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Sample records for acidic aqueous media

  1. Activation of Carbonyl-Containing Molecules with Solid Lewis Acids in Aqueous Media

    SciTech Connect

    Román-Leshkov, Yuriy; Davis, Mark E.

    2011-09-28

    Current interest in reacting carbonyl-containing molecules in aqueous media is primarily due to the growing emphasis on conversion of biomass to fuels and chemicals. Recently, solid Lewis acids have been shown to perform catalytic reactions with carbonyl-containing molecules such as sugars in aqueous media. Here, catalysis mediated by Lewis acids is briefly discussed, Lewis acid solids that perform catalysis in aqueous media are then described, and the review is concluded with a few comments on the outlook for the future.

  2. Bismuth catalysts in aqueous media.

    PubMed

    Kobayashi, Shū; Ueno, Masaharu; Kitanosono, Taku

    2012-01-01

    Several bismuth-catalyzed synthetic reactions, which proceed well in aqueous media, are discussed. Due to increasing demand of water as a solvent in organic synthesis, catalysts that can be used in aqueous media are becoming more and more important. Although bismuth Lewis acids are not very stable in water, it has been revealed that they can be stabilized by basic ligands. Chiral amine and related basic ligands combined with bismuth Lewis acids are particularly useful in asymmetric catalysis in aqueous media. On the other hand, bismuth hydroxide is stable and works as an efficient catalyst for carbon-carbon bond-forming reactions in water. PMID:21769719

  3. Electrochemistry of poly(vinylferrocene) modified electrodes in aqueous acidic media

    NASA Astrophysics Data System (ADS)

    Issa, Touma B.; Singh, Pritam; Baker, Murray V.

    A cyclic voltammetric study of the electrochemistry and chemical stability of the poly(vinylferrocene) (PVFc) redox couple, coated on a gold substrate, in aqueous solutions of H 2SO 4, HClO 4 and HCl was carried out. It was found that the anodic peak potential ( Epa) did not depend on the acid concentration in the range (1.0 × 10 -2 to 1.0 × 10 -7 mol L -1). However, the Epa values shifted linearly to less positive potentials when investigated in more concentrated acid solutions in the range 1-5 mol L -1. The slope of the Epa versus acid concentration graph was found to be in the order H 2SO 4 > HCl > HClO 4. In this regard PVFc behaved very similar to 1,1'-bis(11-mercaptoundecyl)ferrocene (Fc(C 11SH) 2) except for its chemical stability. In H 2SO 4 media the PVFc was found to be much less stable than 1,1'-Fc(C 11SH) 2. The dependence of Epa on acid concentration could be used to monitor state of charge of lead-acid batteries. However, for this application Fc(C 11SH) 2 would be a better choice because of its superior chemical stability.

  4. Lipase in biphasic alginate beads as a biocatalyst for esterification of butyric acid and butanol in aqueous media.

    PubMed

    Ng, Choong Hey; Yang, Kun-Lin

    2016-01-01

    Esterification of organic acids and alcohols in aqueous media is very inefficient due to thermodynamic constraints. However, fermentation processes used to produce organic acids and alcohols are often conducted in aqueous media. To produce esters in aqueous media, biphasic alginate beads with immobilized lipase are developed for in situ esterification of butanol and butyric acid. The biphasic beads contain a solid matrix of calcium alginate and hexadecane together with 5 mg/mL of lipase as the biocatalyst. Hexadecane in the biphasic beads serves as an organic phase to facilitate the esterification reaction. Under optimized conditions, the beads are able to catalyze the production of 0.16 mmol of butyl butyrate from 0.5 mmol of butyric acid and 1.5 mmol of butanol. In contrast, when monophasic beads (without hexadecane) are used, only trace amount of butyl butyrate is produced. One main application of biphasic beads is in simultaneous fermentation and esterification (SFE) because the organic phase inside the beads is very stable and does not leach out into the culture medium. SFE is successfully conducted with an esterification yield of 6.32% using biphasic beads containing iso-octane even though the solvent is proven toxic to the butanol-producing Clostridium spp. PMID:26672465

  5. Combination of best promoter and micellar catalyst for chromic acid oxidation of 1-butanol to 1-butanal in aqueous media at room temperature.

    PubMed

    Saha, Rumpa; Ghosh, Aniruddha; Saha, Bidyut

    2014-04-24

    In aqueous acidic media, picolinic acid, 2,2'-bipyridine and 1,10-phenanthroline promoted Cr(VI) oxidation of 1-butanol produces 1-butanal. 1-butanal is separated from mixture by fractional distillation. The anionic surfactant (SDS) and neutral surfactant (TX-100) accelerate the process while the cationic surfactant (CPC) retards the reaction. Combination of bipy and SDS is the best choice for chromic acid oxidation of 1-butanol to 1-butanal in aqueous media.

  6. Mukaiyama Aldol Reactions in Aqueous Media

    PubMed Central

    Kitanosono, Taku; Kobayashi, Shū

    2013-01-01

    Mukaiyama aldol reactions in aqueous media have been surveyed. While the original Mukaiyama aldol reactions entailed stoichiometric use of Lewis acids in organic solvents under strictly anhydrous conditions, Mukaiyama aldol reactions in aqueous media are not only suitable for green sustainable chemistry but are found to produce singular phenomena. These findings led to the discovery of a series of water-compatible Lewis acids such as lanthanide triflates in 1991. Our understanding on these beneficial effects in the presence of water will be deepened through the brilliant examples collected in this review. 1 Introduction 2 Rate Enhancement by Water in the Mukaiyama Aldol Reaction 3 Lewis Acid Catalysis in Aqueous or Organic Solvents 3.1 Water-Compatible Lewis Acids 4 Lewis-Base Catalysis in Aqueous or Organic Solvents 5 The Mukaiyama Aldol Reactions in 100% Water 6 Asymmetric Catalysts in Aqueous Media and Water 7 Conclusions and Perspective PMID:24971045

  7. Lewis Acid Pairs for the Activation of Biomass-derived Oxygenates in Aqueous Media

    SciTech Connect

    Roman, Yuriy

    2015-09-14

    The objective of this project is to understand the mechanistic aspects behind the cooperative activation of oxygenates by catalytic pairs in aqueous media. Specifically, we will investigate how the reactivity of a solid Lewis acid can be modulated by pairing the active site with other catalytic sites at the molecular level, with the ultimate goal of enhancing activation of targeted functional groups. Although unusual catalytic properties have been attributed to the cooperative effects promoted by such catalytic pairs, virtually no studies exist detailing the use heterogeneous water-tolerant Lewis pairs. A main goal of this work is to devise rational pathways for the synthesis of porous heterogeneous catalysts featuring isolated Lewis pairs that are active in the transformation of biomass-derived oxygenates in the presence of bulk water. Achieving this technical goal will require closely linking advanced synthesis techniques; detailed kinetic and mechanistic investigations; strict thermodynamic arguments; and comprehensive characterization studies of both materials and reaction intermediates. For the last performance period (2014-2015), two technical aims were pursued: 1) C-C coupling using Lewis acid and base pairs in Lewis acidic zeolites. Tin-, zirconium-, and hafnium containing zeolites (e.g., Sn-, Zr-, and Hf-Beta) are versatile solid Lewis acids that selectively activate carbonyl functional groups. In this aim, we demonstrate that these zeolites catalyze the cross-aldol condensation of aromatic aldehydes with acetone under mild reaction conditions with near quantitative yields. NMR studies with isotopically labeled molecules confirm that acid-base pairs in the Si-O-M framework ensemble promote soft enolization through α-proton abstraction. The Lewis acidic zeolites maintain activity in the presence of water and, unlike traditional base catalysts, in acidic solutions. 2) One-pot synthesis of MWW zeolite nanosheets for activation of bulky substrates. Through

  8. The Oxidation of Ascorbic Acid by Hexacyanoferrate(III) Ion in Acidic Aqueous Media.

    ERIC Educational Resources Information Center

    Martins, Luis J. A.; da Costa, J. Barbosa

    1988-01-01

    Describes a kinetic and mechanistic investigation of ascorbic acid by a substitution-inert complex in acidic medium suitable for the undergraduate level. Discusses obtaining the second order rate constant for the rate determining step at a given temperature and comparison with the value predicted on the basis of the Marcus cross-relation. (CW)

  9. The Kinetic Aspects of the Interaction of Nitrite Ions with Sulfanilic Acid and 1-Naphthylamine in Aqueous and Micellar Media

    NASA Astrophysics Data System (ADS)

    Korneeva, O. I.; Chernova, R. K.; Doronin, S. Yu.

    2008-04-01

    The kinetics of the reaction of nitrite ions with sulfanilic acid and 1-naphthylamine in aqueous and micellar (sodium dodecyl sulfate) media was studied step-by-step. The diazotization of sulfanilic acid with the nitrite ion was found to occur virtually instantaneously. Anionic surfactant micelles did not influence the rate of this reaction. The calculated effective rate constants and activation energies of the azo coupling reaction between synthesized sulfophenyldiazonium and 1-naphthylamine showed that the passage from water into the micellar medium decelerated the reaction. It was found that sodium dodecyl sulfate micelles played the role of a reagent separator.

  10. A novel liquid plasma AOP device integrating microwaves and ultrasounds and its evaluation in defluorinating perfluorooctanoic acid in aqueous media.

    PubMed

    Horikoshi, Satoshi; Sato, Susumu; Abe, Masahiko; Serpone, Nick

    2011-09-01

    A simplified and energy-saving integrated device consisting of a microwave applicator and an ultrasonic homogenizer has been fabricated to generate liquid plasma in a medium possessing high dielectric factors, for example water. The microwave waveguide and the ultrasonic transducer were interconnected through a tungsten/titanium alloy stick acting both as the microwave antenna and as the horn of the ultrasonic homogenizer. Both microwaves and ultrasonic waves are simultaneously transmitted to the aqueous media through the tungsten tip of the antenna. The microwave discharge liquid plasma was easily generated in solution during ultrasonic cavitation. The simple device was evaluated by carrying out the degradation of the perfluorooctanoic acid (PFOA), a system highly recalcitrant to degradation by conventional advanced oxidation processes (AOPs). PFOA is 59% degraded in an aqueous medium after only 90 s of irradiation by the plasma. Intermediates were identified by electrospray mass spectral techniques in the negative ion mode.

  11. L-ascorbic acid quenching of singlet delta molecular oxygen in aqueous media: generalized antioxidant property of vitamin C

    SciTech Connect

    Chou, P.T.; Khan, A.U.

    1983-09-30

    L-ascorbic acid quenches singlet (/sup 1/..delta../sub g/) molecular oxygen in aqueous media (pH 6.8 for (/sup 1/H)H/sub 2/O and pD 7.2 for (/sup 2/H)D/sub 2/O) as measured directly by monitoring (0,0) /sup 1/..delta../sub g/ ..-->.. /sup 3/..sigma../sub g//sup -/ emission at 1.28 micron. Singlet oxygen was generated at room temperature in the solutions via photosensitization of sodium chrysene sulfonate; this sulfonated polycyclic hydrocarbon was synthesized to provide a water soluble chromophore inert to usual dye-ascorbate photobleaching. A marked isotope effect is found; k/sub Q//sup H/sub 2/O/ is 3.3 times faster than k/sub Q//sup D/sub 2/O/, suggesting ascorbic acid is chemically quenching singlet oxygen.

  12. Curcumin-cysteine and curcumin-tryptophan conjugate as fluorescence turn on sensors for picric Acid in aqueous media.

    PubMed

    Gogoi, Bedanta; Sen Sarma, Neelotpal

    2015-06-01

    Rapid detection of picric acid in real sample is of outmost importance from the perspective of health, safety, and environment. In this study, a very simple and cost-effective detection of picric acid is accomplished by developing a couple of biobased conjugates curcumin-cysteine (CC) and curcumin-tryptophan (CT), which undergo efficient fluorescence turn on toward picric acid in aqueous media. Both the probes experience about 26.5-fold fluorescence enhancements at 70 nM concentration of the analyte. Here, the fluorescence turn on process is governed by the aggregation induced emission, which is induced from the electrostatic interaction between the conjugates with picric acid. The detection limit of CC and CT are about 13.51 and 13.54 nM of picric acid, respectively. Importantly, both the probes exhibit high selectivity and low interference of other analogues toward the detection of picric acid. In addition, the probes are highly photostable, show low response time and are practically applicable for sensing picric acid in real environmental samples, which is the ultimate goal of this work. PMID:25955402

  13. Dissociation quotient of benzoic acid in aqueous sodium chloride media to 250{degrees}C

    SciTech Connect

    Kettler, R.M.; Palmer, D.A.; Wesolowski, D.J.

    1995-04-01

    The dissociation quotient of benzoic acid was determined potentiometrically in a concentration cell fitted with hydrogen electrodes. The hydrogen ion molality of benzoic acid/benzoate solutions was measured relative to a standard aqueous HCl solution at seven temperatures from 5 to 250{degrees}C and at seven ionic strengths ranging from 0.1 to 5.0 molal (NaCl). The molal dissociation quotients and selected literature data were fitted in the isocoulombic (all anionic) form by a six-term equation. This treatment yielded the following thermodynamic quantities for the acid dissociation equilibrium at 25{degrees}C and 1 bar: logK{sub a} = -4.206{+-}0.006, {Delta}H{sub a}{sup 0} = 0.3{+-}0.3 kJ-mol{sup {minus}1}, {Delta}S{sub a}{sup 0} = -79.6{+-}1.0 J-mol{sup {minus}1}-K{sup {minus}1}, and {Delta}C{sub p;a}{sup 0} = -207{+-}5 J-mol{sup {minus}1}-K{sup {minus}1}. A five-term equation derived to describe the dependence of the dissociation constant on solvent density is accurate to 250{degrees}C and 200 MPa.

  14. J-aggregate formation of a water-soluble porphyrin in acidic aqueous media

    NASA Astrophysics Data System (ADS)

    Ohno, Osamu; Kaizu, Youkoh; Kobayashi, Hiroshi

    1993-09-01

    J aggregate of a water-soluble porphyrin, 5,10,15,20-tetra(4-sulfophenyl)porphyrin (H2TPPS44-), formed in acidified aqueous solutions, exhibits sharp and intense absorption bands at 491 and 707 nm. These characteristic transitions, J bands, are of linear oscillators polarized in the long axis of rodlike aggregate. The molecules in the aggregate stack so as to lift the degeneracy of the porphyrin planar oscillator excited states. Measurements of flow-induced linear dichroism, circular dichroism, magnetic circular dichroism, as well as polarized fluorescence excitation spectra provide evidence not only of linear oscillator character of the intense J band at 491 nm, but also of presence of another diffuse absorption band around at 420 nm polarized in the short axis of the aggregate, which is the counterpart of the 491 nm band of porphyrin Soret origin. Extrinsic circular dichroism is induced upon addition of L-tartaric acid or by mechanical swirling flow in the period of aggregate growth. Resonance Raman spectrum of the aggregate is rather similar to that of the monomeric diacid except the polarization. The observed shifts of Raman peaks to lower frequency are ascribed to a deformation of porphyrin moiety and/or hydrophobic interaction between component molecules in the aggregate. The sharp and intense J bands polarized in the long axis of aggregate cannot be well described without taking into account the participation of interporphyrin charge resonance excited states, whereas the broadbands polarized in the short axis are exclusively ascribed to exciton resonance excited states. The porphyrin J band is characterized as sustaining an exchange narrowing by fast migration of excitation over the whole system of chromophores in a linear array of the porphyrin planar oscillators in slipped face-to-face stacking.

  15. Kinetic and thermodynamic characterization of C-N bond rotation by N-methylacetohydroxamic acid in aqueous media.

    PubMed

    Sippl, Stefanie P; White, Paul B; Fry, Charles G; Volk, Sarah E; Ye, Lingxiao; Schenck, Heather L

    2016-01-01

    Hydroxamic acids (HAs) perform tasks in medicine and industry that require bidentate metal binding. The two favored conformations of HAs are related by rotation around the C(=O)-N bond. The conformations are unequal in stability. Recently, we reported that the most stable conformation of a small secondary HA in water places the oxygen atoms anti to one another. The barrier to C-N bond rotation may therefore modulate metal binding by secondary HAs in aqueous media. We have now determined the activation barrier to C-N rotation from major to minor conformation of a small secondary HA in D2O to be 67.3 kJ/mol. The HA rotational barrier scales with solvent polarity, as is observed in amides, although the HA barrier is less than that of a comparable tertiary amide in aqueous solution. Successful design of new secondary HAs to perform specific tasks requires solid understanding of rules governing HA structural behavior. Results from this work provide a more complete foundation for HA design efforts.

  16. Elucidation of adsorption processes at the surface of Pt(331) model electrocatalysts in acidic aqueous media.

    PubMed

    Pohl, Marcus D; Colic, Viktor; Scieszka, Daniel; Bandarenka, Aliaksandr S

    2016-04-28

    The Pt(331) surface has long been known to be the most active pure metal electrocatalyst for the oxygen reduction reaction (ORR) in acidic media. Its activity is often higher than those known for the Pt-based alloys towards ORR, being comparable with the most active Pt3Ni(111), Pt3Y or Pt5Gd, and being more active than e.g. polycrystalline Pt3Ni. Multiple active sites at this surface offer adsorption energies which are close to the optimal binding energy with respect to the main ORR intermediates; nevertheless, the exact location of these sites is still not clear. Taking into account the unique surface geometry of Pt(331), some adsorbates (including some oxygenated ORR-intermediates) should also contribute to the electronic structure of the neighbouring catalytic centres. However, the experimental elucidation of the specific adsorption of oxygenated species at this surface appears to be a non-trivial task. Such information holds the keys to the understanding of the high activity of this material and would enable the rational design of nanostructured ORR catalysts even without alloying. In this work, the electrified Pt(331)/electrolyte interface has been characterised using cyclic voltammetry (CV) combined with potentiodynamic electrochemical impedance spectroscopy (PDEIS) in 0.1 M HClO4 solutions. The systems were studied in the potential region between 0.05 V and 1.0 V vs. RHE, where the adsorption of *H, *OH and *O species is possible in both O2-free and O2-saturated electrolytes. Our CV and PDEIS results support the hypothesis that in contrast to Pt(111), many Pt(331) surface sites are likely blocked by *O species at the polymer electrolyte membrane fuel cell benchmark potential of 0.9 V (RHE). We propose a model illustrated by simplified adsorbate structures at different electrode potentials, which is, however, able to explain the voltammetric and impedance data, and which is in good agreement with previously reported electrocatalytic measurements. PMID

  17. Determination of the optimum conditions for boric acid extraction with carbon dioxide gas in aqueous media from colemanite containing arsenic

    SciTech Connect

    Ata, O.N.; Colak, S.; Copur, M.; Celik, C.

    2000-02-01

    The Taguchi method was used to determine optimum conditions for the boric acid extraction from colemanite ore containing As in aqueous media saturated by CO{sub 2} gas. After the parameters were determined to be efficient on the extraction efficiency, the experimental series with two steps were carried out. The chosen experimental parameters for the first series of experiments and their ranges were as follows: (1) reaction temperature, 25--70 C; (2) solid-to-liquid ratio (by weight), 0.091 to 0.333; (3) gas flow rate (in mL/min), 66.70--711; (4) mean particle size, {minus}100 to {minus}10 mesh; (5) stirring speed, 200--600 rpm; (6) reaction time, 10--90 min. The optimum conditions were found to be as follows: reaction temperature, 70 C; solid-to-liquid ratio, 0.091; gas flow rate, 711 (in mL/min); particle size, {minus}100 mesh; stirring speed, 500 rpm; reaction time, 90 min. Under these optimum conditions, the boric acid extraction efficiency from the colemanite containing As was approximately 54%. Chosen experimental parameters for the second series of experiments and their ranges were as follows: (1) reaction temperature, 60--80 C; (2) solid-to-liquid ratio (by weight), 0.1000 to 0.167; (3) gas pressure (in atm), 1.5; 2.7; (4) reaction time, 45--120 min. The optimum conditions were found to be as follows: reaction temperature, 70 C; solid-to-liquid ratio, 0.1; gas pressure, 2.7 atm; reaction time, 120 min. Under these optimum conditions the boric acid extraction efficiency from the colemanite ore was approximately 75%. Under these optimum conditions, the boric acid extraction efficiency from calcined colemanite ore was approximately 99.55%.

  18. Electrochemical degradation of trichloroacetic acid in aqueous media: influence of the electrode material.

    PubMed

    Esclapez, M D; Díez-García, M I; Sàez, V; Bonete, P; González-García, José

    2013-01-01

    The electrochemical degradation of trichloroacetic acid (TCAA) in water has been analysed through voltammetric studies with a rotating disc electrode and controlled-potential bulk electrolyses. The influence of the mass-transport conditions and initial concentration of TCAA for titanium, stainless steel and carbon electrodes has been studied. It is shown that the electrochemical reduction of TCAA takes place prior to the massive hydrogen evolution in the potential window for all electrode materials studied. The current efficiency is high (> 18%) compared with those normally reported in the literature, and the fractional conversion is above 50% for all the electrodes studied. Only dichloroacetic acid (DCAA) and chloride anions were routinely detected as reduction products for any of the electrodes, and reasonable values of mass balance error were obtained. Of the three materials studied, the titanium cathode gave the best results. PMID:23530352

  19. Conversion of carbohydrate biomass to γ-valerolactone by using water-soluble and reusable iridium complexes in acidic aqueous media.

    PubMed

    Deng, Jin; Wang, Yan; Pan, Tao; Xu, Qing; Guo, Qing-Xiang; Fu, Yao

    2013-07-01

    Mild-mannered manipulation: A catalytic method for the conversion of carbohydrate biomass to γ-valerolactone in acidic aqueous media has been developed. The water-soluble iridium complexes were observed to be extremely catalytically active for providing γ-valerolactone in high yields with high TONs. The homogeneous catalysts can also be recycled and reused by applying a simple phase separation process. PMID:23757330

  20. Supramolecular Polymers in Aqueous Media.

    PubMed

    Krieg, Elisha; Bastings, Maartje M C; Besenius, Pol; Rybtchinski, Boris

    2016-02-24

    This review discusses one-dimensional supramolecular polymers that form in aqueous media. First, naturally occurring supramolecular polymers are described, in particular, amyloid fibrils, actin filaments, and microtubules. Their structural, thermodynamic, kinetic, and nanomechanical properties are highlighted, as well as their importance for the advancement of biologically inspired supramolecular polymer materials. Second, five classes of synthetic supramolecular polymers are described: systems based on (1) hydrogen-bond motifs, (2) large π-conjugated surfaces, (3) host-guest interactions, (4) peptides, and (5) DNA. We focus on recent studies that address key challenges in the field, providing mechanistic understanding, rational polymer design, important functionality, robustness, or unusual thermodynamic and kinetic properties. PMID:26727633

  1. Changing the Action of Iron from Stoichiometric to Electrocatalytic in the Hydrogenation of Ketones in Aqueous Acidic Media.

    PubMed

    Gottardo, Marina; Easton, Max; Fabos, Viktoria; Guo, Si-Xuan; Zhang, Jie; Perosa, Alvise; Selva, Maurizio; Bond, Alan M; Masters, Anthony F; Maschmeyer, Thomas

    2015-11-01

    Cyclohexanone, a model compound chosen to conveniently represent small oxygenates present in the aqueous phase of biomass hydrothermal upgrading streams, was hydrogenated in the presence of electrodeposited iron(0) using aqueous formic or sulfuric acid as a hydrogen donor. Under these conditions, zero-valent iron is consumed stoichiometrically and serves as both a formic acid decomposition site and a hydrogen transfer agent. However, the resulting iron(II) can be used to continuously regenerate iron(0) when a potential is applied to the glassy carbon working electrode. Controlled potential electrolysis experiments show a 17% conversion of cyclohexanone (over 1000 seconds) to cyclohexanol with >80% efficiency of iron deposition from an iron(II) sulfate solution containing formic or sulfuric acid. In the absence of electrodeposited iron, formation of cyclohexanol could not be detected.

  2. Changing the Action of Iron from Stoichiometric to Electrocatalytic in the Hydrogenation of Ketones in Aqueous Acidic Media.

    PubMed

    Gottardo, Marina; Easton, Max; Fabos, Viktoria; Guo, Si-Xuan; Zhang, Jie; Perosa, Alvise; Selva, Maurizio; Bond, Alan M; Masters, Anthony F; Maschmeyer, Thomas

    2015-11-01

    Cyclohexanone, a model compound chosen to conveniently represent small oxygenates present in the aqueous phase of biomass hydrothermal upgrading streams, was hydrogenated in the presence of electrodeposited iron(0) using aqueous formic or sulfuric acid as a hydrogen donor. Under these conditions, zero-valent iron is consumed stoichiometrically and serves as both a formic acid decomposition site and a hydrogen transfer agent. However, the resulting iron(II) can be used to continuously regenerate iron(0) when a potential is applied to the glassy carbon working electrode. Controlled potential electrolysis experiments show a 17% conversion of cyclohexanone (over 1000 seconds) to cyclohexanol with >80% efficiency of iron deposition from an iron(II) sulfate solution containing formic or sulfuric acid. In the absence of electrodeposited iron, formation of cyclohexanol could not be detected. PMID:26382111

  3. Suitable combination of promoter and micellar catalyst for kilo fold rate acceleration on benzaldehyde to benzoic acid conversion in aqueous media at room temperature: A kinetic approach

    NASA Astrophysics Data System (ADS)

    Ghosh, Aniruddha; Saha, Rumpa; Ghosh, Sumanta K.; Mukherjee, Kakali; Saha, Bidyut

    2013-05-01

    The kinetics of oxidation of benzaldehyde by chromic acid in aqueous and aqueous surfactant (sodium dodecyl sulfate, SDS, alkyl phenyl polyethylene glycol, Triton X-100 and N-cetylpyridinium chloride, CPC) media have been investigated in the presence of promoter at 303 K. The pseudo-first-order rate constants (kobs) were determined from a logarithmic plot of absorbance as a function time. The rate constants were found to increase with introduction of heteroaromatic nitrogen base promoters such as Picolinic acid (PA), 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen). The product benzoic acid has been characterized by conventional melting point experiment, NMR, HRMS and FTIR spectral analysis. The mechanism of both unpromoted and promoted reaction path has been proposed for the reaction. In presence of the anionic surfactant SDS, cationic surfactant CPC and neutral surfactant TX-100 the reaction can undergo simultaneously in both aqueous and micellar phase with an enhanced rate of oxidation in the micellar phase. Both SDS and TX-100 produce normal micellar effect whereas CPC produce reverse micellar effect in the presence of benzaldehyde. The observed net enhancement of rate effects has been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. SDS and bipy combination is the suitable one for benzaldehyde oxidation.

  4. Suitable combination of promoter and micellar catalyst for kilo fold rate acceleration on benzaldehyde to benzoic acid conversion in aqueous media at room temperature: a kinetic approach.

    PubMed

    Ghosh, Aniruddha; Saha, Rumpa; Ghosh, Sumanta K; Mukherjee, Kakali; Saha, Bidyut

    2013-05-15

    The kinetics of oxidation of benzaldehyde by chromic acid in aqueous and aqueous surfactant (sodium dodecyl sulfate, SDS, alkyl phenyl polyethylene glycol, Triton X-100 and N-cetylpyridinium chloride, CPC) media have been investigated in the presence of promoter at 303 K. The pseudo-first-order rate constants (kobs) were determined from a logarithmic plot of absorbance as a function time. The rate constants were found to increase with introduction of heteroaromatic nitrogen base promoters such as Picolinic acid (PA), 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen). The product benzoic acid has been characterized by conventional melting point experiment, NMR, HRMS and FTIR spectral analysis. The mechanism of both unpromoted and promoted reaction path has been proposed for the reaction. In presence of the anionic surfactant SDS, cationic surfactant CPC and neutral surfactant TX-100 the reaction can undergo simultaneously in both aqueous and micellar phase with an enhanced rate of oxidation in the micellar phase. Both SDS and TX-100 produce normal micellar effect whereas CPC produce reverse micellar effect in the presence of benzaldehyde. The observed net enhancement of rate effects has been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. SDS and bipy combination is the suitable one for benzaldehyde oxidation.

  5. FIA titrations of phenothiazine derivatives in aqueous micellar and non-aqueous media.

    PubMed

    Nemcová, Irena; Nesmerák, Karel; Rychlovský, Petr; Koutníková, Jitka

    2005-02-15

    New methods of flow injection analysis (FIA) neutralization titrations of phenothiazine derivatives in aqueous micellar medium of a cationic surfactant using potentiometric and spectrophotometric detection were proposed; titrations with a mixing gradient chamber and high-speed titrations were compared. The FIA titration method in non-aqueous media based on an official method of determination (titration with perchloric acid in anhydrous acetic acid) was also developed. Under optimized reaction conditions and flow-through parameters, the calibration range and equations, the sensitivity, and the repeatability of all methods were found and discussed. All titrations were assayed for medicinal forms.

  6. Palladium-catalyzed mono-N-allylation of unprotected anthranilic acids with allylic alcohols in aqueous media.

    PubMed

    Hikawa, Hidemasa; Yokoyama, Yuusaku

    2011-10-21

    Palladium-catalyzed N-allylation of anthranilic acids 1a-j with allyl alcohol 2a in the presence of Pd(OAc)(2), sodium diphenylphosphinobenzene-3-sulfonate (TPPMS) in THF-H(2)O at room temperature gave only mono-N-allylated anthranilic acids 3a-j in good yields (70-98%). The reactions of 4-bromoanthranilic acid 1i with 2-methyl-3-buten-2-ol 2b showed complete chemoselectivity in N-allylation (neutral conditions) and C-vinylation (basic conditions). In our catalytic system, the keys to success are use of an unprotected anthranilic acid as a starting material and the presence of water in the reaction medium. The carboxyl group of anthranilic acid and water may play important roles for the smooth generation of the π-allyl palladium species by activation of the hydroxyl group of the allylic alcohol. PMID:21919524

  7. Photochemistry of aqueous pyruvic acid.

    PubMed

    Griffith, Elizabeth C; Carpenter, Barry K; Shoemaker, Richard K; Vaida, Veronica

    2013-07-16

    The study of organic chemistry in atmospheric aerosols and cloud formation is of interest in predictions of air quality and climate change. It is now known that aqueous phase chemistry is important in the formation of secondary organic aerosols. Here, the photoreactivity of pyruvic acid (PA; CH3COCOOH) is investigated in aqueous environments characteristic of atmospheric aerosols. PA is currently used as a proxy for α-dicarbonyls in atmospheric models and is abundant in both the gas phase and the aqueous phase (atmospheric aerosols, fog, and clouds) in the atmosphere. The photoreactivity of PA in these phases, however, is very different, thus prompting the need for a mechanistic understanding of its reactivity in different environments. Although the decarboxylation of aqueous phase PA through UV excitation has been studied for many years, its mechanism and products remain controversial. In this work, photolysis of aqueous PA is shown to produce acetoin (CH3CHOHCOCH3), lactic acid (CH3CHOHCOOH), acetic acid (CH3COOH), and oligomers, illustrating the progression from a three-carbon molecule to four-carbon and even six-carbon molecules through direct photolysis. These products are detected using vibrational and electronic spectroscopy, NMR, and MS, and a reaction mechanism is presented accounting for all products detected. The relevance of sunlight-initiated PA chemistry in aqueous environments is then discussed in the context of processes occurring on atmospheric aerosols.

  8. Conformation and protonation of 2,2'-bipyridine and 4,4'-bipyridine in acidic aqueous media and acidic ZSM-5 zeolites: a Raman scattering study.

    PubMed

    Moissette, A; Batonneau, Y; Brémard, C

    2001-12-12

    In situ FT-Raman scattering spectroscopy was used to monitor the sorption kinetics of 2,2'- and 4,4'-bipyridine in acidic ZSM-5 zeolites. The data processing of all the Raman spectra was applied to extract the characteristic Raman spectra of occluded species and respective Raman contribution generated from many spectral data which resolves spectrum of mixture into pure component spectra without any prior information. The assignment of the extracted spectra was performed according to careful comparison with corresponding spectra extracted from a set of Raman spectra recorded during the protonation of 2,2'- or 4,4'-bipyridine (bpy) in hydrochloric acid aqueous solutions. The data processing of the Raman spectra recorded during the slow sorption of 4,4'-bpy in acidic H(n)ZSM-5 (n = 3, 6) zeolites provides specific Raman spectrum of N,N'-diprotonated dication 4,4'-bpyH(2)(2+) as unique species generated in the void space of acidic ZSM-5 zeolites. No evidence of Lewis acid sites was found during the sorption of 4,4'-bpy by Raman scattering spectroscopy. The data processing of the Raman spectra recorded during the slow sorption of 2,2'-bpy in acidic H(n)ZSM-5 (n = 3, 6) zeolites provides specific Raman spectrum of trans-N-monoprotonated cation 2,2'-bpyH+ as major species generated in the void space of acidic ZSM-5 zeolites at loading corresponding to 1 mol per unit cell. The trans/cis interconversion occurs at higher loading even after the complete uptake of the sorbate and indicates some rearrangement in the void space over a long time. The cations were found to be located in straight channels in the vicinity of the intersection with the zigzag channel of the porous materials with the expected conformations deduced from ab initio calculations. However, the motions of occluded species within the channel of ZSM-5 are hindered but remain in the range of the isotropic limit of a liquid at room temperature.

  9. Insights into the interplay of Lewis and Brønsted acid catalysts in glucose and fructose conversion to 5-(hydroxymethyl)furfural and levulinic acid in aqueous media.

    PubMed

    Choudhary, Vinit; Mushrif, Samir H; Ho, Christopher; Anderko, Andrzej; Nikolakis, Vladimiros; Marinkovic, Nebojsa S; Frenkel, Anatoly I; Sandler, Stanley I; Vlachos, Dionisios G

    2013-03-13

    5-(Hydroxymethyl)furfural (HMF) and levulinic acid production from glucose in a cascade of reactions using a Lewis acid (CrCl3) catalyst together with a Brønsted acid (HCl) catalyst in aqueous media is investigated. It is shown that CrCl3 is an active Lewis acid catalyst in glucose isomerization to fructose, and the combined Lewis and Brønsted acid catalysts perform the isomerization and dehydration/rehydration reactions. A CrCl3 speciation model in conjunction with kinetics results indicates that the hydrolyzed Cr(III) complex [Cr(H2O)5OH](2+) is the most active Cr species in glucose isomerization and probably acts as a Lewis acid-Brønsted base bifunctional site. Extended X-ray absorption fine structure spectroscopy and Car-Parrinello molecular dynamics simulations indicate a strong interaction between the Cr cation and the glucose molecule whereby some water molecules are displaced from the first coordination sphere of Cr by the glucose to enable ring-opening and isomerization of glucose. Additionally, complex interactions between the two catalysts are revealed: Brønsted acidity retards aldose-to-ketose isomerization by decreasing the equilibrium concentration of [Cr(H2O)5OH](2+). In contrast, Lewis acidity increases the overall rate of consumption of fructose and HMF compared to Brønsted acid catalysis by promoting side reactions. Even in the absence of HCl, hydrolysis of Cr(III) decreases the solution pH, and this intrinsic Brønsted acidity drives the dehydration and rehydration reactions. Yields of 46% levulinic acid in a single phase and 59% HMF in a biphasic system have been achieved at moderate temperatures by combining CrCl3 and HCl.

  10. Aqueous Photochemistry of Glyoxylic Acid.

    PubMed

    Eugene, Alexis J; Xia, Sha-Sha; Guzman, Marcelo I

    2016-06-01

    Aerosols affect climate change, the energy balance of the atmosphere, and public health due to their variable chemical composition, size, and shape. While the formation of secondary organic aerosols (SOA) from gas phase precursors is relatively well understood, studying aqueous chemical reactions contributing to the total SOA budget is the current focus of major attention. Field measurements have revealed that mono-, di-, and oxo-carboxylic acids are abundant species present in SOA and atmospheric waters. This work explores the fate of one of these 2-oxocarboxylic acids, glyoxylic acid, which can photogenerate reactive species under solar irradiation. Additionally, the dark thermal aging of photoproducts is studied by UV-visible and fluorescence spectroscopies to reveal that the optical properties are altered by the glyoxal produced. The optical properties display periodicity in the time domain of the UV-visible spectrum of chromophores with absorption enhancement (thermochromism) or loss (photobleaching) during nighttime and daytime cycles, respectively. During irradiation, excited state glyoxylic acid can undergo α-cleavage or participate in hydrogen abstractions. The use of (13)C nuclear magnetic resonance spectroscopy (NMR) analysis shows that glyoxal is an important intermediate produced during direct photolysis. Glyoxal quickly reaches a quasi-steady state as confirmed by UHPLC-MS analysis of its corresponding (E) and (Z) 2,4-dinitrophenylhydrazones. The homolytic cleavage of glyoxylic acid is proposed as a fundamental step for the production of glyoxal. Both carbon oxides, CO2(g) and CO(g) evolving to the gas-phase, are quantified by FTIR spectroscopy. Finally, formic acid, oxalic acid, and tartaric acid photoproducts are identified by ion chromatography (IC) with conductivity and electrospray (ESI) mass spectrometry (MS) detection and (1)H NMR spectroscopy. A reaction mechanism is proposed based on all experimental observations. PMID:27192089

  11. Alum Catalyzed Simple, Efficient, and Green Synthesis of 2-[3-Amino-5-methyl-5-(pyridin-3-yl)-1,5-dihydro-4H-1,2,4-triazol-4-yl]propanoic Acid Derivatives in Aqueous Media

    PubMed Central

    Sachdeva, Harshita; Dwivedi, Diksha; Saroj, Rekha

    2013-01-01

    Alum (KAl(SO4)2·12H2O) is an inexpensive, efficient, and nontoxic catalyst used for the synthesis of 2-[3-amino-5-methyl-5-(pyridin-3-yl)-1,5-dihydro-4H-1,2,4-triazol-4-yl]propanoic acid derivatives in aqueous media by the reaction of 3-acetyl pyridine (1), amino acids (2)/(6), and thiosemicarbazide (4) at 80°C. This methodology offers significant improvements for the synthesis of products with regards to the yield of products, simplicity in operation, and green aspects by avoiding toxic catalysts which uphold the motto of green chemistry. Synthesized compounds have been characterized by FT-IR, 13C NMR, and 1HNMR spectroscopy. PMID:24288503

  12. Investigation of aqueous stability of taxol in different release media.

    PubMed

    Amini-Fazl, Mohammad Sadegh; Mobedi, Hamid; Barzin, Jalal

    2014-04-01

    In the present study, the aqueous stability of taxol in different aqueous media and immiscible aqueous/organic systems at 37 °C was investigated. The aqueous media included phosphate buffered saline (PBS) and PBS containing 10% methanol, 10% ethanol, 10% hydroxypropyl β-cyclodextrin (HP-βCD), 1% sodium citrate and 1% Tween 80. The immiscible systems consisted of PBS/octanol, PBS/dichloromethane, PBS/chloroform and PBS/ethyl acetate. The concentrations of taxol and related derivatives in each of the media were determined through the high-performance liquid chromatography assay. Results showed that hydrolysis and epimerization were two major types of degradation for taxol in the aqueous media starting from the initial hours of contact (6 hours). Addition of Tween 80 to PBS moderately increased the aqueous stability of taxol. As well, using PBS containing 10% HP-βCD inhibited the taxol hydrolysis, while epimerization still in process. In the case of immiscible systems, except for PBS/ethyl acetate system, no evidences of taxol hydrolysis were observed. Meanwhile, epimerization of taxol in PBS/dichloromethane and PBS/chloroform systems underwent due to the ability of C-Cl bonds to form hydrogen bonding with the hydroxyl group of C7 of taxol.

  13. CHEMICAL SYNTHESES IN AQUEOUS MEDIA USING MICROWAVES

    EPA Science Inventory

    The development of efficient, selective and eco-friendly synthetic methods has remained a major focus of our research group. Microwave (MW) irradiation as alternative energy source in conjunction with water as reaction media has proven to be a successful 'greener' chemical appro...

  14. An efficient tandem approach for the synthesis of functionalized 2-pyridone-3-carboxylic acids using three-component reaction in aqueous media.

    PubMed

    Mehrparvar, Saber; Balalaie, Saeed; Rabbanizadeh, Mahnaz; Ghabraie, Elmira; Rominger, Frank

    2014-08-01

    Novel analogs of 2-pyridone-3-carboxylic acids 4a-l have been prepared by the three-component reaction of 3-formyl chromone, Meldrum's acid, and primary amines in the presence of a catalytic amount of diammonium hydrogen phosphate in water. Good-to-high yields, easy work-up, and an environmentally friendly profile are the advantages of this method for the synthesis of 2-pyridone-3-carboxylic acid derivatives.

  15. Vibrational analysis of amino acids and short peptides in aqueous media. V. The effect of the disulfide bridge on the structural features of the peptide hormone somatostatin-14.

    PubMed

    Hernández, Belén; Carelli, Claude; Coïc, Yves-Marie; De Coninck, Joël; Ghomi, Mahmoud

    2009-09-24

    To emphasize the role played by the S-S bridge in the structural features of somatostatin-14 (SST-14), newly recorded CD and Raman spectra of this cyclic peptide and its open analogue obtained by Cys-->Ser substitution are presented. CD spectra of both peptides recorded in aqueous solutions in the 100-500 microM concentration range are strikingly similar. They reveal principally that random conformers constitute the major population in both peptides. Consequently, the S-S bridge has no structuring effect at submillimolar concentrations. In methanol, the CD spectrum of somatostatin-14 keeps globally the same spectral shape as that observed in water, whereas its open analogue presents a major population of helical conformers. Raman spectra recorded as a function of peptide concentration (5-20 mM) and also in the presence of 150 mM NaCl provide valuable conformational information. All Raman spectra present a mixture of random and beta-hairpin structures for both cyclic and open peptides. More importantly, the presence or the absence of the disulfide bridge does not seem to influence considerably different populations of secondary structures within this range of concentrations. CD and Raman data obtained in the submillimolar and millimolar ranges of concentrations, respectively, lead us to accept the idea that SST-14 monomers aggregate upon increasing concentration, thus stabilizing beta-hairpin conformations in solution. However, even at high concentrations, random conformers do not disappear. Raman spectra of SST-14 also reveal a concentration effect on the flexibility of the S-S linkage and consequently on that of its cyclic part. In conclusion, although the disulfide linkage does not seem to markedly influence the SST-14 conformational features in aqueous solutions, its presence seems to be necessary to ensure the flexibility of the cyclic part of this peptide and to maintain its closed structure in lower dielectric constant environments.

  16. Application of surfactant-templated ordered mesoporous material as sorbent in micro-solid phase extraction followed by liquid chromatography-triple quadrupole mass spectrometry for determination of perfluorinated carboxylic acids in aqueous media.

    PubMed

    Lashgari, Maryam; Basheer, Chanbasha; Kee Lee, Hian

    2015-08-15

    In the present study, micro-solid phase extraction (µ-SPE) followed by liquid chromatography-triple tandem mass spectrometery (LC-MS/MS) was developed for the determination of perfluorocarboxylic acids (PFCAs) at trace levels in water samples. The µ-SPE device comprised of a porous polypropylene membrane bag containing 5mg sorbent. The membrane bag acted as a clean-up filter and prevented matrix compounds from interfering with the extraction process. Analysis was carried out by LC-MS/MS in negative electrospray ionization mode. MS/MS parameters were optimized for multiple reaction monitoring. Calcined and non-calcined MCM-41, as silica-ordered mesoporous materials, were used as sorbents in µ-SPE for the extraction of five PFCAs-perfluoropentanoic acid (PFPA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA)-from aqueous media. The performances of these two sorbents were compared with other sorbents such as octadecylsilane (C18) modified silica, HayeSep-A, HayeSep-B, and Porapak-R. It was found that non-calcined MCM-41 showed better extraction performance for the analytes considered. Parameters influencing extraction efficiency, such as desorption time, extraction time, desorption solvent, and salt concentration, were investigated. The effect of the matrix on MS signals (suppression or enhancement) was also evaluated. Only minor effects on ionization efficiencies were observed. The developed method proved to be convenient and offered good sensitivity and reproducibility. The limits of detection ranged from 0.02 to 0.08ng L(-1), with a relative standard deviations between 1.9 and 10.5. It was successfully applied to the extraction of PFCAs in river and rain water samples. As expected from the ubiquitous nature of PFCAs, contamination at low levels was detected for some analytes in the samples (with the highest concentration recorded for PFOA). Satisfactory relative recoveries ranging

  17. Application of surfactant-templated ordered mesoporous material as sorbent in micro-solid phase extraction followed by liquid chromatography-triple quadrupole mass spectrometry for determination of perfluorinated carboxylic acids in aqueous media.

    PubMed

    Lashgari, Maryam; Basheer, Chanbasha; Kee Lee, Hian

    2015-08-15

    In the present study, micro-solid phase extraction (µ-SPE) followed by liquid chromatography-triple tandem mass spectrometery (LC-MS/MS) was developed for the determination of perfluorocarboxylic acids (PFCAs) at trace levels in water samples. The µ-SPE device comprised of a porous polypropylene membrane bag containing 5mg sorbent. The membrane bag acted as a clean-up filter and prevented matrix compounds from interfering with the extraction process. Analysis was carried out by LC-MS/MS in negative electrospray ionization mode. MS/MS parameters were optimized for multiple reaction monitoring. Calcined and non-calcined MCM-41, as silica-ordered mesoporous materials, were used as sorbents in µ-SPE for the extraction of five PFCAs-perfluoropentanoic acid (PFPA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA)-from aqueous media. The performances of these two sorbents were compared with other sorbents such as octadecylsilane (C18) modified silica, HayeSep-A, HayeSep-B, and Porapak-R. It was found that non-calcined MCM-41 showed better extraction performance for the analytes considered. Parameters influencing extraction efficiency, such as desorption time, extraction time, desorption solvent, and salt concentration, were investigated. The effect of the matrix on MS signals (suppression or enhancement) was also evaluated. Only minor effects on ionization efficiencies were observed. The developed method proved to be convenient and offered good sensitivity and reproducibility. The limits of detection ranged from 0.02 to 0.08ng L(-1), with a relative standard deviations between 1.9 and 10.5. It was successfully applied to the extraction of PFCAs in river and rain water samples. As expected from the ubiquitous nature of PFCAs, contamination at low levels was detected for some analytes in the samples (with the highest concentration recorded for PFOA). Satisfactory relative recoveries ranging

  18. Aqueous thermal degradation of gallic acid

    NASA Astrophysics Data System (ADS)

    Snow Boles, Jennifer; Crerar, David A.; Grissom, Grady; Key, Tonalee C.

    1988-02-01

    Aqueous thermal degradation experiments show gallic acid, a naturally occurring aromatic carboxylic compound, decomposes rapidly at temperatures between 105° and 150°C, with an activation energy of 22.9 or 27.8 kcal/ mole, depending on pH of the starting solution. Pyrogallol is the primary product identified, indicating degradation via decarboxylation and a carbanion transition state. Relatively rapid degradation of vanillic, phthalic, ellagic and tannic acids has also been observed, suggesting that these and perhaps other aromatic acids could be short-lived in deep formation waters.

  19. Aqueous thermal degradation of gallic acid

    SciTech Connect

    Boles, J.S.; Crerar, D.A.; Grissom, G.; Key, T.C.

    1988-02-01

    Aqueous thermal degradation experiments show gallic acid, a naturally occurring aromatic carboxylic compound, decomposes rapidly at temperatures between 105/sup 0/ and 150/sup 0/C, with an activation energy of 22.9 or 27.8 kcal/mole, depending on pH of the starting solution. Pyrogallol is the primary product identified, indicating degradation via decarboxylation and a carbanion transition state. Relatively rapid degradation of vanillic, phthalic, ellagic and tannic acids has also been observed,suggesting that these and perhaps other aromatic acids could be short-lived in deep formation waters.

  20. Recent advances in photocatalytic treatment of pollutants in aqueous media.

    PubMed

    Reddy, P Anil Kumar; Reddy, P Venkata Laxma; Kwon, Eilhann; Kim, Ki-Hyun; Akter, Tahmina; Kalagara, Sudhakar

    2016-05-01

    Photocatalysis can be an excellent solution for resolving the world's energy and environmental problems. It has a wide range of applications for the decontamination of diverse hazardous pollutants in aqueous media. Technological progress in this research field has been achieved toward the improvement of the solar sensitivity to enhance the efficiency of pollutant decontamination. As a result, various strategies have been introduced to upgrade photocatalytic performance with the modification of prototypical photocatalyst such as doping, dye sensitization, semiconductor coupling, mesoporous supports, single site, and nano-based catalysts. In this review, a brief survey is presented to describe those strategies based on the evaluation made against various pollutants (such as pharmaceuticals, pesticides, heavy metals, detergents, and dyes) in aqueous media. PMID:26915711

  1. Carbonated aqueous media for quench heat treatment of steels

    NASA Astrophysics Data System (ADS)

    Nayak, U. Vignesh; Rao, K. M. Pranesh; Pai, M. Ashwin; Prabhu, K. Narayan

    2016-09-01

    Distilled water and polyalkylene glycol (PAG)-based aqueous quenchants of 5 and 10 vol.% with and without carbonation were prepared and used as heat transfer media during immersion quenching. Cooling curves were recorded during quenching of an inconel 600 cylindrical probe instrumented with multiple thermocouples. It was observed that the vapor stage duration was prolonged and the wetting front ascended uniformly for quenching with carbonated media. The cooling data were analyzed by determining the critical cooling parameters and by estimating the spatially dependent probe/quenchant interfacial heat flux transients. The study showed significantly reduced values of heat transfer rate for carbonated quenchants compared to quenchants without carbonation. Further, the reduction was more pronounced in the case of PAG-based carbonated quenchants than carbonated distilled water. The results also showed the dependence of heat transfer characteristics of the carbonated media on polymer concentration. The effect of quench uniformity on the microstructure of the material was assessed.

  2. Carbonated aqueous media for quench heat treatment of steels

    NASA Astrophysics Data System (ADS)

    Nayak, U. Vignesh; Rao, K. M. Pranesh; Pai, M. Ashwin; Prabhu, K. Narayan

    2016-07-01

    Distilled water and polyalkylene glycol (PAG)-based aqueous quenchants of 5 and 10 vol.% with and without carbonation were prepared and used as heat transfer media during immersion quenching. Cooling curves were recorded during quenching of an inconel 600 cylindrical probe instrumented with multiple thermocouples. It was observed that the vapor stage duration was prolonged and the wetting front ascended uniformly for quenching with carbonated media. The cooling data were analyzed by determining the critical cooling parameters and by estimating the spatially dependent probe/quenchant interfacial heat flux transients. The study showed significantly reduced values of heat transfer rate for carbonated quenchants compared to quenchants without carbonation. Further, the reduction was more pronounced in the case of PAG-based carbonated quenchants than carbonated distilled water. The results also showed the dependence of heat transfer characteristics of the carbonated media on polymer concentration. The effect of quench uniformity on the microstructure of the material was assessed.

  3. Eletrochemical reduction of patulin and 5-hydroxymethylfurfural in both neutral and acid non-aqueous media. Their electroanalytical determination in apple juices.

    PubMed

    Damián Chanique, Gerardo; Heraldo Arévalo, Alejandro; Alicia Zon, María; Fernández, Héctor

    2013-07-15

    The electro-reduction of patulin mycotoxin and 5-hydroxymethylfurfural at glassy carbon electrodes in acetonitrile +0.1 mol L(-1) tetrabutylammonium perchlorate, in both the absence and the presence of different aliquots of trifluoroacetic acid is reported. 5-hydroxymethylfurfural is the most common interference in the determination of patulin in products derived from apples. The electrochemical techniques were cyclic and square wave voltammetries, and controlled potential bulk electrolysis. The number of electrons exchanged in the patulin electro-reduction of n=1 could be inferred from controlled potential bulk electrolysis measurements. Ultraviolet-visible and infrared spectroscopies were used to identify patulin electro-reduction product/s. A value of (2.1±0.1)×10(-5) cm(2) s(-1) for the patulin diffusion coefficient was calculated from convoluted cyclic voltammograms. A method based on square wave voltammetry was developed for the quantitative determination of patulin in both fresh, and commercial apple juices in the presence of 5-hydroxymethylfurfural. Calibration curves obtained from solutions of the commercial reagent, and commercial apple juices were linear in the range from 3.0×10(-7) to 2.2×10(-5) mol L(-1). The lowest concentration measured experimentally for a signal to noise ratio of 3:1 was 3×10(-7) mol L(-1) (45 ppb) and a recovery percent of 84% was determined for commercial apple juices. This electroanalytical methodology appears as a good screening method for the determination of patulin in apple juices.

  4. Composition and process for separating cesium ions from an acidic aqueous solution also containing other ions

    DOEpatents

    Dietz, Mark L.; Horwitz, E. Philip; Bartsch, Richard A.; Barrans, Jr., Richard E.; Rausch, David

    1999-01-01

    A crown ether cesium ion extractant is disclosed as is its synthesis. The crown ether cesium ion extractant is useful for the selective purification of cesium ions from aqueous acidic media, and more particularly useful for the isolation of radioactive cesium-137 from nuclear waste streams. Processes for isolating cesium ions from aqueous acidic media using the crown ether cesium extractant are disclosed as are processes for recycling the crown ether cesium extractant and processes for recovering cesium from a crown ether cesium extractant solution.

  5. Composition and process for separating cesium ions from an acidic aqueous solution also containing other ions

    DOEpatents

    Dietz, M.L.; Horwitz, E.P.; Bartsch, R.A.; Barrans, R.E. Jr.; Rausch, D.

    1999-03-30

    A crown ether cesium ion extractant is disclosed as is its synthesis. The crown ether cesium ion extractant is useful for the selective purification of cesium ions from aqueous acidic media, and more particularly useful for the isolation of radioactive cesium-137 from nuclear waste streams. Processes for isolating cesium ions from aqueous acidic media using the crown ether cesium extractant are disclosed as are processes for recycling the crown ether cesium extractant and processes for recovering cesium from a crown ether cesium extractant solution. 4 figs.

  6. Plastic shaping of aqueous alumina suspensions with saccharides and dicarboxylic acids

    SciTech Connect

    Goel, H.; Schilling, C.H.; Biner, S.B.

    1996-06-01

    Traditional methods for the shape-forming of engineering ceramics entail plastic deformation of powder slurries containing hazardous organic liquids as suspending media. Replacing these organics with aqueous media requires the development of environmentally-benign, water-soluble additives which serve as plasticizers and binders. Fundamental studies were performed with aqueous suspensions of colloidal {alpha}-Al{sub 2}O{sub 3} to evaluate the role of sucrose, maltodextrin, and oxalic acid on viscosity, sedimentation and filtration characteristics, plastic flow behavior of filter cakes, and sinterability. Maltodextrin and oxalic acid systems exhibited superior results, including filtration to high packing-densities and clay-like plasticity with minimal cracking.

  7. Acceleration of suspending single-walled carbon nanotubes in BSA aqueous solution induced by amino acid molecules.

    PubMed

    Kato, Haruhisa; Nakamura, Ayako; Horie, Masanori

    2015-01-01

    Single-walled carbon nanotube (SWCNT) suspensions in aqueous media were prepared using bovine serum albumin (BSA) and amino acid molecules. It was found that the amino acid molecules clearly decreased the time required for suspending the SWCNTs in BSA aqueous solutions. Dynamic light scattering measurements revealed that the particle sizes of the SWCNTs suspended in aqueous media with and without amino acid molecules were approximately the same and stable for more than one week. The zeta potential values of the BSA molecules in pure water and amino acid aqueous solutions were different, and these values were also reflected in the surface potential of colloidal SWCNT particles in the corresponding aqueous media, thus inducing different dispersibility of SWCNTs in aqueous media. Pulsed field gradient nuclear magnetic resonance measurements showed that the interactions between the SWCNTs and the amino acid molecules are weak and comprise chemical exchange interactions and not bonding interactions. Amino acid molecules play a fascinating role in the preparation of SWCNT suspensions in BSA aqueous media by increasing electrostatic repulsive interactions between SWCNT colloidal particles and consequently enhancing the dispersion ability of the BSA molecules.

  8. Lignin transformations and reactivity upon ozonation in aqueous media

    NASA Astrophysics Data System (ADS)

    Khudoshin, A. G.; Mitrofanova, A. N.; Lunin, V. V.

    2012-03-01

    The reaction of ozone with lignin in aqueous acidic solutions is investigated. The Danckwerst model is used to describe the kinetics of gas/liquid processes occurring in a bubble reactor. The efficient ozonation rate of a soluble lignin analog, sodium lignosulfate, is determined. The main lines of the reaction between ozone and lignin are revealed on the basis of kinetic analysis results and IR and UV spectroscopy data.

  9. Speciation in aqueous solutions of nitric acid.

    PubMed

    Hlushak, S; Simonin, J P; De Sio, S; Bernard, O; Ruas, A; Pochon, P; Jan, S; Moisy, P

    2013-02-28

    In this study, speciation in aqueous solutions of nitric acid at 25 °C was assessed in two independent ways. First, Raman experiments were carried out and interpreted in terms of free nitrate ions, ion pairs and neutral HNO(3) molecules. In parallel, a model was developed to account for the formation of these two kinds of pairs. It was based on an extension of the binding mean spherical approximation (BiMSA), or associative MSA (AMSA), in which the size and the charge of the ions in the chemical pair may differ from those of the free ions. A simultaneous fit of the osmotic coefficient and of the proportion of free ions (obtained from Raman spectroscopy experiments) led to an estimation of the speciation in nitric acid solutions. The result obtained using this procedure was compared with the estimation obtained from the Raman experiments.

  10. Sorption of tetracycline antibiotics on hyper-crosslinked polystyrene from aqueous and aqueous-organic media

    NASA Astrophysics Data System (ADS)

    Udalova, A. Yu.; Dmitrienko, S. G.; Apyari, V. V.

    2015-06-01

    The sorption of tetracycline, oxytetracycline, chlortetracycline, and doxycycline on hyper-cross-linked polystyrene from aqueous and aqueous-organic solutions is studied under static and dynamic conditions in order to extend the range of the sorbents suitable for sorption isolation and the preconcentration of tetracycline antibiotics. Features of tetracycline sorption depending on the acidity of a solution and the nature and concentration of the compounds are explained. It is shown that hyper-crosslinked polystyrene can be used for the group sorption preconcentration of these compounds.

  11. State of Supported Nickel Nanoparticles during Catalysis in Aqueous Media

    SciTech Connect

    Chase, Zizwe; Kasakov, Stanislav; Shi, Hui; Vjunov, Aleksei; Fulton, John L.; Camaioni, Donald M.; Balasubramanian, Mahalingam; Zhao, Chen; Wang, Yong; Lercher, Johannes A.

    2015-11-09

    The state of Ni supported on HZSM-5 zeolite, silica, and sulfonated carbon was determined during aqueous phase catalysis of phenol hydrodeoxygenation using in situ extended X-ray absorption fine structure spectroscopy (EXAFS). On sulfonated carbon and HZSM-5 supports, the NiO and Ni(OH)2 were readily reduced to Ni(0) under reaction conditions (~35 bar H2 in aqueous phenol solutions containing up to 0.5 wt. % phosphoric acid at 473 K). On the silica support, less than 70% of the Ni was converted to Ni(0) under reaction conditions, which is attributed to the formation of Ni phyllosilicates. Over a broad range of reaction conditions there was no leaching of Ni from the supports. In contrast, rapid leaching of the Ni(II) from HZSM-5 was observed, when 15 wt. % aqueous acetic acid was substituted for the aqueous phenol solution. Once the metallic state of Ni was established there was no leaching in 15 wt. % acetic acid at 473 K and 35 bar H2. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES), Division of Chemical Sciences, Geosciences & Biosciences. The STEM was supported under the Laboratory Directed Research and Development Program: Chemical Imaging Initiative at Pacific Northwest National Laboratory (PNNL), a multi-program national laboratory operated for DOE by Battelle under Contract DE-AC05-76RL01830. STEM was performed at EMSL, a DOE Office of Science user facility sponsored by the Office of Biological and Environmental Research and located at PNNL.

  12. Cation exchange properties of zeolites in hyper alkaline aqueous media.

    PubMed

    Van Tendeloo, Leen; de Blochouse, Benny; Dom, Dirk; Vancluysen, Jacqueline; Snellings, Ruben; Martens, Johan A; Kirschhock, Christine E A; Maes, André; Breynaert, Eric

    2015-02-01

    Construction of multibarrier concrete based waste disposal sites and management of alkaline mine drainage water requires cation exchangers combining excellent sorption properties with a high stability and predictable performance in hyper alkaline media. Though highly selective organic cation exchange resins have been developed for most pollutants, they can serve as a growth medium for bacterial proliferation, impairing their long-term stability and introducing unpredictable parameters into the evolution of the system. Zeolites represent a family of inorganic cation exchangers, which naturally occur in hyper alkaline conditions and cannot serve as an electron donor or carbon source for microbial proliferation. Despite their successful application as industrial cation exchangers under near neutral conditions, their performance in hyper alkaline, saline water remains highly undocumented. Using Cs(+) as a benchmark element, this study aims to assess the long-term cation exchange performance of zeolites in concrete derived aqueous solutions. Comparison of their exchange properties in alkaline media with data obtained in near neutral solutions demonstrated that the cation exchange selectivity remains unaffected by the increased hydroxyl concentration; the cation exchange capacity did however show an unexpected increase in hyper alkaline media.

  13. Influence of nitric acid treatment in different media on X-ray structural parameters of coal

    SciTech Connect

    Sudip Maity; Ashim Choudhury

    2008-11-15

    The treatment of coal with nitric acid in aqueous and non-aqueous media introduces changes in the chemical and spatial structure of the organic mass. Four coals of different rank have been treated with nitric acid in aqueous and glacial acetic acid media for assessing the changes in the structural parameters by the X-ray diffraction (XRD) technique. Slow-scan XRD has been performed for the raw and treated coals, and X-ray structural parameters (d002, Lc, and Nc) and aromaticity (fa) have been determined by profile-fitting software. Considerable variation of the structural parameters has been observed with respect to the raw coals. The d002 values have decreased in aqueous medium but increased in acetic acid medium; however, Lc, Nc, and fa values have increased in aqueous medium but decreased in acetic acid medium. It is also observed that considerable oxidation takes place during nitric acid treatment in aqueous medium, but nitration is the predominant phenomenon in acetic acid medium. Disordering of the coal structure increases in acetic acid medium, but a reverse trend is observed in the aqueous medium. As a result, structurally modified coals (SMCs) are derived as new coal-derived substances. 15 refs., 6 figs., 3 tabs.

  14. Heterocyclics as corrosion inhibitors for acid media

    SciTech Connect

    Ajmal, M.; Khan, M.A.W.; Ahmad, S.; Quraishi, M.A.

    1996-12-01

    The available literature on the use of heterocyclic compounds as corrosion inhibitors in acid media has been reviewed. It has been noted that the workers in this field have either used sulfur or nitrogen containing heterocyclic compounds for studying inhibition action. The authors have synthesized compounds containing sulfur and nitrogen both in the same ring and studied their inhibition action in acid media. These compounds were found to be better inhibitors than those containing either atoms alone.

  15. Comparison of homogeneous and heterogeneous catalysts for glucose-to-fructose isomerization in aqueous media.

    PubMed

    Choudhary, Vinit; Pinar, Ana B; Lobo, Raul F; Vlachos, Dionisios G; Sandler, Stanley I

    2013-12-01

    Herein, the first comparison of the mechanisms of glucose-to-fructose isomerization in aqueous media enabled by homogeneous (CrCl3 and AlCl3 ) and heterogeneous catalysts (Sn-beta) by using isotopic-labeling studies is reported. A pronounced kinetic isotope effect (KIE) was observed if the deuterium label was at the C2 position, thus suggesting that a hydrogen shift from the C2 to C1 positions was the rate-limiting step with the three catalysts. (13) C and (1) H NMR spectroscopic investigations confirmed that an intra-hydride-transfer reaction pathway was the predominant reaction channel for all three catalysts in aqueous media. Furthermore, the deuterium atom in the labeled glucose could be mapped onto hydroxymethylfurfural and formic acid through reactions that followed the isomerization step in the presence of Brønsted acids. In all three catalysts, the active site appeared to be a bifunctional Lewis-acidic/Brønsted-basic site, based on a speciation model and first-principles calculations. For the first time, a mechanistic similarities between the homogeneous and heterogeneous catalysis of aldose-to-ketose isomerization is established and it is suggested that learning from homogeneous catalysis could assist in the development of improved heterogeneous catalysts.

  16. Perfluorooctyl bromide dispersions in aqueous media for biomedical applications.

    PubMed

    Habif, S S; Normand, P E; Oleksiak, C B; Rosano, H L

    1992-01-01

    In studying perfluorooctyl bromide (PFOB) dispersions in aqueous media, we have used two types of surfactant: egg yolk phospholipids (EYP) and polyglycerol esters (PGE). Our interest in these dispersions arises from their potential biomedical applications as imaging solutions and oxygen-carrying solutions (i.e., blood substitutes). For EYP systems, we have identified the dispersion structure as consisting of (a) PFOB droplets (250-nm diameter) stabilized by a phospholipid monolayer adsorbed irreversibly at the o/w interface and (b) small empty phospholipid vesicles. With both surfactants commercial preparations yielded stable systems, while purified samples, being non-dispersible, could not be made to act as emulsifiers. In both cases, minor components in the commercial surfactant were found to be necessary for the formation of a stable dispersion, enabling the transport of the pure surfactant to the PFOB/water interface.

  17. Synthetic pathways to vanadyl organophosphonates through aqueous media

    SciTech Connect

    Gendraud, P.; Bigey, L.; Roy, M.E. de; Besse, J.P.

    1997-01-01

    Synthesis of vanadyl(IV) organophosphonates VORPO{sub 3}{center_dot}nH{sub 2}O (with R = CH{sub 3}, C{sub 2}H{sub 5}, C{sub 6}H{sub 5}) has been investigated by reaction of VOSO{sub 4}{center_dot}5H{sub 2}O + RPO{sub 3}H{sub 2} under refluxing conditions in aqueous media. The influence of different parameters is discussed, and compounds are characterized by X-ray powder diffraction, TGA, IR, XANES, and EXAFS. For example, three crystallographic forms of VOC{sub 6}H{sub 5}PO{sub 3}{center_dot}2H{sub 2}O obtained differ from each other in the location of the trans water molecule in the layered structure.

  18. Perfluorooctyl bromide dispersions in aqueous media for biomedical applications.

    PubMed

    Habif, S S; Normand, P E; Oleksiak, C B; Rosano, H L

    1992-01-01

    In studying perfluorooctyl bromide (PFOB) dispersions in aqueous media, we have used two types of surfactant: egg yolk phospholipids (EYP) and polyglycerol esters (PGE). Our interest in these dispersions arises from their potential biomedical applications as imaging solutions and oxygen-carrying solutions (i.e., blood substitutes). For EYP systems, we have identified the dispersion structure as consisting of (a) PFOB droplets (250-nm diameter) stabilized by a phospholipid monolayer adsorbed irreversibly at the o/w interface and (b) small empty phospholipid vesicles. With both surfactants commercial preparations yielded stable systems, while purified samples, being non-dispersible, could not be made to act as emulsifiers. In both cases, minor components in the commercial surfactant were found to be necessary for the formation of a stable dispersion, enabling the transport of the pure surfactant to the PFOB/water interface. PMID:1369226

  19. PROCESS FOR RECOVERING URANIUM FROM AQUEOUS PHOSPHORIC ACID LIQUORS

    DOEpatents

    Schmitt, J.M.

    1962-09-01

    A liquid-liquid extraction method is given for recovering uranium values from aqueous solutions. An acidic aqueous solution containing uranium values is contacted with an organic phase comprising an organic diluent and the reaction product of phosphorous pentoxide and a substantially pure dialkylphosphoric acid. The uranium values are transferred to the organic phase even from aqueous solutions containing a high concentration of strong uranium complexing agents such as phosphate ions. (AEC)

  20. Acidities of Water and Methanol in Aqueous Solution and DMSO

    ERIC Educational Resources Information Center

    Gao, Daqing

    2009-01-01

    The relative acidities of water and methanol have been a nagging issue. In gas phase, methanol is more acidic than water by 36.0 kJ/mol; however, in aqueous solution, the acidities of methanol and water are almost identical. The acidity of an acid in solution is determined by both the intrinsic gas-phase ionization Gibbs energy and the solvent…

  1. Atmospheric-pressure air microplasma jets in aqueous media for the inactivation of Pseudomonas fluorescens cells

    SciTech Connect

    Zhang, Xianhui; Yang, Si-ze; Liu, Dongping; Song, Ying; Sun, Yue

    2013-05-15

    The hollow fiber-based cold air microplasma jet array running at atmospheric pressure has been designed to inactivate Pseudomonas fluorescens (P. fluorescens) cells in vitro in aqueous media. The influences of electrode configurations, air flow rate, and applied voltage on the discharge characteristics of the single microplasma jet operating in aqueous media are presented, and the bactericidal efficiency of the hollow fibers-based and large-volume microplasma jet array is reported. Optical emission spectroscopy is utilized to identify excited species during the antibacterial testing of plasma in solutions. These well-aligned and rather stable air microplasma jets containing a variety of short-lived species, such as OH and O radicals and charged particles, are in direct contact with aqueous media and are very effective in killing P. fluorescens cells in aqueous media. This design shows its potential application for atmospheric pressure air plasma inactivation of bacteria cells in aqueous media.

  2. State of Supported Nickel Nanoparticles during Catalysis in Aqueous Media.

    PubMed

    Chase, Zizwe A; Kasakov, Stanislav; Shi, Hui; Vjunov, Aleksei; Fulton, John L; Camaioni, Donald M; Balasubramanian, Mahalingam; Zhao, Chen; Wang, Yong; Lercher, Johannes A

    2015-11-01

    The state of Ni supported on HZSM-5 zeolite, silica, and sulfonated carbon was studied during aqueous-phase catalysis of phenol hydrodeoxygenation using in situ extended X-ray absorption fine structure spectroscopy. On sulfonated carbon and HZSM-5 supports, NiO and Ni(OH)2 were readily reduced to Ni(0) under reaction conditions (≈35 bar H2 in aqueous phenol solutions containing up to 0.5 wt. % phosphoric acid at 473 K). In contrast, Ni supported on SiO2 was not stable in a fully reduced Ni(0) state. Water enables the formation of Ni(II) phyllosilicate, which is more stable, that is, difficult to reduce, than either α-Ni(OH)2 or NiO. Leaching of Ni from the supports was not observed over a broad range of reaction conditions. Ni(0) particles on HZSM-5 were stable even in presence of 15 wt. % acetic acid at 473 K and 35 bar H2 .

  3. State of Supported Nanoparticle Ni during Catalysis in Aqueous Media

    SciTech Connect

    Chase, Zizwe; Vjunov, Aleksei; Fulton, John; Camaioni, Donald; Balasubramanian, Mahalingam; Lercher, Johannes

    2015-11-09

    The state of Ni supported on HZSM-5 zeolite, silica, and sulfonated carbon was studied during aqueous-phase catalysis of phenol hydrodeoxygenation using in situ extended X-ray absorption fine structure spectroscopy. On sulfonated carbon and HZSM-5 supports, NiO and Ni(OH)(2) were readily reduced to Ni-0 under reaction conditions (approximate to 35bar H-2 in aqueous phenol solutions containing up to 0.5wt.% phosphoric acid at 473K). In contrast, Ni supported on SiO2 was not stable in a fully reduced Ni-0 state. Water enables the formation of Ni-II phyllosilicate, which is more stable, that is, difficult to reduce, than either -Ni(OH)(2) or NiO. Leaching of Ni from the supports was not observed over a broad range of reaction conditions. Ni-0 particles on HZSM-5 were stable even in presence of 15wt.% acetic acid at 473K and 35bar H-2.

  4. State of Supported Nickel Nanoparticles during Catalysis in Aqueous Media.

    PubMed

    Chase, Zizwe A; Kasakov, Stanislav; Shi, Hui; Vjunov, Aleksei; Fulton, John L; Camaioni, Donald M; Balasubramanian, Mahalingam; Zhao, Chen; Wang, Yong; Lercher, Johannes A

    2015-11-01

    The state of Ni supported on HZSM-5 zeolite, silica, and sulfonated carbon was studied during aqueous-phase catalysis of phenol hydrodeoxygenation using in situ extended X-ray absorption fine structure spectroscopy. On sulfonated carbon and HZSM-5 supports, NiO and Ni(OH)2 were readily reduced to Ni(0) under reaction conditions (≈35 bar H2 in aqueous phenol solutions containing up to 0.5 wt. % phosphoric acid at 473 K). In contrast, Ni supported on SiO2 was not stable in a fully reduced Ni(0) state. Water enables the formation of Ni(II) phyllosilicate, which is more stable, that is, difficult to reduce, than either α-Ni(OH)2 or NiO. Leaching of Ni from the supports was not observed over a broad range of reaction conditions. Ni(0) particles on HZSM-5 were stable even in presence of 15 wt. % acetic acid at 473 K and 35 bar H2 . PMID:26407246

  5. Conformation of poly(γ-glutamic acid) in aqueous solution.

    PubMed

    Muroga, Yoshio; Nakaya, Asami; Inoue, Atsuki; Itoh, Daiki; Abiru, Masaya; Wada, Kaori; Takada, Masako; Ikake, Hiroki; Shimizu, Shigeru

    2016-04-01

    Local conformation and overall conformation of poly(γ-DL-glutamic acid) (PγDLGA) and poly(γ-L-glutamic acid) (PγLGA) in aqueous solution was studied as a function of degree of ionization ε by (1) H-NMR, circular dichroism, and potentiometric titration. It was clarified that their local conformation is represented by random coil over an entire ε range and their overall conformation is represented by expanded random-coil in a range of ε > ε(*) , where ε(*) is about 0.3, 0.35, 0.45, and 0.5 for added-salt concentration of 0.02M, 0.05M, 0.1M, and 0.2M, respectively. In a range of ε < ε(*) , however, ε dependence of their overall conformation is significantly differentiated from each other. PγDLGA tends to aggregate intramolecularly and/or intermolecularly with decreasing ε, but PγLGA still behaves as expanded random-coil. It is speculated that spatial arrangement of adjacent carboxyl groups along the backbone chain essentially affects the overall conformation of PγGA in acidic media.

  6. The IUPAC aqueous and non-aqueous experimental pKa data repositories of organic acids and bases.

    PubMed

    Slater, Anthony Michael

    2014-10-01

    Accurate and well-curated experimental pKa data of organic acids and bases in both aqueous and non-aqueous media are invaluable in many areas of chemical research, including pharmaceutical, agrochemical, specialty chemical and property prediction research. In pharmaceutical research, pKa data are relevant in ligand design, protein binding, absorption, distribution, metabolism, elimination as well as solubility and dissolution rate. The pKa data compilations of the International Union of Pure and Applied Chemistry, originally in book form, have been carefully converted into computer-readable form, with value being added in the process, in the form of ionisation assignments and tautomer enumeration. These compilations offer a broad range of chemistry in both aqueous and non-aqueous media and the experimental conditions and original reference for all pKa determinations are supplied. The statistics for these compilations are presented and the utility of the computer-readable form of these compilations is examined in comparison to other pKa compilations. Finally, information is provided about how to access these databases.

