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Sample records for aqueous acidic solution

  1. 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.

  2. 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…

  3. 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.

  4. 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.

  5. 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.

  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. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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%.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  10. 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.

  11. 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

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

    PubMed

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

    2013-07-01

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

  13. 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

  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. 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. 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.

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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).

  3. 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.

  4. 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.

  5. 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.

  6. Interfacial structures of acidic and basic aqueous solutions

    SciTech Connect

    Tian, C.; Ji, N.; Waychunas, G.; Shen, Y.R.

    2008-10-20

    Phase-sensitive sum-frequency vibrational spectroscopy was used to study water/vapor interfaces of HCl, HI, and NaOH solutions. The measured imaginary part of the surface spectral responses provided direct characterization of OH stretch vibrations and information about net polar orientations of water species contributing to different regions of the spectrum. We found clear evidence that hydronium ions prefer to emerge at interfaces. Their OH stretches contribute to the 'ice-like' band in the spectrum. Their charges create a positive surface field that tends to reorient water molecules more loosely bonded to the topmost water layer with oxygen toward the interface, and thus enhances significantly the 'liquid-like' band in the spectrum. Iodine ions in solution also like to appear at the interface and alter the positive surface field by forming a narrow double-charge layer with hydronium ions. In NaOH solution, the observed weak change of the 'liquid-like' band and disappearance of the 'ice-like' band in the spectrum indicates that OH{sup -} ions must also have excess at the interface. How they are incorporated in the interfacial water structure is however not clear.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  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. 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

  16. 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.

  17. [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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Methylene blue adsorption from aqueous solution by activated carbon: effect of acidic and alkaline solution treatments.

    PubMed

    Ijagbemi, Christianah O; Chun, Ji I; Han, Da H; Cho, Hye Y; O, Se J; Kim, Dong S

    2010-01-01

    The removal of Methylene Blue (MB) from aqueous solution using activated carbon (AC) has been investigated. Adsorption experiments were conducted and the maximum adsorption capacity was determined. The effect of experimental parameters such as pH, dye concentration and temperature were studied on the adsorption process. Equilibrium data were mathematically modeled using the Langmuir and Freundlich adsorption models to describe the equilibrium isotherms at different dye concentrations and temperature. Parameters of best-fit model were calculated and discussed. To understand the mechanism of adsorption, kinetic models were employed to follow the adsorption processes; the pseudo-first-order best described the adsorption of MB onto AC. It was found that pH plays a major role in the adsorption process; adsorption capacity was influenced by the physical and surface chemical properties of carbon and the pH of the solution. 99.0% MB removal was achieved at equilibrium.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. 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.

  13. 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.

  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. PMID:25389749

  15. [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

  16. [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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Solution properties and taste behavior of lactose monohydrate in aqueous ascorbic acid solutions at different temperatures: Volumetric and rheological approach.

    PubMed

    Sarkar, Abhijit; Sinha, Biswajit

    2016-11-15

    The densities and viscosities of lactose monohydrate in aqueous ascorbic acid solutions with several molal concentrations m=(0.00-0.08)molkg(-1) of ascorbic acid were determined at T=(298.15-318.15)K and pressure p=101kPa. Using experimental data apparent molar volume (ϕV), standard partial molar volume (ϕV(0)), the slope (SV(∗)), apparent specific volumes (ϕVsp), standard isobaric partial molar expansibility (ϕE(0)) and its temperature dependence [Formula: see text] the viscosity B-coefficient and solvation number (Sn) were determined. Viscosity B-coefficients were further employed to obtain the free energies of activation of viscous flow per mole of the solvents (Δμ1(0≠)) and of the solute (Δμ2(0≠)). Effects of molality, solute structure and temperature and taste behavior were analyzed in terms of solute-solute and solute-solvent interactions; results revealed that the solutions are characterized predominantly by solute-solvent interactions and lactose monohydrate behaves as a long-range structure maker. PMID:27283672

  7. 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.

  8. 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

  9. 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

  10. 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

  11. 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.

  12. CESIUM RECOVERY FROM AQUEOUS SOLUTIONS

    DOEpatents

    Goodall, C.A.

    1960-09-13

    A process is given for precipitating cesium on zinc ferricyanide (at least 0.0004 M) from aqueous solutions containing mineral acid in a concentration of from 0.2 N acidity to 0.61 N acid-deficiency and advantageously, but not necessarily, also aluminum nitrate in a concentration of from l to 2.5 M.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. Cesium recovery from aqueous solutions

    DOEpatents

    Goodhall, C. A.

    1960-09-13

    A process for recovering cesium from aqueous solutions is given in which precipitation on zinc ferricyanide is used. The precipitation is preferably carried out in solutions containing at least 0.0004M zinc ferricyanide, an acidity ranging from 0.2N mineral acid to 0.61N acid deficiency, and 1 to 2.5M aluminum nitrate. (D.L.C.)

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  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. 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.

  14. 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

  15. 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

  16. 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

  17. CESIUM RECOVERY FROM AQUEOUS SOLUTIONS

    DOEpatents

    Schneider, R.A.

    1961-06-20

    Cesium may be precipitated from an aqueous solution whose acidity ranges between a pH of 1.5 and a molarity of 5 on cobaltous, zinc, cadmium, nickel, or ferrous cobalticyanide. This precipitation brings about a separation from most fission products. Ruthenium which coprecipitates to a great degree can be removed by dissolving in sulfuric acid and boiling the solution in the presence of periodic acid for volatilization; other coprecipitated fission products can then be precipitated from the sulfuric acid solution with a ferric hydroxide carrier.

  18. 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.

  19. 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

  20. Reflectance of aqueous solutions

    NASA Technical Reports Server (NTRS)

    Querry, M. R.

    1972-01-01

    The optical properties and optical constants of water and aqueous solutions were studied to develop an accurate tabulation of graphical representations of the optical constants through a broad spectrum. Manuscripts of articles are presented concerning extinction coefficients, relative specular reflectance, and temperature effect on the water spectrum. Graphs of absolute reflectance, phase shifts, index of refraction, and extinction coefficients for water, heavy water and aqueous solutions are included.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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

  6. 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.

  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. 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

  9. 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.

  10. 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.

  11. 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

  12. Solute-enhanced production of gamma-valerolactone (GVL) from aqueous solutions of levulinic acid

    DOEpatents

    Dumesic, James A; Wettstein, Stephanie G; Alonso, David Martin; Gurbuz, Elif Ispir

    2015-02-24

    A method to produce levulinic acid (LA) and gamma-valerolactone (GVL) from biomass-derived cellulose or lignocellulose by selective extraction of LA using GVL and optionally converting the LA so isolated into GVL, with no purifications steps required to yield the GVL.

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. [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

  4. 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

  5. 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.

  6. 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

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. Thermodynamic and Ultrasonic Properties of Ascorbic Acid in Aqueous Protic Ionic Liquid Solutions

    PubMed Central

    Singh, Vickramjeet; Sharma, Gyanendra; Gardas, Ramesh L.

    2015-01-01

    In this work, we report the thermodynamic and ultrasonic properties of ascorbic acid (vitamin C) in water and in presence of newly synthesized ammonium based protic ionic liquid (diethylethanolammonium propionate) as a function of concentration and temperature. Apparent molar volume and apparent molar isentropic compression, which characterize the solvation state of ascorbic acid (AA) in presence of protic ionic liquid (PIL) has been determined from precise density and speed of sound measurements at temperatures (293.15 to 328.15) K with 5 K interval. The strength of molecular interactions prevailing in ternary solutions has been discussed on the basis of infinite dilution partial molar volume and partial molar isentropic compression, corresponding volume of transfer and interaction coefficients. Result has been discussed in terms of solute-solute and solute-solvent interactions occurring between ascorbic acid and PIL in ternary solutions (AA + water + PIL). PMID:26009887

  18. Stabilized aqueous hydrogen peroxide solution

    SciTech Connect

    Malin, M.J.; Sciafani, L.D.

    1988-05-17

    This patent describes a stabilized aqueous hydrogen peroxide solution having a pH below 7 and an amount of Ferric ion up to about 2 ppm comprising hydrogen peroxide, acetanilide having a concentration which ranges between 0.74 M Mol/L and 2.22 mMol/L, and o-benzene disulfonic acid or salt thereof at a concentration between about 0.86 mMol/L to about 1.62 mMol/L.

  19. 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.

  20. 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.

  1. 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)

  2. 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.

  3. Rheology and interfacial properties of aqueous solutions of the diblock polyelectrolyte poly(styrene-block-acrylic acid)

    NASA Astrophysics Data System (ADS)

    Kimerling, Abigail

    In aqueous solutions diblock polyelectrolytes with amphiphilic character form aggregate structures, which affect physical properties such as viscosity, elasticity, surface tension, and film hydrophilicity. Potential applications for diblock polyelectrolyte solutions include coatings, inks, oil recovery agents, personal care products, and biomaterials. By varying the diblock polyelectrolyte and solution properties, the solutions can be tuned to meet the needs of particular applications. The research objective was to identify the influences of block length, pH, and ionic strength on the rheological and interfacial properties of poly(styrene- b-acrylic acid) (PS-PAA) solutions. Six polymers with varied PS and PAA block lengths were examined, all at 1.0 wt% in aqueous solutions. The hydrophobicity of the PS block causes the formation of spherical micelles in aqueous solutions. Increasing the solution pH ionizes the PAA block, which leads to an increase in micelle corona thickness due to repulsions between chains. Major trends observed in the rheological and interfacial properties can be understood in terms of expected changes in the micelle size and interfacial self-assembly with pH, ionic strength, and block length. Addition of NaOH was found to increase the solution pH and initially led to increases in solution viscosity, elasticity, surface tension, and film hydrophilicity. This effect was attributed to creation of larger micelles and greater inter-micellar repulsions as the PAA chain became more fully charged. However, when the concentration of NaOH exceeded a critical value, the solution viscosity, elasticity, and film hydrophilicity decreased. It is believed this was due to charge shielding by excess sodium ions, leading to shrinkage of the micelle corona and smaller micelles. Increasing the PS-PAA solution ionic strength by adding NaCl also provided charge shielding, as observed by decreases in solution viscosity and elasticity. Increasing the length of either

  4. 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

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. REDUCTION OF PLUTONIUM VALUES IN AN ACIDIC AQUEOUS SOLUTION WITH FORMALDEHYDE

    DOEpatents

    Olson, C.M.

    1959-06-01

    A method is given for reducing Pu to the tetravalent state and lowering the high acidity of dissolver solutions containing U and Pu. Formaldehyde is added to the HNO/sub 3/ solution of U and Pu to effect a formaldehyde to HNO/sub 3/ molar ratio of 0.375:1 to 1.5:1. The Pu can then be removed from the solution by carrier precipitation using BiPO/sub 4/ or by ion exchange. (T.R.H.)

  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. PMID:25600471

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  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. Spectrofluorimetric study of the interaction of ciprofloxacin with amino acids in aqueous solution following solvatochromic studies

    NASA Astrophysics Data System (ADS)

    Alizadeh, Kamal; Mobarrez, Mahsa; Ganjali, Mohammad Reza; Norouzi, Parviz; Chaichi, Mohammad Javad

    Complexation of a fluoroquinolone derivative (ciprofloxacin), L, and some amino acids has been studied using spectrofluorimetric method. Results indicated that ciprofloxacin have a greater tendency to form a 1:1 complex with aspartic acid and arginine than the other tested molecules. The fluorescence of ciprofloxacin exhibits quenching process while it has been titrated with these amino acids. Formation constant values (Kf) for complex formed between ciprofloxacin and amino acids were also calculated. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were studied too. Possible reasons for the observed stability sequence were discussed based on the structures proposed for the resulting complexes. Besides the solution studies, solvatochromic properties of the ciprofloxacin are discussed by studying its spectra in a selection of different solvents.

  18. Poly (vinylsulfonic acid) assisted synthesis of aqueous solution stable vaterite calcium carbonate nanoparticles.

    PubMed

    Nagaraja, Ashvin T; Pradhan, Sulolit; McShane, Michael J

    2014-03-15

    Calcium carbonate nanoparticles of the vaterite polymorph were synthesized by combining CaCl2 and Na2CO3 in the presence of poly (vinylsulfonic acid) (PVSA). By studying the important experimental parameters we found that controlling PVSA concentration, reaction temperature, and order of reagent addition the particle size, monodispersity, and surface charge can be controlled. By increasing PVSA concentration or by decreasing temperature CCNPs with an average size from ≈150 to 500 nm could be produced. We believe the incorporation of PVSA into the reaction plays a dual role to (1) slow down the nucleation rate by sequestering calcium and to (2) stabilize the resulting CCNPs as the vaterite polymorph, preventing surface calcification or aggregation into microparticles. The obtained vaterite nanoparticles were found to maintain their crystal structure and surface charge after storage in aqueous buffer for at least 5 months. The aqueous stable vaterite nanoparticles could be a useful platform for the encapsulation of a large variety of biomolecules for drug delivery or as a sacrificial template toward capsule formation for biosensor applications.

  19. The effect of high-energy radiation on aqueous solution of Acid Red 1 textile dye

    NASA Astrophysics Data System (ADS)

    Földváry, Cs. M.; Wojnárovits, L.

