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Sample records for surface treated montmorillonite

  1. Adsorption of organic phenols onto hexadecyltrimethylammonium-treated montmorillonite

    SciTech Connect

    Kim, Young S.; Song, Dong I.; Jeon, Young W.; Choi, Sang J.

    1996-12-01

    Montmorillonite used as an adsorbent was organically modified by using a cationic surfactant, hexadecyltrimethylammonium (HDTMA), to enhance the removal capacity of organic phenol contaminants dissolved in an aqueous solution. This modification produces a change of the surface property of montmorillonite from hydrophilic to organophilic. The single- and multicomponent competitive adsorptions were performed in a batch reactor to investigate the removal of three toxic organic phenols, 2-chlorophenol, 3-cyanophenol, and 4-nitrophenol, on the modified HDTMA-montmorillonite. It was observed from the experimental results that the adsorption affinity for HDTMA-montmorillonite was 2-chlorophenol, 4-nitrophenol, 3-cyanophenol in decreasing order. Langmuir and the Redlich-Peterson models were used to analyze the single-component adsorption results, while the IAST and the LCM models predicted the multicomponent adsorption equilibria. These models yielded favorable representations of both individual and competitive adsorption behaviors.

  2. 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

  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. Acidity of edge surface sites of montmorillonite and kaolinite

    NASA Astrophysics Data System (ADS)

    Liu, Xiandong; Lu, Xiancai; Sprik, Michiel; Cheng, Jun; Meijer, Evert Jan; Wang, Rucheng

    2013-09-01

    Acid-base chemistry of clay minerals is central to their interfacial properties, but up to now a quantitative understanding on the surface acidity is still lacking. In this study, with first principles molecular dynamics (FPMD) based vertical energy gap technique, we calculate the acidity constants of surface groups on (0 1 0)-type edges of montmorillonite and kaolinite, which are representatives of 2:1 and 1:1-type clay minerals, respectively. It shows that tbnd Si-OH and tbnd Al-OH2OH groups of kaolinite have pKas of 6.9 and 5.7 and those of montmorillonite have pKas of 7.0 and 8.3, respectively. For each mineral, the calculated pKas are consistent with the experimental ranges derived from fittings of titration curves, indicating that tbnd Si-OH and tbnd Al-OH2OH groups are the major acidic sites responsible to pH-dependent experimental observations. The effect of Mg substitution in montmorillonite is investigated and it is found that Mg substitution increases the pKas of the neighboring tbnd Si-OH and tbnd Si-OH2 groups by 2-3 pKa units. Furthermore, our calculation shows that the pKa of edge tbnd Mg-(OH2)2 is as high as 13.2, indicating the protonated state dominates under common pH. Together with previous adsorption experiments, our derived acidity constants suggest that tbnd Si-O- and tbnd Al-(OH)2 groups are the most probable edge sites for complexing heavy metal cations.

  5. 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.

  6. FT-IR spectroscopic investigations of surface and intercalated 2-aminopyrimidine adsorbed on sepiolite and montmorillonite from Anatolia

    NASA Astrophysics Data System (ADS)

    Akyz, S.; Akyz, T.

    2003-06-01

    The adsorption of 2-amino pyrimidine (2APM) on sepiolite and montmorillonite has been investigated using FT-IR spectrometry. The intercalation of 2-amino pyrimidine within montmorillonite has been shown by X-ray diffraction to increase the interlayer spacings. 2APM interacted with montmorillonite by direct or indirect coordination (through water molecules) to the exchangeable cations. Adsorption on sepiolite was due to hydrogen bonding with surface Si-OH groups. It is concluded that endocyclic nitrogen is mainly involved in coordination. Moreover, amino group hydrogens may be involved in hydrogen bonding interaction with water molecules (NHOH 2).

  7. 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.

  8. 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

  9. 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

  10. 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.

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

    PubMed

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

    2016-04-01

    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

  12. 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.

  13. 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.

  14. Selective removal and inactivation of bacteria by nanoparticle composites prepared by surface modification of montmorillonite with quaternary ammonium compounds.

    PubMed

    Khalil, Rowaida K S

    2013-10-01

    The purpose of the present study was to prepare new nanocomposites with antibacterial activities by surface modification of montmorillonite using quaternary ammonium compounds that are widely applied as disinfectants and antiseptics in food-processing environments. The intercalation of four quaternary ammonium compounds namely benzalkonium chloride, cetylpyridinium chloride monohydrate, hexadecyltrimethylammonium bromide, tetraethylammonium chloride hydrate into montmorillonite layers was confirmed by X-ray diffraction. The antibacterial influences of the modified clay variants against important foodborne pathogens differed based on modifiers quantities, microbial cell densities, and length of contact. Elution experiments through 0.1g of the studied montmorillonite variants indicated that Staphylococcus aureus, Pseudomonas aeroginosa, and Listeria monocytogenes were the most sensitive strains. 1g of hexadecyltrimethylammonium bromide intercalated montmorillonites demonstrated maximum inactivation of L. monocytogenes populations, with 4.5logc.f.u./ml units of reduction. In adsorption experiments, 0.1g of tetraethylammonium chloride hydrate montmorillonite variants significantly reduced the growth of Escherichia coli O157:H7, L. monocytogenes, and S. aureus populations by 5.77, 6.33, and 7.38log units respectively. Growth of wide variety of microorganisms was strongly inhibited to undetectable levels (montmorillonite variants. This investigation highlights that reduction in counts of microbial populations adsorbed to the new nanocomposites was substantially different from that in elution experiments, where interactions of nanocomposites with bacteria were specific and more complex than simple ability to inactivate. Treatment columns packed with modified variants maintained their inactivation capacity to the growth of Salmonella Tennessee and S. aureus populations after 48h of incubation at room temperature with maximum reductions of 6.3 and 5.0log units respectively. New nanocomposites presented in this research may have potential applications in industrial scale for the control of foodborne pathogens by their incorporation into high-performance filters in food processing plant environments where selectivity in removal and/or inactivation of species in fluid flow streams is desirable. Nevertheless, extensive in vitro and in vivo studies of these new nanocomposites is essential to outpace the understanding of their potential impacts and consequences on human health and the environment if they will make an appearance in commercialized food packaging and containment food materials in the future. PMID:23709187

  15. 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...

  16. 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...

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. 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.

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

    PubMed

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

    1995-09-01

    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, Mssbauer 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 Mssbauer 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. Mssbauer 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. PMID:11538594

  7. 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...

  8. 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.

  9. Surface chemistry of kaolinite and Na-montmorillonite in aqueous electrolyte solutions at 25 and 60 C: Experimental and modeling study

    NASA Astrophysics Data System (ADS)

    Tertre, E.; Castet, S.; Berger, G.; Loubet, M.; Giffaut, E.

    2006-09-01

    The aqueous interfacial chemistry of kaolinite and Na-montmorillonite samples was investigated by potentiometric measurements using acid/base continuous titrations and batch experiments at 25 and 60 C. Using the batch experimental method, a continuous drift of pH was observed reflecting the mineral dissolution. Consequently, the continuous titration method appears to be the best way of studying solid surface reactions. For each clay mineral, the net proton surface excess/consumption was calculated as a function of pH and ionic strength (0.025, 0.1 and 0.5 M). At 25 C, and according to the literature data, the pH corresponding to zero net proton consumption for montmorillonite appears to depend on ionic strength, whereas the value for kaolinite is constant and close to 5. Similar results are obtained at 60 C, which suggests that the point of zero net proton consumption for clay minerals does not depend on temperature, at least up to 60 C. On the other hand, the temperature rise induces a slight increase of the net proton surface excess. Finally, the diffuse double layer formalism (DDLM) is used to model the experimental data. The model involves two processes: the protonation/deprotonation of two types of edge sites (aluminol and silanol) and H +/Na + exchange reactions on basal surfaces, while a tiny proportion of the negative structural charge remains uncompensated. This last process maintains a negative surface potential whatever the pH of the solution, which is in agreement with electrokinetic data.

  10. 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.

  11. 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

  12. Modeling the Adsorption of Oxalate onto Montmorillonite.

    PubMed

    Ramos, M Elena; Emiroglu, Caglayan; Garca, David; Sainz-Daz, 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

  13. The acid-base titration of montmorillonite

    NASA Astrophysics Data System (ADS)

    Bourg, I. C.; Sposito, G.; Bourg, A. C.

    2003-12-01

    Proton binding to clay minerals plays an important role in the chemical reactivity of soils (e.g., acidification, retention of nutrients or pollutants). If should also affect the performance of clay barriers for waste disposal. The surface acidity of clay minerals is commonly modelled empirically by assuming generic amphoteric surface sites (>SOH) on a flat surface, with fitted site densities and acidity constant. Current advances in experimental methods (notably spectroscopy) are rapidly improving our understanding of the structure and reactivity of the surface of clay minerals (arrangement of the particles, nature of the reactive surface sites, adsorption mechanisms). These developments are motivated by the difficulty of modelling the surface chemistry of mineral surfaces at the macro-scale (e.g., adsorption or titration) without a detailed (molecular-scale) picture of the mechanisms, and should be progressively incorporated into surface complexation models. In this view, we have combined recent estimates of montmorillonite surface properties (surface site density and structure, edge surface area, surface electrostatic potential) with surface site acidities obtained from the titration of alpha-Al2O3 and SiO2, and a novel method of accounting for the unknown initial net proton surface charge of the solid. The model predictions were compared to experimental titrations of SWy-1 montmorillonite and purified MX-80 bentonite in 0.1-0.5 mol/L NaClO4 and 0.005-0.5 mol/L NaNO3 background electrolytes, respectively. Most of the experimental data were appropriately described by the model after we adjusted a single parameter (silanol sites on the surface of montmorillonite were made to be slightly more acidic than those of silica). At low ionic strength and acidic pH the model underestimated the buffering capacity of the montmorillonite, perhaps due to clay swelling or to the interlayer adsorption of dissolved aluminum. The agreement between our model and the experimental data illustrates the complementarity of molecular and macro-scale descriptions of the clay reactivity.

  14. 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

  15. Analysis of peptides synthesized in the presence of SAz-1 montmorillonite and Cu(2+) exchanged hectorite.

    PubMed

    Porter, T L; Eastman, M P; Bain, E; Begay, S

    2001-07-01

    We have investigated the synthesis of oligopeptides containing glycine and tyrosine in the presence of the clay minerals montmorillonite (non-exchanged, SAz-1) and Cu(2+) exchanged hectorite. In both cases, homopolymers of the two amino acids are formed, as are mixed peptides. In the case of Cu(2+) hectorite, mixed oligopeptides up to trimers are detected in small amounts. For montmorillonite, heterogeneous oligopeptides up to hexamers are detected. Our experiments indicate montmorillonite is more effective in promoting oligopeptide formation than Cu(2+) hectorite. Analysis of the oligopeptide sequences formed on the montmorillonite surfaces indicates preferential synthesis of certain Gly-Tyr sequences over others. PMID:11429201

  16. Interpreting the Frictional Behavior of the Smectite Clay Montmorillonite

    NASA Astrophysics Data System (ADS)

    Moore, D. E.; Lockner, D. A.

    2004-12-01

    Montmorillonite has been the most widely tested phyllosilicate mineral in soil and rock mechanics friction investigations, but many of the published data are contradictory, with reported values of the coefficient of friction (= shear stress/effective normal stress) ranging from 0.06 to 0.78. We report some new laboratory and petrographic data which illustrate that this wide variation is in part a function of the large difference in coefficient of friction between thoroughly dried (0.7 or greater) and water-saturated (0.3 or lower) montmorillonite. Dry montmorillonite gouge is subject to standard frictional processes such as abrasion, wear, and fracture during shear. In contrast, shear of water-saturated montmorillonite gouge is concentrated in thin films of water that are adsorbed onto the (001) surfaces of the platy grains. Our recent studies suggest that the water-saturated shear strength of sheet-structure minerals increases with the strength of the bonding of the polar water molecules to the (001) surfaces, and the relative weakness of water-saturated montmorillonite may be largely owing to its small layer charge. Values of the coefficient of friction for montmorillonite that are considered to represent water-saturated, equilibrated conditions increase from 0.06 at effective normal stresses below 1 MPa to 0.30 at 300 MPa. This correlation is attributed to decreasing thickness of the surface water films with increasing effective normal stress. Similar stress dependence of frictional strength can be demonstrated for the serpentine minerals, muscovite, biotite, phlogopite, chlorite, kaolinite, and talc, and it is considered to be characteristic of sheet silicates. This behavior contrasts with that of most other silicate minerals, for which the coefficient of friction exhibits little pressure sensitivity below 200 MPa effective normal stress and then decreases at higher stresses (Byerlee's law). Most of the published strength data for montmorillonite fall outside the range of values for water-saturated, equilibrated samples. Of these, the samples that are overly strong for a given set of experimental conditions may have been only partially saturated. Those samples that are weaker than the water-saturated, equilibrated samples at a given effective normal stress appear to result from inadequate drainage and consequent build-up of internal pore pressure. The velocity dependence of montmorillonite strength has not been extensively investigated, but water-saturated montmorillonite gouge is velocity-strengthening over the range of conditions tested to date whereas dry and partially saturated montmorillonite gouge may be velocity weakening at some velocities. These results highlight the hazards of interpreting fault-zone behavior based on experiments that do not approximate natural conditions.

  17. Peptide formation mechanism on montmorillonite under thermal conditions.

    PubMed

    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 150C for 336h 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. PMID:24917118

  18. 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.

  19. 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.

  20. 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.

  1. 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...

  2. Aflatoxin Toxicity Reduction in Feed by Enhanced Binding to Surface-Modified Clay Additives

    PubMed Central

    Jaynes, William F.; Zartman, Richard E.

    2011-01-01

    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 (Kd = 24,100) retained more aflatoxin B1 (AfB1) from aqueous corn flour than untreated montmorillonite (Kd = 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 (Kd = 13,800) and carnitine (Kd = 3960) adsorbed much more AfB1 from aqueous corn flour than the untreated clay (Kd = 944). A choline-treated clay prepared from a reduced-charge, high-charge montmorillonite (Kd = 20,100) adsorbed more AfB1 than the choline-treated high-charge montmorillonite (Kd = 1340) or the untreated montmorillonite (Kd = 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

  3. 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.

  4. 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

  5. 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.

  6. Adsorption of methyl green on montmorillonite

    NASA Astrophysics Data System (ADS)

    Margulies, Leon; Rozen, Harel

    1986-03-01

    Adsorption of the dye methyl green (MG) on Na -montmorillonite (Clay) takes place through a cation exchange mechanism. At low and high MG loads, each MG molecule replaces approximately two and one Na + ions, respectively. Interactions between MG and Clay were studied using visible absorption and FTIR spectroscopies, and the orientation of the adsorbed molecules were determined by infrared linear dichroism and X-ray powder diffraction. The dye molecules are preferentially oriented with their plane parallel to the clay surface. The influence of MG load on the adsorption of two additional organic molecules, benzyl benzoate and benzophenone, was also studied.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Method of treating the surface of a glass member

    NASA Technical Reports Server (NTRS)

    Rice, S. H.; Spencer, R. S. (inventors); 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.

  12. 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

  13. 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.

  14. 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.

  15. The adsorption and reaction of adenine nucleotides on montmorillonite

    NASA Astrophysics Data System (ADS)

    Ferris, James P.; Hagan, William J.

    1986-03-01

    The binding of AMP to Zn2+-montmorillonite was investigated in the presence of buffers and salts. Good's buffers, piperazine-N,N'-bis(2-ethanesulfonate) [PIPES] and morpholine-N-2-ethanesulfonate [MES], perturbed the exchangeable cations to a lesser extent (only 9% of Zn2+ displaced by 0.2 M buffer) than was observed with imidazole and lutidine buffers or NaCl and KCl salts (up to 80% of Zn2+ displaced). AMP adsorption isotherms measured in the presence of 0.2 M PIPES, MES or Na2SO4 exhibited normal Langmuir-type behavior. The adsorption coefficient, KL, is 3-fold greater in the presence of HEPES or PIPES than it is in the absence of buffers. Basal spacings measured by X-ray diffraction for Zn2+-montmorillonite are 13 and 15 in the presence of PIPES, while a value of 12.8 was determined in the absence of PIPES. These data are interpreted in a model in which the adsorption of AMP is mediated by a Zn2+ complex of PIPES in different orientations in the interlamellar region of the montmorillonite. The type of exchangeable cation does not affect the ability of the lattice-bound Fe3+ in the montmorillonite to oxidize diaminomaleonitrile (DAMN). Exchangeable Cu2+ oxidizes DAMN, but exchangeable Fe3+ is nearly ineffective as an oxidant. The addition if DISN to 3'-AMP bound to Zn2+-montmorillonite in the presence of 0.2 M PIPES resulted in a higher yield of 2', 3'-cAMP than is observed with a comparable concentration of Zn2+, a result which implicates surface catalystis by the montmorillonite.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  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. 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.

  2. 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.

  3. 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.

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

    PubMed

    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 (23gkg(-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. PMID:25528132

  5. 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

  6. XAS of uranium(VI) sorbed onto silica, alumina, and montmorillonite

    NASA Astrophysics Data System (ADS)

    Sylwester, E. R.; Allen, P. G.; Hudson, E. A.

    2000-07-01

    The purpose of this work is to determine the speciation (oxidation state and molecular structure) of uranium sorbed onto surfaces of silica, alumina, and montmorillonite, in order to investigate the modes of uranium sorption on these minerals. Characterization of actinide sorption onto silicates, aluminates, and aluminosilicates such as montmorillonite is vital for the prediction of the environmental impact and risk assessment of actinide migration from nuclear waste storage sites, underground test sites, and mining sites.

  7. 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...

  8. Structural properties of reduced Upton montmorillonite

    NASA Astrophysics Data System (ADS)

    Gates, W. P.; Stucki, J. W.; Kirkpatrick, R. J.

    1996-12-01

    Reduction of octahedral Fe in the crystalline structure of smectites influences, possibly controls, surface-sensitive physical and chemical properties. The purpose of this study was to investigate if reduction of structural Fe by Na-dithionite or bacteria affects the chemical environment of constituent cations in montmorillonite, employing solid state multinuclear (29Si and 27Al) magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Reduction of structural Fe resulted in a positive (down field) chemical shift of the main Si Q3 (Q3(0Al)) site which was strongly correlated with Fe(II) content and inferred that distortions in Si-OT (T=Si, Al) bond angles and Si-O bond lengths occur with increasing layer charge. The line width (W) of the 29Si Q3 signal also increased with increasing levels of reduction. No change occurred in the position of the peak maximum for the octahedral Al (27AlVI) signal; however, an increased W was observed for this peak with increasing Fe(II) content. These results are attributed to decreases in Si-O-T bond angles and Si-O bond distances, corresponding to a better fit between the tetrahedral and octahedral sheets brought about by the presence of Fe(II) in the clay structure. The increased 27AlVI signal width (W) may also be due to a lessening of the paramagnetic influence of Fe(III) nuclei and enhancement of 27AlVI signals with different quadrupole coupling constants (QCC). Multinuclear MAS NMR analyses of dithioniteand microbially-reduced montmorillonite indicate that reduction of structural Fe caused reversible changes in the smectite structure, at least as far as this method could discern.

  9. Adsorption of phosphate on hydroxyaluminum- and hydroxyiron-montmorillonite complexes.

    PubMed

    Zhu, Mao-Xu; Ding, Kui-Ying; Xu, Shao-Hui; Jiang, Xin

    2009-06-15

    One hydroxyaluminum-montmorillonite complex (HyAl-Mt), two hydroxyiron-montmorillonite complexes (HyFe-Mts) with different iron contents, and three hydroxyiron/aluminum-montmorillonite complexes (HyFeAl-Mts) with various Fe:Al molar ratios were synthesized. Behavior and kinetics of phosphate (P) sorption on selected Mt-complexes mentioned above were investigated under acidic conditions. The results indicated that the intercalations of polymeric HyFe and/or HyAl ions in interlayers of Na-saturated montmorillonite (Na-Mt) caused significant changes in surface properties of the Na-Mt, such as cation exchange capacity, specific surface area, pH at zero point of charge. In pH range tested (3.0-6.5), P adsorption on the Mt-complexes decreased with increasing pH, whereas the effect became weaker with increasing Fe contents in the Mt-complexes. The adsorption capacities of the HyFeAl-Mts were greater than those of the HyAl-Mt and HyFe-Mt, which could be attributed to decreasing crystallinity of Fe and Al oxides in the HyFeAl-Mts. The equilibrium adsorption of P on the Mt-complexes could be well described using the Langmuir isotherm, and the kinetics of P adsorption could be well described by both the pseudo-second-order and Elovich models. An increase in Fe contents in the Mt-complexes could enhance the initial kinetic rate of P adsorption, as suggested by the Elovich models. It is inferred that a great number of Fe-related active sorption sites have been located on the outer surfaces of the HyFe-Mt, as indicated by extremely high alpha value in the Elovich model. Previous studies focusing mainly on P sorption on HyAl-Mt complexes might have underestimated the contributions of Mt-complexes to P retention in acidic soils high in Fe contents. PMID:19038495

  10. 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...

  11. 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

  12. Controllable surface morphology and properties via mist polymerization on a plasma-treated polymethyl methacrylate surface.

    PubMed

    Wan, S J; Wang, L; Xu, X J; Zhao, C H; Liu, X D

    2014-02-14

    Surface modification by grafting polymers on solid materials is an important strategy used to improve surface properties. This article reports that under appropriate conditions, very thin layers with desired morphologies may be constructed on a plasma-treated substrate by feeding a small quantity of a monomer with a mist stream carrying droplets produced from monomer solutions. We investigate the effects of process parameters that affect layer morphology, including exposure time to the mist stream, concentration of the monomer solution, and solvent selectivity. For a methyl methacrylate solution in ethanol, nanoparticles are uniformly grown with increasing monomer concentration or exposure time and finally form a porous layer at 3.65 mol L(-1) for 30 min. Decreasing solvent polarity not only affects surface morphology, but also increases hydrophobicity of the resulting surface. With 2,2,3,4,4,4-hexafluorobutyl methacrylate as the monomer, SEM and AFM micrographs indicated that mist polymerization results in numerous microspheres on the activated surface. These experimental results were interpreted by a mechanism in terms of an in situ polymerization accompanied by a phase transformation of the resulting polymer. Specifically, plasma treatment provides highly active cations and radicals to initiate very rapid polymerization, and the resulting polymers are consequently deposited from the liquid onto the surface under phase transition mechanisms. PMID:24835436

  13. 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.

  14. Water condensation on zinc surfaces treated by chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Narhe, R. D.; Gonzlez-Vias, Wenceslao; Beysens, D. A.

    2010-06-01

    Water condensation, a complex and challenging process, is investigated on a metallic (Zn) surface, regularly used as anticorrosive surface. The Zn surface is coated with hydroxide zinc carbonate by chemical bath deposition, a very simple, low-cost and easily applicable process. As the deposition time increases, the surface roughness augments and the contact angle with water can be varied from 75 to 150, corresponding to changing the surface properties from hydrophobic to ultrahydrophobic and superhydrophobic. During the condensation process, the droplet growth laws and surface coverage are found similar to what is found on smooth surfaces, with a transition from Cassie-Baxter to Wenzel wetting states at long times. In particular, it is noticeable in view of corrosion effects that the water surface coverage remains on order of 55%.

  15. Comparative studies on montmorillonite-supported zero-valent iron nanoparticles produced by different methods: reactivity and stability.

    PubMed

    Jia, Hanzhong; Wang, Chuanyi

    2013-01-01

    To mitigate the aggregation and enhance the reactivity of nanosized zero-valent iron (nZVI), montmorillonite is employed as a template-supporting matrix to prepare nZVI through two different pathways: heterogeneous nucleation and homogeneous nucleation processes. Dispersed sub-nanosized ZVI clusters with an average size around 0.5 nm (perpendicular to the clay layers) are intercalated in clay interlayers when using montmorillonite as a template in preparation via heterogeneous nucleation process. However, the particle sizes spanned from 0.62 nm (perpendicular to the clay layers) for the ZV1 intercalated in montmorillonite interlayers to 1-50 nm for the ZVI residing on an external surface when using montmorillonite as a dispersion agent in the preparation via homogeneous nucleation. Furthermore, parallel batch experiments have been conducted with nZVIs synthesized by the two different methods in solutions of nitrobenzene and their reactivity is evaluated via response of nZVI to nitrobenzene remediation. As a result, the reactivity of ZVI synthesized by heterogeneous nucleation is greater than that by homogeneous nucleation, which is inversely correlated to the size of ZVI supported by montmorillonite clay. Evaluation of the stability of montmorillonite-supported ZVI showed that ZVI intercalated in the interlayers of montmorillonite is more stable than that located on the external surface, which can be attributed to the protective effect of montmorillonite layers on ZVI from oxidation. These results suggest that the great reactivity and high stability of montmorillonite-intercalated ZVI synthesized through heterogeneous nucleation process warrants its significant potential in developing in situ remediation and treatment technologies for organic contaminants. PMID:23530312

  16. Synthesis and properties of melamine-formaldehyde/ montmorillonite nanocomposites.

    PubMed

    Wang, Haitao; Meng, Xiangfu; Qian, Zhongzhong; Zhoul, Hu; Ding, Yanfen; Zhang, Shimin; Yang, Mingshu

    2008-04-01

    In this paper, intercalated and partially exfoliated melamine-formaldehyde (MF)/montmorillonite (MMT) nanocomposites have been synthesized successfully via in-situ polymerization based on pristine montmorillonite, acidified montmorillonite and organic modified montmorillonite respectively. The obtained nanocomposites were characterized by XRD, TEM, TGA, and Raman spectroscopy. Free formaldehyde content of those composites was also determined by acetyl acetone technique. It was found that acidified montmorillonite and organic modified montmorillonite could catalyze the polycondensation reaction of methylolmelamines. The thermal stability and chemical resistance of those two nanocomposites were also improved dramatically compared to pure melamine-formaldehyde resin. PMID:18572577

  17. Modeling the sorption of zinc and nickel on Ca-montmorillonite

    NASA Astrophysics Data System (ADS)

    Bradbury, Michael H.; Baeyens, Bart

    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 terms of cation exchange and surface complexation mass action equations. A major objective of the experimental/modelling programme 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 3) 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 characterising 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.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  19. 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.

  20. 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.

  1. Helmholtz Fermi surface harmonics: an efficient approach for treating anisotropic problems involving Fermi surface integrals

    NASA Astrophysics Data System (ADS)

    Eiguren, Asier; Gurtubay, Idoia G.