  7. Sonochemical and photosonochemical degradation of 4-chlorophenol in aqueous media.

    PubMed

    Hamdaoui, Oualid; Naffrechoux, Emmanuel

    2008-09-01

    The degradation of 4-chlorophenol (4-CP) in aqueous media by 516 kHz ultrasonic irradiation was investigated in order to clarify the degradation mechanism. The degradation of concentrated 4-CP solution by means of ultrasound, UV irradiation and their combined application was also studied. The obtained results indicate that *OH radical are the primary reactive species responsible for 4-CP ultrasonic degradation. Very little 4-CP degradation occurs if the sonolysis is carried out in the presence of the *OH radical scavenger tert-butyl alcohol, also indicating that little or no pyrolysis of the compound occurs. The dominant degradation mechanism is the reaction of substrate with *OH radicals at the gas bubble-liquid interface rather than high temperature direct pyrolysis in ultrasonic cavities. This mechanism can explain the lower degradation rate of the ionic form of 4-CP that is partly due to the rapid dissociation of *OH radicals in alkaline solutions. The sonochemical destruction of concentrated 4-CP aqueous solution is obtained with low rate. Coupling photolysis with ultrasound irradiation results in increased efficiency compared to the individual processes operating at common conditions. Interestingly, the photosonochemical decomposition rate constant is greater than the additive rate constants of the two processes. This may be the result of three different oxidative processes direct photochemical action, high frequency sonochemistry and reaction with ozone produced by UV irradiation of air, dissolved in liquid phase because of the geyser effect of ultrasound streaming. Additionally, the photodecomposition, at 254 nm, of hydrogen peroxide produced by ultrasound generating *OH radical can partly explain the destruction enhancement. PMID:18468475

  8. Sonochemical and photosonochemical degradation of 4-chlorophenol in aqueous media.

    PubMed

    Hamdaoui, Oualid; Naffrechoux, Emmanuel

    2008-09-01

    The degradation of 4-chlorophenol (4-CP) in aqueous media by 516 kHz ultrasonic irradiation was investigated in order to clarify the degradation mechanism. The degradation of concentrated 4-CP solution by means of ultrasound, UV irradiation and their combined application was also studied. The obtained results indicate that *OH radical are the primary reactive species responsible for 4-CP ultrasonic degradation. Very little 4-CP degradation occurs if the sonolysis is carried out in the presence of the *OH radical scavenger tert-butyl alcohol, also indicating that little or no pyrolysis of the compound occurs. The dominant degradation mechanism is the reaction of substrate with *OH radicals at the gas bubble-liquid interface rather than high temperature direct pyrolysis in ultrasonic cavities. This mechanism can explain the lower degradation rate of the ionic form of 4-CP that is partly due to the rapid dissociation of *OH radicals in alkaline solutions. The sonochemical destruction of concentrated 4-CP aqueous solution is obtained with low rate. Coupling photolysis with ultrasound irradiation results in increased efficiency compared to the individual processes operating at common conditions. Interestingly, the photosonochemical decomposition rate constant is greater than the additive rate constants of the two processes. This may be the result of three different oxidative processes direct photochemical action, high frequency sonochemistry and reaction with ozone produced by UV irradiation of air, dissolved in liquid phase because of the geyser effect of ultrasound streaming. Additionally, the photodecomposition, at 254 nm, of hydrogen peroxide produced by ultrasound generating *OH radical can partly explain the destruction enhancement.

  9. Role of solvent properties of aqueous media in macromolecular crowding effects.

    PubMed

    Ferreira, Luisa A; Madeira, Pedro P; Breydo, Leonid; Reichardt, Christian; Uversky, Vladimir N; Zaslavsky, Boris Y

    2016-01-01

    Analysis of the macromolecular crowding effects in polymer solutions show that the excluded volume effect is not the only factor affecting the behavior of biomolecules in a crowded environment. The observed inconsistencies are commonly explained by the so-called soft interactions, such as electrostatic, hydrophobic, and van der Waals interactions, between the crowding agent and the protein, in addition to the hard nonspecific steric interactions. We suggest that the changes in the solvent properties of aqueous media induced by the crowding agents may be the root of these "soft" interactions. To check this hypothesis, the solvatochromic comparison method was used to determine the solvent dipolarity/polarizability, hydrogen-bond donor acidity, and hydrogen-bond acceptor basicity of aqueous solutions of different polymers (dextran, poly(ethylene glycol), Ficoll, Ucon, and polyvinylpyrrolidone) with the polymer concentration up to 40% typically used as crowding agents. Polymer-induced changes in these features were found to be polymer type and concentration specific, and, in case of polyethylene glycol (PEG), molecular mass specific. Similarly sized polymers PEG and Ucon producing different changes in the solvent properties of water in their solutions induced morphologically different α-synuclein aggregates. It is shown that the crowding effects of some polymers on protein refolding and stability reported in the literature can be quantitatively described in terms of the established solvent features of the media in these polymers solutions. These results indicate that the crowding agents do induce changes in solvent properties of aqueous media in crowded environment. Therefore, these changes should be taken into account for crowding effect analysis. PMID:25616385

  10. Role of solvent properties of aqueous media in macromolecular crowding effects.

    PubMed

    Ferreira, Luisa A; Madeira, Pedro P; Breydo, Leonid; Reichardt, Christian; Uversky, Vladimir N; Zaslavsky, Boris Y

    2016-01-01

    Analysis of the macromolecular crowding effects in polymer solutions show that the excluded volume effect is not the only factor affecting the behavior of biomolecules in a crowded environment. The observed inconsistencies are commonly explained by the so-called soft interactions, such as electrostatic, hydrophobic, and van der Waals interactions, between the crowding agent and the protein, in addition to the hard nonspecific steric interactions. We suggest that the changes in the solvent properties of aqueous media induced by the crowding agents may be the root of these "soft" interactions. To check this hypothesis, the solvatochromic comparison method was used to determine the solvent dipolarity/polarizability, hydrogen-bond donor acidity, and hydrogen-bond acceptor basicity of aqueous solutions of different polymers (dextran, poly(ethylene glycol), Ficoll, Ucon, and polyvinylpyrrolidone) with the polymer concentration up to 40% typically used as crowding agents. Polymer-induced changes in these features were found to be polymer type and concentration specific, and, in case of polyethylene glycol (PEG), molecular mass specific. Similarly sized polymers PEG and Ucon producing different changes in the solvent properties of water in their solutions induced morphologically different α-synuclein aggregates. It is shown that the crowding effects of some polymers on protein refolding and stability reported in the literature can be quantitatively described in terms of the established solvent features of the media in these polymers solutions. These results indicate that the crowding agents do induce changes in solvent properties of aqueous media in crowded environment. Therefore, these changes should be taken into account for crowding effect analysis.

  11. Extraction preconcentration and photometric determination of chlorophenols and naphthols in aqueous media

    SciTech Connect

    Korenman, Ya.I.; Kalinkina, S.P.; Sukhanov, P.T.

    1994-11-01

    Mono- and bicyclic hydroxy compounds (phenol, chlorophenols, naphthols, and naphtholsulfonic acids) are industrial toxicants; these compounds occur in waste water from the production of dyestuffs, polymer materials, perfumes, drugs, varnishes, paints, and pesticides. Phenol, chlorophenols, and naphthols are carcinogenic toxicants; they may constitute a threat to living organisms in reservoirs and biologically active silts. The presence of these compounds changes the oxygen balance of water basins. The maximum permissible concentration of these compounds in water varies from 10{sup {minus}1} (naphthols) to 10{sup {minus}4} mg/L (chlorophenols). For the reliable determination of microquantities of toxicants in water, we proposed procedures that include extraction by lower alcohols, organic acids, and hexane or hexane-hexanol solutions of solvotropic reagents (dialkyl phthalates and trialkyl phthalates). A set of extraction photometric procedures has been developed for the total and selective determination of microquantities of phenol and naphthol toxicants in aqueous media.

  12. Para-nitrobenzyl esterases with enhanced activity in aqueous and nonaqueous media

    DOEpatents

    Arnold, Frances H.; Moore, Jeffrey C.

    1998-01-01

    A method for isolating and identifying modified para-nitrobenzyl esterases which exhibit improved stability and/or esterase hydrolysis activity toward selected substrates and under selected reaction conditions relative to the unmodified para-nitrobenzyl esterase. The method involves preparing a library of modified para-nitrobenzyl esterase nucleic acid segments (genes) which have nucleotide sequences that differ from the nucleic acid segment which encodes for unmodified para-nitrobenzyl esterase. The library of modified para-nitrobenzyl nucleic acid segments is expressed to provide a plurality of modified enzymes. The clones expressing modified enzymes are then screened to identify which enzymes have improved esterase activity by measuring the ability of the enzymes to hydrolyze the selected substrate under the selected reaction conditions. Specific modified para-nitrobenzyl esterases are disclosed which have improved stability and/or ester hydrolysis activity in aqueous or aqueous-organic media relative to the stability and/or ester hydrolysis activity of unmodified naturally occurring para-nitrobenzyl esterase.

  13. Para-nitrobenzyl esterases with enhanced activity in aqueous and nonaqueous media

    DOEpatents

    Arnold, Frances H.; Moore, Jeffrey C.

    1999-01-01

    A method for isolating and identifying modified para-nitrobenzyl esterases which exhibit improved stability and/or esterase hydrolysis activity toward selected substrates and under selected reaction conditions relative to the unmodified para-nitrobenzyl esterase. The method involves preparing a library of modified para-nitrobenzyl esterase nucleic acid segments (genes) which have nucleotide sequences that differ from the nucleic acid segment which encodes for unmodified para-nitrobenzyl esterase. The library of modified para-nitrobenzyl nucleic acid segments is expressed to provide a plurality of modified enzymes. The clones expressing modified enzymes are then screened to identify which enzymes have improved esterase activity by measuring the ability of the enzymes to hydrolyze the selected substrate under the selected reaction conditions. Specific modified para-nitrobenzyl esterases are disclosed which have improved stability and/or ester hydrolysis activity in aqueous or aqueous-organic media relative to the stability and/or ester hydrolysis activity of unmodified naturally occurring para-nitrobenzyl esterase.

  14. Para-nitrobenzyl esterases with enhanced activity in aqueous and nonaqueous media

    DOEpatents

    Arnold, F.H.; Moore, J.C.

    1998-04-21

    A method is disclosed for isolating and identifying modified para-nitrobenzyl esterases. These enzymes exhibit improved stability and/or esterase hydrolysis activity toward selected substrates and under selected reaction conditions relative to the unmodified para-nitrobenzyl esterase. The method involves preparing a library of modified para-nitrobenzyl esterase nucleic acid segments (genes) which have nucleotide sequences that differ from the nucleic acid segment which encodes for unmodified para-nitrobenzyl esterase. The library of modified para-nitrobenzyl nucleic acid segments is expressed to provide a plurality of modified enzymes. The clones expressing modified enzymes are then screened to identify which enzymes have improved esterase activity by measuring the ability of the enzymes to hydrolyze the selected substrate under the selected reaction conditions. Specific modified para-nitrobenzyl esterases are disclosed which have improved stability and/or ester hydrolysis activity in aqueous or aqueous-organic media relative to the stability and/or ester hydrolysis activity of unmodified naturally occurring para-nitrobenzyl esterase. 43 figs.

  15. Para-nitrobenzyl esterases with enhanced activity in aqueous and nonaqueous media

    DOEpatents

    Arnold, F.H.; Moore, J.C.

    1999-05-25

    A method is disclosed for isolating and identifying modified para-nitrobenzyl esterases which exhibit improved stability and/or esterase hydrolysis activity toward selected substrates and under selected reaction conditions relative to the unmodified para-nitrobenzyl esterase. The method involves preparing a library of modified para-nitrobenzyl esterase nucleic acid segments (genes) which have nucleotide sequences that differ from the nucleic acid segment which encodes for unmodified para-nitrobenzyl esterase. The library of modified para-nitrobenzyl nucleic acid segments is expressed to provide a plurality of modified enzymes. The clones expressing modified enzymes are then screened to identify which enzymes have improved esterase activity by measuring the ability of the enzymes to hydrolyze the selected substrate under the selected reaction conditions. Specific modified para-nitrobenzyl esterases are disclosed which have improved stability and/or ester hydrolysis activity in aqueous or aqueous-organic media relative to the stability and/or ester hydrolysis activity of unmodified naturally occurring para-nitrobenzyl esterase. 43 figs.

  16. Study of 3-Ethylamino-but-2-enoic acid phenylamide as a new ligand for preconcentration of lanthanides from aqueous media by liquid-liquid extraction prior to ICP-MS analysis.

    PubMed

    Varbanova, Evelina K; Angelov, Plamen A; Stefanova, Violeta M

    2016-11-01

    In the present work the potential of a new ligand 3-Ethylamino-but-2-enoic acid phenylamide (representing the class of enaminones) for selective preconcentration of lanthanides (La, Ce, Eu, Gd and Er) from aqueous medium is examined. Liquid-liquid extraction parameters, such as pH of the water phase, type and volume of organic solvent, quantity of ligand and reaction time are optimized on model solutions. Recovery of lanthanides by re-extraction with nitric acid makes the LLE procedure compatible with Inductively Coupled Plasma Mass Spectrometry. Spectral and non-spectral interferences are studied. Two isotopes per element are measured (with exception of La) for dynamic evaluation of the potential risk of spectral interference in variable real samples. The selectivity of complex formation reaction towards concomitant alkali and alkali-earth elements eliminates the interferences from sample matrix. Subjecting the standards to the optimized extraction procedure in combination with Re as internal standard is recommended as calibration strategy. The accuracy of developed method is approved by analysis of CRM Bush branches and leaves (NCS DC 73348) and recovery of spiked water and plant samples. The method's limits of detection for both studied objects are in the ranges from 0.2 ((158)Gd) to 3.7 ((139)La) ngl(-1) and 0.02 ((158)Gd) to 0.37((139)La) ngg(-1) for waters and plants respectively. The studied compound is an effective new ligand for preconcentration/separation of lanthanides from aqueous medium by LLE and subsequent determination by ICP-MS. PMID:27591629

  17. Mixed ligand two dimensional Cd(ii)/Ni(ii) metal organic frameworks containing dicarboxylate and tripodal N-donor ligands: Cd(ii) MOF is an efficient luminescent sensor for detection of picric acid in aqueous media.

    PubMed

    Rachuri, Yadagiri; Parmar, Bhavesh; Bisht, Kamal Kumar; Suresh, Eringathodi

    2016-05-01

    Two dimensional metal organic frameworks (MOFs) [Cd(5-BrIP)(TIB)]n () and [Ni2(5-BrIP)2(TIB)2]n (), involving the aromatic polycarboxylate ligand 5-bromo isophthalic acid (H2BrIP), flexible tripodal ligand 1,3,5-tris(imidazol-1-ylmethyl)benzene (TIB) and Cd(ii)/Ni(ii) metal nodes have been synthesized by different methods. These compounds were characterized by various analytical methods, and variable temperature X-ray diffraction data showed thermal stability of both MOFs up to 350 °C. Phase purity as well as water stability of the MOFs were established by powder X-ray diffraction, and the structural diversity of the compounds were investigated by single-crystal X-ray diffraction. Both the MOFs are mixed ligand 2D nets, and the topology of the network can be described as a binodal 3,5-c connected net with 3,5L2 topology having the point symbol {4(2)·6(7)·8}{4(2)·6}. Sensing of picric acid [2,4,6-trinitrophenol, TNP] by luminescence quenching among a large range of nitroanalytes in aqueous phase by the Cd(ii) luminescent MOF (LMOF) were been investigated. Structural studies on 1 : 1 co-crystals () of TIB and TNP were carried out. The selective and sensitive fluorescence quenching response of towards electron-deficient TNP over other nitro analytes in aqueous phase was demonstrated by fluorescence quenching titration. Concomitant occurrence of electron transfer/energy transfer processes and electrostatic interaction favours the selective sensing of TNP. A Cd(ii) LMOF ()-coated paper strip that we developed demonstrated fast and selective response to TNP, by the complete quenching of the blue fluorescence upon excitation of the paper strip at 365 nm radiation in its presence. PMID:27067118

  18. Aqueous-phase source of formic acid in clouds

    NASA Technical Reports Server (NTRS)

    Chameides, W. L.; Davis, D. D.

    1983-01-01

    The coupled gas- and aqueous-phase cloud chemistry of HCOOH were examined for controlling factors in the acidity of cloud and rainwater. Attention was given to the aqueous OH/HO2 system that yields an OH species that is highly reactive with other species, notably SO2 and the formaldehyde/formic acid complex. A numerical model was developed to simulate the cloud chemistry in the remote troposphere, with considerations given to CH4-CO-NO(x)-O3-H(x)O(y) system. It was determined that aqueous phase OH radicals can produce and destroy formic acid droplets in daylight conditions, as well as control formic acid levels in rainwater. It is sugested that the same types of reactions may be involved in the control of acetic acid and other organic acids.

  19. Facile synthesis of magnetic biochar/Fe3O4 nanocomposites using electro-magnetization technique and its application on the removal of acid orange 7 from aqueous media.

    PubMed

    Jung, Kyung-Won; Choi, Brian Hyun; Jeong, Tae-Un; Ahn, Kyu-Hong

    2016-11-01

    This study introduces a new methodology to synthesize magnetic biochar/Fe3O4 nanocomposites (M-BC) from marine macroalgae using a facile electro-magnetization technique. M-BC was prepared by stainless steel electrode-based electrochemical system, followed by pyrolysis. Physical and chemical analyses revealed that the porosity and magnetic properties were simultaneously improved via the electro-magnetization process, which enabled not only higher adsorption performance, but also easier separation/recovery from aqueous media at post-adsorption stage using a bar magnet. The adsorption equilibrium studies reveal that the Sips model satisfactorily predicts the adsorption capacity, which found to be 190, 297, and 382mgg(-1) at 10, 20, and 30°C, respectively. The overall findings indicate that one-step electro-magnetization technique can be effectively utilized for the fabrication of biochar with concurrent acquisition of porosity and magnetism, which can bring about new directions in the practical use of adsorption process in environment remediation and mitigate crises originating from it. PMID:27638463

  20. Oxytetracycline recovery from aqueous media using computationally designed molecularly imprinted polymers.

    PubMed

    Rodríguez-Dorado, Rosalía; Carro, Antonia M; Chianella, Iva; Karim, Kal; Concheiro, Angel; Lorenzo, Rosa A; Piletsky, Sergey; Alvarez-Lorenzo, Carmen

    2016-09-01

    Polymers for recovery/removal of the antimicrobial agent oxytetracycline (OTC) from aqueous media were developed with use of computational design and molecular imprinting. 2-Hydroxyethyl methacrylate, 2-acrylamide-2-methylpropane sulfonic acid (AMPS), and mixtures of the two were chosen according to their predicted affinity for OTC and evaluated as functional monomers in molecularly imprinted polymers and nonimprinted polymers. Two levels of AMPS were tested. After bulk polymerization, the polymers were crushed into particles (200-1000 μm). Pressurized liquid extraction was implemented for template removal with a low amount of methanol (less than 20 mL in each extraction) and a few extractions (12-18 for each polymer) in a short period (20 min per extraction). Particle size distribution, microporous structure, and capacity to rebind OTC from aqueous media were evaluated. Adsorption isotherms obtained from OTC solutions (30-110 mg L(-1)) revealed that the polymers prepared with AMPS had the highest affinity for OTC. The uptake capacity depended on the ionic strength as follows: purified water > saline solution (0.9 % NaCl) > seawater (3.5 % NaCl). Polymer particles containing AMPS as a functional monomer showed a remarkable ability to clean water contaminated with OTC. The usefulness of the stationary phase developed for molecularly imprinted solid-phase extraction was also demonstrated. Graphical Abstract Selection of functional monomers by molecular modeling renders polymer networks suitable for removal of pollutants from contaminated aqueous environments, under either dynamic or static conditions.

  1. Oxytetracycline recovery from aqueous media using computationally designed molecularly imprinted polymers.

    PubMed

    Rodríguez-Dorado, Rosalía; Carro, Antonia M; Chianella, Iva; Karim, Kal; Concheiro, Angel; Lorenzo, Rosa A; Piletsky, Sergey; Alvarez-Lorenzo, Carmen

    2016-09-01

    Polymers for recovery/removal of the antimicrobial agent oxytetracycline (OTC) from aqueous media were developed with use of computational design and molecular imprinting. 2-Hydroxyethyl methacrylate, 2-acrylamide-2-methylpropane sulfonic acid (AMPS), and mixtures of the two were chosen according to their predicted affinity for OTC and evaluated as functional monomers in molecularly imprinted polymers and nonimprinted polymers. Two levels of AMPS were tested. After bulk polymerization, the polymers were crushed into particles (200-1000 μm). Pressurized liquid extraction was implemented for template removal with a low amount of methanol (less than 20 mL in each extraction) and a few extractions (12-18 for each polymer) in a short period (20 min per extraction). Particle size distribution, microporous structure, and capacity to rebind OTC from aqueous media were evaluated. Adsorption isotherms obtained from OTC solutions (30-110 mg L(-1)) revealed that the polymers prepared with AMPS had the highest affinity for OTC. The uptake capacity depended on the ionic strength as follows: purified water > saline solution (0.9 % NaCl) > seawater (3.5 % NaCl). Polymer particles containing AMPS as a functional monomer showed a remarkable ability to clean water contaminated with OTC. The usefulness of the stationary phase developed for molecularly imprinted solid-phase extraction was also demonstrated. Graphical Abstract Selection of functional monomers by molecular modeling renders polymer networks suitable for removal of pollutants from contaminated aqueous environments, under either dynamic or static conditions. PMID:27488280

  2. Coupled diffusion in aqueous weak acid + alkanolamine absorbents

    SciTech Connect

    Leaist, D.G.; Li, Y.; Poissant, R.

    1998-11-01

    Taylor dispersion and differential refractometry are used to measure ternary interdiffusion coefficients (D{sub ik}) for aqueous solutions of acetic acid + triethanolamine (TEA) and aqueous solutions of oxalic acid + TEA at 25 C. The D{sub ik} coefficients give the coupled fluxes of acid and TEA driven by the gradient in the concentration of each solute. Ternary Fick equations with variable D{sub ik} coefficients are integrated numerically to calculate accurate concentration profiles and the moving reaction front produced by the interdiffusion of TEA and acetic or oxalic acid. Ternary diffusion coefficients are also used to predict the rate of dissolution of oxalic acid in 1.00 mol/dm{sup 3} aqueous TEA, a process analogous to the absorption of a diprotic acid gas by an alkanolamine absorbent. The diffusion of oxalic acid drives a significant counterflow of TEA. The resulting buildup of TEA at the surface of the dissolving acid increases the interfacial concentration of TEA from 1.00 to 1.20 mol/dm{sup 3}, which in turn increases the solubility of the acid by 0.20 mol/dm{sup 3}. Nernst-Planck equations are used to predict D{sub ik} coefficients for aqueous weak acid + alkanolamine solutions. The fluxes of these solutes are shown to be strongly coupled by the electric field that is generated by the diffusing ions.

  3. Removal of 1-ethyl-3-methylimidazolium cations with bacterial biosorbents from aqueous media.

    PubMed

    Won, Sung Wook; Choi, Sun Beom; Mao, Juan; Yun, Yeoung-Sang

    2013-01-15

    This study aims to determine whether biosorption can be used for the removal of ionic liquids (ILs), especially their cationic parts, from aqueous media. As a model IL, 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) was used. Five types of bacterial biosorbents were prepared from fermentation wastes through chemical modification of the bacterial surface. Screening study was performed to compare the cationic [EMIM] biosorption capacity among the bacterial biosorbents, indicating that the succinated Escherichia coli biomass (SB-E) was the best biosorbent for removing [EMIM] cations. The [EMIM] biosorption performance of SB-E was evaluated in detail through various experiments. The optimal pH range for [EMIM] biosorption was from 7 to 10, and biosorption equilibrium was reached within 10 min. The maximum uptake of SB-E was also estimated to be 72.6 mg/g. Moreover, [EMIM] cations were easily desorbed from [EMIM]-sorbed SB-E by adding acetic acid. PMID:23246948

  4. Oxidation of dibenzothiophene catalyzed by hemoglobin and other hemoproteins in various aqueous-organic media

    SciTech Connect

    Klyachko, N.L. Klibanov, A.M. )

    1992-10-01

    Biocatalytic oxidation of dibenzothiophene (a model of organic sulfur in coal) with hydrogen peroxide was investigated. It was found that various hemoproteins, both enzymic (e.g., horseradish peroxidase) and nonenzymic (e.g., bovine blood hemoglobin), readily oxidized dibensothiophene to its S-oxide and, to a minor extent, further to its S-dioxide (sulfone). This process catalyzed by hemoglobin was competent as an oxidation catalyst even in nearly dry organic solvents (with protic, acidic solvents being optimal), the highest conversions were observed in predominantly aqueous media. The hemoglobin-catalyzed oxidation of dibenzothiophene at low concentrations of the protein stopped long before all the substrate was oxidized. This phenomenon was caused by inactivation of hemoglobin by hydrogen peroxide that destroyed the heme moiety. The maximal degree of the hemoglobin-catalyzed dibenzothiophene oxidation was predicted, and found, to be strongly dependent on the reaction medium composition. 24 refs., 7 figs., 3 tabs.

  5. Aqueous infrared carboxylate absorbances: Aliphatic di-acids

    USGS Publications Warehouse

    Cabaniss, S.E.; Leenheer, J.A.; McVey, I.F.

    1998-01-01

    Aqueous attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of 18 aliphatic di-carboxylic acids are reported as a function of pH. The spectra show isosbestic points and intensity changes which indicate that Beer's law is obeyed, and peak frequencies lie within previously reported ranges for aqueous carboxylates and pure carboxylic acids. Intensity sharing from the symmetric carboxylate stretch is evident in many cases, so that bands which are nominally due to alkyl groups show increased intensity at higher pH. The asymmetric stretch of the HA- species is linearly related to the microscopic acidity constant of the H2A species, with ??pK 2 intervening atoms). The results suggest that aqueous ATR-FTIR may be able to estimate 'intrinsic' pKa values of carboxylic acids, in addition to providing quantitative estimates of ionization. ?? 1998 Elsevier Science B.V. All rights reserved.

  6. Decomposition Studies of Triphenylboron, Diphenylborinic Acid and Phenylboric Acid in Aqueous Alkaline Solutions Containing Copper

    SciTech Connect

    Crawford, C.L.; Peterson, R. A.

    1997-02-11

    This report documents the copper-catalyzed chemical kinetics of triphenylboron, diphenylborinic acid and phenylboric acid (3PB, 2PB and PBA) in aqueous alkaline solution contained in carbon-steel vessels between 40 and 70 degrees C.

  7. Polymerization of beta-amino acids in aqueous solution

    NASA Technical Reports Server (NTRS)

    Liu, R.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1998-01-01

    We have compared carbonyl diimidazole (CDI) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as activating agents for the oligomerization of negatively-charged alpha- and beta-amino acids in homogeneous aqueous solution. alpha-Amino acids can be oligomerized efficiently using CDI, but not by EDAC. beta-Amino acids can be oligomerized efficiently using EDAC, but not by CDI. Aspartic acid, an alpha- and beta-dicarboxylic acid is oligomerized efficiently by both reagents. These results are explained in terms of the mechanisms of the reactions, and their relevance to prebiotic chemistry is discussed.

  8. Stabilities and partitioning of arenonium ions in aqueous media.

    PubMed

    Lawlor, D A; More O'Ferrall, R A; Rao, S N

    2008-12-31

    The phenathrenonium ion is formed as a reactive intermediate in the solvolysis of 9-dichloroacetoxy-9,10-dihydrophenanthrene in aqueous acetonitrile and undergoes competing reactions with water acting as a base and nucleophile. Measurements of product ratios in the presence of azide ion as a trap and 'clock' yield rate constants kp = 3.7 x 10(10) and kH2O = 1.5 x 10(8) s(-1), respectively. Combining these with rate constants for the reverse reactions (protonation of phenanthrene and acid-catalyzed aromatization of its water adduct) gives equilibrium constants pKa = -20.9 and pK(R) = -11.6. For a series of arenonium and benzylic cations, correlation of log kp with pKa, taking account of the limit to kp set by the relaxation of water (10(11) s(-1)), leads to extrapolation of kp = 9.0 x 10(10) s(-1) and pKa = -24.5 for the benzenonium ion and kp = 6.5 x 10(10) s(-1) and pKa = -22.5 for the 1-naphthalenonium ion. Combining these pKa's with estimates of equilibrium constants pKH2O for the hydration of benzene and naphthalene, and the relationship pKR = pKa + pKH2O based on Hess's law, gives pKR = -2.3 and -8.0 respectively, and highlights the inherent stability of the benzenonium ion. A correlation exists between the partitioning ratio, kp/kH2O, for carbocations reacting in water and KH2O the equilibrium constant between the respective reaction products, i.e., log(kp/kH2O) = 0.46pKH2O - 3.7. It implies that kp exceeds kH2O only when KH2O > 10(8). This is consistent with the proton transfer (a) possessing a lower intrinsic reactivity than reaction of the carbocation with water as a nucleophile and (b) being rate-determining in the hydration of alkenes (and dehydration of alcohols) except when the double bond of the alkene is unusually stabilized, as in the case of aromatic molecules. PMID:19063609

  9. Solvation and protonation of coumarin 102 in aqueous media: a fluorescence spectroscopic and theoretical study.

    PubMed

    Hessz, Dóra; Hégely, Bence; Kállay, Mihály; Vidóczy, Tamás; Kubinyi, Miklós

    2014-07-17

    The ground- and excited-state protonation of Coumarin 102 (C102), a fluorescent probe applied frequently in heterogeneous systems with an aqueous phase, has been studied in aqueous solutions by spectroscopic experiments and theoretical calculations. For the dissociation constant of the protonated form in the ground state, pKa = 1.61 was obtained from the absorption spectra; for the excited-state dissociation constant, pKa* = 2.19 was obtained from the fluorescence spectra. These values were closely reproduced by theoretical calculations via a thermodynamic cycle (the value of pKa* also by calculations via the Förster cycle) using an implicit–explicit solvation model (polarized continuum model + addition of a solvent molecule). The theoretical calculations indicated that (i) in the ground state, C102 occurs primarily as a hydrogen-bonded water complex, with the oxo group as the binding site, (ii) this hydrogen bond becomes stronger upon excitation, and (iii) in the ground state, the amino nitrogen atom is the protonation site, and in the excited state, the carboxy oxygen atom is the protonation site. A comprehensive analysis of fluorescence decay data yielded the values kpr = 3.27 × 10(10) M(–1) s(–1) for the rate constant of the excited-state protonation and kdpr = 2.78 × 10(8) s(–1) for the rate constant of the reverse process (kpr and kdpr were treated as independent parameters). This, considering the relatively long fluorescence lifetimes of neutral C102 (6.02 ns) and its protonated form (3.06 ns) in aqueous media, means that a quasi-equilibrium state of excited-state proton transfer is reached in strongly acidic solutions.

  10. Raman spectra of amino acids and their aqueous solutions

    NASA Astrophysics Data System (ADS)

    Zhu, Guangyong; Zhu, Xian; Fan, Qi; Wan, Xueliang

    2011-03-01

    Amino acids are the basic "building blocks" that combine to form proteins and play an important physiological role in all life-forms. Amino acids can be used as models for the examination of the importance of intermolecular bonding in life processes. Raman spectra serve to obtain information regarding molecular conformation, giving valuable insights into the topology of more complex molecules (peptides and proteins). In this paper, amino acids and their aqueous solution have been studied by Raman spectroscopy. Comparisons of certain values for these frequencies in amino acids and their aqueous solutions are given. Spectra of solids when compared to those of the solute in solution are invariably much more complex and almost always sharper. We present a collection of Raman spectra of 18 kinds of amino acids ( L-alanine, L-arginine, L-aspartic acid, cystine, L-glutamic acid, L-glycine, L-histidine, L-isoluecine, L-leucine, L-lysine, L-phenylalanine, L-methionone, L-proline, L-serine, L-threonine, L-tryptophan, L-tyrosine, L-valine) and their aqueous solutions that can serve as references for the interpretation of Raman spectra of proteins and biological materials.

  11. Persistent Ion Pairing in Aqueous Hydrochloric Acid

    SciTech Connect

    Baer, Marcel D.; Fulton, John L.; Balasubramanian, Mahalingam; Schenter, Gregory K.; Mundy, Christopher J.

    2014-07-03

    For strong acids, like hydrochloric acid, the complete dissociation into an excess proton and conjugated base as well as the formation of independent solvated charged fragments is assumed. The existence of a chloride-Hyronium (Cl-H3O+) contact ion pairs even in moderate concentration hydrochloric acid (2.5 m) demonstrates that the counter ions do not behave merely as spectators. Through the use of modern extended X-ray absorption fine structure (EXAFS) measurements in conjunction with state-of-the-art density functional theory (DFT) simulations, we are able to obtain an unprecedented view into the molecular structure of medium to high concentrated electrolytes. Here we report that the Cl-H3O+ contact ion pair structure persists throughout the entire concentration range studied and that these structures differ significantly from moieties studied in micro-solvated hydrochloric acid clusters. Characterizing distinct populations of these ion pairs gives rise to a novel molecular level description of how to think about the activity of the proton that impacts our picture of the pH scale. Funding for CJM, GKS, and JLF was provided by DOE Office of Science, Office of Basic Energy Science, Division of Chemical Sciences, Geosciences, and Biosciences. Funding for MDB was provided throught the Laboratory Directed Research and Development program at Pacific Northwest National Laboratory. MB was funded through Argonne National Laboratory.

  12. Microwave-Assisted Hydrogenation of Codeine in Aqueous Media

    PubMed Central

    Taktak, F.; Bulduk, I.

    2012-01-01

    An efficient one-pot microwave-assisted hydrogenation of codeine was achieved in aqueous solution. This technique is simple, fast, environmentally friendly, and highly efficient. Structure of produced dihydrocodeine was approved by using FT-IR, 1H NMR, 13C NMR, EIMS, and elemental analysis technique. Its purity analysis was performed by using HPLC and assay analysis was performed by using potentiometric titration methods. PMID:24052836

  13. Amino-acid contamination of aqueous hydrochloric acid.

    NASA Technical Reports Server (NTRS)

    Wolman, Y.; Miller, S. L.

    1971-01-01

    Considerable amino-acid contamination in commercially available analytical grade hydrochloric acid (37% HCl) was found. One bottle contained 8,300 nmol of amino-acids per liter. A bottle from another supplier contained 6,700 nmol per liter. The contaminants were mostly protein amino-acids and several unknowns. Data on the volatility of the amino-acids during HCl distillation were also obtained.

  14. Cyanide detection using a benzimidazole derivative in aqueous media

    NASA Astrophysics Data System (ADS)

    Li, Jian-Bin; Hu, Jing-Han; Chen, Juan-Juan; Qi, Jing

    2014-12-01

    A novel cyanide selective fluorescent chemosensor S1 based on benzimidazole group and naphthalene group as the fluorescence signal group had been designed and synthesized. The receptor could instantly detect CN- anion over other anions such as F-, Cl-, Br-, I-, AcO-, H2PO4-, HSO4-, SCN- and ClO4- by fluorescence spectroscopy changes in aqueous solution (H2O/DMSO, 8:2, v/v) with specific selectivity and high sensitivity. The fluorescence color of the solution containing sensor S1 induced a remarkable color change from pale blue to mazarine only after the addition of CN- in aqueous solution while other anions did not cause obvious color change. Moreover, further study demonstrates the detection limit on fluorescence response of the sensor to CN- is down to 8.8 × 10-8 M, which is far lower than the WHO guideline of 1.9 × 10-6 M. Test strips based on S1 were fabricated, which could act as a convenient and efficient CN- test kit to detect CN- in pure water for “in-the-field” measurement. Thus, the probe should be potential applications in an aqueous environment for the monitoring of cyanide.

  15. Cyanide detection using a benzimidazole derivative in aqueous media.

    PubMed

    Li, Jian-Bin; Hu, Jing-Han; Chen, Juan-Juan; Qi, Jing

    2014-12-10

    A novel cyanide selective fluorescent chemosensor S1 based on benzimidazole group and naphthalene group as the fluorescence signal group had been designed and synthesized. The receptor could instantly detect CN(-) anion over other anions such as F(-), Cl(-), Br(-), I(-), AcO(-), H2PO4(-), HSO4(-), SCN(-) and ClO4(-) by fluorescence spectroscopy changes in aqueous solution (H2O/DMSO, 8:2, v/v) with specific selectivity and high sensitivity. The fluorescence color of the solution containing sensor S1 induced a remarkable color change from pale blue to mazarine only after the addition of CN(-) in aqueous solution while other anions did not cause obvious color change. Moreover, further study demonstrates the detection limit on fluorescence response of the sensor to CN(-) is down to 8.8×10(-8)M, which is far lower than the WHO guideline of 1.9×10(-6)M. Test strips based on S1 were fabricated, which could act as a convenient and efficient CN(-) test kit to detect CN(-) in pure water for "in-the-field" measurement. Thus, the probe should be potential applications in an aqueous environment for the monitoring of cyanide.

  16. H 2SO 4/HNO 3/HCl—Functionalization and its effect on dispersion of carbon nanotubes in aqueous media

    NASA Astrophysics Data System (ADS)

    Osorio, A. G.; Silveira, I. C. L.; Bueno, V. L.; Bergmann, C. P.

    2008-12-01

    Chemical functionalization is a procedure used in materials science to oxidize the surface of materials. Several researchers use this technique to improve carbon nanotubes (CNTs) interaction and dispersion. The present article evaluates the effect of different functionalization methodologies on dispersion of CNTs in aqueous media. Sulfuric, nitric and chloridric acids were used on the first functionalization. For the second procedure tested the addition of chloridric acid was eliminated; and the third functionalization was done using only nitric acid. Experimental results obtained by Raman spectroscopy indicated the maintenance of the structure of CNTs after all oxidations. The presence of other structures was proved by thermogravimetry decomposition and the addition of functional groups was confirmed by transform Fourier infrared spectroscopy. From these experimental results, we conclude that all methodologies used showed a percentage of adsorption of functional groups on the CNTs. However, based on dispersion analysis in aqueous media, it is observed that this adsorption showed more efficiency on the first functionalization method, followed by the second method.

  17. Fundamental investigation of the transport properties of superacids in aqueous and non-aqueous media

    NASA Astrophysics Data System (ADS)

    Suarez, Sophia

    In the quest to develop more efficient energy providers one of the main focus of research has been on the improvement of ion transport. In lithium battery research this has led to the incorporation of various lithium salts, ceramics and plasticizers into the poly(ethylene)oxide (PEO) matrix, the polymer most used In Proton Conduction Membrane (PCM) fuel cell research this has led to the development of new membranes, which are designed with to replicate Nafion's ((c)DuPont) proton transport but also improve upon its deficiency of transporting intact fuel molecules and its dependence upon the presence of solvating water molecules. To better understand the process of ion transport, NMR was used to investigate dynamic properties such as D (self-diffusion coefficient) and T1 (spin-lattice relaxation time) of various proton and lithium ion-conducting systems. Ionic conductivity and viscosity measurements were also performed. The systems studied includes aqueous superacid solutions (trifluoromethanesulfonic (TFSA), para-toluenesulfonic (PTSA) and bis(trifluoromethanesulfonyl)imide (TFSI)); nano-porous (NP-) PCM's incorporating various ceramics and 3M fuel/2M H2SO4 solutions; and P(EO)20LiBETI (LiN(SO 2CF2CF3)2 composite incorporating SiO 2 ceramic nano particles. The objective of the study of the superacid solutions was to determine the effect of concentration on the transport. It was found that beyond the ionic conductivity maximum, fluctuations in both D and T1 supports the existence of local ordering in the ionic network, caused by the reduced solvent dielectric coefficient and increasing viscosity. Of the three superacids TFSA was the most conductive and most affected by reduced solvent concentration. For the P(EO)20LiBETI composite the aim was to determine the effect of the ceramic on the ion transport of the composite in a solvent free environment. Results show that the ceramic causes only modest increase in the lithium transport below 90°C. The objective in the

  18. Mechanistic study of the reaction of L-ascorbic acid with hexacyanometalate(III) ions of iron(III), ruthenium(III), and osmium(III) in aqueous acidic solution at elevated pressures

    SciTech Connect

    Kagayama, Nobuyoshi; Sekiguchi, Mitsuhiro; Inada, Yasuhiro; Takagi, Hideo D.; Funahashi, Shigenobu )

    1994-04-27

    Oxidation reactions of L-ascorbic acid by three hexacyanometalate(III) ions in aqueous acidic media are studied at elevated pressures. Kinetic parameters characterizing two parallel paths involving ascorbic acid (H[sub 2]Asc) and ascorbate ion (HAsc[sup [minus

  19. γ-Irradiation of malic acid in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Negron-Mendoza, Alicia; Graff, Rebecca L.; Ponnamperuma, Cyril

    1980-12-01

    The γ-irradiation of malic acid in aqueous solutions was studied under initially oxygenated and oxygen-free conditions in an attempt to determine the possible interconversion of malic acid into other carboxylic acids, specifically those associated with Krebs cycle. The effect of dose on product formation of the system was investigated. Gas-liquid chromatography combined with mass spectrometry was used as the principal means of identification of the non-volatile products. Thin layer chromotography and direct probe mass spectroscopy were also employed. The findings show that a variety of carboxylic acids are formed, with malonic and succinic acids in greatest abundance. These products have all been identified as being formed in the γ-irradiation of acetic acid, suggesting a common intermediary. Since these molecules fit into a metabolic cycle, it is strongly suggestive that prebiotic pathways provided the basis for biological systems.

  20. GREENER AND CONTROLLED SYNTHESIS OF NOBLE NANOSTRUCTURES IN AQUEOUS MEDIA USING MICROWAVE IRRADIATION

    EPA Science Inventory

    Microwave-assisted spontaneous reduction of gold salts is described using sugar solutions such as alpha-D-glucose, sucrose and maltose, etc. The expeditious reactions are conducted in aqueous media using microwave irradiation wherein the reduction occurs within 30 to 60 seconds ...

  1. Trifluoromethylation of arenediazonium salts with fluoroform-derived CuCF3 in aqueous media.

    PubMed

    Lishchynskyi, Anton; Berthon, Guillaume; Grushin, Vladimir V

    2014-09-14

    A new protocol has been developed for trifluoromethylation of arenediazonium salts with moisture-sensitive CuCF3 (from fluoroform) in aqueous media. The reaction is governed by a radical mechanism, tolerates a broad variety of functional groups, and is applicable to the synthesis of complex, polyfunctionalized molecules. PMID:25052336

  2. Calculation of Hamaker constants in non-aqueous fluid media

    SciTech Connect

    BELL,NELSON S.; DIMOS,DUANE B.

    2000-05-09

    Calculations of the Hamaker constants representing the van der Waals interactions between conductor, resistor and dielectric materials are performed using Lifshitz theory. The calculation of the parameters for the Ninham-Parsegian relationship for several non-aqueous liquids has been derived based on literature dielectric data. Discussion of the role of van der Waals forces in the dispersion of particles is given for understanding paste formulation. Experimental measurements of viscosity are presented to show the role of dispersant truncation of attractive van der Waals forces.

  3. Terahertz characteristics of electrolytes in aqueous Luria-Bertani media

    NASA Astrophysics Data System (ADS)

    Oh, Seung Jae; Son, Joo-Hiuk; Yoo, Ocki; Lee, Dong-Hee

    2007-10-01

    We measured the optical constants of aqueous biomaterial mixtures with various electrolyte concentrations using terahertz time-domain spectroscopy. The mixtures were divided into water and other electrolyte parts in mass fractions for analysis. The optical constants of the electrolyte, excluding water, were obtained by applying the ideal mixture equation, and the power absorption of the electrolyte was observed to be larger than that of water above 1THz. Data from the measurement were fitted with the modified double Debye model, and the reorientation and hydrogen-bond formation decomposition times were found to decrease as the electrolyte concentration increased.

  4. β-Cyclodextrin as a Metal-anionic Porphyrin Complexation Accelerator in Aqueous Media.

    PubMed

    Ohtomo, Takao; Yokoyama, Aya; Konno, Mitsuyuki; Ohno, Osamu; Igarashi, Shukuro; Takagai, Yoshitaka

    2016-01-01

    The rate of the complexation reaction between anionic porphyrins and 11 metal ions was found to be accelerated by the presence of β-cyclodextrin (β-CD) in aqueous media at room temperature without the need for additional heating or sonication. The porphyrin complexation reaction with metal ions under aqueous conditions can be difficult due to the strong hydration energy between the metal ions and water. In this study, the specific role of β-CD as an accelerator was determined and found to enhance the typically slow reaction of the porphyrin with metal ions. A significant acceleration effect was exhibited when the model anionic porphyrin, 5,10,15,20-tetraphenyl-21H,23H-porphine-tetrasulfonic acid, and Pb(II) ions were combined in the presence of β-CD. Other than for Hg ion, the addition of β-CD decreased the metalation reaction time from 30 to 2 min. The order in the degree of acceleration was Pb > Zn, Cd > Cu > Fe, Pd > Sn > Ag, Co, Mn. Using Pb(II) as the model ion, it was determined that the complexation rate constant was enhanced by a factor of 2.4, while the dissociation rate constant was diminished by a factor of 135 in the presence of added β-CD relative to that in its absence. Overall, the complex was much more stable (formation equilibrium constant 324-fold greater in the β-CD medium. The formation of a ternary complex (cf. bicapped complex; (β-CD)2-porphyrin-metal ion) was demonstrated through the use of nuclear magnetic-resonance spectroscopy and mass spectrometry. This acceleration effect is expected to be applicable systems in which porphyrin ligands are employed for determining of metal ions in chemical analysis and separation science. PMID:27302582

  5. β-Cyclodextrin as a Metal-anionic Porphyrin Complexation Accelerator in Aqueous Media.

    PubMed

    Ohtomo, Takao; Yokoyama, Aya; Konno, Mitsuyuki; Ohno, Osamu; Igarashi, Shukuro; Takagai, Yoshitaka

    2016-01-01

    The rate of the complexation reaction between anionic porphyrins and 11 metal ions was found to be accelerated by the presence of β-cyclodextrin (β-CD) in aqueous media at room temperature without the need for additional heating or sonication. The porphyrin complexation reaction with metal ions under aqueous conditions can be difficult due to the strong hydration energy between the metal ions and water. In this study, the specific role of β-CD as an accelerator was determined and found to enhance the typically slow reaction of the porphyrin with metal ions. A significant acceleration effect was exhibited when the model anionic porphyrin, 5,10,15,20-tetraphenyl-21H,23H-porphine-tetrasulfonic acid, and Pb(II) ions were combined in the presence of β-CD. Other than for Hg ion, the addition of β-CD decreased the metalation reaction time from 30 to 2 min. The order in the degree of acceleration was Pb > Zn, Cd > Cu > Fe, Pd > Sn > Ag, Co, Mn. Using Pb(II) as the model ion, it was determined that the complexation rate constant was enhanced by a factor of 2.4, while the dissociation rate constant was diminished by a factor of 135 in the presence of added β-CD relative to that in its absence. Overall, the complex was much more stable (formation equilibrium constant 324-fold greater in the β-CD medium. The formation of a ternary complex (cf. bicapped complex; (β-CD)2-porphyrin-metal ion) was demonstrated through the use of nuclear magnetic-resonance spectroscopy and mass spectrometry. This acceleration effect is expected to be applicable systems in which porphyrin ligands are employed for determining of metal ions in chemical analysis and separation science.

  6. Development of chiral catalysts for Mukaiyama aldol reactions in aqueous media.

    PubMed

    Kitanosono, Taku; Kobayashi, Shū

    2014-02-01

    Since the discovery of the Mukaiyama aldol reaction in 1973, tremendous efforts have been made to develop a definitive catalyst that catalyzes asymmetric Mukaiyama aldol reactions under mild conditions with broad substrate tolerance. Forty years later, an exhaustive search for a water-compatible Lewis acid was able to uncover the hidden potential of iron(II) and bismuth(III), leading to the establishment of broadly applicable and versatile catalytic systems for asymmetric Mukaiyama aldol reactions in aqueous media. The ternary catalytic system was able to expand the substrate generality considerably as the most distinguished catalyst ever reported. The superiority of this methodology over conventional methods has also been demonstrated in terms of high catalytic activity, simplicity of experimental procedures, and a wide substrate range including aqueous aldehydes, for which the stereochemistry had been regarded as difficult to control. Furthermore, a facile synthesis of the chiral ligand underscores its versatility. The reaction did not proceed at all without use of water. In the postulated mechanism, water plays prominent roles in: (1) producing the active metal complexes with a high water-exchange rate constant (3.2 × 10(6)) to activate substrates effectively and to catalyze the reaction through a rapid proton transfer on the order of picoseconds; (2) facilitating the catalytic turnover with simultaneous desilylation as direct access to aldol adducts or facile recovery of active metal complexes; and (3) stabilizing rigid transition states composed of metal complexes and reactants through entropy-driven aggregation derived from the highest cohesive energy density. PMID:24449534

  7. Small scale flow processes in aqueous heterogeneous porous media

    SciTech Connect

    Rashidi, M.; Dickenson, E.

    1996-04-01

    Small scale flow processes in aqueous heterogeneous porous systems have been studied experimentally via novel nonintrusive fluorescence imaging techniques. The techniques involve 3D visualization and quantification of flow fields within a refractive index-matched transparent porous column. The refractive index-matching yields a transparent porous medium, free from any scattering and refraction at the solid-liquid interfaces, as a result allowing direct optical probing at any point within the porous system. By illuminating the porous regions within the column with a planar sheet of laser beam, flow processes through the porous medium can be observed microscopically, and qualitative and quantitative in-pore transport information can be obtained at a good resolution and a good accuracy. A CCD camera is used to record the fluorescent images at every vertical plane location while sweeping back and forth across the column. These digitized flow images are then analyzed and accumulated over a 3D volume within the column. Series of flow experiments in aqueous, refractive index-matched, porous systems packed with natural mineral particles have been performed successfully in these laboratories.

  8. Does Nitric Acid Dissociate at the Aqueous Solution Surface?

    SciTech Connect

    Lewis, Tanza; Winter, Berndt; Stern, Abraham C.; Baer, Marcel D.; Mundy, Christopher J.; Tobias, Douglas J.; Hemminger, J. C.

    2011-11-03

    Nitric acid is a prevalent component of atmospheric aerosols, and the extent of nitric acid dissociation at aqueous interfaces is relevant to its role in heterogeneous atmospheric chemistry. Several experimental and theoretical studies have suggested that the extent of dissociation of nitric acid near aqueous interfaces is less than in bulk solution. Here, dissociation of HNO3 at the surface of aqueous nitric acid is quantified using X-ray photoelectron spectroscopy of the nitrogen local electronic structure. The relative amounts of undissociated HNO3(aq) and dissociated NO3-(aq) are identified by the distinguishable N1s core-level photoelectron spectra of the two species, and we determine the degree of dissociation, αint, in the interface (the first ~3 layers of solution) as a function of HNO3 concentration. Our measurements show that dissociation is decreased by approximately 20% near the solution interface compared with bulk, and furthermore that dissociation occurs even in the top-most solution layer. The experimental results are supported by first-principles MD simulations, which show that hydrogen-bonds between HNO3 and water molecules at the solution surface stabilize the molecular form at low concentration, in analogy to the stabilization of molecular HNO3 that occurs in bulk solution at high concentration. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for DOE.

  9. Investigation of acyl migration in mono- and dicaffeoylquinic acids under aqueous basic, aqueous acidic, and dry roasting conditions.

    PubMed

    Deshpande, Sagar; Jaiswal, Rakesh; Matei, Marius Febi; Kuhnert, Nikolai

    2014-09-17

    Acyl migration in chlorogenic acids describes the process of migration of cinnamoyl moieties from one quinic acid alcohol group to another, thus interconverting chlorogenic acid regioisomers. It therefore constitutes a special case of transesterification reaction. Acyl migration constitutes an important reaction pathway in both coffee roasting and brewing, altering the structure of chlorogenic acid initially present in the green coffee bean. In this contribution we describe detailed and comprehensive mechanistic studies comparing inter- and intramolecular acyl migration involving the seven most common chlorogenic acids in coffee. We employe aqueous acidic and basic conditions mimicking the brewing of coffee along with dry roasting conditions. We show that under aqueous basic conditions intramolecular acyl migration is fully reversible with basic hydrolysis competing with acyl migration. 3-Caffeoylquinic acid was shown to be most labile to basic hydrolysis. We additionally show that the acyl migration process is strongly pH dependent with increased transesterification taking place at basic pH. Under dry roasting conditions acyl migration competes with dehydration to form lactones. We argue that acyl migration precedes lactonization, with 3-caffeoylquinic acid lactone being the predominant product.

  10. Optical properties of natural phenols in aqueous media

    NASA Astrophysics Data System (ADS)

    Vusovich, Olga; Sultimova, Natalia; Tchaikovskaya, Olga; Sokolova, Irina; Vasilieva, Nina

    2015-11-01

    Currently, the study of the photochemistry of natural phenols is relevant as it has a fundamental and a practical importance. The optical properties of natural phenols are studied: 3-methoxy-4-hydroxybenzaldehyde (vanillin) and 3- hydroxy-4-methoxybenzaldehyde (isovanillin), 4-hydroxy-3-methoxybenzoic acid (vanillic acid). The processes of proton transfer in the investigated molecules in ground and excited states under exposure to lamp and laser emissions are presented using the methods of electron spectroscopy and quantum chemistry.

  11. Near infrared photochemistry of pyruvic acid in aqueous solution.

    PubMed

    Larsen, Molly C; Vaida, Veronica

    2012-06-21

    Recent experimental and theoretical results have suggested that organic acids such as pyruvic acid, can be photolyzed in the ground electronic state by the excitation of the OH stretch vibrational overtone. These overtones absorb in the near-infrared and visible regions of the spectrum where the solar photons are plentiful and could provide a reaction pathway for the organic acids and alcohols that are abundant in the earth's atmosphere. In this paper the overtone initiated photochemistry of aqueous pyruvic acid is investigated by monitoring the evolution of carbon dioxide. In these experiments CO(2) is being produced by excitation in the near-infrared, between 850 nm and ∼1150 nm (11,765-8696 cm(-1)), where the second OH vibrational overtone (Δν = 3) of pyruvic acid is expected to absorb. These findings show not only that the overtone initiated photochemical decarboxylation reaction occurs but also that in the aqueous phase it occurs at a lower energy than was predicted for the overtone initiated reaction of pyruvic acid in the gas phase (13,380 cm(-1)). A quantum yield of (3.5 ± 1.0) × 10(-4) is estimated, suggesting that although this process does occur, it does so with a very low efficiency.

  12. The dispersion and aggregation of graphene oxide in aqueous media

    NASA Astrophysics Data System (ADS)

    Wang, Meng; Niu, Yang; Zhou, Jihan; Wen, Hao; Zhang, Zhenyu; Luo, Da; Gao, Dongliang; Yang, Juan; Liang, Dehai; Li, Yan

    2016-07-01

    Graphene oxide (GO), as a typical two-dimensional material, possesses a range of oxygen-containing groups and shows surfactant and/or polyelectrolyte-like characteristics. Herein, GO sheets with narrow size distribution were prepared by an ultracentrifugation-based process and the aggregation behaviour of GO in pure water and an electrolyte aqueous solution were studied using laser light scattering (LLS). When adding common electrolytes, such as NaCl and MgCl2, into the GO dispersions, aggregation occurs and irreversible coagulation eventually occurs too. However, the GO dispersion can still remain stable when adding excess AlCl3. The zeta potential of the GO dispersion changes from negative to positive after the addition of access AlCl3, indicating that electrostatic repulsion is still responsible for the dispersion of GO, which is in good agreement with the LLS results. This finding on the dispersion of GO may be applied in the solution processing of GO. It also expands the scope of the design and preparation of new GO-based hybrid materials with different functions.Graphene oxide (GO), as a typical two-dimensional material, possesses a range of oxygen-containing groups and shows surfactant and/or polyelectrolyte-like characteristics. Herein, GO sheets with narrow size distribution were prepared by an ultracentrifugation-based process and the aggregation behaviour of GO in pure water and an electrolyte aqueous solution were studied using laser light scattering (LLS). When adding common electrolytes, such as NaCl and MgCl2, into the GO dispersions, aggregation occurs and irreversible coagulation eventually occurs too. However, the GO dispersion can still remain stable when adding excess AlCl3. The zeta potential of the GO dispersion changes from negative to positive after the addition of access AlCl3, indicating that electrostatic repulsion is still responsible for the dispersion of GO, which is in good agreement with the LLS results. This finding on the

  13. The dispersion and aggregation of graphene oxide in aqueous media.

    PubMed

    Wang, Meng; Niu, Yang; Zhou, Jihan; Wen, Hao; Zhang, Zhenyu; Luo, Da; Gao, Dongliang; Yang, Juan; Liang, Dehai; Li, Yan

    2016-08-14

    Graphene oxide (GO), as a typical two-dimensional material, possesses a range of oxygen-containing groups and shows surfactant and/or polyelectrolyte-like characteristics. Herein, GO sheets with narrow size distribution were prepared by an ultracentrifugation-based process and the aggregation behaviour of GO in pure water and an electrolyte aqueous solution were studied using laser light scattering (LLS). When adding common electrolytes, such as NaCl and MgCl2, into the GO dispersions, aggregation occurs and irreversible coagulation eventually occurs too. However, the GO dispersion can still remain stable when adding excess AlCl3. The zeta potential of the GO dispersion changes from negative to positive after the addition of access AlCl3, indicating that electrostatic repulsion is still responsible for the dispersion of GO, which is in good agreement with the LLS results. This finding on the dispersion of GO may be applied in the solution processing of GO. It also expands the scope of the design and preparation of new GO-based hybrid materials with different functions. PMID:27432559

  14. A novel colorimetric HSO4- sensor in aqueous media

    NASA Astrophysics Data System (ADS)

    Li, Ping; Zhang, You-Ming; Lin, Qi; Li, Jun-Qiang; Wei, Tai-Bao

    2012-05-01

    A novel and sensitive anion receptor 3, bearing Schiff base structure, nitrophenyl azobenzol and carboxyl groups, was developed and characterized as a single chemosensor for the recognition of HSO4- anion. The different responses of UV-vis spectra and color changes of 3 could be applied to the recognition for HSO4- over other anions such as F-, CI-, Br-, I-, AcO-, H2PO4- and CIO4- by the naked eye. Furthermore, the anion binding interaction of receptor-anion was also studied using UV-vis and 1H NMR titration which revealed that 3 displayed a remarkable binding ability for the HSO4- with an association constant Ka = 6.59 × 104 M-1. And the detection limitation of HSO4- with the receptor 3 was 2.0 × 10-6 mol L-1 in aqueous solution. Most importantly, the qualitative detection of HSO4- using receptor 3 was attempted with test kit which was made from receptor 3.

  15. Anodic electrodeposition of NiTSPP from aqueous basic media.

    PubMed

    Pérez-Morales, Marta; Muñoz, Eulogia; Martín-Romero, María T; Camacho, Luis

    2005-06-01

    The oxidative electrodeposition of NiTSPP (tetrakis(4-sulfonatophenyl) Ni porphyrin) on ITO electrode from 0.1 M NaOH aqueous solution has been studied, and UV-visible and reflection FTIR spectroscopies have been used to analyze the composition of such film. By use of UV-vis spectroscopy, small absorbance of the film and an almost nulling effect on the Soret band of the porphyrin along the Ni(III)/Ni(II) redox process were observed. The reflection FTIR spectroscopy detected the presence of Ni-OH groups in the reduced film and as well the state of the porphyrin molecules as radical cation. Moreover, the porphyrin has been quantified by means of the area of the vibration bands assigned to the sulfonate groups by using as reference a Langmuir-Blodgett film containing a known surface concentration of NiTSPP. These results lead us propose the formation of a conductor salt by electrocrystallization, with stoichiometries TSPP/Ni(II)(OH)2 and TSPP/Ni(III)OOH, for its reduced and oxidized forms, respectively. In these two forms, the porphyrin rings will be present as radical cation, which may be stabilized through its dimerization or polymerization. PMID:15924477

  16. Anodic electrodeposition of NiTSPP from aqueous basic media.

    PubMed

    Pérez-Morales, Marta; Muñoz, Eulogia; Martín-Romero, María T; Camacho, Luis

    2005-06-01

    The oxidative electrodeposition of NiTSPP (tetrakis(4-sulfonatophenyl) Ni porphyrin) on ITO electrode from 0.1 M NaOH aqueous solution has been studied, and UV-visible and reflection FTIR spectroscopies have been used to analyze the composition of such film. By use of UV-vis spectroscopy, small absorbance of the film and an almost nulling effect on the Soret band of the porphyrin along the Ni(III)/Ni(II) redox process were observed. The reflection FTIR spectroscopy detected the presence of Ni-OH groups in the reduced film and as well the state of the porphyrin molecules as radical cation. Moreover, the porphyrin has been quantified by means of the area of the vibration bands assigned to the sulfonate groups by using as reference a Langmuir-Blodgett film containing a known surface concentration of NiTSPP. These results lead us propose the formation of a conductor salt by electrocrystallization, with stoichiometries TSPP/Ni(II)(OH)2 and TSPP/Ni(III)OOH, for its reduced and oxidized forms, respectively. In these two forms, the porphyrin rings will be present as radical cation, which may be stabilized through its dimerization or polymerization.

  17. Interaction of steroid--peroxidase conjugates with cellulose immunosorbents in aqueous and micellar media.

    PubMed

    Eryomin, A N; Metelitza, D I

    1998-10-01

    In 0.1 M bicarbonate buffer (pH 9.0) and in microemulsions of aerosol OT (AOT) and its mixture with Triton X-45 in heptane, antibodies against cortisol (anti-COR) and progesterone (anti-PROG) were covalently immobilized on fine-porous cellulose filters (0.6 cm diameter) after sodium periodate oxidation. Immunosorbents obtained in different media were characterized in terms of antibody-bound density and antigen-binding capacity with respect to peroxidase--steroid conjugates HP--COR-11 and HP--PROG-4 containing 11 molecules of cortisol and four progesterone molecules, respectively. For all immunosorbents antigen-binding capacity expressed as peroxidase activity of immune complexes formed on the solid cellulose phase in aqueous and micellar media was determined. Dissociation constants of immunocomplexes on the cellulose formed in aqueous and micellar media were determined using ELISA. In all cases Kd values in aqueous media were approximately 10-8 M and were significantly lower than corresponding values of dissociation constants of immune complexes in mixed microemulsions of AOT and Triton X-45. PMID:9864448

  18. Study on the fluorescence characteristics of bromadiolone in aqueous and organized media and application in analysis.

    PubMed

    Subbiah, Deepa; Kala, Subramanian; Mishra, Ashok K

    2005-12-01

    The fluorescence spectroscopic behavior of bromadiolone (anticoagulant rodenticide), a substituted 4-hydroxycoumarin derivative, was investigated in water and in organized media like micelles and cyclodextrins. A detailed study on various photophysical parameters like fluorescence intensity (I(F)), quantum yield (phi), lifetime (tau) and steady state fluorescence anisotropy (r) of bromadiolone in aqueous and in organized media was carried out. Bromadiolone in aqueous solution was observed to be in an aggregated state, thereby showing weak emission due to self-quenching. Marked enhancement of fluorescence intensity was observed in organized media like micelles and beta-cyclodextrin. A preliminary investigation has been done to find out whether this enhancement of fluorescence can be used to develop a sensitive analytical method for determination of bromadialone in aqueous media. A linear relationship between the fluorescence intensity and concentration of bromadiolone was observed in the range of 0.15-7.9 microg ml(-1) in cetyltrimethylammonium bromide (CTAB) and 0.5-26.4 microg ml(-1) in beta-cyclodextrin medium. The lower detection limit was found to be 37 ng ml(-1) in presence of CTAB and 23 ng ml(-1) in beta-cyclodextrin. Comparison with 4-hydroxycoumarin, an unsubstituted analogue, was made. PMID:15982718

  19. Derivatization in gas chromatographic determination of phenol and aniline traces in aqueous media

    NASA Astrophysics Data System (ADS)

    Gruzdev, I. V.; Zenkevich, I. G.; Kondratenok, B. M.

    2015-06-01

    Substituted anilines and phenols are the most common hydrophilic organic environmental toxicants. The principles of gas chromatographic determination of trace amounts of these compounds in aqueous media at concentrations <=0.1 μg litre-1 based on synthesis of their derivatives (derivatization) directly in the aqueous phase are considered. Conversion of relatively hydrophilic analytes into more hydrophobic derivatives makes it possible to achieve such low detection limits and optimize the protocols of extractive preconcentration and selective chromatographic detection. Among the known reactions, this condition is best met by electrophilic halogenation of compounds at the aromatic moiety. The bibliography includes 177 references.

  20. Aspecific and specific intermolecular interactions in aqueous media.

    PubMed

    van Oss, C J

    1990-06-01

    Aspecific as well as specific interactions involve the same noncovalent forces, consisting of Lifshitz-van der Waals, Lewis acid/base, electrostatic, and thermal or Brownian movement interactions. In vivo, aspecific interactions between, e.g., cells and/or biopolymers usually are repulsive, while specific interactions are always attractive. The differences between the two classes of interactions can be shown to lie in the fact that aspecifically interacting bodies are large, while specifically interacting sites are small, or have a small radius of curvature, and in the fact that aspecifically interacting surfaces are homogeneous, whereas specific sites have a heterogeneous composition.

  1. Methanol Uptake by Low Temperature Aqueous Sulfuric Acid Solutions

    NASA Technical Reports Server (NTRS)

    Iraci, L. T.; Essin, A. M.; Golden, D. M.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    The global methanol budget is currently unbalanced, with source terms significantly larger than the sinks terms. To evaluate possible losses of gaseous methanol to sulfate aerosols, the solubility and reactivity of methanol in aqueous sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosols is under investigation. Methanol will partition into sulfate aerosols according to its Henry's law solubility. Using standard uptake techniques in a Knudsen cell reactor, we have measured the effective Henry's law coefficient, H*, for cold (196 - 220 K) solutions ranging between 45 and 70 wt % H2SO4. We have found that methanol solubility ranges from approx. 10(exp 5) - 10(exp 7) M/atm for UT/LS conditions. Solubility increases with decreasing temperature and with increasing sulfuric acid content. Although methanol is slightly more soluble than are acetone and formaldehyde, current data indicate that uptake by clean aqueous sulfuric acid particles will not be a significant sink for methanol in the UT/LS. These solubility measurements include uptake due to physical solvation and any rapid equilibria which are established in solution. Reaction between primary alcohols and sulfuric acid does occur, leading to the production of alkyl sulfates. Literature values for the rate of this reaction suggest that formation of CH3OSO3H is not significant over our experimental time scale for solutions below 80 wt % H2SO4. To confirm this directly, results obtained using a complementary equilibrium measurement technique will also be presented.

  2. Methanol Uptake By Low Temperature Aqueous Sulfuric Acid Solutions

    NASA Technical Reports Server (NTRS)

    Iraci, Laura T.; Essin, Andrew M.; Golden, David M.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    To evaluate the role of upper tropospheric and lower stratospheric aerosols in the global budget of methanol, the solubility and reactivity of CH3OH in aqueous sulfuric acid solutions are under investigation. Using standard uptake techniques in a Knudsen cell reactor, we have measured the effective Henry's law coefficient, H(*), for methanol dissolution into 45 to 70 percent by weight H2SO4. We find that methanol solubility ranges from 10(exp 5) to 10(exp 8) M/atm and increases with decreasing temperature and with increasing sulfuric acid content. These solubility measurements include uptake due to physical solvation and all rapid equilibria which are established in solution. Our data indicate that simple uptake by aqueous sulfuric acid particles will not be a significant sink for methanol in the UT/LS. These results differ from those recently reported in the literature, and an explanation of this disparity will be presented. In addition to solvation, reaction between primary alcohols and sulfuric acid does occur, leading to the production of alkyl sulfates. Literature values for the rate of this reaction suggest that formation of CH3OSO3H may proceed in the atmosphere but is not significant under our experimental conditions. Results obtained using a complementary equilibrium measurement technique confirm this directly. In addition, the extent of methanol sequestration via formation of mono- and dimethylsulfate will be evaluated under several atmospheric conditions.

  3. Recovery of lactic acid from simultaneous saccharification and fermentation media using anion exchange resins.

    PubMed

    Moldes, A B; Alonso, J L; Parajó, J C

    2003-07-01

    The physicochemical properties (capacity, kinetics and selectivity) of the ion exchange resins Amberlite IRA900, IRA400, IRA96 and IRA67 were determined to evaluate their comparative suitability for lactic acid recovery. Both the kinetics of lactic acid sorption from aqueous solutions and the equilibrium were assessed using mathematical models, which provided a close interpretation of the experimental results. The best resins (Amberlite IRA96 and IRA67) were employed in further fixed-bed operation using aqueous lactic acid solutions as feed. In this set of experiments, parameters such as capacity, regenerant consumption, percentage of lactic acid recovery and product concentration were measured. Amberlite IRA67, a weak base resin, was selected for lactic acid recovery from SSF (simultaneous saccharification and fermentation) broths. Owing to the presence of nutrients and ions other than lactate, a slightly decreased capacity was determined when using SSF media instead aqueous lactic acid solutions, but quantitative lactic acid recoveries at constant capacities were obtained in four sequential load/regeneration cycles.

  4. Multiple-acid equilibria in adsorption of carboxylic acids from dilute aqueous solution

    SciTech Connect

    Husson, S.M.; King, C.J.

    1999-02-01

    Equilibria were measured for adsorption of carboxylic acids from aqueous, binary-acid mixtures of lactic and succinic acids and acetic and formic acids onto basic polymeric sorbents. The experimentally determined adsorption isotherms compared well with model predictions, confirming that simple extensions from adsorption of individual acids apply. Fixed-bed studies were carried out that establish the efficacy of chromatographic fractionation of lactic and succinic acids using basic polymeric sorbents. Finally, sequential thermal and solvent regeneration of lactic and acetic acid-laden sorbents was investigated as a method to fractionate among coadsorbed volatile and nonvolatile acids. Essentially complete removal of the acetic acid from the acid-laden sorbent was achieved by vaporization under the conditions used; a small amount of loss of lactic acid (about 11%) was observed.

  5. Sequence-specific association in aqueous media by integrating hydrogen bonding and dynamic covalent interactions.

    PubMed

    Li, Minfeng; Yamato, Kazuhiro; Ferguson, Joseph S; Gong, Bing

    2006-10-01

    Oligoamide strands that associate in a sequence-specific fashion into hydrogen-bonded duplexes in nonpolar solvents were converted into disulfide cross-linked duplexes in aqueous media. Thus, by incorporating trityl-protected thiol groups, which allows the reversible formation of disulfide bonds, into the oligoamide strands, only duplexes consisting of complementary hydrogen-bonding sequences were formed in aqueous solution as well as in methanol. The sequence-specific cross-linking of oligoamide strands was confirmed by MALDI-TOF, reverse-phase HPLC, and by isolating a cross-linked duplex. This study demonstrates that the sequence-specificity characteristic of multiply hydrogen-bonded systems can be extended into competitive media through the interplay of H-bonding and reversible covalent interactions, based on which a new class of molecular associating and ligating units that are compatible with both polar and nonpolar environments can be conveniently obtained.

  6. One-step synthesis of azole- and benzazole-based sulfonamides in aqueous media.

    PubMed

    Zali-Boeini, Hassan; Najafi, Zhaleh; Abtahi, Bahareh; Ghaleshahi, Hajar Golshadi

    2015-05-01

    Several benzazoles (benzoxazoles, benzothiazoles, and benzimidazoles) and azoles (1H-1,2,4-triazole-5(4H)-thiones and 1,2,4-oxadiazoles) bearing a sulfonamide moiety were efficiently prepared via the reactions of dimethyl (arylsulfonyl) dithioimidocarbonate derivatives and their 2-aminobenzene precursors, thiosemicarbazides, and amidoximes, respectively, in the presence of K(2)CO(3) as a base in aqueous ethanol (25%) as a green media in moderate to excellent yields. PMID:25613859

  7. Specific fluorescent sensing of aluminium using naphthalene benzimidazole derivative in aqueous media

    NASA Astrophysics Data System (ADS)

    Velmurugan, K.; Mathankumar, S.; Santoshkumar, S.; Amudha, S.; Nandhakumar, R.

    2015-03-01

    Naphthalene benzimidazole conjugate bearing a hydroxyl group was synthesized. Its binding properties towards various metal ions were examined and it showed a high selectivity and sensitivity towards Al3+ ions in aqueous media. The recognition processes follows a photo induced electron transfer (PET) mechanism assisted with the restricted intramolecular C-C single bond rotation and are scarcely influenced by other coexisting metal ions. In addition, determination of Al3+ in a variety of sewage water samples was also determined.

  8. Asymmetrical Self-assembly From Fluorinated and Sulfonated Block Copolymers in Aqueous Media

    SciTech Connect

    Wang, Xiaojun; Hong, Kunlun; Baskaran, Durairaj; Goswami, Monojoy; Sumpter, Bobby G; Mays, Jimmy

    2011-01-01

    Block copolymers of fluorinated isoprene and partially sulfonated styrene form novel tapered rods and ribbon-like micelles in aqueous media due to a distribution of sulfonation sites and a large Flory-Huggins interaction parameter. A combination of microscopy, light scattering, and simulation demonstrates the presence of these unique nanostructures. This study sheds light on the micellization behavior of amphiphilic block polymers by revealing a new mechanism of self-assembly.

  9. [28]Hexaphyrin derivatives for anion recognition in organic and aqueous media.

    PubMed

    Figueira, Flávio; Farinha, Andreia S F; Muteto, Paulino V; Polêto, Marcelo D; Verli, Hugo; Gomes, M Teresa S R; Tomé, Augusto C; Cavaleiro, José A S; Tomé, João P C

    2016-02-01

    Hexaphyrin-based anion chemosensors are reported for the first time. The meso-hexakis(ethylenediamine)-substituted [28]hexaphyrins 2 and 3 revealed strong affinity for F(-), AcO(-) and H2PO4(-). Adsorption constants in aqueous media were determined on a gold piezoelectric crystal coated with 2 and 3. (1)H NMR titrations and molecular dynamics simulations showed the main interactions between hosts and guests.

  10. Advancements in quantum cascade laser-based infrared microscopy of aqueous media.

    PubMed

    Haase, K; Kröger-Lui, N; Pucci, A; Schönhals, A; Petrich, W

    2016-06-23

    The large mid-infrared absorption coefficient of water frequently hampers the rapid, label-free infrared microscopy of biological objects in their natural aqueous environment. However, the high spectral power density of quantum cascade lasers is shifting this limitation such that mid-infrared absorbance images can be acquired in situ within signal-to-noise ratios of up to 100. Even at sample thicknesses well above 50 μm, signal-to-noise ratios above 10 are readily achieved. The quantum cascade laser-based microspectroscopy of aqueous media is exemplified by imaging an aqueous yeast solution and quantifying glucose consumption, ethanol generation as well as the production of carbon dioxide gas during fermentation. PMID:27032367

  11. Advancements in quantum cascade laser-based infrared microscopy of aqueous media.

    PubMed

    Haase, K; Kröger-Lui, N; Pucci, A; Schönhals, A; Petrich, W

    2016-06-23

    The large mid-infrared absorption coefficient of water frequently hampers the rapid, label-free infrared microscopy of biological objects in their natural aqueous environment. However, the high spectral power density of quantum cascade lasers is shifting this limitation such that mid-infrared absorbance images can be acquired in situ within signal-to-noise ratios of up to 100. Even at sample thicknesses well above 50 μm, signal-to-noise ratios above 10 are readily achieved. The quantum cascade laser-based microspectroscopy of aqueous media is exemplified by imaging an aqueous yeast solution and quantifying glucose consumption, ethanol generation as well as the production of carbon dioxide gas during fermentation.