    2007-08-01

    The effect of high-energy radiation on Acid Red 1 (AR1) azo-dye solution was investigated by UV-Vis spectroscopy and chemical oxygen demand (COD) measurements. Doses in the order of 10 kGy cause complete decolouration of the 10 -3-10 -4 mol dm -3 solutions; however, for complete mineralization doses higher by 1-2 order of magnitude are needed. Hydrated electrons and H rad atom are more effective in fading reaction, while the rad OH radicals have higher efficiency in mineralization. The HO 2•/O 2•- radical-radical anion pair is rather inefficient in fading reaction.

  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. RECOVERY OF TETRAVALENT CATIONS FROM AQUEOUS SOLUTIONS

    DOEpatents

    Moore, R.L.

    1958-05-01

    The recovery of plutonium, zirconium, and tetravalent cerium values from aqueous solutions is described. It consists of adding an alkyl phosphate to a nnineral acid aqueous solution containing the metal to be recovered, whereby a precipitate forms with the tetravalent values, and separating the precipitate from the solution. All alkyl phosphates, if water-soluble, are suitable for the process; however, monobutyl phosphate has been found best.

  2. 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

  3. 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

  4. Influence of trace elements on stabilization of aqueous solutions of ascorbic acid.

    PubMed

    Dolińska, Barbara; Ostróżka-Cieślik, Aneta; Caban, Artur; Rimantas, Klimas; Leszczyńska, Lucyna; Ryszka, Florian

    2012-12-01

    Together with vitamin C, zinc, selenium, manganese, and magnesium play a vital role in the preservation of organs scheduled for transplantation. In the present study, it is shown that addition of 1 mg/l of these elements influences the stability of 0.3 mM ascorbic acid solutions. The solution's stability was estimated using an accelerated stability test. The concentration of vitamin C was measured using a validated spectrophotometric method, which uses the reduction of 2,6-dichlorophenoloindophenol by ascorbic acid. Elevated temperatures, the factor accelerating substances' decomposition reaction rate, were used in the tests. The research was conducted at two temperatures at intervals of 10 °C: 80 ± 0.1 and 90 ± 0.1 °C. It was stated that the studied substances' decomposition occurred in accordance with the equation for first-order reactions. The function of the logarithmic concentration (log%C) over time was revealed to be rectilinear. This dependence was used to determine the kinetics of decomposition reaction rate parameters. The stabilization of vitamin C solutions was measured as the time in which 10 % of the substance decomposed at 20 and 0 °C. Addition of Se(IV) or Mg(II) ions significantly increase the stability of ascorbic acid solution (∼34 and ∼16 %, respectively), but Zn(II) causes a significant decrease in stability by ∼23 %. Addition of Mn(II) has no significant influence on vitamin C stability.

  5. Self-consistent field theory investigation of the behavior of hyaluronic acid chains in aqueous salt solutions

    NASA Astrophysics Data System (ADS)

    Nogovitsin, E. A.; Budkov, Yu. A.

    2012-04-01

    In this work we continue to develop a field-theoretic methodology, which combines the technique of Gaussian equivalent representation for the calculation of functional integrals with the continuous Gaussian thread model of flexible polymers for solving statistical-mechanical problems of polyelectrolyte solutions. We present new analytic expressions for the osmotic pressure, the potential of mean force, and the monomer-monomer pair distribution function, and employ them to investigate the structural and thermodynamic quantities of the polyelectrolyte system. We demonstrate the applicability of the method for systems of polyelectrolyte chains in which the monomers interact via a Yukawa-type pair potential. As a specific example, the present work focuses on aqueous solutions of hyaluronic acid with added salts NaCl and CaCl2. Hyaluronic acid is a high molecular weight linear polysaccharide, which has a multitude of roles in biological tissues. We conclude that the effect of sodium chloride and calcium chloride on the osmotic properties of hyaluronic acid solutions can be accounted for by their contributions to the ionic strength. Nevertheless, the effects of coiling and self-association can be stimulated in solution by added salt.

  6. 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

  7. 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.

  8. 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

  9. Nucleic Acids Bind to Nanoparticulate iron (II) Monosulphide in Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Hatton, Bryan; Rickard, David

    2008-06-01

    In the hydrothermal FeS-world origin of life scenarios nucleic acids are suggested to bind to iron (II) monosulphide precipitated from the reaction between hydrothermal sulphidic vent solutions and iron-bearing oceanic water. In lower temperature systems, the first precipitate from this process is nanoparticulate, metastable FeSm with a mackinawite structure. Although the interactions between bulk crystalline iron sulphide minerals and nucleic acids have been reported, their reaction with nanoparticulate FeSm has not previously been investigated. We investigated the binding of different nucleic acids, and their constituents, to freshly precipitated, nanoparticulate FeSm. The degree to which the organic molecules interacted with FeSm is chromosomal DNA > RNA > oligomeric DNA > deoxadenosine monophosphate ≈ deoxyadenosine ≈ adenine. Although we found that FeSm does not fluoresce within the visible spectrum and there is no quantum confinement effect seen in the absorption, the mechanism of linkage of the FeSm to these biomolecules appears to be primarily electrostatic and similar to that found for the attachment of ZnS quantum dots. The results of a preliminary study of similar reactions with nanoparticulate CuS further supported the suggestion that the interaction mechanism was generic for nanoparticulate transition metal sulphides. In terms of the FeS-world hypothesis, the results of this study further support the idea that sulphide minerals precipitated at hydrothermal vents interact with biomolecules and could have assisted in the formation and polymerisation of nucleic acids.

  10. 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

  11. 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.

  12. 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.

  13. Biosorption of clofibric acid and carbamazepine in aqueous solution by agricultural waste rice straw.

    PubMed

    Liu, Zhanguang; Zhou, Xuefei; Chen, Xiaohua; Dai, Chaomeng; Zhang, Juan; Zhang, Yalei

    2013-12-01

    Due to their widespread use, clofibric acid (CA) and carbamazepine (CBZ) have been frequently detected simultaneously at relatively high concentrations in aquatic environments. In this study, agricultural waste rice straw was employed as a potentially low-cost, effective and easy-to-operate biosorbent (RSB) to remove CA and CBZ. The adsorption of both pharmaceuticals followed pseudo second-order kinetics, and intraparticle diffusion was an important rate-limiting step. The adsorption isotherms of both drugs were fit well with Freundlich model. The adsorption of CA onto RSB was exothermic and was more likely to be dominated by physical processes, while the adsorption of CBZ was endothermic. Solution pH was determined to be the most important factor for CA adsorption, such that the adsorption capacity of CA onto RSB increased with the decline of solution pH. In the lower range of solution pH below 3.1, the CA removal efficiency was enhanced with the increase of biosorbent dosage. The CBZ removal efficiency was enhanced with the increase of RSB dosage without pH control. The maximum adsorption capacities were 126.3 mg/g for CA and 40.0 mg/g for CBZ. PMID:24649668

  14. Adsorption of methyl violet in aqueous solutions by poly(acrylamide-co-acrylic acid) hydrogels

    NASA Astrophysics Data System (ADS)

    Şolpan, D.; Duran, S.; Saraydin, D.; Güven, O.

    2003-02-01

    In this study, Acrylamide(AAm)/Acrylic Acid(AAc) monomer mixtures which contain different quantities of acrylic acid have been irradiated to form hydrogels with γ-radiation. Acrylamide/Acrylic Acid (AAm/AAc) monomer mixtures which contain 15%, 20%, 30% AAm and irradiated with 8.0 kGy were used for swelling and diffusion studies in water and solutions of methyl violet. Diffusions of water and methyl violet within the hydrogels were found to be non-Fickian in character. In experiments on the adsorption of methyl violet, Type-S adsorption was found. Poly(AAm-co-AAc) hydrogel adsorbed methyl violet, while poly(AAm) hydrogel did not adsorb any dye. (Δ H) Heat of adsorption, (Δ G) Free energy of adsorption, (Δ S) Entropy of adsorption were calculated. These results show that poly(AAm-co-AAc) hydrogels can be used as a sorbent for water pollutants such as dyes and treatment of these organic contaminants from wastewater.

  15. [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.

  16. 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.

  17. Thermodynamic characteristics of acid-base equilibria of DL-α-alanyl-DL-norleucine in aqueous solutions at 298 K

    NASA Astrophysics Data System (ADS)

    Lytkin, A. I.; Chernikov, V. V.; Krutova, O. N.; Bychkova, S. A.; Skvortsov, I. A.

    2015-09-01

    Protolytic equilibria in aqueous solutions of DL-α-alanyl-DL-norleucine are studied via potentiometry and calorimetry. Measurements are made at 298.15 K and ionic strengths of 0.5, 1.0, and 1.5 (against a background of potassium nitrate). The thermodynamic characteristics (p K, Δ G, Δ H, Δ S) of the stepwise dissociation of the dipeptide both in aqueous-salt solutions and in standard solution are obtained for the first time.

  18. 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

  19. 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).

  20. Removal of cationic dyes by poly(acrylamide-co-acrylic acid) hydrogels in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Şolpan, Dilek; Duran, Sibel; Torun, Murat

    2008-04-01

    Poly(acrylamide-co-acrylic acid (poly(AAm-co-AAc)) hydrogels prepared by irradiating with γ-radiation were used in experiments on swelling, diffusion, and uptake of some cationic dyes such as Safranine-O (SO) and Magenta (M). Poly(AAm-co-AAc) hydrogels irradiated at 8.0 kGy have been used for swelling and diffusion studies in water and cationic dye solutions. The maximum swellings in water, and SO, and M solutions observed are 2700%, 3500%, and 4000%, respectively. Diffusions of water and cationic dyes within hydrogels have been found to be non-Fickian in character. Adsorption of the cationic dyes onto poly(AAm-co-AAc) hydrogels is studied by the batch adsorption technique. The adsorption type was found Langmuir type in the Giles classification system. The moles of adsorbed dye for SO and M per repeating unit in hydrogel (binding ratio, r) have been calculated as 3834×10 -6 and 1323×10 -6, respectively. These results show that poly(AAm-co-AAc) hydrogels can be used as adsorbent for water pollutants such as cationic dyes.

  1. 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.

  2. 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

  3. SEPARATION OF RUTHENIUM FROM AQUEOUS SOLUTIONS

    DOEpatents

    Callis, C.F.; Moore, R.L.

    1959-09-01

    >The separation of ruthenium from aqueous solutions containing uranium plutonium, ruthenium, and fission products is described. The separation is accomplished by providing a nitric acid solution of plutonium, uranium, ruthenium, and fission products, oxidizing plutonium to the hexavalent state with sodium dichromate, contacting the solution with a water-immiscible organic solvent, such as hexone, to extract plutonyl, uranyl, ruthenium, and fission products, reducing with sodium ferrite the plutonyl in the solvent phase to trivalent plutonium, reextracting from the solvent phase the trivalent plutonium, ruthenium, and some fission products with an aqueous solution containing a salting out agent, introducing ozone into the aqueous acid solution to oxidize plutonium to the hexavalent state and ruthenium to ruthenium tetraoxide, and volatizing off the ruthenium tetraoxide.

  4. 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.

  5. ADSORPTION OF CERIUM VALUES FROM AQUEOUS SOLUTIONS

    DOEpatents

    Roberts, F.P.

    1963-08-13

    Cerium can be removed from aqueous nitric acid (2 to 13 M) solutions by passing the latter over a PbO/sub 2/-containing anion exchange resin. The cerium is taken up by the resin, while any lanthanides, yttrium, and strontium present remain in the solution. (AEC)

  6. 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.

  7. 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

  8. 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

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  11. 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.

  12. Electrocatalytic and photocatalytic hydrogen production from acidic and neutral-pH aqueous solutions using iron phosphide nanoparticles.

    PubMed

    Callejas, Juan F; McEnaney, Joshua M; Read, Carlos G; Crompton, J Chance; Biacchi, Adam J; Popczun, Eric J; Gordon, Thomas R; Lewis, Nathan S; Schaak, Raymond E

    2014-11-25

    Nanostructured transition-metal phosphides have recently emerged as Earth-abundant alternatives to platinum for catalyzing the hydrogen-evolution reaction (HER), which is central to several clean energy technologies because it produces molecular hydrogen through the electrochemical reduction of water. Iron-based catalysts are very attractive targets because iron is the most abundant and least expensive transition metal. We report herein that iron phosphide (FeP), synthesized as nanoparticles having a uniform, hollow morphology, exhibits among the highest HER activities reported to date in both acidic and neutral-pH aqueous solutions. As an electrocatalyst operating at a current density of -10 mA cm(-2), FeP nanoparticles deposited at a mass loading of ∼1 mg cm(-2) on Ti substrates exhibited overpotentials of -50 mV in 0.50 M H2SO4 and -102 mV in 1.0 M phosphate buffered saline. The FeP nanoparticles supported sustained hydrogen production with essentially quantitative faradaic yields for extended time periods under galvanostatic control. Under UV illumination in both acidic and neutral-pH solutions, FeP nanoparticles deposited on TiO2 produced H2 at rates and amounts that begin to approach those of Pt/TiO2. FeP therefore is a highly Earth-abundant material for efficiently facilitating the HER both electrocatalytically and photocatalytically.