    2015-03-01

    We present a new efficient numerical approach for representing an-isotropic physical quantities and/or matrix elements defined on the Fermi surface (FS) of metallic materials. The method introduces a set of numerically calculated generalized orthonormal functions, which are the solutions of the Helmholtz equation defined on the FS, where the periodicity of the reciprocal space is treated as a boundary condition. In essence, what we introduce is a generalization of the Spherical Harmonics for any periodic Fermi Surface and regardless of its topology. The main motivation of the approach is to handle an-isotropic many-body problems very efficiently. In this context we demonstrate how our theory reduces, by several orders of magnitude, the computational effort when applied to several well know many-body theoretical models such as the electron-phonon. Moreover, the method is demonstrated to be very robust in handling problems with any crystal structure or topology of the FS. We illustrate the method showing applications on several relevant surface and bulk systems.

  2. 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

  3. 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 claysmontmorillonite (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.

  4. 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

  5. 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).

  6. Complementary electrowetting devices on plasma-treated fluoropolymer surfaces.

    PubMed

    Kim, D Y; Steckl, A J

    2010-06-15

    A reversal of the normal two-fluid competitive (water vs oil) electrowetting (nEW) on dielectric has been achieved by plasma irradiation of the normally hydrophobic fluoropolymer followed by thermal annealing. This process first renders the surface hydrophilic and then returns it to its normal hydrophobic properties as measured by water droplet contact and rolling angles. In the plasma-irradiated and annealed EW device (pEW), the normal two-fluid EW action is reversed after an initial charging step, with the oil layer being displaced at zero voltage and being returned at high voltage. A possible explanation of this effect is a plasma-induced modification of the fluoropolymer, rendering it more susceptible to charge injection and trapping at high voltage. nEW and pEW devices exhibit complementary EW operation, as verified by oil movement and optical transmission. This method can lead to low-power operation of two-fluid EW devices. PMID:20329778

  7. Pu(V) and Pu(IV) sorption to montmorillonite.

    PubMed

    Begg, James D; Zavarin, Mavrik; Zhao, Pihong; Tumey, Scott J; Powell, Brian; Kersting, Annie B

    2013-05-21

    Plutonium (Pu) adsorption to and desorption from mineral phases plays a key role in controlling the environmental mobility of Pu. Here we assess whether the adsorption behavior of Pu at concentrations used in typical laboratory studies (?10(-10) [Pu] ? 10(-6) M) are representative of adsorption behavior at concentrations measured in natural subsurface waters (generally <10(-12) M). Pu(V) sorption to Na-montmorillonite was examined over a wide range of initial Pu concentrations (10(-6)-10(-16) M). Pu(V) adsorption after 30 days was linear over the wide range of concentrations studied, indicating that Pu sorption behavior from laboratory studies at higher concentrations can be extrapolated to sorption behavior at low, environmentally relevant concentrations. Pu(IV) sorption to montmorillonite was studied at initial concentrations of 10(-6)-10(-11) M and was much faster than Pu(V) sorption over the 30 day equilibration period. However, after one year of equilibration, the extent of Pu(V) adsorption was similar to that observed for Pu(IV) after 30 days. The continued uptake of Pu(V) is attributed to a slow, surface-mediated reduction of Pu(V) to Pu(IV). Comparison between rates of adsorption of Pu(V) to montmorillonite and a range of other minerals (hematite, goethite, magnetite, groutite, corundum, diaspore, and quartz) found that minerals containing significant Fe and Mn (hematite, goethite, magnetite, and groutite) adsorbed Pu(V) faster than those which did not, highlighting the potential importance of minerals with redox couples in increasing the rate of Pu(V) removal from solution. PMID:23614502

  8. 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 Schfer

    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.

  9. 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 400C 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

  10. 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.

  11. Iron-montmorillonite: a spectral analog of Martian soil.

    PubMed

    Banin, A; Margulies, L; Chen, Y

    1985-02-15

    Light absorption and reflectance by smectite clays containing various adsorbed ions were measured in the UV, VIS, and NIR ranges and compared to Martian dust and surface soil spectra. Structural iron in the octahedral sheet of smectites is responsible for a characteristic absorption feature in the UV at 240-260 nm, resulting from an O2 --> Fe3+ charge transfer that is similar to one observed in the Martian spectrum. Adsorbed iron affects, via crystal field absorptions, the reflectance of montmorillonite in the VIS and NIR (to 1.3 micrometers), causing stronger absorption and higher opacity in the wavelength range 0.4-0.6 micrometer, without developing any specific pronounced absorption feature. In both general appearance and presence of, or lack of, spectral features, the iron-montmorillonite reflectance spectra in the VIS and NIR are similar to the Martian spectra. At present, however, spectral similarity cannot be used as the sole criterion for constraining Martian mineralogy since several other minerals, other than Fe-smectites, show sufficient similitude to the Martian spectra; other properties have to be explored and combined to obtain a definitive identification. PMID:11542022

  12. 40 CFR 721.10573 - Magnesium hydroxide surface treated with substituted alkoxysilanes (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 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...

  13. 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...

  14. 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).

  15. Montmorillonite, Oligonucleotides, RNA and Origin of Life

    NASA Astrophysics Data System (ADS)

    Ertem, Gzen

    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).

  16. Sorption speciation of nickel(II) onto Ca-montmorillonite: batch, EXAFS techniques and modeling.

    PubMed

    Tan, XiaoLi; Hu, Jun; Montavon, Gilles; Wang, XiangKe

    2011-11-01

    The sorption speciation of Ni(II) on Ca-montmorillonite was evaluated using a combination of batch experiments, extended X-ray absorption fine structure (EXAFS) spectroscopy and modeling. The pH and temperature at the aqueous-montmorillonite interface affects both the extent of Ni(II) sorption as well as the local atomic structure of the adsorbed Ni(II) ions. At 0.001 mol L(-1) Ca(NO(3))(2) and low pH, the study reveals that the majority of Ni(II) is adsorbed in the interlayers of Ca-montmorillonite coordinated by six water molecules in an octahedron as an outer-sphere complex. At higher pH, inner-sphere surface complexes are formed. The Ni-Si/Al distances (R(Ni-Al) = 3.00 , R(Ni-Si1) = 3.10 and R(Ni-Si2) = 3.26 ) determined by EXAFS confirm the formation of mononuclear complexes located at the edges of Ca-montmorillonite platelets at pH 7.5 and 8.5. At pH 10.0, the Ni-Ni/Si distances (R(Ni-Ni) = 3.07 and R(Ni-Si) = 3.26 ) indicates the formation of Ni-phyllosilicate precipitates. A rise in temperature promotes inner-sphere complexation, which in turn leads to an increase in Ni(II) sorption on Ca-montmorillonite. Sorption edges are fitted excellently by surface complexation model (SCM) with the aid of surface species determined from EXAFS spectroscopy. PMID:21918750

  17. Surface characteristics and printing properties of PET fabric treated by atmospheric dielectric barrier discharge plasma

    NASA Astrophysics Data System (ADS)

    Rashed, U. M.; Ahmed, H.; Al-Halwagy, A.; Garamoon, A. A.

    2009-01-01

    PET (Poly ethylene terephthalate) fabric was treated using dielectric barrier discharge (DBD) as a type of low temperature plasma under atmospheric pressure for 1 to 15min and different powers ranging between 0.3 to 5W. Effects of DBD treatment on the surface of a test PET fabric are examined, reported and discussed. The surface analysis and characterization were performed using X-ray diffraction (XRD), Fourier transition infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) before and following the DBD processing. SEM analysis shows significant surface morphology changes in plasma treated polyester fabric surface, while FTIR analysis indicates that the reactivity of the surface was increased. The discharge parameters used are correlated with the changes in the surface characteristics found after DBD processing of various durations, in atmospheric air environment.

  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. 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.

  20. 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.

  1. 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.

  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. Insights into tetracycline adsorption onto kaolinite and montmorillonite: experiments and modeling.

    PubMed

    Zhao, Yanping; Gu, Xueyuan; Li, Shiyin; Han, Ruiming; Wang, Guoxiang

    2015-11-01

    Adsorption of tetracycline (TC) on kaolinite and montmorillonite was investigated using batch adsorption experiments with different pH, ionic strength, and surface coverage. As a result, pH and ionic strength-dependent adsorption of TC was observed for the two clay minerals. The adsorption of TC decreased with the increase of pH and ionic strength, and high initial TC concentration had high adsorption. In addition, a triple-layer model was used to predict the adsorption and surface speciation of TC on the two minerals. As a result, four complex species on kaolinite (?X(-)?H3TC(+), ?X(-)?H2TC(), ?SOH(0)?H2TC(), and ?SOH(0)?HTC(-)) and three species on montmorillonite (?X(-)?H3TC(+), ?X(-)?H2TC(), and ?SOH(0)?HTC(-)) were structurally constrained by spectroscopy, and these species were also successfully fitted to the adsorption edges of TC. Three functional groups of TC were involved in these adsorption reactions, including the positively charged dimethylamino group, the C=O amide I group, and the C=O group at the C ring. Combining adsorption experiments and model in this study, the adsorption of TC on kaolinite and montmorillonite was mainly attributed to cation exchange on the surface sites (?X(-)) compared to surface complexation on the edge sites (?SOH) at natural soil pH condition. Moreover, the surface adsorption species, the corresponding adsorption modes, and the binding constants for the surface reactions were also estimated. PMID:26122570

  4. 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.

  5. Extent of coverage of surfaces treated with hydrophobizing microemulsions: A mass spectrometry and contact angle study

    NASA Astrophysics Data System (ADS)

    Nagy, Andras; Kennedy, Joseph P.; Wang, Ping; Wesdemiotis, Chrys; Hanton, Scott D.

    2006-03-01

    Glass surfaces were treated with various hydrophobizing microemulsions (HME) containing mineral seal oil or polyisobutylene as hydrophobes emulsified by dimethyl dicoco ammonium chloride (i.e. mimicking commercial car wash practices) and characterized by mass spectrometry (MS) and contact angle measurements. The cationic emulsifier mediates the anchoring of hydrophobes to the polar glass surface. It is demonstrated that by the use of even very low (0.3-3.0 w%) HME concentrations the surfaces become hydrophobic and repel water even after numerous (20) rinsing cycles. According to MS evidence, however, the surfaces are not fully saturated with hydrophobes and the unprotected areas remain vulnerable to environmental damage.

  6. Evaluation of Stability of Surface-Treated Mini-Implants in Diabetic Rabbits

    PubMed Central

    Oh, Nam-Hee; Kim, Eun-Young; Paek, Janghyun; Kook, Yoon-Ah; Jeong, Do-Min; Cho, Il-Sik; Nelson, Gerald

    2014-01-01

    Introduction. The purpose of this study was to investigate effects of surface treatment of mini-implants in diabetes-induced rabbits by comparing osseointegration around mini-implants. Methods. Twelve New Zealand white rabbits were divided into two groups (alloxan-induced diabetic group and control group). A total of 48 mini-implants were placed after four weeks of diabetic induction. 24 mini-implants were surface-treated with SLA (sandblasted with large grit, and acid etched) and the remaining 24 mini-implants had smooth surfaces. Four weeks after placement, 32 mini-implants were removed from 4 control and 4 diabetic rabbits. Insertion and removal torques were measured. The remaining 16 mini-implants from the two groups were histomorphometrically analyzed. Results. Maximum insertion torque showed no difference between diabetic and control groups, but total insertion energy was higher in control group. In surface-treated mini-implants, maximum removal torque was higher in both diabetic and control groups. Bone-implant contact (BIC) was increased in the control group when compared to the diabetic group. Surface-treated group had higher BIC than smooth surface group in both control and diabetic groups. However, there was no significantly statistical difference. Conclusions. Type 1 diabetes mellitus and surface treatment method of mini-implant affected primary stability of mini-implants. In addition, the use of orthodontic mini-implants in a diabetic patient is likely to show results similar to the healthy patient. PMID:24971093

  7. 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

  8. 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.

  9. Dechlorinating chloroacetanilide herbicides by dithionite-treated aquifer sediment and surface soil.

    PubMed

    Boparai, Hardiljeet K; Shea, Patrick J; Comfort, Steve D; Snow, Daniel D

    2006-05-01

    The prevalent use of chloroacetanilide herbicides has resulted in nonpoint contamination of some groundwater and surface water. We determined the efficacy of dithionite-treated sediment and soils to transform chloroacetanilides. When used alone, dithionite rapidly dechlorinates chloroacetanilides in water, with the following order of reactivity: propachlor > alachlor > acetochlor > metolachlor. Stoichiometric release of chloride occurs during reaction with dithionite, and thiosulfate herbicide derivatives are produced. Treating aquifer sediment with dithionite reduces native Fe(lII), creating a redox barrier of Fe(ll)-bearing minerals and surface-bound Fe(ll). Washing the reduced sediment (buffered with citrate-bicarbonate) with oxygen-free water removed Fe(ll) and excess dithionite and no alachlor transformation was observed. In contrast, a dithionite-treated surface soil, rich in clay and iron, effectively dechlorinated alachlor after washing. Exposing alachlor to aquifer sediment treated with dithionite in potassium carbonate buffer (pH 8.5-9.0) produced dechlorinated alachlor as the major degradation product. Our results provide proof-of-concept that dechlorination of chloroacetanilide herbicides by dithionite and dithionite-treated aquifer sediment and soil is a remediation option in natural environments where iron-bearing minerals are abundant. PMID:16719109

  10. 40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (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... manganese ferrite with acrylic ester polymer (generic). (a) Chemical substance and significant new uses... manganese ferrite with acrylic ester polymer (PMN P-09-582) is subject to reporting under this section...

  11. 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.

  12. Surface reconstruction of O2 plasma-treated polystyrene under controlled humidity conditions

    NASA Astrophysics Data System (ADS)

    Li, Junwei; Yu, Hyuk

    2002-03-01

    The time evolution of O2 -plasma treated polystyrene (PS) surfaces was investigated upon storing them under controlled relative humidity conditions. The methods of water contact angle, X-ray photoelectron spectroscopy (XPS), sum frequency generation (SFG) vibrational spectroscopy, and atomic force microscopy were used to evaluate the surface properties and structure. Oxygen containing chemical groups are generated on the PS surface after O2 -plasma treatment, demonstrated by water contact angle and XPS. The surface polarity decays markedly with time, as assessed by steady increase in the water contact angle as a function of the storage time, from zero to around 60^. This is interpreted as arising from surface rearrangement processes to bury polar groups away from the uppermost layer of the surfaces, which is in contact with air with relative humidity (RH) of 5 (that the depth profile of oxygen is essentially constant with respect to time. Thus, we infer that the surface reorganization and the motion of oxygen containing groups are confined within the XPS probing depth. SFG spectroscopy, which is intrinsically interface-specific, was used to detect the chemical structure of PS surface at the molecular level after various storage times. The results are interpreted as follows. During the aging of the plasma treated PS surfaces, the oxygen containing groups undergo reorientation processes toward the polymer bulk, and the PS surface is covered predominantly by CH2 moiety. The asymptotic contact angle however is still around 60^, indicating that the surfaces have not fully reverted to that of the untreated PS. The aging behaviors under different relative humidities are shown to be the same from 5 ((faster in higher relative humidity.

  13. Prebiotic RNA Synthesis by Montmorillonite Catalysis

    NASA Astrophysics Data System (ADS)

    Jheeta, Sohan; Joshi, Prakash C.

    2014-08-01

    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.

  14. 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

  15. Prebiotic RNA synthesis by montmorillonite catalysis.

    PubMed

    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

  16. 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.

  17. Constructing covalent interface in rubber/clay nanocomposite by combining structural modification and interlamellar silylation of montmorillonite.

    PubMed

    Zha, Chao; Wang, Wencai; Lu, Yonglai; Zhang, Liqun

    2014-11-12

    Strong interfacial interaction and nanodispersion are necessary for polymer nanocomposites with expectations on mechanical performance. In this work, montmorillonite (MMT) was first structurally modified by acid treatment to produce more silanol groups on the layer surface. This was followed by chemical modification of ?-methacryloxy propyl trimethoxysilane molecule (KH570) through covalent grafting with the silanol groups. (29)Si and (27)Al magic angle spinning (MAS) NMR results revealed the microstructural changes of MMT after acid treatment and confirmed the increase of silanol groups on acid-treated MMT surfaces. Thermogravimetric analysis indicated an increase in the grafted amount of organosilane on the MMT surface. X-ray diffraction (XRD) showed that the functionalization process changed the highly ordered stacking structure of the MMT mineral into a highly disordered structure, indicating successful grafting of organosilane to the interlayer surface of the crystalline sheets. The styrene-butadiene rubber (SBR)/MMT nanocomposites were further prepared by co-coagulating with SBR latex and grafted-MMT aqueous suspension. During vulcanization, a covalent interface between modified MMT and rubber was established through peroxide-radical-initiated reactions, and layer aggregation was effectively prevented. The SBR/MMT nanocomposites had highly and uniformly dispersed MMT layers, and the covalent interfacial interaction was finally achieved and exhibited high performance. PMID:25322875

  18. 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.

  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. Mechanical, chemical and biological evaluation of energetically treated polymer surfaces for biomedical applications

    NASA Astrophysics Data System (ADS)

    Klapperich, Catherine Mary

    2000-10-01

    Bioengineering is a rapidly emerging field where polymers are finding significant applications. In almost all cases, the surface of a polymer is critical to its performance as a biomaterial. The material properties, fracture strength, friction, wear, corrosion and degradation are all critical variables in the performance of the material. This thesis explores the mechanical behavior, the chemical character and the biological activity of untreated and energetically modified polymer surfaces with an emphasis on ultra high molecular weight polyethylene (UHMWPE). UHMWPE is the primary polymer used in total joint replacements. First, macroscopic friction and wear tests were performed on untreated UHMWPE to determine the tribological properties. Transmission electron microscopy and environmental scanning electron microscopy were used to illustrate the microstructural evolution of the polymer during sliding. A delamination wear model is proposed to explain the wear behavior of UHMWPE. Next, several low temperature radio frequency plasma treatments are described and characterized using contact angle and x-ray photoelectron spectroscopy measurements. The surface mechanical behavior of several untreated polymers (UHMWPE, LDPE, HDPE, PC and PMMA) are characterized using a nanoindentation technique. The plasma treated samples along with two sets of ion (argon and oxygen) beam treated and one set of electron beam crosslinked UHMWPE samples are evaluated and compared using the nanoindentation technique. Elastic modulus and hardness values, along with information about the adhesion and creep behavior of all of the materials are presented. The details and limitations of nanoindentation on polymeric materials are discussed. Finally, the cytotoxicity and hemolytic behavior of the plasma treated UHMWPE surfaces are evaluated using the MTT and hemolysis assays. This study leads to a better understanding of several energetically treated biopolymers and suggests future work for the design of functionally specialized biomaterial surfaces.

  1. Research on cell behavior related to anodized and hydrothermally treated titanium surface

    NASA Astrophysics Data System (ADS)

    Chen, Chin-Sung; Tsao, Yuan-Li; Wang, Duen-Jeng; Ou, Shih-Fu; Cheng, Han-Yi; Chiang, Yi-Chen; Ou, Keng-Liang

    2013-04-01

    In vitro cell response is believed related to the physical and chemical properties of substrate. In this study, the cell adhesion affected by mechanical stimulation from substrate was evaluated by culturing the MG-63 osteoblast-like cells on Ti plates with different chemical composition and surface topography. Three types of surface, surface with machined grooves, with pores, and with pillars, was fabricated by mechanically abraded (control), anodized (AO) and anodized following with hydrothermally treated (HYT) Ti plates, individually. Cells exhibited earlier spreading on the AO and HYT surface after 5 h culturing, resulted from chemical factor, i.e., calcium and phosphate containing on the surface. After 24 h cells completely flattened on the HYT surface but not on the AO surface; this improved cell adhesion behavior was primarily attributed to physical factor that is specific surface topography provides cell relatively large mechanical stimulation. The finite element method was used to evaluate the stress distributions which cells were suffered. For the HYT group, analyzed data indicated that cell received larger stress stimulation than control group (P > 0.01); therefore it can explain the fact that the superior cell adhesion resulted from the specific geometry of HYT coated-surface.

  2. 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.

  3. Flame treatment on plastic: A new surface free energy statistical prediction model and characterization of treated surfaces

    NASA Astrophysics Data System (ADS)

    Mazzola, L.; Bemporad, E.; Carassiti, F.

    2011-01-01

    Flame treatments on polymeric materials improve surface free energy (SFE) and consequently the wettability and adhesion of coatings, metallizations, varnish and glues. In this paper, using a statistical methodological approach based on DoE technique and multivariate analysis of flame treatment process parameters, a mathematical model of SFE and wettability is obtained. Contact angle experimental technique was applied to measure the improvement of wettability and SFE. In order to study the oxygen diffusion within the polymer, morphological variation and change of its structure, analyses of treated surface sample were carried out on micro and nano scales. X-ray photoelectron spectroscopy analysis, performed before and after flame treatment, showed the O-radical group improvement on a polymeric surface. Focused ion beam and transmission electron microscopy technology were used to determine the exact thickness of the polymeric material influenced by flame treatment, identifying a composite change on nano scale and a porosity change on microscale.

  4. 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

  5. Fullerene-containing liquid crystal spatiotemporal light modulators with surface-electromagnetic-wave-treated conducting layers

    NASA Astrophysics Data System (ADS)

    Vasilyev, P. Ya.; Kamanina, N. V.

    2007-01-01

    We have studied the switching characteristics of multilayer electrooptical structures comprising quartz substrates, transparent conducting layers, and an oriented nematic liquid crystal (NLC) film doped with photosensitive charge-transfer complexes based on electrooptically active organic monomer or polymer molecules and fullerenes. The transparent conducting layers treated with surface electromagnetic waves are used for the orientation of NLC molecules. The surface relief with variable permittivity, which is created by this treatment, not only ensures the alignment of NLC molecules, but also significantly influences the relaxation times of the electrooptical mesophase, thus making possible effective control over the switching times of the electrooptical light modulator within 1-1.5 ms.

  6. 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

  7. 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.

  8. Dislodgeable copper, chromium and arsenic from CCA-treated wood surfaces.

    PubMed

    Stilwell, David; Toner, Michael; Sawhney, Brij

    2003-08-01

    Chromated copper arsenate (CCA) is commonly used to preserve wood, but its use poses risk of arsenic exposure. In order to evaluate the extent of exposure to As from physical contact with CCA-treated wood, dislodgeable As from treated wood surfaces (as well as Cu and Cr) was determined as a function of weathering time using dampened polyester wipe materials. Six sets of 2.5-m-long CCA-treated boards, three-four boards per set, were purchased from lumber yards and cut into 30- or 60-cm coupons. A total of 44 such coupons were placed outdoors and the dislodgeable CCA components from the surfaces of the wooden coupons were periodically determined over a 1- or 2-year period by a systematic wipe method followed by nitric acid extraction of the CCA components from the cloth. In all 316 samples, appreciable amounts of the three elements, Cu, Cr and As, were detected. The amounts of surface-dislodgeable As, the most potentially hazardous element and the one of major concern in this study, varied from 5 to 122 microg/100 cm(2) with an average value of 37+/-22 microg/100 cm(2). There was considerable variation in As dislodged among coupons, boards, sets and time. Test coupons that tended to release relatively higher (or lower amounts) over time initially, continued to do so over time. However, the amounts of arsenic dislodged over time did not follow a simple pattern. While the As dislodged tended to decrease with time during the first year, it approached the initial value or increased somewhat during the second year, presumably due to surface rejuvenation effects caused by erosion and weathering. When all the data were normalized to the initial values, no trend emerged, as indicated by the average normalized value of 1.0+/-0.4 for As dislodged over time. Apparently, on installations constructed with CCA-treated wood, arsenic may remain available for a number of years. PMID:12873405

  9. The effects of some laser parameters on the surface and near surface region of laser treated cast iron cylinder bore

    NASA Astrophysics Data System (ADS)

    Mjlinger, K.; Szab, P. J.

    2010-07-01

    The environmental and pollution materials emission standards in Europe are going to be more and more strict. In order to keep the standards, a large European automotive manufacturer makes a laser treatment on the cast iron cylinder bores of the V-engine blocks. Samples of laser treated cast iron cylinder bore with lamellar graphite were investigated. Four samples were treated with Nd-YAG laser and Yb-fiber laser sources in three different configurations. Microhardness measurements were made to evaluate the hardness profile of the treated layer. In order to evaluate the microstructure and grain size of the laser treated layer, scanning electron microscopic (SEM) images were taken in cross section with a SEM/focused ion beam (FIB) dual beam electron microscope. The opened graphite area percent were also determined by image analysis method on the surface after laser treatment with a SEM in backscattered electron (BSE) mode, because the outburned graphite holes are the oil reservoirs for lubrication during operating conditions of the engine.

  10. 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

  11. Effects of pH on dielectric relaxation of montmorillonite, allophane, and imogolite suspensions

    SciTech Connect

    Ishida, Tomoyuki; Makino, Tomoyuki

    1999-04-01

    Dielectric measurements were performed on montmorillonite, allophane, and imogolite suspensions under various pH conditions, using time domain reflectometry over the frequency range 10 kHz--20 GHz. A dielectric relaxation peak due to bound water could be observed for all the clays. Allophane has two peaks, indicating that its peaks are very similar to those of silica-alumina gels. Although imogolite has a similar chemical composition, only one peak was found. The relaxation strength of montmorillonite is greater than that of the other two clays. For all the clays, the relaxation strength depended on the pH. A change in the relaxation strength according to a change in pH is explained in terms of the different network structures of the clay particles. It is suggested that bound water influences the network structure formation. In montmorillonite, a great relaxation process detected at low frequency is caused by surface polarization of counterions. The change in measure of the structural unit with the pH, identified from Schwartz`s theory, has a tendency similar to that postulated by other experimental techniques, and surface charge densities identified are close to those estimated from CEC.

  12. 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.

  13. 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.

  14. Surface properties of low alloy steel treated by plasma nitrocarburizing prior to laser quenching process

    NASA Astrophysics Data System (ADS)

    Wang, Y. X.; Yan, M. F.; Li, B.; Guo, L. X.; Zhang, C. S.; Zhang, Y. X.; Bai, B.; Chen, L.; Long, Z.; Li, R. W.

    2015-04-01

    Laser quenching (LQ) technique is used as a part of duplex treatments to improve the thickness and hardness of the surface layers of steels. The present study is to investigate the surface properties of low alloy steel treated by plasma nitrocarburizing (PNC) prior to a laser quenching process (PNC+LQ). The microstructure and properties of PNC+LQ layer determined are compared with those obtained by PNC and LQ processes. OM, XRD, SEM and EDS analyses are utilized for microstructure observation, phases identification, morphology observation and chemical composition detection, respectively. Microhardness tester and pin-on-disc tribometer are used to investigate the mechanical properties of the modified layers. Laser quenching of plasma nitrocarburized (PNC+LQ) steel results in much improved thickness and hardness of the modified layer in comparison with the PNC or LQ treated specimens. The mechanism is that the introduction of trace of nitrogen decreases the eutectoid point, that is, the transformation hardened region is enlarged under the same temperature distribution. Moreover, the layer treated by PNC+LQ process exhibits enhanced wear resistance, due to the lubrication effect and optimized impact toughness, which is contributed to the formation of oxide film consisting of low nitrogen compound (FeN0.076) and iron oxidation (mainly of Fe3O4).