  12. Mass-spectrometric determination of trace elements in aqueous media without preconcentration

    SciTech Connect

    Foss, G. O.

    1981-10-01

    Feasibility of using a low pressure glow discharge as an ion source for the mass spectrometric determination of trace elements in aqueous media was investigated. A cryogenically cooled hollow cathode ion source was developed to analyze aqueous samples without external preconcentration. Aqueous solutions containing seventy elements were analyzed and the detection limits, sensitivity factors, and linear regression correlation coefficients were determined. A standard test solution of trace elements in water was analyzed and the concentrations of trace elements were calculated using the sensitivity factors determined previously. The results compared favorably within the error limits predicted by the semiquantitative survey methods used. Tap water and natural lake water samples were examined and minimal interference effects due to organic compounds and biological compounds were noted. A research ion optical system (RIOS) was developed as a flexible mass analyzer for the development of new ion sources. The RIOS is a double focussing mass analyzer designed utilizing the Mattauch-Herzog geometry with externally adjustable slit assemblies.

  13. Dephosphorization of Steelmaking Slag by Leaching with Acidic Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Qiao, Yong; Diao, Jiang; Liu, Xuan; Li, Xiaosa; Zhang, Tao; Xie, Bing

    2015-12-01

    In the present paper, dephosphorization of steelmaking slag by leaching with acidic aqueous solution composed of citric acid, sodium hydroxide, hydrochloric acid and ion-exchanged water was investigated. The buffer solution of C6H8O7-NaOH-HCl system prevented changes in the pH values. Kinetic parameters including leaching temperature, slag particle size and pH values of the solution were optimized. The results showed that temperature has no obvious effect on the dissolution ratio of phosphorus. However, it has a significant effect on the dissolution ratio of iron. The dephosphorization rate increases with the decrease of slag particle size and the pH value of the solution. Over 90% of the phosphorus can be dissolved in the solution while the corresponding leaching ratio of iron was only 30% below the optimal condition. Leaching kinetics of dephosphorization follow the unreacted shrinking core model with a rate controlled step by the solid diffusion layer, the corresponding apparent activation energy being 1.233 kJ mol-1. A semiempirical kinetic equation was established. After leaching, most of the nC2S-C3P solid solution in the steelmaking slag was selectively dissolved in the aqueous solution and the iron content in the solid residue was correspondingly enriched.

  14. Dephosphorization of Steelmaking Slag by Leaching with Acidic Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Qiao, Yong; Diao, Jiang; Liu, Xuan; Li, Xiaosa; Zhang, Tao; Xie, Bing

    2016-09-01

    In the present paper, dephosphorization of steelmaking slag by leaching with acidic aqueous solution composed of citric acid, sodium hydroxide, hydrochloric acid and ion-exchanged water was investigated. The buffer solution of C6H8O7-NaOH-HCl system prevented changes in the pH values. Kinetic parameters including leaching temperature, slag particle size and pH values of the solution were optimized. The results showed that temperature has no obvious effect on the dissolution ratio of phosphorus. However, it has a significant effect on the dissolution ratio of iron. The dephosphorization rate increases with the decrease of slag particle size and the pH value of the solution. Over 90% of the phosphorus can be dissolved in the solution while the corresponding leaching ratio of iron was only 30% below the optimal condition. Leaching kinetics of dephosphorization follow the unreacted shrinking core model with a rate controlled step by the solid diffusion layer, the corresponding apparent activation energy being 1.233 kJ mol-1. A semiempirical kinetic equation was established. After leaching, most of the nC2S-C3P solid solution in the steelmaking slag was selectively dissolved in the aqueous solution and the iron content in the solid residue was correspondingly enriched.

  15. Differing stabilities of snake venom cardiotoxins in acidic aqueous acetonitrile.

    PubMed

    Osthoff, G

    1990-01-01

    1. Although snake venom cardiotoxins constitute a homologous family of proteins, subclasses with different structural and biological properties exist. 2. By using circular dichroism spectroscopy of twelve cardiotoxins belonging to two structural classes and one non-classified group, this investigation indicated that cardiotoxins differ in their stabilities towards denaturation in acidic aqueous acetonitrile, as used in some reversed-phase high performance liquid chromatography separations. 3. It was also shown that cardiotoxins of the structural class II are in general less stable towards this denaturation than class I and non-classified cardiotoxins.

  16. Fermentation of aqueous plant seed extracts by lactic acid bacteria

    SciTech Connect

    Schafner, D.W.; Beuchat, R.L.

    1986-05-01

    The effects of lactic acid bacterial fermentation on chemical and physical changes in aqueous extracts of cowpea (Vigna unguiculata), peanut (Arachis hypogea), soybean (Glycine max), and sorghum (Sorghum vulgare) were studied. The bacteria investigated were Lactobacillus helveticus, L. delbrueckii, L. casei, L. bulgaricus, L. acidophilus, and Streptococcus thermophilus. Organisms were inoculated individually into all of the seed extracts; L. bulgaricus and S. thermophilus were also evaluated together as inocula for fermenting the legume extracts. During fermentation, bacterial population and changes in titratable acidity, pH, viscosity, and color were measured over a 72 h period at 37 degrees C. Maximum bacterial populations, titratable acidity, pH, and viscosity varied depending upon the type of extract and bacterial strain. The maximum population of each organism was influenced by fermentable carbohydrates, which, in turn, influenced acid production and change in pH. Change in viscosity was correlated with the amount of protein and titratable acidity of products. Color was affected by pasteurization treatment and fermentation as well as the source of extract. In the extracts inoculated simultaneously with L. bulgaricus and S. thermophilus, a synergistic effect resulted in increased bacterial populations, titratable acidity, and viscosity, and decreased pH in all the legume extracts when compared to the extracts fermented with either of these organisms individually. Fermented extracts offer potential as substitutes for cultured dairy products. 24 references.

  17. In vitro characterization of polycaprolactone matrices generated in aqueous media

    PubMed Central

    Pok, Seok Won; Wallace, Kristin N.; Madihally, Sundararajan V.

    2010-01-01

    In this study, a novel process of dissolving polycaprolactone (PCL) matrices in glacial acetic acid was explored in which matrices spontaneously formed upon contact with water. Scanning electron microscopy analysis showed rough architecture and holes on the self-assembled matrix relative to matrices formed after dissolving in chloroform. Immersion in the gelatin solution reduced its roughness and number of micropores. Atomic force microscopy (AFM) analysis confirmed the increased roughness of the self-assembled matrices. The roughness of the matrices decreased after incubation in 1 N NaOH for 10 min. AFM analysis also revealed that the self-assembled matrix had a net positive surface charge, whereas chloroform–cast matrix had a negative surface charge. The surface charge of self-assembled matrix after immersion in gelatin changed to negative. However, incubation in NaOH did not affect the surface charge. The tensile properties were tested in both the dry state (25 °C) and the wet state (37 °C) by immersion in phosphate-buffered saline. Self-assembled matrix had lower elastic modulus, break stress and break strain than chloroform–cast matrix in both states. The elastic modulus in the wet condition was reduced by half in self-assembled matrix but tensile strain increased. Samples were further analyzed by ramp-hold test for assessing stress relaxation behavior. Both self-assembled and chloroform–cast matrices had similar trends in stress relaxation behavior. However, stress accumulation in self-assembled matrix was half that of chloroform–cast matrix. In vitro cell cultures were conducted using human foreskin fibroblast (HFF-1) in serum-free medium. Cytoskeletal actin staining showed cell adhesion and spreading on all matrices. Cell retention was significantly increased in self-assembled matrix compared to chloroform–cast matrix. Addition of gelatin improved the retention of seeded cells on the surface. In summary, PCL matrices generated using this novel

  18. Hydrogen generation from alcohols (α-hydroxy carboxylic acids) and alcohol-ammonia coupling in aqueous media catalysed by water-soluble bipyridine-Cp*Ir (Rh or Os) catalyst: a computational mechanism insight

    NASA Astrophysics Data System (ADS)

    Zhang, Dan-Dan; Chen, Xian-Kai; Liu, Hui-Ling; Huang, Xu-Ri

    2015-06-01

    Density functional theory (DFT) calculations were performed to elucidate the mechanism of the dehydrogenative oxidation of various primary alcohols (or α-hydroxy carboxylic acids) and the dehydrogenative coupling of alcohols with ammonia catalysed by the same water-soluble Cp*Ir complex bearing a 2-pyridonate-based ligand (A-Ir). Another two new catalysts A-Rh and A-Os are computationally designed for the dehydrogenative oxidation of alcohols. The plausible pathway for alcohol dehydrogenation includes three steps: alcohol oxidation to aldehyde (step I); the generation of dihydrogen in the metal coordination sphere (step II); and the liberation of dihydrogen accompanied with the regeneration of active catalyst A (step III). Among them, the step I follows bifunctional concerted double hydrogen transfer mechanism rather than the β-H elimination. For step II, the energy barriers involving the addition of one or two water molecules are higher than in absence of water. Our results also confirm that A-Ir can be applied in the dehydrogenation of various α-hydroxy carboxylic acids by the similar mechanism. Remarkably, A-Ir is also found to be efficient for the coupling reactions of various primary benzyl alcohols with ammonia to afford amides.

  19. Phosphate Sorption and Desorption on Pyrite in Primitive Aqueous Scenarios: Relevance of acidic → Alkaline Transitions

    NASA Astrophysics Data System (ADS)

    de Souza-Barros, Fernando; Braz-Levigard, Raphael; Ching-San, Yonder; Monte, Marisa M. B.; Bonapace, José A. P.; Montezano, Viviane; Vieyra, Adalberto

    2007-02-01

    Phosphate (P i) sorption assays onto pyrite in media simulating primeval aquatic scenarios affected by hydrothermal emissions, reveal that acidic conditions favour P i sorption whereas mild alkaline media as well as those simulating sulfur oxidation to SO2- 4 revert this capture process. Several mechanisms relevant to P i availability in prebiotic eras are implicated in the modulation of these processes. Those favouring sorption are: (a) hydrophobic coating of molecules, such as acetate that could be formed in the vicinity of hydrothermal vents; (b) water and Mg2+ bridging in the interface mineral-aqueous media; (c) surface charge neutralization by monovalent cations (Na+ and K+). The increase of both the medium pH and the SO2- 4 trapping by the mineral interface would provoke the release of sorbed P i due to charge polarization. Moreover it is shown that P i self-modulates its sorption, a mechanism that depends on the abundance of SO2- 4 in the interface. The relevance of the proposed mechanisms of P i capture, release and trapping arises from the need of abundant presence of this molecule for primitive phosphorylations, since similarly to contemporary aqueous media inorganic phosphate concentrations in primitive seas should have been low. It is proposed that the presence of sulphide minerals with high affinity to P i could have trapped this molecule in an efficient manner, allowing its concentration in specific niches. In these niches, the conditions studied in the present work would have been relevant for its availability in soluble form, specially in primitive insulated systems with pH gradients across the wall.

  20. Phosphate sorption and desorption on pyrite in primitive aqueous scenarios: relevance of acidic --> alkaline transitions.

    PubMed

    de Souza-Barros, Fernando; Braz-Levigard, Raphael; Ching-San, Yonder; Monte, Marisa M B; Bonapace, José A P; Montezano, Viviane; Vieyra, Adalberto

    2007-02-01

    Phosphate (P(i)) sorption assays onto pyrite in media simulating primeval aquatic scenarios affected by hydrothermal emissions, reveal that acidic conditions favour P(i) sorption whereas mild alkaline media--as well as those simulating sulfur oxidation to SO(2-) (4)--revert this capture process. Several mechanisms relevant to P(i) availability in prebiotic eras are implicated in the modulation of these processes. Those favouring sorption are: (a) hydrophobic coating of molecules, such as acetate that could be formed in the vicinity of hydrothermal vents; (b) water and Mg(2+) bridging in the interface mineral-aqueous media; (c) surface charge neutralization by monovalent cations (Na+ and K+). The increase of both the medium pH and the SO(2-) (4) trapping by the mineral interface would provoke the release of sorbed P(i) due to charge polarization. Moreover it is shown that P(i) self-modulates its sorption, a mechanism that depends on the abundance of SO(2-) (4) in the interface. The relevance of the proposed mechanisms of P(i) capture, release and trapping arises from the need of abundant presence of this molecule for primitive phosphorylations, since--similarly to contemporary aqueous media--inorganic phosphate concentrations in primitive seas should have been low. It is proposed that the presence of sulphide minerals with high affinity to P(i) could have trapped this molecule in an efficient manner, allowing its concentration in specific niches. In these niches, the conditions studied in the present work would have been relevant for its availability in soluble form, specially in primitive insulated systems with pH gradients across the wall.

  1. Plutonium scrap waste processing based on aqueous nitrate and chloride media

    SciTech Connect

    Navratil, J D

    1985-05-13

    A brief review of plutonium scrap aqueous waste processing technology at Rocky Flats is given. Nitric acid unit operations include dissolution and leaching, anion exchange purification and precipitation. Chloride waste processing consists of cation exchange and carbonate precipitation. Ferrite and carrier precipitation waste treatment processes are also described. 3 figs.

  2. Antioxidant activity of propyl gallate in aqueous and lipid media: a theoretical study.

    PubMed

    Medina, Manuel E; Iuga, Cristina; Alvarez-Idaboy, Juan Raúl

    2013-08-21

    In this work, we have carried out a quantum chemistry and computational kinetics study on the reactivity of propyl gallate towards ˙OOH, ˙OOCH3 and ˙OOCHCH2 radicals, in aqueous and lipid media. We have considered three reaction mechanisms: hydrogen transfer (HT), radical adduct formation (RAF) and single electron transfer (SET). Rate constants and relative branching ratios for the different paths contributing to the overall reaction, at 298.15 K, are reported. Our results show that propyl gallate reacts mainly through the HT mechanism, independently of the solvent or the peroxyl radical, contrary to other phenols such as catechols and guayacols previously studied, which react mainly via the SET mechanism. In aqueous media at physiological pH, the calculated rate constants towards the ˙OOH, ˙OOCH3 and ˙OOCHCH2 radicals are 4.56 × 10(8), 1.59 × 10(6) and 4.05 × 10(8) M(-1) s(-1), while in lipid media the rate constants are 2.94 × 10(4), 7.73 × 10(3) and 9.94 × 10(5) M(-1) s(-1). Thus, a propyl gallate molecule acts as a very efficient peroxyl radical scavenger, both in aqueous and lipid media. Since the gallate moiety is a part of other naturally occurring polyphenols such as aflavine gallates and epigallocatechin gallates, the results of this study could be extrapolated to these compounds. Even if these compounds have other antioxidant structures or enhancers, the activity of the gallate moiety could be considered as a lower limit to their antioxidant activity.

  3. Formation of isomers of anionic hemiesters of sugars and carbonic acid in aqueous medium.

    PubMed

    Dos Santos, Vagner B; Vidal, Denis T R; Francisco, Kelliton J M; Ducati, Lucas C; do Lago, Claudimir L

    2016-06-16

    Hemiesters of carbonic acid can be freely formed in aqueous media containing HCO3(-)/CO2 and mono- or poly-hydroxy compounds. Herein, (13)C NMR spectroscopy was used to identify isomers formed in aqueous solutions of glycerol (a prototype compound) and seven carbohydrates, as well as to estimate the equilibrium constant of formation (Keq). Although both isomers are formed, glycerol 1-carbonate corresponds to 90% of the product. While fructose and ribose form an indistinct mixture of isomers, the anomers of d-glucopyranose 6-carbonate correspond to 74% of the eight isomers of glucose carbonate that were detected. The values of Keq for the disaccharides sucrose (4.3) and maltose (4.2) are about twice the values for the monosaccharides glucose (2.0) and fructose (2.3). Ribose (Keq = 0.89)-the only sugar without a significant concentration of a species containing a -CH2OH group in an aqueous solution-resulted in the smallest Keq. On the basis of the Keq value and the concentrations of HCO3(-) and glucose in blood, one can anticipate a concentration of 2-4 µmol L(-1) for glucose 6-carbonate, which corresponds to ca. of 10% of its phosphate counterpart (glucose 6-phosphate).

  4. Synthesis of MnO{sub 2} phases from LiMn{sub 2}O{sub 4} in aqueous acidic media. Mechanisms of phase transformations, reactivity, and effect of Bi species

    SciTech Connect

    Larcher, D.; Courjal, P.; Gerand, B.; Blyr, A.; Pasquier, A. du; Tarascon, J.M.; Urbina, R.H.

    1998-10-01

    The nature of the phases obtained by acid digestion of LiMn{sub 2}O{sub 4} phases prepared at 800 C from a mixture of MnO{sub 2} (EMD) and Li{sub 2}CO{sub 3} was investigated. The authors found that the complete transformation toward {alpha}-MnO{sub 2} and then {gamma}-MnO{sub 2} observed for LiMn{sub 2}O{sub 4} treated in 2.5 M H{sub 2}SO{sub 4} for 24 h at 95 C is highly dependent on the amount of water in the reaction medium. The {lambda} {yields} {alpha}/{gamma} transformation was found to be the result of a dissolution-crystallization mechanism that can be completely avoided by adding a soluble Bi, Pb, or Tl salt to the reaction medium. By coupling energy dispersive spectroscopy analysis, infrared spectroscopy, and potentiometric titration, the authors demonstrated the presence of Bi species adsorbed at the surface of the {lambda}-MnO{sub 2} oxide thus modifying its reactivity. In addition, the kinetics of the {lambda} {yields} {alpha}/{gamma} phase transformation was found to depend on the amount of added Bi salt, suggesting the complexing role of Bi toward Mn (Bi-Mn complexes), thereby affecting the crystallization step of the reaction. The same treatment was applied to LiMn{sub 2}O{sub 4} in the presence of a Bi salt in anhydrous electrolyte (LiPF{sub 6}/ethylene carbonate/dimethyl carbonate). In this case, the spinel oxide dissolution slows down and BiF{sub 3} precipitates. With respect to recent findings about the mechanisms involved in the electrochemical capacity failure at elevated temperature in Li-ion LiMn{sub 2}O{sub 4} cells, these results open new alternatives to solve this recurrent problem.

  5. Organic Reactions in Aqueous Media (by Chao-Jun Li and Tak-Hang Chan)

    NASA Astrophysics Data System (ADS)

    Rosan, Reviewed Alan M.

    2000-06-01

    of the diastereoselectivity that often accompanies carbonyl attack by indium, tin, and zinc organometals (Barbier-Grignard reaction). The liberal use, on nearly every page, of clear, detailed drawings enhances the text, and substantive errors are few. Inexplicably, water is described as serving as a presumptive weak Lewis acid (pages 54-55) in the aqueous Mukaiyama reaction. Occasional slips of grammar, spelling, and syntax, including confusion over the difference between media and medium, are relatively minor. Some expressions, such as "olefinated", are unfortunate and there are several mysterious changes in font. This is not a textbook and no problems are offered. Many technical advances, some occurring since this book was published, have impacted the economic and environmental advantages of water. However, these more recent findings, involving the use of triphase aqueous-fluorous-organic systems, the discovery of living homogeneous ROMP catalysis in water, the utilization of supercritical water oxidation for toxic cleanup, and the utility of biphasic supercritical carbon dioxide-water emulsions, can be appreciated within the broad scope of reactivity described here. With the emerging wide interest, technical feasibility, and rapid innovative advances and an increasingly vast literature in this area, this book is most useful as a selected compendium rather than a definitive treatise. It is certainly suitable as a reference in a special topics or an advanced course. Rich with well-explicated examples and reactions, it is an invitingly readable and valuable survey of this fascinating area.

  6. Multicatalytic colloids with highly scalable, adjustable, and stable functionalities in organic and aqueous media

    NASA Astrophysics Data System (ADS)

    Kim, Donghee; Cheong, Sanghyuk; Ahn, Yun Gyong; Ryu, Sook Won; Kim, Jai-Kyeong; Cho, Jinhan

    2016-03-01

    Despite a large number of developments of noble metal (or metal oxide) NP-based catalysts, it has been a great challenge to prepare high-performance recyclable catalysts with integrated functionalities that can be used in various solvent media. Here, we report on layer-by-layer (LbL) assembled multicatalysts with high catalytic performance, showing high dispersion and recycling stability in organic and aqueous media. The remarkable advantages of our approach are as follows. (i) Various metal or metal oxide NPs with desired catalytic performance can be easily incorporated into multilayered shells, forming densely packed arrays that allow one colloid to be used as a multicatalyst with highly integrated and controllable catalytic properties. (ii) Additionally, the dispersion stability of catalytic colloids in a desired solvent can be determined by the type of ultrathin outermost layer coating each colloid. (iii) Lastly, the covalent bonding between inorganic NPs and dendrimers within multilayer shells enhances the recycling stability of multicatalytic colloids. The resulting core-shell colloids including OA-Fe3O4 NPs, TOABr-Pd NPs, and OA-TiO2 NPs exhibited excellent performance in the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) and photocatalysis in aqueous media and in the Sonogashira coupling reaction (99% yield) in organic media. Given that the catalytic properties of recyclable colloids reported to date have entirely depended on the functionality of a single catalytic NP layer deposited onto colloids in selective solvent media, our approach provides a basis for the design and exploitation of high-performance recyclable colloids with integrated multicatalytic properties and high dispersion stability in a variety of solvents.Despite a large number of developments of noble metal (or metal oxide) NP-based catalysts, it has been a great challenge to prepare high-performance recyclable catalysts with integrated functionalities that can be used in various solvent

  7. Xylose Isomerization to Xylulose and Its Dehydration to Furfural in Aqueous Media

    SciTech Connect

    Choudhary, Vinit; Pinar, Ana B; Sandler, Stanley I; Vlachos, Dion G.; Lobo, Raul F

    2011-12-02

    A nonenzymatic route for xylose isomerization in an aqueous medium using zeolite Sn-beta as a catalyst is demonstrated. Xylulose and lyxose are the primary and secondary products. The maximum yield to xylulose is 27%, with an 11% yield to lyxose at ~60% xylose conversion at 100 °C. When the Sn-beta zeolite is combined with a Brønsted acid catalyst, furfural forms in a single pot from xylose in an aqueous medium at much lower temperatures than typically employed for this reaction.

  8. Multicatalytic colloids with highly scalable, adjustable, and stable functionalities in organic and aqueous media.

    PubMed

    Kim, Donghee; Cheong, Sanghyuk; Ahn, Yun Gyong; Ryu, Sook Won; Kim, Jai-Kyeong; Cho, Jinhan

    2016-04-01

    Despite a large number of developments of noble metal (or metal oxide) NP-based catalysts, it has been a great challenge to prepare high-performance recyclable catalysts with integrated functionalities that can be used in various solvent media. Here, we report on layer-by-layer (LbL) assembled multicatalysts with high catalytic performance, showing high dispersion and recycling stability in organic and aqueous media. The remarkable advantages of our approach are as follows. (i) Various metal or metal oxide NPs with desired catalytic performance can be easily incorporated into multilayered shells, forming densely packed arrays that allow one colloid to be used as a multicatalyst with highly integrated and controllable catalytic properties. (ii) Additionally, the dispersion stability of catalytic colloids in a desired solvent can be determined by the type of ultrathin outermost layer coating each colloid. (iii) Lastly, the covalent bonding between inorganic NPs and dendrimers within multilayer shells enhances the recycling stability of multicatalytic colloids. The resulting core-shell colloids including OA-Fe3O4 NPs, TOABr-Pd NPs, and OA-TiO2 NPs exhibited excellent performance in the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) and photocatalysis in aqueous media and in the Sonogashira coupling reaction (99% yield) in organic media. Given that the catalytic properties of recyclable colloids reported to date have entirely depended on the functionality of a single catalytic NP layer deposited onto colloids in selective solvent media, our approach provides a basis for the design and exploitation of high-performance recyclable colloids with integrated multicatalytic properties and high dispersion stability in a variety of solvents.

  9. First structural characterization of a protactinium(V) single oxo bond in aqueous media.

    PubMed

    Le Naour, Claire; Trubert, Didier; Di Giandomenico, Maria V; Fillaux, Clara; Den Auwer, Christophe; Moisy, Philippe; Hennig, Christoph

    2005-12-12

    The present work describes the first structural studies of protactinium(V) in sulfuric and hydrofluoric acid media using X-ray absorption spectroscopy. The results show unambiguously the absence of the trans-dioxo bond that characterizes the other early actinide elements such as U and Np. In concentrated sulfuric acid (13 M), Pa(V) is proved to exhibit a single oxo bond as postulated in the literature for species in more dilute media. In a 0.5 M HF medium, XANES and EXAFS spectra indicate the absence of any oxo bond: Pa(V) exists in the form of a pure fluoro complex.

  10. First structural characterization of a protactinium(V) single oxo bond in aqueous media.

    PubMed

    Le Naour, Claire; Trubert, Didier; Di Giandomenico, Maria V; Fillaux, Clara; Den Auwer, Christophe; Moisy, Philippe; Hennig, Christoph

    2005-12-12

    The present work describes the first structural studies of protactinium(V) in sulfuric and hydrofluoric acid media using X-ray absorption spectroscopy. The results show unambiguously the absence of the trans-dioxo bond that characterizes the other early actinide elements such as U and Np. In concentrated sulfuric acid (13 M), Pa(V) is proved to exhibit a single oxo bond as postulated in the literature for species in more dilute media. In a 0.5 M HF medium, XANES and EXAFS spectra indicate the absence of any oxo bond: Pa(V) exists in the form of a pure fluoro complex. PMID:16323942

  11. Sorption of acid red 57 from aqueous solution onto sepiolite.

    PubMed

    Alkan, Mahir; Demirbaş, Ozkan; Celikçapa, Sermet; Doğan, Mehmet

    2004-12-10

    Sepiolite, a highly porous mineral, is becoming widely used as an alternative material in areas where sorptive, catalytic and rheological applications are required. High ion exchange capacity and high surface area and more importantly its relatively cheap price make it an attractive adsorbent. In this study, the adsorption of acid red 57 by natural mesoporous sepiolite has been examined in order to measure the ability of this mineral to remove coloured textile dyes from wastewater. For this purpose, a series of batch adsorption tests of acid red 57 from aqueous sepiolite solutions have been systematically investigated as a function of parameters such as pH, ionic strength and temperature. Adsorption equilibrium was reached within 1h. The removal of acid red 57 decreases with pH from 3 to 9 and temperature from 25 to 55 degrees C, whereas it increases with ionic strength from 0 to 0.5 mol L(-1). Adsorption isotherms of acid red on sepiolite were determined and correlated with common isotherm equations such as Langmuir and Freundlich models. It was found that the Langmuir model appears to fit the isotherm data better than the Freundlich model. The physical properties of this adsorbent were consistent with the parameters obtained from the isotherm equations. Approximately, 21.49% weight loss was observed. The surface area value of sepiolite was 342 m2 g(-1) at 105 degrees C, and it increased to 357 m2 g(-1) at 200 degrees C. Further increase in temperature caused channel plugging and crystal structure deformation, as a result the surface area values showed a decrease with temperature. The data obtained from adsorption isotherms at different temperatures have been used to calculate some thermodynamic quantities such as the Gibbs energy, heat and entropy of adsorption. The thermodynamic data indicate that acid red 57 adsorption onto sepiolite is characterized by physical adsorption. The dimensionless separation factor (RL) have shown that sepiolite can be used for

  12. pH-responsive supramolecular polymerization in aqueous media driven by electrostatic attraction-enhanced crown ether-based molecular recognition.

    PubMed

    Ji, Xiaofan; Zhu, Kelong; Yan, Xuzhou; Ma, Yingjie; Li, Jinying; Hu, Bingjie; Yu, Yihua; Huang, Feihe

    2012-07-26

    All the previously reported supramolecular polymers based on crown ether-based molecular recognition have been prepared in anhydrous organic solvents. This is mainly due to the weakness of crown ether-based molecular recognition in the presence of water. Here we report a linear supramolecular polymer constructed from a heteroditopic monomer in an aqueous medium driven by crown ether-based molecular recognition through the introduction of electrostatic attraction. In addition, the reversible transition between the linear supramolecular polymer and oligomers is achieved by adding acid and base. This study realizes the breakthrough of the solvent for supramolecular polymerization driven by crown ether-based molecular recognition from anhydrous organic solvents to aqueous media. It is helpful for achieving supramolecular polymerization driven by crown ether-based molecular recognition in a completely aqueous medium.

  13. Reactive Transport in Porous Media: Pore-scale Mass Exchange between Aqueous Phase and Biofilms

    NASA Astrophysics Data System (ADS)

    Hassanizadeh, S.; Qin, C.

    2013-12-01

    In the presence of water and necessary nutrients, biofilms can grow on soil grain surfaces. They occupy void pore spaces blocking water flow. As a result, some hydrodynamic properties of porous media like porosity and permeability will be reduced. This ultimately leads to a condition known as bioclogging. Also, biofilms can degrade certain compounds. So, the features of bioclogging and biodegradation in porous media with biofilms have given rise to a broad range of environmental and engineering applications, such as bioremediation, biobarriers, microbial enhanced oil recovery, and protection of steel corrosion. To date, a number of macroscale and pore-scale models for describing biodegradation in porous media with biofilms are available in the literature. At the macro scale, to simplify numerical implementation, a ';one-equation' model is normally preferred. In this approach, only the solute concentration in aqueous phase is modeled associated with the consumption of solute in biofilms. Because the solute concentration in biofilms is different from that in aqueous phase, an effectiveness factor may be used in Monod kinetics for relating reaction rate within biofilms to the solute concentration in aqueous phase. Notice that this approach has its validity domains like local equilibrium and reaction-rate limited consumption. Another approach to modeling biodegradation is referred to as a ';two-equation' model, in which one needs to simultaneously track the solute concentrations in both aqueous phase and biofilms. In addition, the two concentrations may be related by a first-order kinetic mass exchange model. This first-rate exchange model is normally represented by a constant mas exchange coefficient multiplied by the concentration difference in the two domains. Here, one may question if complex advection-diffusion-reaction processes can be represented just by a constant mass exchange coefficient. In addition, the kinetic model of mass exchange between aqueous phase

  14. Polymer surface interacts with calcium in aqueous media to induce stem cell assembly.

    PubMed

    Hung, Kun-Che; Hsu, Shan-Hui

    2015-10-28

    Bioinspired surface with functional group rearrangement abilities are highly desirable for designing functional materials. Calcium ion (Ca(2+) ) is a pivotal life element and the ion transport is tightly regulated through calcium channels. It is demonstrated here that Ca(2+) can be transported by polymer surface to induce cell assembly. A series of polyurethane materials is synthesized with different abilities to rearrange the surface functional groups in response to aqueous environment. It is observed that surface recruitment of carboxyl and amino groups from the bulk material can interact with Ca(2+) and facilitate its translocation from aqueous media into cells. The surface rearrangement of functional group triggers the calcium trafficking and turns on signals involving cell merging and assembly. This observation provides an insight on adjusting material-calcium interaction to design nature-inspired smart interfaces to induce cell organization and tissue regeneration.

  15. Monitoring of the fermentation media of citric acid by the trimethylsilyl derivatives of the organic acids formed.

    PubMed

    Ghassempour, Alireza; Nojavan, Saeed; Talebpour, Zahra; Amiri, Ali Asghar; Najafi, Nahid Mashkouri

    2004-10-20

    In this approach, a derivatization method is described for monitoring of organic acids in fermentation media without any separation step. The aqueous phase of fermentation media was evaporated and heated in a silylation reagent to form trimethylsilyl (TMS) derivatives. The silylated compounds are analyzed by 29Si nuclear magnetic resonance (29Si NMR) and gas chromatography-mass spectrometry (GC-MS). 29Si NMR can qualitatively monitor the components produced in the Krebs cycle. Quantification of these compounds is investigated by using selected ion monitoring mode of mass spectrometry. In this mode, mass to charge (m/z) values of their [M - 15]+ ions, which are 465, 275, 247, 221, 335, 251, and 313 of TMS derivatives of citric, alpha-ketoglutaric, succinic, fumaric, l-malic, oxaloacetic, and palmitic (as an internal standard), acids, respectively, are used. The limit of detection and the linear working range for derivatized citric acid were found to be 0.1 mg L(-1) and 10-3 x 10(4) mg L(-1). The relative standard deviation of the method for five replicates was 2.1%. The average recovery efficiency for citric acid added to culture media was approximately 97.2%. Quantitative results of GC-MS are compared with those obtained by an ultraviolet-visible method.

  16. Determination of acidity constants of sparingly soluble drugs in aqueous solution by the internal standard capillary electrophoresis method.

    PubMed

    Cabot, Joan Marc; Fuguet, Elisabet; Rosés, Martí

    2014-12-01

    A set of 33 drugs with different solubilities, ranging from soluble to very insoluble, has been chosen in order to evaluate the performance of the internal standard CE method to determine acidity constants of compounds with limited solubility. The set of drugs tested in this work has been chosen as a function of their intrinsic solubility. For the most insoluble compounds, several analytical conditions to overcome the insolubility in aqueous buffers have been tested. This paper assesses the compound solubility limits for the IS-CE method in aqueous pKa determinations, and also compares the determined pKa s with the results from the literature data obtained by other methods. It is proved that IS-CE method determines acidity constants of sparingly soluble drugs in aqueous media (compounds with logS down to around -6), whereas other reference methods require the use of aqueous-organic solvent buffers and extrapolation procedures to obtain the aqueous pKa for the same compounds.

  17. Sorption and desorption studies of radioiodine onto silver chloride via batch equilibration with its aqueous media.

    PubMed

    Mostafa, M; Ramadan, H E; El-Amir, M A

    2015-12-01

    The uncontrolled spread out of radioiodine (especially (1)(3)(1)I) produced from nuclear activities or accidents, due to its high volatility, to the biosphere represents an environmental impact because of its concentration in the thyroid gland and accumulation on soil surface. This work represents a simple method for isolation of radioiodine from aqueous solution in the form of insoluble solid compound and further recovery of it in aqueous phase for any further controlled use. Crystalline silver chloride was prepared and characterized. Batch sorption of (131)I onto the prepared AgCl was studied from different aqueous media (H2O and NaOH of different concentrations) and at different I(-):Ag molar ratios (from alkaline media) for different times at 25 °C. It was found that the sorption yield of (131)I from 2.5 M NaOH solution (at I(-):Ag and S2O3(2-):I(-) molar ratios of 0.025 and 2, respectively) reached 97.7% after 6 h and only slightly increased to 98.6% after 16 h of contact time. The presence of H2O2 adversely affected the batch sorption process. The included REDOX and precipitation reactions were discussed. Batch desorption of the sorbed (131)I from AgCl into aqueous phase was studied with NaOCl solutions of different concentrations and different contact times at 25 °C. Desorption yield of (131)I was found to be 94.5% with 10 mL of 0.5 M NaOCl solution after contact time of 16 h. Kinetic analysis has been performed for both batch sorption and desorption processes.

  18. Arene-ruthenium(II) complexes with hydrophilic P-donor ligands: versatile catalysts in aqueous media.

    PubMed

    Crochet, Pascale; Cadierno, Victorio

    2014-09-01

    In the last few years there has been increasing interest in the use of water as a reaction medium for catalysis, and therefore in designing water-soluble transition-metal catalysts. Half-sandwich (η(6)-arene)-ruthenium(ii) complexes are a versatile and well-known family of ruthenium compounds that exhibit a rich catalytic and coordination chemistry. This Perspective article focuses on the catalytic applications in aqueous media of (η(6)-arene)-ruthenium(ii) complexes containing water-soluble phosphines, and related hydrophilic P-donor ligands.

  19. Photoinduced interaction of riboflavin dye with different reducing agents in aqueous and liposome media.

    PubMed

    Bhowmik, Benoy B; Sil, Arpita

    2004-02-01

    The photoelectrochemical and spectral studies of riboflavin have been carried out in aqueous and phosphatidylcholine (PC) liposome media in presence of different reducing agents such as I-, Br-, Cl-, Fe2+, Fe(CN)6(4-) and Cu+. The results from both the studies support the photoinduced electron transfer from the reducing agent to the excited riboflavin dye. Moreover, a good correlation between photovoltages/Stern-Volmer quenching constants versus reduction potentials of the reducing agents also confirms the above electron transfer in the photoexcited state. An alternative method has been developed to determine the Stern-Volmer quenching constant. PMID:14726001

  20. Influence of ions on aqueous acid-base reactions.

    PubMed

    Cox, M Jocelyn; Siwick, Bradley J; Bakker, Huib J

    2009-01-12

    We study the effects of bromide salts on the rate and mechanism of the aqueous proton/deuteron-transfer reaction between the photoacid 8-hydroxy-1,3,6-pyrenetrisulfonic acid (HPTS) and the base acetate. The proton/deuteron release is triggered by exciting HPTS with 400 nm femtosecond laser pulses. Probing the electronic and vibrational resonances of the photoacid, the conjugate photobase, the hydrated proton/deuteron and the accepting base with femtosecond visible and mid-infrared pulses monitors the proton transfer. Two reaction channels are identified: 1) direct long-range proton transfer over hydrogen-bonded water bridges that connect the acid and base and 2) acid dissociation to produce fully solvated protons followed by proton scavenging from solution by acetate. We observe that the addition of salt affects the long-range reaction pathway, and reduces both the rate at which protons are released to solution by HPTS and the rate at which solvated protons are scavenged from solution by acetate. We study the dependence of these effects on the nature and concentration of the dissolved salt.

  1. Surface oxide growth on platinum electrode in aqueous trifluoromethanesulfonic acid.

    PubMed

    Furuya, Yoshihisa; Mashio, Tetsuya; Ohma, Atsushi; Dale, Nilesh; Oshihara, Kenzo; Jerkiewicz, Gregory

    2014-10-28

    Platinum in the form of nanoparticles is the key and most expensive component of polymer electrolyte membrane fuel cells, while trifluoromethanesulfonic acid (CF3SO3H) is the smallest fluorinated sulfonic acid. Nafion, which acts as both electrolyte and separator in fuel cells, contains -CF2SO3H groups. Consequently, research on the electrochemical behaviour of Pt in aqueous CF3SO3H solutions creates important background knowledge that can benefit fuel cell development. In this contribution, Pt electro-oxidation is studied in 0.1 M aqueous CF3SO3H as a function of the polarization potential (E(p), 1.10 ≤ E(p) ≤ 1.50 V), polarization time (t(p), 10(0) ≤ t(p) ≤ 10(4) s), and temperature (T, 278 ≤ T ≤ 333 K). The critical thicknesses (X1), which determines the applicability of oxide growth theories, is determined and related to the oxide thickness (d(ox)). Because X1 > d(ox) for the entire range of E(p), t(p), and T values, the formation of Pt surface oxide follows the interfacial place-exchange or the metal cation escape mechanism. The mechanism of Pt electro-oxidation is revised and expanded by taking into account possible interactions of cations, anions, and water molecules with Pt. A modified kinetic equation for the interfacial place exchange is proposed. The application of the interfacial place-exchange and metal cation escape mechanisms leads to an estimation of the Pt(δ+)-O(δ-) surface dipole (μ(PtO)), and the potential drop (V(ox)) and electric field (E(ox)) within the oxide. The Pt-anion interactions affect the oxidation kinetics by indirectly influencing the electric field within the double layer and the surface oxide. PMID:25362330

  2. Surface oxide growth on platinum electrode in aqueous trifluoromethanesulfonic acid

    NASA Astrophysics Data System (ADS)

    Furuya, Yoshihisa; Mashio, Tetsuya; Ohma, Atsushi; Dale, Nilesh; Oshihara, Kenzo; Jerkiewicz, Gregory

    2014-10-01

    Platinum in the form of nanoparticles is the key and most expensive component of polymer electrolyte membrane fuel cells, while trifluoromethanesulfonic acid (CF3SO3H) is the smallest fluorinated sulfonic acid. Nafion, which acts as both electrolyte and separator in fuel cells, contains -CF2SO3H groups. Consequently, research on the electrochemical behaviour of Pt in aqueous CF3SO3H solutions creates important background knowledge that can benefit fuel cell development. In this contribution, Pt electro-oxidation is studied in 0.1 M aqueous CF3SO3H as a function of the polarization potential (Ep, 1.10 ≤ Ep ≤ 1.50 V), polarization time (tp, 100 ≤ tp ≤ 104 s), and temperature (T, 278 ≤ T ≤ 333 K). The critical thicknesses (X1), which determines the applicability of oxide growth theories, is determined and related to the oxide thickness (dox). Because X1 > dox for the entire range of Ep, tp, and T values, the formation of Pt surface oxide follows the interfacial place-exchange or the metal cation escape mechanism. The mechanism of Pt electro-oxidation is revised and expanded by taking into account possible interactions of cations, anions, and water molecules with Pt. A modified kinetic equation for the interfacial place exchange is proposed. The application of the interfacial place-exchange and metal cation escape mechanisms leads to an estimation of the Ptδ+-Oδ- surface dipole (μPtO), and the potential drop (Vox) and electric field (Eox) within the oxide. The Pt-anion interactions affect the oxidation kinetics by indirectly influencing the electric field within the double layer and the surface oxide.

  3. Decomposition of perfluorocarboxylic acids (PFCAs) by heterogeneous photocatalysis in acidic aqueous medium.

    PubMed

    Panchangam, Sri Chandana; Lin, Angela Yu-Chen; Shaik, Khaja Lateef; Lin, Cheng-Fang

    2009-09-01

    Decomposition of perfluorocarboxylic acids (PFCAs) is of prime importance since they are recognized as persistent organic pollutants and are widespread in the environment. PFCAs with longer carbon chain length are particularly of interest because of their noted recalcitrance, toxicity, and bioaccumulation. Here in this study, we demonstrate efficient decomposition of three important PFCAs such as perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) by heterogeneous photocatalysis with TiO(2) as a photocatalyst in acidic aqueous solutions. The PFCAs were decomposed into shorter carbon chain length PFCAs and fluoride ions. Photoholes of excited TiO(2) generated upon UV-irradiation are found to be the oxidation sites for PFCAs. Therefore, creation and sustenance of these photoholes in the acidic aqueous medium has enhanced the decomposition of PFCAs. Heterogeneous photocatalytic treatment achieved more than 99% decomposition and 38% complete mineralization of PFOA in 7h. The decomposition of other PFCAs was as high as 99% with a defluorination efficiency of 38% for PFDA and 54% for PFNA. The presence of perchloric acid was found to enhance the decomposition by facilitating the ionization of PFCAs. The oxygen present in the medium served both as an oxidant and an electron acceptor. The mechanistic details of PFCA decomposition and their corresponding mineralization are elaborated.

  4. One-Step Dipping Method for Covalently Grafting Polymer Films onto a Si Surface from Aqueous Media.

    PubMed

    Zhang, Junhong; Li, Ming; Zhang, Wenqi; Cao, Liqiang

    2016-08-30

    A facile and one-pot dipping method was proposed in this article for the first time to prepare vinylic polymer films on a silicon (Si) surface. This novel process was conducted in acidic aqueous media containing 4-nitrobenzene diazonium (NBD) tetrafluoroborate, hydrofluoric acid (HF), and vinylic monomers at room temperature in the open air and without any apparatus requirement. The formation of the polyvinyl film was confirmed by corroborating evidence from ellipsometry, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscope (AFM) analysis. The results revealed that both polymers of poorly water soluble methyl methacrylate (MMA) and water-soluble acrylic acid (AA) monomers were covalently grafted onto the Si surface via this simple process. The polyvinyl film was composed of polynitrophenyl (PNP) and polyvinyl, where PNP was doped into polyvinyl chains throughout the entire film. From a mechanistic point of view, the simple dipping method took advantage of the ability of the NBD cation to be spontaneously reduced at the Si surface at open circuit potential, providing aryl radicals. These radicals can be covalently bonded to the Si surface to form the PNP primer layer. Although the PNP sublayer was thinner and difficult to detect, it was necessary to graft polyvinyl chains. Furthermore, the aryl radicals were used to initiate the polymerization of vinylic monomers. The radical-terminated polyvinyl chains formed in the solution were then added to the aromatic rings of the primer layer to form the expected polyvinyl film. PMID:27441573

  5. Lifetime and dissolution kinetics of zinc oxide nanoparticles in aqueous media

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Tong, Tiezheng; Xie, Minwei; Gaillard, Jean-François

    2016-08-01

    We have assessed the persistence and lifetime of ZnO nanoparticles (ZnO-NPs) by performing dissolution experiments in three different aqueous media. These experiments were performed at ZnO-NP concentration levels close to the solubility of zincite (˜8 μM or 650 μg l-1 of ZnO)—a concentration that is orders of magnitude higher than current estimated relevant environmental concentrations. The kinetics were followed by voltammetry, while maintaining the pH at about 7.5 using a CO2/N2 gas mixture to remove di-oxygen interference. Our results show that, under these conditions, ZnO-NPs readily dissolve with a lifetime expectancy that does not exceed 90 min. Water chemistry, especially the presence of dissolved organic matter (DOM), plays an important role in ZnO-NP dissolution. Dissolution rates significantly increase in the presence of strong chelating agents, EDTA and L-cysteine, while the addition of polymeric DOM, such as sodium alginate, has the opposite effect. Our results suggest that ZnO-NPs are unlikely to persist in natural aqueous media and that the toxicity should be primarily related to the released Zn2+ ions rather than effects commonly associated to the presence of nanoparticles.

  6. Lifetime and dissolution kinetics of zinc oxide nanoparticles in aqueous media

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Tong, Tiezheng; Xie, Minwei; Gaillard, Jean-François

    2016-08-01

    We have assessed the persistence and lifetime of ZnO nanoparticles (ZnO-NPs) by performing dissolution experiments in three different aqueous media. These experiments were performed at ZnO-NP concentration levels close to the solubility of zincite (∼8 μM or 650 μg l‑1 of ZnO)—a concentration that is orders of magnitude higher than current estimated relevant environmental concentrations. The kinetics were followed by voltammetry, while maintaining the pH at about 7.5 using a CO2/N2 gas mixture to remove di-oxygen interference. Our results show that, under these conditions, ZnO-NPs readily dissolve with a lifetime expectancy that does not exceed 90 min. Water chemistry, especially the presence of dissolved organic matter (DOM), plays an important role in ZnO-NP dissolution. Dissolution rates significantly increase in the presence of strong chelating agents, EDTA and L-cysteine, while the addition of polymeric DOM, such as sodium alginate, has the opposite effect. Our results suggest that ZnO-NPs are unlikely to persist in natural aqueous media and that the toxicity should be primarily related to the released Zn2+ ions rather than effects commonly associated to the presence of nanoparticles.

  7. Calix[4]arene based dipodal receptor nanohybrids for selective determination of chloride ions in aqueous media.

    PubMed

    Kaur, Harpreet; Singh, Jasminder; Chopra, Shweta; Kaur, Navneet

    2016-01-01

    A chemical sensor based on p-tert butyl calix[4]arene has been synthesized and characterized using an assortment of spectroscopic techniques such as (1)H NMR, (13)C NMR, and elemental analysis. For sensor application, organic nanoparticles (N1) of 1 have been primed by implementing re-precipitation technique, which were further employed for preparing organic-inorganic hybrid (H1) by decorating N1 with gold nanoparticles. Both N1 and H1 were characterized using UV-visible, fluorescence, and DLS studies. Photo-physical changes due to anion binding with H1 were scrutinized using UV-visible absorption spectrometer and found it to promptly and selectively recognize Cl(-) ions in aqueous media. Thus, H1 can be effectively used for recognition of Cl(-) ions in aqueous media over a wide pH range, in samples of real time importance with a detection limit of 2.84×10(-9) M with a linear detection range up to 50 μM.

  8. PolyMUMPs MEMS device to measure mechanical stiffness of single cells in aqueous media

    NASA Astrophysics Data System (ADS)

    Warnat, S.; King, H.; Forbrigger, C.; Hubbard, T.

    2015-02-01

    A method of experimentally determining the mechanical stiffness of single cells by using differential displacement measurements in a two stage spring system is presented. The spring system consists of a known MEMS reference spring and an unknown cellular stiffness: the ratio of displacements is related to the ratio of stiffness. A polyMUMPs implementation for aqueous media is presented and displacement measurements made from optical microphotographs using a FFT based displacement method with a repeatability of ~20 nm. The approach was first validated on a MEMS two stage spring system of known stiffness. The measured stiffness ratios of control structures (i) MEMS spring systems and (ii) polystyrene microspheres were found to agree with theoretical values. Mechanical tests were then performed on Saccharomyces cerevisiae (Baker’s yeast) in aqueous media. Cells were placed (using a micropipette) inside MEMS measuring structures and compressed between two jaws using an electrostatic actuator and displacements measured. Tested cells showed stiffness values between 5.4 and 8.4 N m-1 with an uncertainty of 11%. In addition, non-viable cells were tested by exposing viable cells to methanol. The resultant mean cell stiffness dropped by factor of 3 × and an explicit discrimination between viable and non-viable cells based on mechanical stiffness was seen.

  9. Zeolite molecular sieves have dramatic acid-base effects on enzymes in nonaqueous media.

    PubMed

    Fontes, Nuno; Partridge, Johann; Halling, Peter J; Barreiros, Susana

    2002-02-01

    Zeolite molecular sieves very commonly are used as in situ drying agents in reaction mixtures of enzymes in nonaqueous media. They often affect enzyme behavior, and this has been interpreted in terms of altered hydration. Here, we show that zeolites can also have dramatic acid-base effects on enzymes in low water media, resulting from their cation-exchange ability. Initial rates of transesterification catalyzed by cross-linked crystals of subtilisin were compared in supercritical ethane, hexane, and acetonitrile with water activity fixed by pre-equilibration. Addition of zeolite NaA (4 A powder) still caused remarkable rate enhancements (up to 20-fold), despite the separate control of hydration. In the presence of excess of an alternative solid-state acid-base buffer, however, zeolite addition had no effect. The more commonly used Merck molecular sieves (type 3 A beads) had similar but somewhat smaller effects. All zeolites have ion-exchange ability and can exchange H+ for cations such as Na+ and K+. These exchanges will tend to affect the protonation state of acidic groups in the protein and, hence, enzymatic activity. Zeolites pre-equilibrated in aqueous suspensions of varying pH-pNa gave very different enzyme activities. Their differing basicities were demonstrated directly by equilibration with an indicator dissolved in toluene. The potential of zeolites as acid-base buffers for low-water media is discussed, and their ability to overcome pH memory is demonstrated.

  10. A nanofiber functionalized with dithizone by co-electrospinning for lead (II) adsorption from aqueous media.

    PubMed

    Deng, Jianjun; Kang, Xuejun; Chen, Liqin; Wang, Yu; Gu, Zhongze; Lu, Zuhong

    2011-11-30

    An electrospun nanofiber was utilized as a sorbent in packed fiber solid phase extraction (PFSPE) for selective separation and preconcentration of lead (II). The nanofiber had a polystyrene (PS) backbone, which was functionalized with dithizone (DZ) by co-electrospinning of a PS solution containing DZ. The nanofiber exhibited its performance in a cartridge prepared by packing 5mg of nanofiber. The nanofiber was characterized by a scanning electron microscope and IR spectra. The diameter of the nanofiber was less than 400 nm. After being activated by 2.0 mol L(-1) NaOH aqueous solution, the nanofiber quantitatively sorbed lead (II) at pH 8.5, and the metal ion could be desorbed from it by three times of elution with a small volume of 0.1 mol L(-1) HNO(3) aqueous solution. The breakthrough capacity was 16 μg mg(-1). The nanofiber could be used for concentration of lead (II) from water and other aqueous media, such as plasma with stable recovery in a simple and convenient manner. PMID:21945687

  11. Electrodiffusion of molecules in aqueous media: a robust, discretized description for electroporation and other transport phenomena.

    PubMed

    Smith, Kyle C; Weaver, James C

    2012-06-01

    Electrically driven transport of molecules and ions within aqueous electrolytes is of long-standing interest, with direct relevance to applications that include the delivery/release of biologically active solutes to/from cells and tissues. Examples include iontophoretic and electroporation-mediated drug delivery. Here, we describe a robust method for characterizing electrodiffusive transport in physiologic aqueous media. Specifically, we treat the case of solute present in sufficiently low concentration as to negligibly contribute to the total ionic current within the system. In this limiting case, which applies to many systems of interest, the predominant electrical behavior due to small ions is decoupled from solute transport. Thus, electrical behavior may be characterized using existing methods and treated as known in characterizing electrodiffusive molecular transport. First, we present traditional continuum equations governing electrodiffusion of charged solutes within aqueous electrolytes and then adapt them to discretized systems. Second, we examine the time-dependent and steady-state interfacial concentration gradients that result from the combination of diffusion and electrical drift. Third, we show how interfacial concentration gradients are related to electric field strength and duration. Finally, we examine how discretization size affects the accuracy of these methods. Overall these methods are motivated by and well suited to addressing an outstanding goal: estimation of the net ionic and molecular transport facilitated by electroporation in biological systems.

  12. Study of monoprotic acid-base equilibria in aqueous micellar solutions of nonionic surfactants using spectrophotometry and chemometrics.

    PubMed

    Babamoradi, Hamid; Abdollahi, Hamid

    2015-10-01

    Many studies have shown the distribution of solutes between aqueous phase and micellar pseudo-phase in aqueous micellar solutions. However, spectrophotometric studies of acid-base equilibria in these media do not confirm such distribution because of the collinearity between concentrations of chemical species in the two phases. The collinearity causes the number of detected species to be equal to the number of species in a homogenous solution that automatically misinterpreted as homogeneity of micellar solutions, therefore the collinearity is often neglected. This interpretation is in contradiction to the distribution theory in micellar media that must be avoided. Acid-base equilibrium of an indicator was studied in aqueous micellar solutions of a nonionic surfactant to address the collinearity using UV/Visible spectrophotometry. Simultaneous analysis (matrix augmentation) of the equilibrium and solvation data was applied to eliminate the collinearity from the equilibrium data. A model was then suggested for the equilibrium that was fitted to the augmented data to estimate distribution coefficients of the species between the two phases. Moreover, complete resolution of concentration and spectral profiles of species in each phase was achieved.

  13. Effects of chemical oxidants on perfluoroalkyl acid transport in one-dimensional porous media columns.

    PubMed

    McKenzie, Erica R; Siegrist, Robert L; McCray, John E; Higgins, Christopher P

    2015-02-01

    In situ chemical oxidation (ISCO) is a remediation approach that is often used to remediate soil and groundwater contaminated with fuels and chlorinated solvents. At many aqueous film-forming foam-impacted sites, perfluoroalkyl acids (PFAAs) can also be present at concentrations warranting concern. Laboratory experiments were completed using flow-through one-dimensional columns to improve our understanding of how ISCO (i.e., activated persulfate, permanganate, or catalyzed hydrogen peroxide) could affect the fate and transport of PFAAs in saturated porous media. While the resultant data suggest that standard ISCO is not a viable remediation strategy for PFAA decomposition, substantial changes in PFAA transport were observed upon and following the application of ISCO. In general, activated persulfate decreased PFAA transport, while permanganate and catalyzed hydrogen peroxide increased PFAA transport. PFAA sorption increased in the presence of increased aqueous polyvalent cation concentrations or decreased pH. The changes in contaminant mobility were greater than what would be predicted on the basis of aqueous chemistry considerations alone, suggesting that the application of ISCO results in changes to the porous media matrix (e.g., soil organic matter quality) that also influence transport. The application of ISCO is likely to result in changes in PFAA transport, where the direction (increased or decreased transport) and magnitude are dependent on PFAA characteristics, oxidant characteristics, and site-specific factors. PMID:25621878

  14. Effects of chemical oxidants on perfluoroalkyl acid transport in one-dimensional porous media columns.

    PubMed

    McKenzie, Erica R; Siegrist, Robert L; McCray, John E; Higgins, Christopher P

    2015-02-01

    In situ chemical oxidation (ISCO) is a remediation approach that is often used to remediate soil and groundwater contaminated with fuels and chlorinated solvents. At many aqueous film-forming foam-impacted sites, perfluoroalkyl acids (PFAAs) can also be present at concentrations warranting concern. Laboratory experiments were completed using flow-through one-dimensional columns to improve our understanding of how ISCO (i.e., activated persulfate, permanganate, or catalyzed hydrogen peroxide) could affect the fate and transport of PFAAs in saturated porous media. While the resultant data suggest that standard ISCO is not a viable remediation strategy for PFAA decomposition, substantial changes in PFAA transport were observed upon and following the application of ISCO. In general, activated persulfate decreased PFAA transport, while permanganate and catalyzed hydrogen peroxide increased PFAA transport. PFAA sorption increased in the presence of increased aqueous polyvalent cation concentrations or decreased pH. The changes in contaminant mobility were greater than what would be predicted on the basis of aqueous chemistry considerations alone, suggesting that the application of ISCO results in changes to the porous media matrix (e.g., soil organic matter quality) that also influence transport. The application of ISCO is likely to result in changes in PFAA transport, where the direction (increased or decreased transport) and magnitude are dependent on PFAA characteristics, oxidant characteristics, and site-specific factors.

  15. Highly sensitive and selective fluorescence sensor based on functional SBA-15 for detection of Hg2+ in aqueous media.

    PubMed

    Song, Chunxia; Zhang, Xiaolin; Jia, Cuiying; Zhou, Peng; Quan, Xie; Duan, Chunying

    2010-04-15

    A new Rhodamine-based chemosensor RBSN designed for the selective detection of Hg(2+) in aqueous media is synthesized and structural characterized. It features brightness blue emission in the presence of Hg(2+) with the fluorescent detection limit for Hg(2+) in aqueous media being ppb levels and exhibits excellent Hg(2+)-specific luminescence enhancement over various competitive cations, including alkali and alkaliearth, the first-row transition metals and heavy metals. By immobilizing RBSN to the mesoporous SBA-15, a highly selective and sensitive chemosensor toward mercury cations in aqueous solution was achieved. RBSN/SBA-15 could quantitatively determinate mercury cations at ppb level in the practical environmental media, suggesting the possibility for real-time quantitative detection of Hg(2+) and the convenience for potential application in toxicological and environmental science.

  16. Amino Acids Profiles in Biological Media

    SciTech Connect

    Iordache, A.; Horj, E.; Morar, S.; Cozar, O.; Culea, M.; Ani, A. R.; Mesaros, C.

    2010-08-04

    An accurate analytical method was developed to determine amino acids in some biological specimens by GC/MS technique. Stable isotopes provide useful tools for a variety of studies, offering ideal internal standards in quantitative information. Isotopic dilution gas chromatography--mass spectrometry (ID-GC/MS) is the techniques used for quantitative analysis of compounds labeled with stable isotopes. A Trace DSQ Thermo Finnigan quadrupole mass spectrometer coupled with a Trace GC was used. Amino acids were separated on a Rtx-5 MS capillary column, 30 mx0.25 mm, 0.25 {mu}m film thickness, using a temperature program from 50 deg. C, 1 min, 6 deg. C/min at 100 deg. C, 4 deg. C/min at 200 deg. C, 20 deg. C/min at 300 deg. C, (3 min). The transfer line temperature was 250 deg. C, the injector temperature 200 deg. C and ion source temperature 250 deg. C; splitter: 10:1. Electron energy was 70 eV and emission current, 100 {mu}A. The amino acids were purified on a Dowex 50W-W8 exchange resin and were derivatized in a procedure following two steps to obtain trifluoroacetyl butyl esters. The identification of amino acids was obtained by using NIST library but also by using amino acid standards.

  17. Amino Acids Profiles in Biological Media

    NASA Astrophysics Data System (ADS)

    Iordache, A.; Horj, E.; Ani, A. R.; Mesaros, C.; Morar, S.; Cozar, O.; Culea, M.

    2010-08-01

    An accurate analytical method was developed to determine amino acids in some biological specimens by GC/MS technique. Stable isotopes provide useful tools for a variety of studies, offering ideal internal standards in quantitative information. Isotopic dilution gas chromatography—mass spectrometry (ID-GC/MS) is the techniques used for quantitative analysis of compounds labeled with stable isotopes. A Trace DSQ Thermo Finnigan quadrupole mass spectrometer coupled with a Trace GC was used. Amino acids were separated on a Rtx-5 MS capillary column, 30 m×0.25 mm, 0.25 μm film thickness, using a temperature program from 50 °C, 1 min, 6 °C/min at 100 °C, 4 °C/min at 200 °C, 20 °C/min at 300 °C, (3 min). The transfer line temperature was 250 °C, the injector temperature 200 °C and ion source temperature 250 °C; splitter: 10:1. Electron energy was 70 eV and emission current, 100 μA. The amino acids were purified on a Dowex 50W-W8 exchange resin and were derivatized in a procedure following two steps to obtain trifluoroacetyl butyl esters. The identification of amino acids was obtained by using NIST library but also by using amino acid standards.

  18. Photochemical transformation of an iron(III)-arsenite complex in acidic aqueous solution.

    PubMed

    Pozdnyakov, Ivan P; Ding, Wei; Xu, Jing; Chen, Long; Wu, Feng; Grivin, Vjacheslav P; Plyusnin, Victor F

    2016-03-01

    Surface complexation between arsenious acid anions (As(III)) and ferric (hydr)oxides in water is important for the transformation and transfer of inorganic arsenic species. The mechanisms of formation and the photochemistry of dissolved Fe(III)-As(III) complexes in acidic aqueous solution are still unclear. Here, the photooxidation of As(III) in the presence of Fe(III) ions in acidic media has been investigated by laser flash and steady-state photolysis. At low arsenite concentrations (<1 mM), As(III) is oxidized by the ˙OH radical generated by photolysis of the FeOH(2+) complex. At higher arsenite concentrations (>10 mM), photoactive Fe(III)-As(III) complexes are formed (ϕ≈ 0.012). At all arsenite concentrations, a white FeAsO4 colloid is formed during As(III) photolysis in the presence of Fe(III) ions. Solid Fe(III)-As(III) complexes have been prepared and characterized, and the photochemical transformation of As(III) into As(V) in solid Fe(III)-As(III) complexes has been confirmed. These findings are important for a better understanding of the evolution of As(III) species under environmental conditions and should provide guidance for detoxification of As(III)-polluted water systems.

  19. [Mechanism of action of combined extremely weak magnetic field on aqueous solution of amino acid].

    PubMed

    Zhadin, M N; Bakharev, B V; Bobkova, N V

    2014-01-01

    The fundamental physical mechanisms of resonance action of an extremely weak (40 nT) alternating magnetic field at the cyclotron frequency combined with a weak (40 μT) static magnetic field, on living systems are analyzed in the present work. The experimental effects of such sort of magnetic fields were described in different papers: the very narrow resonant peaks in electrical conductivity of the aqueous solutions in the in vitro experiments and the biomedical in vivo effects on living animals of magnetic fields with frequencies tuned to some amino acids. The existing experimental in vitro data had a good repeatability in different laboratories and countries. Unfortunately, for free ions such sort of effects are absolutely impossible because the dimensions of an ion rotation radius should be measured by meters at room temperature and at very low static magnetic fields used in all the above experiments. Even for bound ions these effects should be also absolutely impossible from the positions of classic physics because of rather high viscosity of biological liquid media (blood plasma, cerebrospinal liquid, cytoplasm). Only modern quantum electrodynamics of condensed media opens the new ways for solving these problems. The proposed article is devoted to analysis of quantum mechanisms of these effects. PMID:25707253

  20. Evolution of hydrogen from acidic aqueous and aqueous-alcoholic solutions by reduced forms of isopolytungstates

    SciTech Connect

    Saidkhanov, S.S.; Parmon, V.N.; Savinov, E.N.

    1986-02-10

    The authors determine the specific nature of the hydrogen-releasing polytungstate (PT) species and investigate the features of H/sub 2/ evolution by this species. In aqueous and aqueous-alcohol solutions, reoxidation of the doubly reduced form of hexatungstate proceeds spontaneously, accompanied by hydrogen evolution; in contrast, the reduced form of the PT is stable with respect to reoxidation.

  1. Optical properties of chitosan in aqueous solution of L- and D-ascorbic acids

    NASA Astrophysics Data System (ADS)

    Malinkina, Olga N.; Shipovskaya, Anna B.; Kazmicheva, Olga F.

    2016-04-01

    The optical properties of aqueous chitosan solutions in L- and D-ascorbic acids were studied by optical rotatory dispersion and spectrophotometry. The specific optical rotation [α] of all chitosan solutions tested was positive, in contrast to aqueous solutions of the ascorbic acid enantiomers, which exhibit an inverse relationship of [α] values. Significant differences in the absolute values of [α] of the chitosan solutions at polymer-acid ratios exceeding the equimolar one were found.

  2. Dissolution properties of co-amorphous drug-amino acid formulations in buffer and biorelevant media.

    PubMed

    Heikkinen, A T; DeClerck, L; Löbmann, K; Grohganz, H; Rades, T; Laitinen, R

    2015-07-01

    Co-amorphous formulations, particularly binary drug-amino acid mixtures, have been shown to provide enhanced dissolution for poorly-soluble drugs and improved physical stability of the amorphous state. However, to date the dissolution properties (mainly intrinsic dissolution rate) of the co-amorphous formulations have been tested only in buffers and their supersaturation ability remain unexplored. Consequently, dissolution studies in simulated intestinal fluids need to be conducted in order to better evaluate the potential of these systems in increasing the oral bioavailability of biopharmaceutics classification system class II drugs. In this study, solubility and dissolution properties of the co-amorphous simvastatin-lysine, gibenclamide-serine, glibenclamide-threonine and glibenclamide-serine-threonine were studied in phosphate buffer pH 7.2 and biorelevant media (fasted and fed state simulated intestinal fluids (FaSSIF and FeSSIF, respectively)). The co-amorphous formulations were found to provide a long-lasting supersaturation and improve the dissolution of the drugs compared to the crystalline and amorphous drugs alone in buffer. Similar improvement, but in lesser extent, was observed in biorelevant media suggesting that a dissolution advantage observed in aqueous buffers may overestimate the advantage in vivo. However, the results show that, in addition to stability advantage shown earlier, co-amorphous drug-amino acid formulations provide dissolution advantage over crystalline drugs in both aqueous and biorelevant conditions.

  3. Electrochemical degradation of perchloroethylene in aqueous media: an approach to different strategies.

    PubMed

    Sáez, Verónica; Esclapez Vicente, M D; Frías-Ferrer, Angel J; Bonete, Pedro; González-García, José

    2009-05-01

    An approaching study to the electrochemical degradation of perchloroethylene (PCE) in water has been carried out using controlled current density degradation electrolyses. The different electrochemical strategies to degrade perchloroethylene in aqueous media (i.e. cathodic, anodic and dual treatments) have been checked using divided and undivided configurations. The influence of the initial concentration, pH and current density on the general behavior of the system has been studied, and special attention was paid to the nature of the byproducts formed and to the analysis of the closed mass balance at the end of the reaction. Results from several analytical techniques have been compared. Undivided configuration provides the best results in these experimental conditions, with degradation percentages higher than 50% and with only 6% of the initial perchloroethylene concentration remaining in the system. PMID:19303130

  4. Saccharides as efficacious solubilisers for highly lipophilic compounds in aqueous media.

    PubMed

    Bertau, Martin; Jörg, Gerhard

    2004-06-01

    The bioavailability of lipophilic substrates is critical for biotransformations with isolated enzymes as well as with whole cells. With the example of a series of lipophilic ketones the suitability of saccharides as potent solubilisers for highly lipophilic substrates was demonstrated. Best results were obtained for d-glucose, which increased substrate solubility up to 50 times. In whole-cell biocatalysis the sugar acts both as solubiliser and as carbon source for which reason this procedure does not impair cell physiology and is unique in being environmentally benign. The capability of saccharides to solubilise lipophilic compounds in aqueous media sources from their ability to form hydrophilic and lipophilic domains at hydrophobic interfaces, thus forming cyclodextrin-like structures around the lipophilic substrate.

  5. Electrophoretic deposition of titanium dioxide films on copper in aqueous media.

    PubMed

    Laamari, M; Ben Youssef, A; Bousselmi, L

    2016-01-01

    Electrophoretic deposition was used to produce titanium dioxide (TiO2) nanostructured films on copper substrate in aqueous media for photocatalytic application. Polyvinyl pyrrolidone (PVP) with a weight rate from 0 to 15% was added to TiO2 P25 suspension in order to enhance film adhesion. The films were characterized by X-ray diffraction, optical microscopy, contact angle measurement, nanoindentation, scratch test and photoluminescence. The photocatalytic activity of the films was tested with amido black 10B under UV irradiation. The results indicated that the morphology and the mechanical properties of films depended on the added PVP amount. Scratch test showed that adhesion strength rose with increased PVP amount. The photocatalytic activity indicated that TiO2 film synthesized with 13% PVP had the highest efficiency. PMID:27438247

  6. Heterogeneous reactions of epoxides in acidic media.

    PubMed

    Lal, Vinita; Khalizov, Alexei F; Lin, Yun; Galvan, Maria D; Connell, Brian T; Zhang, Renyi

    2012-06-21

    Epoxides have recently been identified as important intermediates in the gas phase oxidation of hydrocarbons, and their hydrolysis products have been observed in ambient aerosols. To evaluate the role of epoxides in the formation of secondary organic aerosols (SOA), the kinetics and mechanism of heterogeneous reactions of two model epoxides, isoprene oxide and α-pinene oxide, with sulfuric acid, ammonium bisulfate, and ammonium sulfate have been investigated using complementary experimental techniques. Kinetic experiments using a fast flow reactor coupled to an ion drift-chemical ionization mass spectrometer (ID-CIMS) show a fast irreversible loss of the epoxides with the uptake coefficients (γ) of (1.7 ± 0.1) × 10(-2) and (4.6 ± 0.3) × 10(-2) for isoprene oxide and α-pinene oxide, respectively, for 90 wt % H(2)SO(4) and at room temperature. Experiments using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) reveal that diols are the major products in ammonium bisulfate and dilute H(2)SO(4) (<25 wt %) solutions for both epoxides. In concentrated H(2)SO(4) (>65 wt %), acetals are formed from isoprene oxide, whereas organosulfates are produced from α-pinene oxide. The reaction of the epoxides with ammonium sulfate is slow and no products are observed. The epoxide reactions using bulk samples and Nuclear Magnetic Resonance (NMR) spectroscopy reveal the presence of diols as the major products for isoprene oxide, accompanied by aldehyde formation. For α-pinene oxide, organosulfate formation is observed with a yield increasing with the acidity. Large yields of organosulfates in all NMR experiments with α-pinene oxide are attributed to the kinetic isotope effect (KIE) from the use of deuterated sulfuric acid and water. Our results suggest that acid-catalyzed hydrolysis of epoxides results in the formation of a wide range of products, and some of the products have low volatility and contribute to SOA growth under ambient conditions

  7. Water as a promoter and catalyst for dioxygen electrochemistry in aqueous and organic media.

    SciTech Connect

    Staszak-Jirkovsky, Jakub; Subbaraman, Ram; Strmcnik, Dusan; Harrison, Katherine L.; Diesendruck, Charles E.; Assary, Rajeev; Frank, Otakar; Kobr, Lukas; Wiberg, Gustav K.H; Genorio, Bostjan; Connell, Justin G.; Lopes, Pietro P.; Stamenkovic, Vojislav R.; Curtiss, Larry; Moore, Jeffrey S.; Zavadil, Kevin R.; Markovic, Nenad M.

    2015-11-01

    Water and oxygen electrochemistry lies at the heart of interfacial processes controlling energy transformations in fuel cells, electrolyzers, and batteries. Here, by comparing results for the ORR obtained in alkaline aqueous media to those obtained in ultradry organic electrolytes with known amounts of H2O added intentionally, we propose a new rationale in which water itself plays an important role in determining the reaction kinetics. This effect derives from the formation of HOad center dot center dot center dot H2O (aqueous solutions) and LiO2 center dot center dot center dot H2O (organic solvents) complexes that place water in a configurationally favorable position for proton transfer to weakly adsorbed intermediates. We also find that, even at low concentrations (<10 ppm), water acts simultaneously as a promoter and as a catalyst in the production of Li2O2, regenerating itself through a sequence of steps that include the formation and recombination of H+ and OH-. We conclude that, although the binding energy between metal surfaces and oxygen intermediates is an important descriptor in electrocatalysis, understanding the role of water as a proton-donor reactant may explain many anomalous features in electrocatalysis at metal-liquid interfaces.

  8. Tritium release from Ti-T layers in air, in aqueous media and in animal experiments.

    PubMed

    Bíró, J; Fehér, I; Máté, L; Varga, L

    1978-01-01

    In connection with Ti-T incorporation hazard to which operators of neutron generators are exposed the release of tritium from Ti-T preparations of different ages was studied in experiments carried out in air, in aqueous media and in living animals. Samples were prepared with activities from 10 to 30 mCi and the effect of storage on the tritium release rate was also observed. In 250 days a fraction of 10(-3) of the tritium activity was absorbed by aqueous liquids. In air the release varied from 10(-6) to 10(-7) per hour. The Ti-T samples of different ages, introduced surgically into the abdominal cavity of rats, showed the tritium release rate to decrease with time. The tritium activity observable in the circulation was 5 to 6 orders of magnitude smaller compared with the introduced value. The observations permit the inference that in the case of Ti-T incorporation only a minor fraction of the tritium burden can be assessed from the activity measured in the urine. PMID:754442

  9. Development of a correlation for aqueous-vapor phase mass transfer in porous media

    NASA Astrophysics Data System (ADS)

    Szatkowski, Andrew; Imhoff, Paul T.; Miller, Cass T.

    1995-03-01

    In many situations vapor-phase extraction procedures (e.g., soil venting, air sparging, and bioventing) may be suitable methods for remediating porous media contaminated by volatile organic compounds. This has led to increased study of operative processes in these systems, including aqueous-vapor phase mass transfer. Past work has shown the importance of the flow regime on this process, but a quantitative estimate of mass-transfer coefficients is lacking, especially for systems not confounded by uncertainties involving interfacial area between the phases. An experimental investigation was conducted to isolate the resistance to aqueous-vapor phase mass transfer at the phase boundary, using an ideal porous medium system. Mass-transfer coefficients were measured for toluene for a wide range of Reynolds numbers. An empirical model was fit to the data in dimensionless form. The mass-transfer model was coupled with an available interfacial area model, yielding a dimensionless expression for the mass-transfer rate coefficient. This expression was used to compare results from this work to three other experimental studies reported in the literature. These comparisons showed that for experiments where infiltrating water flowed uniformly within the porous medium, the predicted mass-transfer coefficients were within a factor of 5 of the measured coefficients. Mass transfer was significantly slower than the rate predicted, using the results from this work, in experiments where infiltrating water flowed nonuniformly.

  10. Study of the dehydrochlorination of DDT in basic media in sulfobetaine aqueous micellar solutions

    SciTech Connect

    Rodriguez, A.; Mar Graciani, M. del; Guinda, A.; Munoz, M.; Moya, M.L.

