue; Shinoda, Keiji

    2014-02-01

    The oligomerization of amino acids is an essential process in the chemical evolution of proteins, which are precursors to life on Earth. Although some researchers have observed peptide formation on clay mineral surfaces, the mechanism of peptide bond formation on the clay mineral surface has not been clarified. In this study, the thermal behavior of glycine (Gly) adsorbed on montmorillonite was observed during heating experiments conducted at 150 °C for 336 h under dry, wet, and dry-wet conditions to clarify the mechanism. Approximately 13.9 % of the Gly monomers became peptides on montmorillonite under dry conditions, with diketopiperazine (cyclic dimer) being the main product. On the other hand, peptides were not synthesized in the absence of montmorillonite. Results of IR analysis showed that the Gly monomer was mainly adsorbed via hydrogen bonding between the positively charged amino groups and negatively charged surface sites (i.e., Lewis base sites) on the montmorillonite surface, indicating that the Lewis base site acts as a catalyst for peptide formation. In contrast, peptides were not detected on montmorillonite heated under wet conditions, since excess water shifted the equilibrium towards hydrolysis of the peptides. The presence of water is likely to control thermodynamic peptide production, and clay minerals, especially those with electrophilic defect sites, seem to act as a kinetic catalyst for the peptide formation reaction.

  6. Surface characterization of plasma-treated polypropylene fibers

    SciTech Connect

    Wei, Q.F

    2004-06-15

    Plasma treatment is increasingly being used for surface modification of different materials in many industries. In this study, different techniques were employed to characterize the surface properties of plasma treated polypropylene fibers. The chemical nature of the fiber sufaces has been investigated by X-ray photoelectron spectroscopy (XPS). The XPS examination indicated the presence of oxygen-containing functional groups on fiber surfaces after plasma treatment. The Atomic Force Microscopy (AFM) scans revealed the evolution of surface morphology under different experimental conditions. A Philips Environmental Scanning Electron Microscopy (ESEM) was also used to study the wetting behavior of the fibers. In the ESEM, relative humidity can be raised to 100% to facilitate the water condensation onto fiber surfaces for wetting observation. The ESEM observation revealed that the plasma treatment significantly altered the surface wettability of polypropylene fibers.

  7. Adsorption of ferrous ions onto montmorillonites

    NASA Astrophysics Data System (ADS)

    Qin, Dawei; Niu, Xia; Qiao, Min; Liu, Gang; Li, Hongxin; Meng, Zhenxiao

    2015-04-01

    The adsorption of Fe (II) onto montmorillonites was investigated through initial concentration, contact time, pH and temperature. During the whole adsorption process, the ascorbic acid (Vitamin C) was added as a kind of antioxidant, at the same time, deionized water (after boiling) and nitrogen protection were also used to avoid oxidation. The Fe2+/Fetotal ratio of the iron exists in the Fe-montmorillonites was found more than 95%. Two kinetic models, including pseudo-first-order and pseudo-second-order model, were used to analyze the adsorption process of Fe (II) on montmorillonites. The results of our study showed that adsorption process fitted with pseudo-second-order well. Adsorption isotherms showed that Langmuir model was better than Freundlich model. The thermodynamic parameters ΔG0 and ΔH0 were 3.696 kJ/mol and 6.689 kJ/mol (we just gave the values at 298 K), respectively. The positive values at different temperatures showed that the adsorption process was non-spontaneous and endothermic. The characteristics of materials were determined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Surface area and porosity analyzer, Thermogravimetric analysis (TGA), Differential scanning calorimeter (DSC) and Zeta potential distribution.

  8. Aflatoxin toxicity reduction in feed by enhanced binding to surface-modified clay additives.

    PubMed

    Jaynes, William F; Zartman, Richard E

    2011-06-01

    Animal feeding studies have demonstrated that clay additives, such as bentonites, can bind aflatoxins in ingested feed and reduce or eliminate the toxicity. Bentonite deposits are found throughout the world and mostly consist of expandable smectite minerals, such as montmorillonite. The surfaces of smectite minerals can be treated with organic compounds to create surface-modified clays that more readily bind some contaminants than the untreated clay. Montmorillonites treated with organic cations, such as hexadecyltrimethylammonium (HDTMA) and phenyltrimethylammonium (PTMA), more effectively remove organic contaminants, such as benzene and toluene, from water than untreated clay. Similarly, montmorillonite treated with PTMA (K(d) = 24,100) retained more aflatoxin B1 (AfB1) from aqueous corn flour than untreated montmorillonite (K(d) = 944). Feed additives that reduced aflatoxin toxicity in animal feeding studies adsorbed more AfB1 from aqueous corn flour than feed additives that were less effective. The organic cations HDTMA and PTMA are considered toxic and would not be suitable for clay additives used in feed or food, but other non-toxic or nutrient compounds can be used to prepare surface-modified clays. Montmorillonite (SWy) treated with choline (K(d) = 13,800) and carnitine (K(d) = 3960) adsorbed much more AfB1 from aqueous corn flour than the untreated clay (K(d) = 944). A choline-treated clay prepared from a reduced-charge, high-charge montmorillonite (K(d) = 20,100) adsorbed more AfB1 than the choline-treated high-charge montmorillonite (K(d) = 1340) or the untreated montmorillonite (K(d) = 293). Surface-modified clay additives prepared using low-charge smectites and nutrient or non-toxic organic compounds might be used to more effectively bind aflatoxins in contaminated feed or food and prevent toxicity. PMID:22069725

  9. Utilization of surface-treated rubber particles from waste tires

    SciTech Connect

    Smith, F.G. |

    1994-12-01

    During a 12-month program, the author successfully demonstrated commercial applications for surface-treated rubber particles in two major markets: footwear (shoe soles and components) and urethane-foam carpet underlay (padding). In these markets, he has clearly demonstrated the ease of using R-4080 and R-4030 surface-treated rubber particles in existing manufacturing plants and processes and have shown that the material meets or exceeds existing standards for performance, quality, and cost-effectiveness. To produce R-4080 and R-4030, vulcanized rubber, whole-tire material is finely ground to particles of nominal 80 and mesh size respectively. Surface treatment is achieved by reacting these rubber particles with chlorine gas. In this report, the author describes the actual test and evaluations of the participant companies, and identifies other potential end uses.

  10. Effect of in-situ bonding system and surface modification of montmorillonite on the properties of butyl rubber/MMT composites

    NASA Astrophysics Data System (ADS)

    Halim, S. F.; Lawandy, S. N.; Nour, M. A.

    2012-07-01

    Isobutylene-isoprene rubber (IIR)/nanoclay composites were prepared by solution intercalation method. Cloisite Na+ nanoclays and organo-modified montmorillonite (OMT) Cloisite 10 A,.15 A and 20 A were used in this study. The effect of In-situ bonding system HRH (hexametylene tetramine: resorcinol: hydrated silica) on the dispersion of used nanoclays in the rubber matrix were examined by X-ray diffraction and atomic force microscopy (AFM). Characterization of the prepared composites was performed by studying the rheometeric and mechanical properties. The burning out behavior of the nanocomposites with and without the bonding system was also measured.

  11. Induced hydrophobic recovery of oxygen plasma-treated surfaces

    PubMed Central

    Guckenberger, David J.; Berthier, Erwin; Young, Edmond W. K.; Beebe, David J.

    2014-01-01

    Plasma treatment is a widely used method in microfabrication laboratories and the plasticware industry to functionalize surfaces for device bonding and preparation for mammalian cell culture. However, spatial control of plasma treatment is challenging because it typically requires a tedious masking step that is prone to alignment errors. Currently, there are no available methods to actively revert a surface from a treated hydrophilic state to its original hydrophobic state. Here, we describe a method that relies on physical contact treatment (PCT) to actively induce hydrophobic recovery of plasma-treated surfaces. PCT involves applying brushing and peeling processes with common wipers and tapes to reverse the wettability of hydrophilized surfaces while simultaneously preserving hydrophilicity of non-contacted surfaces. We demonstrate that PCT is a user-friendly method that allows 2D and 3D surface patterning of hydrophobic regions, and the protection of hydrophilic surfaces from unwanted PCT-induced recovery. This method will be useful in academic and industrial settings where plasma treatment is frequently used. PMID:22592853

  12. Induced hydrophobic recovery of oxygen plasma-treated surfaces.

    PubMed

    Guckenberger, David J; Berthier, Erwin; Young, Edmond W K; Beebe, David J

    2012-07-01

    Plasma treatment is a widely used method in microfabrication laboratories and the plasticware industry to functionalize surfaces for device bonding and preparation for mammalian cell culture. However, spatial control of plasma treatment is challenging because it typically requires a tedious masking step that is prone to alignment errors. Currently, there are no available methods to actively revert a surface from a treated hydrophilic state to its original hydrophobic state. Here, we describe a method that relies on physical contact treatment (PCT) to actively induce hydrophobic recovery of plasma-treated surfaces. PCT involves applying brushing and peeling processes with common wipers and tapes to reverse the wettability of hydrophilized surfaces while simultaneously preserving hydrophilicity of non-contacted surfaces. We demonstrate that PCT is a user-friendly method that allows 2D and 3D surface patterning of hydrophobic regions, and the protection of hydrophilic surfaces from unwanted PCT-induced recovery. This method will be useful in academic and industrial settings where plasma treatment is frequently used. PMID:22592853

  13. Adsorption of ammonia on treated stainless steel and polymer surfaces

    NASA Astrophysics Data System (ADS)

    Vaittinen, O.; Metsälä, M.; Persijn, S.; Vainio, M.; Halonen, L.

    2014-05-01

    Adsorption of dynamically diluted ammonia at part-per-billion to low part-per-million concentrations in dry nitrogen was studied with treated and non-treated stainless steel and polymer test tubes. The treatments included electropolishing and two types of coatings based on amorphous silicon. Cavity ring-down spectroscopy with an external cavity diode laser operating in the near-infrared wavelength range was used to monitor the adsorption process in real time in continuous-flow conditions to obtain quantitative assessment of the adsorptive properties of the studied surfaces. The investigated polymers were all less adsorptive than any of the treated or non-treated stainless steel surfaces. Some of the commercial coatings reduced the adsorption loss of stainless steel by a factor of ten or more. Polyvinylidene fluoride was found to be superior (less adsorption) to the four other studied polymer coatings. The number of adsorbed ammonia molecules per surface area obtained at different ammonia gas phase concentrations was modeled with Langmuir and Freundlich isotherms. The time behavior of the adsorption-desorption process occurring in the time scale of seconds and minutes was simulated with a simple kinetic model.

  14. Method of treating the surface of a glass member

    NASA Technical Reports Server (NTRS)

    Rice, S. H.; Spencer, R. S. (Inventor); Fleetwood, C. M., Jr.

    1977-01-01

    A method is described of treating a surface of a glass member intended to abut a transparent element for disrupting the light interference fringes formed between the surfaces. The method involves the steps of grinding the surface to form irregularities thereon; bathing the surface with an aqueous solution containing between substantially 41.3 percent and 45.7 percent by volume of sulfuric acid and between substantially 54.3 percent and 58.7 percent by volume of hydrofluoric acid for a time sufficient to polish the irregularities until the glass member is about 90 percent light transmissive; and washing the glass member with a liquid having a temperature substantially lower than the temperature of the aqueous solution for preventing further reaction between the aqueous solution and the surface.

  15. Stability of plasma treated superhydrophobic surfaces under different ambient conditions.

    PubMed

    Chen, Faze; Liu, Jiyu; Cui, Yao; Huang, Shuai; Song, Jinlong; Sun, Jing; Xu, Wenji; Liu, Xin

    2016-05-15

    Plasma hydrophilizing of superhydrophobic substrates has become an important area of research, for example, superhydrophobic-(super)hydrophilic patterned surfaces have significant practical applications such as lab-on-chip systems, cell adhesion, and control of liquid transport. However, the stability of plasma-induced hydrophilicity is always considered as a key issue since the wettability tends to revert back to the untreated state (i.e. aging behavior). This paper focuses on the stability of plasma treated superhydrophobic surface under different ambient conditions (e.g. temperature and relative humidity). Water contact angle measurement and X-ray photoelectron spectroscopy are used to monitor the aging process. Results show that low temperature and low relative humidity are favorable to retard the aging process and that pre-storage at low temperature (-10°C) disables the treated surface to recover superhydrophobicity. When the aging is performed in water, a long-lasting hydropholicity is obtained. As the stability of plasma-induced hydrophilcity over a desired period of time is a very important issue, this work will contribute to the optimization of storage conditions of plasma treated superhydrophobic surfaces. PMID:26945118

  16. Biodegradable nanocomposites from toughened polyhydroxybutyrate and titanate-modified montmorillonite clay

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Montmorillonite clay treated with neopentyl (diallyl)oxy tri( dioctyl) pyrophosphato-titanate was used as a reinforcement for toughened bacterial bioplastic, Polyhydroxybutyrate (PHB) in order to develop novel biodegradable nanocomposites. The modified clay, PHB, toughening partner and specific comp...

  17. Role of Alumina and Montmorillonite in Changing the Sorption of Herbicides to Biochars.

    PubMed

    Li, Jianfa; Li, Saijun; Dong, Huaping; Yang, Shengshuang; Li, Yimin; Zhong, Jiaxing

    2015-06-24

    The influence of biochars on the fate of herbicides in soil depends mostly on environmental factors among which the role of soil minerals is not clear. Two wood-derived biochars produced at 400 °C (BC400) and 600 °C (BC600) were treated with alumina and montmorillonite to investigate their interaction with biochars and the influence of herbicide sorption. Both minerals exhibited a pore-expanding effect that was likely relative to the removal of authigenic organic matter away from the biochars' surface. Alumina brought more remarkable pore expansion by doubling the surface area of the BC400 biochar and the mesopore area of the BC600 biochar. Consequently, more adsorption sites were accessible for herbicide molecules, which resulted in higher sorption of herbicides (acetochlor and metribuzin) to the mineral-treated biochars than to the untreated biochars. The results are useful for understanding the change of surface and sorption properties of biochars with soil applications. PMID:26035027

  18. Surface characterization of silica glass substrates treated by atomic hydrogen

    SciTech Connect

    Inoue, Hiroyuki; Masuno, Atsunobu; Ishibashi, Keiji; Tawarayama, Hiromasa; Zhang, Yingjiu; Utsuno, Futoshi; Koya, Kazuo; Fujinoki, Akira; Kawazoe, Hiroshi

    2013-12-15

    Silica glass substrates with very flat surfaces were exposed to atomic hydrogen at different temperatures and durations. An atomic force microscope was used to measure root-mean-square (RMS) roughness and two-dimensional power spectral density (PSD). In the treatment with atomic hydrogen up to 900 °C, there was no significant change in the surface. By the treatment at 1000 °C, the changes in the RMS roughness and the PSD curves were observed. It was suggested that these changes were caused by etching due to reactions of atomic hydrogen with surface silica. By analysis based on the k-correlation model, it was found that the spatial frequency of the asperities became higher with an increase of the treatment time. Furthermore, the data showed that atomic hydrogen can flatten silica glass surfaces by controlling heat-treatment conditions. - Highlights: • Silica glass surface was treated by atomic hydrogen at various temperatures. • Surface roughness was measured by an atomic force microscope. • Roughness data were analyzed by two-dimensional power spectral density. • Atomic hydrogen can flatten silica glass surfaces.

  19. Flame retardant polypropylene nanocomposites reinforced with surface treated carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Guleria, Abhishant

    Polypropylene nanocomposites are prepared by reinforcing carbon nanotubes by ex-situ solution mixing method. Interfacial dispersion of carbon nanotubes in polypropylene have been improved by surface modification of CNTs and adding surfactants. Polypropylene nanocomposites fabrication was done after treating CNTs. Firstly, oxidation of CNTs followed by silanization for addition of functionalized groups on the surface of CNTs. Maleic anhydride grafted PPs were used as surfactants. Maleic anhydrides with two different molecular weights were LAMPP and HMAPP. Successful oxidation of CNTs by nitric acid and functionalized CNTs by 3-Aminopropyltriethoxysilane was confirmed by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) with evidence of absorption peak at 1700 and 1100-1000 cm-1. Scanning electron microscopy (SEM) micrographs revealed that the CNTs dispersion quality was improved by directly adding LMAPP/HMAPP into PP/CNTs system and the PP-CNTs adhesion was enhanced through both the CNTs surface treatment and the addition of surfactant. Thermal gravimetric analysis (TGA) revealed an enhanced thermal stability in the PP/CNTs and PP/CNTs/MAPP. Differential scanning calorimetry (DSC) characterization demonstrated that the crystalline temperature, fusion heat and crystalline fraction of hosting PP were decreased with the introduction of CNTs and surface treated CNTs; however, melting temperature was only slightly changed. Melting rheological behaviors including complex viscosity, storage modulus, and loss modulus indicated significant changes in the PP/MAPP/CNTs system before and after functionalization of CNTs, and the mechanism were also discussed in details.

  20. Raman mapping of plasma-treated and grafted polymer surfaces

    NASA Astrophysics Data System (ADS)

    Fredericks, Peter; Keen, Imelda; Rintoul, Llewellyn

    2001-10-01

    The grafting of polystyrene (PS) onto various polypropylene (PP) containing substrates, previously treated by exposure to a plasma, has been followed by Raman microspectroscopic mapping. The substrates consisted of either pure PP, or blends of PP and ethylene-propylene rubber (EPR). For exactly the same section of polymer surface, Raman spectra were obtained at 1 micrometers intervals for small sections of each substrate, the surface after plasma-treatment, and the surface after PS grafting. Typically, the size of the sections studied was 50 micrometers X 50 micrometers . Raman maps were constructed indicating the crystallinity variation across the surface, and also the distribution of the EPR component in the substrate, and after plasma treatment. Raman maps were also constructed to show the distribution of the PS at the surface after the grafting reaction. Grafting was found to be heterogeneous. The overall amount of grafted PS depended on the amount of EPR in the substrate. For a particular substrate, increased concentrations of grafted PS were correlated with positions on the surface which had higher EPR after plasma treatment.

  1. The Catalytic Behaviour of NanoAg@montmorillonite Composite Materials

    NASA Astrophysics Data System (ADS)

    Karlíková, Martina; Kvítek, Libor; Prucek, Robert; Panáček, Aleš; Filip, Jan; Pechoušek, Jiří; Adegboyega, Nathaniel F.

    The preparation of nanoAg@montmorillonite composite materials and their catalytic activity is reported in this article. The nanoAg@montmorillonite composite materials were prepared by the adsorption of silver NPs, with an average size about 30 nm, from their aqueous dispersion onto two types of montmorillonite with different chemical composition. Silver NPs were prepared via modified Tollens process, which involves the reduction of [Ag(NH3)2]+ complex cation by maltose. The amount of silver NPs anchored onto the MMT surfaces was determined by UV-VIS spectroscopy; the decrease in absorbance of the dispersion after the adsorption was monitored. Prepared nanocomposite materials were subsequently characterized by means of transmission electron microscopy (TEM) and powder X-ray diffraction (XRD). The reduction of 4-nitrophenol by sodium borohydride was chosen to examine the catalytic properties of the synthesized silver nanocomposite materials.

  2. Alkylammonium montmorillonites as adsorbents for organic vapors from air

    SciTech Connect

    Harper, M.; Purnell, C.J. )

    1990-01-01

    Montmorillonite clays may be modified by the exchange of the inorganic interlayer cations with alkylammonium ions, resulting in a fixed internal porosity. The pore size and shape depend on the nature of the alkylammonium ion. A number of different ions were used to prepare adsorbents with varying properties, and these were examined for their potential application to sampling organic vapors in air. Characterization involved determination of nitrogen and water contents, surface area, interlayer spacing, thermal stability, and breakthrough volumes of organic vapors. The adsorbent that showed the most promise (tetramethylammonium montmorillonite (TMA)) was further evaluated for use as an adsorbent in both thermal- and solvent-desorable sampling systems.

  3. Surface energy increase of oxygen-plasma-treated PET

    SciTech Connect

    Cioffi, M.O.H.; Voorwald, H.J.C.; Mota, R.P

    2003-03-15

    Prosthetic composite is a widely used biomaterial that satisfies the criteria for application as an organic implant without adverse reactions. Polyethylene therephthalate (PET) fiber-reinforced composites have been used because of the excellent cell adhesion, biodegradability and biocompatibility. The chemical inertness and low surface energy of PET in general are associated with inadequate bonds for polymer reinforcements. It is recognized that the high strength of composites, which results from the interaction between the constituents, is directly related to the interfacial condition or to the interphase. A radio frequency plasma reactor using oxygen was used to treat PET fibers for 5, 20, 30 and 100 s. The treatment conditions were 13.56 MHz, 50 W, 40 Pa and 3.33x10{sup -7} m{sup 3}/s. A Rame-Hart goniometer was used to measure the contact angle and surface energy variation of fibers treated for different times. The experimental results showed contact angle values from 47 deg. to 13 deg. and surface energies from 6.4x10{sup -6} to 8.3x10{sup -6} J for the range of 5 to 100 s, respectively. These results were confirmed by the average ultimate tensile strength of the PET fiber/ polymethylmethacrylate (PMMA) matrix composite tested in tensile mode and by scanning electron microscopy.

  4. The mechanism of montmorillonite catalysis in RNA synthesis

    NASA Astrophysics Data System (ADS)

    Joshi, Prakash

    The formation of complex prebiotic molecules on the early Earth is likely to have involved a component of mineral catalysis. Amongst the variety of clay minerals that have been investigated by us for their ability to catalyze the formation of RNA oligomers is montmorillonite. These are 2:1 layer silicates that have a wide range of chemical compositions [(Na,Ca)0.33(Al,Fe,Mg)2(Si,Al)4O10(OH)2.nH2O]. They are commonly produced by the weathering of silicic volcanic ashes to form Bentonite. Once formed, montmorillonites gradually transform to Illites at a modest pressure and temperature. Of the many samples of montmorillonite that we have experimentally examined, a selected subset has been observed to be catalytic for RNA synthesis (Joshi et. al., 2009; Aldersley et al., 2011). Those that have been observed to be excellent catalysts come from a restricted range of elemental compositions. The recent identification of phyllosilicates including montmorillonite on Mars (Bishop et al., 2008) raises the possibility that such processes may have taken place there too. The extent of catalysis depended not only upon the magnitude of the negative charge on the montmorillonite lattice and the number of cations associated with it, but also on the pH at which the reaction is promoted. The isotherm and catalysis studies were extended to provide binding information and catalytic outcomes over a wide pH range. When cations in raw montmorillonite are completely replaced by sodium ions, the resulting Na+-montmorillonite does not catalyze oligomer formation because the ions saturate the interlayer between the platelets of montmorillonite, which blocks the binding of the activated monomers. Acid washed montmorillonite titrated to pH 6-8 with alkali metal ions, serves as the model catalyst for this RNA synthesis (Aldersley et. al., 2011). The optimal binding occurred in the region of maximal oligomer formation. X-ray diffraction studies revealed changes in layer separations of montmorillonite as reaction occurs. The application of the Scherer equation to the X-ray diffraction data showed differences in domain size. Modeling of the size of the activated nucleotide monomers and the charge on the montmorillonite surface provided an interpretation of how these factors influence adsorption. This research provides a basis for further understanding of the physical processes in the mechanism of this catalysis in prebiotic reactions. This research was supported by NASA Astrobiology Institute Grant NNA09DA80A. References: Aldersley, M.F., Joshi, P.C., Price, J.D., Ferris, J.P. The role of montmorillonite in its catalysis of RNA synthesis. Appl. Clay Sci. 54,1-14, 2011. Bishop, J.L., Dobrea, E.J.N., Mckeown, N.K., Parenta, M. Phyllos- ilicate diversity and past aqueous activity revealed at Mawrth Vallis, Mars. Science 321, 830-833, 2008. Joshi, P.C., Aldersley, M.F., Delano, J.W., Ferris, J.P., Mechanism of montmorillonite catalysis in the formation of RNA oligomers, J. Am. Chem. Soc., 131, 13369-13374, 2009.

  5. Montmorillonites Modified with Carbonaceous Deposits.

    PubMed

    Grzybek; Klinik; Motak; Papp; Zyla

    2000-07-15

    The mechanism of formation of carbonaceous deposits on montmorillonites was studied for systems prepared by sorption of polymers on pillared montmorillonites and subsequent carbonization. Temperature-programmed desorption of ammonia and X-ray photoelectron spectroscopy showed that polymer was attached to Al-OH acidic sites of smectite layers. Pillars were not influenced to a greater extent. Islands of carbonaceous material were formed, but the amount of deposited carbon depended strongly upon carbonization conditions. The hydrophylic and acidic properties of carbon-covered silica aluminas differed strongly from those of the starting material. Copyright 2000 Academic Press. PMID:10873313

  6. Transformation of montmorillonite to kaolinite during weathering

    USGS Publications Warehouse

    Altschuler, Z.S.; Dwornik, E.J.; Kramer, H.

    1963-01-01

    Extensive deposits of kaolinite in Florida are formed by transformation of montmorillonite during low-temperature supergene weathering. The transformation occurs by intracrystalline leaching of interlayer cations and tetrahedral silica layers. Interposition of stripped layers within montmorillonite creates a regular 1:1 mixed-layered montmorillonite-kaolinite, a new clay structure. Kaolin-like layers are nourished by lateral epitaxy, as the iron-rich montmorillonite decomposes. Hexagonal outgrowths of new kaolinite develop at the edges of montmorillonite flakes and nucleate new vertical growth. Kaolinitic sands impregnated with goethite are ultimately formed, and the released silica enriches groundwater and forms secondary chert.

  7. The effects of microstructural changes on montmorillonite-microbial interactions

    NASA Astrophysics Data System (ADS)

    Spence, Adrian; Robinson, Claion; Hanson, Richard E.

    2014-01-01

    Clay minerals are important natural adsorbents of soil organic matter (SOM) and therefore are natural modulators of soil-atmospheric carbon fluxes. Although such effects have been reported, little is known about the spatial distribution of organic matter (OM) on the surfaces of soil minerals and even less is known about the effects of microstructural changes on clay-organo interactions. Here we employ acid hydrolysis to induce varying degrees of microstructural changes to montmorillonite clay mineral as a function of time and combine IR spectroscopy, X-ray diffraction, and SEM-EDX as primary techniques to independently provide molecular-level information on the effects these changes on microbial interactions with the mineral. We observed that progressive dissolution of octahedral cations and the simultaneous enrichment of amorphous silica are prominent structural changes induced by hydrolysis, and that the adsorption of microbial-derived components (in particular lipids) on the surfaces of acid-treated clay decreases with increasing acid dissolution time. Although the precise mechanism(s) of interactions remains unclear, we speculate that this adsorption behavior is most likely due to spatial co-variation of microbial-derived OM with octahedral cations in the mineral, acid erosion of biochemically active binding sites, and/or a progressive increase in the hydrophilicity of the mineral surfaces by acid attack over time.

  8. Molecular dynamics simulation of the intercalation behaviors of methane hydrate in montmorillonite.

    PubMed

    Yan, KeFeng; Li, XiaoSen; Xu, ChunGang; Lv, QiuNan; Ruan, XuKe

    2014-06-01

    The formation and mechanism of CH4 hydrate intercalated in montmorillonite are investigated by molecular dynamics (MD) simulation. The formation process of CH4 hydrate in montmorillonite with 1 ~ 8 H2O layers is observed. In the montmorillonite, the "surface H2O" constructs the network by hydrogen bonds with the surface Si-O ring of clay, forming the surface cage. The "interlayer H2O" constructs the network by hydrogen bonds, forming the interlayer cage. CH4 molecules and their surrounding H2O molecules form clathrate hydrates. The cation of montmorillonite has a steric effect on constructing the network and destroying the balance of hydrogen bonds between the H2O molecules, distorting the cage of hydrate in clay. Therefore, the cages are irregular, which is unlike the ideal CH4 clathrate hydrates cage. The pore size of montmorillonite is another impact factor to the hydrate formation. It is quite easier to form CH4 hydrate nucleation in montmorillonite with large pore size than in montmorillonite with small pore. The MD work provides the constructive information to the investigation of the reservoir formation for natural gas hydrate (NGH) in sediments. PMID:24906646

  9. Development of Surface Complexation Models of Cr(VI) Adsorption on Soils, Sediments and Model Mixtures of Kaolinite, Montmorillonite, γ-Alumina, Hydrous Manganese and Ferric Oxides and Goethite

    SciTech Connect

    Koretsky, Carla

    2013-11-29

    Hexavalent chromium is a highly toxic contaminant that has been introduced into aquifers and shallow sediments and soils via many anthropogenic activities. Hexavalent chromium contamination is a problem or potential problem in the shallow subsurface at several DOE sites, including Hanford, Idaho National Laboratory, Los Alamos National Laboratory and the Oak Ridge Reservation (DOE, 2008). To accurately quantify the fate and transport of hexavalent chromium at DOE and other contaminated sites, robust geochemical models, capable of correctly predicting changes in chromium chemical form resulting from chemical reactions occurring in subsurface environments are needed. One important chemical reaction that may greatly impact the bioavailability and mobility of hexavalent chromium in the subsurface is chemical binding to the surfaces of particulates, termed adsorption or surface complexation. Quantitative thermodynamic surface complexation models have been derived that can correctly calculate hexavalent chromium adsorption on well-characterized materials over ranges in subsurface conditions, such pH and salinity. However, models have not yet been developed for hexavalent chromium adsorption on many important constituents of natural soils and sediments, such as clay minerals. Furthermore, most of the existing thermodynamic models have been developed for relatively simple, single solid systems and have rarely been tested for the complex mixtures of solids present in real sediments and soils. In this study, the adsorption of hexavalent chromium was measured as a function of pH (3-10), salinity (0.001 to 0.1 M NaNO3), and partial pressure of carbon dioxide(0-5%) on a suite of naturally-occurring solids including goethite (FeOOH), hydrous manganese oxide (MnOOH), hydrous ferric oxide (Fe(OH)3), γ-alumina (Al2O3), kaolinite (Al2Si2O5(OH)4), and montmorillonite (Na3(Al, Mg)2Si4O10(OH)2�nH2O). The results show that all of these materials can bind substantial quantities of hexavalent chromium, especially at low pH. Unexpectedly, experiments with the clay minerals kaolinite and montmorillonite suggest that hexavalent chromium may interact with these solids over much longer periods of time than expected. Furthermore, hexavalent chromium may irreversibly bind to these solids, perhaps because of oxidation-reduction reactions occurring on the surfaces of the clay minerals. More work should be done to investigate and quantify these chemical reactions. Experiments conducted with mixtures of goethite, hydrous manganese oxide, hydrous ferric oxide, γ-alumina, montmorillonite and kaolinite demonstrate that it is possible to correctly predict hexavalent chromium binding in the presence of multiple minerals using thermodynamic models derived for the simpler systems. Further, these models suggest that of the six solid considered in this study, goethite is typically the solid to which most of the hexavalent chromium will bind. Experiments completed with organic-rich and organic-poor natural sediments demonstrate that in organic-rich substrates, organic matter is likely to control uptake of the hexavalent chromium. The models derived and tested in this study for hexavalent chromium binding to γ-alumina, hydrous manganese oxide, goethite, hydrous ferric oxide and clay minerals can be used to better predict changes in hexavalent chromium bioavailability and mobility in contaminated sediments and soils.

  10. Nickel and Lead Sequestration in Manganese Oxide-coated Montmorillonite

    SciTech Connect

    Boonfueng,T.; Axe, L.; Xu, Y.; Tyson, T.

    2006-01-01

    Amorphous hydrous manganese oxide (HMO) is an important mineral in soils and sediments influencing the mobility and bioavailability of metal contaminants. In this study, nickel and lead sorption to discrete HMO and HMO-coated montmorillonite was investigated mechanistically. The effect of pH and concentration revealed that when normalized to the mass of oxide present, the HMO-coated montmorillonite behaved similarly to the discrete Mn oxide, where both ions sorbed onto HMO-coated montmorillonite as inner-sphere complexes. Ni coordinated to the vacancy sites in the Mn oxide structure, while Pb formed bidentate corner-sharing complexes. These coordination environments were observed not only as a function of loading, pH, and ionic strength, but also in long-term studies where sorption increased by as much as 100% (from 6 x 10{sup -4} to 1.2 x 10{sup -3} mol Ni/g HMO-coated montmorillonite). In this slower sorption process, intraparticle diffusion, the internal surface sites along microporous walls appear to be no different than external ones. Best fit diffusivities ranged from 10{sup -12} to 10{sup -13} cm{sup 2}/s for Ni and 10{sup -17} to 10{sup -20} cm{sup 2}/s for Pb. The significant difference in the diffusivities for the two ions is consistent with site activation theory, where theoretical surface diffusivities were predicted and given their error were in agreement with experimental results. Mn oxides sequester heavy metals in the environment.

  11. Cotransport of bismerthiazol and montmorillonite colloids in saturated porous media

    NASA Astrophysics Data System (ADS)

    Shen, Chongyang; Wang, Hong; Lazouskaya, Volha; Du, Yichun; Lu, Weilan; Wu, Junxue; Zhang, Hongyan; Huang, Yuanfang

    2015-06-01

    While bismerthiazol [N,N‧-methylene-bis-(2-amino-5-mercapto-1,3,4-thiadiazole)] is one of the most widely used bactericides, the transport of bismerthiazol in subsurface environments is unclear to date. Moreover, natural colloids are ubiquitous in the subsurface environments. The cotransport of bismerthiazol and natural colloids has not been investigated. This study conducted laboratory column experiments to examine the transport of bismerthiazol in saturated sand porous media both in the absence and presence of montmorillonite colloids. Results show that a fraction of bismerthiazol was retained in sand and the retention was higher at pH 7 than at pH 4 and 10. The retention did not change with ionic strength. The retention was attributed to the complex of bismerthiazol with metals/metal oxides on sand surfaces through ligand exchange. The transport of bismerthiazol was enhanced with montmorillonite colloids copresent in the solutions and, concurrently, the transport of montmorillonite colloids was facilitated by the bismerthiazol. The transport of montmorillonite colloids was enhanced likely because the bismerthiazol and the colloids competed for the attachment/adsorption sites on collector surfaces and the presence of bismerthiazol changed the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies between colloids and collectors. The transport of bismerthiazol was inhibited if montmorillonite colloids were pre-deposited in sand because bismerthiazol could adsorb onto the colloid surfaces. The adsorbed bismerthiazol could be co-remobilized with the colloids from primary minima by decreasing ionic strength. Whereas colloid-facilitated transport of pesticides has been emphasized, our study implies that transport of colloids could also be facilitated by the presence of pesticides.

  12. 40 CFR 721.10222 - Styrenyl surface treated manganese ferrite (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Styrenyl surface treated manganese... Specific Chemical Substances § 721.10222 Styrenyl surface treated manganese ferrite (generic). (a) Chemical... as styrenyl surface treated manganese ferrite (PMN P-09-581) is subject to reporting under...

  13. Montmorillonite enhanced ciprofloxacin transport in saturated porous media with sorbed ciprofloxacin showing antibiotic activity

    NASA Astrophysics Data System (ADS)

    Chen, Hao; Gao, Bin; Yang, Liu-Yan; Ma, Lena Q.

    2015-02-01

    Antibiotic ciprofloxacin (CIP) is immobile in the subsurface but it has been frequently detected in the aquatic system. Therefore it is important to investigate the factors impacting CIP's mobilization in aquifer. Laboratory columns packed with sand were used to test colloid-facilitated CIP transport by 1) using kaolinite or montmorillonite to mobilize presorbed-CIP in a column or 2) co-transporting with CIP by pre-mixing them before transport. The Langmuir model showed that CIP sorption by montmorillonite (23 g kg- 1) was 100 times more effective than sand or kaolinite. Even with strong CIP complexation ability to Fe/Al coating on sand surface, montmorillonite promoted CIP transport, but not kaolinite. All presorbed-CIP by sand was mobilized by montmorillonite after 3 pore volumes through co-transporting of CIP with montmorillonite. The majority of CIP was fixed onto the montmorillonite interlayer but still showed inhibition of bacteria growth. Our results suggested that montmorillonite with high CIP sorption ability can act as a carrier to enhance CIP's mobility in aquifer.

  14. Comparison of removal torques between laser-treated and SLA-treated implant surfaces in rabbit tibiae

    PubMed Central

    Kang, Nam-Seok; Li, Lin-Jie

    2014-01-01

    PURPOSE The purpose of this study was to compare removal torques and surface topography between laser treated and sandblasted, large-grit, acid-etched (SLA) treated implants. MATERIALS AND METHODS Laser-treated implants (experimental group) and SLA-treated implants (control group) 8 mm in length and 3.4 mm in diameter were inserted into both sides of the tibiae of 12 rabbits. Surface analysis was accomplished using a field emission scanning electron microscope (FE-SEM; Hitachi S-4800; Japan) under ×25, ×150 and ×1,000 magnification. Surface components were analyzed using energy dispersive spectroscopy (EDS). Rabbits were sacrificed after a 6-week healing period. The removal torque was measured using the MGT-12 digital torque meter (Mark-10 Co., Copiague, NY, USA). RESULTS In the experimental group, the surface analysis showed uniform porous structures under ×25, ×150 and ×1,000 magnification. Pore sizes in the experimental group were 20-40 mm and consisted of numerous small pores, whereas pore sizes in the control group were 0.5-2.0 mm. EDS analysis showed no significant difference between the two groups. The mean removal torque in the laser-treated and the SLA-treated implant groups were 79.4 Ncm (SD = 20.4; range 34.6-104.3 Ncm) and 52.7 Ncm (SD = 17.2; range 18.7-73.8 Ncm), respectively. The removal torque in the laser-treated surface implant group was significantly higher than that in the control group (P=.004). CONCLUSION In this study, removal torque values were significantly higher for laser-treated surface implants than for SLA-treated surface implants. PMID:25177474

  15. Chitosan-Montmorillonite microspheres: A sustainable fertilizer delivery system.

    PubMed

    dos Santos, Bruna Rodrigues; Bacalhau, Fabiana Britti; Pereira, Tamires dos Santos; Souza, Claudinei Fonseca; Faez, Roselena

    2015-08-20

    Controlled release fertilizers are efficient tools that increase the sustainability of agricultural practices. However, the biodegradability of the matrices and the determination of the release into soil still require some investigation. This paper describes the preparation of potassium-containing microspheres based on chitosan and montmorillonite clay and the in situ soil release. The chitosan-montmorillonite microspheres were prepared using a coagulation method and different proportions of montmorillonite. The structural, thermal and morphological properties as well the water swelling and fertilizer sorption capacity were evaluated. The best formulations were applied in soil, and the fertilizer release was monitored using time-domain reflectometry (TDR). Montmorillonite clay provides better sorption properties than the chitosan microspheres because of the rough and porous surface. Due to these properties, high levels of fertilizer were sorbed onto the material. ChMMT33-containing potassium shows two specific periods of fertilizer release: the first one lasted approximately three days and was assigned to the external fertilizer on the microspheres. The second was assigned to the internal fertilizer. TDR is an important and fast tool and was used to determine the fertilizer release and the ion movement in the soil. PMID:25965492

  16. Method and system for treating an interior surface of a workpiece using a charged particle beam

    DOEpatents

    Swenson, David Richard

    2007-05-23

    A method and system of treating an interior surface on an internal cavity of a workpiece using a charged particle beam. A beam deflector surface of a beam deflector is placed within the internal cavity of the workpiece and is used to redirect the charged particle beam toward the interior surface to treat the interior surface.

  17. Exfoliation and intercalation of montmorillonite by small peptides

    PubMed Central

    Block, Karin A.; Trusiak, Adrianna; Katz, Al; Alimova, Alexandra; Wei, Hui; Gottlieb, Paul; Steiner, Jeffrey C.

    2015-01-01

    Understanding structural changes in clay minerals induced by complexation with organic matter is relevant to soil science and agricultural applications. In this study, the effect of peptide storage in montmorillonite and the thermal stability of peptide-clay complexes was examined through characterization by X-ray diffraction (XRD), electron microscopy, UV absorption, and thermogravimetric analysis (TGA). XRD analysis of small peptide-montmorillonite clay complexes produced profiles consisting of reflections associated with the smectite 001 reflection and related peaks similar to that produced by a mixed layer clay mineral structure. Shifts in higher order diffraction maxima were attributed to disorder caused by the intercalation with the peptides. Increasing peptide concentrations resulted in greater shifts towards smaller 2θ from 6.37° (1.39 nm) to 5.45° (1.62 nm) as the interlayer space expanded. The expansion was accompanied by broadening of the 001 reflection (FWHM increases from 0.51 to 1.22° 2θ). The XRD line broadening was interpreted as caused by poorer crystallinity resulting from intercalation and tactoid exfoliation. SEM images revealed montmorillonite platelets with upwardly rolled edges that tend toward cylindrical structures with the production of tubules. High-resolution TEM images revealed bending of montmorillonite platelets, confirming exfoliation. The distribution of basal spacings in the micrographs was determined from the spatial frequencies obtained by Fourier analysis of density profiles. The distribution indicated the presence of discrete coherent crystallite domains. XRD and TGA results indicated that higher peptide concentrations resulted in a greater fraction of intercalated peptides and that surface adsorption of peptides mediated intercalation. Therefore, higher peptide concentration led to more stable organoclay complexes. However, UV absorption and TGA found that peptide adsorption onto montmorillonite had a finite limit at approximately 16% by weight. PMID:25825549

  18. REVEGETATION AUGMENTATION OF SURFACE MINES WITH TREATED ACID MINE DRAINAGE

    EPA Science Inventory

    This study provided a field demonstration of an earlier feasibility study. Treated acid mine drainage was utilized to augment revegetation on graded spoil areas. Acid mine drainage was treated utilizing limestone (rock dust) and the resulatant water was spray irrigated under high...

  19. Cation exchange interaction between antibiotic ciprofloxacin and montmorillonite.

    PubMed

    Wang, Chih-Jen; Li, Zhaohui; Jiang, Wei-Teh; Jean, Jiin-Shuh; Liu, Chia-Chuan

    2010-11-15

    Exploring the interactions between antibiotics and soils/minerals is of great importance in resolving their fate, transport, and elimination in the environment due to their frequent detection in wastewater, river water, sewage sludge and soils. This study focused on determining the adsorption properties and mechanisms of interaction between antibiotic ciprofloxacin and montmorillonite (SAz-1), a swelling dioctahedral mineral with Ca(2+) as the main interlayer cation. In acidic and neutral aqueous solutions, a stoichiometric exchange between ciprofloxacin and interlayer cations yielded an adsorption capacity as high as 330 mg/g, corresponding to 1.0 mmol/g. When solution pH was above its pK(a2) (8.7), adsorption of ciprofloxacin was greatly reduced due to the net repulsion between the negatively charged clay surfaces and the ciprofloxacin anion. The uptake of ciprofloxacin expanded the basal spacing (d(001)) of montmorillonite from 15.04 to 17.23 A near its adsorption capacity, confirming cation exchange within the interlayers in addition to surface adsorption. Fourier transform infrared results further suggested that the protonated amine group of ciprofloxacin in its cationic form was electrostatically attracted to negatively charged sites of clay surfaces, and that the carboxylic acid group was hydrogen bonded to the basal oxygen atoms of the silicate layers. The results indicate that montmorillonite is an effective sorbent to remove ciprofloxacin from water. PMID:20675045

  20. HF- and NH4OH-treated (111)Si surfaces studied by spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Utani, Katsuyuki; Suzuki, Takahiro; Adachi, Sadao

    1993-04-01

    Spectroscopic ellipsometry has been used to study HF- and NH4OH-treated (111)Si surfaces. The ellipsometric data indicate that aqueous HF etching results in the removal of the surface oxide and leaves behind Si surfaces terminated by atomic hydrogen. Chemical treatment by aqueous NH4OH solution provides a bare Si surface, but further etching of Si leads to roughening of the sample surfaces. Both the HF- and NH4OH-treated surfaces become hydrophobic as the surface is hydrogen-terminated (HF) or the surface oxide layer is etched completely away (NH4OH).

  1. Spectroscopic ellipsometry studies of HF treated Si (100) surfaces

    NASA Astrophysics Data System (ADS)

    Yao, Huade; Woollam, John A.; Alterovitz, Samuel A.

    1993-06-01

    Both ex situ and in situ spectroscopic ellipsometry (SE) measurements were employed to investigate the effect of HF cleaning on Si surfaces. The hydrogen-terminated (H-terminated) Si surface was modeled as an equivalent dielectric layer, and monitored in real time by SE measurements. The SE analyses indicate that, after a 20-sec 9:1 HF dip without rinse, the Si (100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si (100) surface was observed, in an ultrahigh vacuum chamber (UHV), and analyzed by the in situ SE. Evidence for desorption of the H-terminated Si surface layer, after being heated to about 550 C in the UHV chamber, is presented and discussed. This is the first use of an ex situ and in situ real-time, nondestructive technique capable of showing state of passivation, the rate of reoxidation, and the surface roughness of the H-terminated Si surfaces.

  2. Spectroscopic ellipsometry studies of HF treated Si (100) surfaces

    NASA Astrophysics Data System (ADS)

    Yao, Huade; Woollam, John A.; Alterovitz, Samuel A.

    1993-08-01

    Both ex situ and in situ spectroscopic ellipsometry (SE) measurements were employed to investigate the effects of HF cleaning on Si surfaces. The hydrogen-terminated (H-terminated) Si surface was modeled as an equivalent dielectric layer, and monitored in real time by SE measurements. The SE analyses indicate that after a 20-s 9:1 HF dip without rinse, the Si(100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si(100) surface was observed, in an ultrahigh vacuum (UHV) chamber, and analyzed by the in situ SE. Evidence for desorption of the H-terminated Si surface-layer, after being heated to approximately 550 C in the UHV chamber, is presented and discussed. This is the first use of an ex situ and in situ real-time, nondestructive technique capable of showing state of passivation, the rate of reoxidation, and the surface roughness of the H-terminated Si surfaces.

  3. Controlled Release of Agrochemicals Intercalated into Montmorillonite Interlayer Space

    PubMed Central

    2014-01-01

    Periodic application of agrochemicals has led to high cost of production and serious environmental pollution. In this study, the ability of montmorillonite (MMT) clay to act as a controlled release carrier for model agrochemical molecules has been investigated. Urea was loaded into MMT by a simple immersion technique while loading of metalaxyl was achieved by a rotary evaporation method. The successful incorporation of the agrochemicals into the interlayer space of MMT was confirmed by several techniques, such as, significant expansion of the interlayer space, reduction of Barrett-Joyner-Halenda (BJH) pore volumes and Brunauer-Emmett-Teller (BET) surface areas, and appearance of urea and metalaxyl characteristic bands on the Fourier-transform infrared spectra of the urea loaded montmorillonite (UMMT) and metalaxyl loaded montmorillonite (RMMT) complexes. Controlled release of the trapped molecules from the matrix was done in water and in the soil. The results reveal slow and sustained release behaviour for UMMT for a period of 10 days in soil. For a period of 30 days, MMT delayed the release of metalaxyl in soil by more than 6 times. It is evident that MMT could be used to improve the efficiency of urea and metalaxyl delivery in the soil. PMID:24696655

  4. Controlled release of agrochemicals intercalated into montmorillonite interlayer space.

    PubMed

    Wanyika, Harrison

    2014-01-01

    Periodic application of agrochemicals has led to high cost of production and serious environmental pollution. In this study, the ability of montmorillonite (MMT) clay to act as a controlled release carrier for model agrochemical molecules has been investigated. Urea was loaded into MMT by a simple immersion technique while loading of metalaxyl was achieved by a rotary evaporation method. The successful incorporation of the agrochemicals into the interlayer space of MMT was confirmed by several techniques, such as, significant expansion of the interlayer space, reduction of Barrett-Joyner-Halenda (BJH) pore volumes and Brunauer-Emmett-Teller (BET) surface areas, and appearance of urea and metalaxyl characteristic bands on the Fourier-transform infrared spectra of the urea loaded montmorillonite (UMMT) and metalaxyl loaded montmorillonite (RMMT) complexes. Controlled release of the trapped molecules from the matrix was done in water and in the soil. The results reveal slow and sustained release behaviour for UMMT for a period of 10 days in soil. For a period of 30 days, MMT delayed the release of metalaxyl in soil by more than 6 times. It is evident that MMT could be used to improve the efficiency of urea and metalaxyl delivery in the soil. PMID:24696655

  5. Octachlorodibenzodioxin formation on Fe(III)-montmorillonite clay.

    PubMed

    Gu, Cheng; Li, Hui; Teppen, Brian J; Boyd, Stephen A

    2008-07-01

    Polychlorinated dibenzo-p-dioxins (PCDDs) are ubiquitous and highly toxic environmental contaminants found in surface and subsurface soils and in clay deposits. Interestingly, the congener profiles of such PCDDs are inexplicably dissimilar to those of known anthropogenic (e.g., pesticide manufacture, waste incineration) or natural (e.g., forest fire) sources. Characteristic features of soil or clay-associated PCDDs are the dominance of octachlorodibenzo-p-dioxin (OCDD) as the most abundant congener and very low levels of polychlorinated dibenzofurans (PCDFs). These propensities led to the hypothesis of in situ PCDD formation in soils and geologic clay deposits. In this study, we demonstrate the formation of OCDD on the naturally occurring and widely distributed clay mineral montmorillonite under environmentally relevant conditions. When pentachlorophenol (PCP)was mixed with Fe(III)-montmorillonite, significant amounts of OCDD were rapidly (minutes to days) formed (approximately 5 mg OCDD/kg clay) at ambient temperature in the presence of water. This reaction is initiated by single electron transfer from PCP to Fe(III)-montmorillonite thereby forming the PCP radical cation. Subsequent dimerization, dechlorination, and ring closure reactions result in formation of OCDD. This study provides the first direct evidence for clay-catalyzed formation of OCDD supporting the plausibility of its in situ formation in soils. PMID:18678002

  6. Preparation of montmorillonite/titania nanocomposite and enhanced electrorheological activity.

    PubMed

    Xiang, Liqin; Zhao, Xiaopeng

    2006-04-01

    We prepared a new type of electrorheological particle composed of TiO2 nanocrystallites-coated montmorillonite (MMT/TiO2) nanocomposite by the sol-gel technique. The characterizations including TGA, XRD, TEM, SEM, EDS, and FTIR showed that TiO2 was deposited on the surface of the MMT flakes with anatase nanocrystallite. An obviously enhanced ER effect was found in the MMT/TiO2 nanocomposites based ER fluids compared with pure MMT and TiO2. Furthermore, the temperature and sedimentation stabilities of the MMT/TiO2 ER fluids had also been improved greatly. Interestingly, the content of TiO2 was demonstrated to have an important influence on the ER effect. When the content of TiO2 was about 20 wt%, the ER effect of MMT/TiO2 ER fluid reached its maximum, which was about 5 times that of pure MMT ER fluid and 27 times that of pure TiO2 ER fluid. Based on dielectric analysis, the significant ER enhancement by formation nanocrystallites-coated montmorillonite was attributed to the enhanced interfacial polarization in this nanocomposite particle due to the effective limitation of the long-range drift of active ions in montmorillonite particles. PMID:16203011

  7. Montmorillonite: A multifunctional mineral catalyst for the prebiological formation of phosphate esters

    NASA Astrophysics Data System (ADS)

    Ferris, James P.; Huang, Chun-Hsien; Hagan, William J.

    1988-03-01

    Reaction of diiminosuccinonitrile (DISN) with 3'-AMP in the presence of alkali- and alkaline earth-montmorillonites results in the formation of 2',3'-cAMP in aqueous solution. Little or no 2',3'-cAMP is produced when metal ion concentrations equivalent to that of the metal ion associated with the homoionic clays are used instead of mobntmorillionite. Yields comparable to those obtained with DISN are obtained when diaminomaleonitrile (DAMN) is used in place of DISN as the condensing agent. DAMN, a compound which is more stable than DISN in aqueous solution, is oxidized to DISN on the surface of the clay by Fe+3 in the clay lattice. DISN, the true condensing agent, is thus generated in the presence of the bound 3'-AMP on the montmorillonite surface. The montmorillonite catalyzes the DISN-mediated formation of 2',3'-cAMP and this product, which binds much less strongly than does the 3'-AMP, is desorbed from the clay surface. This research established that the montmorillonite performs four different functions in its role as catalyst: (1) Binding one of the substrate molecules (3'-AMP) (2) Activating the second substrate (DAMN) (3) Catalyzing the formation of 2',3'-cAMP (4) Releasing the reaction product so another substrate molecules can bind to the montmorillonite.

  8. Surface chemical composition analysis of heat-treated bamboo

    NASA Astrophysics Data System (ADS)

    Meng, Fan-dan; Yu, Yang-lun; Zhang, Ya-mei; Yu, Wen-ji; Gao, Jian-min

    2016-05-01

    In this study, the effect of heat treatment on the chemical composition of bamboo slivers was studied. The chemical properties of the samples were examined by chemical analysis. Results showed a decrease in the contents of holocellulose and α-cellulose, as well as an increase in the contents of lignin and extractives. Changes in the chemical structure of bamboo components were analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). FTIR spectroscopy results indicated that hemicellulose contents decrease, whereas lignin contents increase after heat treatment. Ester formation linked to lignin decreased the hygroscopicity of the bamboo samples and consequently improved their dimensional stability and durability. XPS spectroscopy results showed that hemicelluloses and celluloses are relatively more sensitive to the heating process than lignin. As a consequence, hemicellulose and cellulose contents decreased, whereas lignin contents increased during heat treatment. The results obtained in this study provide useful information for the future utilization of heat-treated bamboo.

  9. Bone regeneration performance of surface-treated porous titanium.

    PubMed

    Amin Yavari, Saber; van der Stok, Johan; Chai, Yoke Chin; Wauthle, Ruben; Tahmasebi Birgani, Zeinab; Habibovic, Pamela; Mulier, Michiel; Schrooten, Jan; Weinans, Harrie; Zadpoor, Amir Abbas

    2014-08-01

    The large surface area of highly porous titanium structures produced by additive manufacturing can be modified using biofunctionalizing surface treatments to improve the bone regeneration performance of these otherwise bioinert biomaterials. In this longitudinal study, we applied and compared three types of biofunctionalizing surface treatments, namely acid-alkali (AcAl), alkali-acid-heat treatment (AlAcH), and anodizing-heat treatment (AnH). The effects of treatments on apatite forming ability, cell attachment, cell proliferation, osteogenic gene expression, bone regeneration, biomechanical stability, and bone-biomaterial contact were evaluated using apatite forming ability test, cell culture assays, and animal experiments. It was found that AcAl and AnH work through completely different routes. While AcAl improved the apatite forming ability of as-manufactured (AsM) specimens, it did not have any positive effect on cell attachment, cell proliferation, and osteogenic gene expression. In contrast, AnH did not improve the apatite forming ability of AsM specimens but showed significantly better cell attachment, cell proliferation, and expression of osteogenic markers. The performance of AlAcH in terms of apatite forming ability and cell response was in between both extremes of AnH and AsM. AcAl resulted in significantly larger volumes of newly formed bone within the pores of the scaffold as compared to AnH. Interestingly, larger volumes of regenerated bone did not translate into improved biomechanical stability as AnH exhibited significantly better biomechanical stability as compared to AcAl suggesting that the beneficial effects of cell-nanotopography modulations somehow surpassed the benefits of improved apatite forming ability. In conclusion, the applied surface treatments have considerable effects on apatite forming ability, cell attachment, cell proliferation, and bone ingrowth of the studied biomaterials. The relationship between these properties and the bone-implant biomechanics is, however, not trivial. PMID:24811260

  10. Surface treated polyethylene fibres as reinforcement for acrylic resins.

    PubMed

    Andreopoulos, A G; Papaspyrides, C D; Tsilibounidis, S

    1991-01-01

    The use of poly(methyl methacrylate) as a bone and dental cement material over several decades has provided us with experience related to processing and performance. A recognized disadvantage of such cements is their mechanical behaviour, expressed by low crack propagation resistance, impact strength, fatigue resistance and reduced fracture toughness. Many attempts have been made to resolve these problems either by modifying the poly(methyl methacrylate) chemical structure via copolymerization or incorporating reinforcing additives. The latter is of great importance, because it can lead to the preparation of composite materials with considerably improved performance. Besides reinforcement, the incorporation of additives, such as fibres, results in better processing characteristics, e.g. lowers polymerization exotherm. In this work, poly(methyl methacrylate) reinforced with Tekmilon ultra high modulus polyethylene fibres was studied, focussing on the interfacial bonding between matrix and reinforcement. Some finishing agents were used to treat the fibres and their efficiency was mainly evaluated through the effect on the mechanical properties of the composite material prepared. PMID:2009351

  11. Surface Treated Natural Fibres as Filler in Biocomposites

    NASA Astrophysics Data System (ADS)

    Schwarzova, I.; Stevulova, N.; Singovszka, E.; Terpakova, E.

    2015-11-01

    Biocomposites based on natural fibres as organic filler have been studied for several years because traditional building materials such as concrete are increasingly being replaced by advanced composite materials. Natural fibres are a potential replacement of glass fibres in composite materials. Inherent advantages such as low density, biodegradability and comparable specific mechanical properties make natural fibres an attractive option. However, limitations such as poor thermal stability, moisture absorption and poor compatibility with matrix are challenges that need to be resolved. The primary objective of this research was to study the effect of surface treatment on properties of hemp hurds like a natural lignocellulosic material and composites made thereof. Industrial hemp fibre is the one of the most suitable fibres for use in composite materials because of its good specific properties, as well as it being biologically degradable and CO2 neutral. Improving interfacial bonding between fibres and matrix is an important factor in using hemp fibres as reinforcement in composites. In order to improve interfacial bonding, modifications can be made to the hemp fibres to remove non- cellulosic compounds, separate hemp fibres from their bundles, and modify the fibre surface. This paper contains the comparison of FTIR spectra caused by combination of physical and chemical treatment of hemp material with unmodified sample. Modification of hemp hurds was carried out by NaOH solution and by ultrasonic treatment (deionized water and NaOH solution were used as the cleaning mediums).

  12. Modelling the sorption of Zn and Ni on Ca-montmorillonite

    SciTech Connect

    Bradbury, M.H.; Baeyens, B.

    1999-02-01

    In some previous work titration and Ni/Zn sorption edge/isotherm measurements carried out under a wide variety of experimental conditions on purified Na-montmorillonite were modelled in terns of cation exchange and surface complexation mass action equations. A major objective of the experimental/modelling program is to understand and predict sorption in commercial bentonite systems. Since montmorillonite is the dominant clay mineral in bentonite and is often present in a mixed Na/Ca form, a natural extension to the previous investigations was to study Ni/Zn sorption on a conditioned Ca-montmorillonite. An important open question was whether the same basic parameters such as site types, site capacities, and acidity constants could be used for both materials and to see to what extent the Ni and Zn surface complexation constants were influenced by the form of the montmorillonite. Sorption edges for Ni and Zn at different Ca(NO{sub 3}){sub 2} background electrolyte concentrations, together with sorption isotherms measured over a range of pH values, are presented and modelled using the MINSORB code. The parameters characterizing the sorption of Ni and Zn on Na- and Ca-montmorillonite systems are compared. Finally, examples are given that illustrate how the modelling can provide insight into the sorption processes.

  13. Montmorillonite nanodevices for the colon metronidazole delivery.

    PubMed

    Calabrese, Ilaria; Cavallaro, Gennara; Scialabba, Cinzia; Licciardi, Mariano; Merli, Marcello; Sciascia, Luciana; Turco Liveri, Maria Liria

    2013-11-30

    The adsorption profiles of the antibiotic metronidazole (MNE) into the K10-montmorillonite (MMT-K10) clay and the subsequent release have been investigated as a function of pH and MNE/MMT-K10 ratio, in order to evaluate the potential of the MNE/MMT-K10 hybrids as controlled drug delivery system. The adsorption mechanism has been first elucidated by performing complementary equilibrium and kinetic studies and through the X-ray diffractometry (XRD) characterization of the obtained composite materials. The gathered results allowed us to propose a mechanism consisting of a multi-step pathway involving the neutral and the cationic form of the drug, which interact with different sites of the clay surfaces, i.e. the interlayer region and the faces of the lamella. In a second step the drug release kinetics has been studied under physiological pH mimicking conditions simulating the oral drug administration and delivery. For the sake of comparison the commercial formulation has also been employed for the release studies. The investigation of the release profiles and the comparison with the commercial formulation of the drug reveal that the new-tailor made formulation could be fruitful exploited for successfully prolonged the action of drug in the desired site. PMID:24076230

  14. Exfoliation of montmorillonite in protein solutions.

    PubMed

    Kolman, Krzysztof; Steffen, Werner; Bugla-Płoskońska, Gabriela; Skwara, Aleksandra; Pigłowski, Jacek; Butt, Hans-Jürgen; Kiersnowski, Adam

    2012-05-15

    In the study we demonstrate a method to obtain stable, exfoliated montmorillonite-protein complexes by adsorption of the proteins extracted from hen-egg albumen. Analysis of the process by means of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the complexes are formed by sequential adsorption of ovotransferrin, ovalbumins, ovomucoid and lysozyme on the surface of the silicate. Structural studies performed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the adsorption of ovotransferrin and albumins is accompanied by disintegration of clay stacks into discrete platelets. Further analysis by dynamic light scattering (DLS) revealed that at protein to silicate weight ratios exceeding 20, the synergistic adsorption of albumen components leads to reaggregation of silicate platelets into disordered, microgel-like particles. By means of DLS it was found that exfoliation predominantly leads to formation of particles with average hydrodynamic radii (R(h)) of 0.19 μm while their aggregation causes formation of particles having R(h) in of approx. 0.5 μm and larger. PMID:22405581

  15. Surface characteristics, corrosion and bioactivity of chemically treated biomedical grade NiTi alloy.

    PubMed

    Chembath, Manju; Balaraju, J N; Sujata, M

    2015-11-01

    The surface of NiTi alloy was chemically modified using acidified ferric chloride solution and the characteristics of the alloy surface were studied from the view point of application as a bioimplant. Chemically treated NiTi was also subjected to post treatments by annealing at 400°C and passivation in nitric acid. The surface of NiTi alloy after chemical treatment developed a nanogrid structure with a combination of one dimensional channel and two dimensional network-like patterns. From SEM studies, it was found that the undulations formed after chemical treatment remained unaffected after annealing, while after passivation process the undulated surface was filled with oxides of titanium. XPS analysis revealed that the surface of passivated sample was enriched with oxides of titanium, predominantly TiO2. The influence of post treatment on the corrosion resistance of chemically treated NiTi alloy was monitored using Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) in Phosphate Buffered Saline (PBS) solution. In the chemically treated condition, NiTi alloy exhibited poor corrosion resistance due to the instability of the surface. On the other hand, the breakdown potential (0.8V) obtained was highest for the passivated samples compared to other surface treated samples. During anodic polarization, chemically treated samples displayed dissolution phenomenon which was predominantly activation controlled. But after annealing and passivation processes, the behavior of anodic polarization was typical of a diffusion controlled process which confirmed the enhanced passivity of the post treated surfaces. The total resistance, including the porous and barrier layer, was in the range of mega ohms for passivated surfaces, which could be attributed to the decrease in surface nickel content and formation of compact titanium oxide. The passivated sample displayed good bioactivity in terms of hydroxyapatite growth, noticed after 14days immersion in Hanks' solution. PMID:26249609

  16. Self-Cleaning Features of Plasma-Treated Surfaces with Self-Assembled Monolayer Coating

    NASA Astrophysics Data System (ADS)

    Lee, Sang‑Joon; Paik, Bu‑Geun; Kim, Guk‑Bae; Jang, Young‑Gil

    2006-02-01

    A biomimic surface was coated onto a poly(tetrafluoroethylene) (PTFE) substrate. The coated PTFE surface was found to have nanoscale roughness and high hydrophobicity. In the first preparation step, the PTFE surface was modified by plasma etching. A self-assembled monolayer (SAM) of octadecyltrichlorosilane (ODTS) was then deposited onto the modified surface with a thickness of a 2-3 nm. This surface was found to have self-cleaning features similar to those of a lotus leaf. The self-cleaning features were confirmed by comparing the contact and sliding angles of the original PTFE surface, a PTFE surface plasma treated, and a PTFE surface plasma treated and SAM coated. The PTFE surface treated with plasma and SAM coated had an increased contact angle and a decreased sliding angle compared with the other surfaces. It also exhibited increased stability and slow aging. The quantity of oxygen-containing groups that can be greatly influenced by plasma treatment, SAM coating, and aging, seems to play an important role in surface modification.

  17. Amino acid conjugated self assembling molecules for enhancing surface wettability of fiber laser treated titanium surfaces

    NASA Astrophysics Data System (ADS)

    Akkan, Cagri K.; Hür, Deniz; Uzun, Lokman; Garipcan, Bora

    2016-03-01

    Surface wetting properties of implants are one of the most critical parameter, which determine the interaction of proteins and cells with the implant surface. In this regards, acid etching and sand blasting are the mostly used methods at surface modification of Titanium (Ti) for enhanced surface wettability. Besides, these kinds of modifications may cause a conflict whether the surface wettability is influenced by the process related surface contaminations or by the surface roughness. In contrast, lasers might be an option for the alteration of surface wetting properties via supporting micro and/or nano surface topographies while preventing surface chemical contaminations. In this work, we focused on two steps of surface processing approaches of Ti surface: physical and chemical modifications. Herein, we hierarchically structured Ti surfaces by using microsecond modulated pulsed fiber laser. Subsequently, laser structured and non-structured Ti surfaces were further modified with novel histidine and leucine Amino Acid conjugated Self-Assembled Molecules (His1-SAMs2 and Leu3-SAMs) to alter the surface wettability by introducing biologically hydrophilic and hydrophobic groups. Modification of Ti surfaces with His-SAMs and Leu-SAMs ended up with stable wetting properties when compared to non-modified surfaces after 7 days which may enhances the cell-surface interaction.

  18. Fractionation of humic acids upon adsorption on montmorillonite and palygorskite

    NASA Astrophysics Data System (ADS)

    Alekseeva, T. V.; Zolotareva, B. N.

    2013-06-01

    The adsorption of three humic acid (HA) preparations by clays—montmorillonite (Wyoming, USA) and palygorskite (Kolomenskoe district, Moscow oblast)—has been studied. The HA preparations were isolated from samples of the humus-accumulative horizons of a leached chernozem (Voronezh) and a chestnut soil (Volgograd), and a commercial preparation of sodium humate (Aldrich) was also used. The solid-state 13C NMR spectroscopy and IR spectroscopy revealed the selective adsorption of structural HA fragments (alkyls, O-alkyls (carbohydrates), and acetal groups) on these minerals. As a result, the aromaticity of the organic matter (OM) in the organic-mineral complexes (OMCs) and the degree of its humification have been found to be lower compared to the original HA preparations. The fractionation of HAs is controlled by the properties of the mineral surfaces. The predominant enrichment of OMCs with alkyls has been observed for montmorillonite, as well as an enrichment with O-alkyls (carbohydrates) for palygorskite. A decrease in the C : N ratio has been noted in the elemental composition of the OM in complexes, which reflected its more aromatic nature and (or) predominant sorption of N-containing structural components of HA molecules. The adsorption of HA preparations by montmorillonite predominantly occurs on the external surface of mineral particles, and the interaction of nonpolar alkyl groups of HAs with this mineral belongs to weak (van der Waals, hydrophobic) interactions. The adsorption of HA preparations by palygorskite is at least partly of chemical nature: Si-OH groups of minerals are involved in the adsorption process. The formation of strong bonds between the OM and palygorskite explains the long-term (over 300 million years) retention of fossil fulvate-type OM in its complex with palygorskite, which we revealed previously.

  19. 40 CFR 721.10573 - Magnesium hydroxide surface treated with substituted alkoxysilanes (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Magnesium hydroxide surface treated... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10573 Magnesium hydroxide surface... to reporting. (1) The chemical substance identified generically as magnesium hydroxide...

  20. MALDI analysis of oligonucleotides directly from montmorillonite.

    PubMed

    Zagorevskii, Dmitri V; Aldersley, Michael F; Ferris, James P

    2006-09-01

    Oligonucleotides synthesized on a montmorillonite catalyst were analyzed directly. By mixing the catalyst with a matrix (2,4,6-trihydroxyacetophenone or 6-aza-2-thiothymine) and dibasic ammonium citrate, higher molecular weight products were detected compared with "classical" methods such as gel electrophoresis and HPLC with UV as a detector. The oligomers (30-mers and higher) were detected by mass spectrometry even though their concentration was less than 10(-4)% of the total content of the RNA. This method is different from the (MALDI) analysis of the eluates from montmorillonite, which otherwise requires desalting. Placing reaction mixtures with a high concentration of buffers on homoionic, preferably Li-containing, montmorillonite does not require desalting. PMID:16809045

  1. Adsorption of polyetheramines on montmorillonite at high pH.

    PubMed

    Cui, Yannan; van Duijneveldt, Jeroen S

    2010-11-16

    Adsorption of a series of polyetheramines on montmorillonite in aqueous suspension was investigated by a range of methods: elemental analysis, atomic absorption spectroscopy, measurement of pH, conductivity and electrophoretic mobility, and small-angle X-ray scattering. Adsorption proceeds through an ion exchange mechanism. The maximum surface coverage attained is equivalent to about 40% of the cationic exchange capacity of the clay. Adsorption of the poly(oxypropylene) block adjacent to the amine group onto the clay surface may contribute to this. Surprisingly the adsorption takes place at pH conditions well above the pK(a) of the amine surfactants, where they are not protonated in the bulk solution. The surface coverage as a function of molar mass broadly agrees with predictions assuming adsorbed polymers adopt a densely packed mushroom configuration at the clay surface. PMID:20964298

  2. Biocidal action of ozone-treated polystyrene surfaces on vegetative and sporulated bacteria

    NASA Astrophysics Data System (ADS)

    Mahfoudh, Ahlem; Barbeau, Jean; Moisan, Michel; Leduc, Annie; Séguin, Jacynthe

    2010-03-01

    Surfaces of materials can be modified to ensure specific interaction features with microorganisms. The current work discloses biocidal properties of polystyrene (PS) Petri-dish surfaces that have been exposed to a dry gaseous-ozone flow. Such treated PS surfaces are able to inactivate various species of vegetative and sporulated bacteria on a relatively short contact time. Denaturation of proteins seems likely based on a significant loss of enzymatic activity of the lysozyme protein. Characterization of these surfaces by atomic-force microscopy (AFM), Fourier-transform infra-red (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) reveals specific structural and chemical modifications as compared to untreated PS. Persistence of the biocidal properties of these treated surfaces is observed. This ozone-induced process is technically simple to achieve and does not require active precursors as in grafting.

  3. Characterization of the surface and the interphase of PVC-copper amine-treated wood composites

    NASA Astrophysics Data System (ADS)

    Jiang, Haihong; Kamdem, D. Pascal

    2010-05-01

    Contact angles and surface energy of wood, as well as interfacial shear strength between wood and polyvinyl chloride (PVC) were investigated and used to monitor the modifications generated on the surfaces of wood treated with a copper ethanolamine solution. An increase in surface energy of wood after treatments promotes wetting of PVC on wood surfaces. Improved interfacial shear strength between treated wood and PVC matrix can be attributed to the formation of a stronger wood-PVC interphase. This suggests that treatment may be used to improve the adhesion between wood surface and PVC in the formulation of wood fiber composites to yield products with enhanced mechanical properties and better biological and physical performance against decay and insect destroying wood.

  4. Synthesis and Characterization of the Hybrid Clay- Based Material Montmorillonite-Melanoidin: A Potential Soil Model

    SciTech Connect

    V Vilas; B Matthiasch; J Huth; J Kratz; S Rubert de la Rosa; P Michel; T Schäfer

    2011-12-31

    The study of the interactions among metals, minerals, and humic substances is essential in understanding the migration of inorganic pollutants in the geosphere. A considerable amount of organic matter in the environment is associated with clay minerals. To understand the role of organic matter in the environment and its association with clay minerals, a hybrid clay-based material (HCM), montmorillonite (STx-1)-melanoidin, was prepared from L-tyrosine and L-glutamic acid by the Maillard reaction. The HCM was characterized by elemental analysis, nuclear magnetic resonance, x-ray photoelectron spectroscopy (XPS), scanning transmission x-ray microscopy (STXM), and thermal analysis. The presence of organic materials on the surface was confirmed by XPS and STXM. The STXM results showed the presence of organic spots on the surface of the STx-1 and the characterization of the functional groups present in those spots. Thermal analysis confirmed the existence of organic materials in the montmorillonite interlayer, indicating the formation of a composite of melanoidin and montmorillonite. The melanoidin appeared to be located partially between the layers of montmorillonite and partially at the surface, forming a structure that resembles the way a cork sits on the top of a champagne bottle.

  5. Surface modification of argon/oxygen plasma treated vulcanized ethylene propylene diene polymethylene surfaces for improved adhesion with natural rubber

    NASA Astrophysics Data System (ADS)

    Basak, Ganesh C.; Bandyopadhyay, Abhijit; Neogi, Sudarsan; Bhowmick, Anil K.

    2011-01-01

    Vulcanized ethylene propylene diene polymethylene (EPDM) rubber surface was treated in a radio frequency capacitatively coupled low pressure argon/oxygen plasma to improve adhesion with compounded natural rubber (NR) during co-vulcanization. The plasma modified surfaces were analyzed by means of contact angle measurement, surface energy, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray sulfur mapping and atomic force microscopy. Several experimental variables such as plasma power, length of exposure time and composition of the argon-oxygen gas mixture were considered. It was delineated that plasma treatment changed both surface composition and roughness, and consequently increased peel strength. The change in surface composition was mainly ascribed to the formation of C-O and -Cdbnd O functional groups on the vulcanized surfaces. A maximum of 98% improvement in peel strength was observed after plasma treatment.