  15. 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.

  16. Montmorillonite-induced Bacteriophage ?6 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 ?6 is investigated. ?6 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, ?6 serves as a model for reoviruses, a human pathogen. Experiments were conducted with ?6 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 ?6 virus and its P. syringae host cells. TEM of aggregate showing several disassembled NCs.

  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. 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.

  19. 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

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

    PubMed

    Akpomie, Kovo G; Dawodu, Folasegun A

    2015-11-01

    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 0.1g, particle size of 100?m and equilibrium contact time of 180min. 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 (5.7mg/g)>Cu (1.58mg/g)>Mn (0.59mg/g)>Cd (0.33mg/g)>Pb (0.10mg/g)?Ni (0.10mg/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

  1. Influence of organic ligands on Cr desorption from hydroxy-Cr intercalated montmorillonite.

    PubMed

    Dubbin, William E

    2004-02-01

    Retention of metals as hydroxy precipitates on mineral surfaces is an important process maintaining environmental quality. Hydroxy precipitates of Cr(III) are particularly important because appreciable mobilisation of intercalated, hydrolysed Cr from montmorillonite is currently thought to occur only via oxidative dissolution. The present study examines the potential of oxalate, tartrate, and citrate to desorb Cr from both hydroxy-Cr and hydroxy Al-Cr precipitates sorbed to montmorillonite. For all intercalated clays there was an initial very rapid dissolution, followed by a slow but sustained Cr release that more closely followed a parabolic rate law, the latter indicative of transport-controlled dissolution. The initial rapid dissolution persisted longer for the pure Cr clay ( approximately 48 h) than for the coprecipitated Al-Cr clay ( approximately 24 h). At the end of the 30 d reaction, however, most Cr remained sorbed to the montmorillonite in all systems. Citrate, for example, solubilised only approximately 10% of the total sorbed Cr from the pure Cr clays. Aluminum presence decreased Cr solubilisation rate due to Al accumulation at the polymer margins. Moreover, Al presence maintained the integrity of the intercalated polymers and prevented c-axis expansion beyond 1.4 nm, thus restricting the supply of organic ligand to the inter-layer region. Oxalate, tartrate, and citrate were shown to be effective chelators of sorbed Cr and these ligands may therefore play an important role in the mobilisation and cycling of this metal in soils and sediments. PMID:14664835

  2. 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.

    2016-01-20

    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

  3. 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.

  4. 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.

  5. Adhesion strength measurements of excimer-laser-treated PTFE surfaces using liquid photoreagents

    NASA Astrophysics Data System (ADS)

    Hopp, Bela; Smausz, Tomi; Kresz, Norbert; Ignacz, Ferenc

    2003-04-01

    The most known feature of polytetrafluoroethylene (PTFE) is its adhesion behavior: it is hydrophobic and oleophobic at the same time. This can cause serious problems and obstacles during the surface treatment and fixing of PTFE objects. During our experiments Teflon films were irradiated by an ArF excimer laser beam in presence of liquid photoreagents containing amine groups (aminoethanol, 1,2-diaminoethane, triethylene-tetramine). In consequence of the treatment the adhesion of the modified surfaces significantly increased, the samples could be glued and moistened. The adhesion strength of the glued surfaces was measured in the function of the applied laser fluence. The adhesion strength increased drastically between 0 - 1 mJ/cm2 and showed saturation above 1 mJ/cm2 at approximately 5 - 9 MPa values depending on the applied photoreagents. On the basis of our experiments it was found that the treatment with triethylene-tetramine was the most effective. The surface chemical modifications of the treated Teflon samples can be due to the incorporation of amine groups into the surface layer.

  6. Disassembly of the cystovirus ?6 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 ?6 used in this study is a good model for enveloped pathogens. The interaction between ?6 and montmorillonite (MMT) clay (the primary component of bentonite) is explored by transmission electron microscopy. The analyses show that MMT-?6 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

  7. Adsorption of cytochrome c on montmorillonite nanoplates: protein concentration dependence.

    PubMed

    Hristova, Svetlana H; Zhivkov, Alexandar M

    2015-05-15

    Cytochrome c [cytC] is a mitochondrial hemoprotein functioning as electron carrier in the respiratory chain of the biological cells. Being adsorbed on colloid particles cytC can be introduced in the cells by phagocytoses. In the present work we study the adsorption of cytC on montmorillonite (MM) particles combining the electro-optic and electrophoretic techniques. MM particles were chosen as nanoplates having negative pH-independent charge and high ratio surface/mass. The measurements were done at pH 6.5 where cytC globule is positively charged. The main employed method is the electric light scattering based on orientation of colloid particles in sinusoidal electric field. Interfacial electric polarizability was obtained from the degree of orientation at steady-state and the particle size - from the relaxation time after the field switching off. Microelectrophoresis was used to monitor the alteration of the surface charge at protein adsorption. The cytC-concentration dependence of the polarizability and the mobility shows out that the total (net) charge of cytC-MM complex turns its sign from negative to positive, the isoelectric point appears at 5:3 mg/mg (0.135 mol/kg) cytC/MM and saturated protein adsorption is reached at additional twofold increasing of cytC/MM ratio. The suspension is stable at low and high protein concentrations, at intermediate ones aggregation arises. PMID:25678159

  8. Disassembly of the cystovirus ?6 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 clayvirus 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 ?6 used in this study is a good model for enveloped pathogens. The interaction between ?6 and montmorillonite (MMT) clay (the primary component of bentonite) is explored by transmission electron microscopy. The analyses show that MMT?6 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

  9. 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.

  10. 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.

  11. 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

  12. 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.

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

    PubMed

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

    2014-10-20

    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

  14. 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

  15. 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

  16. 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 CO 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

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. Infrared study of HDTMA+ intercalated montmorillonite.

    PubMed

    Hongping, He; Ray, Frost L; Jianxi, Zhu

    2004-10-01

    In this paper, FTIR spectroscopy using attenuated total reflection (ATR) and KBr pressed disk techniques has been used to characterize sorbed water and HDTMA+ in organo-clay. Sorbed water content decreases with the intercalation of HDTMA+. With the decrease of the sorbed water content, the position of the nu2 mode shifts to higher frequency dramatically while the stretching vibration shifts to lower frequency slightly, indicating that H2O is less strongly hydrogen bonded. This might be resulted from the polarization of H2O molecules by the changeable cations and HDTMA+. FTIR spectra show that both antisymmetric and symmetric CH2 stretching absorption bands shift to low frequencies with increase of amine concentration within the galleries of montmorillonite, elucidating the increase of ordered conformation. Furthermore, the present study demonstrates that the antisymmetric CH2 stretching mode is more sensitive to the conformational ordering than the symmetric stretching mode. When KBr pressed disk technique used, two well resolved absorption bands at 730 and 720 cm(-1), and at 1473 and 1463 cm(-1), corresponding to the methylene scissoring and rocking modes, respectively, could be observed in FTIR spectra of organo-clays with relative higher concentration of surfactant. However, the FTIR spectra using ATR technique only display singlets and they are independent of amine concentration and chain conformation. Our present study demonstrates that FTIR spectroscopy using KBr pressed disk technique is more suitable to probe the conformational ordering of surfactant in organo-clays than that suing ATR technique does. PMID:15350922

  3. 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 catalysts 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

  4. 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

  5. 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

  6. 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.

  7. Oxidation mechanism of the ammonium-fluoride-treated Si(100) surface

    SciTech Connect

    Kluth, G.J.; Maboudian, R.

    1996-11-01

    High-resolution electron energy loss (HREEL) spectroscopy, Auger electron spectroscopy, and low-energy electron diffraction have been employed to examine the initial oxidation stage of ammonium-fluoride-treated Si(100) surfaces exposed to air. The NH{sub 4}F treatment results in a hydrogen-terminated surface, as shown by the presence of the Si{endash}H stretch (2100 cm{sup {minus}1}), SiH{sub 2} scissor (910 cm{sup {minus}1}), and SiH bend (650 cm{sup {minus}1}) in the HREEL spectra. Initial oxidation on this surface occurs through oxygen insertion in the silicon backbonds, as indicated by the presence of the asymmetric bridge-bonded oxygen stretch in the region between 1060 and 1160 cm{sup {minus}1}. Oxygen is observed in both surface and bulk bridge-bonding sites for even the shortest air exposures, suggesting that initial oxygen uptake is not taking place in a layer-by-layer fashion. Auger electron spectroscopy shows a slow uptake of oxygen over the first few days of air exposure, followed by more rapid oxidation. Over the first two weeks of air exposure, the Si{endash}H stretch at 2100 cm{sup {minus}1} gradually disappears, accompanied by the appearance of oxygen backbonded Si{endash}H peaks around 2250 cm{sup {minus}1}. This behavior indicates that, despite the increase in oxygen uptake, the hydrogen termination remains intact, and further confirms that oxygen uptake occurs through insertion in the silicon backbonds. Water is found to play a significant role in the initial oxidation. {copyright} {ital 1996 American Institute of Physics.}

  8. Structure of tetraalkylammonium ionic liquids in the interlayer of modified montmorillonite

    NASA Astrophysics Data System (ADS)

    Duarte, Daniel; Salanne, Mathieu; Rotenberg, Benjamin; Bizeto, Marcos A.; Siqueira, Leonardo J. A.

    2014-07-01

    We perform molecular dynamics simulations of tetraalkylammonium ionic liquids confined in the interlayer of montmorillonite (MMT). We study the structure and energetics of the systems, which consist of cations with two different alkyl chain lengths and several ionic liquid concentrations. The results we obtained for the structure, namely the presence of a strong layering in all systems and the formation of nonpolar domains with interdigitated alkyl chains in some cases, are largely consistent with previous surface force balance experiments performed on similar systems. Finally, we show that swelling of the organo-modified MMT by a large amount of ionic liquid seems energetically favorable in all cases.

  9. Structure of tetraalkylammonium ionic liquids in the interlayer of modified montmorillonite.

    PubMed

    Duarte, Daniel; Salanne, Mathieu; Rotenberg, Benjamin; Bizeto, Marcos A; Siqueira, Leonardo J A

    2014-07-16

    We perform molecular dynamics simulations of tetraalkylammonium ionic liquids confined in the interlayer of montmorillonite (MMT). We study the structure and energetics of the systems, which consist of cations with two different alkyl chain lengths and several ionic liquid concentrations. The results we obtained for the structure, namely the presence of a strong layering in all systems and the formation of nonpolar domains with interdigitated alkyl chains in some cases, are largely consistent with previous surface force balance experiments performed on similar systems. Finally, we show that swelling of the organo-modified MMT by a large amount of ionic liquid seems energetically favorable in all cases. PMID:24920411

  10. 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

  11. 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.

  12. LiBr treated porous silicon used for efficient surface passivation of crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Zarroug, Ahmed; Haddadi, Ikbel; Derbali, Lotfi; Ezzaouia, Hatem

    2015-04-01

    A simple but effective passivation method of both front and rear surfaces using porous silicon (PS) has been developed. This paper investigates the effect of LiBr on the passivation of PS. The immersion of as-etched PS in dilute LiBr solution followed by an annealing in an infrared furnace, under a controlled atmosphere at different temperatures, led to the passivation of the PS layer and the improvement of the electronic properties of the crystalline silicon substrates. The influence of substrate temperature was investigated, since the processed wafers were found to be sensitive to heat, which in turn was optimized to have a gettering effect. The bromide of lithium can effectively saturate dangling bonds and hence contributed to the formation of a stable passivation film, at both front and back surfaces. Such a reaction was found to have a beneficial effect on the passivation process of the PS layer grown on both sides. The obtained results exhibited a significant improvement of the minority carrier lifetime, which is an important parameter that defines the quality of crystalline silicon substrates, and an apparent enhancement of its photoluminescence (PL). The internal quantum efficiency was investigated and found to be significantly improved. The qualitative effect of the above-mentioned procedure proved a significant enhancement of the electronic quality of the treated substrates.

  13. 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.

  14. 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.

  15. Formation of RNA Oligomers on Montmorillonite: Site of Catalysis

    NASA Astrophysics Data System (ADS)

    Ertem, Gzen; Ferris, James P.

    1998-10-01

    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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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

  1. The Effect of Surface Treated Nanoparticles on Single and Multi-Phase Flow in Porous Media

    NASA Astrophysics Data System (ADS)

    DiCarlo, D. A.; Aminzadeh, B.; Chung, D.; Zhang, X.; Wung, R.; Huh, C.; Bryant, S. L.

    2013-12-01

    Surface treated nanoparticles have been suggested to be an additive to CO2 storage scenarios. This is because 1) the nanoparticles have been shown to freely transport through permeable media, and 2) the nanoparticles can stabilize a CO2 in water foam by adhering to the surface of CO2 bubbles/droplets preventing their coalescence. In terms of storage, The formation of CO2 foam will limit the CO2 mobility which can potentially help limit the CO2 leakage. Here, we will show how nanoparticles in porous media can have many interesting properties in single and multi-phase flow. For multi-phase CO2, we have performed experiments where high pressure liquid CO2 displaces brine and vice versa with and without nanoparticles in the brine. We measure the displacement pattern and in-situ CO2 saturation using CT scanning and measure the pressure drop using pressure transducers. We find that the flow is less preferential and the pressure drop is greater than when nanoparticles are present. This suggest the formation of in-situ foam/emulsion. We also show that on a brine chase, the residual saturation of CO2 is greater in the presence of nanoparticles. In terms of nanoparticle transport, it is observed that nanoparticles accumulate at the front of a brine/octane displacement. We hypothesize that this occurs due to the nanoparticles being size excluded from portions of the pore-space. To determine if this occurs in single phase flow, we have also performed experiments single-phase flow with the nanoparticles and tracer. We find that the nanoparticles arrive roughly 5% faster than the tracer. This also has implications for the positioning of nanoparticles in the pore space and how this can change the effective viscosity of the nanoparticle suspension.

  2. 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.

  3. 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

  4. 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.

  5. Synthesis of silver/montmorillonite nanocomposites using ?-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 ?-irradiation technique in the absence of any reducing agent or heat treatment. Silver nitrate and ?-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 ?-irradiation technique. The properties of Ag/MMT nanocomposites and the diameters of Ag-NPs were studied as a function of ?-irradiation doses. The interlamellar space limited particle growth (d-spacing [ds] = 1.241.42 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 21.5730.63 nm. Scanning electron microscopy images indicated that there were structure changes between the initial MMT and Ag/MMT nanocomposites under the increased doses of ?-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 ?-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 ?-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

  6. Properties of aged montmorillonite-wheat gluten composite films.

    PubMed

    Olabarrieta, Idoia; Gllstedt, Mikael; Ispizua, Iban; Sarasua, Jose-Ramon; Hedenqvist, Mikael S

    2006-02-22

    The properties of new and aged glycerol-plasticized vital wheat gluten films containing < or =4.5 wt % natural or quaternary ammonium salt modified montmorillonite clay were investigated. The films were cast from pH 4 or pH 11 ethanol/water solutions. The films, aged for < or =120 days, were characterized by tensile testing, X-ray diffraction, and transmission electron microscopy. In addition, water vapor permeability (11% relative humidity) and the content of volatile components were measured. The large reduction in the water vapor permeability with respect to the pristine polymer suggests that the clay platelets were evenly distributed within the films and oriented preferably with the platelet long axis parallel to the film surface. The film prepared from pH 11 solution containing natural clay was, as revealed by transmission electron microscopy and X-ray diffraction, almost completely exfoliated. This film was consequently also the strongest, the stiffest, and the most brittle and, together with the pH 11 film containing modified clay, it also showed the greatest decrease in water vapor permeability. The large blocking effect of the clay had no effect on the aging kinetics of the films. During aging, the pH 4 and pH 11 film strength and the pH 4 film stiffness increased and the pH 4 film ductility decreased at the same rate with or without clay. This suggests that the aging was not diffusion rate limited, that is, that the loss of volatile components or the migration of glycerol or glycerol/wheat gluten phase separation was not limited by diffusion kinetics. The aging rate seemed to be determined by slow structural changes, possibly involving protein denaturation and aggregation processes. PMID:16478249

  7. First Low-Iron Materials on Mars and Possibility of a Major Montmorillonite Component

    NASA Astrophysics Data System (ADS)

    Clark, B. C.; Richter, L.; Gellert, R.; Farrand, W.; Ming, D. W.; Morris, R. V.; Yen, A.

    2005-12-01

    During exploration of Columbia Hills at Gusev crater, the Spirit rover of the MER mission has discovered several separate occurrences of material with a unique elemental signature. As measured by x-ray fluorescence emission using the APXS instrument, these samples stand out for their low Fe content, accompanied by corresponding increases in Al and Si but without high concentrations of mineralogically important cations such as Ca, Mg, Na, or K. No previous martian samples, from five landed missions and numerous martian meteorites, have such low iron content. Chemical trends implicate Mg sulfates and Ca phosphates are important but minor accessory minerals. Moessbauer analysis indicates some or all Ti to be present as ilmenite. The remaining component has high Al and Si abundances in proportions within the range of classical montmorillonite compositions found at various locations on Earth, including their correspondingly low concentrations of major cations. Typically the result of weathering of basaltic ash and often associated with more arid environments, the formation of montmorillonite or its alteration-product precursor implies that significant aqueous activity to facilitate geochemical separations occurred. In addition, various of these samples contain trace element anomalies that are unique for martian materials, including enrichments in Cu, Ni, Y, Ga, Cr, and possibly Pb, Co, Sr, and Zn. Adsorption by high cation exchange minerals such as montmorillonite clays or other alteration materials (allophane, silica, imogolite) often bear similar fingerprints due to their high-area charged surfaces which confer affinities for multivalent metal ions in solution. Samples of this "Independence Class" of materials have been found at three separated sites in the upper portion of Husband Hill. The samples are disparate in form, including clods (or peds), an outcrop, and a "rock". Their lighter color and rugged morphology are a common feature. The latter may indicate susceptibility to fragmentation, with possible derivation from a deeper-lying layer of source material.

  8. 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

  9. Uranium uptake by hectorite and montmorillonite: a solution chemistry and polarized EXAFS study.

    PubMed

    Schlegel, Michel L; Descostes, Michael

    2009-11-15

    The mechanism of U(VI) retention on montmorillonite and hectorite at high ionic strength (0.5 M NaCl) was investigated by solution chemistry and, at near-neutral pH, polarized EXAFS spectroscopy. Uranium(VI) sorption increases from pH 3 to 7 on the two clays, but with a steeper edge for hectorite. Uranium(VI) is no longer retained at pH > 9, presumably owing to the formation of soluble anionic complexes. Polarized EXAFS showed that U(VI) retains its uranyl conformation on montmorillonite (U_mont) and hectorite (U_hect), with uranyl O at 1.79(2) A for U_mont and 1.82(2) A for U_hect, and split equatorial O shells at 2.29(2) and 2.47(2) A (U_mont), or 2.35(2) and 2.53(2) A (U_hect). An additional atomic shell of approximately 0.5 Al/Si at 3.3 A is detected for U_mont, but neither the oxygen nor the cationic shell exhibit clear angular dependence. These results indicate the formation of mononuclear complexes at the edges of montmorillonite platelets, with the orientation of the uranyl axis equal to the magic angle, as constrained by the edges' structural properties. In contrast to U_mont, the U-O signal varies with the polarization angle in U_hect, and the cationic Mg/Si contribution at 3.2 A is weak. The structure of this surface complex is not completely elucidated; it may correspond either to sorption on silanol sites, or to coprecipitation. These results lay out the fundamental molecular-scale basis to understand U retention by neoformed clay layers of nuclear glasses. PMID:20028057

  10. 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

  11. 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.

  12. 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

  13. Synergistic effect of cationic and anionic surfactants for the modification of Ca-montmorillonite

    SciTech Connect

    Zhang, Zepeng; Zhang, Jichu; Liao, Libing; Xia, Zhiguo

    2013-05-15

    Highlights: ? The basal spacing of MMTCTABSDS reaches 5.30 nm. ? MMTCTABSDS shows perfect dispersion property and excellent heat resistance. ? SDS helped to improve the heat resistance and decrease the surface energy of the MMTCTABSDS particles. - Abstract: The synergistic effect of cationic surfactant (CTAB) and anionic surfactant (SDS) for the modification of Ca-montmorillonite (Ca-MMT) has been developed, and the novel cationanion modified organomontmorillonite (MMTCTABSDS) was prepared. X-ray diffraction (XRD) analysis indicates that the interlayer spacing of montmorillonite was well expanded by the intercalation of CTAB and SDS and the basal spacing increased from 1.54 nm (Ca-MMT) to 5.30 nm (MMTCTABSDS). Thermogravimetric analysis (TG) showed that the MMTCTABSDS displayed excellent heat resistance. Scanning electron microscopy (SEM) analysis proved that the MMTCTABSDS exhibited excellent dispersion property and the plates with few silicate layers can be observed. Contact angle tests indicated that the hydrophilicity of MMTCTABSDS was lower than that of Ca-MMT and higher than that of MMTCTAB. It was verified that SDS contributed to expanding the interlayer space, further improved the heat resistance of the MMTCTAB and decreased the surface energy of the MMTCTABSDS particles.

  14. 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.

  15. Interfacial interaction of in situ Cu growth on tetrasulfide self-assembled monolayer on plasma treated parylene surface

    SciTech Connect

    Pimanpang, S.; Wang, Pei-I; Juneja, Jasbir S.; Wang, G.-C.; Lu, T.-M.

    2006-09-15

    The interfacial reactions of in situ grown Cu and functionalized parylene surfaces were examined using the x-ray photoelectron spectroscopy (XPS). It is observed that bis[3(triethoxysilane)propyl]tetrasulfide (tetrasulfide) forms a self-assembled monolayer (SAM) only on a parylene surface treated with either He plasma or N{sub 2} plasma, but not on the as-deposited parylene surface due to its lack of functional groups. The functional groups on the plasma treated parylene surface facilitate the formation of tetrasulfide SAM that subsequently improves the reactivity of parylene to Cu. The XPS spectra show a strong shift ({approx}1.1 eV) of the S 2p peaks from a higher binding energy to a lower binding energy, which suggests the existence of an interaction between sulfide and Cu. In addition, the result of a higher XPS intensity ratio of Cu 2p{sub 3/2}/C 1s for Cu growth on tetrasulfide SAM/plasma treated parylene surface than that of an as-deposited parylene surface indicates that the formation of tetrasulfide moiety (-SSSS-) on functionalized parylene surface leads to the increase of Cu growth rate.

  16. 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.

  17. 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 (?) 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.

  18. Knockdown and mortality of adults of eight species of stored-product beetles exposed to four surfaces treated with spinosad.

    PubMed

    Toews, Michael D; Subramanyam, Bhadriraju; Rowan, Jaclyn M

    2003-12-01

    Contact toxicity of a commercial bacterial fermentation insecticide, spinosad, to adults of eight stored-product beetles was evaluated on four different surfaces. Aqueous spinosad suspension was sprayed with an airbrush to 30.5-cm2 surfaces of concrete, galvanized steel, unwaxed floor tile, or waxed floor tile to obtain deposits of 0.05 or 0.1 mg (AI)/cm2. Control surfaces were sprayed with distilled water. Approximately 24 h after distilled water or spinosad application, 30 adult beetles were confined, by species, to each untreated and spinosad-treated surface. Insects on surfaces were exposed for 24 h to assess knockdown at 25 +/- 1 degree C and 50 +/- 10% RH, and then were held on food for an additional 24 h to assess mortality. Knockdown and mortality of each insect species on all four surfaces were significantly greater on spinosad-treated surfaces than on distilled water-treated surfaces. Knockdown and mortality of all species on all surfaces was similar at the two spinosad deposit levels. Except for Tribolium spp., mortality of all other species exposed to spinosad was 99-100%. Tribolium spp. were highly susceptible to spinosad on concrete (98-100% mortality); however, on unwaxed floor tile, steel, and waxed floor tile recovery on food after knockdown resulted in only 72-92% mortality. Our results suggest that spinosad has excellent contact activity against adults of stored-product insects, especially on concrete, and has potential for use as a general surface, spot, or crack/crevice spray to control insects in empty bins, warehouses, food-processing facilities, and retail stores. PMID:14977140

  19. 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.

  20. Effect of reactive species on surface crosslinking of plasma-treated polymers investigated by surface force microscopy

    NASA Astrophysics Data System (ADS)

    Tajima, S.; Komvopoulos, K.

    2006-09-01

    Polymer surface modification by ions, uncharged particles, and photons of inductively coupled Ar plasma was investigated with a surface force microscope. Optical windows consisting of crystals with different cutoff wavelengths and a metal shield were used to deconvolute the effects of the various plasma species on the modification of the surface nanomechanical properties of polyethylene. The extent of surface crosslinking was related to the frictional energy dissipated during nanoscratching. It is shown that surface crosslinking is primarily due to the simultaneous effects of uncharged particles and vacuum ultraviolet photons, while the ion bombardment effect is secondary.

  1. 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

  2. Surface characteristics and osteoblastic cell response of alkali-and heat-treated titanium-8tantalum-3niobium alloy

    PubMed Central

    Lee, Bo-Ah; Kang, Choong-Hee; Vang, Mong-Sook; Jung, Young-Suk; Piao, Xing Hui; Kim, Ok-Su; Chung, Hyun-Ju

    2012-01-01

    Purpose The aim of the present study was to evaluate the biological response of alkali- and heat-treated titanium-8tantalum-3niobium surfaces by cell proliferation and alkaline phosphatase (ALP) activity analysis. Methods Commercial pure titanium (group cp-Ti) and alkali- and heat-treated titanium-8tantalum-3niobium (group AHT) disks were prepared. The surface properties were evaluated using scanning electron microscopy, energy dispersed spectroscopy and X-ray photoelectron spectroscopy (XPS). The surface roughness was evaluated by atomic force microscopy and a profilometer. The contact angle and surface energy were also analyzed. The biological response of fetal rat calvarial cells on group AHT was assessed by cell proliferation and ALP activity. Results Group AHT showed a flake-like morphology microprofile and dense structure. XPS analysis of group AHT showed an increased amount of oxygen in the basic hydroxyl residue of titanium hydroxide groups compared with group cp-Ti. The surface roughness (Ra) measured by a profilometer showed no significant difference (P>0.05). Group AHT showed a lower contact angle and higher surface energy than group cp-Ti. Cell proliferation on group AHT surfaces was significantly higher than on group cp-Ti surfaces (P<0.05). In comparison to group cp-Ti, group AHT enhanced ALP activity (P<0.05). Conclusions These results suggest that group AHT stimulates osteoblast differentiation. PMID:23346470

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

    PubMed Central

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

    2012-01-01

    The cell migration plays a crucial role in a variety of physiological and pathological processes and can be regulated by the cellsubstrate interactions. We found previously that the poly(sodium 4-styrenesulphonate) (PSS)/poly(diallyldimethylammonium) chloride (PDADMAC) multilayers post-treated in 15 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

  4. 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

  5. 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.