  13. Study of the dose response of the system ferrous ammonium sulfate-sucrose-xylenol orange in acid aqueous solution

    NASA Astrophysics Data System (ADS)

    Juarez-Calderon, J. M.; Negron-Mendoza, A.; Ramos-Bernal, S.

    2014-11-01

    An aqueous solution of ammonium ferrous sulfate-sucrose-xylenol orange in sulfuric acid (FSX) is proposed as a dosimetric system for the processes of gamma irradiation in a range between 0.3 and 6 Gy. This system is based on the indirect oxidation of ferrous ion by an organic compound (sucrose) to ferric ion and on the formation of a color complex of Fe3+ in an acidic medium with xylenol orange (a dye). After gamma radiation, an observable change occurs in the color of the system. Irradiation was executed at three different temperatures (13 °C, 22 °C, and 40 °C). A spectrometric readout method at 585 nm was employed to evaluate the system's dose response. In all of the cases analyzed, the responses had a linear behavior, and a slight effect of irradiation temperature was observed. Post-irradiation response was also evaluated and showed the stability of the solutions 24 h after the irradiation. The results obtained suggest that FSX might be used as a dosimeter for low doses of gamma irradiation because it provides a stable signal, good reproducibility, and an accessible technique for analysis.

  14. 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.

  15. Determination of the acid dissociation constant of the biosurfactant monorhamnolipid in aqueous solution by potentiometric and spectroscopic methods.

    PubMed

    Lebrón-Paler, Ariel; Pemberton, Jeanne E; Becker, Bridget A; Otto, William H; Larive, Cynthia K; Maier, Raina M

    2006-11-15

    The acid dissociation constant in water for a monorhamnolipid mixture extracted from Pseudomonas aeruginosa ATCC 9027 has been determined using potentiometry and two spectroscopic approaches at concentrations below and above the critical micelle concentration (cmc). Potentiometric titrations resulted in pKa values ranging from 4.28 +/- 0.16 to 5.50 +/- 0.06 depending on concentration. 1H NMR spectrochemical titrations at concentrations below the cmc revealed a pKa value of 4.39 +/- 0.06. ATR-FT-IR spectrochemical titrations on solutions well above the cmc gave a pKa value of 4.84 +/- 0.05. The value of 4.28 for the free rhamnolipid molecule for concentrations below the cmc differs markedly from that reported previously. However, the pKa of 5.50 for surface-adsorbed and solution aggregates correlates closely to that previously reported. Differences in these pKa values are rationalized in terms of the pH- and concentration-dependent aggregation behavior of rhamnolipids in aqueous solution.

  16. 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.

  17. 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.

  18. Polyacrylic acid brushes grafted from P(St-AA)/Fe3O4 composite microspheres via ARGET-ATRP in aqueous solution for protein immobilization.

    PubMed

    Xie, Liqin; Lan, Fang; Li, Wenliao; Liu, Ziyao; Ma, Shaohua; Yang, Qi; Wu, Yao; Gu, Zhongwei

    2014-11-01

    Recently, the atom transfer radical polymerization (ATRP) of acrylic monomers in many reaction systems has been successfully accomplished. However, its application in aqueous solution is still a challenging task. In this work, polyacrylic acid (PAA) brushes with tunable length were directly grafted from P(St-AA)/Fe3O4 composite microspheres in aqueous solution via an improved method, activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP). This reaction was carried out in environment-friendly solvent. As well, this method overcame the sensitivity of the catalyst. Due to the strong coordination interaction of carboxyl groups, PAA brushes were employed for immobilizing gold nanoparticles, which were prepared via the in situ reduction of chloroauric acid. The PAA brushes modified magnetic composite microspheres decorating with gold nanoparticles were efficient for specific immobilization and separation of bovine serum albumin (BSA) from aqueous solution under the external magnetic field.

  19. 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.

  20. SEPARATION OF PLUTONIUM FROM AQUEOUS SOLUTIONS BY ION-EXCHANGE

    DOEpatents

    Schubert, J.

    1958-06-01

    A process is described for the separation of plutonium from an aqueous solution of a plutonium salt, which comprises adding to the solution an acid of the group consisting of sulfuric acid, phosphoric acid, and oxalic acid, and mixtures thereof to provide an acid concentration between 0.0001 and 1 M, contacting the resultant solution with a synthetic organic anion exchange resin, and separating the aqueous phase and the resin which contains the plutonium.

  1. Thermodynamics of DL-α-aminobutyric acid induced solvation mechanism in aqueous KCl solutions at 288.15-308.15 K

    NASA Astrophysics Data System (ADS)

    Mondal, S.; Ghosh, S.; Hossain, A.; Mahali, K.; Roy, S.; Dolui, B. K.

    2016-09-01

    The solubilities of DL-α-aminobutyric acid in KCl solutions of different concentrations are measured at 288.15-308.15 K. Gibbs energies and entropies have been determined for transfer of α-aminobutyric acid form water to aqueous KCl solution at 298.15 K. The cavity, dipole-dipole and other interactions affecting the solubility, as well as stability of the amino acid in solution are also evaluated. Gibbs energy and entropy of transfer due to interactions are computed to create the model of the complex solute-solvent and solventsolvent interactions. Molar volume, densities, dipole moment of solvent and diameter of co-solvent in aqueous potassium chloride are also evaluated.

  2. RECOVERY OF PROTACTINIUM FROM AQUEOUS SOLUTIONS

    DOEpatents

    Elson, R.E.

    1959-07-14

    The recovery of fluoride complexed protactinium from aqueous acidic solutions by solvent extraction is described. Generally the prccess of the invention com rises mixing an aqueous solution containing protactinium in a complexed form with an organic solvent which is specific for protactinium, such as diisopropyl carbinol, then decomposing the protactinium complex by adjusting the acidity of the aqueous solution to between 0-3 to 0-9 M in hydrogen ion concentration, and introducing a source of aluminum ions in sufficient quantity to establish a concentration of 0.5 to 1.2 M aluminum ion, whereupon decomposition of the protactinium fluoride complex takes place and the protactinium ion is taken up by the organic solvent phase.

  3. 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.

  4. Structures of polynuclear complexes of palladium(II) and platinum(II) formed by slow hydrolysis in acidic aqueous solution.

    PubMed

    Torapava, Natallia; Elding, Lars I; Mändar, Hugo; Roosalu, Kaspar; Persson, Ingmar

    2013-06-01

    The aqua ions of palladium(II) and platinum(II) undergo extremely slow hydrolysis in strongly acidic aqueous solution, resulting in polynuclear complexes. The size and structures of these species have been determined by EXAFS and small angle X-ray scattering, SAXS. For palladium(II), the EXAFS data show that the Pd-O and Pd···Pd distances are identical to those of crystalline palladium(II) oxide, but the intensities of the Pd···Pd distances in the Fourier transform at 3.04 and 3.42 Å are significantly lower compared to those of crystalline PdO. Furthermore, no Pd···Pd distances beyond 4 Å are observed. These observations strongly indicate that the polynuclear palladium(II) complexes are oxido- and hydroxido-bridged species with the same core structure as solid palladium(II) oxide. Based on the number of Pd···Pd distances, as derived from the EXAFS data, their size can be estimated to be approximately two unit cells, or ca. 1.0 nm(3). For platinum(II), EXAFS data of the polynuclear species formed in the slow hydrolysis process show Pt-O and Pt···Pt distances identical to those of amorphous platinum(II) oxide, precipitating from the solution studied. The Pt···Pt distances are somewhat different from those reported for crystalline platinum(II) oxide. The polynuclear platinum(II) complexes have a similar structure to the palladium ones, but they are somewhat larger, with an estimated diameter of 1.5-3.0 nm. It has not been possible to precipitate any of these species by ultracentrifugation. They are detectable by SAXS, indicating diameters between 0.7 and 2 nm, in excellent agreement with the EXAFS observations. The number of oxido- relative to hydroxido bridges will increase with increasing size of the complex. The charge of the complexes will remain about the same, +4, at growth, with approximate formulas [Pd10O4(OH)8(H2O)12](4+) and [Pt14O8(OH)8(H2O)12](4+) for complexes with a size of 2 and 3 unit cells of the corresponding solid metal oxide

  5. REMOVAL OF CHLORIDE FROM AQUEOUS SOLUTIONS

    DOEpatents

    Hyman, M.L.; Savolainen, J.E.

    1960-01-01

    A method is given for dissolving reactor fuel elements in which the uranium is associated with a relatively inert chromium-containing alloy such as stainless steel. An aqueous mixture of acids comprising 2 to 2.5 molar hydrochloric acid and 4 to 8 molar nitric acid is employed in dissolving the fuel element. In order io reduce corrosion in subsequent processing of the resulting solution, chloride values are removed from the solution by contacting it with concentrated nitric acid at an elevated temperature.

  6. 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.

  7. Efficient photocatalytic degradation of acid fuchsin in aqueous solution using separate porous tetragonal-CuFe2O4 nanotubes.

    PubMed

    Jing, Panpan; Li, Jianan; Pan, Lining; Wang, Jianbo; Sun, Xiaojun; Liu, Qingfang

    2015-03-01

    To develop a new promising magnetic photocatalyst, homogeneous tetragonal-CuFe2O4 (t-CuFe2O4) nanotubes were successfully synthesized via the electrospinning technique followed by heating treatment. The detailed investigation of chemical phase and microstructure reveals that the obtained samples are inversely spinel CuFe2O4 nanotubes with an average diameter of about 272±2nm, which are assembled by numerous CuFe2O4 single crystal nanoparticles with regular polyhedron structure and possess a very outstanding porous feature. Furthermore, element mapping, UV-vis adsorption spectrum, N2 adsorption-desorption isotherm, and magnetic hysteresis loop indicate that these t-CuFe2O4 nanotubes have uniform component distribution, strong light response in the range of 200 nm-800 nm, considerable specific surface area of 12.8 m(2)/g and porosity of 15.5 nm, and enough magnetization of about 18 emu/g. Therefore, the t-CuFe2O4 nanotubes show an excellent catalytic activity and durability for the photodecomposition of acid fuchsin dye in aqueous solution under a simulated sunlight source. Furthermore, these CuFe2O4 nanotubes could be acted as an eco-friendly and recyclable photocatalyst because they can be efficiently separated from the residual solution. Finally, a mechanism is presented for the significant photocatalytic performance of the porous CuFe2O4 nanotubes.

  8. Contact ion pair formation between hard acids and soft bases in aqueous solutions observed with 2DIR spectroscopy.

    PubMed

    Sun, Zheng; Zhang, Wenkai; Ji, Minbiao; Hartsock, Robert; Gaffney, Kelly J

    2013-12-12

    The interaction of charged species in aqueous solution has important implications for chemical, biological, and environmental processes. We have used 2DIR spectroscopy to study the equilibrium dynamics of thiocyanate chemical exchange between free ion (NCS(-)) and contact ion pair configurations (MNCS(+)), where M(2+) = Mg(2+) or Ca(2+). Detailed studies of the influence of anion concentration and anion speciation show that the chemical exchange observed with the 2DIR measurements results from NCS(-) exchanging with other anion species in the first solvation shell surrounding Mg(2+) or Ca(2+). The presence of chemical exchange in the 2DIR spectra provides an indirect, but robust, determinant of contact ion pair formation. We observe preferential contact ion pair formation between soft Lewis base anions and hard Lewis acid cations. This observation cannot be easily reconciled with Pearson's acid-base concept or Collins' Law of Matching Water Affinities. The anions that form contact ion pairs also correspond to the ions with an affinity for water and protein surfaces, so similar physical and chemical properties may control these distinct phenomena. PMID:23895531

  9. Contact ion pair formation between hard acids and soft bases in aqueous solutions observed with 2DIR spectroscopy.

    PubMed

    Sun, Zheng; Zhang, Wenkai; Ji, Minbiao; Hartsock, Robert; Gaffney, Kelly J

    2013-12-12

    The interaction of charged species in aqueous solution has important implications for chemical, biological, and environmental processes. We have used 2DIR spectroscopy to study the equilibrium dynamics of thiocyanate chemical exchange between free ion (NCS(-)) and contact ion pair configurations (MNCS(+)), where M(2+) = Mg(2+) or Ca(2+). Detailed studies of the influence of anion concentration and anion speciation show that the chemical exchange observed with the 2DIR measurements results from NCS(-) exchanging with other anion species in the first solvation shell surrounding Mg(2+) or Ca(2+). The presence of chemical exchange in the 2DIR spectra provides an indirect, but robust, determinant of contact ion pair formation. We observe preferential contact ion pair formation between soft Lewis base anions and hard Lewis acid cations. This observation cannot be easily reconciled with Pearson's acid-base concept or Collins' Law of Matching Water Affinities. The anions that form contact ion pairs also correspond to the ions with an affinity for water and protein surfaces, so similar physical and chemical properties may control these distinct phenomena.

  10. 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.