  6. Immobilization of Bone Morphogenetic Protein on DOPA- or Dopamine-Treated Titanium Surfaces to Enhance Osseointegration

    PubMed Central

    Kang, Jeonghwa; Tada, Seiichi; Kitajima, Takashi; Son, Tae Il; Aigaki, Toshiro; Ito, Yoshihiro

    2013-01-01

    Titanium was treated with 3,4-dihydroxy-L-phenylalanine (DOPA) or dopamine to immobilize bone morphogenetic protein-2 (BMP2), a biomolecule. DOPA and dopamine solutions turned into suspensions, and precipitates were produced at high pH. Both treatments produced a brown surface on titanium that was thicker at high pH than low pH. Dopamine produced a thicker layer than DOPA. The hydrophobicity of the surfaces increased after treatment with dopamine independent of pH. Furthermore, there were more amino groups in the layers formed at pH 8.5 than pH 4.5 in both treatments. Dopamine treatment produced more amino groups in the layer than DOPA. BMP2 was immobilized on the treated surfaces via a coupling reaction using carbodiimide. More BMP2 was immobilized on surfaces treated at pH 8.5 than pH 4.5 in both treatments. The immobilized BMP induced specific signal transduction and alkali phosphatase, a differentiation marker. Thus, the present study demonstrates that titanium treated with DOPA or dopamine can become bioactive via the surface immobilization of BMP2, which induces specific signal transduction. PMID:24459666

  7. Study on the surface properties of wood/polyethylene composites treated under plasma

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Tao, Yan; Lv, Xinying; Zhang, Yanhua; Di, Mingwei

    2010-11-01

    Wood/polyethylene (PE) composites are widely used in many fields for its excellent properties, but they are hard to adhere for the surface lacking of polarity. So low-pressure glow discharge of air plasma was used to improve the adhesion properties of wood/PE composites. The composites were treated by plasma under different discharge power. And the changes on the surface properties of the treated and untreated composites were studied by contact angle, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) analysis. The measurement showed that the contact angle decreased after plasma treatment, and the contact angle decreased gradually with the increasing of discharge power. The FTIR analysis results showed that the polar groups such as hydroxyl, carbonyl and carboxyl were formed on the surface of the composites treated under plasma. SEM and AFM results showed that the roughness of plasma treated samples increased. XPS analysis results indicated that the content of carbon element decreased while the content of oxygen element in the composition of wood/PE composites surface element increased and it reached a balance in a higher power, meanwhile a lot of carboxyl groups were formed. The newly formed polar groups are benefit for the adhesion of composites. The shear bonding strength test showed that the adhesion properties of wood/PE composites improved effectively after plasma treatment.

  8. Cellular Performance Comparison of Biomimetic Calcium Phosphate Coating and Alkaline-Treated Titanium Surface

    PubMed Central

    Wei, Mei

    2013-01-01

    The influence of biomimetic calcium phosphate coating on osteoblasts behavior in vitro is not well established yet. In this study, we investigated the behavior of osteoblastic rat osteosarcoma 17/2.8 cells (ROS17/2.8) on two groups of biomaterial surfaces: alkaline-treated titanium surface (ATT) and biomimetic calcium phosphate coated ATT (CaP). The cell attachment, proliferation, differentiation, and morphology on these surfaces were extensively evaluated to reveal the impact of substrate surface on osteoblastic cell responses. It was found that the ROS17/2.8 cells cultured on the ATT surface had higher attachment and proliferation rates compared to those on the CaP surface. Our results also showed that the calcium phosphate coatings generated in this work have an inhibiting effect on osteoblast adhesion and further influenced the proliferation and differentiation of osteoblast compared to the ATT surface in vitro. Cells on the ATT surface also exhibited a higher alkaline phosphatase activity than on the CaP surface after two weeks of culture. Immunofluorescence staining and scanning electron microscopy results showed that the cells adhered and spread faster on the ATT surface than on the CaP surface. These results collectively suggested that substrate surface properties directly influence cell adhesion on different biomaterials, which would result in further influence on the cell proliferation and differentiation. PMID:24455730

  9. Surface work function of indium tin oxide treated using plasma immersion ion implantation

    NASA Astrophysics Data System (ADS)

    He, Long; Wu, Zhonghang; Li, Zebin; Ju, Jiaqi; Ou, Qiongrong; Liang, Rongqing

    2013-05-01

    Oxygen plasma immersion ion implantation (O-PIII) was introduced to modify the surface of indium tin oxide (ITO) thin films. X-ray photoelectron spectroscopy and Kelvin probe were employed to study the surface work function of the treated ITO films. The results showed that the surface work function of ITO can be further enhanced by O-PIII treatment based on an oxygen inductively coupled plasma (O-ICP). The change in surface work function correlated largely with the surface stoichiometry and the high work function should be attributed to the elimination of oxygen vacancies. The surface work function of the modified ITO films showed a rapid decreasing trend with a time-dependent curve immediately after O-ICP and O-PIII treatments. However, a stabler modification effect was achieved by O-PIII.

  10. Montmorillonite, Oligonucleotides, RNA and Origin of Life

    NASA Astrophysics Data System (ADS)

    Ertem, Gözen

    2004-12-01

    Na-montmorillonite prepared from Volclay by the titration method facilitates the self-condensation of ImpA, the 5'-phosphorimidazolide derivative of adenosine. As was shown by AE-HPLC analysis and selective enzymatic hydrolysis of products, oligo(A)s formed in this reaction are 10 monomer units long and contain 67% 3',5'-phosphodiester bonds (Ferris and Ertem, 1992a). Under the same reaction conditions, 5'-phosphorimidazolide derivatives of cytidine, uridine and guanosine also undergo self-condensation producing oligomers containing up to 12-14 monomer units for oligo(C)s to 6 monomer units for oligo(G)s. In oligo(C)s and oligo(U)s, 75-80% of the monomers are linked by 2',5'-phosphodiester bonds. Hexamer and higher oligomers isolated from synthetic oligo(C)s formed by montmorillonite catalysis, which contain both 3',5'- and 2',5'-linkages, serve as catalysts for the non-enzymatic template directed synthesis of oligo(G)s from activated monomer 2-MeImpG, guanosine 5'-phospho-2-methylimidazolide (Ertem and Ferris, 1996). Pentamer and higher oligomers containing exclusively 2',5'-linkages, which were isolated from the synthetic oligo(C)s, also serve as templates and produce oligo(G)s with both 2',5'- and 3',5'-phosphodiester bonds. Kinetic studies on montmorillonite catalyzed elongation rates of oligomers using the computer program SIMFIT demonstrated that the rate constants for the formation of oligo(A)s increased in the order of 2-mer <3-mer <4-mer ... <7-mer (Kawamura and Ferris, 1994). A decameric primer, dA(pdA)8pA bound to montmorillonite was elongated to contain up to 50 monomer units by daily addition of activated monomer ImpA to the reaction mixture (Ferris, Hill and Orgel, 1996). Analysis of dimer fractions formed in the montmorillonite catalyzed reaction of binary and quaternary mixtures of ImpA, ImpC, 2-MeImpG and ImpU suggested that only a limited number of oligomers could have formed on the primitive Earth rather than equal amounts of all possible isomers (Ertem and Ferris, 2000). Formation of phosphodiester bonds between mononucleotides by montmorillonite catalysis is a fascinating discovery, and a significant step forward in efforts to find out how the first RNA-like oligomers might have formed in the course of chemical evolution. However, as has been pointed out in several publications, these systems should be regarded as models rather than a literal representation of prebiotic chemistry (Orgel, 1998; Joyce and Orgel, 1999; Schwartz, 1999).

  11. Montmorillonite, oligonucleotides, RNA and origin of life

    NASA Technical Reports Server (NTRS)

    Ertem, Gozen

    2004-01-01

    Na-montmorillonite prepared from Volclay by the titration method facilitates the self-condensation of ImpA, the 5'-phosphorimidazolide derivative of adenosine. As was shown by AE-HPLC analysis and selective enzymatic hydrolysis of products, oligo(A)s formed in this reaction are 10 monomer units long and contain 67% 3',5'-phosphodiester bonds (Ferris and Ertem, 1992a). Under the same reaction conditions, 5'-phosphorimidazolide derivatives of cytidine, uridine and guanosine also undergo self-condensation producing oligomers containing up to 12-14 monomer units for oligo(C)s to 6 monomer units for oligo(G)s. In oligo(C)s and oligo(U)s, 75-80% of the monomers are linked by 2',5'-phosphodiester bonds. Hexamer and higher oligomers isolated from synthetic oligo(C)s formed by montmorillonite catalysis, which contain both 3',5'- and 2',5'-linkages, serve as catalysts for the non-enzymatic template directed synthesis of oligo(G)s from activated monomer 2-MeImpG, guanosine 5'-phospho-2-methylimidazolide (Ertem and Ferris, 1996). Pentamer and higher oligomers containing exclusively 2',5'-linkages, which were isolated from the synthetic oligo(C)s, also serve as templates and produce oligo(G)s with both 2',5'- and 3',5'-phosphodiester bonds. Kinetic studies on montmorillonite catalyzed elongation rates of oligomers using the computer program SIMFIT demonstrated that the rate constants for the formation of oligo(A)s increased in the order of 2-mer < 3-mer < 4-mer ... < 7-mer (Kawamura and Ferris, 1994). A decameric primer, dA(pdA)8pA bound to montmorillonite was elongated to contain up to 50 monomer units by daily addition of activated monomer ImpA to the reaction mixture (Ferris, Hill and Orgel, 1996). Analysis of dimer fractions formed in the montmorillonite catalyzed reaction of binary and quaternary mixtures of ImpA, ImpC, 2-MeImpG and ImpU suggested that only a limited number of oligomers could have formed on the primitive Earth rather than equal amounts of all possible isomers (Ertem and Ferris, 2000). Formation of phosphodiester bonds between mononucleotides by montmorillonite catalysis is a fascinating discovery, and a significant step forward in efforts to find out how the first RNA-like oligomers might have formed in the course of chemical evolution. However, as has been pointed out in several publications, these systems should be regarded as models rather than a literal representation of prebiotic chemistry (Orgel, 1998; Joyce and Orgel, 1999; Schwartz, 1999).

  12. Influence of ambient conditions on the ageing behaviour of plasma-treated PET surfaces

    NASA Astrophysics Data System (ADS)

    De Geyter, N.; Morent, R.; Leys, C.

    2008-06-01

    Plasma treatment is often used to modify the surface properties of polymer films, since it offers numerous advantages over the conventional surface modification techniques. However, plasma-treated polymer films have a tendency to revert back to the untreated state (ageing process). Therefore, the stability of plasma induced changes on polymer surfaces over a desired period of time is a very important issue. The objective of this study is to examine the effect of storage conditions (relative humidity, temperature and pressure) on the ageing behaviour in air of plasma-treated polyethylene terephthalate (PET) films. Plasma treatment is performed using a dielectric barrier discharge (DBD) operating in air at medium pressure (5.0 kPa). Results show that the ageing process can be suppressed by storing the PET films at low temperature or by decreasing the relative humidity of the surrounding air. In this paper, it is also shown that decreasing pressure has no influence on the ageing process.

  13. Fibroblastic response and surface characterization of O(2)-plasma-treated thermoplastic polyetherurethane.

    PubMed

    Schlicht, Henning; Haugen, Håvard J; Sabetrasekh, Roya; Wintermantel, Erich

    2010-04-01

    Injection-molded samples of thermoplastic polyetherurethane (TPU) were treated with low-temperature oxygen plasma for different processing times in order to enhance cellular attachment for a gastric implant. Its effects were investigated by contact angle measurement, surface topography, cytotoxicity and cell colonization tests. No significant changes were found in the surface roughness of plasma treatment with plasma treatment time of less than 5 min. Longer treatment showed significantly higher surface roughness. It seems that there was a link between the changes in contact angle and enhanced cell growth on the treated surface, although only for the range up to plasma treatment times of 3 min. Prolonged treatment times did not cause any major changes in the water contact angle, but strongly improved the number of growing cells on the surface. Plasma treatment for 3-7 min led to a twofold increase in the number of cells compared to untreated samples and did not significantly alter the WST-1 nor worsened the lactate dehydrogenase activity compared to the control. Thus, it appears that O(2) plasma treatment is a suitable surface modification method for a gastric implant made of TPU in order to improve surface cell attachment where 3-7 min is the recommended treatment time. PMID:20208128

  14. Preparation and characterization of antibacterial silver/vermiculites and silver/montmorillonites

    NASA Astrophysics Data System (ADS)

    Valášková, Marta; Hundáková, Marianna; Kutláková, Kateřina Mamulová; Seidlerová, Jana; Čapková, Pavla; Pazdziora, Erich; Matějová, Kateřina; Heřmánek, Martin; Klemm, Volker; Rafaja, David

    2010-11-01

    The reason for the preparation and characterization of the novel antibacterial silver/vermiculites (Ag/V) together with the silver/montmorillonites (Ag/M) was that the information on the vermiculite structure change and stability of Ag/V in water as well as its effect on bacteria are sporadic. The vermiculite (V), (Si 3.02Al 0.98) IV (Mg 2.27Al 0.12Fe0.283+Fe0.052+Ti 0.07) VI O 10(OH) 2 Ca 0.09Na 0.21K 0.50 from West China and montmorillonite (M), (Si 3.96Al 0.04) IV (Al 1.20Fe0.343+Mg 0.42Ti 0.02) VI O 10 (OH) 2Ca 0.15Na 0.14K 0.08 from Ivančice (Czech Republic), fraction <0.4 μm were the starting clay materials for sample preparation. The samples V1 and M1 were prepared via reaction of the V and M with the 0.01 mol L -1 AgNO 3 aqueous solution. The samples V2 and M2 were treated with the aqueous solution of AgNO 3 for two times. The cation exchange and reduced metallic silver on M1 and V1 evoked the specific surface area (SSA) diminution, the mean particle-size diameter extension and appearance of micropores with radius (<0.4 nm). Repeated silver cation exchange in M2 and V2 reduced particle size, increased slightly SSA and micropores with radius of 0.4-0.5 nm. Samples Ag/V and Ag/M showed higher content of pores with radius 0.5-1.0 nm than original V and M. The Ag concentration was found higher in Ag/V than in Ag/M and higher in repeatedly treated samples: 0.9 wt.% Ag in V1, 1.4 wt.% Ag in V2, 0.6 wt.% Ag in M1 and 1.0 wt.% Ag in M2. Vermiculite structure consisting of the hydrated interstratified phases and the mica-like phase changed to the cation-one-zero layer hydrate interstratification structure in V1 and to the random of two-one layer hydrate interstratifications in V2. Infrared and Mössbauer spectroscopy revealed no changes in the structure of the clay minerals that could be related directly to the sorption and crystallization of silver. Transmission electron microscopy showed that the silver nanoparticles size distribution was much narrower for the samples Ag/M than for Ag/V. The mean size of the Ag particles was between 40 and 50 nm. Although the Ag nanoparticles did not adhere sufficiently at the clay minerals surface and migrated moderately into water, all samples under study were approved to be effective inhibitors of the bacterial growth persisting for the whole testing period of 6 days. Silver/vermiculite was antimicrobial more efficient against Klebsiella pneumoniae and Pseudomonas aeruginosa than silver/montmorillonite.

  15. Structural analysis of heat-treated birch (Betule papyrifera) surface during artificial weathering

    NASA Astrophysics Data System (ADS)

    Huang, Xianai; Kocaefe, Duygu; Kocaefe, Yasar; Boluk, Yaman; Krause, Cornélia

    2013-01-01

    Effect of artificial weathering on the surface structural changes of birch (Betule papyrifera) wood, heat-treated to different temperatures, was studied using the fluorescence microscopy and the scanning electron microscopy (SEM). Changes in the chemical structure of wood components were analyzed by FTIR in order to understand the mechanism of degradation taking place due to heat treatment and artificial weathering. The results are compared with those of the untreated (kiln-dried) birch. The SEM analysis results show that the effect of weathering on the cell wall of the untreated birch surface is more than that of heat-treated samples. The FTIR spectroscopy results indicate that lignin is the most sensitive component of heat-treated birch to the weathering degradation process. Elimination of the amorphous and highly crystallised cellulose is observed for both heat-treated and untreated wood during weathering. It is also observed that heat treatment increases the lignin and crystallised cellulose contents, which to some extent protects heat-treated birch against degradation due to weathering.

  16. Further work on sodium montmorillonite as catalyst for the polymerization of activated amino acids

    NASA Technical Reports Server (NTRS)

    Eirich, F. R.; Paecht-Horowitz, M.

    1986-01-01

    When the polycondensation of amino acid acylates was catalyzed with Na-montmorillonite, the polypeptides were consistently found to exhibit a distribution of discrete molecular weights, for as yet undiscovered reasons. One possible explanation was connected to the stepwise mode of monomer addition. New experiments have eliminated this possibility, so that there is the general assumption that this discreteness is the result of a preference of shorter oligomers to add to others of the same length, a feature that could be attributed to some structure of the platelet aggregates of the montmorillonite. The production of optical stereoisomers is anticipated when D,L-amino acids are polymerized on montmorillonite. Having used an optically active surface, the essence of the results lies not only in the occurrence of optically active oligomers and polymers, but also in the fact that the latter exhibit the same molecular weight characteristics as the D,L-polymers. Preparatory to work contemplated on a parallel synthesis of amino acid and nucleotide oligomers, studies were continued on the co-adsorption of amino acids, nucleotides, and amino acid-nucleotides on montmorillonite.

  17. Laser restoring the glass surface treated with acid-based paint

    NASA Astrophysics Data System (ADS)

    Strusevich, Anastasia V.; Poltaev, Yuriy A.; Sinev, Dmitrii A.

    2013-11-01

    The modern city facilities are often being attacked by graffiti artists, and increasingly vandals leave "tags" using paints, which compound based on acids, hydrofluoric or acetic commonly. These paints not only ink the surface, but also increase the surface roughness, and such impact can not be corrected by conventional cleaning. Thus, it was requested to develop technology that would not only clean the surface, but also to restore its structure by smoothing out irregularities and roughness formed after exposure in acid. In this work we investigated the effect of restoring the surface of the glass, spoiled by acid-based paint and then treated with CO2-laser. During the experiments, it was found that it is real to create the single-step laser surface restoring technology.

  18. Preparation and Characterization of Novel Montmorillonite Nanocomposites

    NASA Astrophysics Data System (ADS)

    Mansa, Rola

    Clay minerals have historically played a consequential role in human health. While the beginnings were rooted in geophagy, a primitive act of consuming earth, the health-related uses of clay minerals have evolved and diversified over time.. As excipients in pharmaceutical formulations, clay minerals can attribute novel properties onto intercalated compounds. Intercalating oxybenzone, a UV filter, within the interlamellar space of montmorillonite is desirable in order to minimize direct contact with skin. Intercalating resveratrol, a compound known for attributing beneficial effects onto human health, may be advantageous since this compound is susceptible to cis-trans isomerisation. The strategy of using alkylammonium--modified clay was undertaken and proved successful for the intercalation of oxybenzone. The field of biopolymer/layered silicate nanocomposites is heavily researched for use in a multitude of applications. Novel montmorillonite nanocomposites were prepared with neutral guar gum and cationic guar gum, using an environmentally friendly process and are fully characterized.

  19. Spectra investigation on surface characteristics of graphene oxide nanosheets treated with tartaric, malic and oxalic acids

    NASA Astrophysics Data System (ADS)

    Teng, Xiyao; Yan, Manqing; Bi, Hong

    2014-01-01

    The surface characteristics of graphene oxide nanosheets (GO) treated respectively with tartaric acid, malic acid and oxalic acid, have been investigated by mainly using optical spectroscopic methods including Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible (UV-Vis) absorption and Raman spectroscopy. Additionally, the electrochemical property of the products has also been studied. The data revealed that oxygen-containing groups such as sbnd OH, sbnd COOH and sbnd Cdbnd O on the GO surface have been almost removed and thus reduced graphene oxide nanosheets (RGN) were obtained. Interestingly, the number of sp2 domains of RGN increases as treated by tartaric acid < malic acid < oxalic acid whereas the steric hindrance (SH) decreases and the ionization constant (IC) differs among these three acids. Furthermore, the specific capacitances (Cs) of GO have been greatly promoted from 2.4 F g-1 to 100.8, 112.4, and 147 F g-1 after treated with tartaric, malic and oxalic acids, respectively. This finding agrees well with the spectra result of the tendency of surface conjugated degree alteration. We claim that the difference in both SH and IC among these acids is the main reason for the diverse surface characteristics as well as the improved Cs of the RGN.

  20. Adsorption of aniline and toluidines on montmorillonite

    SciTech Connect

    Essington, M.E. )

    1994-09-01

    Bentonite clay liners are commonly employed to mitigate the movement of contaminants from waste disposal sites. In order to assess the ability of clay liner material to restrict the mobility of amine compounds under a variety of chemical conditions and to further elucidate amine adsorption characteristics, the adsorption of aniline and o-, m-, and p-toluidine on Ca[sup 2+]- and K[sup +]-saturated Wyoming bentonite (SWy-1) was investigated. Adsorption experiments were performed under conditions of varied pH and ionic environment. Amine adsorption on montmorillonite is pH dependent. Maximum amine adsorption occurs when solution pH is approximately equal to the pK[sub a] of the anilinium ion deprotonation reaction (pH 4.45-5.08). An amine adsorption envelope results from the combined influence of increasing anilinium ion and anilinium-aniline complex formation (as pH decreases to the pK[sub a]) and amine competition with H[sup +] for surface sites, decreasing anilinium-aniline complex concentration, and decreasing aniline available for water bridging with exchangeable Ca[sup 2+] and K[sup +] (as solution pH decreases below the pK[sub a]). For any given amine, maximum adsorption increases with decreasing ionic strength. Maximum amine adsorption is greater in the Ca[sup 2+] systems than in the K[sup +] systems at equivalent cation charge and reflects the formation of an amine water bridge with the exchangeable Ca[sup 2+]. Amine adsorption is also greater in chloride systems compared with sulfate systems at comparable cation concentrations, possibly due to the formation of aqueous anilinium-sulfate complexes. The amine compounds are retained mainly by bentonite through a cation exchange process, the capacity of the clay to adsorb the amine compounds being a significant percentage of the exchange capacity at the pK[sub a]. However, amine retention decreases with increasing pH and is minimal at solution pH values greater than 7. 19 refs., 6 figs.

  1. [Characterization of Wood Surface Treated with Electroless Copper Plating by Near Infrared Spectroscopy Technology].

    PubMed

    Qin, Jing; Zhang, Mao-mao; Zhao, Guang-jie; Yang, Zhong

    2015-05-01

    Wood electromagnetic shielding material, which was made by treating wood with electroless plating, not only keep the superior characteristics of wood, but also improve the conductivity, thermal conductivity and electromagnetic shielding properties of wood. The emergence of this material opens the way to the value-added exploitation of wood and widens the processing and application field for the electromagnetic shielding material. In order to explore the feasibility of using NIR technology to investigate the properties of wood electromagnetic shielding material, this study analysis the samples before and after copper plated process by the NIR spectroscopy coupled with principal component analysis (PCA). The results showed that (1) there exist significant differences between samples before and after copper plated process both on the spectral shape and absorption, and the great differences can also be seen in the samples with different treat time, especially for the samples with 5 min treat time; (2) after PCA analysis, six clusters from the samples before and after copper plated process were separately distributed in the score plot, and the properties of untreated wood and sensitized wood were similar, and the properties of samples for 25 and 40 min treat time were also similar in order that these samples were close to each other, all of which might suggest that the NIR spectroscopy reflected major feature information about material treatment; (3) After comparing the PCA performance between NIR and visible spectral region, it could be found that the classification performance of samples before and after copper plated process based on the NIR region were better than that based on the visible region, and the information of color on the surface of samples were preferably reflected in the visible region, which could indicate that there are more information about samples' surface characters using the visible spectroscopy coupled with NIR spectroscopy and it is feasible to use visible-NIR technology to investigate the surface characteristics of natural polymers treated with electroless copper plating. PMID:26415438

  2. Time-related surface modification of denture base acrylic resin treated by atmospheric pressure cold plasma.

    PubMed

    Qian, Kun; Pan, Hong; Li, Yinglong; Wang, Guomin; Zhang, Jue; Pan, Jie

    2016-01-01

    The changes of denture base acrylic resin surface properties under cold plasma and the relationships with time were investigated. Cold plasma treated the specimens for 30 s, 60 s, 90 s, and 120 s, respectively. Water contact angles were measured immediately after the treatment, 48 h, 15 days and 30 days later. Surface roughness was measured with 3-D laser scanning microscope. Candida albicans adherence was evaluated by CFU counting. Chemical composition was monitored by X-ray photoelectron spectroscopy analysis. Water contact angle reduced after treated for 30 s. No changes were observed with time prolonged, except the durability. There were no differences in roughness among all groups. However, treatment groups showed significantly lower C. albicans adherence. XPS demonstrated a decrease in C/O, and this reduction was affected by treatment time. Cold plasma was an effective means of increasing hydrophilicity of acrylic resin and reducing C. albicans adherence without affecting physical properties. PMID:26830829

  3. Nature of the activity increase of surface Raney nickel treated with cadmium nitrate and sulfate solutions

    SciTech Connect

    Korovin, N.V.; Savel'eva, O.N.; Udris, E.Y.

    1986-09-01

    The laws of cadmium adsorption at nickel surface Raney catalysts (Ni /SUB src/ ) were studied and compared following the exposure of these catalysts to solutions of cadmium nitrate and cadmium sulfate. In both cases cadmium adsorption was shown to occur in the underpotential region, and to be irreversible. During the treatment of Ni /SUB SRC/ in Cd (NO/sub 3/)/sub 2/ solutions, cadmium hydroxide precipitates at the electrode surfaces in addition to the specific adsorption of cadmium; this is due to a reduction of the NO/sub 3//sup -/ ions and alkalization of the solution layer next to the electrode. It was found that the additional reduction of hydrogen overpotential found in alkaline solutions at Ni /SUB src/ following treatment with nitrate solutions, relative to Ni /SUB src/ treated with sulfate solutions, is due to an optimum surface oxidation of the electrodes by the nitrate ions rather than to the presence of phase cadmium or cadmium hydroxide at the surface.

  4. An investigative study of polymer adsorption onto montmorillonite clay

    NASA Astrophysics Data System (ADS)

    McConnell Boykin, Cheri Lynn

    For colloidal systems with adsorbed polymer, the mechanisms governing stabilization and flocculation are defined by the critical overlap concentration, c*. Below c*, steric stabilization or bridging flocculation are viable mechanisms of adsorption, while above c* associative thickening stabilization, depletion stabilization or depletion flocculation may occur. While these types of systems have been described by their mechanism of interaction, few studies have been geared towards evaluating and actually defining these interactions. This research focuses on elucidating the mechanisms of interaction for a series of polyacrylamide copolymers adsorbed onto montmorillonite clay. The well-defined copolymers synthesized and characterized for these studies include: nonionic polyacrylamide, (PAm); cationic poly(acrylamide-co-[3-(methacryloylamino) propyl] trimethylammonium chloride), (PAmMaap Quat); nonionic/anionic poly(acrylamide-co-acrylic acid), (PAmAA); and anionic poly(acrylamide-co-[2-acrylamido-2-methylpropane sulfonic acid]), (PAmAmps). By combining the results from the following experiments it was possible to determine the mechanisms of interaction for each of the clay/polymer systems at pH 3, 7 and 10. The adsorption capacity of each of the copolymers was determined from constructing adsorption isotherms while the polymer conformation was determined from 13C NMR line-broadening experiments. FTIR spectroscopy verified which surface of the clay was involved in adsorption along with the polymer moiety bound to the surface. Finally, the stabilization behavior was evaluated from statistically designed phase diagrams as a function of polymer and clay concentrations. By evaluating the phase behavior as well as c* for the polymer/solvent systems, it was determined that there was no direct correlation between c* for a polymer/solvent system and the mechanism of interaction for colloid/polymer/solvent systems previously defined by Vincent, Sato and Napper. In general, the nonionic polymers act as H-bond acceptors (amide and acid moieties) and donators (acid groups) which result in associatively stabilized homogeneous montmorillonite clay dispersions. The cationic copolymers exhibit strong, irreversible interactions with the clay resulting in heterogeneous bridging flocculation, which was shown to be dependent on the charge density of the copolymer. Furthermore, the anionic copolymers show no signs of adsorption, but create a network of repulsive forces with the montmorillonite clay, which ultimately results in depletion stabilization with some degree of depletion flocculation.

  5. Site-Specific Quantification of Surface N-Glycoproteins in Statin-Treated Liver Cells.

    PubMed

    Xiao, Haopeng; Tang, George X; Wu, Ronghu

    2016-03-15

    The frequent modification of cell-surface proteins by N-linked glycans is known to be correlated with many biological processes. Aberrant glycosylation on surface proteins is associated with different cellular statuses and disease progression. However, it is extraordinarily challenging to comprehensively and site-specifically analyze glycoproteins located only on the cell surface. Currently mass spectrometry (MS)-based proteomics provides the possibility to analyze the N-glycoproteome, but effective separation and enrichment methods are required for the analysis of surface glycoproteins prior to MS measurement. The introduction of bio-orthogonal groups into proteins accelerates research in the robust visualization, identification, and quantification of proteins. Here we have comprehensively evaluated different sugar analogs in the analysis of cell-surface N-glycoproteins by combining copper-free click chemistry and MS-based proteomics. Comparison of three sugar analogs, N-azidoacetylgalactosamine (GalNAz), N-azidoacetylglucosamine (GlcNAz), and N-azidoacetylmannosamine (ManNAz), showed that metabolic labeling with GalNAz resulted in the greatest number of glycoproteins and glycosylation sites in biological duplicate experiments. GalNAz was then employed for the quantification experiment in statin-treated HepG2 liver cells, and 280 unique N-glycosylated sites were quantified from 168 surface proteins. The quantification results demonstrated that many glycosylation sites on surface proteins were down-regulated in statin-treated cells compared to untreated cells because statin prevents the synthesis of dolichol, which is essential for the formation of dolichol-linked precursor oligosaccharides. Several glycosylation sites in proteins that participate in the Alzheimer's disease pathway were down-regulated. This method can be extensively applied for the global analysis of the cell-surface N-glycoproteome. PMID:26894747

  6. Application of clays to removal of red tide organisms II. Coagulation of different species of red tide organisms with montmorillonite and effect of clay pretreatment

    NASA Astrophysics Data System (ADS)

    Zhi-Ming, Yu; Jing-Zhong, Zou; Xi-Nian, Ma

    1994-12-01

    Study on the coagulation of four species of red tide organisms ( Nitzschia pungens, Skeletonema costatum, Prorocentrum minimum and Noctiluca scintillans) with montmorillonite, and the effect of montmorillonite pretreatment on the coagulation shows that the capability for montmorillonite to coagulate with them is in the order: N. pungens > S. costatum > P. minimum > N. scintillans. The coagulation is discussed from the aspects of the structure, shape, size, movement, habit, etc. of different species and the results are explained theoretically. The experimental results also indicate that the treatment of montmorillonite with acid can enhance its coagulating capability. This is due to the fact that Al(OH2){6/+3}, exchanged from the clay lattice by hydrogen ion H+, forms hydroxy-aluminum polymers on the surface of the montmorillonite. The hydroxy-aluminum polymers positively charge and increase the positive characteristic of the clay surface, and also serves as a bridge between adjacent surfaces of particles. These two functions enhance the montmorillonite's capability for coagulating with the organism cells.

  7. Comparative SIMS investigations on surface contamination of Pt Ir alloy treated by different cleaning procedures

    NASA Astrophysics Data System (ADS)

    Sharma, D. R.; Chakraborty, B. R.; Das, M. L.

    1998-09-01

    A comparative study of the surface contamination of Pt-Ir alloy, treated by different cleaning procedures has been carried out using Secondary Ion Mass Spectrometry (SIMS) technique. The Pt-Ir (10%) alloy is basically the standard mass material of the international prototype of the Kilogram. The effect of the conventional cleaning method on the surface of one of the Pt-Ir sample is examined, not only on the top most surface but also a little deep inside the surface, to identify the causes of long term instability of primary standard mass material. In addition to the usual atmospheric contaminants (carbon and oxygen), the results obtained show the presence of contaminants such as sodium, calcium, potassium, magnesium, etc. on the surface of Pt-Ir alloy samples not hitherto observed using other surface analytical techniques like AES, and XPS. In another experiment, four samples, one uncleaned and three cleaned by solvent and/or steam washing, were studied to compare the effect of cleaning procedures on the Pt-Ir samples. It is concluded from the above results that steam cleaning may be advantageous for standard mass stability compared to other cleaning procedures where solvents are used.

  8. Influence of montmorillonites exchange capacity on the basal spacing of cation–anion organo-montmorillonites

    SciTech Connect

    Sanqin, Wu; Zepeng, Zhang; Yunhua, Wang; Libing, Liao; Jiansheng, Zhang

    2014-11-15

    Graphical abstract: This picture shows the distribution of organic modifier (CTAB and SDS) in Mt interlayer and the basal spacing changes of Mt modified by CTAB and SDS. Organic modifier molecule in Mt interlayer is more and more orderly. The basal spacing of Mt is from 1.5 nm to 5 nm as modifier added. - Highlights: • The d{sub 001} of Ca-Mt, R-Na-Mt, Na-Mt modified by CTAB and SDS can reach 5 nm. • It is easier to get cation–anion OMt with greater d{sub 001} if CEC is lower. • The organic molecules distribution in cation–anion OMt was analyzed. • The influence mechanism of Ca-Mt CEC on the d{sub 001} was discussed. - Abstract: With cationic and anionic surfactants cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfonate (SDS) as modifiers, Ca-montmorillonites (Ca-Mt), artificial Na-montmorillonites (R-Na-Mt) and natural Na-montmorillonites (Na-Mt) with different cation exchange capacity (CEC) were modified by solution intercalation method, respectively. Then cation–anion organo-montmorillonites (OMt) were prepared. The influence of CEC on the basal spacing of cation–anion OMt and the influence mechanism were discussed by X-ray diffraction (XRD) and zeta potential testing. The results indicate that the basal spacing of cation–anion OMt is related to CEC. For the same type montmorillonites, the basal spacing of cation–anion OMt decreases with the increase of CEC and it is easier to get cation–anion OMt with greater basal spacing when CEC is lower. Moreover, the CEC of Na-Mt has the greatest influence on the basal spacing of cation–anion OMt.

  9. Prebiotic RNA Synthesis by Montmorillonite Catalysis

    PubMed Central

    Jheeta, Sohan; Joshi, Prakash C.

    2014-01-01

    This review summarizes our recent findings on the role of mineral salts in prebiotic RNA synthesis, which is catalyzed by montmorillonite clay minerals. The clay minerals not only catalyze the synthesis of RNA but also facilitate homochiral selection. Preliminary data of these findings have been presented at the “Horizontal Gene Transfer and the Last Universal Common Ancestor (LUCA)” conference at the Open University, Milton Keynes, UK, 5–6 September 2013. The objective of this meeting was to recognize the significance of RNA in LUCA. We believe that the prebiotic RNA synthesis from its monomers must have been a simple process. As a first step, it may have required activation of the 5'-end of the mononucleotide with a leaving group, e.g., imidazole in our model reaction (Figure 1). Wide ranges of activating groups are produced from HCN under plausible prebiotic Earth conditions. The final step is clay mineral catalysis in the presence of mineral salts to facilitate selective production of functional RNA. Both the clay minerals and mineral salts would have been abundant on early Earth. We have demonstrated that while montmorillonite (pH 7) produced only dimers from its monomers in water, addition of sodium chloride (1 M) enhanced the chain length multifold, as detected by HPLC. The effect of monovalent cations on RNA synthesis was of the following order: Li+ > Na+ > K+. A similar effect was observed with the anions, enhancing catalysis in the following order: Cl− > Br− > I−. The montmorillonite-catalyzed RNA synthesis was not affected by hydrophobic or hydrophilic interactions. We thus show that prebiotic synthesis of RNA from its monomers was a simple process requiring only clay minerals and a small amount of salt. PMID:25370375

  10. Characterization of Surface Treated Aero Engine Alloys by Rayleigh Wave Velocity Dispersion

    NASA Astrophysics Data System (ADS)

    Köhler, B.; Barth, M.; Schubert, F.; Bamberg, J.; Baron, H.-U.

    2010-02-01

    In aero engines mechanically high stressed components made of high-strength alloys like IN718 and Ti6Al4V are usually surface treated by shot-peening. Other methods, e.g. laser-peening, deep rolling and low plasticity burnishing are also available. All methods introduce compres-sive residual stress desired for minimize sensitivity to fatigue or stress corrosion failure mechanisms, resulting in improved performance and increased lifetime of components. Beside that, also cold work is introduced in an amount varying from method to method. To determine the remaining life time of critical aero engine components like compressor and turbine discs, a quantitative non-destructive determination of compressive stresses is required. The opportunity to estimate residual stress in surface treated aero engine alloys by SAW phase velocity measurements has been re-examined. For that original engine relevant material IN718 has been used. Contrary to other publications a significant effect of the surface treatment to the sound velocity was observed which disappeared after thermal treatment. Also preliminary measurements of the acousto-elastic coefficient fit into this picture.

  11. Hepatitis B surface antigen clearance in inactive hepatitis B surface antigen carriers treated with peginterferon alfa-2a

    PubMed Central

    Li, Ming-Hui; Xie, Yao; Zhang, Lu; Lu, Yao; Shen, Ge; Wu, Shu-Ling; Chang, Min; Mu, Cai-Qin; Hu, Lei-Ping; Hua, Wen-Hao; Song, Shu-Jing; Zhang, Shu-Feng; Cheng, Jun; Xu, Dao-Zhen

    2016-01-01

    AIM: To examine the association between interferon (IFN) therapy and loss of hepatitis B surface antigen (HBsAg) in inactive HBsAg carriers. METHODS: This was a retrospective cohort study in inactive HBsAg carriers, who were treatment-naive, with a serum HBsAg level < 100 IU/mL and an undetectable hepatitis B virus (HBV) DNA level (< 100 IU/mL). All the 20 treated patients received subcutaneous PEG-IFN alfa-2a 180 μg/wk for 72 wk and were then followed for 24 wk. There were 40 untreated controls matched with 96 wk of observation. Serum HBsAg, HBV DNA, and alanine aminotransferases were monitored every 3 mo in the treatment group and every 3-6 mo in the control group. RESULTS: Thirteen (65.0%) of 20 treated patients achieved HBsAg loss, 12 of whom achieved HBsAg seroconversion. Mean HBsAg level in treated patients decreased to 6.69 ± 13.04 IU/mL after 24 wk of treatment from a baseline level of 26.22 ± 33.00 IU/mL. Serum HBV DNA level remained undetectable (< 100 IU/mL) in all treated patients during the study. HBsAg level of the control group decreased from 25.72 ± 25.58 IU/mL at baseline to 17.11 ± 21.62 IU/mL at week 96 (P = 0.108). In the control group, no patient experienced HBsAg loss/seroconversion, and two (5.0%) developed HBV reactivation. CONCLUSION: IFN treatment results in HBsAg loss and seroconversion in a considerable proportion of inactive HBsAg carriers with low HBsAg concentrations.

  12. Osteoclasts but not osteoblasts are affected by a calcified surface treated with zoledronic acid in vitro

    SciTech Connect

    Schindeler, Aaron . E-mail: AaronS@chw.edu.au; Little, David G.

    2005-12-16

    Bisphosphonates are potent inhibitors of osteoclast-mediated bone resorption. Recent interest has centered on the effects of bisphosphonates on osteoblasts. Chronic dosing of osteoblasts with solubilized bisphosphonates has been reported to enhance osteogenesis and mineralization in vitro. However, this methodology poorly reflects the in vivo situation, where free bisphosphonate becomes rapidly bound to mineralized bone surfaces. To establish a more clinically relevant cell culture model, we cultured bone cells on calcium phosphate coated quartz discs pre-treated with the potent nitrogen-containing bisphosphonate, zoledronic acid (ZA). Binding studies utilizing [{sup 14}C]-labeled ZA confirmed that the bisphosphonate bound in a concentration-dependent manner over the 1-50 {mu}M dose range. When grown on ZA-treated discs, the viability of bone-marrow derived osteoclasts was greatly reduced, while the viability and mineralization of the osteoblastic MC3T3-E1 cell line were largely unaffected. This suggests that only bone resorbing cells are affected by bound bisphosphonate. However, this system does not account for transient exposure to unbound bisphosphonate in the hours following a clinical dosing. To model this event, we transiently treated osteoblasts with ZA in the absence of a calcified surface. Osteoblasts proved highly resistant to all transitory treatment regimes, even when utilizing ZA concentrations that prevented mineralization and/or induced cell death when dosed chronically. This study represents a pharmacologically more relevant approach to modeling bisphosphonate treatment on cultured bone cells and implies that bisphosphonate therapies may not directly affect osteoblasts at bone surfaces.

  13. Modification of the Steel Surface Treated by a Volume Discharge Plasma in Nitrogen at Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Erofeev, M. V.; Shulepov, M. A.; Ivanov, Yu. F.; Oskomov, K. V.; Tarasenko, V. F.

    2016-03-01

    Effect of volume discharge plasma initiated by an avalanche electron beam on the composition, structure, and properties of the surface steel layer is investigated. Voltage pulses with incident wave amplitude up to 30 kV, full width at half maximum of about 4 ns, and wave front of about 2.5 ns were applied to the gap with an inhomogeneous electric field. Changes indicating the hardening effect of the volume discharge initiated by an avalanche electron beam are revealed in St3-grade steel specimens treated by the discharge of this type.

  14. Selenite Adsorption Mechanisms on Pure and Coated Montmorillonite: An EXAFS and XANES Spectroscopic Study

    SciTech Connect

    Peak, Derek; Saha, U.K.; Huang, P.M.

    2008-06-09

    Selenite (SeO{sub 3}{sup 2-}) is an oxyanion of environmental importance due to its toxicity to animals at higher concentrations, notably waterfowl and grazing animals. Sorption of SeO{sub 3}{sup 2-} with mineral phases typically controls the movement and bioaccessibility of SeO{sub 3}{sup 2-} in soils and sediments. Previous studies have successfully utilized synchrotron-based Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES) spectroscopy to determine SeO{sub 3}{sup 2-} bonding mechanisms on Fe and Mn oxides, but the direct evidence of SeO{sub 3}{sup 2-} surface complexation mechanisms on important mineral phases such as Al hydroxide and aluminosilicate minerals is still lacking. In this study both EXAFS and XANES spectroscopy was conducted on aqueous SeO{sub 3}{sup 2-} solutions and on a variety of Al-bearing sorption samples at pH 4.5. The sorbents chosen were a hydroxyaluminosilicate (HAS) polymer, a hydroxyaluminum (HYA) polymer, montmorillonite, and both HYA and HAS coated montmorillonite. For SeO{sub 3}{sup 2-} sorption on montmorillonite, only bidentate binuclear inner-sphere complexation was observed. For the hydroxyaluminum and hydroxyaluminosilicate polymers, a mixture of outer-sphere and bidentate binuclear inner-sphere was observed. When montmorillonite was coated with either HYA or HAS polymers then adsorption behavior was intermediate between that of the mineral and the pure polymer. Since temperate soils often contain aluminum-hydroxy and aluminosilicate coated minerals rather than discrete Al hydroxide minerals and pristine clay surfaces, the adsorption mechanisms observed on these coated surfaces are more realistic of the natural environment than sorption on pure minerals.

  15. Enhanced cell growth on nanotextured GaN surface treated by UV illumination and fibronectin adsorption.

    PubMed

    Li, Jingying; Han, Qiusen; Wang, Xinhuan; Yang, Rong; Wang, Chen

    2014-11-01

    Semiconductors are important materials used for the development of high-performance biomedical devices. Gallium nitride (GaN) is a well-known III-nitride semiconductor with excellent optoelectronic properties as well as high chemical stability and biocompatibility. The formation of tight interfaces between GaN substrates and cells would be crucial for GaN-based devices used for probing and manipulating biological processes of cells. Here we report a strategy to greatly enhance cell adhesion and survival on nanotextured GaN surface which was treated by UV illumination and fibronectin (FN) adsorption. Cell studies showed that the UV/FN treatment greatly enhanced cell adhesion and growth on nanotextured GaN surfaces. These observations suggest new opportunities for novel nanotextured GaN-based biomedical devices. PMID:25264283

  16. Cavitation erosion of cobalt based STELLITE alloys, cemented carbides and surface treated low alloy steels

    SciTech Connect

    Heathcock, C.J.; Ball, A.

    1981-03-30

    Results are given for erosion-resistance tests involving several STELLITE alloys, cemented carbides and surface-treated alloy steels. It is shown that the cobalt-rich, solid-solution phase of the STELLITE alloys is the basis of their erosion resistance, while the erosion of cemented carbides is predominantly controlled by the binder phase. It is also found that nickel-based tungsten carbides are more erosion-resistant than those based on cobalt. It is demonstrated for the case of the low-alloy steels that surface treatment can improve their erosion rates, and that application of a proprietary nitrocarburizing method to the same steels results in a similar performance improvement only after the initial loss of the compound layer.

  17. Pedogenic formation of montmorillonite from a 2:1-2:2 intergrade clay mineral

    USGS Publications Warehouse

    Malcolm, R.L.; Nettleton, W.D.; McCracken, R.J.

    1969-01-01

    Montmorillonite was found to be the dominant clay mineral in surface horizons of certain soils of the North Carolina Coastal Plain whereas a 2:1-2:2 intergrade clay mineral was dominant in subjacent horizons. In all soils where this clay mineral sequence was found, the surface horizon was low in pH (below 4??5) and high in organic matter content. In contrast, data from studies of other soils of this region (Weed and Nelson, 1962) show that: (1) montmorillonite occurs infrequently; (2) maximum accumulation of the 2:1-2:2 intergrade normally occurs in the surface horizon and decreases with depth in the profile; (3) organic matter contents are low; and (4) pH values are only moderately acid (pH 5-6). It is theorized that the montmorillonite in the surface horizon of the soils studied originated by pedogenic weathering of the 2:1-2:2 intergrade clay mineral. The combined effects of low pH (below 4??5) and high organic matter content in surface horizons are believed to be the agents responsible for this mineral transformation. The protonation and solubilization (reverse of hydrolysis) of Al-polymers in the interlayer of expansible clay minerals will occur at or below pH 4??5 depending on the charge and steric effects of the interlayer. A low pH alone may cause this solubilization and thus mineral transformation, but in the soils studied the organic matter is believed to facilitate and accelerage the transformation. The intermediates of organic matter decomposition provide an acid environment, a source of protons, and a source of watersoluble mobile organic substances (principally fulvic acids) which have the ability to complex the solubilized aluminum and move it down the profile. This continuous removal of solubilized aluminum would provide for a favorable gradient for aluminum solubilization. The drainage class or position in a catena is believed to be less important than the chemical factors in formation of montmorillonite from 2:1-2:2 intergrade, because montmorillonite is present in all drainage classes if the surface horizon is low in pH and high in organic matter. ?? 1969.

  18. Surface and crystalline analysis of aluminum oxide single crystal treated by quasistationary compression plasma flow

    SciTech Connect

    Maletic, S.; Popovic, D.M.; Cubrovic, V.; Zekic, A.A.; Dojcilovic, J.

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer The effects of treatment of Al{sub 2}O{sub 3} (0001) surface by CPF are analyzed. Black-Right-Pointing-Pointer Oriented low-dimensional structures are occurred for the treated Al{sub 2}O{sub 3} crystal. Black-Right-Pointing-Pointer The dimension of these ripples are 1 {mu}m and the distance between them is about 10 {mu}m. Black-Right-Pointing-Pointer The ripple-shaped structures contain a higher percentage of oxygen than the surroundings. Black-Right-Pointing-Pointer Results could promote CPF as a tool for producing organized oxygen-rich structures. -- Abstract: Material such as aluminum oxide (Al{sub 2}O{sub 3}) is important in electronics industry. On the other hand, plasma is one of the most efficient and sophisticated tools for materials processing. In this work a treatment of Al{sub 2}O{sub 3} (0001) surface by quasistationary compression plasma flow (CPF) is analyzed in detail. Offline metrology was performed using dielectric measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). Oriented low-dimensional periodic structures are occurred for the plasma treated Al{sub 2}O{sub 3} single crystal. In the paper is reported that these oriented ripple-shaped structures contain a higher percentage of oxygen than the surrounding crystal surface. This could be the framework for usage of CPF as a tool in manufacturing of surfaces containing the highly organized oxygen-rich structures.

  19. Sorption/Desorption Interactions of Plutonium with Montmorillonite

    NASA Astrophysics Data System (ADS)

    Begg, J.; Zavarin, M.; Zhao, P.; Kersting, A. B.

    2012-12-01

    Plutonium (Pu) release to the environment through nuclear weapon development and the nuclear fuel cycle is an unfortunate legacy of the nuclear age. In part due to public health concerns over the risk of Pu contamination of drinking water, predicting the behavior of Pu in both surface and sub-surface water is a topic of continued interest. Typically it was assumed that Pu mobility in groundwater would be severely restricted, as laboratory adsorption studies commonly show that naturally occurring minerals can effectively remove plutonium from solution. However, evidence for the transport of Pu over significant distances at field sites highlights a relative lack of understanding of the fundamental processes controlling plutonium behavior in natural systems. At several field locations, enhanced mobility is due to Pu association with colloidal particles that serve to increase the transport of sorbed contaminants (Kersting et al., 1999; Santschi et al., 2002, Novikov et al., 2006). The ability for mineral colloids to transport Pu is in part controlled by its oxidation state and the rate of plutonium adsorption to, and desorption from, the mineral surface. Previously we have investigated the adsorption affinity of Pu for montmorillonite colloids, finding affinities to be similar over a wide range of Pu concentrations. In the present study we examine the stability of adsorbed Pu on the mineral surface. Pu(IV) at an initial concentration of 10-10 M was pre-equilibrated with montmorillonite in a background electrolyte at pH values of 4, 6 and 8. Following equilibration, aliquots of the suspensions were placed in a flow cell and Pu-free background electrolyte at the relevant pH was passed through the system. Flow rates were varied in order to investigate the kinetics of desorption and hence gain a mechanistic understanding of the desorption process. The flow cell experiments demonstrate that desorption of Pu from the montmorillonite surface cannot be modeled as a simple first order process. Furthermore, a pH dependence was observed, with less desorbed at pH 4 compared to pH 8. We suggest the pH dependence is likely controlled by reoxidation of Pu(IV) to Pu(V) and aqueous speciation. We will present models used to describe desorption behavior and discuss the implications for Pu transport. References: Kersting, A.B.; Efurd, D.W.; Finnegan, D.L.; Rokop, D.J.; Smith, D.K.; Thompson J.L. (1999) Migration of plutonium in groundwater at the Nevada Test Site, Nature, 397, 56-59. Novikov A.P.; Kalmykov, S.N.; Utsunomiya, S.; Ewing, R.C.; Horreard, F.; Merkulov, A.; Clark, S.B.; Tkachev, V.V.; Myasoedov, B.F. (2006) Colloid transport of plutonium in the far-field of the Mayak Production Association, Russia, Science, 314, 638-641. Santschi, P.H.; Roberts, K.; Guo, L. (2002) The organic nature of colloidal actinides transported in surface water environments. Environ. Sci. Technol., 36, 3711-3719. This work was funded by U. S. DOE Office of Biological & Environmental Sciences, Subsurface Biogeochemistry Research Program, and performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344. LLNL-ABS-570161

  20. Effect of Surface Treated Silicon Dioxide Nanoparticles on Some Mechanical Properties of Maxillofacial Silicone Elastomer

    PubMed Central

    Zayed, Sara M.; Alshimy, Ahmad M.; Fahmy, Amal E.

    2014-01-01

    Current materials used for maxillofacial prostheses are far from ideal and there is a need for novel improved materials which mimic as close as possible the natural behavior of facial soft tissues. This study aimed to evaluate the effect of adding different concentrations of surface treated silicon dioxide nanoparticles (SiO2) on clinically important mechanical properties of a maxillofacial silicone elastomer. 147 specimens of the silicone elastomer were prepared and divided into seven groups (n = 21). One control group was prepared without nanoparticles and six study groups with different concentrations of nanoparticles, from 0.5% to 3% by weight. Specimens were tested for tear strength (ASTM D624), tensile strength (ASTM D412), percent elongation, and shore A hardness. SEM was used to assess the dispersion of nano-SiO2 within the elastomer matrix. Data were analyzed by one-way ANOVA and Scheffe test (α = 0.05). Results revealed significant improvement in all mechanical properties tested, as the concentration of the nanoparticles increased. This was supported by the results of the SEM. Hence, it can be concluded that the incorporation of surface treated SiO2 nanoparticles at concentration of 3% enhanced the overall mechanical properties of A-2186 silicone elastomer. PMID:25574170

  1. Adhesive forces and surface properties of cold gas plasma treated UHMWPE

    PubMed Central

    Preedy, Emily Callard; Brousseau, Emmanuel; Evans, Sam L.; Perni, Stefano; Prokopovich, Polina

    2014-01-01

    Cold atmospheric plasma (CAP) treatment was used on ultra-high molecular weight polyethylene (UHMWPE), a common articulating counter material employed in hip and knee replacements. UHMWPE is a biocompatible polymer with low friction coefficient, yet does not have robust wear characteristics. CAP effectively cross-links the polymer chains of the UHMWPE improving wear performance (Perni et al., Acta Biomater. 8(3) (2012) 1357). In this work, interactions between CAP treated UHMWPE and spherical borosilicate sphere (representing model material for bone) were considered employing AFM technique. Adhesive forces increased, in the presence of PBS, after treatment with helium and helium/oxygen cold gas plasmas. Furthermore, a more hydrophilic surface of UHMWPE was observed after both treatments, determined through a reduction of up to a third in the contact angles of water. On the other hand, the asperity density also decreased by half, yet the asperity height had a three-fold decrease. This work shows that CAP treatment can be a very effective technique at enhancing the adhesion between bone and UHMWPE implant material as aided by the increased adhesion forces. Moreover, the hydrophilicity of the CAP treated UHMWPE can lead to proteins and cells adhesion to the surface of the implant stimulating osseointegration process. PMID:25431523

  2. High capacity mercury adsorption on freshly ozone-treated carbon surfaces

    PubMed Central

    Manchester, Shawn; Wang, Xuelei; Kulaots, Indrek; Gao, Yuming; Hurt, Robert H.

    2008-01-01

    A set of carbon materials was treated by a choice of common oxidizers to investigate the mercury capture capacities at varying temperature conditions. It was found that ozone treatment dramatically increases the mercury capture capacity of carbon surfaces by factors up to 134, but the activity is easily destroyed by exposure to the atmosphere, to water vapor, or by mild heating. Freshly ozone-treated carbon surfaces are shown to oxidize iodide to iodine in solution and this ability fades with aging. FTIR analysis shows broad C–O stretch features from 950 to 1300 cm−1, which decay upon atmospheric exposure and are similar to the C-O-C asymmetric stretch features of ethylene secondary ozonide. The combined results suggest that the ultra-high mercury capture efficiency is due to a subset of labile C-O functional groups with residual oxidizing power that are likely epoxides or (epoxide-containing) secondary ozonides. The results open the possibility for in situ ozonolysis to create high-performance carbon-based Hg sorbents. PMID:19255621

  3. Adsorption of human salivary mucin MG1 onto glow-discharge plasma treated acrylic resin surfaces.

    PubMed

    Yildirim, M S; Kesimer, M; Hasirci, N; Kiliç, N; Hasanreisoğlu, U

    2006-10-01

    It has been suggested that altering the surface properties of acrylic resin material may change the nature of the adsorbed pellicle affecting denture retention and microbial adherence. This study aimed at evaluating the adsorption of salivary high molecular-weight mucins, a major component of denture pellicle, onto modified acrylic resin surfaces. (Poly) methylmethacrylate specimens were treated by glow discharge plasma technique, using hydrophilic 2-Hydroxyethylmethacrylate monomer or oxygen (O(2)) gas and hydrophobic Hexamethyldisiloxane monomer, at different discharge powers. Acrylic samples were incubated with high-molecular weight mucin, MG1 purified from saliva, the adsorbed fractions were transferred to nitrocellulose membranes by slot-blot technique, stained by periodic acid-Schiff and colour intensities were analysed by a colour densitometer. Higher amounts of mucins were adsorbed on all the surfaces modified by glow-discharge plasma treatment. Within the limitations of this study, it was concluded that glow-discharge plasma altered the surfaces of acrylic resin denture base materials and significantly increased the adsorption of high molecular-weight mucins at varying levels depending on plasma parameters. PMID:16938107

  4. In vitro screening procedure for characterization of thrombogenic properties of plasma treated surfaces.

    PubMed

    Modic, Martina; Mozetič, Miran

    2016-01-01

    Estimation of thrombogenic surface properties is an important aspect of hemocompatibility studies. To improve our understanding of interaction between blood and biomaterial surfaces, there is a need to employ standardized methods that are both effective and efficient. This contribution details a systematic approach for the in vitro analysis of plasma modified polymer surfaces and human blood platelet interaction, following the recently introduced ISO 10933-4 guidelines. A holistic multistep process is presented that considers all aspects of testing procedure, including blood collection, platelet function testing, and incubation parameters, right through to a comparison and evaluation of the different methods and analysis available. In terms of detection and analysis, confocal light microscopy is shown to offer many advantages over the widely used scanning electron microscopy technique; this includes simpler, less-invasive sample preparation, and less time-consuming analysis procedure. On the other hand, as an alternative to microscopy techniques, toxicology sulforhodamine B based assay (TOX assay) was also evaluated. It has been shown that the assay could be used for rapid estimation of relative concentration of blood platelets on the surface of plasma treated materials, especially when samples do not allow the implementation of microscopy techniques. PMID:27154919

  5. Adsorption of hexavalent chromium onto montmorillonite modified with hydroxyaluminum and cetyltrimethylammonium bromide

    NASA Astrophysics Data System (ADS)

    Hu, Bingjie; Luo, Hanjin

    2010-11-01

    Aluminum hydroxypolycation and cetyltrimethylammonium bromide (CTMAB) were chosen to synthesize inorganic-organic pillared montmorillonite. Three different methods were employed for the intercalation. The characteristics of natural and modified montmorillonite were determined with X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), X-ray photoelectron spectrum (XPS), and zeta potential. It was found that aluminum hydroxypolycation and CTMAB had either entered the interlayer or sorbed on the external surface of the clay. Different intercalation orders can result in different structures. Batch adsorption of hexavalent chromium (Cr 6+) onto modified montmorillonite was also investigated. The experimental data revealed that if aluminum hydroxypolycation was intercalated before CTMAB, the adsorption capacity was better than that of intercalated simultaneously or CTMAB pre-intercalated. The pH of the solution and environmental temperature had significant influences on the adsorption of Cr 6+. The optimal pH for the removal was about 4, and the temperature of 298 K was best suitable. All adsorption processes were rapid during the first 5 min and reached equilibrium in 20 min. The adsorption kinetics can be described quite well by pseudo-second-order model. The adsorption rates of ACM, CAM and ACCOM were 3.814, 0.915, and 3.143 mg/g/min, respectively. The adsorption capacities of Cr 6+ at 298 K on ACM, CAM, and ACCOM inferred from the Langmuir model were 11.970, 6.541, and 9.090 mg/g, respectively. The adsorption of Cr 6+ on modified montmorillonite was mainly induced by the surface charge and the complexation reaction between CTMA + and hexavalent chromium species at the edge of the clay particle.

  6. High-Power Diode Laser Surface Treated HVOF Coating to Combat High Energy Particle Impact Wear

    NASA Astrophysics Data System (ADS)

    Mann, B. S.; Arya, Vivek; Pant, B. K.

    2013-07-01

    High-velocity oxy-fuel (HVOF)-sprayed coatings have performed exceptionally well in low-energy particle impact wear and are accepted worldwide. However, their application for high-energy particle impact wear (HEPIW) requires a different approach and more efforts. HVOF-coating systems typically use WC-Co, WC-Co-Cr, WC-Ni-Cr, and FeCrAlY-Cr3C2 powders. WC-Co-Cr powders are preferred when there is a high demand for corrosion resistance. WC-10Co-4Cr coating powder has been selected in the current study. To improve coating properties such as microhardness, fracture toughness, and HEPIW resistance, a new approach of surface treatment with robotically controlled high-power diode laser (HPDL) is attempted. The robotically controlled HVOF-coating deposition and laser surface treatment were monitored using real-time diagnostic control. The HPDL-treated coating has been compared with "as-sprayed" HVOF coating for HEPIW resistance, fracture toughness, microhardness and microstructure. The coating characteristics and properties after laser surface treatment have improved many times compared with "as-sprayed" HVOF coating. This is due to the elimination of pores in the coating and formation of a metallurgical bond between coating and substrate. This new development opens up a possibility of using such laser treatments in specialized areas where HEPIW damages are acute. The fracture toughness and HEPIW resistance along with optical micrographs of HPDL-treated and untreated HVOF coatings are discussed and reported in this article. HEPIW resistance is observed to be proportional to the product of fracture toughness and microhardness of the HVOF coating.

  7. Polymerization of serine guanylate in the presence of montmorillonite

    NASA Technical Reports Server (NTRS)

    Paecht-Horowitz, M.

    1981-01-01

    Serine guanylate was prepared and its polymerization studied in the presence of montmorillonite and in its absence. In water, without clay, serine guanylate polymerizes in the same way as does serine adenylate. In the presence of montmorillonite, serine guanylate polymerizes to a lesser extent and produces also lower degrees of polymerization than does serine adenylate. It is postulated that the reason for this difference in behavior might lie in the fact that guanylic acid is much more acidic than adenylic acid; hence would bind much more strongly to the edges of montmorillonite and thus, by blocking these sites, would inhibit the catalytic activity of the clay.

  8. Estimating Dermal Transfer of Copper Particles from the Surfaces of Pressure-Treated Lumber and Implications for Exposure

    EPA Science Inventory

    Lumber pressure-treated with micronized copper was examined for the release of copper and copper micro/nanoparticles using a surface wipe method to simulate dermal transfer. In 2003, the wood industry began replacing CCA treated lumber products for residential use with copper ba...

  9. Carbonate formation in Wyoming montmorillonite under high pressure carbon dioxide

    SciTech Connect

    Romanov, V; Hur, T -B; Baltrus, J; Howard, B; Harbert, W

    2013-01-16

    Carbonation reaction with silicate minerals that are common components of the host rock and cap rock within geological storage reservoirs and the associated structural deformation were investigated for better understanding of the geochemical reactions associated with geologic CO2 storage. Exposure of a model expanding clay, Wyoming montmorillonite, SWy-2, to high-pressure CO2 resulted in the formation of a mineral carbonate phase via dry CO2�clay mineral interactions at two different temperatures. The experimental evidence suggests that the properties of CO2 fluid at 70 ◦C provide more favorable conditions for carbonate formation at the clay surface less accessible to CO2 at 22 ◦C. The carbonation reaction occurred predominantly within the first couple of days of exposure to the fluid and then proceeded slower with continuing exposure. As compared to the as-received clay under the same ambient conditions, the (0 0 1) basal spacing of the clay bearing carbonates (after the CO2 exposure) was slightly expanded at a relative humidity (RH) level of 12% but it was slightly collapsed at the RH level of 40%. Experimental observations suggest that the carbonation reaction occurs at the external surface as well as internal surface (interlayer) of the clay particles.

  10. Surface treated titanium dioxide nanoparticles as inorganic UV filters in sunscreen products.

    PubMed

    Veronovski, Nika; Lenik, Maja; Lubej, Andrej; Verhovek, Dejan

    2014-01-01

    TiO(2) nanoparticles were used in this research as an inorganic UV absorber for preparation of a sunscreen that ensures optically transparent films with adequate SPF. TiO(2) nanoparticles in rutile crystal form, produced in Cinkarna Celje, were used in this research. The elementary principle of the nanograde TiO(2) production is the sulphate synthesis process, which is upgraded for the synthesis of final nano product. TiO(2) nanoparticles were subsequently surface modified by coating with sodium silicate as the source of silica. The resulting silica coated TiO(2) nanoparticles were examined by scanning (SEM) and transmission electron microscopy (TEM). Uniform particles distribution and homogeneous amorphous coatings, formed in heterogeneous nucleation of silica molecules on the surface of TiO(2) nanoparticles, were observed. Sun-protection factor (SPF) of 28 was determined for sunscreen with incorporated 9.0 wt. % TiO(2) nanoparticles, surface treated with 5.0 wt. % silica according to the "Method for the In Vitro Determination of UVA Protection Provided by Sunscreen Products". PMID:25286215

  11. Isolation of the ocular surface to treat dysfunctional tear syndrome associated with computer use.

    PubMed

    Yee, Richard W; Sperling, Harry G; Kattek, Ashballa; Paukert, Martin T; Dawson, Kevin; Garcia, Marcie; Hilsenbeck, Susan

    2007-10-01

    Dysfunctional tear syndrome (DTS) associated with computer use is characterized by mild irritation, itching, redness, and intermittent tearing after extended staring. It frequently involves foreign body or sandy sensation, blurring of vision, and fatigue, worsening especially at the end of the day. We undertook a study to determine the effectiveness of periocular isolation using microenvironment glasses (MEGS) alone and in combination with artificial tears in alleviating the symptoms and signs of dry eye related to computer use. At the same time, we evaluated the relative ability of a battery of clinical tests for dry eye to distinguish dry eyes from normal eyes in heavy computer users. Forty adult subjects who used computers 3 hours or more per day were divided into dry eye sufferers and controls based on their scores on the Ocular Surface Disease Index (OSDI). Baseline scores were recorded and ocular surface assessments were made. On four subsequent visits, the subjects played a computer game for 30 minutes in a controlled environment, during which one of four treatment conditions were applied, in random order, to each subject: 1) no treatment, 2) artificial tears, 3) MEGS, and 4) artificial tears combined with MEGS. Immediately after each session, subjects were tested on: a subjective comfort questionnaire, tear breakup time (TBUT), fluorescein staining, lissamine green staining, and conjunctival injection. In this study, a significant correlation was found between cumulative lifetime computer use and ocular surface disorder, as measured by the standardized OSDI index. The experimental and control subjects were significantly different (P<0.05) in the meibomian gland assessment and TBUT; they were consistently different in fluorescein and lissamine green staining, but with P>0.05. Isolation of the ocular surface alone produced significant improvements in comfort scores and TBUT and a consistent trend of improvement in fluorescein staining and lissamine green staining. Isolation plus tears produced a significant improvement in lissamine green staining. The subjective comfort inventory and the TBUT test were most effective in distinguishing between the treatments used. Computer users with ocular surface complaints should have a detailed ocular surface examination and, if symptomatic, they can be effectively treated with isolation of the ocular surface, artificial tears therapy, and effective environmental manipulations. PMID:17938840

  12. Optimization of electrocoagulation process to treat grey wastewater in batch mode using response surface methodology

    PubMed Central

    2014-01-01

    Background Discharge of grey wastewater into the ecological system causes the negative impact effect on receiving water bodies. Methods In this present study, electrocoagulation process (EC) was investigated to treat grey wastewater under different operating conditions such as initial pH (4–8), current density (10–30 mA/cm2), electrode distance (4–6 cm) and electrolysis time (5–25 min) by using stainless steel (SS) anode in batch mode. Four factors with five levels Box-Behnken response surface design (BBD) was employed to optimize and investigate the effect of process variables on the responses such as total solids (TS), chemical oxygen demand (COD) and fecal coliform (FC) removal. Results The process variables showed significant effect on the electrocoagulation treatment process. The results were analyzed by Pareto analysis of variance (ANOVA) and second order polynomial models were developed in order to study the electrocoagulation process statistically. The optimal operating conditions were found to be: initial pH of 7, current density of 20 mA/cm2, electrode distance of 5 cm and electrolysis time of 20 min. Conclusion These results indicated that EC process can be scale up in large scale level to treat grey wastewater with high removal efficiency of TS, COD and FC. PMID:24410752

  13. Physiochemical Changes and Optimization of Phosphate-Treated Shrimp (Litopenaeus vannamei ) Using Response Surface Methodology.

    PubMed

    Omar, Saiah Djebbour; Yang, Je-Eun; Oh, Sang-Cheol; Kim, Dae-Wook; Lee, Yang-Bong

    2016-03-01

    The objective of this study was to determine the factors responsible for the changed physiochemical properties of unpeeled shrimp treated in cold phosphate solution (2~4°C) with the intervention of 4 factors: phosphate concentration, dipping time, rotation speed, and volume of brine solution. Response surface analysis was used to characterize the effect of the phosphate treatment on shrimps by running 33 treatments for optimizing the experiment. For each treatment, phosphate amount, moisture content, and weight gain were measured. The results showed that phosphate concentration is the most important factor than other factors for facilitating phosphate penetration in the meat of the shrimp and for getting the best result. The optimum condition of phosphate-treated shrimp in this study was 110 to 120 min dipping time, 500 to 550 mL brine solution for 100 g shrimp sample, and 190 to 210 rpm agitation speed. The studied conditions can be applied in fisheries and other food industries for good phosphate treatments. PMID:27069905

  14. Physiochemical Changes and Optimization of Phosphate-Treated Shrimp (Litopenaeus vannamei ) Using Response Surface Methodology

    PubMed Central

    Omar, Saiah Djebbour; Yang, Je-Eun; Oh, Sang-Cheol; Kim, Dae-Wook; Lee, Yang-Bong

    2016-01-01

    The objective of this study was to determine the factors responsible for the changed physiochemical properties of unpeeled shrimp treated in cold phosphate solution (2~4°C) with the intervention of 4 factors: phosphate concentration, dipping time, rotation speed, and volume of brine solution. Response surface analysis was used to characterize the effect of the phosphate treatment on shrimps by running 33 treatments for optimizing the experiment. For each treatment, phosphate amount, moisture content, and weight gain were measured. The results showed that phosphate concentration is the most important factor than other factors for facilitating phosphate penetration in the meat of the shrimp and for getting the best result. The optimum condition of phosphate-treated shrimp in this study was 110 to 120 min dipping time, 500 to 550 mL brine solution for 100 g shrimp sample, and 190 to 210 rpm agitation speed. The studied conditions can be applied in fisheries and other food industries for good phosphate treatments. PMID:27069905

  15. Study of antibacterial activity of Ag and Ag2CO3 nanoparticles stabilized over montmorillonite.

    PubMed

    Sohrabnezhad, Sh; Pourahmad, A; Mehdipour Moghaddam, M J; Sadeghi, A

    2014-10-28

    Silver carbonate and silver nanoparticles (NPs) over of stabilizer montmorillonite (MMT) have been synthesized in aqueous and polyol solvent, respectively. Dispersions of silver nanoparticles have been prepared by the reduction of silver nitrate over of MMT in presence and absence of Na2CO3 compound in ethylene glycol. It was observed that montmorillonite was capable of stabilizing formed Ag nanoparticles through the reduction of Ag(+) ions in ethylene glycol. Na2CO3 was used as carbonate source in synthesis of Ag2CO3 NPs in water solvent and also for controlling of Ag nanoparticles size in ethylene glycol medium. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and ultraviolet-visible diffuse reflectance spectroscopy (DRS). The TEM images showed that Ag NPs size in presence Na2CO3 salts was smaller than without that. The results indicated intercalation of Ag and Ag2CO3 nanoparticles into the montmorillonite clay layers. The diffuse reflectance spectra exhibited a strong surface plasmon resonance (SPR) adsorption peak in the visible region, resulting from Ag nanoparticles. The antibacterial testing results showed that the Ag2CO3-MMT nanocomposite exhibited an antibacterial activity higher than Ag-MMT sample against Escherichia coli. PMID:25467663

  16. Study of antibacterial activity of Ag and Ag2CO3 nanoparticles stabilized over montmorillonite

    NASA Astrophysics Data System (ADS)

    Sohrabnezhad, Sh.; Pourahmad, A.; Mehdipour Moghaddam, M. J.; Sadeghi, A.

    2015-02-01

    Silver carbonate and silver nanoparticles (NPs) over of stabilizer montmorillonite (MMT) have been synthesized in aqueous and polyol solvent, respectively. Dispersions of silver nanoparticles have been prepared by the reduction of silver nitrate over of MMT in presence and absence of Na2CO3 compound in ethylene glycol. It was observed that montmorillonite was capable of stabilizing formed Ag nanoparticles through the reduction of Ag+ ions in ethylene glycol. Na2CO3 was used as carbonate source in synthesis of Ag2CO3 NPs in water solvent and also for controlling of Ag nanoparticles size in ethylene glycol medium. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and ultraviolet-visible diffuse reflectance spectroscopy (DRS). The TEM images showed that Ag NPs size in presence Na2CO3 salts was smaller than without that. The results indicated intercalation of Ag and Ag2CO3 nanoparticles into the montmorillonite clay layers. The diffuse reflectance spectra exhibited a strong surface plasmon resonance (SPR) adsorption peak in the visible region, resulting from Ag nanoparticles. The antibacterial testing results showed that the Ag2CO3-MMT nanocomposite exhibited an antibacterial activity higher than Ag-MMT sample against Escherichia coli.

  17. Treatment of an automobile effluent from heavy metals contamination by an eco-friendly montmorillonite

    PubMed Central

    Akpomie, Kovo G.; Dawodu, Folasegun A.