  6. 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.

  7. Characterization and Catalytic Performance of Montmorillonites with Mixed Aluminium/Lanthanide Pillars

    NASA Astrophysics Data System (ADS)

    Gonzlez, F.; Pesquera, C.; Blanco, C.

    Pillared montmorillonites with mixed Al/lanthanide pillars were prepared. The materials present characteristics that are very different from montmorillonite pillared with only aluminium. Nuclear magnetic resonance studies indicated total absence of tetrahedral aluminium in the pillars when lanthanide cations are incorporated between the clay layers. They have a high thermal stability, high specific surface area and porosity, with pores at the limit between the microporosity and mesoporosity. The textural parameters maintained high values up to 700 C. The number and the strength of the acid sites in these materials were also high. The increase of the conversion in dehydration of 1-butanol as in hydroisomerization of n-heptane shows their better behaviour as acid catalysts. The Al/lanthanide-pillared samples showed increased conversion and improved the selectivity towards the products of cracking. The study of 1-butanol dehydration showed that there is an increase in the acidity, thermal stability and smaller deactivation by carbonaceous deposits in the Al/lanthanide-pillared sample.

  8. Binding of adenine and adenine-related compounds to the clay montmorillonite and the mineral hydroxylapatite.

    PubMed

    Winter, D; Zubay, G

    1995-06-01

    The first living things may have consisted of no more than RNA or RNA-like molecules bound to the surfaces of mineral particles. A key aspect of this theory is that these mineral particles have binding sites for RNA and its prebiotic precursors. The object of this study is to explore the binding properties of two of the best studied minerals, montmorillonite and hydroxylapatite, for possible precursors of RNA. The list of compounds investigated includes purines, pyrimidines, nucleosides, nucleotides, nucleotide coenzymes, diaminomaleonitrile and aminoimidazole carboxamide. Affinities for hydroxylapatite are dominated by ionic interactions between negatively charged small molecules and positively charged sites in the mineral. Binding to montmorillonite presents a more complex picture. These clay particles have a high affinity for organic ring structures which is augmented if they are positively charged. This binding probably takes place on the negatively charged faces of these sheet-like clay particles. Additional binding sites on the edges of these sheets have a moderate affinity for negatively charged molecules. Small molecules that bind to these minerals sometimes bind independently to sites on the minerals and sometimes bind cooperatively with favorable interactions between the bound molecules. PMID:11536682

  9. Adsorption of cationic monomeric and gemini surfactants on montmorillonite and adsolubilization of vitamin E.

    PubMed

    Sakai, Kenichi; Nakajima, Erimi; Takamatsu, Yuichiro; Sharma, Suraj C; Torigoe, Kanjiro; Yoshimura, Tomokazu; Esumi, Kunio; Sakai, Hideki; Abe, Masahiko

    2008-01-01

    Adsorption of a cationic gemini surfactant (1,2-bis(dodecyldimethylammonio) ethane dibromide, 12-2-12) and the corresponding monomeric surfactant (dodecyltrimethylammonium bromide, DTAB) on montmorillonite has been characterized with a combination of adsorption isotherm, interlayer spacing and FT-IR spectroscopic data. Adsolubilization of vitamin E into the adsorbed surfactant layers has also been studied. The adsorption isotherm data reveal that the adsorption of the two surfactants is driven by the two factors: one is the cation exchange that occurs on the interlayer basal planes and the other is the hydrophobic interaction between hydrocarbon chains of the surfactants. Although the adsorbed amount measured in the saturation region (in mol g(-1)) is almost identical for the two surfactants, the conformation of the intercalated surfactant molecules differs significantly from each other. The adsorption of DTAB results in a lateral bilayer arrangement in the limited interlayer space, whereas 12-2-12 gives a normal bilayer arrangement in the expanded interlayer space. Adsolubilization of vitamin E takes place into the adsorbed surfactant layers, and interestingly, all the vitamin E molecules added in the montmorillonite suspensions are hybridized at lower surfactant concentrations due to the great specific surface area of the clay material. Since the maximum adsolubilization amount is usually obtained just below the critical micelle concentration, the gemini surfactant is deemed to be more efficient than the corresponding monomeric one to achieve the great adsolubilization amount. PMID:18622125

  10. Sorption of chlorimuron-ethyl on montmorillonite clays: effects of exchangeable cations, pH, and ionic strength.

    PubMed

    Ren, Wenjie; Teng, Ying; Zhou, Qixing; Paschke, Albrecht; Schrmann, Gerrit

    2014-10-01

    Sorption interaction of chlorimuron-ethyl with montmorillonite clays was investigated under varied types of exchangeable cation, pH, and ionic strength conditions. Chlorimuron-ethyl sorption on bentonites exhibited pronounced cation dependency, and the sorption ability increased as the sequence Ca(2+)- < Na(+)- < Al(3+)- < Fe(3+)-bentonite, due to different sorption mechanisms, whereas the cation dependency was influenced by the clay type and much weaker for montmorillonites. The decrease of pH at the range of 4.0-6.0 prominently increased sorption of chlorimuron-ethyl on all cation-exchanged montmorillonite clays, and nearly a neglected sorption (about 2 %) can be observed at pH over 7.0. In the presence of CaCl2, sorption of chlorimuron-ethyl on Fe(3+)-bentonite was promoted because of complexion of Ca(2+) and the surface of Fe(3+)-bentonite. However, as the concentration of CaCl2 increased, chlorimuron-ethyl sorption on Ca(2+)- and Fe(3+)-exchanged bentonite decreased, suggesting that Ca bridging was not the prevailing mechanism for sorption of chlorimuron-ethyl on these clays. Furthermore, chlorimuron-ethyl sorption was relatively sensitive to pH, and the change of pH may obscure effect of other factors on the sorption, so it was quite necessary to control pH at a constant value when the effect of other factor was being studied. PMID:25028319

  11. Influence of surface topography and pore architecture of alkali-treated titanium on in vitro apatite deposition

    NASA Astrophysics Data System (ADS)

    Ravelingien, Matthieu; Hervent, Anne-Sophie; Mullens, Steven; Luyten, Jan; Vervaet, Chris; Remon, Jean Paul

    2010-03-01

    Alkali-treated titanium surfaces have earlier shown to induce bone-like apatite deposition. In the present study, the effect of surface topography of two-dimensional and pore architecture of three-dimensional alkali-treated titanium substrates on the in vitro bioactivity was investigated. Titanium plates with a surface roughness of Ra = 0.13 ?m, 0.56 ?m, 0.83 ?m, and 3.63 ?m were prepared by Al 2O 3 grit-blasting. Simple tetragonal and face-centered Ti6Al4V scaffolds with spatial gaps of 450-1100 ?m and 200-700 ?m, respectively, were fabricated by a three-dimensional fiber deposition (3DFD) technique. After alkali treatment, the titanium plates with a surface roughness of Ra = 0.56 ?m were completely covered with hydroxyapatite globules after 7 days in simulated body fluid (SBF), while the coverage of the samples with other surface roughness values remained incomplete. Similarly, face-centered Ti 6Al 4 scaffolds with spatial gaps of 200-700 ?m exhibited a full surface coverage after 21 days in SBF, while simple tetragonal scaffolds with spatial gaps of 450-1100 ?m were only covered for 45-65%. This indicates the importance of surface topography and pore architecture for in vitro bioactivity.

  12. 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...

  13. 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.

  14. The role of fluoride in montmorillonite-catalyzed RNA synthesis.

    PubMed

    Aldersley, Michael F; Joshi, Prakash C

    2014-05-01

    The montmorillonite-catalyzed reactions of the 5'-phosphorimidazolide of adenosine in the presence of fluoride were investigated to complete our study on the effect of salts on this type of reaction. Both anions and cations have been found to influence the oligomerization reactions of the activated nucleotides, being used here as a model system for pre-biotic RNA synthesis. However, in total contrast to the behavior of the activated nucleotides in the presence of montmorillonite and other salts, alkali metal fluorides did not yield any detectable oligomerization products except in very dilute (<0.005 M) solutions of fluoride. Instead, 5'-phosphorofluoridates were formed. Their identity was confirmed by a combination of HPLC, mass spectrometry, synthesis, and NMR. PMID:24756181

  15. 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.

  16. 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

  17. 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

  18. Characterization of wet-chemically treated silicon interfaces by surface photovoltage measurements.

    PubMed

    Angermann, H

    2002-10-01

    A non-destructive and surface-sensitive surface photovoltage (SPV) technique was employed to investigate the influence of important wet-chemical treatments on the electronic surface properties. The preparation-induced surface roughness as well as the hydrogen and oxide coverage were additionally determined by spectroscopic ellipsometry (SE). High values of interface charge and a high density of rechargeable interface states were observed on atomically rough surfaces and interfaces after HF-treatment and conventional wet-chemical oxidation. Both interface charge and density of rechargeable interface states could be reduced significantly by preparing an atomically flat Si surface and a well-ordered silicon/silicon oxide interface by applying special H-termination and hot-water oxidation procedures. PMID:12397491

  19. 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?=?316 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: MarsOrigin of lifeMontmorilloniteMineral catalysisLayer charge densityXray diffractometry. Astrobiology 10, 743749. PMID:20854214

  20. 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.

  1. 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.

  2. 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

  3. 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 ? = 50 ?s. 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.

  4. Analysis of Defects on Chemically-Treated CdZnTe Surfaces

    NASA Astrophysics Data System (ADS)

    Hossain, A.; Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; Gul, R.; Kim, K.-H.; Roy, U. N.; Tong, X.; Yang, G.; James, R. B.

    2015-09-01

    In this work, we focused on investigating the various defects that extend into the near-surface region of CdZnTe (CZT) crystals, and on exploring processing techniques for producing a smooth, non-conductive surface that is ideal for growing thin films and depositing contacts. We determined the surface's features and the chemical species present using atomic-force microscopy, x-ray photoelectron spectroscopy, and scanning electron microscopy (SEM), coupled with energy-dispersive spectroscopy. We revealed crystallographic defects, e.g., sub-grains and dislocations on the CZT crystals' surfaces, after employing selected chemical etchants, and then characterized them using optical microscopy, SEM and optical profilometer. Our experimental data imply that the surface defects and chemical species induced by chemical processing may alter the material's interfacial behavior, and ultimately significantly influence the performance of radiation detectors.

  5. 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

    2015-07-01

    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 (? w of unmodified sample = 88 2, ? 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

  6. Effect of Silica Surface Area on Molecular Structures of Lead in Thermally Treated Mixtures of Lead Acetate and Silica Oxide

    SciTech Connect

    Wei Yuling; Cheng, K.-W.; Cheng, Nicky; Wang, H. Paul

    2007-02-02

    The extent of lead dispersion can affect lead molecular environment in lead silicate. Mixtures of lead acetate and silica oxide were heated at 500 and 1100 deg. C for two hours. Two silica oxides (a quartz, syn and an amorphous SiO2) of different surface areas were used in this study. The final products were investigated with X-ray absorption spectroscopy, X-ray diffraction, BET surface meter, and scanning electron microscopy. The XRD results observe the existence of PbSiO3, Pb(0), and PbO (litharge, syn) only in the mixture of lead acetate and quartz heated at 1100 deg. C, as well as SiO2 (cristobalite, syn). The mixture of lead acetate and the amorphous SiO2 heated at 1100 deg. C basically remains as amorphous although its XRD patterns do show some low-intensity peaks of SiO2 (cristobalite, syn). Both BET and SEM results indicate that sintering occurs at 1100 deg. C. Results from the fitting of Fourier transformed Pb LIII-edge EXAFS spectra from the heated mixtures shows that both first-shell (Pb-O) interatomic distance and coordination number depend on the type of starting materials and the thermal treatment temperature. Pb first-shell coordination number decreases with increasing temperature for both low-surface area and high-surface area mixtures. The high-surface area mixture after heating at 500 deg. C have greater first-shell coordination number than the corresponding low-surface area sample. However, after thermal treatment at 1100 deg. C, both mixtures have similar first-shell coordination number. The interatomic distance for the first shell for all thermally treated mixtures is 2.18-2.28 A. The high-surface area mixture treated at 1100 deg. C has the shortest first-shell interatomic distance (2.18 A)

  7. Iterative Inversion Method for Eddy Current Evaluation of Near-Surface Residual Stress Profile in Surface-Treated Metals

    SciTech Connect

    Abu-Nabah, Bassam A.; Nagy, Peter B.

    2007-03-21

    Because of their frequency-dependent penetration depth, eddy current measurements are capable of mapping the near-surface depth profile of the electric conductivity. This technique can be used to nondestructively characterize the subsurface residual stress distribution in certain types of shot-peened metals, e.g., in nickel-base superalloys. To predict the depth-dependent, but frequency-independent, intrinsic electric conductivity from the frequency-dependent apparent eddy current conductivity (AECC), a highly convergent iterative inversion procedure is presented. The proposed technique exploits three specific features of the subsurface electric conductivity variation caused by near-surface residual stresses in shot-peened metals. First, compressive residual stresses are limited to a shallow surface region of depth much less than typical probe coil diameters. Second, the change in electric conductivity due to residual stresses is always very small, typically less than 1%. Third, the electric conductivity profile is fairly smooth and continuous. The accuracy of the proposed iterative inversion procedure is one order of magnitude better than that of the previously developed simpler method (J. Appl. Phys. 96, 1257 2004)

  8. 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.

  9. Changes in wetting properties of silica surface treated with DPPC in the presence of phospholipase A 2 enzyme

    NASA Astrophysics Data System (ADS)

    Wi?cek, Agnieszka Ewa

    2010-10-01

    Wetting properties of silica plates contacted with dipalmitoylphosphatidylcholine (DPPC) or DPPC/enzyme (phospholipase PLA 2) in NaCl solution were determined by thin layer wicking and with a help of Washburn equation. The wicking experiments were performed both for bare plates and the silica plates precontacted overnight with the probe liquid saturated vapors the silica plates, as well as untreated and DPPC (or DPPC/enzyme) treated. Adsorption of DPPC on original silica plates increases a bit hydrophobic character of silica surface in such a way that hydrocarbon chains are directed outwards and the polar part towards the silica surface. However, after the enzyme action the products of DPPC hydrolysis by PLA 2 (palmitic acid and lysophosphatidylcholine) increase again hydrophilic character of silica surface (an increase in acid-base interactions, ?sAB). The changes of silica surface wettability are evidently dependent on the time of enzyme contacting with DPPC in NaCl solution. Although, the changes of total surface free energy of silica after treatment with DPPC/enzyme solution are minor about 2-6 mJ/m 2, the changes of the electron-donor ( ?s-) and Lifshitz-van der Waals ( ?sLW) component of the surface free energy are noticeable. Despite, these results are somehow preliminary, it seems that thin layer wicking method is an interesting tool for investigation of the effect of adsorbed DPPC on hydrophobicity/hydrophilicity of silica surface and influence of enzyme PLA 2 action.

  10. 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.

  11. Environmental ageing of irradiated polypropylene/montmorillonite nanocomposites obtained in molten state

    NASA Astrophysics Data System (ADS)

    Komatsu, L. G. H.; Oliani, W. L.; Lugao, A. B.; Parra, D. F.

    2014-04-01

    Nanocomposites of High Melt Strength Polypropylene (HMSPP) were obtained in organoclay concentrations of 0.1, 5 and 10 wt% using the montmorillonite (MMT). The clay was dispersed through the melting intercalation technique using a twin-screw extruder. The dumbbell samples were manufactured and settled in device for natural ageing assay. The mechanical properties (elongation and rupture strength) were evaluated and the thermal behavior was investigated by differential scanning calorimetry (DSC). The morphology of the nanocomposites was observed by scanning electron microscopy (SEM). Nanocomposites HMSPP/MMT showed intense cracks at the surface after 3 months of environmental ageing but not as deeply as in the HMSPP. The carbonyl index (CI) was calculated using infrared spectroscopy (FT-IR) technique in which the nanocomposites showed CI values lower than the HMSPP.

  12. 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.

  13. 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

  14. 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.

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

    PubMed

    Ertem, Gzen; 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, [CH?-(CH?)(n)-NH?](+), where n?=?3-16 and 18, and then measuring d(???), 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

  16. 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.

  17. Surface functional properties of native, acid-treated, and reduced soy glycinin. 1. Foaming properties.

    PubMed

    Wagner, J R; Guguen, J

    1999-06-01

    Foaming properties of native and chemically modified glycinin were evaluated. Effects of ionic strength and glycinin composition and concentration on foam formation and stabilization were studied. Glycinin was modified by means of combined treatments: cold or hot acidic treatments, with or without later disulfide bridges reduction. Modified proteins obtained from glycinin present different degrees of dissociation, deamidation, and as consequence, varied surface hydrophobicity and molecular size. Parameters of forming and stabilizing of foam were correlated with both deamidation and dissociation degrees of modified and native glycinin samples. A positive relationship was observed between surface behavior and foaming properties of different protein species. Results show that dissociation, deamidation, and reduction have produced structural changes on glycinin (increased surface hydrophobicity, increased net charge, decreased molecular size) which enhance the adsorption and anchorage of proteins at the air-water interface and, consequently, improve the foam forming and stabilizing capacities. PMID:10794605

  18. 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

  19. Hydrogen effect on zirconium alloy surface treated by pulsed electron beam

    NASA Astrophysics Data System (ADS)

    Pushilina, N. S.; Lider, A. M.; Kudiiarov, V. N.; Chernov, I. P.; Ivanova, S. V.

    2015-01-01

    Influence of modification by pulsed electron beam (PEB) and hydrogen adsorption in zirconium alloys have been investigated. Treatment of Zr-1Nb alloy by high-current PEB allows for a decrease in the amount of hydrogen absorbed by the samples during the hydrogenation process from gas atmosphere in the temperature range of (350-550 C). The effect of the PEB surface treatment on the hydrogen adsorption connected with the formation of a protective oxide film after PEB irradiation and also by the formation of a specific hardening structure under the action of irradiation at temperatures exceeding the melting temperature from the subsequent high-speed surface cooling.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. A mechanistic description of Ni and Zn sorption on Na-montmorillonite Part I: Titration and sorption measurements

    NASA Astrophysics Data System (ADS)

    Baeyens, Bart; Bradbury, Michael H.

    1997-09-01

    In this paper experimental investigations into the acid/base titration characteristics of Na-montmorillonite and the sorption behaviour of Ni and Zn under a wide variety of conditions are presented. From these measurements the dominant sorption mechanisms could be deduced. In the following paper (Bradbury and Baeyens, 1997) the titration and sorption data are analysed to determine the parameters in cation exchange and surface complexation based models which together provide a quantitative description of the titration and sorption data. A conditioning procedure was applied to the SWy-1 Na-montmorillonite starting material in order to remove background metal impurities, soluble salts and sparingly soluble minerals which could influence titration and sorption measurements. The purified clay, in the homo-ionic Na form, was thoroughly physico-chemically characterised before carrying out batch titration measurements on suspensions in 0.1 and 0.5 M NaClO 4. The influence of background impurities, not removed by the conditioning, and cation exchange processes on the form of the titration curves is discussed. Titration data can be analysed to yield site capacities and protonation/deprotonation constants for the amphoteric surface hydroxyl groups (?SOH). The acid endpoint in the titration data was used to estimate an ?SOH site capacity of 0.08 mol kg -1. The sorption of Ni and Zn on conditioned Na-montmorillonite was studied at trace concentrations as a function of pH over a range from 3 to 10 to produce so-called "sorption edges". In the case of Ni, such measurements were carried out as a function of the NaClO 4 background electrolyte concentration. In addition, sorption isotherms were determined for both nuclides at several fixed pH values in 0.1 M NaClO 4. From the form of the "edges" it was deduced that two main sorption mechanisms were controlling the uptake of Ni and Zn onto the clay mineral; a pH-independent component, identified as cation exchange on the permanent charge sites, and a pH-dependent one, interpreted as surface complexation on the amphoteric surface hydroxyl groups. The non-linearity of the sorption isotherms indicated that at least two different ?SOH type sites were contributing to the overall sorption on Na-montmorillonite.

  6. 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

  7. 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.

  8. 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

  9. Remediation studies of trace metals in natural and treated water using surface modified biopolymer nanofibers

    NASA Astrophysics Data System (ADS)

    Musyoka, Stephen Makali; Ngila, Jane Catherine; Mamba, Bhekie B.

    In this study, remediation results of trace metals in natural water and treated water using three functionalized nanofiber mats of cellulose and chitosan are reported. The nanofiber materials, packed in mini-columns, were employed for the remediation of five toxic trace metals (Cd, Pb, Cu, Cr and Ni) from natural water samples. Trace metals in real water samples were undetectable as the concentrations were lower than the instruments detection limits of 0.27 10-3 (Cd) and 4.2 10-2 (Pb) ?g mL-1, respectively. However, after percolation through the functionalised biosorbents in cartridges, detectability of the metal ions was enhanced. The starting volume of the natural water sample was 100 mL, which was passed through a column containing the nanofibers sorbent and the retained metals eluted with 5 mL of 2.0 M nitric acid. The eluate was analyzed for metals concentrations. An enrichment factor of 20 for the metals was realized as a result of the pre-concentration procedure applied to handle the determination of the metals at trace levels. The order of remediation of the studied metals using the nanofibers was as follows: chitosan/PAM-g-furan-2,5-dione < cellulose-g-furan-2,5-dione < cellulose-g-oxolane-2,5-dione. The modified biopolymer nanofibers were able to adsorb trace metals from the river water and treated water, thereby confirming their capability of water purification. These materials are proposed as useful tools and innovative approach for improving the quality of drinking for those consumers in small scale households.

  10. 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

  11. 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.

  12. 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.

  13. Nature of flocculation and tactoid formation in montmorillonite: the role of pH.

    PubMed

    Segad, M; kesson, T; Cabane, B; Jnsson, Bo

    2015-11-28

    The dissolution and swelling properties of montmorillonite at different pH have been studied, using small angle X-ray scattering (SAXS), imaging and osmotic stress methods combined with Monte Carlo simulations. The acidity of montmorillonite dispersions has been varied as well as the counterions to the net negatively charged platelets. At low pH, Na montmorillonite dissolves and among other species Al(3+) is released, hydrated, polymerized and then it replaces the counterions in the clay. This dramatically changes the microstructure of Na montmorillonite, which instead of having fully exfoliated platelets, turns into a structure of aggregated platelets, so-called tactoids. Montmorillonite dispersion still has a significant extra-lamellar swelling among the tactoids due to the presence of very small nanoplatelets. PMID:26477672

  14. Intestinal permeability of oxytetracycline from chitosan-montmorillonite nanocomposites.

    PubMed

    Salcedo, Inmaculada; Sandri, Giuseppina; Aguzzi, Carola; Bonferoni, Cristina; Cerezo, Pilar; Snchez-Espejo, Rita; Viseras, Csar

    2014-05-01

    A nanocomposite based on chitosan and montmorillonite was developed as carrier to improve oral bioavailability of oxytetracycline. The nanocomposite was prepared by simple solid-liquid interaction and loaded with the drug. The loaded nanocomposite was characterized by X-ray powder diffraction, thermal analysis, FTIR spectroscopy and zeta potential. Caco-2 cell cultures were used to evaluate in vitro cytotoxicity and drug permeation. Confocal laser scanning microscopy was also performed to evaluate the eventual entrapment of drug into the Caco-2 cells. Results showed that the nanocomposite was internalized into the cells and effectively enhanced drug permeation, being also biocompatible towards Caco-2 cells. PMID:24290103

  15. 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

  16. 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.

  17. 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.

  18. Intercalation in montmorillonite of molybdenum cations containing the Mo 6Cl 8 cluster core

    NASA Astrophysics Data System (ADS)

    Christiano, Steven P.; Pinnavaia, Thomas J.

    1986-10-01

    Molybdenum cations containing the Mo 6Cl 8 cluster core have been intercalated in montmorillonite. Cluster ions of the type [Mo 6Cl 8(H 2O) 6- n(OH) n] (4- n)+ were formed by argentometric titration of [Mo 6Cl 8]Cl 4 2H 2O to remove the four terminally bonded chlorines. At pH = 1.5 the clusters occupy the gallery region between the silicate layers of montmorillonite by displacement of Na +. The relationship between Na + released and cluster bound indicates the cluster intercalates mainly as monopositive cations ( n = 3), along with some dispositive cations ( n = 2). As the cluster loading approaches the cation exchange capacity of the clay, the gallery acidity decreases and additional cluster binds as neutral molecules with n = 4. Thus the maximum cluster loading (80 mmoles/100 g) exceeds the value expected on the basis of ion exchange alone (60 mmoles/100 g). The gallery height of 7.3 for the new intercalate is compatible with the C 4 axis of the Mo 6Cl 8 core being oriented perpendicular to the silicate layers. Thermolysis of the intercalated clusters at 240C results in the oxidation of the intercalated clusters to molybdenum oxide. Cluster decomposition is accompanied by the collapse of some galleries, while others remain propped open by 3.9 . The latter value corresponds to two layers of oxygen in the galleries. Thus the oxide is nonuniformly distributed on both the internal and external surfaces of the clay. Complete gallery collapse is observed at 300C.

  19. Surface analytical study of CuInSe[sub 2] treated in Cd-containing partial electrolyte solution

    SciTech Connect

    Asher, S.E.; Ramanathan, K.; Wiesner, H.; Moutinho, H. ) Niles, D.W. )

    1999-03-01

    Junction formation in CuInSe[sub 2] (CIS) has been studied by exposing thin films and single-crystal samples to solutions containing NH[sub 4]OH and CdSO[sub 4]. The treated samples were analyzed by secondary ion mass spectrometry to determine the amount and distribution of Cd deposited on the surface of the films. Cadmium is found to react with the surface for all the solution exposure times and temperatures studied. The reaction rapidly approaches the endpoint and remains relatively unchanged for subsequent solution exposure. Cadmium in-diffusion, as measured by secondary ion mass spectrometry, is obscured by topography effects in the thin-film samples and by ion-beam mixing and topography in the single-crystal sample. [copyright] [ital 1999 American Institute of Physics.

  20. Surface analytical study of CuInSe{sub 2} treated in Cd-containing partial electrolyte solution

    SciTech Connect

    Asher, S.E.; Ramanathan, K.; Wiesner, H.; Moutinho, H. Niles, D.W.

    1999-03-01

    Junction formation in CuInSe{sub 2} (CIS) has been studied by exposing thin films and single-crystal samples to solutions containing NH{sub 4}OH and CdSO{sub 4}. The treated samples were analyzed by secondary ion mass spectrometry to determine the amount and distribution of Cd deposited on the surface of the films. Cadmium is found to react with the surface for all the solution exposure times and temperatures studied. The reaction rapidly approaches the endpoint and remains relatively unchanged for subsequent solution exposure. Cadmium in-diffusion, as measured by secondary ion mass spectrometry, is obscured by topography effects in the thin-film samples and by ion-beam mixing and topography in the single-crystal sample. {copyright} {ital 1999 American Institute of Physics.}

  1. 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.