  11. Exploring Solute-Solvent Interactions of -Amino Acids in Aqueous [] Arrangements by Volumetric, Viscometric, Refractometric, and Acoustic Approach

    NASA Astrophysics Data System (ADS)

    Roy, Mahendra Nath; Roy, Milan Chandra; Basak, Saptarshi

    2014-05-01

    Qualitative and quantitative analysis of molecular interaction prevailing in glycine, l-alanine, l-valine, and aqueous solution of ionic liquid (IL) [1-ethylpyridinium tetrafluoroborate (] have been investigated by thermophysical properties. The apparent molar volume (), viscosity -coefficient, molal refraction (), and adiabatic compressibility ( of glycine, l-alanine, and l-valine have been studied in 0.001 mol , 0.003 mol , and 0.005 mol aqueous 1-ethylpyridinium tetrafluoroborate [] solutions at 298.15 K from the values of densities , viscosities (), refractive index (, and speed of sound , respectively. The extent of interaction, i.e., the solute-solvent interaction is expressed in terms of the limiting apparent molar volume (, viscosity -coefficient, and limiting apparent molar adiabatic compressibility (. The limiting apparent molar volumes (, experimental slopes ( derived from the Masson equation, and viscosity - and -coefficients using the Jones-Dole equation have been interpreted in terms of ion-ion and ion-solvent interactions, respectively. Molal refractions ( have been calculated with the help of the Lorentz-Lorenz equation. The role of the solvent (aqueous IL solution) and the contribution of solute-solute and solute-solvent interactions to the solution complexes have also been analyzed through the derived properties.

  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. [Surface organic modification of acid vermiculite and its adsorption of hydrophobic micro pollutants in aqueous solutions].

    PubMed

    Jiang, Zheng-Ming; Yu, Xu-Biao; Hu, Yun; Ren, Yuan; Li, Xue-Hui; Wei, Chao-Hai

    2013-07-01

    To solve the problems of intercalated organoclay such as low surface area and inhomogeneous organic loading, natural vermiculite was activated by acid leaching and then modified by trimethylchlorosilane (CTMS) and triethylchlorosilane (CTES). The modified materials were characterized by FTIR, BET, SEM and TG. Experimental results indicated that the surface area of the modified acid vermiculite (361.0 m2 x g(-1)) was much larger than that of the intercalated organovermiculite (6.0 m2 x g(-1)), moreover, the organic groups were grafted onto the surface covalently. Diethyl phthalate (DEP), a typical hydrophobic micro-organic pollutant, was used to test the adsorption capacity of different adsorbents. The adsorption amounts of DEP were 63.7, 51.2 and 15.7 mg x g(-1) for CTES, CTMS and intercalated organovermiculite in this study, respectively. The high organic affinity of modified acid vermiculite was due to both the bigger surface area and the homogeneous organic loading. The adsorption kinetics was found to follow the pseudosecond-order model. The isotherms exhibited linear characteristics and could be described by Henry and Freundlich equations, indicating that the partition process is the main control mechanism of the removal of DEP.

  15. Acidity of the amidoxime functional group in aqueous solution. A combined experimental and computational study

    DOE PAGESBeta

    Mehio, Nada; Lashely, Mark A.; Nugent, Joseph W.; Tucker, Lyndsay; Correia, Bruna; Do-Thanh, Chi-Linh; Dai, Sheng; Hancock, Robert D.; Bryantsev, Vyacheslav S.

    2015-01-26

    Poly(acrylamidoxime) adsorbents are often invoked in discussions of mining uranium from seawater. It has been demonstrated repeatedly in the literature that the success of these materials is due to the amidoxime functional group. While the amidoxime-uranyl chelation mode has been established, a number of essential binding constants remain unclear. This is largely due to the wide range of conflicting pKa values that have been reported for the amidoxime functional group in the literature. To resolve this existing controversy we investigated the pKa values of the amidoxime functional group using a combination of experimental and computational methods. Experimentally, we used spectroscopicmore » titrations to measure the pKa values of representative amidoximes, acetamidoxime and benzamidoxime. Computationally, we report on the performance of several protocols for predicting the pKa values of aqueous oxoacids. Calculations carried out at the MP2 or M06-2X levels of theory combined with solvent effects calculated using the SMD model provide the best overall performance with a mean absolute error of 0.33 pKa units and 0.35 pKa units, respectively, and a root mean square deviation of 0.46 pKa units and 0.45 pKa units, respectively. Finally, we employ our two best methods to predict the pKa values of promising, uncharacterized amidoxime ligands. Hence, our study provides a convenient means for screening suitable amidoxime monomers for future generations of poly(acrylamidoxime) adsorbents used to mine uranium from seawater.« less

  16. Acidity of the amidoxime functional group in aqueous solution. A combined experimental and computational study

    SciTech Connect

    Mehio, Nada; Lashely, Mark A.; Nugent, Joseph W.; Tucker, Lyndsay; Correia, Bruna; Do-Thanh, Chi-Linh; Dai, Sheng; Hancock, Robert D.; Bryantsev, Vyacheslav S.

    2015-01-26

    Poly(acrylamidoxime) adsorbents are often invoked in discussions of mining uranium from seawater. It has been demonstrated repeatedly in the literature that the success of these materials is due to the amidoxime functional group. While the amidoxime-uranyl chelation mode has been established, a number of essential binding constants remain unclear. This is largely due to the wide range of conflicting pKa values that have been reported for the amidoxime functional group in the literature. To resolve this existing controversy we investigated the pKa values of the amidoxime functional group using a combination of experimental and computational methods. Experimentally, we used spectroscopic titrations to measure the pKa values of representative amidoximes, acetamidoxime and benzamidoxime. Computationally, we report on the performance of several protocols for predicting the pKa values of aqueous oxoacids. Calculations carried out at the MP2 or M06-2X levels of theory combined with solvent effects calculated using the SMD model provide the best overall performance with a mean absolute error of 0.33 pKa units and 0.35 pKa units, respectively, and a root mean square deviation of 0.46 pKa units and 0.45 pKa units, respectively. Finally, we employ our two best methods to predict the pKa values of promising, uncharacterized amidoxime ligands. Hence, our study provides a convenient means for screening suitable amidoxime monomers for future generations of poly(acrylamidoxime) adsorbents used to mine uranium from seawater.

  17. Schiff base formation and recognition of amino sugars, aminoglycosides and biological polyamines by 2-formyl phenylboronic acid in aqueous solution.

    PubMed

    Gutiérrez-Moreno, Nini J; Medrano, Felipe; Yatsimirsky, Anatoly K

    2012-09-14

    Interactions of 2-, 3- and 4-formyl phenylboronic acids (FPBAs) with sugars, amino sugars, aminoglycosides and various poly- and monoamines have been studied by UV-vis, (1)H and (11)B NMR titrations in water at variable pH. Behavior of 2-FPBA was anomalous in several aspects. Transformation of the acid into its conjugate base was slow in NMR time scale and was accompanied by intramolecular cyclization affording the respective benzoboroxole. The equilibrium constants for imine formation (K(imine)) between 2-FPBA and simple monoamines including amino sugars were ca. 2 orders of magnitude larger than those with other isomers. Still one order of magnitude larger K(imine) values were observed for 2-FPBA with aminoglycosides (kanamycin, amikacin, gentamicin, neomycin) and polyamines (spermine, spermidine). The examination of UV-vis and (11)B NMR spectra of imines formed with 2-FPBA showed that formally neutral Schiff bases in fact were zwitterionic species containing a protonated imine group and an anionic B(OH)(3)(-) group. The enhanced stability of imines with monoamines can therefore be attributed to the electrostatic stabilization provided by the zwitterionic structure and further increased stability of imines with antibiotics and polyamines is explicable by additional stabilization of the borate anionic group by ion paring with ammonium groups not involved in Schiff base formation. Thanks to high molar absorptivity of protonated imines interaction of 2-FPBA with aminoglycosides allows detecting them spectrophotometrically in a μM concentration range in neutral aqueous solutions in the presence of sugars, amino sugars and amino acids.

  18. Schiff base formation and recognition of amino sugars, aminoglycosides and biological polyamines by 2-formyl phenylboronic acid in aqueous solution.

    PubMed

    Gutiérrez-Moreno, Nini J; Medrano, Felipe; Yatsimirsky, Anatoly K

    2012-09-14

    Interactions of 2-, 3- and 4-formyl phenylboronic acids (FPBAs) with sugars, amino sugars, aminoglycosides and various poly- and monoamines have been studied by UV-vis, (1)H and (11)B NMR titrations in water at variable pH. Behavior of 2-FPBA was anomalous in several aspects. Transformation of the acid into its conjugate base was slow in NMR time scale and was accompanied by intramolecular cyclization affording the respective benzoboroxole. The equilibrium constants for imine formation (K(imine)) between 2-FPBA and simple monoamines including amino sugars were ca. 2 orders of magnitude larger than those with other isomers. Still one order of magnitude larger K(imine) values were observed for 2-FPBA with aminoglycosides (kanamycin, amikacin, gentamicin, neomycin) and polyamines (spermine, spermidine). The examination of UV-vis and (11)B NMR spectra of imines formed with 2-FPBA showed that formally neutral Schiff bases in fact were zwitterionic species containing a protonated imine group and an anionic B(OH)(3)(-) group. The enhanced stability of imines with monoamines can therefore be attributed to the electrostatic stabilization provided by the zwitterionic structure and further increased stability of imines with antibiotics and polyamines is explicable by additional stabilization of the borate anionic group by ion paring with ammonium groups not involved in Schiff base formation. Thanks to high molar absorptivity of protonated imines interaction of 2-FPBA with aminoglycosides allows detecting them spectrophotometrically in a μM concentration range in neutral aqueous solutions in the presence of sugars, amino sugars and amino acids. PMID:22842531

  19. 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.

  20. 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

  1. 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

  2. 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.

  3. Acid-base interactions and complex formation while recovering copper(II) ions from aqueous solutions using cellulose adsorbent in the presence of polyvinylpyrrolidone

    NASA Astrophysics Data System (ADS)

    Nikiforova, T. E.; Kozlov, V. A.; Islyaikin, M. K.

    2012-12-01

    The sorption properties of nontreated cotton cellulose and cellulose modified with polyvinylpyrrolidone with respect to copper(II) ions are investigated. It is established that modified cellulose adsorbents have high sorption capability associated with the formation of new sorption centers during treatment with nitrogen-containing polymer. A mechanism is proposed for acid-base interactions in aqueous solutions of acids, bases, and salts during copper(II) cation recovery using cellulose adsorbent with the participation of polyvinylpyrrolidone.

  4. 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

  5. Factors affecting the removal of chlorendic acid from aqueous solutions using high energy electron irradiation

    SciTech Connect

    Taylor, T.C.; Cooper, W.J.; Nickelsen, M.G. ); Kurucz, C.N.; Waite, T.D. )

    1990-01-01

    Irradiation of water has been studied for many years. In pure water, the product distribution is well known and results in the formation of several highly reactive radical species. These radical species, e{sup {minus}} ag, H{sup {sm bullet}} and OH{sup {sm bullet}}, are known to react with many organic compounds. Thus, it appears that this treatment may be of interest in treating waste streams which contain compounds of known threat to the environment. This paper will provide initial results of experiments on the removal of chlorendic acid in wastewater.

  6. 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

  7. SEPARATION OF SCANDIUM FROM AQUEOUS SOLUTIONS

    DOEpatents

    Peppard, D.F.; Nachtman, E.S.

    1958-02-25

    This patent relates to a process for the separation of scandium from yttrium, thorium, and trivalent rare earths and with their separation from each other. It has been found that scandium and yttrium can be separated from trivalent rare earths in acidic solution, for example, a solution 6 M in HCl, by contacting with tributyl phosphate, whereupon the scandum is preferentially extracted into the organic phase, leaving the yttrium and trivalent rare earths in the aqueous phase.

  8. Surface modification of activated carbon for enhanced adsorption of perfluoroalkyl acids from aqueous solutions.

    PubMed

    Zhi, Yue; Liu, Jinxia

    2016-02-01

    The objective of the research was to examine the effect of increasing carbon surface basicity on uptake of perfluorooctane sulfonic (PFOS) and carboxylic acids (PFOA) by activated carbon. Granular activated carbons made from coal, coconut shell, wood, and phenolic-polymer-based activated carbon fibers were modified through high-temperature and ammonia gas treatments to facilitate systematical evaluation of the impact of basicity of different origins. Comparison of adsorption isotherms and adsorption distribution coefficients showed that the ammonia gas treatment was more effective than the high-temperature treatment in enhancing surface basicity. The resultant higher point of zero charges and total basicity (measured by total HCl uptake) correlated with improved adsorption affinity for PFOS and PFOA. The effectiveness of surface modification to enhance adsorption varied with carbon raw material. Wood-based carbons and activated carbon fibers showed enhancement by one to three orders of magnitudes while other materials could experience reduction in adsorption towards either PFOS or PFOA.

