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Sample records for acidic aqueous conditions

  1. 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.

  2. 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.

  3. 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%.

  4. Thermal stability of 5-o-caffeoylquinic acid in aqueous solutions at different heating conditions.

    PubMed

    Dawidowicz, Andrzej L; Typek, Rafal

    2010-12-22

    Chlorogenic acid is a naturally occurring phenolic compound found in all higher plants. This component, being the ester of caffeic acid with quinic acid, is an important biosynthetic intermediate and plays an important role in the plant's response to stress. Potential uses of chlorogenic acid are suggested in pharmaceuticals, foodstuffs, feed additives, and cosmetics due to its recently discovered biomedical activity. This finding caused new interest in chlorogenic acid properties, its isomers, and its natural occurrence. It has been found that as many as nine compounds (chlorogenic acid derivatives and its reaction product with water) can be formed from 5-o-caffeoylquinic acid during the heating of its water solution. Three of them, two hydroxylated 5-o-caffeoylquinic acid derivatives and 4,5-dicaffeoylquinic acid, have been not reported, yet. The amount of each formed component depends on the heating time and temperature. The presented results are important for researchers investigating plant metabolism and looking for new plant components. The transformation product can be mistakenly treated as a new component, not found before in the examined plant, or can be a cause of erroneous quantitative estimations of plant composition.

  5. 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.

  6. UV – INDUCED SYNTHESIS OF AMINO ACIDS FROM AQUEOUS STERILIZED SOLUTION OF AMMONIUM FORMATE AND AMMONIA UNDER HETROGENEOUS CONDITIONS

    PubMed Central

    Bisht, G.; Bisht, L. S.

    1990-01-01

    Irradiation of sterilized aqueous solution of ammonium formate and ammonia with UV light in the presence and or absence of certain inorganic sensitizers for 25 hrs. gave six ninhydrin positive products in appreciable amounts. Out of the six products observed fiver were characterized as lysine, serine, glutemic acid, n-amino butyric acid and leucine. The sensitizing effect of additives on ammonium formate was observed in the order; uranium oxide > ammonium formate > ferric oxide > arsenic oxide. PMID:22556511

  7. Quantitative evaluation of noncovalent interactions between polyphosphate and dissolved humic acids in aqueous conditions.

    PubMed

    Fang, Wei; Sheng, Guo-Ping; Wang, Long-Fei; Ye, Xiao-Dong; Yu, Han-Qing

    2015-12-01

    As one kind of phosphorus species, polyphosphate (poly-P) is ubiquitous in natural environments, and the potential interactions between poly-P and humic substances in the sediments or natural waters would influence the fate of poly-P in the environments. However, the mechanism of the interactions has not yet been understood clearly. In this work, the characteristics and mechanisms of the interactions between humic acids (HA) and two model poly-P compounds with various chain lengths have been investigated. Results show that a stable polyphosphate-HA complex would be formed through the noncovalent interactions, and hydrogen bond might be the main driving force for the binding process, which might be formed between the proton-accepting groups of poly-P (e.g., PO and P-O(-)) and the oxygen containing functional groups in HA. Our findings implied that the presence of humic substances in natural waters, soils and sediments would influence the potential transport and/or mobility of environmental poly-P. PMID:26367705

  8. Quantitative evaluation of noncovalent interactions between polyphosphate and dissolved humic acids in aqueous conditions.

    PubMed

    Fang, Wei; Sheng, Guo-Ping; Wang, Long-Fei; Ye, Xiao-Dong; Yu, Han-Qing

    2015-12-01

    As one kind of phosphorus species, polyphosphate (poly-P) is ubiquitous in natural environments, and the potential interactions between poly-P and humic substances in the sediments or natural waters would influence the fate of poly-P in the environments. However, the mechanism of the interactions has not yet been understood clearly. In this work, the characteristics and mechanisms of the interactions between humic acids (HA) and two model poly-P compounds with various chain lengths have been investigated. Results show that a stable polyphosphate-HA complex would be formed through the noncovalent interactions, and hydrogen bond might be the main driving force for the binding process, which might be formed between the proton-accepting groups of poly-P (e.g., PO and P-O(-)) and the oxygen containing functional groups in HA. Our findings implied that the presence of humic substances in natural waters, soils and sediments would influence the potential transport and/or mobility of environmental poly-P.

  9. Universal reaction mechanism of boronic acids with diols in aqueous solution: kinetics and the basic concept of a conditional formation constant.

    PubMed

    Furikado, Yuki; Nagahata, Tomomi; Okamoto, Takuya; Sugaya, Tomoaki; Iwatsuki, Satoshi; Inamo, Masahiko; Takagi, Hideo D; Odani, Akira; Ishihara, Koji

    2014-10-01

    To establish a detailed reaction mechanism for the condensation between a boronic acid, RB(OH)2, and a diol, H2L, in aqueous solution, the acid dissociation constants (Ka(BL)) of boronic acid diol esters (HBLs) were determined based on the well-established concept of conditional formation constants of metal complexes. The pKa values of HBLs were 2.30, 2.77, and 2.00 for the reaction systems, 2,4-difluorophenylboronic acid and chromotropic acid, 3-nitrophenylboronic acid and alizarin red S, and phenylboronic acid and alizarin red S, respectively. A general and precise reaction mechanism of RB(OH)2 with H2L in aqueous solution, which can serve as a universal reaction mechanism for RB(OH)2 and H2L, was proposed on the basis of (a) the relative kinetic reactivities of the RB(OH)2 and its conjugate base, that is, the boronate ion, toward H2L, and (b) the determined pKa values of HBLs. The use of the conditional formation constant, K', based on the main reaction: RB(OH)2 + H2L (K1)⇌ RB(L)(OH)(-) + H3O(+) instead of the binding constant has been proposed for the general reaction of uncomplexed boronic acid species (B') with uncomplexed diol species (L') to form boronic acid diol complex species (esters, BL') in aqueous solution at pH 5-11: B' + L' (K')⇌ BL'. The proposed reaction mechanism explains perfectly the formation of boronic acid diol ester in aqueous solution.

  10. 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.

  11. Electrochemical efficacy of a carboxylated multiwalled carbon nanotube filter for the removal of ibuprofen from aqueous solutions under acidic conditions.

    PubMed

    Bakr, Ahmed Refaat; Rahaman, Md Saifur

    2016-06-01

    This study provides insight into the efficiency of a functionalized multiwalled carbon nanotube filter for the removal of an anti-inflammatory drug, ibuprofen, through conventional filtration and electrochemical filtration processes. A comparison was made between carboxylated multiwalled carbon nanotubes (MWNTs-COOH) and pristine multiwalled carbon nanotubes (MWNTs) in order to emphasize the enhanced performance of MWNTs-COOH for the removal of ibuprofen using an electrochemical filtration process under acidic conditions. Ibuprofen-removal trials were evaluated based on absorbance values obtained using a UV/Vis spectrophotometer, and possible degradation products were identified using liquid chromatography mass spectrometry (LC-MS). The results exhibited near complete removal of ibuprofen by MWNTs-COOH at lower applied potentials (2 V), at lower flow rates, and under acidic conditions, which can be attributed to the generation of superoxides and their active participation in simultaneous degradation of ibuprofen, and its by-products, under these conditions. At higher applied potential (3 V), the possible participation of both bulk indirect oxidation reactions, and direct electron transfer were hypothesized for the removal behavior over time (breakthrough). At 3 V under acidic conditions, near 100% removal of the target molecule was achieved and was attributed to the enhanced generation of electroactive species toward bulk chemical reactions and a possible contribution from direct electron transfer under these conditions. The degradation by-products of ibuprofen were effectively removed by allowing longer residence time during the filtration process. Moreover, the effect of temperature was studied, yet showed a non-significant effect on the overall removal process.

  12. 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

  13. Aqueous Suzuki Coupling Reactions of Basic Nitrogen-Containing Substrates in the Absence of Added Base and Ligand: Observation of High Yields under Acidic Conditions.

    PubMed

    Li, Zhao; Gelbaum, Carol; Fisk, Jason S; Holden, Bruce; Jaganathan, Arvind; Whiteker, Gregory T; Pollet, Pamela; Liotta, Charles L

    2016-09-16

    A series of aqueous heterogeneous Suzuki coupling reactions of substrates containing basic nitrogen centers with phenylboronic acid in the absence of added base and ligand is presented. High yields of products were obtained by employing aryl bromides containing aliphatic 1°, 2°, and 3° amine substituents, and good to high yields were obtained by employing a variety of substituted bromopyridines. In the former series, the pH of the aqueous phase changed from basic to acidic during the course of the reaction, while in the latter series the aqueous phase was on the acidic side of the pH scale throughout the entire course of reaction. A mechanistic interpretation for these observations, which generally preserves the oxo palladium catalytic cycle widely accepted in the literature, is presented. PMID:27559749

  14. Aqueous Suzuki Coupling Reactions of Basic Nitrogen-Containing Substrates in the Absence of Added Base and Ligand: Observation of High Yields under Acidic Conditions.

    PubMed

    Li, Zhao; Gelbaum, Carol; Fisk, Jason S; Holden, Bruce; Jaganathan, Arvind; Whiteker, Gregory T; Pollet, Pamela; Liotta, Charles L

    2016-09-16

    A series of aqueous heterogeneous Suzuki coupling reactions of substrates containing basic nitrogen centers with phenylboronic acid in the absence of added base and ligand is presented. High yields of products were obtained by employing aryl bromides containing aliphatic 1°, 2°, and 3° amine substituents, and good to high yields were obtained by employing a variety of substituted bromopyridines. In the former series, the pH of the aqueous phase changed from basic to acidic during the course of the reaction, while in the latter series the aqueous phase was on the acidic side of the pH scale throughout the entire course of reaction. A mechanistic interpretation for these observations, which generally preserves the oxo palladium catalytic cycle widely accepted in the literature, is presented.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Hematite Spherules in Basaltic Tephra Altered Under Aqueous, Acid-Sulfate Conditions on Mauna Kea Volcano, Hawaii: Possible Clues for the Occurrence of Hematite-Rich Spherules in the Burns Formation at Meridiani Planum, Mars

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Ming, D. W.; Graff, T. G.; Arvidson, R. E.; Bell, J. F., III; Squyres, S. W.; Mertzman, S. A.; Gruener, J. E.; Golden, D. C.; Robinson, G. A.

    2005-01-01

    Iron-rich spherules (>90% Fe2O3 from electron microprobe analyses) approx.10-100 microns in diameter are found within sulfate-rich rocks formed by aqueous, acid-sulfate alteration of basaltic tephra on Mauna Kea volcano, Hawaii. Although some spherules are nearly pure Fe, most have two concentric compositional zones, with the core having a higher Fe/Al ratio than the rim. Oxide totals less than 100% (93-99%) suggest structural H2O and/or /OH. The transmission Moessbauer spectrum of a spherule-rich separate is dominated by a hematite (alpha-Fe2O3) sextet whose peaks are skewed toward zero velocity. Skewing is consistent with Al(3+) for Fe(3+) substitution and structural H2O and/or /OH. The grey color of the spherules implies specular hematite. Whole-rock powder X-ray diffraction spectra are dominated by peaks from smectite and the hydroxy sulfate mineral natroalunite as alteration products and plagioclase feldspar that was present in the precursor basaltic tephra. Whether spherule formation proceeded directly from basaltic material in one event (dissolution of basaltic material and precipitation of hematite spherules) or whether spherule formation required more than one event (formation of Fe-bearing sulfate rock and subsequent hydrolysis to hematite) is not currently constrained. By analogy, a formation pathway for the hematite spherules in sulfate-rich outcrops at Meridiani Planum on Mars (the Burns formation) is aqueous alteration of basaltic precursor material under acid-sulfate conditions. Although hydrothermal conditions are present on Mauna Kea, such conditions may not be required for spherule formation on Mars if the time interval for hydrolysis at lower temperatures is sufficiently long.

  3. 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)

  4. 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…

  5. 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.

  6. 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.

  7. 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.

  8. Syntheses of the Water-Dispersible Glycolic Acid Capped ZnS:Mn Nanocrystals at Different pH Conditions, and Their Aggregation and Luminescence Quenching Effects in Aqueous Solution.

    PubMed

    Sim, Yu Jin; Hwang, Cheong-Soo

    2016-06-01

    Water-dispersible ZnS:Mn nanocrystals were prepared by capping their surface with polar glycolic acid molecules at three different pH conditions. The produced ZnS:Mn-GA nanocrystals were characterized by XRD, HR-TEM, ICP-AES, and FT-IR spectroscopy. The optical properties were also measured by UV-Visible and room temperature photoluminescence (PL) spectroscopy. In the PL spectra, theses ZnS:Mn-GA nanocrystals showed broad emission peaks around 595 nm, and the calculated relative quantum efficiencies against an organic dye standard were in the range from 2.16 to 5.52%. The measured particle size from the HR-TEM images was about 3.7 nm on average, which were also supported by the calculations with the Debye-Scherrer methods. In addition, the surface charges of the nanocrystals were determined by an electrophoretic method, which showed pH dependent charge values of the nanocrytals: +0.88 mV (pH 2), +0.82 mV (pH 7), and -0.59 mV (pH 12) respectively. In addition, the degrees of aggregation of the nanocrystals in aqueous solutions were determined by a hydrodynamic light scattering method. As a result, formations of micrometer size agglomerates for all the ZnS:Mn-GA nanocrystals in water was observed at room temperature. This was probably caused by intermolecular attraction between the capping molecules. In addition, the ZnS:Mn-GA with the negative surface charge was presumed to be suitable for further coordination to a transition metal ion on the surface of the nanocrystal. As a result, fast luminescence quenching was observed after addition of aqueous solution containing Cu2+ ions.

  9. Syntheses of the Water-Dispersible Glycolic Acid Capped ZnS:Mn Nanocrystals at Different pH Conditions, and Their Aggregation and Luminescence Quenching Effects in Aqueous Solution.

    PubMed

    Sim, Yu Jin; Hwang, Cheong-Soo

    2016-06-01

    Water-dispersible ZnS:Mn nanocrystals were prepared by capping their surface with polar glycolic acid molecules at three different pH conditions. The produced ZnS:Mn-GA nanocrystals were characterized by XRD, HR-TEM, ICP-AES, and FT-IR spectroscopy. The optical properties were also measured by UV-Visible and room temperature photoluminescence (PL) spectroscopy. In the PL spectra, theses ZnS:Mn-GA nanocrystals showed broad emission peaks around 595 nm, and the calculated relative quantum efficiencies against an organic dye standard were in the range from 2.16 to 5.52%. The measured particle size from the HR-TEM images was about 3.7 nm on average, which were also supported by the calculations with the Debye-Scherrer methods. In addition, the surface charges of the nanocrystals were determined by an electrophoretic method, which showed pH dependent charge values of the nanocrytals: +0.88 mV (pH 2), +0.82 mV (pH 7), and -0.59 mV (pH 12) respectively. In addition, the degrees of aggregation of the nanocrystals in aqueous solutions were determined by a hydrodynamic light scattering method. As a result, formations of micrometer size agglomerates for all the ZnS:Mn-GA nanocrystals in water was observed at room temperature. This was probably caused by intermolecular attraction between the capping molecules. In addition, the ZnS:Mn-GA with the negative surface charge was presumed to be suitable for further coordination to a transition metal ion on the surface of the nanocrystal. As a result, fast luminescence quenching was observed after addition of aqueous solution containing Cu2+ ions. PMID:27427703

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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

  19. Timescales and conditions for the aqueous alteration of chondrites

    NASA Astrophysics Data System (ADS)

    Jilly, Christine E.

    It has become well-recognized that water played a critical role in the early geological evolution of materials through observation of hydrated phases in chondritic meteorites. However, details about the mechanism, timing, and conditions of aqueous alteration are poorly constrained. This dissertation investigates water-driven processes in Renazzo-like (CR) carbonaceous chondrites, with some comparison to the heavily altered and Mighei-like (CM) chondrites. CR chondrites were chosen as the focus of this study, as they are the only chondrite group to range from practically anhydrous to completely hydrated, providing petrographic context for the aqueous alteration process. The central goal of the thesis is to elucidate the complete mechanism of aqueous alteration, from primary anhydrous components to secondary minerals. This research uses a variety of micro-analytical techniques to address three main objectives: 1) to detail the petrographic context, 2) to quantify the onset and duration of alteration using radiometric dating, and 3) to constrain the fluid chemistry and conditions for aqueous alteration. On a microscopic scale, fine-grained matrices and glassy mesostases were the first phases to become altered, allowing for elemental transport over short distances (< 100 microns). As alteration progressed, the iron-metal was oxidized, and silicate phenocrysts were pseudomorphically replaced. 53Mn-53 Cr radiometric dating of secondary carbonates in CR chondrites show that aqueous alteration began quickly after accretion of the parent body, ~4 Myr after the beginning of the Solar System. This is contemporaneous with dolomite formation in the CM chondrite Sutter's Mill and with carbonate formation in other CM chondrites. However, the calcite age from a heavily hydrated CR lithology indicates that late-stage alteration occurred ~12 Myr after the beginning of the Solar System. The oxygen isotopic compositions of magnetite and carbonate minerals reveal that altering fluid

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Attenuation of aqueous benzene in soils under saturated flow conditions.

    PubMed

    Kim, S-B; Kim, D-J; Yun, S-T

    2006-01-01

    The fate of aqueous benzene in subsurface was investigated in this study, focusing on the role of sorption and biodegradation on the benzene attenuation under dynamic flow conditions. Two sets of column tests were conducted in Plexiglass flow cells packed uniformly with sandy aquifer materials. The first set of the experiment was conducted with a step-type injection of benzene with different powder activated carbon (PAC) contents: (1) PAC = 0 %; (2) PAC = 0.5 %; (3) PAC = 2.0%. The second set was performed as a pulse-type with different test conditions: (4) benzene; (5) benzene and bacteria (Pseudomonas aeruginosa); (6) benzene and bacteria (P. aeruginosa) with hydrogen peroxide. In addition, numerical experiments were performed to examine the role of sorption processes on the benzene attenuation. In the step mode experiments, the KCl breakthrough curves (BTCs) reached the input concentration while the benzene BTCs were considerably lower than those of KCl with slight retardation for all cases, indicating that both reversible/retardation and irreversible sorption occurred. The pulse type tests showed that attenuation of benzene increased in the presence of bacteria due to biodegradation. The benzene attenuation by microbial degradation increased furthermore in the presence of hydrogen peroxide owing to sufficient supply of dissolved oxygen in soil column. Numerical experiments demonstrated that retardation could not contribute to the attenuation of benzene in soils but could only extend its breakthrough time. Experimental results indicated that aqueous benzene could be attenuated by irreversible sorption and biodegradation during transport through the subsurface. Additionally, the attenuation of aqueous benzene is closely related to organic carbon content and oxygen level existing in contaminated aquifers.

  5. Multiphase Chemistry of Pyruvic Acid Under Atmospherically Relevant Conditions

    NASA Astrophysics Data System (ADS)

    Vaida, V.; Monod, A.; Doussin, J. F.; Reed Harris, A. E.; Griffith, E. C.; Kroll, J. A.; Rapf, R.

    2014-12-01

    Chemistry in the natural environment proceeds in multiple phases and is subject to effects from atmospheric constituents and conditions. This presentation will use pyruvic acid as a case study to demonstrate the complexity of atmospheric multiphase chemistry. The photophysics and photochemistry of pyruvic acid proceeds on different potential energy surfaces with different reaction mechanisms, rates, and products in gas versus the aqueous phase. While the gas phase reaction generally decreases the complexity of products, the aqueous chemistry creates higher molecular weight, surface-active compounds. The studies presented involve a combination of laboratory studies that focus on the photochemistry of pyruvic acid in both the gas and aqueous phases. Further, experiments in an environmental simulation chamber (CESAM) that follow the photochemistry chemistry of pyruvic acid under atmospherically relevant conditions will be presented to highlight the effect of pressure, oxygen, relative humidity, and phase on the photochemistry of pyruvic acid. The results provide new input for atmospheric chemistry models that is required to better describe the behavior of α-keto acids in the environment.

  6. 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.

  7. 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.

  8. 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.

  9. Hydrodefluorination and hydrogenation of fluorobenzene under mild aqueous conditions.

    PubMed

    Baumgartner, Rebekka; McNeill, Kristopher

    2012-09-18

    Fluorinated organic compounds are increasingly used in many applications, and their release to the environment is expected. It is therefore important to find suitable methods for degradation of fluorinated compounds under environmentally relevant conditions. In this study, a simple heterogeneous rhodium-based catalytic system (Rh/Al(2)O(3) and H(2)) for hydrodefluorination and hydrogenation of fluorobenzene under mild aqueous conditions (1 atm of H(2), ambient temperature) was developed and the underlying reaction mechanism was investigated. Fluorobenzene degraded rapidly (t(1/2) ≈ 0.2 h) to form cyclohexane and fluoride (F(-)) as the stable end products, with benzene and cyclohexene observed as intermediates. Cyclohexadiene intermediates were not observed but were expected to form during the hydrogenation of benzene. Three postulated but unobserved fluorinated intermediates were subjected to the catalytic reaction conditions, and it was concluded that they most likely do not form during the fluorobenzene degradation reaction. Isotope labeling experiments showed that the unsaturated intermediates undergo rapid and reversible hydrogenation/dehydrogenation under the reaction conditions and also that fully saturated compounds are unreactive in the catalytic system. Both molecular hydrogen and water were sources of hydrogen in the final cyclohexane product. Kinetic fitting indicated that sorption/desorption of fluorobenzene onto the catalyst surface plays an important role in the mechanism. PMID:22871102

  10. 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.

  11. 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.

  12. Promoted oxidation of phenol in aqueous solution using molecular oxygen at mild conditions

    SciTech Connect

    Vogel, F.; Harf, J.; Hug, A.; Rohr, P.R. von

    1999-05-01

    Wet oxidation with molecular oxygen at mild conditions (temperature < 200 C, pressure {le} 2 MPa) is an economically attractive pretreatment step for non-biodegradable aqueous waste streams. In order to overcome the low reactivity of molecular oxygen towards organic molecules at these mild process conditions, an initiator was used in combination with ferrous ions in the acidic range. The promoted oxidation of phenol in aqueous solution was investigated in a 4 liters stirred autoclave. It was possible to degrade the phenol at temperatures as low as 100 C without observing an induction time. The remaining solution contained mainly acetic and formic acid and was well biodegradable. The oxidative behavior of the oxygen/phenol system could be explained using the well-known autoxidation mechanism for aliphatic molecules. 4-hydroperoxy-phenol is suggested as a key intermediate. Measured products are p-benzoquinone, hydroquinone, catechol, maleic, oxalic, pyruvic, formic, and acetic acid. Dimers could also be identified in sample extracts. A global pathway including all identified products is presented.

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. Polymerization of amino acids under primitive earth conditions.

    NASA Technical Reports Server (NTRS)

    Flores, J. J.; Ponnamperuma, C.

    1972-01-01

    Small amounts of peptides were obtained when equal amounts of methane and ammonia were reacted with vaporized aqueous solutions of C14-labeled glycine, L-alanine, L-aspartic acid, L-glutamic acid and L-threonine in the presence of a continuous spark discharge in a 24-hr cyclic process. The experiment was designed to demonstrate the possibility of peptide synthesis under simulated primeval earth conditions. It is theorized that some dehydration-condensation processes may have taken place, with ammonium cyanide, the hydrogencyanide tetramer or aminonitriles as intermediate products, during the early chemical evolution of the earth.

  18. 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)

  19. 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

  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. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. Amyloid Aggregates Arise from Amino Acid Condensations under Prebiotic Conditions.

    PubMed

    Greenwald, Jason; Friedmann, Michael P; Riek, Roland

    2016-09-12

    Current theories on the origin of life reveal significant gaps in our understanding of the mechanisms that allowed simple chemical precursors to coalesce into the complex polymers that are needed to sustain life. The volcanic gas carbonyl sulfide (COS) is known to catalyze the condensation of amino acids under aqueous conditions, but the reported di-, tri-, and tetra-peptides are too short to support a regular tertiary structure. Here, we demonstrate that alanine and valine, two of the proteinogenic amino acids believed to have been among the most abundant on a prebiotic earth, can polymerize into peptides and subsequently assemble into ordered amyloid fibers comprising a cross-β-sheet quaternary structure following COS-activated continuous polymerization of as little as 1 mm amino acid. Furthermore, this spontaneous assembly is not limited to pure amino acids, since mixtures of glycine, alanine, aspartate, and valine yield similar structures. PMID:27511635

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. Application of maghemite nanoparticles as sorbents for the removal of Cu(II), Mn(II) and U(VI) ions from aqueous solution in acid mine drainage conditions

    NASA Astrophysics Data System (ADS)

    Etale, Anita; Tutu, Hlanganani; Drake, Deanne C.

    2016-06-01

    The adsorptive removal of Cu(II), Mn(II) and U(VI) by maghemite nanoparticles (NPs) was investigated under acid mine drainage (AMD) conditions to assess NP potential for remediating AMD-contaminated water. The effects of time, NP and metal concentration, as well as manganese and sulphate ions were quantified at pH 3. Adsorption of all three ions was rapid, and equilibrium was attained in 5 min or less. 56 % of Cu, 53 % of Mn and 49 % of U were adsorbed. In addition, adsorption efficiencies were enhanced by ≥10 % in the presence of manganese and sulphate ions, although Cu sorption was reduced in 1:2 Cu-to-Mn solutions. Adsorption also increased with pH: 86 % Cu, 62 % Mn and 77 % U were removed from solution at pH 9 and increasing initial metal concentrations. Increasing NP concentrations did not, however, always increase metal removal. Kinetics data were best described by a pseudo-second-order model, implying chemisorption, while isotherm data were better fitted by the Freundlich model. Metal removal by NPs was then tested in AMD-contaminated surface and ground water. Removal efficiencies of up to 46 % for Cu and 54 % for Mn in surface water and 8 % for Cu and 50 % for Mn in ground water were achieved, confirming that maghemite NPs can be applied for the removal of these ions from AMD-contaminated waters. Notably, whereas sulphates may increase adsorption efficiencies, high Mn concentrations in AMD will likely inhibit Cu sorption.

  13. 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.

  14. 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

  15. 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.

  16. Effects of surface condition on aqueous corrosion and environmental embrittlement of iron aluminides

    SciTech Connect

    Perrin, R.L.; Buchanan, R.A.

    1996-08-01

    Effects of retained high-temperature surface oxides, produced during thermomechanical processing and/or heat treatment, on the aqueous-corrosion and environmental-embrittlement characteristics of Fe{sub 3}Al-based iron aluminides (FA-84, FA-129 and FAL-Mo), a FeAl-based iron aluminide (FA-385), and a disordered low-aluminum Fe-Al alloy (FAPY) were evaluated. All tests were conducted at room temperature in a mild acid-chloride solution. In cyclic-anodic-polarization testing for aqueous-corrosion behavior, the surface conditions examined were: as-received (i.e., with the retained high-temperature oxides), mechanically cleaned and chemically cleaned. For all materials, the polarization tests showed the critical pitting potentials to be significantly lower in the as-received condition than in the mechanically-cleaned and chemically-cleaned conditions. These results indicate detrimental effects of the retained high-temperature oxides in terms of increased susceptibilities to localized corrosion. In 200-hour U-bend stress-corrosion-cracking tests for environmental-embrittlement behavior, conducted at open-circuit corrosion potentials and at a hydrogen-charging potential of {minus}1500 mV (SHE), the above materials (except FA-385) were examined with retained oxides and with mechanically cleaned surfaces. At the open-circuit corrosion potentials, none of the materials in either surface condition underwent cracking. At the hydrogen-charging potential, none of the materials with retained oxides underwent cracking, but FA-84, FA-129 and FAL-Mo in the mechanically cleaned condition did undergo cracking. These results suggest beneficial effects of the retained high-temperature oxides in terms of increased resistance to environmental hydrogen embrittlement.

  17. 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.

  18. Reduction kinetics of aqueous U(VI) in acidic chloride brines to uraninite by methane, hydrogen or C-graphite under hydrothermal conditions: Implications for the genesis of unconformity-related uranium ore deposits

    NASA Astrophysics Data System (ADS)

    Dargent, Maxime; Truche, Laurent; Dubessy, Jean; Bessaque, Gilles; Marmier, Hervé

    2015-10-01

    The formation of hydrothermal uranium ore deposits involves the reduction of dissolved U(VI)(aq) to uraninite. However, the nature of the reducing agent and the kinetics of such a process are currently unknown. These questions are addressed through dedicated experiments performed under conditions relevant for the genesis of unconformity-related uranium (URU) deposits. We tested the efficiency of the following potential reductants supposed to be involved in the reaction: H2, CH4, C-graphite and dissolved Fe(II). Results demonstrate the great efficiency of H2, CH4 and C-graphite to reduce U(VI)(aq) into uraninite in acidic chloride brines, unlike dissolved Fe(II). Times needed for H2 (1.4 bar), CH4 (2.4 bar) and C-graphite (water/carbon mass ratio = 10) to reduce 1 mM of U(VI)(aq) in an acidic brine (1 m LiCl, pH ≈ 1 fixed by HCl) to uraninite at 200 °C are 12 h, 3 days and 4 months, respectively. The effects of temperature (T) between 100 °C and 200 °C, H2 partial pressure (0.14, 1.4, and 5.4 bar), salinity (0.1, 1 and 3.2 m LiCl) and pH at 25 °C (0.8 and 3.3) on the reduction rate were also investigated. Results show that increasing temperature and H2 partial pressure increase the reaction rate, whereas increasing salinity or pH have the reverse effect. The reduction of uranyl to uraninite follows an apparent zero-order with respect to time, whatever the considered electron donor. From the measured rate constants, the following values of activation energy (Ea), depending on the nature of the electron donor, have been derived: EaC-graphite = 155 ± 3 kJ mol-1, EaCH4 = 143 ± 6 kJ mol-1, and EaH2 = 124 ± 15 kJ mol-1 at T < 150 °C and 32 ± 6 kJ mol-1 at T > 150 °C. An empirical relationship between the reaction rate, the hydrogen partial pressure, the uranyl speciation, and the temperature is also proposed. This allows an estimation of the time of formation of a giant U ore deposit such as McArthur River (Canada). The duration of the mineralizing event is

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Optical spectroscopy of simple aqueous solutions under extreme conditions

    NASA Astrophysics Data System (ADS)

    Vass, H.; Edington, D.; Crain, J.

    2003-06-01

    We report the results of an extensive series of Brillouin scattering experiments on simple aqueous solutions with a view to exploring their dynamical properties over a wide range of temperatures and pressures. For all solutes studied that inhibit freezing and allow access to temperatures far below the normal supercooling limit of water, we find clear spectroscopic evidence of GHz-range viscoelastic behavior below ≈-40 °C. This is manifested by a dramatic rise in the Brillouin mode frequencies accompanied by initial broadening and subsequent narrowing of the spectral linewidths on cooling. We find similar behavior in pure compressed (to between 2 and 4 kbar) supercooled water. This suggests that the low-temperature viscoelastic dynamics of these solutions is dominated by the behavior of the aqueous component which evidently exhibits a pronounced decrease in relaxation time though the temperature range over which it occurs is inaccessible unless freezing is suppressed either by pressure or the presence of solutes. No firm conclusion can be drawn concerning the proposed second critical point at these very low temperatures though it is not required for a consistent interpretation of the data. In the high-temperature regime, where the hydrogen bond structure is disrupted, we find considerable chemical sensitivity (even among the three chloride salts NaCl, CsCl, and CaCl2) in the dynamics especially in the vicinity of the liquid-gas critical point. This is in contrast to the low-temperature case where the cooperative dynamics of the water network dominates and appears to remain intact in the presence of a wide variety of solutes.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. Mutagenic effect by phenylalanine during gamma-irradiation of plasmid DNA in aqueous solution under oxic conditions.

    PubMed

    Reitsma-Wijker, C A; Slotman, B J; Lafleur, M V

    2000-11-01

    Irradiation of DNA in aqueous solution or in cells with gamma-rays results in different mutational spectra, indicating that in both situations different patterns of DNA damages are induced. One of the causes for these different types of damages might be the formation of secondary, organic radicals, if cells are irradiated. Some organic compounds, including the amino acid phenylalanine, are well known to produce radicals during irradiation. Under oxic conditions these secondary radicals react with oxygen, thus forming peroxyl radicals which can be very harmful to DNA, and which may, therefore, induce DNA damage leading to mutations. This study examines the influence of the presence of phenylalanine during gamma-irradiation of DNA in aqueous solution under oxic conditions. The results indicate that the formation of phenylalanine radicals influences the types of induced mutations in the gamma-radiation-induced mutation spectrum. The most prominent difference is the increase in G:C to T:A transversions and the decrease in G:C to A:T transitions in the presence of phenylalanine. Further, it appears that the gamma-radiation-induced mutation spectrum after irradiation of DNA in aqueous solution is more comparable to the intracellular gamma-radiation-induced mutation spectrum in E. coli cells, if phenylalanine is present during irradiation. Therefore, these results suggest that the presence of phenylalanine during irradiation of DNA in aqueous solution gives a better impression of gamma-radiation-induced mutations in bacterial systems than water only. PMID:11035161

  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. 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.

  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. 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

  5. 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

  6. 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.

  7. 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.

  8. Experimental Low Temperature Aqueous Alteration of Allende Under Reducing Conditions

    NASA Astrophysics Data System (ADS)

    Duke, C. L.; Brearley, A. J.

    1999-03-01

    This abstract presents the results of a series of low temperature hydrothermal alteration experiments that were carried out in an anoxic environment. The results are compared with the results of previous experiments run under oxidizing conditions.

  9. 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.

  10. 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

  11. Smectite Formation from Basaltic Glass Under Acidic Conditions on Mars

    NASA Technical Reports Server (NTRS)

    Peretyazhko, T. S.; Sutter, B.; Morris, R. V.; Agresti, D. G.; Le, L.; Ming, D. W.

    2015-01-01

    Massive deposits of phyllosilicates of the smectite group, including Mg/Fe-smectite, have been identified in Mars's ancient Noachian terrain. The observed smectite is hypothesized to form through aqueous alteration of basaltic crust under neutral to alkaline pH conditions. These pH conditions and the presence of a CO2-rich atmosphere suggested for ancient Mars were favorable for the formation of large carbonate deposits. However, the detection of large-scale carbonate deposits is limited on Mars. We hypothesized that smectite deposits may have formed under acidic conditions that prevented carbonate precipitation. In this work we investigated formation of saponite at a pH of approximately 4 from Mars-analogue synthetic Adirondack basaltic glass of composition similar to Adirondack class rocks located at Gusev crater. Hydrothermal (200º Centigrade) 14 day experiments were performed with and without 10 millimoles Fe(II) or Mg under anoxic condition [hereafter denoted as anoxic_Fe, anoxic_Mg and anoxic (no addition of Fe(II) or Mg)] and under oxic condition [hereafter denoted as oxic (no addition of Fe(II) or Mg)]. Characterization and formation conditions of the synthesized saponite provided insight into the possible geochemical conditions required for saponite formation on Mars.

  12. 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...

  13. 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...

  14. 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

  15. 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.

  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. PMID:27378357

  17. Aqueous alteration of VHTR fuels particles under simulated geological conditions

    NASA Astrophysics Data System (ADS)

    Ait Chaou, Abdelouahed; Abdelouas, Abdesselam; Karakurt, Gökhan; Grambow, Bernd

    2014-05-01

    Very High Temperature Reactor (VHTR) fuels consist of the bistructural-isotropic (BISO) or tristructural-isotropic (TRISO)-coated particles embedded in a graphite matrix. Management of the spent fuel generated during VHTR operation would most likely be through deep geological disposal. In this framework we investigated the alteration of BISO (with pyrolytic carbon) and TRISO (with SiC) particles under geological conditions simulated by temperatures of 50 and 90 °C and in the presence of synthetic groundwater. Solid state (scanning electron microscopy (SEM), micro-Raman spectroscopy, electron probe microanalyses (EPMA) and X-ray photoelectron spectroscopy (XPS)) and solution analyses (ICP-MS, ionique chromatography (IC)) showed oxidation of both pyrolytic carbon and SiC at 90 °C. Under air this led to the formation of SiO2 and a clay-like Mg-silicate, while under reducing conditions (H2/N2 atmosphere) SiC and pyrolytic carbon were highly stable after a few months of alteration. At 50 °C, in the presence and absence of air, the alteration of the coatings was minor. In conclusion, due to their high stability in reducing conditions, HTR fuel disposal in reducing deep geological environments may constitute a viable solution for their long-term management.

  18. 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

  19. 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.

  20. 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.

  1. 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

  2. Polyelectrolyte brushes: a novel stable lubrication system in aqueous conditions.

    PubMed

    Kobayashi, Motoyasu; Terada, Masami; Takahara, Atsushi

    2012-01-01

    Surface-initiated controlled radical copolymerizations of 2-dimethylaminoethyl methacrylate (DMAEMA), 2-(methacryloyloxy)ethyl phosphorylcholine (MPC), 2-(methacryloyloxy)ethyltrimethylammonium chloride) (MTAC), and 3-sulfopropyl methacrylate potassium salt (SPMK) were carried out on a silicon wafer and glass ball to prepare polyelectrolyte brushes with excellent water wettability. The frictional coefficient of the polymer brushes was recorded on a ball-on-plate type tribometer by linear reciprocating motion of the brush specimen at a selected velocity of 1.5 x 10(-3) m s-1 under a normal load of 0.49 N applied to the stationary glass ball (d = 10 mm) at 298 K. The poly(DMAEMA-co-MPC) brush partially cross-linked by bis(2-iodoethoxy)ethane maintained a relatively low friction coefficient around 0.13 under humid air (RH > 75%) even after 200 friction cycles. The poly(SPMK) brush revealed an extremely low friction coefficient around 0.01 even after 450 friction cycles. We supposed that the abrasion of the brush was prevented owing to the good affinity of the poly(SPMK) brush for water forming a water lubrication layer, and electrostatic repulsive interactions among the brushes bearing sulfonic acid groups. Furthermore, the poly(SPMK-co-MTAC) brush with a chemically cross-linked structure showed a stable low friction coefficient in water even after 1400 friction cycles under a normal load of 139 MPa, indicating that the cross-linking structure improved the wear resistance of the brush layer.

  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. 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.

  6. 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

  7. 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.