  2. 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.

  3. 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 ?-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.

  4. 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

  5. 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

  6. 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

  7. Comprehensive study of hydrostatic pressure treated human umbilical cord blood cells via response surface method.

    PubMed

    Szraz, Leonra; Sznsi, Dra; Oldak, Tomasz; Balogh, Istvn

    2014-10-01

    Amelioration of the survival parameters of cryopreserved samples after thawing has already been addressed through several techniques including vitrification to avoid the formation of ice cores. However, this approach cannot be followed in the case of samples with higher volumes. Hydrostatic pressure (HP) treatment has been proven to increase some qualifying parameters (e.g., motility, insemination efficiency) of certain biological samples. Accordingly, the preparation of umbilical cord blood (UCB) samples through an active (mechanical) pre-stressing process to increase the survival rate of cryopreserved samples can be regarded as a novel strategy that calls for basic experimental studies. The goal of our study was to assess the effects of HP treatment on the qualifying parameters (DNA fragmentation by agarose gel electrophoresis and capillary electrophoresis, Total Nucleotide Cell (TNC) count, CD34+/CD45+ count, and superoxide dismutase activity (SOD) of human umbilical cord blood (UCB) derived cells). The experimental arrangement was set to provide data for response-surface analysis to take into account the common effects of the individual variables of pressure and time exposure. 3D visualization of experimental data revealed that 50-min long HP treatment at 12.5 MPa can significantly (? = 0.05) enhance white blood cell (WBC) and CD34+/CD45+ cell counts. However no DNA fragmentation was observed even at higher pressures, SOD activity was triggered over 15.0 MPa. As a conclusion, HP treatment may contribute to the optimal cryopreservation of UCB cells by significantly increasing WBC and CD34+/CD45+ cell counts without adverse effects neither on DNA stability nor on triggering SOD activity. PMID:25106745

  8. Sorption of lambda-cyhalothrin, cypermethrin, deltamethrin and fenvalerate to quartz, corundum, kaolinite and montmorillonite.

    PubMed

    Oudou, H Chaaieri; Hansen, H C Bruun

    2002-12-01

    Sorption to mineral surfaces may be important for retention and degradation of hydrophobic pesticides in subsoils and aquifers poor in organic matter. In this work the title pyrethroids have been used to investigate selective interactions with the surfaces of four minerals. Sorption of the four pyrethroids was quantified in batch experiments with initial pyrethroid concentrations of 1-100 microg/l. Sorption to centrifuge tubes used in the batch experiments accounted for 25-60% of total sorption. Net sorption was obtained from total sorption after subtracting the amounts of pyrethroids sorbed to centrifuge tubes used. All isotherms could be fitted by the Freundlich equation with n ranging between 0.9 and 1.1. Bonding affinities per unit surface area decreased in the order: corundum > quartz > montmorillonite approximately equal kaolinite. A similar sequence as found for the total surface tension of the minerals. All minerals showed the same selectivity order with respect to sorption affinity of the four pyrethroids: lambda-cyhalothrin > deltamethrin > cypermethrin > fenvalerate, which shows that the most hydrophobic compound is sorbed most strongly. Stereochemical properties of the four pyrethroid formulations may also contribute to the selectivity pattern. PMID:12489725

  9. 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

  10. 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.

  11. 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

  12. 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.

  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. 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.

  15. 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.

  16. 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.

  17. U(VI) sorption on montmorillonite in the absence and presence of carbonate: A macroscopic and microscopic study

    NASA Astrophysics Data System (ADS)

    Marques Fernandes, M.; Baeyens, B.; Dhn, R.; Scheinost, A. C.; Bradbury, M. H.

    2012-09-01

    The mechanism of U(VI) sorption on montmorillonite (Na-SWy-1) in the absence and presence of carbonate was investigated through a combination of different approaches: macroscopic sorption experiments, surface complexation modelling using the 2 Site Protolysis Non Electrostatic Surface Complexation and Cation Exchange sorption model and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. U(VI) sorption measurements were performed in the absence of carbonate at fixed ionic strength (0.1 M NaClO4) as a function of pH at U(VI) trace concentration (9 10-8 M) and as a function of U(VI) concentration (10-7-10-4 M) at a fixed pH (5, 6.8 and 8). In the presence of carbonate, experiments were carried out in equilibrium with atmospheric pCO2 and in 1, 3 and 5 mM NaHCO3. The pH dependent sorption measurements at trace concentration in the absence of carbonate were modelled by considering the formation of the following surface species, tbnd SOUO2+, tbnd SOUOOH, tbnd SOUO(OH)2- and tbnd SOUO(OH)32- on the strong sites. From the isotherms the formation of tbnd SOUO2+ and tbnd SOUOOH on the weak sites was inferred. Two additional surface complexes on the strong sites, tbnd SOUOCO3- and tbnd SOUO(CO)23- and one surface complex on the weak sites, SOUOCO3-, were necessary to reproduce the sorption data obtained in the presence of carbonate. The EXAFS measurements did not allow to verify the formation of ternary uranyl-carbonate complexes on the montmorillonite surface. However, the obtained fit results, i.e. splitting of the equatorial oxygen shell, one Si/Al shell at 3.09 and one Si/Al at 3.29 or one Fe shell at 3.42 , clearly indicate that under the given experimental conditions (pH, U(VI) loading) U(VI) forms inner-sphere surface complexes on montmorillonite edge sites via binding to aluminum octahedra and/or silicon tetrahedra.

  18. 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.

  19. 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.

  20. 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

  1. Fe(II) sorption on a synthetic montmorillonite. A combined macroscopic and spectroscopic study.

    PubMed

    Soltermann, Daniela; Fernandes, Maria Marques; Baeyens, Bart; Dhn, Rainer; Mieh-Brendl, Jocelyne; Wehrli, Bernhard; Bradbury, Michael H

    2013-07-01

    Extended X-ray absorption fine structure (EXAFS) and Mssbauer spectroscopy combined with macroscopic sorption experiments were employed to investigate the sorption mechanism of Fe(II) on an iron-free synthetic montmorillonite (Na-IFM). Batch sorption experiments were performed to measure the Fe(II) uptake on Na-IFM at trace concentrations as a function of pH and as a function of sorbate concentration at pH 6.2 and 6.7 under anoxic conditions (O2 < 0.1 ppm). A two-site protolysis nonelectrostatic surface complexation and cation exchange sorption model was used to quantitatively describe the uptake of Fe(II) on Na-IFM. Two types of clay surface binding sites were required to model the Fe(II) sorption, the so-called strong (?S(S)OH) and weak (?S(W)OH) sites. EXAFS data show spectroscopic differences between Fe sorbed at low and medium absorber concentrations that were chosen to be characteristic for sorption on strong and weak sites, respectively. Data analysis indicates that Fe is located in the continuity of the octahedral sheet at trans-symmetric sites. Mssbauer spectroscopy measurements confirmed that iron sorbed on the weak edge sites is predominantly present as Fe(II), whereas a significant part of surface-bound Fe(III) was produced on the strong sites (?12% vs ?37% Fe(III) species to total sorbed Fe). PMID:23249208

  2. Synthesis and photocatalytic performances of the TiO2 pillared montmorillonite.

    PubMed

    Chen, Daimei; Zhu, Qian; Zhou, Fengsan; Deng, Xutao; Li, Fatang

    2012-10-15

    TiO(2) pillared clay materials were prepared by montmorillonite (Mt) and acidic solutions of hydrolyzed Ti alkoxides in the presence of high-molecular-weight polyoxypropylene (POP)-backboned di-quaternary salts (POP). The as-prepared materials were characterized by means of XRD, FTIR, TG-DTA, XRF, specific surface area and porosity determinations, TEM and SEM, respectively. The experiments showed that the resulting material was a porous delaminated structure containing pillared fragments and nano-scaled TiO(2) particles well dispersed among each other. Introducing polymer surfactant POP as an expanding agent of Mt cannot only promote the formation of the delaminated structure, but significantly improve the porosity and surface area of the composites. The resulting TiO(2) pillared Mt exhibited a good thermal stability as indicated by its surface area after calcination at 800 C. No phase transformation from anatase to rutile was observed even under calcination at 900 C. The grain size of anatase in as-prepared sample decreased with the increase of the POP concentration, but increased with the increment of calcination temperature. The photocatalytic performances of these new porous materials were evaluated by using methylene blue degradation. The composite solid exhibited superior photocatalyic property and the maximum removal efficiency was up to 98% within 90 min. PMID:22884731

  3. 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.

  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(?-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. Development of chitosan/montmorillonite nanocomposites with encapsulated ?-tocopherol.

    PubMed

    Dias, Marali Vilela; Machado Azevedo, Viviane; Borges, Soraia Vilela; Soares, Nilda de Ftima Ferreira; de Barros Fernandes, Regiane Victria; Marques, Joo Jos; Medeiros, Eber Antonio Alves

    2014-12-15

    Nanocomposites of chitosan (CS) were developed and characterized in a full factorial design with varying levels of montmorillonite (MMTNa) and encapsulated tocopherol (toc-encap). The structural properties (XRD, FTIR), morphology (TEM), hygroscopic properties (water vapour permeability, hydrophobicity, sorption isotherms) and optical properties (haze, CIELab parameters) of the resulting materials were evaluated. Toc-encap contents up to 10% influenced the intercalation of MMTNa in the CS matrix, resulting in films with reduced water vapour permeability (3.4810(-11)(g/msPa)), increased hydrophobicity (?GHydroph |7.93-59.54|mJm(-2)) and lower equilibrium moisture content (EMC), thus showing potential for active food packaging materials. At levels above 10%, toc-encap agglomerates occurred, which deteriorated the properties of the resulting films, as shown with the TEM. As the toc-encap content increased, the films became slightly more yellow, more irregular and less transparent, with a higher haze index. PMID:25038682

  6. 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 73wt% 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 6wt%, while the further addition of MMT (to 8wt%) 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 8wt% MMT, indicating that the increased tortuosity of the permeant path was effective on barrier properties of the film. PMID:26769511

  7. Preparation of montmorillonite clays containing DTMPPA for Zinc extraction

    NASA Astrophysics Data System (ADS)

    Bouazza, D.; Miloudi, H.; Sassi, M.; Boos, A.; Goetz, G.; Tayeb, A.; Bengueddach, A.

    2006-05-01

    Di(2,4,4-trimethylpentyl)phosphinic acid, DTMPPA (Cyanex 272), was introduced into homoionic clays containing sodium by using two methods: a dry impregnation method (process 1) and an intercalation method (process 2). The total amount of loaded extractant was determined by NaOH titration of washings and/or mother-solutions in both cases. The solids obtained were characterized by infrared spectroscopy (IR), X-Ray diffraction and TGA DTA analysis. The montmorillonite clays containing DTMPPA were used to successfully remove zinc from sulphuric dilute acidic solutions (pH 2 5), at constant ionic strength, I=1. The metal extraction depends on pH. The clay containing DTMPPA loaded by process 1, that contains more DTMPPA than the clay loaded by process 2, shows a better performance in the extraction of zinc.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Persistence of parathion and its oxidation to paraoxon on the soil surface as related to worker reentry into treated crops.

    PubMed

    Spencer, W F; Cliath, M M; Davis, K R

    1975-09-01

    Soil and dust samples from beneath citrus trees contained relatively high concentrations of paraoxon and parathion for at least 45 days after parathion was applied at normal rates. These data indicate that parathion dripping on dry soil from sprayed crops, or sprayed directly on the soil surface, can persist for long periods and be oxidized to the highly toxic paraoxon. The residue concentrations are much higher on the loose dust particles than in the bulk soil. The data indicate that the soil or grove floor should be considered as a possible contributing source of toxicant along with foliage, or dust on foliage, to workers reentering treated fields. In any event, the data confirmed the high rates of oxidation of parathion to paraoxon on particulate matter, whether on foliage (SPEAR et al., 1974) or at the soil surface. The particulate matter appears to contribute to the accumulation of paraoxon, either by enhancing oxidation of parathion to paraoxon or by decreasing dissipation of paraoxon. PMID:1174737

  13. 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

  14. 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

  15. 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...

  16. 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...

  17. 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

  18. 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

  19. 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, Jrg

    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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. Effects of Surface Morphology on the Wear and Corrosion Resistance of Post-Treated Nitrided and Nitrocarburized 42CrMo4 Steel

    NASA Astrophysics Data System (ADS)

    Sola, Ramona; Poli, Giorgia; Veronesi, Paolo; Giovanardi, Roberto

    2014-06-01

    The surface of alloyed carbon steel was subjected to thermochemical modification by nitrocarburizing and nitriding with or without postoxidation in order to improve its mechanical properties, corrosion, and wear resistance. Treated samples were characterized by testing their basic properties (compound layer thickness, nitriding, nitrocarburizing depth, and surface hardness) according to standards. Detailed estimation of the modified metal surface was performed by additional testing: X-ray diffraction, microstructure, surface roughness and topography, and wear and corrosion resistance. The surface layer obtained after nitrocarburizing treatment consists mainly of ?-Fe2-3(N,C) and ?'-Fe4(N,C); similarly, the nitrided surface is formed by ?-Fe2-3N and ?'-Fe4N iron nitrides. The surface layer after postoxidation contains additionally Fe3O4. The results obtained show that nitrocarburization, nitridation, and postoxidation result in better mechanical, wear, and corrosion resistance of 42CrMo4 steel, and postoxidized sample properties are influenced by surface morphology.

  6. 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.

  7. Anopheline and culicine mosquitoes are not repelled by surfaces treated with the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana

    PubMed Central

    2010-01-01

    Background Entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, are promising bio-pesticides for application against adult malaria mosquito vectors. An understanding of the behavioural responses of mosquitoes towards these fungi is necessary to guide development of fungi beyond the 'proof of concept' stage and to design suitable intervention tools. Methods Here we tested whether oil-formulations of the two fungi could be detected and avoided by adult Anopheles gambiae s.s., Anopheles arabiensis and Culex quinquefasciatus. The bioassays used a glass chamber divided into three compartments (each 250 250 250 mm): release, middle and stimulus compartments. Netting with or without fungus was fitted in front of the stimulus compartment. Mosquitoes were released and the proportion that entered the stimulus compartment was determined and compared between treatments. Treatments were untreated netting (control 1), netting with mineral oil (control 2) and fungal conidia formulated in mineral oil evaluated at three different dosages (2 1010, 4 1010 and 8 1010 conidia m-2). Results Neither fungal strain was repellent as the mean proportion of mosquitoes collected in the stimulus compartment did not differ between experiments with surfaces treated with and without fungus regardless of the fungal isolate and mosquito species tested. Conclusion Our results indicate that mineral-oil formulations of M. anisopliae and B. bassiana were not repellent against the mosquito species tested. Therefore, both fungi are suitable candidates for the further development of tools that aim to control host-seeking or resting mosquitoes using entomopathogenic fungi. PMID:20799937

  8. 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

  9. Poly(lactide)-vitamin E derivative/montmorillonite nanoparticle formulations for the oral delivery of Docetaxel.

    PubMed

    Feng, Si-Shen; Mei, Lin; Anitha, Panneerselvan; Gan, Chee Wee; Zhou, Wenyou

    2009-07-01

    Four systems of nanoparticles of biodegradable polymers were developed in this research for oral delivery of anticancer drugs with Docetaxel used as a model drug, which include the poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs), the poly(lactide)-vitamin E TPGS nanoparticles (PLA-TPGS NPs), the poly(lactic-co-glycolic acid)-montmorillonite nanoparticles (PLGA/MMT NPs) and the poly(lactide)-vitamin E TPGS/montmorillonite nanoparticles (PLA-TPGS/MMT NPs). Vitamin E TPGS stands for d-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS), which is a water-soluble derivative of natural vitamin E formed by esterification of vitamin E succinate with polyethylene glycol (PEG) 1000. The design was made to take advantages of TPGS in nanoparticle technology such as high emulsification effects and high drug encapsulation efficiency, and those in drug formulation such as high cellular adhesion and adsorption. MMT of similar effects is also a detoxifier, which may cure some side effects caused by the formulated drug. The drug-loaded NPs were prepared by a modified solvent extraction/evaporation method and then characterized for their MMT content, size and size distribution, surface charge and morphology, physical status and encapsulation efficiency of the drug in the NPs, and in vitro drug release profile. Cellular uptake of the coumarin 6-loaded NPs was investigated. In vitro cancer cell viability experiment showed that judged by IC(50), the PLA-TPGS/MMT NP formulation was found 2.89, 3.98, 2.12-fold more effective and the PLA-TPGS NP formulation could be 1.774, 2.58, 1.58-fold more effective than the Taxotere((R)) after 24, 48, 72h treatment, respectively. In vivo PK experiment with SD rats showed that oral administration of the PLA-TPGS/MMT NP formulation and the PLA-TPGS NP formulation could achieve 26.4 and 20.6 times longer half-life respectively than i.v. administration of Taxotere((R)) at the same 10mg/kg dose. One dose oral administration of the NP formulations could realize almost 3 week sustained chemotherapy in comparison of 22h of i.v. administration of Taxotere((R)). The oral bioavailability can be enhanced from 3.59% for Taxotere((R)) to 78% for the PLA-TPGS/MMT NP formulation and 91% for the PLA-TPGS NP formulation respectively. Oral chemotherapy by nanoparticles of biodegradable polymers is feasible. PMID:19299012

  10. High-Frequency Eddy Current Conductivity Spectroscopy for Near-Surface Residual Stress Profiling in Surface-Treated Nickel-Base Superalloys

    SciTech Connect

    Abu-Nabah, Bassam A.; Nagy, Peter B.

    2007-03-21

    Recent research indicated that eddy current conductivity measurements can be exploited for nondestructive evaluation of subsurface residual stress in surface-treated components. This technique is based on the so-called piezoresistive effect, i.e., the stress-dependence of electric conductivity. Previous experimental studies were conducted on excessively peened (Almen 10-16A peening intensity levels) nickel-base superalloy specimens that exhibited harmful cold work in excess of 30% plastic strain. The main reason for choosing peening intensities above recommended normal levels was that the eddy current penetration depth could not be decreased below 0.2 mm without conducting accurate measurements above 10 MHz, which is beyond the operational range of most commercially available eddy current instruments. In this paper we report the development of a new high-frequency eddy current conductivity measuring system that offers an extended inspection frequency range up to 80 MHz with a single probe coil. In addition, the new system offers better reproducibility, accuracy, and measurement speed than the previously used conventional system.

  11. 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.

  12. Simultaneous adsorption of Cd(2+) 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

  13. 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.

  14. 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

  15. Poly(D,?L-lactide-co-glycolide)/montmorillonite nanoparticles for improved oral delivery of exemestane.

    PubMed

    Li, Zhen; Liu, Kexin; Sun, Pengyuan; Mei, Lin; Hao, Tangna; Tian, Yan; Tang, Zeyao; Li, Lei; Chen, Dawei

    2013-01-01

    The aim of this study was to develop poly(D,L-lactide-co-glycolide)/montmorillonite (PLGA/MMT) nanoparticles formulations for improved oral delivery of exemestane. Exemestane-loaded PLGA nanoparticles and PLGA/MMT nanoparticles were prepared by a modified solvent extraction/evaporation technology with vitamin E succinated polyethylene glycol 1000 (TPGS) as emulsifier. The content of MMT was estimated by thermal gravimetric analysis. The drug encapsulation efficiency and invitro drug release kinetics were measured by high-performance liquid chromatography. The size, size distribution, surface charge and morphology of the exemestane-loaded nanoparticles were characterized using a Zetasizer Nano ZS and field emission scanning electron microscopy. The physical status of exemestane in the nanoparticles was characterized by differential scanning calorimetry. Invitro cellular uptake of coumarin-6-loaded nanoparticles was investigated by confocal laser scanning microscope, demonstrating that the fluorescence nanoparticles were internalized by Caco-2 cells (as an invitro gastrointestinal model). The results of invitro cytotoxicity experiment on MCF-7 cells (as a model of breast cancer cells) showed the exemestane-loaded nanoparticles resulted in lower cell viability versus the pure exemestane solution. The cytotoxicity against MCF-7 cells for exemestane-loaded nanoparticles and pure exemestane solution was dependent on the drug concentration and incubation time. In conclusion, this study indicates the capability of PLGA nanoparticles and PLGA/MMT nanoparticles in enhancing the oral delivery of exemestane. PMID:23517067

  16. 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

  17. 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

  18. 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.

  19. 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

  20. 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

  1. 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

  2. Modified montmorillonite clay microparticles for stable oil-in-seawater emulsions.

    PubMed

    Dong, Jiannan; Worthen, Andrew J; Foster, Lynn M; Chen, Yunshen; Cornell, Kevin A; Bryant, Steven L; Truskett, Thomas M; Bielawski, Christopher W; Johnston, Keith P

    2014-07-23

    Environmentally benign clay particles are of great interest for the stabilization of Pickering emulsions. Dodecane-in-synthetic seawater (SSW) emulsions formed with montmorillonite (MMT) clay microparticles modified with bis(2-hydroxyethyl)oleylamine were stable against coalescence, even at clay concentrations down to 0.1% w/v. Remarkably, as little as 0.001% w/v surfactant lowered the hydrophilicity of the clay to a sufficient level for stabilization of oil-in-SSW emulsions. The favorable effect of SSW on droplet size reduction and emulsion stability enhancement is hypothesized to be due to reduced electrostatic repulsion between adsorbed clay particles and a consequent increase in the continuous phase (an aqueous clay suspension) viscosity. Water/oil (W/O) emulsions were inverted to O/W either by decreasing the mass ratio of surfactant-to-clay (transitional inversion) or by increasing the water volume fraction (catastrophic inversion). For both types of emulsions, coalescence was minimal and the sedimentation or creaming was highly correlated with the droplet size. For catastrophic inversions, the droplet size of the emulsions was smaller in the case of the preferred curvature. Suspensions of concentrated clay in oil dispersions in the presence of surfactant were stable against settling. The mass transfer pathways during emulsification of oil containing the clay particles were analyzed on the droplet size/stability phase diagrams to provide insight for the design of dispersant systems for remediating surface and subsurface oceanic oil spills. PMID:24932773

  3. 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

  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. Effects of Graded Levels of Montmorillonite on Performance, Hematological Parameters and Bone Mineralization in Weaned Pigs

    PubMed Central

    Duan, Q. W.; Li, J. T.; Gong, L. M.; Wu, H.; Zhang, L. Y.

    2013-01-01

    The aim of this study was to investigate the effects of graded levels of montmorillonite, a constituent of clay, on performance, hematological parameters and bone mineralization in weaned pigs. One hundred and twenty, 35-d-old crossbred pigs (DurocLarge WhiteLandrace, 10.501.20 kg) were used in a 28-d experiment and fed either an unsupplemented corn-soybean meal basal diet or similar diets supplemented with 0.5, 1.0, 2.5 or 5.0% montmorillonite added at the expense of wheat bran. Each treatment was replicated six times with four pigs (two barrows and two gilts) per replicate. Feed intake declined (linear and quadratic effect, p< 0.01) with increasing level of montmorillonite while feed conversion was improved (linear and quadratic effect, p<0.01). Daily gain was unaffected by dietary treatment. Plasma myeloperoxidase declined linearly (p = 0.03) with increasing dietary level of montmorillonite. Plasma malondialdehyde and nitric oxide levels were quadratically affected (p<0.01) by montmorillonite with increases observed for pigs fed the 0.5 and 1.0% levels which then declined for pigs fed the 2.5 and 5.0% treatments. In bone, the content of potassium, sodium, copper, iron, manganese and magnesium were decreased (linear and quadratic effect, p<0.01) in response to an increase of dietary montmorillonite. These results suggest that dietary inclusion of montmorillonite at levels as high as 5.0% does not result in overt toxicity but could induce potential oxidative damage and reduce bone mineralization in pigs. PMID:25049749

  6. 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 = 1.241.47 nm); therefore, Ag NPs formed on the MMT suspension with d-average = 4.198.53 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

  7. 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.

  8. Mechanism of amitriptyline adsorption on Ca-montmorillonite (SAz-2).

    PubMed

    Chang, Po-Hsiang; Jiang, Wei-Teh; Li, Zhaohui; Kuo, Chung-Yih; Jean, Jiin-Shuh; Chen, Wan-Ru; Lv, Guocheng

    2014-07-30

    The uptake of amitriptyline (AMI) from aqueous environment by Ca-montmorillonite (SAz-2) was studied in a batch system under different physicochemical conditions. The adsorbent was characterized by X-ray diffraction and Fourier transform infrared (FTIR) analyses. The AMI adsorption on SAz-2 obeyed the Langmuir isotherm with a capacity of 330mg/g (1.05mmol/g) at pH 6-7. The adsorption kinetics was fast, almost reaching equilibrium in 2h, and followed a pseudo-second-order kinetic model. Desorption of exchangeable cations correlated with the AMI adsorption well, indicating that cation exchange was the major mechanism. X-ray diffraction patterns showing significant expansions of the d001 spacing and characteristic FTIR band shifts toward higher frequencies after AMI adsorption onto SAz-2 indicated that the adsorbed AMI molecules were intercalated into the interlayers of the mineral. Thermodynamic parameters based on partitioning coefficients suggested that the AMI adsorption was an endothermic physisorption at high adsorption levels. At low and higher AMI adsorption levels, the intercalated AMI molecules take a horizontal monolayer and bilayer conformation, respectively. The higher adsorption capacity suggested that SAz-2 could be a good candidate to remove AMI from wastewater and would be an important environmental sink for the fate and transport of AMI in soils and groundwater. PMID:24373983

  9. Study of potential toxic effects on rainbow trout hepatocytes of surface water treated with chlorine or alternative disinfectants.

    PubMed

    Ferraris, Michela; Chiesara, Enzo; Radice, Sonia; Giovara, Anita; Frigerio, Silvia; Fumagalli, Roberta; Marabini, Laura

    2005-06-01

    This study evaluates the effects of disinfection on the formation of toxic compounds in lake water treated with sodium hypochlorite, chlorine dioxide and peracetic acid (a disinfectant not previously used in drinking water processes). Chlorine reacts with the natural organic matter or contaminants in surface waters and produces a complex mixture of disinfection by-products (DBPs), some of which have been shown to be carcinogenic, mutagenic and/or teratogenic in animal studies. To define the potential toxicity on aquatic animals, disinfected drinking waters obtained from a pilot plant fed with water coming from Lake Trasimeno (Perugia) were collected, adsorbed by using silica C18 cartridges, and then eluted in sequence with ethylacetate, dichloromethane and methanol. The eluates were concentrated under vacuum and resuspended in dimethylsulfoxide (DMSO). Primary cultures of rainbow trout hepatocytes were exposed to three amounts of water concentrate (equivalent to 0.5, 0.25 and 0.125 l of disinfected water per ml of culture medium) for 24 h at 20 degrees C, after which their viability, glutathione content (GSH), free radical production (ROS) and cytochrome P4501A3 expression were determined. The disinfected water samples were collected during different seasons in order to evaluate a possible correlation between seasonal water variations and formation of toxic compounds. None of the water concentrates showed any cytotoxic effect or variations in GSH content, but significant increases in ROS production were detected in the autumn water concentrates from the treatments with sodium hypochlorite and chlorine dioxide. Cytochrome P4501A3 expression was not modified in the hepatocytes exposed to the water concentrates irrespective to the sampling season. PMID:15910903

  10. 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.