    2000-04-04

    The reaction of dehydrochlorination of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane, DDT, with hydroxide ions has been studied in aqueous micellar solutions of N-tetradecyl-N,N-dimethyl-3-ammino-1-propane-sulfonate, SB3-14, and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, SB3-16. A simple expression for the observed rate constant, k{sub obs}, based on the pseudophase model, could explain the influence of changes in the surfactant concentration on k{sub obs}. The kinetic effects of added electrolytes (NaF, NaCl, NaBr, and NaNO{sub 3}) on the reaction rate in SB3-14 micellar media have also been studied. They were rationalized by considering the binding of the anions, which come from the added salt, to the sulfobetaine micelles and their competition with the reactive hydroxide ions for the micellar surface. Conductivity measurements have been a helpful tool in the discussion of the kinetic effects of added salts and permitted the estimation of equilibrium constants for the distribution of the anions between the zwitterionic micelles and the aqueous phase.

  11. Self-assembly of light-harvesting crystalline nanosheets in aqueous media.

    PubMed

    Shahar, Chen; Baram, Jonathan; Tidhar, Yaron; Weissman, Haim; Cohen, Sidney R; Pinkas, Iddo; Rybtchinski, Boris

    2013-04-23

    A methodology leading to facile self-assembly of crystalline aromatic arrays in dilute aqueous solutions would enable efficient fabrication and processing of organic photonic and electronic materials in water. In particular, soluble 2D crystalline nanosheets may mimic the properties of photoactive thin films and self-assembled monolayers, covering large areas with ordered nanometer-thick material. We designed such solution-phase arrays using hierarchical self-assembly of amphiphilic perylene diimides in aqueous media. The assemblies were characterized by cryogenic transmission electron microscopy (cryo-TEM), revealing crystalline order and 2D morphology (confirmed by AFM studies). The order and morphology are preserved upon drying as evidenced by TEM and AFM. The 2D crystalline-like structures exhibit broadening and red-shifted absorption bands in UV-vis spectra, typical for PDI crystals and liquid crystals. Photophysical studies including femtosecond transient absorption spectroscopy reveal that two of the assemblies are superior light-harvesters due to excellent solar spectrum coverage and fast exciton transfer, in one case showing exciton diffusion comparable to solid-state crystalline systems based on perylene tetracarboxylic dianhidride (PTCDA).

  12. New crystallization of fatty acids from aqueous ethanol solution combined with liquid-liquid extraction

    SciTech Connect

    Maeda, Kouji; Nomura, Yoshihisa; Tai, Kimihiko; Ueno, Yoshitaka; Fukui, Keisuke; Hirota, Syouji

    1999-06-01

    A new separation process of saturated fatty acids (lauric acid-myristic acid) using crystallization from an aqueous ethanol solution has been examined. There were two vessels in this separation process: an extraction vessel and a crystallization vessel. The fatty acids in the aqueous phase were first extracted from their organic phase (melt) in the extraction vessel. The fatty acids in the aqueous phase were continuously introduced to the crystallization vessel, and then the fatty acids were crystallized there. The crystals of the fatty acids were collected continuously above the aqueous phase in the crystallization vessel. In this process, the yield and the purity of the crystals over time were measured, and it was found that the purity of lauric acid increased unsteadily up to 0.98 mole fraction of lauric acid with an increase in the yield of the low yield range. The mole fraction of ethanol in the aqueous phase could be significant to control the relationship between the yield and the purity of the crystals. Three different mole fractions of lauric acid in the organic phase were used to be separated in this process. Moreover, the authors have considered the effective separations of this process, and the maximum yield and purity of the crystals have been estimated by a simple mass balance.

  13. Multiple glass transitions and freezing events of aqueous citric acid.

    PubMed

    Bogdan, Anatoli; Molina, Mario J; Tenhu, Heikki; Loerting, Thomas

    2015-05-14

    Calorimetric and optical cryo-microscope measurements of 10-64 wt % citric acid (CA) solutions subjected to moderate (3 K/min) and slow (0.5 and 0.1 K/min) cooling/warming rates and also to quenching/moderate warming between 320 and 133 K are presented. Depending on solution concentration and cooling rate, the obtained thermograms show one freezing event and from one to three liquid-glass transitions upon cooling and from one to six liquid-glass and reverse glass-liquid transitions, one or two freezing events, and one melting event upon warming of frozen/glassy CA/H2O. The multiple freezing events and glass transitions pertain to the mother CA/H2O solution itself and two freeze-concentrated solution regions, FCS1 and FCS2, of different concentrations. The FCS1 and FCS2 (or FCS22) are formed during the freezing of CA/H2O upon cooling and/or during the freezing upon warming of partly glassy or entirely glassy mother CA/H2O. The formation of two FCS1 and FCS22 regions during the freezing upon warming to our best knowledge has never been reported before. Using an optical cryo-microscope, we are able to observe the formation of a continuous ice framework (IF) and its morphology and reciprocal distribution of IF/(FCS1 + FCS2). Our results provide a new look at the freezing and glass transition behavior of aqueous solutions and can be used for the optimization of lyophilization and freezing of foods and biopharmaceutical formulations, among many other applications where freezing plays a crucial role.

  14. DETERMINATION AND QUANTIFICATION OF NON-AQUEOUS PHASE LIQUID MIXTURES IN ENVIRONMENTAL MEDIA

    SciTech Connect

    Rucker, G

    2006-09-22

    It is important to recognize the presence of Non-Aqueous Phase Liquids (NAPLs) in soils at a waste site in order to design and construct a successful remediation system. NAPLs often manifest as a complex, multi-component mixture of organic compounds that can occur in environmental media, such as vadose zone soil, where the mixture will partition and equilibrate with soil particles, pore vapor, and pore water. Complex organic mixtures can greatly complicate the determination and quantification of NAPL in soil due to inter-media transfer. NAPL thresholds can also change because of mixture physical properties and can disguise the presence of NAPL. A unique analytical method and copyrighted software have been developed at the Department of Energy's Savannah River Site that facilitates solution of this problem. The analytical method uses a classic chemistry approach and applies the principals of solubility limit theory, Raoult's Law, and equilibrium chemistry to derive an accurate estimation of NAPL presence and quantity. The method is unique because it calculates an exact result that is mass balanced for each physical state, chemical mixture component, and mixture characteristics. The method is also unique because the solution can be calculated on both a wet weight and dry weight basis--a factor which is often overlooked. The software includes physical parameters for 300 chemicals in a database that self-loads into the model to save time. The method accommodates up to 20 different chemicals in a multi-component mixture analysis. A robust data display is generated including important parameters of the components and mixture including: NAPL thresholds for individual chemical components within the mixture, mass distribution in soil for each physical state, molar fractions, density, vapor pressure, solubility, mass balance, media concentrations, residual saturation, and modest graphing capabilities. This method and software are power tools to simplify otherwise tedious

  15. Thermodynamics of the complexation of arabinogalactan with salicylic and p-aminobenzoic acids in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Mudarisova, R. Kh.; Badykova, L. A.

    2016-03-01

    The thermodynamics of complexation of arabinogalactan with salicylic and p-aminobenzoic acids in aqueous solutions is studied by means spectroscopy. The standard thermodynamic characteristics (Δ H°; Δ G°; Δ S°) of complexation are calculated.

  16. Acid tolerance of rhizobium trifolii in culture media

    SciTech Connect

    Thornton, F.C.; Davey, C.B.

    1983-01-01

    Tolerance to acidity (pH 4.2 to 4.6), low P (1 to 6 ..mu..M) and high Al (15 to 40..mu..M) for 100 strains of Rhizobium trifolii was assessed in liquid culture media in the laboratory. Response to acidity and Al varied among strains as evidenced by lower maximum cell densities and reduced growth rates, most preceded by a lag phase. Tolerance to acidity did not imply tolerance to Al in all cases. Strains were capable of tolerating higher levels of Al if acidity was reduced. Limitations in rhizobial growth due to low P concentrations were not as severe a stress as high acidity or high Al concentration.

  17. Thallium Transfer from Hydrochloric Acid Media into Pure Ionic Liquids.

    PubMed

    Tereshatov, Evgeny E; Boltoeva, Maria Yu; Mazan, Valerie; Volia, Merinda F; Folden, Charles M

    2016-03-10

    Pure hydrophobic ionic liquids are known to extract metallic species from aqueous solutions. In this work we have systematically investigated thallium (Tl) extraction from aqueous hydrochloric acid (HCl) solutions into six pure fluorinated ionic liquids, namely imidazolium- and pyrrolidinium-based ionic liquids with bis(trifluoromethanesulfonyl)imide and bis(fluorosulfonyl)-imide anions. The dependence of the Tl extraction efficiency on the structure and composition of the ionic liquid ions, metal oxidation state, and initial metal and aqueous acid concentrations have been studied. Tl concentrations were on the order of picomolar (analyzed using radioactive tracers) and millimolar (analyzed using inductively coupled plasma mass spectrometry). The extraction of the cationic thallium species Tl(+) is higher for ionic liquids with more hydrophilic cations, while for the TlX(z)(3-z) anionic species (where X = Cl(-) and/or Br(-)), the extraction efficiency is greater for ionic liquids with more hydrophobic cations. The highest distribution value of Tl(III) was approximately 2000. An improved mathematical model based on ion exchange and ion pair formation mechanisms has been developed to describe the coextraction of two different anionic species, and the relative contributions of each mechanism have been determined. PMID:26769597

  18. A Simple and Effective Ratiometric Fluorescent Probe for the Selective Detection of Cysteine and Homocysteine in Aqueous Media.

    PubMed

    Na, Risong; Zhu, Meiqing; Fan, Shisuo; Wang, Zhen; Wu, Xiangwei; Tang, Jun; Liu, Jia; Wang, Yi; Hua, Rimao

    2016-01-01

    Biothiols such as cysteine (Cys) and homocysteine (Hcy) are essential biomolecules participating in molecular and physiological processes in an organism. However, their selective detection remains challenging. In this study, ethyl 2-(3-formyl-4-hydroxyphenyl)-4-methylthiazole-5-carboxylate (NL) was synthesized as a ratiometric fluorescent probe for the rapid and selective detection of Cys and Hcy over glutathione (GSH) and other amino acids. The fluorescence intensity of the probe in the presence of Cys/Hcy increased about 3-fold at a concentration of 20 equiv. of the probe, compared with that in the absence of these chemicals in aqueous media. The limits of detection of the fluorescent assay were 0.911 μM and 0.828 μM of Cys and Hcy, respectively. ¹H-NMR and MS analyses indicated that an excited-state intramolecular proton transfer is the mechanism of fluorescence sensing. This ratiometric probe is structurally simple and highly selective. The results suggest that it has useful applications in analytical chemistry and diagnostics. PMID:27527138

  19. Surfactant-Amino Acid and Surfactant-Surfactant Interactions in Aqueous Medium: a Review.

    PubMed

    Malik, Nisar Ahmad

    2015-08-01

    An overview of surfactant-amino acid interactions mainly in aqueous medium has been discussed. Main emphasis has been on the solution thermodynamics and solute-solvent interactions. Almost all available data on the topic has been presented in a lucid and simple way. Conventional surfactants have been discussed as amphiphiles forming micelles and amino acids as additives and their effect on the various physicochemical properties of these conventional surfactants. Surfactant-surfactant interactions in aqueous medium, various mixed surfactant models, are also highlighted to assess their interactions in aqueous medium. Finally, their applied part has been taken into consideration to interpret their possible uses.

  20. Uptake of Hypobromous Acid (HOBr) by Aqueous Sulfuric Acid Solutions: Low-Temperature Solubility and Reaction

    NASA Technical Reports Server (NTRS)

    Iraci, Laura T.; Michelsen, Rebecca R.; Ashbourn, Samatha F. M.; Rammer, Thomas A.; Golden, David M.

    2005-01-01

    Hypobromous acid (HOBr) is a key species linking inorganic bromine to the chlorine and odd hydrogen chemical families. We have measured the solubility of HOBr in 45 - 70 wt% sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosol composition. Over the temperature range 201 - 252 K, HOBr is quite soluble in sulfuric acid, with an effective Henry's law coefficient, H* = 10(exp 4) - 10(exp 7) mol/L/atm. H* is inversely dependent on temperature, with Delta H = -46.2 kJ/mol and Delta S = -106.2 J/mol/K for 55 - 70 wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into aqueous 45 wt% H2SO4, the solubility can be described by log H* = 3665/T - 10.63. For 55 - 70 wt% H2SO4, log H* = 2412/T - 5.55. At temperatures colder than approx. 213 K, the solubility of HOBr in 45 wt% H2SO4 is noticeably larger than in 70 wt% H2SO4. The solubility of HOBr is comparable to that of HBr, indicating that upper tropospheric and lower stratospheric aerosols should contain equilibrium concentrations of HOBr which equal or exceed those of HBr. Our measurements indicate chemical reaction of HOBr upon uptake into aqueous sulfuric acid in the presence of other brominated gases followed by evolution of gaseous products including Br2O and Br2, particularly at 70 wt% H2SO4.

  1. Experimental and Theoretical Studies of the Acid-Catalyzed Conversion of Furfuryl Alcohol to Levulinic Acid in Aqueous Solution

    SciTech Connect

    González Maldonado, Gretchen M.; Assary, Rajeev S.; Dumesic, James; Curtiss, Larry A.

    2012-01-01

    The conversion of furfuryl alcohol (FAL) to levulinic acid over AmberlystTM 15 in aqueous media was investigated using a combination of liquid chromatography-mass spectrometry (LC-MS) measurements, isotopic labeling studies, nuclear magnetic resonance (NMR) spectroscopy, and ab initio quantum chemical calculations using the G4MP2 method. The results of these combined studies showed that one of the major reaction pathways takes place via a geminal diol species (4,5,5-trihydroxypentan-2-one, denoted as intermediate A), formed by the addition of two water molecules to FAL, where two of the oxygen atoms from FAL are retained. This geminal diol species can also be produced from another intermediate found to be a dimer-like species, denoted as intermediate B. This dimer-like species is formed at the early stages of reaction, and it can also be converted to intermediate A, indicating that intermediate B is the product of the reaction of FAL with another early intermediate. Quantum chemical calculations suggested this to be a protonated acyclic species. Reaction of this early intermediate with water produces intermediate A, while reaction with FAL produces intermediate B.

  2. Behaviors of acrylamide/itaconic acid hydrogels in uptake of uranyl ions from aqueous solutions

    SciTech Connect

    Karadag, E.; Saraydin, D.; Gueven, O.

    1995-12-01

    In this study, adsorptions of uranyl ions from two different aqueous uranyl solutions by acrylamide-itaconic acid hydrogels were investigated by a spectroscopic method. The hydrogels were prepared by irradiating with {gamma}-radiation. In the experiment of uranyl ions adsorption, Type II adsorption was found. One gram of acrylamide-itaconic acid hydrogels sorbed 178-219 mg uranyl ions from the solutions of uranyl acetate, 42-76 mg uranyl ions from the aqueous solutions of uranyl nitrate, while acrylamide hydrogel did not sorb any uranyl ion. For the hydrogel containing 40 mg of itaconic acid and irradiated to 3.73 kGy, swelling of the hydrogels was observed in water (1660%), in the aqueous solution of uranyl acetate (730%), and in the aqueous solution of uranyl nitrate (580%). Diffusions of water onto hydrogels were a non-Fickian type of diffusion, whereas diffusions of uranyl ions were a Fickian type of diffusion.

  3. Succinic acid in aqueous solution: connecting microscopic surface composition and macroscopic surface tension.

    PubMed

    Werner, Josephina; Julin, Jan; Dalirian, Maryam; Prisle, Nønne L; Öhrwall, Gunnar; Persson, Ingmar; Björneholm, Olle; Riipinen, Ilona

    2014-10-21

    The water-vapor interface of aqueous solutions of succinic acid, where pH values and bulk concentrations were varied, has been studied using surface sensitive X-ray photoelectron spectroscopy (XPS) and molecular dynamics (MD) simulations. It was found that succinic acid has a considerably higher propensity to reside in the aqueous surface region than its deprotonated form, which is effectively depleted from the surface due to the two strongly hydrated carboxylate groups. From both XPS experiments and MD simulations a strongly increased concentration of the acid form in the surface region compared to the bulk concentration was found and quantified. Detailed analysis of the surface of succinic acid solutions at different bulk concentrations led to the conclusion that succinic acid saturates the aqueous surface at high bulk concentrations. With the aid of MD simulations the thickness of the surface layer could be estimated, which enabled the quantification of surface concentration of succinic acid as a multiple of the known bulk concentration. The obtained enrichment factors were successfully used to model the surface tension of these binary aqueous solutions using two different models that account for the surface enrichment. This underlines the close correlation of increased concentration at the surface relative to the bulk and reduced surface tension of aqueous solutions of succinic acid. The results of this study shed light on the microscopic origin of surface tension, a macroscopic property. Furthermore, the impact of the results from this study on atmospheric modeling is discussed.

  4. A pulse radiolysis study of salicylic acid and 5-sulpho-salicylic acid in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Kishore, Kamal; Mukherjee, T.

    2006-01-01

    Reactions of H, OH, eaq- and some one-electron oxidants have been studied with salicylic acid and 5-sulpho-salicylic acid in aqueous solutions. Rate constants for the reaction of eaq- with these compounds were of the order of 10 9 dm 3 mol -1 s -1 and this reaction led to the formation of reducing radicals which could transfer electron to methyl viologen. Other one-electron reductants were not able to reduce these compounds. OH radicals reacted with these compounds by addition pathway with very high rate constants (>10 10 dm 3 mol -1 s -1) while O rad - radical anions could oxidize these molecules to give phenoxyl type of radicals. Amongst the one-electron oxidants, only N 3rad and SO 4rad - could oxidize salicylic acid while 5-sulpho-salicylic acid could be oxidized only by SO 4- radicals indicating that while one-electron reduction potential for semi-oxidized SA may be<1.33 V vs. NHE (the E o1 for N 3rad radical), it is more than 1.33 V vs. NHE for semi-oxidized SSA species.

  5. Molecular Modeling of Ammonium, Calcium, Sulfur, and Sodium Lignosulphonates in Acid and Basic Aqueous Environments

    NASA Astrophysics Data System (ADS)

    Salazar Valencia, P. J.; Bolívar Marinez, L. E.; Pérez Merchancano, S. T.

    2015-12-01

    Lignosulphonates (LS), also known as lignin sulfonates or sulfite lignin, are lignins in sulfonated forms, obtained from the "sulfite liquors," a residue of the wood pulp extraction process. Their main utility lies in its wide range of properties, they can be used as additives, dispersants, binders, fluxing, binder agents, etc. in fields ranging from food to fertilizer manufacture and even as agents in the preparation of ion exchange membranes. Since they can be manufactured relatively easy and quickly, and that its molecular size can be manipulated to obtain fragments of very low molecular weight, they are used as transport agents in the food industry, cosmetics, pharmaceutical and drug development, and as molecular elements for the treatment of health problems. In this paper, we study the electronic structural and optical characteristics of LS incorporating ammonium, sulfur, calcium, and sodium ions in acidic and basic aqueous media in order to gain a better understanding of their behavior and the very interesting properties exhibit. The studies were performed using the molecular modeling program HyperChem 5 using the semiempirical method PM3 of the NDO Family (neglect of differential overlap), to calculate the structural properties. We calculated the electronic and optical properties using the semiempirical method ZINDO / CI.

  6. Characterization of Aqueous Oleic Acid/Oleate Dispersions by Fluorescent Probes and Raman Spectroscopy.

    PubMed

    Suga, Keishi; Kondo, Dai; Otsuka, Yoko; Okamoto, Yukihiro; Umakoshi, Hiroshi

    2016-08-01

    Oleic acid (OA) and oleates form self-assembled structures dispersible in aqueous media. Herein, the physicochemical properties of OA/oleate assemblies were characterized using fluorescent probes and Raman spectroscopy, under relatively high dilution (<100 mM of total amphiphile) at 25 °C. Anisotropy analysis using 1,6-diphenyl-1,3,5-hexatriene showed that the microviscosity of the OA/oleate assembly was highest at pH 7.5 (the pH range of 6.9-10.6 was investigated). The fluorescence spectra of 6-lauroyl-2-dimethylaminonaphthalene revealed the dehydrated environments on membrane surfaces at pH < 7.7. The pH-dependent Raman peak intensity ratios, chain torsion (S = I1124/I1096) and chain packing (R = I2850/I2930), showed local maxima, indicating the occurrence of metastable phases, such as dispersed cubic phase (pH = 7.5), vesicle (pH = 8.5), and dispersed cylindrical micelle (pH = 9.7). These results suggest that large-scale OA/oleate assemblies could possess particular membrane properties in a narrow pH region, e.g., at pH 7.5, and 9.7.

  7. Silica coating of luminescent quantum dots prepared in aqueous media for cellular labeling

    SciTech Connect

    Ma, Yunfei; Li, Yan Zhong, Xinhua

    2014-12-15

    Graphical abstract: A facile route based on modified Stöber method was used for the synthesis of silica coated QDs (QD@SiO{sub 2}) starting from aqueously prepared CdTe/CdS QDs. The resultant QD@SiO{sub 2} exhibited a significant increase in emission efficiency compared with that of the initial QDs, along with a small size (∼5 nm in diameter), great stability and low cytotoxicity, which makes it a good candidate as robust biomarker. - Highlights: • We present a facile modified Stöber method to prepare highly luminescent QD@SiO{sub 2}. • The PL efficiency of QDs increases significantly after silica coating. • QD@SiO{sub 2} exhibits small size (∼5 nm) and great dispersibility in aqueous solution. • QD@SiO{sub 2} presents extraordinary photo and colloidal stability. • The silica shell eliminates QD cytotoxicity, providing the access of bioconjugation. - Abstract: Silica coating is an effective approach for rendering luminescent quantum dots (QDs) with water dispersibility and biocompatibility. However, it is still challenging to prepare silica-coated QDs (QD@SiO{sub 2}) with high emission efficiency, small size and great stability in favor for bioapplication. Herein, we reported a modified Stöber method for silica coating of aqueously-prepared CdTe/CdS QDs. With the coexistence of Cd{sup 2+} and thioglycolic acid (TGA), a thin silica shell was formed around QDs by the hydrolysis of tetraethyl orthosilicate (TEOS). The resultant QD@SiO{sub 2} with a small size (∼5 nm in diameter) exhibits significantly higher emission efficiencies than that of the initial QDs. Also, QD@SiO{sub 2} has extraordinary photo and colloidal stability (pH range of 5–13, 4.0 M NaCl solution). Protected by the silica shell, the cytotoxicity of QDs could be reduced. Moreover, the QD@SiO{sub 2} conjugated with folic acid (FA) presents high specific binding toward receptor-positive HeLa cells over receptor-negative A549 cells.

  8. Spectral behaviour of eosin Y in different solvents and aqueous surfactant media.

    PubMed

    Chakraborty, Moumita; Panda, Amiya Kumar

    2011-10-15

    Photophysical behaviour of the anionic xanthene dye, eosin Y (EY) was investigated in solvents of different polarities as well as in the presence of aqueous cationic surfactants. From the correlation between E(T)(30) and Kosower Z values of EY in different solvents, subsequent parameters for EY were determined in the presence of surfactants. A red shift, both in the absorption and emission spectra of EY, was observed with decreasing solvent polarity. Dimerisation of EY was found to be dependent on solvent polarity. Cationic surfactants retarded the process of dimerisation, which were evident from the lower dimerisation constant (K(D)) values, compared to that of in pure water. Dye-surfactant interaction constants were determined at different temperatures (298-318 K) and subsequently the thermodynamic parameters, viz., ΔG°, ΔH° and ΔS° were evaluated using the interaction constant values. The fluorescence spectra of EY followed the same trend as in the absorption spectra, although with lesser extents. Stokes shifts were calculated and correlated with the polarity of the medium. Fluorescence of EY was initially quenched by the cationic surfactants in their pre-micellar region, which then followed a red shift with intensity enhancement. Fluorescence quenching was found to be of Stern-Volmer type where the excited state lifetime of EY remained unchanged in different surfactant media. However, the anisotropy value of EY was changed in the post micellar region of surfactants.

  9. CEC column behaviour of butyl and lauryl methacrylate monoliths prepared in non-aqueous media.

    PubMed

    Cantó-Mirapeix, Amparo; Herrero-Martínez, José M; Mongay-Fernández, Carlos; Simó-Alfonso, Ernesto F

    2009-02-01

    Polymeric monolithic stationary phases for capillary electrochromatography were prepared using two bulk monomers, butyl methacrylate (BMA) and lauryl methacrylate (LMA), by in situ polymerization in non-aqueous media. The effect of 1,4-butanediol/1-propanol ratio on porous properties was investigated separately for each monomer, keeping the proportion of monomers to pore-forming solvents fixed at 40:60 wt:wt. Also, mixtures of BMA and LMA at different 1,4-butanediol/1-propanol ratios were studied for tailoring the morphological features of the monolithic columns. The chromatographic performance of the different columns was evaluated by means of van Deemter plots of polycyclic aromatic hydrocarbons. Mercury-intrusion porosimetry, SEM, and nitrogen-adsorption measurements were also performed in order to understand their retention behaviour and porous properties. A comparison of these features was also performed for monoliths made with one bulk monomer (BMA or LMA) and with mixtures of both. These mixed monoliths showed satisfactory efficiencies and analysis times compared with those made with one bulk monomer; thus, the BMA-LMA monoliths constitute an attractive alternative to manipulate the electrochromatographic properties of methacrylate beds in CEC. PMID:19170053

  10. 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.

  11. Polyion complex micellar nanoparticles for integrated fluorometric detection and bacteria inhibition in aqueous media.

    PubMed

    Li, Yamin; Hu, Xianglong; Tian, Sidan; Li, Yang; Zhang, Guoqing; Zhang, Guoying; Liu, Shiyong

    2014-02-01

    The development of portable and inexpensive detection methods can significantly contribute to the prevention of water-borne infectious diseases caused by pathogenic bacteria. Here we designed a nanosystem capable of both bacterial detection and inhibition, where polyion complex (PIC) micelles are constructed from negatively-charged tetraphenylethylene (TPE) sulfonate derivatives, which exhibit the aggregation-induced emission (AIE) feature, and cationic diblock copolymers, poly(ethylene oxide)-b-quaternized poly(2-(dimethylamino)ethyl methacrylate) (PEO-b-PQDMA). Upon contacting with bacteria, the PIC nanosystem disintegrates presumably due to competitive binding of polycation blocks with negatively-charged bacterial surfaces. This process is accompanied by a conspicuous quenching of TPE fluorescence emission, serving as a real-time module for microbial detection. Furthermore, the sharp decrease in CFU is indicative of prominent anti-microbial activities. Thus, PIC micelles possess dual functions of fluorometric detection and inhibition for bacteria in aqueous media. By tuning the charge density of TPE sulfonate derivatives and chain length of cationic PQDMA blocks, optimal performance against Gram-negative Escherichia coli has been achieved with a detection limit of 5.5 × 10(4) CFU/mL and minimum inhibitory concentration (MIC) of 19.7 μg/mL. Tests against Gram-positive Staphylococcus aureus were also conducted to demonstrate versatility of the nanosystem.

  12. Biosorption of acidic textile dyestuffs from aqueous solution by Paecilomyces sp. isolated from acidic mine drainage.

    PubMed

    Çabuk, Ahmet; Aytar, Pınar; Gedikli, Serap; Özel, Yasemin Kevser; Kocabıyık, Erçin

    2013-07-01

    Removal of textile dyestuffs from aqueous solution by biosorption onto a dead fungal biomass isolated from acidic mine drainage in the Çanakkale Region of Turkey was investigated. The fungus was found to be a promising biosorbent and identified as Paecilomyces sp. The optimal conditions for bioremediation were as follows: pH, 2.0; initial dyestuff concentration, 50 mg l(-1) for Reactive Yellow 85 and Reactive Orange 12, and 75 mg l(-1) for Reactive Black 8; biomass dosage, 2 g l(-1) for Reactive Yellow 85, 3 g l(-1) for Reactive Orange 12, 4 g l(-1) for Reactive Black 8; temperature, 25 °C; and agitation rate, 100 rpm. Zeta potential measurements indicated an electrostatic interaction between the binding sites and dye anions. Fourier transform infrared spectroscopy showed that amine, hydroxyl, carbonyl, and amide bonds were involved in the dyestuff biosorption. A toxicity investigation was also carried out before and after the biosorption process. These results showed that the toxicities for the reactive dyestuffs in aqueous solutions after biosorption studies decreased. The Freundlich and Langmuir adsorption models were used for the mathematical description of the biosorption equilibrium, and isotherm constants were evaluated for each dyestuff. Equilibrium data of biosorption of RY85 and RO12 dyestuffs fitted well to both models at the studied concentration and temperature.

  13. Rosmarinic acid content in antidiabetic aqueous extract of Ocimum canum Sims grown in Ghana

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rosmarinic acid (RA) is an important polyphenol that is found in a variety of herbs including Ocimum canum sims (locally called eme or akokobesa in Ghana). Aqueous extracts from the leaves of O.canum are used as an antidiabetic herbal medicine in Ghana. Interestingly, rosmarinic acid content and p...

  14. KINETIC ASPECTS OF CATION-ENHANCED AGGREGATION IN AQUEOUS HUMIC ACIDS. (R822832)

    EPA Science Inventory

    The cation-enhanced formation of hydrophobic domains in aqueous humic acids has been shown to be a slow process, consistent with the evolution and disintegration of humic acid configurations over periods lasting from days to weeks. After the addition of a magnesium salt to a humi...

  15. Self-assembly and foaming properties of fatty acid-lysine aqueous dispersions.

    PubMed

    Novales, Bruno; Riaublanc, Alain; Navailles, Laurence; Houssou, Bérénice Houinsou; Gaillard, Cédric; Nallet, Frédéric; Douliez, Jean-Paul

    2010-04-20

    We report on dispersions of fatty acid-lysine salts in aqueous solutions which are further used to produce foams. The alkyl chain length is varied from dodecyl to stearic. In aqueous solutions, the lysine salt of the dodecyl chain yields an isotropic solution, probably micelles, whereas for longer alkyl chains, vesicles formed but crystallized upon resting at room temperature or when kept at 4 degrees C. Solid-state NMR showed that in vesicles fatty acids are embedded in a lamellar arrangement passing from a gel to a fluid state upon heating; the transition temperature at which it occurs was determined by DSC. Those results are confirmed by small-angle neutron scattering which also give additional information on the bilayer structure. Incredibly stable foams are obtained using the palmitic acid/Lys salt whereas for other alkyl chain length, poor or no foam is formed. We conclude that the foamability is related to the phase behavior in aqueous solution. PMID:20334439

  16. Improvement in Aqueous Solubility of Retinoic Acid Receptor (RAR) Agonists by Bending the Molecular Structure.

    PubMed

    Hiramatsu, Michiaki; Ichikawa, Yuki; Tomoshige, Shusuke; Makishima, Makoto; Muranaka, Atsuya; Uchiyama, Masanobu; Yamaguchi, Takao; Hashimoto, Yuichi; Ishikawa, Minoru

    2016-08-01

    Aqueous solubility is a key requirement for many functional molecules, e. g., drug candidates. Decrease of the partition coefficient (log P) by chemical modification, i.e., introduction of hydrophilic group(s) into molecules, is a classical strategy for improving aqueous solubility. We have been investigating alternative strategies for improving the aqueous solubility of pharmaceutical compounds by disrupting intermolecular interactions. Here, we show that introducing a bend into the molecular structure of retinoic acid receptor (RAR) agonists by changing the substitution pattern from para to meta or ortho dramatically enhances aqueous solubility by up to 890-fold. We found that meta analogs exhibit similar hydrophobicity to the parent para compound, and have lower melting points, supporting the idea that the increase of aqueous solubility was due to decreased intermolecular interactions in the solid state as a result of the structural changes.

  17. Improvement in Aqueous Solubility of Retinoic Acid Receptor (RAR) Agonists by Bending the Molecular Structure.

    PubMed

    Hiramatsu, Michiaki; Ichikawa, Yuki; Tomoshige, Shusuke; Makishima, Makoto; Muranaka, Atsuya; Uchiyama, Masanobu; Yamaguchi, Takao; Hashimoto, Yuichi; Ishikawa, Minoru

    2016-08-01

    Aqueous solubility is a key requirement for many functional molecules, e. g., drug candidates. Decrease of the partition coefficient (log P) by chemical modification, i.e., introduction of hydrophilic group(s) into molecules, is a classical strategy for improving aqueous solubility. We have been investigating alternative strategies for improving the aqueous solubility of pharmaceutical compounds by disrupting intermolecular interactions. Here, we show that introducing a bend into the molecular structure of retinoic acid receptor (RAR) agonists by changing the substitution pattern from para to meta or ortho dramatically enhances aqueous solubility by up to 890-fold. We found that meta analogs exhibit similar hydrophobicity to the parent para compound, and have lower melting points, supporting the idea that the increase of aqueous solubility was due to decreased intermolecular interactions in the solid state as a result of the structural changes. PMID:27378357

  18. Isolation and quantitation of Clostridium difficile in aqueous and fecal matter using two types of selective media.

    PubMed

    Housman, Seth T; Banevicius, Mary Anne; Lamb, Lucinda M; Nicolau, David P

    2016-06-01

    We evaluated the isolation and quantitation of Clostridium difficile from aqueous and fecal samples utilizing ChromID CDIF and cycloserine, cefoxitin, and fructose-containing agar with horse blood and taurocholate media. Growth was similar between the two. ChromID CDIF provided enhanced isolation and required no ethanol pretreatment to inhibit normal flora. ChromID CDIF also improved turn-around time, requiring only 24 hours' incubation.

  19. The Extension of Colloid Chemistry from Aqueous to Non-Aqueous Media with Application to Nanofluid Research

    NASA Astrophysics Data System (ADS)

    Clary, Dan

    Cyclodextrins are cyclic molecules composed of glucose units. The inner cavity of cyclodextrins is noted for its ability to form stable inclusion complexes with a wide variety of guests. A cyclodextrin-glucose host-guest complex was prepared and utilized as both a salt reductant and a particle stabilizer in the generation of aqueous metal colloids including Ag, Au, Pd, and Pt. The resulting colloids demonstrated remarkable stability---3 years and running, in some cases---and have been evaluated for thermal conductivity. Evaluation of the reaction products when the complex is used to reduce Pd 2+ demonstrated a unique comproportionation reaction in which the guest undergoes a two electron oxidation to produce a Pd atom. The resulting atom reduces a neighboring Pd2+ ion to yield two Pd + ions. The monovalent species, in contrast to Pd2+, can then oxidize the host to form atoms which rapidly aggregate to yield particles. Highly stable, crystalline copper(II) oxide particles were prepared which can be isolated as a powder and redispursed in low dielectric media such as hydrocarbons or chloroform. Mass concentrations of up to 20% (1.65 M) were achieved in octane, dodecane, and eicosane and remained stable for at least ten days at room temperature as observed by visible spectroscopy. Quasi-spherical particle shape was observed with the largest fraction possessing a diameter of 9 nm and 90% of the population existing within the range of 5 to 15 nm. The colloidal systems were characterized using FAA, XRD, TEM, UV-Vis, DSC, and a simple device inspired by Newton's Law of cooling which was employed to measure cooling/heating rates. Thermodynamic measurements of sodium oleate-stabilized CuO particles suspended in dodecane and eicosane reveal a decrease in Cp, DeltaH fus , and cooling/heating rates of the resulting colloid with large increases in particle mass concentration. Irradiation with 350 nm photons of anhydrous, air-free octane or toluene solutions of copper(II) oleate

  20. Does excited-state proton-transfer reaction contribute to the emission behaviour of 4-aminophthalimide in aqueous media?

    PubMed

    Khara, Dinesh Chandra; Banerjee, Sanghamitra; Samanta, Anunay

    2014-06-23

    4-Aminophthalimide (AP) is an extensively used molecule both for fundamental studies and applications primarily due to its highly solvent-sensitive fluorescence properties. The fluorescence spectrum of AP in aqueous media was recently shown to be dependent on the excitation wavelength. A time-dependent blue shift of its emission spectrum is also reported. On the basis of these findings, the excited-state solvent-mediated proton-transfer reaction of the molecule, which was proposed once but discarded at a later stage, is reintroduced. We report on the fluorescence behaviour of AP and its imide-H protected derivative, N-BuAP, to prove that a solvent-assisted excited-state keto-enol transformation does not contribute to the steady-state and time-resolved emission behaviour of AP in aqueous media. Our results also reveal that the fluorescence of AP in aqueous media arises from two distinct hydrogen-bonded species. The deuterium isotope effect on the fluorescence quantum yield and lifetime of AP, which was thought to be a reflection of the excited-state proton-transfer reaction in the system, is explained by considering the difference in the influence of H(2)O and D(2)O on the nonradiative rates and ground-state exchange of the proton with the solvent.

  1. Formation of Thioxopyrrolidines and Dithiocarbamates from 4-Methylthio-3-butenyl Isothiocyanates, the Pungent Principle of Radish, in Aqueous Media.

    PubMed

    Matsuoka, H; Toda, Y; Yanagi, K; Takahashi, A; Yoneyama, K; Uda, Y

    1997-01-01

    Reaction products of 4-methylthio-3-butenyl isothiocyanate (MTBI), the radish pungent principle, in aqueous media were identified and their antimicrobial activities were examined. A rapid degradation of MTBI in aqueous media afforded a mixture of 3-(hydroxy)methylene-2-thioxopyrrolidine (1), (Z)-3-(methylthio)-methylene-2-thioxopyrrolidine (2), its (E)-isomer (3), methyl 4-methylthiobutyldithiocarbamate (4), methyl (Z)-4-methylthio-3-butenyldithiocarbarnaie (5), and its (E)-isomer (6). The products 1, 2, and 3 were detected at all pHs examined, while 4, 5, and 6 were formed at pH over 6.0. The formation of 4 from 6 was accompanied by an oxidation of methanethiol released from MTBI in aqueous media. Antimicrobial activities of 2 and 3 against all microbes examined were much lower than that of 1, which had MICs ranging from 50 to 400 μg/ml. As for 4, 5, and 6, antifungal activities were comparable to that of 1, but little antibacterial activities were observed. The antimicrobial activities of the six products were considered to be far lower than that of MTBI.

  2. Staudinger ligation towards cyclodextrin dimers in aqueous/organic media. Synthesis, conformations and guest-encapsulation ability

    PubMed Central

    Manouilidou, Malamatenia D; Lazarou, Yannis G; Mavridis, Irene M

    2014-01-01

    Summary β-Cyclodextrin (β-CD) dimers have been prepared using the bioorthogonal Staudinger ligation for the first time. In addition to a known linker, methyl 2-(diphenylphosphanyl)terephthalate, a doubly active linker was specifically developed that enabled connection of two β-CD units in a single step and in aqueous/organic media, under mild conditions and with good yields. A three-carbon spacer between the β-CD torus and the azido group was required for facile dimer formation. The products, as studied by NMR spectroscopy, were found to adopt closed conformations by intramolecular self-inclusion. On the other hand, association via intermolecular binding was also observed in aqueous solution, confirmed by DOSY NMR experiments. Despite self-inclusion, the β-CD cavities were capable of guest encapsulation, as shown by titration experiments: the binding constant with 1-adamantylamine was similar to that of natural β-CD. Theoretical calculations for isolated molecules (PM3 level of theory) and in the presence of solvent [water, PM3(COSMO)] as well as DFT calculations suggested that the compounds prefer to adopt conformations which bring the phenyl groups either inside the β-CD cavity (inclusion) or over its narrow side (vicinal). Thus, Staudinger ligation could be the method of choice for linking CDs exhibiting (i) ease of preparation in aqueous media, in short steps, under mild conditions and in good yields, (ii) satisfactory aqueous solubility and independent binding capacity of the cavities. PMID:24778732

  3. Ultrasonic degradation of oxalic acid in aqueous solutions.

    PubMed

    Dükkanci, M; Gündüz, G

    2006-09-01

    This paper describes the ultrasonic degradation of oxalic acid. The effects of ultrasonic power, H(2)O(2), NaCl, external gases on the degradation of oxalic acid were investigated. Reactor flask containing oxalic acid was immersed in the ultrasonic bath with water as the coupling fluid. Representative samples withdrawn were analysed by volumetric titration. Degradation degree of oxalic acid increased with increasing ultrasonic power. It was observed that H(2)O(2) has negative contribution on the degradation of oxalic acid and there was an optimum concentration of NaCl for enhancing the degradation degree of oxalic acid. Although bubbling nitrogen gave higher degradation than that for bubbling air, both gases (for 20 min before sonication and during sonication together) could not help to enhance the degradation of oxalic acid when compared with the degradation without gas passage. PMID:16352455

  4. Dissociation of equimolar mixtures of aqueous carboxylic acids in ionic liquids: role of specific interactions.

    PubMed

    Shukla, Shashi Kant; Kumar, Anil

    2015-04-30

    Hammett acidity function observes the effect of protonation/deprotonation on the optical density/absorbance of spectrophotometric indicator. In this work, the Hammett acidity, H0, of equimolar mixtures of aqueous HCOOH, CH3COOH, and CH3CH2COOH was measured in 1-methylimidazolium-, 1-methylpyrrolidinium-, and 1-methylpiperidinium-based protic ionic liquids (PILs) and 1-butyl-3-methylimidazolium-based aprotic ionic liquid (AIL) with formate (HCOO(-)) anion. Higher H0 values were observed for the equimolar mixtures of aqueous carboxylic acids in protic ionic liquids compared with those of the aprotic ionic liquid because of the involvement of the stronger specific interactions between the conjugate acid of ionic liquid and conjugate base of carboxylic acids as suggested by the hard-soft acid base (HSAB) theory. The different H0 values for the equimolar mixtures of aqueous carboxylic acids in protic and aprotic ionic liquids were noted to depend on the activation energy of proton transfer (Ea,H(+)). The higher activation energy of proton transfer was obtained in AIL, indicating lower ability to form specific interactions with solute than that of PILs. Thermodynamic parameters determined by the "indicator overlapping method" further confirmed the involvement of the secondary interactions in the dissociation of carboxylic acids. On the basis of the thermodynamic parameter values, the potential of different ionic liquids in the dissociation of carboxylic acids was observed to depend on the hydrogen bond donor acidity (α) and hydrogen bond acceptor basicity (β), characteristics of specific interactions.

  5. Phosphorylation of glyceric acid in aqueous solution using trimetaphosphate.

    PubMed

    Kolb, V; Orgel, L E

    1996-02-01

    The phosphorylation of glyceric acid is an interesting prebiotic reaction because it converts a simple, potentially prebiotic organic molecule into phosphate derivatives that are central to carbohydrate metabolism. We find that 0.05 M glyceric acid in the presence of 0.5 M trimetaphosphate in alkaline solution gives a mixture of 2- and 3-phosphoglyceric acids in combined yields of up to 40%. PMID:11536746

  6. Phosphorylation of Glyceric Acid in Aqueous Solution Using Trimetaphosphate

    NASA Technical Reports Server (NTRS)

    Kolb, Vera; Orgel, Leslie E.

    1996-01-01

    The phosphorylation of glyceric acid is an interesting prebiotic reaction because it converts a simple, potentially prebiotic organic molecule into phosphate derivatives that are central to carbohydrate metabolism. We find that 0.05 M glyceric acid in the presence of 0.5 M trimetaphosphate in alkaline solution gives a mixture of 2- and 3-phosphoglyceric acids in combined yields of up to 40%.

  7. A theoretical study on the pH dependence of X-ray emission spectra for aqueous acetic acid

    NASA Astrophysics Data System (ADS)

    Nishida, Naohiro; Tokushima, Takashi; Takahashi, Osamu

    2016-04-01

    We performed theoretical calculations to reproduce the site-selective XES spectra for aqueous acetic acid at the oxygen K-edge. The shape of the experimental XES spectra obtained from aqueous acetic acid drastically changed when the pH value was high. Structure sampling of an aqueous acetic acid cluster model was performed by the ab initio molecular dynamics trajectory. Relative XES peak intensities for the core-hole excited state dynamics simulations were calculated using density functional theory. We found that the theoretical XES spectra reproduced well the experimental spectra and that these calculations gave us electronic and molecular structure information about aqueous acetic acid.

  8. Effects of organic acids, amino acids and ethanol on the radio-degradation of patulin in an aqueous model system

    NASA Astrophysics Data System (ADS)

    Yun, Hyejeong; Lim, Sangyong; Jo, Cheorun; Chung, Jinwoo; Kim, Soohyun; Kwon, Joong-Ho; Kim, Dongho

    2008-06-01

    The effects of organic acids, amino acids, and ethanol on the radio-degradation of patulin by gamma irradiation in an aqueous model system were investigated. The patulin, dissolved in distilled water at a concentration of 50 ppm, was practically degraded by the gamma irradiation at the dose of 1.0 kGy, while 33% of the patulin remained in apple juice. In the aqueous model system, the radio-degradation of patulin was partially inhibited by the addition of organic acids, amino acids, and ethanol. The proportions of remaining patulin after irradiation with the dose of 1.0 kGy in the 1% solution of malic acid, citric acid, lactic acid, acetic acid, ascorbic acid, and ethanol were 31.4%, 2.3%, 31.2%, 6.1%, 50.8%, and 12.5%, respectively. During 30 days of storage, the remaining patulin was reduced gradually in the solution of ascorbic acid and malic acid compared to being stable in other samples. The amino acids, serine, threonine, and histidine, inhibited the radio-degradation of patulin. In conclusion, it was suggested that 1 kGy of gamma irradiation (recommended radiation doses for radicidation and/or quarantine in fruits) is effective for the reduction of patulin, but the nutritional elements should be considered because the radio-degradation effects are environment dependent.

  9. Extraction of steroidal glucosiduronic acids from aqueous solutions by anionic liquid ion-exchangers

    PubMed Central

    Mattox, Vernon R.; Litwiller, Robert D.; Goodrich, June E.

    1972-01-01

    A pilot study on the extraction of three steroidal glucosiduronic acids from water into organic solutions of liquid ion-exchangers is reported. A single extraction of a 0.5mm aqueous solution of either 11-deoxycorticosterone 21-glucosiduronic acid or cortisone 21-glucosiduronic acid with 0.1m-tetraheptylammonium chloride in chloroform took more than 99% of the conjugate into the organic phase; under the same conditions, the very polar conjugate, β-cortol 3-glucosiduronic acid, was extracted to the extent of 43%. The presence of a small amount of chloride, acetate, or sulphate ion in the aqueous phase inhibited extraction, but making the aqueous phase 4.0m with ammonium sulphate promoted extraction strongly. An increase in the concentration of ion-exchanger in the organic phase also promoted extraction. The amount of cortisone 21-glucosiduronic acid extracted by tetraheptylammonium chloride over the pH range of 3.9 to 10.7 was essentially constant. Chloroform solutions of a tertiary, a secondary, or a primary amine hydrochloride also will extract cortisone 21-glucosiduronic acid from water. The various liquid ion exchangers will extract steroidal glucosiduronic acid methyl esters from water into chloroform, although less completely than the corresponding free acids. The extraction of the glucosiduronic acids from water by tetraheptylammonium chloride occurs by an ion-exchange process; extraction of the esters does not involve ion exchange. PMID:5075264

  10. Release of nitrous acid and nitrogen dioxide from nitrate photolysis in acidic aqueous solutions.

    PubMed

    Scharko, Nicole K; Berke, Andrew E; Raff, Jonathan D

    2014-10-21

    Nitrate (NO3(-)) is an abundant component of aerosols, boundary layer surface films, and surface water. Photolysis of NO3(-) leads to NO2 and HONO, both of which play important roles in tropospheric ozone and OH production. Field and laboratory studies suggest that NO3¯ photochemistry is a more important source of HONO than once thought, although a mechanistic understanding of the variables controlling this process is lacking. We present results of cavity-enhanced absorption spectroscopy measurements of NO2 and HONO emitted during photodegradation of aqueous NO3(-) under acidic conditions. Nitrous acid is formed in higher quantities at pH 2-4 than expected based on consideration of primary photochemical channels alone. Both experimental and modeled results indicate that the additional HONO is not due to enhanced NO3(-) absorption cross sections or effective quantum yields, but rather to secondary reactions of NO2 in solution. We find that NO2 is more efficiently hydrolyzed in solution when it is generated in situ during NO3(-) photolysis than for the heterogeneous system where mass transfer of gaseous NO2 into bulk solution is prohibitively slow. The presence of nonchromophoric OH scavengers that are naturally present in the environment increases HONO production 4-fold, and therefore play an important role in enhancing daytime HONO formation from NO3(-) photochemistry.

  11. Control of Electrostatic Interactions Between F-Actin And Genetically Modified Lysozyme in Aqueous Media

    SciTech Connect

    Sanders, L.K.; Xian, W.; Guaqueta, C.; Strohman, M.; Vrasich, C.R.; Luijten, E.; Wong, G.C.L.

    2009-06-04

    The aim for deterministic control of the interactions between macroions in aqueous media has motivated widespread experimental and theoretical work. Although it has been well established that like-charged macromolecules can aggregate under the influence of oppositely charged condensing agents, the specific conditions for the stability of such aggregates can only be determined empirically. We examine these conditions, which involve an interplay of electrostatic and osmotic effects, by using a well defined model system composed of F-actin, an anionic rod-like polyelectrolyte, and lysozyme, a cationic globular protein with a charge that can be genetically modified. The structure and stability of actin-lysozyme complexes for different lysozyme charge mutants and salt concentrations are examined by using synchrotron x-ray scattering and molecular dynamics simulations. We provide evidence that supports a structural transition from columnar arrangements of F-actin held together by arrays of lysozyme at the threefold interstitial sites of the actin sublattice to marginally stable complexes in which lysozyme resides at twofold bridging sites between actin. The reduced stability arises from strongly reduced partitioning of salt between the complex and the surrounding solution. Changes in the stability of actin-lysozyme complexes are of biomedical interest because their formation has been reported to contribute to the persistence of airway infections in cystic fibrosis by sequestering antimicrobials such as lysozyme. We present x-ray microscopy results that argue for the existence of actin-lysozyme complexes in cystic fibrosis sputum and demonstrate that, for a wide range of salt conditions, charge-reduced lysozyme is not sequestered in ordered complexes while retaining its bacterial killing activity.

  12. Control of electrostatic interactions between F-actin and genetically modified lysozyme in aqueous media

    SciTech Connect

    Sanders, Lori K.; Xian, Wujing; Guaqueta, Camilo; Strohman, Michael J.; Vrasich, Chuck R.; Luijten, Erik; Wong, Gerard C.L.

    2008-07-11

    The aim for deterministic control of the interactions between macroions in aqueous media has motivated widespread experimental and theoretical work. Although it has been well established that like-charged macromolecules can aggregate under the influence of oppositely charged condensing agents, the specific conditions for the stability of such aggregates can only be determined empirically. We examine these conditions, which involve an interplay of electrostatic and osmotic effects, by using a well defined model system composed of F-actin, an anionic rod-like polyelectrolyte, and lysozyme, a cationic globular protein with a charge that can be genetically modified. The structure and stability of actin-lysozyme complexes for different lysozyme charge mutants and salt concentrations are examined by using synchrotron x-ray scattering and molecular dynamics simulations. We provide evidence that supports a structural transition from columnar arrangements of F-actin held together by arrays of lysozyme at the threefold interstitial sites of the actin sublattice to marginally stable complexes in which lysozyme resides at twofold bridging sites between actin. The reduced stability arises from strongly reduced partitioning of salt between the complex and the surrounding solution. Changes in the stability of actin-lysozyme complexes are of biomedical interest because their formation has been reported to contribute to the persistence of airway infections in cystic fibrosis by sequestering antimicrobials such as lysozyme. We present x-ray microscopy results that argue for the existence of actin-lysozyme complexes in cystic fibrosis sputum and demonstrate that, for a wide range of salt conditions, charge-reduced lysozyme is not sequestered in ordered complexes while retaining its bacterial killing activity.

  13. Modeling reactive geochemical transport of concentrated aqueous solutions in variably saturated media

    SciTech Connect

    Zhang, Guoxiang; Zheng, Zuoping; Wan, Jiamin

    2004-01-28

    Concentrated aqueous solutions (CAS) have unique thermodynamic and physical properties. Chemical components in CAS are incompletely dissociated, especially those containing divalent or polyvalent ions. The problem is further complicated by the interaction between CAS flow processes and the naturally heterogeneous sediments. As the CAS migrates through the porous media, the composition may be altered subject to fluid-rock interactions. To effectively model reactive transport of CAS, we must take into account ion-interaction. A combination of the Pitzer ion-interaction and the ion-association model would be an appropriate way to deal with multiple-component systems if the Pitzer' parameters and thermodynamic data of dissolved components and the related minerals are available. To quantify the complicated coupling of CAS flow and transport, as well as the involved chemical reactions in natural and engineered systems, we have substantially extended an existing reactive biogeochemical transport code, BIO-CORE{sup 2D}{copyright}, by incorporating a comprehensive Pitzer ion-interaction model. In the present paper, the model, and two test cases against measured data were briefly introduced. Finally we present an application to simulate a laboratory column experiment studying the leakage of the high alkaline waste fluid stored in Hanford (a site of the U.S. Department of Energy, located in Washington State, USA). With the Pitzer ion-interaction ionic activity model, our simulation captures measured pH evolution. The simulation indicates that all the reactions controlling the pH evolution, including cation exchanges, mineral precipitation and dissolution, are coupled.

  14. Diglycolamic acid modified silica gel for the separation of hazardous trivalent metal ions from aqueous solution.

    PubMed

    Suneesh, A S; Syamala, K V; Venkatesan, K A; Antony, M P; Vasudeva Rao, P R

    2015-01-15

    The surface of the silica gel was modified with diglycolamic acid moieties and the product (Si-DGAH) was characterized by elemental analysis, TG-DTA, (1)H and (29)Si NMR and scanning electron microscopy (SEM). The adsorption behavior of hazardous americium (III) and europium (III) in Si-DGAH was studied from aqueous nitric acid medium to examine the feasibility using the modified silica for the separation of Am(III) and Eu(III) from aqueous wastes. In this context, the effect of various parameters such as the duration of equilibration, and concentrations of europium, nitric acid, sodium nitrate and diethylenetriaminepentaacetic acid (DTPA) in aqueous phase, on the distribution coefficient (K(d)) of Am(III) and Eu(III) was investigated. The distribution coefficient of ∼10(3) mL/g (>99.9% extraction) was obtained for both Am(III) and Eu(III) at pH 3, and the K(d) values decreased with increase in the concentration of nitric acid. Rapid kinetics of extraction in the initial stages of equilibration, followed by the establishment of equilibrium occurred within 30 min. The extraction data were fitted into Langmuir adsorption model and the apparent europium extraction capacity was determined. Europium loading capacity of the sorbent was determined at various feed pH by column method. The study indicated the possibility of using diglycolamic acid-modified silica for the separation of Eu(III) and Am(III) from aqueous wastes. PMID:25454425

  15. Photocatalytic Oxidation of Sulfurous Acid in an Aqueous Medium

    ERIC Educational Resources Information Center

    Romero, Alicia; Hernandez, Willie; Suarez, Marco F.

    2005-01-01

    The effect of some parameters on sulfurous acid and sulfur oxidation kinetics such as initial concentration of sulfurous acid, oxygen, TiO[2] crystalline concentration, the power of black light, and quantity of TiO[2] is investigated. The experiments can be performed in an undergraduate physical chemistry laboratory with an inexpensive…

  16. Multi-walled carbon nanotubes in aqueous phytic acid for enhancing biosensor

    NASA Astrophysics Data System (ADS)

    Guo, Xiaoyu; Miao, Yun; Ye, Pingping; Wen, Ying; Yang, Haifeng

    2014-04-01

    The poor dispersion of carbon based nanomaterials without strong acid pretreatment in aqueous solution is a fundamental problem, limiting its applications in biology-related fields. A good dispersion of multi-walled carbon nanotubes (MWCNTs) in water was realized by 50 wt.% phytic acid (PA) solution. As an application case, the PA-MWCNTs dispersion in aqueous solution was used for the immobilization of horseradish peroxidase (HRP) and its direct electrochemistry was realized. The constructed biosensor has a sound limit of detection, wide linear range, and high affinity for hydrogen peroxide (H2O2) as well as being free from interference of co-existing electro-active species.

  17. Cr(VI) adsorption on functionalized amorphous and mesoporous silica from aqueous and non-aqueous media

    SciTech Connect

    Perez-Quintanilla, Damian . E-mail: isabel.sierra@urjc.es

    2007-08-07

    A mesoporous silica (SBA-15) and amorphous silica (SG) have been chemically modified with 2-mercaptopyridine using the homogeneous route. This synthetic route involved the reaction of 2-mercaptopyridine with 3-chloropropyltriethoxysilane prior to immobilization on the support. The resulting material has been characterized by powder X-ray diffraction, nitrogen gas sorption, FT-IR and MAS NMR spectroscopy, thermogravimetry and elemental analysis. The solid was employed as a Cr(VI) adsorbent from aqueous and non-aqueous solutions at room temperature. The effect of several variables (stirring time, pH, metal concentration and solvent polarity) has been studied using the batch technique. The results indicate that under the optimum conditions, the maximum adsorption value for Cr(VI) was 1.83 {+-} 0.03 mmol/g for MP-SBA-15, whereas the adsorption capacity of the MP-SG was 0.86 {+-} 0.02 mmol/g. On the basis of these results, it can be concluded that it is possible to modify chemically SBA-15 and SG with 2-mercaptopyridine and to use the resulting modified silicas as effective adsorbents for Cr(VI)

  18. Incorporation of alpha-Ketoglutaric Acid as a Fixed Bed Scrubber Media for the Neutralization of Hydrazine Family Hypergolic Fuels

    NASA Technical Reports Server (NTRS)

    DeVor, R. W.; Santiago-Maldonado, E.; Parkerson, J. K.

    2010-01-01

    A candidate scrubber media, alpha-ketoglutaric acid (aKGA) adsorbed onto a silica-based substrate was examined as a potential alternative to the hydrazine-family hypergolic fuel neutralization techniques currently utilized at NASA/Kennedy Space Center (KSC). Helvenson et. al. has indicated that aKGA will react with hydrazines to produce non-hazardous, possibly biodegradable products. Furthermore, the authors have previously tested and demonstrated the use of aKGA aqueous solutions as a replacement neutralizing agent for citric acid, which is currently used as a scrubbing agent in liquid scrubbers at KSC. Specific properties examined include reaction efficiency, the loading capacity of aKGA onto various silica substrates, and the comparison of aKGA media performance to that of the citric acid vapor scrubber systems at KSC and a commercial vapor scrubber media. Preliminary investigations showed hydrophobic aerogel particles to be an ideal substrate for the deposition of the aKGA. Current studies have shown that the laboratory produced aKGA-Aerogel absorbent media are more efficient and cost effective than a commercially available fixed bed scrubber media, although much less cost effective than liquid-based citric acid scrubbers (although possibly safer and less labor intensive). A comparison of all three alternative scrubber technologies (liquid aKGA, solid-phase aKGA, and commercially available sorbent materials) is given considering both hypergolic neutralization capabilities and relative costs (as compared to the current citric acid scrubbing technology in use at NASA/KSC).

  19. Investigation of the swelling behaviour of hydrogels in aqueous acid or alkaline solutions

    NASA Astrophysics Data System (ADS)

    Althans, Daniel; Enders, Sabine

    2014-09-01

    For development of tailor made drug delivery systems using poly(N-isopropylacrylamide) hydrogels, the influence of acids and bases added to the aqueous solution on the swelling behaviour as function of concentration, temperature and kind of acid or base were investigated experimentally. The selected acids are formic, acetic, propionic, lactic, succinic, α-ketoglutaric and citric acid. The applied bases are sodium and potassium hydroxide. The swelling behaviour was characterised by the degree of swelling and by the uptake of acids by the hydrogel in the swollen state. In the case of weak acids the properties of the swollen hydrogel as well as the phase transition temperature and phase transition acid concentration depends on the type of acids, whereas the properties of the shrunken state do not depend on the acid used. In the case of strong bases, the properties of the shrunken and swollen state depend on the ionic strength, but not on the base applied.

  20. Protein imprinting and recognition via forming nanofilms on microbeads surfaces in aqueous media

    NASA Astrophysics Data System (ADS)

    Lu, Yan; Yan, Chang-Ling; Wang, Xue-Jing; Wang, Gong-Ke

    2009-12-01

    In this paler, we present a technique of forming nanofilms of poly-3-aminophenylboronic acid (pAPBA) on the surfaces of polystyrene (PS) microbeads for proteins (papain and trypsin) in aqueous. Papain was chosen as a model to study the feasibility of the technique and trypsin as an extension. Obtained core-shell microbeads were characterized using scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and BET methods. The results show that pAPBA formed nanofilms (60-100 nm in thickness) on the surfaces of PS microbeads. The specific surface area of the papain-imprinted beads was about 180 m 2 g -1 and its pore size was 31 nm. These imprinted microbeads exhibit high recognition specificity and fast mass transfer kinetics. The specificity of these imprinted beads mainly originates from the spatial effect of imprinted sites. Because the protein-imprinted sites were located at, or close to, the surface, the imprinted beads have good site accessibility toward the template molecules. The facility of the imprinting protocol and the high recognition properties of imprinted microbeads make the approach an attractive solution to problems in the field of biotechnology.

  1. Cooperativity between various types of polar solute-solvent interactions in aqueous media.

    PubMed

    Madeira, Pedro P; Bessa, Ana; Loureiro, Joana A; Álvares-Ribeiro, Luís; Rodrigues, Alírio E; Zaslavsky, Boris Y

    2015-08-21

    Partition coefficients of seven low molecular weight compounds were measured in multiple aqueous two-phase systems (ATPSs) formed by pairs of different polymers. The ionic composition of each ATPS was varied to include 0.01M sodium phosphate buffer (NaPB), pH 7.4 and 0.1M Na2SO4, 0.15M NaCl, and 0.15M NaClO4 all in 0.01M NaPB, pH 7.4. The differences between the solvent features of the coexisting phases in all the ATPSs were estimated from partitioning of a homologous series of dinitrophenylated-amino acids and by the solvatochromic method. The solute-specific coefficients for the compounds examined were determined by the multiple linear regression analysis using the modified linear solvation energy relationship equation. It is established that the solute specific coefficients characterizing different types of the solute-water interactions (dipole-dipole, dipole-ion, and H-bonding) for a given solute change in the presence of different salt additives in the solute specific manner. It is also found that these characteristics are linearly interrelated. It is suggested that there is a cooperativity between various types of solute-water interactions governed by the solute structure.

  2. Surface modifications using a water-stable silanetriol in neutral aqueous media.

    PubMed

    Spirk, Stefan; Ehmann, Heike M; Kargl, Rupert; Hurkes, Natascha; Reischl, Martin; Novak, Jiri; Resel, Roland; Wu, Ming; Pietschnig, Rudolf; Ribitsch, Volker

    2010-10-01

    Surface modifications of glass slides employing the sterically hindered tert-butyl substituted silanetriol are described. To the best of our knowledge, this is the first time that a stable silanetriol has been directly used for this purpose. So far unprecedented, this process runs under neutral aqueous conditions and in the absence of organic solvents, which makes coating protocols accessible to acid-sensitive substrates. The layer thickness and surface topography are investigated by the Sarfus technique, by X-ray reflectivity, and by atomic force microscopy (AFM). These techniques yield values of 0.8±0.1 (XRR) and 0.6±0.2 nm (Sarfus) for layer thickness and 0.33 nm for root mean square roughness (AFM). The modified surfaces have hydrophobic and oleophilic character and contact angles (CA) between 60° (formamide, CH2I2) and 90° (water) are obtained. The thin coatings allow a structuring by UV/ozone treatment in order to get hydrophilic and hydrophobic compartments on the surfaces. For all coatings, surface free energies are calculated using different models. To determine the isoelectric points (IEP) of the modified surfaces, we performed zeta-potential measurements. Correlations between zeta potentials and hydrophilicity of the surfaces are shown.

  3. Morphological and phase evolution of TiO 2 nanocrystals prepared from peroxotitanate complex aqueous solution: Influence of acetic acid

    NASA Astrophysics Data System (ADS)

    Chang, Jeong Ah; Vithal, Muga; Baek, In Chan; Seok, Sang Il

    2009-04-01

    Nanosized anatase and rutile TiO 2 having different shape, phase and size have been prepared from aqueous solutions of peroxo titanium complex starting from titanium(IV) isopropoxide (TTIP), acetic acid and hydrogen peroxide (H 2O 2) in water/isopropanol media by a facile sol-gel process. The TiO 2 nanocrystals are characterized by powder X-ray diffraction (XRD), Raman spectroscopy, FT-IR spectroscopy, TEM, high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) techniques. The influence of pH and the sequence of addition of reaction contents on the phase and morphology of TiO 2 are studied. The reasons for the observation of only anatase and/or mixture of anatase and rutile are given.

  4. Radiolysis of aqueous solutions of 2-aminoethanethiosulfuric acid. [Gamma radiation

    SciTech Connect

    Grachev, S.A.; Koroleva, I.K.; Kropachev, E.V.; Litvyakova, G.I.

    1982-07-10

    In the radiolysis products of aerated and deaerated solutions of the 2-aminoethanethiosulfuric acid the authors have identified cystamine monoxide, cystamine, taurine, mercamine, the sulfate ion, the sulfite ion, and the dithionate ion. The yields of these products under different conditions have been determined. Results indicated that the sulfate ion is formed both from the divalent and the hexavalent sulfur atom of the 2-aminoethanethiosulfuric acid moelcule. A possible radiolysis mechanism is discussed.

  5. Atmospheric Implications of Aqueous Solvation on the Photochemistry of Pyruvic Acid

    NASA Astrophysics Data System (ADS)

    Reed Harris, A. E.; Ervens, B.; Shoemaker, R.; Kroll, J. A.; Rapf, R.; Griffith, E. C.; Monod, A.; Vaida, V.

    2014-12-01

    Formation of aerosol from organic compounds is under investigation in order to better predict the overall radiative forcing from atmospheric aerosols and their influence on global climate. One possible formation pathway for secondary organic aerosol (SOA), which is now becoming more widely accepted, is from bulk aqueous photoreactions in atmospheric particles that create low volatility compounds. These products may remain particulate upon droplet evaporation, increasing SOA mass in the atmosphere. SOA formed in this manner may account for some of the discrepancy between measured and predicted amounts of SOA. This presentation will describe the photochemistry of pyruvic acid, an α-keto acid found in the atmosphere, in aqueous solutions representative of solutes in fogs, clouds, and wet aerosols. Solvation of pyruvic acid in water changes the photodissociation mechanism and products from that of the gas phase. The photoproducts from the aqueous phase are higher in molecular weight and therefore possible SOA precursors. Further, these polymers partition to the surface of water and are expected to modify the the surface properties of atmospheric aerosols that determine the kinetics of water uptake. The reaction mechanism of pyruvic acid as a function of its environment and concentration will be presented along with the kinetics obtained for the photochemistry in aqueous solution. These results are used as input in an atmospheric model to evaluate the atmospheric consequences of solvation of pyruvic acid on its atmospheric reactivity and its role as a global sink.

  6. Histological effects of aqueous acids and gaseous hydrogen chloride on bean leaves

    SciTech Connect

    Swiecki, T.J.; Endress, A.G.; Taylor, O.C.

    1982-01-01

    Primary leaves of Phaseoulus vulgaris L. (pinto bean), 9 or 12 days from sowing, were exposed to aqueous acids, chloride salts, or hydrogen chloride gas. Leaves were examined for the presence and severity of resultant visible injury and samples for light and scanning electron microscopy. Exposure to 0.06 N HCl, HNO/sub 3/, H/sub 2/SO/sub 4/ or 14.5-19.0 mg m/sup -3/ gaseous HCl for 20 min evoked similar foliar injury including glazing and necrosis of the laminas. This injury appeared to result initially from plasmolysis and collapse of the epidermis and subsequently of the underlying mesophyll. Cellular injury was accompanied by various cytoplasmic alterations. Microscopic symptoms observed in leaves exposed to gaseous HCl or aqueous acids included vesicles and particulates within the larger vacuoles. Similar symptoms were present in leaves exposed to polyethylene glycol 6000. Differential effects included formation of necrotic pits and preferential injury to paravascular tissues in leaves treated with aqueous acids and crystalline chloroplast inclusions in gaseous HCl-treated and water-stressed leaves. The visible and microscopic appearances of leaves exposed to aqueous acids or gaseous HCl were compared and related to injury stemming from acid precipitation and a possible mechanism of action for gaseous HCl phytotoxicity.

  7. Dissolution state of cellulose in aqueous systems. 2. Acidic solvents.

    PubMed

    Alves, Luis; Medronho, Bruno; Antunes, Filipe E; Topgaard, Daniel; Lindman, Björn

    2016-10-20

    Cellulose is insoluble in water but can be dissolved in strong acidic or alkaline conditions. How well dissolved cellulose is in solution and how it organizes are key questions often neglected in literature. The typical low pH required for dissolving cellulose in acidic solvents limits the use of typical characterization techniques. In this respect, Polarization Transfer Solid State NMR (PT ssNMR) emerges as a reliable alternative. In this work, combining PT ssNMR, microscopic techniques and X-ray diffraction, a set of different acidic systems (phosphoric acid/water, sulfuric acid/glycerol and zinc chloride/water) is investigated. The studied solvent systems are capable to efficiently dissolve cellulose, although degradation occurs to some extent. PT ssNMR is capable to identify the liquid and solid fractions of cellulose, the degradation products and it is also sensitive to gelation. The materials regenerated from the acidic dopes were found to be highly sensitive to the solvent system and to the presence of amphiphilic additives in solution. PMID:27474617

  8. Protonation and complex formation of 5-sulfosalicylate in NaCl, CaCl2 and MgCl2 aqueous media. Speciation in synthetic seawater.

    PubMed

    Foti, Claudia; Gianguzza, Antonio; Orecchio, Santino; Piazzese, Daniela

    2002-01-01

    The binding capacity of 5-sulfosalicylic acid (ssa) towards cationic macro-components of natural waters has been investigated in different ionic media (NaCl, MgCl2 and CaCl2 aqueous solutions) and in the ionic strength range 0 < or = I < or = 1 mol dm-3. In order to contribute to the speciation of this multi-sites ligand, measurements have been carried out also in a synthetic seawater (SSWE) containing the major components of seawater (Na+, K+, Ca2+, Mg2+, Cl- and SO4(2-)). Measurements have been performed by potentiometry ([H+]-glass electrode), at t = 25 degrees C. A critical analysis on the experimental and literature data is also given.

  9. Aqueous solutions of acidic ionic liquids for enhanced stability of polyoxometalate-carbon supercapacitor electrodes

    NASA Astrophysics Data System (ADS)

    Hu, Chenchen; Zhao, Enbo; Nitta, Naoki; Magasinski, Alexandre; Berdichevsky, Gene; Yushin, Gleb

    2016-09-01

    Nanocomposites based on polyoxometalates (POMs) nanoconfined in microporous carbons have been synthesized and used as electrodes for supercapacitors. The addition of the pseudocapacitance from highly reversible redox reaction of POMs to the electric double-layer capacitance of carbon lead to an increase in specific capacitance of ∼90% at 1 mV s-1. However, high solubility of POM in traditional aqueous electrolytes leads to rapid capacity fading. Here we demonstrate that the use of aqueous solutions of protic ionic liquids (P-IL) as electrolyte instead of aqueous sulfuric acid solutions offers an opportunity to significantly improve POM cycling stability. Virtually no degradation in capacitance was observed in POM-based positive electrode after 10,000 cycles in an asymmetric capacitor with P-IL aqueous electrolyte. As such, POM-based carbon composites may now present a viable solution for enhancing energy density of electrical double layer capacitors (EDLC) based on pure carbon electrodes.

  10. Acid gas treating by aqueous alkanolamines. Annual report, January-December 1994

    SciTech Connect

    Sandall, O.C.; Rinker, E.B.; Ashour, S.

    1994-12-01

    The objective of this work is to investigate the simulateneous absorption or desorption of CO2 and H2S into and from a mixed aqueous amine solvent consisting of methyldiethanolamine (MDEA) and diethanolamine (DEA). In work completed this year the authors have measured the density, viscosity and surface tension of pure MDEA and DEA over a range in temperatures. The diffusivity of N2O was measured in aqueous blends of MDEA and DEA at 50 wt% total amine for various ratios of DEA to MDEA over the temperature range 20 to 80 deg. C. A theoretically-based model has been developed for the correlation of the physical solubility of N2O in aqueous amine solutions. A penetration theory type model which was developed to describe acid gas absorption in aqueous amine solutions was used to carry out a sensitivity analysis for the various parameters affecting the rate of absorption of CO2 in MDEA solutions.

  11. Acid gas absorption in aqueous solutions of mixed amines

    SciTech Connect

    Rinker, E.B.; Ashour, S.S.; Sandall, O.C.

    1996-12-31

    A mass transfer model has been developed to describe the rate of absorption (or desorption) of H{sub 2}S and CO{sub 2} in aqueous blends of a tertiary and a secondary or a primary amine. The model is based on penetration theory, and all significant chemical reactions are incorporated in the model. The reactions are taken to be reversible, with reactions involving only a proton transfer considered to be at equilibrium. The particular amines studied in this research were methyldiethanolamine (MDEA), a tertiary amine, and diethanolamine (DEA), a secondary amine. Key physicochemical data needed in the model, such as diffusion coefficients, kinetic rate constants, and gas solubilities, were measured. Experimental absorption rates of CO{sub 2} and H{sub 2}S were measured in a model gas-liquid contacting device and were compared with model predictions. Experiments were carried out for single amine solutions (both MDEA and DEA) and for amine blends.

  12. Ascorbic acid levels of aqueous humor of dogs after experimental phacoemulsification.

    PubMed

    De Biaggi, Christianni P; Barros, Paulo S M; Silva, Vanessa V; Brooks, Dennis E; Barros, Silvia B M

    2006-01-01

    Phacoemulsification has been successfully employed in humans and animals for lens extraction. This ultrasonic extracapsular surgical technique induces hydroxyl radical formation in the anterior chamber, which accumulates despite irrigation and aspiration. In this paper we determined the total antioxidant status of aqueous humor after phacoemulsification by measuring aqueous humor ascorbic acid levels. Mixed-breed dogs (n = 11; weighing about 10 kg) with normal eyes as determined by slit-lamp biomicroscopy, applanation tonometry, and indirect ophthalmoscopy had phacoemulsification performed in one eye with the other eye used as a control. Samples of aqueous humor were obtained by anterior chamber paracentesis before surgery and at days 1, 2, 3, 7, and 15 after surgery. Total aqueous humor antioxidant status was inferred from the capacity of aqueous humor to inhibit free radical generation by 2,2-azobis (2-amidopropane) chlorine. Ascorbic acid concentrations were measured by high-pressure liquid chromatography with UV detection. Protein content was determined with the biuret reagent. Statistical analysis was performed by anova followed by the paired t-test. Total antioxidant capacity was reduced from 48 to 27 min during the first 24 h with a gradual increase thereafter, remaining statistically lower than the control eye until 7 days postoperatively. Reduced levels of ascorbic acid followed this reduction in antioxidant capacity (from 211 to 99 microm after 24 h), remaining lower than the control eye until 15 days postoperatively. Protein concentration in aqueous humor increased from 0.62 mg/mL to 30.8 mg/mL 24 h after surgery, remaining statistically lower than the control eye until 15 days postoperatively. Paracentesis alone did not significantly alter the parameters measured. These results indicate that after phacoemulsification, the aqueous humor ascorbic acid levels and antioxidant defenses in aqueous humor are reduced, indirectly corroborating free radical

  13. Improvement of extraction capability of magnetic molecularly imprinted polymer beads in aqueous media via dual-phase solvent system.