    2014-01-01

    Unmodified montmorillonite clay was utilized as a low cost adsorbent for the removal of heavy metals from a contaminated automobile effluent. Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy were used to characterize the adsorbent. Batch sorption experiments were performed at an optimum effluent pH of 6.5, adsorbent dose of 0.1 g, particle size of 100 μm and equilibrium contact time of 180 min. Thermodynamic analysis was also conducted. Equilibrium data were analyzed by the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models. A heterogeneous surface of the adsorbent was indicated by the Freundlich model. The Langmuir maximum adsorption capacity of the montmorillonite for metals was found in the following order: Zn (5.7 mg/g) > Cu (1.58 mg/g) > Mn (0.59 mg/g) > Cd (0.33 mg/g) > Pb (0.10 mg/g) ≡ Ni (0.10 mg/g). This was directly related to the concentration of the metal ions in solution. The pseudo-first order, pseudo-second order, intraparticle diffusion and liquid film diffusion models were applied for kinetic analysis. The mechanism of sorption was found to be dominated by the film diffusion mechanism. The results of this study revealed the potential of the montmorillonite for treatment of heavy metal contaminated effluents. PMID:26644939

  18. Molecular dynamics simulation of diffusion and electrical conductivity in montmorillonite interlayers

    DOE PAGESBeta

    Greathouse, Jeffery A.; Cygan, Randall T.; Fredrich, Joanne T.; Jerauld, Gary R.

    2016-02-01

    In this study, the diffusion of water and ions in the interlayer region of smectite clay minerals represents a direct probe of the type and strength of clay–fluid interactions. Interlayer diffusion also represents an important link between molecular simulation and macroscopic experiments. Here we use molecular dynamics simulation to investigate trends in cation and water diffusion in montmorillonite interlayers, looking specifically at the effects of layer charge, interlayer cation and cation charge (sodium or calcium), water content, and temperature. For Na-montmorillonite, the largest increase in ion and water diffusion coefficients occurs between the one-layer and two-layer hydrates, corresponding to themore » transition from inner-sphere to outer-sphere surface complexes. Calculated activation energies for ion and water diffusion in Na-montmorillonite are similar to each other and to the water hydrogen bond energy, suggesting the breaking of water–water and water–clay hydrogen bonds as a likely mechanism for interlayer diffusion. A comparison of interlayer diffusion with that of bulk electrolyte solutions reveals a clear trend of decreasing diffusion coefficient with increasing electrolyte concentration, and in most cases the interlayer diffusion results are nearly coincident with the corresponding bulk solutions. Trends in electrical conductivities computed from the ion diffusion coefficients are also compared.« less

  19. Fe(II) uptake on natural montmorillonites. I. Macroscopic and spectroscopic characterization.

    PubMed

    Soltermann, Daniela; Marques Fernandes, Maria; Baeyens, Bart; Dähn, Rainer; Joshi, Prachi A; Scheinost, Andreas C; Gorski, Christopher A

    2014-01-01

    Iron is an important redox-active element that is ubiquitous in both engineered and natural environments. In this study, the retention mechanism of Fe(II) on clay minerals was investigated using macroscopic sorption experiments combined with Mössbauer and extended X-ray absorption fine structure (EXAFS) spectroscopy. Sorption edges and isotherms were measured under anoxic conditions on natural Fe-bearing montmorillonites (STx, SWy, and SWa) having different structural Fe contents ranging from 0.5 to 15.4 wt % and different initial Fe redox states. Batch experiments indicated that, in the case of low Fe-bearing (STx) and dithionite-reduced clays, the Fe(II) uptake follows the sorption behavior of other divalent transition metals, whereas Fe(II) sorption increased by up to 2 orders of magnitude on the unreduced, Fe(III)-rich montmorillonites (SWy and SWa). Mössbauer spectroscopy analysis revealed that nearly all the sorbed Fe(II) was oxidized to surface-bound Fe(III) and secondary Fe(III) precipitates were formed on the Fe(III)-rich montmorillonite, while sorbed Fe is predominantly present as Fe(II) on Fe-low and dithionite-reduced clays. The results provide compelling evidence that Fe(II) uptake characteristics on clay minerals are strongly correlated to the redox properties of the structural Fe(III). The improved understanding of the interfacial redox interactions between sorbed Fe(II) and clay minerals gained in this study is essential for future studies developing Fe(II) sorption models on natural montmorillonites. PMID:24930689

  20. Cuprous Ion Conducting Montmorillonite- Polypyrrole Nanocomposites

    NASA Astrophysics Data System (ADS)

    Krishantha, D. M. M.; Rajapakse, R. M. G.; Tennakoon, D. T. B.; Bandara, W. M. A. T.; Thilakarathna, P. N. L.

    2006-06-01

    Solid state polymer-Silicate nanocomposite based on Polypyrrole-Cu+-montmorilonite were prepared and electrical properties were investigated. In this preparation, Na-montmorillonite (Na+-MMT) was purified by repeated washing with distilled water and the intergallery cations were exchanged for Cu(II). The cupric ions exchanged-MMT(Cu(II)-- MMT) was again exposed to pyrrole in aqueous acidic solution to yield polypyrrole-Cu+-MMT nanocomposite. DC polarization test and AC impedance measurement reveal that the materials are mixed conductors. The ionic conductivity is due to the motion of cuprous ions which is facilitated by microstructure of polypyrrrole present in the intergalleries. An electrochemical cell was fabricated using the materials which can be represented by Cu(s)/ Cu+-PPY-MMT/Cu2SO4 (s)/Na2SO4(S)-Na2S2O8(s)/ and gave a 1.00 V. The cell is rechargeable.

  1. Montmorillonite-induced Bacteriophage φ6 Disassembly

    NASA Astrophysics Data System (ADS)

    Trusiak, A.; Gottlieb, P.; Katz, A.; Alimova, A.; Steiner, J. C.; Block, K. A.

    2012-12-01

    It is estimated that there are 1031 virus particles on Earth making viruses an order of magnitude more prevalent in number than prokaryotes with the vast majority of viruses being bacteriophages. Clays are a major component of soils and aquatic sediments and can react with RNA, proteins and bacterial biofilms. The clays in soils serve as an important moderator between phage and their host bacteria, helping to preserve the evolutionary balance. Studies on the effects of clays on viral infectivity have given somewhat contradictory results; possibly a consequence of clay-virus interactions being dependent on the unique structure of particular viruses. In this work, the interaction between montmorillonite and the bacteriophage φ6 is investigated. φ6 is a member of the cystovirus family that infects Pseudomonas syringe, a common plant pathogen. As a member of the cystovirus family with an enveloped structure, φ6 serves as a model for reoviruses, a human pathogen. Experiments were conducted with φ6 suspended in dilute, purified homoionic commercial-grade montmorillonite over a range of virus:clay ratios. At a 1:100000 virus:clay ratio, the clay reduced viral infectivity by 99%. The minimum clay to virus ratio which results in a measurable reduction of P. syringae infection is 1:1. Electron microscopy demonstrates that mixed suspensions of smectite and virus co-aggregate to form flocs encompassing virions within the smectite. Both free viral particles as well as those imbedded in the flocs are seen in the micrographs to be missing the envelope- leaving only the nucleocapsid (NC) intact; indicating that smectite inactivates the virus by envelope disassembly. These results have strong implications in the evolution of both the φ6 virus and its P. syringae host cells. TEM of aggregate showing several disassembled NCs.

  2. Dissolution of alkaline earth sulfates in the presence of montmorillonite

    USGS Publications Warehouse

    Eberl, D.D.; Landa, E.R.

    1985-01-01

    In a study of the effect of montmorillonite on the dissolution of BaSO4 (barite), SrSO4 (celestite), and 226Ra from U mill tailings, it was found that: (1) More of these substances dissolve in an aqueous system that contains montmorillonite than dissolve in a similar system without clay, due to the ion exchange properties of the clay; (2) Na-montmorillonite is more effective in aiding dissolution than is Ca-montmorillonite; (3) the amount of Ra that moves from mill tailings to an exchanger increases as solution sulfate activity decreases. Leaching experiments suggest that 226Ra from H2SO4-circuit U mill tailings from Edgemont, South Dakota, is not present as pure Ra sulfate or as an impurity in anhydrite or gypsum; it is less soluble, and probably occurs as a trace constituent in barite.

  3. Biocompatibility evaluation of surface-treated AISI 316L austenitic stainless steel in human cell cultures.

    PubMed

    Martinesi, M; Bruni, S; Stio, M; Treves, C; Bacci, T; Borgioli, F

    2007-01-01

    The effects of AISI 316L austenitic stainless steel, tested in untreated state or subjected to glow-discharge nitriding (at 10 or 20 hPa) and nitriding + post-oxidizing treatments, on human umbilical vein endothelial cells (HUVEC) and on peripheral blood mononuclear cells (PBMC) were evaluated. All the treated samples showed a better corrosion resistance in PBS and higher surface hardness in comparison with the untreated alloy. In HUVEC put in contact for 72 h with the sample types, proliferation and apoptosis decreased and increased, respectively, in the presence of the nitrided + post-oxidized samples, while only slight differences in cytokine (TNF-alpha, IL-6, and TGF-beta1) release were registered. Intercellular adhesion molecule-1 (ICAM-1) increased in HUVEC incubated with all the treated samples, while vascular cell adhesion molecule-1 (VCAM-1) and E-selectin increased in the presence of all the sample types. PBMC incubated for 48 h with the samples showed a decrease in proliferation and an increase in apoptosis in the presence of the untreated samples and the nitrided + post-oxidized ones. All the sample types induced a remarkable increase in TNF-alpha and IL-6 release in PBMC culture medium, while only the untreated sample and the nitrided at 10 hPa induced an increase in ICAM-1 expression. In HUVEC cocultured with PBMC, previously put in contact with the treated AISI 316L samples, increased levels of ICAM-1 were detected. In HUVEC coincubated with the culture medium of PBMC, previously put in contact with the samples under study, a noteworthy increase in ICAM-1, VCAM-1, and E-selectin levels was always registered, with the exception of VCAM-1, which was not affected by the untreated sample. In conclusion, even if the treated samples do not show a marked increase in biocompatibility in comparison with the untreated alloy, their higher corrosion resistance may suggest a better performance as the contact with physiological environment becomes longer. PMID:16983653

  4. Disassembly of the cystovirus ϕ6 envelope by montmorillonite clay.

    PubMed

    Block, Karin A; Trusiak, Adrianna; Katz, Al; Gottlieb, Paul; Alimova, Alexandra; Wei, Hui; Morales, Jorge; Rice, William J; Steiner, Jeffrey C

    2014-02-01

    Prior studies of clay-virus interactions have focused on the stability and infectivity of nonenveloped viruses, yielding contradictory results. We hypothesize that the surface charge distribution of the clay and virus envelope dictates how the components react and affect aggregation, viral stability, and infectivity. The bacteriophage Cystoviridae species φ6 used in this study is a good model for enveloped pathogens. The interaction between φ6 and montmorillonite (MMT) clay (the primary component of bentonite) is explored by transmission electron microscopy. The analyses show that MMT-φ6 mixtures undergo heteroaggregation, forming structures in which virtually all the virions are either sequestered between MMT platelet layers or attached to platelet edges. The virions swell and undergo disassembly resulting in partial or total envelope loss. Edge-attached viral envelopes distort to increase contact area with the positively charged platelet edges indicating that the virion surface is negatively charged. The nucleocapsid (NCs) remaining after envelope removal also exhibit distortion, in contrast to detergent-produced NCs which exhibit no distortion. This visually discernible disassembly is a mechanism for loss of infectivity previously unreported by studies of nonenveloped viruses. The MMT-mediated sequestration and disassembly result in reduced infectivity, suggesting that clays may reduce infectivity of enveloped pathogenic viruses in soils and sediments. PMID:24357622

  5. Disassembly of the cystovirus ϕ6 envelope by montmorillonite clay

    PubMed Central

    Block, Karin A; Trusiak, Adrianna; Katz, Al; Gottlieb, Paul; Alimova, Alexandra; Wei, Hui; Morales, Jorge; Rice, William J; Steiner, Jeffrey C

    2014-01-01

    Prior studies of clay–virus interactions have focused on the stability and infectivity of nonenveloped viruses, yielding contradictory results. We hypothesize that the surface charge distribution of the clay and virus envelope dictates how the components react and affect aggregation, viral stability, and infectivity. The bacteriophage Cystoviridae species φ6 used in this study is a good model for enveloped pathogens. The interaction between φ6 and montmorillonite (MMT) clay (the primary component of bentonite) is explored by transmission electron microscopy. The analyses show that MMT–φ6 mixtures undergo heteroaggregation, forming structures in which virtually all the virions are either sequestered between MMT platelet layers or attached to platelet edges. The virions swell and undergo disassembly resulting in partial or total envelope loss. Edge-attached viral envelopes distort to increase contact area with the positively charged platelet edges indicating that the virion surface is negatively charged. The nucleocapsid (NCs) remaining after envelope removal also exhibit distortion, in contrast to detergent-produced NCs which exhibit no distortion. This visually discernible disassembly is a mechanism for loss of infectivity previously unreported by studies of nonenveloped viruses. The MMT-mediated sequestration and disassembly result in reduced infectivity, suggesting that clays may reduce infectivity of enveloped pathogenic viruses in soils and sediments. PMID:24357622

  6. Montmorillonite-levan nanocomposites with improved thermal and mechanical properties.

    PubMed

    Chen, Xiaoming; Gao, Hongsheng; Ploehn, Harry J

    2014-01-30

    This work reports on the structure and properties of novel nanocomposites composed of exfoliated montmorillonite clay blended with levan, a polysaccharide produced by Bacillus sp. Dry levan is very brittle, making it difficult to obtain stand-alone films. MMT-levan composites were prepared by solution blending in water, coating on plastic surfaces, partial drying at 50°C, and conditioning in air at 50-60% relative humidity. This process results in freestanding, transparent, and flexible films of pure levan and MMT-levan composites plasticized by 10-15 wt% water. XRD patterns from levan-MMT composites indicate an MMT interlayer spacing 0.62 nm greater than that of the starting MMT, suggesting re-stacking of MMT platelets coated by adsorbed, uncoiled levan molecules. FTIR results suggest that levan adheres to MMT via water-mediated hydrogen bonding between the levan's hydroxyl groups and MMT surface oxygens. MMT-levan composites have improved thermal stability and a well-defined glass transition temperature that increases with MMT loading. The tensile moduli of levan-MMT composites increase by as much as 480% relative to pure levan. The XRD and mechanical property results suggest that MMT reinforces levan through a filler network structure composed of MMT platelets bridged by adsorbed levan molecules, enhanced when the MMT loading becomes high enough (5-10wt% MMT) to induce an isotropic-nematic transition in MMT platelet orientation. PMID:24299812

  7. Characterization of Na+-montmorillonite-catalyzed reaction of racemic ribonucleotides.

    PubMed

    Urata, Hidehito; Fujimori, Mami; Aono, Chie; Hrada, Emi; Matsumoto, Tomoko; Yamakawa, Tomomi; Akagi, Masao

    2005-01-01

    We have reported that the oligomerization of racemic mononucleotides catalyzed by montmorillonite clay proceeds efficiently and gives up to 8-mer. Here, we attempted to identify the dimer products to show the characteristics of the racemic reaction. The results suggested that homochiral pApAs are formed in somewhat higher yield than heterochiral pApAs. Therefore, the oligomerization of racemic mononucleotides catalyzed by montmorillonite shows the homochiral selectivity. PMID:17150660

  8. Corrosion properties of excimer laser surface treated Al-SiC metal matrix composite

    SciTech Connect

    Zhang, X.M.; Man, H.C.; Yue, T.M.

    1996-11-01

    Indeed, the ultimate goal is to engineer and design metal matrix composites (MMCs) to have good inherent corrosion resistance, however, no significant breakthroughs have been achieved for MMCs that are prone to corrosion. Though, a significant amount of efforts have been spent to understand the corrosion behavior of MMC materials, only few studies were devoted to explore protection methods for improving corrosion resistance of MMCs. Among these, much effort was dedicated to some anodizing and chemical conversion techniques which in many respects have raised environmental concerns. Except a few, little work was found in applying the unique properties of lasers for surface modification of MMC materials with the aim to improve corrosion properties. Among these few, CO{sub 2} lasers were generally used and the unique properties of excimer lasers have not been explored. In fact, intensive research activities on surface treatment of metallic materials and ceramics using excimer laser radiation were only started a few years ago. Since, excimer lasers emit radiation in the ultraviolet (UV) range with an extremely short pulse duration in the range of nanoseconds. Under such a condition, amorphous structures are likely to form, and which by virtue of having no grain boundaries and have the likelihood of avoiding any segregation and interfacial precipitates could have a significant effect on the corrosion resistance of excimer laser treated materials.

  9. Atomic and electronic structures of heat treated 6H SiC surface

    NASA Astrophysics Data System (ADS)

    Jikimoto, T.; Wang, J. L.; Saito, T.; Hirai, M.; Kusaka, M.; Iwami, M.; Nakata, T.

    1998-06-01

    We have studied heat-treated (950-1300°C) 6H-SiC(0001)Si and (0001¯)C face with photoemission spectroscopy using synchrotron radiation (SR-PES) and low energy electron diffraction (LEED). We observed LEED patterns of SiC 1×1, 3× 3, 3× 3+6 3×6 3 and graphite 1×1 sequentially with increasing heating temperature for (0001)Si face and SiC 1×1 for (0001¯)C face, respectively. We have measured Si(2p) spectra and valence band energy distribution curves (VB-EDCs). The trend of sublimation of Si atoms from surface is different between Si- and C-face. 3× 3 superstructure must be Si-derived. The 6 3×6 3 structure could be explained as a moiré pattern caused by monolayer-graphite sitting on SiC surface. Si 3s-derived state of SiC 1×1 is different between SiC 1×1 for Si- and C-face. It is suggested that a single crystal graphite layer grows on Si-face and a polycrystalline graphite is formed on C-face for heated specimens above 1150°C.

  10. The Performance of Ce Surface Treated Ferritic Stainless Steels for Solid Oxide Fuel Cell Interconnects

    SciTech Connect

    Alman, D.E.; Jablonski, P.D.

    2007-09-01

    This research deals with the effect of a Ce surface treatment on the behavior of Fe-Cr-Mn ferritic stainless steels which may have application in SOFC technology. This treatment consisted of applying a slurry of CeO2 and a halide activator to the surface of coupons. After the slurry dried the coupons were heated to 900C in a controlled atmosphere furnace for 12 hours. The effectiveness of the treatment on commercial (Type 409 (12Cr), Type 430 (18Cr), Crofer 22APU (22Cr), Type 446(26Cr)) and experimental (NETL F9 (12Cr) and NETL F5 (22Cr)) alloys as a function of Cr content will be presented. The oxidation behavior of the alloys was assessed by exposing coupons (untreated and treated) to moist air at 800C. Area specific resistance (ASR) was measured at 800C. In general, the rare earth treatment effectively reduced the oxidation rate, resulting in thinner oxide scales and less internal oxidation.

  11. Influence of montmorillonite on antimicrobial activity of tetracycline and ciprofloxacin

    NASA Astrophysics Data System (ADS)

    Lv, Guocheng; Pearce, Cody W.; Gleason, Andrea; Liao, Libing; MacWilliams, Maria P.; Li, Zhaohui

    2013-11-01

    Antibiotics are used not only to fight infections and inhibit bacterial growth, but also as growth promotants in farm livestock. Farm runoff and other farm-linked waste have led to increased antibiotic levels present in the environment, the impact of which is not completely understood. Soil, more specifically clays, that the antibiotic contacts may alter its effectiveness against bacteria. In this study a swelling clay mineral montmorillonite was preloaded with antibiotics tetracycline and ciprofloxacin at varying concentrations and bioassays were conducted to examine whether the antibiotics still inhibited bacterial growth in the presence of montmorillonite. Escherichia coli was incubated with montmorillonite or antibiotic-adsorbed montmorillonite, and then the number of viable bacteria per mL was determined. The antimicrobial activity of tetracycline was affected in the presence of montmorillonite, as the growth of non-resistant bacteria was still found even when extremely high TC doses were used. Conversely, in the presence of montmorillonite, ciprofloxacin did inhibit E. coli bacterial growth at high concentrations. These results suggest that the effectiveness of antimicrobial agents in clayey soils depends on the amount of antibiotic substance present, and on the interactions between the antibiotic and the clays in the soil, as well.

  12. The lower cation exchange capacity limit of montmorillonite

    SciTech Connect

    Meier, L.P.; Nuesch, R.

    1999-09-01

    Wyoming montmorillonite (Volclay) with different charges were produced by Li-incorporation and the interlayer cations were replaced by tetramethyl ammonium. Their XRD pattern showed a regular sequence of expanded and collapsed interlayers. The regularly interstratified structure corresponds to a regularity of Reichweite R = 1. The expanded part of the interlayers was calculated by comparing XRD pattern with simulations using NEWMOD software. The calculations of the cation exchange capacity CEC for the expanded interlayer part gives a constant value of 65 {+-} 2 mmol/100 g fully swellable montmorillonite. This value is denoted as the lower CEC limit of montmorillonite. The authors propose a model which considers montmorillonite to be a stacked two-dimensional polyelectrolyte. The model proposes that interlayers of the stack collapse spontaneously by cation shifting into the neighboring interlayers, if the charge density of a montmorillonite has a value below the lower CEC value. The shifted cations of the collapsed interlayer increase the charge density in the neighboring interlayers and prevent their collapse. A regularly interstratified structure arises with the sequence expanded/collapsed/expanded interlayer, which can be observed by XRD. The behavior of low charged montmorillonite is explained with the properties of a two-dimensional polyelectrolyte. Below the critical layer charge, the Van der Waals forces dominate over electrostatic repulsive forces and the interlayers collapse.

  13. Wastewater effects on montmorillonite suspensions and hydraulic properties of sandy soils

    SciTech Connect

    Tarchitzky, J.; Golobati, Y.; Keren, R.; Chen, Y.

    1999-06-01

    Recycled wastewater effluent is an important source of irrigation water in arid and semiarid regions. In these regions, however, irrigation water quality is one of the main factors limiting plant growth. Wastewater effluents generally contain high concentrations of suspended and dissolved solids, both organic and inorganic. Inorganic dissolved solids are only minimally removed from the effluent during conventional sewage treatment. As a result, most of the salts added during domestic and industrial usage remain in the irrigation water and may eventually reach the soil. A number of researchers have reported reduced hydraulic conductivity for soils to which treated wastewater has been applied. In this research, the influence of dissolved organic matter (DOM) contained in reclaimed wastewater effluents on the flocculation of montmorillonite and on the hydraulic properties of soils was studied. Flocculation values (FVs) for Na-montmorillonite increased with increasing concentrations of DOM at all pH levels analyzed. Maximum FV levels were exhibited for Na-montmorillonite at the highest DOM concentrations. The effect of DOM on FV can be explained by the mechanisms of edge-charge reversal and mutual flocculation. The hydraulic conductivity (HC) of a sandy soil was determined in the laboratory by leaching columns with an electrolyte solution chemically similar to that of the wastewater effluent (but without DOM). In columns treated with wastewater effluent, the HC exhibited a sharp decrease to only 20% of its initial value. The adverse effect of DOM on HC was evident for this soil despite a relatively low exchangeable sodium percentage (ESP). The reduction in HC is likely to be the result of decreases soil pore-size, which reflects two processes: (1) retention of part of the DOM during water percolation; and (2) a change in pore-size distribution due to swelling and dispersion of clay particles. The latter may result from a higher percentage of adsorbed sodium combined with the presence of humic substances from the wastewater effluent.

  14. Adsorption of HCN onto sodium montmorillonite dependent on the pH as a component to chemical evolution

    NASA Astrophysics Data System (ADS)

    Colin-Garcia, M.; Heredia, A.; Negron-Mendoza, A.; Ortega, F.; Pi, T.; Ramos-Bernal, S.

    2014-10-01

    The aim of this work is to study the behaviour of hydrogen cyanide (HCN) adsorbed onto mineral surfaces (sodium montmorillonite, a clay mineral) in different pH environments as a possible prebiotic process for complexation of organics. Our experimental results show that specific sites on the surface of the clay increased the concentration of HCN molecules dependent on the pH values. Moreover, this adsorption can occur through physical and chemical interactions enhanced by the channel structure of the sodium montmorillonite. The three-dimensional channelling structure of the clay accumulates the organics, hindering the releasing (desorption) of the organic molecules. A molecular model developed here also confirms the role of the pH as a regulating factor in the adsorption of HCN onto the inorganic surfaces and the possibility for further reactions forming more complex molecules, as an abiotic mechanism important in prebiotic chemical evolution processes.

  15. Preparation of ZrO2/Al2O3-montmorillonite composite as catalyst for phenol hydroxylation

    PubMed Central

    Fatimah, Is

    2013-01-01

    Zirconium dispersed in aluminum-pillared montmorillonite was prepared as a catalyst for phenol hydroxylation. The effects of varying the Zr content on the catalyst’s physicochemical character and activity were studied with XRD, BET surface area analysis, surface acidity measurements and scanning electron microscopy before investigating the performance for phenol conversion. The zirconia dispersion significantly affects the specific surface area, the total surface acidity and surface acidity distribution related to the formation of porous zirconia particles on the surface. The prepared samples exhibited excellent catalytic activity during phenol hydroxylation. PMID:25685535

  16. Nanoscale protein arrays of rich morphologies via self-assembly on chemically treated diblock copolymer surfaces

    NASA Astrophysics Data System (ADS)

    Song, Sheng; Milchak, Marissa; Zhou, Hebing; Lee, Thomas; Hanscom, Mark; Hahm, Jong-in

    2013-03-01

    Well-controlled assembly of proteins on supramolecular templates of block copolymers can be extremely useful for high-throughput biodetection. We report the adsorption and assembly characteristics of a model antibody protein to various polystyrene-block-poly(4-vinylpyridine) templates whose distinctive nanoscale structures are obtained through time-regulated exposure to chloroform vapor. The strong adsorption preference of the protein to the polystyrene segment in the diblock copolymer templates leads to an easily predictable, controllable, rich set of nanoscale protein morphologies through self-assembly. We also demonstrate that the chemical identities of various subareas within individual nanostructures can be readily elucidated by investigating the corresponding protein adsorption behavior on each chemically distinct area of the template. In our approach, a rich set of intricate nanoscale morphologies of protein arrays that cannot be easily attained through other means can be generated straightforwardly via self-assembly of proteins on chemically treated diblock copolymer surfaces, without the use of clean-room-based fabrication tools. Our approach provides much-needed flexibility and versatility for the use of block copolymer-based protein arrays in biodetection. The ease of fabrication in producing well-defined and self-assembled templates can contribute to a high degree of versatility and simplicity in acquiring an intricate nanoscale geometry and spatial distribution of proteins in arrays. These advantages can be extremely beneficial both for fundamental research and biomedical detection, especially in the areas of solid-state-based, high-throughput protein sensing.

  17. Surface chemical changes of atmospheric pressure plasma treated rabbit fibres important for felting process

    NASA Astrophysics Data System (ADS)

    Štěpánová, Vlasta; Slavíček, Pavel; Stupavská, Monika; Jurmanová, Jana; Černák, Mirko

    2015-11-01

    We introduce the atmospheric pressure plasma treatment as a suitable procedure for in-line industrial application of rabbit fibres pre-treatment. Changes of rabbit fibre properties due to the plasma treatment were studied in order to develop new technology of plasma-based treatment before felting. Diffuse Coplanar Surface Barrier Discharge (DCSBD) in ambient air at atmospheric pressure was used for plasma treatment. Scanning electron microscopy was used for determination of the fibres morphology before and after plasma treatment. X-ray photoelectron spectroscopy and attenuated total reflectance-Fourier transform infrared spectroscopy were used for evaluation of reactive groups. The concentration of carbon decreased and conversely the concentration of nitrogen and oxygen increased after plasma treatment. Aging effect of plasma treated fibres was also investigated. Using Washburn method the significant increase of fibres wettability was observed after plasma treatment. New approach of pre-treatment of fibres before felting using plasma was developed. Plasma treatment of fibres at atmospheric pressure can replace the chemical method which consists of application of strong acids on fibres.

  18. Phosphorus removal in a surface-flow constructed wetland treating agricultural runoff.

    PubMed

    Beutel, Marc W; Morgan, Matthew R; Erlenmeyer, Jonathan J; Brouillard, Elaine S

    2014-05-01

    Agricultural runoff is a leading source of phosphorus (P) pollution to lakes and streams. The objective of this study was to evaluate P removal dynamics in a constructed treatment wetland (CTW) treating agricultural irrigation return flows. The CTW included a sedimentation basin (SB) followed by two surface-flow wetlands in parallel. Typical retention times and total P (TP) loading were 1.4 d and 50 to 110 g m yr P, respectively, for the SB and 5 to 6 d and 4 to 10 g m yr P, respectively, for wetlands. On the basis of this multiyear study, concentration removal efficiency in the SB averaged 21% for TP and 32% for reactive phosphorus (RP). Concentration removal efficiency in wetlands averaged 37 and 43% for TP and 22 and 33% for RP. Areal first-order removal rates for TP averaged 22 and 31 m yr in wetlands. Total P removal in wetlands exhibited a strong seasonal pattern, with minimum removal in the summer when high temperatures likely enhanced P release from decaying plant biomass. The performance of the CTW was stochastic, with removal unpredictably poorer in some years in part as a result of muskrat bioturbation and plant harvesting. In years before muskrat impacts, concentration removal efficiencies in wetlands were 50% for TP and 65% for RP. PMID:25602836

  19. Properties of thermo-chemically surface treated carbon fibers and of their epoxy and vinyl ester composites

    SciTech Connect

    Vautard, Frederic; Ozcan, Soydan; Meyer III, Harry M

    2012-01-01

    High strength carbon fibers were surface treated by a continuous gas phase thermo-chemical surface treatment. The surface and the mechanical properties of the fibers were investigated before and after treatment and compared to the properties obtained with a conventional industrial electro-chemical surface treatment. An increase of the oxygen atomic content from 3 % to 20 % with a preferential generation of carboxylic acid functionalities and hydroxyl groups was highlighted after the thermo-chemical surface treatment, compared to an oxygen atomic content of 7 % and a wide variety of oxygen moieties with the electro-chemical surface treatment. The tensile strength of the fibers increased slightly after the thermo-chemical surface treatment and remained the same after the electro-chemical surface treatment. Short beam shear and 90 flexural tests of composites revealed that the improvement of interfacial adhesion with a vinyl ester matrix was limited, revealing that oxidation of the carbon fiber surface alone cannot tremendously improve the mechanical properties of carbon fiber-vinyl ester composites. Atomic force microscopy showed that the creation of roughness with both surface treatments at a nanometric scale. Although the surface is slightly rougher after the electro-chemical surface treatment and is expected to lead to higher adhesion due to mechanical interlocking between the fiber surface and the matrix, the effect of covalent bonding coming from the high concentration of chemical groups on the surface results in higher adhesion strength, as obtained with the thermo-chemical surface treatment.

  20. Effects of exchanged cation on the microporosity of montmorillonite

    USGS Publications Warehouse

    Rutherford, D.W.; Chiou, C.T.; Eberl, D.D.

    1997-01-01

    The micropore volumes of 2 montmorillonites (SAz- 1 and SWy-1), each exchanged with Ca, Na, K, Cs and tetramethylammonium (TMA) ions, were calculated from the measured vapor adsorption data of N2 and neo-hexane by use of t- and ??s-plots. The corresponding surface areas of the exchanged clays were determined from Brunauer-Emmett-Teller (BET) plots of N2 adsorption data. Micropore volumes and surface areas of the samples increased with the size of exchanged cation: TMA > Cs > K> Ca > Na. The SAz-1 exchanged clays showed generally greater micropore volumes and surface areas than the corresponding SWy-1 clays. The vapor adsorption data and d(001) measurements for dry clay samples were used together to evaluate the likely locations and accessibility of clay micropores, especially the relative accessibility of their interlayer spacing. For both source clays exchanged with Na, Ca and K ions, the interlayer spacing appeared to be too small to admit nonpolar gases and the accessible micropores appeared to have dimensions greater than 5.0 A??, the limiting molecular dimension of neo -hexane. In these systems, there was a good consistency of micropore volumes detected by N2 and neo-hexane. When the clays were intercalated with relatively large cations (TMA and possibly Cs), the large layer expansion created additional microporosity, which was more readily accessible to small N2 than to relatively large neo-hexane. Hence, the micropore volume as detected by N2 was greater than that detected by neo-hexane. The micropore volumes with pore dimensions greater than 5 A?? determined for clays exchanged with Na, Ca and K likely resulted from the pores on particle edges and void created by overlap regions of layers. The increase in micropore volumes with pore dimensions less than 5 A?? determined for clays exchanged with TMA and possibly Cs could be caused by opening of the interlayer region by the intercalation of these large cations.

  1. The origin of the pozzolanic activity of calcined clay minerals: A comparison between kaolinite, illite and montmorillonite

    SciTech Connect

    Fernandez, Rodrigo; Martirena, Fernando; Scrivener, Karen L.

    2011-01-15

    This paper investigates the decomposition of three clayey structures (kaolinite, illite and montmorillonite) when thermally treated at 600 {sup o}C and 800 {sup o}C and the effect of this treatment on their pozzolanic activity in cementitious materials. Raw and calcined clay minerals were characterized by the XRF, XRD, {sup 27}Al NMR, DTG and BET techniques. Cement pastes and mortars were produced with a 30% substitution by calcined clay minerals. The pozzolanic activity and the degree of hydration of the clinker component were monitored on pastes using DTG and BSE-IA, respectively. Compressive strength and sorptivity properties were assessed on standard mortars. It was shown that kaolinite, due to the amount and location of OH groups in its structure, has a different decomposition process than illite or montmorillonite, which results in an important loss of crystallinity. This explains its enhanced pozzolanic activity compared to other calcined clay-cement blends.

  2. Microscopic structure and properties of discrete water layer in Na-exchanged montmorillonite.

    PubMed

    Emmerich, Katja; Koeniger, Franz; Kaden, Heike; Thissen, Peter

    2015-06-15

    In this work, we focus on the atomic structure of the water interlayer of Na-exchanged montmorillonite. For two different surface charge densities, namely -0.086 and -0.172 C/m(2), the adsorption process in the presence of water is described by first principles calculations. We describe the interactions and forces for every water molecule entering the interlayer during the swelling process. In particular, the dielectric permittivity of the water interlayer is calculated. Finally, we confirm our results performing ab initio thermodynamics calculations leading to a wide range of realistic experimental scenarios. PMID:25710385

  3. Five year water and nitrogen balance for a constructed surface flow wetland treating agricultural drainage waters.

    PubMed

    Borin, Maurizio; Tocchetto, Davide

    2007-07-15

    The performance of a constructed surface flow wetland in reducing diffuse N pollution coming from croplands is being investigated in an ongoing experiment, begun in 1998 in NE Italy. The 0.32 ha wetland is vegetated with Phragmites australis (Cav.) Trin. and Typha latifolia (L.). It receives drainage water from 6 ha of land managed for an experiment on drainage systems, where maize, sugarbeet, winter wheat and soybean are cultivated. During the period 1998-2002, the wetland received from 4698 to 8412 mm of water per year (on average, about 9 times the environmental rainfall); its water regimen was discontinuous and flooding occurred on a variable number of days per year (from 13 to 126). Nitric nitrogen was the most important form of element load. Its concentration in the inflow water over time was rather discontinuous, with median values ranging from 0.2 (in 2001) to 4.5 (in 2000) mg L(-1). Inflow nitric N concentrations were occasionally in the 5-15 mg L(-1) range. Concentrations reduced passing through the wetland, with a more evident effect in the last year. Over 5 years, the wetland received slightly more than 2000 kg ha(-1) of nitrogen, 87% in nitric form mostly from farmland drainage. The remaining 13% of N was applied as organic slurry directly onto the wetland, with 5 distributions during 1998 to assess wetland performance in treating occasional organic loads. Field drainage loads had a discontinuous time pattern and occurred mostly during autumn-winter, with the exception of the 2001-2002 season which was a very dry. The wetland discharged 206 kg ha(-1) of N, over the 5-year period, with an apparent removal efficiency of about 90%. The disappearance was mostly due to plant uptake (1110 kg ha(-1)) and soil accumulation (570 kg ha(-1)), with the contribution of denitrification being estimated at around 7%. PMID:17270250

  4. Polymerization of alanine in the presence of a non-swelling montmorillonite

    NASA Technical Reports Server (NTRS)

    Paecht-Horowitz, M.; Lahav, N.

    1977-01-01

    Alanine, starting from alanine-adenylate, has been polymerized in the presence of non-swelling Al-montmorillonite. The yield of polymerization is much lower than that obtained in the presence of swelling Na-montmorillonite. The possibility that the changing interlayer spacing in Na-montmorillonite might be responsible for its catalytic properties, is discussed.

  5. The characteristics of treated zone processed by pulsed Nd-YAG laser surface remelting on hot work steel

    NASA Astrophysics Data System (ADS)

    Zhang, Zhihui; Lin, Pengyu; Cong, Dalong; Kong, Shuhua; Zhou, Hong; Ren, Luquan

    2014-12-01

    In this study, the surface of H13 steel was treated using laser surface remelting. Some important characteristics of the treated zone (biomimetic strengthening units) were investigated, e.g. size, cross-sectional morphology, microstructure and hardness as functions of average peak power density and effective peak power density. The results indicate that different combinations of average peak power density and effective peak power density could vary the appearance of cross-sectional morphology, microstructure and hardness. An appropriate range of EPPD for preparing the treated zone was acquired: 595-1448 W/mm2. In this range, the depth/width ratio of 0.31-0.47 and microhardness of 559-667 HV were obtained.

  6. Surface wettability and energy effects on the biological performance of poly-3-hydroxybutyrate films treated with RF plasma.

    PubMed

    Syromotina, D S; Surmenev, R A; Surmeneva, M A; Boyandin, A N; Nikolaeva, E D; Prymak, O; Epple, M; Ulbricht, M; Oehr, C; Volova, T G

    2016-05-01

    The surface properties of poly-3-hydroxybutyrate (P3HB) membranes were modified using oxygen and an ammonia radio-frequency (RF, 13.56MHz) plasma. The plasma treatment procedures used in the study only affected the surface properties, including surface topography, without inducing any significant changes in the crystalline structure of the polymer, with the exception being a power level of 250W. The wettability of the modified P3HB surfaces was significantly increased after the plasma treatment, irrespective of the treatment procedure used. It was revealed that both surface chemistry and surface roughness changes caused by the plasma treatment affected surface wettability. A treatment-induced surface aging effect was observed and resulted in an increase in the water contact angle and a decrease in the surface free energy. However, the difference in the water contact angle between the polymers that had been treated for 4weeks and the untreated polymer surfaces was still significant. A dependence between cell adhesion and proliferation and the polar component of the surface energy was revealed. The increase in the polar component after the ammonia plasma modification significantly increased cell adhesion and proliferation on biodegradable polymer surfaces compared to the untreated P3HB and the P3HB modified using an oxygen plasma. PMID:26952446

  7. Influences of surface chemistry and swelling of salt-treated polyelectrolyte multilayers on migration of smooth muscle cells.

    PubMed

    Han, Lulu; Mao, Zhengwei; Wu, Jindan; Zhang, Yuying; Gao, Changyou

    2012-12-01

    The cell migration plays a crucial role in a variety of physiological and pathological processes and can be regulated by the cell-substrate interactions. We found previously that the poly(sodium 4-styrenesulphonate) (PSS)/poly(diallyldimethylammonium) chloride (PDADMAC) multilayers post-treated in 1-5 M NaCl solutions result in continuous changes of their physico-chemical properties such as thickness, chemical composition, surface charge, swelling ratio and wettability. In this study, the responses of human smooth muscle cells (SMCs) on these salt-treated multilayers, particularly the governing factors of cellular migration that offer principles for designing therapeutics and implants, were disclosed. The cell migration rate was slowest on the 3 M NaCl-treated multilayers, which was comparable with that on tissue culture plates, but it was highest on 5 M NaCl-treated multilayers. To elucidate the intrinsic mechanisms, cell adhesion, proliferation, adhesion and related gene expressions were further investigated. The SMCs preferred to attach, spread and proliferate on the PSS-dominated surfaces with well-organized focal adhesion and actin fibres, especially on the 3 M NaCl-treated multilayers, while were kept round and showed low viability on the PDADMAC-dominated surfaces. The relative mRNA expression levels of adhesion-related genes such as fibronectin, laminin and focal adhesion kinase, and migration-related genes such as myosin IIA and Cdc42 were compared to explain the different cellular behaviours. These results reveal that the surface chemistry and the swelling of the salt-treated multilayers govern the cell migration behaviours. PMID:22896570

  8. Hybrid collagen-based hydrogels with embedded montmorillonite nanoparticles.

    PubMed

    Nistor, Manuela Tatiana; Vasile, Cornelia; Chiriac, Aurica P

    2015-08-01

    Montmorillonite nanoparticles have been physically incorporated within a crosslinked collagen/poly(N-isopropyl acrylamide) network in order to adjust the properties of the stimuli-responsive hybrid systems. The research underlines both the influence of hydrogel composition and nanoparticle type on hybrid hydrogel properties. The dispersion of the montmorillonite nanoparticles in polymeric matrix have been visualized by SEM, TEM and AFM techniques and quantitatively and qualitatively estimated using near infrared chemical imaging. The electrical charge of the nanoparticles influenced the polymeric chain arrangement and the pore size. The morphologies of the nanoparticulated layers are partially exfoliated or intercalated and uniformly dispersed through the polymeric semi-interpenetrated network based on collagen and poly(N-isopropyl acrylamide). The hybrid hydrogels exhibit pseudoplastic behavior and the addition of nanoparticles has resulted in the increase of the complex viscosity. The adhesion capacity was affected mainly by the presence of organically modified montmorillonites. PMID:26042709

  9. Speciation of uranium(VI) sorption complexes on montmorillonite

    SciTech Connect

    Chisholm-Brause, C.J.; Morris, D.E.; Richard, R.E.

    1992-05-01

    Environmental contaminant releases that contain uranium are among the most serious problems that must be confronted by restoration programs. To facilitate restoration, information concerning the speciation of uranium is needed. Under oxidizing conditions, dissolved uranium is predominantly in the U(VI) (uranyl) form and is quite mobile in the environment, however sorption onto soils may retard its movement. In this study, we have investigated the effects of changes in solution speciation on the nature of uranyl sorption complexes on montmorillonite, a common soil constituent. Aqueous U(VI) solutions between pH 3 to 7 were batch-equilibrated with montmorillonite for several days; specific pH values were selected such that the solutions consisted of dominantly monomeric, oligomeric, or a mix of monomeric and oligomeric aqueous uranyl species. Emission spectroscopy was used to investigate the nature of U(VI) sorbed to montmorillonite.

  10. Retention of gases by hexadecyltrimethylammonium-montmorillonite clays.

    PubMed

    Volzone, C; Rinaldi, J O; Ortiga, J

    2006-05-01

    Intercalated montmorillonite clays with different amounts of organic hexadecyltrimethylammonium (HDTMA) cations were studied to analyse their CO, CH(4), and SO(2) gas retentions. Equilibrium adsorption was measured by using a standard volumetric apparatus at 25 degrees C and 0.1 MPa. The solids were characterised by X-ray diffraction. The levels of adsorption of SO(2) by organo-montmorillonites (0.3595-1.6403 mmol/g) were higher than those of CO (up to 0.0202 mmol/g) and CH(4) (up to 0.0273 mmol/g) gases. HDTMA montmorillonites may be effective adsorbents for removing SO(2) and for its potential separation in the presence of CO and/or CH(4) molecules, which can be present in contaminated air. PMID:16182436

  11. Formation of RNA oligomers on montmorillonite: site of catalysis

    NASA Technical Reports Server (NTRS)

    Ertem, G.; Ferris, J. P.

    1998-01-01

    Certain montmorillonites catalyze the self condensation of the 5'-phosphorimidazolide of nucleosides in pH 8 aqueous electrolyte solutions at ambient temperatures leading to formation of RNA oligomers. In order to establish the nature of the sites on montmorillonite responsible for this catalytic activity, oligomerization reactions were run with montmorillonites which had been selectively modified (I) at the edges by (a) fluoride treatment, (b) silylation, (c) metaphosphate treatment of the anion exchange sites (II) in the interlayer by (a) saturation with quaternary alkylammonium ions of increasing size, (b) aluminum polyoxo cations. High pressure liquid chromatography, HPLC, analysis of condensation products for their chain lengths and yields indicated that modification at the edges did not affect the catalytic activity to a significant extent, while blocking the interlayer strongly inhibited product formation.

  12. [In vivo study of bacterial invasion in root planed and citric acid treated radicular surfaces of periodontally involved human teeth].

    PubMed

    Ito, K; Arai, N; Otogoto, J; Murai, S

    1989-06-01

    The purpose of this study was to investigate whether plaque bacteria invade the exposed radicular dentin after root planing or chemical root treatment in vivo. Eighteen caries-free human periodontally involved teeth with hopeless prognoses were studied. Fourteen teeth were scaled and root planed with hand curette type scalers. The proximal surface of each treated tooth was designated as the RP surface. The remaining half of the proximal surface was treated with citric acid (pH 1.0) for 3 minutes and was designated as the CA surface. Four untreated teeth served as controls. After 4 weeks, the teeth were extracted, and were processed for light microscopy and for scanning electron microscopy concerning bacterial invasion into the supragingival radicular dentin. The following results were obtained. 1. Radicular cementum was present on most untreated tooth surfaces. However, bacteria were never seen in the dentinal tubules. 2. Bacterial invasion into the dentinal tubules was observed in five of the 10 proximal surfaces (50% of the RP surfaces) and in nine of the 10 proximal surfaces (90% of the CA surfaces). 3. The depth (9.5 +/- 24.1 microns vs 84.6 +/- 136.3 microns) and percentage (0.8 +/- 2.1% vs 20.3 +/- 17.3%) of bacterial invasion in the dentinal tubules of the RP surfaces was lower than that of the CA surfaces. 4. Cocci and short rods were present in the supragingival dentinal tubules. 5. Since CA surfaces may accelerate bacterial invasion the citric acid treatment might be harmful in patients with inadequate plaque control. PMID:2700200

  13. Modified montmorillonite as vector for gene delivery.

    PubMed

    Lin, Feng-Huei; Chen, Chia-Hao; Cheng, Winston T K; Kuo, Tzang-Fu

    2006-06-01

    Currently, gene delivery systems can be divided into two parts: viral or non-viral vectors. In general, viral vectors have a higher efficiency on gene delivery. However, they may sometimes provoke mutagenesis and carcinogenesis once re-activating in human body. Lots of non-viral vectors have been developed that tried to solve the problems happened on viral vectors. Unfortunately, most of non-viral vectors showed relatively lower transfection rate. The aim of this study is to develop a non-viral vector for gene delivery system. Montmorillonite (MMT) is one of clay minerals that consist of hydrated aluminum with Si-O tetrahedrons on the bottom of the layer and Al-O(OH)2 octahedrons on the top. The inter-layer space is about 12 A. The room is not enough to accommodate DNA for gene delivery. In the study, the cationic hexadecyltrimethylammonium (HDTMA) will be intercalated into the interlayer of MMT as a layer expander to expand the layer space for DNA accommodation. The optimal condition for the preparation of DNA-HDTMA-MMT is as follows: 1 mg of 1.5CEC HDTMA-MMT was prepared under pH value of 10.7 and with soaking time for 2 h. The DNA molecules can be protected from nuclease degradation, which can be proven by the electrophoresis analysis. DNA was successfully transfected into the nucleus of human dermal fibroblast and expressed enhanced green fluorescent protein (EGFP) gene with green fluorescence emission. The HDTMA-MMT has a great potential as a vector for gene delivery in the future. PMID:16488006

  14. Immobilization of self-assembled pre-dispersed nano-TiO2 onto montmorillonite and its photocatalytic activity.

    PubMed

    Zhang, Tingting; Luo, Yuan; Jia, Bing; Li, Yan; Yuan, Lingling; Yu, Jiang

    2015-06-01

    The immobilization of pre-dispersed TiO2 colloids onto the external surface of the clay mineral montmorillonite (Mt) was accomplished and regulated via a self-assembly method employing the cationic surfactant cetyltrimethylammonium bromide (CTAB). The role of CTAB in the synthesis process was investigated by preparing a series of TiO2-CTAB-Mt composites (TCM) with various CTAB doses. The results indicated that a uniform and continuous TiO2 film was deposited on the external surface of montmorillonite in the composite synthesized with 0.1 wt.% of CTAB, and the TCM nano-composites showed much higher values for specific surface area, average pore size and pore volume than the raw montmorillonite clay. Then, the formed TCM materials were applied in photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP) in aqueous solution. The degradation efficiency reached as high as 94.7%. Based on the degradation intermediates benezoquinone, fumaric acid and oxalic acid identified by LC-MS analysis, a mechanism for the photocatalytic oxidation of 2,4-DCP on TiO2/Mt nano-composites is proposed. PMID:26040737

  15. Surface analytical characterisation of Nd:YAG-laser pre-treated Al Mg3 as a preparation for bonding

    NASA Astrophysics Data System (ADS)

    Langer, M.; Rechner, R.; Thieme, M.; Jansen, I.; Beyer, E.

    2012-07-01

    The contribution summarises results of the surface pre-treatment of Al Mg3 (EN-AW-5754) for bonding applications. Mainly the sheet samples were irradiated with a pulsed solid-state laser in different atmospheres. Afterwards the pre-treated surfaces were analysed by quantitative topographic measurements, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and electrochemical impedance spectroscopy (EIS). The effect of surface pre-treatment on the strength of adhesively bonded specimens was evaluated by tensile lap-shear strength tests. The results were compared with conventional pre-treatment methods, such as anodic oxidation and others.

  16. Possible selective adsorption of enantiomers by Na-montmorillonite

    NASA Technical Reports Server (NTRS)

    Friebele, E.; Shimoyama, A.; Ponnamperuma, C.

    1981-01-01

    Racemic amino acids including (D,L) alpha-alamine, (D,L) alpha-aminobutyric acid, (D,L) valine, and (D,L) norvaline were incubated with Na-montmorillonite at 100% CEC at three hydrogen ion concentrations, and amino acid adsorption was determined by ion exchange chromatography. Enantiomers were analyzed by gas chromatography. Differences in the quantities of D and L enantiomers in any of the fractions was no larger than a few percent. Although a large difference in the adsorption of the amino acid enantiomers was not observed, the analysis may indicate a small preferential adsorption (0.5-2%) of L-amino acids by Na-montmorillonite.

  17. PARAMETERS OF TREATED STAINLESS STEEL SURFACES IMPORTANT FOR RESISTANCE TO BACTERIAL CONTAMINATION

    EPA Science Inventory

    Use of materials that are resistant to bacterial contamination could enhance food safety during processing. Common finishing treatments of stainless steel surfaces used for components of poultry processing equipment were tested for resistance to bacterial attachment. Surface char...

  18. A comparative study and evaluation of sulfamethoxazole adsorption onto organo-montmorillonites.

    PubMed

    Lu, Laifu; Gao, Manglai; Gu, Zheng; Yang, Senfeng; Liu, Yuening

    2014-12-01

    Three organo-montmorillonites were prepared using surfactants, and their adsorption behaviors toward sulfamethoxazole (SMX) were investigated. The surfactants used were cetyltrimethyl ammonium bromide (CTMAB), 3-(N,N-dimethylhexadecylammonio) propane sulfonate (HDAPS) and 1,3-bis(hexadecyldimethylammonio)-propane dibromide (BHDAP). The properties of the organo-montmorillonites were characterized by X-ray diffraction, scanning electron microscopy and N2 adsorption-desorption isotherm measurements. Results showed that the interlayer spacing of montmorillonite was increased and the surface area as well as the morphology were changed. Batch adsorption experiments showed that the surfactant loading amount had a great effect on the adsorption of SMX. The adsorption process was pH dependent and the maximum adsorption capacity was obtained at pH3 for HDAPS-Mt, while CTMAB-Mt and BHDAP-Mt showed a high removal efficiency at 3-11. The adsorption capacity increased with the initial SMX concentration and contact time but decreased with increasing solution ionic strength. Kinetic data were best described by the pseudo second-order model. Equilibrium data were best represented by the Langmuir model, and the Freundlich constant (n) indicated a favorable adsorption process. The maximum adsorption capacity of SMX was 235.29 mg/g for CTMAB-Mt, 155.28 mg/g for HDAPS-Mt and 242.72 mg/g for BHDAP-Mt. Thermodynamic parameters were calculated to evaluate the spontaneity and endothermic or exothermic nature. The adsorption mechanism was found to be dominated by electrostatic interaction, while hydrophobic interaction played a secondary role. PMID:25499502

  19. Study of Np(V) Sorption by Ionic Exchange on Na, K, Ca and Mg-Montmorillonite

    NASA Astrophysics Data System (ADS)

    Benedicto, A.; Begg, J.; Zhao, P.; Kersting, A. B.; Zavarin, M.

    2012-12-01

    The transport behavior of actinides in soil and ground water are highly influenced by clay minerals due to their ubiquity in the environment, reactivity and colloidal properties. Neptunium(V) has been introduced in the environment as a result of nuclear weapons testing [e.g. 1, 2] and is a radionuclide of potential interest for safety assessment of high level radioactive waste disposal because its long half-life and high toxicity [3]. Surface complexation and ionic exchange have been identified as Np(V) sorption mechanisms onto montmorillonite. At pH below 5, Np(V) sorption is mainly attributed to ionic exchange. This study examines Np(V) ion exchange on Na, K, Ca and Mg forms of montmorillonite. Experiments were carried out using 237Np concentrations between 2 x 10-8 M and 5 x 10-6 M at three different ionic strengths 0.1, 0.01 and 0.001M. The pH was maintained at 4.5. Np(V) sorption to montmorillonite homoionized with monovalent cations (Na and K) demonstrated a markedly different behavior to that observed for montmorillonite homoionized with divalent cations (Ca and Mg). Np sorption to Na and K-montmorillonite was greater than Np sorption to Ca and Mg-montmorillonite. Isotherms with Na and K-montmorillonite showed a strong dependence on ionic strength: the percentage of Np adsorbed was near zero at 0.1M ionic strength, but increased to 30% at 0.001 M ionic strength. This suggests ionic exchange is the main Np adsorption mechanism under the experimental conditions investigated. Dependence on ionic strength was not observed in the Np sorption isotherms for Ca and Mg-montmorillonite indicating a low exchange capacity between Np and divalent cations. Modeling of the sorption experimental data will allow determination of the Na+↔NpO2+ and K+↔NpO2+ ionic exchange constants on montmorillonite. References: [1] A. R. Felmy; K. J. Cantrell; S. D. Conradson, Phys. Chem. Earth 2010, 35, 292-297 [2] D. K. Smith; D. L. Finnegan; S. M. Bowen, J. Environ. Radioact. 2003, 67, (1), 35-51 [3] N. Kozai; T. Ohnuki; S. Muraoka, J. Nucl. Sci. Technol. 1993, 30, (11), 1153-1159 This work was funded by U. S. DOE Office of Biological & Environmental Sciences, Subsurface Biogeochemistry Research Program, and performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344. A. Benedicto was supported by a Spanish Ministry of Science and Innovation 'FPI' pre-doctoral contract in CIEMAT (Spain). LLNL-ABS-570160

  20. Mechanical properties of the sodium montmorillonite interlayer intercalated with amino acids.

    PubMed

    Katti, Dinesh R; Ghosh, Pijush; Schmidt, Steven; Katti, Kalpana S

    2005-01-01

    Nanosized montmorillonite clay dispersed in small amounts in polymer results in polymer nanocomposites having superior engineering properties compared to those of the native polymer. These nanoinclusions are created by treating clay with an organic modifier which makes clay organophilic and results in intercalation or exfoliation of the montmorillonite. The modifiers used are usually long carbon chains with alkylammonium or alkylphosphonium cations. In this work, we have investigated the use of some alternative molecules which can act as modifiers for clay composites using clay for reinforcing a matrix of biopeptides or proteins. Such composites have potential applications in the fields of biomedical engineering and pharmaceutical science. In this work, the amino acids arginine and lysine are used as modifiers. The intercalation and mechanical behavior of the interlayer spacing with these amino acids as inclusions under compression and tension are studied using molecular dynamics simulations. Significant differences in the responses are observed. This work also provides an insight into the orientation and interaction of amino acids in the interlayer under different stress paths. PMID:16283756

  1. Effect of phosphate on U(VI) sorption to montmorillonite: Ternary complexation and precipitation barriers

    NASA Astrophysics Data System (ADS)

    Troyer, Lyndsay D.; Maillot, Fabien; Wang, Zheming; Wang, Zimeng; Mehta, Vrajesh S.; Giammar, Daniel E.; Catalano, Jeffrey G.

    2016-02-01

    Phosphate addition is a potential treatment method to lower the solubility of U(VI) in soil and groundwater systems by causing U(VI) phosphate precipitation as well as enhancing adsorption. Previous work has shown that iron oxide surfaces may facilitate the nucleation of U(VI) phosphate minerals and, that under weakly acidic conditions, phosphate also enhances U(VI) adsorption to such phases. Like iron oxides, clays are important reactive phases in the subsurface but little is known about the interaction of U(VI) and phosphate with these minerals. The effect of aqueous phosphate on U(VI) binding to Wyoming montmorillonite (SWy-2) in air-equilibrated systems was investigated. Equilibrium U(VI) uptake to montmorillonite was determined at pH 4, 6 and 8 at discrete initial phosphate concentrations between 0 and 100 μM. The observed behavior of U(VI) indicates a transition from adsorption to precipitation with increasing total uranium and phosphate concentrations at all pH values. At the highest phosphate concentration examined at each pH value, a barrier to U(VI) phosphate nucleation is observed. At lower concentrations, phosphate has no effect on macroscopic U(VI) adsorption. To assess the mechanisms of U(VI)-phosphate interactions on smectite surfaces, U(VI) speciation was investigated under selected conditions using laser-induced fluorescence spectroscopy (LIFS) and extended X-ray absorption fine-structure (EXAFS) spectroscopy. Samples above the precipitation threshold display EXAFS and LIFS spectral signatures consistent with the autunite family of U(VI) phosphate minerals. However, at lower U(VI) concentrations, changes in LIFS spectra upon phosphate addition suggest that U(VI)-phosphate ternary surface complexes form on the montmorillonite surface at pH 4 and 6 despite the lack of a macroscopic effect on adsorption. The speciation of solid-associated U(VI) below the precipitation threshold at pH 8 is dominated by U(VI)-carbonate surface complexes. This work reveals that ternary complexation may occur without a macroscopic signature, which is attributed to phosphate not appreciably binding to smectite in the absence of U(VI), with U(VI) surface complexes serving as the sole reactive surface sites for phosphate. This study shows that phosphate does not enhance U(VI) adsorption to smectite clay minerals, unlike oxide phases, and that a barrier to homogeneous nucleation of U(VI) phosphates was not affected by the presence of the smectite surface.

  2. Solvent-based nanocomposite coatings I. Dispersion of organophilic montmorillonite in organic solvents.

    PubMed

    Burgentzlé, D; Duchet, J; Gérard, J F; Jupin, A; Fillon, B

    2004-10-01

    This study aims to determine the relevant parameters controlling the organophilic montmorillonite dispersion in various organic solvents which can be used as dispersion media for polymer coatings. These suspensions were studied at three scales: At nanometer scale by looking to interlayer distance: When the solvent surface energy is higher than the organophilic clay surface energy, i.e., gamma solvent > or = gamma montmorillonite, the intercalated organic chains of the quaternary ammonium modifier swell, leading to an increase of the interlayer distance. The balance between hydrophilic and hydrophobic character is the key to dispersion of nanoclays. At micrometer scale by studying the rheological behaviour of clay suspensions: Gels are formed by percolation of microgels, based on swollen 3-4 platelet tactoids. The viscoelastic properties and the flow behavior reveal the gel structuration by measuring the gel stiffness and the flowing stress. At macroscopic scale analyzed from the swelling of the nanoclay into solvents: The compatibility between solvent and organophilic clay governs the macroscopic swelling, i.e., interactions between organic chains borne by the intercalated ions and solvents govern the final suspension morphologies. The same methodology can be adopted for monomers or prepolymers selected for one in situ intercalation/exfoliation processing route. PMID:15313634

  3. Hexadimethrine-montmorillonite nanocomposite: Characterization and application as a pesticide adsorbent

    NASA Astrophysics Data System (ADS)

    Gámiz, B.; Hermosín, M. C.; Cornejo, J.; Celis, R.

    2015-03-01

    The goal of this work was to prepare and characterize a novel functional material by the modification of SAz-1 montmorillonite with the cationic polymer hexadimethrine (SA-HEXAD), and to explore the potential use of this nanocomposite as a pesticide adsorbent. Comparative preparation and characterization with the well-known hexadecyltrimethylammonium-modified SAz-1 montmorillonite (SA-HDTMA) was also assessed. The characterization was performed by elemental analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), physisorption of N2, scanning electron microscopy (SEM) and Z potential measurements. The characterization and adsorption experiments showed that the extent of pesticide adsorption was markedly subjected to the structure and features of the surface of each organo-clay and also to the nature of the considered pesticide. SA-HEXAD displayed a high affinity for anionic pesticides which, presumably, were adsorbed by electrostatic attraction on positively-charged ammonium groups of the polymer not directly interacting with the clay. In contrast, SA-HDTMA displayed great adsorption of both uncharged and anionic pesticides with predominance of hydrophobic interactions. This work provided information about the surface properties of a new organic-inorganic nanohybrid material, SA-HEXAD, and its potential as an adsorbent for the removal of anionic organic pollutants from aqueous solutions.

  4. Modeling of alkyl quaternary ammonium cations intercalated into montmorillonite lattice

    SciTech Connect

    Daoudi, El Mehdi; Boughaleb, Yahia; El Gaini, Layla; Meghea, Irina; Bakasse, Mina

    2013-05-15

    Highlights: ► The modification of montmorillonites by three surfactants increases the basal spacing. ► The model proposed show a bilayer conformation for the surfactant ODTMA. ► The DODMA and TOMA surfactants adopt a paraffin type arrangement. ► Behavior of surfactants in interlayer space was confirmed by TGA and ATR analysis. - Abstract: The objective of this work was to study the conformation of the quaternary ammonium cations viz., octadecyl trimethyl ammonium (ODTMA), dioctadecyl dimethyl ammonium (DMDOA) and trioctadecyl methyl ammonium (TOMA) intercalated within montmorillonite. The modified montmorillonite was characterized by X-ray diffraction in small angle (SAXS), thermal analysis (TGA) and infrared spectroscopy of attenuated total reflection (ATR). The modification of organophilic montmorillonites by the three surfactants ODTMA, DMDOA and TOMA increases the basal spacing from their respective intercalated distances of 1.9 nm, 2.6 nm and 3.4 nm respectively. The increase in the spacing due to the basic organic modification was confirmed by the results of thermal analysis (TGA) and infrared spectroscopy (ATR), and also supported by theoretical calculations of longitudinal and transversal chain sizes of these alkyl quaternary ammonium cations.

  5. Chlorpyrifos-treated crops in the vicinity of surface water contamination in the San Joaquin Valley, California, USA.

    PubMed

    Starner, Keith; Goh, Kean S

    2013-09-01

    Due to frequent contamination of streams in the San Joaquin Valley, California, USA, with the insecticide chlorpyrifos, researchers are working to identify crop-specific management practices that will reduce the offsite movement of this compound into surface waters. To guide this effort, crops treated with chlorpyrifos in the vicinity of contaminated streams were identified; walnut, alfalfa, and almond were the primary crops identified. Use was higher on walnut and almond, but due to irrigation practices offsite movement in surface runoff may be more likely from alfalfa. Based on these findings, development of management practices to reduce off-site movement of chlorpyrifos in irrigation runoff from treated alfalfa fields is recommended. PMID:23749038

  6. Morphology and Structure of Amino-fatty Acid Intercalated Montmorillonite

    NASA Astrophysics Data System (ADS)

    Reyes, Larry; Sumera, Florentino

    2015-04-01

    Natural clays and its modified forms have been studied for their wide range of applications, including polymer-layered silicate, catalysts and adsorbents. For nanocomposite production, montmorillonite (MMT) clays are often modified with organic surfactants to favor its intermixing with the polymer matrix. In the present study, Na+-montmorillonite (Na+-MMT) was subjected to organo-modification with a protonated 12-aminolauric acid (12-ALA). The amount of amino fatty acid surfactants loaded was 25, 50, 100 and 200% the cation exchange capacity (CEC) of Na+-MMT (25CEC-AMMT, 50CEC-AMMT, 100CEC-AMMT and 200CEC-AMMT). Fatty acid-derived surfactants are an attractive resource of intercalating agents for clays due to their renewability and abundance. X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) were performed to determine the occurrence of intercalation of 12-ALA and their molecular structure in the clay's silicates. XRD analysis revealed that the interlayer spacing between the alumino-silicate layers increased from 1.25 nm to 1.82 nm with increasing ALA content. The amino fatty acid chains were considered to be in a flat monolayer structure at low surfactant loading, and a bilayered to a pseudotrilayered structure at high surfactant loading. On the other hand, FTIR revealed that the alkyl chains adopt a gauche conformation, indicating their disordered state based on their CH2symmetric and asymmetric vibrations. Thermogravimetric analyses (TGA) allows the determination of the moisture and organic content in clays. Here, TGA revealed that the surfactant in the clay was thermally stable, with Td ranging from 353° C to 417° C. The difference in the melting behavior of the pristine amino fatty acids and confined fatty acids in the interlayer galleries of the clay were evaluated by Differential Scanning Calorimerty (DSC). The melting temperatures (Tm) of the amino fatty acid in the clay were initially found to be higher than those of the free amino fatty acid, but decreased with increasing surfactant loading. This suggested that the amino fatty acid may be tethered to the clay structure via ionic interaction and/or ion-dipole attraction. Significant changes in the clay morphology, particle size and surface charge were observed after organo-modification. Scanning electron microscopy (SEM) revealed that the organo-clays have a disordered and flaky morphology, while the unmodified MMT appeared to be dispersed spherical grains. The effective (Z) diameter of Na+-MMT was found to be ~520 nm, but increased up to ~937 nm upon intercalation of 12-ALA. The zeta potential (ξ) of the clay materials, on the other hand, ranged from -33 mV for undmodified MMT to -16 mv (200CEC-AMMT clay). The possible occupational hazards of working with nanoclays should also be explored. Presently, the MTT-dye reduction assay was performed to determine cell viability of mouse monocyte-macrophages (J774A.1) after direct exposure to the clays. The cytotoxicity of the clays exhibited a chemistry and dose dependent response, with unmodified Na+-MMT as the most cytotoxic while the organo-clays exhibited low toxicity. These results demonstrated the successful intercalation of the surfactant for the production of organophilic clay materials for a wide range of applications.

  7. Nonequilibrium structural condition in the medical TiNi-based alloy surface layer treated by electron beam

    SciTech Connect

    Neiman, Aleksei A. Lotkov, Aleksandr I.; Meisner, Ludmila L. Semin, Viktor O.; Koval, Nikolai N.; Teresov, Anton D.

    2014-11-14

    The research is devoted to study the structural condition and their evolution from the surface to the depth of TiNi specimens treated by low-energy high-current electron beams with surface melting at a beam energy density E = 10 J/cm{sup 2}, number of pulses N = 10, and pulse duration τ = 50 μs. Determined thickness of the remelted layer, found that it has a layered structure in which each layer differs in phase composition and structural phase state. Refinement B2 phase lattice parameters in local areas showed the presence of strong inhomogeneous lattice strain.

  8. Effect of adsorbed iron on thermoluminescence and electron spin resonance spectra of Ca-Fe-exchanged montmorillonite

    NASA Technical Reports Server (NTRS)

    Coyne, Lelia M.; Banin, Amos

    1986-01-01

    The ESR spectra and the natural and gamma-induced thermoluminescence (TL) glow curves of a series of variably cation-exchanged Fe-Ca-clays prepared from SWy-1 montmorillonite were examined. The ESR signal intensity associated with surface Fe increased linearly with surface Fe content up to a nominal concentration of 50 percent exchangeable Fe. At above 50 percent exchangeable Fe, no appreciable increase in the signal was noted. The TL intensity decreased linearly with increasing surface Fe up to 50 percent nominal exchangeable Fe. At above 50 percent, the signal was not appreciably further diminished. Possible effects of Fe on quenching of TL are considered.

  9. Influence of laser surface treated on the characterization and corrosion behavior of Al-Fe aerospace alloys

    NASA Astrophysics Data System (ADS)

    Pariona, Moisés Meza; Teleginski, Viviane; dos Santos, Kelly; de Lima, Angela A. O. C.; Zara, Alfredo J.; Micene, Katieli Tives; Riva, Rudimar

    2013-07-01

    In this research laser surface remelting without protective coating with a 2 kW Yb-fiber laser (IPG YLR-2000S) was applied in the Al-1.5 wt.%Fe alloy in order to investigate the layer treated with different techniques of superficial characterization, thereby, the technique of optical microscopy, atomic force microscopy and low-angle X-ray diffraction were used. The present work mainly focuses on the corrosion study by diverse techniques in aggressive environment of the laser-treated area and the substrate material was carried out, thereby, at open circuit potential testing, the results have shown a displacement to more anodic values in the corrosion potential for the laser-treated specimen when compared to the untreated specimen; in potentiodynamic polarization tests have shown that as a result of the laser treatment, the corrosion current can be reduced by as much as ten times, and a passive region was obtained, which served as an effective barrier for reducing anodic dissolution and finally, the result in cyclic polarization curves of the untreated sample there was a greater area of the hysteresis loop, implying that it is more susceptible to corrosion. This study was complemented by other techniques mentioned above in order to elucidate this study. Laser surface remelting process has definitely modified the surface film, which results in higher corrosion resistance, a large range of passivation and a lower area of the hysteresis loop.

  10. Microbiological investigations of oxygen plasma treated parylene C surfaces for metal implant coating.

    PubMed

    Golda-Cepa, M; Brzychczy-Wloch, M; Engvall, K; Aminlashgari, N; Hakkarainen, M; Kotarba, A

    2015-01-01

    Parylene C surface was modified by the use of oxygen plasma treatment and characterized by microscopic and surface-sensitive techniques (E-SEM, AFM, XPS, LDI-TOF-MS, contact angle). The influence of the treatment on surface properties was investigated by calculations of surface free energy (Owens-Wendt method). Moreover, early adhesion (Culture Plate Method, Optical Microscopy Test) and biofilm formation ability (Cristal Violet Assay) on the parylene C surface was investigated. The bacteria strains which are common causative agents of medical device-associated infections (Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa--reference strains and clinical isolates) were used. It was concluded that chemical (oxygen insertion) and physical (nanotopography generation) changes, have a significant impact on the biocompatibility in terms of increased hydrophilicity (θ w of unmodified sample = 88° ± 2°, θ w of 60 min modified sample = 17.6° ± 0.8°) and surface free energy (SFE of unmodified sample = 42.4 mJ/m(2), and for 60 min modified sample = 70.1 mJ/m(2)). At the same time, no statistical effect on biofilm production and bacteria attachment to the modified surface of any of the tested strains was observed. PMID:25953568

  11. Chemical and structural modifications of laser treated WTi surfaces at different ambient conditions

    NASA Astrophysics Data System (ADS)

    Petrović, S.; Peruško, D.; Milovanović, D.; Siketić, Z.; Jakšić, M.; Kovač, J.; Gaković, B.; Milosavljević, M.; Trtica, M.

    2011-11-01

    In this work we have studied the influence of laser modification on the composition and structure of tungsten titanium (WTi) thin films, deposited on n-type (100) silicon wafers. After deposition, the samples were multi-pulse laser irradiated in a nitrogen, oxygen, and helium ambient. The composition of the WTi/Si sample was determined by Elastic Recoil Detection Analysis (ERDA). Surface morphology was monitored by Atomic Force Microscopy (AFM). In the experiment, typical laser output parameters were: wavelength 1064 nm, pulse duration 150 ps, and laser pulse energy 30 mJ. Surface concentrations of W and Ti, as well as the concentration of gas components nitrogen and oxygen were determinated before and after the action of laser radiation in different ambient conditions. The contents of W and Ti decreased after irradiation due to adsorbed gases from the surrounding atmosphere. After surface irradiation in the inert ambient (He), the concentrations of the components were not significantly changed. In other cases, oxygen was the dominant component at the surface, probably due to the high affinity of thin film components. Also, the morphological changes occurred at the surface of WTi, as an increase in the surface roughness and formation of the granular structures are a result of laser-induced surface oxidation and recrystallization.

  12. A comparative study of the acidity toward the aqueous phase and adsorptive properties of Al{sub 13}-pillared montmorillonite and Al{sub 13}-pillared saponite

    SciTech Connect

    Bergaoui, L.; Mrad, I.; Ghorbel, A.; Lambert, J.F.

    1999-04-15

    The selectivity of an Al{sub 13}-pillared saponite and an Al{sub 13}-pillared montmorillonite for Cd{sup 2+} and Cu{sup 2+} adsorption was studied. The quantity of metal adsorbed on both pillared clays depends on the pH of the solution and the pillars density. Adsorption equilibria are regulated by the protonation equilibria of the amphoteric sites on the pillars. Pillared clays adsorb more cadmium and copper than classic aluminum hydroxides which is simply attributable to a higher density of surface aluminum groups. Significant differences in behavior are observed between pillared montmorillonite and pillared saponite. Pillared montmorillonite appears to be more acidic, which is correlated with a more advanced degree of structural modification of the pillars on calcination. The authors propose a tentative, partial structural model of pillar transformation compatible with these differences. At the same time, both pillared clays have similar affinities for cadmium II at low pH (5--6), but pillared montmorillonite seems to be a more efficient cadmium trap at pH = 8 when its surface groups are negatively ionized. Thus, the nature of the clay layers conditions the structural modifications of the intercalated [Al{sub 13}] polycations, which in turn determine adsorptive behavior.

  13. Enhanced electro-oxidation of alcohols at electrochemically treated polycrystalline palladium surface

    NASA Astrophysics Data System (ADS)

    Wang, Lianqin; Bevilacqua, Manuela; Chen, Yan-Xin; Filippi, Jonathan; Innocenti, Massimo; Lavacchi, Alessandro; Marchionni, Andrea; Miller, Hamish; Vizza, Francesco

    2013-11-01

    The present study demonstrates the effectiveness of an electrochemical treatment consisting in cycles of constant potential oxidation and reduction of polycrystalline palladium surface in the enhancement of the electro-oxidation of ethanol, ethylene glycol and glycerol. The rise of the activity after the treatment has been ascribed to the increase of both surface area and density of low coordination surface atoms. FTIR spectra showed that a change in the reaction products distribution also occurs, resulting, in some cases, in an increased tendency to cleave the C-C bond.