  8. Polyelectrolyte brushes: a novel stable lubrication system in aqueous conditions.

    PubMed

    Kobayashi, Motoyasu; Terada, Masami; Takahara, Atsushi

    2012-01-01

    Surface-initiated controlled radical copolymerizations of 2-dimethylaminoethyl methacrylate (DMAEMA), 2-(methacryloyloxy)ethyl phosphorylcholine (MPC), 2-(methacryloyloxy)ethyltrimethylammonium chloride) (MTAC), and 3-sulfopropyl methacrylate potassium salt (SPMK) were carried out on a silicon wafer and glass ball to prepare polyelectrolyte brushes with excellent water wettability. The frictional coefficient of the polymer brushes was recorded on a ball-on-plate type tribometer by linear reciprocating motion of the brush specimen at a selected velocity of 1.5 x 10(-3) m s-1 under a normal load of 0.49 N applied to the stationary glass ball (d = 10 mm) at 298 K. The poly(DMAEMA-co-MPC) brush partially cross-linked by bis(2-iodoethoxy)ethane maintained a relatively low friction coefficient around 0.13 under humid air (RH > 75%) even after 200 friction cycles. The poly(SPMK) brush revealed an extremely low friction coefficient around 0.01 even after 450 friction cycles. We supposed that the abrasion of the brush was prevented owing to the good affinity of the poly(SPMK) brush for water forming a water lubrication layer, and electrostatic repulsive interactions among the brushes bearing sulfonic acid groups. Furthermore, the poly(SPMK-co-MTAC) brush with a chemically cross-linked structure showed a stable low friction coefficient in water even after 1400 friction cycles under a normal load of 139 MPa, indicating that the cross-linking structure improved the wear resistance of the brush layer. PMID:23285641

  9. Interaction of model aryl- and alkyl-boronic acids and 1,2-diols in aqueous solution.

    PubMed

    Marinaro, William A; Prankerd, Richard; Kinnari, Kaisa; Stella, Valentino J

    2015-04-01

    The goal of this work was to quantitate ester formation between alkyl and aryl boronic acids and vicinal-diols or 1,2-diols in aqueous solution. As used here, 1,2-diols includes polyols with one or more 1,2-diol pairs. Multiple techniques were used including apparent pKa shifts of the boronic acids using UV spectrophotometry (for aryl acids) and titration (for aryl and alkyl acids). Isothermal microcalorimetry was also used, with all reactions being enthalpically favored. For all the acids and 1,2-diols and the conditions studied, evidence only supported 1:1 ester formation. All the esters formed were found to be significantly more acidic, as Lewis acids, by 3-3.5 pKa units than the corresponding nonesterified boronic acid. The equilibrium constants for ester formation increased with increasing number of 1,2-diol pairs but stereochemistry may also play a role as sorbitol with five possible 1,2-diol pairs and five isomers (taking into account the stereochemistry of the alcohol groups) was twice as efficient at ester formation compared with mannitol, also with five possible 1,2-diol pairs but only three isomers. Alkyl boronic acids formed esters to a greater extent than aryl acids. Although some quantitative differences were seen between the various techniques used, rank ordering of the structure/reactivity was consistent. Formulation implications of ester formation between boronic acids and 1,2-diols are discussed. PMID:25600471

  10. Interaction of model aryl- and alkyl-boronic acids and 1,2-diols in aqueous solution.

    PubMed

    Marinaro, William A; Prankerd, Richard; Kinnari, Kaisa; Stella, Valentino J

    2015-04-01

    The goal of this work was to quantitate ester formation between alkyl and aryl boronic acids and vicinal-diols or 1,2-diols in aqueous solution. As used here, 1,2-diols includes polyols with one or more 1,2-diol pairs. Multiple techniques were used including apparent pKa shifts of the boronic acids using UV spectrophotometry (for aryl acids) and titration (for aryl and alkyl acids). Isothermal microcalorimetry was also used, with all reactions being enthalpically favored. For all the acids and 1,2-diols and the conditions studied, evidence only supported 1:1 ester formation. All the esters formed were found to be significantly more acidic, as Lewis acids, by 3-3.5 pKa units than the corresponding nonesterified boronic acid. The equilibrium constants for ester formation increased with increasing number of 1,2-diol pairs but stereochemistry may also play a role as sorbitol with five possible 1,2-diol pairs and five isomers (taking into account the stereochemistry of the alcohol groups) was twice as efficient at ester formation compared with mannitol, also with five possible 1,2-diol pairs but only three isomers. Alkyl boronic acids formed esters to a greater extent than aryl acids. Although some quantitative differences were seen between the various techniques used, rank ordering of the structure/reactivity was consistent. Formulation implications of ester formation between boronic acids and 1,2-diols are discussed.

  11. 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

  12. 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%.

  13. 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.

  14. 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.

  15. Hybrid palm-oil/styrene-maleimide nanoparticles synthesized in aqueous dispersion under different conditions.

    PubMed

    Samyn, Pieter; Van Nieuwkerke, Dieter; Schoukens, Gustaaf; Stanssens, Dirk; Vonck, Leo; Van den Abbeele, Henk

    2015-01-01

    Poly(styrene-co-maleic anhydride) was imidized with ammonium hydroxide and palm oil, resulting in an aqueous dispersion of hybrid nanoparticles with diameters 85-180 nm (dispersed) or 20-50 nm (dried). The reaction conditions were optimized for different precursors by evaluating the relative amount ammonium hydroxide and maximizing the incorporated palm oil up to 70 wt.%. The interactions between palm oil and polymer phase have been studied by TEM, IR, Raman spectroscopy and thermal analysis (TGA, [TM] DSC). From Raman spectra, the amount of imide and reacted oil were quantified. Through concurring effects of imidization and coupling of fatty acids, the imidization needs a slight excess of NH3 relatively to maleic anhydride. The oxidative stability highly depends on oxidative crosslinking of free or non-reacted oil. Comparing the imide content from spectroscopic and thermal analysis suggests that a complex rigid imide phase without strong relaxation behavior has formed in combination with oil.

  16. Effect of surface condition on the aqueous corrosion behavior of iron aluminies

    SciTech Connect

    Buchanan, R.A.; Perrin, R.L.

    1995-08-01

    The effects of retained high-temperature surface oxides, produced during thermomechanical processing and/or heat treatment, on the aqueous-corrosion characteristics of Fe-Al-based alloys were evaluated by electrochemical methods. Cyclic anodic polarization evaluations were conducted at room temperature in a mild acid-chloride solution (pH = 4,200 ppm Cl{sup {minus}}) on the Fe{sub 3}Al-based iron aluminides, FA-84 (Fe-28Al-2Cr-0.05B, at %), FA-129 (Fe-28Al-5Cr-0.5Nb-0.2C, at %), and FAL-Mo (Fe-28Al-5Cr-1Mo-0.04B-0.08Zr, at %), on the FeAl-based iron aluminide, FA-385 (Fe-35.65Al-0.20Mo-0.05Zr-0.11C, at %). The surface conditions evaluated were: As received (i.e. with the retained high-temperature oxides), mechanically cleaned (ground through 600-grit SiC paper), and chemically cleaned (10% HNO{sub 3}, 2%HF, at 43 {degree}C). The principal electrochemical parameter of interest was the critical putting potential with lower values indicating less resistance to chloride-induced localized corrosion. For all materials evaluated, the critical pitting potential was found to be significantly lower in the as-received condition than in the mechanically-cleaned and chemically-cleaned conditions. Mechanisms responsible for the detrimental high-temperature-oxide effect are under study.

  17. 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

  18. Removal characteristics of As(III) and As(V) from acidic aqueous solution by steel making slag.

    PubMed

    Oh, Chamteut; Rhee, Sungsu; Oh, Myounghak; Park, Junboum

    2012-04-30

    This study focused on the environmental risk of steel making slag itself, arsenic removal mechanism and re-leaching possibility of arsenic to aqueous state after the adsorption. The purpose of the study is to promote the use of steel making slag as a low-cost adsorbent for arsenic in aqueous system. Calcium was easily dissolved out from the slag and become the dominant substance in the leachate. Some of the calcium could form amorphous calcium carbonate in alkaline condition, and arsenic in the aqueous solution would be removed by being co-precipitated with or adsorbed onto the amorphous calcium carbonate. Most of the amorphous calcium carbonate containing arsenic would be bound to amorphous iron oxide of the slag. When the slag was used as an adsorbent for arsenic removal, a little amount of toxic chemicals were leached from the slag itself under pH 0.8 to 13.6. Also, 70-80% of arsenic laden on the slag was bound to amorphous iron oxide which would not easily desorb unless given a reducing and complexing condition. Showing 95-100% removal efficiency near initial pH 2, the slag, therefore, could be used as an appropriate adsorbent for eliminating arsenic in acidic aqueous solution.

  19. 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…

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Single step signal group-imidazole labeling of organic phosphate groups under aqueous conditions

    DOEpatents

    Giese, R.W.; Wang, P.

    1996-04-30

    Compounds and methods for single step, covalent labeling of the phosphate group of an organic substance under aqueous conditions are described. The labeling compound includes any kind of detectable signal group covalently bound to an imidazole moiety, which can be imidazole or a substituted imidazole. A preferred labeling compound has the formula shown in the accompanying diagram. 4 figs.

  5. Single step signal group-imidazole labeling of organic phosphate groups under aqueous conditions

    DOEpatents

    Giese, Roger W.; Wang, Poguang

    1996-01-01

    Compounds and methods for single step, covalent labeling of the phosphate group of an organic substance under aqueous conditions are described. The labeling compound includes any kind of detectable signal group covalently bound to an imidazole moiety, which can be imidazole or a substituted imidazole. A preferred labeling compound has the formula ##STR1##

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. Electrochemiluminescence of tris(8-hydroxyquinoline-5-sulfonic acid)aluminum(III) in aqueous solution.

    PubMed

    Muegge, Brian D; Brooks, Sean; Richter, Mark M

    2003-03-01

    The electrochemiluminescence (ECL) of tris(8-hydroxyquinoline-5-sulfonic acid)aluminum(III) in aqueous solution is reported. ECL is generated by complexing aluminum ions with the chelating agent 8-hydroxyquinoline-5-sulfonic acid (HQS) to form Al(HQS)3, followed by oxidation in the presence of tri-n-propylamine (TPrA). The ECL intensity peaks a potential corresponding to oxidation of both TPrA and Al(HQS)3, and the ECL emission spectrum (lambda(max) = 499 nm) matches the photoluminescence emission spectrum, indicating that the emission is from a Al(HQS)3* excited state. ECL efficiencies (phi(ecl), photons generated per redox event) of 0.002 using Ru(bpy)3(2+) (phi(ecl) = 1) as relative standard. Conditions for ECL emission were optimized and used to generate a calibration curve that was linear over the 7 x 10(-6)-4 x 10(-4) M (5-281 mg/L (ppm)) range with a theoretical limit of detection of 1 ppm. The ECL of several metal ions other than aluminum with HQS and effects on Al(HQS)3 ECL were also examined.

  16. In situ decarboxylation of acetic and formic acids in aqueous inclusions as a possible way to produce excess CH4

    NASA Astrophysics Data System (ADS)

    Ong, Anthony; Pironon, Jacques; Robert, Pascal; Dubessy, Jean; Caumon, Marie-Camille; Randi, Aurélien; Chailan, Olivier; Girard, Jean-Pierre

    2013-04-01

    Accurate reconstruction of diagenetic P-T conditions in petroleum reservoirs from fluid inclusion data relies on valid measurements of methane concentration in aqueous inclusions. Techniques have been developed (Raman spectrometry) to provide sufficiently accurate data, assuming measured methane concentration has not been modified after aqueous inclusion entrapment. In petroleum reservoirs, acetic (CH3COOH) and formic (HCOOH) acids are the most commonly reported organic acids, and the concentration of the total organic acids can be as high as 10,000 ppm at temperature below 120°C. This study investigates the likelihood that organic acids derived from petroleum fluids and dissolved in formation water might suffer decarboxylation upon post-entrapment heating within the fluid inclusion chamber upon post-entrapment heating, thereby generating excess CH4 in the inclusions. Four different experiments were conducted in Fused Silica Capillary Capsules (FSCCs), mimicking fluid inclusions. The capsules were loaded with acetic (CH3COOH) or formic (HCOOH) acid solution and were heated to 250°C for short durations (< 72hrs) in closed system conditions, with or without applying a fixed PH2. Reaction products were characterized by Raman and FT-IR spectrometry. The beginning of the decarboxylation of acetic acid is reached in 32 h at 250°C, with production of CH4 and CO2. Complete decarboxylation of formic acid is reached in 5 h at 250°C, with production of CO2, CO and H2. The lack of CH4 production in experiments with formic acid may be attributed to the relatively short duration of the experiments and/or the loss of H2 through the FSCC by diffusion during the experiment. Further experiments with a longer heating duration should be performed to assess the possibility of reducing the CO2 into CH4 from the formic acid. 2) The injection of H2 in the FSCC as a way to promote CO2 reduction did not promote decarboxylation in the duration of our experiment. These results suggest

  17. 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...

  18. 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.

  19. 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.

  20. 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...

  1. 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...

  2. 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...

  3. 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.

  4. 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...

  5. 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...

  6. 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...

  7. 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...

  8. 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...

  9. 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.

  10. 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.

  11. Photochemical oxidation of chloride ion by ozone in acid aqueous solution.

    PubMed

    Levanov, Alexander V; Isaykina, Oksana Ya; Amirova, Nazrin K; Antipenko, Ewald E; Lunin, Valerii V

    2015-11-01

    The experimental investigation of chloride ion oxidation under the action of ozone and ultraviolet radiation with wavelength 254 nm in the bulk of acid aqueous solution at pH 0-2 has been performed. Processes of chloride oxidation in these conditions are the same as the chemical reactions in the system O3 - OH - Cl(-)(aq). Despite its importance in the environment and for ozone-based water treatment, this reaction system has not been previously investigated in the bulk solution. The end products are chlorate ion ClO3(-) and molecular chlorine Cl2. The ions of trivalent iron have been shown to be catalysts of Cl(-) oxidation. The dependencies of the products formation rates on the concentrations of O3 and H(+) have been studied. The chemical mechanism of Cl(-) oxidation and Cl2 emission and ClO3(-) formation has been proposed. According to the mechanism, the dominant primary process of chloride oxidation represents the complex interaction with hydroxyl radical OH with the formation of Cl2(-) anion-radical intermediate. OH radical is generated on ozone photolysis in aqueous solution. The key subsequent processes are the reactions Cl2(-) + O3 → ClO + O2 + Cl(-) and ClO + H2O2 → HOCl + HO2. Until the present time, they have not been taken into consideration on mechanistic description and modelling of Cl(-) oxidation. The final products are formed via the reactions 2ClO → Cl2O2, Cl2O2 + H2O → 2H(+) + Cl(-) + ClO3(-) and HOCl + H(+) + Cl(-) ⇄ H2O + Cl2. Some portion of chloride is oxidized directly by O3 molecule with the formation of molecular chlorine in the end.

  12. Photochemical oxidation of chloride ion by ozone in acid aqueous solution.

    PubMed

    Levanov, Alexander V; Isaykina, Oksana Ya; Amirova, Nazrin K; Antipenko, Ewald E; Lunin, Valerii V

    2015-11-01

    The experimental investigation of chloride ion oxidation under the action of ozone and ultraviolet radiation with wavelength 254 nm in the bulk of acid aqueous solution at pH 0-2 has been performed. Processes of chloride oxidation in these conditions are the same as the chemical reactions in the system O3 - OH - Cl(-)(aq). Despite its importance in the environment and for ozone-based water treatment, this reaction system has not been previously investigated in the bulk solution. The end products are chlorate ion ClO3(-) and molecular chlorine Cl2. The ions of trivalent iron have been shown to be catalysts of Cl(-) oxidation. The dependencies of the products formation rates on the concentrations of O3 and H(+) have been studied. The chemical mechanism of Cl(-) oxidation and Cl2 emission and ClO3(-) formation has been proposed. According to the mechanism, the dominant primary process of chloride oxidation represents the complex interaction with hydroxyl radical OH with the formation of Cl2(-) anion-radical intermediate. OH radical is generated on ozone photolysis in aqueous solution. The key subsequent processes are the reactions Cl2(-) + O3 → ClO + O2 + Cl(-) and ClO + H2O2 → HOCl + HO2. Until the present time, they have not been taken into consideration on mechanistic description and modelling of Cl(-) oxidation. The final products are formed via the reactions 2ClO → Cl2O2, Cl2O2 + H2O → 2H(+) + Cl(-) + ClO3(-) and HOCl + H(+) + Cl(-) ⇄ H2O + Cl2. Some portion of chloride is oxidized directly by O3 molecule with the formation of molecular chlorine in the end. PMID:26077317

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. Formation of Amino Acids on the Sonolysis of Aqueous Solutions Containing Acetic Acid, Methane, or Carbon Dioxide, in the Presence of Nitrogen Gas.

    PubMed

    Dharmarathne, Leena; Grieser, Franz

    2016-01-21

    The sonolysis of aqueous solutions containing acetic acid, methane, or carbon dioxide in the presence of nitrogen gas was found to produce a number of different amino acids at a rate of ∼1 to 100 nM/min, using ultrasound at an operating power of 70 W and 355 kHz. Gas-phase elementary reactions are suggested, and discussed, to account for the formation of the complex biomolecules from the low molar mass solutes used. On the basis of the results, a new hypothesis is presented to explain the formation of amino acids under primitive atmospheric conditions and how their formation may be linked to the eventual abiotic genesis of life on Earth.

  18. Formation of Amino Acids on the Sonolysis of Aqueous Solutions Containing Acetic Acid, Methane, or Carbon Dioxide, in the Presence of Nitrogen Gas.

    PubMed

    Dharmarathne, Leena; Grieser, Franz

    2016-01-21

    The sonolysis of aqueous solutions containing acetic acid, methane, or carbon dioxide in the presence of nitrogen gas was found to produce a number of different amino acids at a rate of ∼1 to 100 nM/min, using ultrasound at an operating power of 70 W and 355 kHz. Gas-phase elementary reactions are suggested, and discussed, to account for the formation of the complex biomolecules from the low molar mass solutes used. On the basis of the results, a new hypothesis is presented to explain the formation of amino acids under primitive atmospheric conditions and how their formation may be linked to the eventual abiotic genesis of life on Earth. PMID:26695890

  19. Removal and recovery of furfural, 5-hydroxymethylfurfural, and acetic acid from aqueous solutions using a soluble polyelectrolyte.

    PubMed

    Carter, Brian; Gilcrease, Patrick C; Menkhaus, Todd J

    2011-09-01

    In the cellulosic ethanol process, furfural, 5-hydroxymethylfurfural (HMF), and acetic acid are formed during the high temperature acidic pretreatment step needed to convert biomass into fermentable sugars. These compounds can inhibit cellulase enzymes and fermentation organisms at relatively low concentrations (≥ 1 g/L). Effective removal of these inhibitory compounds would allow the use of more severe pretreatment conditions to improve sugar yields and lead to more efficient fermentations; if recovered and purified, they could also be sold as valuable by-products. This study investigated the separation of aldhehydes (furfural and HMF) and organic acid (acetic acid) inhibitory compounds from simple aqueous solutions by using polyethyleneimene (PEI), a soluble cationic polyelectrolyte. PEI added to simple solutions of each inhibitor at a ratio of 1 mol of functional group to 1 mol inhibitor removed up to 89.1, 58.6, and 81.5 wt% of acetic acid, HMF, and furfural, respectively. Furfural and HMF were recovered after removal by washing the polyelectrolyte/inhibitor complex with dilute sulfuric acid solution. Recoveries up to 81.0 and 97.0 wt% were achieved for furfural and HMF, respectively. The interaction between PEI and acetic acid was easily disrupted by the addition of chloride ions, sulfate ions, or hydroxide ions. The use of soluble polymers for the removal and recovery of inhibitory compounds from biomass slurries is a promising approach to enhance the efficiency and economics of an envisioned biorefinery.

  20. Stability of lysozyme in aqueous extremolyte solutions during heat shock and accelerated thermal conditions.

    PubMed

    Avanti, Christina; Saluja, Vinay; van Streun, Erwin L P; Frijlink, Henderik W; Hinrichs, Wouter L J

    2014-01-01

    The purpose of this study was to investigate the stability of lysozyme in aqueous solutions in the presence of various extremolytes (betaine, hydroxyectoine, trehalose, ectoine, and firoin) under different stress conditions. The stability of lysozyme was determined by Nile red Fluorescence Spectroscopy and a bioactivity assay. During heat shock (10 min at 70°C), betaine, trehalose, ectoin and firoin protected lysozyme against inactivation while hydroxyectoine, did not have a significant effect. During accelerated thermal conditions (4 weeks at 55°C), firoin also acted as a stabilizer. In contrast, betaine, hydroxyectoine, trehalose and ectoine destabilized lysozyme under this condition. These findings surprisingly indicate that some extremolytes can stabilize a protein under certain stress conditions but destabilize the same protein under other stress conditions. Therefore it is suggested that for the screening extremolytes to be used for protein stabilization, an appropriate storage conditions should also be taken into account.

  1. Preparation and characterization of aqueous dispersions of high amylose starch and conjugated linoleic acid complex.

    PubMed

    Seo, Tae-Rang; Kim, Hee-Young; Lim, Seung-Taik

    2016-11-15

    Crystalline starch-CLA complexes were prepared by blending an alcoholic solution of conjugated linoleic acid (CLA) in an aqueous high-amylose maize starch dispersion. Recovery yield of CLA in the precipitates obtained by centrifuging the dispersion was dependent on reaction conditions such as temperature, time and pH. The CLA recovery reached a maximum when the reaction was performed at 90°C for 6h at neutral pH, with 67.7% of the initial CLA being co-precipitated with starch. The precipitates contained amylose-CLA complex exhibiting a V6I-type crystalline structure under X-ray diffraction analysis and a type II polymorph under DSC analysis. Ultrasonic treatment for the re-dispersed starch-CLA complex in water resulted in the reduction of hydrodynamic diameter of the complex particles to 201.5nm. The dispersion exhibited a zeta potential of -27.0mV and remained stable in an ambient storage without forming precipitates for more than 4weeks. PMID:27283663

  2. Complete mineralization of perfluorooctanoic acid (PFOA) by γ-irradiation in aqueous solution

    PubMed Central

    Zhang, Ze; Chen, Jie-Jie; Lyu, Xian-Jin; Yin, Hao; Sheng, Guo-Ping

    2014-01-01

    Decomposition of perfluorooctanoic acid (C7F15COOH, PFOA) has been gaining increasing interests because it is a ubiquitous environmental contaminant and resistant to the most conventional treatment processes. In this work, the rapid and complete mineralization of PFOA and simultaneous defluorination were achieved by γ-ray irradiation with a 60Co source. The degradation rate of PFOA by γ-ray irradiation would be high, and a pseudo-first-order kinetic rate constant of 0.67 h−1 could be achieved in the N2 satured condition at pH 13.0. The experimental results and quantum chemical calculation confirmed that two radicals, i.e., hydroxyl radical (·OH) and aqueous electrons (eaq−), were responsible for the degradation of PFOA, while only either eaq− or ·OH might not be able to accomplish complete mineralization of PFOA. The synergistic effects of ·OH and eaq− involved in the cleavage of C-C and C-F bonds, and therefore complete mineralization of PFOA were achieved. The intermediate products were identified and the degradation pathway was also proposed. The results of this study may offer a useful, high-efficient approach for complete mineralizing fluorochemicals and other persistent pollutants. PMID:25492109

  3. Complete mineralization of perfluorooctanoic acid (PFOA) by γ-irradiation in aqueous solution

    NASA Astrophysics Data System (ADS)

    Zhang, Ze; Chen, Jie-Jie; Lyu, Xian-Jin; Yin, Hao; Sheng, Guo-Ping

    2014-12-01

    Decomposition of perfluorooctanoic acid (C7F15COOH, PFOA) has been gaining increasing interests because it is a ubiquitous environmental contaminant and resistant to the most conventional treatment processes. In this work, the rapid and complete mineralization of PFOA and simultaneous defluorination were achieved by γ-ray irradiation with a 60Co source. The degradation rate of PFOA by γ-ray irradiation would be high, and a pseudo-first-order kinetic rate constant of 0.67 h-1 could be achieved in the N2 satured condition at pH 13.0. The experimental results and quantum chemical calculation confirmed that two radicals, i.e., hydroxyl radical (.OH) and aqueous electrons (eaq-), were responsible for the degradation of PFOA, while only either eaq- or .OH might not be able to accomplish complete mineralization of PFOA. The synergistic effects of .OH and eaq- involved in the cleavage of C-C and C-F bonds, and therefore complete mineralization of PFOA were achieved. The intermediate products were identified and the degradation pathway was also proposed. The results of this study may offer a useful, high-efficient approach for complete mineralizing fluorochemicals and other persistent pollutants.

  4. Photodecomposition of tetrabromobisphenol A in aqueous humic acid suspension by irradiation with light of various wavelengths.

    PubMed

    Han, Sang Kuk; Yamasaki, Toshihide; Yamada, Ken-ichi

    2016-03-01

    The reactive species generated in aqueous 3,3',5,5'-tetrabromobisphenol A (TBBPA)/humic acid (HA) suspensions above the TBBPA pKa (∼7.4), under various light-irradiation conditions, namely ambient and ultraviolet light, were investigated using electron paramagnetic resonance (EPR) spectroscopy and liquid chromatography-mass spectrometry (LC-MS). We confirmed that singlet oxygen and OH radicals are the key reactive oxygen species generated at wavelengths greater than 400 and 300 nm, respectively. The amount of 2,6-dibromo-p-benzosemiquinone anion radicals (2,6-DBSQ(•-)) formed under irradiation at 400 nm increased linearly with respect to irradiation time; the initial reaction rate was 7.03 × 10(-9) mol g(-1) HA s(-1). The rate increased with increasing pH and light intensity. LC-MS and EPR spectroscopy showed that tribromohydroxybisphenol A was formed under irradiation at 300 nm via reaction of OH radicals with TBBPA. This study, for the first time, shows that the main byproducts formed during irradiation at wavelengths above 300 nm are 2,6-DBSQ(•-) and tribromohydroxybisphenol A, generated from singlet oxygen ((1)O2) and OH radicals, respectively. Photodecomposition of TBBPA in the environment may occur by formation of (1)O2 and OH radicals.

  5. Activated Persulfate Oxidation of Perfluorooctanoic Acid (PFOA) in Groundwater under Acidic Conditions

    PubMed Central

    Yin, Penghua; Hu, Zhihao; Song, Xin; Liu, Jianguo; Lin, Na

    2016-01-01

    Perfluorooctanoic acid (PFOA) is an emerging contaminant of concern due to its toxicity for human health and ecosystems. However, successful degradation of PFOA in aqueous solutions with a cost-effective method remains a challenge, especially for groundwater. In this study, the degradation of PFOA using activated persulfate under mild conditions was investigated. The impact of different factors on persulfate activity, including pH, temperature (25 °C–50 °C), persulfate dosage and reaction time, was evaluated under different experimental conditions. Contrary to the traditional alkaline-activated persulfate oxidation, it was found that PFOA can be effectively degraded using activated persulfate under acidic conditions, with the degradation kinetics following the pseudo-first-order decay model. Higher temperature, higher persulfate dosage and increased reaction time generally result in higher PFOA degradation efficiency. Experimental results show that a PFOA degradation efficiency of 89.9% can be achieved by activated persulfate at pH of 2.0, with the reaction temperature of 50 °C, molar ratio of PFOA to persulfate as 1:100, and a reaction time of 100 h. The corresponding defluorination ratio under these conditions was 23.9%, indicating that not all PFOA decomposed via fluorine removal. The electron paramagnetic resonance spectrometer analysis results indicate that both SO4−• and •OH contribute to the decomposition of PFOA. It is proposed that PFOA degradation occurs via a decarboxylation reaction triggered by SO4−•, followed by a HF elimination process aided by •OH, which produces one-CF2-unit-shortened perfluoroalkyl carboxylic acids (PFCAs, Cn−1F2n−1COOH). The decarboxylation and HF elimination processes would repeat and eventually lead to the complete mineralization all PFCAs. PMID:27322298

  6. Activated Persulfate Oxidation of Perfluorooctanoic Acid (PFOA) in Groundwater under Acidic Conditions.

    PubMed

    Yin, Penghua; Hu, Zhihao; Song, Xin; Liu, Jianguo; Lin, Na

    2016-01-01

    Perfluorooctanoic acid (PFOA) is an emerging contaminant of concern due to its toxicity for human health and ecosystems. However, successful degradation of PFOA in aqueous solutions with a cost-effective method remains a challenge, especially for groundwater. In this study, the degradation of PFOA using activated persulfate under mild conditions was investigated. The impact of different factors on persulfate activity, including pH, temperature (25 °C-50 °C), persulfate dosage and reaction time, was evaluated under different experimental conditions. Contrary to the traditional alkaline-activated persulfate oxidation, it was found that PFOA can be effectively degraded using activated persulfate under acidic conditions, with the degradation kinetics following the pseudo-first-order decay model. Higher temperature, higher persulfate dosage and increased reaction time generally result in higher PFOA degradation efficiency. Experimental results show that a PFOA degradation efficiency of 89.9% can be achieved by activated persulfate at pH of 2.0, with the reaction temperature of 50 °C, molar ratio of PFOA to persulfate as 1:100, and a reaction time of 100 h. The corresponding defluorination ratio under these conditions was 23.9%, indicating that not all PFOA decomposed via fluorine removal. The electron paramagnetic resonance spectrometer analysis results indicate that both SO₄(-)• and •OH contribute to the decomposition of PFOA. It is proposed that PFOA degradation occurs via a decarboxylation reaction triggered by SO₄(-)•, followed by a HF elimination process aided by •OH, which produces one-CF₂-unit-shortened perfluoroalkyl carboxylic acids (PFCAs, Cn-1F2n-1COOH). The decarboxylation and HF elimination processes would repeat and eventually lead to the complete mineralization all PFCAs. PMID:27322298

  7. Activated Persulfate Oxidation of Perfluorooctanoic Acid (PFOA) in Groundwater under Acidic Conditions.

    PubMed

    Yin, Penghua; Hu, Zhihao; Song, Xin; Liu, Jianguo; Lin, Na

    2016-01-01

    Perfluorooctanoic acid (PFOA) is an emerging contaminant of concern due to its toxicity for human health and ecosystems. However, successful degradation of PFOA in aqueous solutions with a cost-effective method remains a challenge, especially for groundwater. In this study, the degradation of PFOA using activated persulfate under mild conditions was investigated. The impact of different factors on persulfate activity, including pH, temperature (25 °C-50 °C), persulfate dosage and reaction time, was evaluated under different experimental conditions. Contrary to the traditional alkaline-activated persulfate oxidation, it was found that PFOA can be effectively degraded using activated persulfate under acidic conditions, with the degradation kinetics following the pseudo-first-order decay model. Higher temperature, higher persulfate dosage and increased reaction time generally result in higher PFOA degradation efficiency. Experimental results show that a PFOA degradation efficiency of 89.9% can be achieved by activated persulfate at pH of 2.0, with the reaction temperature of 50 °C, molar ratio of PFOA to persulfate as 1:100, and a reaction time of 100 h. The corresponding defluorination ratio under these conditions was 23.9%, indicating that not all PFOA decomposed via fluorine removal. The electron paramagnetic resonance spectrometer analysis results indicate that both SO₄(-)• and •OH contribute to the decomposition of PFOA. It is proposed that PFOA degradation occurs via a decarboxylation reaction triggered by SO₄(-)•, followed by a HF elimination process aided by •OH, which produces one-CF₂-unit-shortened perfluoroalkyl carboxylic acids (PFCAs, Cn-1F2n-1COOH). The decarboxylation and HF elimination processes would repeat and eventually lead to the complete mineralization all PFCAs.

  8. [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.

  9. 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.

  10. Intrinsic formation of nanocrystalline neptunium dioxide under neutral aqueous conditions relevant to deep geological repositories.

    PubMed

    Husar, Richard; Hübner, René; Hennig, Christoph; Martin, Philippe M; Chollet, Mélanie; Weiss, Stephan; Stumpf, Thorsten; Zänker, Harald; Ikeda-Ohno, Atsushi

    2015-01-25

    The dilution of aqueous neptunium carbonate complexes induces the intrinsic formation of nanocrystalline neptunium dioxide (NpO2) particles, which are characterised by UV/Vis and X-ray absorption spectroscopies and transmission electron microscopy. This new route of nanocrystalline NpO2 formation could be a potential scenario for the environmental transport of radionuclides from the waste repository (i.e. under near-field alkaline conditions) to the geological environment (i.e. under far-field neutral conditions).

  11. Homogeneous ice freezing temperatures and ice nucleation rates of aqueous ammonium sulfate and aqueous levoglucosan particles for relevant atmospheric conditions.

    PubMed

    Knopf, Daniel Alexander; Lopez, Miguel David

    2009-09-28

    Homogeneous ice nucleation from micrometre-sized aqueous (NH4)2SO4 and aqueous levoglucosan particles is studied employing the optical microscope technique. A new experimental method is introduced that allows us to control the initial water activity of the aqueous droplets. Homogeneous ice freezing temperatures and ice melting temperatures of these aqueous solution droplets, 10 to 80 microm in diameter, are determined. Homogeneous ice nucleation from aqueous (NH4)2SO4 particles 5-39 wt% in concentration and aqueous levoglucosan particles with initial water activities of 0.85-0.99 yield upper limits of the homogeneous ice nucleation rate coefficients of up to 1x10(10) cm(-3) s(-1). The experimentally derived homogeneous ice freezing temperatures and upper limits of the homogeneous ice nucleation rate coefficients are compared with corresponding predictions of the water-activity-based ice nucleation theory [T. Koop, B. P. Luo, A. Tsias and T. Peter, Nature, 2000, 406, 611]. It is found that the water-activity-based ice nucleation theory can capture the experimentally derived ice freezing temperatures and homogeneous ice nucleation rate coefficients of the aqueous (NH4)2SO4 and aqueous levoglucosan particles. However, the level of agreement between experimentally derived and predicted values, in particular for homogeneous ice nucleation rate coefficients, crucially depends on the extrapolation method to obtain water activities at corresponding freezing temperatures. It is suggested that the combination of experimentally derived ice freezing temperatures and homogeneous ice nucleation rate coefficients can serve as a better validation of the water-activity-based ice nucleation theory than when compared to the observation of homogeneous ice freezing temperatures alone. The atmospheric implications with regard to the application of the water-activity-based ice nucleation theory and derivation of maximum ice particle production rates are briefly discussed.

  12. Alumino-silicate speciation in aqueous fluids at deep crustal conditions

    NASA Astrophysics Data System (ADS)

    Mookherjee, M.; Keppler, H.; Manning, C. E.

    2014-12-01

    Alumina and silica are major oxides in most crustal rocks. While SiO2 is quite soluble in aqueous fluids at metamorphic conditions, behavior of Al2O3 in crustal metamorphic fluids has been poorly understood. It is known that alumina is dramatically less soluble in aqueous fluids and hence it is difficult to explain the common occurrence of quartz with aluminous minerals in metamorphic veins. In order to understand this complex behavior of alumina, we investigated aluminum speciation in aqueous fluids in equilibrium with corundum using in situ Raman spectroscopy in hydrothermal diamond anvil cells to 20 kbar and 1000 oC. In order to better understand the spectral features of the aqueous fluids, we used first principles simulations based on density functional theory to calculate and predict the energetics and vibrational spectra for various aluminum species that are likely to be present in aqueous solutions. The Raman spectra of pure water in equilibrium with Al2O3 are devoid of any characteristic spectral features. In contrast, aqueous fluids with KOH solution in equilibrium with Al2O3 show a sharp band at ~620 cm-1 which could be attributed to the [Al(OH)4]1- species. The band grows in intensity with temperature along an isochore. In the limited pressure, temperature and density explored in the present study, we do not find any evidence for the polymerization of the [Al(OH)4]1- species to dimers [(OH)2-Al-O2-Al(OH)2]2- or [(OH)3-Al-O-Al(OH)3]2-. This is likely due to the relatively low concentration of Al in the solutions and does not rule out significant polymerization at higher pressures and temperatures. We are also investigating the effect of SiO2 on the solubility of Al2O3 and the relative energetics of formation of pure alumina dimer [(OH)3-Al-O-Al(OH)3]2- vs. the aluminosilicate dimers, [(OH)3-Al-O-Si(OH)3]2- at deep crustal conditions. Acknowledgement- MM is supported by the US National Science Foundation grant (EAR-1250477).

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. Composition and freezing of aqueous H2SO4/HNO3 solutions under polar stratospheric conditions

    NASA Technical Reports Server (NTRS)

    Beyer, K. D.; Seago, S. W.; Chang, H. Y.; Molina, M. J.

    1994-01-01

    The results of laboratory investigations of the freezing behavior of aqueous acid solutions indicate that in the stratosphere H2SO/H2O aerosol droplets would not freeze at temperatures above the ice frost point in the absence of HNO3; however, in the presence of typical levels of HNO3 liquid sulfuric acid aerosols take up significant amounts of HNO3 and H2O vapors and freeze much more readily. This is a consequence of the very rapid change in composition of the liquid droplets as the temperature drops to within two to three degrees of the equilibrium temperature at which HNO3 and H2O vapors would co-condense to form a liquid solution. In the high latitude stratosphere this HNO3/H2O 'dew point' is typically around 192-194 K at 100 mbar.

  20. 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.

  1. On the selective growth of titania polymorphs in acidic aqueous medium

    SciTech Connect

    Li, Haoguang; Afanasiev, Pavel

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer Mutual influence of peptizing and anions addition of titania hydrothermal growth was studied. Black-Right-Pointing-Pointer Sulfate and chloride control TiO{sub 2} phase or particles shape depending on the order of introduction. Black-Right-Pointing-Pointer A rationale of difference between sulfate and chloride effect was provided. Black-Right-Pointing-Pointer Ground state DFT and semi-empirical calculations of Ti species support the conclusions. -- Abstract: The influence of preparation conditions on the phase composition and morphology of titania was studied for the solids synthesized by hydrothermal treatment (HT) and peptizing of hydrous TiO{sub 2} sols in acidic medium. Mutual influence of peptizing and of additive anions (SO{sub 4}{sup 2-}, Cl{sup -}) on the nature of obtained polymorphs was for the first time systematically studied and coherently explained. The solids were characterized by XRD, Raman spectroscopy, and transmission electron microscopy. It was found that peptizing step preceding HT and the presence of anions play a crucial role for the selective formation of TiO{sub 2} anatase or rutile polymorphs. Low temperature peptizing leads to acicular rutile particles, whereas HT produces highly dispersed anatase. However if the HT was preceded by peptizing step, rutile was obtained in most cases. The influence of additives strongly depends on the moment of their introduction. Sulfate and chloride species can act as phase growth controllers, or as morphology modifiers. Sulfate hindered formation of rutile and favored anatase al low temperatures, but for already formed rutile seed, sulfate acted only as a shape controller. By contrast, chloride showed a strong tendency to promote rutile growth, whatever the conditions. A qualitative model was proposed explaining the effects observed, supported by ground state DFT and semi-empirical calculations of the aqueous Ti species.

  2. 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.

  3. 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).

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. Mixing Acid Salts and Layered Double Hydroxides in Nanoscale under Solid Condition.

    PubMed

    Nakayama, Hirokazu; Hayashi, Aki

    2014-01-01

    The immobilization of potassium sorbate, potassium aspartate and sorbic acid in layered double hydroxide under solid condition was examined. By simply mixing two solids, immobilization of sorbate and aspartate in the interlayer space of nitrate-type layered double hydroxide, so called intercalation reaction, was achieved, and the uptakes, that is, the amount of immobilized salts and the interlayer distances of intercalation compounds were almost the same as those obtained in aqueous solution. However, no intercalation was achieved for sorbic acid. Although intercalation of sorbate and aspartate into chloride-type layered double hydroxide was possible, the uptakes for these intercalation compounds were lower than those obtained using nitrate-type layered double hydroxide. The intercalation under solid condition could be achieved to the same extent as for ion-exchange reaction in aqueous solution, and the reactivity was similar to that observed in aqueous solution. This method will enable the encapsulation of acidic drug in layered double hydroxide as nano level simply by mixing both solids. PMID:25080007

  10. [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

  11. [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.

  12. Sulfur removal from Gediz lignite using aqueous sodium hydroxide solutions under mild oxidative conditions

    SciTech Connect

    Yaman, S.; Kuecuekbayrak, S.

    1999-11-01

    Sulfur removal from a high-sulfur Turkish lignite (Gediz) using aqueous sodium hydroxide solutions having dissolved oxygen was investigated under mild oxidative conditions. Effects of the parameters such as sodium hydroxide/lignite weight ratio, temperature, and partial pressure of oxygen were investigated within the ranges of 0.05--0.8, 423--498 K, and 1--2 MPa, respectively. Optimum values of these parameters were determined regarding sulfur removal and coal recovery. Influences of dry oxidation of the lignite sample as a pretreatment at 573 K and subsequent washing of some treated lignite samples with 1 N HCl were investigated.