  9. Enhanced removal of 8-quinolinecarboxylic acid in an activated carbon cloth by electroadsorption in aqueous solution.

    PubMed

    López-Bernabeu, S; Ruiz-Rosas, R; Quijada, C; Montilla, F; Morallón, E

    2016-02-01

    The effect of the electrochemical treatment (potentiostatic treatment in a filter-press electrochemical cell) on the adsorption capacity of an activated carbon cloth (ACC) was analyzed in relation with the removal of 8-quinolinecarboxylic acid pollutant from water. The adsorption capacity of an ACC is quantitatively improved in the presence of an electric field (electroadsorption process) reaching values of 96% in comparison to 55% in absence of applied potential. In addition, the cathodic treatment results in higher removal efficiencies than the anodic treatment. The enhanced adsorption capacity has been proved to be irreversible, since the removed compound remains adsorbed after switching the applied potential. The kinetics of the adsorption processes is also improved by the presence of an applied potential. PMID:26433936

  10. Spectrophotometric determination of Rare Earth Elements in aqueous nitric acid solutions for process control.

    PubMed

    Rodionova, Oxana Ye; Tikhomirova, Tatyana I; Pomerantsev, Alexey L

    2015-04-15

    Noninvasive analytical control is of special interest for the complicated and hazardous production processes. On-line monitoring provides a unique opportunity to determine critical concentrations rapidly and without serious risks to operating personnel and the environment. Models for quantitative determination of concentrations of Rare Earth Elements in complex mixtures in nitric acid serve for these purposes. Here, the feasibility of simultaneous determination of cerium, praseodymium, and neodymium using the whole UV-vis spectroscopic range, together with chemometric data processing, is studied. The predictability of two chemometric techniques, partial least squares regression and correlation constrained multivariate curve resolution-alternating least squares are compared. Models' performances are analyzed in out-of-control cases.

  11. Adsorption of 2,4-Dichlorophenoxyacetic Acid from an Aqueous Solution on Fly Ash.

    PubMed

    Kuśmierek, Krzysztof; Świątkowski, Andrzej

    2016-03-01

    The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on fly ash was studied. The effects of adsorbent dose, contact time, pH, ionic strength, and temperature on the adsorption were investigated. Adsorption kinetic data were analyzed using pseudo-first and pseudo-second order models, and results showed that adsorption kinetics were better represented by the pseudo-second order model. Adsorption isotherms of 2,4-D on fly ash were analyzed using the Freundlich and Langmuir models. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicated that the adsorption process was spontaneous and endothermic. The negative values of ΔG° and the positive value of ΔH° indicate the spontaneous nature of 2,4-D adsorption on fly ash, and that the adsorption process was endothermic. Results showed that fly ash is an efficient, low-cost adsorbent for removal of 2,4-D from water.

  12. Adsorption kinetics and thermodynamics of acid Bordeaux B from aqueous solution by graphene oxide/PAMAMs.

    PubMed

    Zhang, Fan; He, Shengfu; Zhang, Chen; Peng, Zhiyuan

    2015-01-01

    Graphene oxide/polyamidoamines dendrimers (GO/PAMAMs) composites were synthesized via modifying GO with 2.0 G PAMAM. The adsorption behavior of the GO/PAMAMs for acid Bordeaux B (ABB) was studied and the effects of media pH, adsorption time and initial ABB concentration on adsorption capacity of the adsorbent were investigated. The optimum pH value of the adsorption of ABB onto GO/PAMAMs was 2.5. The maximum adsorption capacity increased from 325.78 to 520.83 mg/g with the increase in temperature from 298 to 328 K. The equilibrium data followed the Langmuir isotherm model better than the Freundlich model. The kinetic study illustrated that the adsorption of ABB onto GO/PAMAMs fit the pseudo-second-order model. The thermodynamic parameters indicated that the adsorption process was physisorption, and also an endothermic and spontaneous process. PMID:26398038

  13. Spectrophotometric determination of Rare Earth Elements in aqueous nitric acid solutions for process control.

    PubMed

    Rodionova, Oxana Ye; Tikhomirova, Tatyana I; Pomerantsev, Alexey L

    2015-04-15

    Noninvasive analytical control is of special interest for the complicated and hazardous production processes. On-line monitoring provides a unique opportunity to determine critical concentrations rapidly and without serious risks to operating personnel and the environment. Models for quantitative determination of concentrations of Rare Earth Elements in complex mixtures in nitric acid serve for these purposes. Here, the feasibility of simultaneous determination of cerium, praseodymium, and neodymium using the whole UV-vis spectroscopic range, together with chemometric data processing, is studied. The predictability of two chemometric techniques, partial least squares regression and correlation constrained multivariate curve resolution-alternating least squares are compared. Models' performances are analyzed in out-of-control cases. PMID:25818140

  14. Surface modification of activated carbon for enhanced adsorption of perfluoroalkyl acids from aqueous solutions.

    PubMed

    Zhi, Yue; Liu, Jinxia

    2016-02-01

    The objective of the research was to examine the effect of increasing carbon surface basicity on uptake of perfluorooctane sulfonic (PFOS) and carboxylic acids (PFOA) by activated carbon. Granular activated carbons made from coal, coconut shell, wood, and phenolic-polymer-based activated carbon fibers were modified through high-temperature and ammonia gas treatments to facilitate systematical evaluation of the impact of basicity of different origins. Comparison of adsorption isotherms and adsorption distribution coefficients showed that the ammonia gas treatment was more effective than the high-temperature treatment in enhancing surface basicity. The resultant higher point of zero charges and total basicity (measured by total HCl uptake) correlated with improved adsorption affinity for PFOS and PFOA. The effectiveness of surface modification to enhance adsorption varied with carbon raw material. Wood-based carbons and activated carbon fibers showed enhancement by one to three orders of magnitudes while other materials could experience reduction in adsorption towards either PFOS or PFOA. PMID:26469934

  15. Enhanced removal of 8-quinolinecarboxylic acid in an activated carbon cloth by electroadsorption in aqueous solution.

    PubMed

    López-Bernabeu, S; Ruiz-Rosas, R; Quijada, C; Montilla, F; Morallón, E

    2016-02-01

    The effect of the electrochemical treatment (potentiostatic treatment in a filter-press electrochemical cell) on the adsorption capacity of an activated carbon cloth (ACC) was analyzed in relation with the removal of 8-quinolinecarboxylic acid pollutant from water. The adsorption capacity of an ACC is quantitatively improved in the presence of an electric field (electroadsorption process) reaching values of 96% in comparison to 55% in absence of applied potential. In addition, the cathodic treatment results in higher removal efficiencies than the anodic treatment. The enhanced adsorption capacity has been proved to be irreversible, since the removed compound remains adsorbed after switching the applied potential. The kinetics of the adsorption processes is also improved by the presence of an applied potential.

  16. NMR spectra and potentiometry studies of aluminum(III) binding with coenzyme NAD+ in acidic aqueous solutions.

    PubMed

    Yang, Xiaodi; Bi, Shuping; Yang, Xiaoliang; Yang, Li; Hu, Jun; Liu, Jian; Yang, Zhengbiao

    2003-06-01

    Complexation and conformational studies of coenzyme NAD+ with aluminum were conducted in acidic aqueous solutions (pH 2-5) by means of potentiometry as well as multinuclear (1H, 13C, 31P, 27Al) and two-dimensional (1H, 1H-NOESY) NMR spectroscopy. These led to the following results: (1) Al could coordinate with NAD+ through the following binding sites: N7' of adenine and pyrophosphate free oxygen (O(A)1, O(N)1,O(A)2) to form various mononuclear 1:1 (AlLH23+, AlLH2+) and 2:1 (AlL2-) species, and dinuclear 2:2 (Al2L22+) species. (2) The conformations of NAD+ and Al-NAD+ depended on the solvents and different species in the complexes. The results suggest the occurrence of an Al-linked complexation, which causes structural changes at the primary recognition sites and secondary conformational alterations for coenzymes. This finding will help us to understand role of Al in biological enzyme reaction systems.

  17. Rhodamine-modified upconversion nanophosphors for ratiometric detection of hypochlorous acid in aqueous solution and living cells.

    PubMed

    Zhou, Yi; Pei, Wenbo; Wang, Chenyuan; Zhu, Jixin; Wu, Jiansheng; Yan, Qinyu; Huang, Ling; Huang, Wei; Yao, Cheng; Loo, Joachim Say Chye; Zhang, Qichun

    2014-09-10

    Hypochlorous acid (HOCl), a reactive oxygen species (ROS) produced by myeloperoxidase (MPO) enzyme-mediated peroxidation of chloride ions, acts as a key microbicidal agent in immune systems. However, misregulated production of HOCl could damage host tissues and cause many inflammation-related diseases. Due to its biological importance, many efforts have been focused on developing fluorescent probes to image HOCl in living system. Compared with those conventional fluorescent probes, up-conversion luminescence (UCL) detection system has been proven to exhibit a lot of advantages including no photo-bleaching, higher light penetration depth, no autofluorescence and less damage to biosamples. Herein, we report a novel water-soluble organic-nano detection system based on rhodamine-modified UCNPs for UCL-sensing HOCl. Upon the interaction with HOCl, the green UCL emission intensity in the detection system were gradually decreased, but the emissions in the NIR region almost have no change, which is very important for the ratiometric UCL detection of HOCl in aqueous solution. More importantly, RBH1-UCNPs could be used for the ratiometric UCL visualization of HOCl released by MPO-mediated peroxidation of chloride ions in living cells. This organic-nano system could be further developed into a novel next-generation imaging technique for bio-imaging HOCl in living system without background noise. PMID:24497481

  18. Kinetics and thermodynamic studies for removal of acid blue 129 from aqueous solution by almond shell

    PubMed Central

    2014-01-01

    Efficiency and performance of Almond shell (AS) adsorbent for the removal and recovery of Acid Blue 129 (AB129) from wastewater is presented in this report. The influence of variables including pH, initial dye concentration, adsorbent dosage, particle size, contact time and temperature on the dye removal have been investigated in batch method by one at a time optimization method. The experimental equilibrium data were tested by four widely used isotherm models namely, Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich (D–R). It was found that adsorption of AB129 on AS well with the Langmuir isotherm model, implying monolayer coverage of dye molecules onto the surface of the adsorbent. More than 98% removal efficiency was obtained within 14 min at adsorbent dose of 0.4 g for initial dye concentration of 40 mg/L at pH 2. Kinetics of the adsorption process was tested by pseudo-first-order and pseudo-second-order kinetics, and intraparticle diffusion mechanism. Pseudo-second-order kinetic model provided a better correlation for the experimental data studied in comparison to the pseudo-first-order model. Calculation of various thermodynamic parameters such as, Gibb’s free energy, entropy and enthalpy of the on-going adsorption process indicate feasibility and endothermic nature of AB129 adsorption on all adsorbents. This work can be used in design of adsorption columns for dyes removal. PMID:24620822

  19. Synthesis and Evaluation of Molecularly Imprinted Silica Gel for 2-Hydroxybenzoic Acid in Aqueous Solution

    PubMed Central

    Abdul Raof, Siti Farhana; Mohamad, Sharifah; Abas, Mhd Radzi

    2013-01-01

    A molecularly imprinted silica gel sorbent for selective removal of 2-Hydroxybenzoic acid (2-HA) was prepared by a surface imprinting technique with a sol-gel process. The 2-HA molecularly imprinted silica gel (2-HA-MISG) sorbent was evaluated by various parameters, including the influence of pH, static, kinetic adsorption and selectivity experiments. The optimum adsorption capacity to the 2-HA appeared to be around pH 2 by the polymer. Morevoer, the imprinted sorbent displayed fast uptake kinetics, obtained within 20 min. The adsorption capacity of the 2-HA-MISG (76.2 mg g−1) was higher than that of the non-imprinted silica gel (NISG) (42.58 mg g−1). This indicates that the 2-HA-MISG offers a higher affinity for 2-HA than the NISG. The polymer displays good selectivity and exhibits good reusability. Experimental results show the potential of molecularly imprinted silica sorbent for selective removal of 2-HA. PMID:23493059

  20. Sequence dependent N-terminal rearrangement and degradation of peptide nucleic acid (PNA) in aqueous solution

    NASA Technical Reports Server (NTRS)

    Eriksson, M.; Christensen, L.; Schmidt, J.; Haaima, G.; Orgel, L.; Nielsen, P. E.

    1998-01-01

    The stability of the PNA (peptide nucleic acid) thymine monomer inverted question markN-[2-(thymin-1-ylacetyl)]-N-(2-aminoaminoethyl)glycine inverted question mark and those of various PNA oligomers (5-8-mers) have been measured at room temperature (20 degrees C) as a function of pH. The thymine monomer undergoes N-acyl transfer rearrangement with a half-life of 34 days at pH 11 as analyzed by 1H NMR; and two reactions, the N-acyl transfer and a sequential degradation, are found by HPLC analysis to occur at measurable rates for the oligomers at pH 9 or above. Dependent on the amino-terminal sequence, half-lives of 350 h to 163 days were found at pH 9. At pH 12 the half-lives ranged from 1.5 h to 21 days. The results are discussed in terms of PNA as a gene therapeutic drug as well as a possible prebiotic genetic material.

  1. Adsorption of 2,4-Dichlorophenoxyacetic Acid from an Aqueous Solution on Fly Ash.

    PubMed

    Kuśmierek, Krzysztof; Świątkowski, Andrzej

    2016-03-01

    The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on fly ash was studied. The effects of adsorbent dose, contact time, pH, ionic strength, and temperature on the adsorption were investigated. Adsorption kinetic data were analyzed using pseudo-first and pseudo-second order models, and results showed that adsorption kinetics were better represented by the pseudo-second order model. Adsorption isotherms of 2,4-D on fly ash were analyzed using the Freundlich and Langmuir models. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicated that the adsorption process was spontaneous and endothermic. The negative values of ΔG° and the positive value of ΔH° indicate the spontaneous nature of 2,4-D adsorption on fly ash, and that the adsorption process was endothermic. Results showed that fly ash is an efficient, low-cost adsorbent for removal of 2,4-D from water. PMID:26931534

  2. 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.