  14. The effects of oil on As(V) adsorption on illite, kaolinite, montmorillonite and chlorite

    NASA Astrophysics Data System (ADS)

    Wainipee, Wimolporn; Cuadros, Javier; Sephton, Mark A.; Unsworth, Catherine; Gill, Martin G.; Strekopytov, Stanislav; Weiss, Dominik J.

    2013-11-01

    The effect of oil on As(V) adsorption on clay minerals has been investigated using batch experiments at low and high pH, NaCl concentration and oil contents. Four clay minerals were chosen because of their abundance in sediments and their different crystal chemistry: illite, kaolinite, montmorillonite, and chlorite. The values for pH were 4 and 8 and salt concentrations were 0.001 and 0.7 M NaCl to appreciate the effects of changing salinity, e.g. from fresh water to seawater conditions. For the coating experiments, a well-characterised oil was used to survey the main effects of complex organic mixtures on adsorption and oil to clay mineral (w/w) ratios were 0.0325 and 0.3250. As(V) adsorption increased with increasing NaCl concentration, suggesting that the mechanisms of As(V) adsorption are related to the formation of surface complexes in which Na+ ions act as bridges between the clay surface and the As(V) anions. Cation bridging is also indicated by zeta potential measurements which show that higher NaCl concentrations along with the presence of As(V) can cause the clay particles and adsorbed ions to have a more negative overall charge. Adsorption is lower at higher pH due to the reduced number of positively charged sites on the edge of clay mineral layers. Oil coating reduces As(V) adsorption by decreasing the available surface area of clay minerals, except in the case of oil-coated montmorillonite, where surface area following dispersion in water is increased. The main variables controlling As(V) adsorption are surface area and surface charge density, as confirmed by a simplified quantitative model. These findings advance our ability to predict the effects of complex pollution events in various freshwater and marine settings.

  15. Monte Carlo study of the adsorption and aggregation of alkyltrimethylammonium chloride on the montmorillonite-water interface.

    PubMed

    Klebow, Birthe; Meleshyn, Artur

    2012-09-18

    Organically modified clays exhibit adsorption capacities for cations, anions, and nonpolar organic compounds, which make them valuable for various environmental technical applications. To improve the understanding of the adsorption processes, the molecular-scale characterization of the structures of organic aggregates assembled on the external basal surfaces of clay particles is essential. The focus of this Monte Carlo simulation study was on the effects of the surface coverage and the alkyl chain length n on the structures of alkyltrimethylammonium chloride ((C(n)TMA)Cl) aggregates assembled on the montmorillonite-water interface. We found that the amount of adsorbed C(n)TMA(+) ions is independent of the alkyl chain length and increases with the C(n)TMA(+) surface coverage. The C(n)TMA(+) ions predominantly adsorb as inner-sphere complexes; the fraction of outer-sphere adsorbed ions equals only about 10%. The conformational order of the C(n)TMA(+) alkyl chains substantially decreases with decreasing alkyl chain length. In agreement with previous experiments, the amount of C(n)TMA(+) ions that are aggregated at the mineral surface increases with increasing chain length. The maximum value of 0.66 C(n)TMA(+) adsorption complex per unit cell area of the clay surface considerably exceeds the amount of cations required to compensate the negative charge of the montmorillonite surface. Furthermore, in most of the studied systems, fractions of Na(+) surface cations remain adsorbed on montmorillonite. The resulting interfacial positive charge excess is counterbalanced by coadsorbed chloride ions forming ion pairs with both C(n)TMA(+) and Na(+). PMID:22894657

  16. Treated enamel surface patterns associated with five orthodontic adhesive systems--surface morphology and shear bond strength.

    PubMed

    Shinya, Makiha; Shinya, Akikazu; Lassila, Lippo V J; Gomi, Harunori; Varrela, Juha; Vallittu, Pekka K; Shinya, Akiyoshi

    2008-01-01

    The chief aim of this study was to evaluate the influence of three different types of pretreatment solutions (phosphoric acid, self-etching primers, and polyacrylic acid) on enamel surfaced when used in association with one of the five orthodontic adhesive systems. In the same vein, the shear bond strength of orthodontic metal brackets was also measured to evaluate the influence of bonding procedure. After the enamel surfaces of extracted human maxillary incisors were pretreated with the five adhesive systems, scanning electron microscopy (SEM) was used to observe the effects of pretreatment on enamel. Additionally, the shear bond strength of metal brackets bonded with the five adhesives was measured (n=6). SEM observation revealed different etching patterns on the enamel surface after pretreatment. As for shear bond strength, no statistically significant differences were observed among the five different adhesives (p>0.05). It was found that self-etching primers and polyacrylic acid produced a less aggressive etching pattern than phosphoric acid. Nonetheless, all the five adhesive systems provided acceptable bond strength and attachment of orthodontic brackets. PMID:18309605

  17. Functional attachment of horse radish peroxidase to plasma-treated surfaces

    NASA Astrophysics Data System (ADS)

    Bilek, Marcela M.; McKenzie, David R.; Nosworthy, Neil; Davies, Kerrie; Morrow, Richard; Thordarson, Palli; Gan, Bee K.; dos Remedios, Cristobal G.

    2004-02-01

    Controlling the interaction of surfaces with macromolecules, such as proteins and antibodies, is the key to producing biocompatible prosthetic devices, biosensors and diagnostic arrays. The development of technologies to control these interactions will result in the early detection of disease and have the potential to dramatically reduce costs associated with clinical treatment. For example, tethering functional anti-bodies to a surface in a patterned array allows the selection of specific proteins from a microlitre serum sample, immediately identifying diseases, well before the symptoms are manifested. Unfortunately, simple physical absorption of proteins onto most surfaces results in changes in their structure and loss of function. The use of ions from plasmas allows flexibility in surface modification by accessing a variety of ion energies and activated chemical species. In this paper we describe plasma based techniques which are being developed to modify the chemistry and morphology of surfaces in order to optimise their interaction with biomolecules. Early results of plasma processes to activate surfaces for non specific attachment of proteins by hydrophilic /hydrophobic interactions are presented, with particular attention to the time stability of such treatments, which is of special interest.

  18. Removal of hexavalent chromium from aqueous solution using exfoliated polyaniline/montmorillonite composite.

    PubMed

    Chen, Jun; Hong, Xiaoqin; Zhao, Yongteng; Zhang, Qianfeng

    2014-01-01

    Exfoliated polyaniline/montmorillonite (PANI/MMT) composites with nanosheet structure were successfully prepared by in situ chemical oxidation polymerization with MMT platelets as the scaffold. Amphoteric polymer, (2-methacryloyloxyethyl)trimethyl ammonium chloride and methacrylate acid copolymer, was used to modify montmorillonite and a large number of carboxylic acids were introduced on the surface of the clay platelets, which can be used as a dopant of PANI and play a 'bridge' role to combine PANI with clay. Adsorption experiments were carried out to study the effects of pH, contact time, Cr(VI) concentration, adsorbent dose and temperature. The adsorption of Cr(VI) on the PANI/MMT was highly pH dependent and the adsorption kinetics followed a pseudo-second-order model. The Langmuir isothermal model described the adsorption isotherm data well and the maximum adsorption capacity increased with the increase in temperature. Thermodynamic investigation indicated that the adsorption process is spontaneous, endothermic and marked with an increase in randomness at the adsorbent - liquid interface. The maximum adsorption capacity of the PANI/MMT composites for Cr(VI) was 308.6 mg/g at 25 °C. The excellent adsorption characteristic of exfoliated PANI/MMT composites will render it a highly efficient and economically viable adsorbent for Cr(VI) removal. PMID:25116498

  19. Surface characteristics and cell-adhesion performance of titanium treated with direct-current gas plasma comprising nitrogen and oxygen

    NASA Astrophysics Data System (ADS)

    Hirano, Mitsuhiro; Yamane, Misao; Ohtsu, Naofumi

    2015-11-01

    In this study, we attempted to form titanium oxynitride (TiOxNy) layers on titanium (Ti) surfaces using direct-current (DC) plasmas generated from gas mixture comprising hydrogen, nitrogen, and oxygen. Additionally, the effect of gas mixture ratio on the surface characteristics and cell-adhesion performance was investigated. Scanning probe microscopy (SPM) images showed that the plasma-treated surfaces were slightly rougher than untreated Ti surfaces, owing to the formation of new layers. Chemical state analysis using X-ray photoelectron spectroscopy (XPS) revealed that the layers were comprised TiOxNy, titanium nitride (TiN), and titanium dioxide (TiO2); the concentrations of TiOxNy and TiN decreased and that of TiO2 increased with an increase in the amount of oxygen in the gas. An increase in the amount of oxygen gas did not affect the layer thickness, which was approximately 25 nm. Furthermore, no differences in cell morphology and cell-adhesion performance were found between the specimens treated with various plasma gases. This is probably because the treatment insufficiently improved the hydrophilicity. Layers composed of TiOxNy, TiN, and TiO2 were formed using the DC plasma treatment; however, the layers did not improve the cell-adhesion at an initial stage after the seeding.

  20. Nanoscale evaluation of laser-based surface treated 12Ni maraging steel

    NASA Astrophysics Data System (ADS)

    Grum, J.; Slabe, J. M.

    2005-07-01

    Maraging steels are used in several high-tech areas. Among them are highly thermo-mechanically loaded vital parts of die casting dies for pressure die casting of aluminium and magnesium alloys. From the economic point of view, the operation life of dies is extremely important to the price of the castings. Operational life can be successfully extended by a regular maintenance of die parts. Laser surfacing is a very promising process for rebuilding of worn out surfaces of vital die parts. In this research, the state in the maraging steel 1.2799 (DIN) after the application of laser surfacing process has been analysed using scanning electron microscope. The analysis revealed diverse microstructure through-depth of the laser-surfaced specimens. On the basis of the estimated size and volume fraction of the nano-precipitates in the individual microstructure zones located through-depth of the heat-affected zone, a through-depth variation of microhardness was predicted. The results are supported by Vickers microhardness tests. It was confirmed that the mechanical properties of the 1.2799 maraging steel strongly depend on the characteristic at the nano or micro level. Some of the results obtained can be also applied to laser surface heat treatment of maraging steels.

  1. Analysis of the release characteristics of cu-treated antimicrobial implant surfaces using atomic absorption spectrometry.

    PubMed

    Zietz, Carmen; Fritsche, Andreas; Finke, Birgit; Stranak, Vitezslav; Haenle, Maximilian; Hippler, Rainer; Mittelmeier, Wolfram; Bader, Rainer

    2012-01-01

    New developments of antimicrobial implant surfaces doped with copper (Cu) ions may minimize the risk of implant-associated infections. However, experimental evaluation of the Cu release is influenced by various test parameters. The aim of our study was to evaluate the Cu release characteristics in vitro according to the storage fluid and surface roughness. Plasma immersion ion implantation of Cu (Cu-PIII) and pulsed magnetron sputtering process of a titanium copper film (Ti-Cu) were applied to titanium alloy (Ti6Al4V) samples with different surface finishing of the implant material (polished, hydroxyapatite and corundum blasted). The samples were submersed into either double-distilled water, human serum, or cell culture medium. Subsequently, the Cu concentration in the supernatant was measured using atomic absorption spectrometry. The test fluid as well as the surface roughness can alter the Cu release significantly, whereby the highest Cu release was determined for samples with corundum-blasted surfaces stored in cell medium. PMID:22162672

  2. In situ X-ray Photoemission Spectroscopy Analysis of Aromatic Polyester Surface Treated with Argon Plasma

    NASA Astrophysics Data System (ADS)

    Narushima, Kazuo; Okamoto, Nanami

    2013-10-01

    Effects of surface modification treatment by argon plasma processing of two types of aromatic polyester, poly(ethylene terephthalate) (PET) and poly(oxybenzonate-co-oxynaphthoate) (POCO), were investigated. This paper presents a description of our experiment and a discussion of the surface modification mechanism, which uses a simple and inexpensive procedure to conduct analysis without breaking vacuum after plasma processing. In situ analysis of the chemical composition of a polymer surface was attempted without exposing the sample to air after argon plasma processing. In particular, the respective actions of each active species were investigated for electrons and ions in argon plasma. Electrons and ions in argon plasma break some polymer bonds. Specifically, ester groups are broken and oxygen atoms are kicked out in PET and POCO. No oxygen functional group is formed after argon plasma processing, but such groups are formed if the sample is exposed to air.

  3. The research on the interfacial compatibility of polypropylene composite filled with surface treated carbon fiber

    NASA Astrophysics Data System (ADS)

    Li, J.

    2009-07-01

    Dielectric barrier discharges (DBD) in ambient air are used on carbon fiber to improve the fiber surface activity. Carbon fibers with length of 75 μm are placed into the plasma configuration. The interaction between modified carbon fibers and polypropylene (PP) was studied by three-point bending (TPB) test. The chemical changes induced by the treatments on carbon fiber surface are examined using X-ray photoelectron spectroscopy (XPS). XPS results reveal that the carbon fiber modified with the DBD at atmospheric pressure show a significant increase in oxygen and nitrogen concentration. These results demonstrate that the surface of the carbon fiber is more active and hydrophilic after plasma treatments using a DBD operating in ambient air.

  4. Analysis of cell surface alterations in Legionella pneumophila cells treated with human apolipoprotein E.

    PubMed

    Palusinska-Szysz, Marta; Zdybicka-Barabas, Agnieszka; Cytryńska, Małgorzata; Wdowiak-Wróbel, Sylwia; Chmiel, Elżbieta; Gruszecki, Wiesław I

    2015-03-01

    Binding of human apolipoprotein E (apoE) to Legionella pneumophila lipopolysaccharide was analysed at the molecular level by Fourier-transform infrared spectroscopy, thereby providing biophysical evidence for apoE-L. pneumophila lipopolysaccharide interaction. Atomic force microscopy imaging of apoE-exposed L. pneumophila cells revealed alterations in the bacterial cell surface topography and nanomechanical properties in comparison with control bacteria. The changes induced by apoE binding to lipopolysaccharide on the surface of L. pneumophila cells may participate in: (1) impeding the penetration of host cells by the bacteria; (2) suppression of pathogen intracellular growth and eventually; and (3) inhibition of the development of infection. PMID:25176171

  5. Treated wastewater effluent as a source of microbial pollution of surface water resources.

    PubMed

    Naidoo, Shalinee; Olaniran, Ademola O

    2014-01-01

    Since 1990, more than 1.8 billion people have gained access to potable water and improved sanitation worldwide. Whilst this represents a vital step towards improving global health and well-being, accelerated population growth coupled with rapid urbanization has further strained existing water supplies. Whilst South Africa aims at spending 0.5% of its GDP on improving sanitation, additional factors such as hydrological variability and growing agricultural needs have further increased dependence on this finite resource. Increasing pressure on existing wastewater treatment plants has led to the discharge of inadequately treated effluent, reinforcing the need to improve and adopt more stringent methods for monitoring discharged effluent and surrounding water sources. This review provides an overview of the relative efficiencies of the different steps involved in wastewater treatment as well as the commonly detected microbial indicators with their associated health implications. In addition, it highlights the need to enforce more stringent measures to ensure compliance of treated effluent quality to the existing guidelines. PMID:24366046

  6. Treated Wastewater Effluent as a Source of Microbial Pollution of Surface Water Resources

    PubMed Central

    Naidoo, Shalinee; Olaniran, Ademola O.

    2013-01-01

    Since 1990, more than 1.8 billion people have gained access to potable water and improved sanitation worldwide. Whilst this represents a vital step towards improving global health and well-being, accelerated population growth coupled with rapid urbanization has further strained existing water supplies. Whilst South Africa aims at spending 0.5% of its GDP on improving sanitation, additional factors such as hydrological variability and growing agricultural needs have further increased dependence on this finite resource. Increasing pressure on existing wastewater treatment plants has led to the discharge of inadequately treated effluent, reinforcing the need to improve and adopt more stringent methods for monitoring discharged effluent and surrounding water sources. This review provides an overview of the relative efficiencies of the different steps involved in wastewater treatment as well as the commonly detected microbial indicators with their associated health implications. In addition, it highlights the need to enforce more stringent measures to ensure compliance of treated effluent quality to the existing guidelines. PMID:24366046

  7. Electrical characteristics of TMAH-surface treated Ni/Au/Al2O3/GaN MIS Schottky structures

    NASA Astrophysics Data System (ADS)

    Reddy, M. Siva Pratap; Lee, Jung-Hee; Jang, Ja-Soon

    2014-03-01

    The electrical characteristics and reverse leakage mechanisms of tetramethylammonium hydroxide (TMAH) surface-treated Ni/Au/Al2O3/GaN metal-insulator-semiconductor (MIS) diodes were investigated by using the current-voltage ( I-V) and capacitance-voltage ( C-V) characteristics. The MIS diode was formed on n-GaN after etching the AlGaN in the AlGaN/GaN heterostructures. The TMAH-treated MIS diode showed better Schottky characteristics with a lower ideality factor, higher barrier height and lower reverse leakage current compared to the TMAH-free MIS diode. In addition, the TMAH-free MIS diodes exhibited a transition from Poole-Frenkel emission at low voltages to Schottky emission at high voltages, whereas the TMAH-treated MIS diodes showed Schottky emission over the entire voltage range. Reasonable mechanisms for the improved device-performance characteristics in the TMAH-treated MIS diode are discussed in terms of the decreased interface state density or traps associated with an oxide material and the reduced tunneling probability.

  8. Montmorillonite Clay-Catalyzed Synthesis of RNA Oligomers

    NASA Astrophysics Data System (ADS)

    Ferris, J. P.; Miyakawa, S.; Huang, W.; Joshi, P.

    2005-12-01

    It is proposed that catalysis had a central role in the origins of life. This will be illustrated using the montmorillonite clay-catalyzed synthesis of oligomers of RNA from activated monomers, (Ferris and Ertem, 1993) a possible step in the origin of the RNA world (Ferris, 2005). Structural analysis of oligomers formed in the reaction of the activated monomer of 5'-AMP with that of 5'-CMP demonstrated that the oligomers formed were not produced by random synthesis but rather the sequences observed were directed by the montmorillonite catalyst (Miyakawa and Ferris, 2003). RNA oligomers containing up to 40 mers have been synthesized in reactions performed in water at 25 oC in the presence of montmorillonite (Huang and Ferris, 2003). Analysis of the structure elements in these oligomers from the 7 to 39 mers showed that they did not vary. Reaction of D, L-mixtures of the activated monomers of A and U resulted in the formation of greater amounts of the homochiral amounts of dimers and trimers of A than would be expected if there was no selectivity in the reaction. A limited number of the dimers and trimers of U were also formed but here the selectivity was for the formation of an excess of heterochiral products (Joshi et al., 2000). A postulate that explains why homochiral trimers of U are not formed and the significance of catalysis in prebiotic synthesis will be discussed. Ferris, J.P. (2005) Origins of life, molecular basis of. In R.A. Meyers, Ed. Encyclopedia of Molecular Cell Biology and Molecular Medicine, 10. Wiley-VCH Verlag, Weinheim, Germany. Ferris, J.P., and Ertem, G. (1993) Montmorillonite catalysis of RNA oligomer formation in aqueous solution. A model for the prebiotic formation of RNA. J. Am. Chem. Soc., 115, 12270-12275. Huang, W., and Ferris, J.P. (2003) Synthesis of 35-40 mers of RNA oligomers from unblocked monomers. A simple approach to the RNA world. Chem. Commun., 1458-1459. Joshi, P.C., Pitsch, S., and Ferris, J.P. (2000) Homochiral selection in the montmorillonite-catalyzed and uncatalyzed prebiotic synthesis of RNA. Chem. Commun., 2497-2498. Miyakawa, S., and Ferris, J.P. (2003) Sequence- and Regioselectivity in the montmorillonite-catalyzed synthesis of RNA. J. Am. Chem. Soc., 125, 8202-8208.

  9. Characterization of plasma treated surfaces for food safety by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Sulovská, Kateřina; Lehocký, Marián.

    2014-10-01

    A physico-chemical approach to modify surfaces not only for use in medicine, but also for preservation of food is nowadays widely studied to lower the risks of increased number of bacterial pathogens that are in a direct contact with people. Food safety is very important part of preserving sustainability during crises, especially after the enterohaemorrhagic Escherichia coli outbreak in Europe in 2011. One of the possibility how we can protect food against various pathogens is the modification of packing materials that are directly in contact with preserved food. This contribution deals with the characterization of modified surfaces with antibacterial properties via Terahertz spectroscopy. For the purpose of this paper, three monomers were used for grafting onto air radiofrequency plasma activated low density polyethylene surface, which created a brush-like structure. Next, the antibacterial agents, Irgasan and Chlorhexidine, were anchored to these surfaces. These antibacterial agents were selected for supposed effect on two most frequently occurring bacterial strains - Escherichia coli and Staphylococcus aureus. Materials were further tested for the presence of antibacterial agent molecules, in our case by means of terahertz spectroscopy. Each material was tested on two spectroscopes - the SPECTRA and the OSCAT terahertz instruments.

  10. Survival-rate analysis of surface treated dental zirconia (Y-TZP) ceramics.

    PubMed

    Oblak, Cedomir; Verdenik, Ivan; Swain, Michael V; Kosmac, Tomaz

    2014-10-01

    The role of surface preparation, hydrothermal ageing exposure and subsequent cyclic fatigue testing on the biaxial strength of a dental Y-TZP material are investigated. The initial strength and survival rate of a dental Y-TZP ceramic material to fatigue testing was found to be highly dependent upon surface preparation more so than exposure to various hydrothermal exposure conditions. The results suggest that the monoclinic phase generated by either surface damage (especially sandblasting) and to a lesser extent hydrothermal exposure does appear to mitigate strength and fatigue degradation. The results are discussed in terms of the size of defects generated following various surface treatments and the role of cyclic fatigue induced crack growth. A critical ratio is established between the monotonic strength and fatigue stress survival. From the specimens that failed and exhibited reduced strength after cycling a plot of averaged crack growth rate versus max cyclic stress intensity factor was established which closely matched existing results for Y-TZP ceramics. PMID:24781534

  11. Surface Functionalization of Plasma Treated Ultrananocrystalline Diamond/Amorphous Carbon Composite Films

    NASA Astrophysics Data System (ADS)

    Koch, Hermann; Popov, Cyril; Kulisch, Wilhelm; Spassov, G.; Reithmaier, Johann Peter

    Diamond possesses a number of outstanding properties which make it a perspective material as platform for preparation of biosensors. The diamond surface needs to be activated before the chemical attachment of crosslinkers with which biomolecules can interact. In the current work we have investigated the modification of ultrananocrystalline diamond/amorphous carbon (UNCD/a-C) films by oxygen and ammonia plasmas. Afterwards the layers were functionalized in a further step to obtain thiol-active maleimide groups on the surface. We studied the possibility for direct binding of maleimide to terminal OH-groups on the UNCD surface and for silanization with 3-aminopropyltriethoxysilane (APTES) to obtain NH2-groups for the following attachment of sulfosuccinimidyl 4-(N-maleimidomethyl)-cyclohexane-1-carboxylate (SSMCC). The thiol-bearing fluorescein-related dye 5-((2-(and-3)-S-(acetylmercapto) succinoyl) amino) fluorescein (SAMSA) was immobilized as an model biomolecule to evaluate the achieved thiol-activity by fluorescence microscopy. The results of the above mentioned surface modification and functionalization steps were investigated by Auger electron spectroscopy (AES) and contact angle measurements.

  12. Radionuclide desorption kinetics on synthetic Zn/Ni-labeled montmorillonite nanoparticles

    NASA Astrophysics Data System (ADS)

    Huber, F. M.; Heck, S.; Truche, L.; Bouby, M.; Brendlé, J.; Hoess, P.; Schäfer, T.

    2015-01-01

    Sorption/desorption kinetics for selected radionuclides (99Tc(VII), 232Th(IV), 233U(VI), 237Np(V), 242Pu and 243Am(III)) under Grimsel (Switzerland) ground water conditions (pH 9.7 and ionic strength of ∼1 mM) in the presence of synthetic Zn or Ni containing montmorillonite nanoparticles and granodiorite fracture filling material (FFM) from Grimsel were examined in batch studies. The structurally bound Zn or Ni in the octahedral sheet of the synthetic colloids rendered them suitable as colloid markers. Only a weak interaction of the montmorillonite colloids with the fracture filling material occurs over the experimental duration of 10,000 h (∼13 months). The tri- and tetravalent radionuclides are initially strongly associated with nanoparticles in contrast to 99Tc(VII), 233U(VI) and 237Np(V) which showed no sorption to the montmorillonite colloids. Radionuclide desorption of the nanoparticles followed by sorption to the fracture filling material is observed for 232Th(IV), 242Pu and 243Am(III). Based on the conceptual model that the driving force for the kinetically controlled radionuclide desorption from nanoparticles and subsequent association to the FFM is the excess in surface area offered by the FFM, the observed desorption kinetics are related to the colloid/FFM surface area ratio. The observed decrease in concentration of the redox sensitive elements 99Tc(VII), 233U(VI) and 237Np(V) may be explained by reduction to lower oxidation states in line with Eh-pH conditions prevailing in the experiments and thermodynamic considerations leading to (i) precipitation of a sparingly soluble phase, (ii) sorption to the fracture filling material, (iii) possible formation of eigencolloids and/or (iv) sorption to the montmorillonite colloids. Subsequent to the sorption/desorption kinetics study, an additional experiment was conducted investigating the potential remobilization of radionuclides/colloids attached to the FFM used in the sorption/desorption kinetic experiments by contacting this FFM with pure Grimsel groundwater for 7 days. A positive correlation of 242Pu, 232Th(IV) and 237Np was observed with the Zn and Ni concentrations in the desorption experiments indicating a remobilization of sorbed montmorillonite colloids. The results of the study in hand highlight (i) the novel use of structural labeled colloids to decrease the uncertainties in the determination of nanoparticle attachment providing more confidence in the derived radionuclide desorption rates. Moreover, the data illustrate (ii) the importance of radionuclide colloid desorption to be considered in the analysis and application of colloid facilitated transport both in laboratory or in-situ experiments and numerical model simulations and (iii) a possible remobilization of sorbed colloids and associated radionuclides by desorption from the matrix material (FFM) under non-equilibrium conditions. the characterization of the properties of these synthetic Ni/Zn-clay colloids by various analytical methods, to decrease the uncertainty in the determination of the nanoparticle attachment behavior in the experiments by evaluating the appropriateness of the colloid labeling technique of natural clays, to compare newly obtained radionuclide sorption/desorption kinetics using the synthetic colloids in the presence of Grimsel fracture filling material in comparison to FEBEX bentonite nanoparticles, to observe a possible radionuclide/colloid remobilization subsequent to the sorption experiments.

  13. The performance of chitosan/montmorillonite nanocomposite during the flocculation and floc storage processes of Microcystis aeruginosa cells.

    PubMed

    Wang, Zhiyuan; Wang, Chao; Wang, Peifang; Qian, Jin; Hou, Jun; Ao, Yanhui; Wu, Baohai

    2015-07-01

    This study aimed to investigate the performance of chitosan-modified nano-sized montmorillonite (CTS/NMMT) during the flocculation of Microcystis aeruginosa (MA). The release of intracellular microcystins (MCs) caused by the damage of intact MA cells during the flocculation and floc storage processes was also comprehensively evaluated through scanning electron microscopy (SEM) and measurement of K(+) and Mg(2+) release. With the application of the Box-Behnken experimental design combined with response surface methodology, the quadratic statistical model was established to predict and optimize the interactive effects of content of CTS/NMMT, weight ratio of NMMT to CTS, and agitation time on the removal efficiency of MA cells. A maximum removal of 94.7 % MA cells was observed with content of CTS/NMMT 300-320 mg L(-1), weight ratio of NMMT to CTS 14-16, and agitation time 16-50 min. During the flocculation process, CTS/NMMT aggregated MA cells as flocs and served as a protection shield for cells. The extracellular and intracellular microcystin-leucine-arginine (MC-LR) decreased remarkably and the yield of intracellular MC-LR showed a decreasing trend during the flocculation. The cell integrity was slightly damaged by the mechanical actions rather than by the flocculant. During the floc storage process, cell lysis and membrane damage were remarkably aggravated. The noticeable increase of K(+) and Mg(2+) release indicated that CTS/NMMT damaged the integrity of most MA cells in the flocs and liberated the intracellular MC-LR. Meanwhile, NMMT and CTS polymers assisted the adsorptive removal of extracellular MC-LR released to water. The flocs should be timely treated within 12 h to prevent the leakage of MCs. PMID:25940464

  14. Bond strengths of a self-etching adhesive to dentin surfaces treated with saliva, blood, and different hemostatic agents.

    PubMed

    Unlu, Nimet; Cebe, Fatma; Cebe, Mehmet Ata; Cetin, Ali Riza; Cobanoglu, Nevin

    2015-01-01

    The aim of this study was to evaluate the microtensile bond strengths of a self-etching adhesive to dentin surfaces after treatment with 4 different hemostatic agents in the presence of saliva and blood. After testing, no significant differences were found between the mean bond strength of Clearfil SE (CSE) Bond resin adhesive to normal dentin and those of CSE to dentin treated with the hemostatic agents ViscoStat Clear, Astringedent, or Astringedent X (P > 0.05). However, the mean bond strength of CSE Bond to dentin treated with Ankaferd Blood Stopper (ABS) was significantly greater than those of the other groups (P < 0.05). Thus, while 3 of the tested hemostatic agents did not have significant effects on the bond strength of composite resin to dentin, ABS increased the bond strength of CSE Bond to dentin. PMID:26147164

  15. Surface Remelting Treated High Velocity arc Sprayed FeNiCrAlBRE Coating by Tungsten Inert Gas

    NASA Astrophysics Data System (ADS)

    Tian, H. L.; Wei, S. C.; Chen, Y. X.; Tong, H.; Liu, Y.; Xu, B. S.

    This study aims at evaluating the effect of the TIG (Tungsten Inert Gas) remelting treatment of self-fluxing FeNiCrAlBRE alloy coatings, formed by means of high velocity arc spraying on steel surfaces. The treated and untreated samples were subjected to comparative structural examination using scanning electron microscopes. For quantitative investigation of porosity, a computer image analyser was used. Additionally, the wear resistance and wear volume loss of the worn tracks before and after the remelting process were contrastively evaluated in details. After the sprayed coatings were treated by TIG remelting in a proper conditions, the microstructure examination of the remelted coatings showed that a change of the microstructure from lamellar to cellular structure. Also, the results show that the remelting process decrease the coating defects and make the coating more wearable.

  16. Thermal Characteristics of ThermoBrachytherapy Surface Applicators (TBSA) for Treating Chestwall Recurrence

    PubMed Central

    Arunachalam, K.; Maccarini, P. F.; Craciunescu, O. I.; Schlorff, J. L.; Stauffer, P. R.

    2010-01-01

    Purpose To study temperature and thermal dose distributions of ThermoBrachytherapy Surface Applicators (TBSA) developed for concurrent or sequential high dose rate (HDR) brachytherapy and microwave hyperthermia treatment of chest wall recurrence and other superficial disease. Methods A steady state thermodynamics model coupled with the fluid dynamics of water bolus and electromagnetic radiation of hyperthermia applicator is used to characterize the temperature distributions achievable with TBSA applicators in an elliptical phantom model of the human torso. Power deposited by 915 MHz conformal microwave array (CMA) applicators is used to assess the specific absorption rate (SAR) distributions of rectangular (500 cm2) and L-shaped (875 cm2) TBSA. The SAR distribution in tissue and fluid flow distribution inside the Dual-Input Dual-Output (DIDO) water bolus are coupled to solve the steady state temperature and thermal dose distributions of rectangular TBSA (R-TBSA) for superficial tumor targets extending 1015 mm beneath the skin surface. Thermal simulations are carried out for a range of bolus inlet temperature (Tb=3843C), water flow rate (Qb=24 L/min) and tumor blood perfusion (?b=25 kg/m3/s) to characterize their influence on thermal dosimetry. Results Steady state SAR patterns of R- and L-TBSA demonstrate the ability to produce conformal and localized power deposition inside tumor target sparing surrounding normal tissues and nearby critical organs. Acceptably low variation in tissue surface cooling and surface temperature homogeneity was observed for the new DIDO bolus at 2 L/min water flow rate. Temperature depth profiles and thermal dose volume histograms indicate bolus inlet temperature (Tb) to be the most influential factor on thermal dosimetry. A 42 C water bolus was observed to be the optimal choice for superficial tumors extending 1015 mm from the surface even under significant blood perfusion. Lower bolus temperature may be chosen to reduce thermal enhancement ratio (TER) in the most sensitive skin where maximum radiation dose is delivered and to extend thermal enhancement of radiation dose deeper. Conclusion This computational study indicates that well-localized elevation of tumor target temperature to 4044 C can be accomplished by large surface-conforming TBSA applicators using appropriate selection of coupling bolus temperature. PMID:20224154

  17. Thermal characteristics of thermobrachytherapy surface applicators for treating chest wall recurrence

    NASA Astrophysics Data System (ADS)

    Arunachalam, K.; Maccarini, P. F.; Craciunescu, O. I.; Schlorff, J. L.; Stauffer, P. R.

    2010-04-01

    The aim of this study was to investigate temperature and thermal dose distributions of thermobrachytherapy surface applicators (TBSAs) developed for concurrent or sequential high dose rate (HDR) brachytherapy and microwave hyperthermia treatment of chest wall recurrence and other superficial diseases. A steady-state thermodynamics model coupled with the fluid dynamics of a water bolus and electromagnetic radiation of the hyperthermia applicator is used to characterize the temperature distributions achievable with TBSAs in an elliptical phantom model of the human torso. Power deposited by 915 MHz conformal microwave array (CMA) applicators is used to assess the specific absorption rate (SAR) distributions of rectangular (500 cm2) and L-shaped (875 cm2) TBSAs. The SAR distribution in tissue and fluid flow distribution inside the dual-input dual-output (DIDO) water bolus are coupled to solve the steady-state temperature and thermal dose distributions of the rectangular TBSA (R-TBSA) for superficial tumor targets extending 10-15 mm beneath the skin surface. Thermal simulations are carried out for a range of bolus inlet temperature (Tb = 38-43 C), water flow rate (Qb = 2-4 L min-1) and tumor blood perfusion (?b = 2-5 kg m-3 s-1) to characterize their influence on thermal dosimetry. Steady-state SAR patterns of the R- and L-TBSA demonstrate the ability to produce conformal and localized power deposition inside the tumor target sparing surrounding normal tissues and nearby critical organs. Acceptably low variation in tissue surface cooling and surface temperature homogeneity was observed for the new DIDO bolus at a 2 L min-1 water flow rate. Temperature depth profiles and thermal dose volume histograms indicate bolus inlet temperature (Tb) to be the most influential factor on thermal dosimetry. A 42 C water bolus was observed to be the optimal choice for superficial tumors extending 10-15 mm from the surface even under significant blood perfusion. Lower bolus temperature may be chosen to reduce the thermal enhancement ratio (TER) in the most sensitive skin where maximum radiation dose is delivered and to extend the thermal enhancement of radiation dose deeper. This computational study indicates that well-localized elevation of tumor target temperature to 40-44 C can be accomplished by large surface-conforming TBSAs using appropriate selection of coupling bolus temperature.

  18. Stability and pH-independence of nano-zero-valent iron intercalated montmorillonite and its application on Cr(VI) removal.

    PubMed

    Wu, Limei; Liao, Libing; Lv, Guocheng; Qin, Faxiang

    2015-08-01

    Composite of nano-zero-valent iron and montmorillonite (NZVI/MMT) was prepared by inserting NZVI into the interlayer of montmorillonite. The unique structure montmorillonite with isolated exchangeable Fe(III) cations residing near the sites of structural negative charges inhibited the agglomeration of ZVI and result in the formation of ZVI particles in the montmorillonite interlayer regions. NZVI/MMT was demonstrated to possess large specific surface area and outstanding reducibility that encourage rapid and stable reaction with Cr (VI). Besides, the intercalation also makes NZVI well dispersed and more stable in the interlayer, thereby improving the reaction capacity by 16 times. The effects of pH value, initial concentration of Cr (VI) and reaction time on Cr (VI) removal have also been investigated in detail. According to PXRD and XPS characterization, NZVI/Cr (VI) redox reaction occurred in the interlayer of MMT. The study of NZVI/MMT is instrumental to the development of remediation technologies for persistent environmental contaminants. PMID:26011800

  19. Kinetic Analysis of Spontaneous Whisker Growth on Pre-treated Surfaces with Weak Oxide

    NASA Astrophysics Data System (ADS)

    Su, Chien-Hao; Chen, Hao; Lee, Hsin-Yi; Liu, Cheng Yi; Ku, Ching-Shun; Wu, Albert T.

    2014-09-01

    This study sought to clarify the relationship between cracks in surface oxide layers and the growth behavior of tin whiskers. The number, length, and total volume of extrusions were precisely calculated and residual stress was measured using synchrotron radiation x-ray diffractometry. The aim was to elucidate the influence of stress on the driving force and flux involved in atomic diffusion. The distance between weak spots was shown to be the most significant factor involved in the growth of whiskers. The results could explain why increasing the density of the surface weak spots could reduce the number of long whiskers. Measuring the dimensions of whiskers yielded a precise kinetic model capable of describing the migration of atoms to the root of whiskers, resulting in their spontaneous growth.

  20. Mg ion implantation on SLA-treated titanium surface and its effects on the behavior of mesenchymal stem cell.

    PubMed

    Kim, Beom-Su; Kim, Jin Seong; Park, Young Min; Choi, Bo-Young; Lee, Jun

    2013-04-01

    Magnesium (Mg) is one of the most important ions associated with bone osseointegration. The aim of this study was to evaluate the cellular effects of Mg implantation in titanium (Ti) surfaces treated with sand blast using large grit and acid etching (SLA). Mg ions were implanted into the surface via vacuum arc source ion implantation. The surface morphology, chemical properties, and the amount of Mg ion release were evaluated by scanning electron microscopy (SEM), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), and inductively coupled plasma-optical emission spectrometer (ICP-OES). Human mesenchymal stem cells (hMSCs) were used to evaluate cellular parameters such as proliferation, cytotoxicity, and adhesion morphology by MTS assay, live/dead assay, and SEM. Furthermore, osteoblast differentiation was determined on the basis of alkaline phosphatase (ALP) activity and the degree of calcium accumulation. In the Mg ion-implanted disk, 2.3×10(16) ions/cm(2) was retained. However, after Mg ion implantation, the surface morphology did not change. Implanted Mg ions were rapidly released during the first 7 days in vitro. The MTS assay, live/dead assay, and SEM demonstrated increased cell attachment and growth on the Mg ion-implanted surface. In particular, Mg ion implantation increased the initial cell adhesion, and in an osteoblast differentiation assay, ALP activity and calcium accumulation. These findings suggest that Mg ion implantation using the plasma source ion implantation (PSII) technique may be useful for SLA-treated Ti dental implants to improve their osseointegration capacity. PMID:23827608

  1. The adsorption and reaction of adenine nucleotides on montmorillonite

    NASA Technical Reports Server (NTRS)

    Ferris, James P.; Hagan, William J., Jr.

    1986-01-01

    The binding of AMP to Zn(2+)-montmorillonite is investigated in the presence of salts and Good's zwitterion buffers, PIPES and MES. The initial concentrations of nucleotide and the percent adsorbtion are used to calculate the adsorption isotherms, and the Langmuir adsorption equation is used for the analysis of data. The adsorption coefficient was found to be three times greater in the presence of 0.2 M PIPES than in its absence. In addition, basal spacings measured by X-ray diffraction were increased by the buffer. These results are interpreted in terms of a model in which the adsorption of AMP is mediated by a Zn(2+) complex of PIPES in different orientations in the interlamellar region of the montmorillonite. Mixed ligand complexes of this type are reminiscent of the complexes observed between metal ions and biological molecules in living systems.

  2. Novel hydrophilic carboxymethyl starch/montmorillonite nanocomposite films.

    PubMed

    Wilpiszewska, Katarzyna; Antosik, Adrian Krzysztof; Spychaj, Tadeusz

    2015-09-01

    Preparation of novel carboxymethyl starch (CMS)-based biodegradable films with calcium montmorillonite has been described. The biocomposites were obtained by casting method, glycerol and citric acid were used as plasticizer and crosslinking agent, respectively. The effect of calcium montmorillonite (MMT-Ca) on hydrophilicity (moisture absorption, solubility in water as well as contact angle measurements) was evaluated. Moreover, thermomechanical and mechanical properties of nanocomposites were determined. For all the systems tested intercalated structure of MMT-Ca was revealed, however the most efficient clay platelets dispersion was noted for film containing 5 wt.% MMT-Ca. Such biodegradable CMS/MMT-Ca films exhibiting relatively good mechanical properties could find application in controlled delivery systems as well as in agriculture for seed tapes production where hydrophilicity of polymer carrier is strongly advantageous. PMID:26005142

  3. Hydrophobic recovery of UV/ozone treated poly(dimethylsiloxane): adhesion studies by contact mechanics and mechanism of surface modification

    NASA Astrophysics Data System (ADS)

    Olh, Attila; Hillborg, Henrik; Vancso, G. Julius

    2005-01-01

    Silicone elastomers (Sylgard 184 and 170), based on poly(dimethylsiloxane) (PDMS), were surface treated by a combined exposure to UV and ozone. The effects of the treatments were analyzed as a function of time elapsed after stopping the treatments using different standard surface characterization techniques, such as water contact angle measurements, XPS and atomic force microscopy (AFM). However, the primary focus of this study was to apply the Johnson-Kendall-Roberts (JKR) contact mechanics approach to investigate PDMS samples prior to and following UV/ozone surface treatment. A gradual formation of a hydrophilic, silica-like surface layer with increasing modulus was observed with increasing UV/ozone exposure. A subsequent hydrophobic recovery after UV/ozone exposure was observed, as indicated by increasing contact angles. This supports the hypothesis that the hydrophobic recovery is mainly caused by the gradual coverage of a permanent silica-like structure with free siloxanes and/or reorientation of polar groups. PDMS containing a homogenously dispersed filler (Sylgard 184), exhibited a decreasing surface roughness (by AFM) when the oxidized surface region "collapsed" into a smooth SiO x layer (final surface roughness <2 nm). PDMS containing heterogeneously distributed, aggregated filler particles (Sylgard 170), exhibited an increasing surface roughness with treatment dose, which was attributed to the "collapse" of the oxidized surface region thus exposing the contours of the underlying filler aggregates (final surface roughness 140 nm). A dedicated device was designed and built to study the contact mechanics behavior of PDMS prior to, and following surface treatment. The value of the combined elastic modulus obtained for PDMS lens and semi-infinite flat surface system showed an increase in full agreement with the formation of a silica-like layer exhibiting a high elastic modulus (compared with untreated PDMS). The work of adhesion observed in JKR experiments exhibited an increasing trend as a function of treatment done in agreement with contact angle data. JKR experiments showed hydrophobic recovery behavior as anticipated from contact angle measurements. Single pull-off force measurements by JKR and numerical analysis of full-approach JKR curves were in quantitative agreement regarding practical work of adhesion values.

  4. Synthesis of silver/montmorillonite nanocomposites using γ-irradiation

    PubMed Central

    Shameli, Kamyar; Ahmad, Mansor Bin; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa; Gharayebi, Yadollah; Sedaghat, Sajjad

    2010-01-01

    Silver nanoparticles (Ag-NPs) were synthesized into the interlamellar space of montmorillonite (MMT) by using the γ-irradiation technique in the absence of any reducing agent or heat treatment. Silver nitrate and γ-irradiation were used as the silver precursor and physical reducing agent in MMT as a solid support. The MMT was suspended in the aqueous AgNO3 solution, and after the absorption of silver ions, Ag+ was reduced using the γ-irradiation technique. The properties of Ag/MMT nanocomposites and the diameters of Ag-NPs were studied as a function of γ-irradiation doses. The interlamellar space limited particle growth (d-spacing [ds] = 1.24–1.42 nm); powder X-ray diffraction and transmission electron microscopy (TEM) measurements showed the production of face-centered cubic Ag-NPs with a mean diameter of about 21.57–30.63 nm. Scanning electron microscopy images indicated that there were structure changes between the initial MMT and Ag/MMT nanocomposites under the increased doses of γ-irradiation. Furthermore, energy dispersive X-ray fluorescence spectra for the MMT and Ag/ MMT nanocomposites confirmed the presence of elemental compounds in MMT and Ag-NPs. The results from ultraviolet-visible spectroscopy and TEM demonstrated that increasing the γ-irradiation dose enhanced the concentration of Ag-NPs. In addition, the particle size of the Ag-NPs gradually increased from 1 to 20 kGy. When the γ-irradiation dose increased from 20 to 40 kGy, the particle diameters decreased suddenly as a result of the induced fragmentation of Ag-NPs. Thus, Fourier transform infrared spectroscopy suggested that the interactions between Ag-NPs with the surface of MMT were weak due to the presence of van der Waals interactions. The synthesized Ag/MMT suspension was found to be stable over a long period of time (ie, more than 3 months) without any sign of precipitation. PMID:21170354

  5. Synthesis and Characterization of palladium crystallites intercalated in montmorillonite

    SciTech Connect

    Crocker, M.; Buglass, J.G.; Herold, R.H.M. )

    1993-01-01

    Reduction of electrophilic Pd(II) complexes intercalated in montmorillonite under mild conditions (0[degrees]C in MeOH) has been shown to afford highly despersed metallic palladium, located mainly in the interlamellar regions of the clay. Transmission electron microscopy reveals an unusual platelet morphology for the interlammellar metal particles, suggesting that the clay structure may impose a kinetic constraint on the attainment of a thermodynamically more favorable spherical morphology. 15 refs., 3 figs., 2 tabs.

  6. Surface-treated carbon electrodes with modified potential of zero charge for capacitive deionization.

    PubMed

    Wu, Tingting; Wang, Gang; Zhan, Fei; Dong, Qiang; Ren, Qidi; Wang, Jianren; Qiu, Jieshan

    2016-04-15

    The potential of zero charge (Epzc) of electrodes can greatly influence the salt removal capacity, charge efficiency and cyclic stability of capacitive deionization (CDI). Thus optimizing the Epzc of CDI electrodes is of great importance. A simple strategy to negatively shift the Epzc of CDI electrodes by modifying commercial activated carbon with quaternized poly (4-vinylpyridine) (AC-QPVP) is reported in this work. The Epzc of the prepared AC-QPVP composite electrode is as negative as -0.745 V vs. Ag/AgCl. Benefiting from the optimized Epzc of electrodes, the asymmetric CDI cell which consists of the AC-QPVP electrode and a nitric acid treated activated carbon (AC-HNO3) electrode exhibits excellent CDI performance. For inverted CDI, the working potential window of the asymmetric CDI cell can reach 1.4 V, and its salt removal capacity can be as high as 9.6 mg/g. For extended voltage CDI, the salt removal capacity of the asymmetric CDI cell at 1.2/-1.2 V is 20.6 mg/g, which is comparable to that of membrane CDI using pristine activated carbon as the electrodes (19.5 mg/g). The present work provides a simple method to prepare highly positively charged CDI electrodes and may pave the way for the development of high-performance CDI cells. PMID:26878480

  7. Evidence of irreversible CO2 intercalation in montmorillonite

    SciTech Connect

    Romanov, V

    2013-02-13

    Mitigation of the global climate change via sequestration of anthropogenic carbon dioxide (CO2) in geologic formations requires assessment of the reservoir storage capacity and cap rock seal integrity. The typical cap rock is shale or mudstone rich in clay minerals that may significantly affect the effectiveness of the CO2 trapping. Specific objectives of this study were to conduct experimental investigation into the processes associated with CO2 and H2O trapped in swelling clay, namely, Wyoming and Texas montmorillonite powder. Combined (same-sample) multi-technique data ? manometric sorption isotherm hysteresis, diffuse reflectance infrared spectroscopy ?trapped CO2? fingerprints, irreversible X-ray diffraction patterns for the clay interlayer in intermediate hydration state, and HF acid digestion resulting in formation of non-extractable F:CO2 adducts ? corroborate a hypothesis that carbon dioxide molecules can be irreversibly trapped via anomalous extreme confinement in the galleries associated with montmorillonite interlayer, which may result in formation of carbonates in the longer term. Validation on Arizona montmorillonite lumps substantiated the evidence that such processes may occur in natural clay deposits but possibly on a different scale and at a different rate.

  8. Sulfometuron incorporation in cationic micelles adsorbed on montmorillonite.

    PubMed

    Mishael, Yael Golda; Undabeytia, Tomas; Rytwo, Giora; Papahadjopoulos-Sternberg, Brigitte; Rubin, Baruch; Nir, Shlomo

    2002-05-01

    The aim of this study was to understand the interactions between alkylammonium cations present as monomers and micelles and a clay mineral, montmorillonite, to develop slow release formulations of anionic herbicides, such as sulfometuron (SFM) whose leaching in soils is an environmental and economic problem. In the proposed formulation the herbicide is incorporated in positively charged micelles of quaternary amine cations, which in turn adsorb on the negatively charged clay. The adsorption of hexadecyltrimethylammonium (HDTMA) and octadecyltrimethylammonium (ODTMA) on montmorillonite was studied above and below their critical micelle concentrations (CMC). At concentrations above the CMC, the loading exceeded the clay's cation exchange capacity (CEC) and indicated higher affinity of the cation with the longer alkyl chain. An adsorption model could adequately simulate adsorption at concentrations below the CMC, and yield fair predictions for the effect of ionic strength. The model indicated that above the CMC adsorbed micelles contributed significantly to the amount of ODTMA adsorbed. Evidence for adsorption of ODTMA micelles on montmorillonite was provided by X-ray diffraction, freeze-fracture electron microscopy, and dialysis bag measurements. SFM was not adsorbed directly on the clay mineral, and adsorbed at low levels, when the organic cation was adsorbed as monomers. In contrast, a large fraction of SFM adsorbed on the clay mineral when incorporated in micelles that adsorbed on the clay. PMID:11982411

  9. Iron-montmorillonite - A spectral analog of Martian soil

    NASA Technical Reports Server (NTRS)

    Banin, A.; Margulies, L.; Chen, Y.

    1985-01-01

    Spectral data for smectite clays, particularly for montmorillonite, which contain various adsorbed ions and are measured in the UV, VIS, and NIR ranges are analyzed and compared with Martian soil and dust spectra. It is shown that the structural octahedral iron in smectite clays affects their light absorbance in the UV at 240-260 nm, which results from an O(2-) to Fe(3+) charge transfer, similar to one observed in the Martian spectrum. Adsorbed iron affects, via crystal field absorptions, the reflectance of montmorillonite in the VIS and NIR ranges, resulting in stronger absorption and higher opacity in the range 0.40-0.65 micron. Both in spectral contrast and presence of (or lack of) spectral features, the Fe-montmorillonite spectra in the VIS and NIR are in reasonable agreement with the Martian spectrum. It is found that the spectral characteristics of iron-saturated smectite clays cannot be used to preclude the presence of clays in Martian soils and dust.

  10. Spectroscopic ellipsometric and Raman spectroscopic investigations of pulsed laser treated glassy carbon surfaces

    NASA Astrophysics Data System (ADS)

    Csontos, J.; Ppa, Z.; Grdin, A.; Fle, M.; Budai, J.; Toth, Z.

    2015-05-01

    In this study spectroscopic ellipsometry (SE) and Raman spectroscopy are applied to study structural modification of glassy carbon, due to high intensity laser ablation. Two KrF lasers with different pulse durations (480 fs and 18 ns), an ArF (20 ns), and a frequency doubled Nd:YAG laser (8 ns) were applied to irradiate the surface of glassy carbon targets. The main characteristics of the different laser treatments are compared by introducing the volumetric fluence which takes into account the different absorption values at different wavelengths. SE showed the appearance of a modified layer on the ablated surfaces. In the case of the ns lasers the thickness of this layer was in the range of 10-60 nm, while in the case of fs laser it was less than 20 nm. In all cases the average refractive index (n) of the modified layers slightly decreased compared to the refractive index of glassy carbon. Increase in extinction coefficient (k) was observed in the cases of ArF and fs KrF laser treatment, while the k values decreased significantly in the cases of nanosecond pulse duration KrF and Nd:YAG laser treatments. In the Raman spectra of the ablated areas the characteristic D and G peaks were widened due to appearance of an amorphous phase. Both Raman spectroscopy and SE indicate that the irradiated areas show carbon nanoparticle formation in all cases.

  11. Corrosion behavior of surface treated steel in liquid sodium negative electrode of liquid metal battery

    NASA Astrophysics Data System (ADS)

    Lee, Jeonghyeon; Shin, Sang Hun; Lee, Jung Ki; Choi, Sungyeol; Kim, Ji Hyun

    2016-03-01

    While liquid metal batteries are attractive options for grid-scale energy storage applications as they have flexible siting capacities and small footprints, the compatibility between structural materials such as current collectors and negative electrode such as sodium is one of major issues for liquid metal batteries. Non-metallic elements such as carbon, oxygen, and nitrogen in the liquid sodium influence the material behaviors of the cell construction materials in the battery system. In this study, the compatibility of structural materials with sodium is investigated in high temperature liquid sodium, and electrochemical impedance spectroscopy (EIS) is used to monitor in-situ the corrosion behavior at the surface of materials in sodium. Chemical vapor deposition (CVD) coatings of SiC and Si3N4 are applied as protective barriers against dissolution and corrosion on the steel surface. The results show that CVD coating of Si compounds can delay corrosion of steel in high temperature liquid sodium comparing to the result of as-received specimens, while SiC coating is more durable than Si3N4 coating in high temperature liquid sodium.

  12. Deformable Surface Model for the Evaluation of Abdominal Aortic Aneurysms Treated with an Endovascular Sealing System.

    PubMed

    Casciaro, Mariano E; El-Batti, Salma; Chironi, Gilles; Simon, Alain; Mousseaux, Elie; Armentano, Ricardo L; Alsac, Jean-Marc; Craiem, Damian

    2016-05-01

    Rupture of abdominal aortic aneurysms (AAA) is responsible for 1-3% of all deaths among the elderly population in developed countries. A novel endograft proposes an endovascular aneurysm sealing (EVAS) system that isolates the aneurysm wall from blood flow using a polymer-filled endobag that surrounds two balloon-expandable stents. The volume of injected polymer is determined by monitoring the endobag pressure but the final AAA expansion remains unknown. We conceived and developed a fully deformable surface model for the comparison of pre-operative sac lumen size and final endobag size (measured using a follow-up scan) with the volume of injected polymer. Computed tomography images were acquired for eight patients. Aneurysms were manually and automatically segmented twice by the same observer. The injected polymer volume resulted 9% higher than the aneurysm pre-operative lumen size (p < 0.05), and 11% lower than the final follow-up endobag volume (p < 0.01). The automated method required minimal user interaction; it was fast and used a single set of parameters for all subjects. Intra-observer and manual vs. automated variability of measured volumes were 0.35 ± 2.11 and 0.07 ± 3.04 mL, respectively. Deformable surface models were used to quantify AAA size and showed that EVAS system devices tended to expand the sac lumen size. PMID:26350505

  13. Corrosion resistance, surface mechanical properties, and cytocompatibility of plasma immersion ion implantation-treated nickel-titanium shape memory alloys.

    PubMed

    Yeung, K W K; Poon, R W Y; Liu, X Y; Ho, J P Y; Chung, C Y; Chu, P K; Lu, W W; Chan, D; Cheung, K M C

    2005-11-01

    Nickel-titanium shape memory alloys are promising materials in orthopedic applications because of their unique properties. However, for prolonged use in a human body, deterioration of the corrosion resistance of the materials becomes a critical issue because of the increasing possibility of deleterious ions released from the substrate to living tissues. We have investigated the use of nitrogen, acetylene, and oxygen plasma immersion ion implantation (PIII) to improve the corrosion resistance and mechanical properties of the materials. Our results reveal that the corrosion resistance and mechanical properties such as hardness and elastic modulus are significantly enhanced after surface treatment. The release of nickel is drastically reduced as compared with the untreated control. In addition, our in vitro tests show that the plasma-treated surfaces are well tolerated by osteoblasts. Among the three types of samples, the best biological effects are observed on the nitrogen PIII samples. PMID:16078209

  14. Enthalpy changes accompanying the collapse of montmorillonite layers and the penetration of electrolyte into interlayer space

    SciTech Connect

    Yan, L.; Low, P.F.; Roth, C.B.

    1996-09-25

    The enthalpy changes, {Delta}H, in suspensions of Li-, Na-, and K-montmorillonite were determined as functions of the molal concentrations of LiCl, NaCl, and KCl, respectively, by microcalorimetry. These changes were compared with the corresponding changes in interlayer distance, {lambda}, as determined by X-ray diffraction. It was found that {Delta}H values accompanying the collapse of the montmorillonite layers from {lambda} > 14 nm to {lambda} {approx_equal} 1.0 nm were essentially negligible; however, {Delta}H values accompanying the collapse of layers of Li- and Na-montmorillonite from {lambda} {approx_equal} 1.0 nm to {lambda} {approx_equal} 0.6 nm, and the collapse of layers of K-montmorillonite from {lambda} {approx_equal} 0.6 nm, were not negligible. No additional collapse of Li- and Na-montmorillonite layers occurred after {lambda} {approx_equal} 0.6 nm, and for K-montmorillonite layers after {lambda} {approx_equal} 0.3 nm, but {Delta}H continued to change with increasing salt addition. This change was attributed to the penetration of electrolyte into the interlayer space. A notable observation was that the value of {Delta}H was positive for Li-montmorillonite, but negative for Na- and K-montmorillonite. These observations were interpreted to mean that {Delta}H changes in the montmorillonite suspension were largely attributable to reorganization of the interlayer space by the added electrolytes.

  15. Voltammetric and impedance behaviours of surface-treated nano-crystalline diamond film electrodes

    NASA Astrophysics Data System (ADS)

    Liu, F. B.; Jing, B.; Cui, Y.; Di, J. J.; Qu, M.

    2015-04-01

    The electrochemical performances of hydrogen- and oxygen-terminated nano-crystalline diamond film electrodes were investigated by cyclic voltammetry and AC impedance spectroscopy. In addition, the surface morphologies, phase structures, and chemical states of the two diamond films were analysed by scanning probe microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results indicated that the potential window is narrower for the hydrogen-terminated nano-crystalline diamond film than for the oxygen-terminated one. The diamond film resistance and capacitance of oxygen-terminated diamond film are much larger than those of the hydrogen-terminated diamond film, and the polarization resistances and double-layer capacitance corresponding to oxygen-terminated diamond film are both one order of magnitude larger than those corresponding to the hydrogen-terminated diamond film. The electrochemical behaviours of the two diamond film electrodes are discussed.

  16. Voltammetric and impedance behaviours of surface-treated nano-crystalline diamond film electrodes

    SciTech Connect

    Liu, F. B.; Jing, B.; Cui, Y.; Di, J. J.; Qu, M.

    2015-04-15

    The electrochemical performances of hydrogen- and oxygen-terminated nano-crystalline diamond film electrodes were investigated by cyclic voltammetry and AC impedance spectroscopy. In addition, the surface morphologies, phase structures, and chemical states of the two diamond films were analysed by scanning probe microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results indicated that the potential window is narrower for the hydrogen-terminated nano-crystalline diamond film than for the oxygen-terminated one. The diamond film resistance and capacitance of oxygen-terminated diamond film are much larger than those of the hydrogen-terminated diamond film, and the polarization resistances and double-layer capacitance corresponding to oxygen-terminated diamond film are both one order of magnitude larger than those corresponding to the hydrogen-terminated diamond film. The electrochemical behaviours of the two diamond film electrodes are discussed.

  17. Surface modifications of some nanocomposites containing starch

    NASA Astrophysics Data System (ADS)

    Pascu, M.-C.; Popescu, M.-C.; Vasile, C.

    2008-09-01

    Polymer-layered silicate nanocomposites have attracted strong interest in today's materials research, due to the possible impressive enhancements of material properties, comparatively with those of pure polymers. Several starch/poly(vinylalcohol)/montmorillonite nanocomposites have been subjected to surface modification by physical treatments such as dielectric barrier discharge (DBD) exposure and coating with proteins (albumin) or polysaccharides (chitosan), for improving their biocompatibility. Untreated and treated surfaces have been comparatively studied by contact angle measurements, FT-IR and 2D-FT-IR spectroscopy and optical microscopy. It has been established that enhancement of the surface characteristics depends on the type and number of incorporated nanoparticles as well as on the treatment applied. Coupling of DBD exposure and coating techniques appears to be highly efficient.

  18. Treating Cutaneous T-Cell Lymphoma with Highly Irregular Surfaces with Photon Irradiation Using Rice as Tissue Compensator

    PubMed Central

    Majithia, Lonika; Rong, Yi; Siddiqui, Farzan; Hattie, Todd; Gupta, Nilendu; Weldon, Michael; Chakravarti, Arnab; Wong, Henry K.; Porcu, Pierluigi; Xu-Welliver, Meng

    2015-01-01

    Purpose: Cutaneous T-cell lymphoma (CTCL) is known to have an excellent response to radiotherapy, an important treatment modality for this disease. In patients with extremity and digit involvement, the irregular surface and depth variations create difficulty in delivering a homogenous dose using electrons. We sought to evaluate photon irradiation with rice packing as tissue equivalence and determine clinical tolerance and response. Materials and methods: Three consecutive CTCL patients with extensive lower extremity involvement including the digits were treated using external beam photon therapy with rice packing for tissue compensation. The entire foot was treated to 30–40 Gy in 2–3 Gy per fraction using 6 MV photons prescribed to the mid-plane of an indexed box filled with rice in which the foot was placed. Treatment tolerance and response were monitored with clinical evaluation. Results: All patients tolerated the treatment without treatment breaks. Toxicities included grade 3 erythema and desquamation with resolution within 4 weeks. No late toxicities were observed. All patients had a partial response by 4 weeks after therapy with two patients achieving a complete response. Patients reported improved functionality after treatment. No local recurrence has been observed. Conclusion: Tissue compensation with rice packing offers a convenient, inexpensive, and reproducible method for the treatment of CTCL with highly irregular surfaces. PMID:25759793

  19. Estimating dermal transfer of copper particles from the surfaces of pressure-treated lumber and implications for exposure.

    PubMed

    Platten, William E; Sylvest, Nicholas; Warren, Casey; Arambewela, Mahendranath; Harmon, Steve; Bradham, Karen; Rogers, Kim; Thomas, Treye; Luxton, Todd Peter

    2016-04-01

    Lumber pressure-treated with micronized copper was examined for the release of copper and copper micro/nanoparticles using a surface wipe method to simulate dermal transfer. In 2003, the wood industry began replacing CCA treated lumber products for residential use with copper based formulations. Micronized copper (nano to micron sized particles) has become the preferred treatment formulation. There is a lack of information on the release of copper, the fate of the particles during dermal contact, and the copper exposure level to children from hand-to-mouth transfer. For the current study, three treated lumber products, two micronized copper and one ionic copper, were purchased from commercial retailers. The boards were left to weather outdoors for approximately 1year. Over the year time period, hand wipe samples were collected periodically to determine copper transfer from the wood surfaces. The two micronized formulations and the ionic formulation released similar levels of total copper. The amount of copper released was high initially, but decreased to a constant level (~1.5mgm(-2)) after the first month of outdoor exposure. Copper particles were identified on the sampling cloths during the first two months of the experiment, after which the levels of copper were insufficient to collect interpretable data. After 1month, the particles exhibited minimal changes in shape and size. At the end of 2-months, significant deterioration of the particles was evident. Based on the wipe sample data, a playground visit may result in a potential exposure to 2.58mg of copper, which is near or exceeds the daily tolerable upper intake limits for children under the age of 8, if completely ingested through hand-to-mouth transfer. While nanoparticles were found, there is not enough information to estimate the exposure from the released particles due to a lack of published literature on copper carbonate. PMID:26826852

  20. Adsorption of Lysine on Na-Montmorillonite and Competition with Ca(2+): A Combined XRD and ATR-FTIR Study.

    PubMed

    Yang, Yanli; Wang, Shengrui; Liu, Jingyang; Xu, Yisheng; Zhou, Xiaoyun

    2016-05-17

    Lysine adsorption at clay/aqueous interfaces plays an important role in the mobility, bioavailability, and degradation of amino acids in the environment. Knowledge of these interfacial interactions facilitates our full understanding of the fate and transport of amino acids. Here, X-ray diffraction (XRD) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) measurements were used to explore the dynamic process of lysine adsorption on montmorillonite and the competition with Ca(2+) at the molecular level. Density functional theory (DFT) calculations were employed to determine the peak assignments of dissolved lysine in the solution phase. Three surface complexes, including dicationic, cationic, and zwitterionic structures, were observed to attach to the clay edge sites and penetrate the interlayer space. The increased surface coverage and Ca(2+) competition did not affect the interfacial lysine structures at a certain pH, whereas an elevated lysine concentration contributed to zwitterionic-type coordination at pH 10. Moreover, clay dissolution at pH 4 could be inhibited at a higher surface coverage with 5 and 10 mM lysine, whereas the inhibition effect was inconspicuous or undetected at pH 7 and 10. The presence of Ca(2+) not only could remove a part of the adsorbed lysine but also could facilitate the readsorption of dissolved Si(4+) and Al(3+) and surface protonation. Our results provide new insights into the process of lysine adsorption and its effects on montmorillonite surface sites. PMID:27118104

  1. Odor Events in Surface and Treated Water: The Case of 1,3-Dioxane Related Compounds.

    PubMed

    Quintana, Jordi; Vegué, Lídia; Martín-Alonso, Jordi; Paraira, Miquel; Boleda, M Rosa; Ventura, Francesc

    2016-01-01

    A study has been carried out to identify the origin of the odorous compounds at trace levels detected in surface waters and in Barcelona's tap water (NE Spain) which caused consumer complaints. The malodorous compounds were 2,5,5-trimethyl-1,3-dioxane (TMD) and 2-ethyl-5,5-dimethyl-1,3-dioxane (2EDD) which impart a distinctive sickening or olive-oil odor to drinking water at low ng/L levels. Flavor profile analysis (FPA) or threshold odor number (TON) were used for organoleptic purposes. Levels up to 749 ng/L for TMD and 658 ng/L for 2EDD were measured at the entrance of the drinking water treatment plant. Three wastewater treatment plants (WWTPs) using industrial byproducts coming from resin manufacturing plants to promote codigestion were found to be the origin of the event. Corrective measures were applied, including the prohibition to use these byproducts for codigestion in the WWTPs involved. A similar event was already recorded in the same area 20 years ago. PMID:26592899

  2. Tribocorrosion behaviour of anodic treated titanium surfaces intended for dental implants

    NASA Astrophysics Data System (ADS)

    Alves, A. C.; Oliveira, F.; Wenger, F.; Ponthiaux, P.; Celis, J.-P.; Rocha, L. A.

    2013-10-01

    Tribocorrosion plays an important role in the lifetime of metallic implants. Once implanted, biomaterials are subjected to micro-movements in aggressive biological fluids. Titanium is widely used as an implant material because it spontaneously forms a compact and protective nanometric thick oxide layer, mainly TiO2, in ambient air. That layer provides good corrosion resistance, and very low toxicity, but its low wear resistance is a concern. In this work, an anodizing treatment was performed on commercial pure titanium to form a homogeneous thick oxide surface layer in order to provide bioactivity and improve the biological, chemical and mechanical properties. Anodizing was performed in an electrolyte containing β-glycerophosphate and calcium acetate. The influence of the calcium acetate content on the tribocorrosion behaviour of the anodized material was studied. The concentration of calcium acetate in the electrolyte was found to largely affect the crystallographic structure of the resulting oxide layer. Better tribocorrosion behaviour was noticed on increasing the calcium acetate concentration.

  3. Modification of nanosized natural montmorillonite for ultrasound-enhanced adsorption of Acid Red 17.

    PubMed

    Acisli, Ozkan; Khataee, Alireza; Karaca, Semra; Sheydaei, Mohsen

    2016-07-01

    This work aims to modify montmorillonite (MMT) via dodecyltrimethylammonium bromide (DTMA) and investigate its ability in ultrasound (US) assisted decolorization of a polluted solution. BET surface area of MMT was increased from 19.76 to 42.57m(2)/g and basal spacing of MMT structural layers was increased from 1.13 to 1.69nm by DTMA modification. The application of DTMA-modified MMT (DTMA-MMT) and US for the decolorization of Acid Red 17 (AR17) showed that US could improve the ability of DTMA-MMT on decolorization of AR17 solution due to simultaneous adsorption and sonocatalysis. The ability of US assisted DTMA-MMT was slightly decreased with pH, the initial dye concentration and the presence of inorganic anions. PMID:26964930

  4. Characterization of Aminopropyltriethoxysilane-functionalized Polycaprolactone-Montmorillonite Beads for Heavy Metal Biosorption

    NASA Astrophysics Data System (ADS)

    Magdaluyo, E., Jr.; Dayhon, E.; delos Angeles, M.; dela Cruz, Rj; de Sales-Papa, L.

    2011-10-01

    The study focuses on the fabrication of montmorillonite (MMT) based composites via functionalization with polycaprolactone (PCL) and aminopropyltriethoxysilane (APTS) for adsorption of divalent metal ions Cu2+ and Fe2+. Surface morphology of the composites revealed that the PCL-APTS-MMT beads have finer particle size compared to PCL-MMT. Infrared spectroscopy analyses confirmed the covalent interaction of the PCL to the MMT matrix and the APTS-PCL-MMT composite. Thermogravimetric analysis showed a decrease in thermal stability for the composite powders. Analyses with Langmuir and Freundlich isotherm models revealed greater maximum adsorption capacity for the PCL-APTS-MMT composite compared to PCL-MMT. The divalent ions could be removed by the obtained composite material through the possible mechanisms of ion exchange and chelation.

  5. Correlation between the extent of catalytic activity and charge density of montmorillonites.

    PubMed

    Ertem, Gözen; Steudel, Annett; Emmerich, Katja; Lagaly, Gerhard; Schuhmann, Rainer

    2010-09-01

    The clay mineral montmorillonite is a member of the phyllosilicate group of minerals, which has been detected on martian soil. Montmorillonite catalyzes the condensation of activated monomers to form RNA-like oligomers. Extent of catalysis, that is, the yield of oligomers, and the length of the longest oligomer formed in these reactions widely varies with the source of montmorillonite (i.e., the locality where the mineral is mined). This study was undertaken to establish whether there exists a correlation between the extent of catalytic property and the charge density of montmorillonites. Charge density was determined by saturating the montmorillonites with alkyl ammonium cations that contained increasing lengths of alkyl chains, [CH₃-(CH₂)(n)-NH₃](+), where n = 3-16 and 18, and then measuring d(₀₀₁), interlayer spacing of the resulting montmorillonite-alkyl ammonium-montmorillonite complex by X-ray diffractometry (XRD). Results demonstrate that catalytic activity of montmorillonites with lower charge density is superior to that of higher charge density montmorillonite. They produce longer oligomers that contain 9 to 10 monomer units, while montmorillonite with high charge density catalyzes the formation of oligomers that contain only 4 monomer units. The charge density of montmorillonites can also be calculated from the chemical composition if elemental analysis data of the pure mineral are available. In the next mission to Mars, CheMin (Chemistry and Mineralogy), a combined X-ray diffraction/X-ray fluorescence instrument, will provide information on the mineralogical and elemental analysis of the samples. Possible significance of these results for planning the future missions to Mars for the search of organic compounds and extinct or extant life is discussed. PMID:20854214

  6. Correlation Between the Extent of Catalytic Activity and Charge Density of Montmorillonites

    PubMed Central

    Steudel, Annett; Emmerich, Katja; Lagaly, Gerhard; Schuhmann, Rainer

    2010-01-01

    Abstract The clay mineral montmorillonite is a member of the phyllosilicate group of minerals, which has been detected on martian soil. Montmorillonite catalyzes the condensation of activated monomers to form RNA-like oligomers. Extent of catalysis, that is, the yield of oligomers, and the length of the longest oligomer formed in these reactions widely varies with the source of montmorillonite (i.e., the locality where the mineral is mined). This study was undertaken to establish whether there exists a correlation between the extent of catalytic property and the charge density of montmorillonites. Charge density was determined by saturating the montmorillonites with alkyl ammonium cations that contained increasing lengths of alkyl chains, [CH3-(CH2)n-NH3]+, where n = 3–16 and 18, and then measuring d(001), interlayer spacing of the resulting montmorillonite-alkyl ammonium-montmorillonite complex by X-ray diffractometry (XRD). Results demonstrate that catalytic activity of montmorillonites with lower charge density is superior to that of higher charge density montmorillonite. They produce longer oligomers that contain 9 to 10 monomer units, while montmorillonite with high charge density catalyzes the formation of oligomers that contain only 4 monomer units. The charge density of montmorillonites can also be calculated from the chemical composition if elemental analysis data of the pure mineral are available. In the next mission to Mars, CheMin (Chemistry and Mineralogy), a combined X-ray diffraction/X-ray fluorescence instrument, will provide information on the mineralogical and elemental analysis of the samples. Possible significance of these results for planning the future missions to Mars for the search of organic compounds and extinct or extant life is discussed. Key Words: Mars—Origin of life—Montmorillonite—Mineral catalysis—Layer charge density—X–ray diffractometry. Astrobiology 10, 743–749. PMID:20854214

  7. Relevance of Pore Structure and Diffusion-Accessible Porosity for Calcium-Bromide Diffusion in Na-Montmorillonite

    NASA Astrophysics Data System (ADS)

    Tinnacher, R. M.; Davis, J. A.