  11. 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.

  12. 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.

  13. 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...

  14. 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

  15. 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.

  16. 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.

  17. Microstructures and wear properties of surface treated Ti-36Nb-2Ta-3Zr-0.35O alloy by electron beam melting (EBM)

    NASA Astrophysics Data System (ADS)

    Chen, Zijin; Liu, Yong; Wu, Hong; Zhang, Weidong; Guo, Wei; Tang, Huiping; Liu, Nan

    2015-12-01

    Ti-36Nb-2Ta-3Zr-0.35O (wt.%) (TNTZO, also called gum metal) alloy was surface treated by electron beam melting (EBM), in order to improve wear properties. The microstructures and phase constitutions of the treated surface were characterized by optical microscopy (OM), scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GIXD) and electron backscattered diffraction (EBSD). The results showed that the martensitic phase and dendrites were formed from the ? phase alloy after the EBM treatment, and microstructures in the surface changed with the processing parameters. Compared with the untreated TNTZO alloy, the surface modified TNTZO alloys exhibited higher nano-hardness, 8.0 GPa, and the wear loss was also decreased apparently. The samples treated at a scanning speed of 0.5 m/s exhibited the highest wear resistance due to the fast cooling rate and the precipitation of acicular ?? phase. The relationship between the wear property and the surface microstructure of TNTZO alloy was discussed.

  18. Performance of a sub-surface flow constructed wetland in polishing pre-treated wastewater-a tropical case study.

    PubMed

    Kaseva, M E

    2004-02-01

    This paper reports on the performance of three units of a sub-surface horizontal flow constructed wetland (CW) pilot plant in polishing effluent from the upflow anaerobic sludge blanket (UASB) reactor plant. Studies on the use of UASB for on-site wastewater pre-treatment were initiated in Tanzania for the first time in 1993, while initial research works on the application of CW for polishing effluent from UASB, the results of which are reported in this paper began in 1999. In this study the UASB reactor plant received and pre-treated part of the wastewater from the student's hostels at the University College of Lands and Architectural Studies in Tanzania. Out of the three units, unit B was planted with Phragmites mauritianus, unit C with Typha latifolia and A was used as a control. Both P.mauritianus and T.latifolia have been extensively researched in Europe and USA as suitable species of vegetation in CW. However, very limited studies on the suitability of these wetland plants have been reported under tropical climate. The studied parameters were chemical oxygen demand (COD), nitrate (NO(3)-N), nitrite (NO(2)-N), ammonium (NH(4)-N), faecal coliforms (FC), total coliforms (TC), pH, temperature and dissolved oxygen (DO). The study was carried out at an average hydraulic retention time of 1.93 days (1.85 in unit A, 1.96 in unit B and 1.99 in unit C) obtained as a ratio of the volume of wastewater in the wetland and the volumetric flow rate of wastewater through the wetland unit while taking into consideration the porosity of the media. Better performance for the vegetated units B and C were obtained compared to the control unit A. Nutrients were least removed in all units (NH(4)-N 11.2%, 25.2% and 23% in units A, B and C, respectively, NO(3)-N 32.2%, 40.3% and 44.3% for units A, B and C, respectively, and NO(2)-N 23.9%, 38.5% and 23.1% for units A, B and C, respectively). The COD removal rate was 33.6%, 56.3% and 60.7% for units A, B and C, respectively. The study also indicated that pH increased from the influent to the effluent and that DO increase was related to the decrease of temperature. FC and TC removal ranged from 43% to 72%, with the least removal in unit A. PMID:14723937

  19. Nano-scale structure of Geofluids in Porous Silica and Montmorillonite Clay

    NASA Astrophysics Data System (ADS)

    Rother, G.; Gruszkiewicz, M. S.; Vlcek, L.; Cole, D. R.

    2012-12-01

    Earth's crust, composed of different rocks with varying degrees of nm- micron scale porosity, is source and reservoir of geofluids, and target for geologic carbon storage (GCS). The specific fluid-rock interactions control formation of fluid deposits, subsurface fluid mobility and mixing, and enhanced recovery processes. Rock pore characterization includes surface chemical identity, pore size distribution, ratio of connected to unconnected porosity and surface roughness. The properties of fluids confined in these pores are altered from bulk due to surface-fluid interactions and confined geometry effects. Changes in density, freezing temperature, and diffusion properties of pore fluids have been observed. Using a combination of neutron scattering and excess sorption measurements the physical properties of pore fluids can be quantified. We study both model systems with well-defined pore morphologies and natural rocks with fractal pore characteristics. Synthetic Porous silica glasses possessing tunable pore sizes of 8 - 50 nm serve as proxies for quartz-rich rocks, including sandstones. Natural rocks studied are sandstone, limestone, and shale. Excess sorption isotherms to silica aerogel and mesoporous CPG10 were measured using a high-pressure sorption balance and a vibrating tube densimeter. Strong adsorption of CO2 to the silica surfaces was found at low fluid pressure, followed by formation of a maximum in the excess sorption isotherm. The excess sorption took small and finally even negative values at high pressure. An inverse temperature dependence of the sorption strength was found in the adsorption region at low and intermediate pressure, while the excess sorption showed little temperature dependence at high pressure. A shift of the excess sorption maximum to higher fluid density was observed with increasing pore width. From small-angle neutron scattering data the density and volume of the sorption phase of pore CO2 was calculated using the Adsorbed Phase Model. The sorption behaviour was modelled using Grand Canonical Monte Carlo simulation, which exactly reproduced the excess sorption isotherm data under the assumption of a weakly attractive solid-fluid interaction potential. Caprocks overlying the porous reservoir rock serve to retain buoyant plumes of CO2. Caprocks can be comprised of thick layers of clay or mudstones, thought to be impenetrable to CO2. To quantify the interactions of caprock with CO2, we measured the excess sorption of supercritical CO2 at Na-montmorillonite clay, a proxy for cap rock materials. Very limited amounts of CO2 adsorbed to this clay mineral at low fluid densities. Using neutron diffraction, the change of the clay interlayer spacing was measured as a function of the CO2 density. A jump-like increase of the interlayer spacing upon CO2 addition was found at low pressures, and remained constant with further additions of CO2. These results indicate suitability of montmorillonite clay for carbon storage caprock applications.

  20. 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...

  1. 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

  2. CO2 hydrate nucleation kinetics enhanced by an organo-mineral complex formed at the montmorillonite-water interface.

    PubMed

    Kyung, Daeseung; Lim, Hyung-Kyu; Kim, Hyungjun; Lee, Woojin

    2015-01-20

    In this study, we investigated experimentally and computationally the effect of organo-mineral complexes on the nucleation kinetics of CO2 hydrate. These complexes formed via adsorption of zwitter-ionic glycine (Gly-zw) onto the surface of sodium montmorillonite (Na-MMT). The electrostatic attraction between the ?NH3(+) group of Gly-zw, and the negatively charged Na-MMT surface, provides the thermodynamic driving force for the organo-mineral complexation. We suggest that the complexation of Gly-zw on the Na-MMT surface accelerates CO2 hydrate nucleation kinetics by increasing the mineralwater interfacial area (thus increasing the number of effective hydrate-nucleation sites), and also by suppressing the thermal fluctuation of solvated Na(+) (a well-known hydrate formation inhibitor) in the vicinity of the mineral surface by coordinating with the ?COO() groups of Gly-zw. We further confirmed that the local density of hydrate-forming molecules (i.e., reactants of CO2 and water) at the mineral surface (regardless of the presence of Gly-zw) becomes greater than that of bulk phase. This is expected to promote the hydrate nucleation kinetics at the surface. Our study sheds new light on CO2 hydrate nucleation kinetics in heterogeneous marine environments, and could provide knowledge fundamental to successful CO2 sequestration under seabed sediments. PMID:25532462

  3. 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.

  4. 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

  5. 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.

  6. A comparison of the corrosion behaviour and surface characteristics of vacuum-brazed and heat-treated Ti6Al4V alloy.

    PubMed

    Lee, T M; Chang, E; Yang, C Y

    1998-08-01

    The corrosion characteristics of the brazed Ti6Al4V specimens were analysed and compared with respect to the conventionally heat-treated specimens by an electrochemical corrosion test. The object of this research was to explore the potentiality of the brazed titanium for biomaterials. The characteristics of the 1300 degrees C heat-treated and the 970 degrees C brazed specimens, with passivation and sterilization treatment, were evaluated by measurement of corrosion potential, Ecorr, corrosion current densities, Icorr, polarization resistance of the reacted surface films, Rp, in a potentiodynamic test. The experimental results show that the corrosion rates of the heat-treated and the brazed samples are similar at Ecorr, and the value of Ecorr for the brazed sample is noble to the heat-treated samples. The passive current density of the brazed specimen is either lower or higher than the heat-treated specimen, depending on the polarization potential. By Auger electron spectroscopic and high-resolution X-ray photoelectron spectroscopic analysis on specimens from the potentiostatic test, the elements of copper and nickel in the brazing filler were not detected while less alumina was found in the reacted film of the brazed specimens when compared with the heat-treated specimens. The implication of the results is discussed. PMID:15348855

  7. 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.

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. Influence of operating parameters on surface properties of RF glow discharge oxygen plasma treated TiO?/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

  17. 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

  18. 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

  19. 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.

  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. 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.

  2. 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

  3. 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...

  4. Peptide chain elongation: A possible role of montmorillonite in prebiotic synthesis of protein precursors

    NASA Astrophysics Data System (ADS)

    Bujdk, Juraj; Faybkov, Katarna; Eder, Artur; Yongyai, Yongyos; Rode, Bernd M.

    1995-10-01

    Several studies have proven the ability of montmorillonite to catalyse amino acid condensation under assumed prebiotic conditions, simulating wetting-drying cycles. In this work, the oligomerization of short peptides gly2, gly3, gly4 and ala2 on Ca-and Cu-montmorillonite in drying-wetting cycles at 80 C was studied. The catalytic effect of montmorillonite was found to be much higher than in the case of glycine oligomerization. From gly2 after 3 weeks, 10% oligomers (up to gly6, with gly3 as main products) are formed. Gly3 and gly4 give higher oligomers even after 1 cycle. Ala2 produces both ala3 and ala4, whereas ala does not produce any oligomers under these conditions. Heteroologomerization was observed: ala-gly-gly is formed from ala and gly2. Much higher yields are obtained using Ca-montmorillonite, because copper (II) oxidizes organic molecules. The influence of the reaction mechanism on the preferential oligomerization of oligopeptides is discussed.

  5. 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.

  6. 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...

  7. 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 ...

  8. 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

  9. 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.

  10. Surface physical-morphological and chemical changes leading to performance enhancement of atmospheric pressure plasma treated polyester fabrics for inkjet printing

    NASA Astrophysics Data System (ADS)

    Fang, Kuanjun; Zhang, Chunming

    2009-06-01

    Without any preprocessing, polyester fabric has lower ability to hold on water due to the smooth morphology and chemistry property of polyester fibers. Therefore, patterns directly printed with pigment inks have poor color yields and easily bleed. In this paper, atmospheric pressure plasma was used to pretreat polyester fabric in order to provide an active surface for the inkjet printing. The results showed that surface-modified polyester fabrics could obtain the effects of features with enhanced color yields and excellent pattern sharpness. SEM images indicated that the rough surface of plasma treated fibers could provide more capacities for the fabric to capture inks and also facilitate the penetration of colorant particles into the polyester fabric. XPS analysis revealed that air + 50%Ar plasma introduced more oxygen-containing groups onto the fabric surface than air plasma. Although AFM images indicated that etching effects generated by air plasma treatments were more evident, the air/Ar plasma treated sample has higher K/ S value and better color performance. These studies have also shown that the chemical modification of plasma appears to be relatively more significant for improving the effect of inkjet printing.

  11. 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.

  12. Corrosion Behavior of Surface-Treated Implant Ti-6Al-4V by Electrochemical Polarization and Impedance Studies

    NASA Astrophysics Data System (ADS)

    Paul, Subir; Yadav, Kasturi

    2011-04-01

    Implant materials for orthopedic and heart surgical services demand a better corrosion resistance material than the presently used titanium alloys, where protective oxide layer breaks down on a prolonged stay in aqueous physiological human body, giving rise to localized corrosion of pitting, crevice, and fretting corrosion. A few surface treatments on Ti alloy, in the form of anodization, passivation, and thermal oxidation, followed by soaking in Hank solution have been found to be very effective in bringing down the corrosion rate as well as producing high corrosion resistance surface film as reflected from electrochemical polarization, cyclic polarization, and Electrochemical Impedance Spectroscopy (EIS) studies. The XRD study revealed the presence of various types of oxides along with anatase and rutile on the surface, giving rise to high corrosion resistance film. While surface treatment of passivation and thermal oxidation could reduce the corrosion rate by 1/5th, anodization in 0.3 M phosphoric acid at 16 V versus stainless steel cathode drastically brought down the corrosion rate by less than ten times. The mechanism of corrosion behavior and formation of different surface films is better understood from the determination of EIS parameters derived from the best-fit equivalent circuit.

  13. The Special Features of the Phase Formation and Distribution in the Titanium Nickelide Surface Layers Treated by Electron Beams

    NASA Astrophysics Data System (ADS)

    Meisner, L. L.; Ostapenko, M. G.; Lotkov, A. I.; Neyman, A. A.

    2015-09-01

    The special features inherent in the formation of the structural-phase states on the surface of titanium nickelide samples subjected to multiple low-energy high-current variable energy density pulsed electron beam irradiation are investigated. The parameters of the electron beam operated in the fivefold surface melting regime are as follows: pulse duration ? = 150 ?s, current I = 70 A, and energy densities E 1, E 2, and E 3 = 15, 20, and 30 J/cm2, respectively. The surface layer structure was examined by methods of the x-ray diffraction analysis and transmission electron microscopy. It is found that in the irradiated TiNi samples with E ? 20 J/cm2, the layer containing a martensite phase lies at a certain depth below the surface rather than on the surface. In the irradiated TiNi sample with E 3 = 30 J/cm2, the subsurface region is in a two-phase state ( B2 + B19'), with the B19' phase being predominant. It appears that the lower is the energy density, the smaller is the amount of the martensite phase.

  14. 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 UVvis 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.

  15. Staphylococcus epidermidis adhesion to He, He/O(2) plasma treated PET films and aged materials: contributions of surface free energy and shear rate.

    PubMed

    Katsikogianni, M; Amanatides, E; Mataras, D; Missirlis, Y F

    2008-09-01

    Adhesion studies of bacteria (Staphylococcus epidermidis) to plasma modified PET films were conducted in order to determine the role of the surface free energy under static and dynamic conditions. In particular, we investigated the effect of the ageing time on the physicochemical surface properties of helium (He) and 20% of oxygen in helium (He/O(2)) plasma treated polyethylene terephthalate (PET) as well as on the bacterial adhesion. Treatment conditions especially known to result in ageing sensitive hydrophilicity (hydrophobic recovery) were intentionally chosen in an effort to obtain the widest possible range of surface energy specimens and also to avoid strong changes in the morphological properties of the surface. Both plasma treatments are shown to significantly reduce bacterial adhesion in comparison to the untreated PET. However, the ageing effect and the subsequent decrease in the surface free energy of the substratum surfaces with time - especially in the case of He treated samples - seem to favor bacterial adhesion and aggregation. The dispersion-polar and the Lifshitz-van der Waals (LW) acid-base (AB) thermodynamic approaches were applied to calculate the Gibbs free energy changes of adhesion (DeltaG(adh)) of S. epidermidis interacting with the substrates. There was a strong correlation between the thermodynamic predictions and the measured values of bacterial adhesion, when adhesion was performed under static conditions. By decoupling the (DeltaG(adh)) values into their components, we observed that polar/acid-base interactions dominated the interactions of bacteria with the substrates in aqueous media. However, under flow conditions, the increase in the shear rate restricted the predictability of the thermodynamic models. PMID:18565741

  16. 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.

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. 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 ...

  2. 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.

  3. Surface electrical stimulation for treating swallowing disorders after stroke: a review of the stimulation intensity levels and the electrode placements.

    PubMed

    Poorjavad, Marziyeh; Talebian Moghadam, Saeed; Nakhostin Ansari, Noureddin; Daemi, Mostafa

    2014-01-01

    Neuromuscular electrical stimulation (NMES) for treating dysphagia is a relatively new therapeutic method. There is a paucity of evidence about the use of NMES in patients with dysphagia caused by stroke. The present review aimed to introduce and discuss studies that have evaluated the efficacy of this method amongst dysphagic patients following stroke with emphasis on the intensity of stimulation (sensory or motor level) and the method of electrode placement on the neck. The majority of the reviewed studies describe some positive effects of the NMES on the neck musculature in the swallowing performance of poststroke dysphagic patients, especially when the intensity of the stimulus is adjusted at the sensory level or when the motor electrical stimulation is applied on the infrahyoid muscles during swallowing. PMID:24804147

  4. Surface Electrical Stimulation for Treating Swallowing Disorders after Stroke: A Review of the Stimulation Intensity Levels and the Electrode Placements

    PubMed Central

    Poorjavad, Marziyeh; Talebian Moghadam, Saeed; Daemi, Mostafa

    2014-01-01

    Neuromuscular electrical stimulation (NMES) for treating dysphagia is a relatively new therapeutic method. There is a paucity of evidence about the use of NMES in patients with dysphagia caused by stroke. The present review aimed to introduce and discuss studies that have evaluated the efficacy of this method amongst dysphagic patients following stroke with emphasis on the intensity of stimulation (sensory or motor level) and the method of electrode placement on the neck. The majority of the reviewed studies describe some positive effects of the NMES on the neck musculature in the swallowing performance of poststroke dysphagic patients, especially when the intensity of the stimulus is adjusted at the sensory level or when the motor electrical stimulation is applied on the infrahyoid muscles during swallowing. PMID:24804147

  5. Optimization of magnetic and dielectric properties of surface-treated magnetite-filled epoxy composites by factorial design

    NASA Astrophysics Data System (ADS)

    Boon, M. S.; Mariatti, M.

    2014-04-01

    The effect of surface modification parameters such as 3-aminopropyl triethoxysilane (3APTES) coupling agent concentration (5, 10, and 20 wt%) and treatment duration (3, 5, and 7 h) were studied using design of experiment (DOE) approach. A quadratic model was developed based on response surface analysis. Analysis of variance (ANOVA), R-squared (R-Sq), and normal plot of residuals were applied to determine the accuracy of the models. Multiple responses were simultaneously analyzed by optimization. Magnetic and dielectric properties were used as composite system responses. Solution 1 with 16.66 wt% silane and 7 h treatment time was selected for optimum response. Confirmation study showed that predicted response values match the experimental results.

  6. [XPS characterization of TiN layer on bearing steel surface treated by plasma immersion ion implantation and deposition technique].

    PubMed

    Liu, Hong-xi; Jiang, Ye-hua; Zhan, Zhao-lin; Tang, Bao-yin

    2009-09-01

    Titanium nitride (TIN) hard protective films were fabricated on AISI52100 bearing steel surface employing plasma immersion ion implantation and deposition (PIIID) technique. The TiN films were characterized using a variety of test methods. Atomic force microscope (AFM) revealed that the titanium nitride film has extremely smooth surface, very high uniformity and efficiency of space filling over large areas. X-ray diffraction (XRD) result indicated that (200) crystal face of titanium nitride phase is the preferred orientation and three kinds of titanium components exist in the surface modified layer. Tailor fitting analysis of X-ray photoelectron spectroscopy (XPS) combined with Ar ion etching proved that Ti2p(1/2) and Ti2p(3/2) have two peaks in the titanium nitride film layer, respectively. It is shown that different chemical state exists in titanium compound. N(1s) bond energy of XPS has also three fitting peaks at 396.51, 397. 22 and 399.01 eV, corresponding to the nitrogen atom in TiNxOy, TiN and N--N, respectively. Combined with the XPS Tailor fitting analysis results of O(1s) bond energy, it was shown that there is a large amount of titanium nitride phase in addition to a small amount of simple substance nitrogen and oxide of titanium in the surface layer. The whole film system is made up of TiN, TiO2, N--N and Ti--O--N compound. PMID:19950682

  7. Surface chemical properties of nanoscale domains on UV-treated polystyrene-poly(methyl methacrylate) diblock copolymer films studied using scanning force microscopy.

    PubMed

    Ibrahim, Shaida; Ito, Takashi

    2010-02-01

    This paper reports the surface chemical properties of ca. 20 nm wide domains on a UV-treated thin film of a polystyrene-poly(methyl methacrylate) diblock copolymer (PS-b-PMMA; 0.3 as the PMMA volume fraction). UV irradiation and subsequent acetic acid (AcOH) treatment were used for selectively etching horizontally aligned PMMA domains on a thin PS-b-PMMA film to obtain nanoscale trenches and ridges. The surface charge and hydrophilicity of the trenches (etched PMMA domains) and ridges (PS domains) were investigated using three approaches based on scanning force microscopy. Chemical force titration data with a COOH-terminated tip showed a prominent decrease in adhesion force from pH 3 to 4.5 due to electrostatic repulsion between negatively charged functional groups on the tip and film surface but could not clarify the difference in chemical properties between the two nanoscale domains. Friction force images in n-dodecane showed higher friction over etched PMMA and PS domains with an OH-terminated tip and a CH(3)-terminated tip, respectively, exhibiting higher hydrophilicity of the etched PMMA domains. In an atomic force microscopy image of a UV/AcOH-treated PS-b-PMMA film upon immersion in a ferritin solution, approximately 80% of the ferritin deposited on the film was found on the PS domains. The preferential deposition of ferritin on the PS domains was probably due to the electrostatic repulsion between negatively charged ferritin and negatively charged etched PMMA surface in addition to the hydrophobic interaction between ferritin and the PS surface. These results indicated that the etched PMMA domains were more hydrophilic than the PS domains due to the presence of acidic functional groups (e.g., -COOH groups) at a higher density. PMID:19928977

  8. 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

  9. 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.

  10. Efficacy of a Brazilian calcium montmorillonite against toxic effects of dietary aflatoxins on broilers reared to market weight.

    PubMed

    Eckhardt, J C; Santurio, J M; Zanette, R A; Rosa, A P; Scher, A; Dal Pozzo, M; Alves, S H; Ferreiro, L

    2014-01-01

    1. The protective effect of a natural Brazilian calcium montmorillonite (CaMont) against aflatoxins was studied in broiler chickens. 2. A total of 1056-d-old Cobb male broilers were housed in experimental pens (22 chickens per pen) for 42 d. Three levels of CaMont (0, 2.5 and 5 g/kg) and two levels of aflatoxins (0 and 3 mg/kg) were assayed. Each treatment had 8 replicate pens of 22 broiler chickens each. 3. Of all the chickens tested in the experiment, the ones treated with aflatoxins were the most adversely affected. CaMont treatment at concentrations of 2.5 and 5 g/kg improved body weight of chickens at 42 d of age by 13.3% and 22.7%, increased daily feed intake by 9.7% and 24.7%, and improved the productive efficiency index of chickens by 53% and 66.5%, respectively. 4. Dietary CaMont positively affected parameters such as weight of liver, heart and gizzard; however, serum potassium concentration decreased by 15.3% compared with that of chickens given only the aflatoxin-contaminated diet. 5. CaMont did not cause adverse effects in chickens that did not receive aflatoxins. 6. CaMont at pH 8.5 partially reduced the toxic effects of aflatoxins in broilers when included at levels of 2.5 and 5 g/kg in the diet. PMID:24423730

  11. Gastrointestinal Complications in 147 Consecutive Patients with Peritoneal Surface Malignancy Treated by Cytoreductive Surgery and Perioperative Intraperitoneal Chemotherapy

    PubMed Central

    Casado-Adam, Angela; Alderman, Robert; Stuart, O. Anthony; Chang, David; Sugarbaker, Paul H.

    2011-01-01

    Cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is increasingly used in the treatment of peritoneal carcinomatosis from gastrointestinal malignancies. The purpose of this study is to reevaluate the incidence of gastrointestinal events and identify risk factors associated with this treatment approach. Between January 1, 2006 and December 31, 2009, 147 patients with appendiceal and colorectal carcinomatosis were treated. Gastrointestinal events were analyzed. The overall incidence of grade IIV gastrointestinal events was 17%. There were 4 grade III gastrointestinal events that occurred in 4 patients and 11 grade IV gastrointestinal events that occurred in 8 patients. On univariate analysis of grade IIV events a statistically significant association was observed with the following variables: histological grade, peritoneal cancer index (PCI), small bowel resection, colorectal anastomosis, and the number of anastomoses performed per patient. By multivariate analysis, PCI was identified as the only independent risk factor for gastrointestinal complications. CRS combined with a uniform HIPEC regimen is associated with a 17% gastrointestinal morbidity rate (grade IIV). The frequency of gastrointestinal complications was associated with a large extent of disease measured by PCI (>30). PMID:22312509

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Determination of structural modification in acid activated montmorillonite clay by FT-IR spectroscopy.

    PubMed

    Tyagi, Beena; Chudasama, Chintan D; Jasra, Raksh V

    2006-05-15

    The structural modifications and the Bronsted acid sites generated during the acid treatment of montmorillonite clay with varied concentration of sulphuric acid was determined using FT-IR spectroscopy. Octahedral sheet is affected at low acid concentration resulting into the dissolution of cations; among them Mg2+ cations are prone to dissolve than Fe2+/3+ and Al3+. Tetrahedral sheet is affected at higher acid concentration. The partial substitution of octahedral Al3+ by Mg2+ or Fe2+/3+ cations and the presence of other non-smectite minerals such as kaolinites was also been clearly identified, thus making FT-IR spectroscopy as a rapid technique for monitoring the structural features of montmorillonite clay. PMID:16635584

  17. 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 ? 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.

  18. 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.

  19. 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.

  20. Thermoplastic polymer nanocomposites with montmorillonite-Lab vs industrial scale fabrication

    NASA Astrophysics Data System (ADS)

    Giacomelli, M.; Pielichowski, K.; Leszczy?ska, A.