  13. CO₂ carbonation under aqueous conditions using petroleum coke combustion fly ash.

    PubMed

    González, A; Moreno, N; Navia, R

    2014-12-01

    Fly ash from petroleum coke combustion was evaluated for CO2 capture in aqueous medium. Moreover the carbonation efficiency based on different methodologies and the kinetic parameters of the process were determined. The results show that petroleum coke fly ash achieved a CO2 capture yield of 21% at the experimental conditions of 12 g L(-1), 363°K without stirring. The carbonation efficiency by petroleum coke fly ash based on reactive calcium species was within carbonation efficiencies reported by several authors. In addition, carbonation by petroleum coke fly ash follows a pseudo-second order kinetic model.

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. 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.

  20. Enhanced ozonation of dichloroacetic acid in aqueous solution using nanometer ZnO powders.

    PubMed

    Zhai, Xu; Chen, Zhonglin; Zhao, Shuqing; Wang, He; Yang, Lei

    2010-01-01

    Nanometer zinc oxide (ZnO) powders were used as a catalyst to enhance the ozonation for the degradation of dichloroacetic acid (DCAA) in aqueous solution. The batch experiments were carried out to investigate the effects of key factors such as catalyst dosage, ozone dosage, solution pH and tert-butyl alcohol (t-BuOH) on the degradation efficiency of DCAA. Density functional theory (DFT) was adopted to explore the mechanism of generating hydroxyl radical (*OH) on the ZnO surface. The results showed that adsorption and ozonation processes were not effective for DCAA removal, and the addition of ZnO catalyst improved the degradation efficiency of DCAA during ozonation, which caused an increase of 22.8% for DCAA decomposition compared to the case of ozonation alone after 25 min. Under the same experimental conditions, the DCAA decomposition was enhanced by increasing catalyst dosage from 100 to 500 mg/L and ozone dosage from 0.83 to 3.2 mg/L. The catalytic ozonation process is more pronounced than the ozonation process alone at pH 3.93, 6.88, and 10. With increasing the concentration of t-BuOH from 10 to 200 mg/L, the degradation of DCAA was significantly inhibited in the process of catalytic ozonation, indicating that ZnO catalytic ozonation followed *OH reaction mechanism. Based on the experimental results and DFT analysis, it is deduced that the generation of *OH on the ZnO surface is ascribed to the adsorption of molecule ozone followed by the interaction of adsorbed ozone with active sites of the catalyst surface. It is also concluded that ZnO may be an effective catalyst for DCAA removal, which could promote the formation of *OH derived from the catalytic decomposition of ozone. PMID:21235181

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. On hematite as a target for dating aqueous conditions on Mars

    NASA Astrophysics Data System (ADS)

    Kula, Joseph; Baldwin, Suzanne L.

    2012-07-01

    Hematite spherules, identified by the Opportunity Mars Exploration Rover (MER), have been interpreted as in situ evidence for past aqueous conditions on the Martian surface. Hematite has also been demonstrated as a reliable (U-Th)/He chronometer, although it is not widely used. In the absence of post-formational diffusive He loss, (U-Th)/He ages measured from Martian hematite spherules should yield the time since water was present on Mars. Using published morphologic constraints and He diffusion kinetics for hematite we model He diffusive loss to assess whether Martian hematite spherules will retain original (U-Th)/He ages during long residence times (4.0 Ga) at surface conditions (22 °C). Fractional loss calculations predict <2% diffusive loss at 22 °C over 4.0 Ga, indicating Martian hematite will preserve ages within analytical precision of the (U-Th)/He technique. If present Mars conditions persisted since the Noachian (e.g. 4.0 Ga), hematite spherules likely record ages reflecting the timing of aqueous mineralization. For the 'wetting-upwards' Burn Formation at Meridiani Planum, hematite from the lower eolian dune subunit would be postdepositional providing a minimum age on deposition, while hematite from the upper interdune/playa unit may be syndepositional thus yielding the age of the deposit. Therefore (U-Th)/He hematite ages obtained from samples collected along a vertical profile could potentially constrain the timing and rates of water saturation of the rock column, and the timing of the transition from wet to dry conditions at Meridiani Planum. Determining an absolute paleohydrologic timescale on Mars may reveal if water was available for sufficient durations required for the development of life.

  12. Optimization of the condition for adsorption of gallic acid by Aspergillus oryzae mycelia using Box-Behnken design.

    PubMed

    Zhang, Zhicai; Pang, Qiaoxia; Li, Min; Zheng, Huihua; Chen, Hui; Chen, Keping

    2015-01-01

    Fresh biomass of Aspergillus oryzae (A. oryzae) CGMCC5992 can effectively remove gallic acid from aqueous solution. To improve the removal rate of gallic acid, this study first identified the important factors affecting the removal rate of gallic acid with univariate analysis, and then used four-factor and three-level Box-Behnken design (BBD) with the removal rate of gallic acid as response value, to obtain the optimum conditions for the removal of gallic acid as follows: 6.95 h treatment time, pH 3.70, 7.07 g/L mycelium volume, and 120.64 mg/L initial concentration of gallic acid. Under such optimized condition, the removal rate of gallic acid approached 99.21 %. HPLC-MS analysis proved that the gallic acid in aqueous solution was completely removed by A. oryzae, rather than being metabolized into its derivatives. Scanning electron microscopy (SEM) indicated that the biomass morphology and surface structure of A. oryzae changed after the adsorption of gallic acid. Thus, the present study has provided an optimal condition for A. oryzae removal of gallic acid in water.

  13. 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.

  14. 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.

  15. 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.

  16. Semiconducting polymer encapsulated mesoporous silica particles with conjugated Europium complexes: toward enhanced luminescence under aqueous conditions.

    PubMed

    Zhang, Jixi; Prabhakar, Neeraj; Näreoja, Tuomas; Rosenholm, Jessica M

    2014-01-01

    Immobilization of lanthanide organic complexes in meso-organized hybrid materials for luminescence applications have attracted immense interest due to the possibility of controlled segregation at the nanoscopic level for novel optical properties. Aimed at enhancing the luminescence intensity and stability of the hybrid materials in aqueous media, we developed polyvinylpyrrolidone (PVP) stabilized, semiconducting polymer (poly(9-vinylcarbazole), PVK) encapsulated mesoporous silica hybrid particles grafted with Europium(III) complexes. Monosilylated β-diketonate ligands (1-(2-naphthoyl)-3,3,3-trifluoroacetonate, NTA) were first co-condensed in the mesoporous silica particles as pendent groups for bridging and anchoring the lanthanide complexes, resulting in particles with an mean diameter of ∼ 450 nm and a bimodal pore size distribution centered at 3.5 and 5.3 nm. PVK was encapsulated on the resulted particles by a solvent-induced surface precipitation process, in order to seal the mesopores and protect Europium ions from luminescence quenching by producing a hydrophobic environment. The obtained polymer encapsulated MSN-EuLC@PVK-PVP particles exhibit significantly higher intrinsic quantum yield (Φ(Ln) = 39%) and longer lifetime (τ(obs) = 0.51 ms), as compared with those without polymer encapsulation. Most importantly, a high luminescence stability was realized when MSN-EuLC@PVK-PVP particles were dispersed in various aqueous media, showing no noticeable quenching effect. The beneficial features and positive attributes of both mesoporous silica and semiconducting polymers as lanthanide-complex host were merged in a single hybrid carrier, opening up the possibility of using these hybrid luminescent materials under complex aqueous conditions such as biological/physiological environments.

  17. Simultaneous removal of acid green 25 and mercury ions from aqueous solutions using glutamine modified chitosan magnetic composite microspheres.

    PubMed

    Tao, Xue; Li, Kun; Yan, Han; Yang, Hu; Li, Aimin

    2016-02-01

    In this current work, the magnetic composite microsphere containing glutamine modified chitosan and silica coated Fe3O4 nanoparticles (CS-Gln-MCM) has been successfully prepared and extensively characterized, which is a kind of biodegradable materials. CS-Gln-MCM shows enhanced removal efficiency for both acid green 25 (AG25), an amphoteric dye, and mercury ions (Hg(2+)) from water in the respective while measured pH range compared with chitosan magnetic composite microsphere (CS-MCM) without modification. It is due to the fact that the grafted amino acid provides a variety of additional adsorption active sites and diverse adsorption mechanisms are involved. In AG25 and Hg(2+) aqueous mixture, the modified adsorbents bear preferential adsorption for AG25 over Hg(2+) in strong acidic solutions ascribed to multiple interactions between AG25 and CS-Gln-MCM, such as hydrogen bonding and electrostatic interactions. While, in weak acidic conditions, an efficient simultaneous removal is observed for different adsorption effects involved in aforementioned two pollutants. Besides, CS-Gln-MCM illuminates not only short equilibrium time for adsorption of each pollutant less than 20.0 min but also rapid magnetic separation from water and efficient regeneration after saturated adsorption. Therefore, CS-Gln-MCM bears great application potentials in water treatment. PMID:26618263

  18. Simultaneous removal of acid green 25 and mercury ions from aqueous solutions using glutamine modified chitosan magnetic composite microspheres.

    PubMed

    Tao, Xue; Li, Kun; Yan, Han; Yang, Hu; Li, Aimin

    2016-02-01

    In this current work, the magnetic composite microsphere containing glutamine modified chitosan and silica coated Fe3O4 nanoparticles (CS-Gln-MCM) has been successfully prepared and extensively characterized, which is a kind of biodegradable materials. CS-Gln-MCM shows enhanced removal efficiency for both acid green 25 (AG25), an amphoteric dye, and mercury ions (Hg(2+)) from water in the respective while measured pH range compared with chitosan magnetic composite microsphere (CS-MCM) without modification. It is due to the fact that the grafted amino acid provides a variety of additional adsorption active sites and diverse adsorption mechanisms are involved. In AG25 and Hg(2+) aqueous mixture, the modified adsorbents bear preferential adsorption for AG25 over Hg(2+) in strong acidic solutions ascribed to multiple interactions between AG25 and CS-Gln-MCM, such as hydrogen bonding and electrostatic interactions. While, in weak acidic conditions, an efficient simultaneous removal is observed for different adsorption effects involved in aforementioned two pollutants. Besides, CS-Gln-MCM illuminates not only short equilibrium time for adsorption of each pollutant less than 20.0 min but also rapid magnetic separation from water and efficient regeneration after saturated adsorption. Therefore, CS-Gln-MCM bears great application potentials in water treatment.

  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. Stability of amino acids and their oligomerization under high-pressure conditions: implications for prebiotic chemistry.

    PubMed

    Otake, Tsubasa; Taniguchi, Takashi; Furukawa, Yoshihiro; Kawamura, Fumio; Nakazawa, Hiromoto; Kakegawa, Takeshi

    2011-10-01

    The polymerization of amino acids leading to the formation of peptides and proteins is a significant problem for the origin of life. This problem stems from the instability of amino acids and the difficulty of their oligomerization in aqueous environments, such as seafloor hydrothermal systems. We investigated the stability of amino acids and their oligomerization reactions under high-temperature (180-400°C) and high-pressure (1.0-5.5 GPa) conditions, based on the hypothesis that the polymerization of amino acids occurred in marine sediments during diagenesis and metamorphism, at convergent margins on early Earth. Our results show that the amino acids glycine and alanine are stabilized by high pressure. Oligomers up to pentamers were formed, which has never been reported for alanine in the absence of a catalyst. The yields of peptides at a given temperature and reaction time were higher under higher-pressure conditions. Elemental, infrared, and isotopic analyses of the reaction products indicated that deamination is a key degradation process for amino acids and peptides under high-pressure conditions. A possible NH(3)-rich environment in marine sediments on early Earth may have further stabilized amino acids and peptides by inhibiting their deamination.

  4. Stability of amino acids and their oligomerization under high-pressure conditions: implications for prebiotic chemistry.

    PubMed

    Otake, Tsubasa; Taniguchi, Takashi; Furukawa, Yoshihiro; Kawamura, Fumio; Nakazawa, Hiromoto; Kakegawa, Takeshi

    2011-10-01

    The polymerization of amino acids leading to the formation of peptides and proteins is a significant problem for the origin of life. This problem stems from the instability of amino acids and the difficulty of their oligomerization in aqueous environments, such as seafloor hydrothermal systems. We investigated the stability of amino acids and their oligomerization reactions under high-temperature (180-400°C) and high-pressure (1.0-5.5 GPa) conditions, based on the hypothesis that the polymerization of amino acids occurred in marine sediments during diagenesis and metamorphism, at convergent margins on early Earth. Our results show that the amino acids glycine and alanine are stabilized by high pressure. Oligomers up to pentamers were formed, which has never been reported for alanine in the absence of a catalyst. The yields of peptides at a given temperature and reaction time were higher under higher-pressure conditions. Elemental, infrared, and isotopic analyses of the reaction products indicated that deamination is a key degradation process for amino acids and peptides under high-pressure conditions. A possible NH(3)-rich environment in marine sediments on early Earth may have further stabilized amino acids and peptides by inhibiting their deamination. PMID:21961531

  5. Ion-exchange properties of strontium hydroxyapatite under acidic conditions

    SciTech Connect

    Sugiyama, Shigeru; Nishioka, Hitoshi; Moriga, Toshihiro; Hayashi, Hiromu; Moffat, J.B.

    1998-09-01

    The ion exchange of strontium hydroxyapatite (SrHAp) with Pb{sup 2+} has been investigated under acidic conditions at 293 K. The addition of various acids to the exchanging solution enhanced the exchange capacity in the order HCl > HBr > HF > HNO{sub 3} > no acid, corresponding to the formation of halogen apatites with the former three acids or hydrogen phosphate with HNO{sub 3}. Since the ion-exchange capacity of SrHAp under nonacidic conditions is higher than that of chlorapatite, the aforementioned observations can be attributed to the participation of the protons introduced by the acids.z

  6. Determination of Arrhenius and Thermodynamic Parameters for the Aqueous Reaction of the Hydroxyl Radical with Lactic Acid

    SciTech Connect

    Leigh R. Martin; Stephen P. Mezyk; Bruce J. Mincher

    2009-01-01

    Lactic acid is a major component of the TALSPEAK process planned for use in the separation of trivalent lanthanide and actinide elements. This acid acts both as a buffer, and also to protect the actinide complexant from radiolytic damage. However, there is little kinetic information on the reaction of water radiolysis species with lactic acid, particularly under the anticipated process conditions of aerated aqueous solution at pH~3, where oxidizing reactions are expected to dominate. Here we have determined temperature-dependent reaction rate constants for the reactions of the hydroxyl radical with lactic acid and the lactate ion. For lactic acid this rate constant is given by the equation: ln k1 = (23.85 ± 0.19) – (1120 ± 54) / T, corresponding to an activation energy of 9.31 ± 0.45 kJ mol-1 and a room temperature reaction rate constant of (5.24 ± 0.09) x 108 M-1 s-1 (24.0oC). For the lactate ion, the temperature-dependent rate constant is given by: ln k2 = (24.83 ± 0.14) – (1295 ± 42) / T, for an activation energy of 10.76 ± 0.35 kJ mol-1 and a room temperature value of (7.77 ± 0.11) x 108 M-1 s-1 (22.2oC). These kinetic data have been combined with autotitration measurements to determine the temperature-dependent behavior of the lactic acid pKa value, allowing thermodynamic parameters for the acid dissociation to be calculated as ?Hº = -10.75 ± 1.77 kJ mol-1, ?Sº = -103.9 ± 6.0 J K-1 mol-1 and ?Gº = 20.24 ± 2.52 kJ mol-1 at low ionic strength.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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)

  12. 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.

  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. 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.

  15. 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).

  16. 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.

  17. Extraction and isolation of lithospermic acid B from Salvia miltiorrhiza Bunge using aqueous two-phase extraction followed by high-performance liquid chromatography.

    PubMed

    Guo, Yong Xue; Shi, Chang Zhi; Zhang, Lei; Lv, Lin; Zhang, Yue Yong

    2016-09-01

    A rapid and effective method integrating separation and purification of lithospermic acid B from Salvia miltiorrhiza Bunge was developed by combining an aqueous two-phase system extraction with preparative chromatography. An aqueous two-phase system of n-butyl alcohol/KH2 PO4 was chosen from seven systems. The influence of parameters including concentration of KH2 PO4 , n-butyl alcohol concentration, pH, and the ratio of an aqueous two-phase system to crude extract were investigated using a single factor design. Response surface methodology was subsequently used to find the optimal compositions of an aqueous two-phase system. Keeping a solvent-to-solid ratio of 10, the final optimized composition of an aqueous two-phase system was 39.1% w/w n-butyl alcohol and 22.6% w/w KH2 PO4 . Under these conditions a recovery yield of 99.8% and a high partition coefficient of 310.4 were obtained. In a pilot-scale experiment using optimized conditions, 18.79 g of lithospermic acid B with a purity of 70.5% and in a yield of 99.8% was separated from 0.5 kg of crude extract. Subsequently, 9.94 g lithospermic acid B with a purity of 99.3% and recovery yield of 70.3% was obtained with a preparative chromatographic process, and the two-step total recovery was 70.1%. PMID:27484287

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. Superoxide radical scavenging by phenolic bronchodilators under aprotic and aqueous conditions.

    PubMed

    Zwicker, K; Damerau, W; Dikalov, S; Scholtyssek, H; Schimke, I; Zimmer, G

    1998-08-01

    Asthmatic airway disease is accompanied by the appearance of inflammatory cells which produce reactive oxygen species (ROS). Therefore, the radical scavenging properties of the bronchodilators reproterol, fenoterol, salbutamol and terbutaline toward superoxide anion radicals and hydroperoxyl radicals were investigated in a model system by electron paramagnetic resonance spectroscopy (EPR) and photometric approaches. The substances under study showed activity in superoxide radical scavenging under aprotic and protic conditions as well. The efficiency of the reaction decreased in the order: fenoterol > salbutamol > reproterol > terbutaline > oxyfedrine when DMSO was used as an aprotic solvent. In an aqueous system, the rate constants decreased in the order: fenoterol > reproterol > salbutamol. It is suggested that the antioxidant effect of these beta2-agonists is an additional advantage in treatment of asthmatic lung disease, reducing the negative consequences of airway inflammation. PMID:9744566

  3. Aqueous Dissolution of Silver Iodide and Associated Iodine Release Under Reducing Conditions with Sulfide

    SciTech Connect

    Yaohiro Inagaki; Toshitaka Imamura; Kazuya Idemitsu; Tatsumi Arima; Osamu Kato; Hidekazu Asano; Tsutomu Nishimura

    2007-07-01

    Aqueous dissolution tests of silver iodide (AgI) were performed in Na{sub 2}S solutions in order to evaluate, empirically, dissolution of AgI to release iodine under reducing conditions with sulfide. The results indicated that AgI dissolves to release iodine being controlled by mainly precipitation of Ag{sub 2}S. However, the dissolution of AgI can be depressed to proceed, and the thermodynamic equilibrium cannot be attained easily. Solid phase analysis for the reacted AgI suggested that a thin layer of solid silver forming at AgI surface may evolve to be protective against transportation of reactant species, which can lead to the depression in the dissolution of AgI. (authors)

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Electrical conductivity measurements of aqueous boric acid at 25--350{degree}C at saturation vapor pressure. Final report

    SciTech Connect

    Ho, P.C.; Palmer, D.A.

    1995-09-01

    Electrical conductance measurements of aqueous boric acid solutions (15-110 g/kg-H{sub 2}O {equivalent_to} 0.251--1.815 mol/kg-H{sub 2}O) were measured over the temperature range 25 to 75 C at saturation vapor pressures in glass cells with parallel platinum electrodes. Sixteen series of measurements were made involving three samples of boric acid from different sources. Conductance measurements were also made at 15.5 and 30.5 g/kg-H{sub 2}O over the temperature range 100 to 350 C at 50 C intervals with a metallic cell fitted with concentric platinum electrodes. The specific conductances of H{sub 3}BO{sub 3} (aq)were calculated after correction for the conductance of the solvent (water) and are tabulated in this report. At the specific conditions requested in the project description, namely a concentration of 110 g/kg-H{sub 2}O and 65 C, the specific conductance of boric acid is 293.2 {+-} 1.8 microSiemens/cm based on duplicate measurements of four independent solutions. The results from these tests will be utilized by the Tokamak Physics Experimental Project (TPX).

  2. Spectroscopic study of Mg(II) ion influence on the autoxidation of gallic acid in weakly alkaline aqueous solutions

    NASA Astrophysics Data System (ADS)

    Nikolić, G. M.; Veselinović, A. M.; Nikolić, R. S.; Mitić, S. S.

    2011-12-01

    Gallic acid autoxidation in weakly alkaline aqueous solutions was studied by UV-Vis spectrophotometry and ESR spectroscopy under various conditions. Lowering the pH value from 10 to 8.5 probably changes the mechanism of the autoxidation reaction as evidenced by the different time variations of UV-Vis spectra of solutions. The presence of Mg(II) ions greatly influences the autoxidation reaction at pH 8.5. Although the UV-Vis spectral changes with time follow the similar pattern during the gallic acid autoxidation at pH 10 and at pH 8.5 in the presence of Mg(II) ions, some small differences indicate that Mg(II) ions not only affect the electron density of absorbing species but also influence the overall mechanism of the autoxidation reaction. ESR spectra of free radials formed during the initial stage of gallic acid autoxidation at pH 8.5 in the presence of Mg(II) ions were recorded. Computer simulation of ESR spectra allows partial characterization of these free radicals.

  3. Structural evolution of molybdenum carbides in hot aqueous environments and impact on low-temperature hydroprocessing of acetic acid

    SciTech Connect

    Choi, Jae -Soon; Schwartz, Viviane; Santillan-Jimenez, Eduardo; Crocker, Mark; Lewis, Sr., Samuel A.; Lance, Michael J.; Meyer, III, Harry M.; More, Karren L.

    2015-03-13

    In this paper, we investigated the structural evolution of molybdenum carbides subjected to hot aqueous environments and their catalytic performance in low-temperature hydroprocessing of acetic acid. While bulk structures of Mo carbides were maintained after aging in hot liquid water, a portion of carbidic Mo sites were converted to oxidic sites. Water aging also induced changes to the non-carbidic carbon deposited during carbide synthesis and increased surface roughness, which in turn affected carbide pore volume and surface area. The extent of these structural changes was sensitive to the initial carbide structure and was lower under actual hydroprocessing conditions indicating the possibility of further improving the hydrothermal stability of Mo carbides by optimizing catalyst structure and operating conditions. Mo carbides were active in acetic acid conversion in the presence of liquid water, their activity being comparable to that of Ru/C. Finally, the results suggest that effective and inexpensive bio-oil hydroprocessing catalysts could be designed based on Mo carbides, although a more detailed understanding of the structure-performance relationships is needed, especially in upgrading of more complex reaction mixtures or real bio-oils.

  4. Structural evolution of molybdenum carbides in hot aqueous environments and impact on low-temperature hydroprocessing of acetic acid

    DOE PAGES

    Choi, Jae -Soon; Schwartz, Viviane; Santillan-Jimenez, Eduardo; Crocker, Mark; Lewis, Sr., Samuel A.; Lance, Michael J.; Meyer, III, Harry M.; More, Karren L.

    2015-03-13

    In this paper, we investigated the structural evolution of molybdenum carbides subjected to hot aqueous environments and their catalytic performance in low-temperature hydroprocessing of acetic acid. While bulk structures of Mo carbides were maintained after aging in hot liquid water, a portion of carbidic Mo sites were converted to oxidic sites. Water aging also induced changes to the non-carbidic carbon deposited during carbide synthesis and increased surface roughness, which in turn affected carbide pore volume and surface area. The extent of these structural changes was sensitive to the initial carbide structure and was lower under actual hydroprocessing conditions indicating themore » possibility of further improving the hydrothermal stability of Mo carbides by optimizing catalyst structure and operating conditions. Mo carbides were active in acetic acid conversion in the presence of liquid water, their activity being comparable to that of Ru/C. Finally, the results suggest that effective and inexpensive bio-oil hydroprocessing catalysts could be designed based on Mo carbides, although a more detailed understanding of the structure-performance relationships is needed, especially in upgrading of more complex reaction mixtures or real bio-oils.« less

  5. 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.

  6. 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

  7. 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.

  8. Carboxylic Acids as Indicators of Parent Body Conditions

    NASA Technical Reports Server (NTRS)

    Lerner N. R.; Chang, Sherwood (Technical Monitor)

    1995-01-01

    Alpha-hydroxy and alpha-amino carboxylic acids found on the Murchison meteorite are deuterium enriched. It is postulated that they arose from a common interstellar scurce: the reaction of carbonyl compounds in an aqueous mixture containing HCN and NH3. Carbonyl compounds react with HCN to form alpha-hydroxy nitriles, RR'CO + HCN right and left arrow RR'C(OH)CN. If ammonia is also present, the alpha-hydroxy nitriles will exist in equilibrium with the alpha-amino nitriles, RR'C(OH)CN + NH3 right and left arrow - RRCNH2CN + H2O. Both nitrites are hydrolyzed by water to form carboxylic acids: RR'C(OH)CN + H2O yields RR'C(OH)CO2H and RR'C(NH2)CN + H2O yields RR'C(NH2)CO2H.

  9. Measurement of interaction forces between lignin and cellulose as a function of aqueous electrolyte solution conditions.

    PubMed

    Notley, Shannon M; Norgren, Magnus

    2006-12-19

    The interaction between a lignin film and a cellulose sphere has been measured using the colloidal probe force technique as a function of aqueous electrolyte solution conditions. The lignin film was first studied for its roughness and stability using atomic force microscopy imaging and quartz crystal microbalance measurements, respectively. The film was found to be smooth and stable in the pH range of 3.5-9 and in ionic strengths up to and including 0.01 M. This range of ionic strength and pH was hence used to measure the surface force profiles between lignin and cellulose. Under these solution conditions, the measured forces behaved according to DLVO theory. The force-distance curves could be fitted between the limits of constant charge and constant potential, and the surface potential of the lignin films was determined as a function of pH. At a pH greater than 9.5, a short range steric repulsion was observed, indicating that the film was swelling to a large extent but did not dissolve. Thus, lignin films prepared in this manner are suitable for a range of surface force studies.

  10. 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.

  11. 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

  12. 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.

  13. [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.

  14. Experimental Acid Weathering of Fe-Bearing Mars Analog Minerals and Rocks: Implications for Aqueous Origin of Hematite-Bearing Sediments in Meridiani Planum, Mars

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Koster, A. M.; Ming, D. W.; Morris, R. V.; Mertzman, S. A.

    2011-01-01

    A working hypothesis for Meridiani evaporite formation involves the evaporation of fluids derived from acid weathering of Martian basalts and subsequent diagenesis [1, 2]. However, there are no reported experimental studies for the formation of jarosite and gray hematite (spherules), which are characteristic of Meridiani rocks from Mars analog precursor minerals. A terrestrial analog for hematite spherule formation from basaltic rocks under acidic hydrothermal conditions has been reported [3], and we have previously shown that the hematite spherules and jarosite can be synthetically produced in the laboratory using Fe3+ -bearing sulfate brines under hydrothermal conditions [4]. Here we expand and extend these studies by reacting Mars analog minerals with sulfuric acid to form Meridiani-like rock-mineral compositions. The objective of this study is to provide environmental constraints on past aqueous weathering of basaltic materials on Mars.

  15. Oxidative photodegradation of herbicide fenuron in aqueous solution by natural iron oxide α-Fe2O3, influence of polycarboxylic acids.

    PubMed

    Kribéche, Mohamed El Amine; Mechakra, Hind; Sehili, Tahar; Brosillon, Stephan

    2016-01-01

    The photodegradation of the herbicide fenuron (1,1-dimethyl-3-phenylurea) by using a natural iron oxide (NIO), α-Fe2O3, in aqueous solution at acidic pH has been undertaken. The NIO was characterized by the Raman spectroscopy method. The degradation pathways and the formation of degradation products were studied. A high-pressure mercury lamp and sunlight were employed as light source. Fenuron photodegradation using NIO with oxalic acid followed the pseudo-first-order kinetics, the optimal experimental conditions were [oxalic acid]0 = 10(-3) M and [NIO] = 0.1 g L(-1) at pH 3. A UVA/NIO/oxalic acid system led to a low fenuron half-life (60 min). The results were even better when solar light is used (30 min). The variables studied were the doses of iron oxide, of carboxylic acids, the solution pH and the effect of sunlight irradiation. The effects of four carboxylic acids, oxalic, citric, tartaric and malic acids, on the fenuron photodegradation with NIO have been investigated, oxalic acid was the most effective carboxylic acid used at pH 3. A similar trend was observed for the removal of total organic carbon (TOC), 75% of TOC was removed. The analytical study showed many aromatic intermediates, short-chain carboxylic acids and inorganic ion. PMID:26102217

  16. Fe/Mg smectite formation under acidic conditions on early Mars

    NASA Astrophysics Data System (ADS)

    Peretyazhko, T. S.; Sutter, B.; Morris, R. V.; Agresti, D. G.; Le, L.; Ming, D. W.

    2016-01-01

    Phyllosilicates of the smectite group detected in Noachian and early Hesperian terrains on Mars have been hypothesized to form under neutral to alkaline conditions. These pH conditions would also be favorable for formation of widespread carbonate deposits which have not been detected on Mars. We propose that smectite deposits on Mars formed under moderately acidic conditions inhibiting carbonate formation. We report here the first synthesis of Fe/Mg smectite in an acidic hydrothermal system [200 °C, pHRT ∼ 4 (pH measured at room temperature) buffered with acetic acid] from Mars-analogue, glass-rich, basalt simulant with and without aqueous Mg or Fe(II) addition under N2-purged anoxic and ambient oxic redox conditions. Synthesized Fe/Mg smectite was examined by X-ray-diffraction, Mössbauer spectroscopy, visible and near-infrared reflectance spectroscopy, scanning electron microscopy and electron microprobe to characterize mineralogy, morphology and chemical composition. Alteration of the glass phase of basalt simulant resulted in formation of the Fe/Mg smectite mineral saponite with some mineralogical and chemical properties similar to the properties reported for Fe/Mg smectite on Mars. Our experiments are evidence that neutral to alkaline conditions on early Mars are not necessary for Fe/Mg smectite formation as previously inferred. Phyllosilicate minerals could instead have formed under mildly acidic pH conditions. Volcanic SO2 emanation and sulfuric acid formation is proposed as the major source of acidity for the alteration of basaltic materials and subsequent formation of Fe/Mg smectite.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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.

  12. 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

  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. 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

  15. 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

  16. 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.

  17. 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.

  18. 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

  19. Human Serum Albumin Increases the Stability of Green Tea Catechins in Aqueous Physiological Conditions.

    PubMed

    Zinellu, Angelo; Sotgia, Salvatore; Scanu, Bastianina; Forteschi, Mauro; Giordo, Roberta; Cossu, Annalisa; Posadino, Anna Maria; Carru, Ciriaco; Pintus, Gianfranco

    2015-01-01

    Epicatechin (EC), epigallocatechin (EGC), epicatechingallate (ECG) and epigallocatechingallate (EGCG) are antioxidants present in the green tea, a widely used beverage whose health benefits are largely recognized. Nevertheless, major physicochemical limitations, such as the high instability of catechins, pose important questions concerning their potential pharmacological use. Recent studies indicate that binding of catechins with plasmatic proteins may modulate their plasma concentration, tissue delivery and biological activity. After 5 minutes of incubation with HSA both ECG and EGCG were fully bound to HSA, while after 48h incubation only 41% of EC and 70% of EGC resulted linked. HSA had a strong stabilizing effect on all catechins, which could be found in solution between 29 and 85% even after 48h of incubation. In the absence of HSA, EGC and EGCG disappeared in less than 24h, while ECG and EC were found after 48h at 5 and 50%, respectively. The stabilizing effect of HSA toward EGCG, obtained in aqueous physiological conditions, resulted stronger in comparison to cysteine and HCl, previously reported to stabilize this polyphenol. Because of the multitude of contradictory data concerning in vivo and in vitro antioxidant-based experimentations, we believe our work may shed some light on this debated field of research. PMID:26230943

  20. The management of burns under conditions of limited resources using topical aqueous sulfamylon (mafenide) hydrochloride spray.

    PubMed

    Mendelson, J A

    1997-01-01

    The burn unit establishment in a Vietnamese military hospital (1970 to 1971) is an example of the management of burns under conditions of limited resources. The problems encountered and methods used in their solution are still relevant. This is the first (and possibly still the only) instance of such clinical use of topical Sulfamylon (mafenide) aqueous spray as the sole pregraft antibacterial agent for patients with deep partial-thickness and full-thickness burns (and associated injuries). The mafenide spray open treatment resulted in a bacteriostatic film permitting eschars to remain uninfected while more superficial burns healed and general status improved, enabling delayed grafting to be effective. Use of operating rooms, supplies, and personnel was minimized. The study group contained 211 patients; 86 (approximately 40%) had burns that exceeded 20% body surface area, and 26 (approximately 12%) had burns that exceeded 40% body surface area. As the procedures became fully established, all of the last 110 patients of this series survived. Only 17 deaths occurred in the total series; none were attributed to infection.

  1. Radiolysis of pyridoxine (vitamin B 6) in aqueous solution under different conditions

    NASA Astrophysics Data System (ADS)

    Albarrán, Guadalupe; Ramírez-Cahero, Fernando; Aliev, Roustam

    2008-05-01

    Aqueous solutions of pyridoxine (1 mM) without or with additive of K 3[Fe(CN) 6] (2.5 mM) were gamma-irradiated at different doses and dose rate of 2.16 kGy/h in the absence of air, in the presence of air or by their saturation with N 2O. The radiolytic products were analyzed with HPLC, mass spectrometry and UV spectroscopy. 2,4,5-Trihydroxymethyl-3-pyridinol, pyridoxal, isopyridoxal and 6-hydroxypyridoxine were formed by radiolysis in the absence of K 3[Fe(CN) 6], and their concentrations were much higher in samples saturated with N 2O. Pyridoxi-3,6-quinone was found by radiolysis under all the above-mentioned conditions but only in the presence of K 3[Fe(CN) 6]. Besides, the pyridoxal formation increased in the presence of this oxidizing agent. G values of pyridoxal formation and pyridoxine degradation were quantified. Some details of the radiolytic product formation were discussed.

  2. Carboxylic Acids as Indicators of Parent Body Conditions

    NASA Astrophysics Data System (ADS)

    Lerner, N. R.

    1995-09-01

    Alpha-hydroxy and alpha-amino carboxylic acids found on the Murchison meteorite are deuterium enriched [1]. It is postulated that they arose from a common interstellar source: the reaction of carbonyl compounds in an aqueous mixture containing HCN and NH3. Carbonyl compounds react with HCN to form alph-hydroxy nitriles, RR'CO + HCN <--> RR'C(OH)CN. If ammonia is also present, the alpha-hydroxy nitriles will exist in equilibirum with the alpha-amino nitriles, RR'C(OH)CN +NH3 .<--> RRCNH2CN + H2O. Both nitriles are hydrolyzed by water to form carboxylic acids: RR'C(OH)CN + H2O --> RR'C(OH)CO2H and RR'C(NH2)CN + H2O --> RR'C(NH2)CO2H. Carbonyl compounds observed in the interstellar medium have been shown to be deuterium enriched [2]. The combined alpha-amino acids found on Murchison have deltaD = +1751 o/oo while the combined alpha-hydroxy acids have deltaD = +573. o/oo [1]. This large discrepancy in deltaD values does not preclude common precursors for the alpha-amino acids and the alpha-hydroxy acids. Different relative amounts of specific alpha-amino and alpha-hydroxy acids could lead to quite different combined D/H ratios. If the alpha-hydroxy acids lose significantly more deuterium during synthesis than the alpha-amino acids or if they have a higher rate of H/D exchange with liquid water than alpha-amino acids, the alpha-hydroxy acids would be isotopically lighter than the alpha-amino acids, because the water responsible for the aqueous alteration of the Murchison parent body was deuterium depleted with deltaD = -100. o/oo [3]. To determine between these alternative mechanisms we measured the rates of hydrogen-deuterium exchange of glycolic acid (the alpha-hydroxy analog of glycine), lactic acid (the alpha-hydroxy analog of alanine), and alpha-hydroxy isobutyric acid have been measured in D2O as a function of pH, temperature and the presence of Allende or Murchison minerals. No detectable H/D exchange was observed. Glycine subjected to similar conditons exchanged

  3. Decreased solubilization of Pu(IV) polymers by humic acids under anoxic conditions

    NASA Astrophysics Data System (ADS)

    Xie, Jinchuan; Lin, Jianfeng; Liang, Wei; Li, Mei; Zhou, Xiaohua

    2016-11-01

    Pu(IV) polymer has a very low solubility (log[Pu(IV)aq]total = -10.4 at pH 7.2 and I = 0). However, some aspects of their environmental fate remain unclear. Humic acids are able to complex with Pu4+ ions and their dissolved species (<10 kD) in the groundwater (neutral to alkaline pH) may cause solubilization of the polymers. Also, humic acids have the native reducing capacity and potentially reduce the polymeric Pu(IV) to Pu(III)aq (log[Pu(III)aq]total = -5.3 at pH 7.2 and I = 0). Solubilization and reduction of the polymers can enhance their mobility in subsurface environments. Nevertheless, humic acids readily coat the surfaces of metal oxides via electrostatic interaction and ligand exchange mechanisms. The humic coatings are expected to prevent both solubilization and reduction of the polymers. Experiments were conducted under anoxic and slightly alkaline (pH 7.2) conditions in order to study whether humic acids have effects on stability of the polymers. The results show that the polymeric Pu(IV) was almost completely transformed into aqueous Pu(IV) in the presence of EDTA ligands. In contrast, the dissolved humic acids did not solubilize the polymers but in fact decreased their solubility by one order of magnitude. The humic coatings were responsible for the decreased solubilization. Such coatings limited the contact between the polymers and EDTA ligands, especially at the relatively high concentrations of humic acids (>0.57 mg/L). Solubilization of the humic-coated polymers was thus inhibited to a significant extent although EDTA, having the great complexation ability, was present in the humic solutions. Reduction of Pu(IV) polymers by the humic acids was also not observed in the absence of EDTA. In the presence of EDTA, the polymers were partially reduced to Pu(III)aq by the humic acids of 0.57 mg/L and the percentage of Pu(III)aq accounted for 51.7% of the total aqueous Pu. This demonstrates that the humic acids were able to reduce the aqueous Pu

  4. 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.

  5. 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.

  6. 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).

  7. A GREEN CHEMISTRY APPROACH TO PREPARATION OF CORE (FE OR CU)-SHELL (NOBLE METALS) NANOCOMPOSITES USING AQUEOUS ASCORBIC ACID

    EPA Science Inventory

    A greener method to fabricate novel core (Fe or Cu)-shell (noble metals) nanocomposites of transition metals such as Fe and Cu and noble metals such as Au, Pt, Pd, and Ag using aqueous ascorbic acid is described. Transition metal salts such as Cu and Fe were reduced using ascor...

  8. The role of hydrogen bonds in an aqueous solution of acetylsalicylic acid: a molecular dynamics simulation study.

    PubMed

    Donnamaria, Maria Cristina; de Xammar Oro, Juan Roberto

    2011-10-01

    This work focuses on the role of the dynamic hydrogen bonds (HB) formed in an aqueous solution of aspirin using molecular dynamics simulation. The statistics reveal the existence of internal HB that inhibit the rotational movements of the acetyl and the carboxylic acid groups, forcing the molecule to adopt a closed conformer structure in water, and playing an important role in stabilizing this conformation.