    2013-12-01

    Bentonite is an important hydraulic barrier material in many geotechnical applications, such as geosynthetic clay liners at solid waste landfills, or as proposed backfill material in engineered barrier systems at nuclear waste repositories. The limited permeability of bentonite is at least partially the result of its low porosity and the swelling of Na-montmorillonite, its major mineralogical component, in water. Due to these characteristics, the transport of contaminants through bentonite layers is expected to be limited and dominated by diffusion processes. In bentonite, the majority of the connected porosity is associated with montmorillonite particles, which consist of stacks of negatively-charged smectite layers. As a result, compacted smectite has two types of porosities: (1) large pores between clay particles, where diffusion is less affected by electric-double-layer forces, and (2) very thin interlayer spaces within individual clay particles, where diffusion is strongly impacted by surface charge and ionic strength. As diffusion is expected to take place differently in these two volumes, this essentially creates two 'small-scale diffusion pathways', where each may become dominant under different system conditions. Furthermore, for surface-reactive solutes, these two porous regimes differ with regards to surface complexation reactions. Electrostatic and hydration forces only are thought to govern interlayer binding, whereas chemical bonding with surface ligands is dominant for reactions at edge sites of layered clay particles and for iron oxide nanoparticles on outer basal planes. In this presentation, we will demonstrate the relevance of clay pore structure and diffusion-accessible porosity for solute diffusion rates, and hence, contaminant mobility in bentonites. First, we will discuss the effects of chemical solution conditions on montmorillonite properties, such as clay surface charge, diffusion-accessible porosity, clay tortuosity and constrictivity, and evaluate the implications for metal diffusion coefficients. Furthermore, we will highlight the importance of solute charge for solute diffusion rates based on results from a calcium-bromide (CaBr2) through-diffusion experiment in Na-montmorillonite. In this experiment, dry, purified Na-montmorillonite (SWy-2, Clay Minerals Society) was packed into a diffusion cell, allowed to equilibrate with the background electrolyte (pH=7, I=0.1 M NaCl), and then exposed to a constant CaBr2 concentration gradient between two solution reservoirs. After reaching steady-state conditions for the diffusive fluxes of Ca and Br, cumulative mass data could be used to compute effective and apparent Ca and Br diffusion coefficients. Furthermore, the diffusion data for an uncharged, non-reactive tracer (tritiated water) allowed us to calculate the clay porosity in the system, and to determine Ca and Br sorption distribution coefficients (Kd values). Our results indicate that Ca diffusion in Na-montmorillonite is slower than for the non-reactive tracer, most likely due to Ca exchange reactions within the clay interlayers. In contrast, rates of Br diffusion are faster than for an uncharged tracer, indicating solute-specific differences in diffusion-accessible porosities and/or effective concentration gradients in pore spaces.

  8. Tracking inorganic foulants irreversibly accumulated on low-pressure membranes for treating surface water.

    PubMed

    Yamamura, Hiroshi; Kimura, Katsuki; Higuchi, Kumiko; Watanabe, Yoshimasa; Ding, Qing; Hafuka, Akira

    2015-12-15

    While low-pressure membrane filtration processes (i.e., microfiltration and ultrafiltration) can offer precise filtration than sand filtration, they pose the problem of reduced efficiency due to membrane fouling. Although many studies have examined membrane fouling by organic substances, there is still not enough data available concerning membrane fouling by inorganic substances. The present research investigated changes in the amounts of inorganic components deposited on the surface of membrane filters over time using membrane specimens sampled thirteen times at arbitrary time intervals during pilot testing in order to determine the mechanism by which irreversible fouling by inorganic substances progresses. The experiments showed that the inorganic components that primarily contribute to irreversible fouling vary as filtration continues. It was discovered that, in the initial stage of operation, the main membrane-fouling substance was iron, whereas the primary membrane-fouling substances when operation finished were manganese, calcium, and silica. The amount of iron accumulated on the membrane increased up to the thirtieth day of operation, after which it reached a steady state. After the accumulation of iron became static, subsequent accumulation of manganese was observed. The fact that the removal rates of these inorganic components also increased gradually shows that the size of the exclusion pores of the membrane filter narrows as operation continues. Studying particle size distributions of inorganic components contained in source water revealed that while many iron particles are approximately the same size as membrane pores, the fraction of manganese particles slightly smaller than the pores in diameter was large. From these results, it is surmised that iron particles approximately the same size as the pores block them soon after the start of operation, and as the membrane pores narrow with the development of fouling, they become further blocked by manganese particles approximately the same size as the narrowed pores. Calcium and silica are assumed to accumulate on the membrane due to their cross-linking action and/or complex formation with organic substances such as humic compounds. The present research is the first to clearly show that the inorganic components that contribute to membrane fouling differ according to the stage of membrane fouling progression; the information obtained by this research should enable chemical cleaning or operational control in accordance with the stage of membrane fouling progression. PMID:26414890

  9. Coculture of autologous limbal and conjunctival epithelial cells to treat severe ocular surface disorders: Long-term survival analysis

    PubMed Central

    Subramaniam, Sandhya V; Sejpal, Kunjal; Fatima, Anees; Gaddipati, Subhash; Vemuganti, Geeta K; Sangwan, Virender S

    2013-01-01

    Background: Cultivated limbal epithelium for reconstruction of corneal surface is a well-established procedure; however, it is not adequate for damage which also extensively involves the conjunctiva. In severe cases of ocular surface damage that warrant additional conjunctival transplantation apart from cultivated limbal stem cell transplantation, we describe the long-term survival of a novel method of cocultivating autologous limbal and conjunctival epithelium on a single substrate. Materials and Methods: Forty eyes of 39 patients with severe limbal stem cell deficiency and conjunctival scarring or symblepharon underwent transplantation of autologous cocultivated epithelium on human amniotic membrane. A ring barrier was used to segregate the central limbal and peripheral conjunctival epithelia in vitro. Patients were followed up at regular intervals to assess stability of the ocular surface, defined by absence of conjunctivalization into the central 4 mm of the cornea and absence of diffuse fluorescein staining. Penetrating keratoplasty (PKP) was subsequently performed, where indicated, in patients with surface stability. Results: The cumulative survival probability was 60% at 1 year and 45% at 4 years by Kaplan–Meier analysis (mean follow-up duration: 33 ± 29 months, range: 1–87 months). Best-corrected visual acuity improved to greater than 20/200 in 38% eyes at the last follow-up, compared with 5% eyes before surgery. Immunohistochemistry in five of the corneal buttons excised for PKP showed an epithelial phenotype similar to cornea in all five. Conclusions: Synchronous use of cultured limbal and conjunctival epithelium offers a feasible alternative and a simpler one-step surgical approach to treat severe ocular surface disorders involving limbus and conjunctiva. PMID:23552358

  10. Surface Roughness and Tool Wear on Cryogenic Treated CBN Insert on Titanium and Inconel 718 Alloy Steel

    NASA Astrophysics Data System (ADS)

    Thamizhmanii, S.; Mohideen, R.; Zaidi, A. M. A.; Hasan, S.

    2015-12-01

    Machining of materials by super hard tools like cubic boron nitride (cbn) and poly cubic boron nitride (pcbn) is to reduce tool wear to obtain dimensional accuracy, smooth surface and more number of parts per cutting edge. wear of tools is inevitable due to rubbing action between work material and tool edge. however, the tool wear can be minimized by using super hard tools by enhancing the strength of the cutting inserts. one such process is cryogenic process. this process is used in all materials and cutting inserts which requires wear resistance. the cryogenic process is executed under subzero temperature -186° celsius for longer period of time in a closed chamber which contains liquid nitrogen. in this research, cbn inserts with cryogenically treated was used to turn difficult to cut metals like titanium, inconel 718 etc. the turning parameters used is different cutting speeds, feed rates and depth of cut. in this research, titanium and inconel 718 material were used. the results obtained are surface roughness, flank wear and crater wear. the surface roughness obtained on titanium was lower at high cutting speed compared with inconel 718. the flank wear was low while turning titanium than inconel 718. crater wear is less on inconel 718 than titanium alloy. all the two materials produced saw tooth chips.

  11. Detect-to-treat: development of analysis of bacilli spores in nasal mucus by surfaced-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Inscore, Frank E.; Gift, Alan D.; Farquharson, Stuart

    2004-12-01

    As the war on terrorism in Afghanistan and Iraq continue, future attacks both abroad and in the U.S.A. are expected. In an effort to aid civilian and military personnel, we have been investigating the potential of using a surface-enhanced Raman spectroscopy (SERS) sampling device to detect Bacillus anthracis spores in nasal swab samples. Such a device would be extremely beneficial to medical responders and management in assessing the extent of a bioterrorist attack and making detect-to-treat decisions. The disposable sample device consists of a glass capillary filled with a silver-doped sol-gel that is capable of extracting dipicolinic acid (DPA), a chemical signature of Bacilli, and generating SERS spectra. The sampling device and preliminary measurements of DPA extracted from spores and nasal mucus will be presented.

  12. Surface modified nanoparticles enhance transurothelial penetration and delivery of survivin siRNA in treating bladder cancer

    PubMed Central

    Martin, Darryl T.; Steinbach, Jill M.; Liu, Jingchun; Shimizu, Shogo; Kaimakliotis, Hristos Z.; Wheeler, Marcia A.; Hittelman, Adam B.; Saltzman, W. Mark; Weiss, Robert M.

    2013-01-01

    Penetration of the bladder permeability barrier (BPB) is a major challenge when treating bladder diseases via intravesical delivery. To increase transurothelial migration and tissue and tumor cell uptake, poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) were modified by addition of a low molecular weight (2.5 kDa or 20 kDa) positively charged mucoadhesive polysaccharide, chitosan, to the NP surface. In designing these NPs, we balanced the adhesive properties of chitosan with the release and bioactivity of the siRNA. Chitosan functionalized NPs demonstrated increased binding to and uptake in intravesically instilled mouse bladders and human ureter at 10 times the level of unmodified NPs. Furthermore, we extended the bioactivity of survivin siRNA in vitro for up to 9 days and demonstrated a decrease in proliferation when using chitosan modified NPs relative to unmodified NPs. In addition, treatment of xenograft tumors with chitosan modified NPs that encapsulate survivin siRNA (NP-siSUR-CH2.5) resulted in a 65% reduction in tumor volume and a 75% decrease in survivin expression relative to tumors treated with blank chitosan NPs (NP-Bk-CH2.5). Our low molecular weight chitosan delivery system has the capacity to transport large amounts of siRNA across the urothelium and/or to the tumor site thus increasing therapeutic response. PMID:24222663

  13. Mineral catalysis of the formation of the phosphodiester bond in aqueous solution: The possible role of montmorillonite clays

    NASA Astrophysics Data System (ADS)

    Ferris, James P.; Ertem, Gözen; Kamaluddin; Agarwal, Vipin; Hua, Lu Lin

    The binding of adenosine to Na+-montmorillonite 22A is greater than 5'-AMP, at neutral pH. Adenine derivatives bind more strongly to the clay than the corresponding uracil derivatives. These data are consistent with the protonation of the adenine by the acidic clay surface and a cationic binding of the protonated ring to the anionic clay surface. Other forces must be operative in the binding of uracil derivatives to the clay since the uracil ring system is not basic. The reaction of the 5'-AMP with water soluble carbodiimide in the presence of Na+-montmorillonite results in the formation of 2',5'-pApA (18.9%), 3',5'-pApA (11%), and AppA (4.8%). When poly(U) is used in place of the clay the product yields are 2',5',-pApA (15.5%), 3',5'-pApA (3.7%) and AppA (14.9%). The cyclic nucleotide, c(pA)2 is also formed when poly(U) is used. AppA is the principal reaction product when neither clay nor poly(U) is present in the reaction mixture. When 2'-deoxy-5'-AMP reacts with carbodiimide in the presence of Na+-montmorillonite 22A the products are dpApA (4.8%), dAppApA (4.5%) and dAppA (17.4%). Cyclic 3',5'-dAMP is the main product (14%) of the reaction of 2'-deoxy-3'-AMP.

  14. QINS studies of water diffusion in Na-montmorillonite

    NASA Astrophysics Data System (ADS)

    Gay-Duchosal, Michael; Hugh Powell, D.; Lechner, R. E.; Rufflé, Benoit

    2000-03-01

    We have used quasielastic incoherent neutron scattering (QINS) to study the diffusion of interlayer water in partially orientated Na-montmorillonite samples. In order to observe the anisotropy of the motion we performed measurements for two orthogonal sample orientations and for two different energy resolutions. Fits to the spectra yield phenomenological translational line widths which, for the 135° orientation, can be fitted by a two-dimensional Chudley-Elliott model with a diffusion coefficient D=1.3×10 -9 m 2 s -1and a mean square jump distance l=1.7 Å.

  15. Nanoscale elastic properties of montmorillonite upon water adsorption.

    PubMed

    Ebrahimi, Davoud; Pellenq, Roland J-M; Whittle, Andrew J

    2012-12-11

    Smectites are an important group of clay minerals that experience swelling upon water adsorption. This paper uses molecular dynamics with the CLAYFF force field to simulate isothermal isobaric water adsorption of interlayer Wyoming Na-montmorillonite, a member of the smectite group. Nanoscale elastic properties of the clay-interlayer water system are calculated from the potential energy of the model system. The transverse isotropic symmetry of the elastic constant matrix was assessed by calculating Euclidean and Riemannian distance metrics. Simulated elastic constants of the clay mineral are compared with available results from acoustic and nanoindentation measurements. PMID:23181550

  16. Oligomerization reactions of deoxyribonucleotides on montmorillonite clay - The effect of mononucleotide structure, phosphate activation and montmorillonite composition on phosphodiester bond formation

    NASA Technical Reports Server (NTRS)

    Ferris, James P.; KAMALUDDIN; Ertem, Gozen

    1990-01-01

    The 2(prime)-d-5(prime)-GMP and 2(prime)-d-5(prime)-AMP bind 2 times more strongly to montmorillonite 22A than do 2(prime)-d-5(prime)-CMP and 5(prime)-TMP. The dinucleotide d(pG)2 forms in 9.2 percent yield and the cyclic dinucleotide c(dpG)2 in 5.4 percent yield in the reaction of 2(prime)-d-5(prime)-GMP with EDAC in the presence of montmorillonite 22A. The yield of dimers which contain the phosphodiester bond decreases as the reaction medium is changed from 0.2 M NaCl to a mixture of 0.2 M NaCl and 0.075 M MgCl2. A low yield of d(pA)2 was observed in the condensation reaction of 5(prime)-ImdpA on montmorillonite 22A. The yield of d(pA)2 obtained when EDAC is used as the condensing agent increases with increasing iron content of the Na(+)-montmorillonite used as catalyst. Evidence is presented which shows that the acidity of the Na(+)-montmorillonite is a necessary but not sufficient factor for the montmorillonite catalysis of phosphodiester bond formation.

  17. Oligomerization reactions of deoxyribonucleotides on montmorillonite clay: The effect of mononucleotide structure, phosphate activation and montmorillonite composition on phosphodiester bond formation

    NASA Astrophysics Data System (ADS)

    Ferris, James P.; Kamaluddin; Ertem, Gözen

    1990-05-01

    2'-d-5'-GMP and 2'-d-5'-AMP bind 2 times more strongly to montmorillonite 22A than do 2'-d-5'-CMP and 5'-TMP. The dinucleotide d(pG)2 forms in 9.2% yield and the cyclic dinucleotide c(dpG)2 in 5.4% yield in the reaction of 2'-d-5'-GMP with EDAC in the presence of montmorillonite 22A. The yield of d(pC)2 (2.0%) is significantly lower but comparable to that obtained from 5'-TMP. The yield of dimers which contain the phosphodiester bond decreases as the reaction medium is changed from 0.2 M NaCl to a mixture of 0.2 M NaCl and 0.075 M MgCl2. A low yield of d(pA)2 was observed in the condensation reaction of 5'-ImdpA on montmorillonite 22A. The cyclic nucleotide (3',5'-cdAMP) was obtained in 14% yield from 3'-ImdpA. The yield of d(pA)2 obtained when EDAC is used as the condensing agent increases with increasing iron content of the Na+-montmorillonite used as catalyst. Evidence is presented which shows that the acidity of the Na+-montmorillonite is a necessary but not sufficient factor for the montmorillonite catalysis of phosphodiester bond formation.

  18. Oligomerization reactions of deoxyribonucleotides on montmorillonite clay: the effect of mononucleotide structure, phosphate activation and montmorillonite composition on phosphodiester bond formation.

    PubMed

    Ferris, J P; Kamaluddin; Ertem, G

    1990-01-01

    2'-d-5'-GMP and 2'-d-5'-AMP bind 2 times more strongly to montmorillonite 22A than do 2'-d-5'-CMP and 5'-TMP. The dinucleotide d(pG)2 forms in 9.2% yield and the cyclic dinucleotide c(dpG)2 in 5.4% yield in the reaction of 2'-d-5'-GMP with EDAC in the presence of montmorillonite 22A. The yield of d(pC)2 (2.0%) is significantly lower but comparable to that obtained from 5'-TMP. The yield of dimers which contain the phosphodiester bond decreases as the reaction medium is changed from 0.2 M NaCl to a mixture of 0.2 M NaCl and 0.075 M MgCl2. A low yield of d(pA)2 was observed in the condensation reaction of 5'-ImdpA on montmorillonite 22A. The cyclic nucleotide (3',5'-cdAMP) was obtained in 14% yield from 3'-ImdpA. The yield of d(pA)2 obtained when EDAC is used as the condensing agent increases with increasing iron content of the Na(+)-montmorillonite used as a catalyst. Evidence is presented which shows that the acidity of the Na(+)-montmorillonite is a necessary but not sufficient factor for the montmorillonite catalysis of phosphodiester bond formation. PMID:11537409

  19. LIMITATIONS OF EDDY CURRENT RESIDUAL STRESS PROFILING IN SURFACE-TREATED ENGINE ALLOYS OF VARIOUS HARDNESS LEVELS

    SciTech Connect

    Abu-Nabah, B. A.; Hassan, W. T.; Blodgett, M. P.; Nagy, P. B.

    2010-02-22

    Recent research results indicated that eddy current conductivity measurements might be exploited for nondestructive evaluation of subsurface residual stresses in surface-treated nickel-base superalloy components. This paper presents new results that indicate that in some popular nickel-base superalloys the relationship between the electric conductivity profile and the sought residual stress profile is more tenuous than previously thought. It is shown that in IN718 the relationship is very sensitive to the state of precipitation hardening and, if left uncorrected, could render the eddy current technique unsuitable for residual stress profiling in components of 36 HRC or harder, i.e., in most critical engine applications. The presented experimental results show that the observed dramatic change in the eddy current response of hardened IN718 to surface treatment is caused by very fine nanometer-scale features of the microstructure, such as gamma' and gamma'' precipitates, rather than micrometer-scale features, such as changing grain size or carbide precipitates.

  20. Suitability of macrophytes for nutrient removal from surface flow constructed wetlands receiving secondary treated sewage effluent in Queensland, Australia.

    PubMed

    Greenway, M

    2003-01-01

    From a botanical perspective the major difference between waste stabilisation ponds and wetlands is the dominance of algae or floating plants in the former and emergent plants in the latter. Algae, floating and submerged plants remove nutrients directly from the water column whereas emergent species remove nutrients from the sediment. Water depth is a crucial factor in determining which plant types will become established. Surface flow constructed wetlands offer the greatest potential to grow a wide variety of different types of macrophytes. In assessing the suitability of plant species for nutrient removal, consideration must be given not only to nutrient uptake for growth but also storage of nutrients as plant biomass. A survey of macrophytes in 15 surface flow constructed wetlands treating secondary effluent was conducted in Queensland; 63 native species and 14 introduced species were found. Emergent species have been able to tolerate deeper water than in their natural environment and permanent waterlogging. All species grew well in the higher nutrient enriched wastewater. Submerged, floating leaved-attached and free floating species had the highest tissue nutrient content, followed by aquatic creepers. All these species remove nutrients from the water column. Emergent species had lower nutrient content but a greater biomass and were therefore able to store more nutrients per unit area of wetland. In order to maximise the efficiency of constructed wetlands for nutrient removal, a range of species should be used. Native species should be selected in preference to introduced/exotic species. PMID:14510202

  1. Surface degradation of CeO2 stabilized acrylic polyurethane coated thermally treated jack pine during accelerated weathering

    NASA Astrophysics Data System (ADS)

    Saha, Sudeshna; Kocaefe, Duygu; Boluk, Yaman; Pichette, Andre

    2013-07-01

    The thermally treated wood is a new value-added product and is very important for the diversification of forestry products. It drew the attention of consumers due to its attractive dark brown color. However, it loses its color when exposed to outside environment. Therefore, development of a protective coating for this value added product is necessary. In the present study, the efficiency of CeO2 nano particles alone or in combination with lignin stabilizer and/or bark extracts in acrylic polyurethane polymer was investigated by performing an accelerated weathering test. The color measurement results after accelerated weathering demonstrated that the coating containing CeO2 nano particles was the most effective whereas visual assessment suggested the coating containing CeO2 nano particles and lignin stabilizer as the most effective coating. The surface polarity changed for all the coatings during weathering and increase in contact angle after weathering suggested cross linking and reorientation of the polymer chain during weathering. The surface chemistry altered during weathering was evaluated by ATR-FTIR analysis. It suggested formation of different carbonyl byproducts during weathering. The chain scission reactions of the urethane linkages were not found to be significant during weathering.

  2. Joint replacement components made of hot-forged and surface-treated Ti-6Al-7Nb alloy.

    PubMed

    Semlitsch, M F; Weber, H; Streicher, R M; Schön, R

    1992-01-01

    We have developed a titanium-aluminium alloy with the inert alloying element niobium. The optimal composition was found to be Ti-6Al-7Nb (Protasul-100). This custom-made alloy designed for implants shows the same alpha/beta structure as Ti-6Al-4V and exhibits equally good mechanical properties. The corrosion resistance of Ti-6Al-7Nb in sodium chloride solution is equivalent to that of pure titanium and Ti-6Al-4V. This is due to a very dense and stable passive layer. Highly stressed anchorage stems of different hip prosthesis designs have been made from hot-forged Ti-6Al-7Nb. The polished surfaces of hip, knee and wrist joints made of Ti-6Al-7Nb and articulating against polyethylene are surface-treated by means of a very hard and 3-5 microns thick titanium nitride coating (Tribosul-TiN) or by oxygen diffusion hardening (Tribosul-ODH) to a depth of 30 microns. PMID:1391401

  3. Characterization of cell surface polypeptides of unfertilized, fertilized, and protease-treated zona-free mouse eggs

    SciTech Connect

    Boldt, J.; Gunter, L.E.; Howe, A.M. )

    1989-05-01

    The polypeptide composition of unfertilized, fertilized, and protease-treated zona-free mouse eggs was evaluated in this study. Zona-free eggs were radioiodinated by an Iodogen-catalyzed reaction. Light microscopic autoradiography of egg sections revealed that labeling was restricted to the cell surface. Labeled eggs were solubilized, and cell surface polypeptides were identified by one-dimensional SDS polyacrylamide gel electrophoresis and autoradiography. The unfertilized egg demonstrated 8-10 peptides that incorporated {sup 125}I, with major bands observed at approximately 145-150, 94, and 23 kilodaltons (kD). Zona-free eggs fertilized in vitro and then radiolabeled demonstrated several new bands in comparison to unfertilized eggs, with a major band appearing at approximately 36 kD. Treatment of radiolabeled unfertilized eggs with either trypsin or chymotrypsin (1 mg/ml for 5-20 min) caused enzyme-specific modifications in labeled polypeptides. Trypsin (T) treatment resulted in time-dependant modification of the three major peptides at 145-150, 94, and 23 kD. Chymotrypsin (CT) treatment, in contrast, was associated with loss or modification of the 94 kD band, with no apparent effect on either the 145-150 or 23 kD band. Taken together with previous data indicating that T or CT egg treatment interferes with sperm-egg attachment and fusion, these results suggest a possible role for the 94 kD protein in sperm-egg interaction.

  4. Do contaminants originating from state-of-the-art treated wastewater impact the ecological quality of surface waters?

    PubMed

    Stalter, Daniel; Magdeburg, Axel; Quednow, Kristin; Botzat, Alexandra; Oehlmann, Jörg

    2013-01-01

    Since the 1980s, advances in wastewater treatment technology have led to considerably improved surface water quality in the urban areas of many high income countries. However, trace concentrations of organic wastewater-associated contaminants may still pose a key environmental hazard impairing the ecological quality of surface waters. To identify key impact factors, we analyzed the effects of a wide range of anthropogenic and environmental variables on the aquatic macroinvertebrate community. We assessed ecological water quality at 26 sampling sites in four urban German lowland river systems with a 0-100% load of state-of-the-art biological activated sludge treated wastewater. The chemical analysis suite comprised 12 organic contaminants (five phosphor organic flame retardants, two musk fragrances, bisphenol A, nonylphenol, octylphenol, diethyltoluamide, terbutryn), 16 polycyclic aromatic hydrocarbons, and 12 heavy metals. Non-metric multidimensional scaling identified organic contaminants that are mainly wastewater-associated (i.e., phosphor organic flame retardants, musk fragrances, and diethyltoluamide) as a major impact variable on macroinvertebrate species composition. The structural degradation of streams was also identified as a significant factor. Multiple linear regression models revealed a significant impact of organic contaminants on invertebrate populations, in particular on Ephemeroptera, Plecoptera, and Trichoptera species. Spearman rank correlation analyses confirmed wastewater-associated organic contaminants as the most significant variable negatively impacting the biodiversity of sensitive macroinvertebrate species. In addition to increased aquatic pollution with organic contaminants, a greater wastewater fraction was accompanied by a slight decrease in oxygen concentration and an increase in salinity. This study highlights the importance of reducing the wastewater-associated impact on surface waters. For aquatic ecosystems in urban areas this would lead to: (i) improvement of the ecological integrity, (ii) reduction of biodiversity loss, and (iii) faster achievement of objectives of legislative requirements, e.g., the European Water Framework Directive. PMID:23593263

  5. Do Contaminants Originating from State-of-the-Art Treated Wastewater Impact the Ecological Quality of Surface Waters?

    PubMed Central

    Stalter, Daniel; Magdeburg, Axel; Quednow, Kristin; Botzat, Alexandra; Oehlmann, Jörg

    2013-01-01

    Since the 1980s, advances in wastewater treatment technology have led to considerably improved surface water quality in the urban areas of many high income countries. However, trace concentrations of organic wastewater-associated contaminants may still pose a key environmental hazard impairing the ecological quality of surface waters. To identify key impact factors, we analyzed the effects of a wide range of anthropogenic and environmental variables on the aquatic macroinvertebrate community. We assessed ecological water quality at 26 sampling sites in four urban German lowland river systems with a 0–100% load of state-of-the-art biological activated sludge treated wastewater. The chemical analysis suite comprised 12 organic contaminants (five phosphor organic flame retardants, two musk fragrances, bisphenol A, nonylphenol, octylphenol, diethyltoluamide, terbutryn), 16 polycyclic aromatic hydrocarbons, and 12 heavy metals. Non-metric multidimensional scaling identified organic contaminants that are mainly wastewater-associated (i.e., phosphor organic flame retardants, musk fragrances, and diethyltoluamide) as a major impact variable on macroinvertebrate species composition. The structural degradation of streams was also identified as a significant factor. Multiple linear regression models revealed a significant impact of organic contaminants on invertebrate populations, in particular on Ephemeroptera, Plecoptera, and Trichoptera species. Spearman rank correlation analyses confirmed wastewater-associated organic contaminants as the most significant variable negatively impacting the biodiversity of sensitive macroinvertebrate species. In addition to increased aquatic pollution with organic contaminants, a greater wastewater fraction was accompanied by a slight decrease in oxygen concentration and an increase in salinity. This study highlights the importance of reducing the wastewater-associated impact on surface waters. For aquatic ecosystems in urban areas this would lead to: (i) improvement of the ecological integrity, (ii) reduction of biodiversity loss, and (iii) faster achievement of objectives of legislative requirements, e.g., the European Water Framework Directive. PMID:23593263

  6. Optimization by Response Surface Methodology of the adsorption of Coomassie Blue dye on natural and acid-treated clays.

    PubMed

    de Sales, Priscila F; Magriotis, Zuy M; Rossi, Marco A L S; Resende, Ricardo F; Nunes, Cleiton A

    2013-11-30

    The effect of acid treatment on natural agalmatolite (AN) and natural kaolinite (KN) was investigated, together with the influence of those modifications on the removal of Coomassie Blue (CB) dye. The process was optimized using the Response Surface Methodology (RSM) developed by the application of the quadratic model associated with the Central Composite Design. Adsorption was promoted by initial CB concentration of 25 mg L(-1), pH 2 and adsorbent mass of 0.1 g. The adsorption kinetics study carried out in optimized conditions established that the equilibrium times were 1 h for AN and AA (treated agalmatolite), 4 h for KN and 2 h for KA (treated kaolinite). The kinetics data for AN, KN and KA were best fitted to the pseudo second order model, whilst for AA, the result pointed to the pseudo first order model. In the isotherm of adsorption the maximum quantities were obtained with reference to 11.29 mg g(-1), 9.84 mg g(-1), 22.89 mg g(-1) and 30.08 mg g(-1) for the samples AN, AA, KN and KA respectively. The data fitting showed that the Sips model was the most satisfactory for all the adsorbents. The calculated thermodynamic parameters showed that the process was spontaneous in all the adsorbents, endothermic for the KN and KA samples, exothermic for AN and AA, involved the disorganization of the adsorption system for the KN and KA and its organization for the AN and AA samples. The results showed that the KN and KA samples were more appropriate for use as adsorbents. PMID:24141066

  7. Montmorillonite-phenyltrimethylammonium yields environmentally improved formulations of hydrophobic herbicides.

    PubMed

    El-Nahhal, Y; Nir, S; Serban, C; Rabinovitch, O; Rubin, B

    2000-10-01

    This study aimed to design formulations of hydrophobic herbicides, alachlor and metolachlor, by adsorbing them on the clay mineral montmorillonite preadsorbed by the small organic cation phenyltrimethylammonium (PTMA). An adsorption model that considers electrostatics and specific binding and the possibility of cation adsorption above the cation exchange capacity (CEC) could explain and yield predictions for PTMA adsorption in the presence of NaCl concentrations from 0 to 500 mM. Adsorption of alachlor and metolachlor from aqueous solution on a clay mineral preadsorbed by PTMA was determined by GC and modeled by Langmuir equation. Herbicide interactions with the organoclay were studied by Fourier transform infrared spectroscopy. Leaching of herbicides was determined by a bioassay using a column technique and Setaria viridis as a test plant. The adsorbed amounts of alachlor and metolachlor on montmorillonite preadsorbed by PTMA at a loading of 0. 5 mol/kg (Mont-PTMA0.5) were higher than at a loading up to the CEC, that is, 0.8 mol/kg, and were higher than those obtained by using several other organic cations. Herbicide formulations based on Mont-PTMA0.5 yielded the largest shifts of the infrared peaks of the herbicides. These formulations based on Mont-PTMA0.5 gave slower release and showed improved weed control in comparison with formulations based on other organoclays. These formulations maintained herbicidal activity in the topsoil and yielded the most significant reduction in herbicide leaching. PMID:11052735

  8. Mineral catalysis of the formation of the phosphodiester bond in aqueous solution - The possible role of montmorillonite clays

    NASA Technical Reports Server (NTRS)

    Ferris, James P.; Ertem, Gozen; KAMALUDDIN; Agarwal, Vipin; Hua, Lu Lin

    1989-01-01

    The possible role of montmorillonite clays in the spontaneous formation on the primitive earth of the phosphodiester bond in the presence of water was investigated in experiments measuring the binding of various nucleosides and nucleotides with Na(+)-montmorillonite 22A and the reactions of these compounds with a water-soluble carbodiimide. It was found that, at neutral pH, adenine derivatives bind stronger than the corresponding uracil derivatives, consistent with the protonation of the adenine by the acidic clay surface and a cationic binding of the protonated ring to the anionic clay surface. The reaction of the 5-prime-AMP with carbodiimide resulted in the formation of 2-prime,5-prime-pApA (18.9 percent), 3-prime,5-prime-pApA (11 percent), and AppA (4.8 percent). The yields of these oligomers obtained when poly(U) was used in place of the clay were 15.5 percent, 3.7 percent, and 14.9 percent AppA, respectively.

  9. Swelling properties of montmorillonite and beidellite clay minerals from molecular simulation: Comparison of temperature interlayer cation, and charge location effects

    DOE PAGESBeta

    Teich-McGoldrick, Stephanie L.; Greathouse, Jeffery A.; Jove-Colon, Carlos F.; Cygan, Randall Timothy

    2015-08-27

    In this study, the swelling properties of smectite clay minerals are relevant to many engineering applications including environmental remediation, repository design for nuclear waste disposal, borehole stability in drilling operations, and additives for numerous industrial processes and commercial products. We used molecular dynamics and grand canonical Monte Carlo simulations to study the effects of layer charge location, interlayer cation, and temperature on intracrystalline swelling of montmorillonite and beidellite clay minerals. For a beidellite model with layer charge exclusively in the tetrahedral sheet, strong ion–surface interactions shift the onset of the two-layer hydrate to higher water contents. In contrast, for amore » montmorillonite model with layer charge exclusively in the octahedral sheet, weaker ion–surface interactions result in the formation of fully hydrated ions (two-layer hydrate) at much lower water contents. Clay hydration enthalpies and interlayer atomic density profiles are consistent with the swelling results. Water adsorption isotherms from grand canonical Monte Carlo simulations are used to relate interlayer hydration states to relative humidity, in good agreement with experimental findings.« less

  10. Swelling properties of montmorillonite and beidellite clay minerals from molecular simulation: Comparison of temperature interlayer cation, and charge location effects

    SciTech Connect

    Teich-McGoldrick, Stephanie L.; Greathouse, Jeffery A.; Jove-Colon, Carlos F.; Cygan, Randall Timothy

    2015-08-27

    In this study, the swelling properties of smectite clay minerals are relevant to many engineering applications including environmental remediation, repository design for nuclear waste disposal, borehole stability in drilling operations, and additives for numerous industrial processes and commercial products. We used molecular dynamics and grand canonical Monte Carlo simulations to study the effects of layer charge location, interlayer cation, and temperature on intracrystalline swelling of montmorillonite and beidellite clay minerals. For a beidellite model with layer charge exclusively in the tetrahedral sheet, strong ion–surface interactions shift the onset of the two-layer hydrate to higher water contents. In contrast, for a montmorillonite model with layer charge exclusively in the octahedral sheet, weaker ion–surface interactions result in the formation of fully hydrated ions (two-layer hydrate) at much lower water contents. Clay hydration enthalpies and interlayer atomic density profiles are consistent with the swelling results. Water adsorption isotherms from grand canonical Monte Carlo simulations are used to relate interlayer hydration states to relative humidity, in good agreement with experimental findings.

  11. Comparison of characteristics of montmorillonite supported nano zero valent iron (M-nZVI) and nano zero valent iron (nZVI)

    NASA Astrophysics Data System (ADS)

    How, Ho Kuok; Wan Zuhairi W., Y.

    2015-09-01

    In this study, synthesized montmorillonite supported nano zero valent iron (M-nZVI) and nano zero valent iron (nZVI) are compared physically and chemically. The samples were prepared using chemical reduction method that includes sodium borohydride and ethanol. Due to the tendency of nZVI to aggregate, montmorillonite is used as a supporting material. TEM and FESEM images show that the M-nZVI has decreased the aggregation by dispersing the particles on the surface of montmorillonite whereas images of nZVI show chain-like particle due to aggregation. Both images also show particles synthesized are nanoparticles. With less aggregation, the surface area of the M-nZVI is greater than nZVI which is 45.46 m2/g and 10.49 m2/g respectively. XRD patterns have shown Fe0 are synthesized and small amount of iron oxides are produced. M-nZVI has the capability in reducing aggregation which might lead to the increase in reactivity of the particles thus enhancing the performance of nZVI.

  12. pH profile of the adsorption of nucleotides onto montmorillonite. II - Adsorption and desorption of 5-prime-AMP in iron-calcium montmorillonite systems

    NASA Technical Reports Server (NTRS)

    Banin, A.; Lawless, J. G.; Mazzurco, J.; Church, F. M.; Margulies, L.; Orenberg, J. B.

    1985-01-01

    The interaction of 5-prime-AMP with montmorillonite saturated with various ratios of two metals found ubiquitously on the surface of earth, that is, iron and calcium, is investigated. Adsorption and desorption of the nucleotide were studied in the pH range of 2-12 at three levels of addition: 0.080, 0.268 and 0.803 mmole 5-prime-AMP per gram of clay. Two desorption stages were employed - H2O wash and NaOH extraction (pH = 12.0). 5-prime-AMP was preferentially adsorbed on the Fe-containing clays relative to the Ca clay. The nucleotide was fully recovered by the two desorption stages, mostly by the NaOH extraction. The evidence at hand indicates that 5-prime-AMP reaction with clay is affected by electrostatic interactions involving both attraction and repulsion forces. Some specific adsorption, possibly the result of covalent bonding and complex formation with the adsorbed ion, cannot be ruled out for iron but does not appear to operate for calcium. Changes in pH cause varying degrees of attaction and repulsion of 5-prime-AMP and may have been operating on the primitive earth, leading to sequences of adsorption and release of this biomolecule.

  13. Plutonium(IV) sorption to montmorillonite in the presence of organic matter.

    PubMed

    Boggs, Mark A; Dai, Zurong; Kersting, Annie B; Zavarin, Mavrik

    2015-03-01

    The effect of altering the order of addition in a ternary system of plutonium(IV), organic matter (fulvic acid, humic acid and desferrioxamine B), and montmorillonite was investigated. A decrease in Pu(IV) sorption to montmorillonite in the presence of fulvic and humic acid relative to the binary Pu-montmorillonite system, is attributed to strong organic aqueous complex formation with aqueous Pu(IV). No dependence on the order of addition was observed. In contrast, in the system where Pu(IV) was equilibrated with desferrioxamine B (DFOB) prior to addition of montmorillonite, an increase in Pu(IV) sorption was observed relative to the binary system. When DFOB was equilibrated with montmorillonite prior to addition of Pu(IV), Pu(IV) sorption was equivalent to the binary system. X-ray diffraction and transmission electron microscopy revealed that DFOB accumulated in the interlayer of montmorillonite. The order of DFOB addition plays an important role in the observed sorption/desorption behavior of Pu. The irreversible nature of DFOB accumulation in the montmorillonite interlayer leads to an apparent dependence of Pu sorption on the order of addition in the ternary system. This work demonstrates that the order of addition will be relevant in ternary systems in which at least one component exhibits irreversible sorption behavior. PMID:25562752

  14. Response Surface Optimization of Process Parameters and Fuzzy Analysis of Sensory Data of High Pressure-Temperature Treated Pineapple Puree.

    PubMed

    Chakraborty, Snehasis; Rao, Pavuluri Srinivasa; Mishra, Hari Niwas

    2015-08-01

    The high-pressure processing conditions were optimized for pineapple puree within the domain of 400-600 MPa, 40-60 °C, and 10-20 min using the response surface methodology (RSM). The target was to maximize the inactivation of polyphenoloxidase (PPO) along with a minimal loss in beneficial bromelain (BRM) activity, ascorbic acid (AA) content, antioxidant capacity, and color in the sample. The optimum condition was 600 MPa, 50 °C, and 13 min, having the highest desirability of 0.604, which resulted in 44% PPO and 47% BRM activities. However, 93% antioxidant activity and 85% AA were retained in optimized sample with a total color change (∆E*) value less than 2.5. A 10-fold reduction in PPO activity was obtained at 600 MPa/70 °C/20 min; however, the thermal degradation of nutrients was severe at this condition. Fuzzy mathematical approach confirmed that sensory acceptance of the optimized sample was close to the fresh sample; whereas, the thermally pasteurized sample (treated at 0.1 MPa, 95 °C for 12 min) had the least sensory score as compared to others. PMID:26220205

  15. Surface passivation and bandgap widening in poly-Si treated by using high-pressure water-vapor annealing

    NASA Astrophysics Data System (ADS)

    Jang, Young Rae; Yoo, Keon-Ho

    2015-07-01

    Cast-grown polycrystalline silicon (poly-Si) was treated by using high-pressure water-vapor annealing (HWA) at various temperatures and pressures. The effective carrier lifetime ( τ eff ) was measured by using the microwave photo-conductance decay, and the number of dangling bonds was monitored by using the electron spin resonance (ESR). As the annealing temperature and the pressure were increased, the ESR signal due to dangling bonds disappeared at (600 ℃, 0.1 MPa), but τ eff increased only at higher pressures. The Si-O-Si vibration peaks measured by using Fourier-transform infrared spectroscopy appeared under the conditions where τ eff was increased, and the binding energy measured by using X-ray photoemission spectroscopy and the refractive index measured by using ellipsometry showed that SiO2 was formed at the surface. These results show that the bandgap widening due to the formation SiO2 and to the passivation of dangling bonds is responsible for the increased τ eff .

  16. Polyimide-Silica Hybrids Containing Novel Phenylethynyl Imide Silanes as Coupling Agents for Surface-Treated Titanium Alloy

    NASA Technical Reports Server (NTRS)

    Park, C.; Lowther, S. E.; Smith, J. G., Jr.; Connell, J. W.; Hergenrother, P. M.; SaintClair, T. L.

    2000-01-01

    Polyimide-silica hybrids composed of an organic precursor containing a novel phenylethynyl imide silane and an inorganic precursor were evaluated as an adhesion-promoting interphase between surface-treated titanium alloy and a phenylethynyl-containing imide adhesive. The phenylethynyl groups present in the organic precursor, either as a pendent or end group, can bond chemically with a phenylethynyl-containing imide adhesive during processing, while the silane groups of the organic precursor would react chemically with the inorganic precursor. In addition, the inorganic precursor is able to react with the titanium alloy to form a stable bond with the metal oxide. Bond strength and durability were evaluated by single lap shear tests at various conditions. Lap shear specimens exhibited predominantly cohesive failure after a 3-d water boil with 92% retention of the initial room temperature strength. Morphology and chemical composition of the hybrid interphase were investigated with scanning electron microscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy, which revealed development of a silicon-gradient, hybrid structure between the metal substrate and the adhesive.

  17. Oligomerization reactions of deoxyribonucleotides on montmorillonite clay - The effect of mononucleotide structure on phosphodiester bond formation

    NASA Technical Reports Server (NTRS)

    Ferris, James P.; KAMALUDDIN

    1989-01-01

    The formation of oligomers from deoxynucleotides, catalyzed by Na(+)-montmorillonite, was investigated with special attention given to the effect of the monomer structure on the phosphodiester bond formation. It was found that adenine deoxynucleotides bind more strongly to montmorillonite than do the corresponding ribonucleotides and thymidine nucleotides. Tetramers of 2-prime-dpA were detected in the reaction of 2-prime-d-5-prime-AMP with a water-soluble carbodiimide EDAC in the presence of Na(+)-montmorillonite, illustrating the possible role of minerals in the formation of biopolymers on the primitive earth.

  18. Ultrasensitive electrochemical immunosensor for squamous cell carcinoma antigen detection using lamellar montmorillonite-gold nanostructures as signal amplification.

    PubMed

    Jia, Hongying; Gao, Picheng; Ma, Hongmin; Li, Yueyun; Gao, Jian; Du, Bin; Wei, Qin

    2015-01-01

    Sodium montmorillonites (Na-Mont), which could be transformed from nano-montmorillonites, have large surface area, chemical stability, nontoxicity, high cation exchange property and superior adsorption ability. In this paper, Na-Mont were used as a support of polyaniline (PANI) and gold nanoparticles (AuNPs) via the interaction of aniline and HAuCl4 solution. A sandwich-type electrochemical immunosensor was developed to detect squamous cell carcinoma antigen (SCC-Ag). It used nitrogen-doped graphene sheets (N-GS) for the immobilization of primary anti-SCC antibodies (Ab1) and the combined Na-Mont-PANI-AuNPs nanocomposites as labels. Na-Mont-PANI-AuNPs have excellent catalytic ability towards the reduction of H2O2, thus enhance the sensitivity of the immunosensor. The immunosensor exhibits a wide linear range (1 pg/mL-5 ng/mL), a low detection limit (0.3 pg/mL), good reproducibility, selectivity and stability. This new type of immunosensor with Na-Mont-PANI-AuNPs as labels may provide potential application for the detection of SCC-Ag. PMID:25476381

  19. Green Synthesis of Silver Nano-particles by Macrococcus bovicus and Its Immobilization onto Montmorillonite Clay for Antimicrobial Functionality.

    PubMed

    Abdel-Aziz, Mohamed S; Abou-El-Sherbini, Khaled S; Hamzawy, Esmat M A; Amr, Mohey H A; El-Dafrawy, Shady

    2015-08-01

    Macrococcus bovicus was locally isolated from soil and used in the green synthesis of nano-scaling silver (NSAg). It was immobilized on a sodic-montmorillonite clay (MMT1) and cetyltrimethylammonium bromide-modified montmorillonite (MMT2) which was also calcined at 300 °C (MMT3). The NSAg clays were characterized by X-ray fluorescence, Fourier transform infrared spectra, X-ray diffractometry, surface area measurement, UV-Vis spectrometry, scanning electron microscope, transmission electron microscope and thermogravimetric analysis. NSAg was confirmed to be included in the interparticular cavities of the clay sheets and its mechanical stability was evidenced. The antimicrobial activity of the NSAg-modified clays was investigated against Staphylococcus aureus, Escherichia coli and Candida albicans using the cup plate and the plate count techniques. The antimicrobial activity of the NSAg clays was confirmed and attributed to the caging of NSAg in MMT cavities. MMT3 was found to inhibit the microbial growth to as high as 65 % as observed from the plate count method. Graphical Abstract Scheme of the biosynthesis of nano-scaling Ag and its immobilization and antimicrobial application. PMID:26100387

  20. Intergrown mica and montmorillonite in the Allende carbonaceous chondrite

    NASA Technical Reports Server (NTRS)

    Tomeoka, K.; Buseck, P. R.

    1982-01-01

    High resolution transmission electron microscopy (HRTEM) observations were made of a mixture of mica and montmorillonite from fine-grained calcium, aluminum inclusions (CAI) in the Allende C3(V) meteorite. A petrographic thin section having a diameter of 4 mm contained CAI fragments ranging from less than 1 to 50 microns. The observed textural and chemical characteristics placed the inclusion in the fine-grained alkali-rich spinel aggregate category of Warks' (1979) classifications of CAIs and as type 3 in Kornacki's classifications of fine grains in Allende. Chemical analyses were performed on the phyllosilicate grains observed in the TEM scan by means of an X ray observed, and the proximity to the matrix boundary suggests a metamorphism which included aqueous alteration at a relatively low temperature.

  1. Pomegranate peel pectin films as affected by montmorillonite.

    PubMed

    Oliveira, Túlio Ítalo S; Zea-Redondo, Luna; Moates, Graham K; Wellner, Nikolaus; Cross, Kathryn; Waldron, Keith W; Azeredo, Henriette M C

    2016-05-01

    The industrial production of pomegranate juice has been favored by its alleged health benefits derived from its antioxidant properties. The processing of pomegranate juice involves squeezing juice from the fruit with the seeds and the peels together, leaving a pomace consisting of approximately 73 wt% peels. In this study, pectin was extracted from pomegranate peels, and used to produce films with different contents of montmorillonite (MMT) as a nanoreinforcement material. The nanoreinforcement improved the tensile strength and modulus of films when added at up to 6 wt%, while the further addition of MMT (to 8 wt%) reduced the reinforcement effect, probably because of dispersion problems. The elongation was decreased with increasing MMT concentrations. The water vapor permeability decreased with increasing MMT contents up to 8 wt% MMT, indicating that the increased tortuosity of the permeant path was effective on barrier properties of the film. PMID:26769511

  2. Characterization of synthesized polyurethane/montmorillonite nanocomposites foams

    NASA Astrophysics Data System (ADS)

    Ansari, Farahnaz; Sachse, Sophia; Michalowski, S.; Kavosh, Masoud; Pielichowski, Krzysztof; Njuguna, James

    2014-08-01

    Nanophased hybrid composites based on polyurethane/montmorillonite (PU/MMT) have been fabricated. The nanocomposite which was formed by the addition of a polyol premix with 4,4'-diphenylmethane diisocyanate to obtain nanophased polyurethane foams which were then used for fabrication of nanocomposite panels has been shown to have raised strength, stiffness and thermal insulation properties. The nanophased polyurethane foam was characterized by means of scanning electron microscope (SEM), transmission electron microscope (TEM) measurements and X-ray diffraction (XRD). TEM and SEM analysis indicated that nanophased particles are dispersed homogeneously in the polyurethane matrix on the nanometer scale indicating that PU/MMT is an intercalated nanocomposite with a 2-3 nm nanolayer thickness.

  3. Microemulsion polymerized polyaniline/montmorillonite nanocomposite and its electrorheology.

    PubMed

    Song, D H; Lee, H M; Choi, H J

    2009-02-01

    Conducting polyaniline (PANI) and inorganic Na+-Montmorillonite (Na+-MMT) nanocomposite material was prepared via a microemulsion polymerization method. To observe the morphology of the as-synthesized PANI/Na+-MMT nanocomposite, SEM images were employed. D-spacing of the PANI/Na+-MMT nanocomposite obtained from the XRD was found to become wider than that of pure Na+-MMT particles due to the successful intercalation of PANI into Na+-MMT layers. The fabricated PANI/Na+-MMT nanocomposite based electrorheological (ER) fluid was prepared by dispersing the particles in insulating silicone oil. Dynamic mechanical properties of the ER fluid were investigated via an oscillatory testing method using a vertical oscillation rheometer under an applied electric field, showing typical ER behavior. PMID:19441556

  4. Effect of Montmorillonite Clay upon the polycondensation of Lactic Acid

    NASA Astrophysics Data System (ADS)

    El Amine, Belaouedj Mohammed; Mohammed, Belbachir

    2008-08-01

    The development of synthetic biodegradable polymers, such as poly(α-hydroxy acid), is particularly important for constructing medical devices, drug delivery systems, including scaffolds and sutures, and has attracted growing interest in the biomedical field. Here, we report a novel approach to preparing poly(D, L-lactic acid) (PDLA) as a biodegradable polymer. We investigated in detail the reaction conditions for the simple direct polycondensation of lactic acid, including the reaction times, temperatures, and catalyst. The molecular weight of synthesized PLA is dependent on both the reaction temperature and time. The optimum reaction condition to obtain PDLA by direct polycondensation using Maghnite-H+, a proton exchanged Montmorillonite clay, as catalyst was thus determined to be 120 °C for 28h with a molecular weight of 7970. The method for PDLA synthesis established here will facilitate production of PDLA of various molecular weights, which may have a potential utility as biomaterials.

  5. Evaluation of Subsurface Flow and Free-water Surface Wetlands Treating NPR-3 Produced Water - Year No. 1

    SciTech Connect

    Myers, J. E.; Jackson, L. M.

    2001-10-13

    This paper is a summary of some of the activities conducted during the first year of a three-year cooperative research and development agreement (CRADA) between the Department of Energy (DOE) Rocky Mountain Oilfield Testing Center (RMOTC) and Texaco relating to the treatment of produced water by constructed wetlands. The first year of the CRADA is for design, construction and acclimation of the wetland pilot units. The second and third years of the CRADA are for tracking performance of pilot wetlands as the plant and microbial communities mature. A treatment wetland is a proven technology for the secondary and tertiary treatment of produced water, storm water and other wastewaters. Treatment wetlands are typically classified as either free-water surface (FWS) or subsurface flow (SSF). Both FWS and SSF wetlands work well when properly designed and operated. This paper presents a collection of kinetic data gathered from pilot units fed a slipstream of Wyoming (NPR-3) produced water. The pilot units are set up outdoors to test climatic influences on treatment. Monitoring parameters include evapotranspiration, plant growth, temperature, and NPDES discharge limits. The pilot wetlands (FWS and SSF) consist of a series of 100-gal plastic tubs filled with local soils, gravel, sharp sand and native wetland plants (cattail (Typha spp.), bulrush (Scirpus spp.), dwarf spikerush (Eleocharis)). Feed pumps control hydraulic retention time (HRT) and simple water control structures control the depth of water. The treated water is returned to the existing produced water treatment system. All NPDES discharge limits are met. Observations are included on training RMOTC summer students to do environmental work.

  6. Eco-Friendly Magnetic Iron Oxide Pillared Montmorillonite for Advanced Catalytic Degradation of Dichlorophenol

    EPA Science Inventory

    Eco-friendly pillared montmorillonites, in which the pillars consist of iron oxide are expected to have interesting and unusual magnetic properties that are applicable for environmental decontamination. Completely green and effective composite was synthesized using mild reactio...

  7. Eco-Friendly Magnetic Iron Oxide Pillared Montmorillonite for Advanced Catalytic Degradation of Dichlorophenol

    EPA Science Inventory

    Eco-friendly pillared montmorillonites, in which the pillars consist of iron oxide are expected to have interesting and unusual magnetic properties that are applicable for environmental decontamination. Completely “green” and effective composite was synthesized using mild reactio...

  8. Removal of 8-quinolinecarboxylic acid pesticide from aqueous solution by adsorption on activated montmorillonites.

    PubMed

    Mekhloufi, M; Zehhaf, A; Benyoucef, A; Quijada, C; Morallon, E

    2013-12-01

    Sodium montmorillonite (Na-M), acidic montmorillonite (H-M), and organo-acidic montmorillonite (Org-H-M) were applied to remove the herbicide 8-quinolinecarboxylic acid (8-QCA). The montmorillonites containing adsorbed 8-QCA were investigated by transmission electron microscopy, FT-IR spectroscopy, X-ray diffraction analysis, X-ray fluorescence thermogravimetric analysis, and physical adsorption of gases. Experiments showed that the amount of adsorbed 8-QCA increased at lower pH, reaching a maximum at pH 2. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. The Langmuir model provided the best correlation of experimental data for adsorption equilibria. The adsorption of 8-QCA decreased in the order Org-H-M > H-M > Na-M. Isotherms were also used to obtain the thermodynamic parameters. The negative values of ?G indicated the spontaneous nature of the adsorption process. PMID:23925862

  9. Biodegradable nanocomposites from toughened polyhydroxybutyrate and titanate-modified montmorillonite clay.

    PubMed

    Parulekar, Yashodhan; Mohanty, Amar K; Imam, Syed H

    2007-10-01

    Montmorillonite clay treated with neopentyl (diallyl)oxy tri(dioctyl) pyrophosphato titanate was used as a reinforcement for toughened bacterial bioplastic, Polyhydroxybutyrate (PHB) in order to develop novel biodegradable nanocomposites. The modified clay, PHB, toughening partner and specific compatibilizer were processed by extrusion followed by injection molding. Different microscopy and goniometry techniques, rheology analysis, X-ray diffraction and thermo-mechanical testing were used to characterize the nanocomposites. Results showed that the nanocomposites with 5 wt% titanate-modified clay loading exhibited about 400% improvement in impact properties and 40% reduction in modulus in comparison with virgin PHB. The novel aspect of the titanate-based modification was that the nanocomposites still maintained nearly the same impact strength value as that of toughened PHB. The diffraction patterns suggest exfoliation of the organically modified clays and this was further supported by transmission electron microscopy and melt rheological analysis. The mechanical properties of the nanocomposites were correlated with a modified Halpin-Tsai theoretical model and the predictions matched significantly with the experimental results. Toughened and compatibilized PHB showed significantly lower biodegradation rate than virgin PHB and most significantly the addition of the titanate-modified clay in the same formulation enhanced the biodegradation several fold. PMID:18330176

  10. Electrochemical energy storage in montmorillonite K10 clay based composite as supercapacitor using ionic liquid electrolyte.

    PubMed

    Maiti, Sandipan; Pramanik, Atin; Chattopadhyay, Shreyasi; De, Goutam; Mahanty, Sourindra

    2016-02-15

    Exploring new electrode materials is the key to realize high performance energy storage devices for effective utilization of renewable energy. Natural clays with layered structure and high surface area are prospective materials for electrical double layer capacitors (EDLC). In this work, a novel hybrid composite based on acid-leached montmorillonite (K10), multi-walled carbon nanotube (MWCNT) and manganese dioxide (MnO2) was prepared and its electrochemical properties were investigated by fabricating two-electrode asymmetric supercapacitor cells against activated carbon (AC) using 1.0M tetraethylammonium tetrafluroborate (Et4NBF4) in acetonitrile (AN) as electrolyte. The asymmetric supercapacitors, capable of operating in a wide potential window of 0.0-2.7V, showed a high energy density of 171Whkg(-1) at a power density of ∼1.98kWkg(-1). Such high EDLC performance could possibly be linked to the acid-base interaction of K10 through its surface hydroxyl groups with the tetraethylammonium cation [(C2H5)4N(+) or TEA(+)] of the ionic liquid electrolyte. Even at a very high power density of 96.4kWkg(-1), the cells could still deliver an energy density of 91.1Whkg(-1) exhibiting an outstanding rate capability. The present study demonstrates for the first time, the excellent potential of clay-based composites for high power energy storage device applications. PMID:26609925

  11. Stability of Organically Modified Montmorillonites and Their Polystyrene Nanocomposites After Prolonged Thermal Treatment

    SciTech Connect

    Frankowski,D.; Capracotta, M.; Martin, J.; Khan, S.; Spontak, R.

    2007-01-01

    Melt intercalation of montmorillonite (MMT) into polymeric matrices to improve the mechanical properties of polymers has evolved into a subject of tremendous fundamental and technological interest. The thermal treatment experienced during processing or end use can substantially affect the clay and diminish the target properties of polymer/clay nanocomposites (NCs) because of deintercalation or degradation of surface modifiers. In this work, changes in morphology, chemistry, and thermal stability of organically modified (OM) MMT after annealing in O{sub 2}-rich and N{sub 2} environments are investigated. Degradation of the alkyl ammonium cation occurs at temperatures as low as 105 {sup o}C upon prolonged exposure in an O{sub 2}-rich environment. X-ray diffractometry (XRD) performed in situ establishes the response of two OM-MMTs to elevated temperatures at short times, whereas ex situ XRD provides insight into high-temperature exposure at long times. Active sites on the silicate surfaces are found to induce scission of, as well as chemical interaction with, the chains comprising a polystyrene (PS) matrix. Size-exclusion chromatography indicates that PS chain scission occurs primarily after relatively short annealing times, whereas branching and cross-linking are more prevalent after long exposure times in an O{sub 2}-rich environment.

  12. Sulfosulfuron incorporated in micelles adsorbed on montmorillonite for slow release formulations.

    PubMed

    Mishael, Yael G; Undabeytia, Tomas; Rabinovitz, Onn; Rubin, Baruch; Nir, Shlomo

    2003-04-01

    Slow release formulations of the anionic herbicide sulfosulfuron (SFS) were prepared by incorporating it in micelles of an organic cation octadecyltrimethylammonium, which adsorb on the clay-mineral montmorillonite. The fraction of SFS adsorbed on the micelle-clay complex reached 98%, whereas for monomer-clay complexes, its adsorption was insignificant. Fluorescence studies showed surface contact between the micelles and the clay surface. The rate of SFS release from the micelle-clay formulations in aqueous suspensions was slow (<1%, 72 h). Spraying SFS formulations on a thin soil layer in a funnel, followed by irrigations (50 mm), resulted in complete elution of SFS from the commercial formulation (dispersible granular) versus 4% from the micelle-clay formulation. A plant bioassay in Rehovot soil showed that these respective formulations yielded 23 and 65% of shoot growth inhibition of foxtail. Consequently, the slow release micelle-clay formulations of SFS yield significantly reduced leaching and enhanced biological activity, thus providing environmental and agricultural advantages. PMID:12670166

  13. Preparation and characterization of silver loaded montmorillonite modified with sulfur amino acid

    NASA Astrophysics Data System (ADS)

    Li, Tian; Lin, Oulian; Lu, Zhiyuan; He, Liuimei; Wang, Xiaosheng

    2014-06-01

    The Na+ montmorillonite (MMT) was modified with sulfur containing amino acid (L-cystine, L-cysteine or L-methionine) and characterized by energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectrum (FT-IR). The results showed the modification was smooth and the surface condition of MMT was changed with sulfur containing groups. Then silver was loaded on the modified MMTs via ion-exchange reaction under microwave irradiation, the spectra of X-ray photoelectron spectroscopy (XPS), EDS and FT-IR confirmed the successful loading of massive silver and the strong interaction between sulfur and silver, the silver loaded L-cystine modified MMT (Ag@AA-MMT-3) with a silver content of 10.93 wt% was the highest of all. Further more, the Ag@AA-MMT-3 was under the irradiation of a UV lamp to turn silver ions to silver nano particles (Ag NPs). The XPS, specific surface area (SSA), transmission electron microscopy (TEM), XRD patterns and UV-vis spectra proved the existence of uniform nano scaled metallic Ag NPs. By contrast, the UV irradiated Ag@AA-MMT-3 (Ag@AA-MMT-UV) showed a much better slow release property than Ag@AA-MMT-3 or Ag@MMT. The Ag@AA-MMT-UV showing a large inhibition zone and high inhibition ratio presented very good antibacterial property.

  14. A facile method to synthesize the photocatalytic TiO2/montmorillonite nanocomposites with enhanced photoactivity

    NASA Astrophysics Data System (ADS)

    Chen, Daimei; Zhu, Honglei; Wang, Xue

    2014-11-01

    A new method for immobilizing nano-scaled TiO2 on the surface of montmorillonite (Mt) clay has been developed. First, cationic surfactants were introduced into the Mt galleries through ion exchange and physical adsorption processes. Next a titanium precursor with negative charges was allowed to hydrolyze and condense around the nature clay to form meso-phase assemblies on the external and internal surface of the Mt. After the removal of the surfactant, a highly porous TiO2 pillared clay with mesopores was formed. The cationic surfactant has a templating role, which not only tailored the formation of TiO2 but also controlled the TiO2 content in the composite. The photocatalytic performances of these new porous materials were evaluated by using methylene blue degradation. The photocatalytic activity of these TiO2 composite is higher than that of P25 although TiO2 only accounts for about one-third of the sample's mass in the composite samples.

  15. Characterization of montmorillonite doped PVA/SA blends using X-ray diffraction

    SciTech Connect

    Hemalatha, K.; Somashekarappa, H.; Mahadevaiah,; Somashekar, R.

    2014-04-24

    PVA films doped with Montmorillonite was prepared by slow evaporation technique. These films have been used to record X-ray patterns at room temperature. Correlation lengths and microstructural parameters were computed using in-house program employing X-ray data. Results show that correlation lengths as well as crystallite size increases with increase in the concentration of Montmorillonite which is inconformity with the conductivity studies.

  16. Adsorption enthalpy and adsorption isotherm of tetradecylpyridinium bromide on Na-montmorillonite

    SciTech Connect

    Chen, G.; Song, X.; Zhao, Y.; Han, B.; Yan, H.

    1997-02-01

    The adsorption enthalpy and the adsorption isotherm of tetradecylpyridinium bromide (TPB) onto a Na-montmorillonite suspension and the dilution enthalpy of the TPB solution have been determined at 298.15 K. The dilution process is endothermic and the adsorption process is exothermic. For ion exchange adsorption, the interaction between TP{sup +} and the montmorillonite because the cumulative adsorption enthalpy increases dramatically with adsorption amount. For molecular adsorption, however, the interaction between TPB and the clay is much weaker.

  17. Characterization of montmorillonite doped PVA/SA blends using X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Hemalatha, K.; Mahadevaiah, Somashekarappa, H.; Somashekar, R.

    2014-04-01

    PVA films doped with Montmorillonite was prepared by slow evaporation technique. These films have been used to record X-ray patterns at room temperature. Correlation lengths and microstructural parameters were computed using in-house program employing X-ray data. Results show that correlation lengths as well as crystallite size increases with increase in the concentration of Montmorillonite which is inconformity with the conductivity studies.

  18. Behavior of Listeria monocytogenes on frankfurters surface treated with lauric arginate and/or a liquid smoke extract delivered using the Sprayed Lethality in Container (SLIC®) technology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to determine the viability of Listeria monocytogenes (LM) on commercially-produced frankfurters prepared without lactates that were surface treated with 0 or 4 mL of a blend of LAE (CytoGuard; 1.0% LAE final concentration) diluted in a concentrated liquid smoke extrac...

  19. Low-temperature atomic layer deposition of Al{sub 2}O{sub 3} on blown polyethylene films with plasma-treated surfaces

    SciTech Connect

    Beom Lee, Gyeong; Sik Son, Kyung; Won Park, Suk; Hyung Shim, Joon; Choi, Byoung-Ho

    2013-01-15

    In this study, a layer of Al{sub 2}O{sub 3} was deposited on blown polyethylene films by atomic layer deposition (ALD) at low temperatures, and the surface characteristics of these Al{sub 2}O{sub 3}-coated blown polyethylene films were analyzed. In order to examine the effects of the plasma treatment of the surfaces of the blown polyethylene films on the properties of the films, both untreated and plasma-treated film samples were prepared under various processing conditions. The surface characteristics of the samples were determined by x-ray photoelectron spectroscopy, as well as by measuring their surface contact angles. It was confirmed that the surfaces of the plasma-treated samples contained a hydroxyl group, which helped the precursor and the polyethylene substrate to bind. ALD of Al{sub 2}O{sub 3} was performed through sequential exposures to trimethylaluminum and H{sub 2}O at 60 Degree-Sign C. The surface morphologies of the Al{sub 2}O{sub 3}-coated blown polyethylene films were observed using atomic force microscopy and scanning electron microscopy/energy-dispersive x-ray spectroscopy. Further, it was confirmed that after ALD, the surface of the plasma-treated film was covered with alumina grains more uniformly than was the case for the surface of the untreated polymer film. It was also confirmed via the focused ion beam technique that the layer Al{sub 2}O{sub 3} conformed to the surface of the blown polyethylene film.

  20. Nitrogen behavior in a free water surface constructed wetland used as posttreatment for anaerobically treated swine wastewater effluent.

    PubMed

    De Los Reyes, Catalina Plaza; Pozo, Guillermo; Vidal, Gladys

    2014-01-01

    The aim of this study was to evaluate the behavior of total nitrogen (TN) in its different forms in a Free Water Surface constructed wetland (FWS) used as posttreatment for anaerobically treated swine wastewater. The experiment was conducted in a glasshouse from July 2010 to November 2011. The system consists in a FWS mesocosm inoculated with Typha angustifolia L. using as pretreatment an UASB reactor (upflow anaerobic sludge blanket). The operation are based on the progressive increase of the nitrogen loading rate (NLR) (2.0-30.2 kg TN/ha·d) distributed in 12 loads, with an operational time of 20 d. The results indicate that the behavior of the TN in the FWS, mainly depends on the NLR applied, the amount of dissolved oxygen available and the seasonality. The FWS operated with an NLR between 2.0-30.2 kg TN/ha·d, presents average removal efficiency for TN of 54.8%, with a maximum removal (71.7%) between spring-summer seasons (17.3-21.7°C). The availability of dissolved oxygen hinders the nitrification/denitrification processes in the FWS representing a 0.3-5.6% of TN removed.The main route of TN removal is associated with ammonia volatilization processes (2.6-40.7%), mainly to NLR over 25.8 kg TN/ha· d and with temperatures higher than 18°C. In a smaller proportion, the incorporation of nitrogen via plant uptake was 10.8% whereas the TN accumulated in the sediments was a 5.0% of the TN applied during the entire operation (550 d). An appropriate control of the NLR applied, can reduce the ammonia volatilization processes and the phytotoxicity effects expressed as growth inhibition in 80.0% from 496.0 mg NH(+) 4-N/L (25.8 kg TN/ha·d). PMID:24171422

  1. Anti-graffiti nanocomposite materials for surface protection of a very porous stone

    NASA Astrophysics Data System (ADS)

    Licchelli, Maurizio; Malagodi, Marco; Weththimuni, Maduka; Zanchi, Chiara

    2014-09-01

    The preservation of stone substrates from defacement induced by graffiti represents a very challenging task, which can be faced by applying suitable protective agents on the surface. Although different anti-graffiti materials have been developed, it is often found that their effectiveness is unsatisfactory, most of all when applied on very porous stones, e.g. Lecce stone. The aim of this work was to study the anti-graffiti behaviour of new nanocomposite materials obtained by dispersing montmorillonite nanoparticles (layered aluminosilicates with a high-aspect ratio) into a fluorinated polymer matrix (a fluorinated polyurethane based on perfluoropolyether blocks). Polymeric structure was modified by inducing a cross-linking process, in order to produce a durable anti-graffiti coating with enhanced barrier properties. Several composites were prepared using a naturally occurring and an organically modified montmorillonite clay (1, 3, and 5 % w/w concentrations). Materials were applied on Lecce stone specimens, and then their treated surfaces were soiled by a black ink permanent marker or by a black acrylic spray paint. Several repeated staining/cleaning cycles were performed in order to evaluate anti-graffiti effectiveness. Colorimetric measurements were selected to assess the anti-graffiti performance. It was found that the presence of 3 % w/w organically modified montmorillonite in the polymer coating is enough to induce a durable anti-graffiti effect when the stone surface is stained by acrylic paint. Less promising results are obtained when staining by permanent marker is considered as all the investigated treatments afford a reasonable protection from ink only for the first staining/cleaning cycle.

  2. The Study on Inhibition of Planktonic Bacterial Growth by Non-Thermal Atmospheric Pressure Plasma Jet Treated Surfaces for Dental Application.

    PubMed

    Yoo, Eun-Mi; Uhm, Soo-Hyuk; Kwon, Jae-Sung; Choi, Hye-Sook; Choi, Eun Ha; Kim, Kwang-Mahn; Kim, Kyoung-Nam

    2015-02-01

    Investigation of the effects by non-thermal atmospheric pressure plasma jet (NTAPPJ) treatment on the titanium dental implant surfaces for the inhibition of two common pathogens related with dental infections, Streptococcus mutans and Staphylococcus aureus, was carried out in this study. The commercially pure titanium was used as specimen, which were irradiated by NTAPPJ for 30, 60 and 120 seconds. Specimen without being treated with NTAPPJ was assigned as the control group. The X-ray photoelectron spectroscope and surface contact angle goniometer were used to analyze the effects of NTAPPJ treatment on surface chemistry and hydrophilicity of the specimen. The effects of the NTAPPJ treatment on surfaces, in terms of bacterial attachment, growth, morphology and structural changes were evaluated by the number of colony forming units (CFU) and scanning electron microscopy (SEM) observations. The results showed that there was a reduction of CFUs and the significant change in morphology of bacteria as they were cultured on the titanium surfaces treated with NTAPPJ. These results were related to surface chemical changes and hydrophilicity changes by NTAPPJ. The NTAPPJ treatment is very effective on the dental implant titanium surface treatment that resulted in the inhibition of bacteria and has a great potential to be a promising technique in various clinical dental applications. PMID:26349309

  3. Effects of exchanged cation and layer charge on the sorption of water and EGME vapors on montmorillonite clays

    USGS Publications Warehouse

    Chiou, C.T.; Rutherford, D.W.

    1997-01-01

    The effects of exchanged cation and layer charge on the sorption of water and ethylene glycol monoethyl ether (EGME) vapors on montmorillonite have been studied on SAz-1 and SWy-1 source clays, each exchanged respectively with Ca, Na, K, Cs and tetramethylammonium (TMA) cations. The corresponding lattice expansions were also determined, and the corresponding N2 adsorption data were provided for comparison. For clays exchanged with cations of low hydrating powers (such as K, Cs and TMA), water shows a notably lower uptake than does N2 at low relative pressures (P/P0). By contrast, EGME shows higher uptakes than N2 on all exchanged clays at all P/P0. The anomaly for water is attributed to its relatively low attraction for siloxane surfaces of montmorillonite because of its high cohesive energy density. In addition to solvating cations and expanding interlayers, water and EGME vapors condense into small clay pores and interlayer voids created by interlayer expansion. The initial (dry) interlayer separation varies more significantly with cation type than with layer charge; the water-saturated interlayer separation varies more with cation type than the EGME-saturated interlayer separation. Because of the differences in surface adsorption and interlayer expansion for water and EGME, no general correspondence is found between the isotherms of water and EGME on exchanged clays, nor is a simple relation observed between the overall uptake of either vapor and the cation solvating power. The excess interlayer capacities of water and of EGME that result from lattice expansion of the exchanged clays are estimated by correcting for amounts of vapor adsorption on planar clay surfaces and of vapor condensation into intrinsic clay pores. The resulting data follow more closely the relative solvating powers of the exchanged cations.