    PubMed

    Hu, Yuling; Liu, Ruijin; Zhang, Yi; Li, Gongke

    2009-08-15

    In this study, a novel and simple dual-phase solvent system for the improvement of extraction capability of magnetic molecularly imprinted polymer (MIP) beads in aqueous sample was proposed. The method integrated MIP extraction and micro-liquid-liquid extraction (micro-LLE) into only one step. A magnetic MIP beads using atrazine as template was synthesized, and was applied to aqueous media by adding micro-volume of n-hexane to form a co-extraction system. The magnetic MIP beads preferred to suspend in the organic phase, which shielded them from the disturbance of water molecule. The target analytes in the water sample was extracted into the organic phase by micro-LLE and then further bound to the solid-phase of magnetic MIP beads. The beads specificity was significantly improved with the imprinting efficiency of template increasing from 0.5 to 4.4, as compared with that in pure aqueous media. The extraction capacity, equilibration process and cross-selectivity of the MIP dual-phase solvent extraction system were investigated. The proposed method coupled with high-performance liquid chromatography was applied to the analysis of atrazine, simazine, propazine, simetryn, prometryne, ametryn and terbutryn in complicated sample such as tomato, strawberry juice and milk. The method is selective, sensitive and low organic solvent-consuming, and has potential to broaden the range of MIP application in biological and environmental sample.

  14. Dissolution Mechanism of Upconverting AYF4:Yb,Tm (A = Na or K) Nanoparticles in Aqueous Media.

    PubMed

    Lisjak, Darja; Plohl, Olivija; Vidmar, Janja; Majaron, Boris; Ponikvar-Svet, Maja

    2016-08-16

    The dissolution of upconverting AYF4:Yb,Tm (A = Na or K) nanoparticles (UCNPs) in aqueous media was systematically studied. UCNPs with a cubic structure and sizes of between 10 and 33 nm were synthesized solvothermally in ethylene glycol at 200 °C. The UCNPs of both compositions showed an upconversion fluorescence emission characteristic of Tm(3+). The effects of the A cation, the particle size, the temperature, the pH, and the composition of the aqueous medium on the dissolution of the UCNPs were evaluated. The degree of dissolution was determined from the fraction of dissolved fluoride (F(-)) using potentiometry. Unexpectedly, the composition of aqueous media had the most significant effect on the dissolution of the UCNPs. The highest degree of dissolution and rate were measured for the phosphate-buffered saline (PBS), which can be explained by the formation of stable lanthanide compounds with phosphates. The degree of dissolution was much lower in water and in the phthalate buffer, which was attributed to the release of F(-) as a result of the hydrolysis of the UCNPs' surfaces. PMID:27459496

  15. Photoinduced Atom Transfer Radical Polymerization with ppm-Level Cu Catalyst by Visible Light in Aqueous Media.

    PubMed

    Pan, Xiangcheng; Malhotra, Nikhil; Simakova, Antonina; Wang, Zongyu; Konkolewicz, Dominik; Matyjaszewski, Krzysztof

    2015-12-16

    Photoinduced ATRP was successfully performed in aqueous media. Polymerization of oligo(ethylene oxide) methyl ether methacrylate (OEOMA) in the presence of CuBr2 catalyst and tris(2-pyridylmethyl)amine ligand when irradiated with visible light of 392 nm wavelength at 0.9 mW/cm(2) intensity was well controlled. Linear semi-logarithmic kinetic plots and molecular weights increasing with conversion were observed. Polymers of OEOMA were synthesized with low dispersity (Mw/Mn = 1.12) using only 22 ppm of copper catalyst in the presence of excess bromide anions in highly diluted (90% v/v) aqueous media. The effects of copper concentration, salt, and targeted degrees of polymerization were investigated. The polymerization could be directly regulated by external stimulation, i.e., switching the irradiation on/off, with a good retention of chain-end functionality, as proved by clean chain extension of the OEOMA polymers. This new system could enable applications for controlled aqueous radical polymerization due to its low catalyst loading in the absence of any other chemicals. PMID:26634963

  16. Direct synthesis of formic acid from carbon dioxide by hydrogenation in acidic media

    PubMed Central

    Moret, Séverine; Dyson, Paul J.; Laurenczy, Gábor

    2014-01-01

    The chemical transformation of carbon dioxide into useful products becomes increasingly important as CO2 levels in the atmosphere continue to rise as a consequence of human activities. In this article we describe the direct hydrogenation of CO2 into formic acid using a homogeneous ruthenium catalyst, in aqueous solution and in dimethyl sulphoxide (DMSO), without any additives. In water, at 40 °C, 0.2 M formic acid can be obtained under 200 bar, however, in DMSO the same catalyst affords 1.9 M formic acid. In both solvents the catalysts can be reused multiple times without a decrease in activity. Worldwide demand for formic acid continues to grow, especially in the context of a renewable energy hydrogen carrier, and its production from CO2 without base, via the direct catalytic carbon dioxide hydrogenation, is considerably more sustainable than the existing routes. PMID:24886955

  17. Extremophile mediated hydrogen production for hydrogenation of substrates in aqueous media

    NASA Astrophysics Data System (ADS)

    Anjom, Mouzhgun

    Catalytic hydrogenation reactions are pervasive throughout our economy, from production of margarine as food, liquid fuels for transportation and chiral drugs such as L-DOPA. H2 production from non-fossil fuel feedstocks is highly desirable for transition to the "Hydrogen Economy". Also, the rates of hydrogenation reactions that involve a substrate, H 2 gas and a catalyst are often limited by the solubility of H2 in solvent. The present research thus envisioned designing water-soluble catalysts that could effectively utilize biologically produced H2 in a coupled system to hydrogenate substrates in homogeneous mode (two-phase system). Biological production of H2 as an end product or byproduct of the metabolism of organisms that operate under strict anaerobic conditions has been proposed. However, contrary to what was previously observed, Thermotoga neapolitana, belonging to the order of Thermotogales efficiently produces H2 gas under microaerobic conditions (Van Ooteghem et al. 2004). For H2 production by T. neapolitana in the bacterial growth medium (DSM 5068) at an optimum temperature of 70 C, our results in batch mode show that: (1) H2 was produced from glucose though with 16% efficiency, the rest goes to biomass production, (2) H2 gas was produced even when the cultures were inoculated under microaerobic conditions (up to 8% (v/v) O2) suggesting a protective mechanism for one or more [Fe-Fe] hydrogenases in T. neapolitana, (3) H2 production was pH dependent but addition of simple, non-toxic physiological buffering additives such as Methylene succinic acid increased H2 production and (4) H2 production rate varied linearly in the 100--6800 kPa pressure range. We then screened various water-soluble metal catalysts in batch mode and selected the RhCl3.3H2O/TPPTS (TPPTS is a water-soluble ligand) system that achieved 86% hydrogenation of Methylene succinic acid (an olefin) in an aqueous medium pressurized with preformed H2. When water was replaced with the DSM 5068

  18. STABILITY OF MFI ZEOLITE-FILLED PDMS MEMBRANES DURING PERVAPORATIVE ETHANOL RECOVERY FROM AQUEOUS MIXTURES CONTAINING ACETIC ACID

    EPA Science Inventory

    Pervaporation is a potential process for recovering bioethanol produced from biomass fermentation. Fermentation broths contain ethanol, water, and a variety of other compounds, often including carboxylic acids. The effects of acetic acid on long-term pervaporation of aqueous et...

  19. Chemical modification of amino acids by atmospheric-pressure cold plasma in aqueous solution

    NASA Astrophysics Data System (ADS)

    Takai, Eisuke; Kitamura, Tsuyoshi; Kuwabara, Junpei; Ikawa, Satoshi; Yoshizawa, Shunsuke; Shiraki, Kentaro; Kawasaki, Hideya; Arakawa, Ryuichi; Kitano, Katsuhisa

    2014-07-01

    Plasma medicine is an attractive new research area, but the principles of plasma modification of biomolecules in aqueous solution remain elusive. In this study, we investigated the chemical effects of atmospheric-pressure cold plasma on 20 naturally occurring amino acids in aqueous solution. High-resolution mass spectrometry revealed that chemical modifications of 14 amino acids were observed after plasma treatment: (i) hydroxylation and nitration of aromatic rings in tyrosine, phenylalanine and tryptophan; (ii) sulfonation and disulfide linkage formation of thiol groups in cysteine; (iii) sulfoxidation of methionine and (iv) amidation and ring-opening of five-membered rings in histidine and proline. A competitive reaction experiment using 20 amino acids demonstrated that sulfur-containing and aromatic amino acids were preferentially decreased by the plasma treatment. These data provide fundamental information for elucidating the mechanism of protein inactivation for biomedical plasma applications.

  20. Recovery of acetic acid from dilute aqueous solutions using catalytic dehydrative esterification with ethanol.

    PubMed

    Yagyu, Daisuke; Ohishi, Tetsuo; Igarashi, Takeshi; Okumura, Yoshikuni; Nakajo, Tetsuo; Mori, Yuichiro; Kobayashi, Shū

    2013-03-01

    We have developed a direct esterification of aqueous acetic acid with ethanol (molar ratio=1:1) catalyzed by polystyrene-supported or homogeneous sulfonic acids toward the recovery of acetic acid from wastewater in chemical plants. The equilibrium yield was significantly increased by the addition of toluene, which had a high ability to extract ethyl acetate from the aqueous phase. It was shown that low-loading and alkylated polystyrene-supported sulfonic acid efficiently accelerated the reaction. These results suggest that the construction of hydrophobic reaction environments in water was critical in improving the chemical yield. Addition of inorganic salts was also effective for the reaction under not only biphasic conditions (toluene-water) but also toluene-free conditions, because the mutual solubility of ethyl acetate and water was suppressed by the salting-out effect. Among the tested salts, CaCl(2) was found to be the most suitable for this reaction system. PMID:23290939

  1. Comparison of XAD macroporous resins for the concentration of fulvic acid from aqueous solution

    USGS Publications Warehouse

    Aiken, G.R.

    1979-01-01

    Five macroreticular, nonlonlc AmberlHe XAD resins were evaluated for concentration and Isolation of fulvlc acid from aqueous solution. The capacity of each resin for fulvlc acid was measured by both batch and column techniques. Elution efficiencies were determined by desorptlon with 0.1 N NaOH. Highest recoveries were obtained with the acrylic ester resins which proved to be most efficient for both adsorption and elution of fulvlc acid. Compared to the acrylic ester resins, usefulness of the styrene dvlnybenzene resins to remove fulvlc acid is limited because of slow diffusion-controlled adsorption and formation of charge-transfer complexes, which hinders elution. ?? 1979 American Chemical Society.

  2. Non-invasive Technology to Study Local Passivity Breakdown of Metal Alloys in Aqueous Media

    SciTech Connect

    Alan M. Shipley

    2005-03-09

    Little is known about the basic mechanisms of passive oxide breakdown, repair, and localized corrosion of metals. A non-invasive instrument and methods have been developed to study local events and mechanisms that initiate passivity breakdown and subsequent corrosion of metals in aqueous media. The ''difference viewer imaging technique'' (DVIT) is a rapid, real time, non-invasive assay to study metal surfaces in corrosive solutions. It has a spatial resolution of less than 10.0 ?m (1cm x 1cm sample, 1000 x 1000 pixel CCD) to observe initial corrosion processes of the order of seconds. DVIT is a software-controlled video microscopy system and methods to collect and analyze pixel changes in video images. These images are recorded from a digital CCD video camera and frame grabber package using visible light for illumination. The DVIT system detects changes in video images that represent initial corrosive events that lead to passivity breakdown and re-passivation on metal surfaces in situ. This visual technique is easy to use and apply. It compliments other metal surface measurement techniques and can be used simultaneously with them. DVIT has proven to be more sensitive in detecting changes than scanning microelectrode techniques. DVIT is also much easier than other methods to apply and operate. It has the further advantage of providing a real time image of the entire metal surface under study instead of waiting for a microelectrode to scan a number of data points over a sample then plot the results. This project has fulfilled all specifications as outlined in the Department of Energy solicitation responsible for this grant application and award and exceeded a number of the specifications. Applicable Electronics, Inc. now has a marketable instrument and software package available for sale now. Further development of the system will be ongoing as driven by customer needs and discoveries. This technology has immediate applications in corrosion labs to further study

  3. POLYSTYRENE SULFONIC ACID CATALYZED GREENER SYNTHESIS OF HYDRAZONES IN AQUEOUS MEDIUM USING MICROWAVES

    EPA Science Inventory

    An environmentally benign aqueous protocol for the synthesis of cyclic, bi-cyclic, and heterocyclic hydrazones using polystyrene sulfonic acid (PSSA) as a catalyst has been developed; the simple reaction proceeds efficiently in water in the absence of any organic solvent under mi...

  4. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed...

  5. Rosmarinic acid content in antidiabetic aqueous extract from ocimum canum sims in Ghana

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rosmarinic acid (RA) is an important polyphenol that is found in a variety of herbs including Ocimum canum sims (locally called eme or akokobesa in Ghana). Aqueous extracts from the leaves of O. canum are used as an antidiabetic herbal medicine in Ghana. Analytical TLC was used to examine the compos...

  6. Aqueous-phase hydrogenation of acetic acid over transition metal catalysts

    SciTech Connect

    Olcay, Hakan; Xu, Lijun; Xu, Ye; Huber, George

    2010-01-01

    Catalytic hydrogenation of acetic acid to ethanol has been carried out in aqueous phase on several metals, with ruthenium being the most active and selective. DFT calculations suggest that the initial CO bond scission yielding acetyl is the key step and that the intrinsic reactivity of the metals accounts for the observed activity.

  7. THE ROLE OF SELECTED CATIONS IN THE FORMATION OF PSEUDOMICELLES IN AQUEOUS HUMIC ACID (R822832)

    EPA Science Inventory

    The fluorescence intensity enhancement of a pyrene probe in aqueous humic acid solutions was assessed in terms of added lanthanide and thorium cations. Among the trivalent ions it was found that size played a role, with the small Lu3+ ion producing the greatest increase in pyrene...

  8. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed...

  9. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed...

  10. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed...

  11. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed...

  12. Standard enthalpies of formation of α-aminobutyric acid and products of its dissociation in an aqueous solution

    NASA Astrophysics Data System (ADS)

    Lytkin, A. I.; Chernikov, V. V.; Krutova, O. N.

    2016-08-01

    Heats of solution of crystalline α-aminobutyric acid in water and in aqueous solutions of potassium hydroxide at 298.15 K are measured by means of direct calorimetry. Standard enthalpies of formation of the amino acid and products of its dissociation in an aqueous solution are calculated.

  13. The standard enthalpies of formation of crystalline N-(carboxymethyl)aspartic acid and its aqueous solutions

    NASA Astrophysics Data System (ADS)

    Lytkin, A. I.; Chernyavskaya, N. V.; Volkov, A. V.; Nikol'Skii, V. M.

    2007-07-01

    The energy of combustion of N-(carboxymethyl)aspartic acid (CMAA) was determined by bomb calorimetry in oxygen. The standard enthalpies of combustion and formation of crystalline N-(carboxymethyl)aspartic acid were calculated. The heat effects of solution of crystalline CMAA in water and a solution of sodium hydroxide were measured at 298.15 K by direct calorimetry. The standard enthalpies of formation of CMAA and its dissociation products in aqueous solution were determined.

  14. Fe2+ and Fe3+ initiated peroxidation of sonicated and non-sonicated liposomes made of retinal lipids in different aqueous media.

    PubMed

    Fagali, Natalia; Catalá, Angel

    2009-06-01

    Retina is highly susceptible to oxidative damage due to its high content of polyunsaturated fatty acids (PUFAs), mainly docosahexaenoic acid (22:6 n3). Lipid peroxidation process is thought to be involved in many physiological and pathological events. Many model membranes can be used to learn more about issues that cannot be studied in biological membranes. Sonicated liposomes (SL) and non-sonicated liposomes (NSL) prepared with lipids isolated from bovine retina and characterized by dynamic light-scattering, were submitted to lipid peroxidation, under air atmosphere at 22 degrees C, with Fe(2+) or Fe(3+) as initiator, in different aqueous media. Conjugated dienes and trienes, determined by absorption at 234 and 270 nm respectively, and thiobarbituric acid-reactive substances were measured as a function of time. Peroxidation of SL or NSL initiated with 25 microM FeSO(4) in 20mM Tris-HCl pH 7.4 resulted in an increase in TBARS production after a lag phase of 60 min. Incubation of both types of liposomes in water resulted in shortening of the lag phase at 30 min. When lipid peroxidation was performed in 0.15M NaCl, lag phase completely disappeared. On the other hand, FeCl(3) (25 microM) induced a limited production of TBARS only just after 30 min of incubation. When Fe(2+)- or Fe(3+)-lipid peroxidation of both types of liposomes was carried out in water or 0.15M NaCl, formation of conjugated dienes and conjugated trienes were higher than in reactions carried out in 20mM Tris-HCl pH 7.4. Our results established that both liposome types were susceptible to Fe(2+)- and Fe(3+)-initiated lipid peroxidation. However, Fe(2+) showed a clearly enhanced effect on peroxidation rate and steady state concentration of oxidation products. We verified that peroxidation of liposomes made of retinal lipids is affected not only by type of initiator but also by aqueous media. This model constitutes a useful system to study formation of lipid peroxidation intermediaries and products in

  15. Olefin Metathesis in Homogeneous Aqueous Media Catalyzed by Conventional Ruthenium Catalysts

    PubMed Central

    Binder, Joseph B.; Blank, Jacqueline J.; Raines, Ronald T.

    2008-01-01

    Olefin metathesis in aqueous solvents is sought for applications in green chemistry and with the hydrophilic substrates of chemical biology, such as proteins and polysaccharides. Most demonstrations of metathesis in water, however, utilize exotic complexes. We have examined the performance of conventional catalysts in homogeneous water–organic mixtures, finding that the second-generation Hoveyda–Grubbs catalyst has extraordinary efficiency in aqueous dimethoxyethane and aqueous acetone. High (71–95%) conversions are achieved for ring-closing and cross metathesis of a variety of substrates in these solvent systems. PMID:17949009

  16. Degradation of CYANEX 301 in Contact with Nitric Acid Media

    SciTech Connect

    Philippe Marc; Radu Custelcean; Gary S. Groenewold; John R. Klaehn; Dean R. Peterman; Laetitia H. Delmau

    2012-10-01

    The nature of the degradation product obtained upon contacting CYANEX 301 (bis(2,4,4-trimethylpentyl)dithiophosphinic acid) with nitric acid has been elucidated and found to be a disulfide derivative. The first step to the degradation of CYANEX 301 in toluene has been studied using 31P{1H} NMR after being contacted with nitric acid media. The spectrum of the degradation product exhibits a complex multiplet around dP = 80 ppm. A succession of purifications of CYANEX 301 has resulted in single crystals of the acidic form and the corresponding ammonium salt. Unlike the original CYANEX 301, which consists of a complex diastereomeric mixture displaying all possible combinations of chiral orientations at the 2-methyl positions, the purified crystals were shown by single-crystal X-ray diffraction to be racemates, containing 50:50 mixtures of the [R;R] and [S;S] diastereomers. The comparison between the 31P {1H} NMR spectra of the degradation products resulting from the diastereomerically pure CYANEX 301 and the original diastereomeric mixture has elucidated the influence of the isomeric composition on the multiplicity of the 31P {1H} NMR peak. These NMR data indicate the initial degradation leads to a disulfide-bridged condensation product displaying multiple resonances due to phosphorus–phosphorus coupling, which is caused by the inequivalence of the two P atoms as a result of their different chirality. A total of nine different NMR resonances, six of which display phosphorus–phosphorus coupling, could be assigned, and the identity of the peaks corresponding to phosphorus atoms coupled to each other was confirmed by 31P {1H} homodecoupled NMR analysis.

  17. Mechanisms leading to oligomers and SOA through aqueous photooxidation: insights from OH radical oxidation of acetic acid and methylglyoxal

    NASA Astrophysics Data System (ADS)

    Tan, Y.; Lim, Y. B.; Altieri, K. E.; Seitzinger, S. P.; Turpin, B. J.

    2012-01-01

    Previous experiments have demonstrated that the aqueous OH radical oxidation of methylglyoxal produces low volatility products including pyruvate, oxalate and oligomers. These products are found predominantly in the particle phase in the atmosphere, suggesting that methylglyoxal is a precursor of secondary organic aerosol (SOA). Acetic acid plays a central role in the aqueous oxidation of methylglyoxal and it is a ubiquitous product of gas phase photochemistry, making it a potential "aqueous" SOA precursor in its own right. However, the fate of acetic acid upon aqueous-phase oxidation is not well understood. In this research, acetic acid (20 μM-10 mM) was oxidized by OH radicals, and pyruvic acid and methylglyoxal experimental samples were analyzed using new analytical methods, in order to better understand the formation of SOA from acetic acid and methylglyoxal. Glyoxylic, glycolic, and oxalic acids formed from acetic acid and OH radicals. In contrast to the aqueous OH radical oxidation of methylglyoxal, the aqueous OH radical oxidation of acetic acid did not produce succinic acid and oligomers. This suggests that the methylgloxal-derived oligomers do not form through the acid catalyzed esterification pathway proposed previously. Using results from these experiments, radical mechanisms responsible for oligomer formation from methylglyoxal oxidation in clouds and wet aerosols are proposed. The importance of acetic acid/acetate as an SOA precursor is also discussed. We hypothesize that this and similar chemistry is central to the daytime formation of oligomers in wet aerosols.

  18. Perfluorinated alcohols and acids induce coacervation in aqueous solutions of amphiphiles.

    PubMed

    Khaledi, Morteza G; Jenkins, Samuel I; Liang, Shuang

    2013-02-26

    We have discovered that water-miscible perfluorinated alcohols and acids (FA) can induce simple and complex coacervation in aqueous solutions of a wide range of amphiphilic molecules such as synthetic surfactants, phospholipids, and bile salts as well as polyelectrolytes. This unique phenomenon seems to be nearly ubiquitous, especially for complex coacervate systems composed of mixed catanionic amphiphiles. In addition, coacervation and aqueous phase separation were observed over a wide range of surfactants concentrations and for different mole fractions of the oppositely charged amphiphile.

  19. Regeneration of an aqueous solution from an acid gas absorption process by matrix stripping

    DOEpatents

    Rochelle, Gary T.; Oyenekan, Babatunde A.

    2011-03-08

    Carbon dioxide and other acid gases are removed from gaseous streams using aqueous absorption and stripping processes. By replacing the conventional stripper used to regenerate the aqueous solvent and capture the acid gas with a matrix stripping configuration, less energy is consumed. The matrix stripping configuration uses two or more reboiled strippers at different pressures. The rich feed from the absorption equipment is split among the strippers, and partially regenerated solvent from the highest pressure stripper flows to the middle of sequentially lower pressure strippers in a "matrix" pattern. By selecting certain parameters of the matrix stripping configuration such that the total energy required by the strippers to achieve a desired percentage of acid gas removal from the gaseous stream is minimized, further energy savings can be realized.

  20. Degradation of berenil (diminazene aceturate) in acidic aqueous solution.

    PubMed

    Campbell, Michael; Prankerd, Richard J; Davie, Ashley S; Charman, William N

    2004-10-01

    The trypanocide berenil was assessed for chemical stability over the pH range 1-8 at 37 degrees C and 0.2 M ionic strength. It was found to be sufficiently unstable under acid conditions that its therapeutic efficacy is most likely severely compromised when administered orally. At pH 3, the half-life was 35 min, decreasing to 1.5 min at pH 1.75. Reaction rate constants were corrected for the effects of buffer catalysis and were found to range from 2.00 min(-1) at pH 1 to 6.1 x 10(-6) min(-1) at pH 8. The pH-rate profile displayed a region (pH 1-4) where specific acid catalysis was dominant, followed by a transitional region (pH 5-7), and finally a region (pH >7) where uncatalysed degradation was most important. It is recommended that berenil be enteric coated for formulations to be used in treating Third World parasitic diseases. PMID:15482649

  1. Reduction of hexavalent chromium by ascorbic acid in aqueous solutions.

    PubMed

    Xu, Xiang-Rong; Li, Hua-Bin; Li, Xiao-Yan; Gu, Ji-Dong

    2004-11-01

    Hexavalent chromium is a priority pollutant in the USA and many other countries. Reduction of Cr(VI) to Cr(III) is environmentally favorable as the latter species is not toxic to most living organisms and also has a low mobility and bioavailability. Reduction of Cr(VI) by ascorbic acid (vitamin C) as a reductant was studied using potassium dichromate solution as the model pollutant. Effects of concentration of vitamin C, pH, temperature, irradiation and reaction time on the reduction of Cr(VI) were examined. Cr(VI) might be reduced by vitamin C not only in acidic conditions but also in weakly alkaline solutions. The reduction of Cr(VI) by vitamin C might occur not only under irradiation but also in the dark. Vitamin C is an important biological reductant in humans and animals, and not toxic. It is water-soluble and can easily permeate through various types of soils. The results indicate that vitamin C could be used in effective remediation of Cr(VI)-contaminated soils and groundwater in a wide range of pH, with or without sunlight. PMID:15488923

  2. Reduction of hexavalent chromium by ascorbic acid in aqueous solutions.

    PubMed

    Xu, Xiang-Rong; Li, Hua-Bin; Li, Xiao-Yan; Gu, Ji-Dong

    2004-11-01

    Hexavalent chromium is a priority pollutant in the USA and many other countries. Reduction of Cr(VI) to Cr(III) is environmentally favorable as the latter species is not toxic to most living organisms and also has a low mobility and bioavailability. Reduction of Cr(VI) by ascorbic acid (vitamin C) as a reductant was studied using potassium dichromate solution as the model pollutant. Effects of concentration of vitamin C, pH, temperature, irradiation and reaction time on the reduction of Cr(VI) were examined. Cr(VI) might be reduced by vitamin C not only in acidic conditions but also in weakly alkaline solutions. The reduction of Cr(VI) by vitamin C might occur not only under irradiation but also in the dark. Vitamin C is an important biological reductant in humans and animals, and not toxic. It is water-soluble and can easily permeate through various types of soils. The results indicate that vitamin C could be used in effective remediation of Cr(VI)-contaminated soils and groundwater in a wide range of pH, with or without sunlight.

  3. Effect of Humic Acid on Migration, Distribution and Remediation of Dense Non-aqueous Phase Liquids: A laboratory investigation

    NASA Astrophysics Data System (ADS)

    Cheng, Z.; Wu, J.; Xu, H.; Gao, Y.

    2014-12-01

    Over the last decades, dense non-aqueous phase liquids (DNAPLs) contamination in the subsurface increases with the rapid development of oil industry and becomes the focus of many studies. The migration, distribution and remediation efficiency of DNAPLs in the subsurface environment are greatly affected by the solution chemistry besides the physical heterogeneities of aquifers. Humic acid (HA), which is ubiquitous in natural environments, is a surface active substance exhibiting solubility enhancement behavior for hydrophobic organic compounds such as DNAPLs. Here we reported a laboratory investigation to study the effects of HA on the infiltration, immobilization and subsequent recovery of DNAPL in porous media. Tetrachloroethylene (PCE) was selected as the representative DNAPL in this study. Two-dimensional (2-D) sandbox experiments were conducted to investigate the effects of different HA concentrations on the transport, distribution of PCE and the remediation of PCE using surfactant (Tween 80) flushing in a saturated porous media system. The surfactant flushing of PCE was performed after the PCE transport and distribution had reached equilibrium. A light transmission visualization method with charge-coupled device (CCD) camera was adopted to visualize PCE distribution and quantify its saturation. In addition, the experiments were also designed to gather data for the validation of multiphase flow models. Effluent samples were collected to determine dissolved PCE concentrations. PCE solubilization and PCE-water interfacial tension were experimentally determined in aqueous solutions of varying HA concentrations. The experimental results showed that the presence of HA can have a dramatic impact on PCE flow and entrapment, and significantly improved the recovery of PCE during surfactant enhanced aquifer remediation (SEAR). The findings are of use for better understanding of the migration and entrapment of DNAPLs and developing of SEAR technology.

  4. Detoxification of Hg(II) from aqueous and enzyme media: Pristine vs. tailored calcium alginate hydrogels.

    PubMed

    Sarkar, Kangkana; Ansari, Zarina; Sen, Kamalika

    2016-10-01

    Calcium alginate (CA) hydrogels were tailored using phenolic compounds (PC) like, thymol, morin, catechin, hesperidin, during their preparation. The PC incorporated gels show modified surface features as indicated by scanning electron microscopic images (SEM). The rheological studies show that excepting the hesperidin incorporated gels all the other kinds including calcium alginate pristine have similar mechanical strength. The hesperidine incorporated CA gels had the maximum capacity to adsorb Hg. The Freundlich adsorption isotherms show higher values of adsorption capacity for all PC incorporated CA beads than the pristine CA (PCA). The hesperidin incorporated CA gels were found to show the best adsorption condition at neutral pH and an optimum contact time of 2.5h at 25°C. Considering the possibility of ingested Hg detoxification from human alimentary tract, the hesperidin and morin incorporated CA beads were further modified through incorporation of cod liver oil as the digestion time of fat in stomach is higher. In vitro uptake capacities of Hg in pepsin and pancreatin containing enzyme media were studied with hesperidin and morin incorporated beads and their corresponding fat incorporated beads also. In the pepsin medium, there was no uptake by hesperidin and fat-hesperidin incorporated beads, which is possibly due to the higher acidity of the medium. But in pancreatin medium Hg was taken up by both kinds of beads. Morin and morin-fat incorporated beads were efficient to uptake Hg from both the pepsin and pancreatin medium. The tailored CA beads may therefore serve as efficient scaffolds to rescue Hg ingested individuals. PMID:27208797

  5. Gamma-irradiation of malic acid in aqueous solutions. [prebiotic significance

    NASA Technical Reports Server (NTRS)

    Negron-Mendoza, A.; Graff, R. L.; Ponnamperuma, C.

    1980-01-01

    The gamma-irradiation of malic acid in aqueous solutions was studied under initially oxygenated and oxygen-free conditions in an attempt to determine the possible interconversion of malic acid into other carboxylic acids, specifically those associated with Krebs cycle. The effect of dose on product formation of the system was investigated. Gas-liquid chromatography combined with mass spectrometry was used as the principal means of identification of the nonvolatile products. Thin layer chromatography and direct probe mass spectroscopy were also employed. The findings show that a variety of carboxylic acids are formed, with malonic and succinic acids in greatest abundance. These products have all been identified as being formed in the gamma-irradiation of acetic acid, suggesting a common intermediary. Since these molecules fit into a metabolic cycle, it is strongly suggestive that prebiotic pathways provided the basis for biological systems.

  6. Chromatographic characterisation, under highly aqueous conditions, of a molecularly imprinted polymer binding the herbicide 2,4-dichlorophenoxyacetic acid.

    PubMed

    Legido-Quigley, C; Oxelbark, J; De Lorenzi, E; Zurutuza-Elorza, A; Cormack, P A G

    2007-05-15

    The affinity of a 2,4-dichlorophenoxyacetic acid (2,4-D) molecularly imprinted polymer (MIP), which was synthesised directly in an aqueous organic solvent, for its template (2,4-D) was studied and compared with the affinity exhibited by two other reference (control) polymers, NIPA and NIPB, for the same analyte. Zonal chromatography was performed to establish the optimal selectivity, expressed as imprinting factor (IF), under chromatographic conditions more aqueous than those described so far in the literature. Frontal analysis (FA) was performed on columns packed with these polymers, using an optimized mobile phase composed of methanol/phosphate buffer (50/50, v/v), to extract adsorption isotherm data and retrieve binding parameters from the best isotherm model. Surprisingly, the template had comparable and strong affinity for both MIP (K = 3.8x10(4) M(-1)) and NIPA (K = 1.9x10(4) M(-1)), although there was a marked difference in the saturation capacities of selective and non-selective sites, as one would expect for an imprinted polymer. NIPB acts as a true control polymer in the sense that it has relatively low affinity for the template (K = 8.0x10(2) M(-1)). This work provides the first frontal chromatographic characterization of such a polymer in a water-rich environment over a wide concentration range. The significance of this work stems from the fact that the chromatographic approach used is generic and can be applied readily to other analytes, but also because there is an increasing demand for well-characterised imprinted materials that function effectively in aqueous media and are thus well-suited for analytical science applications involving, for example, biofluids and environmental water samples.

  7. Impact of polymers on the crystallization and phase transition kinetics of amorphous nifedipine during dissolution in aqueous media.

    PubMed

    Raina, Shweta A; Alonzo, David E; Zhang, Geoff G Z; Gao, Yi; Taylor, Lynne S

    2014-10-01

    The commercial and clinical success of amorphous solid dispersions (ASD) in overcoming the low bioavailability of poorly soluble molecules has generated momentum among pharmaceutical scientists to advance the fundamental understanding of these complex systems. A major limitation of these formulations stems from the propensity of amorphous solids to crystallize upon exposure to aqueous media. This study was specifically focused on developing analytical techniques to evaluate the impact of polymers on the crystallization behavior during dissolution, which is critical in designing effective amorphous formulations. In the study, the crystallization and polymorphic conversions of a model compound, nifedipine, were explored in the absence and presence of polyvinylpyrrolidone (PVP), hydroxypropylmethyl cellulose (HPMC), and HPMC-acetate succinate (HPMC-AS). A combination of analytical approaches including Raman spectroscopy, polarized light microscopy, and chemometric techniques such as multivariate curve resolution (MCR) were used to evaluate the kinetics of crystallization and polymorphic transitions as well as to identify the primary route of crystallization, i.e., whether crystallization took place in the dissolving solid matrix or from the supersaturated solutions generated during dissolution. Pure amorphous nifedipine, when exposed to aqueous media, was found to crystallize rapidly from the amorphous matrix, even when polymers were present in the dissolution medium. Matrix crystallization was avoided when amorphous solid dispersions were prepared, however, crystallization from the solution phase was rapid. MCR was found to be an excellent data processing technique to deconvolute the complex phase transition behavior of nifedipine.

  8. Transport of cerium oxide nanoparticles in saturated silica media: influences of operational parameters and aqueous chemical conditions

    PubMed Central

    Zhang, Zhaohan; Gao, Peng; Qiu, Ye; Liu, Guohong; Feng, Yujie; Wiesner, Mark

    2016-01-01

    This paper aimed to investigate the influences of operational parameters and aqueous chemical conditions on transport behaviors of cerium oxides nanoparticles (CeO2-NPs) in saturated silica media. Results indicated that increasing rates of attachment efficiency (α) were related with cationic types, and critical deposition concentration (CDC) for divalent cation (Ca2+ and Mg2+) were more than 31-fold of that for monovalent cation (Na+ and K+). Increase or reduction of electrolyte pH could both promote the mobility of CeO2-NPs in glass beads, while influence was more evident at alkaline conditions. α increased linearly with NPs concentrations, while decreased linearly with flow velocity in the column, and effects were related with electrolyte contents. Presence of surfactants could sharply decreased α, and SDS was more effective to facilitate CeO2-NPs transport than Triton X–100. With DOMs concentrations increasing, α firstly kept constant, then sharply declined, and finally reduced very slowly. The influence of DOMs on NPs deposition was in order of SA > HA > TA >  BSA. Overall, this study revealed that aqueous chemical conditions was crucial to NPs transport in porous media, and would provide significant information for our understanding on the fate and transport of nanoparticles in natural environment. PMID:27694968

  9. Transport of cerium oxide nanoparticles in saturated silica media: influences of operational parameters and aqueous chemical conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaohan; Gao, Peng; Qiu, Ye; Liu, Guohong; Feng, Yujie; Wiesner, Mark

    2016-10-01

    This paper aimed to investigate the influences of operational parameters and aqueous chemical conditions on transport behaviors of cerium oxides nanoparticles (CeO2-NPs) in saturated silica media. Results indicated that increasing rates of attachment efficiency (α) were related with cationic types, and critical deposition concentration (CDC) for divalent cation (Ca2+ and Mg2+) were more than 31-fold of that for monovalent cation (Na+ and K+). Increase or reduction of electrolyte pH could both promote the mobility of CeO2-NPs in glass beads, while influence was more evident at alkaline conditions. α increased linearly with NPs concentrations, while decreased linearly with flow velocity in the column, and effects were related with electrolyte contents. Presence of surfactants could sharply decreased α, and SDS was more effective to facilitate CeO2-NPs transport than Triton X–100. With DOMs concentrations increasing, α firstly kept constant, then sharply declined, and finally reduced very slowly. The influence of DOMs on NPs deposition was in order of SA > HA > TA >  BSA. Overall, this study revealed that aqueous chemical conditions was crucial to NPs transport in porous media, and would provide significant information for our understanding on the fate and transport of nanoparticles in natural environment.

  10. New ceramics incorporated with industrial by-products as pore formers for sorption of toxic chromium from aqueous media

    NASA Astrophysics Data System (ADS)

    Domopoulou, Asimina; Spiliotis, Xenofon; Baklavaridis, Apostolos; Papapolymerou, George; Karayannis, Vayos

    2015-04-01

    The incorporation of secondary resources including various industrial wastes as pore-forming agents into clayey raw material mixtures for the development of tailored porous ceramic microstructures is currently of increasing interest. In the present research, sintered ceramic compacts were developed incorporated with industrial solid by-products as pore formers, and then used as new sorbents for chromium removal from aqueous media. The microstructures obtained were characterized through X-ray diffraction (XRD) analysis as well as scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectrometry (EDX). Sorption potential of chromium from synthetic solutions on the porous ceramics was studied by static adsorption experiments as a function of the pore-former percentage in the ceramic matrix as well as the initial heavy metal (chromium) concentration, solution pH and temperature. Kinetic studies were conducted and adsorption isotherms of chromium were determined using the Langmuir equation. Preliminary experimental results concerning the adsorption characteristics of chromium on the ceramic materials produced appear encouraging for their possible beneficial use as new sorbents for the removal of toxic chromium from aqueous media. Keywords: sorbents, ceramics, industrial solid by-products, pore former, chromium. Acknowledgements: This research has been co-financed by the European Union (European Social Fund - ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program ARCHIMEDES III: Investing in knowledge society through the European Social Fund.

  11. New ceramics incorporated with industrial by-products as pore formers for sorption of toxic chromium from aqueous media

    NASA Astrophysics Data System (ADS)

    Domopoulou, Artemi

    2015-04-01

    The incorporation of secondary resources including various industrial wastes as pore-forming agents into clayey raw material mixtures for the development of tailored porous ceramic microstructures is currently of increasing interest. In the present research, sintered ceramic compacts were developed incorporated with industrial solid by-products as pore formers, and then used as new sorbents for chromium removal from aqueous media. The microstructures obtained were characterized through X-ray diffraction (XRD) analysis as well as scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectrometry (EDX). Sorption potential of chromium from synthetic solutions on the porous ceramics was studied by static adsorption experiments as a function of the pore-former percentage in the ceramic matrix as well as the initial heavy metal (chromium) concentration, solution pH and temperature. Kinetic studies were conducted and adsorption isotherms of chromium were determined using the Langmuir equation. Preliminary experimental results concerning the adsorption characteristics of chromium on the ceramic materials produced appear encouraging for their possible beneficial use as new sorbents for the removal of toxic chromium from aqueous media. Keywords: sorbents, ceramics, industrial solid by-products, pore-former, chromium. Acknowledgements: This research has been co-financed by the European Union (European Social Fund - ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program ARCHIMEDES III: Investing in knowledge society through the European Social Fund.

  12. Crystalline Metaphosphate Acid Salts: Synthesis in Organic Media, Structures, Hydrogen-Bonding Capability, and Implication of Superacidity.

    PubMed

    Chakarawet, Khetpakorn; Knopf, Ioana; Nava, Matthew; Jiang, Yanfeng; Stauber, Julia M; Cummins, Christopher C

    2016-06-20

    Metaphosphate acids cannot be thoroughly studied in aqueous media because their acidity is leveled by the solvent, and the resulting metaphosphates are susceptible to acid-catalyzed hydrolysis. Exploration of metaphosphate acid chemistry has now been made possible with the development of a general synthetic method for organic media soluble metaphosphate acids. Protonation of the [PPN](+) salts ([PPN](+) = [N(PPh3)2](+)) of tri-, tetra-, and hexametaphosphates results in five new metaphosphate acids, [PPN]2[P3O9H] (2), [PPN]4[(P4O12)3H8] (3), [PPN]4[P6O18H2]·2H2O (4), [PPN]3[P6O18H3] (5), and [PPN]2[P6O18H2(H3O)2] (6), obtained in yields of 80, 71, 66, 88, and 76%, respectively. Additionally, our synthetic method can be extended to pyrophosphate to produce [PPN][P2O7H3] (7) in 77% yield. The structural configurations of these oxoacids are dictated by strong hydrogen bonds and the anticooperative effect. Intramolecular hydrogen bonds are observed in 2, 4, and 5 and the previously reported [PPN]2[P4O12H2] (1), while intermolecular hydrogen bonds are observed in 3, 6, and 7. The hydrogen bonds in 3-7 possess short distances and are classified as low-barrier hydrogen bonds. Gas-phase acidity computations reveal that the parent tri- and tetrametaphosphoric acids are superacids. Their remarkable acidity is attributable to the stabilization of their corresponding conjugate bases via intramolecular hydrogen bonding. PMID:27267865

  13. Crystalline Metaphosphate Acid Salts: Synthesis in Organic Media, Structures, Hydrogen-Bonding Capability, and Implication of Superacidity.

    PubMed

    Chakarawet, Khetpakorn; Knopf, Ioana; Nava, Matthew; Jiang, Yanfeng; Stauber, Julia M; Cummins, Christopher C

    2016-06-20

    Metaphosphate acids cannot be thoroughly studied in aqueous media because their acidity is leveled by the solvent, and the resulting metaphosphates are susceptible to acid-catalyzed hydrolysis. Exploration of metaphosphate acid chemistry has now been made possible with the development of a general synthetic method for organic media soluble metaphosphate acids. Protonation of the [PPN](+) salts ([PPN](+) = [N(PPh3)2](+)) of tri-, tetra-, and hexametaphosphates results in five new metaphosphate acids, [PPN]2[P3O9H] (2), [PPN]4[(P4O12)3H8] (3), [PPN]4[P6O18H2]·2H2O (4), [PPN]3[P6O18H3] (5), and [PPN]2[P6O18H2(H3O)2] (6), obtained in yields of 80, 71, 66, 88, and 76%, respectively. Additionally, our synthetic method can be extended to pyrophosphate to produce [PPN][P2O7H3] (7) in 77% yield. The structural configurations of these oxoacids are dictated by strong hydrogen bonds and the anticooperative effect. Intramolecular hydrogen bonds are observed in 2, 4, and 5 and the previously reported [PPN]2[P4O12H2] (1), while intermolecular hydrogen bonds are observed in 3, 6, and 7. The hydrogen bonds in 3-7 possess short distances and are classified as low-barrier hydrogen bonds. Gas-phase acidity computations reveal that the parent tri- and tetrametaphosphoric acids are superacids. Their remarkable acidity is attributable to the stabilization of their corresponding conjugate bases via intramolecular hydrogen bonding.

  14. [Catalytic ozonation by ceramic honeycomb for the degradation of oxalic acid in aqueous solution].

    PubMed

    Zhao, Lei; Sun, Zhi-Zhong; Ma, Jun

    2007-11-01

    Comparative experiments for the degradation of oxalic acid in aqueous solution were carried out in the three processes of ozonation alone, ceramic honeycomb-catalyzed ozonation and ceramic honeycomb adsorption. The results show that the degradation rates of oxalic acid in the ceramic honeycomb-catalyzed ozonation, ozonation alone and ceramic honeycomb adsorption systems are 37.6%, 2.2% and 0.4%, and the presence of ceramic honeycomb catalyst significantly improves the degradation rate of oxalic acid compared to the results from non-catalytic ozonation and adsorption. With the addition of tert-butanol, the degradation rates of oxalic acid in catalytic ozonation system decrease by 24.1%, 29.0% and 30.1%, respectively, at the concentration of 5, 10 and 15 mg x L(-1). This phenomenon indicates that ceramic honeycomb-catalyzed ozonation for the degradation of oxalic acid in aqueous solution follows the mechanism of *OH oxidation, namely the heterogeneous surface of catalyst enhances the initiation of *OH. The results of TOC analysis demonstrate that the process of ceramic honeycomb-catalyzed ozonation can achieve the complete mineralization level without the formation of intermediary degradation products. The experimental results suggest that the reaction temperature has positive relationship with the degradation rate of oxalic acid. The degradation rates of oxalic acid in the ceramic honeycomb-catalyzed ozonation system are 16.4%, 37.6%, 61.3% and 68.2%, at the respective reaction temperature of 10, 20, 30 and 40 degrees C.

  15. Conversion of Aqueous Ammonia-Treated Corn Stover to Lactic Acid by Simultaneous Saccharification and Cofermentation

    NASA Astrophysics Data System (ADS)

    Zhu, Yongming; Lee, Y. Y.; Elander, Richard T.

    Treatment of corn stover with aqueous ammonia removes most of the structural lignin, whereas retaining the majority of the carbohydrates in the solids. After treatment, both the cellulose and hemicellulose in corn stover become highly susceptible to enzymatic digestion. In this study, corn stover treated by aqueous ammonia was investigated as the substrate for lactic acid production by simultaneous saccharification and cofermentation (SSCF). A commercial cellulase (Spezyme-CP) and Lactobacillus pentosus American Type Culture Collection (ATCC) 8041 (Spanish Type Culture Collection [CECT]-4023) were used for hydrolysis and fermentation, respectively. In batch SSCF operation, the carbohydrates in the treated corn stover were converted to lactic acid with high yields, the maximum lactic acid yield reaching 92% of the stoichiometric maximum based on total fermentable carbohydrates (glucose, xylose, and arabinose). A small amount of acetic acid was also produced from pentoses through the phosphoketolase pathway. Among the major process variables for batch SSCF, enzyme loading and the amount of yeast extract were found to be the key factors affecting lactic acid production. Further tests on nutrients indicated that corn steep liquor could be substituted for yeast extract as a nitrogen source to achieve the same lactic acid yield. Fed-batch operation of the SSCF was beneficial in raising the concentration of lactic acid to a maximum value of 75.0 g/L.

  16. Peptidic ligands to control the three-dimensional self-assembly of quantum rods in aqueous media.

    PubMed

    Bizien, Thomas; Even-Hernandez, Pascale; Postic, Marie; Mazari, Elsa; Chevance, Soizic; Bondon, Arnaud; Hamon, Cyrille; Troadec, David; Largeau, Ludovic; Dupuis, Christophe; Gosse, Charlie; Artzner, Franck; Marchi, Valérie

    2014-09-24

    The use of peptidic ligands is validated as a generic chemical platform allowing one to finely control the organization in solid phase of semiconductor nanorods originally dispersed in an aqueous media. An original method to generate, on a macroscopic scale and with the desired geometry, three-dimensional supracrystals composed of quantum rods is introduced. In a first step, nanorods are transferred in an aqueous phase thanks to the substitution of the original capping layer by peptidic ligands. Infrared and nuclear magnetic resonance spectroscopy data prove that the exchange is complete; fluorescence spectroscopy demonstrates that the emitter optical properties are not significantly altered; electrophoresis and dynamic light scattering experiments assess the good colloidal stability of the resulting aqueous suspension. In a second step, water evaporation in a microstructured environment yields superstructures with a chosen geometry and in which nanorods obey a smectic B arrangement, as shown by electron microscopy. Incidentally, bulk drying in a capillary tube generates a similar local order, as evidenced by small angle X-ray scattering.

  17. Pretreatment of rice straw with combined process using dilute sulfuric acid and aqueous ammonia

    PubMed Central

    2013-01-01

    Background Use of lignocellulosic biomass has received attention lately because it can be converted into various versatile chemical compounds by biological processes. In this study, a two-step pretreatment with dilute sulfuric acid and aqueous ammonia was performed efficiently on rice straw to obtain fermentable sugar. The soaking in aqueous ammonia process was also optimized by a statistical method. Results Response surface methodology was employed. The determination coefficient (R2) value was found to be 0.9607 and the coefficient of variance was 6.77. The optimal pretreatment conditions were a temperature of 42.75°C, an aqueous ammonia concentration of 20.93%, and a reaction time of 48 h. The optimal enzyme concentration for saccharification was 30 filter paper units. The crystallinity index was approximately 60.23% and the Fourier transform infrared results showed the distinct peaks of glucan. Ethanol production using Saccharomyces cerevisiae K35 was performed to verify whether the glucose saccharified from rice straw was fermentable. Conclusions The combined pretreatment using dilute sulfuric acid and aqueous ammonia on rice straw efficiently yielded fermentable sugar and achieved almost the same crystallinity index as that of α-cellulose. PMID:23898802

  18. Hydrometallurgical process for the recovery of metal values from spent lithium-ion batteries in citric acid media.

    PubMed

    Chen, Xiangping; Zhou, Tao

    2014-11-01

    In this paper, a hydrometallurgical process has been proposed to recover valuable metals from spent lithium-ion batteries in citric acid media. Leaching efficiencies as high as 97%, 95%, 94%, and 99% of Ni, Co, Mn, and Li were achieved under the optimal leaching experimental conditions of citric acid concentration of 2 mol L(-1), leaching temperature of 80 °C, leaching time of 90 min, liquid-solid ratio of 30 ml g(-1), and 2 vol. % H2O2. For the metals recovery process, nickel and cobalt were selectively precipitated by dimethylglyoxime reagent and ammonium oxalate sequentially. Then manganese was extracted by Na-D2EHPA and the manganese-loaded D2EHPA was stripped with sulfuric acid. The manganese was recovered as MnSO4 in aqueous phase and D2EHPA could be reused after saponification. Finally, lithium was precipitated by 0.5 mol L(-1) sodium phosphate. Under their optimal conditions, the recovery percentages of Ni, Co, Mn, and Li can reach 98%, 97%, 98%, and 89%, respectively. This is a relatively simple route in which all metal values could be effectively leached and recovered in citric acid media.

  19. Hydrometallurgical process for the recovery of metal values from spent lithium-ion batteries in citric acid media.

    PubMed

    Chen, Xiangping; Zhou, Tao

    2014-11-01

    In this paper, a hydrometallurgical process has been proposed to recover valuable metals from spent lithium-ion batteries in citric acid media. Leaching efficiencies as high as 97%, 95%, 94%, and 99% of Ni, Co, Mn, and Li were achieved under the optimal leaching experimental conditions of citric acid concentration of 2 mol L(-1), leaching temperature of 80 °C, leaching time of 90 min, liquid-solid ratio of 30 ml g(-1), and 2 vol. % H2O2. For the metals recovery process, nickel and cobalt were selectively precipitated by dimethylglyoxime reagent and ammonium oxalate sequentially. Then manganese was extracted by Na-D2EHPA and the manganese-loaded D2EHPA was stripped with sulfuric acid. The manganese was recovered as MnSO4 in aqueous phase and D2EHPA could be reused after saponification. Finally, lithium was precipitated by 0.5 mol L(-1) sodium phosphate. Under their optimal conditions, the recovery percentages of Ni, Co, Mn, and Li can reach 98%, 97%, 98%, and 89%, respectively. This is a relatively simple route in which all metal values could be effectively leached and recovered in citric acid media. PMID:25378255

  20. Crystallization and immersion freezing ability of oxalic and succinic acid in multicomponent aqueous organic aerosol particles

    NASA Astrophysics Data System (ADS)

    Wagner, Robert; Höhler, Kristina; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin

    2015-04-01

    This study reports on heterogeneous ice nucleation efficiency of immersed oxalic and succinic acid crystals in the temperature range from 245 to 215 K, as investigated with expansion cooling experiments using suspended particles. In contrast to previous laboratory work with emulsified solution droplets where the precipitation of solid inclusions required a preceding freezing/evaporation cycle, we show that immersed solids readily form by homogeneous crystallization within aqueous solution droplets of multicomponent organic mixtures, which have noneutonic compositions with an excess of oxalic or succinic acid. Whereas succinic acid crystals did not act as heterogeneous ice nuclei, immersion freezing by oxalic acid dihydrate crystals led to a reduction of the ice saturation ratio at freezing onset by 0.066-0.072 compared to homogeneous freezing, which is by a factor of 2 higher than previously reported laboratory data. These observations emphasize the importance of oxalic acid in heterogeneous ice nucleation.

  1. Safety and efficacy evaluation of aqueous citric acid to degrade B-aflatoxins in maize.

    PubMed

    Méndez-Albores, A; Arámbula-Villa, G; Loarca-Piña, M G F; Castaño-Tostado, E; Moreno-Martínez, E

    2005-02-01

    Chemical inactivation of aflatoxin B1 (AFB1) and aflatoxin B2 (AFB2) in maize grain by means of 1N aqueous citric acid was confirmed by the AFLATEST immunoaffinity column method, high performance liquid chromatography (HPLC), and the Ames test (Salmonella-microsomal screening system). The AFLATEST assay showed that aflatoxins in the maize grain with an initial concentration of 29 ng/g were completely degraded and 96.7% degradation occurred in maize contaminated with 93 ng/g when treated with the aqueous citric acid. Aflatoxin fluorescence strength of acidified samples was much weaker than untreated samples as observed in HPLC chromatograms. On the other hand, the Ames test results indicated that the mutagenic activity of acidified samples was greatly reduced compared with that of untreated samples based on his- --> his+ reversions in the Salmonella TA100 strain. Chemical inactivation appears to be a promising method of removing aflatoxin from food commodities.

  2. Ultrasonic Studies of 4-Aminobutyric Acid in Aqueous Metformin Hydrochloride Solutions at Different Temperatures

    NASA Astrophysics Data System (ADS)

    Rajagopal, K.; Jayabalakrishnan, S. S.

    2010-12-01

    Ultrasonic speeds and density data of 4-aminobutyric acid in 0.05 M, 0.10 M, and 0.15 M aqueous metformin hydrochloride (MFHCl) solutions are measured at 308.15 K, 313.15 K, and 318.15 K. The isentropic compressibility ( k S ), the change in isentropic compressibility (Δ k S ), the relative change in isentropic compressibility ({Δ k_S/k_S^0}), the apparent molal compressibility ({k_φ}), the limiting apparent molal compressibility ({k_φ^0 }), the transfer limiting apparent molal compressibility ({Δ k_φ^0}), the hydration number ( n H), and the pair and triplet interaction parameters ( k AH, k AHH) are estimated. The above parameters are used to interpret the solute-solute and solute-solvent interactions of 4-aminobutyric acid in aqueous MFHCl solutions.

  3. Acidity and hydrogen exchange dynamics of iron(II)-bound nitroxyl in aqueous solution.

    PubMed

    Gao, Yin; Toubaei, Abouzar; Kong, Xianqi; Wu, Gang

    2014-10-20

    Nitroxyl-iron(II) (HNO-Fe(II)) complexes are often unstable in aqueous solution, thus making them very difficult to study. Consequently, many fundamental chemical properties of Fe(II)-bound HNO have remained unknown. Using a comprehensive multinuclear ((1)H, (15)N, (17)O) NMR approach, the acidity of the Fe(II)-bound HNO in [Fe(CN)5(HNO)](3-) was investigated and its pK(a) value was determined to be greater than 11. Additionally, HNO undergoes rapid hydrogen exchange with water in aqueous solution and this exchange process is catalyzed by both acid and base. The hydrogen exchange dynamics for the Fe(II)-bound HNO have been characterized and the obtained benchmark values, when combined with the literature data on proteins, reveal that the rate of hydrogen exchange for the Fe(II)-bound HNO in the interior of globin proteins is reduced by a factor of 10(6). PMID:25205463

  4. Effective Removal of Tetracycline from Aqueous Solution by Organic Acid-Coated Magnetic Nanoparticles.

    PubMed

    Guo, Liang; Liang, Yuyan; Chen, Xuelan; Xu, Wei; Wu, Kesheng; Wei, Hua; Xiong, Yonghua

    2016-03-01

    Self-assembled iron oxide nanocomposites are good magnetic nano-adsorbents that can be prepared using simple methods. Four types of organic acid-functionalised (oleic acid, undecenoic acid, caprylic acid or hexanoic acid) magnetic nanoparticles (MNPs) were synthesised through a one-pot chemisorption method for the removal of tetracycline (TC) from aqueous solution. The undecenoic acid-coated MNPs (UA-MNPs) exhibited the highest adsorption efficiency and can be easily retrieved with a low-gradient magnetic separator (0.4 Tesla) at pH 5.0 aqueous solution. The TC adsorption process on the UA-MNPs followed the Langmuir isotherm and the maximum adsorption capacities increased from 86.96 mg g(-1) to 222.2 mg g(-1) with the increase in temperature from 288 K to 318 K. The kinetics of adsorption fits pseudo-second-order model perfectly with a rate constant, 5.946 g mg(-1) min(-1) at 298 K. The positive values of the enthalpy (AH) and the negative value of the free energy (AG) indicated an endothermic and spontaneous adsorption process of TC on the UA-MNPs. Moreover, the UA-MNPs possessed excellent ability to adsorb the other three major types of TC antibiotics, including chlortetracycline, oxytetracycline and doxycycline. PMID:27455621

  5. Humic Acid Effects on the Transport of Colloidal Particles in Unsaturated Porous Media: Humic Acid Dosage, pH, and Ionic Strength Dependence

    NASA Astrophysics Data System (ADS)

    Morales, V. L.; Gao, B.; Steenhuis, T. S.

    2008-12-01

    experiments to obtain effluent breakthrough data, in-situ visualization of internal processes with bright field microscopy, batch adsorption measurements, and changes in hydrophobic interaction energy of colloid and media surfaces for realistic aqueous ionic strength and pH ranges. Such experimental results are expected to provide sufficient evidence to corroborate our speculations that under natural soil water conditions, humic acids may greatly contribute to the immobilization of colloidal particles.

  6. The stability of the acetic acid dimer in microhydrated environments and in aqueous solution.

    PubMed

    Pašalić, Hasan; Tunega, Daniel; Aquino, Adélia J A; Haberhauer, Georg; Gerzabek, Martin H; Lischka, Hans

    2012-03-28

    The thermodynamic stability of the acetic acid dimer conformers in microhydrated environments and in aqueous solution was studied by means of molecular dynamics simulations using the density functional based tight binding (DFTB) method. To confirm the reliability of this method for the system studied, density functional theory (DFT) and second order Møller-Plesset perturbation theory (MP2) calculations were performed for comparison. Classical optimized potentials for liquid simulations (OPLS) force field dynamics was used as well. One focus of this work was laid on the study of the capabilities of water molecules to break the hydrogen bonds of the acetic acid dimer. The barrier for insertion of one water molecule into the most stable cyclic dimer is found to lie between 3.25 and 4.8 kcal mol(-1) for the quantum mechanical methods, but only at 1.2 kcal mol(-1) for OPLS. Starting from different acetic acid dimer structures optimized in gas phase, DFTB dynamics simulations give a different picture of the stability in the microhydrated environment (4 to 12 water molecules) as compared to aqueous solution. In the former case all conformers are converted to the hydrated cyclic dimer, which remains stable over the entire simulation time of 1 ns. These results demonstrate that the considered microhydrated environment is not sufficient to dissociate the acetic acid dimer. In aqueous solution, however, the DFTB dynamics shows dissociation of all dimer structures (or processes leading thereto) starting after about 50 ps, demonstrating the capability of the water environment to break up the relatively strong hydrogen bridges. The OPLS dynamics in the aqueous environment shows--in contrast to the DFTB results--immediate dissociation, but a similar long-term behavior.

  7. Insights Into the Aqueous History of Mars from Acid-Sulfate Weathered Phyllosilicates

    NASA Technical Reports Server (NTRS)

    Craig, P. I.; Ming, D. W.; Rampe, E. B.; Morris, R. V.

    2016-01-01

    Phyllosilicates on Mars are thought to have formed during Mars' earliest Noachian geologic era (approx. 4.1-3.7 Ga). Sulfate formation, on the other hand, requires more acidic conditions which are thought to have occurred later during Mars' Hesperian era (approx. 3.7-3.0 Ga). Therefore, regions on Mars where phyllosilicates and sulfates are found in close proximity to each other provide evidence for the aqueous conditions during this global transition. Both phyllosilicates and sulfates form in the presence of water and thus give clues to the aqueous history of Mars and its potential for habitability. Phyllosilicates that formed during the Noachian era would have been weathered by the prevailing acidic conditions that define the Hesperian. Therefore, the purpose of this study is to characterize the alteration products of acid-sulfate weathered phyllosilicates in laboratory experiments, focusing on the Fe/Mg-smectites commonly identified on Mars. We also compare our results to observations of phyllosilicates and sulfates on Mars in regions such as Endeavour Crater and Mawrth Vallis to understand the formation process of sulfates and constrain the aqueous history of these regions.

  8. Sulfate Mineral Formation from Acid-Weathered Phyllosilicates: Implications for the Aqueous History of Mars

    NASA Technical Reports Server (NTRS)

    Craig, P. I.; Ming, D. W.; Rampe, E. B.; Morris, R. V.

    2015-01-01

    Phyllosilicates on Mars are thought to have formed under neutral to alkaline conditions during Mars' earliest Noachian geologic era (approx. 4.1-3.7 Gya). Sulfate formation, on the other hand, requires more acidic conditions which are thought to have occurred later during Mars' Hesperian era (approx. 3.7-3.0 Gya). Therefore, regions on Mars where phyllosilicates and sulfates are found in close proximity to each other provide evidence for the geologic and aqueous conditions during this global transition. Both phyllosilicates and sulfates form in the presence of water and thus give clues to the aqueous history of Mars and its potential for habitability. Phyllosilicates that formed during the Noachian era may have been weathered by the prevailing acidic conditions that characterize the Hesperian. Therefore, the purpose of this study is to characterize the alteration products resulting from acid-sulfate weathered phyllosilicates in laboratory experiments. This study focuses on two phyllosilicates commonly identified with sulfates on Mars: nontronite and saponite. We also compare our results to observations of phyllosilicates and sulfates on Mars to better understand the formation process of sulfates in close proximity to phyllosilicates on Mars and constrain the aqueous conditions of these regions on Mars.

  9. Silver-Catalyzed Decarboxylative Radical Azidation of Aliphatic Carboxylic Acids in Aqueous Solution.

    PubMed

    Liu, Chao; Wang, Xiaoqing; Li, Zhaodong; Cui, Lei; Li, Chaozhong

    2015-08-12

    We report herein an efficient and general method for the decarboxylative azidation of aliphatic carboxylic acids. Thus, with AgNO3 as the catalyst and K2S2O8 as the oxidant, the reactions of various aliphatic carboxylic acids with tosyl azide or pyridine-3-sulfonyl azide in aqueous CH3CN solution afforded the corresponding alkyl azides under mild conditions. A broad substrate scope and wide functional group compatibility were observed. A radical mechanism is proposed for this site-specific azidation.

  10. Phase equilibria in a system of aqueous arginine with an octane solution of sulfonic acid

    NASA Astrophysics Data System (ADS)

    Kuvaeva, Z. I.; Koval'chuk, I. V.; Vodop'yanova, L. A.; Soldatov, V. S.

    2013-05-01

    The extraction of arginine (Arg) from aqueous salt (0.1 M NaCl) solutions with a sulfo extractant in a wide range of pH values and amino acid concentrations was studied. The 0.1 M solution of dinonylnaphthalenesulfonic acid (HD) in octane was used as an extractant. The degree of extraction was found to be high at pH 0.8-9.0. This can be explained by the effect of additional intermolecular interactions in the extractant phase involving the guanidine group of Arg.

  11. Ultrasound promoted one-pot synthesis of 2-amino-4,8-dihydropyrano[3,2-b]pyran-3-carbonitrile scaffolds in aqueous media: a complementary 'green chemistry' tool to organic synthesis.

    PubMed

    Banitaba, Sayed Hossein; Safari, Javad; Khalili, Shiva Dehghan

    2013-01-01

    A green and simple approach to assembling of 2-amino-4,8-dihydropyrano[3,2-b]pyran-3-carbonitrile scaffolds via three-component reaction of kojic acid, malononitrile, and aromatic aldehydes in aqueous media under ultrasound irradiation is described. The combinatorial synthesis was achieved for this methodology with applying ultrasound irradiation while making use of water as green solvent. In comparison to conventional methods, experimental simplicity, good functional group tolerance, excellent yields, short routine, and selectivity without the need for a transition metal or base catalyst are prominent features of this green procedure. PMID:22939001

  12. Ultrasound promoted one-pot synthesis of 2-amino-4,8-dihydropyrano[3,2-b]pyran-3-carbonitrile scaffolds in aqueous media: a complementary 'green chemistry' tool to organic synthesis.

    PubMed

    Banitaba, Sayed Hossein; Safari, Javad; Khalili, Shiva Dehghan

    2013-01-01

    A green and simple approach to assembling of 2-amino-4,8-dihydropyrano[3,2-b]pyran-3-carbonitrile scaffolds via three-component reaction of kojic acid, malononitrile, and aromatic aldehydes in aqueous media under ultrasound irradiation is described. The combinatorial synthesis was achieved for this methodology with applying ultrasound irradiation while making use of water as green solvent. In comparison to conventional methods, experimental simplicity, good functional group tolerance, excellent yields, short routine, and selectivity without the need for a transition metal or base catalyst are prominent features of this green procedure.

  13. The Solubility of Xenon in Simple Organic Solvents and in Aqueous Amino Acid Solutions.

    NASA Astrophysics Data System (ADS)

    Himm, Jeffrey Frank

    We have measured the Ostwald solubility (L) of ('133)Xe in a variety of liquids, including normal alkanes, normal alkanols, and aqueous solutions of amino acids, NaCl, and sucrose. For the alkanes and alkanols, measurements were made in the temperature range from 10-50(DEGREES)C. Values of L were found to decrease with increasing temperature, and also with increasing chain length, for both series of solvents. Thermodynamic properties of solution (enthalpy and entropy of solution) are calculated using both mole fraction and number density scales. Results are interpreted using Uhlig's model of the solvation process. Measurements of L in aqueous amino acid solutions were made at 25(DEGREES)C. Concentrations of amino acids in solution varied from near saturation for each of the amino acids studied to pure water. In all solutions, except those with NaCl, L decreases linearly with increasing solution molarity. Hydration numbers (H), the mean number of water molecules associated with each solute molecule, were determined for each amino acid, for NaCl, and for sucrose. Values of H obtained ranged from near zero (arginine, H = 0.2 (+OR-) 0.5) to about 16 (NaCl, H = 16.25 (+OR-) 0.3).

  14. Statistical Thermodynamic Model for Surface Tension of Aqueous Organic Acids with Consideration of Partial Dissociation.

    PubMed

    Boyer, Hallie C; Dutcher, Cari S

    2016-06-30

    With statistical mechanics, an isotherm-based surface tension model for single solute aqueous solutions was derived previously (Wexler et al. J. Phys. Chem. Lett. 2013) for the entire concentration range, from infinite dilution to pure liquid solute, as a function of solute activity. In recent work (Boyer et al. J. Phys. Chem. Lett. 2015), empirical model parameters were reduced through physicochemical interpretations of both electrolyte and organic solutes, enabling surface tension predictions for systems where there is little or no data. The prior binary model is extended in the current work for the first time to treat multicomponent systems to predict surface tensions of partially dissociating organic acids (acetic, butyric, citric, formic, glutaric, maleic, malic, malonic, oxalic, propionic, and succinic acids). These organic acids are especially applicable to the study of atmospheric aqueous aerosols, due to their abundance in the atmosphere. In the model developed here, surface tension depends explicitly on activities of both the neutral organic and deprotonated components of the acid. The relative concentrations of the nondissociated and dissociated mole fractions are found using known dissociation constants. Model parameters strongly depend on molecular size, number of functional groups, O:C ratio, and number of carbons. For all organic acids in this study, fully predictive modeling of surface tensions is demonstrated.

  15. The dissolution of quartz in dilute aqueous solutions of organic acids at 25 degree C

    SciTech Connect

    Bennett, P.C.; Melcer, M.E.; Siegel, D.I.; Hassett, J.P. )

    1988-06-01

    The dissolution of quartz in dilute aqueous solutions of organic acids at 25{degree}C and standard pressure was investigated by the batch dissolution method. The bulk dissolution rate of quartz in 20 mmole/Kg citrate solutions at pH 7 was 8 to 10 times faster than that in pure water. After 1750 hours the concentration of dissolved silica in the citrate solution was 167 {mu}mole/Kg compared to 50 {mu}mole/Kg in water and a 20 mmole/Kg solution of acetate at pH 7. Solutions of salicylic, oxalic, and humic acids also accelerated the dissolution of quartz in aqueous solution at pH 7. The rate of dissolution in organic acids decreased sharply with decreasing pH. The possibility of a silica-organic acid complex was investigated using UV-difference spectroscopy. Results suggest that dissolved silica is complexed by citrate, oxalate and pyruvate at pH 7 by an electron-donor acceptor complex, whereas no complexation occurs between silica and acetate, lactate, malonate, or succinate. Three models are proposed for the solution and surface complexation of silica by organic acid which result in the accelerated dissolution and increased solubility of quartz in organic rich water.

  16. The dissolution of quartz in dilute aqueous solutions of organic acids at 25°C

    NASA Astrophysics Data System (ADS)

    Bennett, P. C.; Melcer, M. E.; Siegel, D. I.; Hassett, J. P.

    1988-06-01

    The dissolution of quartz in dilute aqueous solutions of organic acids at 25° and standard pressure was investigated by the batch dissolution method. The bulk dissolution rate of quartz in 20 mmole/Kg citrate solutions at pH 7 was 8 to 10 times faster than that in pure water. After 1750 hours the concentration of dissolved silica in the citrate solution was 167 μmole/Kg compared to 50 μmole/Kg in water and a 20 mmole/Kg solution of acetate at pH 7. Solutions of salicylic, oxalic, and humic acids also accelerated the dissolution of quartz in aqueous solution at pH 7. The rate of dissolution in organic acids decreased sharply with decreasing pH. The possibility of a silica-organic acid complex was investigated using UV-difference spectroscopy. Results suggest that dissolved silica is complexed by citrate, oxalate and pyruvate at pH 7 by an electron-donor acceptor complex, whereas no complexation occurs between silica and acetate, lactate, malonate, or succinate. Three models are proposed for the solution and surface complexation of silica by organic acid anions which result in the accelerated dissolution and increased solubility of quartz in organic rich water.

  17. Statistical Thermodynamic Model for Surface Tension of Aqueous Organic Acids with Consideration of Partial Dissociation.

    PubMed

    Boyer, Hallie C; Dutcher, Cari S

    2016-06-30

    With statistical mechanics, an isotherm-based surface tension model for single solute aqueous solutions was derived previously (Wexler et al. J. Phys. Chem. Lett. 2013) for the entire concentration range, from infinite dilution to pure liquid solute, as a function of solute activity. In recent work (Boyer et al. J. Phys. Chem. Lett. 2015), empirical model parameters were reduced through physicochemical interpretations of both electrolyte and organic solutes, enabling surface tension predictions for systems where there is little or no data. The prior binary model is extended in the current work for the first time to treat multicomponent systems to predict surface tensions of partially dissociating organic acids (acetic, butyric, citric, formic, glutaric, maleic, malic, malonic, oxalic, propionic, and succinic acids). These organic acids are especially applicable to the study of atmospheric aqueous aerosols, due to their abundance in the atmosphere. In the model developed here, surface tension depends explicitly on activities of both the neutral organic and deprotonated components of the acid. The relative concentrations of the nondissociated and dissociated mole fractions are found using known dissociation constants. Model parameters strongly depend on molecular size, number of functional groups, O:C ratio, and number of carbons. For all organic acids in this study, fully predictive modeling of surface tensions is demonstrated. PMID:27219322

  18. Aqueous Phase Photo-Oxidation of Succinic Acid: Changes in Hygroscopic Properties and Reaction Products

    NASA Astrophysics Data System (ADS)

    Hudson, P. K.; Ninokawa, A.; Hofstra, J.; de Lijser, P.

    2013-12-01

    Atmospheric aerosol particles have been identified as important factors in understanding climate change. The extent to which aerosols affect climate is determined, in part, by hygroscopic properties which can change as a result of atmospheric processing. Dicarboxylic acids, components of atmospheric aerosol, have a wide range of hygroscopic properties and can undergo oxidation and photolysis reactions in the atmosphere. In this study, the hygroscopic properties of succinic acid aerosol, a non-hygroscopic four carbon dicarboxylic acid, were measured with a humidified tandem differential mobility analyzer (HTDMA) and compared to reaction products resulting from the aqueous phase photo-oxidation reaction of hydrogen peroxide and succinic acid. Reaction products were determined and quantified using gas chromatography-flame ionization detection (GC-FID) and GC-mass spectrometry (GC-MS) as a function of hydrogen peroxide:succinic acid concentration ratio and photolysis time. Although reaction products include larger non-hygroscopic dicarboxylic acids (e.g. adipic acid) and smaller hygroscopic dicarboxylic acids (e.g. malonic and oxalic acids), comparison of hygroscopic growth curves to Zdanovskii-Stokes-Robinson (ZSR) predictions suggests that the hygroscopic properties of many of the product mixtures are largely independent of the hygroscopicity of the individual components. This study provides a framework for future investigations to fully understand and predict the role of chemical reactions in altering atmospheric conditions that affect climate.

  19. 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.

  20. Synthesis of Starch-Stabilized Ag Nanoparticles and Hg2+ Recognition in Aqueous Media

    NASA Astrophysics Data System (ADS)

    Fan, Yingju; Liu, Zhen; Wang, Le; Zhan, Jinhua

    2009-10-01

    The starch-stabilized Ag nanoparticles were successfully synthesized via a reduction approach and characterized with SPR UV/Vis spectroscopy, TEM, and HRTEM. By utilizing the redox reaction between Ag nanoparticles and Hg2+, and the resulted decrease in UV/Vis signal, we develop a colorimetric method for detection of Hg2+ ion. A linear relationship stands between the absorbance intensity of the Ag nanoparticles and the concentration of Hg2+ ion over the range from 10 ppb to 1 ppm at the absorption of 390 nm. The detection limit for Hg2+ ions in homogeneous aqueous solutions is estimated to be ~5 ppb. This system shows excellent selectivity for Hg2+ over other metal ions including Na+, K+, Ba2+, Mg2+, Ca2+, Fe3+, and Cd2+. The results shown herein have potential implications in the development of new colorimetric sensors for easy and selective detection and monitoring of mercuric ions in aqueous solutions.