  9. Biosorption of methyl blue onto tartaric acid modified wheat bran from aqueous solution

    PubMed Central

    2012-01-01

    Tartaric acid modified wheat bran was utilized as adsorbent to remove methyl blue, a basic dye from aqueous solution. Batch experiments were carried out to study the effect of various experimental parameters such as initial solution pH, contact time, initial dye concentration and adsorbent dosage, on dye adsorption. The results showed that the modification of wheat bran by tartaric acid significantly improved its adsorption capacity, and made this material a suitable adsorbent to remove methyl blue. The adsorption capacity of modified wheat bran was about 1.6 times higher than that of unmodified one. The amount of methyl blue adsorbed was found to vary with initial solution pH, adsorbent dosage, contact time and initial methyl blue concentration. Kinetics study showed that the overall adsorption rate of methyl blue was illustrated by pseudo-second-order kinetic model. The applicability of the Langmuir and Freundlich models for the data was tested. Both models adequately described the experimental data of the biosorption of methyl blue. The maximum adsorption capacity for methyl blue calculated from Langmuir model was 25.18 mg/g. The study has shown the effectiveness of modified wheat bran in the removal of methyl blue, and that it can be considered as an attractive alternative to the more expensive technologies used in wastewater treatment. PMID:23369295

  10. Preparation of aqueous alpha-lipoic acid dispersions with octenylsuccinylated high amylose starch.

    PubMed

    Li, Yi-Xuan; Lim, Seung-Taik

    2016-04-20

    Aqueous dispersions prepared with OSA-modified high amylose starch were investigated in comparison with native high amylose starch and beta-cyclodextrin using alpha-lipoic acid as a model substance. Alpha-lipoic acid (ALA), a lipophilic antioxidant essential for energy metabolism in human, was dispersed in gelatinized starch solutions (1.0% w/v) at different temperatures (50-90°C) and times (3-12h). High amylose starch modified with 3% OSA (dry starch base) was most favored in maximizing the dispersibility of ALA (84% recovery) under mild heating (70°C for 3h). The optimally prepared dispersion was milky white and contained particles with a narrow size distribution (200-300nm). The precipitate isolated from the dispersion contained crystalline V-complexes of ALA and amylose while the supernatant contained free ALA accounting for 1/3 of total ALA, indicating OSA-modified high amylose starch stabilized ALA either by complexing with amylose or by retarding aggregation of ALA.

  11. A chemiluminescence-based continuous flow aqueous ozone analyzer using photoactivated chromotropic acid.

    PubMed

    Takayanagi, Toshio; Dasgupta, Purnendu K

    2005-05-15

    Ozone has become the oxidant of choice for water disinfection, especially in large water treatment facilities. This paper describes a fast and sensitive method for the determination of ozone content by reaction with photoactivated chromotropic acid (CA, 4,5-dihydroxynaphthalene-2,7-disulfonic acid), which results in intense chemiluminescence (CL). Freshly ozonated water from a recirculating ozonizer/reservoir is injected into a carrier stream of deionized water in the flow-injection mode. This flow mixes with a stream of photoactivated CA solution in a spiral cell placed directly on top of an inexpensive miniature (8mm diameter active area) photomultiplier tube (PMT). Alkaline CA is photoactivated by passing it through a FEP-Teflon((R)) coil (residence time approximately 50s) wrapped around a 1W UV lamp emitting at 254nm; without photoactivation, the signal is approximately 70-fold lower. The S/N=3 limit of detection for aqueous ozone is 3mugl(-1) and good response slope is obtained up to an ozone concentration of 1.4mgl(-1), the highest that could be made in this study. The response obeyed a quadratic equation with r(2)=0.9984. No interference from permanganate ion is observed. The proposed system was applied to the monitoring of ozonation status of a playa lake water that exhibited significant ozone demand.

  12. Removal of aqueous perfluorooctanoic acid (PFOA) using starch-stabilized magnetite nanoparticles.

    PubMed

    Gong, Yanyan; Wang, Lin; Liu, Juncheng; Tang, Jingchun; Zhao, Dongye

    2016-08-15

    Fully stabilized magnetite (Fe3O4) nanoparticles were prepared with a water-soluble starch as a stabilizer and tested for removal of aqueous perfluorooctanoic acid (PFOA). The presence of starch at ≥0.2wt% can fully stabilize 0.1g/L as Fe of the Fe3O4 nanoparticles. The particle stabilization technique resulted in 2.4 times higher PFOA uptake. Fourier transform infrared spectra suggested that the main PFOA removal mechanism was inner-sphere complexation. Batch kinetic experiments revealed that the starch-stabilized nanoparticles facilitated a rapid PFOA uptake with a sorption equilibrium time of 30min, and the sorption process followed a pseudo-second-order kinetic model. The Langmuir model was able to well interpret the adsorption isotherm, with a maximum adsorption capacity of 62.5mg/g. Increasing pH from 4.7 to 9.6 led to a sharp increase (by 2.6 times) in PFOA uptake. The presence of 12mg/L humic acid inhibited PFOA uptake by 96%, while effect of ionic strength (CaCl2=0-2mmol/L) was negligible. The nanoparticles significantly reduced the biological toxicity of PFOA. The results demonstrated promise of starch-stabilized Fe3O4 nanoparticles as a "green" adsorbent for effective removal of PFOA in soil and groundwater. PMID:27100000

  13. Improving aqueous solubility and antitumor effects by nanosized gambogic acid-mPEG2000 micelles

    PubMed Central

    Cai, Lulu; Qiu, Neng; Xiang, Mingli; Tong, Rongsheng; Yan, Junfeng; He, Lin; Shi, Jianyou; Chen, Tao; Wen, Jiaolin; Wang, Wenwen; Chen, Lijuan

    2014-01-01

    The clinical application of gambogic acid, a natural component with promising antitumor activity, is limited due to its extremely poor aqueous solubility, short half-life in blood, and severe systemic toxicity. To solve these problems, an amphiphilic polymer-drug conjugate was prepared by attachment of low molecular weight (ie, 2 kDa) methoxy poly(ethylene glycol) methyl ether (mPEG) to gambogic acid (GA-mPEG2000) through an ester linkage and characterized by 1H nuclear magnetic resonance. The GA-mPEG2000 conjugates self-assembled to form nanosized micelles, with mean diameters of less than 50 nm, and a very narrow particle size distribution. The properties of the GA-mPEG2000 micelles, including morphology, stability, molecular modeling, and drug release profile, were evaluated. MTT (3-(4,5-dimethylthiazo l-2-yl)-2,5 diphenyl tetrazolium bromide) tests demonstrated that the GA-mPEG2000 micelle formulation had obvious cytotoxicity to tumor cells and human umbilical vein endothelial cells. Further, GA-mPEG2000 micelles were effective in inhibiting tumor growth and prolonged survival in subcutaneous B16-F10 and C26 tumor models. Our findings suggest that GA-mPEG2000 micelles may have promising applications in tumor therapy. PMID:24403830

  14. Preparation of aqueous alpha-lipoic acid dispersions with octenylsuccinylated high amylose starch.

    PubMed

    Li, Yi-Xuan; Lim, Seung-Taik

    2016-04-20

    Aqueous dispersions prepared with OSA-modified high amylose starch were investigated in comparison with native high amylose starch and beta-cyclodextrin using alpha-lipoic acid as a model substance. Alpha-lipoic acid (ALA), a lipophilic antioxidant essential for energy metabolism in human, was dispersed in gelatinized starch solutions (1.0% w/v) at different temperatures (50-90°C) and times (3-12h). High amylose starch modified with 3% OSA (dry starch base) was most favored in maximizing the dispersibility of ALA (84% recovery) under mild heating (70°C for 3h). The optimally prepared dispersion was milky white and contained particles with a narrow size distribution (200-300nm). The precipitate isolated from the dispersion contained crystalline V-complexes of ALA and amylose while the supernatant contained free ALA accounting for 1/3 of total ALA, indicating OSA-modified high amylose starch stabilized ALA either by complexing with amylose or by retarding aggregation of ALA. PMID:26876852

  15. Adsorption of Acid Red 57 from aqueous solutions onto polyacrylonitrile/activated carbon composite.

    PubMed

    El-Bindary, Ashraf A; Diab, Mostafa A; Hussien, Mostafa A; El-Sonbati, Adel Z; Eessa, Ahmed M

    2014-04-24

    The adsorption of Acid Red 57 (AR57) onto Polyacrylonitrile/activated carbon (PAN/AC) composite was investigated in aqueous solution in a batch system with respect to contact time, pH and temperature. Physical characteristics of (PAN/AC) composite such as fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were obtained. Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were determined. The activation energy of adsorption was also evaluated for the adsorption of AR57 onto (PAN/AC) composite. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data. The dynamic data fitted the pseudo-second-order kinetic model well. The activation energy, change of free energy, enthalpy and entropy of adsorption were also evaluated for the adsorption of AR57 onto (PAN/AC) composite. The thermodynamics of the adsorption indicated spontaneous and exothermic nature of the process. The results indicate that (PAN/AC) composite could be employed as low-cost material for the removal of acid dyes from textile effluents. PMID:24463242

  16. Removal of aqueous perfluorooctanoic acid (PFOA) using starch-stabilized magnetite nanoparticles.

    PubMed

    Gong, Yanyan; Wang, Lin; Liu, Juncheng; Tang, Jingchun; Zhao, Dongye

    2016-08-15

    Fully stabilized magnetite (Fe3O4) nanoparticles were prepared with a water-soluble starch as a stabilizer and tested for removal of aqueous perfluorooctanoic acid (PFOA). The presence of starch at ≥0.2wt% can fully stabilize 0.1g/L as Fe of the Fe3O4 nanoparticles. The particle stabilization technique resulted in 2.4 times higher PFOA uptake. Fourier transform infrared spectra suggested that the main PFOA removal mechanism was inner-sphere complexation. Batch kinetic experiments revealed that the starch-stabilized nanoparticles facilitated a rapid PFOA uptake with a sorption equilibrium time of 30min, and the sorption process followed a pseudo-second-order kinetic model. The Langmuir model was able to well interpret the adsorption isotherm, with a maximum adsorption capacity of 62.5mg/g. Increasing pH from 4.7 to 9.6 led to a sharp increase (by 2.6 times) in PFOA uptake. The presence of 12mg/L humic acid inhibited PFOA uptake by 96%, while effect of ionic strength (CaCl2=0-2mmol/L) was negligible. The nanoparticles significantly reduced the biological toxicity of PFOA. The results demonstrated promise of starch-stabilized Fe3O4 nanoparticles as a "green" adsorbent for effective removal of PFOA in soil and groundwater.

  17. Chemisorption of Perfluorooctanoic Acid on Powdered Activated Carbon Initiated by Persulfate in Aqueous Solution.

    PubMed

    Sun, Bo; Ma, Jun; Sedlak, David L

    2016-07-19

    Perfluorooctanoic acid (PFOA) is a perfluorocarboxylic acid that is difficult to treat by most conventional methods. As a result, it is often removed from solution by adsorption on powdered activated carbon (PAC), followed by incineration of the spent carbon. To provide a new approach for treatment, PFOA was exposed to sulfate radicals (SO4(-•)) produced by thermolysis of persulfate (S2O8(2-)) in the presence of PAC. Under acidic conditions, thermal activation of persulfate resulted in transformation of PFOA to shorter-chain-length perfluorinated compounds, as previously reported. However, when thermolysis of persulfate occurred under circumneutral pH conditions in the presence of PAC, a new removal pathway for PFOA was observed. Under these conditions, the removal of PFOA was attributable to chemisorption, a process in which PAC catalyzed persulfate decomposition and reacted with the transformation products to produce covalently bound PFOA. At PAC concentrations between 200 and 1000 mg/L and an initial PFOA concentration of 0.5 μM, covalent bonding resulted in removal of 10-40% of the PFOA. Under these conditions, the process resulted in removal of more than half of a more hydrophilic perfluoroalkyl acid (i.e., perfluorobutanoic acid, PFBA), which was greater than the amount of PFBA removed by physical adsorption on PAC. Although the high reaction temperatures (i.e., 80 °C) and relatively high doses of PAC used in this study may be impractical for drinking water treatment, this process may be applied to the treatment of these recalcitrant compounds in industrial wastewater, reverse osmosis concentrate, and other waters that contain high concentrations of PFOA and other perfluorocarboxylic acids. PMID:27336204

  18. Adsorption behavior of antimony(III) oxyanions on magnetite surface in aqueous organic acid environment

    NASA Astrophysics Data System (ADS)

    Mittal, Vinit K.; Bera, Santanu; Narasimhan, S. V.; Velmurugan, S.

    2013-02-01

    Antimony(III) adsorption is observed on magnetite (Fe3O4) surface under acidic and reducing condition through surface hydroxyl (SOH) groups bonding on Fe3O4 surface. Desorption of adsorbed Sb(III) is observed from Fe3O4 surface along with iron release in organic acid at 85 °C after 5 h of experiment. Tartaric acid (TA) shows minimum Sb(III) adsorption on Fe3O4 among the organic acid studied. The reason is TA having two sets of adjacent functional groups viz. Odbnd Csbnd OH and Csbnd OH which are responsible for the formation of five-membered bidendate chelate with Sb(III). Other oxyanions, cations or complexing agents along with TA influences the Sb(III) adsorption on Fe3O4. The surface of magnetite is modified by the addition of fatty acids viz. Lauric acid, benzoic acid to bind the Ssbnd OH groups present on the surface. This results in delaying the process of adsorption without changing the quantity of saturation adsorption of Sb(III) on Fe3O4 surface.

  19. Formation of 4(5)-Methylimidazole in Aqueous d-Glucose-Amino Acids Model System.

    PubMed

    Karim, Faris; Smith, J Scott

    2016-01-01

    The International Agency for Research on Cancer (IRAC) has classified 4(5)-methylimidazole (4-MeI) as a group 2B possible human carcinogen. Thus, how 4-MeI forms in a D-glucose (Glu) amino acids (AA) model system is important, as it is how browning is affected. An aqueous solution of Glu was mixed individually in equimolar amounts at 3 concentrations (0.05, 0.1, and 0.15 M) with aqueous solutions of L-Alanine (Ala), L-Arginine (Arg), Glycine (Gly), L-Lysine (Lys), and L-Serine (Ser). The Glu-AA mixtures were reacted at 60, 120, and 160 °C for 1 h. The 4-MeI levels were measured by gas chromatography-mass spectrometry after derivatization with isobutylchloroformate. No 4-MeI was formed at 60 °C for any treatment combination; however, at 120 °C and 0.05 M, Glu-Arg and Glu-Lys produced 0.13 and 0.14 mg/kg of 4-MeI. At 160 °C and 0.05 M all treatment combinations formed 4-MeI. At 160 °C and 0.15 M, the observed levels of Glu-Ala, Glu-Arg, Glu-Gly, Glu-Lys, and Glu-Ser were 0.21, 1.00, 0.15, 0.22, and 0.16 mg/kg. The AA type, reactant concentrations, and temperature significantly affected (P < 0.001) formation of 4-MeI as well as browning. Glu-Lys treatment in all combinations produced the most browning, but Glu-Arg produced the most 4-MeI. This method showed that foods processed using low temperatures may have reduced levels of 4-MeI.

  20. Unsaturated C3,5,7,9-Monocarboxylic Acids by Aqueous, One-Pot Carbon Fixation: Possible Relevance for the Origin of Life.

    PubMed

    Scheidler, Christopher; Sobotta, Jessica; Eisenreich, Wolfgang; Wächtershäuser, Günter; Huber, Claudia

    2016-06-10

    All scientific approaches to the origin of life share a common problem: a chemical path to lipids as main constituents of extant cellular enclosures. Here we show by isotope-controlled experiments that unsaturated C3,5,7,9-monocarboxylic acids form by one-pot reaction of acetylene (C2H2) and carbon monoxide (CO) in contact with nickel sulfide (NiS) in hot aqueous medium. The primary products are toto-olefinic monocarboxylic acids with CO-derived COOH groups undergoing subsequent stepwise hydrogenation with CO as reductant. In the resulting unsaturated monocarboxylic acids the double bonds are mainly centrally located with mainly trans-configuration. The reaction conditions are compatible with an origin of life in volcanic-hydrothermal sub-seafloor flow ducts.

  1. Unsaturated C3,5,7,9-Monocarboxylic Acids by Aqueous, One-Pot Carbon Fixation: Possible Relevance for the Origin of Life

    PubMed Central

    Scheidler, Christopher; Sobotta, Jessica; Eisenreich, Wolfgang; Wächtershäuser, Günter; Huber, Claudia

    2016-01-01

    All scientific approaches to the origin of life share a common problem: a chemical path to lipids as main constituents of extant cellular enclosures. Here we show by isotope-controlled experiments that unsaturated C3,5,7,9-monocarboxylic acids form by one-pot reaction of acetylene (C2H2) and carbon monoxide (CO) in contact with nickel sulfide (NiS) in hot aqueous medium. The primary products are toto-olefinic monocarboxylic acids with CO-derived COOH groups undergoing subsequent stepwise hydrogenation with CO as reductant. In the resulting unsaturated monocarboxylic acids the double bonds are mainly centrally located with mainly trans-configuration. The reaction conditions are compatible with an origin of life in volcanic-hydrothermal sub-seafloor flow ducts. PMID:27283227

  2. Removal of dicyclohexyl acetic acid from aqueous solution using ultrasound, ozone and their combination.

    PubMed

    Kumar, Pardeep; Headley, John; Peru, Kerry; Bailey, Jon; Dalai, Ajay

    2014-01-01

    Naphthenic acids are a complex mixture of organic components, some of which include saturated alkyl-substituted cycloaliphatic carboxylic acids and acyclic aliphatic acids. They are naturally found in hydrocarbon deposits like oil sand, petroleum, bitumen and crude oil. In this study, the oxidation of a relatively high molecular weight naphthenic acid (Dicyclohexyl acetic acid) was investigated using ozonation, ultrasonication and hydrogen peroxide alone and their combinations. Effects on oxidation of dicyclohexyl acetic acid (DAA) were measured for different concentrations of ozone ranging between 0.7 to 3.3 mg L(-1) and pH in the range 6 to 10. Ultrasonication and hydrogen peroxide alone were not effective to oxidize dicyclohexyl acetic acid, but combining ultrasonication with H2O2 had a significant effect on oxidation of dicyclohexyl acetic acid with maximum removal reaching to 84 ± 2.2% with 81 ± 2.1% reduction in chemical oxygen demand (COD). Synergistic effects were observed for combining ultrasonication with ozonation and resulted in 100% DAA removal with 98 ± 0.8% reduction in COD within 15 min at 3.3 mg L(-1) ozone concentration and 130 Watts ultrasonication power. The reaction conditions obtained for the maximum oxidation of DAA and COD removal were used for the degradation of naphthenic acids mixture extracted from oil sands process water (OSPW). The percentage oxidation of NAs mixture extracted from OSPW was 89.3 ± 1.1% in ozonation and combined ozonation and ultrasonication, but COD removal observed was 65 ± 1.2% and 78 ± 1.4% for ozonation and combined ozonation and ultrasonication treatments, respectively.

  3. Prebiotic Nitrogen Fixation by FeS Reduction of Nitrite Under Acidic Conditions

    NASA Technical Reports Server (NTRS)

    Summers, David P.; Mead, Susan C. (Technical Monitor)

    1999-01-01

    Theories for the origin of life require the availability of reduced nitrogen for the formation of such species as amino acid and nucleic acids. In a strongly reducing atmosphere, compounds essential to the chemical evolution of life, such as amino acids, can form by reactions between HCN, NH3, and carbonyl compounds produced in spark discharges. However, under non-reducing atmospheres, electric discharges produced NO rather than HCN or NH3. This raises the questions of; how ammonia can be formed under a neutral atmosphere, and what conditions are needed such formation to occur? On possibility is the conversion of NO into nitric and nitrous acids (through HNO) and rained into the oceans. The reduction of nitrite by aqueous Fe(II) (6 Fe(+2) + 7 H(+) + NO2(-) yields 6 Fe(III) + 2 H2O + NH3) such as was present on the early Earth could then have produced ammonia. However, this reaction does not proceed at pHs less than 7.3. An alternative is reduction by other forms of Fe(II), such as FeS. We will present results that show that FeS can reduce nitrite to ammonia at pHs as low as pH 5 under a variety of conditions.

  4. Gene Expressions for Signal Transduction under Acidic Conditions

    PubMed Central

    Fukamachi, Toshihiko; Ikeda, Syunsuke; Wang, Xin; Saito, Hiromi; Tagawa, Masatoshi; Kobayashi, Hiroshi

    2013-01-01

    Although it is now well known that some diseased areas, such as cancer nests, inflammation loci, and infarction areas, are acidified, little is known about cellular signal transduction, gene expression, and cellular functions under acidic conditions. Our group showed that different signal proteins were activated under acidic conditions compared with those observed in a typical medium of around pH 7.4 that has been used until now. Investigations of gene expression under acidic conditions may be crucial to our understanding of signal transduction in acidic diseased areas. In this study, we investigated gene expression in mesothelioma cells cultured at an acidic pH using a DNA microarray technique. After 24 h culture at pH 6.7, expressions of 379 genes were increased more than twofold compared with those in cells cultured at pH 7.5. Genes encoding receptors, signal proteins including transcription factors, and cytokines including growth factors numbered 35, 32, and 17 among the 379 genes, respectively. Since the functions of 78 genes are unknown, it can be argued that cells may have other genes for signaling under acidic conditions. The expressions of 37 of the 379 genes were observed to increase after as little as 2 h. After 24 h culture at pH 6.7, expressions of 412 genes were repressed more than twofold compared with those in cells cultured at pH 7.5, and the 412 genes contained 35, 76, and 7 genes encoding receptors, signal proteins including transcription factors, and cytokines including growth factors, respectively. These results suggest that the signal pathways in acidic diseased areas are different, at least in part, from those examined with cells cultured at a pH of around 7.4. PMID:24705103

  5. Interaction of some metals between marine-origin humic acids and aqueous solutions

    SciTech Connect

    Huljev, D.J.

    1986-08-01

    The interaction of metal ions (carrier-free form) in aquatic medium with humic acids is a complicated process depending on the properties of humic acids (elementary, chemical, and trace element composition), metals studied (valence, charge, chemical form, concentration), and medium used (pH, ionic strength). The use of radionuclides was found to be very suitable for a rapid and precise determination of the distribution coefficient K/sub d/ (ratio of the concentration of a certain trace metal association with a gram of humic acid over the concentration of the same trace metal per milliliter of solution) of the investigated system. Isolated humic acids from offshore sediments from the North Adriatic (Lim channel, near Rovinj, Yugoslavia) were characterized according to their elementary composition, the amount of products of hydrolysis, and the trace elements bound. All experiments were carried out between pH 3 and 5. It was found that conditions usually present at the site where humic acid interacts with metal ions (anaerobic conditions, H/sub 2/S) in brackish (21% S) and standard seawater (38% S) are determined in the pH range 3 to 5. The results of the pick-up (uptake) and replacement (release) experiments are presented as a distribution coefficient (K/sub d/), as a function of contact time. Processes of pick-up and replacement of a number of metals under various physicochemical conditions were investigated and special attention was paid to the influence of salinity. With the increase in NaCl concentration and pH in the system, the fixation of ruthenium, zinc, cobalt, and mercury by humic acids decreased.

  6. Theoretical insights into the properties of amino acid ionic liquids in aqueous solution.

    PubMed

    Zhu, Xueying; Ai, Hongqi

    2016-07-01

    This report presents a systematic investigation of the interactions of water molecule(s) with a series of amino acid cations (Gly(+), Ala(+), Val(+), and Leu(+)), halogen anions (Cl(-), Br(-), BF4 (-), and PF6 (-)), and clusters (GlyCl) n (n = 1-5). The results reveal that H-bonds between amino acid ionic liquids (AAILs) and water molecules are crucial to the properties of aqueous solution of AAILs. The properties of AAIL in water solution depend on the alkyl chain of the amino acid cation, the size of the halogen anion, and the number of water molecules, which provides a certain theoretical basis for the design and application of new AAILs. A series of calculations for some different models showed that quadruple-GlyCl hydrate represents a basic unit for the Gly-water binary system, and can be employed as the simplest model for studying an AAIL-water cluster. On the basis of this model, the effects of water on the hygroscopicity, speed of solubility, viscosity, density, solution enthalpy, and polarity of the AAIL were also predicted. Most importantly, unlike traditional ILs, the novel GlyCl-type AAIL favors interaction of its cationic part, rather than its anionic part, with surrounding water molecules, thus amino acid cationic ILs expand the types of IL available, increasing the choice of ILs for different purposes. We hope that the application of this AAIL in many fields will lead to optimization of this class of compound and be of benefit to the environment. Graphical Abstract Quadruple-GlyCl hydrate represents the basic unit for a GlyCl-water binary system, which can be employed as the simplest model for studying an amino acid ionic liquid (AAIL)-water cluster. The effects of available water on some properties of AAIL are predicted. GlyCl-type AAIL is a novel IL, which prefers its cationic part over its anionic part for interaction with surrounding water molecules. The properties of AAIL in water solution can be adjusted by varying the ion used and the

  7. Theoretical insights into the properties of amino acid ionic liquids in aqueous solution.

    PubMed

    Zhu, Xueying; Ai, Hongqi

    2016-07-01

    This report presents a systematic investigation of the interactions of water molecule(s) with a series of amino acid cations (Gly(+), Ala(+), Val(+), and Leu(+)), halogen anions (Cl(-), Br(-), BF4 (-), and PF6 (-)), and clusters (GlyCl) n (n = 1-5). The results reveal that H-bonds between amino acid ionic liquids (AAILs) and water molecules are crucial to the properties of aqueous solution of AAILs. The properties of AAIL in water solution depend on the alkyl chain of the amino acid cation, the size of the halogen anion, and the number of water molecules, which provides a certain theoretical basis for the design and application of new AAILs. A series of calculations for some different models showed that quadruple-GlyCl hydrate represents a basic unit for the Gly-water binary system, and can be employed as the simplest model for studying an AAIL-water cluster. On the basis of this model, the effects of water on the hygroscopicity, speed of solubility, viscosity, density, solution enthalpy, and polarity of the AAIL were also predicted. Most importantly, unlike traditional ILs, the novel GlyCl-type AAIL favors interaction of its cationic part, rather than its anionic part, with surrounding water molecules, thus amino acid cationic ILs expand the types of IL available, increasing the choice of ILs for different purposes. We hope that the application of this AAIL in many fields will lead to optimization of this class of compound and be of benefit to the environment. Graphical Abstract Quadruple-GlyCl hydrate represents the basic unit for a GlyCl-water binary system, which can be employed as the simplest model for studying an amino acid ionic liquid (AAIL)-water cluster. The effects of available water on some properties of AAIL are predicted. GlyCl-type AAIL is a novel IL, which prefers its cationic part over its anionic part for interaction with surrounding water molecules. The properties of AAIL in water solution can be adjusted by varying the ion used and the

  8. Ab Initio Molecular Dynamics Simulations of Amino Acids in Aqueous Solutions: Estimating pKa Values from Metadynamics Sampling.

    PubMed

    Tummanapelli, Anil Kumar; Vasudevan, Sukumaran

    2015-09-17

    Changes in the protonation and deprotonation of amino acid residues in proteins play a key role in many biological processes and pathways. Here, we report calculations of the free-energy profile for the protonation-deprotonation reaction of the 20 canonical α amino acids in aqueous solutions using ab initio Car-Parrinello molecular dynamics simulations coupled with metadynamics sampling. We show here that the calculated change in free energy of the dissociation reaction provides estimates of the multiple pKa values of the amino acids that are in good agreement with experiment. We use the bond-length-dependent number of the protons coordinated to the hydroxyl oxygen of the carboxylic and the amine groups as the collective variables to explore the free-energy profiles of the Bronsted acid-base chemistry of amino acids in aqueous solutions. We ensure that the amino acid undergoing dissociation is solvated by at least three hydrations shells with all water molecules included in the simulations. The method works equally well for amino acids with neutral, acidic and basic side chains and provides estimates of the multiple pKa values with a mean relative error, with respect to experimental results, of 0.2 pKa units. PMID:26331783

  9. Ab Initio Molecular Dynamics Simulations of Amino Acids in Aqueous Solutions: Estimating pKa Values from Metadynamics Sampling.

    PubMed

    Tummanapelli, Anil Kumar; Vasudevan, Sukumaran

    2015-09-17

    Changes in the protonation and deprotonation of amino acid residues in proteins play a key role in many biological processes and pathways. Here, we report calculations of the free-energy profile for the protonation-deprotonation reaction of the 20 canonical α amino acids in aqueous solutions using ab initio Car-Parrinello molecular dynamics simulations coupled with metadynamics sampling. We show here that the calculated change in free energy of the dissociation reaction provides estimates of the multiple pKa values of the amino acids that are in good agreement with experiment. We use the bond-length-dependent number of the protons coordinated to the hydroxyl oxygen of the carboxylic and the amine groups as the collective variables to explore the free-energy profiles of the Bronsted acid-base chemistry of amino acids in aqueous solutions. We ensure that the amino acid undergoing dissociation is solvated by at least three hydrations shells with all water molecules included in the simulations. The method works equally well for amino acids with neutral, acidic and basic side chains and provides estimates of the multiple pKa values with a mean relative error, with respect to experimental results, of 0.2 pKa units.

  10. 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.

  11. Degradation rates of glycerol polyesters at acidic and basic conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Polyesters prepared from glycerol with mixtures of adipic and citric acids were evaluated in the laboratory to estimate degradation rates over a range of pH conditions. These renewable polymers provide a market for glycerol that is generated during biodiesel production. The polyesters were prepared...

  12. Gold supported on zirconia polymorphs for hydrogen generation from formic acid in base-free aqueous medium

    NASA Astrophysics Data System (ADS)

    Bi, Qing-Yuan; Lin, Jian-Dong; Liu, Yong-Mei; He, He-Yong; Huang, Fu-Qiang; Cao, Yong

    2016-10-01

    Formic acid (FA) has attracted considerable attention as a safe and convenient hydrogen storage material for renewable energy transformation. However, development of an efficient heterogeneous catalyst for selective FA decomposition for ultraclean H2 gas in the absence of any alkalis or additives under mild conditions remains a major challenge. Based on our previous work on Au/ZrO2 as a robust and efficient catalyst for FA dehydrogenation in amine system, we report here ZrO2 with different nanocrystal polymorphs supported Au nanoparticles can achieve near completion of FA dehydrogenation in base-free aqueous medium. Of significant importance is that an excellent rate of up to 81.8 L H2 gAu-1 h-1 in open system and highly pressurized gas of 5.9 MPa in closed one can be readily attained at 80 °C for Au/m-ZrO2. In situ diffuse reflectance infrared Fourier transform (DRIFT) and CO2-temperature programmed desorption (TPD) techniques revealed that Au/m-ZrO2 exhibits a higher density of surface basic sites than Au/t-ZrO2 and Au/a-ZrO2. Basic sites in surface can substantially facilitate crucial FA deprotonation process which appears to be a key factor for achieving high dehydrogenation activity. The H/D exchange between solvent of H2O and substrate of FA was observed by the kinetic isotope effect experiments.

  13. Impact of sunlight and humic acid on the deposition kinetics of aqueous fullerene nanoparticles (nC60).

    PubMed

    Qu, Xiaolei; Alvarez, Pedro J J; Li, Qilin

    2012-12-18

    Nanoparticle transport in natural settings is complex due to interactions with the surrounding environment. In this study, the impact of UVA irradiation and humic acid (HA) on deposition of aqueous fullerene nanoparticles (nC₆₀) on a silica surface as a surrogate for natural sediments was studied using packed column experiments and quartz crystal microbalance with dissipation monitoring under various solution conditions. Surface oxidation of nC₆₀ induced by UVA irradiation greatly retarded its deposition due to the increased negative surface charge and hydrophilicity. Dissolved HA, once adsorbed onto the nC₆₀ surface, also hindered its deposition mainly through steric hindrance forces. The extent of this effect depended on the properties and the amount of HA adsorbed, which is a function of ionic strength and HA concentration. HA has limited adsorption on UVA-irradiated nC₆₀ and is expected to play a less important role in its stability. HA immobilized onto the silica surface had a variable effect on nC₆₀ deposition, depending on the complex interplay of Derjaguin-Landau-Verwey-Overbeek (DLVO) and non-DLVO interactions such as electrostatic interaction, steric hindrance, and hydrogen bonding as well as HA molecular conformation. These results highlight the importance of environment-induced changes in nC₆₀ surface chemistry in its fate and transport in aquatic environments.

  14. 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.

  15. [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

  16. Adsorption of Acid Red 57 from aqueous solutions onto surfactant-modified sepiolite.

    PubMed

    Ozcan, Adnan; Ozcan, A Safa

    2005-10-17

    The adsorption of Acid Red 57 (AR57) onto surfactant-modified sepiolite was investigated in aqueous solution in a batch system with respect to contact time, pH and temperature. The surface modification of surfactant-modified sepiolite was controlled using the FTIR technique. The pseudo-first-order, pseudo-second-order kinetic models and the intraparticle diffusion model were used to describe the kinetic data and the rate constants were evaluated. The experimental data fitted very well the pseudo-second-order kinetic model and also followed the intraparticle diffusion model up to 90 min, whereas diffusion is not only the rate controlling step. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were also determined. The Freundlich model agrees with experimental data well. The activation energy, change of free energy, enthalpy and entropy of adsorption were also evaluated for the adsorption of AR57 onto surfactant-modified sepiolite. The results indicate that surfactant-modified sepiolite could be employed as low-cost material for the removal of textile dyes from effluents. PMID:16019142

  17. 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.

  18. Aqueous acidities of primary benzenesulfonamides: Quantum chemical predictions based on density functional theory and SMD.

    PubMed

    Aidas, Kęstutis; Lanevskij, Kiril; Kubilius, Rytis; Juška, Liutauras; Petkevičius, Daumantas; Japertas, Pranas

    2015-11-01

    Aqueous pK(a) of selected primary benzenesulfonamides are predicted in a systematic manner using density functional theory methods and the SMD solvent model together with direct and proton exchange thermodynamic cycles. Some test calculations were also performed using high-level composite CBS-QB3 approach. The direct scheme generally does not yield a satisfactory agreement between calculated and measured acidities due to a severe overestimation of the Gibbs free energy changes of the gas-phase deprotonation reaction by the used exchange-correlation functionals. The relative pK(a) values calculated using proton exchange method compare to experimental data very well in both qualitative and quantitative terms, with a mean absolute error of about 0.4 pK(a) units. To achieve this accuracy, we find it mandatory to perform geometry optimization of the neutral and anionic species in the gas and solution phases separately, because different conformations are stabilized in these two cases. We have attempted to evaluate the effect of the conformer-averaged free energies in the pK(a) predictions, and the general conclusion is that this procedure is highly too costly as compared with the very small improvement we have gained.

  19. 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.

  20. Adsorption of Benzoic Acid in Aqueous Solution by Bagasse Fly Ash

    NASA Astrophysics Data System (ADS)

    Suresh, S.

    2012-09-01

    This paper reports the studies on the benzoic acid (BA) onto bagasse fly ash (BFA) was studied in aqueous solution in a batch system. Physico-chemical properties including surface area, surface texture of the GAC before and after BA adsorption onto BFA were analysed using X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The optimum initial pH for the adsorption of BA was found to be 5.56. The adsorbent dose was 10 g/l for BFA and the equilibrium time 8 h of reaction. Pseudo first and second order models were used to find the adsorption kinetics. It was found that intraparticle diffusion played important role in the adsorption mechanisms of BA and the adsorption kinetics followed pseudo-second order kinetic model rather than the pseudo first order kinetic model. Isotherm data were generated for BA solution having initial concentrations of BA in the range of 10-200 mg/l for the BFA dosage of 10 g/l at temperatures of 288, 303, and 318 K. The adsorption of BA onto BFA was favorably influenced by an increase in temperature. Equilibrium data were well represented by the Redlich-Peterson isotherm model. Values of the change in entropy ( ΔS 0), heat of adsorption ( ΔH 0) for adsorption of BA on BFA was found to be 120.10 and 19.61 kJ/mol respectively. The adsorption of BA onto BFA was an endothermic reaction. Desorption of BA from BFA was studied by various solvents method. Acetic acid was found to be a better eluant for desorption of BA with a maximum desorption efficiency of 55.2 %. Owing to its heating value, spent BFA can be used as a co-fuel for the production of heat in boiler furnaces.

  1. Towards the experimental decomposition rate of carbonic acid (H2CO3) in aqueous solution.

    PubMed

    Tautermann, Christofer S; Voegele, Andreas F; Loerting, Thomas; Kohl, Ingrid; Hallbrucker, Andreas; Mayer, Erwin; Liedl, Klaus R

    2002-01-01

    Dry carbonic acid has recently been shown to be kinetically stable even at room temperature. Addition of water molecules reduces this stability significantly, and the decomposition (H2CO3 + nH2O --> (n+1)H2O + CO2) is extremely accelerated for n = 1, 2, 3. By including two water molecules, a reaction rate that is a factor of 3000 below the experimental one (10 s(-1)) at room temperature was found. In order to further remove the gap between experiment and theory, we increased the number of water molecules involved to 3 and took into consideration different mechanisms for thorough elucidation of the reaction. A mechanism whereby the reaction proceedes via a six-membered transition state turns out to be the most efficient one over the whole examined temperature range. The determined reaction rates approach experimental values in aqueous solution reasonably well; most especially, a significant increase in the rates in comparison to the decomposition reaction with fewer water molecules is found. Further agreement with experiment is found in the kinetic isotope effects (KIE) for the deuterated species. For water-free carbonic acid, the KIE (i.e., kH2CO3/kD2CO3) for the decomposition reaction is predicted to be 220 at 300 K, whereas it amounts to 2.2-3.0 for the investigated mechanisms including three water molecules. This result is therefore reasonably close to the experimental value of 2 (at 300 K). These KIEs are in much better accordance with the experiment than the KIE for decomposition with fewer water entities. PMID:11822465

  2. Experimental aqueous alteration of the Allende meteorite under oxidizing conditions: Constraints on asteroidal alteration

    NASA Astrophysics Data System (ADS)

    Jones, Catherine L.; Brearley, Adrian J.