  4. Synthesis and characterization of TiO2 pillared montmorillonites: application for methylene blue degradation.

    PubMed

    Chen, Daimei; Du, Gaoxiang; Zhu, Qian; Zhou, Fengsan

    2013-11-01

    TiO2 pillared clay composites were prepared by modifying of montmorillonite (Mt) with cetyl-trimethyammoniumbromide (CTAB) and then using an acidic solution of hydrolyzed Ti alkoxide to intercalate into the interlayer space of the organic modified Mt. The as-prepared materials were characterized by XRD, FTIR, TEM, SEM TG-DTA, specific surface area and porosity measurements. The composites had a porous delaminated structure with pillared fragments and well dispersed TiO2 nanoparticles. Introduction of CTAB into the synthetic system accelerated the hydrolysis and condensation of the Ti source, which promoted TiO2 formation. In addition, the CTAB also significantly increased the porosity and surface area of the composites. A number of anatase particles, with crystal sizes of 5-10 nm, were homogenously distributed on the surface of the Mt as the result of the templating role of CTAB. The resultant TiO2 pillared Mt exhibited good thermal stability as indicated by its surface area after calcination at 800°C. No phase transformations from anatase to rutile were observed even under calcination at 900°C. The grain size of the anatase in prepared sample increased from 2.67 nm to 13.42 nm as the calcination temperature increased from 300°C to 900°C. The photocatalytic performance of these new porous materials was evaluated by using methylene blue degradation. The composite exhibited better photocatalytic property than P 25. The maximum removal efficiency of this composite was up to 99% within 60 min. PMID:23957927

  5. In vitro biocompatibility and antimicrobial activity of poly(ε-caprolactone)/montmorillonite nanocomposites.

    PubMed

    Corrales, T; Larraza, I; Catalina, F; Portolés, T; Ramírez-Santillán, C; Matesanz, M; Abrusci, C

    2012-12-10

    A triblock copolymer based on poly(ε-caprolactone) (PCL) and 2-(N,N-diethylamino)ethyl methacrylate (DEAEMA)/2-(methyl-7-nitrobenzofurazan)amino ethyl acrylate (NBD-NAcri), was synthesized via atom transfer radical polymerization (ATRP). The corresponding chlorohydrated copolymer, named as PCL-b-DEAEMA, was prepared and anchored via cationic exchange on montmorillonite (MMT) surface. (PCL)/layered silicate nanocomposites were prepared through melt intercalation, and XRD and TEM analysis showed an exfoliated/intercalated morphology for organomodified clay. The surface characterization of the nanocomposites was undertaken by using contact angle and AFM. An increase in the contact angle was observed in the PCL/MMT(PCL-b-DEAEMA) nanocomposites with respect to PCL. The AFM analysis showed that the surface of the nanocomposites became rougher with respect to the PCL when MMTk10 or MMT(PCL-b-DEAEMA) was incorporated, and the value increased with the clay content. The antimicrobial activity of the nanocomposites against B. subtilis and P. putida was tested. It is remarkable that the biodegradation of PCL/MMT(PCL-b-DEAEMA) nanocomposites, monitored by the production of carbon dioxide and by chemiluminescence emission, was inhibited or retarded with respect to the PCL and PCL/1-MMTk10. It would indicate that nature of organomodifier in the clay play an important role in B. subtilis and P. putida adhesion processes. Biocompatibility studies demonstrate that both PCL and PCL/MMT materials allow the culture of murine L929 fibroblasts on its surface with high viability, very low apoptosis, and without plasma membrane damage, making these materials very adequate for tissue engineering. PMID:23153018

  6. Pulsed electric linear dichroism of triphenylmethane dyes adsorbed on montmorillonite K10 in aqueous media

    SciTech Connect

    Yamaoka, Kiwamu; Sasai, Ryo

    2000-05-01

    Electric linear dichroism (ELD) spectra of two cationic triphenylmethane dyes, crystal violet (CV) and malachite green (MG), bound to sodium montmorillonite K10 (MK-10) were studied at 20 C in aqueous media at two mixing ratios, D/S, of 0.10 and 0.24 in the 700- to 400 nm wavelength region and in the applied electric field strength range between 0 and 3 kV/cm. The specific parallel and perpendicular dichroism ({Delta}A{sub {parallel}}/A and {Delta}A{sub {perpendicular}}/A) spectra of dye-adsorbed MK-10 suspension were measured at a fixed field strength with an apparatus equipped with a 512-channel photodiode array detector. By changing the field strength over a wide range, a series of the reduced dichroism values of the bound dyes were measured at a fixed wavelength. By fitting these dichroism values to theoretical orientation functions, the intrinsic reduced dichroism ({Delta}A/A){sub int} spectra at the limiting high fields (ELD spectrum) were determined for CV and MG bound to MK-10. No appreciable difference was observed at the two D/S values. The ELD spectra of these bound dyes are undulatory but never constant, throughout their absorption region; thus, the dye plane does not lie flatly either on the surface or between layers of MK-10 particle.

  7. Sonocatalytic removal of an organic dye using TiO2/Montmorillonite nanocomposite.

    PubMed

    Khataee, Alireza; Sheydaei, Mohsen; Hassani, Aydin; Taseidifar, Mojtaba; Karaca, Semra

    2015-01-01

    The sonocatalytic performance of the synthesized TiO2/Montmorillonite K10 (TiO2/MMT) nanocomposite was studied in removal of Basic Blue 3 (BB3) from water. The TiO2/MMT nanocomposite was prepared by hydrothermal method. Scanning electron microscope, X-ray diffraction and Fourier transform infrared were used to characterize the synthesized nanocomposite. The average size of TiO2 nanoparticles decreased from 60-80nm to 40-60nm through the immobilization of this semiconductor on the surface of MMT. The obtained results indicated that the sonocatalytic activity of TiO2/MMT nanocomposite was higher than that of pure TiO2 nanoparticles and MMT particles. Furthermore, the main influence factors on the sonocatalytic activity such as the BB3 concentration, pH of solution, TiO2/MMT dose, power of ultrasonic generator, and inorganic salts were studied. The intermediates of BB3 degradation during the sonocatalytic process in the presence of the TiO2/MMT nanocomposite have been monitored by gas chromatography-mass spectrometry. PMID:25060118

  8. Transparent films based on PLA and montmorillonite with tunable oxygen barrier properties.

    PubMed

    Svagan, Anna J; Åkesson, Anna; Cárdenas, Marité; Bulut, Sanja; Knudsen, Jes C; Risbo, Jens; Plackett, David

    2012-02-13

    Polylactide (PLA) is viewed as a potential material to replace synthetic plastics (e.g., poly(ethylene terephthalate) (PET)) in food packaging, and there have been a number of developments in this direction. However, for PLA to be competitive in more demanding uses such as the packaging of oxygen-sensitive foods, the oxygen permeability coefficient (OP) needs to be reduced by a factor of ~10. To achieve this, a layer-by-layer (Lbl) approach was used to assemble alternating layers of montmorillonite clay and chitosan on extruded PLA film surfaces. When 70 bilayers were applied, the OP was reduced by 99 and 96%, respectively, at 20 and 50% RH. These are, to our knowledge, the best improvements in oxygen barrier properties ever reported for a PLA/clay-based film. The process of assembling such multilayer structures was characterized using a quartz crystal microbalance with dissipation monitoring. Transmission electron microscopy revealed a well-ordered laminar structure in the deposited multilayer coatings, and light transmittance results demonstrated the high optical clarity of the coated PLA films. PMID:22229499

  9. Simultaneous adsorption of Cd²⁺ and BPA on amphoteric surfactant activated montmorillonite.

    PubMed

    Liu, Chongmin; Wu, Pingxiao; Zhu, Yajie; Tran, Lytuong

    2016-02-01

    The study mainly investigated the simultaneous adsorption of bisphenol A (BPA) and Cd(2+) from aqueous solution on octadecane-betaine modified montmorillonite (BS-Mt). The characteristics of the obtained materials were analyzed by X-ray diffraction (XRD), Fourier-transform infrared (FTIR), Specific surface area (BET) and Scanning electron microscopy/Energy disperse spectroscopy (SEM/EDS), confirming that BS-18 was successfully introduced into Mt. Also, factors including initial solution pH, initial Cd(2+)/BPA concentration, contact time and adsorbent dosage on the adsorption processes were shown to be crucial for Cd(2+) adsorption, whereas had negligible effects on BPA adsorption. In this study, we found that pseudo-second-order model fitted well with the adsorption kinetic studies for both Cd(2+) and BPA with an equilibrium time of 24 h. The Cd(2+) and BPA adsorption isotherm could be well described by Freundlich model and Langmuir model, respectively. On the basis of kinetic models, the maximum adsorption capacity of Cd(2+) in aqueous solution was slightly enhanced after modification, indicating that Cd(2+) adsorption on BS-Mt was mainly attributed to direct electrostatic attraction and the chelate reaction, while the dramatic enhancement of maximum adsorption capacity for BPA was due to the hydrophobic interaction. PMID:26451652

  10. Removal of herbicides from aqueous solutions by modified forms of montmorillonite.

    PubMed

    Park, Yuri; Sun, Zhiming; Ayoko, Godwin A; Frost, Ray L

    2014-02-01

    This investigation for the removal of agricultural pollutants, imazaquin and atrazine was conducted using montmorillonite (MMT) exchanged with organic cations through ion exchange. The study found that the adsorption of the herbicides was affected by the degree of organic cation saturations, the size of organic cations and the different natures of the herbicides. The modified clays intercalated with the larger surfactant molecules at the higher concentrations tended to enhance the adsorption of imazaquin and atrazine. In particular, the organoclays were highly efficient for the removal of imazaquin while the adsorption of atrazine was minimal due to the different hydrophobicities. Both imazaquin and atrazine were influenced by the changes of pH. The amphoteric imazaquin exists as an anion at the pH 5-7 and the anionic imazaquin was protonated to a neutral and further a cationic form when the pH is lower. The weak base, atrazine was also protonated at lower pH values. The anionic imazaquin had a strong affinity to the organoclays on the external surface as well as in the interlayer space of the MMT through electrostatic and hydrophobic interactions. In this study, the electrostatic interaction can be the primary mechanism involved during the adsorption process. This study also investigated a comparative adsorption for the imazaquin and atrazine and the lower adsorption of atrazine was enhanced and this phenomenon was due to the synergetic effect. This work highlights a potential mechanism for the removal of specific persistence herbicides from the environment. PMID:24267339

  11. Activity of laccase immobilized on TiO2-montmorillonite complexes.

    PubMed

    Wang, Qingqing; Peng, Lin; Li, Guohui; Zhang, Ping; Li, Dawei; Huang, Fenglin; Wei, Qufu

    2013-01-01

    The TiO2-montmorillonite (TiO2-MMT) complex was prepared by blending TiO2 sol and MMT with certain ratio, and its properties as an enzyme immobilization support were investigated. The pristine MMT and TiO2-MMT calcined at 800 °C (TiO2-MMT800) were used for comparison to better understand the immobilization mechanism. The structures of the pristine MMT, TiO2-MMT, and TiO2-MMT800 were examined by HR-TEM, XRD and BET. SEM was employed to study different morphologies before and after laccase immobilization. Activity and kinetic parameters of the immobilized laccase were also determined. It was found that the TiO2 nanoparticles were successfully introduced into the MMT layer structure, and this intercalation enlarged the "d value" of two adjacent MMT layers and increased the surface area, while the calcination process led to a complete collapse of the MMT layers. SEM results showed that the clays were well coated with adsorbed enzymes. The study of laccase activity revealed that the optimum pH and temperature were pH = 3 and 60 °C, respectively. In addition, the storage stability for the immobilized laccase was satisfactory. The kinetic properties indicated that laccase immobilized on TiO2-MMT complexes had a good affinity to the substrate. It has been proved that TiO2-MMT complex is a good candidate for enzyme immobilization. PMID:23771020

  12. Hemicelluloses/montmorillonite hybrid films with improved mechanical and barrier properties.

    PubMed

    Chen, Ge-Gu; Qi, Xian-Ming; Li, Ming-Peng; Guan, Ying; Bian, Jing; Peng, Feng; Yao, Chun-Li; Sun, Run-Cang

    2015-01-01

    A facile and environmentally friendly method was introduced to incorporate montmorillonite (MMT) as an inorganic phase into quaternized hemicelluloses (QH) for forming hemicellulose-based films. Two fillers, polyvinyl alcohol (PVA) and chitin nanowhiskers (NCH), were added into the hemicelluloses/MMT hybrid matrices to prepare hybrid films, respectively. The hybrid films were nanocomposites with nacre-like structure and multifunctional characteristics including higher strength and good oxygen barrier properties via the electrostatic and hydrogen bonding interactions. The addition of PVA and NCH could induce changes in surface topography, and effectively enhance mechanical strength, thermal stability, transparency, and oxygen barrier properties. The tensile strengths of the composite films FPVA(0.3), FPVA(0.5), and FNCH(0.8) were 53.7, 46.3, and 50.1 MPa, respectively, which were 171%, 134%, and 153% larger than the FQH-MMT film (19.8 MPa). The tensile strength, and oxygen transmission rate of QH-MMT-PVA film were better than those of quaternized hemicelluloses/MMT films. Thus, the proper filler is very important for the strength of the hybrid film. These results provide insights into the understanding of the structural relationships of hemicellulose-based composite films in coating and packaging application for the future. PMID:26549418

  13. Cd(II) Sorption on Montmorillonite-Humic acid-Bacteria Composites

    PubMed Central

    Du, Huihui; Chen, Wenli; Cai, Peng; Rong, Xingmin; Dai, Ke; Peacock, Caroline L.; Huang, Qiaoyun

    2016-01-01

    Soil components (e.g., clays, bacteria and humic substances) are known to produce mineral-organic composites in natural systems. Herein, batch sorption isotherms, isothermal titration calorimetry (ITC), and Cd K-edge EXAFS spectroscopy were applied to investigate the binding characteristics of Cd on montmorillonite(Mont)-humic acid(HA)-bacteria composites. Additive sorption and non-additive Cd(II) sorption behaviour is observed for the binary Mont-bacteria and ternary Mont-HA-bacteria composite, respectively. Specifically, in the ternary composite, the coexistence of HA and bacteria inhibits Cd adsorption, suggesting a “blocking effect” between humic acid and bacterial cells. Large positive entropies (68.1 ~ 114.4 J/mol/K), and linear combination fitting of the EXAFS spectra for Cd adsorbed onto Mont-bacteria and Mont-HA-bacteria composites, demonstrate that Cd is mostly bound to bacterial surface functional groups by forming inner-sphere complexes. All our results together support the assertion that there is a degree of site masking in the ternary clay mineral-humic acid-bacteria composite. Because of this, in the ternary composite, Cd preferentially binds to the higher affinity components-i.e., the bacteria. PMID:26792640

  14. Synthesis of polyacrylamide-montmorillonite clay nanocomposite using non-conventional electrochemical technique.

    PubMed

    Srivastava, Monika; Prakash, Rajiv

    2012-01-01

    Synthesis of polymer-clay nanocomposite by in-situ incorporation of polyacrylamide in organically modified montmorillonite (MMT) clay layers is being reported using non-conventional electrochemical technique "plasma electrolysis." A luminous sheath of plasma is sustained between an electrode (anode) and the surface of surrounding liquid electrolyte at sufficiently high voltage, for synthesis of polymer or nanocomposite. Using this technique, radical generation capability is explored as a new tool for radical polymerization and in-situ composite formation of polyacrylamide. Polyacrylamide-MMT clay nanocomposite is synthesized by taking acrylamide and MMT clay in K2SO4 electrolyte solution at the anodic potential of 660 V. Polyacrylamide and polyacrylamide-MMT clay nanocomposites are characterized for their structural and thermal properties. Intercalation in MMT clay layers of homogeneous nanocomposite is supported by X-ray diffraction, FTIR, DSC, TGA and SEM/TEM techniques. This novel method produces homogeneous interactive composite with high yield, and shows potential to replace chemical initiators based harsh synthetic processes used for conventional polymer-nanocomposites formation. PMID:22524007

  15. Cd(II) Sorption on Montmorillonite-Humic acid-Bacteria Composites.

    PubMed

    Du, Huihui; Chen, Wenli; Cai, Peng; Rong, Xingmin; Dai, Ke; Peacock, Caroline L; Huang, Qiaoyun

    2016-01-01

    Soil components (e.g., clays, bacteria and humic substances) are known to produce mineral-organic composites in natural systems. Herein, batch sorption isotherms, isothermal titration calorimetry (ITC), and Cd K-edge EXAFS spectroscopy were applied to investigate the binding characteristics of Cd on montmorillonite(Mont)-humic acid(HA)-bacteria composites. Additive sorption and non-additive Cd(II) sorption behaviour is observed for the binary Mont-bacteria and ternary Mont-HA-bacteria composite, respectively. Specifically, in the ternary composite, the coexistence of HA and bacteria inhibits Cd adsorption, suggesting a "blocking effect" between humic acid and bacterial cells. Large positive entropies (68.1 ~ 114.4 J/mol/K), and linear combination fitting of the EXAFS spectra for Cd adsorbed onto Mont-bacteria and Mont-HA-bacteria composites, demonstrate that Cd is mostly bound to bacterial surface functional groups by forming inner-sphere complexes. All our results together support the assertion that there is a degree of site masking in the ternary clay mineral-humic acid-bacteria composite. Because of this, in the ternary composite, Cd preferentially binds to the higher affinity components-i.e., the bacteria. PMID:26792640

  16. Hemicelluloses/montmorillonite hybrid films with improved mechanical and barrier properties

    NASA Astrophysics Data System (ADS)

    Chen, Ge-Gu; Qi, Xian-Ming; Li, Ming-Peng; Guan, Ying; Bian, Jing; Peng, Feng; Yao, Chun-Li; Sun, Run-Cang

    2015-11-01

    A facile and environmentally friendly method was introduced to incorporate montmorillonite (MMT) as an inorganic phase into quaternized hemicelluloses (QH) for forming hemicellulose-based films. Two fillers, polyvinyl alcohol (PVA) and chitin nanowhiskers (NCH), were added into the hemicelluloses/MMT hybrid matrices to prepare hybrid films, respectively. The hybrid films were nanocomposites with nacre-like structure and multifunctional characteristics including higher strength and good oxygen barrier properties via the electrostatic and hydrogen bonding interactions. The addition of PVA and NCH could induce changes in surface topography, and effectively enhance mechanical strength, thermal stability, transparency, and oxygen barrier properties. The tensile strengths of the composite films FPVA(0.3), FPVA(0.5), and FNCH(0.8) were 53.7, 46.3, and 50.1 MPa, respectively, which were 171%, 134%, and 153% larger than the FQH-MMT film (19.8 MPa). The tensile strength, and oxygen transmission rate of QH-MMT-PVA film were better than those of quaternized hemicelluloses/MMT films. Thus, the proper filler is very important for the strength of the hybrid film. These results provide insights into the understanding of the structural relationships of hemicellulose-based composite films in coating and packaging application for the future.

  17. Hemicelluloses/montmorillonite hybrid films with improved mechanical and barrier properties

    PubMed Central

    Chen, Ge-Gu; Qi, Xian-Ming; Li, Ming-Peng; Guan, Ying; Bian, Jing; Peng, Feng; Yao, Chun-Li; Sun, Run-Cang

    2015-01-01

    A facile and environmentally friendly method was introduced to incorporate montmorillonite (MMT) as an inorganic phase into quaternized hemicelluloses (QH) for forming hemicellulose-based films. Two fillers, polyvinyl alcohol (PVA) and chitin nanowhiskers (NCH), were added into the hemicelluloses/MMT hybrid matrices to prepare hybrid films, respectively. The hybrid films were nanocomposites with nacre-like structure and multifunctional characteristics including higher strength and good oxygen barrier properties via the electrostatic and hydrogen bonding interactions. The addition of PVA and NCH could induce changes in surface topography, and effectively enhance mechanical strength, thermal stability, transparency, and oxygen barrier properties. The tensile strengths of the composite films FPVA(0.3), FPVA(0.5), and FNCH(0.8) were 53.7, 46.3, and 50.1 MPa, respectively, which were 171%, 134%, and 153% larger than the FQH-MMT film (19.8 MPa). The tensile strength, and oxygen transmission rate of QH-MMT-PVA film were better than those of quaternized hemicelluloses/MMT films. Thus, the proper filler is very important for the strength of the hybrid film. These results provide insights into the understanding of the structural relationships of hemicellulose-based composite films in coating and packaging application for the future. PMID:26549418

  18. Photocatalytic reactions of nanocomposite of ZnS nanoparticles and montmorillonite

    NASA Astrophysics Data System (ADS)

    Praus, P.; Reli, M.; Kočí, K.; Obalová, L.

    2013-06-01

    ZnS nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) were deposited on montmorillonite (MMT) forming a ZnS-CTA-MMT nanocomposite. The nanocomposite was characterized by scanning electron microscopy (SEM), Fourier transformed infrared (FTIR) and UV diffuse reflectance spectra (DRS) spectrometry, X-ray powder diffraction (XRD) and specific surface area measurements. Thereafter, it was used for photocatalytic reactions under UV irradiation (Hg lamp) in three different reaction media with different pH: NaOH solution, HCl solution and water. Prior to the photocatalytic reactions the dispersions were saturated by carbon dioxide to buffer the systems. The main reaction products in gas phase determined by gas chromatography were hydrogen and methane. The reactions were monitored by measuring oxidation-reduction potentials. The highest yields of hydrogen were obtained in the dispersion acidified by HCl but the concentrations of methane were similar in all tested media. Hydrogen was supposed to be formed by the reaction of two hydrogen radicals. Methane was formed by the reduction of carbon dioxide and by the partial decomposition of CTAB.

  19. Hybrid materials: Magnetite-Polyethylenimine-Montmorillonite, as magnetic adsorbents for Cr(VI) water treatment.

    PubMed

    Larraza, Iñigo; López-Gónzalez, Mar; Corrales, Teresa; Marcelo, Gema

    2012-11-01

    Hybrid materials formed by the combination of a sodium rich Montmorillonite (MMT), with magnetite nanoparticles (40 nm, Fe(3)O(4) NPs) coated with Polyethylenimine polymer (PEI 800 g/mol or PEI 25000 g/mol) were prepared. The intercalation of the magnetite nanoparticles coated with PEI among MMT platelets was achieved by cationic exchange. The resulting materials presented a high degree of exfoliation of the MMT sheets and a good dispersion of Fe(3)O(4) NPs on both the surface and among the layers of MMT. The presence of amine groups in the PEI structure not only aids the exfoliation of the MMT layers, but also gives to the hybrid material the necessary functionality to interact with heavy metals. These hybrid materials were used as magnetic sorbent for the removal of hexavalent chromium from water. The effect that pH, Cr(VI) concentration, and adsorbent material composition have on the Cr(VI) removal efficiency was studied. A complete characterization of the materials was performed. The hybrid materials showed a slight dependence of the removal efficiency with the pH in a wide range (1-9). A maximum amount of adsorption capacity of 8.8 mg/g was determined by the Langmuir isotherm. Results show that these hybrid materials can be considered as potential magnetic adsorbent for the Cr(VI) removal from water in a wide range of pH. PMID:22841705

  20. Structure-property relationships in isotactic poly(propylene)/ethylene propylene rubber/montmorillonite nanocomposites.

    PubMed

    Causin, Valerio; Marega, Carla; Marigo, Antonio; Ferraro, Giuseppe; Ferrara, Angelo; Selleri, Roberta

    2008-04-01

    Nanocomposites based on isotactic polypropylene/ethylene propylene rubber (iPP/EPR) were prepared adding different amounts of montmorillonite and maleated polypropylene. The structure and morphology of the samples were characterized by small angle X-ray scattering, wide angle X-ray diffraction, electronic and optical microscopy and differential scanning calorimetry, iPP showed a polymorphic behavior. Clay disrupted the ordered crystallization of iPP and had a key role in shaping the distribution of iPP and EPR phases: larger filler contents brought about smaller, less coalesced and more homogeneous rubber domains. Clay distributed itself only in the continuous phase and not in the rubber domains. Tactoids persisted on the surface of the sample, while delamination proceeded to a greater degree in the bulk of the materials. Melt flow rate, impact strength, flexural and tensile properties, were also measured and a structure-property correlation was sought. Clay produced its most significant effect on physical-mechanical properties by controlling the size of rubber domains in the heterophasic matrix. This allowed to obtain nanocomposites with increased stiffness and impact strength, a remarkable achievement for polymer layered-silica nanocomposites that usually suffer the drawback of being stiffer than the unfilled matrix, but at the same time with a lower resistance to impact. A beneficial effect of clay on thermal stability was also observed. PMID:18572583

  1. Seeming steady-state uphill diffusion of 22Na+ in compacted montmorillonite.

    PubMed

    Glaus, Martin A; Birgersson, Martin; Karnland, Ola; Van Loon, Luc R

    2013-10-15

    Whereas the transport of solutes in nonreactive porous media can mostly be described by diffusion driven by the concentration gradients in the external bulk water phase, the situation for dense clays and clay rocks has been less clear for a long time. The presence of fixed negative surface charges complicates the application of Fick's laws in the case of ionic species. Here we report the seeming uphill diffusion of a (22)Na(+) tracer in compacted sodium montmorillonite, that is, transport directed from a low to a high tracer concentration reservoir. In contrast to the classical through-diffusion technique the present experiments were carried out under the conditions of a gradient in the background electrolyte and using equal initial (22)Na(+) tracer concentrations on both sides of the clay sample. We conclude that the dominant driving force for diffusion is the concentration gradient of exchangeable cations in the nanopores. Commonly used diffusion models, based on concentration gradients in the external bulk water phase, may thus predict incorrect fluxes both in terms of magnitude and direction. PMID:24059910

  2. Interactions between Nafion resin and protonated dodecylamine modified montmorillonite: a solid state NMR study.

    PubMed

    Zhang, Limin; Xu, Jun; Hou, Guangjin; Tang, Huiru; Deng, Feng

    2007-07-01

    A series of nanocomposites have been prepared from perfluorosulfonylfluoride copolymer resin (Nafion) and layered montmorillonite (MMT) modified with protonated dodecylamine by conventional sol-gel intercalation. The structure of these nanocomposite materials have been characterized using FT-IR, elemental analysis, XRD and solid state NMR techniques, including 19F magic-angle spinning (MAS) NMR, 19F NMR relaxation time measurements, 29Si MAS, 1H MAS, 1H-13C cross-polarization magic-angle spinning (CPMAS), and 1H-13C heteronuclear correlation (HETCOR) 2D NMR. The results showed that thermal stability of Nafion was improved moderately by the addition of dodecylamine modified MMT without intercalation. FT-IR and 29Si MAS NMR results indicated that dodecylamine modification did not result in obvious changes in the MMT lattice structure. The XRD results showed that the protonated dodecylamine has been embedded and intercalated into the MMT interlayers, whereas Nafion was not. Elemental analysis results also suggested that some dodecylamine was adsorbed on the surface of MMT. 1H-13C HETCOR 2D NMR experiment clearly indicated that strong electrostatic interactions were present between the NH+3 group of dodecylamine and the fluorine-containing groups (CF3, OCF2, and SCF2) of Nafion resin. Such electrostatic interactions are probably the major contributors for the improved thermal stability of the resultant composite materials. PMID:17382953

  3. Bisphenol A sorption by organo-montmorillonite: implications for the removal of organic contaminants from water.

    PubMed

    Park, Yuri; Sun, Zhiming; Ayoko, Godwin A; Frost, Ray L

    2014-07-01

    Remediation of bisphenol A (BPA) from aqueous solutions by adsorption using organoclays synthesized from montmorillonite (MMT) with different types of organic surfactant molecules was demonstrated. High adsorption capacities of the organoclays for the uptake of BPA were observed and these demonstrated their potential application as strong adsorbents for noxious organic water contaminants. The adsorption of BPA was significantly influenced by pH, with increased adsorption of BPA in acidic pH range. However, the organoclays intercalated with highly loaded surfactants and/or large surfactant molecules were less influenced by the pH of the environment and this was thought to be due to the shielding the negative charge from surfactant molecules and the development of more positive charge on the clay surface, which leads to the attraction of anionic BPA even at alkaline pH. The hydrophobic phase created by loaded surfactant molecules contributed to a partitioning phase, interacting with BPA molecules strongly through hydrophobic interaction. Pseudo-second order kinetic model and Langmuir isotherm provided the best fit for the adsorption of BPA onto the organoclays. In addition, the adsorption process was spontaneous and exothermic with lower temperature facilitating the adsorption of BPA onto the organoclays. The described process provides a potential pathway for the removal of BPA from contaminated waters. PMID:24412097

  4. Sonocatalytic removal of naproxen by synthesized zinc oxide nanoparticles on montmorillonite.

    PubMed

    Karaca, Melike; Kıranşan, Murat; Karaca, Semra; Khataee, Alireza; Karimi, Atefeh

    2016-07-01

    ZnO/MMT nanocomposite as sonocatalyst was prepared by immobilizing synthesized ZnO on the montmorillonite surface. The characteristics of as-prepared nanocomposite were studied by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD) techniques. The synthesized samples were used as a catalyst for sonocatalytic degradation of naproxen. ZnO/MMT catalyst in the presence of ultrasound irradiation was more effective compared to pure ZnO nanoparticles and MMT particles in the sonocatalysis of naproxen. The effect of different operational parameters on the sonocatalytic degradation of naproxen including initial drug concentration, sonocatalyst dosage, solution pH, ultrasonic power and the presence of organic and inorganic scavengers were evaluated. It was found that the presence of the scavengers suppressed the sonocatalytic degradation efficiency. The reusability of the nanocomposite was examined in several consecutive runs, and the degradation efficiency decreased only 2% after 5 repeated runs. The main intermediates of naproxen degradation were determined by gas chromatography-mass spectrometry (GC-Mass). PMID:26964947

  5. XPS study on the weakest zone in the adhesion structure between resin containing 4-META and precious metal alloys treated with different surface modification methods.

    PubMed

    Ohno, H; Endo, K; Yamane, Y; Kawashima, I

    2001-03-01

    Three precious metal alloys, Type IV gold alloy, 14 K gold alloy, and silver-based alloy, were treated with different surface modifications including a metal primer (VBATDT) application, a SiOx coating method, high-temperature oxidation, modification method with a liquid Ga-Sn alloy, and tin electroplating. Then thin PMMA films were bonded with a resin containing 4-META. Water durability at the adhesion interface was evaluated after water immersion, followed by thermal cycling used liquid nitrogen. The weakest zone at the interface was investigated using XPS only for the Ag-Pd alloy specimens that had been surface-treated with as-polishing, adhesive primer, and the SiOx coating method, since peeling of the PMMA film on the surface of specimens surface-treated by other methods was not observed. Metal elements were detected from the resin side at the adhesion interface. The chemical states of Cu in the resin before argon ion etching were characterized as metal oxides and/or states of chemical interaction with 4-META, VBATDT, or SiOx. PMID:11441491

  6. Determination of bulk and surface superconducting properties of N2-doped cold worked, heat treated and electro-polished SRF grade niobium

    DOE PAGESBeta

    Chetri, Santosh; Larbalestier, David C.; Lee, Peter J.; Dhakal, Pashupati; Sung, Zu -Hawn

    2015-12-01

    In this study, nitrogen-doped cavities show significant performance improvement in the medium accelerating field regime due to a lowered RF surface resistivity. However, the mechanism of enhancement has not been clearly explained. Our experiments explore how N2-doping influences Nb bulk and surface superconducting properties, and compare the N2-doped properties with those obtained previously with conventionally treated samples. High purity Nb-rod was mechanically deformed and post treated based on a typical SRF cavity treatment recipe. The onset of flux penetration at Hc1, and the upper and the surface critical fields, Hc2 and Hc3, were characterized by magnetic hysteresis and AC susceptibilitymore » techniques. The surface depth profile responsible for superconductivity was examined by changing AC amplitude in AC susceptibility, and the microstructure was directly observed with EBSD-OIM. We are also investigating surface chemistry for detailed composition using XPS. We have found that N2-doping at 800 °C significantly reduces the Hc3/Hc2 ratio towards the ideal value of ~1.7, and conclude that AC susceptibility is capable of following changes to the surface properties induced by N2-doping.« less

  7. Determination of bulk and surface superconducting properties of N2-doped cold worked, heat treated and electro-polished SRF grade niobium

    SciTech Connect

    Chetri, Santosh; Larbalestier, David C.; Lee, Peter J.; Dhakal, Pashupati; Sung, Zu -Hawn

    2015-12-01

    In this study, nitrogen-doped cavities show significant performance improvement in the medium accelerating field regime due to a lowered RF surface resistivity. However, the mechanism of enhancement has not been clearly explained. Our experiments explore how N2-doping influences Nb bulk and surface superconducting properties, and compare the N2-doped properties with those obtained previously with conventionally treated samples. High purity Nb-rod was mechanically deformed and post treated based on a typical SRF cavity treatment recipe. The onset of flux penetration at Hc1, and the upper and the surface critical fields, Hc2 and Hc3, were characterized by magnetic hysteresis and AC susceptibility techniques. The surface depth profile responsible for superconductivity was examined by changing AC amplitude in AC susceptibility, and the microstructure was directly observed with EBSD-OIM. We are also investigating surface chemistry for detailed composition using XPS. We have found that N2-doping at 800 °C significantly reduces the Hc3/Hc2 ratio towards the ideal value of ~1.7, and conclude that AC susceptibility is capable of following changes to the surface properties induced by N2-doping.

  8. Competitive sorption and selective sequence of Cu(II) and Ni(II) on montmorillonite: Batch, modeling, EPR and XAS studies

    NASA Astrophysics Data System (ADS)

    Yang, Shitong; Ren, Xuemei; Zhao, Guixia; Shi, Weiqun; Montavon, Gilles; Grambow, Bernd; Wang, Xiangke

    2015-10-01

    Heavy metal ions that leach from various industrial and agricultural processes are simultaneously present in the contaminated soil and water systems. The competitive sorption of these toxic metal ions on the natural soil components and sediments significantly influences their migration, bioavailability and ecotoxicity in the geochemical environment. In this study, the competitive sorption and selectivity order of Cu(II) and Ni(II) on montmorillonite are investigated by combining the batch experiments, X-ray diffraction (XRD), electron paramagnetic resonance (EPR), surface complexation modeling and X-ray Absorption Spectroscopy (XAS). The batch experimental data show that the coexisting Ni(II) exhibits a negligible influence on the sorption behavior of Cu(II), whereas the coexisting Cu(II) reduces the Ni(II) sorption percentage and changes the shape of the Ni(II) sorption isotherm. The sorption species of Cu(II) and Ni(II) on montmorillonite over the acidic and near-neutral pH range are well simulated by the surface complexation modeling. However, this model cannot identify the occurrence of surface nucleation and the co-precipitation processes at a highly alkaline pH. Based on the results of the EPR and XAS analyses, the microstructures of Cu(II) on montmorillonite are identified as the hydrated free Cu(II) ions at pH 5.0, inner-sphere surface complexes at pH 6.0 and the surface dimers/Cu(OH)2(s) precipitate at pH 8.0 in the single-solute and the binary-solute systems. For the Ni(II) sorption in the single-solute system, the formed microstructure varies from the hydrated free Ni(II) ions at the pH values of 5.0 and 6.0 to the inner-sphere surface complexes at pH 8.0. For the Ni(II) sorption in the binary-solute system, the coexisting Cu(II) induces the formation of the inner-sphere complexes at pH 6.0. In contrast, Ni(II) is adsorbed on montmorillonite via the formation of Ni phyllosilicate co-precipitate/α-Ni(OH)2(s) precipitate at pH 8.0. The selective sequence of Cu(II) > Ni(II) for binding on montmorillonite can be ascribed to the differences in the metal properties and the compatibility between the configurations of the montmorillonite binding sites and those of the Cu(II)O6/Ni(II)O6 polyhedra. The derived findings in this study could provide significant information for the evaluation of the competitive sorption behaviors at solid/water interfaces and the fate of the coexisting heavy metal ions in multicomponent environmental systems.

  9. Effects of Dextrose and Lipopolysaccharide on the Corrosion Behavior of a Ti-6Al-4V Alloy with a Smooth Surface or Treated with Double-Acid-Etching

    PubMed Central

    Faverani, Leonardo P.; Assunção, Wirley G.; de Carvalho, Paulo Sérgio P.; Yuan, Judy Chia-Chun; Sukotjo, Cortino; Mathew, Mathew T.; Barao, Valentim A.

    2014-01-01

    Diabetes and infections are associated with a high risk of implant failure. However, the effects of such conditions on the electrochemical stability of titanium materials remain unclear. This study evaluated the corrosion behavior of a Ti-6Al-4V alloy, with a smooth surface or conditioned by double-acid-etching, in simulated body fluid with different concentrations of dextrose and lipopolysaccharide. For the electrochemical assay, the open-circuit-potential, electrochemical impedance spectroscopy, and potentiodynamic test were used. The disc surfaces were characterized by scanning electron microscopy and atomic force microscopy. Their surface roughness and Vickers microhardness were also tested. The quantitative data were analyzed by Pearson's correlation and independent t-tests (α = 0.05). In the corrosion parameters, there was a strong lipopolysaccharide correlation with the Ipass (passivation current density), Cdl (double-layer capacitance), and Rp (polarization resistance) values (p<0.05) for the Ti-6Al-4V alloy with surface treatment by double-acid-etching. The combination of dextrose and lipopolysaccharide was correlated with the Icorr (corrosion current density) and Ipass (p<0.05). The acid-treated groups showed a significant increase in Cdl values and reduced Rp values (p<0.05, t-test). According to the topography, there was an increase in surface roughness (R2 = 0.726, p<0.0001 for the smooth surface; R2 = 0.405, p = 0.036 for the double-acid-etching-treated surface). The microhardness of the smooth Ti-6Al-4V alloy decreased (p<0.05) and that of the treated Ti-6Al-4V alloy increased (p<0.0001). Atomic force microscopy showed changes in the microstructure of the Ti-6Al-4V alloy by increasing the surface thickness mainly in the group associated with dextrose and lipopolysaccharide. The combination of dextrose and lipopolysaccharide affected the corrosion behavior of the Ti-6Al-4V alloy surface treated with double-acid-etching. However, no dose-response corrosion behavior could be observed. These results suggest a greater susceptibility to corrosion of titanium implants in diabetic patients with associated infections. PMID:24671257

  10. Comparison of the protection effectiveness of acrylic polyurethane coatings containing bark extracts on three heat-treated North American wood species: Surface degradation

    NASA Astrophysics Data System (ADS)

    Kocaefe, Duygu; Saha, Sudeshna

    2012-04-01

    High temperature heat-treatment of wood is a very valuable technique which improves many properties (biological durability, dimensional stability, thermal insulating characteristics) of natural wood. Also, it changes the natural color of wood to a very attractive dark brown color. Unfortunately, this color is not stable if left unprotected in external environment and turns to gray or white depending on the wood species. To overcome this problem, acrylic polyurethane coatings are applied on heat-treated wood to delay surface degradations (color change, loss of gloss, and chemical modifications) during aging. The acrylic polyurethane coatings which have high resistance against aging are further modified by adding bark extracts and/or lignin stabilizer to enhance their effectiveness in preventing the wood aging behavior. The aging characteristic of this coating is compared with acrylic polyurethane combined with commercially available organic UV stabilizers. In this study, their performance on three heat-treated North American wood species (jack pine, quaking aspen and white birch) are compared under accelerated aging conditions. Both the color change data and visual assessment indicate improvement in protective characteristic of acrylic polyurethane when bark extracts and lignin stabilizer are used in place of commercially available UV stabilizer. The results showed that although acrylic polyurethane with bark extracts and lignin stabilizer was more efficient compared to acrylic polyurethane with organic UV stabilizers in protecting heat-treated jack pine, it failed to protect heat-treated aspen and birch effectively after 672 h of accelerated aging. This degradation was not due to the coating adhesion loss or coating degradation during accelerated aging; rather, it was due to the significant degradation of heat-treated aspen and birch surface beneath this coating. The XPS results revealed formation of carbonyl photoproducts after aging on the coated surfaces and chain scission of Csbnd N of urethane linkages.

  11. Influence of operating parameters on surface properties of RF glow discharge oxygen plasma treated TiO₂/PET film for biomedical application.

    PubMed

    Pandiyaraj, K Navaneetha; Deshmukh, R R; Mahendiran, R; Su, Pi-G; Yassitepe, Emre; Shah, Ismat; Perni, Stefano; Prokopovich, Polina; Nadagouda, Mallikarjuna N

    2014-03-01

    In this paper, a thin transparent titania (TiO2) film was coated on the surface of flexible poly(ethylene terephthalate) (PET) film using the sol-gel method. The surface properties of the obtained TiO2/PET film were further improved by RF glow discharge oxygen plasma as a function of exposure time and discharge power. The changes in hydrophilicity of TiO2/PET films were analyzed by contact angle measurements and surface energy. The influence of plasma on the surface of the TiO2/PET films was analyzed by atomic force microscopy (AFM) as well as the change in chemical state and composition that were investigated by X-ray photo electron spectroscopy (XPS). The cytotoxicity of the TiO2/PET films was analyzed using human osteoblast cells and the bacterial eradication behaviors of TiO2/PET films were also evaluated against Staphylococcus bacteria. It was found that the surface roughness and incorporation of oxygen containing polar functional groups of the plasma treated TiO2/PET films increased substantially as compared to the untreated one. Moreover the increased concentration of Ti(3+) on the surface of plasma treated TiO2/PET films was due to the transformation of chemical states (Ti(4+)→Ti(3+)). These morphological and chemical changes are responsible for enhanced hydrophilicity of the TiO2/PET films. Furthermore, the plasma treated TiO2/PET film exhibited no citotoxicity against osteoblast cells and antibacterial activity against Staphylococcus bacteria which can find application in manufacturing of biomedical devices. PMID:24433917

  12. Nanoporous silver cathode surface treated by atomic layer deposition of CeO x for low-temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Chean Neoh, Ke; Han, Gwon Deok; Kim, Manjin; Kim, Jun Woo; Jong Choi, Hyung; Park, Suk Won; Shim, Joon Hyung

    2016-05-01

    We evaluated the performance of solid oxide fuel cells (SOFCs) with a 50 nm thin silver (Ag) cathode surface treated with cerium oxide (CeO x ) by atomic layer deposition (ALD). The performances of bare and ALD-treated Ag cathodes were evaluated on gadolinia-doped ceria (GDC) electrolyte supporting cells with a platinum (Pt) anode over 300 °C-450 °C. Our work confirms that ALD CeO x treatment enhances cathodic performance and thermal stability of the Ag cathode. The performance difference between cells using a Ag cathode optimally treated with an ALD CeO x surface and a reference Pt cathode is about 50% at 450 °C in terms of fuel cell power output in our experiment. The bare Ag cathode completely agglomerated into islands during fuel cell operation at 450 °C, while the ALD CeO x treatment effectively protects the porosity of the cathode. We also discuss the long-term stability of ALD CeO x -treated Ag cathodes related to the microstructure of the layers.

  13. Nanoporous silver cathode surface treated by atomic layer deposition of CeO x for low-temperature solid oxide fuel cells.

    PubMed

    Neoh, Ke Chean; Han, Gwon Deok; Kim, Manjin; Kim, Jun Woo; Choi, Hyung Jong; Park, Suk Won; Shim, Joon Hyung

    2016-05-01

    We evaluated the performance of solid oxide fuel cells (SOFCs) with a 50 nm thin silver (Ag) cathode surface treated with cerium oxide (CeO x ) by atomic layer deposition (ALD). The performances of bare and ALD-treated Ag cathodes were evaluated on gadolinia-doped ceria (GDC) electrolyte supporting cells with a platinum (Pt) anode over 300 °C-450 °C. Our work confirms that ALD CeO x treatment enhances cathodic performance and thermal stability of the Ag cathode. The performance difference between cells using a Ag cathode optimally treated with an ALD CeO x surface and a reference Pt cathode is about 50% at 450 °C in terms of fuel cell power output in our experiment. The bare Ag cathode completely agglomerated into islands during fuel cell operation at 450 °C, while the ALD CeO x treatment effectively protects the porosity of the cathode. We also discuss the long-term stability of ALD CeO x -treated Ag cathodes related to the microstructure of the layers. PMID:27008979

  14. New polyelectrolyte complex from pectin/chitosan and montmorillonite clay.

    PubMed

    da Costa, Marcia Parente Melo; de Mello Ferreira, Ivana Lourenço; de Macedo Cruz, Mauricio Tavares

    2016-08-01

    A new nanocomposite hydrogel was prepared by forming a crosslinked hybrid polymer network based on chitosan and pectin in the presence of montmorillonite clay. The influence of clay concentration (0.5 and 2% wt) as well as polymer ratios (1:1, 1:2 and 2:1) was investigated carefully. The samples were characterized by different techniques: transmission and scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, swelling degree and compression test. Most samples presented swelling degree above 1000%, which permits characterizing them as superabsorbent material. Images obtained by transmission electron microscopy showed the presence of clay nanoparticles into hydrogel. The hydrogels' morphological properties were evaluated by scanning electron microscope in high and low-vacuum. The micrographs showed that the samples presented porous. The incorporation of clay produced hydrogels with differentiated morphology. Thermogravimetric analysis results revealed that the incorporation of clay in the samples provided greater thermal stability to the hydrogels. The compression resistance also increased with addition of clay. PMID:27112858

  15. Morphological and thermal properties of cellulose-montmorillonite nanocomposites.

    PubMed

    Cerruti, Pierfrancesco; Ambrogi, Veronica; Postiglione, Alessandro; Rychlý, Jozef; Matisová-Rychlá, Lyda; Carfagna, Cosimo

    2008-11-01

    Cellulose-layered montmorillonite (MMT) nanocomposites were prepared by precipitation from N-methylmorpholine- N-oxide (NMMO)/water solutions. Two hybrid samples were obtained to investigate the influence of the reaction time on the extent of clay dispersion within the matrix. It was observed that longer contact times are needed to yield nanocomposites with a partially exfoliated morphology. The thermal and thermal oxidative properties of the hybrids, which might be of interest for fire-resistant final products, were investigated by thermogravimetry and chemiluminescence (CL). The nanocomposites exhibited increased degradation temperatures compared to plain cellulose, and the partially exfoliated sample showed the maximum stability. This result was explained in terms of hindered transfer of heat, oxygen, and degraded volatiles due to the homogeneously dispersed clay filler. Kinetic analysis of the decomposition process showed that the degradation of regenerated cellulose and cellulose-based hybrids occurred through a multistep mechanism. Moreover, the presence of nanoclay led to drastic changes in the dependence of the activation energy on the degree of degradation. CL analysis showed that longer permanence in NMMO/water solutions brought about the formation of carbonyl compounds on the polymer backbone. Moreover, MMT increased the rate of dehydration and oxidation of cellulose functional moieties. As a consequence, cellulose was found to be less stable at temperatures lower than 100 degrees C. Conversely, at higher temperatures, the hindering of oxygen transfer prevailed, determining an increase in thermo-oxidative stability. PMID:18842055

  16. Catalytic Ethanol Dehydration over Different Acid-activated Montmorillonite Clays.

    PubMed

    Krutpijit, Chadaporn; Jongsomjit, Bunjerd

    2016-01-01

    In the present study, the catalytic dehydration of ethanol to obtain ethylene over montmorillonite clays (MMT) with mineral acid activation including H2SO4 (SA-MMT), HCl (HA-MMT) and HNO3 (NA-MMT) was investigated at temperature range of 200 to 400°C. It revealed that HA-MMT exhibited the highest catalytic activity. Ethanol conversion and ethylene selectivity were found to increase with increased reaction temperature. At 400°C, the HA-MMT yielded 82% of ethanol conversion having 78% of ethylene yield. At lower temperature (i.e. 200 to 300°C), diethyl ether (DEE) was a major product. The highest activity obtained from HA-MMT can be attributed to an increase of weak acid sites and acid density by the activation of MMT with HCl. It can be also proven by various characterization techniques that in most case, the main structure of MMT did not alter by acid activation (excepted for NA-MMT). Upon the stability test for 72 h during the reaction, the MMT and HA-MMT showed only slight deactivation due to carbon deposition. Hence, the acid activation of MMT by HCl is promising to enhance the catalytic dehydration of ethanol. PMID:27041515

  17. Effect of sonication on the particle size of montmorillonite clays.

    PubMed

    Poli, Alessandra L; Batista, Tatiana; Schmitt, Carla C; Gessner, Fergus; Neumann, Miguel G

    2008-09-15

    This paper reports on the effect of sonication on SAz-1 and SWy-1 montmorillonite suspensions. Changes in the size of the particles of these materials and modifications of their properties have been investigated. The variation of the particle size has been analyzed by DLS (dynamic light scattering). In all cases the clay particles show a bimodal distribution. Sonication resulted in a decrease of the larger modal diameter, as well as a reduction of its volume percentage. Simultaneously, the proportion of the smallest particles increases. After 60 min of sonication, SAz-1 presented a very broad particle size distribution with a modal diameter of 283 nm. On the other hand, the SWy-1 sonicated for 60 min presents a bimodal distribution of particles at 140 and 454 nm. Changes in the properties of the clay suspensions due to sonication were evaluated spectroscopically from dye-clay interactions, using Methylene Blue. The acidic sites present in the interlamellar region, which are responsible for dye protonation, disappeared after sonication of the clay. The changes in the size of the scattering particles and the lack of acidic sites after sonication suggest that sonication induces delamination of the clay particles. PMID:18572177

  18. Synthesis of silver nanoparticles in montmorillonite and their antibacterial behavior

    PubMed Central

    Shameli, Kamyar; Ahmad, Mansor Bin; Zargar, Mohsen; Yunus, Wan Md Zin Wan; Rustaiyan, Abdolhossein; Ibrahim, Nor Azowa

    2011-01-01

    Silver nanoparticles (Ag NPs) were synthesized by the chemical reducing method in the external and interlamellar space of montmorillonite (MMT) as a solid support at room temperature. AgNO3 and NaBH4 were used as a silver precursor and reducing agent, respectively. The most favorable experimental conditions for synthesizing Ag NPs in the MMT are described in terms of the initial concentration of AgNO3. The interlamellar space limits changed little (d-spacing = 1.24–1.47 nm); therefore, Ag NPs formed on the MMT suspension with d-average = 4.19–8.53 nm diameter. The Ag/MMT nanocomposites (NCs), formed from AgNO3/MMT suspension, were characterizations with different instruments, for example UV-visible, PXRD, TEM, SEM, EDXRF, FT-IR, and ICP-OES analyzer. The antibacterial activity of different sizes of Ag NPs in MMT were investigated against Gram-positive, ie, Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) and Gram-negative bacteria, ie, Escherichia coli, Escherichia coli O157:H7, and Klebsiella pneumoniae, by the disk diffusion method using Mueller-Hinton agar (MHA). The smaller Ag NPs were found to have significantly higher antibacterial activity. These results showed that Ag NPs can be used as effective growth inhibitors in different biological systems, making them applicable to medical applications. PMID:21674015

  19. Preparation and characterization of bone cements incorporated with montmorillonite.

    PubMed

    Kwon, Soon Yong; Cho, Eun Hee; Kim, Sung Soo

    2007-10-01

    Bone cements incorporated with montmorillonite (MMT) were prepared in an attempt to improve their mechanical properties. The cements were characterized using particle size analysis, gel permeation chromatography, viscosity measurements, unreacted monomer analysis, X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and mechanical properties. The average particle size and molecular weight of the PMMA powders used were 47 microm and 100,000 g/mol, respectively. The incorporation of MMT led to an increase in viscosity of the bone cement but did not severely affect its setting temperature or the amount of residual monomer. Regardless of the MMT mixing methods used, in this case MMT being mixing in liquid and powder components, sodium MMT (SMMT) was not well dispersed in the bone cements, which was believed to be due to its hydrophilicity. Organophilic MMT (OMMT) was better dispersed in the liquid component than in the powder component. The compressive and tensile strength of the bone cement containing the OMMT mixed into the liquid component were significantly higher than those of the bone cement without MMT (p < 0.05). PMID:17385224

  20. The effect of dispersion technique of montmorillonite on polyisocyanurate nanocomposites

    NASA Astrophysics Data System (ADS)

    Cabulis, U.; Fridrihsone, A.; Andersons, J.; Vlcek, T.

    2014-05-01

    The biomass represents an abundant, renewable, competitive and low cost resource that can play an alternative role to petrochemical resources. The central topic of the research activity reported is the use of rape seed oil (RO) as a raw material for the production of rigid polyisocyanurate foams (PIR). The content of the renewable resource-derived polymers achieved in ready foams is up to 20%. By using biopolymers as a matrix, a prospective way is to reinforce them with nanoparticles, organically modified clays, for improvement of mechanical properties while, at the same time, replacing petrochemical raw materials. Organoclay Cloisite® 15A was tested as a filler of PIR foams. Three different techniques - ultrasonification, mixing by three-roll mills, and high-pressure homogenization were used for dispergation of nanoclays in polyols. Composite polyisocyanurate foams and solid polymer samples were produced and tested for stiffness and strength. This paper discusses the studies into the use of RO as a renewable source in rigid PIR foams filled with organomodified montmorillonite clay with loadings from 1 to 5% by weight.

  1. Method for treating underground formations

    SciTech Connect

    Noles, J.R.; Walker, C.O.; White, N.F.

    1981-04-14

    Disclosed is a method for treating subterranean formations such as underground petroleum-containing formations penetrated by a well, and particularly a formation penetrated by a producing well which formation contain a plurality of zones, one or more of which are producing petroleum and one or more of which are producing water. The treatment selectively reduces the permeability of the water-producing intervals without adversely affecting the permeability of the oil producing intervals, thereby reducing the production of water and reducing the water-oil ratio of the fluid being produced from the well. The treatment method involves introducing an effective amount of a liquid comprising a hydrocarbon having dispersed therein an unhydrated water swellable clay such as bentonite, a sodium montmorillonite. The clay swells on contacting water in the water-producing intervals and plugs or reduces the permeability of the flow channels in the water-producing intervals.

  2. Oligomerization reactions of deoxyribonucleotides on montmorillonite clay: The effect of mononucleotide structure on phosphodiester bond formation

    NASA Astrophysics Data System (ADS)

    Ferris, James P.; Kamaluddin

    1989-11-01

    Adenine deoxynucleotides bind more strongly to Na+-montmorillonite than do the corresponding ribonucleotides. Thymidine nucleotides binds less strongly to Na+-montmorillonite than do the corresponding adenine deoxynucleotides. Oligomers of 2'-dpA up to the tetramer were detected in the reaction 2'-d-5'-AMP with EDAC (a water-soluble carbodiimide) in the presence of Na+-montmorillonite. Reaction of 3'-d-5'-AMP with EDAC on Na+-montmorillonite yields 3'-d-2',5'-pApA while the reaction of 2'-d-3'-AMP yields almost exclusively 3',5'-cdAMP. The reaction of 5'-TMP under the same reaction conditions give 3',5'-cpTpT and 3',5'-pTpT while 3'-TMP gives mainly 3',5'-cpT. The yield of dinucleotide products (dpNpN) containing the phosphodiester bond is 1% or less when Na+-montmorillonite is omitted from the reaction mixture.

  3. Oligomerization reactions of deoxyribonucleotides on montmorillonite clay: the effect of mononucleotide structure on phosphodiester bond formation.

    PubMed

    Ferris, J P; Kamaluddin

    1989-01-01

    Adenine deoxynucleotides bind more strongly to Na(+)-montmorillonite than do the corresponding ribonucleotides. Thymidine nucleotides binds less strongly to Na(+)-montmorillonite than do the corresponding adenine deoxynucleotides. Oligomers of 2'-dpA up to the tetramer were detected in the reaction 2'-d-5'-AMP with EDAC (a water-soluble carbodiimide) in the presence of Na(+)-montmorillonite. Reaction of 3'-d-5'-AMP with EDAC on Na(+)-montmorillonite yields 3'-d-2',5'-pApA while the reaction of 2'-d-3'-AMP yields almost exclusively 3',5'-cdAMP. The reaction of 5'-TMP under the same reaction conditions give 3',5'-cpTpT and 3',5'-pTpT while 3'-TMP gives mainly 3',5'-cpT. The yield of dinucleotide products (dpNpN) containing the phosphodiester bond is 1% or less when Na(+)-montmorillonite is omitted from the reaction mixture. PMID:11538680

  4. Nanocomposites prepared from acrylonitrile butadiene rubber and organically modified montmorillonite with vinyl groups

    NASA Astrophysics Data System (ADS)

    Han, Mijeong; Kim, Hoonjung; Kim, Eunkyoung

    2006-01-01

    Nanocomposites were prepared from acrylonitrile-butadiene rubber (NBR), vinyl groups containing organically modified montmorillonite and additives, such as zinc oxide, stearic acid, and sulfur. The organically modified montmorillonites used in these nanocomposites were prepared by ion exchange reactions of N,N'-dimethylalkyl-(p-vinylbenzyl)-ammonium chlorides (DAVBAs, alkyl = octyl, dodecyl, and octadecyl) with sodium montmorillonite (Na+-MMT). NBR nanocomposites were obtained by controlling both the mixing and vulcanization conditions, by using a Brabender mixer and hot-press process. X-ray diffraction (XRD) analysis shows that, depending on the amount of montmorillonite that is added, both exfoliated and intercalated nanocomposite structures are formed. The NBR/DAVBA-MMT nanocomposites exhibit much higher mechanical properties (e.g., tensile strength, Young's modulus, 300% modulus, and hardness) as well as gas barrier properties as compared to NBR Na+-MMT or NBR composites generated from modified montmorillonites without vinyl groups. Consistent with the results of XRD, transmission electron microscopy (TEM) reveals that the intercalation and exfoliation structures of the nanocomposites coexist and that the DAVBA-MMT layers are well dispersed in NBR.

  5. Gene expression of human osteoblasts cells on chemically treated surfaces of Ti-6Al-4V-ELI.

    PubMed

    Oliveira, D P; Palmieri, A; Carinci, F; Bolfarini, C

    2015-06-01

    Surface modifications of titanium alloys are useful methods to enhance the biological stability of intraosseous implants and to promote a well succeeded osseointegration in the early stages of implantation. This work aims to investigate the influence of chemically modified surfaces of Ti-6Al-4V-ELI (extra-low interstitial) on the gene expression of human osteoblastic (HOb) cells. The surface treatments by acid etching or acid etching plus alkaline treatment were carried out to modify the topography, effective area, contact angle and chemical composition of the samples. The surface morphology was investigated using: scanning electron microscopy (SEM) and confocal laser-scanning microscope (CLSM). Roughness measurements and effective surface area were obtained using the CLSM. Surface composition was analysed by energy dispersive X-ray spectroscopy (EDX) and by X-Ray Diffraction (XRD). The expression levels of some bone related genes (ALPL, COL1A1, COL3A1, SPP1, RUNX2, and SPARC) were analysed using real-time Reverse Transcription Polymerase Chain Reaction (real-time RT-PCR). The results showed that all the chemical modifications studied in this work influenced the surface morphology, wettability, roughness, effective area and gene expression of human osteoblasts. Acid phosphoric combined to alkaline treatment presented a more accelerated gene expression after 7days while the only phosphoric etching or chloride etching combined to alkaline treatment presented more effective responses after 15days. PMID:25842132

  6. Significant long-term reduction in n-channel MESFET subthreshold leakage using ammonium-sulfide surface treated gates

    NASA Technical Reports Server (NTRS)

    Neudeck, P. G.; Carpenter, M. S.; Melloch, Michael R.; Cooper, James A., Jr.

    1991-01-01

    Ammonium-sulfide (NH4)2S treated gates have been employed in the fabrication of GaAs MESFETs that exhibit a remarkable reduction in subthreshold leakage current. A greater than 100-fold reduction in drain current minimum is observed due to a decrease in Schottky gate leakage. The electrical characteristics have remained stable for over a year during undesiccated storage at room temperature, despite the absence of passivation layers.

  7. The effects of steam on the surface properties of palygorskite: Implications for palygorskite-water interactions

    NASA Astrophysics Data System (ADS)

    Kadakia, Abhy

    Early studies on the effects of steam on montmorillonite reported a loss of osmotic swelling capacity and gelling ability of montmorillonite (Bish et al., 1997; Couture, 1985; Oscarson and Dixon, 1989; Zhu, 2009). However, the crystal structure, cation-exchange capacity, and hydration/dehydration behavior of montmorillonite were preserved. Similar steaming experiments were conducted in the current studies on palygorskite (PFl-1) at 225°C for six days in Teflon-lined Parr vessels. All untreated and steam-treated materials were examined by X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), ζ-potential, and rheological measurements. XRD and TGA data show that the crystal structure, mineralogy, and dehydration behavior of steamed palygorskites were unchanged after steam treatment. XPS revealed no changes in binding-energy peak positions of the surface Si, Mg, and O ions (XPS provides no information on the chemical state of H atoms). Rheological measurements showed that suspensions of steam-treated palygorskite in deionized H2O (5% w/w) are unstable, and the suspensions are Newtonian in nature. The flow curves also revealed a significant reduction in yield stresses after steam treatment, indicating collapse of the clay particle network in water. The ζ-potential decreased after steam treatment, with untreated palygorskite having a value of -26.1 mV and steam-treated material having a value of -18.3 mV. The reduction of surface charge may be sufficient to reduce the electrostatic repulsion between the clay particles, thereby allowing van der Waal attractive forces to dominate. Hence, steam-treated palygorskite flocculates and settles quickly in water. The decreased ζ-potentials are likely associated with decreased Lewis basicity, which can render the clay particles less hydrophilic or even moderately hydrophobic. Both N 2 (BET) and ethylene glycol monoethyl ether (EGME) adsorption surface areas of palygorskite decreased by 40-50% after steam treatment. The reduced affinity for water and EGME may represent a reduced affinity for polar molecules in general. These results, particularly the XPS spectra and the observed large changes in rheological properties, suggest that steam altered the H + ion environment and/or concentration on palygorskite's surface. Exposing palygorskite to steam may have significant implications for its industrial applications, adversely affecting some applications and enhancing others.

  8. Zearalenone removal in synthetic media and aqueous part of canned corn by montmorillonite K10 and pillared montmorillonite K10.

    PubMed

    Bekci, Zehra Molu; Antep, Mine Kurtbay; Merdivan, Melek; Yurdakoç, Kadir

    2011-06-01

    The capacities of montmorillonite K10 (K10), aluminum pillared K10 (Al-K10), and iron pillared K10 (Fe-K10) to eliminate zearalenone (ZEN) from synthetic media and the aqueous part of canned corn were studied. Original clay and pillared clays were characterized in terms of X-ray powder diffraction analysis and N(2) adsorption-desorption isotherms. The maximum amounts of adsorption of ZEN by K10, Al-K10, and Fe-K10 at 25°C and pH 7 were 0.202, 1.305, and 1.028 mg/g and 0.264, 0.096, and 0.255 mg/g, calculated from Langmuir and Freundlich isotherms, respectively. The adsorption of ZEN was also studied as a function of adsorbent amount (1 to 30 mg), ZEN concentration (2 to 20 mg/liter), pH of solution (pH 4 to 10), and contact time. Pillared clays could be an excellent alternative for removing ZEN in contaminated food samples and are potentially low-cost adsorbents with a promising future as an alternative to more costly materials. PMID:21669073

  9. Variation of arsenic concentration on surfaces of in-service CCA-treated wood planks in a park and its influencing field factors.

    PubMed

    Tang, Ya; Gao, Wei; Wang, Xiuli; Ding, Shiming; An, Taicheng; Xiao, Weiyang; Wong, Ming H; Zhang, Chaosheng

    2015-01-01

    Wood preservatives can protect wood from dry rot, fungi, mould and insect damage, and chromated copper arsenate (CCA) has been used as an inorganic preservative for many years. However, wood treated with CCA has been restricted from residential uses in the EU from June 30, 2004, due to its potential toxicity. Such a regulation is not in place in China yet, and CCA-treated wood is widely used in public parks. A portable XRF analyser was used to investigate arsenic (As) concentration on surfaces of in-service CCA-treated wood planks in a popular park as well as the influencing field factors of age in-service, immersion and human footfall. With a total of 1207 readings, the observed As concentrations varied from below the detection limit (<10 mg/kg) to 15,746 mg/kg with a median of 1160 mg/kg. Strong variation of As concentrations were observed in different wood planks of the same age, on the surface of the same piece of wood, inside the same piece of wood, and different surfaces of walkway planks, hand rails and poles in the field. The oldest planks exhibited high As concentrations, which was related to its original treatment with high retention of CCA preservative. The effect of immersion in the field for about 4 months was insignificant for As concentration on the surfaces. However, a significant reduction of As was observed for immersion combined with human footfall (wiping by shoes). Human traffic in general caused slightly reduced and more evenly distributed As concentrations on the wood surfaces. The strong variation, slow aging and relatively weak immersion effects found in this study demonstrate that the in-service CCA-treated wood poses potential health risks to the park users, due to easy dermal contact especially when the wood is wet after rainfall. It is suggested that further comprehensive investigations and risk assessments of CCA-treated wood in residential areas in China are needed, and precautionary measures should be considered to reduce the potential risks to residents and visitors, especially children. PMID:25512245

  10. Influence of gas and treatment time on the surface modification of EPDM rubber treated at afterglow microwave plasmas

    NASA Astrophysics Data System (ADS)

    da Maia, J. V.; Pereira, F. P.; Dutra, J. C. N.; Mello, S. A. C.; Becerra, E. A. O.; Massi, M.; Sobrinho, A. S. da Silva

    2013-11-01

    The ethylene propylene diene monomer (EPDM) rubber possesses excellent physical/chemical bulk properties, is cost-effective, and has been used in the mechanical and aerospace industry. However, it has an inert surface and needs a surface treatment in order to improve its adhesion properties. Plasma modification is the most accepted technique for surface modification of polymers without affecting the properties of the bulk. In this study, an afterglow microwave plasma reactor was used to generate the plasma species responsible for the EPDM surface modification. The plasma modified surfaces were analyzed by means of contact angle measurement, adhesion tests, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. Two experimental variables were analyzed: type of the plasma gases and exposure time were considered. The predominant failure mode was adhesive, for long treatment times a mixture of adhesive and cohesive failure can be observed and the best conditions tested there was an increase of the rupture strength of about 27%, that can be associated mainly with the creation of oxygen containing functional groups on the rubber surface (CO, COC and CO) identified by spectroscopic methods. The predominant failure mode was adhesive, for long treatment times a mixture of adhesive and cohesive failure can be observed. In various conditions tested the contact angles easily decreased more than 500%. What can be concluded that high wettability is a necessary condition to obtain good adhesion, but this is not a sufficient condition.

  11. Thermal fatigue resistance of H13 steel treated by selective laser surface melting and CrNi alloying

    NASA Astrophysics Data System (ADS)

    Tong, Xin; Dai, Ming-jiang; Zhang, Zhi-hui

    2013-04-01

    In this study, the selective laser surface melting and laser surface alloying technologies were adopted to improve the thermal fatigue resistance of medium carbon hot-work die steel (H13) by a CO2 laser. Two kinds of mixed chromium (Cr) and nickel (Ni) powders were used as the laser alloying materials, and the effects of the mixing ratio on the thermal fatigue resistance were investigated thoroughly. Some important results such as cross-sectional morphology, phases, hardness and thermal fatigue behavior were analyzed and evaluated. It indicates that the laser surface alloying technique using mixed powder with ratio of 75%Cr-25%Ni can considerably enhance the thermal fatigue resistance of the H13 steel. The laser alloyed zone has excellent properties such as preventing crack initiation and oxidation corrosion compared with original H13. Thermal cracking and oxidation corrosion that occurred at substrate surface can be surrounded and intercepted by a gridded laser strengthened structure. Therefore, the naturally developed cracks could be effectively prevented. Theses results and analysis show that laser surface technique can be positively used to improve surface mechanical properties of H13 dies.

  12. Determination of the surface energy of kaolinite and serpentine using PACHA formalism-comparison with immersion experiments.

    PubMed

    Salles, Fabrice; Henry, Marc; Douillard, Jean-Marc

    2006-11-15

    Clays play an important role in a wide variety of industrial processes. Indeed, they present interesting surface properties. For these reasons, we study the surface energy of models of clays by solid state calculations using electronegativities equalization. In this article, we focus on kaolinite and serpentine, two clays characterized by a simple structure of the TO type. We describe the clays and their structures and we develop a simple model from solid state calculations used to determine the surface energy. The results are in agreement with a recent interpretation of the immersion of kaolinite in water. This article must be related to some others focusing on solid surface energy, especially some treating talc and chlorites, and montmorillonites saturated by alkaline cations, to be published. PMID:16978637

  13. Photoinduced catalytic adsorption of model contaminants on Bi/Cu pillared montmorillonite in the visible light range

    EPA Science Inventory

    Montmorillonite K10 clay was pillared with BiCl3 and Cu(NO3)2 to extend its applicability as catalytic adsorbent to degrade aqueous solution of anionic azo-dye Methyl Orange (MO) in the presence of visible light irradiation. The preparation of Bi/Cu-montmorillonite utilized benig...

  14. Intercalation behavior of poly(ethylene glycol) in organically modified montmorillonite

    NASA Astrophysics Data System (ADS)

    Zhu, Shipeng; Peng, Hongmei; Chen, Jinyao; Li, Huilin; Cao, Ya; Yang, Yunhua; Feng, Zhihai

    2013-07-01

    In this paper, two kinds of organically modified montmorillonite (OMMT) were prepared using alkylammonium surfactants with different alkyl chain numbers. XRD results showed the interlayer spacing of OMMT increased with low concentration surfactants. With further increasing the surfactants concentration, the interlayer spacing of OMMT was unchanged. Meanwhile, FTIR was used to characterize the local environments of surfactants in the interlayer space of OMMT. The results suggested that the double chain surfactant D-18 preferred to adopt highly ordered conformation compared with single chain surfactant S-18 in interlayer space of OMMT. It indicated that the surface property of the OMMT is affected by the concentration and configuration of the intercalated surfactants. Moreover, the effect of the OMMT type, or more particularly the chemical nature of the organic modifier in the interlayer spacing and the poly(ethylene glycol) (PEG) concentration onintercalation behavior of PEG chains in OMMT were investigated with XRD and DSC.The results indicated that PEG chains could not intercalate into Na-MMT when the surfactants were saturated in interlayer space of Na-MMT. PEG chains could intercalate into the interlayer space of SM when the S-18 concentration was lower than 2.00CEC, implying that the low surfactant concentration modified SM provided a better environment (presumably through the balanced hydrophobic and hydrophilic surfaces) for the PEG intercalation as well. However, PEG did not intercalate into the interlayer space of DM when the D-18 concentration was higher than 1.00CEC. It could be attributed to the hydrophobic double alkyl chains of DM increased with D-18. The increased hydrophobic properties in the interlayer space of 1.50DM hybrids can prevent the intercalation of hydrophilic PEG.

  15. A curcumin activated carboxymethyl cellulose-montmorillonite clay nanocomposite having enhanced curcumin release in aqueous media.

    PubMed

    Madusanka, Nadeesh; de Silva, K M Nalin; Amaratunga, Gehan

    2015-12-10

    A novel curcumin activated carboxymethylcellulose-montmorillonite nanocomposite is reported. A superabsorbent biopolymer; carboxymethyl cellulose (CMC) was used as an emulsifier for curcumin which is a turmeric derived water insoluble polyphenolic compound with antibacterial/anti-cancer properties. Montmorillonite (MMT) nanoclay was incorporated in the formulation as a matrix material which also plays a role in release kinetics. It was observed that water solubility of curcumin in the nanocomposite has significantly increased (60% release within 2h and 30 min in distilled water at pH 5.4) compared to pure curcumin. The prepared curcumin activated carboxymethylcellulose-montmorillonite nanocomposite is suitable as a curcumin carrier having enhanced release and structural properties. PMID:26428174

  16. Nanocomposite membranes based on quaternized polysulfone and functionalized montmorillonite for anion-exchange membranes

    NASA Astrophysics Data System (ADS)

    Liao, Xiaofeng; Ren, Li; Chen, Dongzhi; Liu, Xiaohong; Zhang, Hongwei

    2015-07-01

    In this paper, functionalized montmorillonite is intercalated with cetyl trimethyl ammonium chloride and (3-aminopropyl)triethoxysilane. Quaternized polysulfone/functionalized montmorillonite nanocomposite membranes are fabricated to evaluate their potential in anion-exchange membrane fuel cells. Fourier transform infrared spectroscopy, thermogravimetric analyzer and X-ray diffractometer are used to confirm the success of intercalation. The performances of the composite membranes for the anion-exchange membrane fuel cells in terms of their water uptake, mechanical property and ionic conductivity are investigated. Compared with other anion-exchange membranes, the nanocomposite membrane containing 5% montmorillonite modified by cetyl trimethyl ammonium chloride exhibits lower water uptake, higher ultimate stress and larger ionic conductivity. It exhibits an ionic conductivity of 4.73 × 10-2 S cm-1 at 95 °C.

  17. Tribological characterization of surface-treated commercially pure titanium for femoral heads in total hip replacement: a feasibility study.

    PubMed

    Cotogno, G; Holzwarth, U; Franchi, M; Rivetti, S; Chiesa, R

    2006-12-01

    Most noncemented total hip replacements combine a titanium alloy stem, a CoCrMo femoral head and an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup. In spite of its nickel content of up to 1% and the resulting biocompatibility issues in some clinical situations, the higher cost and some difficulties in machining, CoCrMo alloy is preferred to titanium alloys thanks to its outstanding tribological properties, higher hardness and elastic modulus. Nowadays most of the heads of hip prostheses use CoCrMo as bearing material. The present study investigates the effect of various surface treatments and combinations of treatments, such as electrochemical oxidation (anodization), laser surface melting and barrel polishing, on the tribological properties of commercially pure grade 2 titanium. The aim of the study was to characterize surface treatments capable of improving the tribological properties of titanium surface to the same extent as CoCrMo. The tribological properties were characterized by multidirectional pin-on-flat screening wear tests, using UHMWPE pins as bearing surface. The experiments showed the possibility of improving the wear resistance of titanium to the degree of CoCrMo. Although further efforts will be required to optimize the treatments studied, the results are encouraging enough to warrant pursuing this direction of investigation. PMID:17219358

  18. Improved performance of dye-sensitized solar cells with surface-treated TiO{sub 2} as a photoelectrode

    SciTech Connect

    Park, Su Kyung; Chung, Chinkap; Kim, Dae-Hwan; Kim, Cham; Lee, Sang-Ju; Han, Yoon Soo

    2012-10-15

    We report on the effects of surface-modified TiO{sub 2} on the performance of dye-sensitized solar cells (DSSCs). TiO{sub 2} surface was modified with Na{sub 2}CO{sub 3} via a simple dip coating process and the modified TiO{sub 2} was applied to photoelectrodes of DSSCs. By dipping of TiO{sub 2} layer into aqueous Na{sub 2}CO{sub 3} solution, the DSSC showed a power conversion efficiency of 9.98%, compared to that (7.75%) of the reference device without surface treatment. The UV–vis absorption spectra, the impedance spectra and the dark current studies revealed that the increase of all parameters was attributed to the enhanced dye adsorption, the prolonged electron lifetime and the reduced interfacial resistance.