  1. Acid stability of anti-Helicobacter pyroli IgY in aqueous polyol solution.

    PubMed

    Lee, Kyong Ae; Chang, Sung Keun; Lee, Yoon Jin; Lee, Jong Hwa; Koo, Nan Sook

    2002-09-30

    IgY was separated from a hen's egg yolk that was immunized with Helicobacter pyroli. The anti-H. pyroli IgY activity at acidic pH and the suppressive effect of polyol on acid-induced inactivation of IgY were investigated. Sorbitol and xylitol were used as polyols. IgY was quite stable at pH 5-7. Irreversible inactivation of IgY was observed at pH below 4, and proceeded rapidly at pH below 3. The acid stability of IgY was enhanced in the presence of 30% sorbitol or above. In a 50% aqueous sorbitol solution, an acid-induced inactivation was almost completely suppressed at pH 3. However, the improvement of IgY activity was not observed in the aqueous xylitol solution. IgY showed almost the same activity as native IgY when sucrose was substituted for sorbitol. On the other hand, the xylitol replacement with sucrose did not enhance the acid stability of IgY. The acid-induced inactivation of IgY was related to tryptophyl fluorescence. Fluorescence emission spectra suggested that structural changes near the tryptophan residues may occur under acidic conditions. An increase in sorbitol concentration induced a blue shift. The fluorescence emission of IgY in a 50% sorbitol solution had a peak at 330 nm, which was the same emission peak that was exhibited by native IgY. Sorbitol could, therefore, be used as a good stabilizer of IgY under acidic conditions. PMID:12359091

  2. [Studies on carbonization of saccharides by using aqueous solution of various acids].

    PubMed

    Zhang, Xin; He, An-Qi; Kang, Ting-Guo; Xia, Jin-Ming; Weng, Shi-Fu; Xu, Yi-Zhuang; Wu, Jin-Guang

    2014-09-01

    The authors tried to establish an approach to use acids to convert biomass into a fuel with higher carbon content and lower oxygen content in a zero-energy-consumption fashion. Considering that biomass is composed of monosaccharide, we used aqueous solutions of variation acids including hydrochloric acid, sulfuric acid and perchloric acid to treat 2-deoxy-ribose and fructose at ambient temperature and pressure. Black substances were produced after a period of time when 2-deoxy-ribose and fructose were mixed with aqueous solutions containing 8 mol · L(-1) acids. The black substance was collected and characterized by using elemental analysis, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Elemental analysis results indicate that the contents of carbon increases significantly in the black substances in comparison with 2-deoxy-ribose and fructose. Moreover, XPS results indicate that the content of oxygen in the black substance undergoes a significant decrease compared with pure 2-deoxy-ribose and fructose. In the XPS spectra, the is peaks of 2-deoxy-ribose, strong sub peak at 286. 05 eV, which is assigned to carbon linked to oxygen directly, dominate in the C is peak envelop. After treatment by HClO4, the peak decreased dramatically. This result also supports the conclusion that the content of oxygen in mono-saccharide is significantly reduced after treatment by acids. In the FTIR spectra of the black substances, strong peaks can be observed around 1 600 cm(-1), indicating that C==C bond is formed in the product. The above results suggest that treatments with acids may be developed as a new zero-energy-consumption approach to convert biomass in a new fuel with improved energy output efficiency. PMID:25532323

  3. [Studies on carbonization of saccharides by using aqueous solution of various acids].

    PubMed

    Zhang, Xin; He, An-Qi; Kang, Ting-Guo; Xia, Jin-Ming; Weng, Shi-Fu; Xu, Yi-Zhuang; Wu, Jin-Guang

    2014-09-01

    The authors tried to establish an approach to use acids to convert biomass into a fuel with higher carbon content and lower oxygen content in a zero-energy-consumption fashion. Considering that biomass is composed of monosaccharide, we used aqueous solutions of variation acids including hydrochloric acid, sulfuric acid and perchloric acid to treat 2-deoxy-ribose and fructose at ambient temperature and pressure. Black substances were produced after a period of time when 2-deoxy-ribose and fructose were mixed with aqueous solutions containing 8 mol · L(-1) acids. The black substance was collected and characterized by using elemental analysis, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Elemental analysis results indicate that the contents of carbon increases significantly in the black substances in comparison with 2-deoxy-ribose and fructose. Moreover, XPS results indicate that the content of oxygen in the black substance undergoes a significant decrease compared with pure 2-deoxy-ribose and fructose. In the XPS spectra, the is peaks of 2-deoxy-ribose, strong sub peak at 286. 05 eV, which is assigned to carbon linked to oxygen directly, dominate in the C is peak envelop. After treatment by HClO4, the peak decreased dramatically. This result also supports the conclusion that the content of oxygen in mono-saccharide is significantly reduced after treatment by acids. In the FTIR spectra of the black substances, strong peaks can be observed around 1 600 cm(-1), indicating that C==C bond is formed in the product. The above results suggest that treatments with acids may be developed as a new zero-energy-consumption approach to convert biomass in a new fuel with improved energy output efficiency.

  4. Pyrene-Capped CdSe@ZnS Nanoparticles as Sensitive Flexible Oxygen Sensors in Non-Aqueous Media**

    PubMed Central

    González-Carrero, Soranyel; de la Guardia, Miguel; Galian, Raquel E; Pérez-Prieto, Julia

    2014-01-01

    A flexible, highly sensitive sensor of oxygen in non-aqueous solvents is described. It consists of CdSe/ZnS nanoparticles decorated with a considerable number of pyrene units, thus making the formation of the pyrene excimer possible. The emission of the pyrene excimer and that of the nanoparticle are suitably separated from each other and also from the excitation wavelength. This sensor can be applied as a ratiometric oxygen sensor by using the linear response of the pyrene excimer lifetime combined with the linear response of the nanoparticle excited state lifetime. This nanohybrid has been assayed in seven media with different dielectric constants and viscosities over the whole oxygen concentration range. In addition, the sensor versatility provides an easy way for monitoring oxygen diffusion through systems. PMID:25478315

  5. A facile approach for cupric ion detection in aqueous media using polyethyleneimine/PMMA core-shell fluorescent nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Zeng, Fang; Wu, Shuizhu; Su, Junhua; Zhao, Jianqing; Tong, Zhen

    2009-09-01

    A facile approach was developed to produce a dye-doped core-shell nanoparticle chemosensor for detecting Cu2+ in aqueous media. The core-shell nanoparticle sensor was prepared by a one-step emulsifier-free polymerization, followed by the doping of the fluorescent dye Nile red (9-diethylamino- 5H-benzo[alpha] phenoxazine-5-one, NR) into the particles. For the nanoparticles, the hydrophilic polyethyleneimine (PEI) chain segments serve as the shell and the hydrophobic polymethyl methacrylate (PMMA) constitutes the core of the nanoparticles. The non-toxic and biocompatible PEI chain segments on the nanoparticle surface exhibit a high affinity for Cu2+ ions in aqueous media, and the quenching of the NR fluorescence is observed upon binding of Cu2+ ions. This makes the core-shell nanoparticle system a water-dispersible chemosensor for Cu2+ ion detection. The quenching of fluorescence arises through intraparticle energy transfer (FRET) from the dye in the hydrophobic PMMA core to the Cu2+/PEI complexes on the nanoparticle surface. The energy transfer efficiency for PEI/PMMA particles with different diameters was determined, and it is found that the smaller nanoparticle sample exhibits higher quenching efficiency, and the limit for Cu2+ detection is 1 µM for a nanoparticle sample with a diameter of ~30 nm. The response of the fluorescent nanoparticle towards different metal ions was investigated and the nanoparticle chemosensor displays high selectivity and antidisturbance for the Cu2+ ion among the metal ions examined (Na+, K+, Mg2+, Ca2+, Zn2+, Hg2+, Mn2+, Fe2+, Ni2+, Co2+ and Pb2+). This emulsifier-free, biocompatible and sensitive fluorescent nanoparticle sensor may find applications in cupric ion detection in the biological and environmental areas.

  6. Interaction of Some Amino Acids with Sodium Dodecyl Sulphate in Aqueous Solution at Different Temperatures

    NASA Astrophysics Data System (ADS)

    Ali, Anwar; Itoo, Firdoos Ahmad; Ansari, Nizamul Haque

    2011-05-01

    The density ρ, and viscosity η of 0.00, 0.05, 0.10, 0.15, and 0.20 mol kg-1 glycine (Gly), dlalanine (Ala), dl-serine (Ser), and dl-valine (Val) have been measured in 0.002 mol kg-1 aqueous sodium dodecyl sulphate (SDS) at 298.15, 303.15, 308.15, and 313.15 K. These data have been used to calculate the apparent molar volume φv, infinite dilution apparent molar volume φv°, and the standard partial molar volumes of transfer φv° (tr), of the amino acids from water to the aqueous SDS solutions. Falkenhagen coefficient A, Jones-Dole coefficient B, free energies of activation per mole of solvent (aqueous SDS) Δμ1°*, and per mole solute (amino acids) Δμ2°*, also enthalpy ΔH* and entropy ΔS* of activation of viscous flow were evaluated using viscosity data. The molar refraction RD was calculated by using experimental values of the refractive index nD of the systems. The results have been interpreted in terms of ion-ion, ion-polar and hydrophobic-hydrophobic group interactions. The volume of the transfer data suggest that ion-ion intertactions are predominant.

  7. Influence of Acidity on Uranyl Nitrate Association in Aqueous Solutions: A Molecular Dynamics Simulation Study

    SciTech Connect

    de Almeida, Valmor F; Cui, Shengting; Khomami, Bamin; Ye, Xianggui; Smith, Rodney Bryan

    2010-01-01

    Uranyl ion complexation with water and nitrate is a key aspect of the uranium/plutonium extraction process. We have carried out a molecular dynamics simulation study to investigate this complexation process, including the molecular composition of the various complex species, the corresponding structure, and the equilibrium distribution of the complexes. The observed structures of the complexes suggest that in aqueous solution, uranyls are generally hydrated by 5 water molecules in the equatorial plane. When associating with nitrate ions, a water molecule is replaced by a nitrate ion, preserving the five-fold coordination and planar symmetry. Analysis of the pair correlation function between uranyl and nitrate suggests that nitrates bind to uranyl in aqueous solution mainly in a monodentate mode, although a small portion of bidentates occur. Dynamic association and dissociation between uranyls and nitrates take place in aqueous solution with a substantial amount of fluctuation in the number of various uranyl nitrate species. The average number of the uranyl mononitrate complexes shows a dependence on acid concentration consistent with equilibrium-constant analysis, namely, the concentration of [UO2NO3]+ increases with nitric acid concentration.

  8. Kinetics of CO2 Absorption into Aqueous Basic Amino Acid Salt: Potassium Salt of Lysine Solution.

    PubMed

    Shen, Shufeng; Yang, Ya-nan; Bian, Yangyang; Zhao, Yue

    2016-02-16

    Aqueous amino acid salts are considered as an attractive alternative to alkanolamine solvents (e.g., MEA) for carbon dioxide (CO2) absorption. The kinetics of CO2 into unloaded aqueous solutions of potassium lysinate (LysK) was studied using a wetted wall column at concentrations ranging from 0.25 to 2.0 M and temperatures from 298 to 333 K. Physicochemical properties of aqueous LysK solutions such as density, viscosity, and physical solubility of CO2 were measured to evaluate the reaction rate constants. The reaction pathway is described using zwitterion mechanism taking into account the effect of ionic strength on the reaction rate. Under the fast pseudo-first-order regime, the reaction rate parameters were obtained and correlated in a power-law reaction rate expression. LysK shows higher chemical reactivity toward CO2 than the industrial standard MEA and most of amino acid salts. Its reaction rate constants increase considerably with concentration and temperature. The reaction order is found to be an average value of 1.58 with respect to LysK. The forward second-order kinetic rate constant, k2 0 , are obtained as 31615 and 84822 m3 kmol−1 s−1 at 298 and 313 K, respectively with activation energy of 51.0 kJ mol−1. The contribution of water to the zwitterion deprotonation seems to be more significant than that of LysK for the above-mentioned kinetic conditions PMID:26751093

  9. Chemo-, Regio-, and Stereoselective Copper(II)-Catalyzed Boron Addition to Acetylenic Esters and Amides in Aqueous Media.

    PubMed

    Nelson, Amanda K; Peck, Cheryl L; Rafferty, Sean M; Santos, Webster L

    2016-05-20

    Aqueous conditions were developed for conducting an open-to-air, copper(II)-catalyzed addition of pinBBdan to alkynoates and alkynamides. The simple and mild β-borylation protocol proceeds in a remarkably chemo-, regio-, and stereoselective fashion to afford 1,8-diaminonaphthalene protected (Z)-β-boryl enoates and primary, secondary, and tertiary enamides in good to excellent yields. These reactions demonstrate a high tolerance toward a variety of alkyl, aryl, and heteroatom functional groups and provide convenient access to a diverse range of vinylboronic acid derivatives. PMID:27104638

  10. Interaction of Atmospheric-Pressure Air Microplasmas with Amino Acids as Fundamental Processes in Aqueous Solution.

    PubMed

    Zhou, Renwu; Zhou, Rusen; Zhuang, Jinxing; Zong, Zichao; Zhang, Xianhui; Liu, Dongping; Bazaka, Kateryna; Ostrikov, Kostya

    2016-01-01

    Plasma medicine is a relatively new field that investigates potential applications of cold atmospheric-pressure plasmas in bioengineering, such as for bacterial inactivation and degradation of organic molecules in water. In order to enunciate mechanisms of bacterial inactivation at molecular or atomic levels, we investigated the interaction of atmospheric-pressure air microplasmas with amino acids in aqueous solution by using high-resolution mass spectrometry (HRMS). Results show that the oxidation effect of plasma-induced species on the side chains of the amino acids can be categorized into four types, namely hydroxylation, nitration, dehydrogenation and dimerization. In addition, relative activities of amino acids resulting from plasma treatment come in descending order as follows: sulfur-containing carbon-chain amino acids > aromatic amino acids > five-membered ring amino acids > basic carbon-chain amino acids. Since amino acids are building blocks of proteins vital to the growth and reproduction of bacteria, these results provide an insight into the mechanism of bacterial inactivation by plasma. PMID:27183129

  11. Interaction of Atmospheric-Pressure Air Microplasmas with Amino Acids as Fundamental Processes in Aqueous Solution

    PubMed Central

    Zhou, Renwu; Zhou, Rusen; Zhuang, Jinxing; Zong, Zichao; Zhang, Xianhui; Liu, Dongping; Bazaka, Kateryna; Ostrikov, Kostya

    2016-01-01

    Plasma medicine is a relatively new field that investigates potential applications of cold atmospheric-pressure plasmas in bioengineering, such as for bacterial inactivation and degradation of organic molecules in water. In order to enunciate mechanisms of bacterial inactivation at molecular or atomic levels, we investigated the interaction of atmospheric-pressure air microplasmas with amino acids in aqueous solution by using high-resolution mass spectrometry (HRMS). Results show that the oxidation effect of plasma-induced species on the side chains of the amino acids can be categorized into four types, namely hydroxylation, nitration, dehydrogenation and dimerization. In addition, relative activities of amino acids resulting from plasma treatment come in descending order as follows: sulfur-containing carbon-chain amino acids > aromatic amino acids > five-membered ring amino acids > basic carbon-chain amino acids. Since amino acids are building blocks of proteins vital to the growth and reproduction of bacteria, these results provide an insight into the mechanism of bacterial inactivation by plasma. PMID:27183129

  12. Interaction of Atmospheric-Pressure Air Microplasmas with Amino Acids as Fundamental Processes in Aqueous Solution.

    PubMed

    Zhou, Renwu; Zhou, Rusen; Zhuang, Jinxing; Zong, Zichao; Zhang, Xianhui; Liu, Dongping; Bazaka, Kateryna; Ostrikov, Kostya

    2016-01-01

    Plasma medicine is a relatively new field that investigates potential applications of cold atmospheric-pressure plasmas in bioengineering, such as for bacterial inactivation and degradation of organic molecules in water. In order to enunciate mechanisms of bacterial inactivation at molecular or atomic levels, we investigated the interaction of atmospheric-pressure air microplasmas with amino acids in aqueous solution by using high-resolution mass spectrometry (HRMS). Results show that the oxidation effect of plasma-induced species on the side chains of the amino acids can be categorized into four types, namely hydroxylation, nitration, dehydrogenation and dimerization. In addition, relative activities of amino acids resulting from plasma treatment come in descending order as follows: sulfur-containing carbon-chain amino acids > aromatic amino acids > five-membered ring amino acids > basic carbon-chain amino acids. Since amino acids are building blocks of proteins vital to the growth and reproduction of bacteria, these results provide an insight into the mechanism of bacterial inactivation by plasma.

  13. DEVELOPMENT OF PROTOTYPE TITANATE ION EXCHANGE LOADED MEMBRANES FOR STRONTIUM, CESIUM AND ACTINIDE DECONTAMINATION FROM AQUEOUS MEDIA

    SciTech Connect

    Oji, L; Keisha Martin, K; David Hobbs, D

    2008-05-30

    We have successfully incorporated high surface area particles of titanate ion exchange materials (monosodium titanate and crystalline silicotitanate) with acceptable particle size distribution into porous and inert support membrane fibrils consisting of polytetrafluoroethylene (Teflon{reg_sign}), polyethylene and cellulose materials. The resulting membrane sheets, under laboratory conditions, were used to evaluate the removal of surrogate radioactive materials for cesium-137 and strontium-90 from high caustic nuclear waste simulants. These membrane supports met the nominal requirement for nonchemical interaction with the embedded ion exchange materials and were porous enough to allow sufficient liquid flow. Some of this 47-mm size stamped out prototype titanium impregnated ion exchange membrane discs was found to remove more than 96% of dissolved cesium-133 and strontium-88 from a caustic nuclear waste salt simulants. Since in traditional ion exchange based column technology monosodium titanate (MST) is known to have great affinity for the sorbing of other actinides like plutonium, neptunium and even uranium, we expect that the MST-based membranes developed here, although not directly evaluated for uptake of these three actinides because of costs associated with working with actinides which do not have 'true' experimental surrogates, would also show significant affinity for these actinides in aqueous media. It was also observed that crystalline silicotitanate impregnated polytetrafluoroethylene or polyethylene membranes became less selective and sorbed both cesium and strontium from the caustic aqueous salt simulants.

  14. The infrared optical constants of sulfuric acid at 250 K. [spectral reflectance measurement of aqueous solutions

    NASA Technical Reports Server (NTRS)

    Pinkley, L. W.; Williams, D.

    1976-01-01

    Results are presented for measurements of the IR spectral reflectance at near-normal incidence of aqueous solutions of sulfuric acid with acid concentrations of 75% and 95.6% by weight. Kramers-Kronig analyses of the reflectance data are employed to obtain values of the optical constants n(nu) and k(nu) in the spectral range from 400 to 6000 cm to the -1 power. The optical constants of these solutions at 250 K and 300 K are compared. It is found that in spectral regions remote from strong absorption bands, the values of the n(nu) indices obtained at 250 K agree with the values given by Lorentz-Lorenz correction of the same indices at 300 K. All absorption bands observed at 300 K are found to be present at 250 K with slight shifts in frequency and with significant differences in the k(nu) indices at the band maxima. Based on these results, it is concluded that the clouds of Venus probably consist of droplets of aqueous solutions of sulfuric acid with acid concentrations of about 75% by weight.

  15. Aqueous-phase photolysis of biacetyl (An α-dicarbonyl compound): A sink for biacetyl, and a source of acetic acid, peroxyacetic acid, hydrogen peroxide, and the highly oxidizing acetylperoxyl radical in aqueous aerosols, fogs, and clouds

    NASA Astrophysics Data System (ADS)

    Faust, Bruce C.; Powell, Kendall; Rao, C. Janakiram; Anastasio, Cort

    Aqueous-phase photolysis of biacetyl represents a heretofore uncharacterized sink for biacetyl and source of organic acids and peroxides to aqueous aerosols, and fog and cloud drops. The photolysis half-life of aqueous-phase biacetyl is approximately 1.0-1.6 h for a solar zenith angle of 36° (midday equinox sunlight in Durham, NC). Major products of aqueous biacetyl photolysis are acetic acid, peroxyacetic acid, and hydrogen peroxide. Pyruvic acid and methylhydroperoxide are minor photoproducts. Common atmospheric reductants (H-atom donors), such as formate, formaldehyde, glyoxal, phenol (as a model for phenolic compounds) and α- D-glucose (as a model for carbohydrates), substantially increase the quantum yields of peroxyacetic acid Formate also significantly increases the quantum yields of hydrogen peroxide. The highly oxidizing acetylperoxyl radical is proposed as a key intermediate in the photolysis of aqueous biacetyl. The sources and reactions of acetylperoxyl radicals in aqueous aerosols, fogs, and clouds should be investigated in future studies of atmospheric water-drop chemistry.

  16. Kinetics of acid-catalyzed degradation of cyclosporin A and its analogs in aqueous solution.

    PubMed

    Oliyai, R; Safadi, M; Meier, P G; Hu, M K; Rich, D H; Stella, V J

    1994-03-01

    The kinetics and mechanism of the degradation of cyclosporin A have been studied under aqueous acidic conditions. The rate of degradation was found to be specific acid-catalyzed over the pH range studied (1-4), with isocyclosporin A as the predominant degradation product. Selective reduction of the olefinic bond of the amino acid 2-N-methyl-(R)-((E)-2-butenyl)-4-methyl-L-threonine (MeBmt) did not affect the overall degradation kinetics and product distribution of cyclosporin A. These observations indicate that the alternative degradation pathway involving intramolecular alkoxy addition to the olefinic bond of amino acid MeBmt apparently does not significantly contribute to the overall degradation kinetics of cyclosporin A in the pH range 1-4. The chemical reactivity of O-acetyl-cyclosporin A was examined to probe the governing mechanism for the isomerization of cyclosporin A. Under identical conditions, O-acetyl-cyclosporin A showed a much greater chemical stability than cyclosporin A, consistent with a mechanism involving the hydroxyoxazolidine intermediate. The chemical stability of cyclosporin C, which contains two beta-hydroxyl groups, was also examined. The rate and product distribution for the degradation of cyclosporin C suggest that under aqueous acidic conditions it undergoes N,O-acyl migration solely at the amino acid residue MeBmt. Additionally, the impact of side-chain bulkiness of amino acid MeBmt was examined by studying the degradation kinetics of a series of cyclosporin A analogs.(ABSTRACT TRUNCATED AT 250 WORDS)

  17. MICROWAVE-ASSISTED CYCLOCONDENSATION OF HYDRAZINE DERIVATIVES WITH ALKYL DIHALIDES OR DITOSYLATES IN AQUEOUS MEDIA: SYNTHESES OF PYRAZOLE, PYRAZOLIDINE AND PHTHALAZINE DERIVATIVES

    EPA Science Inventory

    Direct synthesis of 4,5-dihydro-pyrazole, pyrazolidine, and 1,2-dihydro-phthalazine derivatives via double alkylation of hydrazines by alkyl dihalides or ditosylates were accomplished in aqueous media under microwave irradiation conditions; the environmentally friendlier chemical...

  18. Real-time analysis of multiple anion mixtures in aqueous media using a single receptor.

    PubMed

    Havel, Vaclav; Yawer, Mirza Arfan; Sindelar, Vladimir

    2015-03-18

    Bambusuril-based receptors have been used in conjunction with (1)H NMR spectroscopy to recognize mixtures of inorganic anions in aqueous solutions. This was achieved by examining complexation-induced changes in the receptors' (1)H NMR fingerprints. This approach enables the simultaneous identification of up to 9 anions and the quantification of up to 5 anions using a single receptor in DMSO-d6 containing 5% D2O. Toxic perchlorate was recognized and quantified at 0.1 μM (1.8 ppb, mol mol(-1)) concentration in pure water.

  19. Controlled self-assembly and luminescence characteristics of Eu(III) complexes in binary aqueous/organic media.

    PubMed

    Morikawa, Masa-Aki; Tsunofuri, Shohei; Kimizuka, Nobuo

    2013-10-22

    Luminescence of sodium tetrakis(naphthoyl trifluoroacetonato) europium(III) (Na[Eu(nta)4]) in binary aqueous-ethanol media is quenched continuously with an increase in the water content, which is ascribed to commonly observed relaxation of photoexcited lanthanide complexes through vibrational coupling with coordinating water. Meanwhile, replacement of sodium ion with an ammonium amphiphile 1 gives a lipid complex 1[Eu(nta)4] which shows distinct changes: its luminescence quantum yield Φ is remarkably increased to ~0.6 above the water content of ~60 vol. %. This unusual enhancement in luminescence intensity occurs in response to self-assembly of 1[Eu(nta)4] into nanoparticles. The lipid counterions provide a hydrophobic atmosphere inside nanoparticles, and they simultaneously form monolayers on the nanoparticle surface that enhance dispersion stability. The size of nanoparticles is tunable depending on the volume fraction of water in the binary media. The lipid-assisted self-assembly of lanthanide complexes provides a unique means to fabricate luminescent nanomaterials, and this approach will be widely applied to fabricate functional coordination nanomaterials.

  20. Ionic clusters vs shear viscosity in aqueous amino acid ionic liquids.

    PubMed

    Chaban, Vitaly V; Fileti, Eudes Eterno

    2015-03-01

    Aqueous solutions of amino acid ionic liquids (AAILs) are of high importance for applications in protein synthesis and solubilization, enzymatic reactions, templates for synthetic study, etc. This work employs molecular dynamics simulations using our own force field to investigate shear viscosity and cluster compositions of three 1-ethyl-3-methylimidazolium (emim) amino acid salts: [emim][ala], [emim][met], and [emim][trp] solutions (2, 5, 10, 20, and 30 mol %) in water at 310 K. We, for the first time, establish simple correlations between cluster composition, on one side, and viscosity, on another side. We argue that knowledge about any of these properties alone is enough to derive insights regarding the missed properties, using the reported correlations. The numerical observations and qualitative correlations are discussed in the context of the chemical structure of the amino acid anions, [ala], [met], and [trp]. The reported results will enhance progress in the efficient design and applications of AAILs and their solutions.

  1. Solubility of methanol in low-temperature aqueous sulfuric acid and implications for atmospheric particle composition

    NASA Technical Reports Server (NTRS)

    Iraci, Laura T.; Essin, Andrew M.; Golden, David M.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    Using traditional Knudsen cell techniques, we find well-behaved Henry's law uptake of methanol in aqueous 45 - 70 wt% H2SO4 solutions at temperatures between 197 and 231 K. Solubility of methanol increases with decreasing temperature and increasing acidity, with an effective Henry's law coefficient ranging from 10(exp 5) - 10(exp 8) M/atm. Equilibrium uptake of methanol into sulfuric acid aerosol particles in the upper troposphere and lower stratosphere will not appreciably alter gas-phase concentrations of methanol. The observed room temperature reaction between methanol and sulfuric acid is too slow to provide a sink for gaseous methanol at the temperatures of the upper troposphere and lower stratosphere. It is also too slow to produce sufficient quantities of soluble reaction products to explain the large amount of unidentified organic material seen in particles of the upper troposphere.

  2. Toxicity of aqueous C70-gallic acid suspension in Daphnia magna.

    PubMed

    Seda, Brandon C; Ke, Pu-Chun; Mount, Andrew S; Klaine, Stephen J

    2012-01-01

    The present study assessed the toxic effects of stable aqueous colloidal suspensions of gallic-acid-stabilized C(70) fullerene on Daphnia magna. The suspensions were stabilized through noncovalent surface modification with gallic acid. In addition to whole-organism responses, changes in antioxidative processes in D. magna were quantified. Acute toxicity was observed with 96LC50 for C(70) -gallic acid of 0.4 ± 0.1 mg/L C(70) . Daphnia magna fecundity was significantly reduced in 21-d bioassays at C(70) -gallic aqcid concentrations below quantifiable limits. Antioxidant enzyme activities of glutathione peroxidase and superoxide dismutase as well as lipid peroxidation suggested that exposed organisms experienced oxidative stress. Microscopic techniques used to determine cellular toxicity via apoptosis proved unsuccessful.

  3. Thermosensitivity of bile acid-based oligo(ethylene glycol) stars in aqueous solutions.

    PubMed

    Strandman, Satu; Le Dévédec, Frantz; Zhu, X X

    2011-08-01

    Amphiphilic star-shaped oligo(ethylene glycol)s with a hydrophobic bile acid core and varying number of hydrophilic arms have been made. Their thermal behavior in aqueous solutions depends on the number rather than the length of the arms. The two-armed lithocholate derivative showed the strongest tendency for association and exhibited the lowest cloud point (79 °C) of the oligomers made, as well as another phase separation at a lower temperature (31 °C). The "double thermosensitivity" arising both from the salt-dependent LCST of the oligo(ethylene glycol) segments and the temperature-responsive self-assembly of amphiphilic bile acid derivative provides an interesting path in the design of bile acid-based smart materials.

  4. Thermosensitivity of bile acid-based oligo(ethylene glycol) stars in aqueous solutions.

    PubMed

    Strandman, Satu; Le Dévédec, Frantz; Zhu, X X

    2011-08-01

    Amphiphilic star-shaped oligo(ethylene glycol)s with a hydrophobic bile acid core and varying number of hydrophilic arms have been made. Their thermal behavior in aqueous solutions depends on the number rather than the length of the arms. The two-armed lithocholate derivative showed the strongest tendency for association and exhibited the lowest cloud point (79 °C) of the oligomers made, as well as another phase separation at a lower temperature (31 °C). The "double thermosensitivity" arising both from the salt-dependent LCST of the oligo(ethylene glycol) segments and the temperature-responsive self-assembly of amphiphilic bile acid derivative provides an interesting path in the design of bile acid-based smart materials. PMID:21661073

  5. Solid supported in situ derivatization extraction of acidic degradation products of nerve agents from aqueous samples.

    PubMed

    Chinthakindi, Sridhar; Purohit, Ajay; Singh, Varoon; Tak, Vijay; Dubey, D K; Pardasani, Deepak

    2014-09-12

    This study deals with the solid supported in situ derivatization extraction of acidic degradation products of nerve agents present in aqueous samples. Target analytes were alkyl alkylphosphonic acids and alkylphosphonic acids, which are important environmental signatures of nerve agents. The method involved tert-butyldimethylchlorosilane mediated in situ silylation of analytes on commercially available diatomaceous solid phase extraction cartridges. Various parameters such as derivatizing reagent, its concentration, reaction time, temperature and eluting solvent were optimized. Recoveries of the analytes were determined by GC-MS which ranged from 60% to 86%. The limits of detection (LOD) and limit of quantification (LOQ) with selected analytes were achieved down to 78 and 213ngmL(-1) respectively, in selected ion monitoring mode. The successful applicability of method was also demonstrated on samples of biological origin such as plasma and to the samples received in 34th official proficiency test conducted by the Organization for Prohibition the of Chemical Weapons. PMID:25103280

  6. Experimental Shock Chemistry of Aqueous Amino Acid Solutions and the Cometary Delivery of Prebiotic Compounds

    NASA Astrophysics Data System (ADS)

    Blank, Jennifer G.; Miller, Gregory H.; Ahrens, Michael J.; Winans, Randall E.

    2001-02-01

    A series of shock experiments were conducted to assess the feasibility of the delivery of organic compounds to the Earth via cometary impacts. Aqueous solutions containing near-saturation levels of amino acids (lysine, norvaline, aminobutyric acid, proline, and phenylalanine) were sealed inside stainless steel capsules and shocked by ballistic impact with a steel projectile plate accelerated along a 12-m-long gun barrel to velocities of 0.5-1.9 km sec^-1. Pressure-temperature-time histories of the shocked fluids were calculated using 1D hydrodynamical simulations. Maximum conditions experienced by the solutions lasted 0.85-2.7 μs and ranged from 5.1-21 GPa and 412-870 K. Recovered sample capsules were milled open and liquid was extracted. Samples were analyzed using high performance liquid chromatography (HPLC) and mass spectrometry (MS). In all experiments, a large fraction of the amino acids survived. We observed differences in kinetic behavior and the degree of survivability among the amino acids. Aminobutyric acid appeared to be the least reactive, and phenylalanine appeared to be the most reactive of the amino acids. The impact process resulted in the formation of peptide bonds; new compounds included amino acid dimers and cyclic diketopiperazines. In our experiments, and in certain naturally occurring impacts, pressure has a greater influence than temperature in determining reaction pathways. Our results support the hypothesis that significant concentrations of organic material could survive a natural impact process.

  7. Experimental shock chemistry of aqueous amino acid solutions and the cometary delivery of prebiotic compounds.

    PubMed

    Blank, J G; Miller, G H; Ahrens, M J; Winans, R E

    2001-01-01

    A series of shock experiments were conducted to assess the feasibility of the delivery of organic compounds to the Earth via cometary impacts. Aqueous solutions containing near-saturation levels of amino acids (lysine, norvaline, aminobutyric acid, proline, and phenylalanine) were sealed inside stainless steel capsules and shocked by ballistic impact with a steel projectile plate accelerated along a 12-m-long gun barrel to velocities of 0.5-1.9 km sec-1. Pressure-temperature-time histories of the shocked fluids were calculated using 1D hydrodynamical simulations. Maximum conditions experienced by the solutions lasted 0.85-2.7 microseconds and ranged from 5.1-21 GPa and 412-870 K. Recovered sample capsules were milled open and liquid was extracted. Samples were analyzed using high performance liquid chromatography (HPLC) and mass spectrometry (MS). In all experiments, a large fraction of the amino acids survived. We observed differences in kinetic behavior and the degree of survivability among the amino acids. Aminobutyric acid appeared to be the least reactive, and phenylalanine appeared to be the most reactive of the amino acids. The impact process resulted in the formation of peptide bonds; new compounds included amino acid dimers and cyclic diketopiperazines. In our experiments, and in certain naturally occurring impacts, pressure has a greater influence than temperature in determining reaction pathways. Our results support the hypothesis that significant concentrations of organic material could survive a natural impact process. PMID:11296518

  8. Removal of beta-blockers from aqueous media by adsorption onto graphene oxide.

    PubMed

    Kyzas, George Z; Koltsakidou, Anastasia; Nanaki, Stavroula G; Bikiaris, Dimitrios N; Lambropoulou, Dimitra A

    2015-12-15

    The aim of the present study is the evaluation of graphene oxide (GhO) as adsorbent material for the removal of beta-blockers (pharmaceutical compounds) in aqueous solutions. The composition and morphology of prepared materials were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Atenolol (ATL) and propranolol (PRO) were used as model drug molecules and their behavior were investigated in terms of GhO dosage, contact time, temperature and pH. Adsorption mechanisms were proposed and the pH-effect curves after adsorption were discussed. The kinetic behavior of GhO-drugs system was analyzed after fitting to pseudo-first and -second order equations. The adsorption equilibrium data were fitted to Langmuir, Freundlich and Langmuir-Freundlich model calculating the maximum adsorption capacity (67 and 116 mg/g for PRO and ATL (25 °C), respectively). The temperature effect on adsorption was tested carrying out the equilibrium adsorption experiments at three different temperatures (25, 45, 65 °C). Then, the thermodynamic parameters of enthalpy, free energy and entropy were calculated. Finally, the desorption of drugs from GhO was evaluated by using both aqueous eluants (pH2-10) and organic solvents. PMID:26282775

  9. Evidence for organic synthesis in high temperature aqueous media - facts and prognosis

    NASA Technical Reports Server (NTRS)

    Simoneit, Bernd R. T.

    1995-01-01

    Hydrothermal systems are common along the active tectonic areas of the earth. Potential sites being studied for organic matter alteration and possible organic synthesis are spreading ridges, off-axis systems, back-arc activity, hot spots, volcanism, and subduction. Organic matter alteration, primarily reductive and generally from immature organic detritus, occurs in these high temperature and rapid fluid flow hydrothermal regimes. Hot circulating water (temperature range - warm to greater than 400 C) is responsible for these molecular alterations, expulsion and migration. Compounds that are obviously synthesized are minor components because they are generally masked by the pyrolysis products formed from contemporary natural organic precursors. The reactivity of organic compounds in hot water (200-350 C) has been studied in autoclaves, and supercritical water as a medium for chemistry has also been evaluated. This high temperature aqueous organic chemistry and the strong reducing conditions of the natural systems suggest this as an important route to produce organic compounds on the primitive earth. Thus a better understanding of the potential syntheses of organic compounds in hydrothermal systems will require investigations of the chemistry of condensation, autocatalysis, catalysis and hydrolysis reactions in aqueous mineral buffered systems over a range of temperatures from warm to greater than 400 C.

  10. Removal of beta-blockers from aqueous media by adsorption onto graphene oxide.

    PubMed

    Kyzas, George Z; Koltsakidou, Anastasia; Nanaki, Stavroula G; Bikiaris, Dimitrios N; Lambropoulou, Dimitra A

    2015-12-15

    The aim of the present study is the evaluation of graphene oxide (GhO) as adsorbent material for the removal of beta-blockers (pharmaceutical compounds) in aqueous solutions. The composition and morphology of prepared materials were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Atenolol (ATL) and propranolol (PRO) were used as model drug molecules and their behavior were investigated in terms of GhO dosage, contact time, temperature and pH. Adsorption mechanisms were proposed and the pH-effect curves after adsorption were discussed. The kinetic behavior of GhO-drugs system was analyzed after fitting to pseudo-first and -second order equations. The adsorption equilibrium data were fitted to Langmuir, Freundlich and Langmuir-Freundlich model calculating the maximum adsorption capacity (67 and 116 mg/g for PRO and ATL (25 °C), respectively). The temperature effect on adsorption was tested carrying out the equilibrium adsorption experiments at three different temperatures (25, 45, 65 °C). Then, the thermodynamic parameters of enthalpy, free energy and entropy were calculated. Finally, the desorption of drugs from GhO was evaluated by using both aqueous eluants (pH2-10) and organic solvents.

  11. Sorption kinetic studies of ammonium from aqueous solution on different inorganic and organic media.

    PubMed

    Kucić, Dajana; Cosić, Ivana; Vuković, Marija; Briski, Felicita

    2013-01-01

    In this study, the sorption of ammonium from aqueous solution onto activated carbon, natural zeolite, peat and potting soil was studied by performing batch kinetic sorption experiments. The activated carbon wasn't efficiently removing ammonium at concentrations higher than 50 mg L(-1). Sorption isotherms of ammonium on zeolite, peat and potting soil were determined at 25 degrees C and 200 rpm with the initial concentration of 50-7000 mg L(-1). Equilibrium data were fitted by Freundlich, Langmuir and Temkin isotherm and parameters were evaluated according these models. Langmuir model gives better fit to experimental data than Freundlich and Temkin models. Maximum adsorption capacities were for activated carbon 0.631 mg g(-1), zeolite 58 mg g(-1), peat 595 mg g(-1) and for potting soil 575 mg g(-1). The equilibrium kinetic data were analyzed using adsorption kinetic models: the pseudo-first and second-order equations and were found to follow the pseudo-second-order kinetic model. A comparison between linear and non-linear regression method for estimating the adsorption and kinetics parameters was examined. The obtained results showed that non-linear method may be a better way to determine the kinetic parameters. Thermodynamic studies showed exothermic and endothermic nature of the adsorption of NH4(+) on inorganic and organic adsorbents, respectively. From present results it can be seen that zeolite, peat and potting soil are good adsorbents for removal ammonium from aqueous solution.

  12. Toxicity assessment of free form of heavy metals in aqueous media on earthworm Eudrillus eugeniae.

    PubMed

    Sharma, V; Chaudhari, P R; Satyanarayan, S

    2011-01-01

    Metals are found in free and also in combined forms. In order to get information on the effect of free forms of heavy metals on earthworms the aqueous extracts of metals were tested on earthworms both in individual form and also in combined form. Different concentrations, i.e. 1 ppm, 5 ppm, and 10 ppm, were selected arbitrarily and were used in the experiments. Metals like copper, cadmium, chromium, zinc and lead were used. Earthworms' Eudrillus eugeniae activity, i.e. their response to the toxicity of metals, was monitored continuously for 5 h. It can be concluded that free form/ionic form/dissolved form of heavy metals are more toxic for earthworms, concurrent with findings of workers who have drawn same inference during studies on aquatic organisms. Earthworms can serve as biomarkers for wastewater and sludge treatment studies as they have shown typical adverse body reactions and symptoms altogether different in reaction to each of the metals during aqueous medium studies. It can be inferred that, if earthworms are utilised for treating wastewater and sludges containing these five heavy metals, one can ascertain the presence of individual metal concentrations in the wastewaters and sludges by studying the typical body reactions of earthworms during the treatment.

  13. Vine-shoot waste aqueous extract applied as foliar fertilizer to grapevines: Effect on amino acids and fermentative volatile content.

    PubMed

    Sánchez-Gómez, R; Garde-Cerdán, T; Zalacain, A; Garcia, R; Cabrita, M J; Salinas, M R

    2016-04-15

    The aim of this work was to study the influence of foliar applications of different wood aqueous extracts on the amino acid content of musts and wines from Airén variety; and to study their relationship with the volatile compounds formed during alcoholic fermentation. For this purpose, the foliar treatments proposed were a vine-shoot aqueous extract applied in one and two times, and an oak extract which was only applied once. Results obtained show the potential of Airén vine-shoot waste aqueous extracts to be used as foliar fertilizer, enhancing the wine amino acid content especially when they were applied once. Similar results were observed with the aqueous oak extract. Regarding wine fermentative volatile compounds, there is a close relationship between musts and their wines amino acid content allowing us to discuss about the role of proline during the alcoholic fermentation and the generation of certain volatiles.

  14. Vine-shoot waste aqueous extract applied as foliar fertilizer to grapevines: Effect on amino acids and fermentative volatile content.

    PubMed

    Sánchez-Gómez, R; Garde-Cerdán, T; Zalacain, A; Garcia, R; Cabrita, M J; Salinas, M R

    2016-04-15

    The aim of this work was to study the influence of foliar applications of different wood aqueous extracts on the amino acid content of musts and wines from Airén variety; and to study their relationship with the volatile compounds formed during alcoholic fermentation. For this purpose, the foliar treatments proposed were a vine-shoot aqueous extract applied in one and two times, and an oak extract which was only applied once. Results obtained show the potential of Airén vine-shoot waste aqueous extracts to be used as foliar fertilizer, enhancing the wine amino acid content especially when they were applied once. Similar results were observed with the aqueous oak extract. Regarding wine fermentative volatile compounds, there is a close relationship between musts and their wines amino acid content allowing us to discuss about the role of proline during the alcoholic fermentation and the generation of certain volatiles. PMID:26616933

  15. Isolation and separation of transplutonium elements from other actinides on ion exchange resins from aqueous and aqueous ethanol solutions of sulfuric acid

    SciTech Connect

    Guseva, L.I.; Tikhomirova, G.S.; Stepushkina, V.V.

    1987-11-01

    The behavior of Am, Cm, Bk, Cf, Es, and other actinides, as well as Zr, on an anion exchange resin and a cation exchange resin in aqueous and aqueous alcohol solutions of sulfuric acid was investigated as a function of the concentration of various components of the solution. It was found that the presence of alcohol in sulfuric acid solutions leads to an increase in the distribution coefficients both on cation exchange resins and on anion exchange resins. The possibility of using ion exchange resins for the concentration and separation of transplutonium elements from U, Np, Pu, Zr, and other elements that form strong complexes with sulfate ions in a wide range of sulfuric acid concentrations was demonstrated.

  16. Thermodynamics of aqueous sodium sulfate from the temperatures 273 K to 373 K and mixtures of aqueous sodium sulfate and sulfuric acid at 298. 15 K

    SciTech Connect

    Hovey, J.K.; Pitzer, K.S. ); Rard, J.A. )

    1991-07-01

    New isopiestic vapor-pressure measurements on the aqueous system {l brace}(1{minus}y)H{sub 2}SO{sub 4}+yNA{sub 2}SO{sub 4}{r brace} along with earlier experimental investigations that span the range from y=0 to y=1 and infinitely dilute to supersaturated molalities have been analyzed in terms of the Pitzer ion-interaction model. Refined ion-interaction parameters for aqueous sodium sulfate valid over the temperature range 273 K to 373 K have been calculated and used for analyzing results for mixtures containing sulfuric acid and sodium sulfate at 298.15 K. Analysis of experimental results for these aqueous mixtures required explicit consideration of the dissociation reaction of bisulfate ion. Previous treatments of aqueous sulfuric acid and subsequently the bisulfate dissociation equilibrium valid in the range 273 K to 343 K were employed as a first approximation in representing the mixed solutions. Two sets of Pitzer ion-interaction parameters are presented for (sodium sulfate + sulfuric acid). The validity of the first set is limited in ionic strength and molality to saturated solutions of pure aqueous sodium sulfate (4 mol{center dot}kg{sup {minus}1}). The second set of parameters corresponds to a slightly less precise representation but is valid over the entire range of experimental results considered. Both sets of parameters provide a more complete description of pure sulfuric acid solutions because of the removal of various redundancies of ion-interaction parameters. The specific ion-interaction terms used and the overall fitting procedure are described as well as selected examples of relevant thermodynamic calculations in the mixed system Na{sub 2}SO{sub 4}-H{sub 2}SO{sub 4}-H{sub 2}O. 33 refs., 6 figs., 5 tabs.

  17. Thermodynamics of aqueous sodium sulfate from the temperatures 273 K to 373 K and mixtures of aqueous sodium sulfate and sulfuric acid at 298.15 K

    SciTech Connect

    Hovey, J.K.; Pitzer, K.S.; Rard, J.A.

    1991-07-01

    New isopiestic vapor-pressure measurements on the aqueous system {l_brace}(1{minus}y)H{sub 2}SO{sub 4}+yNA{sub 2}SO{sub 4}{r_brace} along with earlier experimental investigations that span the range from y=0 to y=1 and infinitely dilute to supersaturated molalities have been analyzed in terms of the Pitzer ion-interaction model. Refined ion-interaction parameters for aqueous sodium sulfate valid over the temperature range 273 K to 373 K have been calculated and used for analyzing results for mixtures containing sulfuric acid and sodium sulfate at 298.15 K. Analysis of experimental results for these aqueous mixtures required explicit consideration of the dissociation reaction of bisulfate ion. Previous treatments of aqueous sulfuric acid and subsequently the bisulfate dissociation equilibrium valid in the range 273 K to 343 K were employed as a first approximation in representing the mixed solutions. Two sets of Pitzer ion-interaction parameters are presented for (sodium sulfate + sulfuric acid). The validity of the first set is limited in ionic strength and molality to saturated solutions of pure aqueous sodium sulfate (4 mol{center_dot}kg{sup {minus}1}). The second set of parameters corresponds to a slightly less precise representation but is valid over the entire range of experimental results considered. Both sets of parameters provide a more complete description of pure sulfuric acid solutions because of the removal of various redundancies of ion-interaction parameters. The specific ion-interaction terms used and the overall fitting procedure are described as well as selected examples of relevant thermodynamic calculations in the mixed system Na{sub 2}SO{sub 4}-H{sub 2}SO{sub 4}-H{sub 2}O. 33 refs., 6 figs., 5 tabs.

  18. Reactivity of aminophosphonic acids. Oxidative dephosphonylation of 1-aminoalkylphosphonic acids by aqueous halogens.

    PubMed

    Drabowicz, Józef; Jordan, Frank; Kudzin, Marcin H; Kudzin, Zbigniew H; Stevens, Christian V; Urbaniak, Paweł

    2016-02-01

    The reactions of 1-aminoalkylphosphonic acids with bromine-water, chlorine-water and iodine-water were investigated. The formation of phosphoric(v) acid, as a result of a halogen-promoted cleavage of the Cα-P bond, accompanied by nitrogen release, was observed. The dephosphonylation of 1-aminoalkylphosphonic acids was found to occur quantitatively. In the reactions of 1-aminoalkylphosphonic acids with other halogen-water reagents investigated by (31)P NMR, scission of the Cα-P bond was also observed, the reaction rates being comparable for bromine and chlorine, but much slower for iodine.

  19. ESTIMATION OF HYDROLYSIS RATE CONSTANTS OF CARBOXYLIC ACID ESTER AND PHOSPHATE ESTER COMPOUNDS IN AQUEOUS SYSTEMS FROM MOLECULAR STRUCTURE BY SPARC

    EPA Science Inventory

    SPARC (SPARC Performs Automated Reasoning in Chemistry) chemical reactivity models were extended to calculate hydrolysis rate constants for carboxylic acid ester and phosphate ester compounds in aqueous non- aqueous and systems strictly from molecular structure. The energy diffe...

  20. Adding explicit solvent molecules to continuum solvent calculations for the calculation of aqueous acid dissociation constants.

    PubMed

    Kelly, Casey P; Cramer, Christopher J; Truhlar, Donald G

    2006-02-23

    Aqueous acid dissociation free energies for a diverse set of 57 monoprotic acids have been calculated using a combination of experimental and calculated gas and liquid-phase free energies. For ionic species, aqueous solvation free energies were calculated using the recently developed SM6 continuum solvation model. This model combines a dielectric continuum with atomic surface tensions to account for bulk solvent effects. For some of the acids studied, a combined approach that involves attaching a single explicit water molecule to the conjugate base (anion), and then surrounding the resulting anion-water cluster by a dielectric continuum, significantly improves the agreement between the calculated pK(a) value and experiment. This suggests that for some anions, particularly those concentrating charge on a single exposed heteroatom, augmenting implicit solvent calculations with a single explicit water molecule is required, and adequate, to account for strong short-range hydrogen bonding interactions between the anion and the solvent. We also demonstrate the effect of adding several explicit waters by calculating the pK(a) of bicarbonate (HCO(3)(-)) using as the conjugate base carbonate (CO(3)(2-)) bound by up to three explicit water molecules.

  1. Rosmarinic acid content in antidiabetic aqueous extract of Ocimum canum sims grown in Ghana.

    PubMed

    Berhow, Mark A; Affum, Andrews Obeng; Gyan, Ben A

    2012-07-01

    Rosmarinic acid (RA) is an important antioxidant polyphenol that is found in a variety of spices and herbs, including Ocimum canum Sims (locally called eme or akokobesa in Ghana). Aqueous extracts from the leaves of O. canum are used as an antidiabetic herbal medicine in Ghana. Analytical thin-layer chromatography was used to examine the composition of the polyphenols in leaf extracts. The polyphenol content in the aqueous and methanol extracts from the leaf, as determined by the Folin-Ciocalteu method, were 314 and 315 mg gallic acid equivalent/g leaf sample, respectively. The total flavonoid concentration as determined by the aluminum(III) chloride method was 135 mg catechin equivalent/g leaf sample. High-performance liquid chromatography coupled to an electrospray Quadrupole time-of-flight mass spectrometer was also used to determine the polyphenol fingerprint profile in the leaf extracts of O. canum. Although the average RA concentration in the O. canum leaf extracts from Ghana was 1.69 mg/g dry weight (reported values range from 0.01 to 99.62 mg/g dry weight), this polyphenol was still a prominent peak in addition to caffeic acid derivatives.

  2. Aqueous extracts of Mozambican plants as alternative and environmentally safe acid-base indicators.

    PubMed

    Macuvele, Domingos Lusitaneo Pier; Sithole, Gerre Zebedias Samo; Cesca, Karina; Macuvele, Suzana Lília Pinare; Matsinhe, Jonas Valente

    2016-06-01

    Indicators are substances that change color as the pH of the medium. Many of these substances are dyes of synthetic origin. The mulala plant (Euclea natalensis), which roots are commonly used by rural communities for their oral hygiene, and roseira (Hibiscus rosa-sinensis), an ornamental plant, are abundant in Mozambique. Currently, synthetic acid-base indicators are most commonly used but have environmental implications and, on the other hand, are expensive products, so the demand for natural indicators started. This study investigated the applicability of aqueous extracts of H. rosa-sinensis and E. natalensis as acid-base indicators. Ground on this work, the extracts can be used as acid-base indicators. On the basis of the absorption spectroscopy in both the UV-Vis region and previous studies, it was possible to preliminarily pinpoint anthocyanins and naphthoquinones as responsible for the shifting of colors depending on the pH range of aqueous extracts of H. rosa-sinensis and E. natalensis. These natural indicators are easily accessible, inexpensive, easy to extract, environmentally safe, and locally available. PMID:26936478

  3. ATR FT-IR H 2O spectra of acidic aqueous solutions. Insights about proton hydration

    NASA Astrophysics Data System (ADS)

    Śmiechowski, Maciej; Stangret, Janusz

    2008-04-01

    Proton hydration in aqueous solutions has been recently characterised in our laboratory by means of vibrational spectra of HDO isotopically diluted in H 2O [M. Śmiechowski, J. Stangret, J. Chem. Phys. 125 (2006) 204508]. Here, we attempt to study quantitatively H 2O spectra of acidic aqueous solutions. In principle, H 2O spectra provide more information about the structural state of water molecules, resulting from oscillator couplings in the system, but they are much more difficult in interpretation, when compared with HDO spectra. The spectra of aqueous solutions of monoprotic acids (HCl, HClO 4, HPF 6) have been measured by Attenuated Total Reflectance (ATR) FT-IR spectroscopy. Spectral data have been analysed in a way that led to removal of the contribution of bulk water, in order to separate the spectra of solute-affected water only. The analysis has been focused on the infinite dilution limit behaviour of the spectrum. Changes induced in the affected spectra by temperature have been studied for HPF 6 solutions at 25-45 °C. The stretching vibration fundamental has been found to be primarily affected by counter-anion. Proton-affected H 2O spectrum shows the presence of very wide absorption bands in the range, where bulk water shows negligible own absorption, rather than "absorption continua". They could be adequately resolved into analytical components. These bands have been unaffected by temperature and loosely correlated with the stretching fundamental, as indicated by 2D IR correlation spectra. All spectral effects of the studied acids on H 2O in solution have been quantitatively evidenced and discussed. They seem to be in accordance with the main conclusions about proton hydration derived from recent studies of HDO spectra mentioned above.

  4. A unified molecular picture of the surfaces of aqueous acid, base, and salt solutions

    SciTech Connect

    Mucha, M.; Frigato, Tomaso; Levering, Lori; Allen, Heather C.; Tobias, Douglas J.; Dang, Liem X.; Jungwirth, Pavel

    2005-04-28

    A unified view of the structure of the air/solution interface of simple aqueous electrolytes containing monovalent inorganic ions is developed using molecular dynamics simulations and vibrational sum frequency generation spectroscopy. In salt solutions and bases the positively charged ions, such as alkali cations, are repelled from the air/solution interface, while the anions, such as halides or hydroxide, exhibit a varying propensity for the surface, correlated primarily with the polarizability of the ion. As a result, there is a net depletion of ions from the interfacial layer as a whole, which is connected via the Gibbs adsorption equation to an increase in surface tension with respect to neat water. The behavior of acids, such as aqueous HCl or HBr, is different due to a significant propensity of hydronium cations for the air/solution interface. Therefore, both cations and anions exhibit enhanced concentrations at the surface and, consequently, these acids reduce the surface tension of water. The key to the qualitatively different surface behavior of aqueous salt solutions and bases on one side and acids on the other thus lies in the appreciable adsorption of hydronium cations at the air/solution interface with their “hydrophobic” oxygen side oriented towards the gas phase. The results of the molecular dynamics calculations are supported by surface selective non-linear vibrational spectroscopy, which reveals among other things that the hydronium cations are present at the air/solution interface. The propensity of inorganic ions for the air/solution interface has important implications for heterogeneous chemical processes, in particular for atmospheric chemistry.

  5. Organo/Zn-Al LDH Nanocomposites for Cationic Dye Removal from Aqueous Media

    NASA Astrophysics Data System (ADS)

    Starukh, G.; Rozovik, O.; Oranska, O.

    2016-04-01

    Cationic dye sorption by Zn-Al-layered double hydroxides (LDHs) modified with anionic surfactants was examined using methylene blue (MB) dye as a compound model in aqueous solutions. The modification of Zn-Al LDHs was performed by reconstruction method using dodecyl sulfate anion (DS) solutions. DS contained Zn-Al LDHs were characterized by XRD, FTIR, thermogravimetric, and SEM analysis. The reconstructed organo/Zn-Al LDHs comprise the crystalline phases (DS-intercalated LDHs, hydrotalcite), and the amorphous phase. The intercalation of DS ions into the interlayer galleries and DS adsorption on the surface of the LDHs occurred causing the MB adsorption on the external and its sorption in the internal surfaces of modified LDHs. The presence of DS greatly increased the affinity of organo/Zn-Al LDHs for MB due to hydrophobic interactions between the surfactants and the dye molecules. The optical properties of sorbed MB were studied.

  6. Synergistic inhibitive effect of tartarate and tungstate in preventing steel corrosion in aqueous media

    NASA Astrophysics Data System (ADS)

    Jabeera, B.; Shibli, S. M. A.; Anirudhan, T. S.

    2006-03-01

    The inhibitive effect of tartarate was studied as a coinhibitor with tungstate in preventing carbon steel corrosion in aqueous solutions. Open circuit potential measurements, weight-loss measurements and polarization studies were conducted to understand the domains of corrosion and passivation. Tartarate ions, even at low concentration, showed excellent synergistic corrosion inhibition characteristics. A mixture of 500 ppm each of the inhibitors was found to be optimum inhibitor combination. This inhibitor combination showed inhibition efficiency as high as 98%. Tartarate in the synergistic inhibitor combination did not reveal any dominant role in shifting the surface potential, even though it showed substantial passivation effect. The present study explores and evaluates the synergistic combination as a potential inhibitor system in combating corrosion on carbon steel surface.

  7. Acridine-based complex as amino acid anion fluorescent sensor in aqueous solution

    NASA Astrophysics Data System (ADS)

    Dai, Yanpeng; Xu, Kuoxi; Li, Qian; Wang, Chaoyu; Liu, Xiaoyan; Wang, Peng

    2016-03-01

    Novel acridine-based fluorescence sensors containing alaninol ligands, L1 and D1, were designed and synthesized. The structure of the compound was characterized by IR, 1H NMR, 13C NMR, MS spectra. L1 and D1 possess efficient Cu2 + cation ON-OFF selective signaling behavior based on ligand-to-metal binding mechanism at physiological pH condition. Additionally, the L1-Cu(II) and D1-Cu(II) complexes could further serve as reversible OFF-ON signaling sensing ensemble to allow ratiometric response to amino acid anion in aqueous solution.

  8. Photophysics of Fe(III) complexes with fluorosalicylic acid isomers in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Pozdnyakov, Ivan P.; Melnikov, Alexey A.; Šípoš, Rastislav; Chekalin, Sergey V.; Šima, Jozef

    2016-09-01

    Transient absorption spectroscopy is used to study photophysical processes of 1:1 Fe(III) complexes with all four fluorosalicylic acid isomers (Fe-FSAs) in aqueous solutions. Excited states of Fe-FSAs decay to the ground electronic state with two time constants. The faster process is interpreted as internal conversion to the vibrationally hot electronic ground state and the slower one - as a combination of vibrational cooling and solvation of the ground state. The results obtained for Fe-FSAs and other previously investigated Fe(III) salicylato compounds allow us to reveal the main cause of photochemical stability of the complexes upon charge transfer band excitation.

  9. Aqueous phototransformation of bisphenol S: the competitive radical-attack pathway to p-hydroxybenzenesulfonic acid.

    PubMed

    Wang, Xiaowen; Ma, Jiahai; Wang, Zhenpeng; Guo, Rongrong; Hu, Xuefeng

    2014-01-01

    The kinetics, environmental influencing factors, products and reaction mechanism of aqueous phototransformation of bisphenol S (BPS), as an alternative to bisphenol A, which is of environmental concern, were investigated. p-Hydroxybenzenesulfonic acid, as the major transformation product was confirmed by gas chromatography - mass spectrometry, electrospray ionization, ¹H nuclear magnetic resonance and fluorescence spectrum analysis. A reaction pathway was proposed based on the reactive oxygen species related results by electron paramagnetic resonance and radical traps. The competition of the excited state of BPS between transferring electron to O₂ to •O₂(-) and directly oxidizing H₂O to •OH was revealed.

  10. Evidence for organic synthesis in high temperature aqueous media — Facts and prognosis

    NASA Astrophysics Data System (ADS)

    Simoneit, Bernd R. T.

    1995-06-01

    Hydrothermal systems are common along the active tectonic areas of the earth. Potential sites being studied for organic matter alteration and possible organic synthesis are spreading ridges, off-axis systems, back-arc activity, hot spots, volcanism, and subduction. Organic matter alteration, primarily reductive and generally from immature organic detritus, occurs in these high temperature and rapid fluid flow hydrothermal regimes. Hot circulating water (temperature range — warm to >400 °C) is responsible for these molecular alterations, expuslion and migration. Compounds that are obviously synthesized are minor components because they are generally masked by the pyrolysis products formed from contemporary natural organic precursors. Heterocyclic sulfur compounds have been identified in high temperature zones and hydrothermal petroleums of the Guaymas Basin vent systems. They can be interpreted as being synthesized from formaldehyde and sulfur or HS{x/-} in the hydrothermal fluids. Other products from potential synthesis reactions have not yet been found in the natural systems but are expected based on known industrial processes and inferences from experimental simulation data. Various industrial processes have been reviewed and are of relevance to hydrothermal synthesis of organic compounds. The reactivity of organic compounds in hot water (200 350 °C) has been studied in autoclaves, and supercritical water as a medium for chemistry has also been evaluated. This high temperature aqueous organic chemistry and the strong reducing conditions of the natural systems suggest this as an important route to produce organic compounds on the primitive earth. Thus a better understanding of the potential syntheses of organic compounds in hydrothermal systems will require investigations of the chemistry of condensation, autocatalysis, catalysis and hydrolysis reactions in aqueous mineral buffered systems over a range of temperatures from warm to >400 °C.

  11. The dissolution of calcite in aqueous acid: The influence of humic species

    SciTech Connect

    Compton, R.G.; Sanders, G.H.W. )

    1993-07-01

    The kinetics of proton-induced calcite dissolution in aqueous solution in the presence of humic acids and their sodium salts are reported. In equilibrated acid solutions (pH <4) there is no inhibition by humic material and dissolution proceeds at a rate simply determined by the solution pH. Contrastingly the sodium salts of humic acids were found to have a significant inhibitory effect on the acid catalyzed dissolution. This was quantified using a novel channel flow cell experiment which employed two electrodes, the upstream of which was used to inject protons into a neutral solution, which also contained sodium salts of humic acid, via electrolytic oxidation of dissolved hydroquinone. The two electrodes were located immediately upstream and downstream of a calcite crystal so that the proton injection served to dissolve the calcite in the (inhibiting) presence of humic salts unequilibrated with the solution pH. The amount of H[sup +] which survived passage to the downstream detector'' electrode was used to quantify the rate of dissolution and hence the inhibitory effects of the humic acid. The latter were found to operate in a manner not inconsistent with Langmuirian adsorption.

  12. Adsorption of naphthalene from aqueous solution onto fatty acid modified walnut shells.

    PubMed

    Zhu, Mijia; Yao, Jun; Dong, Lifu; Sun, Jingjing

    2016-02-01

    The removal of polycyclic aromatic hydrocarbons (PAHs) from aqueous solution is challenging to environmental technologists. Agricultural waste is apparently the most attractive materials in removing PAHs because of its abundance, renewability, and economic advantage. The adsorption of PAHs (e.g., naphthalene) onto walnut shell (WNS) and its fatty acid (e.g., capric acid, lauric acid, palmitic acid, and oleic acid)-modified equivalent were investigated in this work to develop low-cost biosorbents for hydrophobic organic compounds. Compared with other modified sorbents, oleic acid graftted walnut shell (OWNS) showed the maximum partition coefficient (4330 ± 8.8 L kg(-1)) because of its lowest polarity and highest aromaticity. The adsorption capacity (7210 μg g(-1)) of OWNS at the temperature of 298 K was observed for an initial naphthalene concentration of 25 mg L(-1) with contact time of 40 h, sorbent dosage of 1 g L(-1), and in neutral condition. Furthermore, the regeneration capability of OWNS implied that it was a promising biosorbent for naphthalene removal.

  13. Uptake of methacrolein into aqueous solutions of sulfuric acid and hydrogen peroxide.

    PubMed

    Liu, Ze; Wu, Ling-Yan; Wang, Tian-He; Ge, Mao-Fa; Wang, Wei-Gang

    2012-01-12

    Multiphase acid-catalyzed oxidation by hydrogen peroxide has been suggested to be a potential route to secondary organic aerosol (SOA) formation from isoprene and its gas-phase oxidation products, but the kinetics and chemical mechanism remain largely uncertain. Here we report the first measurement of uptake of methacrolein into aqueous solutions of sulfuric acid and hydrogen peroxide in the temperature range of 253-293 K. The steady-state uptake coefficients were acquired and increased quickly with increasing sulfuric acid concentration and decreasing temperature. Propyne, acetone, and 2,3-dihydroxymethacrylic acid were suggested as the products. The chemical mechanism is proposed to be the oxidation of carbonyl group and C═C double bonds by peroxide hydrogen in acidic environment, which could explain the large content of polyhydroxyl compounds in atmospheric fine particles. These results indicate that multiphase acid-catalyzed oxidation of methacrolein by hydrogen peroxide can contribute to SOA mass in the atmosphere, especially in the upper troposphere.

  14. Adsorption of naphthalene from aqueous solution onto fatty acid modified walnut shells.

    PubMed

    Zhu, Mijia; Yao, Jun; Dong, Lifu; Sun, Jingjing

    2016-02-01

    The removal of polycyclic aromatic hydrocarbons (PAHs) from aqueous solution is challenging to environmental technologists. Agricultural waste is apparently the most attractive materials in removing PAHs because of its abundance, renewability, and economic advantage. The adsorption of PAHs (e.g., naphthalene) onto walnut shell (WNS) and its fatty acid (e.g., capric acid, lauric acid, palmitic acid, and oleic acid)-modified equivalent were investigated in this work to develop low-cost biosorbents for hydrophobic organic compounds. Compared with other modified sorbents, oleic acid graftted walnut shell (OWNS) showed the maximum partition coefficient (4330 ± 8.8 L kg(-1)) because of its lowest polarity and highest aromaticity. The adsorption capacity (7210 μg g(-1)) of OWNS at the temperature of 298 K was observed for an initial naphthalene concentration of 25 mg L(-1) with contact time of 40 h, sorbent dosage of 1 g L(-1), and in neutral condition. Furthermore, the regeneration capability of OWNS implied that it was a promising biosorbent for naphthalene removal. PMID:26517393

  15. Dissipative crystallization of aqueous mixtures of potassium salts of poly(riboadenylic acid) and poly(ribouridylic acid).

    PubMed

    Okubo, Tsuneo

    2011-10-15

    Dissipative drying patterns of aqueous mixtures of potassium salts of poly(riboadenylic acid) (KPolyA) and poly(ribouridylic acid) (KPolyU) were studied on a cover glass, a watch glass and a glass dish at room temperature. Accumulation of the polymers forming the broad rings near the outside edge and the inner area of the dried film was observed. The fine multiple ring structures formed when the affinity of the polymer with the substrate is strong. Microscopic drying patterns changed drastically depending on the location in the dried film. Microscopic drying patterns were mainly dendritic long rods and sword (halberd)-like rods. They are assigned to the crystals of double-stranded and triple-stranded helices of the A:U and A:2U complexes, respectively. Cross-like drying patterns are also observed originated from the salt-polymer interaction.

  16. Leaching of lead from zinc leach residue in acidic calcium chloride aqueous solution

    NASA Astrophysics Data System (ADS)

    Wang, Le; Mu, Wen-ning; Shen, Hong-tao; Liu, Shao-ming; Zhai, Yu-chun

    2015-05-01

    A process with potentially reduced environmental impacts and occupational hazards of lead-bearing zinc plant residue was studied to achieve a higher recovery of lead via a cost-effective and environmentally friendly process. This paper describes an optimization study on the leaching of lead from zinc leach residue using acidic calcium chloride aqueous solution. Six main process conditions, i.e., the solution pH value, stirring rate, concentration of CaCl2 aqueous solution, liquid-to-solid (L/S) ratio, leaching temperature, and leaching time, were investigated. The microstructure and components of the residue and tailing were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). On the basis of experimental results, the optimum reaction conditions were determined to be a solution pH value of 1, a stirring rate of 500 r·min-1, a CaCl2 aqueous solution concentration of 400 g·L-1, a liquid-to-solid mass ratio of 7:1, a leaching temperature of 80°C, and a leaching time of 45 min. The leaching rate of lead under these conditions reached 93.79%, with an iron dissolution rate of 19.28%. Silica did not take part in the chemical reaction during the leaching process and was accumulated in the residue.

  17. Preparation of monodisperse aqueous microspheres containing high concentration of l-ascorbic acid by microchannel emulsification.

    PubMed

    Khalid, Nauman; Kobayashi, Isao; Neves, Marcos A; Uemura, Kunihiko; Nakajima, Mitsutoshi; Nabetani, Hiroshi

    2015-01-01

    Monodisperse aqueous microspheres containing high concentrations of l-ascorbic acid with different concentrations of sodium alginate (Na-ALG) and magnesium sulfate (MgSO4) were prepared by using microchannel emulsification (MCE). The continuous phase was water-saturated decane containing a 5% (w/w) hydrophobic emulsifier. The flow rate of the continuous phase was maintained at 10 mL h(-1), whereas the pressure applied to the disperse phase was varied between 3 and 25 kPa. The disperse phase optimized for successfully generating aqueous microspheres included 2% (w/w) Na-ALG and 1% (w/w) MgSO4. At a higher MgSO4 concentration, the generated microspheres resulted in coalescence and subsequent bursting. At a lower MgSO4 concentration, unstable and polydisperse microspheres were obtained. The aqueous microspheres generated from the MCs under optimized conditions had a mean particle diameter (dav) of 14-16 µm and a coefficient of variation (CV) of less than 8% at the disperse phase pressures of 5-15 kPa.

  18. Comparison of Fe(II) Photo-Formation Characteristics Between Aqueous Humic Acid Solutions and Aqueous Extracts of Atmospheric Aerosols Collected at Okinawa Island, Japan

    NASA Astrophysics Data System (ADS)

    Saito, K.; Okada, K.; Arakaki, T.

    2007-12-01

    Photochemical cycles of Fe(III)-Fe(II) affects the oxidation and the reduction of transient species such as active oxygen species and various transition metals in the atmospheric condensed phases. Although the importance of organic ligands to iron cycling (e.g. ligand-to-metal charge transfer) is becoming clearer, the mechanism by which photochemical reduction of Fe(III) to Fe(II) are not well understood. Humic acid (HA) is considered as an important organic ligand for Fe(III) complexes in the environment. HA is a collection of organic compounds that exist in nature but whose structures are not well known. Commercially available HAs as received from the manufacturers contain trace amount of iron. Using this residual Fe, we investigated the photochemical formation of Fe(II) in aqueous HA solutions to elucidate the photochemical cycles of Fe(III)-Fe(II) in the atmospheric water drops. We purchased HAs from several different suppliers. We investigated the effects of pH and wavelengths on Fe(II) photo-formation using monochromatic radiations at 313, 334, 366, and 405 nm. Concentrations of photochemically formed Fe(II) were determined by ferrozine-HPLC technique, and the apparent quantum yields were determined based on the total absorbance of the HA solutions. Fe(II) photo-formation characteristics of the aqueous humic acid solutions purchased from different suppliers showed slightly different wavelength dependence. Furthermore, we compared Fe(II) photoformation characteristics observed in aqueous HA solutions with those in the aqueous extracts of atmospheric aerosols collected in Okinawa, Japan. The results showed that the apparent quantum yields of the aerosol extracts were 5-10 times higher than those of the HA solutions. Wavelength-dependence of Fe(II) photo-formation observed in the aqueous extracts of aerosols was similar to that seen in the aqueous HA solutions.

  19. Extraction of p-coumaric acid and ferulic acid using surfactant-based aqueous two-phase system.

    PubMed

    Dhamole, Pradip B; Demanna, Dhanashree; Desai, S A

    2014-09-01

    Ferulic acid (FA) and p-coumaric acid (pCA) are high-value products that can be obtained by alkaline hydrolysis of lignocellulose. Present work explores the potential of surfactant-based cloud-point extraction (CPE) for FA and pCA extraction from corn cob hydrolysate. More than 90 % (w/w) extraction of both FA and pCA was achieved from model system with L92. The partition coefficient of FA and pCA in L92 aqueous phase system was 35 and 55, respectively. A significant enrichment (8-10-fold) of both FA and pCA was achieved in surfactant-rich phase. Furthermore, the downstream process volume was reduced by 10 to 13 times. Optimized conditions (5 % v/v L92 and pH 3.0) resulted into 85 and 89 % extraction of FA and p-CA, respectively, from alkaline corn cob hydrolysate. Biocompatibility tests were carried out for L92 for ethanol fermentation and found to be biocompatible. Thus, the new surfactant-based CPE system not only concentrated FA and pCA but also reduced the process volume significantly. Further, aqueous phase containing sugars can be used for ethanol fermentation. PMID:25082768

  20. Laboratory photochemical processing of aqueous aerosols: formation and degradation of dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls

    NASA Astrophysics Data System (ADS)

    Pavuluri, C. M.; Kawamura, K.; Mihalopoulos, N.; Swaminathan, T.

    2015-07-01

    To better understand the photochemical processing of dicarboxylic acids and related polar compounds, we conducted batch UV irradiation experiments on two types of aerosol samples collected from India, which represent anthropogenic (AA) and biogenic (BA) aerosols, for time periods of 0.5 to 120 h. The irradiated samples were analyzed for molecular compositions of diacids, oxoacids and α-dicarbonyls. The results show that photochemical degradation of oxalic (C2), malonic (C3) and other C8-C12 diacids overwhelmed their production in aqueous aerosols, whereas succinic acid (C4) and C5-C7 diacids showed a significant increase (ca. 10 times) during the course of irradiation experiments. The photochemical formation of oxoacids and α-dicarbonyls overwhelmed their degradation during the early stages of experiment except for ω-oxooctanoic acid (ωC8), which showed a similar pattern to that of C4. We also found a gradual decrease in the relative abundance of C2 to total diacids and an increase in the relative abundance of C4 during prolonged experiment. Based on the changes in concentrations and mass ratios of selected species with the irradiation time, we hypothesize that iron-catalyzed photolysis of C2 and C3 diacids controls their concentrations in Fe-rich atmospheric waters, whereas photochemical formation of C4 diacid (via ωC8) is enhanced with photochemical processing of aqueous aerosols in the atmosphere. This study demonstrates that the ambient aerosols contain abundant precursors that produce diacids, oxoacids and α-dicarbonyls, although some species such as oxalic acid decompose extensively during an early stage of photochemical processing.

  1. Laboratory photochemical processing of aqueous aerosols: formation and degradation of dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls

    NASA Astrophysics Data System (ADS)

    Pavuluri, C. M.; Kawamura, K.; Mihalopoulos, N.; Swaminathan, T.

    2015-01-01

    To better understand the photochemical processing of dicarboxylic acids and related polar compounds, we conducted batch UV irradiation experiments on two types of aerosol samples collected from India, which represent anthropogenic (AA) and biogenic aerosols (BA), for time periods of 0.5 to 120 h. The irradiated samples were analyzed for molecular compositions of diacids, oxoacids and α-dicarbonyls. The results show that photochemical degradation of oxalic (C2) and malonic (C3) and other C8-C12 diacids overwhelmed their production in aqueous aerosols whereas succinic acid (C4) and C5-C7 diacids showed a significant increase (ca. 10 times) during the course of irradiation experiments. The photochemical formation of oxoacids and α-dicarbonyls overwhelmed their degradation during the early stages of experiment, except for ω-oxooctanoic acid (ωC8) that showed a similar pattern to that of C4. We also found a gradual decrease in the relative abundance of C2 to total diacids and an increase in the relative abundance of C4 during prolonged experiment. Based on the changes in concentrations and mass ratios of selected species with the irradiation time, we hypothesize that iron-catalyzed photolysis of C2 and C3 diacids dominates their concentrations in Fe-rich atmospheric waters, whereas photochemical formation of C4 diacid (via ωC8) is enhanced with photochemical processing of aqueous aerosols in the atmosphere. This study demonstrates that the ambient aerosols contain abundant precursors that produce diacids, oxoacids and α-dicarbonyls, although some species such as oxalic acid decompose extensively during an early stage of photochemical processing.