  3. 2010 Water & Aqueous Solutions

    SciTech Connect

    Dor Ben-Amotz

    2010-08-13

    Water covers more than two thirds of the surface of the Earth and about the same fraction of water forms the total mass of a human body. Since the early days of our civilization water has also been in the focus of technological developments, starting from converting it to wine to more modern achievements. The meeting will focus on recent advances in experimental, theoretical, and computational understanding of the behavior of the most important and fascinating liquid in a variety of situations and applications. The emphasis will be less on water properties per se than on water as a medium in which fundamental dynamic and reactive processes take place. In the following sessions, speakers will discuss the latest breakthroughs in unraveling these processes at the molecular level: Water in Solutions; Water in Motion I and II; Water in Biology I and II; Water in the Environment I and II; Water in Confined Geometries and Water in Discussion (keynote lecture and poster winners presentations).

  4. Selective removal of Cr(VI) from aqueous solution by polypyrrole/2,5-diaminobenzene sulfonic acid composite.

    PubMed

    Kera, Nazia H; Bhaumik, Madhumita; Ballav, Niladri; Pillay, Kriveshini; Ray, Suprakas Sinha; Maity, Arjun

    2016-08-15

    A polypyrrole/2,5-diaminobenzenesulfonic acid (PPy/DABSA) composite, synthesised by the in situ oxidative polymerization of pyrrole in the presence of DABSA, was studied as an adsorbent for the removal of Cr(VI) from aqueous solution. The structure and morphology of the composite were investigated by ATR-FTIR, FE-SEM, EDX, TGA, XRD and XPS studies. The adsorption of Cr(VI) by PPy/DABSA composite was highly pH dependent and optimum removal was achieved at pH 2. Adsorption of Cr(VI) was confirmed by EDX and XPS studies. The isotherm data fitted the linear Langmuir model well, with a maximum adsorption capacity of 303mg/g at 25°C. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) were calculated using isotherm data and confirmed that the adsorption process was spontaneous and endothermic. Adsorption kinetics was best described by the pseudo-second-order model. The activation energy of the adsorption process suggested that Cr(VI) was chemisorbed by PPy/DABSA composite. PPy/DABSA composite could be used for three consecutive adsorption-desorption cycles without loss of its original adsorption capacity. Highly selective removal of Cr(VI) was observed even when co-existing ions such as Cu(2+), Zn(2+), Ni(2+), Cl(-), SO4(2)(-) and NO3(-) were present in the solution. In summary, the potential of PPy/DABSA composite for remediating industrial wastewater contaminated by Cr(VI) has been demonstrated.

  5. Cd(II) removal from aqueous solution by adsorption on α-ketoglutaric acid-modified magnetic chitosan

    NASA Astrophysics Data System (ADS)

    Yang, Guide; Tang, Lin; Lei, Xiaoxia; Zeng, Guangming; Cai, Ye; Wei, Xue; Zhou, Yaoyu; Li, Sisi; Fang, Yan; Zhang, Yi

    2014-02-01

    The present study developed an α-ketoglutaric acid-modified magnetic chitosan (α-KA-Fe3O4/CS) for highly efficient adsorption of Cd(II) from aqueous solution. Several techniques, including transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and vibrating sample magnetometer (VSM), were applied to characterize the adsorbent. Batch tests were conducted to investigate the Cd(II) adsorption performance of α-KA-Fe3O4/CS. The maximum adsorption efficiency of Cd(II) appeared at pH 6.0 with the value of 93%. The adsorption amount was large and even reached 201.2 mg/g with the initial Cd(II) concentration of 1000 mg/L. The adsorption equilibrium was reached within 30 min and commendably described by pseudo-second-order model, and Langmuir model fitted the adsorption isotherm better. Furthermore, thermodynamic parameters, free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) of Cd(II) adsorption were also calculated and showed that the overall adsorption process was endothermic and spontaneous in nature because of positive ΔH values and negative ΔG values, respectively. Moreover, the Cd(II)-loaded α-KA-Fe3O4/CS could be regenerated by 0.02 mol/L NaOH solution, and the cadmium removal capacity could still be kept around 89% in the sixth cycle. All the results indicated that α-KA-Fe3O4/CS was a promising adsorbent in environment pollution cleanup.

  6. Selective removal of Cr(VI) from aqueous solution by polypyrrole/2,5-diaminobenzene sulfonic acid composite.

    PubMed

    Kera, Nazia H; Bhaumik, Madhumita; Ballav, Niladri; Pillay, Kriveshini; Ray, Suprakas Sinha; Maity, Arjun

    2016-08-15

    A polypyrrole/2,5-diaminobenzenesulfonic acid (PPy/DABSA) composite, synthesised by the in situ oxidative polymerization of pyrrole in the presence of DABSA, was studied as an adsorbent for the removal of Cr(VI) from aqueous solution. The structure and morphology of the composite were investigated by ATR-FTIR, FE-SEM, EDX, TGA, XRD and XPS studies. The adsorption of Cr(VI) by PPy/DABSA composite was highly pH dependent and optimum removal was achieved at pH 2. Adsorption of Cr(VI) was confirmed by EDX and XPS studies. The isotherm data fitted the linear Langmuir model well, with a maximum adsorption capacity of 303mg/g at 25°C. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) were calculated using isotherm data and confirmed that the adsorption process was spontaneous and endothermic. Adsorption kinetics was best described by the pseudo-second-order model. The activation energy of the adsorption process suggested that Cr(VI) was chemisorbed by PPy/DABSA composite. PPy/DABSA composite could be used for three consecutive adsorption-desorption cycles without loss of its original adsorption capacity. Highly selective removal of Cr(VI) was observed even when co-existing ions such as Cu(2+), Zn(2+), Ni(2+), Cl(-), SO4(2)(-) and NO3(-) were present in the solution. In summary, the potential of PPy/DABSA composite for remediating industrial wastewater contaminated by Cr(VI) has been demonstrated. PMID:27209399

  7. Acid-base and metal ion binding properties of 2-thiocytidine in aqueous solution.

    PubMed

    Brasuń, Justyna; Matera, Agnieszka; Sochacka, Elzbieta; Swiatek-Kozlowska, Jolanta; Kozlowski, Henryk; Operschall, Bert P; Sigel, Helmut

    2008-06-01

    The thionucleoside 2-thiocytidine (C2S) occurs in nature in transfer RNAs; it receives attention in diverse fields like drug research and nanotechnology. By potentiometric pH titrations we measured the acidity constants of H(C2S)(+) and the stability constants of the M(C2S)(2+) and M(C2S-H)(+) complexes (M(2+) = Zn(2+), Cd(2+)), and we compared these results with those obtained previously for its parent nucleoside, cytidine (Cyd). Replacement of the (C2)=O unit by (C2)=S facilitates the release of the proton from (N3)H(+) in H(C2S)(+) (pK (a) = 3.44) somewhat, compared with H(Cyd)(+) (pK (a) = 4.24). This moderate effect of about 0.8 pK units contrasts with the strong acidification of about 4 pK units of the (C4)NH(2) group in C2S (pK (a) = 12.65) compared with Cyd (pK (a) approximately 16.7); the reason for this result is that the amino-thione tautomer, which dominates for the neutral C2S molecule, is transformed upon deprotonation into the imino-thioate form with the negative charge largely located on the sulfur. In the M(C2S)(2+) complexes the (C2)S group is the primary binding site rather than N3 as is the case in the M(Cyd)(2+) complexes, though owing to chelate formation N3 is to some extent still involved in metal ion binding. Similarly, in the Zn(C2S-H)(+) and Cd(C2S-H)(+) complexes the main metal ion binding site is the (C2)S(-) unit (formation degree above 99.99% compared with that of N3). However, again a large degree of chelate formation with N3 must be surmised for the M(C2S-H)(+) species in accord with previous solid-state studies of related ligands. Upon metal ion binding, the deprotonation of the (C4)NH(2) group (pK (a) = 12.65) is dramatically acidified (pK (a) approximately 3), confirming the very high stability of the M(C2S-H)(+) complexes. To conclude, the hydrogen-bonding and metal ion complex forming capabilities of C2S differ strongly from those of its parent Cyd; this must have consequences for the properties of those RNAs which contain this

  8. RECOVERY OF PLUTONIUM FROM AQUEOUS SOLUTIONS

    DOEpatents

    Reber, E.J.

    1959-09-01

    A process is described for recovering plutonium values from aqueous solutions by precipitation on bismuth phosphate. The plutonium is secured in its tetravalent state. bismuth salt is added to the solution, and ant excess of phosphoric acid anions is added to the solution in two approximately equal installments. The rate of addition of the first installment is about two to three times as high as the rate of addition of the second installment, whereby a precipitate of bismuth phosphate forms, the precipitate carrying the plutonium values. The precipitate is separated from the solution.

  9. 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

  10. 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

  11. 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.

  12. Sucrose diffusion in aqueous solution.

    PubMed

    Price, Hannah C; Mattsson, Johan; Murray, Benjamin J

    2016-07-28

    The diffusion of sugar in aqueous solution is important both in nature and in technological applications, yet measurements of diffusion coefficients at low water content are scarce. We report directly measured sucrose diffusion coefficients in aqueous solution. Our technique utilises a Raman isotope tracer method to monitor the diffusion of non-deuterated and deuterated sucrose across a boundary between the two aqueous solutions. At a water activity of 0.4 (equivalent to 90 wt% sucrose) at room temperature, the diffusion coefficient of sucrose was determined to be approximately four orders of magnitude smaller than that of water in the same material. Using literature viscosity data, we show that, although inappropriate for the prediction of water diffusion, the Stokes-Einstein equation works well for predicting sucrose diffusion under the conditions studied. As well as providing information of importance to the fundamental understanding of diffusion in binary solutions, these data have technological, pharmaceutical and medical implications, for example in cryopreservation. Moreover, in the atmosphere, slow organic diffusion may have important implications for aerosol growth, chemistry and evaporation, where processes may be limited by the inability of a molecule to diffuse between the bulk and the surface of a particle. PMID:27364512

  13. Sucrose diffusion in aqueous solution

    PubMed Central

    Murray, Benjamin J.

    2016-01-01

    The diffusion of sugar in aqueous solution is important both in nature and in technological applications, yet measurements of diffusion coefficients at low water content are scarce. We report directly measured sucrose diffusion coefficients in aqueous solution. Our technique utilises a Raman isotope tracer method to monitor the diffusion of non-deuterated and deuterated sucrose across a boundary between the two aqueous solutions. At a water activity of 0.4 (equivalent to 90 wt% sucrose) at room temperature, the diffusion coefficient of sucrose was determined to be approximately four orders of magnitude smaller than that of water in the same material. Using literature viscosity data, we show that, although inappropriate for the prediction of water diffusion, the Stokes–Einstein equation works well for predicting sucrose diffusion under the conditions studied. As well as providing information of importance to the fundamental understanding of diffusion in binary solutions, these data have technological, pharmaceutical and medical implications, for example in cryopreservation. Moreover, in the atmosphere, slow organic diffusion may have important implications for aerosol growth, chemistry and evaporation, where processes may be limited by the inability of a molecule to diffuse between the bulk and the surface of a particle. PMID:27364512

  14. Removal of Mefenamic acid from aqueous solutions by oxidative process: Optimization through experimental design and HPLC/UV analysis.

    PubMed

    Colombo, Renata; Ferreira, Tanare C R; Ferreira, Renato A; Lanza, Marcos R V

    2016-02-01

    Mefenamic acid (MEF) is a non-steroidal anti-inflammatory drug indicated for relief of mild to moderate pain, and for the treatment of primary dysmenorrhea. The presence of MEF in raw and sewage waters has been detected worldwide at concentrations exceeding the predicted no-effect concentration. In this study, using experimental designs, different oxidative processes (H2O2, H2O2/UV, fenton and Photo-fenton) were simultaneously evaluated for MEF degradation efficiency. The influence and interaction effects of the most important variables in the oxidative process (concentration and addition mode of hydrogen peroxide, concentration and type of catalyst, pH, reaction period and presence/absence of light) were investigated. The parameters were determined based on the maximum efficiency to save time and minimize the consumption of reagents. According to the results, the photo-Fenton process is the best procedure to remove the drug from water. A reaction mixture containing 1.005 mmol L(-1) of ferrioxalate and 17.5 mmol L(-1) of hydrogen peroxide, added at the initial reaction period, pH of 6.1 and 60 min of degradation indicated the most efficient degradation, promoting 95% of MEF removal. The development and validation of a rapid and efficient qualitative and quantitative HPLC/UV methodology for detecting this pollutant in aqueous solution is also reported. The method can be applied in water quality control that is generated and/or treated in municipal or industrial wastewater treatment plants.

  15. Removal of Mefenamic acid from aqueous solutions by oxidative process: Optimization through experimental design and HPLC/UV analysis.