  19. FT-IR study of montmorillonite-chitosan nanocomposite materials

    NASA Astrophysics Data System (ADS)

    Paluszkiewicz, C.; Stodolak, E.; Hasik, M.; Blazewicz, M.

    2011-08-01

    Bone defect is one of the most frequent problems in bone tissue reconstruction in which application of a biomaterial filling is necessary. It creates a still rising demand of biomaterials for bone surgery. Polymer-ceramic nanocomposites (e.g. based on chitosan matrix) is a group of novel materials whose properties such as strength, Young's modulus, bioactivity and controlled degradation time make them suitable materials for filling bone defects. Investigations of nanocomposite foils which consisted of biopolymer-chitosan (CS) matrix and montmorillonite (MMT) as a nano-filler was the subject of the work. The nanocomposite materials were produced by a two-step dispersion of the nanoparticles in the biopolymer matrix. The first stage involved mechanical stirring and the second one - ultrasonic agitation. Mechanical tests were performed on the nanocomposites and their Young's modulus was estimated. Significant improvement of mechanical properties of the nanocomposites in comparison with the pure polymer (CS) was observed. The nanocomposite foils (CS/MMT) were subjected to FT-IR spectroscopy investigations whose objective was to explain the reason of the change in mechanical characteristics of the nanocomposites. Transmission and ATR techniques operating in MIR range were used to study the nanocomposites. The FT-IR techniques were used to determine interactions at nanoparticle-biopolymer matrix interface. A pure unmodified CS foil was used as a reference material for FT-IR studies. It was proven that application of FT-IR techniques allows not only to identify phases, but also to explain structural changes in the systems studied.

  20. Effect of Organic Matter on the Flocculation of Colloidal Montmorillonite: A Modeling Approach

    NASA Astrophysics Data System (ADS)

    Furukawa, Y.

    2011-12-01

    The effect of organic matter (OM) on the flocculation of colloidal montmorillonite was investigated through a complementary use of laboratory experiments and computational flocculation modeling. The model, based on Smoluchowski's coagulation model and population balance equation (PEB), was established with two key flocculation parameters, sticking efficiency and breakup parameter. The laboratory flocculation experiments tracked the temporal evolution of the floc sizes for aqueous systems with colloidal bare montmorillonite as well as those with montmorillonite and OM (humic acid, chitin or xanthan gum). The key flocculation parameters were calibrated through the interactive optimization of the model results against the laboratory results. The calibrated flocculation parameter values revealed that OM has a complex influence on the flocculation behavior of montmorillonite. They also showed that the effect of OM on flocculation depends on the types of OM. For example, xanthan gum does not significantly modify the flocculation behavior of montmorillonite that is primarily determined by the electrical double layer repulsion (i.e., zeta-potential) and van der Waals attraction (i.e., DLVO interaction energies), whereas chitin modifies both the sticking efficiency and breakup parameter. This study illustrates that there is no universally predictive correlation between DLVO energies or zeta-potential and flocculation parameters, as some OM has little effect on the DLVO interaction of montmorillonite colloids whereas other types of OM exert non-DLVO interactions such as repulsive hydration, steric repulsion and polymer bridging. Further understanding of the physical-chemical properties of OM is needed in order to predict the flocculation behaviors of estuarine and coastal suspended colloids.

  1. Synthesis and characterization of silver/montmorillonite/chitosan bionanocomposites by chemical reduction method and their antibacterial activity

    PubMed Central

    Shameli, Kamyar; Ahmad, Mansor Bin; Zargar, Mohsen; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa; Shabanzadeh, Parvaneh; Moghaddam, Mansour Ghaffari

    2011-01-01

    Silver nanoparticles (AgNPs) of a small size were successfully synthesized using the wet chemical reduction method into the lamellar space layer of montmorillonite/chitosan (MMT/Cts) as an organomodified mineral solid support in the absence of any heat treatment. AgNO3, MMT, Cts, and NaBH4 were used as the silver precursor, the solid support, the natural polymeric stabilizer, and the chemical reduction agent, respectively. MMT was suspended in aqueous AgNO3/Cts solution. The interlamellar space limits were changed (d-spacing = 1.24–1.54 nm); therefore, AgNPs formed on the interlayer and external surface of MMT/Cts with d-average = 6.28–9.84 nm diameter. Characterizations were done using different methods, ie, ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray fluorescence spectrometry, and Fourier transform infrared spectroscopy. Silver/montmorillonite/chitosan bionanocomposite (Ag/MMT/Cts BNC) systems were examined. The antibacterial activity of AgNPs in MMT/Cts was investigated against Gram-positive bacteria, ie, Staphylococcus aureus and methicillin-resistant S. aureus and Gram-negative bacteria, ie, Escherichia coli, E. coli O157:H7, and Pseudomonas aeruginosa by the disc diffusion method using Mueller Hinton agar at different sizes of AgNPs. All of the synthesized Ag/MMT/Cts BNCs were found to have high antibacterial activity. These results show that Ag/MMT/Cts BNCs can be useful in different biological research and biomedical applications, including surgical devices and drug delivery vehicles. PMID:21499424

  2. Nanoclays reinforced glass ionomer cements: dispersion and interaction of polymer grade (PG) montmorillonite with poly(acrylic acid).

    PubMed

    Fareed, Muhammad A; Stamboulis, Artemis

    2014-01-01

    Montmorillonite nanoclays (PGV and PGN) were dispersed in poly(acrylic acid) (PAA) for utilization as reinforcing filler in glass ionomer cements (GICs). Chemical and physical interaction of PAA and nanoclay (PGV and PGN) was studied. PAA–PGV and PAA–PGN solutions were prepared in different weight percent loadings of PGV and PGN nanoclay (0.5-8.0 wt%) via exfoliation-adsorption method. Characterization was carried out by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and fourier transform infrared (FTIR) spectroscopy. XRD results of PAA–PGN demonstrated that the interlayer space expanded from 12.83 to 16.03 Å indicating intercalation whereas the absence of the peak at d(001) in PAA–PGV indicated exfoliation. XPS scans of PGV and PGN nanoclays depicted the main peak of O 1s photoelectron due to Si–O–M (M = Mg, Al, Fe) whereas, Si–O–Al linkages were identified by Si 2p or Si 2s and Al 2p or Al 2s peaks. The disappearance of the Na peak confirmed that PAA molecules exchanged sodium ions present on surface of silicate layers and significantly reduced the electrostatic van-der-Waals forces between silicate plates resulting in intercalation or exfoliation. FTIR spectra of PAA–nanoclay suspensions demonstrated the presence of a new peak at 1,019 cm(-1) associated with Si–O– stretching vibrations which increased with increasing nanoclays concentration. Information concerning the dispersion of nanoclay in PAA aqueous solutions, chemical reaction and increase interlayer space in montmorillonite nanoclay is particularly useful regarding dispersion and reinforcement of nanoclay in PAA. PMID:24077996

  3. Sodium Montmorillonite/Amine-Containing Drugs Complexes: New Insights on Intercalated Drugs Arrangement into Layered Carrier Material

    PubMed Central

    Vieira, Bárbara A.; Dias, Luiza R. S.; de Sousa, Valéria P.; Castro, Helena C.; Rodrigues, Carlos R.; Cabral, Lucio M.

    2015-01-01

    Layered drug delivery carriers are current targets of nanotechnology studies since they are able to accommodate pharmacologically active substances and are effective at modulating drug release. Sodium montmorillonite (Na-MMT) is a clay that has suitable properties for developing new pharmaceutical materials due to its high degree of surface area and high capacity for cation exchange. Therefore Na-MMT is a versatile material for the preparation of new drug delivery systems, especially for slow release of protonable drugs. Herein, we describe the intercalation of several amine-containing drugs with Na-MMT so we can derive a better understanding of how these drugs molecules interact with and distribute throughout the Na-MMT interlayer space. Therefore, for this purpose nine sodium montmorillonite/amine-containing drugs complexes (Na-MMT/drug) were prepared and characterized. In addition, the physicochemical properties of the drugs molecules in combination with different experimental conditions were assessed to determine how these factors influenced experimental outcomes (e.g. increase of the interlayer spacing versus drugs arrangement and orientation). We also performed a molecular modeling study of these amine-containing drugs associated with different Na-MMT/drug complex models to analyze the orientation and arrangement of the drugs molecules in the complexes studied. Six amine-containing drugs (rivastigmine, doxazosin, 5-fluorouracil, chlorhexidine, dapsone, nystatin) were found to successfully intercalate Na-MMT. These findings provide important insights on the interlayer aspect of the molecular systems formed and may contribute to produce more efficient drug delivery nanosystems. PMID:25803292

  4. Nanomechanical and surface properties of rMSCs post-exposure to CAP treated UHMWPE wear particles

    PubMed Central

    Preedy, Emily Callard; Perni, Stefano; Prokopovich, Polina

    2016-01-01

    Wear debris generated by ultra-high molecular weight polyethylene (UHMWPE) used in joint replacement devices has been of concern due to reductions of the implant longevity. Cold atmospheric plasma (CAP) has been used to improve the wear performance of UHMWPE. Our aim was to investigate the elastic and adhesive properties of rat mesenchymal stem cells (rMSCs), through AFM, after exposure to UHMWPE wear debris pre- and post-CAP treatment. The results indicated that the main changes in cell elasticity and spring constant of MSC exposed to wear particles occurred in the first 24 h of contact and the particle concentration from 0.5 to 50 mg/l did not play a significant role. For UHMWPE treated for 7.5 min, with progression of the wear simulation the results of the CAP treated samples were getting closer to the result of untreated samples; while with longer CAP treatment this was not observed. From the Clinical Editor Joint replacements are now common clinical practice. However, the use of ultra-high molecular weight polyethylene (UHMWPE) still poses a concern, due to the presence of wear debris. The authors here investigated the effects of wear debris after cold atmospheric plasma treatment on rat mesenchymal stem cells. The positive results provided new strategies in future design of joint replacement materials. PMID:26554392

  5. The effect of NaOH concentration on the steam-hydrothermally treated bioactive microarc oxidation coatings containing Ca, P, Si and Na on pure Ti surface.

    PubMed

    Zhou, Rui; Wei, Daqing; Cao, Jianyun; Feng, Wei; Cheng, Su; Du, Qing; Li, Baoqiang; Wang, Yaming; Jia, Dechang; Zhou, Yu

    2015-04-01

    The microarc oxidation (MAO) coating covered pure Ti plates are steam-hydrothermally treated in autoclaves containing NaOH solutions with different concentrations of 0, 0.001, 0.01, 0.1 and 1mol·L(-1). Due to the composition of Ti, O, Ca, P, Si and Na elements in the MAO coating, anatase and hydroxyapatite (HA) crystals are generated from the previously amorphous MAO coating after the steam-hydrothermal treatment. Meanwhile, it is noticed that the amount of HA crystals increases but showing a decline trend in aspect ratio in morphologies with the increasing of NaOH concentration. Interestingly, the steam-hydrothermally treated MAO coatings exhibit better bonding strength with Ti substrate (up to 43.8±1.1MPa) than that of the untreated one (20.1±3.1MPa). In addition, benefiting from the corrosive attack of the dissolved NaOH in water vapor on the MAO coating, Ti-OH is also formed on the steam-hydrothermally treated MAO coating surface, which can trigger apatite nucleation. Thus, the steam-hydrothermally treated MAO coatings exhibit good apatite-inducing ability. PMID:25686996

  6. Improvement of interfacial adhesion and nondestructive damage evaluation for plasma-treated PBO and Kevlar fibers/epoxy composites using micromechanical techniques and surface wettability.

    PubMed

    Park, Joung-Man; Kim, Dae-Sik; Kim, Sung-Ryong

    2003-08-15

    Comparison of interfacial properties and microfailure mechanisms of oxygen-plasma treated poly(p-phenylene-2,6-benzobisoxazole (PBO, Zylon) and poly(p-phenylene terephthalamide) (PPTA, Kevlar) fibers/epoxy composites were investigated using a micromechanical technique and nondestructive acoustic emission (AE). The interfacial shear strength (IFSS) and work of adhesion, Wa, of PBO or Kevlar fiber/epoxy composites increased with oxygen-plasma treatment, due to induced hydrogen and covalent bondings at their interface. Plasma-treated Kevlar fiber showed the maximum critical surface tension and polar term, whereas the untreated PBO fiber showed the minimum values. The work of adhesion and the polar term were proportional to the IFSS directly for both PBO and Kevlar fibers. The microfibril fracture pattern of two plasma-treated fibers appeared obviously. Unlike in slow cooling, in rapid cooling, case kink band and kicking in PBO fiber appeared, whereas buckling in the Kevlar fiber was observed mainly due to compressive and residual stresses. Based on the propagation of microfibril failure toward the core region, the number of AE events for plasma-treated PBO and Kevlar fibers increased significantly compared to the untreated case. The results of nondestructive AE were consistent with microfailure modes. PMID:16256662

  7. Surface-enhanced Raman scattering study of the healing of radial fractures treated with or without Huo-Xue-Hua-Yu decoction therapy

    NASA Astrophysics Data System (ADS)

    Chen, Weiwei; Huang, Hao; Chen, Rong; Feng, Shangyuan; Yu, Yun; Lin, Duo; Lin, Jia

    2014-11-01

    This study aimed to assess, through surface-enhanced Raman scattering (SERS) spectroscopy, the incorporation of calcium hydroxyapatite (CHA ~960 cm-1) and other biochemical substances in the repair of complete radial fractures in rabbits treated with or without Huo-Xue-Hua-Yu decoction (HXHYD) therapy. A total of 18 rabbits with complete radial fractures were randomly divided into two groups; one group was treated with HXHYD therapy and the other without therapy acted as a control. The animals were sacrificed at 15, 30 and 45 d after surgery. Specimens were routinely prepared for SERS measurement and high quality SERS spectra from a mixture of bone tissues and silver nanoparticles were obtained. The mineral-to-matrix ratios from the control and treated groups were calculated. Results showed that both deposition content of CHA measured by SERS spectroscopy and the mineral-to-matrix ratio in the treated group were always greater than those of the control group during the experiment, demonstrating that HXHYD therapy is effective in improving fracture healing and that SERS spectroscopy might be a novel tool to assess fracture healing.

  8. Contributions of adhesive proteins to the cellular and bacterial response to surfaces treated with bioactive polymers: case of poly(sodium styrene sulfonate) grafted titanium surfaces.

    PubMed

    Felgueiras, Helena P; Aissa, Ines Ben; Evans, Margaret D M; Migonney, Véronique

    2015-11-01

    The research developed on functionalized model or prosthetic surfaces with bioactive polymers has raised the possibility to modulate and/or control the biological in vitro and in vivo responses to synthetic biomaterials. The mechanisms underlying the bioactivity exhibited by sulfonated groups on surfaces involves both selective adsorption and conformational changes of adsorbed proteins. Indeed, surfaces functionalized by grafting poly(sodium styrene sulfonate) [poly(NaSS)] modulate the cellular and bacterial response by inducing specific interactions with fibronectin (Fn). Once implanted, a biomaterial surface is exposed to a milieu of many proteins that compete for the surface which dictates the subsequent biological response. Once understood, this can be controlled by dictating exposure of active binding sites. In this in vitro study, we report the influence of binary mixtures of proteins [albumin (BSA), Fn and collagen type I (Col I)] adsorbed on poly(NaSS) grafted Ti6Al4V on the adhesion and differentiation of MC3T3-E1 osteoblast-like cells and the adhesion and proliferation of Staphylococcus aureus (S. aureus). Outcomes showed that poly(NaSS) stimulated cell spreading, attachment strength, differentiation and mineralization, whatever the nature of protein provided at the interface compared with ungrafted Ti6Al4V (control). While in competition, Fn and Col I were capable of prevailing over BSA. Fn played an important role in the early interactions of the cells with the surface, while Col I was responsible for increased alkaline phosphatase, calcium and phosphate productions associated with differentiation. Poly(NaSS) grafted surfaces decreased the adhesion of S. aureus and the presence of Fn on these chemically altered surfaces increased bacterial resistance ≈70% compared to the ungrafted Ti6Al4V. Overall, our study showed that poly(NaSS) grafted Ti6Al4V selectively adsorbed proteins (particularly Fn) promoting the adhesion and differentiation of osteoblast-like cells while reducing bacterial adhesion to create a bioactive surface with potential for orthopaedic applications. PMID:26449451

  9. Synthesis of Polyethylene/Montmorillonite Nanocomposites by In-situ Intercalative Polymerization

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; Li, Sanxi; Karaki, Tomoaki; Adachi, Masatoshi

    2005-01-01

    Ziegler-Natta catalysts were intercalated into the galleries between the silicate layers of modified organic montmorillonite (OMMT) and then polyethylene/montmorillonite (PE/MMT) nanocomposites were prepared via in-situ intercalative polymerization of ethylene. Characterization studies were carried out on MMT, OMMT and PE/MMT by various techniques. They indicated that the space between MMT layers in OMMT was broadened from 1.26 nm to 3.53 nm and the MMT layers were homogeneously dispersed in the PE matrix of PE/MMT. Compared with pure PE, the thermal and mechanical properties of PE/MMT were improved to different extents.

  10. Spectroscopic studies on Rhodamine B intercalated K-10 montmorillonite aqueous dispersions

    NASA Astrophysics Data System (ADS)

    Joseph, Lyjo K.; Suja, H.; Sanjay, G.; Sugunan, S.; Nampoori, V. P. N.; Radhakrishnan, P.

    2015-02-01

    In this paper, the optical absorption and fluorescence studies on rhodamine B (RB) intercalated acid activated K-10 montmorillonite dispersions is presented. The aqueous dispersions were prepared from the dried dye intercalated montmorillonite. The absorption and fluorescence peaks of RB dispersions show a bathochromic shift with respect to the dye concentrations. The samples have a fluorescent emission at 421 nm which is having an intensity variation depending on the concentration of the dyes. The behaviour of samples of same concentration prepared by two different routes is also presented.

  11. A bioluminescence ATP assay for estimating surface hydrophobicity and membrane damage of Escherichia coli cells treated with pulsed electric fields

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pulse Electric Field (PEF) treatments, a non-thermal process have been reported to injure and inactivate bacteria in liquid foods. However, the effect of this treatment on bacterial cell surface charge and hydrophobicity has not been investigated. Apple juice (AJ, pH 3.8) purchased from a wholesale ...

  12. Mechanical properties of nitrogen-rich surface layers on SS304 treated by plasma immersion ion implantation

    NASA Astrophysics Data System (ADS)

    Fernandes, B. B.; Mändl, S.; Oliveira, R. M.; Ueda, M.

    2014-08-01

    The formation of hard and wear resistant surface regions for austenitic stainless steel through different nitriding and nitrogen implantation processes at intermediate temperatures is an established technology. As the inserted nitrogen remains in solid solution, an expanded austenite phase is formed, accounting for these surface improvements. However, experiments on long-term behavior and exact wear processes within the expanded austenite layer are still missing. Here, the modified layers were produced using plasma immersion ion implantation with nitrogen gas and had a thickness of up to 4 μm, depending on the processing temperature. Thicker layers or those with higher surface nitrogen contents presented better wear resistance, according to detailed microscopic investigation on abrasion, plastic deformation, cracking and redeposition of material inside the wear tracks. At the same time, cyclic fatigue testing employing a nanoindenter equipped with a diamond ball was carried out at different absolute loads and relative unloadings. As the stress distribution between the modified layer and the substrate changes with increasing load, additional simulations were performed for obtaining these complex stress distributions. While high nitrogen concentration and/or thicker layers improve the wear resistance and hardness, these modifications simultaneously reduce the surface fatigue resistance.

  13. Surface-Treated versus Untreated Large-Bore Catheters as Vascular Access in Hemodialysis and Apheresis Treatments

    PubMed Central

    Bambauer, Rolf; Schiel, Ralf; Bambauer, Carolin; Latza, Reinhard

    2012-01-01

    Background. Catheter-related infections, thrombosis, and stenosis are among the most frequent complications associated with catheters, which are inserted in vessels. Surface treatment processes of the outer surface, such as ion-beam-assisted deposition, can be used to mitigate such complications. Methods. This retrospective study (1992–2007) evaluated silver-coated (54 patients) and noncoated (105 patients) implanted large-bore catheters used for extracorporeal detoxification. The catheters were inserted into the internal jugular or subclavian veins. After removal, the catheters were cultured for bacterial colonization using standard microbiologic assays. They also were examined using scanning electron microscope. Results. The silver coated catheters showed a tendency towards longer in situ time. The microbiologic examinations of the catheter tips were in both catheter types high positive, but not significant. Conclusion. The silver-coated catheters showed no significantly reduction in infection rate by evaluation of all collected data in this retrospective study. There was no association between both catheters in significantly reducing savings in treatment costs and in reducing patient discomfort. Other new developed catheter materials such as the microdomain-structured inner and outer surface are considered more biocompatible because they mimic the structure of natural biological surface. PMID:22577548

  14. Surface conductivity of InAs/GaSb superlattice infrared detectors treated with thiolated self assembled monolayers

    NASA Astrophysics Data System (ADS)

    Henry, Nathan C.; Brown, Alexander; Knorr, Daniel B.; Baril, Neil; Nallon, Eric; Lenhart, Joseph L.; Tidrow, Meimei; Bandara, Sumith

    2016-01-01

    The surface conductivity of InAs/GaSb based type II superlattice (T2SL) long wavelength infrared material following the deposition of thiolated self-assembled monolayers (SAMs) of cysteamine, octadecanethiol, dodecanethiol, and hexanethiol are reported. Quantitative mobility spectrum analysis (QMSA) was employed to study the mobility and to isolate and identify surface carriers following SAM treatments on planar samples. QMSA data collected following the deposition of the SAMs on InAs/GaSb material correlates well with dark current measurements, demonstrating the usefulness of QMSA as a tool for evaluating surface conductivity and predicting device performance. All samples displayed a reduction in surface conductivity and dark current density following thiol treatment. Dark current densities were reduced to 1.1 × 10-5, 1.3 × 10-5, 1.6 × 10-5, and 5 × 10-6 A/cm2 for hexanethiol, dodecanethiol, octadecanethiol, and cysteamine, respectively, from 5.7 × 10-4 A cm2 for unpassivated devices.

  15. Surface free radicals detection using molecular scavenging method on black spruce wood treated with cold, atmospheric-pressure plasmas

    NASA Astrophysics Data System (ADS)

    Hardy, Jean-Michel; Levasseur, Olivier; Vlad, Mirela; Stafford, Luc; Riedl, Bernard

    2015-12-01

    Formation of surface free radicals on wood surfaces during plasma treatment could be an important factor when it comes to wood coating adhesion enhancement. In order to explore this aspect, freshly sanded black spruce (Picea mariana) wood samples were exposed to either plane-to-plane atmospheric-pressure dielectric barrier discharge (AP-DBD) or the flowing afterglow of an AP-DBD and then dipped in a 2,2-diphenyl-1-picrylhydrazyl (DPPH) solution. Wood veneers (extracted to eliminate small molecules prior to each plasma treatment) showed an increase of their reaction rate toward DPPH after treatment in the AP-DBD operated in nominally pure He; a feature ascribed to the plasma-assisted formation of free radicals on the wood surface. Addition of trace amounts (0.1%) of O2 in the He plasma produced a decrease in DPPH reactivity, suggesting that oxygen-spruce interaction during plasma treatment quenches free radicals formation. Similar experiments performed using the flowing afterglow of AP-DBD operated in either N2 or N2/O2 showed that both treatments do not generate significant amount of surface free radicals. This partially results from oxygen-wood interactions due to the open-air configuration of the afterglow reactor.

  16. Surface and interfacial reaction study of half cycle atomic layer deposited HfO2 on chemically treated GaSb surfaces

    NASA Astrophysics Data System (ADS)

    Zhernokletov, D. M.; Dong, H.; Brennan, B.; Yakimov, M.; Tokranov, V.; Oktyabrsky, S.; Kim, J.; Wallace, R. M.

    2013-04-01

    An in situ half-cycle atomic layer deposition/X-ray photoelectron spectroscopy (XPS) study was conducted in order to investigate the evolution of the HfO2 dielectric interface with GaSb(100) surfaces after sulfur passivation and HCl etching, designed to remove the native oxides. With the first pulses of tetrakis(dimethylamido)hafnium(IV) and water, a decrease in the concentration of antimony oxide states present on the HCl-etched surface is observed, while antimony sulfur states diminished below the XPS detection limit on sulfur passivated surface. An increase in the amount of gallium oxide/sulfide is seen, suggesting oxygen or sulfur transfers from antimony to gallium during antimony oxides/sulfides decomposition.

  17. Surface and interfacial reaction study of half cycle atomic layer deposited HfO{sub 2} on chemically treated GaSb surfaces

    SciTech Connect

    Zhernokletov, D. M.; Dong, H.; Brennan, B.; Kim, J.; Yakimov, M.; Tokranov, V.; Oktyabrsky, S.; Wallace, R. M.; Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080

    2013-04-01

    An in situ half-cycle atomic layer deposition/X-ray photoelectron spectroscopy (XPS) study was conducted in order to investigate the evolution of the HfO{sub 2} dielectric interface with GaSb(100) surfaces after sulfur passivation and HCl etching, designed to remove the native oxides. With the first pulses of tetrakis(dimethylamido)hafnium(IV) and water, a decrease in the concentration of antimony oxide states present on the HCl-etched surface is observed, while antimony sulfur states diminished below the XPS detection limit on sulfur passivated surface. An increase in the amount of gallium oxide/sulfide is seen, suggesting oxygen or sulfur transfers from antimony to gallium during antimony oxides/sulfides decomposition.

  18. Immobilization of NaIO4-treated heparin on PEG-modified 316L SS surface for high anti-thrombin-III binding.

    PubMed

    Chuang, Tzu-Wen; Lin, Dong-Tsamn; Lin, Feng-Huei

    2008-09-01

    Poor compatibility between blood and metallic coronary artery stents is one reason for arterial restenosis; however, the immobilization of anticoagulant agents on the surface of the stent is a feasible method of improving stent compatibility. Heparin, a well-known anticoagulant, has been frequently used to coat the surfaces of certain biomaterials to attain blood compatibility. The compound 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide has often been utilized for the immobilization of heparin, but the critical carboxyl groups of heparin (with regards to heparin's anticoagulant activity) will be reduced by this method. This study examined possible methods of heparin immobilization without consuming these carboxyl groups. The 316L stainless steel surface was first activated with hexamethylene diisocyanate and then coupled with bis-amine-terminated poly (ethylene glycol) (BA-PEG) so as to create active amine groups. Sodium periodate (NaIO(4); SP) was then used to oxidize heparin to form aldehyde groups. The treated heparin could then be grafted onto the activated surface of the test material without losing its carboxyl groups. Effective surface modification of the hexamethylene diisocyanate-activated and BA-PEG-grafted 316L SS surface was confirmed using Fourier Transform Infrared Spectroscopy, electron spectroscopy for chemical analysis and a water contact angle test. After the heparin was immobilized on the BA-PEG-grafted 316L SS surface by SP, the surface showed an improvement in antithrombrin III (AT III) binding ability, its anticoagulant property, and hemocompatibility in comparison with heparin grafted by 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide. PMID:18022801

  19. Synthesis of fructooligosaccharides from Aspergillus niger commercial inulinase immobilized in montmorillonite pretreated in pressurized propane and LPG.

    PubMed

    de Oliveira Kuhn, Graciele; Rosa, Clarissa Dalla; Silva, Marceli Fernandes; Treichel, Helen; de Oliveira, Dbora; Oliveira, J Vladimir

    2013-02-01

    Commercial inulinase from Aspergillus niger was immobilized in montmorillonite and then treated in pressurized propane and liquefied petroleum gas (LPG). Firstly, the effects of system pressure, exposure time, and depressurization rate, using propane and LPG, on enzymatic activity were evaluated through central composite design 2. Residual activities of 145.1 and 148.5% were observed for LPG (30 bar, 6 h, and depressurization rate of 20 bar?min?) and propane (270 bar, 1 h, and depressurization rate of 100 bar?min?), respectively. The catalysts treated at these conditions in both fluids were then used for the production of fructooligosaccharides (FOS) using sucrose and inulin as substrates in aqueous and organic systems. The main objective of this step was to evaluate the yield and productivity in FOS, using alternatives for enhancing enzyme activity by means of pressurized fluids and also using low-cost supports for enzyme immobilization, aiming at obtaining a stable biocatalyst to be used for synthesis reactions. Yields of 18% were achieved using sucrose as substrate in aqueous medium, showing the potential of this procedure, hence suggesting a further optimization step to increase the process yield. PMID:23271628

  20. Adsorption of aniline and toluidines on montmorillonite: Implications for the disposal of shale oil production wastes

    SciTech Connect

    Essington, M.E.; Bowen, J.M.; Wills, R.A.; Hart, B.K.

    1992-01-01

    Bentonite clay liners are commonly employed to mitigate the movement of contaminants from waste disposal sites. Solid and liquid waste materials that arise from the production of shale oil contain a vast array of organic compounds. Common among these compounds are the aromatic amines. in order to assess the ability of clay liner material to restrict organic compound mobility, the adsorption of aniline and o-, m-, and p-toluidine on Ca[sup 2+] - and K[sup +]-saturated Wyoming bentonite was investigated. Adsorption experiments were performed under conditions of varied pH, ionic strength, and dominate electrolyte cation and anion. organic adsorption on Ca[sup 2+] - and K[sup +]-saturated montmorillonite is pH dependent. For any given organic compound, maximum adsorption increases with decreasing ionic strength. organic compound adsorption is inhibited in the presence of sulfate and is greater in the Ca[sup 2+] systems than in the K[sup +] systems at any given ionic strength. High salt content and K[sup +] collapse the bentonite layers and limit access to and compete for adsorption sites. The K[sup +] ion is also more difficult to displace than Ca[sup 2+] from interlayer positions. Fourier transform infrared spectroscopic data show that the aniline compounds are adsorbed on bentonite through the hydrogen bonding of an amine hydrogen to a surface silica oxygen. Sulfate reduces amine adsorption by removing positively charged anilinium species from solution to form negatively charge sulfate complexes. Although adsorption of the substituted amines on bentonite is observed, aniline and toluidine adsorption is minimal in saline systems and not detected in alkaline systems. Thus, in shale oil process waste disposal sites, the mobility of the anilines through bentonite liners will not be mitigated by sorption processes, as spent oil shale leachates are both highly alkaline and saline.

  1. Adsorption of aniline and toluidines on montmorillonite: Implications for the disposal of shale oil production wastes

    SciTech Connect

    Essington, M.E.; Bowen, J.M.; Wills, R.A.; Hart, B.K.

    1992-01-01

    Bentonite clay liners are commonly employed to mitigate the movement of contaminants from waste disposal sites. Solid and liquid waste materials that arise from the production of shale oil contain a vast array of organic compounds. Common among these compounds are the aromatic amines. in order to assess the ability of clay liner material to restrict organic compound mobility, the adsorption of aniline and o-, m-, and p-toluidine on Ca{sup 2+} - and K{sup +}-saturated Wyoming bentonite was investigated. Adsorption experiments were performed under conditions of varied pH, ionic strength, and dominate electrolyte cation and anion. organic adsorption on Ca{sup 2+} - and K{sup +}-saturated montmorillonite is pH dependent. For any given organic compound, maximum adsorption increases with decreasing ionic strength. organic compound adsorption is inhibited in the presence of sulfate and is greater in the Ca{sup 2+} systems than in the K{sup +} systems at any given ionic strength. High salt content and K{sup +} collapse the bentonite layers and limit access to and compete for adsorption sites. The K{sup +} ion is also more difficult to displace than Ca{sup 2+} from interlayer positions. Fourier transform infrared spectroscopic data show that the aniline compounds are adsorbed on bentonite through the hydrogen bonding of an amine hydrogen to a surface silica oxygen. Sulfate reduces amine adsorption by removing positively charged anilinium species from solution to form negatively charge sulfate complexes. Although adsorption of the substituted amines on bentonite is observed, aniline and toluidine adsorption is minimal in saline systems and not detected in alkaline systems. Thus, in shale oil process waste disposal sites, the mobility of the anilines through bentonite liners will not be mitigated by sorption processes, as spent oil shale leachates are both highly alkaline and saline.

  2. Effect of organic matters on CO2 hydrate phase equilibrium conditions in Na-montmorillonite clay

    NASA Astrophysics Data System (ADS)

    Park, T.; Kyung, D.; Lee, W.

    2013-12-01

    Formation of gas hydrates provides an attractive idea for storing greenhouse gases in a long-term stable geological formation. Since the phase equilibrium conditions of gas hydrates indicate the stability of hydrates, estimation of the phase equilibrium conditions of gas hydrates in marine geological conditions is necessary. In this study, we have identified the effects of organic matters (glycine, glucose, and urea) and solid surface (montmorillonite (MMT)) on the three-phase (liquid-hydrate-vapor) equilibrium conditions of CO2 hydrate. CO2 phase equilibrium experiments were conducted using 0.5mol% organic matter solutions with and without 10g soil mineral were experimentally conducted. Addition of organic matters shifted the phase equilibrium conditions of CO2 hydrate to the higher pressure or lower pressure region because of higher competition of water molecules due to the dissolved organic matters. Presence of MMT also leaded to the higher equilibrium pressure due to the interaction of cations with water molecules. By addition of organic matters to the clay suspension, the hydrate phase equilibrium conditions were less inhibited compared to those of MMT and organic matters independently. The diminished magnitudes by addition of organic matters to the clay suspension (MMT > MMT+urea > MMT+glycine > MMT+glucose > DIW) were different to the order of inhibition degree without MMT (Glucose > glycine > urea > DIW). X-ray diffraction (XRD), scanning electron microscope (SEM), and ion chromatography (IC) analysis were conducted to support the hypothesis that the organic matters interact with cations in MMT interlayer space, and leads to the less inhibition of phase equilibrium conditions. The present study provides basic information for the formation and dissociation of CO2 hydrates in the geological formation when sequestering CO2 as a form of CO2 hydrate.

  3. Light microscopic and color television image analysis of the development of staining on chlorhexidine-treated surfaces.

    PubMed

    Addy, M; Prayitno, S W

    1980-01-01

    Tooth staining with the use of chlorhexidine preparations is the major problem of long term application. Evidence suggests that the staining arises from a cationic/anionic interacation of chlorhexidine with components of certain dietary materials. The purpose of this in vitro study was to compare visually the development of tea and coffee staining on acrylic and tooth specimens treated with chlorhexidine and to follow the development of tea staining on perspex by light microscopy and color television image analysis. All specimens were maintained in their respective beverage for 5 days with test specimens removed three times a day and placed for 2 minutes in an 0.2% chlorhexidine solution. Both test tooth and acrylic specimens showed comparably and markedly increased staining by the beverages compared with control specimens. Color television image analysis of test specimens demonstrated more marked and rapid development of tea staining when studied on a daily basis. Microscopic examination revealed the staining to be made up of small particles of material which increased in size and coalesced with time. Again, marked differences were apparent in the stain on test and control specimens. The results of this in vitro method provided further evidence for a dietary aetiology to chlorhexidine staining and were consistent with clinical findings. Such a method may be useful to assess staining arising from the use of other anti-plaque agents. PMID:6928469

  4. Soil surface colonization by phototrophic indigenous organisms, in two contrasted soils treated by formulated maize herbicide mixtures.

    PubMed

    Joly, Pierre; Misson, Benjamin; Perrière, Fanny; Bonnemoy, Frédérique; Joly, Muriel; Donnadieu-Bernard, Florence; Aguer, Jean-Pierre; Bohatier, Jacques; Mallet, Clarisse

    2014-11-01

    Soil phototrophic microorganisms, contributors to soil health and food webs, share their particular metabolism with plants. Current agricultural practices employ mixtures of pesticides to ensure the crops yields and can potentially impair these non-target organisms. However despite this environmental reality, studies dealing the susceptibility of phototrophic microorganisms to pesticide mixtures are scarce. We designed a 3 months microcosm study to assess the ecotoxicity of realistic herbicide mixtures of formulated S-metolachlor (Dual Gold Safeneur(®)), mesotrione (Callisto(®)) and nicosulfuron (Milagro(®)) on phototrophic communities of two soils (Limagne vertisol and Versailles luvisol). The soils presented different colonizing communities, with diatoms and chlorophyceae dominating communities in Limagne soil and cyanobacteria and bryophyta communities in Versailles soil. The results highlighted the strong impairment of Dual Gold Safeneur(®) treated microcosms on the biomass and the composition of both soil phototrophic communities, with no resilience after a delay of 3 months. This study also excluded any significant mixture effect on these organisms for Callisto(®) and Milagro(®) herbicides. We strongly recommend carrying on extensive soil studies on S-metolachlor and its commercial formulations, in order to reconsider its use from an ecotoxicological point of view. PMID:25129149

  5. Surface, optical and photocatalytic properties of silica-supported TiO2 treated with electron beam

    NASA Astrophysics Data System (ADS)

    Wronski, Pawel; Surmacki, Jakub; Abramczyk, Halina; Adamus, Agnieszka; Nowosielska, Magdalena; Maniukiewicz, Waldemar; Kozanecki, Marcin; Szadkowska-Nicze, Magdalena

    2015-04-01

    The influence of high-energy electron beam, (EB), treatment, in the dose range of 100-1000 kGy, on the physicochemical properties of silica-supported TiO2 was examined. TiO2/SiO2 supported oxides were obtained by impregnation of commercial silica gel (2-4 mm) with titanium (IV) n-butoxide. Surface and optical properties of prepared TiO2/SiO2 systems were analyzed using SEM, BET, XRD, Raman and UV-vis spectroscopy. The photoactivity under visible light was tested in discoloration of azo dye solution. No significant structural changes of the TiO2/SiO2 surface were detected as a result of EB treatment. Effect of EB irradiation was observed as an increase of photocatalytic activity in dye decomposition under visible light for TiO2/SiO2 samples containing ca. 23 wt% TiO2. The enhancement of activity was assigned to EB-induced defects and C-modification of TiO2 particles.

  6. Characterization of homoionic Fe 2+-type montmorillonite: Potential chemical species of iron contaminant

    NASA Astrophysics Data System (ADS)

    Kozai, Naofumi; Inada, Koichi; Adachi, Yoshifusa; Kawamura, Sachi; Kashimoto, Yusuke; Kozaki, Tamotsu; Sato, Seichi; Ohnuki, Toshihiko; Sakai, Takuro; Sato, Takahiro; Oikawa, Masakazu; Esaka, Fumitaka; Mitamura, Hisayoshi

    2007-08-01

    Fe 2+-montmorillonite with Fe 2+ ions occupying cation exchange sites is an ideal transformation product in bentonite buffer material. In our previous study on preparation and characterization of Fe 2+-montmorillonite, the montmorillonite sample that adsorbed Fe 2+ ions on almost all of the cation exchange sites was prepared using a FeCl 2 solution under an inert gas condition [N. Kozai, Y. Adachi, S. Kawamura, K. Inada, T. Kozaki, S. Sato, H. Ohashi, T. Ohnuki, T. Banba, J. Nucl. Sci. Technol. 38 (2001) 1141]. In view of the unstable nature of iron(II) chemical species, this study attempted to determine the potential contaminant iron chemical species in the sample. Nondestructive elemental analysis revealed that a small amount of chloride ions remained dispersed throughout the clay particles. The chloride ion retention may be due to the adsorption of FeCl + ion pairs in the initial FeCl 2 solution and the subsequent containment of the Cl - ions that are dissociated from the FeCl + ion pairs during excess salt removal treatment. Two explanations are advanced for the second process: the slow release of the remaining Cl - ions from the collapsed interlayer of the montmorillonite, and the transformation of a minor fraction of the remaining FeCl + ion pairs to iron(III) hydroxide chloride complexes having low solubility.

  7. Development of biodegradable foamlike materials based on casein and sodium montmorillonite clay

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biodegradable foamlike materials based on a naturally occurring polymer (casein protein) and sodium montmorillonite clay (Na+-MMT) were produced through a simple freeze-drying process. By utilizing DL-glyceraldehyde (GC) as a chemical cross-linking agent, the structural integrity of these new aeroge...

  8. Calcium montmorillonite clay reduces urinary biomarkers of fumonisin B1 exposure in rats and humans

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background: Fumonisin B1 (FB1) is often a co-contaminant with aflatoxin (AF) in grains and may enhance AF’s carcinogenicity by acting as a cancer promoter. An oral dose of calcium montmorillonite clay (i.e. NovaSil, NS) was able to reduce aflatoxin exposure in a Ghanaian population at risk. In vitro...

  9. Mixed-layer kaolinite-montmorillonite from the Yucatan Peninsula, Mexico

    USGS Publications Warehouse

    Schultz, L.G.; Shepard, A.O.; Blackmon, P.D.; Starkey, H.C.

    1971-01-01

    Clay beds 1-2 m thick and interbedded with marine limestones probably of early Eocene age are composed of nearly pure mixed-layer kaolinite-montmorillonite. Particle size studies, electron micrographs, X-ray diffraction studies, chemical analyses, cation exchange experiments, DTA, and TGA indicate that clays from three different localities contain roughly equal proportions of randomly interlayered kaolinite and montmorillonite layers. The montmorillonite structural formulas average K0??2Na0??2Ca0??2Mg0??2(Al2??5Fe1??03+Mg0??5)(Al0??75Si7??25)O20+(OH)4-, with a deficiency of structural (OH) in either the montmorillonite or kaolinite layers. Nonexchangeable K+ indicates that a few layers are mica-like. Crystals are mostly round plates 1 10 to 1 20 ?? across. The feature most diagnostic of the mixed-layer character is an X-ray reflection near 8 A?? after heating at 300 ??C. The clays are inferred to have developed by weathering of volcanic ash and subsequent erosion and deposition in protected nearshore basins. ?? 1971.

  10. OXIDATION OF ALCOHOLS OVER FE3+/MONTMORILLONITE-K10 USING HYDROGEN PEROXIDE

    EPA Science Inventory

    Oxidation of various primary and secondary alcohols is studied in liquid phase at atmospheric pressure over Fe3+/montmorillonite-K10 catalyst prepared by ion-exchange method at a pH of 4 in an environmentally friendly protocol using hydrogen peroxide. The catalyst and the method ...

  11. Hydrodynamic and Chemical Factors in Clogging by Montmorillonite in Porous Media

    PubMed Central

    Mays, David C.; Hunt, James R.

    2008-01-01

    Clogging by colloid deposits is important in water treatment filters, groundwater aquifers, and petroleum reservoirs. The complexity of colloid deposition and deposit morphology preclude models based on first principles, so this study extends an empirical approach to quantify clogging using a simple, one-parameter model. Experiments were conducted with destabilized suspensions of sodium- and calcium-montmorillonite to quantify the hydrodynamic and chemical factors important in clogging. Greater clogging is observed at slower fluid velocity, consistent with previous investigations. However, calcium-montmorillonite causes one order of magnitude less clogging per mass of deposited particles compared to sodium-montmorillonite or a previously published summary of clogging in model granular media. Steady state conditions, in which the permeability and the quantity of deposited material are both constant, were not observed, even though the experimental conditions were optimized for that purpose. These results indicate that hydrodynamic aspects of clogging by these natural materials are consistent with those of simplified model systems, and they demonstrate significant chemical effects on clogging for fully destabilized montmorillonite clay. PMID:17874771

  12. Changes in Plant Nutrients, and Microbial Biomass in Different Soil Depths After Long-Term Surface Application of Secondary Treated Wastewater

    NASA Astrophysics Data System (ADS)

    Al-Rashidi, Radhi; Rusan, Munir; Obaid, Karem

    2013-12-01

    Long-term effects of surface application of secondary treated wastewater on plant nutrients dynamics, the cycling of C and N within the system through the determination of microbial biomass, and associated health hazards were studied in different soil locations. Sites that have been irrigated with wastewater for the last 1, 4, 10, and 17 years were identified and used as sampling locations for this study. Two other sites that have not been irrigated with wastewater were sampled as a control. Soil samples were taken from several sites within each location, and at the following depths: 0-20, 20-40, and 40-60 cm. Results obtained indicated that microbial biomass C and N were increased significantly with increasing application period of treated wastewater. Barley plant tissues analysis showed that plant nutrients content was significantly higher in sites which received wastewater for a long period than other sites. No significances in accumulation of lead (Pb) in barley plant tissues were observed with sites received wastewater for different periods. The bacteriological analysis showed that the total bacterial count of surface soil (0-20 cm) was higher in sites irrigated with wastewater for the last 10 and 17 years. The total coliforms ranged from 0.92x102 cfu/g soil to 3.3x102 cfu/g soil, while fecal coliform were less and detected only in top soils at sites irrigated with wastewater for the last 10 and 17 years.

  13. Properties of M40J Carbon/PMR-II-50 Composites Fabricated with Desized and Surface Treated Fibers. Characterization of M40J Desized and Finished Fibers

    NASA Technical Reports Server (NTRS)

    Allred, Ronald E.; Gosau, Jan M.; Shin, E. Eugene; McCorkle, Linda S.; Sutter, James K.; OMalley, Michelle; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    To increase performance and durability of high temperature composites for potential rocket engine components, it is necessary to optimize wetting and interfacial bonding between high modulus carbon fibers and high temperature polyimide resins. It has been previously demonstrated that the electro-oxidative shear treatments used by fiber manufacturers are not effective on higher modulus fibers that have fewer edge and defect sites in the surface crystallites. In addition, sizings commercially supplied on most carbon fibers are not compatible with polyimides. This study was an extension of prior work characterizing the surface chemistry and energy of high modulus carbon fibers (M40J and M60J, Torray) with typical fluorinated polyimide resins, such as PMR-II-50. A continuous desizing system which utilizes environmentally friendly chemical- mechanical processes was developed for tow level fiber and the processes were optimized based on weight loss behavior, surface elemental composition (XPS) and morphology (FE-SEM) analyses, and residual tow strength of the fiber, and the similar approaches have been applied on carbon fabrics. Both desized and further treated with a reactive finish were investigated for the composite reinforcement. The effects of desizing and/or subsequent surface retreatment on carbon fiber on composite properties and performance including fiber-matrix interfacial mechanical properties, thermal properties and blistering onset behavior will be discussed in this presentation.

  14. Reflectance spectra of sulfate-and carbonate-bearing Fe(3+)-doped montmorillonites as Mars soil analogs

    NASA Technical Reports Server (NTRS)

    Bishop, Janice L.; Pieters, Carle M.; Burns, Roger G.

    1993-01-01

    Ferric smectites and ferrihydrite may be common alteration products of igneous lithologies on Mars, and experiments involving montmorillonite enriched with Fe(3+) support the likelihood of ferric smectites on Mars. Mossbauer spectroscopy has been used to identify ferrihydrite (Fe4(O,OH,H2O)12) as the primary ferric material in Fe(3+)-doped montmorillonite. Ferrihydrite is especially interesting due to its role as a precursor in the formation of hematite and goethite. Reflectance spectroscopy in the visible and infrared regions are coupled with Mossbauer spectroscopy in this study to characterize the ferric material in montmorillonites containing Fe(3+), as well as carbonates or sulfates, in the interlayer region.

  15. Dynamics of sulphur compounds in horizontal sub-surface flow laboratory-scale constructed wetlands treating artificial sewage.

    PubMed

    Wiessner, A; Rahman, K Z; Kuschk, P; Kstner, M; Jechorek, M

    2010-12-01

    The knowledge regarding the dynamics of sulphur compounds inside constructed wetlands is still insufficient. Experiments in planted (Juncus effusus) and unplanted horizontal sub-surface-flow laboratory-scale constructed wetlands fed with artificial wastewater were carried out to evaluate the sulphate reduction, the composition and dynamics of generated sulphur compounds, as well as the influence of carbon load and plants on processes of sulphur transformation. In planted and unplanted wetlands, the addition of organic carbon (TOC of about 120mgL(-1)) immediately affected the transformation of up to 90% of the incoming sulphate (150mgL(-1)), directing it mainly towards elemental sulphur (30%) and sulphide (8%). During this experimental period, nearly 52% of the transformed sulphate-sulphur was calculated to be immobilized inside the planted wetland and 66% inside the unplanted one. In subsequent experiments, the deficiency of organic carbon inside the planted wetlands favoured the decrease of elemental sulphur in the pore water coupled to retransformation of depot-sulphur to dissolved sulphate. Nearly 90% of the deposited and reduced sulphur was found to be reoxidized. In principle, the results indicate a substantial improvement of this reoxidation of sulphur by oxygen released by the helophytes. Surplus of organic carbon promotes the ongoing sulphate reduction and the stability of deposed and dissolved reduced sulphur compounds. In contrast, inside the unplanted control wetland, a relative stability of the formed sulphur depots and the generated amount of dissolved sulphur compounds including elemental sulphur could be observed independently of the different loading conditions. PMID:20692006

  16. Effect of chlorine dioxide gas on Salmonella enterica inoculated on navel orange surfaces and its impact on the quality attributes of treated oranges.

    PubMed

    Bhagat, Arpan; Mahmoud, Barakat S M; Linton, Richard H

    2011-01-01

    Microorganisms, including pathogens of public health significance, have been shown to contaminate orange juice during the mechanical extraction of juice. The problem gets exacerbated when washed oranges have high initial microbial load, due to an insufficient postharvest treatment. The objective of this study was to investigate the reduction of Salmonella enterica on orange surfaces using ClO₂ gas treatments to achieve a 5 log reduction, consistent with the recommendations of the U.S. Department of Agriculture-National Advisory Committee on Microbiological Criteria for Foods. A mixed culture of four Salmonella strains, isolated from previous orange juice outbreaks, was spot inoculated onto orange skin surface areas. The oranges were then treated with 0.1, 0.3, and 0.5 mg/L ClO₂ gas for 2-14 minutes at 22°C and 90%-95% relative humidity. Surviving bacteria on treated areas were recovered and enumerated over treatment time on a nonselective medium, tryptic soy agar, followed by culturing onto a selective medium, xylose lysine deoxycholate agar. A >5 log reduction of Salmonella per sample of orange surface was observed with 0.1 and 0.3 mg/L ClO₂ gas treatments at 14 minutes and a similar log reduction was observed at 0.5 mg/L ClO₂ gas at 10 minutes. This result demonstrates that the treatment of oranges with ClO₂ gas is a promising technology that could be successfully employed for the treatment of whole oranges to reduce the risk of Salmonella outbreaks in orange juice. PMID:20932090

  17. Effect of Product Dimensions and Surface Browning Method on Salmonella Contamination in Frozen, Surface-Browned, Breaded Chicken Products Treated with Antimicrobials.

    PubMed

    Moschonas, Galatios; Geornaras, Ifigenia; Stopforth, Jarret D; Woerner, Dale R; Belk, Keith E; Smith, Gary C; Sofos, John N

    2015-12-01

    Not-ready-to-eat breaded chicken products formulated with antimicrobial ingredients were tested for the effect of sample dimensions, surface browning method and final internal sample temperature on inoculated Salmonella populations. Fresh chicken breast meat portions (5 × 5 × 5 cm), inoculated with Salmonella (7-strain mixture; 5 log CFU/g), were mixed with (5% v/w total moisture enhancement) (i) distilled water (control), (ii) caprylic acid (CAA; 0.0625%) and carvacrol (CAR; 0.075%), (iii) CAA (0.25%) and ε-polylysine (POL; 0.5%), (iv) CAR (0.15%) and POL (0.5%), or (v) CAA (0.0625%), CAR (0.075%) and POL (0.5%). Sodium chloride (1.2%) and sodium tripolyphosphate (0.3%) were added to all treatments. The mixtures were then ground and formed into 9 × 5 × 3 cm (150 g) or 9 × 2.5 × 2 cm (50 g) portions. The products were breaded, browned in (i) an oven (208 °C, 15 min) or (ii) deep fryer (190 °C, 15 s), packaged, and stored at -20 °C (8 d). Overall, maximum internal temperatures of 62.4 ± 4.0 °C (9 × 2.5 × 2 cm) and 46.0 ± 3.0 °C (9 × 5 × 3 cm) were reached in oven-browned samples, and 35.0 ± 1.1 °C (9 × 2.5 × 2 cm) and 31.7 ± 2.6 °C (9 × 5 × 3 cm) in fryer-browned samples. Irrespective of formulation treatment, total (after frozen storage) reductions of Salmonella were greater (P < 0.05) for 9 × 2.5 × 2 cm oven-browned samples (3.8 to at least 4.6 log CFU/g) than for 9 × 5 × 3 cm oven-browned samples (0.7 to 2.5 log CFU/g). Product dimensions did not (P ≥ 0.05) affect Salmonella reductions (0.6 to 2.8 log CFU/g) in fryer-browned samples. All antimicrobial treatments reduced Salmonella to undetectable levels (<0.3 log CFU/g) in oven-browned 9 × 2.5 × 2 cm samples. Overall, the data may be useful for the selection of antimicrobials, product dimensions, and surface browning methods for reducing Salmonella contamination. PMID:26495824

  18. UV-O3-treated and protein-coated polymer surfaces facilitate endothelial cell adhesion and proliferation mediated by the PKCalpha/ERK/cPLA2 pathway.

    PubMed

    Formosa, Fabio; Anfuso, Carmelina D; Satriano, Cristina; Lupo, Gabriella; Giurdanella, Giovanni; Ragusa, Nicola; Marletta, Giovanni; Alberghina, Mario

    2008-04-01

    We examined the adhesion and proliferation of immortalized endothelial cells GP8.39 (ECs) onto polyethyleneterephtalate (PET) and polyhydroxymethylsiloxane (PHMS) thin films, functionalized by UV-O(3) treatment and/or protein immobilization. The modified surface topography showed partial oxidation for both polymers, a slight increase in wettability and monopolar basic character for PET, and a hydrophilic bipolar acid-base behaviour for PHMS. UV-O(3) treatment did not induce significant roughness changes (under 1 nm) as shown by atomic force spectroscopy measurements (AFM). The EC adhesion and spreading onto untreated and modified surfaces were investigated both before and after immobilization of collagen (CA) and fibronectin (FN) adlayers. AFM analyses showed an open-weave protein layer on both untreated polymers which became a tight-woven net after UV-O(3) irradiation of underlying films. On day 5 after seeding, cell count analyses on irradiated PET surfaces, CA/FN-coated or not, showed EC adhesion and proliferation significantly greater than those on untreated polymers, indicating that UV-O(3) irradiation promoted fast endothelialization. A less pronounced EC spreading behaviour on treated PHMS was observed. In ECs grown on irradiated and CA- or FN-coated PET, the levels of phospho-protein kinase Calpha (p-PKCalpha, phospho-ERK1/2, and phospho-cytosolic phospholipase A(2) (p-cPLA(2)), all enzymes taken as signaling markers of cell adhesion and proliferation, decreased in comparison to those in CA- or FN-coated untreated PET. In contrast, in ECs grown on UV-O(3)-treated PHMS, Western blot analyses showed increased levels of p-PKCalpha, p-ERK1/2 and p-cPLA(2) in comparison with cells grown onto untreated polymer. The growth response of ECs to the substrates was related to the changes of polarity properties of UV-O(3)-treated polymer films, from hydrophobic/neutral towards hydrophilic/charged layers, and the signaling pathway remodelling to the cell proliferation degree. PMID:18177904

  19. The effect of neodymium on the microcracks generated on the Al-17.5Si alloy surface treated by high current pulsed electron beam

    NASA Astrophysics Data System (ADS)

    Hu, Liang; Gao, Bo; Zhu, Guanglin; Hao, Yi; Sun, Shuchen; Tu, Ganfeng

    2016-02-01

    In the present work, the effect of Nd on the microcracks generated on an Al-17.5Si alloy surface by a high current pulsed electron beam (HCPEB) was investigated. By a newly proposed site-fixed observation, the propagation of microcracks with increasing pulsed numbers first increases and then decreases due to the Nd element. The crack density decreases from 0.0669 mm/mm2 of 5 pulses to 0.00687 mm/mm2 of 50 pulses. EPMA analysis results indicate that Nd is uniformly distributed on the HCPEB-treated alloy surface. Nano-silicon particles and nano-Al cellular structures were formed by TEM observation, showing grain refinement of the alloy surface. The microcrack elimination is attributed to a decrease in the stress concentration in the primary Si phase during the cooling process of HCPEB. The electrochemical measurement shows that the corrosion current density decreases sharply by two magnitudes as the pulsed number increases after adding the Nd element, thus indicating an improved corrosion resistance. In contrast, in the HCPEB-irradiated sample without Nd, this value increases conversely due to the presence of numerous microcracks, thereby demonstrating a decreased corrosion resistance.

  20. Influence of a Cerium Surface Treatment on the Oxidation Behavior of Cr2O3-Forming Alloys (title on slides varies: Oxidation Behavior of Cerium Surface Treated Chromia Forming Alloys)

    SciTech Connect

    Alman, D.E.; Holcomb, G.R.; Adler, T.A.; Jablonski, P.D.

    2007-04-01

    Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This temperature will require the construction of boiler and turbine components from austenitic stainless steels and nickel alloys. Many of the alloys being considered for use are primarily Cr2O3 forming alloys [1-4]. It is well known that the addition of a small amount of reactive elements, such as the rare earths elements Ce, La, and Y, can significantly improve the high temperature oxidation resistance of both iron- and nickel- base alloys. A list of the benefits of the reactive element effect include: (i) slowing scale growth, (ii) enhancing scale adhesion; and (iii) stabilizing Cr2O3 formation at lower Cr levels. The incorporation of the reactive element can be made in the melt or through a surface infusion or surface coating. Surface modifications allow for the concentration of the reactive element at the surface where it can provide the most benefit. This paper will detail a Ce surface treatment developed at NETL that improves the high temperature oxidation resistance of Cr2O3 forming alloys. The treatment consists of painting, dip coating, or spraying the alloy surface with a slurry containing CeO2 and a halide activator followed by a thermal treatment in a mild (x10-3 Torr) vacuum. During treatment the CeO2 reacts with the alloy to for a thin CrCeO3-type scale on the alloy surface. Upon subsequent oxidation, scale growth occurs at a reduced rate on alloys in the surface treated condition compared to those in the untreated condition.

  1. Inhibition of cadmium- induced genotoxicity and histopathological changes in Nile tilapia fish by Egyptian and Tunisian montmorillonite clay.

    PubMed

    Mahrous, Karima F; Hassan, Aziza M; Radwan, Hasnaa A; Mahmoud, M A

    2015-09-01

    Cadmium (Cd) is an important inorganic toxicant widely distributed in the environment because of its various industrial uses. The aims of the current study were to investigate the efficacy of purified Egyptian and Tunisian montmorillonite clays (EMC and TMC) to inhibit genotoxicity and histological alterations induced by cadmium chloride (CdCl2) utilizing the Nile tilapia fish as an in vivo model. Chromosomal aberrations (CAs), micronucleus (MN) frequencies and DNA fingerprinting profile were genotoxic end points and histopathological changes that were used in this investigation. Six groups of fish were treated for 2 weeks and included control group, CdCl2-treated group and groups treated with EMC or TMC alone or in combination with CdCl2. The present results revealed that, treatment of fish with CdCl2 exhibited significant increased in the number of micronucleated erythrocytes (MnRBCs), frequency of CAs and instability of genomic DNA. Treatment of EMC and TMC in combination with CdCl2 significantly reduced the frequency of MnRBCs by the percentage of 53.28% and 60.77% and the frequency of CAs by 43.91% and 52.17% respectively. As well as, normalized DNA fingerprinting profile and significantly improved histopathological picture induced by Cadmium treatment. It is worth mention that both clays have the ability to tightly bind CdCl2 and decreased its cytotoxicity and genotoxicity; however, Tunisian clay was more efficient in binding with the CdCl2 than Egyptian clay. PMID:26001163

  2. Remediation of hexavalent chromium from aqueous solution using clay mineral Fe(II)-montmorillonite: Encompassing anion exclusion impact

    NASA Astrophysics Data System (ADS)

    Vinuth, Mirle; Bhojya Naik, Halehatty Seethya; Manjanna, Jayappa

    2015-12-01

    We have explored the highly efficient and environmentally benign clay mineral, Fe(II)-montmorillonite, for the reduction of Cr(VI) in aqueous solution. Fe(II)-Mt was treated with K2Cr2O7 solution at different pH, temperature and solid-to-liquid ratio. The [Cr2O7]2- was estimated by UV-vis spectra with a correction for anion exclusion impact. In general, the Cr(VI) reduction was rapid at acidic pH and increased with temperature up to 50 °C. A complete reduction occurred in about 5 min at pH 3-5. The time taken for complete reduction at 0 °C, RT (30 °C) and 40 °C are 12 min, 8 min and 5 min, respectively. The reduction followed by immobilization of Cr(III) on the spent clay mineral was well characterized by EDX and chemical extraction analysis. This remediation process could be easily scaled-up for real system applications.

  3. Hydrophobic and electrostatic interaction chromatography for estimating changes in cell surface charge of Escherichia coli cells treated with pulsed electric fields.

    PubMed

    Ukuku, Dike O; Yuk, Hyun-Gyun; Zhang, Howard

    2011-10-01

    Pulsed electric field (PEF) treatments, a nonthermal process, have been reported to injure and inactivate bacteria in liquid foods. However, the effect of this treatment on bacterial cell surface charge and hydrophobicity has not been investigated. Apple juice (pH 3.8) purchased from a wholesale distributor was inoculated with cocktail of Escherichia coli O157:H7 at 7.4 log CFU/mL, processed with a PEF at a field strength of 18.4 kV/cm and 32.2 kV/cm at 25°C, 35°C, and 45°C with a treatment time of 160 μs and a flow rate of 120 mL/min. Bacterial cell surface charge and hydrophobicity of untreated and PEF-treated E. coli O157:H7 were determined immediately and after storage at 5°C and 23°C using hydrophobic and electrostatic interaction chromatography. Similarly, the populations surviving the PEF treatments including injured cells were determined by plating 0.1 mL of the sample on sorbitol MacConkey agar and tryptic soy agar (TSA) plates. The surviving populations of E. coli cells after PEF treatment varied depending on field strength and treatment temperature used. Percent injury in the surviving populations was high immediately after PEF treatment and varied among treatment temperatures. Cell surface charge of E. coli bacteria before PEF treatment averaged 32.10±8.12. PEF treatments at 25°C, 35°C, and 45°C reduced the above surface charge to 26.34±1.24, 14.24±3.30, and 6.72±2.82, respectively. Similarly, the surface hydrophobicity of untreated E. coli cells at 0.194±0.034 was increased to an average of 0.268±0.022, 0.320±0.124, and 0.586±0.123 after PEF treatments at 25°C, 35°C, and 45°C, respectively. The results of this study indicate that PEF treatment affects the outer cell envelope of E. coli bacteria as evidenced by the changes in surface hydrophobicity and cell surface charge leading to injury and subsequent inactivation of the cells. PMID:21668373

  4. Influence of sputter rate and crystal orientation on the distribution of carbon in polycrystalline copper surfaces treated by plasma immersion ion implantation

    SciTech Connect

    Flege, S.; Kraft, G.; Bruder, E.; Ensinger, W.; Baba, K.; Hatada, R.

    2009-07-15

    The sputter rate influences the resulting thickness of the carbon containing layer within a surface that was treated by plasma immersion ion implantation. Choosing a polycrystalline substrate with rather large crystals and a material with an inherent high sputter rate, inhomogeneous distributions of carbon over the substrate area due to different thicknesses of the incorporated carbon can be detected. A correlation of three factors namely the carbon x-ray intensity in electron probe microanalysis, the thickness of the carbon layer, and the sputter rate in depth profiling measurements via secondary ion mass spectrometry can be shown. Essential for these factors is the crystal orientation that is visualized by mapping via electron backscatter diffraction. The differences in carbon content due to the orientation are most likely one of the reasons that the adhesion of diamond-like carbon films on copper does not improve with an interlayer of implanted carbon.

  5. Patterning Method for Silver Nanoparticle Electrodes in Fully Solution-Processed Organic Thin-Film Transistors Using Selectively Treated Hydrophilic and Hydrophobic Surfaces

    NASA Astrophysics Data System (ADS)

    Fukuda, Kenjiro; Takeda, Yasunori; Kobayashi, Yu; Shimizu, Masahiro; Sekine, Tomohito; Kumaki, Daisuke; Kurihara, Masato; Sakamoto, Masatomi; Tokito, Shizuo

    2013-05-01

    Fully solution-processed organic thin-film transistor (OTFT) devices have been fabricated with simple patterning process at a relatively low process temperature of 100 °C. In the patterning process, a hydrophobic amorphous fluoropolymer material, which was used as the gate dielectric layer and the underlying base layer, was treated with an oxygen plasma to selectively change its surface wetting properties from hydrophobic to hydrophilic. Silver source and drain electrodes were successfully formed in the treated areas with highly uniform line widths and without residues between the electrodes. Nonuniformities in the thickness of the silver electrodes originating from the “coffee-ring” effect were suppressed by optimizing the blend of solvents used with the silver nanoparticles, such that the printed electrodes are appropriate for bottom-gate OTFT devices. A fully solution-processed OTFT device using a polymer semiconductor material (PB16TTT) exhibited good electrical performance with no hysteresis in its transfer characteristics and with good linearity in its output characteristics. A relatively high carrier mobility of 0.14 cm2 V-1 s-1 and an on/off ratio of 1×105 were obtained with the fabricated TFT device.

  6. Comparison of the effect of surface application and subsurface incorporation of enhanced treated biosolids on the leaching of heavy metals and nutrients through sand and sandy loam soils.

    PubMed

    Gove, L; Nicholson, F A; Cook, H F; Beck, A J

    2002-02-01

    Use of enhanced treated biosolids such as composted and dried, mesophilic anaerobically digested, dewatered (MADD) biosolids is becoming more popular. This is mainly in response to concerns over the potential for pathogens to enter the food chain. There is, therefore, a need to investigate how enhanced treatment, and methods by which these biosolids are applied, affects the leaching potential of metal and nutrients to ensure that water quality is not compromised. MADD cake (fresh, dried and composted) and MAD liquid sludge were applied by surface application and subsurface incorporation to sand (typic quartzipsamments, %OM = 3.0, pH = 6.5), sandy loam (typic hapludalf, %OM = 4.8, pH = 7.6) and silversand 'repacked semi-structured cores' (0.2 m by 0.1 m diameter) at rates equivalent to 250 kg N ha(-1) yr(-1). Leaching of Zn, Cu, Pb, Ni, N and P was investigated following application of five 8 h simulated rainfall events (4.9 mm h(-1)) in the laboratory. Little difference was observed between leaching of metals and nutrients from soils amended with enhanced treated biosolids (dried and composted MADD cakes) compared with conventional biosolids (fresh MADD cake and MAD liquid). Subsurface incorporation increased the risk of P and metal leaching compared with surface application. Nitrate losses were independent of application method. Similar nutrient losses from control and amended cores indicated that the leaching was derived predominantly from the soil clay and organic matter complexes. Evidence for attenuation of biosolids-derived metals and P by soil-derived clay and/or organic matter was found. Water balance data showed that hydrological regimes of each core were comparable and unlikely to account for observed differences in leaching losses. PMID:11950071

  7. Study on the Surface-Physicochemical-Property Changing of Bentonite by Adapting a New Soil Stabilizer

    NASA Astrophysics Data System (ADS)

    Huang, Wei; Xiang, Wei; Lang, Linzhi; Cui, Deshan

    2015-04-01

    Surface-physicochemical-property of clays has been proved to have direct influence on its mechanic behavior. Specific surface area (SSA) is one of the most important factors for surface-physicochemical-property assessment. The smaller SSA tends higher strength (shear strength, unconfined compressive strength and tensile strength) under different water contents of soil. In this paper, a new soil stabilizer (Tung oil-based sulfonated) is developed and applied to improve the properties of Ca-bentonite. The differences of specific surface area, fractal dimension and micro geometric morphology between raw Ca-bentonite samples and modified ones are investigated based on the data acquired from water vapor, nitrogen adsorption experiments and SEM experiments. Results show that the SSA including external SSA and total SSA of treated samples decrease largely and apparently when compared to that of the raw samples. Furthermore, the higher volume ratio between soil stabilizer and water, the more decrease in SSA. Compared to the ones of raw Ca-bentonite, the external SSA and total SSA of the modified Ca-bentonite samples decrease by 48.5% and 25.2%, respectively, when the volume ratio was 1:50. This result implies that the connection of montmorillonite particles becomes more tightly after the treatment by the soil stabilizer. In addition, an obvious decreasing trend is found in fractal dimension by analysis of water vapor adsorption isotherms. This finding indicates that the pore surface tends to be smoother by the chemical action among particles bonds, more condensable in aggregates and shorter space between the interlayer of montmorillonite. SEM results display that the new soil stabilizer developed a quantity of lamellar aggregates but did not change the structure of montmorillonite. Based on all mentioned above, the results of fractal dimension analysis are verified. Consequently, this study shows that the new soil stabilizer (Tung oil-based sulfonated) has obvious effects on improving the physicochemical properties of bentonite. The findings of this study further indicate that the mechanic behavior of bentonite could be improved by adapting this new soil stabilizer. Keywords: new soil stabilizer; tung oil-based sulfonated; Ca-bentonite; specific surface area; fractal dimension; SEM

  8. Oligomerization reactions of ribonucleotides - The reaction of the 5'-phosphorimidazolide of nucleosides on montmorillonite and other minerals

    NASA Technical Reports Server (NTRS)

    Ferris, James P.; Ertem, Gozen

    1992-01-01

    The reaction of ImpA in the presence of Na(+)-montmorillonite 22A or Na(+)-Volclay in aqueous, pH 8 solution gives a 50-60 percent yield of dimers and trimers (pA)2 and (pA)3. The ratio of 3',5'-phosphodiester bond formation is twice as great as 2',5'-bond formation. The reaction requires the presence of Mg2+ and is inhibited by 0.4 M imidazole. N-methylimidazole enhances the rate of the reaction but does not cause major changes in yield or product composition. Higher yields were obtained when Li+- or Ca2+-montmorillonites were used in place of Na+-montmorillonite. Little or no phosphodiester bond formation was observed with Mg2+- or Al3+-montmorillonite. Montmorillonites other than 22A and Volclay exhibited litle or no catalysis. In addittion, little or no catalysis was exhibited in ferrugenous smectite, nontronite, allophane, imogolite or sepiolite. Oligomers were also formed by the reaction of ImpG, 2-methylImpG, ImpC and ImpU in the presence of Na+-montmorillonite. The pyrimidine nucleotides gave significantly lower yields of oligomers.

  9. Intestinal toxicity evaluation of TiO2 degraded surface-treated nanoparticles: a combined physico-chemical and toxicogenomics approach in caco-2 cells

    PubMed Central

    2012-01-01

    Background Titanium dioxide (TiO2) nanoparticles (NPs) are widely used due to their specific properties, like UV filters in sunscreen. In that particular case TiO2 NPs are surface modified to avoid photocatalytic effects. These surface-treated nanoparticles (STNPs) spread in the environment and might release NPs as degradation residues. Indeed, degradation by the environment (exposure to UV, water and air contact …) will occur and could profoundly alter the physicochemical properties of STNPs such as chemistry, size, shape, surface structure and dispersion that are important parameters for toxicity. Although the toxicity of surface unmodified TiO2 NPs has been documented, nothing was done about degraded TiO2 STNPs which are the most likely to be encountered in environment. The superoxide production by aged STNPs suspensions was tested and compared to surface unmodified TiO2 NPs. We investigated the possible toxicity of commercialized STNPs, degraded by environmental conditions, on human intestinal epithelial cells. STNPs sizes and shape were characterized and viability tests were performed on Caco-2 cells exposed to STNPs. The exposed cells were imaged with SEM and STNPs internalization was researched by TEM. Gene expression microarray analyses were performed to look for potential changes in cellular functions. Results The production of reactive oxygen species was detected with surface unmodified TiO2 NPs but not with STNPs or their residues. Through three different toxicity assays, the STNPs tested, which have a strong tendency to aggregate in complex media, showed no toxic effect in Caco-2 cells after exposures to STNPs up to 100 μg/mL over 4 h, 24 h and 72 h. The cell morphology remained intact, attested by SEM, and internalization of STNPs was not seen by TEM. Moreover gene expression analysis using pangenomic oligomicroarrays (4x 44000 genes) did not show any change versus unexposed cells after exposure to 10 μg/ mL, which is much higher than potential environmental concentrations. Conclusions TiO2 STNPs, degraded or not, are not harmful to Caco-2 cells and are unlikely to penetrate the body via oral route. It is likely that the strong persistence of the aluminium hydroxide layer surrounding these nanoparticles protects the cells from a direct contact with the potentially phototoxic TiO2 core. PMID:22650444

  10. Solid-state synthesis and electrical properties of polyaniline/Cu-montmorillonite nanocomposite

    SciTech Connect

    Bekri-Abbes, Imene; Srasra, Ezzeddine

    2010-12-15

    In this paper, the solid-state synthesis of polyaniline/Cu-montmorillonite nanocomposite is reported. Mixture of anilinium chlorure and Cu exchanged montmorillonite was grinded at room temperature while we vary the molar rate of aniline to interlayer Cu{sup 2+} cations (R) from 0.5 to 6. The properties of the hybrid compounds are characterized by X-ray diffraction, thermogravimetric analysis, SEM, FTIR and impedance spectroscopy. The results showed that the structure and the conductivity of PANI in hybrid materials depend on R. The ac conduction showed a regime of constant dc conductivity at low frequencies and a crossover to a frequency-dependent regime of the type A {omega}{sup s} at high frequencies.

  11. [In vitro adsorption of aflatoxins by means of sorbent compounds: montmorillonite].