  2. Novel Regenerated Solvent Extraction Processes for the Recovery of Carboxylic Acids or Ammonia from Aqueous Solutions Part I. Regeneration of Amine-Carboxylic Acid Extracts

    SciTech Connect

    Poole, L.J.; King, C.J.

    1990-03-01

    Two novel regenerated solvent extraction processes are examined. The first process has the potential to reduce the energy costs inherent in the recovery of low-volatility carboxylic acids from dilute aqueous solutions. The second process has the potential for reducing the energy costs required for separate recovery of ammonia and acid gases (e.g. CO{sub 2} and H{sub 2}S) from industrial sour waters. The recovery of carboxylic acids from dilute aqueous solution can be achieved by extraction with tertiary amines. An approach for regeneration and product recovery from such extracts is to back-extract the carboxylic acid with a water-soluble, volatile tertiary amine, such as trimethylamine. The resulting trimethylammonium carboxylate solution can be concentrated and thermally decomposed, yielding the product acid and the volatile amine for recycle. Experimental work was performed with lactic acid, succinic acid, and fumaric acid. Equilibrium data show near-stoichiometric recovery of the carboxylic acids from an organic solution of Alamine 336 into aqueous solutions of trimethylamine. For fumaric and succinic acids, partial evaporation of the aqueous back extract decomposes the carboxylate and yields the acid product in crystalline form. The decomposition of aqueous solutions of trimethylammonium lactates was not carried out to completion, due to the high water solubility of lactic acid and the tendency of the acid to self-associate. The separate recovery of ammonia and acid gases from sour waters can be achieved by combining steam-stripping of the acid gases with simultaneous removal of ammonia by extraction with a liquid cation exchanger. The use of di-2,4,4-trimethylpentyl phosphinic acid as the liquid cation exchanger is explored in this work. Batch extraction experiments were carried out to measure the equilibrium distribution ratio of ammonia between an aqueous buffer solution and an organic solution of the phosphinic acid (0.2N) in Norpar 12. The concentration

  3. Standard enthalpies of formation of γ-aminobutyric acid and the products of its dissociation in aqueous solution

    NASA Astrophysics Data System (ADS)

    Lytkin, A. I.; Chernikov, V. V.; Krutova, O. N.; Skvortsov, I. A.; Korchagina, A. S.

    2016-09-01

    Heat effects of the dissolution of crystalline γ-aminobutyric acid in water and potassium hydroxide solutions are determined by direct colorimetry at 298.15 K. Standard enthalpies of formation of γ-aminobutyric acid and the products of its dissociation in aqueous solution are calculated.

  4. Simultaneous Extraction and Depolymerization of Fucoidan from Sargassum muticum in Aqueous Media

    PubMed Central

    Balboa, Elena M.; Rivas, Sandra; Moure, Andrés; Domínguez, Herminia; Parajó, Juan Carlos

    2013-01-01

    The biomass components of the invasive seaweed Sargassum muticum were fractionated to allow their separate valorization. S. muticum (Sm) and the solid residue remaining after alginate extraction of this seaweed (AESm) were processed with hot, compressed water (hydrothermal processing) to assess the effects of temperature on fucoidan solubilization. Fucose-containing oligosaccharides were identified as reaction products. Operating under optimal conditions (170 °C), up to 62 and 85 wt% of the dry mass of Sm and AESm were solubilized, respectively. The reaction media were subjected to precipitation, nanofiltration and freeze-drying. The dried products contained 50% and 85% of the fucoidan present in Sm and AESm, respectively; together with other components such as phenolics and inorganic components. The saccharidic fraction, accounting for up to 35% of the dried extracts, contained fucose as the main sugar, and also galactose, xylose, glucose and mannose. The concentrates were characterized for antioxidant activity using the TEAC assay. PMID:24284426

  5. Simultaneous extraction and depolymerization of fucoidan from Sargassum muticum in aqueous media.

    PubMed

    Balboa, Elena M; Rivas, Sandra; Moure, Andrés; Domínguez, Herminia; Parajó, Juan Carlos

    2013-11-01

    The biomass components of the invasive seaweed Sargassum muticum were fractionated to allow their separate valorization. S. muticum (Sm) and the solid residue remaining after alginate extraction of this seaweed (AESm) were processed with hot, compressed water (hydrothermal processing) to assess the effects of temperature on fucoidan solubilization. Fucose-containing oligosaccharides were identified as reaction products. Operating under optimal conditions (170 °C), up to 62 and 85 wt% of the dry mass of Sm and AESm were solubilized, respectively. The reaction media were subjected to precipitation, nanofiltration and freeze-drying. The dried products contained 50% and 85% of the fucoidan present in Sm and AESm, respectively; together with other components such as phenolics and inorganic components. The saccharidic fraction, accounting for up to 35% of the dried extracts, contained fucose as the main sugar, and also galactose, xylose, glucose and mannose. The concentrates were characterized for antioxidant activity using the TEAC assay. PMID:24284426

  6. Exploiting β-Cyclodextrin in Molecular Imprinting for Achieving Recognition of Benzylparaben in Aqueous Media

    PubMed Central

    Asman, Saliza; Mohamad, Sharifah; Muhamad Sarih, Norazilawati

    2015-01-01

    The molecularly imprinted polymer (MIP) based on methacrylic acid functionalized β-cyclodextrin (MAA-β-CD) monomer was synthesized for the purpose of selective recognition of benzylparaben (BzP). The MAA-β-CD monomer was produced by bridging a methacrylic acid (MAA) and β-cyclodextrin (β-CD) using toluene-2,4-diisocyanate (TDI) by reacting the –OH group of MAA and one of the primary –OH groups of β-CD. This monomer comprised of triple interactions that included an inclusion complex, π–π interaction, and hydrogen bonding. To demonstrate β-CD performance in MIPs, two MIPs were prepared; molecularly imprinted polymer-methacrylic acid functionalized β-cyclodextrin, MIP(MAA-β-CD), and molecularly imprinted polymer-methacrylic acid, MIP(MAA); both prepared by a reversible addition fragmentation chain transfer polymerization (RAFT) in the bulk polymerization process. Both MIPs were characterized using the Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), and Brunauer-Emmett-Teller (BET). The presence of β-CD not only influenced the morphological structure, it also affected the specific surface area, average pore diameter, and total pore volume of the MIP. The rebinding of the imprinting effect was evaluated in binding experiments, which proved that the β-CD contributed significantly to the enhancement of the recognition affinity and selective adsorption of the MIP. PMID:25667978

  7. Multicarboxylic hyperbranched polyglycerol modified SBA-15 for the adsorption of cationic dyes and copper ions from aqueous media

    NASA Astrophysics Data System (ADS)

    Chen, Zhengji; Zhou, Li; Zhang, Faai; Yu, Chuanbai; Wei, Zhibo

    2012-04-01

    The aim of the present work was to investigate the potential of multicarboxylic hyperbranched polyglycerol (HPG) modified mesoporous SBA-15 (SBA/HPG-COOH) as adsorbent for the removal of cationic dyes or/and heavy metal ions from aqueous media. The SBA/HPG-COOH adsorbents can be facilely synthesized through two steps: in situ anionic ring-opening polymerization of glycidol and further modification of hydroxyl groups by succinic anhydride. The resulting SBA/HPG-COOH was characterized by means of FTIR, TGA, XRD, SEM and nitrogen adsorption-desorption isotherms. The results demonstrate that the SBA/HPG-COOH was successfully synthesized and the density of carboxylic groups on the SBA/HPG-COOH is calculated to be as high as 1.5 mmol/g, posing a powerful base for adsorbing cationic adsorbates. Four kinds of dyes and copper ions were chosen as representatives to investigate the adsorption ability of SBA/HPG-COOH. The SBA/HPG-COOH adsorbent showed quick adsorption rate, high adsorption capacity (e.g., its saturated adsorption capacity for methylene blue (MB) can reach 0.50 mmol/g, while for unmodified SBA-15 is lower than 0.05 mmol/g), and high selectivity for cationic adsorbates. The fitness of Langmuir adsorption model and pseudo second-order kinetics on describing the adsorption isotherm and kinetics of SBA/HPG-COOH for MB dye was examined, respectively. It is believed that this robust SBA/HPG-COOH adsorbent will find important application in removal of cationic adsorbates from aqueous solution.

  8. Sulphur Kβ emission spectra reveal protonation states of aqueous sulfuric acid

    PubMed Central

    Niskanen, Johannes; Sahle, Christoph J.; Ruotsalainen, Kari O.; Müller, Harald; Kavčič, Matjaž; Žitnik, Matjaž; Bučar, Klemen; Petric, Marko; Hakala, Mikko; Huotari, Simo

    2016-01-01

    In this paper we report an X-ray emission study of bulk aqueous sulfuric acid. Throughout the range of molarities from 1 M to 18 M the sulfur Kβ emission spectra from H2SO4 (aq) depend on the molar fractions and related deprotonation of H2SO4. We compare the experimental results with results from emission spectrum calculations based on atomic structures of single molecules and structures from ab initio molecular dynamics simulations. We show that the S Kβ emission spectrum is a sensitive probe of the protonation state of the acid molecules. Using non-negative matrix factorization we are able to extract the fractions of different protonation states in the spectra, and the results are in good agreement with the simulation for the higher part of the concentration range. PMID:26888159

  9. Sulphur Kβ emission spectra reveal protonation states of aqueous sulfuric acid.

    PubMed

    Niskanen, Johannes; Sahle, Christoph J; Ruotsalainen, Kari O; Müller, Harald; Kavčič, Matjaž; Žitnik, Matjaž; Bučar, Klemen; Petric, Marko; Hakala, Mikko; Huotari, Simo

    2016-02-18

    In this paper we report an X-ray emission study of bulk aqueous sulfuric acid. Throughout the range of molarities from 1 M to 18 M the sulfur Kβ emission spectra from H2SO4 (aq) depend on the molar fractions and related deprotonation of H2SO4. We compare the experimental results with results from emission spectrum calculations based on atomic structures of single molecules and structures from ab initio molecular dynamics simulations. We show that the S Kβ emission spectrum is a sensitive probe of the protonation state of the acid molecules. Using non-negative matrix factorization we are able to extract the fractions of different protonation states in the spectra, and the results are in good agreement with the simulation for the higher part of the concentration range.

  10. Competitive adsorption of boric acid and chromate onto alumina in aqueous solutions.

    PubMed

    Demetriou, A; Pashalidis, I

    2014-01-01

    The competitive adsorption of boric acid and chromate from aqueous solutions by alumina has been investigated by spectrophotometry at pH 8, ionic strength = 0.0, 0.1 and 1.0 M NaClO4, T = 22 ± 3 °C and under normal atmospheric conditions. The experimental data show that addition of excess boric acid in the system leads to the increase of Cr(VI) concentration in solution, indicating the replacement of adsorbed chromate by boron on the alumina surface. Data evaluation results in the determination of the competition reaction constant and the formation constant of the Cr(VI) surface complexes, which are logKCr(VI)-B(III) = -3.5 ± 0.2 and logβ*Cr = 7.6 ± 0.3, respectively.

  11. Solubility and reactivity of peroxyacetyl nitrate (PAN) in dilute aqueous salt solutions and in sulphuric acid

    NASA Astrophysics Data System (ADS)

    Frenzel, A.; Kutsuna, S.; Takeuchi, K.; Ibusuki, T.

    The loss rates of PAN in several dilute aqueous salt solutions (NaBr, Na 2SO 3, KI, NaNO 2, FeCl 3, and FeSO 4) and in sulphuric acid were measured at 279 K with a simple bubbler experiment. They are little different from that in pure water. For 5 M sulphuric acid hydrolysis and solubility were determined in the temperature range of 243-293 K. The hydrolysis rate kh=3.2×10 -4 s -1 at 293 K is close to that in water. The observed temperature dependence of the Henry's Law constant H=10- 6.6±0.6exp((4780±420)/T) M atm -1 leads to enthalpy and entropy of solvation Δ Hsolv=-39.7±3.5 kJ mol -1 and Δ Ssolv=-126±11 J mol -1 K -1, respectively.

  12. Separation of glycols from dilute aqueous solutions via complexation with boronic acids

    SciTech Connect

    Randel, L.A.; King, C.J.

    1991-07-01

    This work examines methods of separating low molecular weight glycols from dilute aqueous solution. Extraction into conventional solvents is generally not economical, since, in the literature reviewed, distribution ratios for the two- to four-carbon glycols are all less than one. Distribution ratios can be increased, however, by incorporating into the organic phase an extracting agent that will complex with the solute of interest. The extracting agent investigated in this work is 3-nitrophenylboronic acid (NPBA). NPBA, a boric acid derivative, reversibly complexes with many glycols. The literature on complexation of borate and related compounds with glycols, including mechanistic data, measurement techniques, and applications to separation processes, provides information valuable for designing experiments with NPBA and is reviewed herein. 88 refs., 15 figs., 24 tabs.

  13. Sunlight-initiated chemistry of aqueous pyruvic acid: building complexity in the origin of life.

    PubMed

    Griffith, Elizabeth C; Shoemaker, Richard K; Vaida, Veronica

    2013-10-01

    Coupling chemical reactions to an energy source is a necessary step in the origin of life. Here, we utilize UV photons provided by a simulated sun to activate aqueous pyruvic acid and subsequently prompt chemical reactions mimicking some of the functions of modern metabolism. Pyruvic acid is interesting in a prebiotic context due to its prevalence in modern metabolism and its abiotic availability on early Earth. Here, pyruvic acid (CH3COCOOH, a C3 molecule) photochemically reacts to produce more complex molecules containing four or more carbon atoms. Acetoin (CH3CHOHCOCH3), a C4 molecule and a modern bacterial metabolite, is produced in this chemistry as well as lactic acid (CH3CHOHCOOH), a molecule which, when coupled with other abiotic chemical reaction pathways, can provide a regeneration pathway for pyruvic acid. This chemistry is discussed in the context of plausible environments on early Earth such as near the ocean surface and atmospheric aerosol particles. These environments allow for combination and exchange of reactants and products of other reaction environments (such as shallow hydrothermal vents). The result could be a contribution to the steady increase in chemical complexity requisite in the origin of life.

  14. Sunlight-initiated Chemistry of Aqueous Pyruvic Acid: Building Complexity in the Origin of Life

    NASA Astrophysics Data System (ADS)

    Griffith, Elizabeth C.; Shoemaker, Richard K.; Vaida, Veronica

    2013-10-01

    Coupling chemical reactions to an energy source is a necessary step in the origin of life. Here, we utilize UV photons provided by a simulated sun to activate aqueous pyruvic acid and subsequently prompt chemical reactions mimicking some of the functions of modern metabolism. Pyruvic acid is interesting in a prebiotic context due to its prevalence in modern metabolism and its abiotic availability on early Earth. Here, pyruvic acid (CH3COCOOH, a C3 molecule) photochemically reacts to produce more complex molecules containing four or more carbon atoms. Acetoin (CH3CHOHCOCH3), a C4 molecule and a modern bacterial metabolite, is produced in this chemistry as well as lactic acid (CH3CHOHCOOH), a molecule which, when coupled with other abiotic chemical reaction pathways, can provide a regeneration pathway for pyruvic acid. This chemistry is discussed in the context of plausible environments on early Earth such as near the ocean surface and atmospheric aerosol particles. These environments allow for combination and exchange of reactants and products of other reaction environments (such as shallow hydrothermal vents). The result could be a contribution to the steady increase in chemical complexity requisite in the origin of life.

  15. Stable Isotope Characteristics of Jarosite: The Acidic Aqueous History of Mars

    NASA Technical Reports Server (NTRS)

    Earl, Lyndsey D.

    2005-01-01

    The Mars Rover Opportunity found jarosite (Na(+) or K(+))Fe3SO4(OH)6 at the Meridiani Planum site. This mineral forms from the evaporation of an aqueous acidic sulfate brine. Oxygen isotope compositions may characterize formation conditions but subsequent isotope exchange may have occurred between the sulfate and hydroxide of jarosite and water. The rate of oxygen isotope exchange depends on the acidity and temperature of the brine, but it has not been investigated in detail. We performed laboratory experiments to determine the rate of oxygen isotope exchange under varying acidities and temperatures to learn more about this process. Barium sulfate samples were precipitated weekly from acidic sodium sulfate brines. The oxygen isotope composition of the precipitated sulfate was obtained using a Finnigan MAT253 Isotope Ratio Mass-Spectrometer. The results show that water was trapped in barium sulfate during precipitation. Trapped water may exchange with sulfate when exposed to high temperatures, thus changing the isotope composition of sulfate and the observed fractionation factor of oxygen isotope exchange between sulfate and water. The results of our research will contribute to the understanding of oxygen isotope exchange rates between water and sulfate under acidic conditions and provide experimental knowledge for the dehydration of barium sulfate samples.

  16. Sulfate Formation From Acid-Weathered Phylosilicates: Implications for the Aqueous History of Mars

    NASA Technical Reports Server (NTRS)

    Craig, P. I.; Ming, D. W.; Rampe, E. B.

    2014-01-01

    Most phyllosilicates on Mars are thought to have formed during the planet's earliest Noachian era, then Mars underwent a global change making the planet's surface more acidic [e.g. 1]. Prevailing acidic conditions may have affected the already existing phyllosilicates, resulting in the formation of sulfates. Both sulfates and phyllosilicates have been identified on Mars in a variety of geologic settings [2] but only in a handful of sites are these minerals found in close spatial proximity to each other, including Mawrth Vallis [3,4] and Gale Crater [5]. While sulfate formation from the acidic weathering of basalts is well documented in the literature [6,7], few experimental studies investigate sulfate formation from acid-weathered phyllosilicates [8-10]. The purpose of this study is to characterize the al-teration products of acid-weathered phyllosilicates in laboratory experiments. We focus on three commonly identified phyllosilicates on Mars: nontronite (Fe-smectite), saponite (Mg-smectite), and montmorillonite (Al-smectite) [1, and references therein]. This information will help constrain the formation processes of sulfates observed in close association with phyllosilicates on Mars and provide a better understanding of the aqueous history of such regions as well as the planet as a whole.

  17. Reusable fluorescent photocrosslinked polymeric sensor for determining lead ions in aqueous media

    NASA Astrophysics Data System (ADS)

    Çubuk, Soner; Taşci, Neşe; Kahraman, Memet Vezir; Bayramoğlu, Gülay; Yetimoğlu, Ece Kök

    2016-04-01

    In this study, 1-vinylimidazole units bearing photocured films were prepared as fluorescent sensors towards Pb2 + in aqueous solutions. The influence of experimental parameters such as pH, time and foreign ion concentrations were investigated. Sensor response was linear over a concentration range of 4.83 × 10- 8 to 4.83 × 10- 7 mol L- 1. The sensor was highly sensitive with a detection limit as low as 1.87 × 10- 8 mol L- 1, and having a selectivity of over four thousand fold. The response time of the sensor was found to be 5 min. When stored in a desiccator at room temperature the sensor showed good stability after a 5 month period. The fluorescence sensors were successful in the determination of Pb2 + in water samples as well as in the determination of the quantitative amount of lead and the results were satisfying. Compared with previously reported literature, the prepared new sensor is highly sensitive and selective.

  18. Redox control for electrochemical dechlorination of trichloroethylene in bicarbonate aqueous media

    PubMed Central

    Mao, Xuhui; Ciblak, Ali; Amiri, Mohammad; Alshawabkeh, Akram N.

    2011-01-01

    The role of iron anode on electrochemical dechlorination of aqueous trichloroethylene (TCE) is evaluated using batch mixed-electrolyte experiments. A significantly higher dechlorination rate, up to 99%, is reported when iron anode and copper foam cathodes are used. In contrast to the oxygen-releasing inert anode, the cast iron anode generates ferrous species, which regulate the electrolyte to a reducing condition (low ORP value) and favor the reduction of TCE. The main products of TCE electrochemical reduction on copper foam cathode include ethene and ethane. The ratio of these two hydrocarbons gases varied with the electrolyte ORP condition and current density as more ethane gas generates at more reducing electrolyte condition and at higher current condition. A pseudo-first order model is used to describe the degradation of TCE, the first order rate constant (k) increased with the current applied, but exhibits a negative relation with initial concentration. Depending on the current, electrolysis by iron anode causes a reduction in the ORP and an increase in the pH of the mixed electrolyte. Enhanced reaction rates in this investigation indicate that the electrochemical reduction using copper foam and iron anode may be a promising process for remediation of groundwater contaminated with chlorinated organic compounds. PMID:21671641

  19. A selective fluorescent 'turn-on' sensor for recognition of Zn2 + in aqueous media

    NASA Astrophysics Data System (ADS)

    Ozdemir, Mecit

    2016-05-01

    A new rhodamine-based fluorescent probe 'RhAP' was synthesized and successfully characterized using FT-IR, 13C NMR and 1H NMR spectroscopies, LC-MS/MS spectrometry and elemental analysis. The RhAP, a colorless and non-fluorescent compound, showed a selective fluorescent response and colorimetric change for Zn2 + in HEPES buffer (10 mM, EtOH:water, 2:1, v/v, pH 7.2). Upon the addition of two equivalents of Zn2 + to a solution of RhAP, a nearly 35-fold enhancement of the fluorescence intensity, with an emission maximum at 578 nm, was observed in comparison to the sensor alone under the same experimental conditions. The complex formation between RhAP and Zn2 + was found to have a 1:1 ratio based on calculations obtained from Job's plot and the mole ratio plot methods. The results showed that RhAP can be used as an effective fluorescent probe for selective detecting of Zn2 + in an aqueous medium.

  20. Interaction of inorganic anions with iron-mineral adsorbents in aqueous media--a review.

    PubMed

    Kumar, Eva; Bhatnagar, Amit; Hogland, William; Marques, Marcia; Sillanpää, Mika

    2014-01-01

    A number of inorganic anions (e.g., nitrate, fluoride, bromate, phosphate, and perchlorate) have been reported in alarming concentrations in numerous drinking water sources around the world. Their presence even in very low concentrations may cause serious environmental and health related problems. Due to the presence and significance of iron minerals in the natural aquatic environment and increasing application of iron in water treatment, the knowledge of the structure of iron and iron minerals and their interactions with aquatic pollutants, especially inorganic anions in water are of great importance. Iron minerals have been known since long as potential adsorbents for the removal of inorganic anions from aqueous phase. The chemistry of iron and iron minerals reactions in water is complex. The adsorption ability of iron and iron minerals towards inorganic anions is influenced by several factors such as, surface characteristics of the adsorbent (surface area, density, pore volume, porosity, pore size distribution, pHpzc, purity), pH of the solution, and ionic strength. Furthermore, the physico-chemical properties of inorganic anions (pore size, ionic radius, bulk diffusion coefficient) also significantly influence the adsorption process. The aim of this paper is to provide an overview of the properties of iron and iron minerals and their reactivity with some important inorganic anionic contaminants present in water. It also summarizes the usage of iron and iron minerals in water treatment technology.

  1. Nanoparticle surface modification by amphiphilic polymers in aqueous media: role of polar organic solvents.

    PubMed

    Sarkar, Biswajit; Venugopal, Vinithra; Bodratti, Andrew M; Tsianou, Marina; Alexandridis, Paschalis

    2013-05-01

    We investigate the role of three polar organic solvents (dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), and glycerol) on the interfacial behavior of Pluronic P105 poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers on protonated silica nanoparticles in an aqueous dispersion. The polymer adsorption and self-assembly have been assessed from critical surface micelle concentration (csmc, measured by pyrene fluorescence spectroscopy) and adsorbed layer thickness (measured by capillary viscometry) data. Above its csmc, PEO-PPO-PEO block copolymers form hydrophobic domains on the nanoparticle surface. Below a critical concentration in water (known as critical displacer concentration, cdc), organic solvents act as displacers (molecules that can displace adsorbed polymer from a solid surface). The critical displacer concentration is obtained from the csmc and the polymer adsorbed layer thickness data. The cdc is found to be dependent on both the amount of nanoparticles present in the system as well as the nature of the displacer. Below the cdc, the csmc increases and the adsorbed polymer layer thickness decreases with increasing organic solvent concentration. Interfacial free energy calculations suggest that DMF, DMSO, and glycerol can adsorb onto the silica particles by displacing adsorbed PEO. These calculations are consistent with the experimental results in that, as a displacer, glycerol is the most effective and DMF is the least effective. Above the cdc, the influence of glycerol or DMSO on csmc is opposite to that of DMF which is attributed to the cosolvent effect.

  2. Nonaqueous and aqueous-organic media for the enantiomeric separations of neutral organophosphorus pesticides by CE.

    PubMed

    Huang, Lu; Lin, Jinming; Xu, Liangjun; Chen, Guonan

    2007-08-01

    The enantiomeric separation of some poorly water-soluble organophosphorus pesticides (OPs) has been investigated using nonaqueous solvent and aqueous-organic solvent systems. In this work, sodium cholate (SC) either with SDS or gamma-CD was used to achieve enantiomeric separations of four neutral and poorly water-soluble OPs, i.e., profenofos, prothiofos, sulprofos, and pyraclofos. Electrophoretic medium consisted of a mixture of methanol (MeOH) with ACN (4:1 v/v) or a mixture of MeOH with H(2)O and ACN (5:4:1 v/v/v). On one hand, NACE was applied for enantiomeric separation of pyraclofos using a large amount of chiral and achiral surfactants (SC and SDS). On the other hand, H(2)O was added to act as a solvent additive to increase the solubility of gamma-CD in the organic solvents such as MeOH and ACN, in which the solubility of gamma-CD was very low. The presence of H(2)O was found to be particularly useful for the enantiomeric separation of profenofos, prothiofos, and sulprofos. In this way, the range of application of the neutral CDs in CE has been extended. In addition, SC was used as the only electrolyte. The proposed method has been applied for the analysis of soil samples. PMID:17592615

  3. Redox control for electrochemical dechlorination of trichloroethylene in bicarbonate aqueous media.

    PubMed

    Mao, Xuhui; Ciblak, Ali; Amiri, Mohammad; Alshawabkeh, Akram N

    2011-08-01

    The role of iron anode on electrochemical dechlorination of aqueous trichloroethylene (TCE) is evaluated using batch mixed-electrolyte experiments. A significantly higher dechlorination rate, up to 99%, is reported when iron anode and copper foam cathodes are used. In contrast to the oxygen-releasing inert anode, the cast iron anode generates ferrous species, which regulate the electrolyte to a reducing condition (low ORP value) and favor the reduction of TCE. The main products of TCE electrochemical reduction on copper foam cathode include ethene and ethane. The ratio of these two hydrocarbons gases varied with the electrolyte ORP condition and current density as more ethane gas generates at more reducing electrolyte condition and at higher current condition. A pseudofirst-order model is used to describe the degradation of TCE; the first-order rate constant (k) increases with the current applied but exhibits a negative relation with initial concentration. Depending on the current, electrolysis by iron anode causes a reduction in the ORP and an increase in the pH of the mixed electrolyte. Enhanced reaction rates in this investigation indicate that the electrochemical reduction using copper foam and iron anode may be a promising process for remediation of groundwater contaminated with chlorinated organic compounds.

  4. Vibrational spectroscopic studies and DFT calculations on tribromoacetate and tribromoacetic acid in aqueous solution.

    PubMed

    Rudolph, Wolfram W; Irmer, Gert

    2011-09-01

    Aqueous solutions of sodium tribromoacetate (NaCBr3CO2) and its corresponding acid (CBr3COOH) have been studied using Raman and infrared spectroscopy. The spectra of the species in solution were assigned according to symmetry Cs. Characteristic bands of CBr3CO2-(aq) and the tribromoacetic acid, CBr3COOH(aq), are discussed. For the hydrated anion, the CO2 group, the symmetric CO2 stretching mode at 1332 cm(-1) and the asymmetric stretching mode at 1651 cm(-1) are characteristic while the CO mode at 1730 cm(-1) is characteristic for the spectra of the acid. The stretching mode, νC-C at 912cm(-1) for CBr3CO2-(aq) is 10 cm(-1) lower in the anion compared with that of the acid. These characteristic modes are compared to those in acetate, CH3CO2-(aq). Coupling of the modes are fairly extensive and therefore DFT calculations have been carried out in order to compare the measured spectra with the calculated ones. The geometrical parameters such as bond length and bond angles of the tribromoacetate, and tribromoacetic acid have been obtained and may be compared with the ones published for other acetates and their conjugated acids. CBr3COOH(aq) is a moderately strong acid and the pKa value derived from quantitative Raman measurements is equal to -0.23 at 23°C. The deuterated acid CBr3COOD in heavy water has been measured as well and the assignments were given.

  5. Bile acid-surfactant interactions at the liquid crystal/aqueous interface.

    PubMed

    He, Sihui; Liang, Wenlang; Cheng, Kung-Lung; Fang, Jiyu; Wu, Shin-Tson

    2014-07-14

    The interaction between bile acids and surfactants at interfaces plays an important role in fat digestion. In this paper, we study the competitive adsorption of cholic acid (CA) at the sodium dodecyl sulfate (SDS)-laden liquid crystal (LC)/aqueous interface formed with cyanobiphenyl (nCB, n = 5-8) and the mixture of 5CB with 4-(4-pentylcyclohexyl)benzonitrile (5PCH). We find that the critical concentration of CA required to displace SDS from the interface linearly decreases from 160 μM to 16 μM by reducing the alkyl chain length of nCB from n = 8 to n = 5 and from 16 μM to 1.5 μM by increasing the 5PCH concentration from 0 wt% to 19 wt% in the 5PCH-5CB binary mixture. Our results clearly demonstrate that the sensitivity of 5PCH-5CB mixtures for monitoring the interaction between CA and SDS at the LC/aqueous interface can be increased by one order of magnitude, compared to 5CB.

  6. Unified molecular picture of the surfaces of aqueous acid, base, and salt solutions.

    PubMed

    Mucha, Martin; Frigato, Tomaso; Levering, Lori M; Allen, Heather C; Tobias, Douglas J; Dang, Liem X; Jungwirth, Pavel

    2005-04-28

    The molecular structure of the interfacial regions of aqueous electrolytes is poorly understood, despite its crucial importance in many biological, technological, and atmospheric processes. A long-term controversy pertains between the standard picture of an ion-free surface layer and the strongly ion specific behavior indicating in many cases significant propensities of simple inorganic ions for the interface. Here, we present a unified and consistent view of the structure of the air/solution interface of aqueous electrolytes containing monovalent inorganic ions. Molecular dynamics calculations show that in salt solutions and bases the positively charged ions, such as alkali cations, are repelled from the interface, whereas the anions, such as halides or hydroxide, exhibit a varying surface propensity, correlated primarily with the ion polarizability and size. The behavior of acids is different due to a significant propensity of hydronium cations for the air/solution interface. Therefore, both cations and anions exhibit enhanced concentrations at the surface and, consequently, these acids (unlike bases and salts) reduce the surface tension of water. The results of the simulations are supported by surface selective nonlinear vibrational spectroscopy, which reveals among other things that the hydronium cations are present at the air/solution interface. The ion specific propensities for the air/solution interface have important implications for a whole range of heterogeneous physical and chemical processes, including atmospheric chemistry of aerosols, corrosion processes, and bubble coalescence.

  7. EXAFS study of the speciation of protactinium(V) in aqueous hydrofluoric acid solutions.

    PubMed

    De Sio, Stéphanie M; Wilson, Richard E

    2014-12-01

    The speciation of protactinium(V) in hydrofluoric acid (HF) solutions was studied using X-ray absorption spectroscopy. Extended X-ray absorption fine structure measurements were performed on an aqueous solution of 0.05 M protactinium(V) with various HF concentrations ranging from 0.5 to 27 M in order to probe the protactinium coordination sphere with respect to the identity and number of coordinating ligands. The resulting fits to the spectra suggest the presence of an eight-coordinate homoleptic fluoro complex in highly concentrated fluoride solutions (27 M), with equilibrium between seven- and eight-coordinate fluoro complexes at moderate acidities, and in more dilute solutions, results indicate that one water molecule is likely to replace a fluoride in the first coordination sphere, at a distance of 2.54-2.57 Å. Comparisons of this chemistry with group V metals, niobium and tantalum, are presented, and the potential implications for these results on the hydrolytic behavior of protactinium in aqueous systems are discussed.

  8. EXAFS study of the speciation of protactinium(V) in aqueous hydrofluoric acid solutions.

    PubMed

    De Sio, Stéphanie M; Wilson, Richard E

    2014-12-01

    The speciation of protactinium(V) in hydrofluoric acid (HF) solutions was studied using X-ray absorption spectroscopy. Extended X-ray absorption fine structure measurements were performed on an aqueous solution of 0.05 M protactinium(V) with various HF concentrations ranging from 0.5 to 27 M in order to probe the protactinium coordination sphere with respect to the identity and number of coordinating ligands. The resulting fits to the spectra suggest the presence of an eight-coordinate homoleptic fluoro complex in highly concentrated fluoride solutions (27 M), with equilibrium between seven- and eight-coordinate fluoro complexes at moderate acidities, and in more dilute solutions, results indicate that one water molecule is likely to replace a fluoride in the first coordination sphere, at a distance of 2.54-2.57 Å. Comparisons of this chemistry with group V metals, niobium and tantalum, are presented, and the potential implications for these results on the hydrolytic behavior of protactinium in aqueous systems are discussed. PMID:25389749

  9. Adsorptions of some heavy metal ions in aqueous solutions by acrylamide/maleic acid hydrogels

    SciTech Connect

    Saraydin, D.; Karadag, E.; Gueven, O.

    1995-10-01

    In this study, acrylamide-maleic acid (AAm/MA) hydrogels in the form of rod have been prepared by {gamma}-radiation. They have been used for adsorption of some heavy metal ions such as uranium, iron, and copper. For the hydrogel containing 40 mg of maleic acid and irradiated at 3.73 kGy, maximum and minimum swellings in the aqueous solutions of the heavy metal ions have been observed with water (1480%) and the aqueous solution of iron(III) nitrate (410%), respectively. Diffusions of water and heavy metal ions onto hydrogels have been found to be of the non-Fickian type of diffusion. In experiments of uranyl ions adsorption, Type II adsorption has been found. One gram of AAa/MA hydrogels sorbed 14-86 mg uranyl ions from solutions of uranyl acetate, 14-90 mg uranyl ions from solutions of uranyl nitrate, 16-39 mg iron ions from solutions of iron(IV) nitrate, and 28-81 mg copper ions from solutions of copper acetate, while acrylamide hydrogel did not sorb any heavy metals ions.

  10. Removal of acidic indigo carmine textile dye from aqueous solutions using radiation induced cationic hydrogels.

    PubMed

    Sari, Müfrettin Murat

    2010-01-01

    This study examined the removal of acidic indigo carmine dyes from aqueous solutions using cationic hydrogels. Irradiated hydrogels were investigated as a new sorbent for dye removal from aqueous solution. Poly(N,N-Diethylamino ethyl methacrylate) [poly(DEAEMA)] hydrogels were prepared by radiation polymerisation of N,N-diethylamino ethyl methacrylate [DEAEMA] monomer in the presence of cross-linking agent, ethylene glycol dimethacrylate [EGDMA], and used for the removal of acidic indigo carmine textile dye. The adsorption of dyes was examined using a batch sorption technique. The effects of pH, time and initial dye concentration on the adsorption capacity of hydrogels were investigated. Maximum gelation ratio was 98.2% at irradiation dose of 5.3 kGy. Maximum equilibrium volume swelling, V/V(0), value was 21.3 at pH 2.8. Maximum amount of adsorbed indigo carmine onto hydrogels was 96.7 mg dye/g gel at pH 2.8, 21 h of adsorption time and 120 mg/L initial dye solution. Swelling and adsorption capacity increased with decreasing of pH. Compared with Congo red, amounts of adsorbed indigo carmine are much higher than those of Congo red. Langmuir isotherm model was the best fit for these poly(DEAEMA) hydrogels-indigo carmine systems.

  11. 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.

  12. Extraction and isolation of TPE from other elements on ion exchangers in aqueous and aqueous-organic solutions of phosphoric acid

    SciTech Connect

    Guseva, L.I.; Tikhomirova, G.S.; Stepushkina, V.V.

    1988-07-01

    The behavior of Am-Es and other actinides on anion and cation exchange resins in aqueous and aqueous-organic solutions of phosphoric acid has been studied in a wide range of concentration of various components of the solution. The sorptivity of transplutonium elements (TPE) on anion exchangers from dilute H/sub 3/PO/sub 4/ with a concentration less than or equal to 1 M in presence of organic solvents (alcohols, ketones, etc.) and on cation exchangers from concentrated H/sub 3/PO/sub 4/ has been found to be significant. The possibility of use of phosphoric acid solutions for isolation of TPE from Th, Pa, U, Np, Pu, and Zr and separation of TPE in different oxidation states in presence of a high-purity oxidant has been shown.

  13. Media.

    ERIC Educational Resources Information Center

    Allen, Lee E., Ed.

    1974-01-01

    Intended for secondary English teachers, the materials and ideas presented here suggest ways to use media in the classroom in teaching visual and auditory discrimination while enlivening classes and motivating students. Contents include "Media Specialists Need Not Apply," which discusses the need for preparation of media educators with…

  14. Fundamental thermochemical properties of amino acids: gas-phase and aqueous acidities and gas-phase heats of formation.

    PubMed

    Stover, Michele L; Jackson, Virgil E; Matus, Myrna H; Adams, Margaret A; Cassady, Carolyn J; Dixon, David A

    2012-03-01

    The gas-phase acidities of the 20 L-amino acids have been predicted at the composite G3(MP2) level. A broad range of structures of the neutral and anion were studied to determine the lowest energy conformer. Excellent agreement is found with the available experimental gas-phase deprotonation enthalpies, and the calculated values are within experimental error. We predict that tyrosine is deprotonated at the CO(2)H site. Cysteine is predicted to be deprotonated at the SH but the proton on the CO(2)H is shared with the S(-) site. Self-consistent reaction field (SCRF) calculations with the COSMO parametrization were used to predict the pK(a)'s of the non-zwitterion form in aqueous solution. The differences in the non-zwitterion pK(a) values were used to estimate the free energy difference between the zwitterion and nonzwitterion forms in solution. The heats of formation of the neutral compounds were calculated from atomization energies and isodesmic reactions to provide the first reliable set of these values in the gas phase. Further calculations were performed on five rare amino acids to predict their heats of formation, acidities, and pK(a) values.

  15. Mechanisms leading to oligomers and SOA through aqueous photooxidation: insights from OH radical oxidation of acetic acid

    NASA Astrophysics Data System (ADS)

    Tan, Y.; Lim, Y. B.; Altieri, K. E.; Seitzinger, S. P.; Turpin, B. J.

    2011-06-01

    Previous experiments have demonstrated that the aqueous OH radical oxidation of methylglyoxal produces low volatility products including oxalate and oligomers. These products are found predominantly in the particle phase in the atmosphere, suggesting that methylglyoxal is a precursor of secondary organic aerosol (SOA). Acetic acid is an important intermediate in aqueous methylglyoxal oxidation and a ubiquitous product of gas phase photochemistry, making it a potential "aqueous" SOA precursor in its own right. Altieri et al. (2008) proposed that acetic acid was the precursor of oligoesters observed in methylglyoxal oxidation. However, the fate of acetic acid upon aqueous-phase oxidation is not well understood. In this research, acetic acid at concentrations relevant to atmospheric waters (20 μM-10 mM) was oxidized by OH radical. Products were analyzed by ion chromatography (IC), electrospray ionization mass spectrometry (ESI-MS), and IC-ESI-MS. The formation of glyoxylic, glycolic, and oxalic acids were observed. In contrast to methylglyoxal oxidation, succinic acid and oligomers were not detected. Using results from these and methylglyoxal + OH radical experiments, radical mechanisms responsible for oligomer formation from methylglyoxal oxidation in clouds and wet aerosols are proposed. The importance of acetic acid/acetate as an SOA precursor is also discussed. We hypothesize that this and similar chemistry is central to the daytime formation of oligomers in wet aerosols.

  16. Aggregation of montmorillonite and organic matter in aqueous media containing artificial seawater

    PubMed Central

    2009-01-01

    Background The dispersion-aggregation behaviors of suspended colloids in rivers and estuaries are affected by the compositions of suspended materials (i.e., clay minerals vs. organic macromolecules) and salinity. Laboratory experiments were conducted to investigate the dispersion and aggregation mechanisms of suspended particles under simulated river and estuarine conditions. The average hydrodynamic diameters of suspended particles (representing degree of aggregation) and zeta potential (representing the electrokinetic properties of suspended colloids and aggregates) were determined for systems containing suspended montmorillonite, humic acid, and/or chitin at the circumneutral pH over a range of salinity (0 – 7.2 psu). Results The montmorillonite-only system increased the degree of aggregation with salinity increase, as would be expected for suspended colloids whose dispersion-aggregation behavior is largely controlled by the surface electrostatic properties and van der Waals forces. When montmorillonite is combined with humic acid or chitin, the aggregation of montmorillonite was effectively inhibited. The surface interaction energy model calculations reveal that the steric repulsion, rather than the increase in electronegativity, is the primary cause for the inhibition of aggregation by the addition of humic acid or chitin. Conclusion These results help explain the range of dispersion-aggregation behaviors observed in natural river and estuarine systems. It is postulated that the composition of suspended particles, specifically the availability of steric polymers such as those contained in humic acid, determine whether the river suspension is rapidly aggregated and settled or remains dispersed in suspension when it encounters increasingly saline environments of estuaries and oceans. PMID:19166595

  17. Catalytic currents of hydrogen evolution by platinum-group metal mercaptoquinolinates in aqueous-organic media

    SciTech Connect

    Ulakhovich, N.A.; Budnikov, G.K.; Medyantseva, E.P.; Romanova, O.N.; Sturis, A.P.

    1986-06-20

    Coordination compounds of Ru(III), Rh(III), Os(III), and Ir(III) with methyl derivatives of 8-mercaptoquinoline catalyze the evolution of hydrogen on mercury and graphite electrodes in a mixture of DMFA and acetate buffer solution. The catalytic activity of the complexes increases with decreasing acidity of the mercapto group. The proposed scheme of the electrode process includes preprotonation of the original complex with the central atom in the 3+ degree of oxidation.

  18. Electron-transfer reactions of oxovanadium(IV) and dioxovanadium(V) ions with metal tris(polypyridine) complexes in aqueous media

    SciTech Connect

    Macartney, D.H.

    1986-06-18

    The kinetics of the oxidation of oxovanadium(IV), VO(H/sub 2/O)/sub 5//sup 2 +/, by RuL/sub 3//sup 3 +/ and NiL/sub 3//sup 3 +/ and the reduction of dioxovanadium(V), VO/sub 2/(H/sub 2/O)/sub 4//sup +/, by OsL/sub 3//sup 3 +/ (L is 2,2'-bipyridine, 1,10-phenanthroline, or a substituted derivative) were studied in acidic aqueous media at 25/sup 0/C. The oxidations of CO/sup 2 +/ displayed an inverse rate dependence on acid concentration with a rate law of the form k/sub obsd/ = k/sub a/ + k/sub b/(H/sup +/)/sup -1/, while the rate constants for the reduction of VO/sub 2//sup +/ increased with (H/sup +/); k/sub obsd/ = k/sub c/ + k/sub d/(H/sup +/). The more reactive vanadium(IV) and -(V) species are the VO(OH)/sup +/ and VO(OH)/sup 2 +/ ions, respectively, and an application of the Marcus relationship to the cross-reaction data yields a self-exchange rate constant of approx.10/sup -3/ M/sup -1/ s/sup -1/ for the VO(OH)/sup +/2+/ couple. The exchange rate constant is similar to the corresponding values derived from Marcus calculations for Fe/sup 2+/3+/(aq) and the isoelectronic TiOH/sup 2+/3+/(aq) couple.

  19. Chromium(VI) reduction by hydrogen sulfide in aqueous media: stoichiometry and kinetics.

    PubMed

    Kim, C; Zhou, Q; Deng, B; Thornton, E C; Xu, H

    2001-06-01

    The objective of this work was to investigate the reaction stoichiometry, kinetics, and mechanism for Cr(VI) reduction by hydrogen sulfide in the aqueous phase. Batch experiments with excess [Cr(VI)] over [H2S]T indicated that the molar amount of sulfide required for the reduction of 1 M Cr(VI) was 1.5, suggesting the following stoichiometry: 2CrO4(2-) + 3H2S + 4H+-->2Cr(OH)3(s) + 3S(s) + 2H2O. Further study with transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) confirmed that chromium hydroxide and elemental sulfur were the stable products. The kinetics of Cr(VI) reduction by hydrogen sulfide was measured under various initial concentrations of Cr(VI) and sulfide as well as pH values controlled by HEPES, phosphate, and borate buffers. Results showed that the overall reaction was second-order, i.e., first-order with respect to Cr(VI) and first-order to sulfide. The reaction rate increased as pH was decreased, and the pH dependence correlated well with the fraction of fully protonated sulfide (H2S) in the pH range of 6.5-10. The nature of buffers did not influence the reaction rate significantly in the homogeneous system. The reaction kinetics could be interpreted by a three-step mechanism: formation of an inner-sphere chromate-sulfide intermediate complex ((H2O4CrVIS)2-), intramolecular electron transfer to form Cr(IV) species, and subsequent fast reactions leading to Cr(III).

  20. Permeability of acetic acid through organic films at the air-aqueous interface.

    PubMed

    Gilman, Jessica B; Vaida, Veronica

    2006-06-22

    Recent field studies of collected aerosol particles, both marine and continental, show that the outermost layers contain long-chain (C >or= 18) organics. The presence of these long-chain organics could impede the transport of gases and other volatile species across the interface. This could effect the particle's composition, lifetime, and heterogeneous chemistry. In this study, the uptake rate of acetic acid vapor across a clean interface and through films of long-chain organics into an aqueous subphase solution containing an acid-base indicator (bromocresol green) was measured under ambient conditions using visible absorption spectroscopy. Acetic acid is a volatile organic compound (VOC) and is an atmospherically relevant organic acid. The uptake of acetic acid through single-component organic films of 1-octadecanol (C(18)H(38)O), 1-triacontanol (C(30)H(62)O), cis-9-octadecen-1-ol (C(18)H(36)O), and nonacosane (C(29)H(60)) in addition to two mixed films containing equimolar 1-triacontanol/nonacosane and equimolar 1-triacontanol/cis-9-octadecen-1-ol was determined. These species represent long-chain organic compounds that reside at the air-aqueous interface of atmospheric aerosols. The cis-9-octadecen-1-ol film had little effect on the net uptake rate of acetic acid vapor into solution; however, the uptake rate was reduced by almost one-half by an interfacial film of 1-triacontanol. The measured uptake rates were used to calculate the permeability of acetic acid through the various films which ranged from 1.5 x 10(-3) cm s(-1) for 1-triacontanol, the least permeable film, to 2.5 x 10(-2) cm s(-1) for cis-9-octadecen-1-ol, the most permeable film. Both mixed films had permeabilities that were between that of the single-component films comprising the mixture. This shows that the permeability of a mixed film may not be solely determined by the most permeable species in the mixture. The permeabilities of all the films studied here are discussed in relation to their

  1. Enhancement of a novel extracellular uricase production by media optimization and partial purification by aqueous three-phase system.

    PubMed

    Ram, Senthoor K; Raval, Keyur; JagadeeshBabu, P E

    2015-01-01

    Uricase (urate: oxygen oxidoreductase, EC 1.7.3.3), an enzyme belonging to the class of oxidoreductases, catalyzes the enzymatic oxidation of uric acid to allantoin and finds a wide variety of application as therapeutic and clinical reagent. In this study, uricase production ability of the bacterial strains isolated from deep litter poultry soil is investigated. The strain with maximum extracellular uricase production capability was identified as Xanthomonas fuscans subsp. aurantifolii based on 16S rRNA sequencing. Effect of various carbon and nitrogen sources on uricase productivity was investigated. The uricase production for this strain was optimized using statistically based experimental designs and resulted in uricase activity of 306 U/L, which is 2 times higher than initial uricase activity. Two-step purification, such as ammonium sulfate precipitation and aqueous two-phase system, was carried out and a twofold increase in yield and specific activity was observed.

  2. Kinetics and reaction engineering of levulinic acid production from aqueous glucose solutions.

    PubMed

    Weingarten, Ronen; Cho, Joungmo; Xing, Rong; Conner, William Curtis; Huber, George W

    2012-07-01

    We have developed a kinetic model for aqueous-phase production of levulinic acid from glucose using a homogeneous acid catalyst. The proposed model shows a good fit with experimental data collected in this study in a batch reactor. The model was also fitted to steady-state data obtained in a plug flow reactor (PFR) and a continuously stirred tank reactor (CSTR). The kinetic model consists of four key steps: (1) glucose dehydration to form 5-hydroxymethylfurfural (HMF); (2) glucose reversion/degradation reactions to produce humins (highly polymerized insoluble carbonaceous species); (3) HMF rehydration to form levulinic acid and formic acid; and (4) HMF degradation to form humins. We use our model to predict the optimal reactor design and operating conditions for HMF and levulinic acid production in a continuous reactor system. Higher temperatures (180-200 °C) and shorter reaction times (less than 1 min) are essential to maximize the HMF content. In contrast, relatively low temperatures (140-160 °C) and longer residence times (above 100 min) are essential for maximum levulinic acid yield. We estimate that a maximum HMF carbon yield of 14% can be obtained in a PFR at 200 °C and a reaction time of 10 s. Levulinic acid can be produced at 57% carbon yield (68% of the theoretical yield) in a PFR at 149 °C and a residence time of 500 min. A system of two consecutive PFR reactors shows a higher performance than a PFR and CSTR combination. However, compared to a single PFR, there is no distinct advantage to implement a system of two consecutive reactors.

  3. Suitability of peracetic acid for sterilization of media for mycoplasma cultures.

    PubMed Central

    Wutzler, P; Sprössig, M; Peterseim, H

    1975-01-01

    The utility of peracetic acid for sterilization of serum and yeast extract additions to mycoplasma medium was studied by culturing six Mycoplasma species. Culture media containing additions that had been sterilized with peracetic acid proved to be as good as filtered components. The use of 0.05 to 0.1% peracetic acid is recommended to sterilize the serum and yeast extract additions since savings in time and equipment can be accomplished. PMID:1100656

  4. Norbadione a: kinetics and thermodynamics of cesium uptake in aqueous and alcoholic media.

    PubMed

    Korovitch, Alexandre; Mulon, Jean-Baptiste; Souchon, Vincent; Leray, Isabelle; Valeur, Bernard; Mallinger, Aurélie; Nadal, Brice; Le Gall, Thierry; Lion, Claude; Ha-Duong, Nguyêt-Thanh; El Hage Chahine, Jean-Michel

    2010-10-01

    Norbadione A (NbA) is a mushroom pigment, which is assumed to be involved in (137)Cs accumulation all over Europe during the Chernobyl nuclear accident. NbA bears seven acid-base functional groups, among which are two enolic and two carboxylic acid moieties. This work deals with complex formation of Cs(+) and NbA in ethanol, ethanol/water (9:1) (M1), and water with, when required, the support of two Cs(+) ionophore probes, calix[4]arene-bis(crown-6-ether)dioxycoumarine (A1) and its tetrasuslfonated form (A2). In ethanol, two Cs(+) complexes are formed, with the affinity constants K(1EtOH) = (1.1 ± 0.25) × 10(5) and K(2EtOH) = (2.1 ± 0.4) × 10(3). In M1, a single Cs(+) complex occurs when only the enols are deprotonated, whereas a bicomplex is formed when both enols and carboxylic acids are deprotonated: K(1M1) = (1.5 ± 0.3) × 10(5) and K(2M1) = (4 ± 2) × 10(3). These data are confirmed by stopped-flow and T-jump kinetics. In ethanol, a fast Cs(+) exchange occurs between NbA and A1: direct rate constant, k(1) = (3.1 ± 0.1) × 10(7) M(-1) s(-1); reverse rate constant k(-1) = (2.8 ± 1) × 10(5) M(-1) s(-1); and Cs(+) exchange constant, K(1Exchange) = (9 ± 4) × 10(-3). In M1, the quenching of A2 fluorescence by NbA is used to determine the kinetics of complex formation with Cs(+): k(2) = (1.8 ± 0.4) × 10(9) M(-1) s(-1); k(-2) = (1.80 ± 0.15) × 10(4) s(-1); and K(1M1) = (1.5 ± 0.5) × 10(5). The affinity of NbA for Cs(+) is probably the result of the particular structure in which the two pulvinic acid arms adopt a conformation that forms two complexation sites composed of the two enolates and/or the two carboxylates. This renders the efficiency in Cs(+) uptake comparable to that of some calixarenes or crown ethers. PMID:20831226

  5. Norbadione a: kinetics and thermodynamics of cesium uptake in aqueous and alcoholic media.

    PubMed

    Korovitch, Alexandre; Mulon, Jean-Baptiste; Souchon, Vincent; Leray, Isabelle; Valeur, Bernard; Mallinger, Aurélie; Nadal, Brice; Le Gall, Thierry; Lion, Claude; Ha-Duong, Nguyêt-Thanh; El Hage Chahine, Jean-Michel

    2010-10-01

    Norbadione A (NbA) is a mushroom pigment, which is assumed to be involved in (137)Cs accumulation all over Europe during the Chernobyl nuclear accident. NbA bears seven acid-base functional groups, among which are two enolic and two carboxylic acid moieties. This work deals with complex formation of Cs(+) and NbA in ethanol, ethanol/water (9:1) (M1), and water with, when required, the support of two Cs(+) ionophore probes, calix[4]arene-bis(crown-6-ether)dioxycoumarine (A1) and its tetrasuslfonated form (A2). In ethanol, two Cs(+) complexes are formed, with the affinity constants K(1EtOH) = (1.1 ± 0.25) × 10(5) and K(2EtOH) = (2.1 ± 0.4) × 10(3). In M1, a single Cs(+) complex occurs when only the enols are deprotonated, whereas a bicomplex is formed when both enols and carboxylic acids are deprotonated: K(1M1) = (1.5 ± 0.3) × 10(5) and K(2M1) = (4 ± 2) × 10(3). These data are confirmed by stopped-flow and T-jump kinetics. In ethanol, a fast Cs(+) exchange occurs between NbA and A1: direct rate constant, k(1) = (3.1 ± 0.1) × 10(7) M(-1) s(-1); reverse rate constant k(-1) = (2.8 ± 1) × 10(5) M(-1) s(-1); and Cs(+) exchange constant, K(1Exchange) = (9 ± 4) × 10(-3). In M1, the quenching of A2 fluorescence by NbA is used to determine the kinetics of complex formation with Cs(+): k(2) = (1.8 ± 0.4) × 10(9) M(-1) s(-1); k(-2) = (1.80 ± 0.15) × 10(4) s(-1); and K(1M1) = (1.5 ± 0.5) × 10(5). The affinity of NbA for Cs(+) is probably the result of the particular structure in which the two pulvinic acid arms adopt a conformation that forms two complexation sites composed of the two enolates and/or the two carboxylates. This renders the efficiency in Cs(+) uptake comparable to that of some calixarenes or crown ethers.

  6. Dithizone as novel and efficient chromogenic probe for cyanide detection in aqueous media through nucleophilic addition into diazenylthione moiety.

    PubMed

    Tavallali, Hossein; Deilamy-Rad, Gohar; Parhami, Abolfath; Kiyani, Sajede

    2014-01-01

    A new selective chemodosimeter probe was developed by the introduction of dithizone (DTZ) as a simple and available dye for detection of cyanide in aqueous media which enables recognition of cyanide over other competing anions such as acetate, dihydrogen phosphate, fluoride and benzoate through covalent bonding. The sensing properties of DTZ were investigated in DMSO/H2O (1:9) and have demonstrated a very high selectivity toward the cyanide anions. A reasonable recognition mechanism was suggested using UV-Vis, (1)H NMR and FTIR spectroscopy techniques. Time dependent density function theory (TDDFT) computations of UV-Vis excitation for DTZ2-CN adduct agreed well with our experimental findings. The detection limit of the new chromogenic probe was measured to be 0.48 μmol L(-1) which is much lower than most recently reported chromogenic probes for cyanide determination. The analytical utility of the method for the analysis of cyanide ions in electroplating wastewater (EPWW), human serum, tap and mineral water samples was demonstrated and the results were compared successfully with the conventional reference method. The short time response and the detection by the naked eye make the method available for the detection and quantitative determination of cyanide in a variety of real samples. PMID:24231750

  7. Nanocomposite-based rapid, visual, and selective luminescence turn-on assay for Hg2+ sensing in aqueous media.

    PubMed

    Cui, Jiabin; An, Mingyue; Wang, Leyu

    2013-10-15

    Composite nanospheres containing dithizone, luminescent LaVO4:Eu(3+) nanoparticles (NPs), and amphiphilic polymer have been composed for the rapid, selective, and visual luminescence turn-on detection of mercury ions (Hg(2+)) in water. Due to the absorption of dithizone, the strong red luminescence of LaVO4:Eu(3+) NPs encapsulated in nanospheres was quenched noticeably. As a result, these as-prepared nanocomposites (NCs) demonstrate very weak red luminescence. However, in the presence of Hg(2+), the red luminescence of nanocomposites was turned on dramatically, which can be attributed to the strong binding of mercury (II) ions by dithizone and forming a complex without absorption in the red emission range. Meanwhile, other cations have no influence on the detection of Hg(2+), suggesting a good selectivity for Hg(2+) sensing. Due to the high photostability and chemical stability of the nanocomposites, operation simplicity, low cost, and good selectivity, this newly developed method is highly desirable for field assay of Hg(2+) in aqueous media ranging from 40.0 nM to 4.0 μM with a limit of detection of 32.0 nM and a good linearity (r=0.9980). Therefore, a facile, rapid, selective, and visual luminescence turn-on technology has been successfully developed for Hg(2+) detection. PMID:24054626

  8. Dithizone as novel and efficient chromogenic probe for cyanide detection in aqueous media through nucleophilic addition into diazenylthione moiety

    NASA Astrophysics Data System (ADS)

    Tavallali, Hossein; Deilamy-Rad, Gohar; Parhami, Abolfath; Kiyani, Sajede

    2014-03-01

    A new selective chemodosimeter probe was developed by the introduction of dithizone (DTZ) as a simple and available dye for detection of cyanide in aqueous media which enables recognition of cyanide over other competing anions such as acetate, dihydrogen phosphate, fluoride and benzoate through covalent bonding. The sensing properties of DTZ were investigated in DMSO/H2O (1:9) and have demonstrated a very high selectivity toward the cyanide anions. A reasonable recognition mechanism was suggested using UV-Vis, 1H NMR and FTIR spectroscopy techniques. Time dependent density function theory (TDDFT) computations of UV-Vis excitation for DTZ2-CN adduct agreed well with our experimental findings. The detection limit of the new chromogenic probe was measured to be 0.48 μmol L-1 which is much lower than most recently reported chromogenic probes for cyanide determination. The analytical utility of the method for the analysis of cyanide ions in electroplating wastewater (EPWW), human serum, tap and mineral water samples was demonstrated and the results were compared successfully with the conventional reference method. The short time response and the detection by the naked eye make the method available for the detection and quantitative determination of cyanide in a variety of real samples.

  9. Effect of Surface Charge on Surface-Initiated Atom Transfer Radical Polymerization from Cellulose Nanocrystals in Aqueous Media.

    PubMed

    Zoppe, Justin O; Xu, Xingyu; Känel, Cindy; Orsolini, Paola; Siqueira, Gilberto; Tingaut, Philippe; Zimmermann, Tanja; Klok, Harm-Anton

    2016-04-11

    Cellulose nanocrystals (CNCs) with different charge densities were utilized to examine the role of electrostatic interactions on surface-initiated atom transfer radical polymerization (SI-ATRP) in aqueous media. To this end, growth of hydrophilic uncharged poly(N,N-dimethylacrylamide) (PDMAM) brushes was monitored by electrophoresis, (1)H NMR spectroscopy, and dynamic light scattering (DLS). Molecular weight and polydispersity of PDMAM brushes was determined by GPC analysis of hydrolytically cleaved polymers. Initiator and polymer brush grafting densities, and thus, initiator efficiencies were derived from elemental analysis. Higher initiator efficiency of polymer brush growth was observed for CNCs with higher anionic surface sulfate half-ester group density, but at the expense of high polydispersity caused by inefficient deactivation. PDMAM grafts with number-average molecular weights up to 530 kDa and polydispersity indices <1.5 were obtained under highly diluted monomer concentrations. The role of surface chemistry on the growth of neutral polymer brushes from CNCs in water is emphasized and a model of the interfacial region at the onset of polymerization is proposed. The results presented here could have implications for other substrates that present surface charges and for the assumption that the kinetics of Cu-mediated SI-CRP are analogous to those conducted in solution. PMID:26901869

  10. The potential of melt-mixed polypropylene-zeolite blends in the removal of heavy metals from aqueous media

    NASA Astrophysics Data System (ADS)

    Motsa, Machawe M.; Thwala, Justice M.; Msagati, Titus A. M.; Mamba, Bhekie B.

    The continued deterioration of the water quality in natural water sources such as rivers and lakes has led to tensions amongst relevant stakeholders to such an extent that cooperative water resource management is being regarded as an ideal solution to culminate conflicts and maximise the benefits. The desire to develop technologies that combine the three most important aspects of integrated water resource management (namely social, economic and environmental) has been encouraged by relevant authorities. This paper therefore reports the application of clinoptilolite-polypropylene (CLI-PP) blends/composites for the removal of lead from aqueous media. Just like many other heavy metals, lead poses a threat to water and soil quality as well as to plant and animal health. The findings on the adsorption behaviour of clinoptilolite-polypropylene composites with respect to Pb 2+ are also reported here, with the aim of extending its application to wastewater and environmental water purification. The batch equilibrium adsorption method was employed and the influence of contact time, pH, initial metal-ion concentration, temperature and pretreatment was determined. The optimum pH was found to be between pH 6 and pH 8 while the maximum sorption of lead at optimal pH was 95%. No big difference was observed between the adsorption behaviour of composites functionalised with 20% and 30% clinoptilolite, respectively. The pretreatment with HCl and NaCl made a slight difference to the adsorption capacity of composites.

  11. Kinetic studies of Cd (II) and Pb (II) ions biosorption from aqueous media using untreated and chemically treated biosorbents.

    PubMed

    Bakyayita, G K; Norrström, A C; Nalubega, M; Kulabako, R N

    2014-01-01

    Untreated and chemically treated Albizia coriaria, Erythrina abyssinica and Musa spp. were studied in batch for uptake of Cd(2+) and Pb(2+) ions at pH 2.0-9.0 and agitation time of 30-390 min. Optimum biosorption conditions were pH 4 for Pb(2+) ions and pH 5 for Cd(2+) ions, contact time was 3.5 hours at 24 ± 1 °C for 10 mg/L biosorbent dosage and initial metal ions concentration of 20 mg/L. Chemical treatment had a 10-17% biosorption efficiency enhancement for Cd(2+) ions and a 1.6-2.3% reduction effect for Pb(2+) ions. The sorption capacities for Cd(2+) and Pb(2+) ions for treated biosorbents were 1.760-1.738 mg g(-1) compared to 1.415-1.539 mg g(-1) for untreated materials. The pseudo second-order model suitably fitted the Cd(2+) and Pb(2+) ions biosorption data with regression coefficients (R(2)) of 0.9784-0.9999. Fitting of the Ho model to the experimental data showed that the biosorption mechanism for both metal ions studied was mainly a chemisorption process. Therefore, treated A. coriaria, E. abyssinica and Musa spp. were potential biosorbents for remediation of Cd(2+) ions and the untreated materials suitable for removing Pb(2+) ions from contaminated aqueous media.

  12. Dithizone as novel and efficient chromogenic probe for cyanide detection in aqueous media through nucleophilic addition into diazenylthione moiety.

    PubMed

    Tavallali, Hossein; Deilamy-Rad, Gohar; Parhami, Abolfath; Kiyani, Sajede

    2014-01-01

    A new selective chemodosimeter probe was developed by the introduction of dithizone (DTZ) as a simple and available dye for detection of cyanide in aqueous media which enables recognition of cyanide over other competing anions such as acetate, dihydrogen phosphate, fluoride and benzoate through covalent bonding. The sensing properties of DTZ were investigated in DMSO/H2O (1:9) and have demonstrated a very high selectivity toward the cyanide anions. A reasonable recognition mechanism was suggested using UV-Vis, (1)H NMR and FTIR spectroscopy techniques. Time dependent density function theory (TDDFT) computations of UV-Vis excitation for DTZ2-CN adduct agreed well with our experimental findings. The detection limit of the new chromogenic probe was measured to be 0.48 μmol L(-1) which is much lower than most recently reported chromogenic probes for cyanide determination. The analytical utility of the method for the analysis of cyanide ions in electroplating wastewater (EPWW), human serum, tap and mineral water samples was demonstrated and the results were compared successfully with the conventional reference method. The short time response and the detection by the naked eye make the method available for the detection and quantitative determination of cyanide in a variety of real samples.

  13. Effect of Surface Charge on Surface-Initiated Atom Transfer Radical Polymerization from Cellulose Nanocrystals in Aqueous Media.

    PubMed

    Zoppe, Justin O; Xu, Xingyu; Känel, Cindy; Orsolini, Paola; Siqueira, Gilberto; Tingaut, Philippe; Zimmermann, Tanja; Klok, Harm-Anton

    2016-04-11

    Cellulose nanocrystals (CNCs) with different charge densities were utilized to examine the role of electrostatic interactions on surface-initiated atom transfer radical polymerization (SI-ATRP) in aqueous media. To this end, growth of hydrophilic uncharged poly(N,N-dimethylacrylamide) (PDMAM) brushes was monitored by electrophoresis, (1)H NMR spectroscopy, and dynamic light scattering (DLS). Molecular weight and polydispersity of PDMAM brushes was determined by GPC analysis of hydrolytically cleaved polymers. Initiator and polymer brush grafting densities, and thus, initiator efficiencies were derived from elemental analysis. Higher initiator efficiency of polymer brush growth was observed for CNCs with higher anionic surface sulfate half-ester group density, but at the expense of high polydispersity caused by inefficient deactivation. PDMAM grafts with number-average molecular weights up to 530 kDa and polydispersity indices <1.5 were obtained under highly diluted monomer concentrations. The role of surface chemistry on the growth of neutral polymer brushes from CNCs in water is emphasized and a model of the interfacial region at the onset of polymerization is proposed. The results presented here could have implications for other substrates that present surface charges and for the assumption that the kinetics of Cu-mediated SI-CRP are analogous to those conducted in solution.

  14. Reactivity of alanylalanine diastereoisomers in neutral and acid aqueous solutions: a versatile stereoselectivity.

    PubMed

    Plasson, Raphaël; Tsuji, Maika; Kamata, Masazumi; Asakura, Kouichi

    2011-10-01

    A good comprehension of the reactivity of peptides in aqueous solution is fundamental in prebiotic chemistry, namely for understanding their stability and behavior in primitive oceans. Relying on the stereoselectivity of the involved reactions, there is a huge interest in amino acid derivatives for explaining the spontaneous emergence of homochirality on primitive Earth. The corresponding kinetic and thermodynamic parameters are however still poorly known in the literature. We studied the reactivity of alanylalanine in acidic to neutral conditions as a model system. The hydrolysis into amino acids, the epimerization of the N-terminal residue, and the cyclization into diketopiperazine could be successfully identified and studied. This kinetic investigation highlighted interesting behaviors. Complex mechanisms were observed in very acidic conditions. The relative kinetic stability of the diastereoisomers of the dipeptide is highly dependent of the pH, with the possibility to dynamically destabilize the thermodynamically more stable diastereoisomers. The existence of the cyclization of dipeptides adds complexity to the system. On one hand it brings additional stereoselectivities; on the other hand fast racemization of heterochiral dipeptides is obtained.

  15. Removal of fluoride in aqueous solution by adsorption on acid activated water treatment sludge

    NASA Astrophysics Data System (ADS)

    Vinitnantharat, Soydoa; Kositchaiyong, Sriwilai; Chiarakorn, Siriluk

    2010-06-01

    This paper reports the use of a pellet of adsorbent made from water treatment sludge (S) and acid activated water treatment sludge (SH) for removal of fluoride in the batch equilibration technique. The influence of pH, adsorbent dosage, temperature and effect of other ions were employed to find out the feasibility of acid activated adsorbent to remove fluoride to the permissible concentration of 0.7 mg/L. The results from the adsorption isotherm followed both Langmuir and Freundlich models and the highest fluoride removal was found for adsorbent activated with acetic acid at 2.0 mol/L. The optimum adsorbent dosage was found at 40 g/L, 0.01 mol/L acid activated adsorbent which was able to adsorb fluoride from 10 down to 0.11 mg/L. The adsorption capacity was decreased when the temperature increased. This revealed that the adsorption of fluoride on SH was exothermic. In the presence of nitrate and carbonate ions in the aqueous solution, fluoride removal efficiency of SH decreased from 94.4% to 86.6% and 90.8%, respectively. However, there is no significant effect in the presence of sulfate and chloride ions.

  16. Reactivity of Alanylalanine Diastereoisomers in Neutral and Acid Aqueous Solutions: a Versatile Stereoselectivity

    NASA Astrophysics Data System (ADS)

    Plasson, Raphaël; Tsuji, Maika; Kamata, Masazumi; Asakura, Kouichi

    2011-10-01

    A good comprehension of the reactivity of peptides in aqueous solution is fundamental in prebiotic chemistry, namely for understanding their stability and behavior in primitive oceans. Relying on the stereoselectivity of the involved reactions, there is a huge interest in amino acid derivatives for explaining the spontaneous emergence of homochirality on primitive Earth. The corresponding kinetic and thermodynamic parameters are however still poorly known in the literature. We studied the reactivity of alanylalanine in acidic to neutral conditions as a model system. The hydrolysis into amino acids, the epimerization of the N-terminal residue, and the cyclization into diketopiperazine could be successfully identified and studied. This kinetic investigation highlighted interesting behaviors. Complex mechanisms were observed in very acidic conditions. The relative kinetic stability of the diastereoisomers of the dipeptide is highly dependent of the pH, with the possibility to dynamically destabilize the thermodynamically more stable diastereoisomers. The existence of the cyclization of dipeptides adds complexity to the system. On one hand it brings additional stereoselectivities; on the other hand fast racemization of heterochiral dipeptides is obtained.

  17. Humic acid transport in saturated porous media: influence of flow velocity and influent concentration.

    PubMed

    Wei, Xiaorong; Shao, Mingan; Du, Lina; Horton, Robert

    2014-12-01

    Understanding the transport of humic acids (HAs) in porous media can provide important and practical evidence needed for accurate prediction of organic/inorganic contaminant transport in different environmental media and interfaces. A series of column transport experiments was conducted to evaluate the transport of HA in different porous media at different flow velocities and influent HA concentrations. Low flow velocity and influent concentration were found to favor the adsorption and deposition of HA onto sand grains packed into columns and to give higher equilibrium distribution coefficients and deposition rate coefficients, which resulted in an increased fraction of HA being retained in columns. Consequently, retardation factors were increased and the transport of HA through the columns was delayed. These results suggest that the transport of HA in porous media is primarily controlled by the attachment of HA to the solid matrix. Accordingly, this attachment should be considered in studies of HA behavior in porous media.

  18. Recovery of rare earth elements from the sulfothermophilic red alga Galdieria sulphuraria using aqueous acid.

    PubMed

    Minoda, Ayumi; Sawada, Hitomi; Suzuki, Sonoe; Miyashita, Shin-ichi; Inagaki, Kazumi; Yamamoto, Takaiku; Tsuzuki, Mikio

    2015-02-01

    The demand for rare earth elements has increased dramatically in recent years because of their numerous industrial applications, and considerable research efforts have consequently been directed toward recycling these materials. The accumulation of metals in microorganisms is a low-cost and environmentally friendly method for the recovery of metals present in the environment at low levels. Numerous metals, including rare earth elements, can be readily dissolved in aqueous acid, but the efficiency of metal biosorption is usually decreased under the acidic conditions. In this report, we have investigated the use of the sulfothermophilic red alga Galdieria sulphuraria for the recovery of metals, with particular emphasis on the recovery of rare earth metals. Of the five different growth conditions investigated where G. sulphuraria could undergo an adaptation process, Nd(III), Dy(III), and Cu(II) were efficiently recovered from a solution containing a mixture of different metals under semi-anaerobic heterotrophic condition at a pH of 2.5. G. sulphuraria also recovered Nd(III), Dy(III), La(III), and Cu(II) with greater than 90% efficiency at a concentration of 0.5 ppm. The efficiency remained unchanged at pH values in the range of 1.5-2.5. Furthermore, at pH values in the range of 1.0-1.5, the lanthanoid ions were collected much more efficiently into the cell fractions than Cu(II) and therefore successfully separated from the Cu(II) dissolved in the aqueous acid. Microscope observation of the cells using alizarin red suggested that the metals were accumulating inside of the cells. Experiments using dead cells suggested that this phenomenon was a biological process involving specific activities within the cells.

  19. Recovery of rare earth elements from the sulfothermophilic red alga Galdieria sulphuraria using aqueous acid.

    PubMed

    Minoda, Ayumi; Sawada, Hitomi; Suzuki, Sonoe; Miyashita, Shin-ichi; Inagaki, Kazumi; Yamamoto, Takaiku; Tsuzuki, Mikio

    2015-02-01

    The demand for rare earth elements has increased dramatically in recent years because of their numerous industrial applications, and considerable research efforts have consequently been directed toward recycling these materials. The accumulation of metals in microorganisms is a low-cost and environmentally friendly method for the recovery of metals present in the environment at low levels. Numerous metals, including rare earth elements, can be readily dissolved in aqueous acid, but the efficiency of metal biosorption is usually decreased under the acidic conditions. In this report, we have investigated the use of the sulfothermophilic red alga Galdieria sulphuraria for the recovery of metals, with particular emphasis on the recovery of rare earth metals. Of the five different growth conditions investigated where G. sulphuraria could undergo an adaptation process, Nd(III), Dy(III), and Cu(II) were efficiently recovered from a solution containing a mixture of different metals under semi-anaerobic heterotrophic condition at a pH of 2.5. G. sulphuraria also recovered Nd(III), Dy(III), La(III), and Cu(II) with greater than 90% efficiency at a concentration of 0.5 ppm. The efficiency remained unchanged at pH values in the range of 1.5-2.5. Furthermore, at pH values in the range of 1.0-1.5, the lanthanoid ions were collected much more efficiently into the cell fractions than Cu(II) and therefore successfully separated from the Cu(II) dissolved in the aqueous acid. Microscope observation of the cells using alizarin red suggested that the metals were accumulating inside of the cells. Experiments using dead cells suggested that this phenomenon was a biological process involving specific activities within the cells. PMID:25283836

  20. The Influence of the Anionic Counter-Ion on the Activity of Ammonium Substituted Hoveyda-Type Olefin Metathesis Catalysts in Aqueous Media

    NASA Astrophysics Data System (ADS)

    Gułajski, Łukasz; Grela, Karol

    Polar olefin metathesis catalysts, bearing an ammonium group are presented. The electron withdrawing ammonium group not only activates the catalysts electronically, but at the same time makes the catalysts more hydrophilic. Catalysts can be therefore efficiently used not only in traditional media, such as methylene chloride and toluene, but also in technical-grade alcohols, alcohol— water mixtures and in neat water. Finally, in this overview the influence of the anionic counter-ion on the activity of ammonium substituted Hoveyda-type olefin metathesis catalysts in aqueous media is presented.