    PubMed

    Colombo, Renata; Ferreira, Tanare C R; Ferreira, Renato A; Lanza, Marcos R V

    2016-02-01

    Mefenamic acid (MEF) is a non-steroidal anti-inflammatory drug indicated for relief of mild to moderate pain, and for the treatment of primary dysmenorrhea. The presence of MEF in raw and sewage waters has been detected worldwide at concentrations exceeding the predicted no-effect concentration. In this study, using experimental designs, different oxidative processes (H2O2, H2O2/UV, fenton and Photo-fenton) were simultaneously evaluated for MEF degradation efficiency. The influence and interaction effects of the most important variables in the oxidative process (concentration and addition mode of hydrogen peroxide, concentration and type of catalyst, pH, reaction period and presence/absence of light) were investigated. The parameters were determined based on the maximum efficiency to save time and minimize the consumption of reagents. According to the results, the photo-Fenton process is the best procedure to remove the drug from water. A reaction mixture containing 1.005 mmol L(-1) of ferrioxalate and 17.5 mmol L(-1) of hydrogen peroxide, added at the initial reaction period, pH of 6.1 and 60 min of degradation indicated the most efficient degradation, promoting 95% of MEF removal. The development and validation of a rapid and efficient qualitative and quantitative HPLC/UV methodology for detecting this pollutant in aqueous solution is also reported. The method can be applied in water quality control that is generated and/or treated in municipal or industrial wastewater treatment plants. PMID:26686073

  16. Efficient degradation of Acid Orange 7 in aqueous solution by iron ore tailing Fenton-like process.

    PubMed

    Zheng, Jianming; Gao, Zhanqi; He, Huan; Yang, Shaogui; Sun, Cheng

    2016-05-01

    An effective method based on iron ore tailing Fenton-like process was studied for removing an azo dye, Acid Orange 7 (AO7) in aqueous solution. Five tailings were characterized by X-ray fluorescence spectroscope (XFS), Brunner-Emmet-Teller (BET) measurement, and Scanning Electron Microscope (SEM). The result of XFS showed that Fe, Si and Ca were the most abundant elements and some toxic heavy metals were also present in the studied tailings. The result of BET analysis indicated that the studied tailings had very low surface areas (0.64-5.68 m(2) g(-1)). The degradation efficiencies of AO7 were positively correlated with the content of iron oxide and cupric oxide, and not related with the BET surface area of the tailings. The co-existing metal elements, particularly Cu, might accelerate the heterogeneous Fenton-like reaction. The effects of other parameters on heterogeneous Fenton-like degradation of AO7 by a converter slag iron tailing (tailing E) which contains highest iron oxide were also investigated. The tailing could be reused 10 times without significant decrease of the catalytic capacity. Very low amount of iron species and almost undetectable toxic elements were leached in the catalytic degradation of AO7 by the tailing E. The reaction products were identified by gas chromatography-mass spectrometry and a possible pathway of AO7 degradation was proposed. This study not only provides an effective method for removing azo dyes in polluted water by employing waste tailings as Fenton-like catalysts, but also uses waste tailings as the secondary resource. PMID:26891355

  17. Oxygen uptake after electron transfer from amines, amino acids and ascorbic acid to triplet flavins in air-saturated aqueous solution.

    PubMed

    Görner, Helmut

    2007-05-25

    The photolysis of lumichrome, riboflavin, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) was studied in air-saturated aqueous solution at room temperature in the presence of appropriate electron donors: ascorbic acid, aromatic amino acids or amines, e.g. ethylenediaminetetraacetate (EDTA). The overall reaction is conversion of oxygen via the hydroperoxyl/superoxide radical into hydrogen peroxide. The quantum yield of oxygen uptake increases with the donor concentration, e.g. up to 0.3 for riboflavin, FMN or FAD in the presence of EDTA or ascorbic acid (0.3-10mM). The formation of H(2)O(2) is initiated by quenching of the acceptor triplet state by the electron donor and subsequent reaction of the semiquinone radical with oxygen. Specific properties of flavins are discussed including the radicals involved and the pH and concentration dependences. The quantum yield of photodegradation is low under air, but substantial under argon, where the major product absorbing in the visible spectral range is the corresponding hydroquinone. PMID:17395476

  18. Physicochemical Behavior of Some Amino Acids/Glycylglycine in Aqueous D-Galactose Solutions at Different Temperatures

    NASA Astrophysics Data System (ADS)

    Ali, Anwar; Patel, Rajan; Shahjahan; Ansari, Nizamul Haque

    2010-03-01

    The apparent molar volumes {(overline{V_2})} for glycine (Gly), l-alanine (Ala), phenylalanine (Phe), and glycylglycine (Gly-Gly) in 0.10 m aqueous d-galactose solutions have been determined from density measurements at (298.15, 303.15, 308.15, and 313.15) K. The data for {(overline{V_2})} were utilized to estimate the partial molar volume at infinite dilution {(overline{V_2^0})} , and experimental slope {(S_v^ast)} . The transfer volume, {(overline{V2^0}_(tr))} , and hydration number, ( n H) were also evaluated. The viscosity data were used to evaluate A- and B-coefficients of the Jones-Dole equation, the free energy of activation of viscous flow per mole of the solvent {left(Δ μ1^{0ast} right)} and the solute {left(Δ μ 2^{0ast} right)} . The molar refractivity ( R D) was calculated from refractive index data. The results were discussed in terms of hydrophilic-ionic, hydrophilic-hydrophobic, and hydrophobic-hydrophobic interactions, and structure-making/-breaking ability of the solute (AAs/peptide) in aqueous d-galactose solutions.

  19. Effect of sodium and potassium salts on the extraction of 1-butanol from aqueous solution by the ethyl esters of soybean oil fatty acids

    SciTech Connect

    Compere, A.L.; Googin, J.M.; Griffith, W.L.

    1985-01-01

    The effect of 0 to 0.15 M sodium chloride, sulfate, and sulfite, and potassium acid phosphate on the extraction of 0.1 to 4.1% 1-butanol from aqueous solutions (derived from fermentation of wood pulp liquors) at 25, 40, and 55 C was evaluated using a factorial experiment. The changes in distribution coefficient were small, with mild increases occurring with increasing temperature and increasing sodium chloride, sodium sulfate, and potassium acid phosphate. Mild decreases in 1-butanol extraction occurred with increasing sodium sulfite. 6 refs., 4 tabs.

  20. 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

  1. Structural changes of nucleic acid base in aqueous solution as observed in X-ray absorption near edge structure (XANES)

    NASA Astrophysics Data System (ADS)

    Shimada, Hiroyuki; Fukao, Taishi; Minami, Hirotake; Ukai, Masatoshi; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro; Saitoh, Yuji

    2014-01-01

    X-ray absorption near edge structure (XANES) spectra for adenine-containing nucleotides, adenosine 5‧-monophosphate (AMP) and adenosine 5‧-triphosphate (ATP) in aqueous solutions at the nitrogen K-edge region were measured. The two intense peaks in XANES spectra are assigned to transitions of 1s electrons to the π∗ orbitals of different types of N atoms with particular bonding characteristics. The difference between their spectra is ascribed to protonation of a particular N atom. Similarity observed in XANES spectra of guanosine 5‧-monophosphate (GMP) and ATP is also interpreted as similar bonding characters of the N atoms in the nucleobase moiety.

  2. Reusable nanocomposite of CoFe2O4/chitosan-graft-poly(acrylic acid) for removal of Ni(II) from aqueous solution

    NASA Astrophysics Data System (ADS)

    Nguyen, Van Cuong; Huynh, Thi Kim Ngoc

    2014-06-01

    In this paper, CoFe2O4/chitosan-graft-poly(acrylic acid) (CoFe2O4/CS-graft-PAA) nanocomposites were prepared successfully by coprecipitation of the compounds in alkaline solution and were used for removal of nickel (II) ions from aqueous solution. The sorption rate was affected significantly by the initial concentration of the solution, sorbent amount, and pH value of the solution. Batch experiments were conducted to investigate the adsorption capacity under different initial concentration (ranging from 25 to 150 mg L-1), solution pH (4.1, 5.3, 6.4 and 7.6), and contact time. These nanocomposites can be recycled conveniently from water with the assistance of an external magnet because of their exceptional properties. The prepared nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), x-ray powder diffraction (XRD), and thermogravimetric analysis (TGA).

  3. Boric acid, “carbonic” acid, and N-containing oxyacids in aqueous solution: Ab initio studies of structure, pKa, NMR shifts, and isotopic fractionations

    NASA Astrophysics Data System (ADS)

    Tossell, J. A.

    2005-12-01

    B(OH) 3 and CO 2 are acidic species of considerable geochemical importance, yet the microscopic nature of the acid dissociation reactions for these B and C species is not well understood. Quantum mechanical methods have recently been applied to the direct ab initio calculation of p Ka values for many organic and inorganic weak acids, but the B and C acids have not yet been considered in detail. In the present study, p Ka values are calculated quantum mechanically for the oxyacids B(OH) 3, H 2CO 3 and HNO 3, which have experimental first p Ka values of 9.2, 6.4 and -1.3, respectively. We calculate the gas-phase reaction free energies at the highly accurate CBS-QB3 ab initio quantum mechanical level and reaction free energies of hydration using a polarizable continuum method. Using a thermodynamic cycle corresponding to the simple dissociation process HA A - + H +, in aqueous solution, we calculate p Ka values of 21.6, 3.8 to 2.2 and -0.8 for the three oxyacids mentioned above, closely matching experiment only for HNO 3. The discrepancies with experiment arise from the more complex nature of the acid dissociation process for B(OH) 3, which involves the addition of H 2O to B(OH) 3 and formation of the B(OH) 4- anion, and from the instability of hypothetical H 2CO 3 compared to the proper hydrated reactant complex CO 2. . . H 2O. When the proper microscopic description of the reactants and products is used the calculated p Ka values for the three acids become 11.1, 7.2 and -0.8, in considerably better agreement with experiment for B(OH) 3 and CO 2. . . H 2O. Thus p Ka calculations using this approach are accurate enough to give information on the actual acid species present in solution and the details of their acid dissociation processes at the microscopic level. 11B and 13C-NMR chemical shifts are also calculated for the various species and compared to experiment. By comparison of our calculations with experiment it is apparent that the 13C-NMR chemical shift has

  4. 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.

  5. Rheological Properties of Aqueous Acid Solutions of Chitosan: Experiment and Calculations of the Viscometric Functions on the Basis of a Mesoscopic Model

    NASA Astrophysics Data System (ADS)

    Shipovskaya, A. B.; Abramov, A. Yu.; Pyshnograi, G. V.; Aziz, Al Joda Hyder Nadom

    2016-05-01

    The rheological properties of chitosan solutions in acetic acid at 20°C in the range of polymer concentrations from 0.5 to 8 mass% and acid concentrations from 2 to 70% have been investigated. With the use of a modified Vinogradov-Pokrovskii model based on the microstructural approach to the description of polymer fluid dynamics, numerical solutions of gradient dependences of viscometric functions of aqueous acid solutions of chitosan have been obtained. It has been established that the numerical solution describes with good accuracy the experimental viscosity rheograms. The values of the highest Newton viscosity ηmax have been calculated. The concentration modes of semidiluted and concentrated solutions have been determined by the dependence of ηmax on the polymer concentration, and the range of concentrations in which the mass transfer mechanism changes and a fluctuation network is formed has been found. It has been shown that the concentration of acetic acid practically does not influence the structure and character of flow of chitosan solutions, the formation concentration of a network, and the efficiency of its labile nodes.

  6. Thermodynamic characteristics of molecular interactions between L-tryptophan and nicotinic acid and uracyl in aqueous buffer solutions at 298 K

    NASA Astrophysics Data System (ADS)

    Badelin, V. G.; Tyunina, E. Yu.; Mezhevoi, I. N.; Tarasova, G. N.

    2015-12-01

    The interaction between L-tryptophan (Trp) and nicotinic acid (NA) and uracyl (Ur) in aqueous buffer solutions (pH 7.35) at different ratios of reagents is studied via the calorimetry of dissolution. The enthalpies of dissolution of the amino acid in the buffer solutions of the ligands at 298.15 K are obtained. The stoichiometric compositions of the complexes being formed and binding constants have been determined. The values of the thermodynamic characteristics for the complex formation of L-tryptophan with nicotinic acid and uracyl are calculated. It is shown that the formation of molecular complexes with 1 : 2 composition is stabilized by the entropy factor for the Trp-NA system, and by the enthalpy factor for the Trp-Ur system.

  7. 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)

  8. Exclusion of Nitrate from Frozen Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Marrocco, H. A.; Michelsen, R. R.