    PubMed

    Ramos Girona, A J; Hernández Giménez, E

    1997-06-01

    Aflatoxins are a group of mycotoxins that can be present as contaminants in a great number of food and feedstuffs. It has been demonstrated that non-nutritive adsorbent compounds are able not only to adsorb aflatoxins but also to prevent its gastrointestinal absorption. The objective of this study is to evaluate the adsorptive capacity of a montmorillonite (a natural silicate) with regard to aflatoxins, and to evaluate the efficacy and stability of the aflatoxin-montmorillonite complex in several pH, temperature and reaction media. Results have demonstrated that, at a concentration of 1% w/v, this adsorbent has a high efficacy in the sorption of aflatoxins, with mean sorption percentages higher than 98% in most of cases. Physisorption is probably the sorption mechanism of this process. PMID:16854176

  12. Radiolysis of aqueous solutions of acetic acid in the presence of Na-montmorillonite.

    PubMed

    Navarro-González, R; Negrón-Mendoza, A; Ramos, S; Ponnamperuma, C

    1990-01-01

    The gamma-irradiation of 0.8 mol dm-3 aqueous, oxygen-free acetic acid solutions was investigated in the presence or absence of Na-montmorillonite. H2, CH4, CO, CO2, and several polycarboxylic acids were formed in all systems. The primary characteristics observed in the latter system were: (1) Higher yield of the decomposition of acetic acid; (2) Lower yield of the formation of polycarboxylic acids; (3) No effect on the formation of methane; (4) Higher yield of the formation of carbon dioxide; and (5) The reduction of Fe3+ in the octahedral sites of Na-montmorillonite. A possible reaction scheme was proposed to account for the observed changes. The results are important in understanding heterogeneous processes in radiation catalysis and might be significant to prebiotic chemistry. PMID:11539119

  13. Amine functionalized K10 montmorillonite: a solid acid-base catalyst for the Knoevenagel condensation reaction.

    PubMed

    Varadwaj, G Bishwa Bidita; Rana, Surjyakanta; Parida, K M

    2013-04-14

    Different amine functionalized K10 montmorillonites were hydrothermally fabricated by a simple method of treatment of the neat clay with different amine solutions and used as heterogeneous catalysts towards the Knoevenagel condensation reaction. Catalytic results show that the di-amine functionalized K10 montmorillonite exhibits high efficacy for promoting this reaction at room temperature and in the absence of a solvent. The solid catalyst was characterized using a variety of different techniques; including Fourier transform infrared spectroscopy (FT-IR), nitrogen physisorption measurements, (29)Si CP MAS NMR spectroscopy, NH3-temperature programmed desorption (NH3-TPD), X-ray powder diffraction (XRD), and field emission scanning electron microscopy (FESEM). The catalyst could be recycled and reused for several runs without any loss of inherent catalytic activity. PMID:23400041

  14. Mössbauer study of the effect of rare earth substitution into montmorillonite

    NASA Astrophysics Data System (ADS)

    Kuzmann, E.; Singh, L. H.; Garg, V. K.; de Oliveira, A. C.; Kovács, E. M.; Molnár, Á. M.; Homonnay, Z.; Kónya, P.; Nagy, N. M.; Kónya, J.

    2016-12-01

    Novel montmorillonites were prepared by the exchange of the interlayer cations with a series of rare earth cations (La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, and Er) and characterized by XRD, XRF, SEM, chemical analysis and 57Fe Mössbauer spectroscopy. An unexpected magnetically split component, assigned to iron being in the interlayer space, was observed in the Mössbauer spectra at 78K in some rare earth cation exchanged montmorillonite. This paper is the initial report about this observation. The transition of iron from the octahedral site to the interlayer and possible incorporation of rare earths in sites different from those which are in the interlayer space was concluded.

  15. Cation exchange capacities of safranin, toluidine and alizarin complexes with montmorillonite

    SciTech Connect

    Peinemann, N.; Helmy, A.K.

    1999-09-01

    To obtain information about the cation exchange capacity (CEC) of montmorillonite as affected by the sorption of charged organic molecules, montmorillonite samples were loaded with different amounts of positively charged molecules of safranin, toluidine blue, and negatively charged alizarin red S. Dye sorption by the clay was carried out by equilibrating samples with different concentrations of the dye. The adsorbed amounts were determined from initial and final dye concentrations using spectrophotometric methods. The CEC of the clay-organic complexes were determined by the BaCl{sub 2} base exchange capacity method. The CEC was found to decrease linearly with the increase in the amount of safranin and toluidine in the complex, giving rise to a 1:1 charge neutralization ratio. For alizarin the CEC increased linearly but was not in proportion to the amounts of alizarin in the complex. This noncumulative phenomenon was attributed to the hindering of free diffusion of exchanging cations by the adsorbed molecules.

  16. Preparation and properties of poly HTBN-based urethane-urea/organo reactive montmorillonite nanocomposites

    NASA Astrophysics Data System (ADS)

    Li, Zai-Feng; Wu, Yuan; Zhang, Fu-Tao; Cao, Yu-Yang; Wu, Shou-Peng; Wang, Ting

    2012-12-01

    With ultrasonic assistant mixing way, an intercalated mixture of polyol/organo reactive montmorillonite (ORMMT) was pretreated. The prepolymer composed MMT clay was prepared by reaction of polyol/ORMMT mixture with toluene diisocyanate (TDI). The resultant prepolymer reacted with extender (DMTDA) and then the polyurethane-urea/organo reactive montmorillonite (PUU/ORMMT) nanocomposites were obtained. The structure, morphology and properties of PUU/ORMMT nanocomposites were characterized by FT-IR, TEM, AFM, strain-stress machine, TGA, and dynamic mechanical analysis (DMA). The results showed that when the OMMT content is 3%, the PUU/ORMMT nanocomposities performed super mechanical properties. Because of the presence of ORMMT, both T g of the soft segment and tan δ of the PUU increased, and the decomposition temperature for the first step and the second step increased respectively. TEM images showed that the organophilic MMT particles in the PUU composite exhibit a high degree of intercalation and exfoliation.

  17. Synthesis and characterization of BiOI/montmorillonite composites with high visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Liu, Chao; Wang, Jizhong; Wang, Xiaojing; Li, Fatang; Zhang, Lei; Chen, Yue

    2015-12-01

    BiOI/montmorillonite composite photocatalysts are synthesized by a facile room temperature method using Bi(NO3)3, KI and montmorillonite (MMT) clay as precursors, and characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and nitrogen adsorption-desorption measurements. The facile synthesis method avoids high temperature treatment, and is based on cheap precursors. The prepared Bi-M-x composites possess a hierarchically nanoplates structure and are composed of BiOI and MMT phases. The degradation rate of the methylene blue reached up to about 95% after 45 min whereas that for the pure BiOI was only 75%. The high photocatalytic Bi-M-x composites would have a potential application in environmental purification owing to its low cost and easy synthesis.

  18. Radiolysis of aqueous solutions of acetic acid in the presence of Na-montmorillonite

    NASA Technical Reports Server (NTRS)

    Navarro-Gonzalez, R.; Negron-Mendoza, A.; Ramos, S.; Ponnamperuma, C.

    1990-01-01

    The gamma-irradiation of 0.8 mol dm-3 aqueous, oxygen-free acetic acid solutions was investigated in the presence or absence of Na-montmorillonite. H2, CH4, CO, CO2, and several polycarboxylic acids were formed in all systems. The primary characteristics observed in the latter system were: (1) Higher yield of the decomposition of acetic acid; (2) Lower yield of the formation of polycarboxylic acids; (3) No effect on the formation of methane; (4) Higher yield of the formation of carbon dioxide; and (5) The reduction of Fe3+ in the octahedral sites of Na-montmorillonite. A possible reaction scheme was proposed to account for the observed changes. The results are important in understanding heterogeneous processes in radiation catalysis and might be significant to prebiotic chemistry.

  19. Urea-montmorillonite-extruded nanocomposites: a novel slow-release material.

    PubMed

    Pereira, Elaine I; Minussi, Fernando B; da Cruz, Camila C T; Bernardi, Alberto C C; Ribeiro, Caue

    2012-05-30

    The present study describes the preparation and characterization of a novel urea slow-release nanocomposite, based on urea intercalation into montmorillonite clay by an extrusion process at room temperature. Nanocomposites with urea contents ranging from 50 to 80 wt % were successfully produced and characterized. Analyses by XRD, DTA, and SEM-EDX confirmed the effectiveness of this simple process to exfoliate the clay lamellae into the urea matrix, forming a product that can be classified as a nanocomposite, due to the exfoliation degree attained. Diametral compression tests showed that the samples were very deformable, and the release rate of active components in water showed that the nanocomposite showed a slow release behavior for urea dissolution, even in low montmorillonite amounts (20% in weight). PMID:22574809

  20. In Situ Molecular Spectroscopic Evidence for CO2 Intercalation into Montmorillonite in Supercritical Carbon Dioxide

    SciTech Connect

    Loring, John S.; Schaef, Herbert T.; Turcu, Romulus VF; Thompson, Christopher J.; Miller, Quin RS; Martin, Paul F.; Hu, Jian Z.; Hoyt, David W.; Qafoku, Odeta; Ilton, Eugene S.; Felmy, Andrew R.; Rosso, Kevin M.

    2012-04-25

    The interaction of anhydrous supercritical CO2 (scCO2) with both kaolinite and ~1W (i.e. close to but less than one layer of hydration) calcium-saturated montmorillonite was investigated under conditions relevant to geologic carbon sequestration (50 °C and 90 bar). The CO2 molecular environment was probed in situ using a combination of three novel high-pressure techniques: X-ray diffraction, magic angle spinning nuclear magnetic resonance spectroscopy and attenuated total reflection infrared spectroscopy. We report the first direct evidence that the expansion of montmorillonite under scCO2 conditions is due to CO2 migration into the interlayer. Intercalated CO2 molecules are rotationally constrained and do not appear to react with waters to form bicarbonate or carbonic acid. In contrast, CO2 does not intercalate into kaolinite. The findings show that predicting the seal integrity of caprock will have complex dependence on clay mineralogy and hydration state.

  1. Hexacyanoferrate(III) transport in coated montmorillonite clay films. Effects of water-soluble polymers

    SciTech Connect

    Sequaris, J.M.

    2000-02-08

    Hexacyanoferrate(III) Fe(CN){sub 6}{sup 3{minus}}, transport through coated montmorillonite clay films at a platinum electrode is studied with the cyclic voltammetric method. Experimental conditions are first established guaranteeing voltammetric detection based on a linear diffusion in the clay film. The square of the ratio (R{sup 2}) of current intensities obtained at the clay modified electrode (CME) and the bare Pt electrode measures the relative variation of the Fe(CN){sub 6}{sup 3{minus}}, diffusion coefficient in the clay film. Thus, the effects of bathing electrolyte concentrations on R{sup 2} are investigated and related to the swelling properties of the montmorillonite clay characterized by X-ray diffraction and sedimentation volume results.

  2. Preventive obesity agent montmorillonite adsorbs dietary lipids and enhances lipid excretion from the digestive tract.

    PubMed

    Xu, Pengfei; Dai, Shu; Wang, Jing; Zhang, Jun; Liu, Jin; Wang, Fang; Zhai, Yonggong

    2016-01-01

    Western diets are typically high in fat and are associated with long-term complications such as obesity and hepatic steatosis. Because of the enjoyable taste of high-fat diets (HFDs), we are interested in determining how to decrease lipid absorption and enhance lipid excretion from the digestive tract after the consumption of eating fatty foods. Montmorillonite was initially characterized as a gastrointestinal mucosal barrier protective agent for the treatment of diarrhoea. Dietary lipid adsorbent- montmorillonite (DLA-M) was isolated and purified from Xinjiang montmorillonite clay via the water extraction method. Here, we show that DLA-M has an unexpected role in preventing obesity, hyperlipidaemia and hepatic steatosis in HFD-fed rats. Interestingly, combined application of polarized light microscopy and lipid staining analyses, showed that DLA-M crystals have dietary lipid-adsorbing ability in vitro and in vivo, which enhances lipid excretion via bowel movements. In summary, our results indicate that DLA-M prevent HFD-induced obesity. This novel dietary lipid-adsorbing agent can help prevent obesity and its comorbidities. PMID:26891902

  3. Preventive obesity agent montmorillonite adsorbs dietary lipids and enhances lipid excretion from the digestive tract

    PubMed Central

    Xu, Pengfei; Dai, Shu; Wang, Jing; Zhang, Jun; Liu, Jin; Wang, Fang; Zhai, Yonggong

    2016-01-01

    Western diets are typically high in fat and are associated with long-term complications such as obesity and hepatic steatosis. Because of the enjoyable taste of high-fat diets (HFDs), we are interested in determining how to decrease lipid absorption and enhance lipid excretion from the digestive tract after the consumption of eating fatty foods. Montmorillonite was initially characterized as a gastrointestinal mucosal barrier protective agent for the treatment of diarrhoea. Dietary lipid adsorbent- montmorillonite (DLA-M) was isolated and purified from Xinjiang montmorillonite clay via the water extraction method. Here, we show that DLA-M has an unexpected role in preventing obesity, hyperlipidaemia and hepatic steatosis in HFD-fed rats. Interestingly, combined application of polarized light microscopy and lipid staining analyses, showed that DLA-M crystals have dietary lipid-adsorbing ability in vitro and in vivo, which enhances lipid excretion via bowel movements. In summary, our results indicate that DLA-M prevent HFD-induced obesity. This novel dietary lipid-adsorbing agent can help prevent obesity and its comorbidities. PMID:26891902

  4. Monte Carlo molecular simulation of the hydration of Na-montmorillonite at reservoir conditions.

    PubMed

    de Pablo, L; Chávez, M L; Sum, A K; de Pablo, J J

    2004-01-01

    The hydration of Na-saturated Wyoming-type montmorillonite is investigated by Monte Carlo simulations at constant stress in the NP(zz)T ensemble and at constant chemical potential in the microVT ensemble, at the sedimentary basin temperature of 353 K and pressure of 625 bar, equivalent to 2-4 km depth. The simulations use procedures established in Chavez-Paez et al. [J. Chem. Phys. 114, 1405 (2001)]. At these conditions, simulations predict a single stable form of 1,2-water layer Na-montmorillonite, containing 164.38 mg/g or 53.37 molecules/layer of adsorbed water and having a spacing of 12.72 A. The corresponding density is 0.32 g/ml. Sodium ions are coordinated with six molecules of water separated 2.30-2.33 A. Water molecules are closer to the central interlayer plane and the spacing is larger than that at 300 K and 1 bar. The interlayer configuration consists of two symmetrical layers of oriented water molecules 1.038 A from the central plane, with the hydrogen atoms in two outermost layers, 3.826 A apart, and the sodium ions on the central plane located between the water layers. The interlayer configuration can be considered to be a stable two-layer intermediate between the one- and two-layer hydrates. Our simulations do not predict formation of other hydrates of Na-montmorillonite at 353 K and 615 bar. PMID:15267930

  5. Sulfentrazone adsorbed on micelle-montmorillonite complexes for slow release in soil.

    PubMed

    Polubesova, Tamara; Nir, Shlomo; Rabinovitz, Onn; Borisover, Mikhail; Rubin, Baruch

    2003-05-21

    Interactions of the herbicide sulfentrazone with the cationic surfactants octadecyltrimethylammonium (ODTMA), hexadecyltrimethylammonium (HDTMA), and benzyldimethylhexadecylammonium (BDMHDA) have been studied for the design of slow-release formulations based on sulfentrazone adsorbed on a micelle-montmorillonite complex. Adsorbed amounts of sulfentrazone on ODTMA- and BDMHDA-montmorillonite complexes were 99.2-99.8% of that added, and desorption of herbicide in water during 24 h was low. After 10 washings in funnels with soil, only 2.6% of herbicide was released from ODTMA-montmorillonite formulations versus 100% release from the commercial formulation. The strong binding of sulfentrazone to micelles was confirmed by pH and spectroscopic measurements and was explained by the formation of ionic pairs between cationic surfactant and anionic herbicide. The ODTMA-clay and commercial formulations of sulfentrazone yield almost complete and 40% growth inhibition of green foxtail, respectively, at 700 g of active ingredient/ha. Hence, the slow release from micelle-clay formulations of sulfentrazone promotes its biological activity and reduces environmental contamination. PMID:12744675

  6. The gap between crystalline and osmotic swelling of Na-montmorillonite: a Monte Carlo study.

    PubMed

    Meleshyn, Artur; Bunnenberg, Claus

    2005-01-15

    Although the swelling of clay during moistening is a broadly experienced occurrence, the mechanisms driving it and especially the reason for the existence of a peculiar gap between crystalline and osmotic swelling of Na-montmorillonite are not yet fully understood. We obtained a deeper insight by means of Monte Carlo simulations of Na-montmorillonite swelling, which yield the swelling curve, interaction energies between and characteristic positions of structural atoms and water molecules. We find that a chainlike structure consisting of Na cations, water molecules, and oxygens of substituted tetrahedrons of neighboring mineral layers is formed in the interlayer space of Na-montmorillonite at a layer spacing of approximately 19 A, where experimental investigations show termination of crystalline swelling. Such a persistent structure may lock the interlayer space, until excess water is able to break this chain by osmotic forces. We suggest that its formation is the reason for the existence of a gap in layer spacings between approximately 19 and approximately 40 A, which have been named "forbidden" layer spacings in experimental studies. PMID:15740215

  7. Enhanced Photoreduction of Nitro-aromatic Compounds by Hydrated Electrons Derived from Indole on Natural Montmorillonite.

    PubMed

    Tian, Haoting; Guo, Yong; Pan, Bo; Gu, Cheng; Li, Hui; Boyd, Stephen A

    2015-07-01

    A new photoreduction pathway for nitro-aromatic compounds (NACs) and the underlying degradation mechanism are described. 1,3-Dinitrobenzene was reduced to 3-nitroaniline by the widely distributed aromatic molecule indole; the reaction is facilitated by montmorillonite clay mineral under both simulated and natural sunlight irradiation. The novel chemical reaction is strongly affected by the type of exchangeable cation present on montmorillonite. The photoreduction reaction is initiated by the adsorption of 1,3-dinitrobenzene and indole in clay interlayers. Under light irradiation, the excited indole molecule generates a hydrated electron and the indole radical cation. The structural negative charge of montmorillonite plausibly stabilizes the radical cation hence preventing charge recombination. This promotes the release of reactive hydrated electrons for further reductive reactions. Similar results were observed for the photoreduction of nitrobenzene. In situ irradiation time-resolved electron paramagnetic resonance and Fourier transform infrared spectroscopies provided direct evidence for the generation of hydrated electrons and the indole radical cations, which supported the proposed degradation mechanism. In the photoreduction process, the role of clay mineral is to both enhance the generation of hydrated electrons and to provide a constrained reaction environment in the galley regions, which increases the probability of contact between NACs and hydrated electrons. PMID:26029791

  8. The structure of montmorillonites modified with zwitterionic surfactants and their sorption ability

    NASA Astrophysics Data System (ADS)

    Zhu, Jianxi; Qing, Yanhong; Ma, Lingya; Zhu, Runliang; He, Hongping

    2015-06-01

    In this work, a novel organo-clays, zwitterionic surfactant modified montmorillonites (ZSMMs) were synthesized by using sulphobetaine and montmorillonites. The structures of ZSMMs were characterized by X ray diffraction (XRD) methods; the surfactant loading levels were measured by Total organic carbon (TOC) analysis, and their sorptive characteristics toward p-nitrophenol and nitrobenzene were investigated. XRD and TOC measurements indicated that the amount of adsorbed surfactants and the basal spacing of the ZSMMs increase with alkyl chain length and surfactant concentration. Sorption experiments showed that the capacity of p-nitrophenol to sorb onto the ZSMMs is higher than that of nitrobenzene. Both capacities increase with surfactant loading level; However, sorption capacity decreases when the surfactant concentration is higher than 2.0 CEC. Under the same surfactant loading level, the sorption capacities of p-nitrophenol and nitrobenzene increase with alkyl chain length. Under this experimental condition, the longer alkyl chain leads to a higher sorption capacity for hydrophobic organic compounds. On the basis of the ability of p-nitrophenol and nitrobenzene to sorb onto the montmorillonites, we conclude that the contaminant sorption coefficients, normalized with organic carbon content, highly depend on surfactant loading levels.

  9. Characterization of chitosan/montmorillonite membranes as adsorbents for Bezactiv Orange V-3R dye.

    PubMed

    Nesic, Aleksandra R; Velickovic, Sava J; Antonovic, Dusan G

    2012-03-30

    The synthesis, characterization and environmental application of chitosan/montmorillonite membrane for adsorption Bezactiv Orange V-3R were investigated. Chitosan/montmorillonite membranes were synthesized in different ratios, containing 10-50% of montmorillonite (MMT) in membrane. These membranes were characterized by using Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG) and scanning electron microscopy (SEM). The adsorption kinetics were investigated using three different concentrations of Bezactiv Orange dye (30, 50 and 80 mg/L). The adsorption capacity increases with increasing amount of MMT in membranes. These membranes show the highest adsorption capacity when the initial dye concentration was 80 mg/L. The results show that the optimum condition for adsorption of Bezactiv Orange is pH 6. A comparison of kinetic models was evaluated for the pseudo-first and pseudo-second order and intra-particle diffusion. The experimental data were fitted to the pseudo-second order kinetic model, and also followed by intra-particle diffusion. Intra-particle diffusion is not the only rate-controlling step. The Langmuir and Freundlich adsorption isotherms were applied to experimental equilibrium data at different concentration of dye solution. The results indicated the competency of chitosan/MMT membranes adsorbent for Bezactiv Orange adsorption. PMID:22305598

  10. Synthesis and characterization of montmorillonite clay intercalated with molecular magnetic compounds

    SciTech Connect

    Martins, Marcel G.; Martins, Daniel O.T.A.; Carvalho, Beatriz L.C. de; Mercante, Luiza A.; Soriano, Stéphane; Andruh, Marius; Vieira, Méri D.; Vaz, Maria G.F.

    2015-08-15

    In this work montmorillonite (MMT) clay, whose matrix was modified with an ammonium salt (hexadecyltrimethylammonium bromide – CTAB), was employed as an inorganic host for the intercalation of three different molecular magnetic compounds through ion exchange: a nitronyl nitroxide derivative 2-[4-(N-ethyl)-pyridinium]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (p-EtRad{sup +}) and two binuclear coordination compounds, [Ni(valpn)Ln]{sup 3+}, where H{sub 2}valpn stands for 1,3-propanediyl-bis(2-iminomethylene-6-methoxy-phenol), and Ln=Gd{sup III}; Dy{sup III}. The pristine MMT and the intercalated materials were characterized by X-ray powder diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and magnetic measurements. The X-ray diffraction data analysis showed an increase of the interlamellar space of the intercalated MMT, indicating the intercalation of the magnetic compounds. Furthermore, the magnetic properties of the hybrid compounds were investigated, showing similar behavior as the pure magnetic guest species. - Graphical abstract: Montmorillonite clay was employed as inorganic host for the intercalation of three different molecular magnetic compounds through ion exchange - Highlights: • Montmorillonite was employed as a host material. • Three molecular magnetic compounds were intercalated through ion exchange. • The compounds were successful intercalated maintaining the layered structure. • The hybrid materials exhibited similar magnetic behavior as the pure magnetic guest.

  11. Remediation of arsenic-contaminated groundwater using media-injected permeable reactive barriers with a modified montmorillonite: sand tank studies.

    PubMed

    Luo, Ximing; Liu, Haifei; Huang, Guoxin; Li, Ye; Zhao, Yan; Li, Xu

    2016-01-01

    A modified montmorillonite (MMT) was prepared using an acid activation-sodium activation-iron oxide coating method to improve the adsorption capacities of natural MMTs. For MMT, its interlamellar distance increased from 12.29 to 13.36 Å, and goethite (α-FeOOH) was intercalated into its clay layers. Two novel media-injected permeable reactive barrier (MI-PRB) configurations were proposed for removing arsenic from groundwater. Sand tank experiments were conducted to investigate the performance of the two MI-PRBs: Tank A was filled with quartz sand. Tank B was packed with quartz sand and zero-valent iron (ZVI) in series, and the MMT slurry was respectively injected into them to form reactive zones. The results showed that for tank A, total arsenic (TA) removal of 98.57 % was attained within the first 60 mm and subsequently descended slowly to 88.84 % at the outlet. For tank B, a similar spatial variation trend was observed in the quartz sand layer, and subsequently, TA removal increased to ≥99.80 % in the ZVI layer. TA removal by MMT mainly depended on both surface adsorption and electrostatic adhesion. TA removal by ZVI mainly relied on coagulation/precipitation and adsorption during the iron corrosion. The two MI-PRBs are feasible alternatives for in situ remediation of groundwater with elevated As levels. PMID:26347414

  12. Spectral properties of mixtures of montmorillonite and dark grains - Implications for remote sensing minerals containing chemically and physically adsorbed water

    NASA Technical Reports Server (NTRS)

    Clark, R. N.

    1983-01-01

    The spectral properties from 0.4 to 3 microns of montmorillonite plus dark carbon grains (called opaques) of various sizes are studied as a function of the weight fraction of opaques present. The reflectance level and band depths of the 1.4-, 1.9-, 2.2-, and 2.8-micron water and/or OH absorption features are analyzed using derived empirical relationships and scattering theory. It is found that the absorption band depths and reflectance level are a very nonlinear function of the weight fraction of opaques present but can be predicted in many cases by simple scattering theory. The 2.8-micron bound water fundamental band is the most difficult absorption feature to suppress. The overtone absorptions are suppressed a greater amount than the fundamental but are still apparent even when 10-20 wt pct opaques are present. The relationships observed and the simple scattering theory presented show that quantitative compositional remote sensing studies are feasible for surfaces containing complex mineral mixtures.

  13. Montmorillonite-alginate nanocomposite as a drug delivery system--incorporation and in vitro release of irinotecan.

    PubMed

    Iliescu, Ruxandra Irina; Andronescu, Ecaterina; Ghitulica, Cristina Daniela; Voicu, Georgeta; Ficai, Anton; Hoteteu, Mihai

    2014-03-25

    The scope of the present study was the preparation and characterization of irinotecan nanocomposite beads based on montmorillonite (Mt) and sodium alginate (AL) as drug carriers. After irinotecan (I) incorporation into Mt, the resulting hybrid was compounded with alginate, and I-Mt-AL nanocomposite beads were obtained by ionotropic gelation technique. The structure and surface morphology of the hybrid and composite materials were established by means of X-ray diffraction (XRD), IR spectroscopy (FT-IR), thermal analysis (TG-DTA) and scanning electron microscopy (SEM). Irinotecan incorporation efficiency in Mt and in alginate beads was determined both by UV-vis spectroscopy and thermal analysis and was found to be high. The hybrid and composite materials were tested in vitro in simulated intestinal fluid (pH 7.4, at 37 °C) in order to establish if upon administering the beads at the site of a resected colorectal tumor, the delivery of the drug is sustained and can represent an alternative to the existing systemic chemotherapy. The in vitro drug release test results clearly suggested that Mt, and Mt along with AL were able to control the release of irinotecan by making it sustained, without any burst effect, and by reducing the released amount and the release rate. The nanocomposite beads may be a promising drug delivery system in chemotherapy. PMID:23998956

  14. Preparation, characterization and in vitro biological study of biomimetic three-dimensional gelatin-montmorillonite/cellulose scaffold for tissue engineering.

    PubMed

    Haroun, Ahmed A; Gamal-Eldeen, Amira; Harding, David R K

    2009-12-01

    This work focused on studying the effect of blending gelatin (Gel) with Cellulose (Cel), in the presence of montmorillonite (MMT), on the swelling behavior, in vitro degradation and surface morphology. Additionally, the effect of the prepared biocomposites on the characteristics of the human osteosarcoma cells (Saos-2), including proliferation, scaffold/cells interactions, apoptosis and their potential of the cells to induce osteogenesis and differentiation was evaluated. The crosslinked biocomposites with glutaraldehyde (GA) or N,N-methylene-bisacrylamide (MBA) was prepared via an intercalation process and freeze-drying technique. Properties including SEM morphology, X-ray diffraction characterization and in vitro biodegradation were investigated. The successful generation of 3-D biomimetic porous scaffolds incorporating Saos-2 cells indicated their potential for de novo bone formation that exploits cell-matrix interactions. In vitro studies revealed that the scaffolds containing 12 and 6% MMT crosslinked by 5 and 0.5% GA seem to be the two most efficient and effective biodegradable scaffolds, which promoted Saos-2 cells proliferation, migration, expansion, adhesion, penetration, spreading, and differentiation, respectively. MMT improved cytocompatibility between the osteoblasts and the biocomposite. In vitro analysis indicated good biocompatibility of the scaffold and presents the scaffold as a new potential candidate as suitable biohybrid material for tissue engineering. PMID:19629650

  15. Preparation, characterization and properties of amino-functionalized montmorillonite and composite layer-by-layer assembly with inorganic nanosheets

    NASA Astrophysics Data System (ADS)

    Huang, Guo-bo; Ge, Chang-hua; He, Bing-jing

    2011-06-01

    An amino-functionalized montmorillonite (APTMS-MMT) was prepared by the grafting of 3-aminopropyltrimethoxysilane (APTMS) on the surface of MMT via the ultrasonic synthesis process and characterized by a variety of techniques: FT-IR, thermogravimetic analysis (TGA), particles size analysis and ζ-potential measurement. The results showed the size and size distribution of APTMS-MMT particles were decreased, and the ζ-potential of particles was increased obviously via the ultrasonic synthesis process. The particles of 30% APTMS-MMT US (MMT modified with 30 wt% APTMS with ultrasonic synthesis process) had a z-average diameter of about 500 nm and a polydispersity index of 0.2. The resultant 30% APTMS-MMT US was dispersed uniformly and stably in water. The poly(acrylic acid) (PAA)/APTMS-MMT multilayer films were grown through layer-by-layer (LBL) deposition of PAA and APTMS-MMT. SEM results indicated that the ultrasonic synthesis of APTMS-MMT increased dispersability of clay sheets at high loadings. The thermal stability and mechanical properties of PAA/APTMS-MMT composites were investigated by TGA and tensile test respectively. The results showed the ultrasonic synthesis of APTMS-MMT enhanced the thermal stability and mechanical properties of PAA/APTMS-MMT composites significantly. PAA/30% APTMS-MMT US composite displayed 3 times higher strength and 6 times higher Young's modulus when compared with pure PAA polymer.

  16. Modulation of cytochrome P450 and induction of DNA damage in Cyprinus carpio exposed in situ to surface water treated with chlorine or alternative disinfectants in different seasons.

    PubMed

    Canistro, Donatella; Melega, Simone; Ranieri, Dario; Sapone, Andrea; Gustavino, Bianca; Monfrinotti, Monica; Rizzoni, Marco; Paolini, Moreno

    2012-01-01

    Epidemiological studies have shown an association between consumption of disinfected drinking water and adverse health outcomes. The chemicals used to disinfect water react with occurring organic matter and anthropogenic contaminants in the source water, resulting in the formation of disinfection by-products (DBPs). The observations that some DBPs are carcinogenic in animal models have raised public concern over the possible adverse health effects for humans. Here, the modulation of liver cytochrome P450-linked monooxygenases (MFO) and the genotoxic effects in erythrocytes of Cyprinus carpio fish exposed in situ to surface drinking water in the presence of disinfectants, such as sodium hypochlorite (NaClO), chlorine dioxide (ClO(2)) and peracetic acid (PAA), were investigated in winter and summer. A complex induction/suppression pattern of CYP-associated MFOs in winter was observed for all disinfectants. For example, a 3.4- to 15-fold increase was recorded of the CYP2B1/2-linked dealkylation of penthoxyresorufin with NaClO (10 days) and PAA (20 days). In contrast, ClO(2) generated the most notable inactivation, the CYP2E1-supported hydroxylation of p-nitrophenol being decreased up to 71% after 10 days' treatment. In summer, the degree of modulation was modest, with the exception of CYP3A1/2 and CYP1A1 supported MFOs (62% loss after 20 days PAA). The micronucleus (MN) induction in fish circulating erythrocytes was also analysed as an endpoint of genotoxic potential in the same fish population. Significant increases of MN induction were detected at the latest sampling time on fish exposed to surface water treated with chlorinate-disinfectants, both in winter (NaClO) and summer (NaClO and ClO(2)), while no effect was observed in fish exposed to PAA-treated water. These results show that water disinfection may be responsible for harmful outcomes in terms of MFO perturbation and DNA damage; if extrapolated to humans, they ultimately offer a possible rationale for the increased urinary cancer risk recorded in regular drinking water consumers. PMID:22001235

  17. Epoxy-based nanocomposites for electrical energy storage. II: Nanocomposites with nanofillers of reactive montmorillonite covalently-bonded with barium titanate

    NASA Astrophysics Data System (ADS)

    Polizos, G.; Tomer, V.; Manias, E.; Randall, C. A.

    2010-10-01

    Barium titanate (BT) and montmorillonite (MMT) nanoparticles were covalently-bonded by organically modifying the particle surfaces and chemically reacting them in solution. These integrated two-material hybrid inorganic nanofillers were subsequently dispersed in epoxy resin and nanocomposites were obtained at several weight fractions. The inorganic component consisted of well dispersed BT spherical nanoparticles that are surrounded by attached layered MMT nanoplatelets, with the latter having the ability to react with the epoxy matrix. The thermodynamic properties of the glass transition process, the macroscopic mechanical properties of the nanocomposites, and the dynamics of the polymer segments at the inorganic interfaces, all indicate that this filler configuration enhances the polymer-ceramic interfaces. Polarization as a function of electric field and dielectric breakdown show improvements in the electrical properties of these composites, compared to the corresponding unfilled epoxy, despite the expected reduction in crosslinking density. The resulting nanocomposites have a property set which can be utilized in energy storage and power system applications.

  18. Ultra-violet protection and water repellency of polyester fabrics treated by surface deposition of nickel under the effect of low temperature plasma

    NASA Astrophysics Data System (ADS)

    Kan, C. W.; Yuen, C. W. M.

    2007-12-01

    This paper is aimed at understanding the textile properties of nickel-deposited polyester fabric after treating with low temperature plasma treatment. Low temperature plasma treatment with oxygen gas was employed in this paper to activate a hydrophilic surface for the polyester fabrics and hence facilitate the nickel deposition through an electroless plating process. The textile properties of plasma-induced electroless nickel-plated polyester fabrics were evaluated by different standard testing methods in terms of both physical and chemical performances. The electroless nickel plating with plasma treatment improved significantly the performance of nickel-plated polyester fabrics as reflected by the scanning electron microscopy, tensile strength, ultraviolet protection as well as fabric weight. On the contrary, it also enhanced the fabric thickness and colour fastness to crocking. In addition, there was no influence on the performance of colour fastness to light and colourfastness to laundering. Moreover, the application of plasma treatment adversely affected slightly the performance of contact angle and wrinkle recovery property.

  19. Mercury, monomethyl mercury, and dissolved organic carbon concentrations in surface water entering and exiting constructed wetlands treated with metal-based coagulants, Twitchell Island, California

    USGS Publications Warehouse

    Stumpner, Elizabeth B.; Kraus, Tamara E.C.; Fleck, Jacob A.; Hansen, Angela M.; Bachand, Sandra M.; Horwath, William R.; DeWild, John F.; Krabbenhoft, David P.; Bachand, Philip A.M.

    2015-01-01

    Following coagulation, but prior to passage through the wetland cells, coagulation treatments transferred dissolved mercury and carbon to the particulate fraction relative to untreated source water: at the wetland cell inlets, the coagulation treatments decreased concentrations of filtered total mercury by 59–76 percent, filtered monomethyl mercury by 40–70 percent, and dissolved organic carbon by 65–86 percent. Passage through the wetland cells decreased the particulate fraction of mercury in wetland cells that received coagulant-treated water. Changes in total mercury, monomethyl mercury, and dissolved organic carbon concentrations resulting from wetland passage varied both by treatment and season. Despite increased monomethyl mercury in the filtered fraction during wetland passage between March and August, the coagulation-wetland systems generally decreased total mercury (filtered plus particulate) and monomethyl mercury (filtered plus particulate) concentrations relative to source water. Coagulation—either alone or in association with constructed wetlands—could be an effective way to decrease concentrations of mercury and dissolved organic carbon in surface water as well as the bioavailability of mercury in the Sacramento–San Joaquin Delta.

  20. Investigation of nano-size montmorillonite on electron beam irradiated flame retardant polyethylene and ethylene vinyl acetate blends

    NASA Astrophysics Data System (ADS)

    Bee, Soo-Tueen; Hassan, A.; Ratnam, C. T.; Tee, Tiam-Ting; Sin, Lee Tin

    2013-03-01

    This study aims at investigating the effects of montmorillonite (MMT) and electron beam irradiation on alumina trihydrate (ATH) added low density polyethylene and ethylene vinyl acetate (LDPE-EVA) blends. The nano-size MMT was used to improve the flammability and mechanical properties of the ATH added LDPE-EVA blends. The samples were irradiated at the dosage range 0-250 kGy using electron beam accelerator. The limiting oxygen index test (LOI) revealed that the incorporation of MMT into ATH added LDPE-EVA blends could improve the flammability up to 28.4 LOI%. The application of irradiation effect also improved the flame retardancy of the blends for ˜2 LOI% compared to un-irradiated samples. The addition of MMT loading levels from 10 to 20 phr exhibited reinforcing effect for 10.3-14.6% in tensile strength. On the other hand, the increasing of MMT loading levels has gradually decreased the surface and volume resistance of ATH added LDPE-EVA blends. The increase in irradiation dosages from 0 to 150 kGy was found to slightly decrease the surface and volume resistivity of the ATH added LDPE-EVA samples especially at high loading of MMT. The enhancement of mobility of MMT ionic in polymer matrix could lead to the reduction of the surface and volume resistivity. Consequently, this study has demonstrated that addition of MMT and electron beam irradiation to ATH added LDPE-EVA blends have resulted better flammability, mechanical and electrical properties of ATH added LDPE-EVA blends.

  1. Plasmon-assisted degradation of methylene blue with Ag/AgCl/montmorillonite nanocomposite under visible light.

    PubMed

    Sohrabnezhad, Sh; Zanjanchi, M A; Razavi, M

    2014-09-15

    Metal-semiconductor compounds, such as Ag/AgX (X=Cl, Br, I), enable visible light absorption and separation of photogenerated electron-hole through surface plasmon resonance (SPR) effect. However, the electron-hole generated and separated by light are vulnerable in Ag/AgX phase because of the occurrence of secondary recombined. In order to more effectively utilize the SPR photocatalytic effect, nanoparticles are located in a matrix. In this article, Ag/AgCl nanoparticles were synthesized in montmorillonite (MMT) matrix using dispersion method and light irradiation. The structure, composition and optical properties of such material were investigated by transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), X-ray diffraction (XRD) and FTIR. Powder X-ray diffraction showed intercalation of Ag/AgCl nanoparticles into the clay layers. The as-prepared plasmonic photocatalyst exhibited an enhanced and stable photoactivity for the degradation of methylene blue (MB) under visible light. The high activity was attributed to the surface plasmon resonance (SPR) exhibited by Ag nanoparticles on the surface of AgCl. The detection of reactive species by radical scavengers displays that O2- and OH- are the main reactive species for the degradation of MB under visible light irradiation. The studies showed that 20 min illumination under visible light can complete degradation of methylene blue (MB), and indicate a high stability of photocatalytic degradation. The mechanism of separation of the photo-generated electrons and holes at the Ag/AgCl-MMT nanocomposite was discussed. PMID:24769384

  2. Plasmon-assisted degradation of methylene blue with Ag/AgCl/montmorillonite nanocomposite under visible light

    NASA Astrophysics Data System (ADS)

    Sohrabnezhad, Sh.; Zanjanchi, M. A.; Razavi, M.

    2014-09-01

    Metal-semiconductor compounds, such as Ag/AgX (X = Cl, Br, I), enable visible light absorption and separation of photogenerated electron-hole through surface plasmon resonance (SPR) effect. However, the electron-hole generated and separated by light are vulnerable in Ag/AgX phase because of the occurrence of secondary recombined. In order to more effectively utilize the SPR photocatalytic effect, nanoparticles are located in a matrix. In this article, Ag/AgCl nanoparticles were synthesized in montmorillonite (MMT) matrix using dispersion method and light irradiation. The structure, composition and optical properties of such material were investigated by transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), X-ray diffraction (XRD) and FTIR. Powder X-ray diffraction showed intercalation of Ag/AgCl nanoparticles into the clay layers. The as-prepared plasmonic photocatalyst exhibited an enhanced and stable photoactivity for the degradation of methylene blue (MB) under visible light. The high activity was attributed to the surface plasmon resonance (SPR) exhibited by Ag nanoparticles on the surface of AgCl. The detection of reactive species by radical scavengers displays that rad O2- and rad OH- are the main reactive species for the degradation of MB under visible light irradiation. The studies showed that 20 min illumination under visible light can complete degradation of methylene blue (MB), and indicate a high stability of photocatalytic degradation. The mechanism of separation of the photo-generated electrons and holes at the Ag/AgCl-MMT nanocomposite was discussed.

  3. Adsorption of adenine, cytosine, thymine, and uracil on sulfide-modified montmorillonite: FT-IR, Mössbauer and EPR spectroscopy and X-ray diffractometry studies.

    PubMed

    Carneiro, Cristine E A; Berndt, Graciele; de Souza Junior, Ivan G; de Souza, Cláudio M D; Paesano, Andrea; da Costa, Antonio C S; di Mauro, Eduardo; de Santana, Henrique; Zaia, Cássia T B V; Zaia, Dimas A M

    2011-10-01

    In the present work the interactions of nucleic acid bases with and adsorption on clays were studied at two pHs (2.00, 7.00) using different techniques. As shown by Mössbauer and EPR spectroscopies and X-ray diffractometry, the most important finding of this work is that nucleic acid bases penetrate into the interlayer of the clays and oxidize Fe(2+) to Fe(3+), thus, this interaction cannot be regarded as a simple physical adsorption. For the two pHs the order of the adsorption of nucleic acid bases on the clays was: adenine ≈ cytosine > thymine > uracil. The adsorption of adenine and cytosine on clays increased with decreasing of the pH. For unaltered montmorillonite this result could be explained by electrostatic forces between adenine/cytosine positively charged and clay negatively charged. However for montmorillonite modified with Na(2)S, probably van der Waals forces also play an important role since both adenine/cytosine and clay were positively charged. FT-IR spectra showed that the interaction between nucleic acid bases and clays was through NH(+) or NH (2) (+) groups. X-ray diffractograms showed that nucleic acid bases adsorbed on clays were distributed into the interlayer surface, edge sites and external surface functional groups (aluminol, silanol) EPR spectra showed that the intensity of the line g ≈ 2 increased probably because the oxidation of Fe(2+) to Fe(3+) by nucleic acid bases and intensity of the line g = 4.1 increased due to the interaction of Fe(3+) with nucleic acid bases. Mössbauer spectra showed a large decreased on the Fe(2+) doublet area of the clays due to the reaction of nucleic acid bases with Fe(2+). PMID:21717172

  4. Competitive sorption of Cd2+ and Pb2+ from a binary aqueous solution by poly (methyl methacrylate)-grafted montmorillonite clay nanocomposite

    NASA Astrophysics Data System (ADS)

    Bunhu, Tavengwa; Tichagwa, Lilian; Chaukura, Nhamo

    2016-03-01

    Poly(methyl methacrylate)-grafted montmorillonite (PMMAgMMT) clay and sodium-exchanged montmorillonite (NaMMT) clay were prepared through in situ graft polymerisation and used to remove Cd2+ and Pb2+ from synthetic wastewater. The modification of adsorbent materials was confirmed by fourier transform infra-red spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray powder diffraction (XRD) techniques. BET surface area measurements showed NaMMT had a higher surface area than PMMAgMMT. Batch experiments were used to assess the simultaneous uptake of Cd2+ and Pb2+ from a synthetic binary solution. Pb2+ was preferentially sorbed, exhibiting greater affinity for the sorbents compared to Cd2+ as shown by its relatively higher uptake onto the sorbents than Cd2+. The maximum sorption capacities for NaMMT and PMMAgMMT were 18.73 and 19.27 mg/g for Cd2+, and 30.03 and 34.25 mg/g for Pb2+, respectively. The sorption data obeyed the Langmuir model and the pseudo-second order kinetic model with R 2 of at least 0.9800 for both models. The sorbents could also be regenerated up to three cycles without a significant loss in the sorption capacity. FTIR measurements showed the presence of metal-oxygen bonds after sorption, confirming the occurrence of adsorption as one of the heavy metal removal processes. The work demonstrated the potential of using low-cost nanoscale composite material for the removal of Cd2+ and Pb2+ from aqueous solution.

  5. Effects of monovalent, exchangeable cations and electrolytes on the relation between swelling pressure and interlayer distance in montmorillonite

    SciTech Connect

    Zhang, F.; Low, P.F.; Roth, C.B.

    1995-07-01

    An oriented gel of homoionic montmorillonite was supported on a porous filter in a metal environmental chamber fitted with beryllium windows for the transmission of X-rays. Beneath the filter was a shallow reservoir connected to the outside atmosphere. Solution was expressed from the gel into the reservoir by admitting nitrogen gas to the environmental chamber at successively higher pressures. At each pressure the expressed solution in the reservoir was allowed to equilibrate through the filter with the gel and then the distance between the superimposed layers of montmorillonite in the gel was measured by X-ray diffraction. The swelling pressure of the montmorillonite equals the applied pressure at equilibrium. Thus, the relation between the swelling pressure and interlayer distance of the montmorillonite was determined when it was saturated with different exchangeable cations and equilibrated with electrolyte solutions of different concentration. The experimental results showed that, at relatively low concentrations of electrolyte, neither the species of exchangeable cation nor the electrolyte concentration had any effect on the relation between the swelling pressure and the interlayer distance. However, at relatively high concentrations of electrolyte, both of these factors affected this relation. Since the effect of the electrolyte concentration was not described quantitatively by electric double-layer theory, it was assumed that this theory was not applicable and that the added electrolyte reduced swelling by disrupting the hydration shells surrounding the montmorillonite particles.

  6. Investigation of the different binding edge sites for Zn on montmorillonite using P-EXAFS - The strong/weak site concept in the 2SPNE SC/CE sorption model

    NASA Astrophysics Data System (ADS)

    Dähn, Rainer; Baeyens, Bart; Bradbury, Michael H.

    2011-09-01

    The 2 site protolysis non electrostatic surface complexation and cation exchange (2SPNE SC/CE) sorption model has been used over the past decade or so to quantitatively describe the uptake of metals with oxidation states from II to VI on 2:1 clay minerals; montmorillonite and illite. One of the main features in this model is that there are two broad categories of amphoteric edge sorption sites; the so called strong ( tbnd S SOH) and weak ( tbnd S W1OH) sites. Because of their different sorption characteristics, it was expected that the coordination environments of the surface complexes on the two site types would be different. Zn isotherm data on two montmorillonites, Milos and STx-1, were measured and modelled using the 2SPNE SC/CE sorption model. The results were used to define the most favourable experimental conditions under which Zn sorption was either dominated by the strong ( tbnd S SOH, ˜2 mmol kg -1) or by the weak sites ( tbnd S W1OH, ˜40 mmol kg -1). Highly oriented self-supporting films were prepared for polarised extended X-ray absorption fine structure (P-EXAFS) investigations. Montmorillonites often contain Zn incorporated in the clay matrix. The Zn bound in this form was quantified and the results from the analysis of the P-EXAFS spectra were taken into account in the interpretation of the spectra measured at low Zn loadings (˜2 mmol kg -1) and medium Zn loadings (˜30 mmol kg -1). The Zn spectra on the "strong sites" exhibited a pronounced angular dependency and formed surface complexes in the continuity of the Al-octahedral sheets at the montmorillonite edges. In contrast, the Zn "weak site" spectra showed only a weak angular dependency. The spectroscopic evidence indicates the existence of two distinct groups of edge surface binding sites which is consistent with a multi-site sorption model and in particular with the strong/weak site concept intrinsic to the 2SPNE S/CE sorption model.

  7. Treating Meningitis

    MedlinePlus

    ... ways to treat bacterial meningitis. 1 They compared steroids (dexamethasone) with pla- cebo. The doctors gave medication ( ... compared anti- biotics by themselves with antibiotics plus steroids. Dr. Fritz and colleagues compared the mortality (deaths) ...

  8. Optimization of thermophysical properties of Pacific white shrimp (Litopenaeus vannamei) previously treated with freezing-point regulators using response surface methodology.

    PubMed

    Wang, Liang; Liu, Zunying; Zhao, Yuanhui; Dong, Shiyuan; Zeng, Mingyong; Yang, Huicheng

    2015-08-01

    Three freezing-point regulators (glycine, sodium chloride and D-sorbitol) were employed to optimize thermophysical properties of Pacific white shrimp (Litopenaeus vannamei) using response surface methodology (RSM). The independent variables were glycine content (0.250-1.250 %), sodium chloride content (0.500-2.500 %) and D-sorbitol content (0.125-0.625 %) and analysis of variance showed that the effects of glycine, sodium chloride and D-sorbitol on the thermophysical properties were statistically significant (P < 0.05). The coefficient of determination, R (2) values for initial freezing point (T i ), unfreezable water mass fraction (W u ), apparent specific heat (C app ) and Enthalpy (H) were 0.896 ~ 0.999. The combined effects of these independent variables on T i , W u , C app and H were investigated. The results indicated that T i , C app and H varied curvilinearly with increasing of glycine, sodium chloride and D-sorbitol content whereas W u increased nearly linearly. Based on response plots and desirability functions, the optimum combination of process variables for Pacific white shrimp previously treated with freezing-point regulators were 0.876 % for glycine content, 2.298 % for sodium chloride content and 0.589 % for D-sorbitol content, correspondently the optimized thermophysical properties were T i , - 5.086 °C; W u , 17.222 %; C app , 41.038 J/g °C and H, 155.942 J/g, respectively. Briefly, the application of freezing-point regulators depressed T i and obtained the optimum W u , C app and H, which would be obviously beneficial for the exploitation of various thermal processing and food storage. PMID:26243904

  9. Five-year retrospective radiographic follow-up study of dental implants with sandblasting with large grit, and acid etching-treated surfaces

    PubMed Central

    2015-01-01

    Objectives The purpose of this study is to evaluate five-year radiographic follow-up results of the Korean sandblasting with large grit, and acid etching (SLA)-treated implant system. Materials and Methods The subjects of the study are 54 patients who have been followed-up to date, of the patients who underwent implant surgery from May 1, 2009 to April 30, 2011. In all, 176 implant placements were performed. Radiographs were taken before the first surgery, immediately after the first and second surgeries, immediately and six months after the final prosthesis installation, and every year after that. Bone loss was evaluated by the method suggested by Romanos and Nentwig. Results A total of 176 implant placements were performed-122 in men and 54 in women. These patients have been followed-up for an average of 4.9 years. In terms of prosthetic appliances, there were 156 bridges and 20 single prostheses. Nine implants installed in the maxillary molar area, three in the mandibular molar area and two in the maxillary premolar area were included in group M, with bone loss less than 2 mm at the crestal aspect of the implant. Of these, eight implants were single prostheses. In all, six implants failed-four in the mandible and two in the maxilla. All of these failures occurred in single-implant cases. The implant survival rate was 98.1% on the maxilla and 94.3% on the mandible, with an overall survival of 96.6%. Conclusion Within the limitations of this study, implants with the SLA surface have a very superior survival rate in relatively poor bone environments such as the maxilla. PMID:26734558

  10. Effect of Hydration State on the Frictional Properties of Montmorillonite-based Fault Gouge

    NASA Astrophysics Data System (ADS)

    Ikari, M. J.; Marone, C.; Saffer, D. M.; McKiernan, A. W.

    2005-12-01

    Understanding the frictional properties of fault gouge is crucial to understanding the generation and nature of earthquakes and the strength of crustal faults. Montmorillonite is of particular interest because it can exhibit exceptionally low friction and it has been suggested as a candidate source of fault weakness. Previous work shows that the weakness of montmorillonite is associated with its water content. We report on laboratory experiments to examine the effect of hydration state on the frictional properties of simulated fault gouge consisting of mixtures of Ca-montmorillonite powder and quartz sand. Four mixtures were studied (100%, 70%, 50% and 30% montmorillonite) and each was tested at four hydration states: 21 wt% water, 14 wt% water (samples equilibrated to room humidity), 7 wt% water, and 0 wt% water (dry). Samples with water content values approaching 0 wt% were dried in a 105 deg. C oven for at least 24 hours. Time dependent drying curves were constructed in order to reproducibly obtain a given hydration state. Samples reached 14 wt% water when equilibrated with room RH. Higher water content was achieved by equilibrating samples in a sealed environment with saline solutions for at least 24 hours. Experiments were conducted in a servo-controlled apparatus using the double-direct shear configuration. Layers were 3 to 5 mm thick with nominal contact dimensions of 5 cm by 5 cm. For each clay/quartz mixture and hydration state, we measured frictional properties at normal stresses of 5, 15, 25, 40, 70, and 100 MPa. Experiments were conducted under constant shear velocity boundary conditions. Velocity stepping experiments were conducted in the range 1-300 microns/sec. Preliminary results show a systematic decrease in the coefficient of friction with increasing water content and with increasing normal stress and increasing clay content. Friction values for 50/50 mixtures of montmorillonite/quartz range from 0.56 to 0.64 for 0 wt% water and decrease to a range of 0.20 to 0.56 at 14 wt% water. For layers of 100% montmorillonite, friction values are 0.56-0.62 at 0 wt% water and 0.10-0.32 at 14 wt% water. Plotting a-b values obtained from velocity stepping experiments indicate increasingly velocity strengthening frictional behavior (i.e. a-b values become more positive) as water content increases. For all mixtures with 0 and 7 wt% water, there appears to be a critical normal stress value between 25 and 40 MPa below which there is a high variation among a-b values and above which these values become tightly clustered. Ongoing experiments include addition of velocity stepping experiments at higher water content values to further investigate the relationship between water content, clay content, and normal stress as it relates to frictional behavior.

  11. Effect of hydration state on the frictional properties of montmorillonite-based fault gouge

    NASA Astrophysics Data System (ADS)

    Ikari, Matt J.; Saffer, Demian M.; Marone, Chris

    2007-06-01

    We report on laboratory experiments examining the effect of hydration state on the frictional properties of simulated clay and quartz fault gouge. We tested four mixtures of Ca-montmorillonite and quartz (100, 70, 50, and 30% montmorillonite) at four hydration states: dry (<4.50 wt% water), one water interlayer equivalent (4.5-8.7 wt% water), two layers (8.7-16.0 wt% water), and three layer (>16.0 wt% water). We controlled the hydration state using either oven drying (for <13 wt% H2O) or saline solutions (to achieve >13 wt% H2O under conditions of controlled relative humidity). For each clay/quartz mixture and hydration state, we measured frictional properties over a range of normal stresses (5-100 MPa) and sliding velocities (1-300 ?m/s). We observe a systematic decrease in the coefficient of friction (?) with increasing water content, normal stress, and clay content. Values of ? for 50/50 mixtures range from 0.57 to 0.64 dry and decrease to 0.21-0.55 for the most hydrated cases (wet). For layers of 100% montmorillonite, ? ranges from 0.41-0.62 dry to 0.03-0.29 wet. As water content is increased from 0 to 20.0 wt%, the friction rate parameter a-b becomes increasingly positive. Variation in a-b values decreases dramatically as normal stress increases. If our experimental results can be applied to natural fault gouge, the combination of stress state, hydration state, and quartz content that facilitates unstable fault behavior implies that the onset of shallow seismicity in subduction zones is more complicated than a simple transition from smectite to illite.

  12. Sequence- and regio-selectivity in the montmorillonite-catalyzed synthesis of RNA.

    PubMed

    Ertem, G; Ferris, J P

    2000-10-01

    The six binary montmorillonite clay-catalyzed reactions of the 5'-phosphorimidazolides of adenosine, cytidine, guanosine and uridine were performed and the eight dimers from each reaction were separated and analyzed by HPLC. A 16-51-fold higher yield of the 5'-purine-pyrimidine dimers over that of the 5'-pyrimidine-purines was observed. The total yield of the 5'-purine-pyrimidine dimers was in the 50-70% range while that of the 5'-pyrimidine-purine dimers was 1.3-7.0%. Less sequence selectivity was observed in the homodimers formed. Regioselectivity for the formation of 3', 5'-phosphodiester bonds over that found in the absence of clay was observed. The 5'-purine-pyrimidine, 5'-pyrimidine-pyrimidine and 5'-purine-purine dimers had 3', 5'-links in about half of their phosphodiester bonds. The percent phosphodiester links in the 5'-pyrimidine-pyrimidine dimers was 18%, a value close to that observed in the absence of the montmorillonite catalyst. The montmorillonite-catalyzed reaction of all four activated nucleotides was performed and the 24 products were separated and analyzed. The trends observed in the binary reactions were confirmed and the results also showed that the relative reactivity of the activated monomers was A > G > C > U in the ratio 8.2:4.8:1.3:1 respectively. No 5'-pyrimidine-purines with a 5'-U and pG3' pU, pC3' pA and pC3' pG were detected. These studies suggest that a limited population of RNAs would have formed in catalyzed prebiotic reactions. PMID:11002887

  13. Significance of mineral salts in prebiotic RNA synthesis catalyzed by montmorillonite.

    PubMed

    Joshi, Prakash C; Aldersley, Michael F

    2013-06-01

    The montmorillonite-catalyzed reactions of the 5'-phosphorimidazolide of adenosine used as a model generated RNA type oligomers. These reactions were found to be dependent on the presence of mineral salts. Whereas montmorillonite (pH 7) produced only dimers and traces of trimer in water, addition of sodium chloride (0.1-2.0 M) enhanced the chain length of oligomers to 10-mers as detected by HPLC. Maximum catalytic activity was observed with sodium chloride at a concentration between 0.8 and 1.2 M. This concentration of sodium chloride resembled its abundance in the ancient oceans (0.9-1.2 M). Magnesium chloride produced a similar effect but its joint action with sodium chloride did not produce any difference in the oligomer chain length. Therefore, Mg(2+) was not deemed necessary for generating longer oligomers. The effect of monovalent cations upon RNA chain length was: Li(+) > Na(+) > K(+). A similar effect was observed with the anions with enhanced oligomer length in the following order: Cl(-) > Br(-) > I(-). Thus, the smaller ions facilitated the formation of the longest oligomers. Inorganic salts that tend to salt out organic compounds from water and salts which show salt-in effects had no influence on the oligomerization process indicating that the montmorillonite-catalyzed RNA synthesis is not affected by either of these hydrophobic or hydrophilic interactions. A 2.3-fold decrease in the yield of cyclic dimer was observed upon increasing the sodium chloride concentration from 0.2 to 2.0 M. Inhibition of cyclic dimer formation is vital for increasing the yield of linear dimers and longer oligomers. In summary, sodium chloride is likely to have played an essential role in any clay mineral-catalyzed prebiotic RNA synthesis. PMID:23775061

  14. Oligomerization of uridine phosphorimidazolides on montmorillonite: a model for the prebiotic synthesis of RNA on minerals

    NASA Technical Reports Server (NTRS)

    Ding, P. Z.; Kawamura, K.; Ferris, J. P.

    1996-01-01

    The 5'-phosphorimidazolide of uridine reacts on Na(+)-montmorillonite 22A in aqueous solution to give oligomers as long as 7 mers. The maximum chain length increases to 9 mers and the overall oligomer yield increases when 9:1 ImpU, A5' ppA mixtures react under the same conditions. The oligomer yield and maximum chain length decreases with the structure of the added pyrophosphate in the order A5' ppA > A5' ppU > U5' ppU. Structure analysis of individual oligomer fractions was performed by selective enzymatic hydrolyses followed by HPLC analysis of the products. The regioselectivity for 3',5'-bond formation is 80-90% in the 9:1 ImpU, A5' ppA reaction, a percentage comparable to that observed in the 9:1 ImpA, A5' ppA reaction. Oligomerization of ImpU is inhibited by addition of dA5' ppdA, and MeppA. No oligomers containing A5' ppU were products of the 9:1 ImpU,A5' ppA reaction, a finding consistent with the simple addition of the ImpU to the A5' ppA and not the rearrangement of an ImpU-A5' ppA adduct. Concentrations of lysine or arginine which were close to that of the ImpU did not inhibit oligomer formation. Treatment of Na(+)-montmorillonite with 1 M arginine yielded arginine-montmorillonite, an amino acid-mineral adduct which did not catalyze ImpU oligomerization. Neither the 4-9 mers formed in the 9:1 ImpU, A5' ppA reaction nor the 4-9 mers formed by the base hydrolysis of poly(U) served as templates for the formation of oligo(A)s.

  15. Biomedicine in the environment: sorption of the cyclotide kalata B2 to montmorillonite, goethite, and humic acid.

    PubMed

    Ovesen, Rikke Gleerup; Nielsen, John; Hansen, Hans Christian Bruun

    2011-08-01

    Cyclotides are bioactive, stable mini-proteins produced in high amounts in Violaceae and Rubiaceae with promising pharmaceutical and agrochemical applications. Environmental issues must be addressed before large-scale plant cultivation of cyclotides for pharmaceutical or pesticidal purposes can commence. The objective of the present study was to investigate sorption of the cyclotide kalata B2 (kB2), because knowledge of cyclotide biogeochemistry will aid our understanding of environmental fate. The octanol-water partitioning coefficient was determined to be 2.8??0.6 (log?K(OW) ?=?0.4??0.1). Sorption of kB2 by montmorillonite, goethite, and humic acid was investigated at different concentrations and under varying acidity and reached equilibrium within minutes. The kB2 sorption at a solution concentration of 0.2?mg/L to montmorillonite was high (120?mg/g) compared to humic acid (0.60?mg/g) and goethite (0.03?mg/g). Kalata B2 intercalated the interlayer space of montmorillonite. The sorption isotherm for humic acid was linear up to a solution concentration of 0.8?mg/L and concave for montmorillonite and goethite up to an equilibrium solution concentration of 1.5?mg/L. Sorption to goethite was unaffected by pH, but sorption to montmorillonite and humic acid at pH near the isoelectric point (pI) was threefold the sorption when pH?>?the isoelectric point, suggesting that electrostatic interaction/repulsion between kB2 and sorbents play an important role. The strong sorption to montmorillonite reduces exposure to below toxic threshold values. In addition, the transport risk of soluble cyclotides is reduced, but particle-bound cyclotides may be transported to recipient aquatic sediments with the associated risk of adversely affecting sediment-dwelling organisms. PMID:21590795

  16. MANAGING SOURCES TO REDUCE RISK IN AND AROUND THE INDOOR ENVIRONMENT: IMPACT OF COATINGS ON DISLODGEABLE ARSENIC ON THE SURFACES OF CCA-TREATED WOOD

    EPA Science Inventory

    Due to the potential for ingestion of chromated copper arsenate (CCA) by the hand-to-mouth activities of young children who contact CCA treated wood, EPA has used wipe samples to study the potential benefits of paint-like coatings on CCA treated wood. Citizens who may be concern...

  17. Montmorillonite K-10 promoted synthesis of chiral dioxa-caged compounds derived from levoglucosenone.

    PubMed

    Zurita, Mariano A; Avila, Aylén; Spanevello, Rolando A; Suárez, Alejandra G; Sarotti, Ariel M

    2015-01-30

    A short and efficient methodology for the synthesis of chiral dioxa-caged compounds from levoglucosenone, a biomass-derived enone, is herein presented. The key transformation, that involves a cascade 3-step cationic cyclization, was efficiently carried out in high yields and selectivities by Montmorillonite K-10 catalysis. The usefulness of K-10 in related semi-pinacol rearrangements to obtain pyran-3-ones is also shown. Interesting differences in the reactivity pattern was found for epimeric alcohols, and the origins of these findings were determined by DFT calculations. PMID:25497334

  18. Poly(imide)/Organically-Modified Montmorillonite Nanocomposite as a Potential Membrane for Alkaline Fuel Cells

    PubMed Central

    Battirola, Liliane C.; Gasparotto, Luiz H. S.; Rodrigues-Filho, Ubirajara P.; Tremiliosi-Filho, Germano

    2012-01-01

    In this work we evaluated the potentiality of a poly(imide) (PI)/organically-modified montmorillonite (O-MMT) nanocomposite membrane for the use in alkaline fuel cells. Both X-ray diffraction and scanning electron microscopy revealed a good dispersion of O-MMT into the PI matrix and preservation of the O-MMT layered structure. When compared to the pure PI, the addition of O-MMT improved thermal stability and markedly increased the capability of absorbing electrolyte and ionic conductivity of the composite. The results show that the PI/O-MMT nanocomposite is a promising candidate for alkaline fuel cell applications. PMID:24958290

  19. Preparation of poly(oxybutyleneoxymaleoyl) catalyzed by a proton exchanged montmorillonite clay.

    PubMed

    Ferrahi, Mohammed Issam; Belbachir, Mohammed

    2004-01-01

    The polycondensation of tetrahydrofuran with maleic anhydride catalyzed by Maghnite-H+ (Mag-H) was investigated. Maghnite is a montmorillonite sheet silicate clay that is exchanged with protons to produce Maghnite-H [1]. It was found that the polymerization in bulk is initiated by Mag-H in the presence of acetic anhydride at 40 degrees C. The effects of the amounts of Mag-H and acetic anhydride were studied. The polymerization yield increased as the proportions of catalyst and acetic anhydride were increased. PMID:18007497

  20. Layer-by-Layer Assembled 2D Montmorillonite Dielectrics for Solution-Processed Electronics.

    PubMed

    Zhu, Jian; Liu, Xiaolong; Geier, Michael L; McMorrow, Julian J; Jariwala, Deep; Beck, Megan E; Huang, Wei; Marks, Tobin J; Hersam, Mark C

    2016-01-01

    Layer-by-layer assembled 2D montmorillonite nanosheets are shown to be high-performance, solution-processed dielectrics. These scalable and spatially uniform sub-10 nm thick dielectrics yield high areal capacitances of ≈600 nF cm(-2) and low leakage currents down to 6 × 10(-9) A cm(-2) that enable low voltage operation of p-type semiconducting single-walled carbon nanotube and n-type indium gallium zinc oxide field-effect transistors. PMID:26514248

  1. Oligomerization of mononucleotides on montmorillonite: A potential approach to the prebiotic synthesis of RNA. [Abstract only

    NASA Technical Reports Server (NTRS)

    Ferris, James P.; Ertem, Goezen; Ding, Zi Ping; Prabahar, Joseph

    1994-01-01

    The condensation of the 5'-phosphorimidazolide of adenosine (ImpA) on montmorillonite in a pH 8 aqueous solution yields oligomers containing up to 10 monomer units. The regiospecificity of 3',5'-phosphodiester bond formation is enhanced by addition of 10% diadenosine pyrophosphate (AppA) to the reaction mixture. A series of activated derivatives of 5'-AMP was prepared to investigate the effect of the leaving group on oligomer formation. The benzimidazole and p-dimethylamino-pyridine derivatives gave the best yields of oligomers. Factors important for oligomer formation is discussed.

  2. The polymerization of amino acid adenylates on sodium-montmorillonite with preadsorbed polypeptides

    NASA Technical Reports Server (NTRS)

    Paecht-Horowitz, Mella; Eirich, Frederick R.

    1988-01-01

    The spontaneous polymerization of amino acid adenylates on Na-montmorillonite in dilute, neutral suspension, after polypeptides were adsorbed on the clay, is studied. It is found that the degrees of polymerization of the oligopeptides and polypeptides obtained is dependent on the amounts of polypeptides that were preadsorbed. It is concluded that a catalytic activity may derive from c-spacings that offer adsorption sites for the reagent amino acid adenylate within the peripheral recesses of irregularly stacked clay platelets by bringing the anhydride bonds and neutral amino groups into favorable reaction distances.

  3. Kinetic and mechanistic analysis of dinucleotide and oligonucleotide formation from the 5'-phosphorimidazolide of adenosine on Na(+)-montmorillonite

    NASA Technical Reports Server (NTRS)

    Kawamura, K.; Ferris, J. P.

    1994-01-01

    The rate constants for the condensation reaction of the 5'-phosphorimidazolide of adenosine (ImpA) to form dinucleotides and oligonucleotides have been measured in the presence of Na(+)-volclay (a Na(+)-montmorillonite) in pH 8 aqueous solution at 25 degrees C. The rates of the reaction of ImpA with an excess of adenosine 5'-monophosphoramidate (NH2pA), P1,P2-diadenosine 5',5'-pyrophosphate (A5'ppA), or adenosine 5'-monophosphate (5'-AMP or pA) in the presence of the montmorillonite to form NH2pA3'pA, A5'ppA3'pA, and pA3'pA, respectively, were measured. Only 3',5'-linked products were observed. The magnitude of the rate constants decrease in the order NH2pA3'pA > A5'-ppA3'pA > pA3'pA. The binding of ImpA to montmorillonite was measured, and the adsorption isotherm was determined. The binding of ImpA to montmorillonite and the formation of higher oligonucleotides is not observed in the absence of salts. Mg2+ enhances binding and oligonucleotide formation more than Ca2+ and Na+. The rate constants for the oligonucleotide formation were determined from the reaction products formed from 10 to 40 mM ImpA in the presence of Na(+)-montmorillonite using the computer program SIMFIT. The magnitudes of the rate constants for the formation of oligonucleotides increased in the order 2-mer < 3-mer < 4-mer ... 7-mer. The rate constants for dinucleotide and trinucleotide formation are more than 1000 times larger than those measured in the absence of montmorillonite. The rate constants for the formation of dinucleotide, trinucleotide, and tetranucleotide are 41,2.6, and 3.7 times larger than those for the formation of oligo(G)s with a poly(C) template. The hydrolysis of ImpA was accelerated 35 times in the presence of the montmorillonite. The catalytic ability of montmorillonite to form dinucleotides and oligonucleotides is quantitatively evaluated and possible pathways for oligo(A) formation are proposed.

  4. Spherical LDH-Ag°-montmorillonite heterocoagulated system with a pH-dependent sol-gel structure for controlled accessibility of AgNPs immobilized on the clay lamellae.

    PubMed

    Deák, Ágota; Janovák, László; Tallósy, Szabolcs Péter; Bitó, Tamás; Sebők, Dániel; Buzás, Norbert; Pálinkó, István; Dékány, Imre

    2015-02-17

    Aqueous suspensions of spherical ZnMgAl-layered double hydroxides [LDH(sph)] and antibacterial silver nanoparticles (AgNPs) deposited on the lamellae of montmorillonite were used for the synthesis of composites, which behave like coherent gels at low pH (≲4.5) and incoherent sols at higher pH (≳4.5). The composition of the composite was chosen as LDH(sph)/Ag°-montm. = 25:75 wt % in order to ensure a sol-gel transition that can also be characterized by viscometry. This pH-sensitive heterocoagulated system consisting of oppositely charged colloid particles was suitable for the release of antimicrobial AgNPs immobilized on the clay lamellae via a pH-controlled gel-sol transition. The heterocoagulation process was also characterized by surface charge titration measurements. Spherical LDH/Ag°-montmorillonite composite samples were identified by X-ray diffraction (XRD) measurements. The morphological properties of the composites were studied, and the presence of the heterocoagulated structure was confirmed by scanning electron microscopy (SEM). The nanoscale structure of the LDH(sph)-Ag°-montmorillonite composite obtained was also verified by small-angle X-ray scattering (SAXS), and the rheological characteristics were studied at various pH values. The viscosity and yield value of the composite decreased by an order of magnitude upon increasing the pH from 3.0 to 5.5. The sol-gel transition of the composite suspension was reversible in the previously mentioned pH range. PMID:25619227

  5. Treating Syphilis

    PubMed Central

    Colby, W. David

    1992-01-01

    Background information on treating syphilis indicates that some currently recommended approaches to therapy are not optimal. There is no perfect drug schedule available, but penicillin remains the drug of choice. The author's recommendations for treatment and follow up are presented. PMID:21221354

  6. Treating Sludges

    ERIC Educational Resources Information Center

    Josephson, Julian

    1978-01-01

    Discussed are some of the ways to handle municipal and industrial wastewater treatment sludge presented at the 1978 American Chemical Society meeting. Suggestions include removing toxic materials, recovering metals, and disposing treated sewage sludge onto farm land. Arguments for and against land use are also given. (MA)

  7. Gastroretentive montmorillonite-tetracycline nanoclay for the treatment of Helicobacter pylori infection.

    PubMed

    Iannuccelli, Valentina; Maretti, Eleonora; Montorsi, Monia; Rustichelli, Cecilia; Sacchetti, Francesca; Leo, Eliana

    2015-09-30

    The paper aims to explore the potential benefits provided by an organically modified montmorillonite (nanoclay) in the problematic management of the Helicobacter pylori gastric infection that is one of the most prevalent infectious diseases worldwide. Two nanoclay samples were produced by the intercalation of tetracycline (TC) into the interlayer of montmorillonite (MM) under two different pH reaction conditions (pH 3.0 and 8.7). MM/TC nanoclays were characterized by EDX, XRD, FTIR, DSC, drug adsorption extent, in vitro mucoadhesiveness and desorption in simulated gastric media. The reaction between MM and TC led to a complete MM cation (Na(+) and Ca(2+)) exchange process, an increase of MM characteristic interlayer spacing as well as an involvement of NHR3(+) group of TC, regardless of the reaction pH value. However, MM/TC nanoclay obtained under alkaline conditions provided a lower TC adsorption as well as a drug fraction weakly linked to MM in comparison with the nanoclay obtained in acidic conditions. Both the nanoclays exhibited good mucoadhesion properties to porcine mucin and TC desorption occurring mainly via a cation exchange process by H(+) ions. Based on the results obtained, TC intercalation into MM nanoplatelets could represent a potential advantageous approach allowing the antibiotic to distribute homogeneously on the gastric mucosa, diffuse through the gastric mucus layer