    2006-02-01

    We have performed an experimental study of the aqueous alteration of the Allende CV3 carbonaceous chondrite under highly oxidizing conditions, in order to examine the alteration behavior of Allende's anhydrous mineralogy. The experiments were carried out at temperatures of 100, 150, and 200 °C, for time periods between 7 and 180 days, with water/rock ratios ranging from 1:1 to 9:1. Uncrushed cubes of Allende were used so that the spatial relationships between reactant and product phases could be examined in detail. Scanning electron microscope studies show that in all the experiments, even those of short duration (7 days), soluble salts of Ca and Mg (CaSO 4, CaCO 3, and MgSO 4) precipitated on the sample surface, indicating that these elements are rapidly mobilized during alteration. In addition, iron oxides and hydroxides formed on the sample surfaces. The sulfates, carbonates, and the majority of the iron-bearing secondary minerals are randomly distributed over the surface of samples. In some instances the iron oxides and hydroxides are constrained to the boundaries of altering mineral grains. Transmission electron microscope studies show that the FeO-rich olivine in the interior of the samples has altered to form interlayered serpentine/saponite and Fe-oxyhydroxides. The degree of alteration increases significantly with increasing water/rock ratio, and to a lesser extent with increasing duration of heating. The serpentine/saponite forms both by direct replacement of the olivine in crystallographically oriented intergrowths, and by recrystallization of an amorphous Si-rich phase that precipitates in pore space between the olivine grains. The alteration assemblage bears many similarities to those found in altered carbonaceous chondrites, although in detail there are important differences, which we attribute to (a) the relatively high temperatures of our experiments and (b) comparatively short reaction times compared with the natural examples. In terms of mineral

  3. The distribution of methane in groundwater in Alberta (Canada) and associated aqueous geochemistry conditions

    NASA Astrophysics Data System (ADS)

    Humez, Pauline; Mayer, Bernhard; Nightingale, Michael; Becker, Veith; Kingston, Andrew; Taylor, Stephen; Millot, Romain; Kloppmann, Wolfram

    2016-04-01

    Development of unconventional energy resources such as shale gas and coalbed methane has generated some public concern with regard to the protection of groundwater and surface water resources from leakage of stray gas from the deep subsurface. In terms of environmental impact to and risk assessment of shallow groundwater resources, the ultimate challenge is to distinguish: (a) natural in-situ production of biogenic methane, (b) biogenic or thermogenic methane migration into shallow aquifers due to natural causes, and (c) thermogenic methane migration from deep sources due to human activities associated with the exploitation of conventional or unconventional oil and gas resources. We have conducted a NSERC-ANR co-funded baseline study investigating the occurrence of methane in shallow groundwater of Alberta (Canada), a province with a long record of conventional and unconventional hydrocarbon exploration. Our objective was to assess the occurrence and sources of methane in shallow groundwaters and to also characterize the hydrochemical environment in which the methane was formed or transformed through redox processes. Ultimately our aim was to determine whether methane was formed in-situ or whether it migrated from deeper formations into shallow aquifers. Combining hydrochemical and dissolved and free geochemical gas data from 372 groundwater samples obtained from 186 monitoring wells of the provincial groundwater observation well network (GOWN) in Alberta, it was found that methane is ubiquitous in groundwater in Alberta and is predominantly of biogenic origin. The highest concentrations of dissolved biogenic methane (> 0.01 mM or > 0.2 mg/L), characterized by δ13CCH4 values < -55‰, occurred in anoxic Na-Cl, Na-HCO3 and Na-HCO3-Cl type groundwater with negligible concentrations of nitrate and sulfate suggesting that methane was formed in-situ under methanogenic conditions consistent with the redox ladder concept. Despite quite variable gas concentrations and a

  4. Synthesis and chirality of amino acids under interstellar conditions.

    PubMed

    Giri, Chaitanya; Goesmann, Fred; Meinert, Cornelia; Evans, Amanda C; Meierhenrich, Uwe J

    2013-01-01

    Amino acids are the fundamental building blocks of proteins, the biomolecules that provide cellular structure and function in all living organisms. A majority of amino acids utilized within living systems possess pre-specified orientation geometry (chirality); however the original source for this specific orientation remains uncertain. In order to trace the chemical evolution of life, an appreciation of the synthetic and evolutional origins of the first chiral amino acids must first be gained. Given that the amino acids in our universe are likely to have been synthesized in molecular clouds in interstellar space, it is necessary to understand where and how the first synthesis might have occurred. The asymmetry of the original amino acid synthesis was probably the result of exposure to chiral photons in the form of circularly polarized light (CPL), which has been detected in interstellar molecular clouds. This chirality transfer event, from photons to amino acids, has been successfully recreated experimentally and is likely a combination of both asymmetric synthesis and enantioselective photolysis. A series of innovative studies have reported successful simulation of these environments and afforded production of chiral amino acids under realistic circumstellar and interstellar conditions: irradiation of interstellar ice analogues (CO, CO2, NH3, CH3OH, and H2O) with circularly polarized ultraviolet photons at low temperatures does result in enantiomer enriched amino acid structures (up to 1.3% ee). This topical review summarizes current knowledge and recent discoveries about the simulated interstellar environments within which amino acids were probably formed. A synopsis of the COSAC experiment onboard the ESA cometary mission ROSETTA concludes this review: the ROSETTA mission will soft-land on the nucleus of the comet 67P/Churyumov-Gerasimenko in November 2014, anticipating the first in situ detection of asymmetric organic molecules in cometary ices.

  5. Synthesis and chirality of amino acids under interstellar conditions.

    PubMed

    Giri, Chaitanya; Goesmann, Fred; Meinert, Cornelia; Evans, Amanda C; Meierhenrich, Uwe J

    2013-01-01

    Amino acids are the fundamental building blocks of proteins, the biomolecules that provide cellular structure and function in all living organisms. A majority of amino acids utilized within living systems possess pre-specified orientation geometry (chirality); however the original source for this specific orientation remains uncertain. In order to trace the chemical evolution of life, an appreciation of the synthetic and evolutional origins of the first chiral amino acids must first be gained. Given that the amino acids in our universe are likely to have been synthesized in molecular clouds in interstellar space, it is necessary to understand where and how the first synthesis might have occurred. The asymmetry of the original amino acid synthesis was probably the result of exposure to chiral photons in the form of circularly polarized light (CPL), which has been detected in interstellar molecular clouds. This chirality transfer event, from photons to amino acids, has been successfully recreated experimentally and is likely a combination of both asymmetric synthesis and enantioselective photolysis. A series of innovative studies have reported successful simulation of these environments and afforded production of chiral amino acids under realistic circumstellar and interstellar conditions: irradiation of interstellar ice analogues (CO, CO2, NH3, CH3OH, and H2O) with circularly polarized ultraviolet photons at low temperatures does result in enantiomer enriched amino acid structures (up to 1.3% ee). This topical review summarizes current knowledge and recent discoveries about the simulated interstellar environments within which amino acids were probably formed. A synopsis of the COSAC experiment onboard the ESA cometary mission ROSETTA concludes this review: the ROSETTA mission will soft-land on the nucleus of the comet 67P/Churyumov-Gerasimenko in November 2014, anticipating the first in situ detection of asymmetric organic molecules in cometary ices. PMID:22976459

  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. Modeling of matrix acidizing process under reservoir conditions

    NASA Astrophysics Data System (ADS)

    Turegeldieva, Karlygash; Assilbekov, Bakhytzhan; Zhapbasbayev, Uzak; Zolotukhin, Anatoly; Bekibaev, Timur; Kenzhebekov, Nurlan; Gubkin Russian State University of oil; gas Collaboration

    2013-11-01

    Effectiveness of the process depends on the parameters: well choice, geological structure of the reservoir, definition of physical and chemical properties of rocks and fluids, agent choice. There are different mathematical models of the matrix acidizing, including the two scale model. These models describe the process in the core scale and Darcy scale, i.e. in an area with dimensions of several centimeters. It leads to the main problem - how to use these models to the near wellbore scale under reservoir conditions. Some authors have increased the dimensions of the cores in numerical simulations and investigated the influence of the core dimensions to acidizing process. In this paper effort to indirectly solve this problem made. It based on boundary conditions alteration and simultaneous solution of matrix acidizing in damaged zone and reservoir fluid flow models. Furthermore in this work the criterion of the acid injection shut down for optimal breakthrough volume calculation was modified. Influence of boundary conditions on near well-bore zone treatment process was investigated. Science Committee of Ministry of Education and Science of Republic of Kazakhstan.

  8. Sorption of carboxylic acid from carboxylic salt solutions at PHS close to or above the pK.sub.a of the acid, with regeneration with an aqueous solution of ammonia or low-molecular-weight alkylamine

    DOEpatents

    King, C. Judson; Tung, Lisa A.

    1992-01-01

    Carboxylic acids are sorbed from aqueous feedstocks at pHs close to or above the acids' pH.sub.a into a strongly basic organic liquid phase or onto a basic solid adsorbent or moderately basic ion exchange resin. the acids are freed from the sorbent phase by treating it with aqueous alkylamine or ammonia thus forming an alkylammonium or ammonium carobxylate which dewatered and decomposed to the desired carboxylic acid and the alkylamine or ammonia.

  9. Sorption of carboxylic acid from carboxylic salt solutions at pHs close to or above the pK[sub a] of the acid, with regeneration with an aqueous solution of ammonia or low-molecular-weight alkylamine

    DOEpatents

    King, C.J.; Tung, L.A.

    1992-07-21

    Carboxylic acids are sorbed from aqueous feedstocks at pHs close to or above the acids' pH[sub a] into a strongly basic organic liquid phase or onto a basic solid adsorbent or moderately basic ion exchange resin. The acids are freed from the sorbent phase by treating it with aqueous alkylamine or ammonia thus forming an alkylammonium or ammonium carboxylate which dewatered and decomposed to the desired carboxylic acid and the alkylamine or ammonia. 8 figs.

  10. Hydrolysis of aceto-hydroxamic acid under UREX+ conditions

    SciTech Connect

    Alyapyshev, M.; Paulenova, A.; Tkac, P.; Cleveland, M.A.; Bruso, J.E.

    2007-07-01

    Aceto-hydroxamic acid (AHA) is used as a stripping agent In the UREX process. While extraction yields of uranium remain high upon addition of AHA, hexavalent plutonium and neptunium are rapidly reduced to the pentavalent state while the tetravalent species and removed from the product stream. However, under acidic conditions, aceto-hydroxamic acid undergoes hydrolytic degradation. In this study, the kinetics of the hydrolysis of aceto-hydroxamic acid in nitric and perchloric acid media was investigated at several temperatures. The decrease of the concentration of AHA was determined via its ferric complex using UV-Vis spectroscopy. The data obtained were analyzed using the method of initial rates. The data follow the pseudo-first order reaction model. Gamma irradiation of AHA/HNO{sub 3} solutions with 33 kGy/s caused two-fold faster degradation of AHA. The rate equation and thermodynamic data will be presented for the hydrolysis reaction with respect to the concentrations of aceto-hydroxamic acid, nitrate and hydronium ions, and radiation dose. (authors)

  11. Evidence for compounds hydrolyzable to amino acids in aqueous extracts of apollo 11 and apollo 12 lunar fines.

    PubMed

    Harada, K; Hare, P E; Windsor, C R; Fox, S W

    1971-07-30

    Hydrolyzates of aqueous extracts of Apollo 11 fines, an Apollo 12 trench sample, and an Apollo 12 surface sample have been analyzed on an ultrasensitive amino acid analyzer. The total content of amino acids recovered ranged from 20 to 70 parts per billion of lunar soil. Amino acids are not recovered by the direct hydrolysis of lunar fines, presumably because of decomposition in the presence of the large excess of lunar mineral. As judged by retention time, glycine is the dominant amino acid found; alanine is secondarily present in each case in the profile. Only a few amino acids have been recorded in each analysis. The pattern is relatively consistent in the samples from the three locations; the pattern from either hydrolyzed or unhydrolyzed extracts differs markedly from that of hydrolyzed or unhydrolyzed handprints. The evidence is not consistent with contamination of the kind expected by many investigators.

  12. Kinetic and equilibrium studies on the removal of acid dyes from aqueous solutions by adsorption onto activated carbon cloth.

    PubMed

    Hoda, Numan; Bayram, Edip; Ayranci, Erol

    2006-09-01

    Removal of acid dyes Acid Blue 45, Acid Blue 92, Acid Blue 120 and Acid Blue 129 from aqueous solutions by adsorption onto high area activated carbon cloth (ACC) was investigated. Kinetics of adsorption was followed by in situ UV-spectroscopy and the data were treated according to pseudo-first-order, pseudo-second-order and intraparticle diffusion models. It was found that the adsorption process of these dyes onto ACC follows the pseudo-second-order model. Adsorption isotherms were derived at 25 degrees C on the basis of batch analysis. Isotherm data were treated according to Langmuir and Freundlich models. The fits of experimental data to these equations were examined. PMID:16563617

  13. Decolourization performance in C. I. Vat Yellow 1 aqueous suspension using hydrophobically modified poly(acrylic acid).

    PubMed

    Chen, J; Chen, M C

    2011-01-01

    A series of hydrophobically modified poly(acrylic acid) (PAA), poly(2-phenoxyethyl acrylate-co-acrylic acid) (poly(PHEA-co-AA)), have been synthesized and characterized by Ubbelohde type viscometry, Nuclear Magnetic Resonance (1H NMR) spectrometry and Differential Scanning Calorimetry (DSC). The shear thinning Non-Newtonian fluid behavior of their aqueous solution and the dependence on pH and hydrophobic group contents were found through apparent viscosity and rheological property investigating. Decolourization performance in C. I. Vat Yellow 1 aqueous suspension was evaluated through visible absorbance data. Decolourization performance of hydrophobically associated polymer indicates two times better than that of PAA. The quantitative relationship was mainly studied. PMID:21866762

  14. Organic-inorganic interaction between hydroxyapatite and gelatin with the aging of gelatin in aqueous phosphoric acid solution.

    PubMed

    Chang, Myung Chul

    2008-11-01

    Hydroxyapatite (HAp)/gelatin (GEL) nanocomposite was prepared by the solution-precipitation process using Ca(OH)(2) in water and aqueous solution of H(3)PO(4) in GEL. Before the co precipitation process the GEL powders were dissolved in the aqueous phosphoric acid solution for the phosphorylation of GEL molecules. The chemical variation of the phosphorylated GEL macromolecules was investigated by using attenuated total reflection (ATR) measurement. The crystal growth of HAp became bigger with the long-time aging of the GEL molecules in the phosphoric acid solution, and it resulted from the reduction of length scale of the GEL molecules. The degree of the organic-inorganic interaction was decreased because of the degradation of the GEL macromolecules.

  15. Non-aqueous gel polymer electrolyte with phosphoric acid ester and its application for quasi solid-state supercapacitors

    NASA Astrophysics Data System (ADS)

    Łatoszyńska, Anna A.; Żukowska, Grażyna Zofia; Rutkowska, Iwona A.; Taberna, Pierre-Louis; Simon, Patrice; Kulesza, Pawel J.; Wieczorek, Władysław

    2015-01-01

    A mechanically-stable non-aqueous proton-conducting gel polymer electrolyte that is based on methacrylate monomers, is considered here for application in solid-state type supercapacitors. An electrochemical cell using activated carbon as active materials and the new gel polymer electrolyte has been characterized at room temperature using cyclic voltammetry, galvanostatic charge-discharge cycle tests as well as impedance spectroscopy. The use of phosphoric acid ester (instead of phosphoric acid) as a proton donor has led to an increase of both the operation voltage window (up to 1.3 V) and the electrolyte ionic conductivity (on the level of an order of magnitude). The resulting double layer capacitance of the microporous activated carbon was found to be as high as 120 F g-1; even more important, the supercapacitor utilizing non-aqueous proton-conducting gel polymer electrolyte is well-behaved in the wide temperature range (namely, from -40 to 80 °C).

  16. Study of the decomposition pathway of 12-molybdophosphoric acid in aqueous solutions by micro Raman spectroscopy.

    PubMed

    Bajuk-Bogdanović, D; Uskoković-Marković, S; Hercigonja, R; Popa, A; Holclajtner-Antunović, I

    2016-01-15

    Micro Raman spectroscopy was applied to investigate the speciation of heteropoly and isopoly molybdates in 0.05 and 0.005 M aqueous solutions of 12-molybdophosphoric acid at pH values between 1 and 6. For comparative purposes, (31)P NMR spectroscopy was applied too. It is shown that stability of Keggin anion is influenced both by pH and concentration of solution. The Keggin structure is stable in acidic solutions (pH<1.6) while defective Keggin structures are formed with further alkalization (up to pH5.6). Monolacunary anion PMo11O(39)(7-) is the main component in the pH region from 1.6 to 3.4. Further removal of molybdenyl species causes the appearance of other vacant Keggin structures such as PMo9O31(OH)(3)(6-) and PMo6O(25)(9-) at about pH4. At pH5.0, anion PMo6O(25)(9-) is the main species. In solutions with pH greater than 5.0, heteropolymolybdates disappear completely and isopolymolybdates Mo7O(24)(6-) and MoO(4)(2-) are formed in higher amounts. In more diluted solution of 0.005 M, the decomposition scheme of 12-molybdophosphoric acid solution with increasing of pH takes place without observation of significant amounts of Mo7O(24)(6-) species. If alkalinization is performed with 0.5 M instead of 5 M NaOH, there are no significant changes in the Raman spectra of solutions. It is shown that the spectra of evaporated samples may be used for the identification of molecular species in corresponding concentrated solutions. However, Raman spectra of dry residues of more diluted solutions differ from spectra of corresponding solutions due to the reactions performed during the process of drying and cannot be used for unambiguous identification of species in solution. Acidification of 0.05 M solution of Na2MoO4 shows that at pH>5.6, molybdate anion MoO(4)(2-) dominates, while in the pH range between 5.6 and 1, heptamolybdate anion Mo7O(24)(6-) is preferentially formed.

  17. Conductometric and fluorometric studies of sodium dodecyl sulphate in aqueous solution and in the presence of amino acids

    NASA Astrophysics Data System (ADS)

    Ali, Anwar; Malik, Nisar Ahmad; Uzair, Sahar; Ali, Maroof

    2014-10-01

    The critical micelle concentration (CMC) of sodium dodecyl sulphate (SDS) in pure water and in the presence of amino acids (0.01, 0.02 and 0.03 mol kg-1), L-valine (Val) and L-leucine (Leu) was determined from conductometric and fluorometric methods using pyrene as luminescence probe. Depression in the CMC at low concentration of amino acids is attributed to the increased hydrophobic-hydrophobic interaction between the non-polar groups of the surfactant, while, at high concentration, amino acids bind strongly with the anion, DS-, head groups of SDS, thereby, delaying the micelle formation, resulting in increased CMC. A pronounced decrease in the CMC, while a marked increase in λ0+, with decrease in the solvated radius (rather than crystal radius) of the counterions is observed. Negative values of ΔG0m and ΔH0m indicate that micellisation of SDS in the presence of amino acids is thermodynamically spontaneous and exothermic. Highest negative value of ΔH0m in 0.01 m Val, with lowest CMC value, shows that 0.01 m aqueous Val is the most suitable medium favouring the micellisation of SDS. Decrease in I1/I3 from Val to Leu confirms the relative hydrophobicity of two amino acids. The observed values of the packing parameter, P, of SDS in water and in aqueous amino acids suggest that micelles formed are spherical in nature.

  18. Analysis of. gamma. -radiolysis products of aqueous solutions of esters of aliphatic amino acids by the PMR method

    SciTech Connect

    Panin, V.I.; Sidorov, P.S.; Usatyi, A.F.

    1987-09-01

    The ..gamma..-radiolysis of aqueous solutions of methyl esters of aliphatic amino acids and peptides was investigated by the method of nuclear (proton) magnetic resonance (PMR). The resonance lines appearing in the PMR spectra of the irradiated systems were identified, and a conclusion was drawn about the molecular structure of the radiolysis products. The kinetics of the accumulation of radiolysis products was studied, and the values of their radiation yields were estimated.

  19. Water-Soluble Nonconjugated Polymer Nanoparticles with Strong Fluorescence Emission for Selective and Sensitive Detection of Nitro-Explosive Picric Acid in Aqueous Medium.

    PubMed

    Liu, Shi Gang; Luo, Dan; Li, Na; Zhang, Wei; Lei, Jing Lei; Li, Nian Bing; Luo, Hong Qun

    2016-08-24

    Water-soluble nonconjugated polymer nanoparticles (PNPs) with strong fluorescence emission were prepared from hyperbranched poly(ethylenimine) (PEI) and d-glucose via Schiff base reaction and self-assembly in aqueous phase. Preparation of the PEI-d-glucose (PEI-G) PNPs was facile (one-pot reaction) and environmentally friendly under mild conditions. Also, PEI-G PNPs showed a high fluorescence quantum yield in aqueous solution, and the fluorescence properties (such as concentration- and solvent-dependent fluorescence) and origin of intrinsic fluorescence were investigated and discussed. PEI-G PNPs were then used to develop a fluorescent probe for fast, selective, and sensitive detection of nitro-explosive picric acid (PA) in aqueous medium, because the fluorescence can be easily quenched by PA whereas other nitro-explosives and structurally similar compounds only caused negligible quenching. A wide linear range (0.05-70 μM) and a low detection limit (26 nM) were obtained. The fluorescence quenching mechanism was carefully explored, and it was due to a combined effect of electron transfer, resonance energy transfer, and inner filter effect between PA and PEI-G PNPs, which resulted in good selectivity and sensitivity for PA. Finally, the developed sensor was successfully applied to detection of PA in environmental water samples. PMID:27471907

  20. An Aqueous Thermodynamic Model for the Complexation of Sodium and Strontium with Organic Chelates valid to High Ionic Strength. I. Ethylenedinitrilotetraacetic acid (EDTA)

    SciTech Connect

    Felmy, Andrew R.; Mason, Marvin J.

    2003-04-01

    An aqueous thermodynamic model is developed, which accurately describes the effects of Na+ complexation, ionic strength, carbonate concentration, and temperature on the complexation of Sr2+ by ethylenedinitrilotetraacetic acid (EDTA) under basic conditions. The model is developed from the analysis of literature data on apparent equilibrium constants, enthalpies, and heat capacities; as well as on an extensive set of solubility data on SrCO3(c) in the presence of EDTA obtained as part of this study. The solubility data for SrCO3(c) were obtained in solutions ranging in Na2CO3 concentration from 0.01m to 1.8m, in NaNO3 concentration from 0 to 5m, and at temperatures extending to 75?C. The final aqueous thermodynamic model is based upon the equations of Pitzer and requires the inclusion of a NaEDTA3- species. An accurate model for the ionic strength dependence of the ion-interaction coefficients for the SrEDTA2- and NaEDTA3- aqueous species allows the extrapolation of standard state equilibrium constants for these species which are significantly different from the 0.1m reference state values available in the literature. The final model is tested by application to chemical systems containing competing metal ions (i.e., Ca2+) to further verify the proposed model and indicate the applicability of the model parameters to chemical systems containing other divalent metal-EDTA complexes.

  1. Complexes of earth-abundant metals for catalytic electrochemical hydrogen generation under aqueous conditions.

    PubMed

    Thoi, V Sara; Sun, Yujie; Long, Jeffrey R; Chang, Christopher J

    2013-03-21

    Growing global energy demands and climate change motivate the development of new renewable energy technologies. In this context, water splitting using sustainable energy sources has emerged as an attractive process for carbon-neutral fuel cycles. A key scientific challenge to achieving this overall goal is the invention of new catalysts for the reductive and oxidative conversions of water to hydrogen and oxygen, respectively. This review article will highlight progress in molecular electrochemical approaches for catalytic reduction of protons to hydrogen, focusing on complexes of earth-abundant metals that can function in pure aqueous or mixed aqueous-organic media. The use of water as a reaction medium has dual benefits of maintaining high substrate concentration as well as minimizing the environmental impact from organic additives and by-products.

  2. Response of gonococcal clinical isolates to acidic conditions.

    PubMed

    Pettit, R K; McAllister, S C; Hamer, T A

    1999-02-01

    This study examined the response to acidic conditions of four gonococcal isolates -NRL38874 (Proto/IB-2), NRL38884 (Pro/IA-2), NRL38953 (Proto/IB-3) and NRL39029 (Pro/IA-3) - obtained from various sites in patients in whom a diagnosis of pelvic inflammatory disease had been made by laparoscopic examination. Acid tolerance of the clinical isolates was strain and growth phase dependent. Growth of the four strains on solid media was undetectable below pH 5.8. In liquid culture, strain NRL38884 did not survive below pH 5.2; strains NRL38874, NRL38953 and NRL39029 survived to pH 4.5. Between pH 4.2 and pH 5.1, the latter three strains exhibited a peak in survival at pH 4.6-4.7 during log phase, suggesting that there may be a distinct acid tolerance system operating at this pH. SDS-PAGE of whole-cell, total membrane and outer-membrane fractions of the four strains prepared from pH 7.2 and pH 6.1 plate cultures revealed numerous differences in protein composition. Acidic conditions reduced the expression of the reduction modifiable outer-membrane protein Rmp, and induced the expression of many membrane proteins, including gonococcal hsp63. Immunoblotting studies with matched serum samples and strains from patients with pelvic inflammatory disease indicated that IgG recognition of outer-membrane components from strains cultured in acidic and neutral conditions was quite different. The results suggest that the immune system interacts with unique outer-membrane constituents on gonococci colonising sites at different pH.

  3. Immiscible Hydrocarbon and Aqueous Fluids Under Subduction Zone Conditions and Implications for the Deep Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Huang, F.; Daniel, I.; Cardon, H.; Montagnac, G.; Sverjensky, D. A.

    2015-12-01

    Subducting slabs recycle rocks into the deep Earth releasing fluids which may cause partial melting and possible oxidation of the mantle wedge. Recent theoretical studies1 indicate that at pressures greater than about 3.0 GPa these fluids could contain high concentrations of organic and inorganic C-species with a wide range of C-oxidation states at equilibrium. If so, such fluids could play an important role in the deep carbon cycle, including the formation of diamond. However, direct experimental observations of the speciation in the fluids are needed. We studied 1.0 M aqueous Na-formate and 1.0 M Na-acetate solutions in the diamond anvil cell using Raman spectroscopy at 300 ºC and 3.0 GPa for up to 60 hours. Our preliminary results indicate that formate rapidly decomposed to bicarbonate/carbonate species and methane, with no detectable H2. Acetate decomposed much more slowly. Within the first two hours of heating, crystals of Na2CO3 precipitated in the fluid, and kept growing while immiscible droplets of hydrocarbon appeared and persisted throughout the experiments at elevated temperature and pressure. In the aqueous fluid, acetate and HCO3- were present during the first 6 hours, and then CO32- and acetate after 20 hours of heating. The final HCO3- /CO32- ratio was constant indicating a constant pH. This is the first in situ observation of persistent immiscible fluid hydrocarbons formed from an aqueous precursor at upper mantle pressures. Our results suggest that Earth's subduction zone fluids at high pressures might involve fluid hydrocarbon species as well as inorganic and organic aqueous C-species, which considerably broadens the picture of deep carbon sources, cycles and sinks. [1] Sverjensky et at. (2014), Nat. Geosci. 7, 909-913.

  4. Effect of intrajejunal acidity on lipid digestion and aqueous solubilisation of bile acids and lipids in health, using a new simple method of lipase inactivation.

    PubMed Central

    Zentler-Munro, P L; Fine, D R; Fitzpatrick, W J; Northfield, T C

    1984-01-01

    We have investigated whether acid-mediated bile acid precipitation, pancreatic enzyme inactivation, and fatty acid partitioning occur in health when intraluminal pH falls below 5. In order to assess lipolysis and aqueous solubilisation of lipid, we first developed a new technique for inactivating lipase in jejunal aspirate (acid inactivation), and showed it to be more effective and simpler than the established technique (heat inactivation). We then studied 14 healthy subjects, aspirating jejunal content for three hours after a liquid meal, and pooling according to pH. Eighteen per cent of the total aspirate was collected at pH less than 5 compared with 56% at pH greater than 6 (p less than 0.01). Forty eight per cent of the bile acids were precipitated at pH less than 5 compared with 18% at pH greater than 6 (p less than 0.01), leading to a reduction in aqueous phase bile acid concentration at low pH (2.1 mmol/l at pH less than 5 vs 5.8 mmol/l at pH greater than 6, p less than 0.01). Lipase activity was reduced at low pH (133 IU/l at pH less than 5 vs 182 IU/l at pH greater than 6, p less than 0.01), leading to reduced lipolysis at low pH (14% at pH less than 5 vs 32% at pH greater than 6, p less than 0.01). Aqueous phase lipid concentration was reduced at low pH (3.5 mmol/l at pH less than 5 vs 12.5 mmol/l at pH greater than 6, p less than 0.01). This reduction was less dependent on bile acid precipitation than on lipase inactivation and fatty acid partitioning. We conclude that intraluminal acidity influences aqueous solubilisation of bile acids and lipid in health. PMID:6714793

  5. Prebiotic synthesis of adenine and amino acids under Europa-like conditions

    NASA Technical Reports Server (NTRS)

    Levy, M.; Miller, S. L.; Brinton, K.; Bada, J. L.

    2000-01-01

    In order to simulate prebiotic synthetic processes on Europa and other ice-covered planets and satellites, we have investigated the prebiotic synthesis of organic compounds from dilute solutions of NH4CN frozen for 25 years at -20 and -78 degrees C. In addition, the aqueous products of spark discharge reactions from a reducing atmosphere were frozen for 5 years at -20 degrees C. We find that both adenine and guanine, as well as a simple set of amino acids dominated by glycine, are produced in substantial yields under these conditions. These results indicate that some of the key components necessary for the origin of life may have been available on Europa throughout its history and suggest that the circumstellar zone where life might arise may be wider than previously thought.

  6. Prebiotic Synthesis of Adenine and Amino Acids Under Europa-like Conditions

    NASA Technical Reports Server (NTRS)

    Levy, Matthew; Miller, Stanley L.; Brinton, Karen; Bada, Jeffrey L.

    2003-01-01

    In order to simulate prebiotic synthetic processes on Europa and other ice-covered planets and satellites. we have investigated the prebiotic synthesis of organic compounds from dilute solutions of NH4CN frozen for 25 year at -20 and -78 C. In addition the aqueous products of spark discharge reactions from a reducing atmosphere were frozen for 5 years at -20%. We find that both adenine and guanine, as well as a simple set of amino acids dominated by glycine, are produced in substantial yields under these conditions. These results indicate that some of the key components necessary for the origin of life may have been available on Europa throughout its history and suggest that the circumstellar zone where life might arise may be m der than previously thought.

  7. Citric acid modified kenaf core fibres for removal of methylene blue from aqueous solution.

    PubMed

    Sajab, Mohd Shaiful; Chia, Chin Hua; Zakaria, Sarani; Jani, Saad Mohd; Ayob, Mohd Khan; Chee, Kah Leong; Khiew, Poi Sim; Chiu, Wee Siong

    2011-08-01

    Chemically modified kenaf core fibres were prepared via esterification in the presence of citric acid (CA). The adsorption kinetics and isotherm studies were carried out under different conditions to examine the adsorption efficiency of CA-treated kenaf core fibres towards methylene blue (MB). The adsorption capacity of the kenaf core fibres increased significantly after the citric acid treatment. The values of the correlation coefficients indicated that the Langmuir isotherm fitted the experimental data better than the Freundlich isotherm. The maximum adsorption capacity of the CA-treated kenaf core fibres was found to be 131.6mg/g at 60°C. Kinetic models, pseudo-first-order, pseudo-second-order and intraparticle diffusion, were employed to describe the adsorption mechanism. The kinetic data were found to fit pseudo-second-order model equation as compared to pseudo-first-order model. The adsorption of MB onto the CA-treated kenaf core fibres was spontaneous and endothermic.

  8. 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

  9. Mass spectrometric elucidation of triacylglycerol content of Brevoortia tyrannus (menhaden) oil using non-aqueous reversed-phase liquid chromatography under ultra high pressure conditions.

    PubMed

    Dugo, Paola; Beccaria, Marco; Fawzy, Nermeen; Donato, Paola; Cacciola, Francesco; Mondello, Luigi

    2012-10-12

    A non-aqueous reversed phase high performance liquid chromatography method was developed, and optimized for triacylglycerol analysis in a Brevoortia tyrannus (menhaden) oil sample. Four columns were serially coupled to tackle such a task, for a total length of 60 cm of shell-packed stationary phase, and operated under ultra high pressure conditions. As detection, positive-ion atmospheric pressure chemical ionization mass spectrometry was used to attain identification of the analyzed sample components. A number of 137 triacylglycerols containing up to 19 fatty acids, with 14-22 carbon atom alkyl chain length and 0-6 double bonds, were positively identified in the complex lipidic sample. This is the first work that reports an extensive characterization of the triacylglycerol fraction of menhaden oil. PMID:22503927

  10. 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.

  11. Using Acid Number as a Leading Indicator of Refrigeration and Air Conditioning System Performance

    SciTech Connect

    Dennis Cartlidge; Hans Schellhase

    2003-07-31

    This report summarizes a literature review to assess the acidity characteristics of the older mineral oil and newer polyolester (POE) refrigeration systems as well as to evaluate acid measuring techniques used in other non-aqueous systems which may be applicable for refrigeration systems. Failure in the older chlorofluorocarbon/hydrochlorofluorocarbon (CFC/HCFC) / mineral oil systems was primarily due to thermal degradation of the refrigerant which resulted in the formation of hydrochloric and hydrofluoric acids. These are strong mineral acids, which can, over time, severely corrode the system metals and lead to the formation of copper plating on iron surfaces. The oil lubricants used in the older systems were relatively stable and were not prone to hydrolytic degradation due to the low solubility of water in oil. The refrigerants in the newer hydrofluorocarbon (HFC)/POE systems are much more thermally stable than the older CFC/HCFC refrigerants and mineral acid formation is negligible. However, acidity is produced in the new systems by hydrolytic decomposition of the POE lubricants with water to produce the parent organic acids and alcohols used to prepare the POE. The individual acids can therefore vary but they are generally C5 to C9 carboxylic acids. Organic acids are much weaker and far less corrosive to metals than the mineral acids from the older systems but they can, over long time periods, react with metals to form carboxylic metal salts. The salts tend to accumulate in narrow areas such as capillary tubes, particularly if residual hydrocarbon processing chemicals are present in the system, which can lead to plugging. The rate of acid production from POEs varies on a number of factors including chemical structure, moisture levels, temperature, acid concentration and metals. The hydrolysis rate of reaction can be reduced by using driers to reduce the free water concentration and by using scavenging chemicals which react with the system acids. Total acid

  12. Sulfonated methyl esters of fatty acids in aqueous solutions: Interfacial and micellar properties.

    PubMed

    Danov, Krassimir D; Stanimirova, Rumyana D; Kralchevsky, Peter A; Basheva, Elka S; Ivanova, Veronika I; Petkov, Jordan T

    2015-11-01

    The interest to sulfonated methyl esters of fatty acids (SME) has been growing during the last decade, because these surfactants are considered as an environmentally friendly and renewable alternative of the linear alkyl-benzene sulfonates (LAS). Here, we present a quantitative study on the properties of aqueous SME solutions, and especially on their surface tension isotherms, critical micelle concentration (CMC) and its dependence on the concentration of added NaCl. It is demonstrated that the CMC of an ionic surfactant determined by electrical conductivity is insensitive to the presence of a small nonionic admixture, so that the CMC values determined by conductivity represent the CMC of the pure surfactant. Using SME as an example, we have demonstrated the application of a new and powerful method for determining the physicochemical parameters of the pure ionic surfactant by theoretical data analysis ("computer purification") if the used surfactant sample contains nonionic admixtures, which are present as a rule. This method involves fits of the experimental data for surface tension and conductivity by a physicochemical model based on a system of mass-balance, chemical-equilibrium and electric-double-layer equations, which allows us to determine the adsorption and micellization parameters of C12-, C14-, C16- and C18-SME, as well the fraction of nonionic admixtures (if any). Having determined these parameters, we can further predict the interfacial and micellization properties of the surfactant solutions, such as surface tension, adsorption, degree of counterion binding, and surface electric potential at every surfactant, salt and co-surfactant concentrations.

  13. 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.

  14. Sulfonated methyl esters of fatty acids in aqueous solutions: Interfacial and micellar properties.

    PubMed

    Danov, Krassimir D; Stanimirova, Rumyana D; Kralchevsky, Peter A; Basheva, Elka S; Ivanova, Veronika I; Petkov, Jordan T

    2015-11-01

    The interest to sulfonated methyl esters of fatty acids (SME) has been growing during the last decade, because these surfactants are considered as an environmentally friendly and renewable alternative of the linear alkyl-benzene sulfonates (LAS). Here, we present a quantitative study on the properties of aqueous SME solutions, and especially on their surface tension isotherms, critical micelle concentration (CMC) and its dependence on the concentration of added NaCl. It is demonstrated that the CMC of an ionic surfactant determined by electrical conductivity is insensitive to the presence of a small nonionic admixture, so that the CMC values determined by conductivity represent the CMC of the pure surfactant. Using SME as an example, we have demonstrated the application of a new and powerful method for determining the physicochemical parameters of the pure ionic surfactant by theoretical data analysis ("computer purification") if the used surfactant sample contains nonionic admixtures, which are present as a rule. This method involves fits of the experimental data for surface tension and conductivity by a physicochemical model based on a system of mass-balance, chemical-equilibrium and electric-double-layer equations, which allows us to determine the adsorption and micellization parameters of C12-, C14-, C16- and C18-SME, as well the fraction of nonionic admixtures (if any). Having determined these parameters, we can further predict the interfacial and micellization properties of the surfactant solutions, such as surface tension, adsorption, degree of counterion binding, and surface electric potential at every surfactant, salt and co-surfactant concentrations. PMID:26196714

  15. Sorption of estrogens and pesticides from aqueous solution by a humic acid and raw and processed plant materials

    NASA Astrophysics Data System (ADS)

    Loffredo, Elisabetta; Taskin, Eren

    2016-04-01

    The huge number of organic contaminants released in water as a consequence of anthropogenic activities have detrimental effects to environmental systems and human health. Industrial products and byproducts, pharmaceuticals, pesticides, detergents and so on impose increasing costs for wastewater decontamination. Adsorption techniques can be successfully used for the treatment of wastewaters to remove contaminants of various nature. Humic acids (HA) have well-known adsorptive capacities towards hydrophilic and, especially, hydrophobic compounds. In the recent years, alternative low-cost adsorbents, especially originated from agricultural wastes and food industries residues, such as wood chips, almond and coconut shells, peanut and rice husks, are under investigation. Biochar is also considered a promising and relatively low-cost adsorbent, even if there are still knowledge gaps about the influence of feedstock type, pyrolysis conditions, physical and chemical properties on its potential and safe use. In the present work, a HA from a green compost was used along with three other materials of plant origin to remove two estrogens, 4-tert-octylphenol and 17-β-estradiol, and two pesticides, carbaryl and fenuron, from an aqueous solution. The four molecules were spiked in water each at a concentration of 1 mg L-1. The materials were: a biochar obtained from 100% red spruce pellet pyrolysed at 550 °C, spent coffee grounds and spent tea leaves. Kinetics curves and adsorption isotherms studies were performed using a batch equilibrium method. Adsorption data obtained for each compound were fitted to a linear equation and non-linear Freundlich and Langmuir models. Kinetics data of the four compounds onto all adsorbents showed an initial very rapid adsorption which was completed in few hours when it reached equilibrium. The two estrogens were adsorbed onto all materials more quickly than the two less hydrophobic pesticides. Significant differences among adsorbents and the

  16. Acid gas treating by aqueous alkanolamines. Annual report, January-December 1993

    SciTech Connect

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

    1993-12-01

    The objective of the work is to investigate the simultaneous 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 thus far, density, viscosity, gas diffusivity, gas solubility, surface tension, and amine solution vapor pressure have been measured for aqueous MDEA, DEA, and MDEA/DEA mixtures over the temperature range 20 to 100 deg. C and for concentrations up to 50 weight %. A mathematical model, based on the penetration theory, for the simultaneous absorption (desorption) of CO2 and H2S into (from) aqueous solutions of MDEA and DEA has been developed.

  17. Boronic acid-containing aminopyridine- and aminopyrimidinecarboxamide CXCR1/2 antagonists: Optimization of aqueous solubility and oral bioavailability.

    PubMed

    Schuler, Aaron D; Engles, Courtney A; Maeda, Dean Y; Quinn, Mark T; Kirpotina, Liliya N; Wicomb, Winston N; Mason, S Nicholas; Auten, Richard L; Zebala, John A

    2015-09-15

    The chemokine receptors CXCR1 and CXCR2 are important pharmaceutical targets due to their key roles in inflammatory diseases and cancer progression. We have previously identified 2-[5-(4-fluoro-phenylcarbamoyl)-pyridin-2-ylsulfanylmethyl]-phenylboronic acid (SX-517) and 6-(2-boronic acid-5-trifluoromethoxy-benzylsulfanyl)-N-(4-fluoro-phenyl)-nicotinamide (SX-576) as potent non-competitive boronic acid-containing CXCR1/2 antagonists. Herein we report the synthesis and evaluation of aminopyridine and aminopyrimidine analogs of SX-517 and SX-576, identifying (2-{(benzyl)[(5-boronic acid-2-pyridyl)methyl]amino}-5-pyrimidinyl)(4-fluorophenylamino)formaldehyde as a potent chemokine antagonist with improved aqueous solubility and oral bioavailability.

  18. Optimization of polyphenol extraction from red grape pomace using aqueous glycerol/tartaric acid mixtures and response surface methodology.