    2012-09-01

    Fabrication of polypropylene or polyamide-6/montmorillonite nanocomposites in a laboratory- and industrial-scale by melt processing has been described. Depending on the fabrication scale, different technological problems were observed that need to be taken into account during production of PP and PA-6-based nanocomposites with MMT which constitute a promising class of modern materials for engineering and packaging applications. Fabrication of PP and PA-6 nanocomposites with montmorillonite both on laboratory and industrial scale needs to be optimized in terms of processing conditions that include pre-mixing parameters, feeding rate, temperature of the barrel zone and extrusion die, screw speed and head pressure. Proper cleaning procedures need to be applied and the selection of the 'main' fraction enables to get nanostructured materials with enhanced properties.

  1. 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.

  2. Adsorption characteristics of Congo Red onto the chitosan/montmorillonite nanocomposite.

    PubMed

    Wang, Li; Wang, Aiqin

    2007-08-25

    A series of biopolymer chitosan/montmorillonite (CTS/MMT) nanocomposites were prepared by controlling the molar ratio of chitosan (CTS) and montmorillonite (MMT). The nanocomposites were characterized by FTIR and XRD. The effects of different molar ratios of CTS and MMT, initial pH value of the dye solution and temperature on adsorption capacities of samples for Congo Red (CR) dye have been investigated. The adsorption capacities of CTS, MMT and CTS/MMT nanocomposite with CTS to MMT molar ratio of 5:1 for CR were compared. The results indicated that the adsorption capacity of CTS/MMT nanocomposite was higher than the mean values of those of CTS and MMT. The adsorption kinetics and isotherms were also studied. It was shown that all the sorption processes were better fitted by pseudo-second-order equation and the Langmuir equation. PMID:17349744

  3. Synthesis and properties of PDMS/montmorillonite-cetyltrimethylammonium bromide-heparin films.

    PubMed

    Na Meng; Zhou, Ning-Lin

    2014-05-25

    In this study, poly(dimethylsiloxane)(PDMS)/montmorillonite-cetyltrimethylammonium bromide-heparin (PDMS/MMT-CTAB-HEP) films were prepared by solution intercalation technique. The cetyltrimethylammonium bromide-heparin (CTAB-HEP) was intercalated into montmorillonite (MMT) layers forming MMT-CTAB-HEP (modified MMT). The structure and properties of the film were characterized by XRD, TG and SEM. The modified MMT was homogeneously dispersed within the PDMS matrix. The effect of modified MMT on mechanical properties of the film was also investigated. As the modified MMT content was lower than 2wt%, the films showed excellent mechanical properties. The blood compatibility of PDMS/MMT-CTAB-HEP films was further evaluated by hemolysis test and platelet adhesion. Both hemolysis and platelet adhesions tests showed that PDMS/MMT-CTAB-HEP film had better blood compatibility than pure PDMS. PMID:24708954

  4. 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.

  5. 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.

  6. Ionic properties of liquid crystals dispersed with carbon nanotubes and montmorillonite nanoplatelets

    NASA Astrophysics Data System (ADS)

    Liu, Hsuan-Hung; Lee, Wei

    2010-10-01

    The ionic properties of liquid crystals doped with one-dimensional carbon nanotubes, two-dimensional montmorillonite, and a mixture of both are investigated. The results indicate that the relaxation times of electrode polarization and ionic conductivity are time-dependent after the cell fabrication regardless of doping. While all of the dopants are effective in capturing impurity ions, the cells containing the hybrid dopant exhibit the feeblest ionic effect at room temperature.

  7. Calcium montmorillonite clay reduces urinary biomarkers of fumonisin B1 exposure in rats and humans

    PubMed Central

    Robinson, A.; Johnson, N.M.; Strey, A.; Taylor, J.F.; Marroquin-Cardona, A.; Mitchell, N.J.; Afriyie-Gyawu, E.; Ankrah, N.A.; Williams, J.H.; Wang, J.S.; Jolly, P.E.; Nachman, R.J.; Phillips, T.D.

    2012-01-01

    Fumonisin B1 (FB1) is often a co-contaminant with aflatoxin (AF) in grains and may enhance AFs carcinogenicity by acting as a cancer promoter. Calcium montmorillonite (i.e. NovaSil, NS) is a possible dietary intervention to help decrease chronic aflatoxin exposure where populations are at risk. Previous studies show that an oral dose of NS clay was able to reduce AF exposure in a Ghanaian population. In vitro analyses from our laboratory indicated that FB1 (like aflatoxin) could also be sorbed onto the surfaces of NS. Hence, our objectives were to evaluate the efficacy of NS clay to reduce urinary FB1 in a rodent model and then in a human population highly exposed to AF. In the rodent model, male Fisher rats were randomly assigned to either, FB1 control, FB1 + 2% NS or absolute control group. FB1 alone or with clay was given as a single dose by gavage. For the human trial, participants received NS (1.5 or 3 g day?1) or placebo (1.5 g day?1) for 3 months. Urines from weeks 8 and 10 were collected from the study participants for analysis. In rats, NS significantly reduced urinary FB1 biomarker by 20% in 24 h and 50% after 48 h compared to controls. In the humans, 56% of the urine samples analyzed (n = 186) had detectable levels of FB1. Median urinary FB1 levels were significantly (p < 0.05) decreased by > 90% in the high dose NS group (3 g day?1) compared to the placebo. This work indicates that our study participants in Ghana were exposed to FB1 (in addition to AFs) from the diet. Moreover, earlier studies have shown conclusively that NS reduces the bioavailability of AF and the findings from this study suggest that NS clay also reduces the bioavailability FB1. This is important since AF is a proven dietary risk factor for hepatocellular carcinoma (HCC) in humans and FB1 is suspected to be a dietary risk factor for HCC and esophageal cancer in humans. PMID:22324939

  8. Calcium montmorillonite clay reduces urinary biomarkers of fumonisin B? exposure in rats and humans.

    PubMed

    Robinson, A; Johnson, N M; Strey, A; Taylor, J F; Marroquin-Cardona, A; Mitchell, N J; Afriyie-Gyawu, E; Ankrah, N A; Williams, J H; Wang, J S; Jolly, P E; Nachman, R J; Phillips, T D

    2012-01-01

    Fumonisin B? (FB?) is often a co-contaminant with aflatoxin (AF) in grains and may enhance AF's carcinogenicity by acting as a cancer promoter. Calcium montmorillonite (i.e. NovaSil, NS) is a possible dietary intervention to help decrease chronic aflatoxin exposure where populations are at risk. Previous studies show that an oral dose of NS clay was able to reduce AF exposure in a Ghanaian population. In vitro analyses from our laboratory indicated that FB? (like aflatoxin) could also be sorbed onto the surfaces of NS. Hence, our objectives were to evaluate the efficacy of NS clay to reduce urinary FB? in a rodent model and then in a human population highly exposed to AF. In the rodent model, male Fisher rats were randomly assigned to either FB? control, FB??+?2% NS or absolute control group. FB? alone or with clay was given as a single dose by gavage. For the human trial, participants received NS (1.5 or 3?g?day?) or placebo (1.5?g?day?) for 3 months. Urines from weeks 8 and 10 were collected from the study participants for analysis. In rats, NS significantly reduced urinary FB? biomarker by 20% in 24?h and 50% after 48?h compared to controls. In the humans, 56% of the urine samples analysed (n?=?186) had detectable levels of FB?. Median urinary FB? levels were significantly (p?90% in the high dose NS group (3?g?day?) compared to the placebo. This work indicates that our study participants in Ghana were exposed to FB? (in addition to AFs) from the diet. Moreover, earlier studies have shown conclusively that NS reduces the bioavailability of AF and the findings from this study suggest that NS clay also reduces the bioavailability FB?. This is important since AF is a proven dietary risk factor for hepatocellular carcinoma (HCC) in humans and FB? is suspected to be a dietary risk factor for HCC and oesophageal cancer in humans. PMID:22324939

  9. Effect of PAC dosage in a pilot-scale PAC-MBR treating micro-polluted surface water.

    PubMed

    Hu, Jingyi; Shang, Ran; Deng, Huiping; Heijman, Sebastiaan G J; Rietveld, Luuk C

    2014-02-01

    To address the water scarcity issue and advance the traditional drinking water treatment technique, a powdered activated carbon-amended membrane bioreactor (PAC-MBR) is proposed for micro-polluted surface water treatment. A pilot-scale study was carried out by initially dosing different amounts of PAC into the MBR. Comparative results showed that 2g/L performed the best among 0, 1, 2 and 3g/L PAC-MBR regarding organic matter and ammonia removal as well as membrane flux sustainability. 1g/L PAC-MBR exhibited a marginal improvement in pollutant removal compared to the non-PAC system. The accumulation of organic matter in the bulk mixture of 3g/L PAC-MBR led to poorer organic removal and severer membrane fouling. Molecular weight distribution of the bulk liquid in 2g/L PAC-MBR revealed the synergistic effects of PAC adsorption/biodegradation and membrane rejection on organic matter removal. Additionally, a lower amount of soluble extracellular polymer substances in the bulk can be secured in 21 days operation. PMID:24412856

  10. Dissipation of parathion and paraoxon on citrus foliage dust and dry soil surfaces in a treated orchard.

    PubMed

    Winterlin, W; Hall, G; Mourer, C; Walker, G

    1982-01-01

    Pesticides applied to an orchard may be transported via dust from the orchard floor to the foliage. The dust containing the pesticide facilitates oxygen analog formation. This study involves the evaluation of existing methods and new procedures for measuring pesticide fate (parathion and paraoxon) on soil surfaces in a field environment; the results were correlated with dislodgeable foliar residues. Residues in soil dust removed from the ground floor via vacuum varied considerably and did not correlate with dislodgeable foliar residues. Although residues found on masonite plates coated with a thin layer of soil were different from dislodgeable foliar residues, the ratios of paraoxon to parathion was very similar for the first 14 to 21 days. The thin-layer soil on the plates had serious deficiencies including difficulty of preparation in the field, handling of the coated plates, and physical movement of the soil from the plate due to environmental forces including rain. Soil tags prepared from fine mesh window screen saturated with soil resulted in approximately the same residue as the soil plates and at the same time avoided most of the deficiencies experienced with the plates. They were very resistant to physical forces, easy to prepare in the field, and not affected by environmental forces except appreciable quantities of rain. The results should encourage the use of soil screen tags, not in lieu of but along with other methods when conducting field studies with pesticides involving worker safety. PMID:7073313

  11. 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.

  12. 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

  13. Preparation and characterization of montmorillonite modified by phosphorus-nitrogen containing quaternary ammonium salts

    NASA Astrophysics Data System (ADS)

    Huang, Guobo; Gao, Jianrong; Wang, Xu

    2012-02-01

    A novel class of phosphorous-nitrogen containing quaternary ammonium salts (PNQAS) were synthesized and used as modifiers for sodium montmorillonite (Na-MMT). Montmorillonites modified by PNQAS (PNQAS-MMT) were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), dispersibility measurement and thermogravimetric analysis (TGA). The results show that the PNQAS have been intercalated into the montmorillonite layers successfully and the basal spacing of PNQAS-MMT is 1.70-2.65 nm. The XRD results show that the basal spacing of PNQAS-MMT reaches a maximum when PNQAS/CEC molar ratio is above 1.2. The increase of chain length of PNQAS is beneficial to expand the interlayer space of the MMT. The TEM and dispersibility measurement results show that PNQAS-MMT have stronger hydrophobicity and better dispersion than Na-MMT. The TGA results reveal that the thermal stability for PNQAS-MMT is affected by the structure and composition of intercalated PNQAS cations. The Tinital of PNQAS-MMT is between 286 C and 385 C, which can be applied to the modification of the polymer as a halogen-free flame retardant.

  14. 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

  15. Water radiolysis in exchanged-montmorillonites: the H2 production mechanisms.

    PubMed

    Fourdrin, C; Aarrachi, H; Latrille, C; Esnouf, S; Bergaya, F; Le Car, S

    2013-08-20

    The radiolysis of water confined in montmorillonites is studied as a function of the composition of the montmorillonite, the nature of the exchangeable cation, and the relative humidity by following the H2 production under electron irradiation. It is shown that the main factor influencing this H2 production is the water amount in the interlayer space. The effect of the exchangeable cation is linked to its hydration enthalpy. When the water amount is high enough to get a basal distance higher than 1.3 nm, then a total energy transfer from the montmorillonite sheets to the interlayer space occurs, and the H2 production measured is very similar to the one obtained in bulk water. For a basal distance smaller than 1.3 nm, the H2 production increases with the relative humidity and thus with the water amount. Lastly, electron paramagnetic resonance measurements evidence the formation of a new defect induced by ionizing radiation. It consists of a hydrogen radical (H2 precursor) trapped in the structure. This implies that structural hydroxyl bonds can be broken under irradiation, potentially accounting for the observed H2 production. PMID:23875719

  16. 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

  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 ?-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 62.44.0C (9 2.5 2 cm) and 46.03.0C (9נ5נ3 cm) were reached in oven-browned samples, and 35.01.1C (9נ2.5נ2 cm) and 31.72.6C (9נ5נ3 cm) in fryer-browned samples. Irrespective of formulation treatment, total (after frozen storage) reductions of Salmonella were greater (P < 0.05) for 9נ2.5נ2 cm oven-browned samples (3.8 to at least 4.6 log CFU/g) than for 9נ5נ3 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 9נ2.5נ2 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. 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

  19. Silk fibroin/montmorillonite nanocomposites: effect of pH on the conformational transition and clay dispersion.

    PubMed

    Dang, Qinqin; Lu, Shoudong; Yu, Shen; Sun, Pingchuan; Yuan, Zhi

    2010-07-12

    By adjusting the solution pH value below the isoelectric point (pI) of silk fibroin (SF) protein, the SF was in the cation state and it could interact strongly with unmodified anionic montmorillonite (MMT) surface. In this way, novel SF-MMT nanocomposites with good clay dispersion were successfully obtained, which were confirmed by X-ray diffraction and transmission electron microscopy. Further 1H CRAMPS and 13C CP/MAS NMR experimental results revealed that beta-sheet content of SF was remarkably enhanced for nanocomposite prepared below the pI of SF (SF-MMTA) due to the strong interaction between MMT and SF. In SF-MMTA nanocomposite, clay layers acting as an efficient nucleator could efficiently enhance the beta-sheet crystallization. On the contrary, SF preserved the native random coil conformation in SF-MMTN nanocomposites due to the weak interaction between MMT and SF. A tentative model was suggested and used to explain the mechanism of clay dispersion and conformational transition of silk protein. PMID:20509688

  20. 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

  1. 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.

  2. Crystal structure and nanotopographical features on the surface of heat-treated and anodized porous titanium biomaterials produced using selective laser melting

    NASA Astrophysics Data System (ADS)

    Amin Yavari, S.; Wauthle, R.; Bttger, A. J.; Schrooten, J.; Weinans, H.; Zadpoor, A. A.

    2014-01-01

    Porous titanium biomaterials manufactured using additive manufacturing techniques such as selective laser melting are considered promising materials for orthopedic applications where the biomaterial needs to mimic the properties of bone. Despite their appropriate mechanical properties and the ample pore space they provide for bone ingrowth and osseointegration, porous titanium structures have an intrinsically bioinert surface and need to be subjected to surface bio-functionalizing procedures to enhance their in vivo performance. In this study, we used a specific anodizing process to build a hierarchical oxide layer on the surface of porous titanium structures made by selective laser melting of Ti6Al4V ELI powder. The hierarchical structure included both nanotopographical features (nanotubes) and micro-features (micropits). After anodizing, the biomaterial was heat treated in Argon at different temperatures ranging between 400 and 600 C for either 1 or 2 h to improve its bioactivity. The effects of applied heat treatment on the crystal structure of TiO2 nanotubes and the nanotopographical features of the surface were studied using scanning electron microscopy and X-ray diffraction. It was shown that the transition from the initial crystal structure, i.e. anatase, to rutile occurs between 500 and 600 C and that after 2 h of heat treatment at 600 C the crystal structure is predominantly rutile. The nanotopographical features of the surface were found to be largely unchanged for heat treatments carried out at 500 C or below, whereas they were partially or largely disrupted after heat treatment at 600 C. The possible implications of these findings for the bioactivity of porous titanium structures are discussed.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. Influence of sputter rate and crystal orientation on the distribution of carbon in polycrystalline copper surfaces treated by plasma immersion ion implantation

    NASA Astrophysics Data System (ADS)

    Flege, S.; Kraft, G.; Bruder, E.; Baba, K.; Hatada, R.; Ensinger, W.

    2009-07-01

    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.

  8. 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.

  9. 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.

  10. 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

  11. Adsorption of adenine, cytosine, thymine, and uracil on sulfide-modified montmorillonite: FT-IR, Mssbauer and EPR spectroscopy and X-ray diffractometry studies.

    PubMed

    Carneiro, Cristine E A; Berndt, Graciele; de Souza Junior, Ivan G; de Souza, Cludio M D; Paesano, Andrea; da Costa, Antonio C S; di Mauro, Eduardo; de Santana, Henrique; Zaia, Cssia 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 Mssbauer 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. Mssbauer 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

  12. 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

  13. Recurrent Bowen's disease of scalp treated with high dose rate surface mold brachytherapy: a case report and review of the literature

    PubMed Central

    Laviraj, Macharla Anjaneyulu; Kashyap, Lakhan; Purkait, Suvendu; Sharma, Daya Nand; Julka, Pramod Kumar; Rath, Goura Kishor

    2014-01-01

    Our case is a 46-year-old female presenting to us with Bowen's disease of scalp since 5 years. Patient had failed topical therapy with 5% 5-florouracil, 0.1% tacrolimus and was intolerant to topical imiquimod. At presentation, she had 15 cm 10 cm erythematous, hyperpigmented, crusted plaque with irregular border in the superior and lateral aspect of left side of scalp with extension in to forehead. Patient was treated with computed tomography based customized surface mold high dose rate brachytherapy with Iridium-192 to a dose of 35 Gy in 10 fractions (twice daily, 6 hours apart) over 5 days. Patient tolerated the treatment well and showed regression of the lesion with mild dermatitis at the end of treatment. Though dermatitis increased at 2 weeks, at 4 weeks post treatment there was near complete resolution of the lesion with adjacent alopecia. At 8 weeks after completion of the treatment, there was complete resolution of the lesion and patient was asymptomatic. Alopecia in the adjacent area has resolved and the skin pigmentation has begun. Patient is satisfied with both the disease control and the cosmetic outcome of the procedure. Our case report demonstrates successful application of surface mold high dose rate brachytherapy in the treatment of recurrent Bowen's disease of the scalp. Brachytherapy can play an important role in the management of recurrent malignant and premalignant diseases of the complex treatment sites like scalp and it's non-hesitant use should be encouraged in appropriately selected patients at the earliest. PMID:25834584

  14. 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.

  15. 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.

  16. Green synthesis of silver/montmorillonite/chitosan bionanocomposites using the UV irradiation method and evaluation of antibacterial activity

    PubMed Central

    Shameli, Kamyar; Ahmad, Mansor Bin; Yunus, Wan Md Zin Wan; Rustaiyan, Abdolhossein; Ibrahim, Nor Azowa; Zargar, Mohsen; Abdollahi, Yadollah

    2010-01-01

    In this study, silver nanoparticles (Ag-NPs) were synthesized using a green physical synthetic route into the lamellar space of montmorillonite (MMT)/chitosan (Cts) utilizing the ultraviolet (UV) irradiation reduction method in the absence of any reducing agent or heat treatment. Cts, MMT, and AgNO3 were used as the natural polymeric stabilizer, solid support, and silver precursor, respectively. The properties of Ag/MMT/Cts bionanocomposites (BNCs) were studied as the function of UV irradiation times. UV irradiation disintegrated the Ag-NPs into smaller sizes until a relatively stable size and size distribution were achieved. Meanwhile, the crystalline structure and d-spacing of the MMT interlayer, average size and size distribution, surface morphology, elemental signal peaks, functional groups, and surface plasmon resonance of Ag/MMT/Cts BNCs were determined by powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray fluorescence, Fourier transform infrared, and UV-visible spectroscopy. The antibacterial activity of Ag-NPs in MMT/Cts was investigated against Gram-positive bacteria, ie, Staphylococcus aureus and methicillin-resistant S. aureus and Gram-negative bacteria (ie, Escherichia coli) by the disk diffusion method on MullerHinton Agar at different sizes of Ag-NPs. 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 biologic research and biomedical applications, such as surgical devices and drug delivery vehicles. PMID:21116328

  17. 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.

  18. Adsorption of Ba2+ by Ca-exchange clinoptilolite tuff and montmorillonite clay.

    PubMed

    Chvez, M L; de Pablo, L; Garca, T A

    2010-03-15

    The adsorption of barium by Ca-exchanged clinoptilolite and montmorillonite is presented. The kinetics of adsorption of Ba(2+) were evaluated contacting 1g portion of each adsorber with 100mL 0.1N BaCl(2) for 200 h. Adsorption by Ca-clinoptilolite is defined by second-order kinetics of rate constant K(v) 8.232 x 10(-2) g mg(-1)h(-1) and maximum removal of 71.885 mg g(-1). It is a two-stage process initiated by a rapid uptake of Ba(2+) followed by more moderate kinetics. The adsorption isotherms were determined contacting 0.2g of each adsorber with 10 mL 0.1-0.005N BaCl(2)+CaCl(2) solution, Ba(2+)/Ca(2+) ratio 1, for periods of 7 days for the tuff and 2 days for the clay. The equilibrium adsorption is described by the Langmuir model, of equilibrium constant K 0.0151 L mg(-1) and maximum adsorption of 15.29 mg g(-1). The adsorption of Ba(2+) by Ca-exchanged montmorillonite also follows a second-order reaction of rate constant K(v) 3.179 x 10(-2) g mg(-1)h(-1), and calculated separation of 36.74 mg g(-1); the Langmuir isotherm is defined by the constant K 0.034 L mg(-1) and maximum adsorption of 15.29 mg g(-1). X-ray diffraction shows that the exchange of Ba(2+) modifies the d(001) of Ca-montmorillonite from 15.4 to 12.4A. PMID:19926210

  19. 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.

  20. Heats of n-hexane and n-heptane vapor adsorption onto polyhydroxyaluminum montmorillonite

    NASA Astrophysics Data System (ADS)

    Muminov, S. Z.; Khandamov, D. A.; Rakhimova, G. B.

    2011-01-01

    The differential isosteric heat of the adsorption of n-hexane and n-heptane vapors on dehydrated polyhydroxyaluminum montmorillonite was determined. Using the temperature dependence of the parameters of the adsorption equilibrium, it was established that substituting sodium ions for polyhydroxyaluminum cations leads to an increase in the volume of micropores and the adsorption heat of hydrocarbons, and the curves of the adsorption heats of C6H14 and C7H16 are of an extreme nature. The appearance of the maxima is associated with the interaction between and among the adsorbate molecules and active centers, due to consolidation in the process of filling micropore volumes.

  1. 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

  2. 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

  3. Variable Temperature Infrared Spectroscopy Investigations of Benzoic Acid Desorption from Sodium and Calcium Montmorillonite Clays.

    PubMed

    Nickels, Tara M; Ingram, Audrey L; Maraoulaite, Dalia K; White, Robert L

    2015-12-01

    Processes involved in thermal desorption of benzoic acid from sodium and calcium montmorillonite clays are investigated by using variable temperature diffuse reflection Fourier transform infrared spectroscopy (DRIFTS). By monitoring the temperature dependence of infrared absorbance bands while heating samples, subtle changes in molecular vibrations are detected and employed to characterize specific benzoic acid adsorption sites. Abrupt changes in benzoic acid adsorption site properties occur for both clay samples at about 125 C. Difference spectra absorbance band frequency variations indicate that adsorbed benzoic acid interacts with interlayer cations through water bridges and that these interactions can be disrupted by the presence of organic anions, in particular, benzoate. PMID:26647147

  4. 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.

  5. 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.

  6. 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

  7. Solid state characterisation of silver sulfadiazine loaded on montmorillonite/chitosan nanocomposite for wound healing.

    PubMed

    Aguzzi, Carola; Sandri, Giuseppina; Bonferoni, Cristina; Cerezo, Pilar; Rossi, Silvia; Ferrari, Franca; Caramella, Carla; Viseras, Csar

    2014-01-01

    Biopolymer chitosan/montmorillonite nanocomposites loaded with silver sulfadiazine for wound healing purposes were prepared via intercalation solution technique. Structure and morphology of loaded nanocomposites were studied and compared with pure components and unloaded nanocomposites. X-ray diffraction, Fourier transformed infrared spectroscopy, high resolution transmission electron microscopy coupled with energy-dispersion X-ray analysis, thermal and elemental analysis were employed for the characterisation. The results confirmed that the drug was effectively loaded in the three-dimensional nanocomposite structures, in which chitosan chains were adsorbed in monolayers into the clay mineral interlayer spaces. PMID:24077113

  8. 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

  9. 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

  10. 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

  11. 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.

  12. Macro-structural effect of metal surfaces treated using computer-assisted yttrium-aluminum-garnet laser scanning on bone-implant fixation.

    PubMed

    Hirao, Makoto; Sugamoto, Kazuomi; Tamai, Noriyuki; Oka, Kunihiro; Yoshikawa, Hideki; Mori, Yusuke; Sasaki, Takatomo

    2005-05-01

    Porous coatings have been applied to the surface of prosthetic devices to foster stable device fixation. The coating serves as a source of mechanical interlocking and may stimulate healthy bone growth through osseointegrated load transfer in cementless arthroplasty. Joint arthroplasty by porous-coated prostheses is one of the most common surgical treatments, and has provided painless and successful joint mobility. However, long-term success is often impaired by the loss of fixation between the prosthesis and bone. Porous-coated prostheses are associated with several disadvantages, including metal debris from porous coatings (third body wear particles) and irregular micro-texture of metal surfaces. Consequently, quantitative histological analysis has been very difficult. These issues arise because the porous coating treatment is based on addition of material and is not precisely controllable. We recently developed a precisely controllable porous texture technique based on material removal by yttrium-aluminum-garnet laser. Free shapes can be applied to complex, three-dimensional hard metal surfaces using this technique. In this study, tartan check shapes made by crossing grooves and dot shapes made by forming holes were produced on titanium (Ti6A14V) or cobalt chrome (CoCr) and evaluated with computer-assisted histological analysis and measurement of bone-metal interface shear strength. Width of grooves or holes ranged from 100 to 800 mum (100, 200, 500, and 800 microm), with a depth of 500 microm. When the cylindrical porous-texture-treated metal samples (diameter, 5 mm; height, 15 mm) were implanted into a rabbit femoral condyle, bone tissue with bone trabeculae formed in the grooves and holes after 2 or 4 weeks, especially in 500-microm-wide grooves. Abundant osteoconduction was consistently observed throughout 500-microm-wide grooves in both Ti6A14V and CoCr. Speed of osteoconduction was faster in Ti6A14V than in CoCr, especially in the tartan check shape made of 500-microm-wide grooves. In pushout testing, the tartan check shape made of 500-microm-wide grooves had significantly higher bone-metal interface shear strength than the dot shape or commercial porous coating. These results indicate that the tartan check shape made of 500-microm-wide grooves on metal surfaces has potential for clinical application in artificial prosthesis design. PMID:15759257

  13. Competitive and synergistic effects between excimer VUV radiation and O radicals on the etching mechanisms of polyethylene and fluoropolymer surfaces treated by an atmospheric He-O2 post-discharge

    NASA Astrophysics Data System (ADS)

    Dufour, T.; Hubert, J.; Vandencasteele, N.; Viville, P.; Lazzaroni, R.; Reniers, F.