  1. Effects of precursor concentration and acidic sulfate in aqueous glyoxal-OH radical oxidation and implications for secondary organic aerosol.

    PubMed

    Tan, Yi; Perri, Mark J; Seitzinger, Sybil P; Turpin, Barbara J

    2009-11-01

    Previous experiments demonstrated that aqueous OH radical oxidation of glyoxal yields low-volatility compounds. When this chemistry takes place in clouds and fogs, followed by droplet evaporation (or if it occurs in aerosol water), the products are expected to remain partially in the particle phase, forming secondary organic aerosol (SOA). Acidic sulfate exists ubiquitously in atmospheric water and has been shown to enhance SOA formation through aerosol phase reactions. In this work, we investigate how starting concentrations of glyoxal (30-3000 microM) and the presence of acidic sulfate (0-840 microM) affect product formation in the aqueous reaction between glyoxal and OH radical. The oxalic acid yield decreased with increasing precursor concentrations, and the presence of sulfuric acid did not alter oxalic acid concentrations significantly. A dilute aqueous chemistry model successfully reproduced oxalic acid concentrations, when the experiment was performed at cloud-relevant concentrations (glyoxal <300 microM), but predictions deviated from measurements at increasing concentrations. Results elucidate similarities and differences in aqueous glyoxal chemistry in clouds and in wet aerosols. They validate for the first time the accuracy of model predictions at cloud-relevant concentrations. These results suggest that cloud processing of glyoxal could be an important source of SOA. PMID:19924930

  2. Effects of precursor concentration and acidic sulfate in aqueous glyoxal-OH radical oxidation and implications for secondary organic aerosol.

    PubMed

    Tan, Yi; Perri, Mark J; Seitzinger, Sybil P; Turpin, Barbara J

    2009-11-01

    Previous experiments demonstrated that aqueous OH radical oxidation of glyoxal yields low-volatility compounds. When this chemistry takes place in clouds and fogs, followed by droplet evaporation (or if it occurs in aerosol water), the products are expected to remain partially in the particle phase, forming secondary organic aerosol (SOA). Acidic sulfate exists ubiquitously in atmospheric water and has been shown to enhance SOA formation through aerosol phase reactions. In this work, we investigate how starting concentrations of glyoxal (30-3000 microM) and the presence of acidic sulfate (0-840 microM) affect product formation in the aqueous reaction between glyoxal and OH radical. The oxalic acid yield decreased with increasing precursor concentrations, and the presence of sulfuric acid did not alter oxalic acid concentrations significantly. A dilute aqueous chemistry model successfully reproduced oxalic acid concentrations, when the experiment was performed at cloud-relevant concentrations (glyoxal <300 microM), but predictions deviated from measurements at increasing concentrations. Results elucidate similarities and differences in aqueous glyoxal chemistry in clouds and in wet aerosols. They validate for the first time the accuracy of model predictions at cloud-relevant concentrations. These results suggest that cloud processing of glyoxal could be an important source of SOA.

  3. Electrochemical treatment of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) in groundwater impacted by aqueous film forming foams (AFFFs).

    PubMed

    Schaefer, Charles E; Andaya, Christina; Urtiaga, Ana; McKenzie, Erica R; Higgins, Christopher P

    2015-09-15

    Laboratory experiments were performed to evaluate the use of electrochemical treatment for the decomposition of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), as well as other perfluoroalkyl acids (PFAAs), in aqueous film forming foam (AFFF)-impacted groundwater collected from a former firefighter training area and PFAA-spiked synthetic groundwater. Using a commercially-produced Ti/RuO2 anode in a divided electrochemical cell, PFOA and PFOS decomposition was evaluated as a function of current density (0-20 mA/cm(2)). Decomposition of both PFOA and PFOS increased with increasing current density, although the decomposition of PFOS did not increase as the current density was increased above 2.5 mA/cm(2). At a current density of 10 mA/cm(2), the first-order rate constants, normalized for current density and treatment volume, for electrochemical treatment of both PFOA and PFOS were 46 × 10(-5) and 70 × 10(-5) [(min(-1)) (mA/cm(2))(-1) (L)], respectively. Defluorination was confirmed for both PFOA and PFOS, with 58% and 98% recovery as fluoride, respectively (based upon the mass of PFOA and PFOS degraded). Treatment of other PFAAs present in the groundwater also was observed, with shorter chain PFAAs generally being more recalcitrant. Results highlight the potential for electrochemical treatment of PFAAs, particularly PFOA and PFOS, in AFFF-impacted groundwater.

  4. Degradation of hydroxycinnamic acid mixtures in aqueous sucrose solutions by the Fenton process.

    PubMed

    Nguyen, Danny M T; Zhang, Zhanying; Doherty, William O S

    2015-02-11

    The degradation efficiencies and behaviors of caffeic acid (CaA), p-coumaric acid (pCoA), and ferulic acid (FeA) in aqueous sucrose solutions containing the mixture of these hydroxycinnamic acids (HCAs) were studied by the Fenton oxidation process. Central composite design and multiresponse surface methodology were used to evaluate and optimize the interactive effects of process parameters. Four quadratic polynomial models were developed for the degradation of each individual acid in the mixture and the total HCAs degraded. Sucrose was the most influential parameter that significantly affected the total amount of HCA degraded. Under the conditions studied there was a <0.01% loss of sucrose in all reactions. The optimal values of the process parameters for a 200 mg/L HCA mixture in water (pH 4.73, 25.15 °C) and sucrose solution (13 mass %, pH 5.39, 35.98 °C) were 77% and 57%, respectively. Regression analysis showed goodness of fit between the experimental results and the predicted values. The degradation behavior of CaA differed from those of pCoA and FeA, where further CaA degradation is observed at increasing sucrose and decreasing solution pH. The differences (established using UV/vis and ATR-FTIR spectroscopy) were because, unlike the other acids, CaA formed a complex with Fe(III) or with Fe(III) hydrogen-bonded to sucrose and coprecipitated with lepidocrocite, an iron oxyhydroxide. PMID:25585639

  5. Degradation of hydroxycinnamic acid mixtures in aqueous sucrose solutions by the Fenton process.

    PubMed

    Nguyen, Danny M T; Zhang, Zhanying; Doherty, William O S

    2015-02-11

    The degradation efficiencies and behaviors of caffeic acid (CaA), p-coumaric acid (pCoA), and ferulic acid (FeA) in aqueous sucrose solutions containing the mixture of these hydroxycinnamic acids (HCAs) were studied by the Fenton oxidation process. Central composite design and multiresponse surface methodology were used to evaluate and optimize the interactive effects of process parameters. Four quadratic polynomial models were developed for the degradation of each individual acid in the mixture and the total HCAs degraded. Sucrose was the most influential parameter that significantly affected the total amount of HCA degraded. Under the conditions studied there was a <0.01% loss of sucrose in all reactions. The optimal values of the process parameters for a 200 mg/L HCA mixture in water (pH 4.73, 25.15 °C) and sucrose solution (13 mass %, pH 5.39, 35.98 °C) were 77% and 57%, respectively. Regression analysis showed goodness of fit between the experimental results and the predicted values. The degradation behavior of CaA differed from those of pCoA and FeA, where further CaA degradation is observed at increasing sucrose and decreasing solution pH. The differences (established using UV/vis and ATR-FTIR spectroscopy) were because, unlike the other acids, CaA formed a complex with Fe(III) or with Fe(III) hydrogen-bonded to sucrose and coprecipitated with lepidocrocite, an iron oxyhydroxide.

  6. Ionic interactions. Subnanoscale hydrophobic modulation of salt bridges in aqueous media.

    PubMed

    Chen, Shuo; Itoh, Yoshimitsu; Masuda, Takuya; Shimizu, Seishi; Zhao, Jun; Ma, Jing; Nakamura, Shugo; Okuro, Kou; Noguchi, Hidenori; Uosaki, Kohei; Aida, Takuzo

    2015-05-01

    Polar interactions such as electrostatic forces and hydrogen bonds play an essential role in biological molecular recognition. On a protein surface, polar interactions occur mostly in a hydrophobic environment because nonpolar amino acid residues cover ~75% of the protein surface. We report that ionic interactions on a hydrophobic surface are modulated by their subnanoscale distance to the surface. We developed a series of ionic head groups-appended self-assembled monolayers with C2, C6, C8, and C12 space-filling alkyl chains, which capture a dendritic guest via the formation of multiple salt bridges. The guest release upon protonolysis is progressively suppressed when its distance from the background hydrophobe changes from 1.2 (C2) to 0.2 (C12) nanometers, with an increase in salt bridge strength of ~3.9 kilocalories per mole.

  7. Ionic interactions. Subnanoscale hydrophobic modulation of salt bridges in aqueous media.

    PubMed

    Chen, Shuo; Itoh, Yoshimitsu; Masuda, Takuya; Shimizu, Seishi; Zhao, Jun; Ma, Jing; Nakamura, Shugo; Okuro, Kou; Noguchi, Hidenori; Uosaki, Kohei; Aida, Takuzo

    2015-05-01

    Polar interactions such as electrostatic forces and hydrogen bonds play an essential role in biological molecular recognition. On a protein surface, polar interactions occur mostly in a hydrophobic environment because nonpolar amino acid residues cover ~75% of the protein surface. We report that ionic interactions on a hydrophobic surface are modulated by their subnanoscale distance to the surface. We developed a series of ionic head groups-appended self-assembled monolayers with C2, C6, C8, and C12 space-filling alkyl chains, which capture a dendritic guest via the formation of multiple salt bridges. The guest release upon protonolysis is progressively suppressed when its distance from the background hydrophobe changes from 1.2 (C2) to 0.2 (C12) nanometers, with an increase in salt bridge strength of ~3.9 kilocalories per mole. PMID:25931555

  8. An efficient synthesis of porphyrins with different meso substituents that avoids scrambling in aqueous media.

    PubMed

    Nowak-Król, Agnieszka; Plamont, Rémi; Canard, Gabriel; Edzang, Judicaelle Andeme; Gryko, Daniel T; Balaban, Teodor Silviu

    2015-01-19

    We have developed new conditions that afford regioisomerically pure trans-A2B2-, A3B-, and trans-AB2C-porphyrins bearing aryl and arylethynyl substituents. The porphyrins were prepared by the acid-catalyzed condensation of dipyrromethanes with aldehydes followed by oxidation with p-chloranil or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Optimal conditions for the condensation were identified after examining various reaction parameters such as solvent composition, acid concentration, and reaction time. The conditions identified (for aromatic aldehydes: EtOH/H2O 4:1, [DPM] = 4 mM, [aldehyde] = 4 mM, [HCl] = 38 mM, 16 h; for arylethynyl aldehydes: THF/H2O 2:1, [DPM] = 13 mM, [aldehyde] = 13 mM, [HCl] = 150 mM, 3 h) resulted in the formation of porphyrins in yields of 9-38% without detectable scrambling. This synthesis is compatible with diverse functionalities such as ester or nitrile. In total, 20 new trans-A2B2-, A3B-, and trans-AB2C-porphyrins were prepared. The scope and limitations of the two sets of reaction conditions have been explored. The methodological advantage of this approach is its straightforward access to building blocks and the formation of the porphyrin core in higher yields than by any other methodology and by using environmentally benign and nonhazardous chemicals. PMID:25417808

  9. Volatility and oxidative aging of aqueous maleic acid aerosol droplets and the dependence on relative humidity.

    PubMed

    Dennis-Smither, Benjamin J; Marshall, Frances H; Miles, Rachael E H; Preston, Thomas C; Reid, Jonathan P

    2014-07-31

    The microphysical structure and heterogeneous oxidation by ozone of single aerosol particles containing maleic acid (MA) has been studied using aerosol optical tweezers and cavity enhanced Raman spectroscopy. The evaporation rate of MA from aqueous droplets has been measured over a range of relative humidities and the pure component vapor pressure determined to be (1.7 ± 0.2) × 10(-3) Pa. Variation in the refractive index (RI) of an aqueous MA droplet with relative humidity (RH) allowed the subcooled liquid RI of MA to be estimated as 1.481 ± 0.001. Measurements of the hygroscopic growth are shown to be consistent with equilibrium model predictions from previous studies. Simultaneous measurements of the droplet composition, size, and refractive index have been made during ozonolysis at RHs in the range 50-80%, providing insight into the volatility of organic products, changes in the droplet hygroscopicity, and optical properties. Exposure of the aqueous droplets to ozone leads to the formation of products with a wide range of volatilities spanning from involatile to volatile. Reactive uptake coefficients show a weak dependence on ozone concentration, but no dependence on RH or salt concentration. The time evolving RI depends significantly on the RH at which the oxidation proceeds and can even show opposing trends; while the RI increases with ozone exposure at low relative humidity, the RI decreases when the oxidation proceeds at high relative humidity. The variations in RI are broadly consistent with a framework for predicting RIs for organic components published by Cappa et al. ( J. Geophys. Res. 2011 , 116 , D15204 ). Once oxidized, particles are shown to form amorphous phases on drying rather than crystallization, with slow evaporation kinetics of residual water. PMID:25003240

  10. Electrooxidation of homogentisic acid in aqueous and mixed solvent solutions: experimental and theoretical studies.

    PubMed

    Eslami, Marzieh; Namazian, Mansoor; Zare, Hamid R

    2013-03-01

    Electrochemical behavior of homogentisic acid (HGA) has been studied in both aqueous and mixed solvent solution of water-acetonitrile. Physicochemical parameters of the electrochemical reaction of HGA in these solutions are obtained experimentally by cyclic voltammetry method and are also calculated theoretically using accurate ab initio calculations (G3MP2//B3LYP). Solvation energies are calculated using the available solvation model of CPCM. The pH dependence of the redox activity of HGA in aqueous and the mixture solutions at different temperatures was used for the experimental determination of the standard reduction potential and changes of entropy, enthalpy, and Gibbs free energy for the studied reaction. The experimental standard redox potential of the compound in aqueous solution was obtained to be 0.636 V versus the standard hydrogen electrode. There is a good agreement between the theoretical and experimental values (0.702 and 0.636 V) for the standard electrode potential of HGA. The changes of thermodynamic functions of solvation are also calculated from the differences between the solution-phase experimental values and the gas-phase theoretical values. Finally, using the value of solvation energy of HGA in water and acetonitrile solvents which calculated by the CPCM model of energy, we proposed an equation for calculating the standard redox potential of HGA in mixture solution of water and acetonitrile. A good agreement between the result of electrode potential calculated by the proposed equation and the experimental value confirms the validity of the theoretical models used here and the accuracy of experimental methods.

  11. Iridium-based double perovskites for efficient water oxidation in acid media

    NASA Astrophysics Data System (ADS)

    Diaz-Morales, Oscar; Raaijman, Stefan; Kortlever, Ruud; Kooyman, Patricia J.; Wezendonk, Tim; Gascon, Jorge; Fu, W. T.; Koper, Marc T. M.

    2016-08-01

    The development of active, cost-effective and stable oxygen-evolving catalysts is one of the major challenges for solar-to-fuel conversion towards sustainable energy generation. Iridium oxide exhibits the best available compromise between catalytic activity and stability in acid media, but it is prohibitively expensive for large-scale applications. Therefore, preparing oxygen-evolving catalysts with lower amounts of the scarce but active and stable iridium is an attractive avenue to overcome this economical constraint. Here we report on a class of oxygen-evolving catalysts based on iridium double perovskites which contain 32 wt% less iridium than IrO2 and yet exhibit a more than threefold higher activity in acid media. According to recently suggested benchmarking criteria, the iridium double perovskites are the most active catalysts for oxygen evolution in acid media reported until now, to the best of our knowledge, and exhibit similar stability to IrO2.

  12. Iridium-based double perovskites for efficient water oxidation in acid media

    PubMed Central

    Diaz-Morales, Oscar; Raaijman, Stefan; Kortlever, Ruud; Kooyman, Patricia J.; Wezendonk, Tim; Gascon, Jorge; Fu, W. T.; Koper, Marc T. M.

    2016-01-01

    The development of active, cost-effective and stable oxygen-evolving catalysts is one of the major challenges for solar-to-fuel conversion towards sustainable energy generation. Iridium oxide exhibits the best available compromise between catalytic activity and stability in acid media, but it is prohibitively expensive for large-scale applications. Therefore, preparing oxygen-evolving catalysts with lower amounts of the scarce but active and stable iridium is an attractive avenue to overcome this economical constraint. Here we report on a class of oxygen-evolving catalysts based on iridium double perovskites which contain 32 wt% less iridium than IrO2 and yet exhibit a more than threefold higher activity in acid media. According to recently suggested benchmarking criteria, the iridium double perovskites are the most active catalysts for oxygen evolution in acid media reported until now, to the best of our knowledge, and exhibit similar stability to IrO2. PMID:27498694

  13. Iridium-based double perovskites for efficient water oxidation in acid media.

    PubMed

    Diaz-Morales, Oscar; Raaijman, Stefan; Kortlever, Ruud; Kooyman, Patricia J; Wezendonk, Tim; Gascon, Jorge; Fu, W T; Koper, Marc T M

    2016-01-01

    The development of active, cost-effective and stable oxygen-evolving catalysts is one of the major challenges for solar-to-fuel conversion towards sustainable energy generation. Iridium oxide exhibits the best available compromise between catalytic activity and stability in acid media, but it is prohibitively expensive for large-scale applications. Therefore, preparing oxygen-evolving catalysts with lower amounts of the scarce but active and stable iridium is an attractive avenue to overcome this economical constraint. Here we report on a class of oxygen-evolving catalysts based on iridium double perovskites which contain 32 wt% less iridium than IrO2 and yet exhibit a more than threefold higher activity in acid media. According to recently suggested benchmarking criteria, the iridium double perovskites are the most active catalysts for oxygen evolution in acid media reported until now, to the best of our knowledge, and exhibit similar stability to IrO2. PMID:27498694

  14. [Acid oligosaccharides as the active principle of aqueous carrot extracts for prevention and therapy of gastrointestinal infections].

    PubMed

    Kastner, U; Glasl, S; Follrich, B; Guggenbichler, J P; Jurenitsch, J

    2002-01-01

    Adherence of microorganisms to the intestinal mucosa is an important and initial step in the pathogenesis of gastrointestinal infections and mediated by carbohydrate structures on the cell surface. Adherence can be blocked by carbohydrate receptor analogues. Aqueous extracts from carrots (carrot soup) contain acidic oligosaccharides, which are able to block adherence of various enteropathogenic microorganisms to HEp-2 cells and human intestinal mucosa in vitro. Dependent on the grade of polymerisation the most potent blocking ability was seen for trigalacturonic acid. Clinical studies revealed, that aqueous carrot extracts are significantly superior to the basic glucose-electrolyt-solution for oral rehydration in acute gastrointestional infections of children.

  15. Mathematical modeling of cadmium(II) solvent extraction from neutral and acidic chloride media using Cyanex 923 extractant as a metal carrier.

    PubMed

    Leopold, A A; Coll, M T; Fortuny, A; Rathore, N S; Sastre, A M

    2010-10-15

    This paper describes experimental work and the mathematical modeling of solvent extraction of cadmium(II) from neutral and acidic aqueous chloride media with a Cyanex 923 extractant in Exxol D-100. Solvent extraction experiments were carried out to analyze the influence of variations in the composition of the aqueous and organic phases on the efficiency of cadmium(II) extraction. In neutral and acidic chloride conditions, the extraction of cadmium(II) by the organophosphorous extractant Cyanex 923 (L) is based on the solvation mechanism of neutral H(n)CdCl((2+n)) species and the formation of H(n)CdCl((2+n))L(q) complexes in the organic phase, where n=0, 1, 2 and q=1, 2. The mathematical model of cadmium(II) extraction was derived from the mass balances and chemical equilibria involved in the separation system. The model was computed with the Matlab software. The equilibrium parameters for metal extraction, i.e. the stability constants of the aqueous Cd-Cl complexes, the formation constants of the acidic Cd-Cl species and the metal equilibrium extraction constants, were proposed. The optimized constants were appropriate, as there was good agreement when the model was fitted to the experimental data for each of the experiments.

  16. Highly dispersed pd catalyst locked in knitting aryl network polymers for Suzuki-Miyaura coupling reactions of aryl chlorides in aqueous media.

    PubMed

    Li, Buyi; Guan, Zhenhong; Wang, Wei; Yang, Xinjia; Hu, Jianglin; Tan, Bien; Li, Tao

    2012-07-01

    Highly dispersed palladium chloride catalysts locked in triphenylphosphine-functionalized knitting aryl network polymers (KAPs) are developed and exhibit excellent activity under mild conditions in the Suzuki-Miyaura cross-coupling reactions of aryl chlorides in aqueous media. This work highlights that the microporous polymers not only play the role of support materials, but also protect the Pd species from aggregation and precipitation, hence, positively effect the catalysis activity.

  17. Investigation of the mechanisms of using metal complexation and cellulose nanofiber/sodium alginate layer-by-layer coating for retaining anthocyanin pigments in thermally processed blueberries in aqueous media.

    PubMed

    Jung, Jooyeoun; Cavender, George; Simonsen, John; Zhao, Yanyun

    2015-03-25

    This study investigated the mechanisms of anthocyanin pigment retention using Fe(3+)-anthocyanin complexation and cellulose nanofiber (CNF)/sodium alginate (SA) layer-by-layer (LBL) coatings on thermally processed blueberries in aqueous media. Anthocyanin pigments were polymerized through complexation with Fe(3+) but readily degraded by heat (93 °C for 7 min) in the aqueous media because of poor stability. CNF/SA LBL coating was successful to retain anthocyanin pigments in thermally processed blueberries. Fruits coated with CNF containing CaCl2 followed by treatment in a SA bath formed a second hydrogel layer onto the CNF layer (LBL coating system) through cross-linking between Ca(2+) and alginic acid. Methyl-cellulose-modified CNF improved the interactions between CNF, the fruit surface, and the SA layer. This study demonstrated that the CNF/SA LBL coating system was effective to retain anthocyanin pigments on thermally processed whole blueberries, whereas no combined benefit of complexation with coating was observed. Results explained the mechanisms of the new approaches for developing colorful and nutritionally enhanced anthocyanin-rich fruit products.

  18. Poly (vinylsulfonic acid) assisted synthesis of aqueous solution stable vaterite calcium carbonate nanoparticles.

    PubMed

    Nagaraja, Ashvin T; Pradhan, Sulolit; McShane, Michael J

    2014-03-15

    Calcium carbonate nanoparticles of the vaterite polymorph were synthesized by combining CaCl2 and Na2CO3 in the presence of poly (vinylsulfonic acid) (PVSA). By studying the important experimental parameters we found that controlling PVSA concentration, reaction temperature, and order of reagent addition the particle size, monodispersity, and surface charge can be controlled. By increasing PVSA concentration or by decreasing temperature CCNPs with an average size from ≈150 to 500 nm could be produced. We believe the incorporation of PVSA into the reaction plays a dual role to (1) slow down the nucleation rate by sequestering calcium and to (2) stabilize the resulting CCNPs as the vaterite polymorph, preventing surface calcification or aggregation into microparticles. The obtained vaterite nanoparticles were found to maintain their crystal structure and surface charge after storage in aqueous buffer for at least 5 months. The aqueous stable vaterite nanoparticles could be a useful platform for the encapsulation of a large variety of biomolecules for drug delivery or as a sacrificial template toward capsule formation for biosensor applications.

  19. Aqueous chlorination of mefenamic acid: kinetics, transformation by-products and ecotoxicity assessment.

    PubMed

    Adira Wan Khalit, Wan Nor; Tay, Kheng Soo

    2016-05-18

    Mefenamic acid (Mfe) is one of the most frequently detected nonsteroidal anti-inflammatory drugs in the environment. This study investigated the kinetics and the transformation by-products of Mfe during aqueous chlorination. The potential ecotoxicity of the transformation by-products was also evaluated. In the kinetic study, the second-order rate constant (kapp) for the reaction between Mfe and free available chlorine (FAC) was determined at 25 ± 0.1 °C. The result indicated that the degradation of Mfe by FAC is highly pH-dependent. When the pH was increased from 6 to 8, it was found that the kapp for the reaction between Mfe and FAC was decreased from 16.44 to 4.4 M(-1) s(-1). Characterization of the transformation by-products formed during the chlorination of Mfe was carried out using liquid chromatography-quadrupole time-of-flight accurate mass spectrometry. Four major transformation by-products were identified. These transformation by-products were mainly formed through hydroxylation, chlorination and oxidation reactions. Ecotoxicity assessment revealed that transformation by-products, particularly monohydroxylated Mfe which is more toxic than Mfe, can be formed during aqueous chlorination.

  20. Molecular interactions of α-amino acids insight into aqueous β-cyclodextrin systems.

    PubMed

    Ekka, Deepak; Roy, Mahendra Nath

    2013-10-01

    Qualitative and quantitative analysis of molecular interaction prevailing in glycine, L-alanine, L-valine and aqueous solution of β-cyclodextrin (β-CD) have been probed by thermophysical properties. Density (ρ), viscosity (η), and ultrasonic speed (u) measurements have been reported at different temperatures. The extent of interaction (solute-solvent interaction) is expressed in terms of the limiting apparent molar volume ([Formula: see text]), viscosity B-coefficient and limiting apparent molar adiabatic compressibility ([Formula: see text]). The changes on the enthalpy ([Formula: see text]) and entropy ([Formula: see text]) of the encapsulation analysis give information about the driving forces governing the inclusion. The temperature dependence behaviour of partial molar quantities and group contributions to partial molar volumes has been determined for the amino acids. The trends in transfer volumes, [Formula: see text], have been interpreted in terms of solute-cosolute interactions based on a cosphere overlap model. The role of the solvent (aqueous solution of β-CD) and the contribution of solute-solute and solute-solvent interactions to the solution complexes have also been analyzed through the derived properties.

  1. Functionalization of graphene and few-layer graphene with aqueous solution of hydrofluoric acid

    NASA Astrophysics Data System (ADS)

    Nebogatikova, N. A.; Antonova, I. V.; Volodin, V. A.; Prinz, V. Ya.

    2013-08-01

    In the present study, conditions suitable for efficient modification of graphene and few-layer graphene (FLG) films with aqueous solutions of hydrofluoric acid (HF) and for local protection of the graphene against such modification in isopropyl alcohol were identified. A combination of the two treatments gives one a key to nanodesign of graphene-based 2D devices. It was found that a few-minute treatment of graphene or FLG in HF aqueous solutions (∼1 min for graphene and ∼5 min for FLG films about 5 nm thick) leads to strong changes in the structural and electrical properties of graphene involving a step-like increase in resistivity (up to 1011 Ω/□). Two types of materials were obtained after different times of treatment: (i) promising for electronic applications of the material due to a combination of high carrier mobility, high conductivity, and strong current modulation by gate voltage (up to four orders of magnitude); (ii) a material with insulating properties and graphene quantum dots embedded in an insulating matrix.

  2. Aqueous phase hydration and hydrate acidity of perfluoroalkyl and n:2 fluorotelomer aldehydes.

    PubMed

    Rayne, Sierra; Forest, Kaya

    2016-01-01

    The SPARC software program and comparative density functional theory (DFT) calculations were used to investigate the aqueous phase hydration equilibrium constants (Khyd) of perfluoroalkyl aldehydes (PFAlds) and n:2 fluorotelomer aldehydes (FTAlds). Both classes are degradation products of known industrial compounds and environmental contaminants such as fluorotelomer alcohols, iodides, acrylates, phosphate esters, and other derivatives, as well as hydrofluorocarbons and hydrochlorofluorocarbons. Prior studies have generally failed to consider the hydration, and subsequent potential hydrate acidity, of these compounds, resulting in incomplete and erroneous predictions as to their environmental behavior. In the current work, DFT calculations suggest that all PFAlds will be dominantly present as the hydrated form in aqueous solution. Both SPARC and DFT calculations suggest that FTAlds will not likely be substantially hydrated in aquatic systems or in vivo. PFAld hydrates are expected to have pKa values in the range of phenols (ca. 9 to 10), whereas n:2 FTAld hydrates are expected to have pKa values ca. 2 to 3 units higher (ca. 12 to 13). In order to avoid spurious modeling predictions and a fundamental misunderstanding of their fate, the molecular and/or dissociated hydrate forms of PFAlds and FTAlds need to be explicitly considered in environmental, toxicological, and waste treatment investigations. The results of the current study will facilitate a more complete examination of the environmental fate of PFAlds and FTAlds. PMID:26980678

  3. Extraction of nitric acid, uranyl nitrate, and bismuth nitrate from aqueous nitric acid solutions with CMPO

    SciTech Connect

    Spencer, B.B.

    1995-08-01

    DOE sponsored development of the transuranium extraction (TRUEX) process for removing actinides from radioactive wastes. The solvent is a mixture of CMPO and TBP. Since the extraction characteristics of CMPO are not as well understood as those of TBP, the extraction of nitric acid, uranyl nitrate, and bismuth nitrate with CMPO (dissolved in n-dodecane) were studied. Results indicate that CMPO extracts nitric acid with a 1:1 stoichiometry; equilibrium constant is 2. 660{plus_minus}0.092 at 25 C, and extraction enthalpy is -5. 46{plus_minus}0.46 kcal/mol. Slope analysis indicates that uranyl nitrate extracts with a mixed equilibria of 1:1 and 2:1 stoichiometries in nearly equal proportion. Equil. constant of the 2: 1 extraction was 1.213 {times} 10{sup 6}{plus_minus}3.56 {times} 10{sup 4} at 25 C; reaction enthalpy was -9.610{plus_minus}0.594 kcal/mol. Nitration complexation constant is 8.412{plus_minus}0.579, with an enthalpy of -10.72{plus_minus}1.87 kcal/mol. Bismuth nitrate also extracts with a mixed equilibria of (perhaps) 1:1 and 2:1 stoichiometries. A 2:1 extraction equilibrium and a nitrate complexation adequately model the data. Kinetics and enthalpies were also measured.

  4. Fixed bed adsorption of 2-naphthalenesulfonic acid from aqueous solution by composite resin.

    PubMed

    Jia, Dong M; Li, Ya P; Li, Yue J; Li, Yong G; Li, Chang H

    2014-02-01

    Adsorption behavior of the iron impregnated, weakly basic resin D301 (Fe-D301) for removal of 2-naphthalenesulfonic acid (2-NSA) from aqueous solution was studied by using a fixed-bed column. The effects of process variables such as bed height, flow rate, and coexisting ions were investigated. The results indicated that the breakpoint and exhaustion point increased with increasing bed height and decreased with increasing 2-NSA flowrate. Experimental data showed a strong fit to the Bed Depth Service Time model. The coexisting ions in the 2-NSA solution had a clear effect on the breakthrough volume. The high extent of recovery of 2-NSA with good reproducibility provided an effective method for the separation of 2-NSA by the adsorbent Fe-D301.

  5. Optical properties of colloidal aqueous synthesized 3 mercaptopropionic acid stabilized CdS quantum dots

    NASA Astrophysics Data System (ADS)

    Sumanth Kumar, D.; Jai Kumar, B.; Mahesh H., M.

    2016-05-01

    We have explored an easiest and simplest aqueous route to synthesize bright green luminescent CdS QDs using 3-Mercaptopropionic acid (MPA) as a stabilizer in air ambient for solar cell applications. The CdS quantum dots showed a strong quantum confinement effect with good stability, size and excellent photoluminescence. MPA Capping on CdS QDs was confirmed through FTIR. The Optical absorption spectrum revealed the CdS quantum dots are highly transparent in the visible region with absorption peak at 380 nm, confirming the quantum confinement. Photoluminescence showed an emission peak at 525 nm wavelength. The optical band gap energy was found to be 3.19 eV and CdS quantum dots radius calculated using Brus equation is 1.5 nm. The results are presented and discussed in detail.

  6. Electrodeposited Films from Aqueous Tungstic Acid-Hydrogen Peroxide Solutions for Electrochromic Display Devices

    NASA Astrophysics Data System (ADS)

    Yamanaka, Kazusuke

    1987-11-01

    Electrodeposited tungsten oxide films from aqueous tungstic acid-hydrogen peroxide solutions were investigated for applications to electrochromic devices. These films exhibited electrochromism in aprotic electrolyte solutions containing Li-salts. When the films were heat-treated for an hour at temperatures between 100 and 200°C, the electrochromic reactions were rich in reversibility. The coloring efficiency and response rate for the films were favorable and comparable to those for tungsten trioxide evaporated films. A cell life-test was performed on several clock-size cells by applying a 1.2-V, 1-Hz, continuous square wave. The typical amount of charge required for coloration was about 50 C / m2 and remained unchanged even after 107 coloration-bleaching cycles.

  7. The aqueous photolysis of α-pinene in solution with humic acid

    USGS Publications Warehouse

    Goldberg, Marvin C.; Cunningham, Kirkwood M.; Aiken, George R.; Weiner, Eugene R.; ,

    1992-01-01

    Terpenes are produced abundantly by environmental processes but are found in very low concentrations in natural waters. Aqueous photolysis of solutions containing α-pinene, a representative terpene, in the presence of humic acid resulted in degradation of the pinene. Comparison of this reaction to photolysis of α-pinene in the presence of methylene blue leads to the conclusion that the reactive pathway for the abiotic degradation of α-pinene is due to reaction with singlet oxygen produced by irradiation of the humic material. The initial product of single oxygen and α-pinene is a hydroperoxide. Since humic materials are prevalent in most natural waters, this mechanism of photodecomposition for α-pinene probably also applies to other terpenes in surface waters and may be reasonably considered to contribute to their low environmental concentration.

  8. Layer structured graphite oxide as a novel adsorbent for humic acid removal from aqueous solution.

    PubMed

    Hartono, Tri; Wang, Shaobin; Ma, Qing; Zhu, Zhonghua

    2009-05-01

    Layer structured graphite oxide (GO) was prepared from graphite using the Hummers-Offeman method, characterised using N(2) adsorption, XRD, XPS, SEM(TEM), and FT-IR, and tested for humic acid (HA) adsorption in aqueous solution. XRD, XPS, and FT-IR measurements indicate the formation of layered structure with strong functional groups of GO. It is also found that the GO exhibits strong and much higher adsorption capacity of HA than graphite. The maximum adsorption capacity of the GO from the Langmuir isotherm is 190 mg/g, higher than activated carbon. For the adsorption, several parameters will affect the adsorption such as solid loading and pH. HA adsorption will decrease with increasing pH and an optimum GO loading is required for maximum adsorption. PMID:19233379

  9. Cementation and Aqueous Alteration of a Sandstone Unit Under Acidic Conditions in Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Yen, A. S.; Blake, D. F.; Ming, D. W.; Morris, R. V.; Gellert, R.; Clark, B.; Vaniman, D. T.; Chipera, S. J.; Thompson, L. M.; Bristow, T. F.; Rampe, E. B.; Crisp, J. A.

    2016-01-01

    The Curiosity rover landed on Mars in August 2012 to explore the sedimentary history and to assess the habitability of Gale Crater. After 1200 sols of surface operations and over 12 km of traverse distance, the mineralogy of 10 samples has been determined by the CheMin X-ray diffractometer (XRD) and the chemical composition of nearly 300 targets has been established by the Alpha Particle X-ray Spectrometer (APXS). Light-toned fracture zones containing elevated concentrations of silica have been studied by Curiosity's instruments to determine the nature of the fluids that resulted in the enrichment of SiO2. Multiple fluid exposures are evident, and the chemistry and mineralogy data indicate at least two aqueous episodes may have occurred under acidic conditions.

  10. Prompt formation of organic acids in pulse ozonation of terpenes on aqueous surfaces

    NASA Astrophysics Data System (ADS)

    Hoffmann, M. R.; Colussi, A. J.; Enami, S.

    2010-12-01

    A major atmospheric process, the gas-phase ozonation of terpenes yields suites of products via a cascade of chemically activated intermediates that ranges from primary ozonides to dioxiranes. If a similar mechanism operated in water, as it is generally assumed, such intermediates would be deactivated within picoseconds and, henceforth, unable to produce carboxylic acids in microseconds. Herein we report the online electrospray mass spectrometric detection of (M + 2O - H+) and (M + 3O - H+) carboxylates on the surface of aqueous β-caryophyllene (C15H24, M = 204 Da) microjets exposed to a few ppmv O3(g) for < 10 μs. Since neither species is formed on dry solvent microjets, and both incorporate deuterium from D2O, we infer that carboxylates ensue from the interaction of nascent intermediates with interfacial water via a heretofore unreported mechanism. These interfacial events proceed much faster than in bulk liquids saturated with ozone.

  11. A free energy analysis of nucleic acid base stacking in aqueous solution.

    PubMed Central

    Friedman, R A; Honig, B

    1995-01-01

    This paper reports a theoretical study of the free energy contributions to nucleic acid base stacking in aqueous solution. Electrostatic interactions are treated by using the finite difference Poisson-Boltzmann method and nonpolar effects are treated with explicit calculation of van der Waals interactions and/or free energy-surface area relationships. Although for some pairs of bases there is a favorable Coulombic interaction in the stacked conformation, generally the net effect of electrostatic interactions is to oppose stacking. This result is caused by the loss of favorable base-solvent electrostatic interactions, that accompany the partial removal of polar atoms from water in the stacked conformation. Nonpolar interactions, involving the hydrophobic effect and enhancement of van der Waals interactions caused by close-packing, drive stacking. The calculations qualitatively reproduce the experimental dependence of stacking free energy on purine-pyrimidine composition. Images FIGURE 1 PMID:8534823

  12. Removal of Basic Violet 14 from aqueous solution using sulphuric acid activated materials.

    PubMed

    Suresh, S

    2016-01-01

    In this study the adsorption of Basic Violet, 14 from aqueous solution onto sulphuric acid activated materials prepared from Calophyllum inophyllum (CS) and Theobroma cacao (TS) shells were investigated. The experimental data were analysed by Langmuir, Freundlich and Temkin isotherm models. The results showed that CS has a superior adsorption capacity compared to the TS. The adsorption capacity was found to be 1416.43 mg/g for CS and 980.39 mg/g for TS. The kinetic data results at different concentrations were analysed using pseudo first-order and pseudo-second order model. Boyd plot indicates that the dye adsorption onto CS and TS is controlled by film diffusion. The adsorbents were characterised by scanning electron microscopy. The materials used in this study were economical waste products and hence can be an attractive alternative to costlier adsorbents for dye removal in industrial wastewater treatment processes. PMID:27330899

  13. Enhanced copper surface protection in aqueous solutions containing short-chain alkanoic acid potassium salts.

    PubMed

    Abelev, Esta; Starosvetsky, David; Ein-Eli, Yair

    2007-10-23

    The ability of dissolved potassium monocarboxylate salts to produce surface passivation and to inhibit aqueous corrosion of copper was studied. The electrochemical measurements indicate that the inhibiting efficiency of these compounds, with a general formula Cn-1H2n-1COOK or CnK (n=3...12), is dependent on the hydrocarbon chain length. The inhibiting efficiency was higher for a longer hydrocarbon chain of n-alkanoic acid. The degree of copper protection was found to increase with an increase in n-alkanoic acid potassium salt concentration; the optimum concentration of potassium dodecanoate (C12K) in sulfate solutions was found to be 0.07 M. The protective layers formed at the copper surface subsequent to exposure in various n-alkanoic acid potassium salt solutions were characterized by contact angle measurements, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared reflection spectroscopy. Pronounced copper protection was attributed to the growth of a protective film on the copper surface, containing both copper oxides and copper carboxylate compounds. It is suggested that the organic molecules enhance copper protection by covering copper oxides with a thin and dense organic layer, which prevents water molecules or aggressive anions from interacting with the copper surface.

  14. The adsorption of cationic dye from aqueous solution onto acid-activated andesite.

    PubMed

    Tsai, Wen-Tien; Hsu, Hsin-Chieh; Su, Ting-Yi; Lin, Keng-Yu; Lin, Chien-Ming; Dai, Tzong-Hung

    2007-08-25

    The adsorption of cationic dye (i.e., methylene blue) onto acid-activated andesite in aqueous solution was studied in a batch system with respect to its kinetics as a function of agitation speed, initial adsorbate concentration, pH, and adsorbent mass. It was found that the resulting acid-activated adsorbent possessed a mesoporous structure with BET surface areas at around 60m(2)/g. The surface characterization of acid-activated andesite was also performed using the zeta-potential measurements, indicating that the charge sign on the surface of the andesite should be negative in a wide pH range (i.e., 3-11). Furthermore, a simplified kinetic model, pseudo-second-order, was tested to investigate the adsorption behaviors of methylene blue onto the clay samples treated under different process conditions. It was found that the adsorption process could be well described with the model. The adsorption capacity parameter of the model obtained in the present work was significantly in line with the process parameters.

  15. Removal of boron from aqueous solution using magnetic carbon nanotube improved with tartaric acid.

    PubMed

    Zohdi, Nima; Mahdavi, Fariba; Abdullah, Luqman Chuah; Choong, Thomas Sy

    2014-01-06

    Boron removal capacity of multi-walled carbon nanotubes (MWCNTs) modified with tartaric acid was investigated in this study. Modification of MWCNTs with tartaric acid was confirmed by Boehm surface chemistry method and fourier transform infra-red (FT-IR) spectroscopy. Experiments were performed to determine the adsorption isotherm and adsorption thermodynamic parameters of boron adsorption on tartaric acid modified MWCNTs (TA-MWCNTs). The effect of variables including initial pH, dosage of adsorbent, contact time and temperature was investigated. Analysis of data showed that adsorption equilibrium could be better described by Freundlich isotherm and the maximum adsorption capacities obtained at the pH of 6.0 was 1.97 mg/g. The estimated thermodynamic values of free energy (ΔG°), entropy (ΔS°) and enthalpy (ΔH°) indicated a spontaneous and an endothermic process. Furthermore, the TA-MWCNTs was magnetized for separation of boron-contaminated adsorbent from aqueous solution by applying magnetic field. The results showed that magnetic TA-MWCNTs particles were separated effectively after adsorption from contaminated water.

  16. Covalent triazine-based framework: A promising adsorbent for removal of perfluoroalkyl acids from aqueous solution.

    PubMed

    Wang, Bingyu; Lee, Linda S; Wei, Chenhui; Fu, Heyun; Zheng, Shourong; Xu, Zhaoyi; Zhu, Dongqiang

    2016-09-01

    Perfluoroalkyl acids (PFAAs) are highly stable, persistent, and ubiquitous in the environment with significant concerns growing with regards to both human and ecosystem health. Due to the high stability to both biological and chemical attack, the only currently feasible approach for their removal from water is adsorbent technology. The main objective of this study was to assess a covalent triazine-based framework (CTF) adsorbent for removal from aqueous solutions of perfluoro C4, C6, and C8 carboxylates and sulfonates including the two C8s most commonly monitored, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Adsorption affinity and capacity were quantified and compared to three commonly used sorbents: pulverized microporous activated carbon, single-walled carbon nanotubes, and Amberlite IRA-400 anion-exchange resin. CTF adsorbent exhibited pronouncedly higher adsorption affinity and capacity of PFAAs than other test sorbents. The remarkably strong adsorption to CTF can be attributed to the favored electrostatic interaction between the protonated triazine groups on the inner wall of the hydrophobic CTF pore and the negatively charged head groups of the PFAAs intercalated between the CTF layers. The homogeneous, nanosized pores (1.2 nm) of CTF hindered adsorption of a large-sized dissolved humic acid, thus minimizing the suppression of PFAA adsorption. Additionally, regeneration of CTF was easily accomplished by simply raising pH > 11, which inhibited the electrostatic adsorptive interaction of PFAAs. PMID:27389552

  17. The adsorption of cationic dye from aqueous solution onto acid-activated andesite.

    PubMed

    Tsai, Wen-Tien; Hsu, Hsin-Chieh; Su, Ting-Yi; Lin, Keng-Yu; Lin, Chien-Ming; Dai, Tzong-Hung

    2007-08-25

    The adsorption of cationic dye (i.e., methylene blue) onto acid-activated andesite in aqueous solution was studied in a batch system with respect to its kinetics as a function of agitation speed, initial adsorbate concentration, pH, and adsorbent mass. It was found that the resulting acid-activated adsorbent possessed a mesoporous structure with BET surface areas at around 60m(2)/g. The surface characterization of acid-activated andesite was also performed using the zeta-potential measurements, indicating that the charge sign on the surface of the andesite should be negative in a wide pH range (i.e., 3-11). Furthermore, a simplified kinetic model, pseudo-second-order, was tested to investigate the adsorption behaviors of methylene blue onto the clay samples treated under different process conditions. It was found that the adsorption process could be well described with the model. The adsorption capacity parameter of the model obtained in the present work was significantly in line with the process parameters. PMID:17363150

  18. Removal of boron from aqueous solution using magnetic carbon nanotube improved with tartaric acid

    PubMed Central

    2014-01-01

    Boron removal capacity of multi-walled carbon nanotubes (MWCNTs) modified with tartaric acid was investigated in this study. Modification of MWCNTs with tartaric acid was confirmed by Boehm surface chemistry method and fourier transform infra-red (FT-IR) spectroscopy. Experiments were performed to determine the adsorption isotherm and adsorption thermodynamic parameters of boron adsorption on tartaric acid modified MWCNTs (TA-MWCNTs). The effect of variables including initial pH, dosage of adsorbent, contact time and temperature was investigated. Analysis of data showed that adsorption equilibrium could be better described by Freundlich isotherm and the maximum adsorption capacities obtained at the pH of 6.0 was 1.97 mg/g. The estimated thermodynamic values of free energy (ΔG°), entropy (ΔS°) and enthalpy (ΔH°) indicated a spontaneous and an endothermic process. Furthermore, the TA-MWCNTs was magnetized for separation of boron-contaminated adsorbent from aqueous solution by applying magnetic field. The results showed that magnetic TA-MWCNTs particles were separated effectively after adsorption from contaminated water. PMID:24393401

  19. Effect of sensitizer protonation on singlet oxygen production in aqueous and nonaqueous media.

    PubMed

    Arnbjerg, Jacob; Johnsen, Mette; Nielsen, Christian B; Jørgensen, Mikkel; Ogilby, Peter R

    2007-05-31

    The yield of singlet molecular oxygen, O2(a(1)Delta(g)), produced in a photosensitized process can be very susceptible to environmental perturbations. In the present study, protonation of photosensitizers whose chromophores contain amine functional groups is shown to adversely affect the singlet oxygen yield. Specifically, for bis(amino) phenylene vinylenes dissolved both in water and in toluene, addition of a protic acid to the solution alters properties of the system that, in turn, result in a decrease in the efficiency of singlet oxygen production. In light of previous studies on other molecules where protonation-dependent changes in the yield of photosensitized singlet oxygen production have been ascribed to changes in the quantum yield of the sensitizer triplet state, Phi(T), and to possible changes in the triplet state energy, E(T), our results demonstrate that this photosystem can respond to protonation in other ways. Although protonation-dependent changes in the amount of charge-transfer character in the sensitizer-oxygen complex may influence the singlet oxygen yield, it is likely that other processes also play a role. These include (a) protonation-dependent changes in sensitizer aggregation and (b) nonradiative channels for sensitizer deactivation that are enhanced as a consequence of the reversible protonation/deprotonation of the chromophore. The data obtained, although complicated, are relevant for understanding and ultimately controlling the behavior of photosensitizers in systems with microheterogeneous domains that have appreciable pH gradients. These data are particularly important given the use of such bi-basic chromophores as two-photon singlet oxygen sensitizers, with applications in spatially resolved singlet oxygen experiments (e.g., imaging experiments).

  20. The influence of a non-aqueous phase liquid (NAPL) and chemical oxidant application on perfluoroalkyl acid (PFAA) fate and transport.

    PubMed

    McKenzie, Erica R; Siegrist, Robert L; McCray, John E; Higgins, Christopher P

    2016-04-01

    One dimensional column experiments were conducted using saturated porous media containing residual trichloroethylene (TCE) to understand the effects of non-aqueous phase liquids (NAPLs) and chemical oxidation on perfluoroalkyl acid (PFAA) fate and transport. Observed retardation factors and data from supporting batch studies suggested that TCE provides additional sorption capacity that can increase PFAA retardation (i.e., decreased mobility), though the mechanisms remain unclear. Treatment with persulfate activated with FeCl2 and citric acid, catalyzed hydrogen peroxide (CHP), or permanganate did not result in oxidative transformations of PFAAs. However, impacts on PFAA sorption were apparent, and enhanced sorption was substantial in the persulfate-treated columns. In contrast, PFAA transport was accelerated in permanganate- and CHP-treated columns. Ultimately, PFAA transport in NAPL contaminated groundwater is likely influenced by porous media properties, NAPL characteristics, and water quality properties, each of which can change due to chemical oxidant treatment. For contaminated sites for which ISCO is a viable treatment option, changes to PFAA transport and the implications thereof should be included as a component of the remediation evaluation and selection process. PMID:26854608

  1. The influence of a non-aqueous phase liquid (NAPL) and chemical oxidant application on perfluoroalkyl acid (PFAA) fate and transport.

    PubMed

    McKenzie, Erica R; Siegrist, Robert L; McCray, John E; Higgins, Christopher P

    2016-04-01

    One dimensional column experiments were conducted using saturated porous media containing residual trichloroethylene (TCE) to understand the effects of non-aqueous phase liquids (NAPLs) and chemical oxidation on perfluoroalkyl acid (PFAA) fate and transport. Observed retardation factors and data from supporting batch studies suggested that TCE provides additional sorption capacity that can increase PFAA retardation (i.e., decreased mobility), though the mechanisms remain unclear. Treatment with persulfate activated with FeCl2 and citric acid, catalyzed hydrogen peroxide (CHP), or permanganate did not result in oxidative transformations of PFAAs. However, impacts on PFAA sorption were apparent, and enhanced sorption was substantial in the persulfate-treated columns. In contrast, PFAA transport was accelerated in permanganate- and CHP-treated columns. Ultimately, PFAA transport in NAPL contaminated groundwater is likely influenced by porous media properties, NAPL characteristics, and water quality properties, each of which can change due to chemical oxidant treatment. For contaminated sites for which ISCO is a viable treatment option, changes to PFAA transport and the implications thereof should be included as a component of the remediation evaluation and selection process.

  2. Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution I: Acid and Base Coordinate and Charge Dynamics.

    PubMed

    Daschakraborty, Snehasis; Kiefer, Philip M; Miller, Yifat; Motro, Yair; Pines, Dina; Pines, Ehud; Hynes, James T

    2016-03-10

    Protonation by carbonic acid H2CO3 of the strong base methylamine CH3NH2 in a neutral contact pair in aqueous solution is followed via Car-Parrinello molecular dynamics simulations. Proton transfer (PT) occurs to form an aqueous solvent-stabilized contact ion pair within 100 fs, a fast time scale associated with the compression of the acid-base hydrogen-bond (H-bond), a key reaction coordinate. This rapid barrierless PT is consistent with the carbonic acid-protonated base pKa difference that considerably favors the PT, and supports the view of intact carbonic acid as potentially important proton donor in assorted biological and environmental contexts. The charge redistribution within the H-bonded complex during PT supports a Mulliken picture of charge transfer from the nitrogen base to carbonic acid without altering the transferring hydrogen's charge from approximately midway between that of a hydrogen atom and that of a proton. PMID:26879554

  3. Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution I: Acid and Base Coordinate and Charge Dynamics.

    PubMed

    Daschakraborty, Snehasis; Kiefer, Philip M; Miller, Yifat; Motro, Yair; Pines, Dina; Pines, Ehud; Hynes, James T

    2016-03-10

    Protonation by carbonic acid H2CO3 of the strong base methylamine CH3NH2 in a neutral contact pair in aqueous solution is followed via Car-Parrinello molecular dynamics simulations. Proton transfer (PT) occurs to form an aqueous solvent-stabilized contact ion pair within 100 fs, a fast time scale associated with the compression of the acid-base hydrogen-bond (H-bond), a key reaction coordinate. This rapid barrierless PT is consistent with the carbonic acid-protonated base pKa difference that considerably favors the PT, and supports the view of intact carbonic acid as potentially important proton donor in assorted biological and environmental contexts. The charge redistribution within the H-bonded complex during PT supports a Mulliken picture of charge transfer from the nitrogen base to carbonic acid without altering the transferring hydrogen's charge from approximately midway between that of a hydrogen atom and that of a proton.

  4. Citric acid production by Yarrowia lipolytica cultivated on olive-mill wastewater-based media.

    PubMed

    Papanikolaou, Seraphim; Galiotou-Panayotou, Maria; Fakas, Stylianos; Komaitis, Michael; Aggelis, George

    2008-05-01

    Yarrowia lipolytica ACA-DC 50109 cultivated on olive-mill wastewater (O.M.W.)-based media, enriched with commercial-industrial glucose, presented an efficient cell growth. Parameters of growth were unaffected by the presence of O.M.Ws in the growth medium. In diluted O.M.Ws enriched with high glucose amounts (initial sugar concentration, 65 g l(-1)), a notable quantity of total citric acid was produced (28.9 g l(-1)). O.M.W.-based media had a noteworthy stimulating effect on the production of citric acid, since both final citric acid concentration and conversion yield of citric acid produced per unit of sugar consumed were higher when compared with the respective parameters obtained from trials without added O.M.W. Adaptation of the strain in O.M.W.-based media favoured the biosynthesis of cellular unsaturated fatty acids (principally of oleic and palmitoleic acids). Additionally, a non-negligible decrease of the phenolic compounds in the growth medium [up to 15% (wt/wt)], a slight decrease of the phyto-toxicity, and a remarkable decolourisation of the O.M.W. were observed. All these results suggest the potentiality of O.M.Ws utilisation in the fermentation process of citric acid production.

  5. Aquatic photolysis: photolytic redox reactions between goethite and adsorbed organic acids in aqueous solutions

    USGS Publications Warehouse

    Goldberg, M.C.; Cunningham, K.M.; Weiner, Eugene R.

    1993-01-01

    Photolysis of mono and di-carboxylic acids that are adsorbed onto the surface of the iron oxyhydroxide (goethite) results in an oxidation of the organic material and a reduction from Fe(III) to Fe(II) in the iron complex. There is a subsequent release of Fe2+ ions into solution. At constant light flux and constant solution light absorption, the factors responsible for the degree of photolytic reaction include: the number of lattice sites that are bonded by the organic acid; the rate of acid readsorption to the surface during photolysis; the conformation and structure of the organic acid; the degree of oxidation of the organic acid; the presence or absence of an ??-hydroxy group on the acid, the number of carbons in the di-acid chain and the conformation of the di-acid. The ability to liberate Fe(III) at pH 6.5 from the geothite lattice is described by the lyotropic series: tartrate>citrate> oxalate > glycolate > maleate > succinate > formate > fumarate > malonate > glutarate > benzoate = butanoate = control. Although a larger amount of iron is liberated, the series is almost the same at pH 5.5 except that oxalate > citrate and succinate > maleate. A set of rate equations are given that describe the release of iron from the goethite lattice. It was observed that the pH of the solution increases during photolysis if the solutions are not buffered. There is evidence to suggest the primary mechanism for all these reactions is an electron transfer from the organic ligand to the Fe(III) in the complex. Of all the iron-oxyhydroxide materials, crystalline goethite is the least soluble in water; yet, this study indicates that in an aqueous suspension, iron can be liberated from the goethite lattice. Further, it has been shown that photolysis can occur in a multiphase system at the sediment- water interface which results in an oxidation of the organic species and release of Fe2+ to solution where it becomes available for further reaction. ?? 1993.

  6. Chemistry in the Venus clouds: Sulfuric acid reactions and freezing behavior of aqueous liquid droplets

    NASA Astrophysics Data System (ADS)

    Delitsky, M. L.; Baines, K. H.

    2015-11-01

    Venus has a thick cloud deck at 40-70 km altitude consisting of liquid droplets and solid particles surrounded by atmospheric gases. The liquid droplets are highly concentrated aqueous solutions of sulfuric acid ranging in concentration from 70-99 wt%. Weight percent drops off with altitude (Imamura and Hashimoto 2001). There will be uptake of atmospheric gases into the droplet solutions and the ratios of gas-phase to liquid-phase species will depend on the Henry’s Law constant for those solutions. Reactions of sulfuric acid with these gases will form products with differing solubilities. For example, uptake of HCl by H2SO4/H2O droplets yields chlorosulfonic acid, ClSO3H (Robinson et al 1998) in solution. This may eventually decompose to thionyl- or sulfuryl chlorides, which have UV absorbances. HF will also uptake, creating fluorosulfonic acid, FSO3H, which has a greater solubility than the chloro- acid. As uptake continues, there will be many dissolved species in the cloudwaters. Baines and Delitsky (2013) showed that uptake will have a maximum at ~62 km and this is very close to the reported altitude for the mystery UV absorber in the Venus atmosphere. In addition, at very strong concentrations in lower altitude clouds, sulfuric acid will form hydrates such as H2SO4.H2O and H2SO4.4H2O which will have very different freezing behavior than sulfuric acid, with much higher freezing temperatures (Carslaw et al, 1997). Using temperature data from Venus Express from Tellmann et al (2009), and changes in H2SO4 concentrations as a function of altitude (James et al 1997), we calculate that freezing out of sulfuric acid hydrates can be significant down to as low as 56 km altitude. As a result, balloons, aircraft or other probes in the Venus atmosphere may be limited to flying below certain altitudes. Any craft flying at altitudes above ~55 km may suffer icing on the wings, propellers, balloons and instruments which could cause possible detrimental effects (thermal

  7. Extraction of protactinium from mineral acid-alcohol media.

    PubMed

    Alian, A; Sanad, W; Shabana, R

    1968-07-01

    The extraction of protactinium with organic solvents has been investigated in the presence of water-miscible alcohols and acetone. These additives were found to increase considerably the extraction of protactinium in the cases of trilaurylamine, tributyl phosphate and isobutyl methyl ketone. The influence was less in the case of thenoyltrifluoroacetone. In mixtures of an acid with various alcohols, the influence depended on the alcohol concentration, the acidity and on the chain lengths and dielectric constants of the alcohol introduced into the extraction system.

  8. Extraction of protactinium from mineral acid-alcohol media.

    PubMed

    Alian, A; Sanad, W; Shabana, R

    1968-07-01

    The extraction of protactinium with organic solvents has been investigated in the presence of water-miscible alcohols and acetone. These additives were found to increase considerably the extraction of protactinium in the cases of trilaurylamine, tributyl phosphate and isobutyl methyl ketone. The influence was less in the case of thenoyltrifluoroacetone. In mixtures of an acid with various alcohols, the influence depended on the alcohol concentration, the acidity and on the chain lengths and dielectric constants of the alcohol introduced into the extraction system. PMID:18960346

  9. Fluorimetric determination of tin and organotin compounds in hydroorganic and micellar media in the presence of 8-hydroxyquinoline-5-sulfonic acid.

    PubMed

    Jourquin, G; Mahedero, M C; Paredes, S; Vire, J C; Kauffmann, J M

    1996-06-01

    The fluorescence of tin(IV) complexed by 8-hydroxyquinoline-5-sulfonic acid (8-HQSA) has been studied in both aqueous and hydroorganic (acetate buffer and dimethylsulfoxide) media. Several experimental parameters such as pH, DMSO/water ratio and reactant concentration have been investigated to increase the fluorescence of the tin(IV)-8-HQSA complex. A linear relationship between tin(IV) concentration and fluorescence intensity was observed between 1.7 and 20 microM). Mechanistic and quantitative studies in the presence of surfactants have been performed. Judiciously selected micellar media permitted solubilisation and quantitation of tin(IV) as well as dibutyltin compounds. A linear relationship between concentration and fluorescence intensity was found for mono-, di- and tributyltin with detection limits of 0.1 microM, 0.7 microM and 1 microM, respectively.

  10. Optimization, isotherm, kinetic and thermodynamic studies of Pb(II) ions adsorption onto N-maleated chitosan-immobilized TiO₂ nanoparticles from aqueous media.

    PubMed

    Shaker, Medhat A; Yakout, Amr A

    2016-02-01

    Chitosan, CS was chemically engineered by maleic anhydride via simple protocol to produce N-maleated chitosan, MCS which immobilized on anatase TiO2 to synthesize novel eco-friendly nanosorbent (51±3.8 nm), MCS@TiO2 for cost-effective and efficient removal of Pb(II) ions from aqueous media. The chemical structure, surface properties and morphology of MCS@TiO2 were recognized by FTIR, (1)H NMR, XRD, TEM, DLS and zeta-potential techniques. The relations between %removal of Pb(II) and different analytical parameters such as solution acidity (pH), MCS@TiO2 dosage, time of contact and initial Pb(II) concentration were optimized using response surface methodology (RSM) and Box-Behnken design (BBD) statistical procedures. The fitting of the experimental data to four different isotherm models at optimized conditions was carried out by various statistical treatments including the correlation coefficient (r), coefficient of determination (r(2)) and non-linear Chi-square (χ(2)) test analyses which all confirm the suitability of Langmuir model to explain the adsorption isotherm data. Also, statistics predicted that the pseudo-second-order model is the optimum kinetic model among four applied kinetic models to closely describe the rate equation of the adsorption process. Thermodynamics viewed the adsorption as endothermic and feasible physical process. EDTA could release the sorbed Pb(II) ions from MCS@TiO2 with a recovery above 92% after three sorption-desorption cycles. The novel synthesized nanosorbent is evidenced to be an excellent solid phase extractor for Pb(II) ions from wastewaters.

  11. Optimization, isotherm, kinetic and thermodynamic studies of Pb(II) ions adsorption onto N-maleated chitosan-immobilized TiO2 nanoparticles from aqueous media

    NASA Astrophysics Data System (ADS)

    Shaker, Medhat A.; Yakout, Amr A.

    2016-02-01

    Chitosan, CS was chemically engineered by maleic anhydride via simple protocol to produce N-maleated chitosan, MCS which immobilized on anatase TiO2 to synthesize novel eco-friendly nanosorbent (51 ± 3.8 nm), MCS@TiO2 for cost-effective and efficient removal of Pb(II) ions from aqueous media. The chemical structure, surface properties and morphology of MCS@TiO2 were recognized by FTIR, 1H NMR, XRD, TEM, DLS and zeta-potential techniques. The relations between %removal of Pb(II) and different analytical parameters such as solution acidity (pH), MCS@TiO2 dosage, time of contact and initial Pb(II) concentration were optimized using response surface methodology (RSM) and Box-Behnken design (BBD) statistical procedures. The fitting of the experimental data to four different isotherm models at optimized conditions was carried out by various statistical treatments including the correlation coefficient (r), coefficient of determination (r2) and non-linear Chi-square (χ2) test analyses which all confirm the suitability of Langmuir model to explain the adsorption isotherm data. Also, statistics predicted that the pseudo-second-order model is the optimum kinetic model among four applied kinetic models to closely describe the rate equation of the adsorption process. Thermodynamics viewed the adsorption as endothermic and feasible physical process. EDTA could release the sorbed Pb(II) ions from MCS@TiO2 with a recovery above 92% after three sorption-desorption cycles. The novel synthesized nanosorbent is evidenced to be an excellent solid phase extractor for Pb(II) ions from wastewaters.

  12. Optimization, isotherm, kinetic and thermodynamic studies of Pb(II) ions adsorption onto N-maleated chitosan-immobilized TiO₂ nanoparticles from aqueous media.

    PubMed

    Shaker, Medhat A; Yakout, Amr A

    2016-02-01

    Chitosan, CS was chemically engineered by maleic anhydride via simple protocol to produce N-maleated chitosan, MCS which immobilized on anatase TiO2 to synthesize novel eco-friendly nanosorbent (51±3.8 nm), MCS@TiO2 for cost-effective and efficient removal of Pb(II) ions from aqueous media. The chemical structure, surface properties and morphology of MCS@TiO2 were recognized by FTIR, (1)H NMR, XRD, TEM, DLS and zeta-potential techniques. The relations between %removal of Pb(II) and different analytical parameters such as solution acidity (pH), MCS@TiO2 dosage, time of contact and initial Pb(II) concentration were optimized using response surface methodology (RSM) and Box-Behnken design (BBD) statistical procedures. The fitting of the experimental data to four different isotherm models at optimized conditions was carried out by various statistical treatments including the correlation coefficient (r), coefficient of determination (r(2)) and non-linear Chi-square (χ(2)) test analyses which all confirm the suitability of Langmuir model to explain the adsorption isotherm data. Also, statistics predicted that the pseudo-second-order model is the optimum kinetic model among four applied kinetic models to closely describe the rate equation of the adsorption process. Thermodynamics viewed the adsorption as endothermic and feasible physical process. EDTA could release the sorbed Pb(II) ions from MCS@TiO2 with a recovery above 92% after three sorption-desorption cycles. The novel synthesized nanosorbent is evidenced to be an excellent solid phase extractor for Pb(II) ions from wastewaters. PMID:26520475

  13. Stability of Colistin and Colistin Methanesulfonate in Aqueous Media and Plasma as Determined by High-Performance Liquid Chromatography

    PubMed Central

    Li, Jian; Milne, Robert W.; Nation, Roger L.; Turnidge, John D.; Coulthard, Kingsley

    2003-01-01

    The stabilities of colistin and colistin methanesulfonate (CMS) in different aqueous media were studied by specific high-performance liquid chromatography (HPLC) methods. Colistin was stable in water at 4 and 37°C for up to 60 days and 120 h, respectively. However, degradation was observed when colistin was stored in isotonic phosphate buffer (0.067 M, pH 7.4) and human plasma at 37°C. The stability of CMS from three different sources in water was explored by strong-anion-exchange (SAX) HPLC for CMS and by measuring the concentrations of colistin formed from the hydrolysis of CMS. The peaks of CMS in SAX HPLC disappeared almost completely after 12 h at 37°C, but appeared to remain intact for up to 2 days at 4°C. Over the same period, there was no formation of colistin at 4°C. In water, phosphate buffer, and plasma, there was rapid formation of colistin within 24 to 48 h at 37°C from the three sources of CMS. The hydrolysis products were assumed to be a complex mixture of many different sulfomethyl derivatives, including colistin. The stability of a fourth source of CMS in Mueller-Hinton broth examined during 30 min at 37°C revealed no formation of colistin. Along with previous microbiological studies, this suggested that different sulfomethyl CMSs possess intrinsic antibacterial activity. These results will be helpful for understanding the pharmacokinetics and pharmacodynamics of colistin and CMS in humans and animals. PMID:12654671

  14. Structural modification of rhodamine-based sensors toward highly selective mercury detection in mixed organic/aqueous media.

    PubMed

    Huang, Wei; Zhu, Xiang; Wua, Dayu; He, Cheng; Hu, Xiaoyue; Duan, Chunying

    2009-12-21

    In virtue of the sulfurphilic nature of Hg(2+), three new sensors RN1, RN2 and RST1 that combine a thiophene group and one or two rhodamine choromophores, or a thiospirolactam rhodamine chromophore, were designed and prepared for the selective detection of Hg(2+) in aqueous media, respectively. These sensors all displayed good brightness and fluorescence enhancement following Hg(2+) coordination with limits of detection for Hg(2+) at the ppb level. Thus, they have the potential for distinguishing between safe and toxic levels of inorganic mercury in drinking water. RN1 exhibited chromogenic and fluorogenic selectivity over alkali, alkaline earth metals, divalent first-row transition metal ions as well as heavy metals, but the presence of Cu(2+) had a small but significant influence on the absorption detection of Hg(2+). Compared to RN1, the introduction of sufficient sulfur atoms could increase the binding capability of RST1 towards Hg(2+) relative to the sensor RN1, but decrease its Hg specific ability. The existence of some heavy and transition metal ions, such as Pb(2+), Ag(+), Cu(2+) enhance the silent absorption spectra of RST1. Spectral evidence and X-ray structural investigations of the mercury complex revealed a possible 1:2 complexation behaviour between the Hg(2+) ion and the sensor RN1 or RST1. Sensor RN2 which contains two rhodamine carboxhydrazone arms exhibited better selectivity, compared to those of RN1 and RST1. The addition of Cu(2+) only caused a small interference for the absorption detection of Hg(2+) under the same conditions, demonstrating the efficiency of the robust bis-chelating mode with regard to the selectivity for Hg(2+).

  15. Ordered mesoporous carbon film as an effective solid-phase microextraction coating for determination of benzene series from aqueous media.

    PubMed

    Jiang, Hui; Li, Jiansheng; Jiang, Mingyue; Lu, Rui; Shen, Jinyou; Sun, Xiuyun; Han, Weiqing; Wang, Lianjun

    2015-08-12

    The present work reports preparation of ordered mesoporous carbon (OMC) film supported on a graphite fiber as a new type of solid-phase microextraction (SPME) fiber for determination of benzene series from aqueous media. The strategy for the supported OMC film preparation was combined dip-coating technology with solvent evaporation-induced self-assembly (EISA) approach. A graphite fiber was immersed in an ethanol solution containing phenolic resin and Pluronic triblock copolymer. Upon solvent evaporation and subsequent pyrolysis under 700 °C, the phenolic resin and the surfactant self-assembled on the surface of the graphite fiber to form smooth OMC film. X-ray diffraction (XRD), transmission electron microscopy (TEM) and nitrogen isothermal adsorption results indicate that the resultant OMC film possesses well-ordered two dimensional hexagonal mesostructure with pore diameters of 4.5 nm and BET surfaces of 630 m(2)/g. Scanning electron microscopy (SEM) studies show the supported OMC film with thickness at 8.5 μm is continuous and defect-free. The SPME efficiency of the OMC fiber was evaluated by analysis of five benzene series (benzene, toluene, ethylbenzene, p-xylene and m-xylene) from water samples by gas chromatography-flame ionization detection (GC-FID). The analysis results indicate that the prepared OMC fiber has wide linear ranges (0.5-500 μg/L), low detection limits (0.01-0.05 μg/L) and good repeatabilities (4.0-5.8% for one fiber, 2.9-8.7% for fiber-to-fiber). Compared with commercial counterparts, the OMC fiber exhibits improved extraction efficiency for benzene series and PAHs. PMID:26320962

  16. Lignin-assisted exfoliation of molybdenum disulfide in aqueous media and its application in lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Liu, Wanshuang; Zhao, Chenyang; Zhou, Rui; Zhou, Dan; Liu, Zhaolin; Lu, Xuehong

    2015-05-01

    electrochemical performance compared with the pristine MoS2 mineral because of the enhanced ion and electron transfer kinetics. This facile, scalable and eco-friendly aqueous-based process in combination with renewable and ultra-low-cost lignin opens up possibilities for large-scale fabrication of MoS2-based nanocomposites and devices. Moreover, herein we demonstrate that AL is also an excellent surfactant for exfoliation of many other types of layered materials, including graphene, tungsten disulfide and boron nitride, in water, providing rich opportunities for a wider range of applications. Electronic supplementary information (ESI) available: CV of the bulk MoS2 between 1-3 V, electrochemical performances of the exfoliated MoS2 nanosheets between 1-3 V with 10 wt% carbon black, referenced table of exfoliation of MoS2 in aqueous media. See DOI: 10.1039/c5nr01891a

  17. Excess electron reactivity in amino acid aqueous solution revealed by ab initio molecular dynamics simulation: anion-centered localization and anion-relayed electron transfer dissociation.

    PubMed

    Wu, Xiuxiu; Gao, Liang; Liu, Jinxiang; Yang, Hongfang; Wang, Shoushan; Bu, Yuxiang

    2015-10-28

    Studies on the structure, states, and reactivity of excess electrons (EEs) in biological media are of great significance. Although there is information about EE interaction with desolvated biological molecules, solution effects are hardly explored. In this work, we present an ab initio molecular dynamics simulation study on the interaction and reactivity of an EE with glycine in solution. Our simulations reveal two striking results. Firstly, a pre-solvated EE partially localizes on the negatively charged -COO(-) group of the zwitterionic glycine and the remaining part delocalizes over solvent water molecules, forming an anion-centered quasi-localized structure, due to relative alignment of the lowest unoccupied molecular orbital energy levels of potential sites for EE residence in the aqueous solution. Secondly, after a period of anion-centered localization of an EE, the zwitterionic glycine is induced to spontaneously fragment through the cleavage of the N-Cα bond, losing ammonia (deamination), and leaving a ˙CH2-COO(-) anion radical, in good agreement with experimental observations. Introduction of the same groups (-COO(-) or -NH3(+)) in the side chain (taking lysine and aspartic acid as examples) can affect EE localization, with the fragmentation of the backbone part of these amino acids dependent on the properties of the side chain groups. These findings provide insights into EE interaction mechanisms with the backbone parts of amino acids and low energy EE induced fragmentation of amino acids and even peptides and proteins.

  18. Acidity constants in methanol/water mixtures of polycarboxylic acids used in drug salt preparations. Potentiometric determination of aqueous pKa values of quetiapine formulated as hemifumarate.

    PubMed

    Garrido, Gemma; Ràfols, Clara; Bosch, Elisabeth

    2006-05-01

    The acidic dissociation constants in a number of methanol/water mixtures of mono and polycarboxylic acids commonly used in the preparation of drug salts were determined. These solvent mixtures are usually used to determine the pKa of drugs of low aqueous solubility. However, when these drugs are prepared in salt form, the acid-base equilibria of both the basic drug and the counter-anion are involved in the potentiometric titration curves. In these instances, the inclusion of the pKa of acids as constant values in the curve fitting provides easy computation of the drug pKa without the need of any previous step to get the free base. As an application example, the aqueous pKa values of the quetiapine formulated as hemifumarate (Seroquel) were estimated by extrapolation from the experimental pKa in several methanol/water mixtures, which were then calculated according to the suitable constants of fumaric acid. The estimated aqueous pKa values of quetiapine are compared with those directly obtained in aqueous solution by potentiometry and by capillary electrophoresis.

  19. Thermodynamic characteristics of the interaction between nicotinic acid and phenylalanine in an aqueous buffer solution at 298 K

    NASA Astrophysics Data System (ADS)

    Badelin, V. G.; Tyunina, E. Yu.; Mezhevoi, I. N.; Tarasova, G. N.

    2013-08-01

    The interaction between L-phenylalanine and nicotinic acid is studied by solution calorimetry in an aqueous buffer solution (pH 7.35) at different ratios of the reagents. Experimental data on the enthalpy of dissolution of amino acid in the buffer solution of nicotinic acid at 298.15 K are calculated. The values of thermodynamic parameters for the complexation of L-phenylalanine with nicotinic acid are calculated. It is shown that the formation of a 1: 2 molecular complex is stabilized by the entropy factor due to the dominant role of the dehydration effect of initial reagents.

  20. Self-assembly of folic acid: a chiral-aligning medium for enantiodiscrimination of organic molecules in an aqueous environment.

    PubMed

    Lokesh; Suryaprakash, N

    2012-09-10

    Weak orienting medium: Self-assembly of alkaline salt of folic acid yielded a weak liquid-crystalline phase in an aqueous environment. This medium has the ability to discriminate enantiomers. The mesophase exists over a broad range and has the physical parameter dependent tunability of degree of alignment (see scheme).