    PubMed

    Makris, Dimitris P; Passalidi, Vassiliki; Kallithraka, Stamatina; Mourtzinos, Ioannis

    2016-01-01

    Grape pomace is a food industry waste containing a high burden of antioxidant polyphenols and several methodologies have been developed for their efficient extraction. However, a sustainable and environmentally friendly process should involve recovery means composed of benign, non-toxic solvents, such as tartaric acid and glycerol, which are natural food constituents. In this line, this study examined the extraction of polyphenols using aqueous tartaric acid/glycerol solutions. The aim was to assess the role of acid and glycerol concentration in the extraction yield, employing a Box-Behnken experimental design and response surface methodology. The results showed that solutions containing only glycerol (20%, w/v) are more suitable for retrieving polyphenols, flavonoids, and pigments from grape pomace, while tartaric acid exerted a negative effect in this regard, when tested at concentrations up to 2% (w/v).

  19. Chemical constraints governing the origin of metabolism: the thermodynamic landscape of carbon group transformations under mild aqueous conditions

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    2002-01-01

    The thermodynamics of organic chemistry under mild aqueous conditions was examined in order to begin to understand its influence on the structure and operation of metabolism and its antecedents. Free energies (deltaG) were estimated for four types of reactions of biochemical importance carbon-carbon bond cleavage and synthesis, hydrogen transfer between carbon groups, dehydration of alcohol groups, and aldo-keto isomerization. The energies were calculated for mainly aliphatic groups composed of carbon, hydrogen, and oxygen. The energy values showed (1) that generally when carbon-carbon bond cleavage involves groups from different functional group classes (i.e., carboxylic acids, carbonyl groups, alcohols, and hydrocarbons), the transfer of the shared electron-pair to the more reduced carbon group is energetically favored over transfer to the more oxidized carbon group, and (2) that the energy of carbon-carbon bond transformation is primarily determined by the functional group class of the group that changes oxidation state in the reaction (i.e., the functional group class of the group that donates the shared electron-pair during cleavage, or that accepts the incipient shared electron-pair during synthesis). In contrast, the energy of hydrogen transfer between carbon groups is determined by the functional group class of both the hydrogen-donor group and the hydrogen-acceptor group. From these and other observations we concluded that the chemistry involved in the origin of metabolism (and to a lesser degree modern metabolism) was strongly constrained by (1) the limited redox-based transformation energy of organic substrates that is readily dissipated in a few energetically favorable irreversible reactions; (2) the energy dominance of a few transformation half-reactions that determines whether carbon-carbon bond transformation (cleavage or synthesis) is energetically favorable (deltaG < -3.5 kcal/mol), reversible (deltaG between +/-3.5 kcal/mol), or unfavorable (delta

  20. Densities of L-Glutamic Acid HCl Drug in Aqueous NaCl and KCl Solutions at Different Temperatures

    NASA Astrophysics Data System (ADS)

    Ryshetti, Suresh; Raghuram, Noothi; Rani, Emmadi Jayanthi; Tangeda, Savitha Jyostna

    2016-04-01

    Densities (ρ ) of (0.01 to 0.07) {mol}{\\cdot } {kg}^{-1} L-Glutamic acid HCl (L-HCl) drug in water, and in aqueous NaCl and KCl (0.5 and 1.0) {mol}{\\cdot } {kg}^{-1} solutions have been reported as a function of temperature at T = (298.15, 303.15, 308.15, and 313.15) K and atmospheric pressure. The accurate density (ρ ) values are used to estimate the various parameters such as the apparent molar volume (V_{2,{\\upphi }}), the partial molar volume (V2^{∞}), the isobaric thermal expansion coefficient (α 2), the partial molar expansion (E2^{∞}), and Hepler's constant (partial 2V2^{∞}/partial T2)P. The Cosphere overlap model is used to understand the solute-solvent interactions in a ternary mixture (L-HCl drug + NaCl or KCl + water). Hepler's constant (partial 2V2^{∞}/partial T2)_P is utilized to interpret the structure-making or -breaking ability of L-HCl drug in aqueous NaCl and KCl solutions, and the results are inferred that L-HCl drug acts as a structure maker, i.e., kosmotrope in aqueous NaCl solutions and performs as a structure breaker, i.e., chaotrope in aqueous KCl solutions.

  1. GC/MS method for determining carbon isotope enrichment and concentration of underivatized short-chain fatty acids by direct aqueous solution injection of biogas digester samples.

    PubMed

    Mulat, Daniel Girma; Feilberg, Anders

    2015-10-01

    In anaerobic digestion of organic matter, several metabolic pathways are involved during the simultaneous production and consumption of short-chain fatty acids (SCFA) in general and acetate in particular. Understanding the role of each pathway requires both the determination of the concentration and isotope enrichment of intermediates in conjunction with isotope labeled substrates. The objective of this study was to establish a rapid and simple GC/MS method for determining the isotope enrichment of acetate and concentration of underivatized short-chain fatty acids (SCFA) in biogas digester samples by direct liquid injection of acidified aqueous samples. Sample preparation involves only acidification, centrifugation and filtration of the aqueous solution followed by direct injection of the aqueous supernatant solution onto a polar column. With the sample preparation and GC/MS conditions employed, well-resolved and sharp peaks of underivatized SCFA were obtained in a reasonably short time. Good recovery (96.6-102.3%) as well as low detection (4-7 µmol/L) and quantification limits (14-22 µmol/L) were obtained for all the 6 SCFA studied. Good linearity was achieved for both concentration and isotope enrichment measurement with regression coefficients higher than 0.9978 and 0.9996, respectively. The method has a good intra- and inter-day precision with a relative standard deviation (RSD) below 6% for determining the tracer-to-tracee ratio (TTR) of both [2-(13)C]acetate and [U-(13)C]acetate. It has also a good intra- and inter-day precision with a RSD below 6% and 5% for determining the concentration of standard solution and biogas digester samples, respectively. Acidification of biogas digester samples with oxalic acid provided the low pH required for the protonation of SCFA and thus, allows the extraction of SCFA from the complex sample matrix. Moreover, oxalic acid was the source of formic acid which was produced in the injector set at high temperature. The produced

  2. The effect of precipitation conditions and aging upon characteristics of particles precipitated from aqueous solutions

    SciTech Connect

    Rard, J.A.

    1989-10-01

    Precipitation of a dissolved species from aqueous solutions is one of the techniques used to grow particles with certain size or composition characteristics. Various factors affecting the particle properties for sparingly soluble substances are briefly discussed here, including homogeneous versus heterogeneous nucleation, the effect of relative supersaturation on the number of nuclei and their relative size, particle growth by way of Ostwald Ripening, the Ostwald Step Rule and nucleation of metastable phases, diffusion-controlled versus surface reaction-controlled growth, incorporation of dopants into the precipitate, and dendritic growth. 13 refs.

  3. Analysis of iodinated haloacetic acids in drinking water by reversed-phase liquid chromatography/electrospray ionization/tandem mass spectrometry with large volume direct aqueous injection.

    PubMed

    Li, Yongtao; Whitaker, Joshua S; McCarty, Christina L

    2012-07-01

    A large volume direct aqueous injection method was developed for the analysis of iodinated haloacetic acids in drinking water by using reversed-phase liquid chromatography/electrospray ionization/tandem mass spectrometry in the negative ion mode. Both the external and internal standard calibration methods were studied for the analysis of monoiodoacetic acid, chloroiodoacetic acid, bromoiodoacetic acid, and diiodoacetic acid in drinking water. The use of a divert valve technique for the mobile phase solvent delay, along with isotopically labeled analogs used as internal standards, effectively reduced and compensated for the ionization suppression typically caused by coexisting common inorganic anions. Under the optimized method conditions, the mean absolute and relative recoveries resulting from the replicate fortified deionized water and chlorinated drinking water analyses were 83-107% with a relative standard deviation of 0.7-11.7% and 84-111% with a relative standard deviation of 0.8-12.1%, respectively. The method detection limits resulting from the external and internal standard calibrations, based on seven fortified deionized water replicates, were 0.7-2.3 ng/L and 0.5-1.9 ng/L, respectively.

  4. A Simple Purification of Indole-3-Acetic Acid and Abscisic Acid for GC-SIM-MS Analysis by Microfiltration of Aqueous Samples through Nylon

    PubMed Central

    Dunlap, James R.; Guinn, Gene

    1989-01-01

    A simple procedure was developed for the partial purification of plant tissue samples to be analyzed simultaneously for indole-3-acetic acid (IAA) and abscisic acid (ABA). The procedure relies on removal of contaminants by filtration through nylon and partitioning into dichloromethane. This procedure successfully purified both IAA and ABA from muskmelon, cotton, and broccoli tissue. Twenty individual samples can be purified and methylated in 8 h for analysis of free IAA and ABA with gas chromatography-selected ion monitoring-mass spectrometry. The use of microfiltration of aqueous samples through nylon offers new opportunities for improving the efficiency of existing sample purification procedures. PMID:16666735

  5. Dilute-acid hydrolysis of sugarcane bagasse at varying conditions.

    PubMed

    Neureiter, Markus; Danner, Herbert; Thomasser, Christiane; Saidi, Bamusi; Braun, Rudolf

    2002-01-01

    Sugarcane bagasse, a byproduct of the cane sugar industry, is an abundant source of hemicellulose that could be hydrolyzed to yield a fermentation feedstock for the production of fuel ethanol and chemicals. The effects of sulfuric acid concentration, temperature, time, and dry matter concentration on hemicellulose hydrolysis were studied with a 20-L batch hydrolysis reactor using a statistical experimental design. Even at less severe conditions considerable amounts (>29%) of the hemicellulose fraction could be extracted. The percentage of soluble oligosaccharides becomes very low in experiments with high yields in monosaccharides, which indicates that the cellulose fraction is only slightly affected. For the sugar yields, acid concentration appears to be the most important parameter, while for the formation of sugar degradation products, temperature shows the highest impact. It could be demonstrated that the dry matter concentration in the reaction slurry has a negative effect on the xylose yield that can be compensated by higher concentrations of sulfuric acid owing to a positive interaction between acid concentration and dry matter contents.

  6. 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.

  7. ROS initiated oxidation of dopamine under oxidative stress conditions in aqueous and lipidic environments.

    PubMed

    Iuga, Cristina; Alvarez-Idaboy, J Raul; Vivier-Bunge, Annik

    2011-10-27

    Dopamine is known to be an efficient antioxidant and to protect neurocytes from oxidative stress by scavenging free radicals. In this work, we have carried out a systematic quantum chemistry and computational kinetics study on the reactivity of dopamine toward hydroxyl (•OH) and hydroperoxyl (•OOH) free radicals in aqueous and lipidic simulated biological environments, within the density functional theory framework. Rate constants and branching ratios for the different paths contributing to the overall reaction, at 298 K, are reported. For the reactivity of dopamine toward hydroxyl radicals, in water at physiological pH, the main mechanism of the reaction is proposed to be the sequential electron proton transfer (SEPT), whereas in the lipidic environment, hydrogen atom transfer (HAT) and radical adduct formation (RAF) pathways contribute almost equally to the total reaction rate. In both environments, dopamine reacts with hydroxyl radicals at a rate that is diffusion-controlled. Reaction with the hydroperoxyl radical is much slower and occurs only by abstraction of any of the phenolic hydrogens. The overall rate coefficients are predicted to be 2.23 × 10(5) and 8.16 × 10(5) M(-1) s(-1), in aqueous and lipidic environment, respectively, which makes dopamine a very good •OOH, and presumably •OOR, radical scavenger. PMID:21919526

  8. ROS Initiated Oxidation of Dopamine under Oxidative Stress Conditions in Aqueous and Lipidic Environments

    PubMed Central

    2011-01-01

    Dopamine is known to be an efficient antioxidant and to protect neurocytes from oxidative stress by scavenging free radicals. In this work, we have carried out a systematic quantum chemistry and computational kinetics study on the reactivity of dopamine toward hydroxyl (•OH) and hydroperoxyl (•OOH) free radicals in aqueous and lipidic simulated biological environments, within the density functional theory framework. Rate constants and branching ratios for the different paths contributing to the overall reaction, at 298 K, are reported. For the reactivity of dopamine toward hydroxyl radicals, in water at physiological pH, the main mechanism of the reaction is proposed to be the sequential electron proton transfer (SEPT), whereas in the lipidic environment, hydrogen atom transfer (HAT) and radical adduct formation (RAF) pathways contribute almost equally to the total reaction rate. In both environments, dopamine reacts with hydroxyl radicals at a rate that is diffusion-controlled. Reaction with the hydroperoxyl radical is much slower and occurs only by abstraction of any of the phenolic hydrogens. The overall rate coefficients are predicted to be 2.23 × 105 and 8.16 × 105 M–1 s–1, in aqueous and lipidic environment, respectively, which makes dopamine a very good •OOH, and presumably •OOR, radical scavenger. PMID:21919526

  9. Thermodynamic studies of ionic hydration and interactions for amino acid ionic liquids in aqueous solutions at 298.15 K.

    PubMed

    Dagade, Dilip H; Madkar, Kavita R; Shinde, Sandeep P; Barge, Seema S

    2013-01-31

    Amino acid ionic liquids are a special class of ionic liquids due to their unique acid-base behavior, biological significance, and applications in different fields such as templates in synthetic chemistry, stabilizers for biological macromolecules, etc. The physicochemical properties of these ionic liquids can easily be altered by making the different combinations of amino acids as anion along with possible cation modification which makes amino acid ionic liquids more suitable to understand the different kinds of molecular and ionic interactions with sufficient depth so that they can provide fruitful information for a molecular level understanding of more complicated biological processes. In this context, volumetric and osmotic coefficient measurements for aqueous solutions containing 1-ethyl-3-methylimidazolium ([Emim]) based amino acid ionic liquids of glycine, alanine, valine, leucine, and isoleucine are reported at 298.15 K. From experimental osmotic coefficient data, mean molal activity coefficients of ionic liquids were estimated and analyzed using the Debye-Hückel and Pitzer models. The hydration numbers of ionic liquids in aqueous solutions were obtained using activity data. Pitzer ion interaction parameters are estimated and compared with other electrolytes reported in the literature. The nonelectrolyte contribution to the aqueous solutions containing ionic liquids was studied by calculating the osmotic second virial coefficient through an application of the McMillan-Mayer theory of solution. It has been found that the second osmotic virial coefficient which includes volume effects correlates linearly with the Pitzer ion interaction parameter estimated independently from osmotic data as well as the hydrophobicity of ionic liquids. The enthalpy-entropy compensation effect, explained using the Starikov-Nordén model of enthalpy-entropy compensation, and partial molar entropy analysis for aqueous [Emim][Gly] solutions are made by using experimental Gibb

  10. 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

  11. 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.

  12. Separation of clavulanic acid from fermented broth of amino acids by an aqueous two-phase system and ion-exchange adsorption.

    PubMed

    da Silva, Clovis Sacardo; Cuel, Maressa Fabiano; Barreto, Verônica Orlandin; Kwong, Wu Hong; Hokka, Carlos O; Barboza, M

    2012-02-15

    The clavulanic acid is a substance which inhibits the β-lactamases used with penicillins for therapeutic treatment. After the fermentation, by-products of low molecular weight such as amino acids lysine, histidine, proline and tyrosine are present in the fermented broth. To remove these impurities the techniques of extraction by an aqueous two-phase system of 17% polyethylene glycol molecular weight 600 and 15% potassium phosphate were used for a partial purification. A subsequent ion-exchange adsorption was used for the recuperation of the clavulanic acid of the top phase and purification getting a concentration factor of 2 and purification of 100% in relation to the amino acids lysine, histidine, proline and tyrosine.

  13. Precise investigation of the axial ligand substitution mechanism on a hydrogenphosphato-bridged lantern-type platinum(III) binuclear complex in acidic aqueous solution.

    PubMed

    Iwatsuki, Satoshi; Mizushima, Chiho; Morimoto, Naoyuki; Muranaka, Shinji; Ishihara, Koji; Matsumoto, Kazuko

    2005-10-31

    Detailed equilibrium and kinetic studies on axial water ligand substitution reactions of the "lantern-type" platinum(III) binuclear complex, [Pt(2)(mu-HPO(4))(4)(H(2)O)(2)](2)(-), with halide and pseudo-halide ions (X(-) = Cl(-), Br(-), and SCN(-)) were carried out in acidic aqueous solution at 25 degrees C with I = 1.0 M. The diaqua Pt(III) dimer complex is in acid dissociation equilibrium in aqueous solution with -log K(h1) = 2.69 +/- 0.04. The consecutive formation constants of the aquahalo complex () and the dihalo complex () were determined spectrophotometrically to be log = 2.36 +/- 0.01 and log = 1.47 +/- 0.01 for the reaction with Cl(-) and log = 2.90 +/- 0.04 and log = 2.28 +/- 0.01 for the reaction with Br(-), respectively. In the kinetic measurements carried out under the pseudo-first-order conditions with a large excess concentration of halide ion compared to that of Pt(III) dimer (C(X)()- > C(Pt)), all of the reactions proceeded via a one-step first-order reaction, which is a contrast to the consecutive two-step reaction for the amidato-bridged platinum(III) binuclear complexes. The conditional first-order rate constant (k(obs)) depended on C(X)()- as well as the acidity of the solution. From kinetic analyses, the rate-limiting step was determined to be the first substitution process that forms the monohalo species, which is in rapid equilibrium with the dihalo complex. The reaction with 4-penten-1-ol was also kinetically investigated to examine the reactivity of the lantern complex with olefin compounds.

  14. Free energy surface for Brønsted acid-catalyzed glucose ring-opening in aqueous solution.

    PubMed

    Qian, Xianghong

    2013-10-01

    Car-Parrinello-based molecular dynamics coupled with metadynamics simulations were used to determine the mechanism and associated free energy surface for opening the ring structure of cyclic glucopyranose in acidic aqueous solutions. The ring-opening process is initiated by the protonation of the ring oxygen atom and the breakage of the C1-O5 bond. The barrier for this process is about 25 kcal/mol, in good agreement with experimental measurements. Moreover, the glucose cyclic conformation is found to be more stable than the open chain form. The barrier for proton-catalyzed ring-opening in aqueous solution appears to be largely solvent induced due to the high affinity of water molecules for protons. PMID:23992399

  15. in situ formation of rGO quantum dots during GO reduction via interaction with citric acid in aqueous medium

    NASA Astrophysics Data System (ADS)

    Ortega-Amaya, R.; Matsumoto, Y.; Flores-Conde, A.; Pérez-Guzmán, M. A.; Ortega-López, M.

    2016-10-01

    Chemical methods represent an economical approach to the mass production of graphene. Their main drawback is the use of environmentally harmful reagents. This work describes a simple, green method to prepare reduced graphene oxide (rGO) sheets and rGO quantum dots (rGOQD) in a single step using citric acid (CA) as the reductant in aqueous medium at room temperature. The reduction level of the nanocomposite obtained depends strongly on the processing time; the sample treated for 24 h demonstrate significant reduction. It is found that CA not only reduces GO but also functionalizes it to produce well-stabilized rGO aqueous dispersions. Additionally, a mechanism for the reduction and functionalization of GO by CA is proposed.

  16. 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.

  17. Amino acid composition, antinutrients and allergens in the peanut protein fraction obtained by an aqueous enzymatic process.

    PubMed

    Latif, S; Pfannstiel, J; Makkar, H P S; Becker, K

    2013-01-01

    Enzyme-assisted aqueous extraction (EAE) of peanut kernel was used to extract oil and protein. The aqueous fraction (AF) obtained by EAE had a better essential amino acid profile than the residues obtained by solvent extraction (Rs) and cold pressing (Rc). No major difference in the trypsin inhibitor activity among AF, Rs and Rc was observed; however, the trypsin inhibitor activity was drastically reduced in the residue obtained after EAE. AF was subjected to MALDI-TOF/MS, revealing it to be rich in peptides (107) with molecular masses from m/z 700 to 2369Da. AF had an extremely low phytate content and was rich in peptides, which could be used as a food supplement. ESI-MS/MS data were used for the identification of major peanut allergens, viz., Ara h1, h3, h6-8. Their allergenic potential needs to be established. PMID:23017415

  18. Determination of glyphosate and aminomethylphosphonic acid in aqueous soil matrices: a critical analysis of the 9-fluorenylmethyl chloroformate derivatization reaction and application to adsorption studies.

    PubMed

    Báez, María E; Fuentes, Edwar; Espina, María José; Espinoza, Jeannette

    2014-11-01

    The assessment of the environmental fate of glyphosate and its degradation product (aminomethylphosphonic acid) is of great interest given the widespread use of the herbicide. Studies of adsorption-desorption and transport processes in soils require analytical methods with sensitivity, accuracy, and precision suitable for determining the analytes in aqueous equilibrium solutions of varied complexity. In this work, the effect of factors on the yield of the derivatization of both compounds with 9-fluorenylmethyl chloroformate for applying in aqueous solutions derived from soils was evaluated through factorial experimental designs. Interference effects coming from background electrolytes and soil matrices were established. The whole method had a linear response up to 640 ng/mL (R(2) > 0.999) under optimized conditions for high-performance liquid chromatography with fluorescence detection. Limits of detection were 0.6 and 0.4 ng/mL for glyphosate and aminomethylphosphonic acid, respectively. The relative standard deviation was 4.4% for glyphosate (20 ng/mL) and 5.9% for aminomethylphosphonic acid (10 ng/mL). Adsorption of compounds on four different soils was assessed. Isotherm data fitted well the Freundlich model (R(2) > 0.97). Kf constants varied between 93 ± 3.1 and 2045 ± 157 for glyphosate and between 99 ± 4.1 and 1517 ± 56 (μg(1-1/) (n)  mL(1/) (n) ( ) g(-1) ) for aminomethylphosphonic acid, showing the broad range of applicability of the proposed method. PMID:25137606

  19. Determination of glyphosate and aminomethylphosphonic acid in aqueous soil matrices: a critical analysis of the 9-fluorenylmethyl chloroformate derivatization reaction and application to adsorption studies.

    PubMed

    Báez, María E; Fuentes, Edwar; Espina, María José; Espinoza, Jeannette

    2014-11-01

    The assessment of the environmental fate of glyphosate and its degradation product (aminomethylphosphonic acid) is of great interest given the widespread use of the herbicide. Studies of adsorption-desorption and transport processes in soils require analytical methods with sensitivity, accuracy, and precision suitable for determining the analytes in aqueous equilibrium solutions of varied complexity. In this work, the effect of factors on the yield of the derivatization of both compounds with 9-fluorenylmethyl chloroformate for applying in aqueous solutions derived from soils was evaluated through factorial experimental designs. Interference effects coming from background electrolytes and soil matrices were established. The whole method had a linear response up to 640 ng/mL (R(2) > 0.999) under optimized conditions for high-performance liquid chromatography with fluorescence detection. Limits of detection were 0.6 and 0.4 ng/mL for glyphosate and aminomethylphosphonic acid, respectively. The relative standard deviation was 4.4% for glyphosate (20 ng/mL) and 5.9% for aminomethylphosphonic acid (10 ng/mL). Adsorption of compounds on four different soils was assessed. Isotherm data fitted well the Freundlich model (R(2) > 0.97). Kf constants varied between 93 ± 3.1 and 2045 ± 157 for glyphosate and between 99 ± 4.1 and 1517 ± 56 (μg(1-1/) (n)  mL(1/) (n) ( ) g(-1) ) for aminomethylphosphonic acid, showing the broad range of applicability of the proposed method.

  20. Hydrogen-bonding-driven self-assembly of PEGylated organosilica nanoparticles with poly(acrylic acid) in aqueous solutions and in layer-by-layer deposition at solid surfaces.

    PubMed

    Irmukhametova, Galiya S; Fraser, Brian J; Keddie, Joseph L; Mun, Grigoriy A; Khutoryanskiy, Vitaliy V

    2012-01-10

    PEGylated organosilica nanoparticles have been synthesized through self-condensation of (3-mercaptopropyl)trimethoxysilane in dimethyl sulfoxide into thiolated nanoparticles with their subsequent reaction with methoxypoly(ethylene glycol) maleimide. The PEGylated nanoparticles showed excellent colloidal stability over a wide range of pH in contrast to the parent thiolated nanoparticles, which have a tendency to aggregate irreversibly under acidic conditions (pH < 3.0). Due to the presence of a poly(ethylene glycol)-based corona, the PEGylated nanoparticles are capable of forming hydrogen-bonded interpolymer complexes with poly(acrylic acid) in aqueous solutions under acidic conditions, resulting in larger aggregates. The use of hydrogen-bonding interactions allows more efficient attachment of the nanoparticles to surfaces. The alternating deposition of PEGylated nanoparticles and poly(acrylic acid) on silicon wafer surfaces in a layer-by-layer fashion leads to multilayered coatings. The self-assembly of PEGylated nanoparticles with poly(acrylic acid) in aqueous solutions and at solid surfaces was compared to the behavior of linear poly(ethylene glycol). The nanoparticle system creates thicker layers than the poly(ethylene glycol), and a thicker layer is obtained on a poly(acrylic acid) surface than on a silica surface, because of the effects of hydrogen bonding. Some implications of these hydrogen-bonding-driven interactions between PEGylated nanoparticles and poly(acrylic acid) for pharmaceutical formulations are discussed.

  1. Recovery of transplutonium elements from aqueous and water-ethanol solutions of sulfuric acid and their separation from other actinides

    SciTech Connect

    Guseva, L.I.; Tikhomirova, G.S.; Stepushkina, V.V.

    1988-05-01

    The behavior of Am, Cm, Bk, Cf, Es, and other actinides, as well as Zr, on anion and cation exchangers in aqueous and water-ethanol solutions of sulfuric acid as a function of the various components of the solution has been investigated. It has been discovered that the presence of ethanol in sulfuric acid solutions causes an increase in the distribution coefficients both on cation exchangers and on anion exchangers. The possibility of the use of ion exchangers for the preconcentration and separation of transplutonium elements from U, Np, Pu, Zr, and other elements which form strong complexes with sulfate ions over a broad range of concentrations of sulfuric acid has been demonstrated.

  2. Enhanced stability of the model mini-protein in amino acid ionic liquids and their aqueous solutions.

    PubMed

    Chevrot, Guillaume; Fileti, Eudes Eterno; Chaban, Vitaly V

    2015-10-15

    Using molecular dynamics simulations, the structure of model mini-protein was thoroughly characterized in the imidazolium-based amino acid ionic liquids and their aqueous solutions. Complete substitution of water by organic cations and anions further results in hindered conformational flexibility of the mini-protein. This observation suggests that amino acid-based ionic liquids are able to defend proteins from thermally induced denaturation. We show by means of radial distributions that the mini-protein is efficiently solvated by both solvents due to a good mutual miscibility. Amino acid-based anions prevail in the first coordination sphere of positively charged sites of the mini-protein whereas water molecules prevail in the first coordination sphere of negatively charged sites of the mini-protein. PMID:26250927

  3. Simultaneous determination of nitric acid and uranium concentrations in aqueous solution from measurements of electrical conductivity, density, and temperature

    SciTech Connect

    Spencer, B.B.

    1991-01-01

    Nuclear fuel reprocessing plants handle aqueous solutions of nitric acid and uranium in large quantities. Automatic control of process operations requires reliable measurements of these solutes concentration, but this is difficult to directly measure. Physical properties such as solution density and electrical conductivity vary with solute concentration and temperature. Conductivity, density and temperature can be measured accurately with relatively simple and inexpensive devices. These properties can be used to determine solute concentrations will good correlations. This paper provides the appropriate correlations for solutions containing 2 to 6 Molar (M) nitric acid and 0 to 300 g/L uranium metal at temperatures from 25--90{degrees}C. The equations are most accurate below 5 M nitric acid, due to a broad maximum in the conductivity curve at 6 M. 12 refs., 9 figs., 6 tabs.

  4. 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

  5. Effective selenium volatilization under aerobic conditions and recovery from the aqueous phase by Pseudomonas stutzeri NT-I.

    PubMed

    Kagami, Tsubasa; Narita, Takanobu; Kuroda, Masashi; Notaguchi, Emi; Yamashita, Mitsuo; Sei, Kazunari; Soda, Satoshi; Ike, Michihiko

    2013-03-01

    Selenium is an important rare metal and its recovery from waste and wastewater is necessary for its sustainable utilization. Microbial selenium volatilization is suitable for selenium recovery from industrial wastewater because volatile selenium can be recovered in recyclable forms free from other chemicals. We found that Pseudomonas stutzeri NT-I can aerobically transform selenate, selenite, and biogenic elemental selenium into dimethyldiselenide as well as dimethylselenide; these were temporarily accumulated in the aqueous phase and then transferred into the gaseous phase. The rate of selenium volatilization using strain NT-I ranged 6.5-7.6 μmol/L/h in flask experiments and was much higher than the rates reported previously for other microbes. The selenium volatilization rate accelerated to 14 μmol/L/h in a jar fermenter. Furthermore, 82% of the selenium volatilized using strain NT-I was recovered with few impurities within 48 h in a simple gas trap with nitric acid, demonstrating that strain NT-I is a promising biocatalyst for selenium recovery through biovolatilization from the aqueous phase.

  6. Anaerobic conditions improve germination of a gibberellic acid deficient rice

    NASA Technical Reports Server (NTRS)

    Frantz, Jonathan M.; Bugbee, Bruce

    2002-01-01

    Dwarf plants are useful in research because multiple plants can be grown in a small area. Rice (Oryza sativa L.) is especially important since its relatively simple genome has recently been sequenced. We are characterizing a gibberellic acid (GA) mutant of rice (japonica cv 'Shiokari,' line N-71) that is extremely dwarf (20 cm tall). Unfortunately, this GA mutation is associated with poor germination (70%) under aerobic conditions. Neither exogenous GA nor a dormancy-breaking heat treatment improved germination. However, 95% germination was achieved by germinating the seeds anaerobically, either in a pure N2 environment or submerged in unstirred tap water. The anaerobic conditions appear to break a mild post-harvest dormancy in this rice cultivar. Copyright 2002 Crop Science Society of America.

  7. Pretreatment of Dried Distiller Grains with Solubles by Soaking in Aqueous Ammonia and Subsequent Enzymatic/Dilute Acid Hydrolysis to Produce Fermentable Sugars.

    PubMed

    Nghiem, Nhuan P; Montanti, Justin; Kim, Tae Hyun

    2016-05-01

    Dried distillers grains with solubles (DDGS), a co-product of corn ethanol production in the dry-grind process, was pretreated by soaking in aqueous ammonia (SAA) using a 15 % w/w NH4OH solution at a solid/liquid ratio of 1:10. The effect of pretreatment on subsequent enzymatic hydrolysis was studied at two temperatures (40 and 60 °C) and four reaction times (6, 12, 24, and 48 h). Highest glucose yield of 91 % theoretical was obtained for the DDGS pretreated at 60 °C and 24 h. The solubilized hemicellulose in the liquid fraction was further hydrolyzed with dilute H2SO4 to generate fermentable monomeric sugars. The conditions of acid hydrolysis included 1 and 4 wt% acid, 60 and 120 °C, and 0.5 and 1 h. Highest yields of xylose and arabinose were obtained at 4 wt% acid, 120 °C, and 1 h. The fermentability of the hydrolysate obtained by enzymatic hydrolysis of the SAA-pretreated DDGS was demonstrated in ethanol fermentation by Saccharomyces cerevisiae. The fermentability of the hydrolysate obtained by consecutive enzymatic and dilute acid hydrolysis was demonstrated using a succinic acid-producing microorganism, strain Escherichia coli AFP184. Under the fermentation conditions, complete utilization of glucose and arabinose was observed, whereas only 47 % of xylose was used. The succinic acid yield was 0.60 g/g total sugar consumed. PMID:26797927

  8. Cassava starch maltodextrinization/monomerization through thermopressurized aqueous phosphoric acid hydrolysis.

    PubMed

    Fontana, J D; Passos, M; Baron, M; Mendes, S V; Ramos, L P

    2001-01-01

    Kinetic conditions were established for the depolymerization of cassava starch for the production of maltodextrins and glucose syrups. Thin-layer chromatography and high-performance liquid chromatography analyses corroborated that the proper H3PO4 strength and thermopressurization range (e.g., 142-170 degrees C; 2.8-6.8 atm) can be successfully explored for such hydrolytic purposes of native starch granules. Because phosphoric acid can be advantageously maintained in the hydrolysate and generates, after controlled neutralization with ammonia, the strategic nutrient triplet for industrial fermentations (C, P, N), this pretreatment strategy can be easily recognized as a recommended technology for hydrolysis and upgrading of starch and other plant polysaccharides. Compared to the classic catalysts, the mandatory desalting step (chloride removal by expensive anion-exchange resin or sulfate precipitation as the calcium-insoluble salt) can be avoided. Furthermore, properly diluted phosphoric acid is well known as an allowable additive in several popular soft drinks such as colas since its acidic feeling in the mouth is compatible and synergistic with both natural and artificial sweeteners. Glycosyrups from phosphorolyzed cassava starch have also been upgraded to high-value single-cell protein such as the pigmented yeast biomass of Xanthophyllomyces dendrorhous (Phaffia rhodozyma), whose astaxanthin (diketo-dihydroxy-beta-carotene) content may reach 0.5-1.0 mg/g of dry yeast cell. This can be used as an ideal complement for animal feeding as well as a natural staining for both fish farming (meat) and poultry (eggs). PMID:11963875

  9. Shikimic acid ozonolysis kinetics of the transition from liquid aqueous solution to highly viscous glass.

    PubMed

    Steimer, Sarah S; Berkemeier, Thomas; Gilgen, Anina; Krieger, Ulrich K; Peter, Thomas; Shiraiwa, Manabu; Ammann, Markus

    2015-12-14

    Ageing of particulate organic matter affects the composition and properties of atmospheric aerosol particles. Driven by temperature and humidity, the organic fraction can vary its physical state between liquid and amorphous solid, or rarely even crystalline. These transitions can influence the reaction kinetics due to limitations of mass transport in such (semi-) solid states, which in turn may influence the chemical ageing of particles containing such compounds. We have used coated wall flow tube experiments to investigate the reaction kinetics of the ozonolysis of shikimic acid, which serves as a proxy for oxygenated, water-soluble organic matter and can form a glass at room temperature. Particular attention was paid to how the presence of water influences the reaction, since it acts a plasticiser and thereby induces changes in the physical state. We analysed the results by means of a traditional resistor model, which assumes steady-state conditions. The ozonolysis rate of shikimic acid is strongly increased in the presence of water, a fact we attribute to the increased transport of O3 and shikimic acid through the condensed phase at lower viscosities. The analysis using the resistor model suggests that the system undergoes both surface and bulk reaction. The second-order rate coefficient of the bulk reaction is 3.7 (+1.5/-3.2) × 10(3) L mol(-1) s(-1). At low humidity and long timescales, the resistor model fails to describe the measurements appropriately. The persistent O3 uptake at very low humidity suggests contribution of a self-reaction of O3 on the surface. PMID:26536455

  10. Isolation and characterization of ellagic acid derivatives isolated from Casearia sylvestris SW aqueous extract with anti-PLA(2) activity.

    PubMed

    Da Silva, Saulo L; Calgarotto, Andrana K; Chaar, Jamal S; Marangoni, Sérgio

    2008-11-01

    The Casearia sylvestris SW (Flacourtiaceae) is utilized in folk medicine (Brazil and all Latin American) to treat several pathologic processes as inflammation, cancer, microbial infection and snake bites. Studies showed that C. sylvestris aqueous extract can inhibit many toxic effects caused by snake venoms (or caused by phospholipase A(2) isolated) from different species, mainly of Bothrops genus. Inhibition of enzymatic and myotoxic activities, decrease of edema formation and increase of the survival rate of rats injected with lethal doses of bothropic venoms are some toxic effects inhibited by C. sylvestris. In this study, four ellagic acid derivatives from aqueous extracts of C. sylvestris were isolated, characterized, and tested against effects from both total venom and PLA(2) (Asp 49 BthTX-II) from the venom of Bothrops jararacussu. The isolated compounds were as follows: ellagic acid (A), 3'-O-methyl ellagic acid (B), 3,3'-di-O-methyl ellagic acid (C), 3-O-methyl-3',4'-methylenedioxy ellagic acid (D). The inhibition constant values (Ki) for enzymatic activity, as well the IC(50) values found in the edematogenic and myotoxic activities, indicate that the ellagic acid is the best inhibitor of these activities, while compounds C and D are the substances with lowest capacity on inhibiting these same effects. Our results show that the presence of hydroxyls at position 3 or 3' (compounds A and B) increases the capacity of these derivatives on inhibiting these toxic effects. However, the presence of methoxyl groups at position 3 or 3' reduced, but did not completely inhibit the capacity of compounds C and D on inhibiting all the toxic effects studied.

  11. Corrosion of high-alloy materials in aqueous hydrofluoric acid environments

    SciTech Connect

    Pawel, S.J. . Development Div.)

    1994-12-01

    A series of immersion tests for eight high-alloy materials was performed in a variety of hydrofluoric acid (HF) environments. Solution strengths of 0.05%, 1%, 10%, 24%, and 48% HF were examined at 24 C, 50 C, and 76 C. Coupons of each alloy were exposed fully immersed in solution and partially exposed in the aerated vapor above each solution. In addition, a limited number of U-bend tests were performed to examine susceptibility to stress corrosion cracking. Comparison of alloy performance (corrosion rate calculated from weight loss, metallographic evaluation of attack) indicated alloys C-22 (UNS N06022) and C-276 (UNS N10276) exhibited overall superior performance. Other alloys showed useful resistance for a limited range of conditions.

  12. Adsorption of acids and bases from aqueous solutions onto silicon dioxide particles.

    PubMed

    Zengin, Huseyin; Erkan, Belgin

    2009-12-30

    The adsorption of acids and bases onto the surface of silicon dioxide (SiO(2)) particles was systematically studied as a function of several variables, including activation conditions, contact time, specific surface area, particle size, concentration and temperature. The physical properties of SiO(2) particles were investigated, where characterizations were carried out by FT-IR spectroscopy, and morphology was examined by scanning electron microscopy (SEM). The SEM of samples showed good dispersion and uniform SiO(2) particles with an average diameter of about 1-1.5 microm. The adsorption results revealed that SiO(2) surfaces possessed effective interactions with acids and bases, and greatest adsorption capacity was achieved with NaOH, where the best fit isotherm model was the Freundlich adsorption model. The adsorption properties of raw SiO(2) particles were further improved by ultrasonication. Langmuir monolayer adsorption capacity of NaOH adsorbate at 25 degrees C on sonicated SiO(2) (182.6 mg/g) was found to be greater than that of the unsonicated SiO(2) (154.3mg/g). The spontaneity of the adsorption process was established by decreases in DeltaG(ads)(0), which varied from -10.5 to -13.6 kJ mol(-1), in the temperature range 283-338K. PMID:19683387

  13. Deuterium Enrichment of Amino and Hydroxy Acids Found in the Murchison Meteorite: Constraints on Parent Body Conditions

    NASA Technical Reports Server (NTRS)

    Lerner, Narcinda R.; Chang, Sherwood (Technical Monitor)

    1997-01-01

    The alpha-amino and alpha-hydroxy acids found in the Murchison carbonaceous chondrite are deuterium enriched. These compounds are thought to have originated from common deuterium enriched carbonyl precursors, by way of a Strecker synthesis which took place in a solution of HCN, NH3, and carbonyl compounds during the period of aqueous alteration of the meteorite parent body. However, the hydroxy acids found on Murchison are less deuterium enriched than the amino acids. With the objective of determining if the discrepancy in deuterium enrichment between the amino acids and the hydroxy acids found on Murchison is consistent with their formation in a Strecker synthesis, we have measured the deuterium content of alpha-amino and alpha-hydroxy acids produced in solutions of deuterated carbonyl compounds, KCN and NH4Cl, and also in mixtures of such solutions and Allende dust at 263 K and 295 K. Retention of the isotopic signature of the starting carbonyl by both alpha amino acids and alpha hydroxy acids is more dependent upon temperature, concentration and pH than upon the presence of meteorite dust in the solution. The constraints these observations place on Murchison parent body conditions will be discussed.