    2013-08-01

    Among various surface modification techniques, plasma can be used as a source for tailoring the surface properties of diverse materials. HDPE and fluoropolymer surfaces have been treated by the post-discharge of an atmospheric RF-plasma torch supplied with helium and oxygen gases. The plasma-treated surfaces were characterized by measurements of mass losses, water contact angles, x-ray photoelectron spectroscopy and atomic force microscopy. This experimental approach correlated with an optical characterization of the plasma phase allowed us to propose etching mechanisms occurring at the post-discharge/polymer interface. We discuss how competitive and synergistic effects can result from the oxidation and/or the roughening of the surface but also from the excimer VUV radiation, the He metastable species and the O radicals reaching the plasma-polymer interface.

  14. 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.

  15. Antimicrobial silver-montmorillonite nanoparticles to prolong the shelf life of fresh fruit salad.

    PubMed

    Costa, C; Conte, A; Buonocore, G G; Del Nobile, M A

    2011-08-15

    In this work, silver-montmorillonite (Ag-MMT) antimicrobial nanoparticles have been obtained by allowing silver ions from nitrate solutions to replace the Na(+) of natural montmorillonite and then to be reduced by a thermal treatment. Ag-MMT were used as active antimicrobial compounds to improve the shelf life of fresh fruit salad. In order to assess their influence on product shelf life, sensorial and microbiological quality has been monitored during the storage. The microbiological quality was determined by monitoring the principal spoilage microorganisms (mesophilic and psychrotrophic bacteria, coliforms, lactic acid bacteria, yeasts and molds). Additionally, the evolution of sensorial quality was assessed by monitoring color, odor, firmness and product overall quality. The Ag-MMT nanoparticles seemed to be effective in inhibiting microbial growth, above all at the highest tested concentration. Consequently, the sensorial quality of samples stored in the active packaging appeared to be better preserved. Thus, experimental results showed that a significant shelf life prolongation of fresh fruit salad can be obtained by a straightforward new packaging system. PMID:21684619

  16. Engineering New Layered Solids from Exfoliated Inorganics: a Periodically Alternating Hydrotalcite Montmorillonite Layered Hybrid

    PubMed Central

    Chalasani, Rajesh; Gupta, Amit; Vasudevan, Sukumaran

    2013-01-01

    Two-dimensional (2D) nanosheets obtained by exfoliating inorganic layered crystals have emerged as a new class of materials with unique attributes. One of the critical challenges is to develop robust and versatile methods for creating new nanostructures from these 2D-nanosheets. Here we report the delamination of layered materials that belonging to two different classes - the cationic clay, montmorillonite, and the anionic clay, hydrotalcite - by intercalation of appropriate ionic surfactants followed by dispersion in a non-polar solvent. The solids are delaminated to single layers of atomic thickness with the ionic surfactants remaining tethered to the inorganic and consequently the nanosheets are electrically neutral. We then show that when dispersions of the two solids are mixed the exfoliated sheets self-assemble as a new layered solid with periodically alternating hydrotalcite and montmorillonite layers. The procedure outlined here is easily extended to other layered solids for creating new superstructures from 2D-nanosheets by self-assembly. PMID:24336682

  17. Integrating structural and thermodynamic mechanisms for sorption of PCBs by montmorillonite.

    PubMed

    Liu, Cun; Gu, Cheng; Yu, Kai; Li, Hui; Teppen, Brian J; Johnston, Cliff T; Boyd, Stephen A; Zhou, Dongmei

    2015-03-01

    Strong sorption of planar nonionic organic chemicals by clay minerals has been observed for important classes of organic contaminants including polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and dioxins, and such affinity was hypothesized to relate to the interlayer hydrophobicity of smectite clays. In batch sorption experiments of two trichlorobiphenyls on homoionic Na-, K-, Cs-montmorillonites, considerably greater sorption coefficient (Kw) was observed for coplanar 3,3',5-trichlorobiphenyl (PCB 36); log Kw for Na-, K-, and Cs-montmorillonite were 3.69, 3.72, and 4.53 for coplanar PCB 36 vs 1.21, 1.46, and 0.87 for the nonplanar 2,2',6-trichlorobiphenyl (PCB 19). MD simulations were conducted utilizing X-ray diffraction determined clay interlayer distances (d-spacing). The trajectory, density distribution, and radial distribution function of interlayer cation, water, and PCBs collectively indicated that the hydrophobic nature of the interlayer regions was determined by the hydration status of exchangeable cations and the associated d-spacing. The sorption free energies calculated for both coplanar and nonplanar PCB molecules by adaptive biasing force (ABF) method with an extended interlayer-micropore two-phase model consisting of cleaved clay hydrates and "bulk water" are consistent with the Gibbs free energies derived from the measured log Kw, manifesting enhanced sorption of coplanar PCBs was attributed to shape selectivity and hydrophobic interactions. PMID:25629399

  18. 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 and achieve the microorganism localization. PMID:26238817

  19. Epoxy-based nanocomposites for electrical energy storage. I: Effects of montmorillonite and barium titanate nanofillers

    NASA Astrophysics Data System (ADS)

    Tomer, V.; Polizos, G.; Manias, E.; Randall, C. A.

    2010-10-01

    Polymer nanocomposites prepared by epoxy reinforced with high permittivity barium titanate (BT) fillers or high aspect ratio montmorillonite (MMT) fillers exhibited marked changes in their high electric field properties and their relaxation dynamics, depending on the nanoparticle type and concentration, the nanoparticle size, and the epoxy matrix conversion. We investigated epoxy resin composites based on organically modified montmorillonite (oMMT) or BT (BaTiO3) nanoparticles in order to delineate the effects of the high aspect ratio of the MMT and the high permittivity of the BT particles. We also explored the potential benefits of the synergy between the two fillers in systems consisting of epoxy and both oMMT and BT particles. It was observed that the nature of the organic-inorganic interfaces dominate the glass transition temperature and the dielectric properties of these composites. Specifically, using dielectric relaxation spectroscopy, we probed the local dynamics of the polymer at the interfaces. The MMT systems had approximately three orders of magnitude slower interfacial dynamics than those at the BT interfaces, indicating more robust interfaces in the MMT composites than in the BT-based composites; the corresponding energy barriers (activation energies) associated with these motions were also doubled for the MMT systems. Furthermore, we investigated the effect of the decreased glass transition, interfacial area, polymer-phase at the organic-inorganic interface, and of the dielectric breakdown on the electrical energy storage capabilities of these composites.

  20. Magnetism and nuclear magnetic resonance of hectorite and montmorillonite layered silicates

    NASA Astrophysics Data System (ADS)

    Levin, E. M.; Hou, S.-S.; Bud'ko, S. L.; Schmidt-Rohr, K.

    2004-11-01

    The temperature and magnetic-field (H) dependencies of the bulk dc magnetization (M) and the M /H ratio of montmorillonite (MMT), hectorite (HCT), and synthetic mica-montmorillonite (SMMT) clays have been measured and compared with the signal intensity of H1 and Si29 nuclear magnetic resonance (NMR) spectra. MMT exhibits Langevin paramagnetism with an effective magnetic moment of 5.50.1?B per Fe ion whereas SMMT has diamagnetic properties. At 300K, M /H of HCT measured in a magnetic field of H ?1kOe is larger than that of MMT, whereas in a field of 50kOe, the inverse situation is observed. The difference arises because the magnetization of HCT is dominated by a contribution from ferromagneticlike impurities. The H1 and Si29 NMR signals of MMT are broadened beyond detectability due to the paramagnetic effect. Although HCT contains ferromagneticlike components that result in a large M /H in low field, it yields H1 and Si29 NMR spectra with signal intensities similar to those of diamagnetic SMMT. Our data highlight that the quality of the NMR spectra is not related to the low-field magnetic susceptibility but to the bulk magnetization in the high magnetic field used for NMR.

  1. Molecular adhesion at clay nanocomposite interfaces depends on counterion hydration-molecular dynamics simulation of montmorillonite/xyloglucan.

    PubMed

    Wang, Yan; Wohlert, Jakob; Bergenstrhle-Wohlert, Malin; Kochumalayil, Joby J; Berglund, Lars A; Tu, Yaoquan; gren, Hans

    2015-01-12

    Nacre-mimetic clay/polymer nanocomposites with clay platelet orientation parallel to the film surface show interesting gas barrier and mechanical properties. In moist conditions, interfacial adhesion is lowered and mechanical properties are reduced. Molecular dynamic simulations (MD) have been performed to investigate the effects of counterions on molecular adhesion at montmorillonite clay (Mnt)-xyloglucan (XG) interfaces. We focus on the role of monovalent cations K(+), Na(+), and Li(+) and the divalent cation Ca(2+) for mediating and stabilizing the Mnt/XG complex formation. The conformation of adsorbed XG is strongly influenced by the choice of counterion and so is the simulated work of adhesion. Free energy profiles that are used to estimate molecular adhesion show stronger interaction between XG and clay in the monovalent cation system than in divalent cation system, following a decreasing order of K-Mnt, Na-Mnt, Li-Mnt, and Ca-Mnt. The Mnt clay hydrates differently in the presence of different counterions, leading to a chemical potential of water that is highest in the case of K-Mnt, followed by Na-Mnt and Li-Mnt, and lowest in the case of Ca-Mnt. This means that water is most easily displaced from the interface in the case of K-Mnt, which contributes to the relatively high work of adhesion. In all systems, the penalty of replacing polymer with water at the interface gives a positive contribution to the work of adhesion of between 19 and 35%. Our work confirms the important role of counterions in mediating the adsorption of biopolymer XG to Mnt clays and predicts potassium or sodium as the best choice of counterions for a Mnt-based biocomposite design. PMID:25389796

  2. Reactions of lysine with montmorillonite at 80 degrees C: implications for optical activity, H+ transfer and lysine-montmorillonite binding.

    PubMed

    Cuadros, Javier; Aldega, Luca; Vetterlein, Jonathan; Drickamer, Kurt; Dubbin, William

    2009-05-01

    Amino acid-smectite interaction may have catalyzed prebiotic reactions essential for the emergence of life. Lysine solutions (0.05 M) were reacted with Na-smectite in adsorption-desorption experiments. The lysine-smectite complexes were heated at 80 degrees C for 10 days to investigate (1) possible slow processes taking place at surface temperature that would be accelerated at higher temperature and (2) processes taking place in hydrothermal systems. Three sets of experiments were performed: thermal treatment in closed tubes and water added regularly; thermal treatment in closed tubes without adding water; and thermal treatment in open tubes and no added water. After lysine desorption (displacement with 0.1 M CaCl(2)), the solutions were investigated using circular dichroism (CD) and the smectite samples using FTIR and CHN elemental analysis. CD spectra were dependent on the solution pH, which was controlled by lysine protonation state. The lysine protonation state was altered by the adsorption-desorption process, with a higher Lys(+)/Lys(+/-) ratio after desorption. The CD and CHN analyses show that the thermal treatment in a moist state causes stronger smectite-lysine binding. FTIR data suggest that the stronger binding is caused by more or stronger H bonds between -NH(3)(+) lysine groups and smectite basal O atoms. PMID:19185874

  3. Calcium montmorillonite clay in dairy feed reduces aflatoxin concentrations in milk without interfering with milk quality, composition or yield

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study was designed to determine if a calcium montmorillonite clay (Novasil Plus, NSP), can significantly reduce aflatoxin M1 (AFM1) concentrations in milk without affecting dry matter intake (DMI), milk yield, milk composition, vitamin A, or riboflavin concentrations. The study was designed us...

  4. Treating Infertility

    MedlinePLUS

    ... A common problem that leads to male infertility, varicocele , sometimes can be treated with surgery. How are ... contains and nourishes the developing fetus during pregnancy. Varicocele: Varicose veins in the scrotum. If you have ...

  5. 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

  6. 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

  7. 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...

  8. Nanostructure and thermal properties of melt compounded PE/clay nanocomposites filled with an organosilylated montmorillonite

    NASA Astrophysics Data System (ADS)

    Scarfato, Paola; Incarnato, Loredana; Di Maio, Luciano; Dittrich, Bettina; Niebergall, Ute; Böhning, Martin; Schartel, Bernhard

    2015-12-01

    In this work we report on the functionalization of a natural sodium montmorillonite (MMT) with (3-glycidyloxypropyl)trimethoxysilane by a silylation procedure and on its use as nanofiller in melt compounding of polyethylene nanocomposites. The obtained organosilylated clay showed higher interlayer spacing than the original MMT and higher thermal stability with respect to most of commercial organoclays modified with alkylammonium salts. Its addition (at 5wt%) to two different polyethylene matrices (a low density polyethylene, LDPE, and a high density polyethylene, HDPE), processed in a pilot-scale twin-screw extruder, allowed to produce hybrids with nanoscale dispersion of the filler, as demonstrated by X-ray diffraction. Thermogravimetric and differential scanning thermal analyses point out that the obtained nanocomposites do not show noticeable changes in the thermal behavior of both LDPE and HDPE, even if a slight reduction in the overall bulk crystallinity was observed in presence of the nanofillers.

  9. Grafting of sodium montmorillonite with γ-aminopropyltriethoxysilane in ethanol/water dispersing medium

    NASA Astrophysics Data System (ADS)

    Asgari, Mohammad; Abouelmagd, Ahmed; Sundararaj, Uttandaraman

    2016-03-01

    In this work, silane grafted sodium montmorillonite was synthesized by γ-aminopropyltriethoxysilane to make it compatible with the organic polymer. The grafting reaction was examined by Fourier transform infrared (FTIR), 29Si NMR, and thermogravimetric analysis (TGA). The appearance of new peaks for FTIR results confirmed the presence of the grafted silane onto the clay platelets. Besides, 29Si NMR results revealed another extra resonance which belongs to new bonds formed at clay edges and on the internal nanoclay platelets. TGA results confirmed that by increasing the amount of silane, the amount of grafting silane also increased which was shown by increase of mass loss. DTG results showed that by increasing the amount of aminosilane used for modification, the amount of intercalated silane is also increased.

  10. Effect of leaving group on the oligomerization of 5'-AMP on montmorillonite. [Abstract only

    NASA Technical Reports Server (NTRS)

    Prabahar, K. Joseph; Ferris, James P.

    1994-01-01

    The oligomerization of imidazole derivative of 5'-AMP (ImpA) in the presence of montmorillonite clay yields oligomers containing up to 10 monomer units. In these reactions, the heterocyclic base, imidazole is the leaving group. In our present study, we synthesized a series of activated nucleotides of 5'AMP using other leaving groups such as pyrazole, 1,2,4-triazole, piperidine, morpholine, 4-aminopyridine, 4-methylaminopyridine, 4-dimethylaminopyridine, 2-aminobenzimidazole etc. to determine the effect of amine leaving group on the products of the oligomerization reaction. Earlier results from our laboratory showed that the presence AppA in the clay reaction of ImpA enhances the oligomerization reaction to yield higher oligomers. We also studied the effect of AppA in the clay mediated oligomerization reaction of the activated nucleotides. Oligomerization of 2-amino-benzimidazole derivative of 5'-AMP gave higher oligomers containing up to nine monomer units in the presence of AppA.

  11. Removal of Two Species of Harmful Algae Using Gramine Modified Montmorillonite.

    PubMed

    Liu, Su-Li; Wang, Wen-Wen; Liu, Fei; Li, Hong-Ye; Liu, Jie-Sheng; Yang, Wei-Dong

    2016-04-01

    A series of gramine modified montmorillonites (gramine-MMTs) were prepared and characterized by thermogravimetric analysis, X-ray diffraction and zeta potential measurements. These modified clays with various amounts of gramine all exhibited higher removal efficiencies of both Chattonella marina and Alexandrium tamarense than did natural clay. With the augmentation of gramine content in the modified clays, the removal efficiency increased. The 24 h LC50 values of gramine-MMT with 12.68 % of gramine on C. marina and A. tamarense were 9.16 and 10.21 mg L(-1), respectively. These data suggest gramine-MMT might be a promising material to remediate harmful algal blooms. PMID:26920698

  12. Attachment of bacteriophages MS2 and ?X174 onto kaolinite and montmorillonite: non-DLVO interactions

    NASA Astrophysics Data System (ADS)

    Chrysikopoulos, C.; Syngouna, V. I.

    2011-12-01

    This study aims to gain insights into the interaction of virus particles with clay colloids. Bacteriophages MS2 and ?X174 were used as model viruses and kaolinite (KGa-1b) and montmorillonite (STx-1b) as model colloids. The experimental data obtained from batch experiments of MS2 and ?X174 attachment onto KGa-1b and STx-1b suggested that virus attachment is adequately described by the Freundlich isotherm equation. Both MS2 and ?X174 were attached in greater amounts onto KGa-1b than STx-1b. Furthermore, theoretical interaction energy calculations suggested that electrostatic as well as Lewis acid-base interactions are of vital importance in the attachment of viruses onto clay colloids.

  13. Variable Temperature Infrared Spectroscopy Investigation of Benzoic Acid Interactions with Montmorillonite Clay Interlayer Water.

    PubMed

    Nickels, Tara M; Ingram, Audrey L; Maraoulaite, Dalia K; White, Robert L

    2015-07-01

    Molecular interactions between benzoic acid and cations and water contained in montmorillonite clay interlayer spaces are characterized by using variable temperature diffuse reflection infrared Fourier transform spectroscopy (VT-DRIFTS). Using sample perturbation and difference spectroscopy, infrared spectral changes resulting from removal of interlayer water and associated changes in local benzoic acid environments are identified. Difference spectra features can be correlated with changes in specific molecular vibrations that are characteristic of benzoic acid molecular orientation. Results suggest that the carboxylic acid functionality of benzoic acid interacts with interlayer cations through a bridging water molecule and that this interaction is affected by the nature of the cation present in the clay interlayer space. PMID:26037917

  14. Electrospun dual-porosity structure and biodegradation morphology of Montmorillonite reinforced PLLA nanocomposite scaffolds.

    PubMed

    Lee, Yun Hui; Lee, Jong Hoon; An, In-Gu; Kim, Chan; Lee, Doo Sung; Lee, Young Kwan; Nam, Jae-Do

    2005-06-01

    Combining a nanocomposite technique and the electrospinning process, a robust dual-porosity scaffold structure was developed for a facile transport of metabolic nutrients and wastes through the nano-sized pores and for the cell implantation and blood vessel invasion through the micro-sized pores. The montmorillonite (MMT) nano-sized platelets were incorporated into poly(L-lactic acid) (PLLA) solution, which was subsequently electrospun and mechanically entangled by a cold compression molding process for a robust 3-dimensional scaffold structure. Using a salt leaching/gas forming method, micro-sized pores were developed in the electrospun fiber bundles giving a dual-porosity scaffold structure. Compared with the pristine PLLA scaffold, the developed nanocomposite fibrous scaffold structure exhibited increased strength and improved structural integrity during the biodegradation process. The nanocomposite scaffold systems also exhibited many tiny pinholes desirably generated on the scaffold walls without serious fragmentation during biodegradation reactions. PMID:15603811

  15. Models of (ZrO2)n complexes intercalated into montmorillonite.

    PubMed

    Efremov, Dmitrii; Kuznetsova, Tatyana; Doronin, Vladimir; Sadykov, Vladislav

    2005-04-21

    The article discusses the properties of several model zirconium dioxide complexes (ZrO(2))(n)() intercalated into the interlayer space of montmorillonite clay. Grand canonical Monte Carlo simulation was used in a series of numerical experiments during analysis of the low-temperature nitrogen adsorption in the micropores thus generated. The goal of such experiments was to determine the geometrical parameters of introduced molecular complexes of different types inside micropores of various widths. The obtained information was used to characterize textural and structural properties of three pillared interlayer materials prepared by using pillaring species synthesized via aging of zirconyl chloride solutions containing as additives chlorides of Ca, Sr, or Ba. It was found that in the cases of Ba and Ca the interlayer micropores are filled with isolated tetramers (ZrO(2))(4). Meanwhile, the presence of Sr in the pillaring solution, most likely, favors the preservation of larger sheetlike complexes (ZrO(2))(8). PMID:16851854

  16. Biodegradable poly(propylene carbonate)/montmorillonite nanocomposites prepared by direct melt intercalation

    SciTech Connect

    Xu, J.; Li, R.K.Y. . E-mail: RKYLi@cityu.edu.hk; Meng, Y.Z. . E-mail: stdpmeng@zsu.edu.cn; Mai, Y-.W.

    2006-02-02

    Intercalation-exfoliated nanocomposites derived from poly(propylene carbonate) (PPC) and organo-modified montmorillonite (OMMT) were prepared by direct melt blending in an internal mixer. The nano-scale dispersion of the OMMT layers within the PPC matrix was verified using wide angle X-ray scattering and transmission electron microscopy technologies. Static mechanical properties were determined by using a tensile tester. The PPC/OMMT nanocomposites with lower OMMT content showed an increase in thermal decomposition temperature when compared with both pure PPC and the composites prepared from un-modified MMT. Dynamic mechanical analysis indicated that nano-scale OMMT dispersed well within PPC matrix and therefore enhanced the storage modulus of the composites.

  17. Synthesis and Electrorheological Characterization of Polyaniline and NA+-MONTMORILLONITE Clay Nanocomposite

    NASA Astrophysics Data System (ADS)

    Kim, J. W.; Kim, S. G.; Choi, H. J.; Suh, M. S.; Shin, M. J.; Jhon, M. J.

    Polyaniline-Na+-montmorillonite nanocomposite particles were synthesized using an emulsion intercalation method, and electrorheological (ER) fluids were produced by dispersing the synthesized nanocomposite particles in an electrically-insulating silicone oil. The emulsion of an aniline monomer with dodecyl benzenesulfonic acid was inserted into the layers of clay, and polymerization was processed by adding the oxidant initiator solution. DBSA as a emulsifier and a dopant took a important role for polyaniline clay nanocomposite. This insertion of polyaniline was confirmed by X-ray diffraction. To observe its ER properties, we measured the shear viscosity and the shear stress by controlling shear rate. Furthermore, we conducted dynamic tests to investigate the viscoelastic properties of the ER fluid under an electric field in the linear viscoelastic region.

  18. Carboxymethyl starch/montmorillonite composite microparticles: Properties and controlled release of isoproturon.

    PubMed

    Wilpiszewska, Katarzyna; Spychaj, Tadeusz; Pa?dzioch, Waldemar

    2016-01-20

    Preparation of novel high substituted carboxymethyl starch-based microparticles containing sodium montmorillonite (MMT) by crosslinking with Al(3+) was described. For preparing nanocomposite granules carboxymethyl starch (CMS) from native potato starch as well as CMS from amylopectin has been used. The hydrophilic CMS/MMT composite systems were used for herbicide, i.e. isoproturon encapsulation (ca. 75% encapsulation efficiency). The herbicide release rate from CMS/MMT composites in water was significantly reduced when compared to commercial isoproturon: 95% released after ca. 700 h and ca. 24h, respectively. Leaching in soil from composite systems was relatively slower than release in water. After a series of eight irrigations leached about 10% of isoproturon loaded. The CMS/MMT carriers could reduce the potential leaching of herbicide and beneficially reduce pollution of the environment. PMID:26572334

  19. Radiation-induced synthesis of vinyl copolymer based nanocomposites filled with reactive organic montmorillonite clay

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Kyum; Kwen, Hai-Doo; Choi, Seong-Ho

    2012-05-01

    Vinyl copolymer-clay nanocomposites were prepared by ?-irradiation-initiated radical polymerization using a mixture of styrene (St) and divinyl benzene (DVB) in the presence of reactive organic montmorillonite clay (OMMT) in methanol at room temperature. Reactive OMMT was synthesized by a cation exchange reaction of Na+-MMT and 1-[(4-ethylphenyl)methyl]-3-butyl-imidazolium chloride as a reactive organic modifier in an aqueous solution. The microstructures of the nanocomposites were confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The thermal stability was examined by thermo gravimetric analysis (TGA). As a result, the reactive OMMT was a good additive material for preparing vinyl copolymer-clay nanocomposites.

  20. 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)

  1. Influence of Operating Parameters on Surface Properties of RF Glow Discharge Oxygen Plasma Treated TiO2/PET Film for Biomedical Application

    EPA Science Inventory

    Thin transparent titania (TiO2) films were coated on the surface of flexible poly (ethylene terephthalate) (PET) surface using standard sol gel techniques. The TiO2/PET thin film surfaces were further modified by exposing the films to a RF glow discharge oxygen plasma. The exposu...

  2. Multifunctional poly(D,L-lactide-co-glycolide)/montmorillonite (PLGA/MMT) nanoparticles decorated by Trastuzumab for targeted chemotherapy of breast cancer.

    PubMed

    Sun, Bingfeng; Ranganathan, Balu; Feng, Si-Shen

    2008-02-01

    This paper continued our earlier work on the poly(D,L-lactide-co-glycolide)/montmorillonite nanoparticles (PLGA/MMT NPs), which were further decorated by human epidermal growth factor receptor-2 (HER2) antibody Trastuzumab for targeted breast cancer chemotherapy with paclitaxel as a model anticancer drug. Such a NP system is multifunctional, which formulates anticancer drugs with no harmful adjuvant, reduces the side effects of the formulated anticancer drug, promotes synergistic therapeutic effects, and achieves targeted delivery of the therapy. The paclitaxel-loaded PLGA/MMT NPs were prepared by a modified solvent extraction/evaporation technique, which were then decorated with Trastuzumab. The effects of the surface decoration on particle size and size distribution, surface morphology, drug encapsulation efficiency, as well as the drug release kinetics, were investigated. The NP formulation exhibited a biphasic drug release with a moderate initial burst followed by a sustained release profile. The surface decoration speeded the drug release. Surface chemistry analysis was conducted by X-ray photoelectron spectroscopy (XPS), which confirmed the presence of Trastuzumab on the NP surface. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed the stability of the antibody in the NP preparation process. Internalization of the coumarin-6-loaded PLGA/MMT NPs with or without the antibody decoration by both of Caco-2 colon adeno carcinoma cells and SK-BR-3 breast cancer cells was visualized by confocal laser scanning microscopy and quantitatively analyzed, which shows that the antibody decoration achieved significantly higher cellular uptake of the NPs. The results of in vitro cytotoxicity experiment on SK-BR-3 cells further proved the targeting effects of the antibody decoration. Judged by IC50 after 24h culture, the therapeutic effects of the drug formulated in the NPs with surface decoration could be 12.74 times higher than that of the bare NPs and 13.11 times higher than Taxol. PMID:17953985