  14. Novel Regenerated Solvent Extraction Processes for the Recovery of Carboxylic Acids or Ammonia from Aqueous Solutions Part II. Recovery of Ammonia from Sour Waters

    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, SUCCiOlC 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

  15. Acid gas treating by aqueous alkanolamines. Annual report, July-December 1992

    SciTech Connect

    Sandall, O.C.; Rinker, E.B.; Tamimi, A.; Davis, R.A.; Oelschlager, D.W.

    1992-12-01

    The objective of the work is to investigate the simultaneous 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 thus far models have been developed for single gas (either H2S or CO2) absorption into a single amine solution (MDEA or DEA). Density and viscosity measurements have been made for aqueous MDEA, DEA and MDEA/DEA mixtures over the temperature range 20 to 100 C and for concentrations up to 50 weight %.

  16. Gallic Acid Promotes Wound Healing in Normal and Hyperglucidic Conditions.

    PubMed

    Yang, Dong Joo; Moh, Sang Hyun; Son, Dong Hwee; You, Seunghoon; Kinyua, Ann W; Ko, Chang Mann; Song, Miyoung; Yeo, Jinhee; Choi, Yun-Hee; Kim, Ki Woo

    2016-01-01

    Skin is the outermost layer of the human body that is constantly exposed to environmental stressors, such as UV radiation and toxic chemicals, and is susceptible to mechanical wounding and injury. The ability of the skin to repair injuries is paramount for survival and it is disrupted in a spectrum of disorders leading to skin pathologies. Diabetic patients often suffer from chronic, impaired wound healing, which facilitate bacterial infections and necessitate amputation. Here, we studied the effects of gallic acid (GA, 3,4,5-trihydroxybenzoic acid; a plant-derived polyphenolic compound) on would healing in normal and hyperglucidic conditions, to mimic diabetes, in human keratinocytes and fibroblasts. Our study reveals that GA is a potential antioxidant that directly upregulates the expression of antioxidant genes. In addition, GA accelerated cell migration of keratinocytes and fibroblasts in both normal and hyperglucidic conditions. Further, GA treatment activated factors known to be hallmarks of wound healing, such as focal adhesion kinases (FAK), c-Jun N-terminal kinases (JNK), and extracellular signal-regulated kinases (Erk), underpinning the beneficial role of GA in wound repair. Therefore, our results demonstrate that GA might be a viable wound healing agent and a potential intervention to treat wounds resulting from metabolic complications. PMID:27399667

  17. Specific cooperative effect for the enantiomeric separation of amino acids using aqueous two-phase systems with task-specific ionic liquids.

    PubMed

    Wu, Datong; Zhou, Ying; Cai, Pengfei; Shen, Shanshan; Pan, Yuanjiang

    2015-05-22

    Aqueous two-phase systems (ATPS) based on hydrophilic ionic liquid (IL) and inorganic salt solution were designed and prepared for the enantiomeric separation of racemic amino acids. Two different kinds of hydrophilic ionic liquids (IL-1 and IL-2) containing functional groups were synthesized to separate racemic amino acids. Preliminary experiments showed that d-enantiomer of amino acids cooperatively interacted with ILs, which pushed d-enantiomer to remain in the bottom IL-rich phase. By contrast, l-enantiomer was transferred into the top Na2SO4-rich phase. The enantioselectivity of IL-1 was better than that of IL-2 because of their different intermolecular interactions. Various factors influencing separation efficiency were also systematically investigated including extraction time, IL volume and temperature. Furthermore, the mechanism was studied by (1)H NMR and DFT calculations, which showed that the hydrogen bond between the carboxylate and amide groups and the resonance-assisted hydrogen bond between amino and hydroxyl groups conditioned the movement between the residues and ILs. Finally, IL-1 was validated with other general amino acids by the same procedures based on ATPS.

  18. Trivalent chromium removal from aqueous solutions by a sol–gel synthesized silica adsorbent functionalized with sulphonic acid groups

    SciTech Connect

    Gomez-Gonzalez, Sergio Efrain; Carbajal-Arizaga, Gregorio Guadalupe; Manriquez-Gonzalez, Ricardo; De la Cruz-Hernandez, Wencel; Gomez-Salazar, Sergio

    2014-11-15

    Highlights: • Corpuscular sulphonic acid-functionalized silica holds improved uptake of chromium. • Mesopores on adsorbent facilitate (CH{sub 3}COO){sub 2}Cr{sup +} ion uptake on sulphonate sites. • Formation of chromium acetate sulphonate complex proposed from XPS results. • Fixed bed chromium uptake results suggest potential industrial use. - Abstract: A high capacity hybrid silica adsorbent was synthesized via sol–gel processing with sulphonic acid groups as trivalent chromium complex ions chelators from aqueous solutions. The synthesis included co-condensation of tetraethoxysilane (TEOS) with 3-(mercaptopropyl)trimethoxysilane (MPS), and oxidation of thiol to sulphonic acid groups. Chromium uptake kinetic, batch and fixed-bed experiments were performed to assess the removal of this metal from aqueous solutions. {sup 13}C, {sup 29}Si CPMAS NMR, FTIR, XPS were used to characterize the adsorbent structure and the nature of chromium complexes on the adsorbent surface. Chromium maximum uptake was obtained at pH 3 (72.8 mg/g). Elemental analysis results showed ligand density of 1.48 mmol sulphonic groups/g. About 407 mL of Cr(III) solution (311 mg/L) were treated to breakthrough point reaching ≤0.06 mg/L at the effluent. These results comply with USEPA regulation for chromium concentration in drinking water (≤0.1 mg/L). The adsorbent shows potential to be used in chromium separations to the industrial level.

  19. Chemiluminescence studies between aqueous phase synthesized mercaptosuccinic acid capped cadmium telluride quantum dots and luminol-H2O2.

    PubMed

    Kaviyarasan, Kulandaivelu; Anandan, Sambandam; Mangalaraja, Ramalinga Viswanathan; Asiri, Abdullah M; Wu, Jerry J

    2016-08-01

    Mercaptosuccinic acid capped Cadmium telluride quantum dots have been successfully synthesized via aqueous phase method. The products were well characterized by a number of analytical techniques, including FT-IR, XRD, HRTEM, and a corrected particle size analysis by the statistical treatment of several AFM measurements. Chemiluminescence experiments were performed to explore the resonance energy transfer between chemiluminescence donor (luminol-H2O2 system) and acceptor CdTe QDs. The combination of such donor and acceptor dramatically reduce the fluorescence while compared to pristine CdTe QDs without any exciting light source, which is due to the occurrence of chemiluminescence resonance energy transfer (CRET) processes. PMID:27131144

  20. Intermolecular interactions in aqueous solutions of gallic acid at 296-306 K according to spectrofluorimetry and densimetry data

    NASA Astrophysics Data System (ADS)

    Grigoryan, K. R.; Sargsyan, L. S.

    2015-12-01

    Features of intermolecular interactions in aqueous solutions of gallic acid (GA) are studied by means of densimetry and fluorescence spectroscopy (intrinsic fluorescence, 2D spectra, and excitation/ emission matrix fluorescence spectra, 3D) at 296.15, 301.15, and 306.15 K in the concentration range of 5.88 × 10-4-5.88 × 10-2 mol L-1. It is shown by analyzing the concentration and temperature dependences of the apparent molar volumes and fluorescence parameters of GA that the equilibrium between nonassociated and associated species in the solution and the hydration of these species undergo changes.

  1. Chemiluminescence studies between aqueous phase synthesized mercaptosuccinic acid capped cadmium telluride quantum dots and luminol-H2O2

    NASA Astrophysics Data System (ADS)

    Kaviyarasan, Kulandaivelu; Anandan, Sambandam; Mangalaraja, Ramalinga Viswanathan; Asiri, Abdullah M.; Wu, Jerry J.

    2016-08-01

    Mercaptosuccinic acid capped Cadmium telluride quantum dots have been successfully synthesized via aqueous phase method. The products were well characterized by a number of analytical techniques, including FT-IR, XRD, HRTEM, and a corrected particle size analysis by the statistical treatment of several AFM measurements. Chemiluminescence experiments were performed to explore the resonance energy transfer between chemiluminescence donor (luminol-H2O2 system) and acceptor CdTe QDs. The combination of such donor and acceptor dramatically reduce the fluorescence while compared to pristine CdTe QDs without any exciting light source, which is due to the occurrence of chemiluminescence resonance energy transfer (CRET) processes.

  2. Rapid decolorization of acid orange II aqueous solution by amorphous zero-valent iron.

    PubMed

    Zhang, Changqin; Zhu, Zhengwang; Zhang, Haifeng; Hu, Zhuangqi

    2012-01-01

    Some problems including low treatment capacity, agglomeration and clogging phenomena, and short working life, limit the application of pre-treatment methods involving zero-valent iron (ZVI). In this article, ZVI was frozen in an amorphous state through a melt-spinning technique, and the decolorization effect of amorphous ZVI on Acid Orange II solution was investigated under varied conditions of experimental variables such as reaction temperature, ribbon dosage, and initial pH. Batch experiments suggested that the decolorization rate was enhanced with the increase of reaction temperature and ribbon dosage, but decreased with increasing initial solution pH. Kinetic analyses indicated that the decolorization process followed a first order exponential kinetic model, and the surface-normalized decolorization rate could reach 2.09 L/(m2 x min) at room temperature, which was about ten times larger than any previously reported under similar conditions. Recycling experiments also proved that the ribbons could be reused at least four times without obvious decay of decolorization rate and efficiency. This study suggests a tremendous application potential for amorphous ZVI in remediation of groundwater or wastewater contaminated with azo dyes.

  3. UV Irradiation and Humic Acid Mediate Aggregation of Aqueous Fullerene (nC60) Nanoparticles

    EPA Science Inventory

    The transport and fate of engineered nanomaterials is affected by multiple environmental factors, including sunlight and natural organic matter. In this study, the initial aggregation kinetics of aqueous fullerene (nC60) nanoparticles before and after UVA irradiation was investig...

  4. Formic acid enhanced effective degradation of methyl orange dye in aqueous solutions under UV-Vis irradiation.

    PubMed

    Wang, Jingjing; Bai, Renbi

    2016-09-15

    Developing efficient technologies to treat recalcitrant organic dye wastewater has long been of great research and practical interest. In this study, a small molecule, formic acid (FA), was applied as a process enhancer for the degradation of methyl orange (MO) dye as a model recalcitrant organic pollutant in aqueous solutions under the condition of UV-Vis light irradiation and air aeration at the ambient temperature of 25 °C. It was found that the decolouration of the dye solutions can be rapidly achieved, reducing the time, for example, from around 17.6 h without FA to mostly about less than 2 h with the presence of FA. The mineralization rate of MO dye reached as high as 81.8% in 1.5 h in the case of initial MO dye concentration at 25 mg L(-1), which is in contrast to nearly no mineralization of the MO dye for a similar system without the FA added. The study revealed that the generation of the H2O2 species in the system was enhanced and the produced OH radicals effectively contributed to the degradation of the MO dye. Process parameters such as the initial concentration of MO dye, FA dosage and solution pH were all found to have some effect on the degradation efficiency under the same condition of UV-Vis light irradiation and air aeration. The MO dye degradation performance was found to follow a first-order reaction rate to the MO dye concentration in most cases and there existed a positive correlation between the reaction rate constant and the initial FA concentration. Compared to the traditional H2O2/UV-Vis oxidation system, the use of FA as a process-enhancing agent can have the advantages of low cost, easy availability, and safe to use. The study hence demonstrates a promising approach to use a readily available small molecule of FA to enhance the degradation of recalcitrant organic pollutants, such as MO dye, especially for their pre-treatment. PMID:27258621

  5. Oligo-Glycine Synthesis in an Aqueous Solution of Glycine Under Oxidative Conditions

    NASA Astrophysics Data System (ADS)

    Yamagata, Yukio; Yamashita, Atsunori; Inomata, Katsuhiko

    1980-03-01

    Di-and tri-glycine were synthesized in 1M aqueous solution of glycine by bubbling for 90 hr with oxygen discharged in the path from an oxygen cylinder. The peptides were also produced by an incubation at 37°C of 2M glycine solution prepared with 75% hydrogen peroxide, and the yields were traced for 200 days. The final yields were about 0.25% and 0.01% for di-and tri-glycine, respectively. The solution at 166 days of incubation was applied to a Sephadex G 10 column, and the fractions around the top of the chromatogram were found to increase the intensity of ninhydrin color about 4˜5 times after hydrolysis, indicating an existence of oligo-glycine. The solutions of 1M glycine and 0.5M diglycine prepared with 30% hydrogen peroxide were incubated at 37°C for 38 days, and di-and tetra-glycine were detected in the yields of 0.12% and 0.33%, respectively.

  6. A systematic investigation and insight into the formation mechanism of bilayers of fatty acid/soap mixtures in aqueous solutions.

    PubMed

    Xu, Wenlong; Song, Aixin; Dong, Shuli; Chen, Jingfei; Hao, Jingcheng

    2013-10-01

    Vesicles are the most common form of bilayer structures in fatty acid/soap mixtures in aqueous solutions; however, a peculiar bilayer structure called a "planar sheet" was found for the first time in the mixtures. In the past few decades, considerable research has focused on the formation theory of bilayers in fatty acid/soap mixtures. The hydrogen bond theory has been widely accepted by scientists to explain the formation of bilayers. However, except for the hydrogen bond, no other driving forces were proposed systematically. In this work, three kinds of weak interactions were investigated in detail, which could perfectly demonstrate the formation mechanism of bilayer structures in the fatty acid/soap mixtures in aqueous solutions. (i) The influence of hydrophobic interaction was detected by changing the chain length of fatty acid (C(n)H(2n+1)COOH), in which n = 10 to 18, the phase behavior was investigated, and the phase region was presented. With the help of cryogenic transmission electron microscopy (cryo-TEM) observations, deuterium nuclear magnetic resonance ((2)H NMR), and X-ray diffraction (XRD) measurements, the vesicles and planar sheets were determined. The chain length of C(n)H(2n+1)COOH has an important effect on the physical state of the hydrophobic chain, resulting in an obvious difference in the viscoelasticity of the solution samples. (ii) The existence of hydrogen bonds between fatty acids and their soaps in aqueous solutions was demonstrated by Fourier transform infrared (FT-IR) spectroscopy and molecule dynamical simulation. From the pH measurements, the pH ranges of the bilayer formation were at the pKa values of fatty acids, respectively. (iii) Counterions can be embedded in the stern layer of the bilayers and screen the electrostatic repulsion between the COO(-) anionic headgroups. FT-IR characterization demonstrated a bidentate bridging coordination mode between counterions and carboxylates. The conductivity measurements provided the degree

  7. 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

  8. Batch salicylic acid nitration by nitric acid/acetic acid mixture under isothermal, isoperibolic and adiabatic conditions.

    PubMed

    Andreozzi, R; Canterino, M; Caprio, V; Di Somma, I; Sanchirico, R

    2006-12-01

    Runaway phenomena and thermal explosions can originate during the nitration of salicylic acid by means of a nitric acid/acetic acid mixture when the thermal control is lost, mainly as a result of the formation and thermal decomposition of picric acid. The prediction of the behaviour of this system is thus of great importance in view of possible industrial applications and the need to avoid the occurrence of unwanted dangerous events. During a previous investigation a model was developed to simulate its behaviour when the starting concentration of the substrate is too low, thus, preventing the precipitation of poor soluble intermediates. In this work this model is extended to deal with more concentrated systems even in case of a solid phase separating during the process. To this purpose the previously assessed dependence of the solubility of 3-nitro and 5-nitrosalicylic acids upon temperature and nitric acid concentration is included in the model. It is assumed that when 3-nitro and 5-nitrosalicylic acids are partially suspended in the reacting medium a kinetic regime of "dissolution with reaction" is established; that is, the redissolution of these species is a fast process compared to the successive nitration to give dinitroderivatives. Good results are obtained in the comparison of the experimental data with those calculated both in isoperibolic and adiabatic conditions when the revised model is used.

  9. Polyurethane foam loaded with sodium dodecylsulfate for the extraction of 'quat' pesticides from aqueous medium: Optimization of loading conditions.

    PubMed

    Vinhal, Jonas O; Lima, Claudio F; Cassella, Ricardo J

    2016-09-01

    The cationic herbicides paraquat, diquat and difenzoquat are largely used in different cultures worldwide. With this, there is an intrinsic risk of environmental contamination when these herbicides achieve natural waters. The goal of this work was to propose a novel and low-cost sorbent for the removal of the cited herbicides from aqueous medium. The proposed sorbent was prepared by loading polyurethane foam with sodium dodecylsulfate. The influence of several parameters (SDS concentration, HCl concentration and shaking time) on the loading process was investigated. The results obtained in this work demonstrated that all studied variables influenced the loading process, having significant effect on the extraction efficiency of the resulted PUF-SDS. At optimized conditions, the PUF was loaded by shaking 200mg of crushed foam with 200mL of a solution containing 5.0×10(-3)molL(-1) SDS and 0.25molL(-1) HCl, for 30min. The obtained PUF-SDS was efficient for removing the three herbicides from aqueous medium, achieving extraction percentages higher than 90%. The sorption process followed a pseudo second-order kinetics, which presented excellent predictive capacity of the amount of herbicide retained with time. PMID:27213562

  10. Photochemical decomposition of dissolved hydroxylated polybrominated diphenyl ethers under various aqueous conditions.

    PubMed

    Bastos, Patricia Moreira; Eriksson, Johan; Bergman, Ake

    2009-10-01

    The area of fire protection has grown over the last decades with an increasing use of brominated flame retardants (BFRs). Some of the BFRs are phenolic compounds as applied, e.g. tetrabromobisphenol A and 2,4,6-tribromophenol. Others, like the polybrominated diphenyl ethers (PBDEs), can be metabolized to phenolic compounds, i.e. polybrominated phenoxyphenols (OH-PBDEs). OH-PBDEs, have to our knowledge never been commercially produced, but some are well known natural products, and found in high concentrations in biota. The present study is aimed to determine the susceptibility of OH-PBDEs to undergo photolysis when dissolved in water and to compare their reactivity with a couple of PBDE congeners. A previously developed method for studies of photolysis was applied and adapted to include OH-PBDEs in water at pH 7 and 11, water/methanol and water/hydrogen peroxide. The results indicate a change in reaction rates for the photolysis of OH-PBDE in different aqueous media and pH dependence. The results from the present study show that hydroxylated compounds rapidly undergo photolytic transformations in water. The OH-PBDEs are more rapidly transformed then PBDE congeners with similar numbers of bromine substituents. All the OH-PBDEs, independent of structure, are rapidly transformed, with approx. the same rate, when hydrogen peroxide is present, indicating another route of reaction. Polybrominated dibenzo-p-dioxins (PBDDs) are indicated as transformation products upon photolysis of OH-PBDEs with a favorable bromine substitution pattern.

  11. Impact of humic/fulvic acid on the removal of heavy metals from aqueous solutions using nanomaterials: a review.

    PubMed

    Tang, Wang-Wang; Zeng, Guang-Ming; Gong, Ji-Lai; Liang, Jie; Xu, Piao; Zhang, Chang; Huang, Bin-Bin

    2014-01-15

    Nowadays nanomaterials have been widely used to remove heavy metals from water/wastewater due to their large surface area and high reactivity. Humic acid (HA) and fulvic acid (FA) exist ubiquitously in aquatic environments and have a variety of functional groups which allow them to complex with metal ions and interact with nanomaterials. These interactions can not only alter the environmental behavior of nanomaterials, but also influence the removal and transportation of heavy metals by nanomaterials. Thus, the interactions and the underlying mechanisms involved warrant specific investigations. This review outlined the effects of HA/FA on the removal of heavy metals from aqueous solutions by various nanomaterials, mainly including carbon-based nanomaterials, iron-based nanomaterials and photocatalytic nanomaterials. Moreover, mechanisms involved in the interactions were discussed and potential environmental implications of HA/FA to nanomaterials and heavy metals were evaluated.

  12. 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.

  13. Amino acid tautomerization reactions in aqueous solution via concerted and assisted mechanisms using free energy curves from MD simulation.

    PubMed

    Tolosa, Santiago; Hidalgo, Antonio; Sansón, Jorge A

    2012-11-01

    A theoretical study is described of chemical reactions in solution by means of molecular dynamics simulations, with solute-solvent interaction potentials derived from AMBER van der Waals parameters and QM/MM electrostatic charges in solution. The solvent is used as the reaction coordinate, and the free energy curves to calculate the properties related to the reaction mechanism. The proposed scheme is applied to the tautomerization process in aqueous solution for some amino acids H(2)NCHR-COOH (with R = H being glycine, R = CH(3) alanine, R = CH(2)OH serine, and R = CH(2)COOH aspartic acid), focusing on the role of the solvent in the reaction (assisted versus unassisted mechanisms) and on the effect of the hydrophilic/hydrophobic character of the radical R on the activation and reaction energies.

  14. Selective Chemical Conversion of Sugars in Aqueous Solutions without Alkali to Lactic Acid Over a Zn-Sn-Beta Lewis Acid-Base Catalyst

    NASA Astrophysics Data System (ADS)

    Dong, Wenjie; Shen, Zheng; Peng, Boyu; Gu, Minyan; Zhou, Xuefei; Xiang, Bo; Zhang, Yalei

    2016-05-01

    Lactic acid is an important platform molecule in the synthesis of a wide range of chemicals. However, in aqueous solutions without alkali, its efficient preparation via the direct catalysis of sugars is hindered by a side dehydration reaction to 5-hydroxymethylfurfural due to Brønsted acid, which originates from organic acids. Herein, we report that a previously unappreciated combination of common two metal mixed catalyst (Zn-Sn-Beta) prepared via solid-state ion exchange synergistically promoted this reaction. In water without a base, a conversion exceeding 99% for sucrose with a lactic acid yield of 54% was achieved within 2 hours at 190 °C under ambient air pressure. Studies of the acid and base properties of the Zn-Sn-Beta zeolite suggest that the introduction of Zn into the Sn-Beta zeolite sequentially enhanced both the Lewis acid and base sites, and the base sites inhibited a series of side reactions related to fructose dehydration to 5-hydroxymethylfurfural and its subsequent decomposition.

  15. Selective Chemical Conversion of Sugars in Aqueous Solutions without Alkali to Lactic Acid Over a Zn-Sn-Beta Lewis Acid-Base Catalyst

    PubMed Central

    Dong, Wenjie; Shen, Zheng; Peng, Boyu; Gu, Minyan; Zhou, Xuefei; Xiang, Bo; Zhang, Yalei

    2016-01-01

    Lactic acid is an important platform molecule in the synthesis of a wide range of chemicals. However, in aqueous solutions without alkali, its efficient preparation via the direct catalysis of sugars is hindered by a side dehydration reaction to 5-hydroxymethylfurfural due to Brønsted acid, which originates from organic acids. Herein, we report that a previously unappreciated combination of common two metal mixed catalyst (Zn-Sn-Beta) prepared via solid-state ion exchange synergistically promoted this reaction. In water without a base, a conversion exceeding 99% for sucrose with a lactic acid yield of 54% was achieved within 2 hours at 190 °C under ambient air pressure. Studies of the acid and base properties of the Zn-Sn-Beta zeolite suggest that the introduction of Zn into the Sn-Beta zeolite sequentially enhanced both the Lewis acid and base sites, and the base sites inhibited a series of side reactions related to fructose dehydration to 5-hydroxymethylfurfural and its subsequent decomposition. PMID:27222322

  16. Selective Chemical Conversion of Sugars in Aqueous Solutions without Alkali to Lactic Acid Over a Zn-Sn-Beta Lewis Acid-Base Catalyst.

    PubMed

    Dong, Wenjie; Shen, Zheng; Peng, Boyu; Gu, Minyan; Zhou, Xuefei; Xiang, Bo; Zhang, Yalei

    2016-01-01

    Lactic acid is an important platform molecule in the synthesis of a wide range of chemicals. However, in aqueous solutions without alkali, its efficient preparation via the direct catalysis of sugars is hindered by a side dehydration reaction to 5-hydroxymethylfurfural due to Brønsted acid, which originates from organic acids. Herein, we report that a previously unappreciated combination of common two metal mixed catalyst (Zn-Sn-Beta) prepared via solid-state ion exchange synergistically promoted this reaction. In water without a base, a conversion exceeding 99% for sucrose with a lactic acid yield of 54% was achieved within 2 hours at 190 °C under ambient air pressure. Studies of the acid and base properties of the Zn-Sn-Beta zeolite suggest that the introduction of Zn into the Sn-Beta zeolite sequentially enhanced both the Lewis acid and base sites, and the base sites inhibited a series of side reactions related to fructose dehydration to 5-hydroxymethylfurfural and its subsequent decomposition. PMID:27222322

  17. Selective Chemical Conversion of Sugars in Aqueous Solutions without Alkali to Lactic Acid Over a Zn-Sn-Beta Lewis Acid-Base Catalyst.

    PubMed

    Dong, Wenjie; Shen, Zheng; Peng, Boyu; Gu, Minyan; Zhou, Xuefei; Xiang, Bo; Zhang, Yalei

    2016-05-25

    Lactic acid is an important platform molecule in the synthesis of a wide range of chemicals. However, in aqueous solutions without alkali, its efficient preparation via the direct catalysis of sugars is hindered by a side dehydration reaction to 5-hydroxymethylfurfural due to Brønsted acid, which originates from organic acids. Herein, we report that a previously unappreciated combination of common two metal mixed catalyst (Zn-Sn-Beta) prepared via solid-state ion exchange synergistically promoted this reaction. In water without a base, a conversion exceeding 99% for sucrose with a lactic acid yield of 54% was achieved within 2 hours at 190 °C under ambient air pressure. Studies of the acid and base properties of the Zn-Sn-Beta zeolite suggest that the introduction of Zn into the Sn-Beta zeolite sequentially enhanced both the Lewis acid and base sites, and the base sites inhibited a series of side reactions related to fructose dehydration to 5-hydroxymethylfurfural and its subsequent decomposition.

  18. Oxyhalogen-sulfur chemistry: kinetics and mechanism of oxidation of chemoprotectant, sodium 2-mercaptoethanesulfonate, MESNA, by acidic bromate and aqueous bromine.

    PubMed

    Adigun, Risikat Ajibola; Mhike, Morgen; Mbiya, Wilbes; Jonnalagadda, Sreekanth B; Simoyi, Reuben H

    2014-03-27

    The oxidation of a well-known chemoprotectant in anticancer therapies, sodium 2-mercaptoethanesulfonate, MESNA, by acidic bromate and aqueous bromine was studied in acidic medium. Stoichiometry of the reaction is: BrO3(-) + HSCH2CH2SO3H → Br(-) + HO3SCH2CH2SO3H. In excess bromate conditions the stoichiometry was deduced to be: 6BrO3(-) + 5HSCH2CH2SO3H + 6H(+) → 3Br2 + 5HO3SCH2CH2SO3H + 3H2O. The direct reaction of bromine and MESNA gave a stoichiometric ratio of 3:1: 3Br2 + HSCH2CH2SO3H + 3H2O → HO3SCH2CH2SO3H + 6Br(-) + 6H(+). This direct reaction is very fast; within limits of the mixing time of the stopped-flow spectrophotometer and with a bimolecular rate constant of 1.95 ± 0.05 × 10(4) M(-1) s(-1). Despite the strong oxidizing agents utilized, there is no cleavage of the C-S bond and no sulfate production was detected. The ESI-MS data show that the reaction proceeds via a predominantly nonradical pathway of three consecutive 2-electron transfers on the sulfur center to obtain the product 1,2-ethanedisulfonic acid, a well-known medium for the delivery of psychotic drugs. Thiyl radicals were detected but the absence of autocatalytic kinetics indicated that the radical pathway was a minor oxidation route. ESI-MS data showed that the S-oxide, contrary to known behavior of organosulfur compounds, is much more stable than the sulfinic acid. In conditions where the oxidizing equivalents are limited to a 4-electron transfer to only the sulfinic acid, the products obtained are a mixture of the S-oxide and the sulfonic acid with negligible amounts of the sulfinic acid. It appears the S-oxide is the preferred conformation over the sulfenic acid since no sulfenic acids have ever been stabilized without bulky substituent groups. The overall reaction scheme could be described and modeled by a minimal network of 18 reactions in which the major oxidants are HOBr and Br2(aq).

  19. A rapid and sensitive assay of perfluorocarboxylic acids in aqueous matrices by headspace solid phase microextraction-gas chromatography-triple quadrupole mass spectrometry.

    PubMed

    Monteleone, Marcello; Naccarato, Attilio; Sindona, Giovanni; Tagarelli, Antonio

    2012-08-17

    The work aims at developing a rapid and sensitive method for the quantification of perfluorocarboxylic acids in aqueous matrices. The proposed analytical approach is based on the use of solid phase microextraction in headspace mode after a fast derivatization of the carboxylate function by propylchloroformate/propanol mixture. Several fibers were evaluated and the optimization of the parameters affecting the SPME process was carried out using a central composite design. The optimum working conditions in terms of response values were achieved by performing analysis with CAR/PDMS fiber at room temperature, without addition of NaCl, with a sample volume of 6 ml and an extraction time of 10 min. Assay of PFCAs was performed by using a gas chromatography-triple quadrupole mass spectrometry (GC-QqQ MS) system in negative chemical ionization mode with ammonia as reagent gas. An overall evaluation of all analytical parameters shows that the proposed method provides satisfactory results. In particular, the observed accuracies, ranging from 84.4% to 116.8%, and the RSD values in the range 0.4% and 14.5% confirm the effectiveness of the developed protocol in the assay of PFCAs content in aqueous matrices. Moreover, LOD and LOQ values ranging from 0.08 to 6.6 ng l(-1) and from 0.17 to 14.3 ng l(-1), respectively, can be considered very satisfactory. None of the compounds were detected in six samples of river collected in Calabria. PMID:22762954

  20. Application of acid-treated yeast cell wall (AYC) as a pharmaceutical additive. III. AYC aqueous coating onto granules and film formation mechanism of AYC.

    PubMed

    Yuasa, Hiroshi; Kaneshige, Junichi; Ozeki, Tetsuya; Kasai, Takahide; Eguchi, Takahiro; Ishiwaki, Naomu

    2002-04-26

    From the viewpoint of effective utilization of natural resources and development of new pharmaceutical materials, acid-treated yeast cell wall (AYC) was prepared via a novel approach involving acidification of brewers' yeast cell wall. AYC aqueous dispersion containing 5% (w/v) AYC and 0.5% (w/v) glycerol was prepared. Subsequently, AYC was coated onto core granules containing acetaminophen (AAP). Spray mist size under various spray conditions and viscosity of the AYC aqueous dispersion at various AYC concentrations were measured. AYC spray mists were optically observed. The surface of AYC cast film and AYC-coated granules were observed with a confocal scanning laser microscope. We attempted to show the utility of AYC as a novel material for granule coating, following the tablet coating in our previous report. In addition, the film formation mechanism of AYC was investigated. A smooth surface of the AYC-coated granules was obtained at a coating ratio of only 5%, which generally requires approximately 15-30% coating against the core granule weight, with no aggregation. These results are attributable to the fact that the granules were coated with a large number of small mists of AYC and the coating progressed efficiently, and the thin film layer of AYC was formed on the granules by mutual tangling of the hydrogel layers of AYC polysaccharides. AAP release from AYC-coated granules was obviously rapid, suggesting the high utility of AYC as a coating material for the rapidly releasing granules.

  1. Removal of uranium(VI) from aqueous solution using iminodiacetic acid derivative functionalized SBA-15 as adsorbents.

    PubMed

    Wang, Yu-Long; Song, Li-Juan; Zhu, Lu; Guo, Bo-Long; Chen, Su-Wen; Wu, Wang-Suo

    2014-03-01

    Three different functional SBA-15 were prepared by a post-grafting method using three iminodiacetic acid derivatives of ethylenediaminetriacetic acid (ED3A), diethylenetriaminetetraacetic acid (DT4A), and 1,2-cyclohexylenedinitrilotriacetic acid (CyD3A), which were used as adsorbents for removal of uranium(vi) from aqueous solution. These materials were characterized by FT-IR, NMR, TEM, nitrogen adsorption/desorption experiments, and elemental analysis. The effect of pH, ionic strength, contact time, solid-liquid ratio, initial metal ion concentration, temperature, and coexisting ions on uranium(vi) sorption behaviors of the functionalized SBA-15 was studied. Typical sorption isotherms (Langmuir and Freundlich) were determined for the sorption process, and the maximum sorption capacity was calculated. The influence of functional groups on uranium(vi) sorption was also discussed. As a result, compared with other current U(vi) sorbents (granite, kaolin, attapulgite), SBA-15-1,2-cyclohexylenedinitrilotriacetic acid (SBA-15-CyD3A) possessed good selective sorption properties, which had potential application in separation of uranium(vi). PMID:24435450

  2. Removal of uranium(VI) from aqueous solution using iminodiacetic acid derivative functionalized SBA-15 as adsorbents.

    PubMed

    Wang, Yu-Long; Song, Li-Juan; Zhu, Lu; Guo, Bo-Long; Chen, Su-Wen; Wu, Wang-Suo

    2014-03-01

    Three different functional SBA-15 were prepared by a post-grafting method using three iminodiacetic acid derivatives of ethylenediaminetriacetic acid (ED3A), diethylenetriaminetetraacetic acid (DT4A), and 1,2-cyclohexylenedinitrilotriacetic acid (CyD3A), which were used as adsorbents for removal of uranium(vi) from aqueous solution. These materials were characterized by FT-IR, NMR, TEM, nitrogen adsorption/desorption experiments, and elemental analysis. The effect of pH, ionic strength, contact time, solid-liquid ratio, initial metal ion concentration, temperature, and coexisting ions on uranium(vi) sorption behaviors of the functionalized SBA-15 was studied. Typical sorption isotherms (Langmuir and Freundlich) were determined for the sorption process, and the maximum sorption capacity was calculated. The influence of functional groups on uranium(vi) sorption was also discussed. As a result, compared with other current U(vi) sorbents (granite, kaolin, attapulgite), SBA-15-1,2-cyclohexylenedinitrilotriacetic acid (SBA-15-CyD3A) possessed good selective sorption properties, which had potential application in separation of uranium(vi).

  3. Biodegradable hyaluronic acid hydrogels to control release of dexamethasone through aqueous Diels-Alder chemistry for adipose tissue engineering.

    PubMed

    Fan, Ming; Ma, Ye; Zhang, Ziwei; Mao, Jiahui; Tan, Huaping; Hu, Xiaohong

    2015-11-01

    A robust synthetic strategy of biopolymer-based hydrogels has been developed where hyaluronic acid derivatives reacted through aqueous Diels-Alder chemistry without the involvement of chemical catalysts, allowing for control and sustain release of dexamethasone. To conjugate the hydrogel, furan and maleimide functionalized hyaluronic acid were synthesized, respectively, as well as furan functionalized dexamethasone, for the covalent immobilization. Chemical structure, gelation time, morphologies, swelling kinetics, weight loss, compressive modulus and dexamethasone release of the hydrogel system in PBS at 37°C were studied. The results demonstrated that the aqueous Diels-Alder chemistry provides an extremely selective reaction and proceeds with high efficiency for hydrogel conjugation and covalent immobilization of dexamethasone. Cell culture results showed that the dexamethasone immobilized hydrogel was noncytotoxic and preserved proliferation of entrapped human adipose-derived stem cells. This synthetic approach uniquely allows for the direct fabrication of biologically functionalized gel scaffolds with ideal structures for adipose tissue engineering, which provides a competitive alternative to conventional conjugation techniques such as copper mediated click chemistry.

  4. Efficient photochemical decomposition of long-chain perfluorocarboxylic acids by means of an aqueous/liquid CO2 biphasic system.

    PubMed

    Hori, Hisao; Yamamoto, Ari; Kutsuna, Shuzo

    2005-10-01

    Photochemical decomposition of persistent and bioaccumulative long-chain (C9-C11) perfluorocarboxylic acids (PFCAs) with persulfate ion (S2O8(2-)) in an aqueous/liquid CO2 biphasic system was examined to develop a technique to neutralize stationary sources of the long-chain PFCAs. The long-chain PFCAs, namely, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUA), which are used as emulsifying agents and as surface treatment agents in industry, are relatively insoluble in water but are soluble in liquid CO2; therefore, introduction of liquid CO2 to the aqueous photoreaction system reduces the interference of colloidal PFCA particles. When the biphasic system was used to decompose these PFCAs, the extent of reaction was 6.4-51 times as high as that achieved in the absence of CO2. In the biphasic system, PFNA, PFDA, and PFUA (33.5-33.6 micromol) in 25.0 mL of water were 100%, 100%, and 77.1% decomposed, respectively, after 12 h of irradiation with a 200-W xenon-mercury lamp; F- ions were produced as a major product, and short-chain PFCAs, which are less bioaccumulative than the original PFCAs, were minor products. All of the initial S2O8(2-) was transformed to SO42-. The system also efficiently decomposed PFCAs at lower concentrations (e.g., 4.28-16.7 micromol of PFDA in 25.0 mL) and was successfully applied to decompose PFNA in floor wax.

  5. Optimization of Aqueous Extraction Conditions for Recovery of Phenolic Content and Antioxidant Properties from Macadamia (Macadamia tetraphylla) Skin Waste

    PubMed Central

    Dailey, Adriana; Vuong, Quan V.

    2015-01-01

    The macadamia is native to Australia and is now grown commercially around the world. Macadamia skin, known as waste, has been generated abundantly, but this ample source has had limited uses as a byproduct. The aim of this study was to develop optimal aqueous extraction conditions for the recovery of phenolic compounds and antioxidant properties from macadamia skin using Response Surface Methodology (RSM). Water was selected for optimizing the extraction conditions because it is a cheap, safe, and environmentally friendly solvent. The results showed that the RSM models were reliable for the prediction and evaluation of the tested variables. Within the tested ranges, temperature (°C), time (min), and sample-to-solvent ratio (g/100 mL), and their interactions, did not significantly affect phenolic compound (TPC), flavonoid, proanthocyanidin, CUPRAC, and FRAP contents. However, the time and the sample-to-solvent ratio significantly affected DPPH antioxidant activity and the ratio significantly affected ABTS antioxidant capacity. The optimal extraction conditions for the recovery of phenolic compounds and antioxidant properties were predicted and validated at a temperature of 90 °C, a time of 20 min, and a sample-to-solvent ratio of 5 g/100 mL. At these conditions, an extract with TPC of 86 mg GAE/g, flavonoids of 30 mg RUE/g, and proanthocyanidins of 97 mg CAE/g could be prepared with potent antioxidant capacity. PMID:26783954

  6. Optimization of Aqueous Extraction Conditions for Recovery of Phenolic Content and Antioxidant Properties from Macadamia (Macadamia tetraphylla) Skin Waste.

    PubMed

    Dailey, Adriana; Vuong, Quan V

    2015-01-01

    The macadamia is native to Australia and is now grown commercially around the world. Macadamia skin, known as waste, has been generated abundantly, but this ample source has had limited uses as a byproduct. The aim of this study was to develop optimal aqueous extraction conditions for the recovery of phenolic compounds and antioxidant properties from macadamia skin using Response Surface Methodology (RSM). Water was selected for optimizing the extraction conditions because it is a cheap, safe, and environmentally friendly solvent. The results showed that the RSM models were reliable for the prediction and evaluation of the tested variables. Within the tested ranges, temperature (°C), time (min), and sample-to-solvent ratio (g/100 mL), and their interactions, did not significantly affect phenolic compound (TPC), flavonoid, proanthocyanidin, CUPRAC, and FRAP contents. However, the time and the sample-to-solvent ratio significantly affected DPPH antioxidant activity and the ratio significantly affected ABTS antioxidant capacity. The optimal extraction conditions for the recovery of phenolic compounds and antioxidant properties were predicted and validated at a temperature of 90 °C, a time of 20 min, and a sample-to-solvent ratio of 5 g/100 mL. At these conditions, an extract with TPC of 86 mg GAE/g, flavonoids of 30 mg RUE/g, and proanthocyanidins of 97 mg CAE/g could be prepared with potent antioxidant capacity. PMID:26783954

  7. Gamma irradiation of isocitric and citric acid in aqueous solution: Relevance in prebiotic chemistry

    SciTech Connect

    Negrón-Mendoza, A. Ramos-Bernal, S.

    2015-07-23

    The radiation chemistry of hydroxy acids like citric and isocitric acids is rather scarce, even though they are crucial compounds in biological systems and for food irradiation. The aim of this work is to study the radiolytic behavior of these acids focused on the interconversion induced by radiation of citric and isocitric acid into other members of the Krebs cycle. The results showed that among the products formed were succinic, malonic, malic and other acids related to metabolic pathways, and these results are correlated with its possible role in chemical evolution processes.

  8. Gamma irradiation of isocitric and citric acid in aqueous solution: Relevance in prebiotic chemistry

    NASA Astrophysics Data System (ADS)

    Negrón-Mendoza, A.; Ramos-Bernal, S.

    2015-07-01

    The radiation chemistry of hydroxy acids like citric and isocitric acids is rather scarce, even though they are crucial compounds in biological systems and for food irradiation. The aim of this work is to study the radiolytic behavior of these acids focused on the interconversion induced by radiation of citric and isocitric acid into other members of the Krebs cycle. The results showed that among the products formed were succinic, malonic, malic and other acids related to metabolic pathways, and these results are correlated with its possible role in chemical evolution processes.

  9. Hydrothermal diamond anvil cell for XAFS studies of first-row transition elements in aqueous solutions up to supercritical conditions

    USGS Publications Warehouse

    Bassett, William A.; Anderson, Alan J.; Mayanovic, Robert A.; Chou, I.-Ming

    2000-01-01

    A hydrothermal diamond anvil cell (HDAC) has been modified by drilling holes with a laser to within 150 ??m of the anvil face to minimize the loss of X-rays due to absorption and scatter by diamond. This modification enables acquisition of K-edge X-ray absorption fine structure (XAFS) spectra from first-row transition metal ions in aqueous solutions at temperatures ranging from 25??C to 660??C and pressures up to 800 MPa. These pressure-temperature (P-T) conditions are more than sufficient for carrying out experimental measurements that can provide data valuable in the interpretation of fluid inclusions in minerals found in ore-forming hydrothermal systems as well as other important lithospheric processes involving water. (C) 2000 Elsevier Science B.V. All rights reserved.

  10. Theoretical study of interactions between cysteine and perfluoropropanoic acid in gas and aqueous phase

    NASA Astrophysics Data System (ADS)

    Holmes, Tiffani M.; Doskocz, Jacek; Wright, Terrance; Hill, Glake A.

    The interaction of perfluoropropanoic acid (PFPA) with the amino acid cysteine was investigated using density functional theory. Previous studies suggest that the peroxisome proliferator chemical, perfluorooctanoic acid, is circulated throughout the body by way of sulfur-containing amino acids. We present conformational analysis of the interactions of PFPA, a small model of perfluorooctanoic acid, with the sulfur-containing amino acid which occur by the process of hydrogen bonding, in which the hydrogen of the sulfhydryl group interacts with the carboxyl oxygen, and the amino nitrogen forms a hydrogen bond with the hydrogen of the bond OH group of the fluorinated alkyl. We also show in our structures a recently characterized weak nonbonded interaction between divalent sulfur and a main chain carboxyl oxygen in proteins. B3LYP calculated free energies and interaction energies predict low-energy, high-interaction conformations for complex systems of perfluorinated fatty acid interactions with cysteine.

  11. Understanding Correlations Between Structure and Redox Properties in Aqueously-Dispersible, Electrically-Conductive, Polymer-Acid-Doped Polyaniline

    NASA Astrophysics Data System (ADS)

    Tarver, Jacob Daniel

    Template synthesis of polyaniline, or PANI, on poly(2-acrylamido-2-methyl-1-propanesulfonic acid), or PAAMPSA, yields aqueously-dispersible PANI-PAAMPSA particles. Through pH-resolved cyclic voltammetry and UV-vis/NIR spectroscopy measurements, PANI-PAAMPSA exhibits stable and reversible transitions to and from PANI's fully oxidized, intermediate, and fully reduced oxidation states of pernigraniline, emeraldine salt, and leucoemeraldine, respectively, in buffer solutions across a pH range of 3-7. Above pH 7, PANI-PAAMPSA exhibits direct transitions between its pernigraniline and leucoemeraldine states. Each of these states possesses unique optical properties, thus imbuing PANI-PAAMPSA with polyelectrochromism without the need to incorporate any comonomers. Transitions between each of PANI's oxidation states approach 95% completion within 10 seconds. Hysteresis, however, is observed in the electrochromic response as the film is subjected to random cycling, a conditioning effect that is attributed to the gradual relaxation of PANI-PAAMPSA particles as the electrostatic interactions between the two polymers is electrochemically moderated. Solvent-annealing PANI-PAAMPSA in dichloroacetic acid (DCA) induces dramatic structural relaxations, resulting in significant enhancements in terms of stability and reversibility in PANI-PAAMPSA's polyelectrochromic response. This DCA treatment equilibrates the structure within PANI-PAAMPSA films, obviating the dynamic relaxation processes that occur during polyelectrochromic switching with untreated films. The influence of internal film structure on PANI-PAAMPSA's polyelectrochromic ability is further investigated as a function of PANI-PAAMPSA particle size by controlling PAAMPSA's molecular characteristics. The kinetics of PANI-PAAMPSA's electrochromic transitions exhibit an inverse relationship between reaction rate and particle size. By modeling the transmission response, analogies are drawn between polymer crystallization

  12. In-situ spectroscopic investigations of the redox behavior of poly(indole-5-carboxylic-acid) modified electrodes in acidic aqueous solutions.

    PubMed

    Talbi, H; Billaud, D; Louarn, G; Pron, A

    2001-03-01

    The oxidation of electrochemically grown poly(indole-5-carboxylic-acid) (P5CO2H) and its spectroscopic properties have been studied by in-situ spectroelectrochemical techniques. The purpose of this paper is to characterize the different modifications on the P5CO2H backbone, induced by the electrochemical oxidation in aqueous acidic solution. We have identified, on the basis of Raman spectra, the vibrational modes associated with neutral and oxidized segments of polymer. It was shown that at least three chemically and optically different species (perhaps other products too) are produced in different potential regimes upon oxidation of this polymer. The results obtained also indicate that the molecular properties of this conducting polymer are better revealed by in-situ resonant spectra than by ex-situ infrared and Raman studies.

  13. Fluorescent Ag nanoclusters prepared in aqueous poly(acrylic acid-co-maleic acid) solutions: a spectroscopic study of their excited state dynamics, size and local environment.

    PubMed

    Dandapat, Manika; Mandal, Debabrata

    2016-01-28

    Stable, fluorescent Ag nanoclusters were prepared in aqueous solutions of Na(+) salt of the carboxylate-rich polymer poly(acrylic acid-co-maleic acid) under brief spells of UV irradiation. The nanoclusters were nearly spherical, with diameters within 1.90 ± 0.50 nm, but displayed a prominent red edge excitation shift (REES) of fluorescence upon exciting within the visible absorption band, indicating heterogeneity of energy level distributions. Spectroscopic studies revealed that irrespective of whether the nanoclusters are excited in their UV or visible absorption bands, their fluorescence always ensues from the same manifold of emissive states, with a broad range of fluorescence lifetimes from ∼150 fs to 1 ns. PMID:26700465

  14. Static and dynamic investigations of poly(aspartic acid) and Pluronic F127 complex prepared by self-assembling in aqueous solution

    NASA Astrophysics Data System (ADS)

    Nita, Loredana E.; Chiriac, Aurica P.; Bercea, Maria; Nistor, Manuela T.

    2015-12-01

    The present investigation is focused on evaluation of self-assembling ability in aqueous solutions of two water soluble polymers: poly(aspartic acid) (PAS) and Pluronic F127 (PL). The intermolecular complexes, realized between polyacid and neutral copolymer surfactant in different ratios, have been studied by combining various characterization techniques as rheology, DLS, spectroscopy, microscopy, chemical imaging, and zeta potential determination, measurements performed in static and/or dynamic conditions. In static conditions, when the equilibrium state between PAS/PL polymeric pair was reached, and depending on the polymers mixture composition, and of experimental rheological conditions, positive or negative deviations from the additive rule are registered. Conformational changes of the macromolecular chains and correspondingly physical interactions are generated between PL and PAS for self-assembly and the formation of interpolymer complex as suprastructure with micellar configuration. The phenomenon was better evidenced in case of 1/1 wt ratio between the two polymers. In dynamic conditions of determination, during "in situ" evaluation of the hydrodynamic diameter, zeta potential and conductivity, when the equilibrium state is not reached and as result either the intermolecular bonds are not achieved, the self-assembling process is not so obvious evidenced.

  15. 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

  16. Coordinating Chiral Ionic Liquids: Design, Synthesis, and Application in Asymmetric Transfer Hydrogenation under Aqueous Conditions

    PubMed Central

    Vasiloiu, Maria; Gaertner, Peter; Zirbs, Ronald; Bica, Katharina

    2015-01-01

    Hydrophilic coordinating chiral ionic liquids with an amino alcohol substructure were developed and efficiently applied to the asymmetric reduction of ketones. Their careful design and adaptability to the desired reaction conditions allow for these chiral ionic liquids to be used as the sole source of chirality in a ruthenium-catalyzed transfer hydrogenation reaction of aromatic ketones. When used in this reaction system, these chiral ionic liquids afforded excellent yields and high enantioselectivities. PMID:26279638

  17. Fast and highly-efficient removal of methylene blue from aqueous solution by poly(styrenesulfonic acid-co-maleic acid)-sodium-modified magnetic colloidal nanocrystal clusters

    NASA Astrophysics Data System (ADS)

    Song, Yu-Bei; Lv, Shao-Nan; Cheng, Chang-Jing; Ni, Guo-Li; Xie, Xiao-Wa; Huang, Wei; Zhao, Zhi-Gang

    2015-01-01

    Magnetic colloidal nanocrystal clusters (MCNCs) modified with different amounts of poly(4-styrenesulfonic acid-co-maleic acid) sodium (PSSMA) have been prepared through simple one-step solvothermal method for removal of methylene blue (MB) from aqueous solution. The prepared MCNCs are characterized by Fourier transform infrared (FT-IR) spectra, scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), nitrogen adsorption-desorption technique and dynamic light scattering (DLS). Moreover, effects of the solution pH, contact time, adsorbent dosage, ionic strength and initial dye concentration on MB adsorption onto the MCNCs are systematically investigated. The PSSMA-modified MCNCs show fast and highly-efficient MB removal capacity, which dramatically depends on the immobilization amounts of PSSMA, solution pH and adsorbent dosage. Their adsorption kinetics and isotherms exhibit that the kinetics and equilibrium adsorptions can be well-described by pseudo-second-order kinetic and Langmuir model, respectively. These magnetic nanocomposites, with high separation efficiency, low production cost and recyclable property, are promising as functional adsorbents for efficient removal of cationic organic pollutants from aqueous solution.

  18. Formation of diphenylthioarsinic acid from diphenylarsinic acid under anaerobic sulfate-reducing soil conditions.

    PubMed

    Hisatomi, Shihoko; Guan, Ling; Nakajima, Mami; Fujii, Kunihiko; Nonaka, Masanori; Harada, Naoki

    2013-11-15

    Diphenylarsinic acid (DPAA) is a toxic phenylarsenical compound often found around sites contaminated with phenylarsenic chemical warfare agents, diphenylcyanoarsine or diphenylchloroarsine, which were buried in soil after the World Wars. This research concerns the elucidation of the chemical structure of an arsenic metabolite transformed from DPAA under anaerobic sulfate-reducing soil conditions. In LC/ICP-MS analysis, the retention time of the metabolite was identical to that of a major phenylarsenical compound synthesized by chemical reaction of DPAA and hydrogen sulfide. Moreover the mass spectra for the two compounds measured using LC/TOF-MS were similar. Subsequent high resolution mass spectral analysis indicated that two major ions at m/z 261 and 279, observed on both mass spectra, were attributable to C12H10AsS and C12H12AsSO, respectively. These findings strongly suggest that the latter ion is the molecular-related ion ([M+H](+)) of diphenylthioarsinic acid (DPTA; (C6H5)2AsS(OH)) and the former ion is its dehydrated fragment. Thus, our results reveal that DPAA can be transformed to DPTA, as a major metabolite, under sulfate-reducing soil conditions. Moreover, formation of diphenyldithioarsinic acid and subsequent dimerization were predicted by the chemical reaction analysis of DPAA with hydrogen sulfide. This is the first report to elucidate the occurrence of DPAA-thionation in an anaerobic soil. PMID:24007995

  19. Surface crystallographic dependence of voltammetric oxidation of polyhydric alcohols and related systems at monocrystalline gold-acidic aqueous interfaces

    NASA Astrophysics Data System (ADS)

    Hamelin, Antoinette; Ho, Yeunghaw; Chang, Si-Chung; Gao, Xiaoping; Weaver, Michael J.

    1992-02-01

    The voltammetric oxidation in aqueous 0.1 Molar perchloric acid of four polyhydric alcohols, ethylene glycol, glycerol, meso-erythritol, and d-mannitol, on seven oriented gold surfaces is reported with the objective of assessing the role of surface crystallographic orientation on the catalytic electrooxidation of such poly-functional reactants. The automatically well-ordered nature of these gold surfaces has been scrutinized by in-situ scanning tunneling microscopy. In particular, the Au(221) and (533) faces were selected since they provide stepped surfaces, 4(111)-(111) and 4(111)-(100), respectively. The results are compared with corresponding data for simple unifunctional reactants, specifically for formic acid oxidation and with results reported previously for carbon monoxide oxidation. In contrast to the last reaction, the electrooxidation rates for both the polyhydric alcoholic and formic acid are greatest on Au(111), with Au(110) displaying unusually low activity. While formic acid electrooxidation is insensitive to the presence of monoatomic surface steps, the polyhydric alcohols (especially mannitol) are substantially less reactive on AU(221) and (533) relative to Au(111).

  20. The uptake of 2-methyl-3-buten-2-ol into aqueous mixed solutions of sulfuric acid and hydrogen peroxide.

    PubMed

    Liu, Ze; Ge, Maofa; Wang, Weigang; Yin, Shi; Tong, Shengrui

    2011-02-14

    Multiphase acid-catalyzed oxidation with hydrogen peroxide (H(2)O(2)) has been suggested recently to be a potential route to SOA formation from isoprene and its gas-phase oxidation products, the kinetics and chemical mechanism of this process have not been well-known yet. In this work, the uptake of 2-methyl-3-buten-2-ol (MBO), an important biogenic hydrocarbon and structurally similar to isoprene, into aqueous mixed solutions of H(2)O(2) and sulfuric acid (H(2)SO(4)) was performed using a rotated wetted-wall reactor coupled to a differentially pumped single-photon ionization time of flight mass spectrometer (RWW-SPI-TOFMS). The reactive uptake coefficients (γ) were acquired for the first time and the reaction pathways were deduced according to products information. The reactive uptake coefficients of MBO into H(2)SO(4)-H(2)O(2) mixed solutions are much greater than that into H(2)SO(4) solutions. Acetaldehyde, acetone and an on-line product, which transformed to isoprene readily in the duration of an off-line experiment, were suggested as products in this process. The further reactions of the carbonyl products can occur in acidic solution, which may play a role in SOA formation. Additionally, in real atmosphere the on-line product is apt to transform to isoprene, an acknowledged precursor of biogenic SOA. Thus, the multiphase acid-catalyzed oxidation of MBO with H(2)O(2) might be a potential contributor to SOA loading.

  1. [Uptake of 3-methyl-3-buten-1-ol into aqueous mixed solution of sulfuric acid and hydrogen peroxide].

    PubMed

    Wang, Tian-He; Liu, Ze; Ge, Mao-Fa; Wang, Wei-Gang

    2011-12-01

    Multiphase acid-catalyzed oxidation with hydrogen peroxide (H2O2) has been suggested recently to be a potential route to SOA formation, but the kinetics and chemical mechanism of this process have not been well-known yet. In this work, the uptake of 3-methyl-3-buten-1-ol (MBO331) into aqueous mixed solutions of H2O2, and sulfuric acid (H2SO4) was performed using a rotated wetted-wall reactor coupled to a VUV single-photon ionization time of flight mass spectrometer (VUV-SPI-TOFMS). The reactive uptake coefficients (gamma) were acquired for the first time and the reaction pathways were deduced according to products information. The uptake of MBO331 into H2SO4/H2O2 was fast, resulting in gamma reaching 2.52 x 10(-4)-1.05 x 10(-2) for 40%-60% H2SO4. Acetaldehyde, acetone and 3-methyl-3, 4-expoxybutane-1-ol were suggested as gas-phase products in this process. 3-methyl-3,4-expoxybutane-1-ol can transform into polyhydroxy compounds while the further reactions of the carbonyl products can occur in acidic solution, which may play a role in SOA formation. Thus, the heterogeneous acid-catalyzed oxidation of MBO331 with H2O2 might be a significant contributor to SOA loading.

  2. Radiation- and photo-induced formation of salicylic acid from phenol and CO{sub 2} in aqueous solution

    SciTech Connect

    Krapfenbauer, K.; Getoff, N.

    1996-12-31

    The concentration of CO{sub 2} in the atmosphere is steady increasing because of the combustion of fossil fuels and the industrial pollution. As a result, global warming has occurred. In the present study the formation of the salicylic acid and other products, originating from the carboxylation of phenol is investigated. It has been found that the formation of salicylic acid strongly depend on several experimental conditions: pH of the solution, concentration of phenol and CO{sub 2}, and absorbed dose. The formation of salicylic acid was also studied in the presence of catalysts. Photo-induced carboxylation of phenol to salicylic acid will be also reported. Probable reaction mechanisms for the salicylic acid formation are suggested. Finally, a comparison is made between the well known industrial Kolbe-Schmitt process for salicylic acid production and the aspects of the present new method for CO{sub 2} utilization.

  3. Structural and vibrational investigation on species derived from the cyclamic acid in aqueous solution by using HATR and Raman spectroscopies and SCRF calculations

    NASA Astrophysics Data System (ADS)

    Brizuela, Alicia B.; Raschi, Ana B.; Castillo, María V.; Davies, Lilian; Romano, Elida; Brandán, Silvia A.

    2014-09-01

    In this study, aqueous solutions at different molar concentrations of sodium cyclamate in water were completely characterized by HATR (Horizontal Attenuated Total Reflectance) and Raman spectroscopies. The theoretical structures of cyclamate ion, the zwitterionic and neutral forms of the cyclamic acid and its dimer were optimized in gas and aqueous solution phases by using the hybrid B3LYP/6-31G* method. The solvent effects for the four species in aqueous solutions were simulated by using self-consistent reaction field (SCRF) calculations employing the integral equation formalism variant (IEFPCM) model. The complete assignments of the vibrational spectra of all the forms of cyclamic acid were performed taking into account the factor group analysis with the Scaled Quantum Mechanics Force Field (SQMFF) methodology. The existence of the zwitterionic and neutral forms of the cyclamic acid and its dimer in a solution of cyclamate in water is evidenced by characteristic bands in the HATR and Raman spectra. The dimerization of cyclamate in aqueous solution was previously reported by conductimetric method. The natural population analysis (NPA) and Merz-Kollman (MK) charges, molecular electrostatic potential (MEP), natural bond orbital (NBO) and atoms in molecules (AIM) calculations predict for all the species the principal donor and acceptor sites for the H bonds formation in aqueous solution. The SQM force fields for the cyclamate ion, the zwitterionic and neutral species of the cyclamic acid were obtained and their corresponding force constants in both phases were reported. Additionally, the solvation energies for those species were reported.

  4. Immobilization of selenate by iron in aqueous solution under anoxic conditions and the influence of uranyl

    NASA Astrophysics Data System (ADS)

    Puranen, Anders; Jonsson, Mats; Dähn, Rainer; Cui, Daqing

    2009-08-01

    In proposed high level radioactive waste repositories a large part of the spent nuclear fuel (SNF) canisters are commonly composed of iron. Selenium is present in spent nuclear fuel as a long lived fission product. This study investigates the influence of iron on the uptake of dissolved selenium in the form of selenate and the effect of the presence of dissolved uranyl on the above interaction of selenate. The iron oxide, and selenium speciation on the surfaces was investigated by Raman spectroscopy. X-ray Absorption Spectroscopy was used to determine the oxidation state of the selenium and uranium on the surfaces. Under the simulated groundwater conditions (10 mM NaCl, 2 mM NaHCO 3, <0.1 ppm O 2) the immobilized selenate was found to be reduced to oxidation states close to zero or lower and uranyl was found to be largely reduced to U(IV). The near simultaneous reduction of uranyl was found to greatly enhance the rate of selenate reduction. These findings suggest that the presence of uranyl being reduced by an iron surface could substantially enhance the rate of reduction of selenate under anoxic conditions relevant for a repository.

  5. 21 CFR 522.144 - Arsenamide sodium aqueous injection.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Arsenamide sodium aqueous injection. 522.144... § 522.144 Arsenamide sodium aqueous injection. (a) Chemical name. dithio diacetic acid, sodium salt. (b... sodium. (c) Sponsor. See No. 050604 in § 510.600(c) of this chapter. (d) Conditions of use. (1) For...

  6. 21 CFR 522.144 - Arsenamide sodium aqueous injection.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Arsenamide sodium aqueous injection. 522.144... § 522.144 Arsenamide sodium aqueous injection. (a) Chemical name. dithio diacetic acid, sodium salt. (b... sodium. (c) Sponsor. See No. 050604 in § 510.600(c) of this chapter. (d) Conditions of use. (1) For...

  7. Enrichment of the Amino Acid L-Isovaline by Aqueous Alteration on CI and CM Meteorite Parent Bodies

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Dworkin, Jason P.

    2009-01-01

    The distribution and enantiomeric composition of the 5-carbon (C(sub 5)) amino acids found in Cl-, CM-, and CR-type carbonaceous meteorites were investigated by using liquid chromatography fluorescence detection/TOF-MS coupled with o-phthaldialdehyde/Nacetyl- l-cysteine derivatization. A large L-enantiomeric excess (ee) of the a-methyl amino acid isovaline was found in the CM meteorite Murchison (L(sub ee) = 18.5 +/- 2.6%) and the Cl meteorite Orguell (L(sub ee) = 15.2 +/- 4.0%). The measured value for Murchison is the largest enantiomeric excess in any meteorite reported to date, and the Orgueil measurement of an isovaline excess has not been reported previously for this or any Cl meteorite. The L-isovaline enrichments in these two carbonaceous meteorites cannot be the result of interference from other C(sub 5) amino acid isomers present in the samples, analytical biases, or terrestrial amino acid contamination. We observed no L-isovaline enrichment for the most primitive unaltered Antarctic CR meteorites EET 92042 and QUE 99177. These results are inconsistent with UV circularly polarized light as the primary mechanism for L-isovaline enrichment and indicate that amplification of a small initial isovaline asymmetry in Murchison and Orgueil occurred during an extended aqueous alteration phase on the meteorite parent bodies. The large asymmetry in isovaline and other alpha-dialkyl amino acids found in altered Ct and CM meteorites suggests that amino acids delivered by asteroids, comets, and their fragments would have biased the Earth's prebiotic organic inventory with left-handed molecules before the origin of life.

  8. Interactions of silicate glasses with aqueous environments under conditions of prolonged contact and flow

    NASA Technical Reports Server (NTRS)

    Barkatt, Aaron; Saad, E. E.; Adiga, R. B.; Sousanpour, W.; Barkatt, AL.; Feng, X.; O'Keefe, J. A.; Alterescu, S.

    1988-01-01

    This paper discusses mechanisms involving saturation and reactions that lead to the formation of altered phases in silicate glasses considered for use in geologic repositories for nuclear waste. It is shown that the rate of dissolution of silicate glasses exposed to a broad range of contact times, leachant compositions, and surface-to-volume ratios is strongly affected by the presence of reactive species such as Al, Mg, and Fe. The reactive materials may originate in the leachant or, under conditions of high surface-to-volume ratio, in the glass itself. The effects of glass composition on the course of the corrosion process can be viewed in terms of the formation of a surface layer on the leached glass; the type, composition, and structure of this layer control the dissolution behavior of the glass.

  9. Physical properties of rocks and aqueous fluids at conditions simulating near- and supercritical reservoirs

    NASA Astrophysics Data System (ADS)

    Kummerow, Juliane; Raab, Siegfried

    2016-04-01

    The growing interest in exploiting supercritical geothermal reservoirs calls for a thorough identification and understanding of physico-chemical processes occuring in geological settings with a high heat flow. In reservoir engineering, electrical sounding methods are common geophysical exploration and monitoring tools. However, a realistic interpretation of field measurements is based on the knowledge of both, the physical properties of the rock and those of the interacting fluid at defined temperature and pressure conditions. Thus, laboratory studies at simulated in-situ conditions provide a link between the field data and the material properties in the depth. The physico-chemical properties of fluids change dramatically above the critical point, which is for pure water 374.21 °C and 221.2 bar. In supercritical fluids mass transfer and diffusion-controlled chemical reactions are enhanced and cause mineral alterations. Also, ion mobility and ion concentration are affected by the change of physical state. All this cause changes in the electrical resistivity of supercritical fluids and may have considerable effects on the porosity and hydraulic properties of the rocks they are in contact with. While there are some datasets available for physical and chemical properties of water and single component salt solutions above their critical points, there exist nearly no data for electrical properties of mixed brines, representing the composition of natural geothermal fluids. Also, the impact of fluid-rock interactions on the electrical properties of multicomponent fluids in a supercritical region is scarcely investigated. For a better understanding of fluid-driven processes in a near- and supercritical geological environment, in the framework of the EU-funded FP7 program IMAGE we have measured (1) the electrical resistivity of geothermal fluids and (2) physical properties of fluid saturated rock samples at simulated in-situ conditions. The permeability and electrical

  10. Long-term degradation study of hyaluronic acid in aqueous solutions without protection against microorganisms.

    PubMed

    Simulescu, Vasile; Kalina, Michal; Mondek, Jakub; Pekař, Miloslav

    2016-02-10

    The degradation of hyaluronan (HA) of different molecular weights (Mw 14.3, 267.2 and 1160.6 kDa, measured for fresh solutions, before degradation) was studied in aqueous solutions by SEC-MALLS determination of molecular mass, polydispersity and conformation parameters. The solutions were stored either at laboratory or refrigerator temperatures for two months. After this period the weight average molecular weight decreased by 90% for 14.3 kDa, 95% for 267.2 kDa and 71% for 1160.6 kDa hyaluronan (room temperature) or 5.6% for 14.3 kDa, 6.2% for 267.2 kDa and 7.7% for 1160.6 kDa hyaluronan (refrigerator temperature). The hyaluronan aqueous solutions studied did not contain sodium azide or other protectants against microorganisms, because the aim of our study was to assess the degradation in solutions to be used in medicine or cosmetics (without any compounds that are poisonous or toxic for the human body). The solvent used to prepare the samples was pure water. The polydispersity of all the samples remained unaltered during the entire degradation at both temperatures. This indicates a non-random mechanism of degradation. PMID:26686177

  11. Hybrid molecularly imprinted poly(methacrylic acid-TRIM)-silica chemically modified with (3-glycidyloxypropyl)trimethoxysilane for the extraction of folic acid in aqueous medium.

    PubMed

    de Oliveira, Fernanda Midori; Segatelli, Mariana Gava; Tarley, César Ricardo Teixeira

    2016-02-01

    In the present study a hybrid molecularly imprinted poly(methacrylic acid-trimethylolpropane trimethacrylate)-silica (MIP) was synthesized and modified with (3-glycidyloxypropyl)trimethoxysilane (GPTMS) with posterior opening of epoxy ring to provide hydrophilic properties of material in the extraction of folic acid from aqueous medium. The chemical and structural aggregates of hybrid material were characterized by means of Fourier Transform Infrared (FT-IR), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Thermogravimetric analysis (TGA) and textural data. Selectivity data of MIP were compared to non-imprinted polymer (NIP) through competitive sorption studies in the presence of caffeine, paracetamol or 4-aminobenzamide yielding relative selectivity coefficients (k′) higher than one unit, thus confirming the selective character of MIP even in the presence of structurally smaller compounds than the folic acid. The lower hydrophobic sorption by bovine serum albumin (BSA) in the MIP as compared to unmodified MIP proves the hydrophilicity of polymer surface by using GPTMS with opening ring. Under acid medium(pH 1.5) the sorption of folic acid onto MIP from batch experiments was higher than the one achieved for NIP. Equilibrium sorption of folic acid was reached at 120 min for MIP, NIP and MIP without GPTMS and kinetic sorption data were well described by pseudo-second-order, Elovich and intraparticle diffusion models. Thus, these results indicate the existence of different binding energy sites in the polymers and a complex mechanism consisting of both surface sorption and intraparticle transport of folic acid within the pores of polymers.

  12. Hybrid molecularly imprinted poly(methacrylic acid-TRIM)-silica chemically modified with (3-glycidyloxypropyl)trimethoxysilane for the extraction of folic acid in aqueous medium.

    PubMed

    de Oliveira, Fernanda Midori; Segatelli, Mariana Gava; Tarley, César Ricardo Teixeira

    2016-02-01

    In the present study a hybrid molecularly imprinted poly(methacrylic acid-trimethylolpropane trimethacrylate)-silica (MIP) was synthesized and modified with (3-glycidyloxypropyl)trimethoxysilane (GPTMS) with posterior opening of epoxy ring to provide hydrophilic properties of material in the extraction of folic acid from aqueous medium. The chemical and structural aggregates of hybrid material were characterized by means of Fourier Transform Infrared (FT-IR), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Thermogravimetric analysis (TGA) and textural data. Selectivity data of MIP were compared to non-imprinted polymer (NIP) through competitive sorption studies in the presence of caffeine, paracetamol or 4-aminobenzamide yielding relative selectivity coefficients (k′) higher than one unit, thus confirming the selective character of MIP even in the presence of structurally smaller compounds than the folic acid. The lower hydrophobic sorption by bovine serum albumin (BSA) in the MIP as compared to unmodified MIP proves the hydrophilicity of polymer surface by using GPTMS with opening ring. Under acid medium(pH 1.5) the sorption of folic acid onto MIP from batch experiments was higher than the one achieved for NIP. Equilibrium sorption of folic acid was reached at 120 min for MIP, NIP and MIP without GPTMS and kinetic sorption data were well described by pseudo-second-order, Elovich and intraparticle diffusion models. Thus, these results indicate the existence of different binding energy sites in the polymers and a complex mechanism consisting of both surface sorption and intraparticle transport of folic acid within the pores of polymers. PMID:26652418

  13. Acetic Acid Increases Stability of Silage under Aerobic Conditions

    PubMed Central

    Danner, H.; Holzer, M.; Mayrhuber, E.; Braun, R.

    2003-01-01

    The effects of various compounds on the aerobic stability of silages were evaluated. It has been observed that inoculation of whole-crop maize with homofermentative lactic acid bacteria leads to silages which have low stability against aerobic deterioration, while inoculation with heterofermentative lactic acid bacteria, such as Lactobacillus brevis or Lactobacillus buchneri, increases stability. Acetic acid has been proven to be the sole substance responsible for the increased aerobic stability, and this acid acts as an inhibitor of spoilage organisms. Therefore, stability increases exponentially with acetic acid concentration. Only butyric acid has a similar effect. Other compounds, like lactic acid, 1,2-propanediol, and 1-propanol, have been shown to have no effect, while fructose and mannitol reduce stability. PMID:12514042

  14. Extraction of electrolytes from aqueous solutions and their spectrophotometric determination by use of acid-base chromoionophores in lipophylic solvents.

    PubMed

    Barberi, Paola; Giannetto, Marco; Mori, Giovanni

    2004-04-01

    The formation of non-absorbing complexes in an organic phase has been exploited for the spectrophotometric determination of ionic analytes in aqueous solutions. The method is based on liquid-liquid extraction of aqueous solution with lipophylic organic phases containing an acid-base chromoionophore, a neutral lypophilic ligand (neutral carrier) selective to the analyte and a cationic (or anionic) exchanger. The method avoids all difficulties of the preparation of the very thin membranes used in optodes, so that it can advantageously be used for the study of the role physical-chemical parameters of the system in order to optimize them and to prepare, if necessary, an optimized optode. Two lipophylic derivatives of Nile Blue and 4',5-dibromofluorescein have been synthesized, in order to ensure their permanence within organic phase. Two different neutral carriers previously characterized by us as ionophores for liquid-membrane Ion Selective Electrodes have been employed. Three different ionic exchangers have been tested. Furthermore, a model allowing the interpolation of experimental data and the determination of the thermodynamic constant of the ionic-exchange equilibrium has been developed and applied. PMID:15242090

  15. Impact of acid mine drainage on benthic communities in streams: the relative roles of substratum vs. aqueous effects.

    PubMed

    DeNicol, Dean M; Stapleton, Michael G

    2002-01-01

    Restoration of streams impacted by acid mine drainage (AMD) focuses on improving water quality, however precipitates of metals on the substrata can remain and adversely affect the benthos. To examine the effects of AMD precipitates independently of aqueous effects, four substrata treatments, clean sandstone, clean limestone, AMD precipitate-coated sandstone and coated limestone, were placed in a circumneutral stream of high water quality for 4 weeks. Iron and Al were the most abundant metals on rocks with AMD precipitate. and significantly decreased after the exposure. Precipitate on the substrata did not significantly affect macroinvertebrate or periphyton density and species composition. In an additional experiment, percent survival of caged live caddisflies was significantly lower when exposed in situ for 5 days in an AMD affected stream than in a reference stream. Caddisfly whole-body concentrations of all combined metals and Fe alone were significantly higher in the AMD stream. Whole-body metal concentrations were higher in killed caddisflies than in live, indicating the importance of passive uptake. The results suggest the aqueous chemical environment of AMD had a greater affect on organisms than a coating of recent AMD precipitate on the substrata (ca. 0.5 mm thick), and treatment that improves water quality in AMD impacted streams has the potential to aid in recovery of the abiotic and biotic benthic environment.

  16. 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.

  17. Corrosion inhibition behavior of propyl phosphonic acid-Zn2+ system for carbon steel in aqueous solution

    NASA Astrophysics Data System (ADS)

    Prabakaran, M.; Venkatesh, M.; Ramesh, S.; Periasamy, V.

    2013-07-01

    The effectiveness of propyl phosphonic acid (PPA) as a corrosion inhibitor in association with a bivalent cation like Zn2+ has been studied. An eco-friendly inhibitor in controlling corrosion of carbon steel in neutral aqueous medium in the absence and presence of Zn2+ has been evaluated by gravimetric method. Impedance studies of the metal/solution interface indicated that the surface film is highly protective against the corrosion of carbon steel in the aqueous environment. Potentiodynamic polarization studies showed that the inhibitor is a mixed inhibitor. X-ray photoelectron spectroscopic analysis (XPS) of the protective film exhibited the presence of the elements viz., iron, phosphorus, oxygen, carbon and zinc. The chemical shifts in the binding energies of these elements inferred that the surface film is composed of oxides/hydroxides of iron(III), Zn(OH)2 and [Fe(II)/(III)-Zn(II)-PPA] complex. Further, the surface analysis techniques viz., FT-IR, AFM and SEM studies confirm the formation of an adsorbed protective film on the carbon steel surface. Based on all these results, a plausible mechanism of corrosion inhibition is proposed.

  18. Flow and morphological conditions associated with the directional solidification of aqueous ammonium chloride

    SciTech Connect

    Magirl, C.S.; Incropera, F.P.

    1993-01-01

    Using 27% aq. NH[sub 4]Cl solutions as transparent analog, shadowgraphy and dye injection were used to observe flow and morphology in unidirectional solidification (UDS) from below. Dendritic crystals that form at the cold surface reject lighter, solute-deficient fluid, and instability is shown by finger-type double-diffusive convection. As the mushy two-phase region grows, perturbations at the liquidus interface cause localized remelting and downward development of channels. Solsutal plumes emanate from the channels, and in time, double-diffusive convection layers also form in the melt. When the solution is chilled at the sides as well as at the bottom, conditions are influenced by detachment and settling of crystals from the sidewall and by plumes from slanted channels. When a slow, oscillatory rocking motion is imposed on UDS, the freckle-type segregates in the final cast is suppressed. Within the melt, plumes and double-diffusive convection are eliminated. Inertially induced convection mixes the melt and produces a dense slurry. Although channels are eliminated from the bottom mushy region, overall heat transfer and macrosegregation in the cavity are unaffected by the slow rocking. Numerical simulations qualitatively predict trends in the field variables and provide insights on interdendritic flows and macrosegregation (freckle-, A-type segregates), although its quantitative predictions are hampered by simplifying assumptions.

  19. Flow and morphological conditions associated with the directional solidification of aqueous ammonium chloride. Annual performance report

    SciTech Connect

    Magirl, C.S.; Incropera, F.P.

    1993-01-01

    Using 27% aq. NH{sub 4}Cl solutions as transparent analog, shadowgraphy and dye injection were used to observe flow and morphology in unidirectional solidification (UDS) from below. Dendritic crystals that form at the cold surface reject lighter, solute-deficient fluid, and instability is shown by finger-type double-diffusive convection. As the mushy two-phase region grows, perturbations at the liquidus interface cause localized remelting and downward development of channels. Solsutal plumes emanate from the channels, and in time, double-diffusive convection layers also form in the melt. When the solution is chilled at the sides as well as at the bottom, conditions are influenced by detachment and settling of crystals from the sidewall and by plumes from slanted channels. When a slow, oscillatory rocking motion is imposed on UDS, the freckle-type segregates in the final cast is suppressed. Within the melt, plumes and double-diffusive convection are eliminated. Inertially induced convection mixes the melt and produces a dense slurry. Although channels are eliminated from the bottom mushy region, overall heat transfer and macrosegregation in the cavity are unaffected by the slow rocking. Numerical simulations qualitatively predict trends in the field variables and provide insights on interdendritic flows and macrosegregation (freckle-, A-type segregates), although its quantitative predictions are hampered by simplifying assumptions.

  20. Radiofluorination of diaryliodonium tosylates under aqueous-organic and cryptand-free conditions.

    PubMed

    Chun, Joong-Hyun; Telu, Sanjay; Lu, Shuiyu; Pike, Victor W

    2013-08-21

    Positron emission tomography (PET) has growing importance as a molecular imaging technique in clinical research and drug development. Methods for producing PET radiotracers utilizing cyclotron-produced [(18)F]fluoride ion (t1/2 = 109.7 min) without the need for complete removal of irradiated target [(18)O]water and addition of cryptand are keenly sought for practical convenience and efficiency. Several structurally diverse diaryliodonium tosylates, XArI(+)Ar'Y TsO(-) (X = H or p-MeO), were investigated in a microfluidic apparatus for their reactivity towards radiofluorination with high specific activity (no-carrier-added) [(18)F]fluoride ion in mixtures of DMF and irradiated target [(18)O]water in the absence of cryptand. Salts bearing a para or ortho electron-withdrawing group Y (e.g., Y = p-CN) reacted rapidly (∼3 min) to give the expected major [(18)F]fluoroarene product, [(18)F]FArY, in useful moderate radiochemical yields even when the solvent had an [(18)O]water content up to 28%. Salts bearing electron-withdrawing groups in meta position (e.g., Y = m-NO2), or an electron-donating substituent (Y = p-OMe), gave low radiochemical yields under the same conditions.