    2013-12-01

    Reactions occurring at the surface of ice, sea ice, and snow in Earth's cryosphere have an impact on the composition of the overlying atmosphere. In order to elucidate reaction mechanisms and model their contributions to atmospheric processes, the morphology of frozen aqueous surfaces and amounts of reactants contained therein must be determined. To this end, the exclusion of nitrate ions to the surface of frozen aqueous solutions has been studied by attenuated total reflection infrared spectroscopy (ATR-IR). In this technique the near-surface region of the frozen films are interrogated to a depth of a few hundred nanometers from the film-crystal interface. Aqueous solutions (0.001 to 0.01 M) of sodium nitrate (NaNO3), magnesium nitrate (Mg(NO3)2), and nitric acid (HNO3) were quickly frozen on the germanium ATR crystal and observed at a constant temperature of about -18°C. In addition to ice and the solutes, liquid water in varying amounts was observed in the spectra. The amount of nitrate in the surface liquid is three to four orders of magnitude higher than in the unfrozen solution. While all the nitrate salts exhibit exclusion to the unfrozen surface, the dynamics are different for different counter-ions. Results are compared to freezing point depression data and the predictions of equilibrium thermodynamics.

  9. REMOVAL OF CHLORIDE FROM AQUEOUS SOLUTIONS

    DOEpatents

    Schulz, W.W.

    1959-08-01

    The removal of chlorides from aqueons solutions is described. The process involves contacting the aqueous chloride containing solution with a benzene solution about 0.005 M in phenyl mercuric acetate whereby the chloride anions are taken up by the organic phase and separating the organic phase from the aqueous solutions.

  10. Thermodynamical characteristics of the reaction of pyridoxal-5'-phosphate with L-amino acids in aqueous buffer solution

    NASA Astrophysics Data System (ADS)

    Barannikov, V. P.; Badelin, V. G.; Venediktov, E. A.; Mezhevoi, I. N.; Guseinov, S. S.

    2011-01-01

    The reaction of pyridoxal-5'-phosphate with L-isomers of alanine, lysine, arginine, aspartic acid, glutamic acid, and glycine in phosphate buffer solution was studied by absorption spectroscopy and the calorimetry of dissolution at physiological acidity of the medium (pH 7.35). The formation constants of Schiff bases during reactions and changes in Gibbs energy, enthalpy, and entropy were determined. It was shown that the formation constant of the Schiff base and its spectral properties depend on the nature of the bound amino acid. The progress of the reaction with a majority of amino acids is governed by the entropy factor due to the predominant role of the dehydration effect of the reaction center of amino acids during chemical reactions. The intramolecular electrostatic interaction of an ionized phosphate group with the positively charged amino group on the end of the chain of amino acid residue stabilizes the Schiff bases formed by lysine and arginine. The extinction coefficient of the base, equilibrium constant, and the exothermic effect of the reaction then increase. The excess negative charge on the end of the chain of amino acid residues of aspartic and glutamic acids destabilizes the molecule of the Schiff base. In this case, the equilibrium constant decreases and the endothermic effect of the reaction increases.

  11. Solubilities and Glass Formation in Aqueous Solutions of the Sodium Salts of Malonic Acid With and Without Ammonium Sulfate.

    PubMed

    Kissinger, Jared A; Buttke, Lukas G; Vinokur, Anastasiya I; Guzei, Ilia A; Beyer, Keith D

    2016-06-01

    The solubility of sodium hydrogen malonate and sodium malonate in water both with and without ammonium sulfate present has been studied using differential scanning calorimetry and infrared spectroscopy. The crystals that form from sodium hydrogen malonate/water solutions were determined to be sodium hydrogen malonate monohydrate by single-crystal X-ray diffractometry. The crystals formed in sodium malonate/water solutions were determined to be sodium malonate monohydrate, a compound whose structure had not been previously known. When ammonium sulfate is added to these respective aqueous systems, the precipitation solids contain sodium sulfate decahydrate under low to moderate ammonium concentrations and lecontite (NaNH4SO4·2H2O) under high ammonium concentrations, which can be found under dry atmospheric conditions. Thus, it appears the presence of malonate and hydrogen malonate ions does not significantly affect the precipitation of inorganic salts in these systems. The glass transition temperatures of all solutions were also determined, and it was observed that the addition of ammonium sulfate slightly lowers the glass transition temperature in these solutions.

  12. Comparison of the influence of polyaspartic acid and polylysine functional groups on the adsorption at the Cr2O3-Aqueous polymer solution interface

    NASA Astrophysics Data System (ADS)

    Ostolska, Iwona; Wiśniewska, Małgorzata

    2014-08-01

    Polyamino acids are a group of synthesized polymers obtained by polymerization of a given kind of amino acid monomer. Because of high biodegradability of this class of polymers, they can be used as flocculation or stabilization agents in the environmental aspects. Therefore determination of their influence on the stability of the aqueous suspension of metal oxides is important. An influence of different functional groups of polyamino acids, their molecular weight and concentration on the adsorption at the chromium (III) oxide (Cr2O3)-aqueous solution interface was determined. Experiments were carried out for four values of solution pH varying from 3 to 10 (3, 4, 7.6 and 10, respectively). Two polymers were used: anionic polyaspartic acid (ASP) of 6800 and 27,000 as well as polylysine (LYS) of 4900 and 33,000 molecular weights. Changes of surface charge density of colloidal Cr2O3 in the presence and in the absence of macromolecular substances were determined using potentiometric titration. In these studies the influence of the concentration and molecular weight of the ionic polymers on the pHpzc value was determined. Additionally, due to the lack of appropriate literature data, potentiometric titration of the selected polymers was performed to determine pKa values.

  13. 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.

  14. 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.

  15. SOLVENT EXTRACTION OF THORIUM VALUES FROM AQUEOUS SOLUTIONS

    DOEpatents

    Warf, J.C.

    1959-04-21

    The separation of thorium values from rare earth metals contained ln aqueous solutions by means of extraction with a water immiscible alkyl phosphate diluted with a hydrocarbon such as hexane is described. While the extraction according to this invention may be carried out from any aqueous salt solution, it is preferred to use solutions containing free mineral acid. Hydrochloric acid and in particular nitric acid are sultable in a concentration ranging from 0.1 to 7 normal. The higher acid concentration results in higher extraction values.

  16. Investigation of the colloidal Cr2O3 removal possibilities from aqueous solution using the ionic polyamino acid block copolymers.

    PubMed

    Ostolska, Iwona; Wiśniewska, Małgorzata

    2015-06-15

    Disposal of the environmentally dangerous metal oxide suspensions from the waste water is an essential problem. The polymers adsorption can be one of the most effective and suitable methods. In the presented paper the ionic diblock copolymers impact on the Cr2O3 suspensions was investigated. The copolymer adsorption layers structure was determined on the basis of the adsorption and electrokinetic (surface charge density and zeta potential) tests. The polymers adsorption amount was measured using the static method from aqueous solutions. Additionally, the application of the turbidimetric method enabled determination of the interactions between the system constituents. Analysis of this data allows the estimation of the most probable stabilization (or destabilization) mechanism of the Cr2O3 suspensions in the presence of the studied macromolecular compounds. Hence, the Cr2O3 suspensions are unstable in the presence of the anionic copolymer at pH 3 and the cationic one in the alkaline medium. PMID:25746566

  17. Interactions of L-Aspartic Acid with Aqueous Solution of 1,2-Propanediol at Different Temperatures: A Volumetric, Compressibility and Viscometric Approach.

    PubMed

    Rani, Ruby; Kumar, Ashwani; Sharma, Tanu; Saini, Balwinder; Bamezai, Rajinder Kumar

    2016-01-01

    The volumetric, acoustic and viscometric methods are used for investigating the interactions of L-aspartic acid (Asp) in aqueous solution of 1,2-propanediol (PD) over a temperature of (298.15, 303.15 and 308.15) K at atmospheric pressure. Using the experimental results, the apparent molar volume, Vφ, limiting apparent molar volume, V0φ, the slope, Sv, and partial molar volume of transfer, V0φ,tr, have been calculated from density data. The apparent molar isentropic compressibility, K φ,s, limiting apparent molar isentropic compressibility, K0φ,s, its slope, Sk, and partial molar compressibility of transfer, K0φ,s, tr, have been calculated from speed of sound data. These values are also used for calculating the number of water molecules hydrated, nH, to the Asp. The viscosity data has also been used to determine relative viscosity ηr, viscosity B-coefficients, temperature derivative of B-coefficients, dB/dT and viscosity B-coefficients of transfer, Btr. The calculated parameters have been discussed in terms of various solute-solute and solute-solvent interactions prevailing in these solutions. Further, a detailed insight into the physicochemical interactions between Asp and aqueous PD, e.g., ion-hydrophilic and hydrophilic-hydrophilic interactions along with the structure-making tendency have been retrieved through the perusal of these calculated parameters. PMID:27640386

  18. Calcium Binding to Amino Acids and Small Glycine Peptides in Aqueous Solution: Toward Peptide Design for Better Calcium Bioavailability.

    PubMed

    Tang, Ning; Skibsted, Leif H

    2016-06-01

    Deprotonation of amino acids as occurs during transfer from stomach to intestines during food digestion was found by comparison of complex formation constants as determined electrochemically for increasing pH to increase calcium binding (i) by a factor of around 6 for the neutral amino acids, (ii) by a factor of around 4 for anions of the acidic amino acids aspartic and glutamic acid, and (iii) by a factor of around 5.5 for basic amino acids. Optimized structures of the 1:1 complexes and ΔHbinding for calcium binding as calculated by density functional theory (DFT) confirmed in all complexes a stronger calcium binding and shorter calcium-oxygen bond length in the deprotonated form. In addition, the stronger calcium binding was also accompanied by a binding site shift from carboxylate binding to chelation by α-amino group and carboxylate oxygen for leucine, aspartate, glutamate, alanine, and asparagine. For binary amino acid mixtures, the calcium-binding constant was close to the predicted geometric mean of the individual amino acid binding constants indicating separate binding of calcium to two amino acids when present together in solution. At high pH, corresponding to conditions for calcium absorption, the binding affinity increased in the order Lys < Arg < Cys < Gln < Gly ∼ Ala < Asn < His < Leu < Glu< Asp. In a series of glycine peptides, calcium-binding affinity was found to increase in the order Gly-Leu ∼ Gly-Gly < Ala-Gly < Gly-His ∼ Gly-Lys-Gly < Glu-Cys-Gly < Gly-Glu, an ordering confirmed by DFT calculations for the dipeptides and which also accounted for large synergistic effects in calcium binding for up to 6 kJ/mol when compared to the corresponding amino acid mixtures.

  19. Aqueous solution speciation of Fe(III) complexes with dihydroxamate siderophores alcaligin and rhodotorulic acid and synthetic analogues using electrospray ionization mass spectrometry.

    PubMed

    Spasojević, I; Boukhalfa, H; Stevens, R D; Crumbliss, A L

    2001-01-01

    Aqueous solutions of Fe3+ complexes of cyclic (alcaligin) and linear (rhodotorulic acid) dihydroxamate siderophores and synthetic linear eight-carbon-chain and two-carbon-chain dihydroxamic acids ([CH3N(OH)C=O)]2(CH2)n; H2Ln; n = 2 and 8) were investigated by electrospray ionization mass spectrometry (ESI-MS). Information was obtained relevant to the structure and the speciation of various Fe(III)-dihydroxamate complexes present in aqueous solution by (1) comparing different ionization techniques (ESI and FAB), (2) altering the experimental parameters (Fe3+/ligand ratio, pH, cone voltage), (3) using high-stability hexacoordinated Fe(III) siderophore complex mixtures (ferrioxamine B/ferrioxamine E) as a calibrant to quantify intrinsically neutral (H+ clustered or protonated) and intrinsically charged complexes, and (4) using mixed-metal complexes containing Fe3+, Ga3+, and Al3+. These results illustrate that for all dihydroxamic acid ligands investigated multiple tris- and bis-chelated mono- and di-Fe(III) species are present in relative concentrations that depend on the pH and Fe/L ratio.

  20. Study of diatoms/aqueous solution interface. I. Acid-base equilibria and spectroscopic observation of freshwater and marine species

    NASA Astrophysics Data System (ADS)

    Gélabert, A.; Pokrovsky, O. S.; Schott, J.; Boudou, A.; Feurtet-Mazel, A.; Mielczarski, J.; Mielczarski, E.; Mesmer-Dudons, N.; Spalla, O.

    2004-10-01

    This work reports on a concerted study of diatom-water interfaces for two marine planktonic ( Thalassiosira weissflogii= TW, Skeletonema costatum= SC) and two freshwater periphytic species ( Achnanthidium minutissimum= AMIN, Navicula minima= NMIN). Proton surface adsorption was measured at 25°C, pH of 3 to 11 and ionic strength of 0.001 to 1.0 M via potentiometric titration using a limited residence time reactor. Electrophoretic mobility of living cells and their frustules was measured as a function of pH and ionic strength. Information on the chemical composition and molecular structure of diatoms surfaces was obtained using FT-IR (in situ attenuated total reflectance) and X-ray Photoelectron Spectroscopy (XPS). The surface area of living cells and their frustules in aqueous solutions was quantified using Small Angle X-ray Scattering Spectroscopy (SAXS). These observations allowed us to identify the nature and to determine the concentration of the major surface functional groups (carboxyl, amine and silanol) responsible for the amphoteric behavior of cell surfaces in aqueous solutions. Taking into account the relative proportion of surface sites inferred from XPS and FT-IR measurements, a surface complexation model of diatom-solution interfaces was generated on the basis of surface titration results. The cell-normalized ratios of the three major surface sites {>COOH}: {>NH 3}: {>SiOH} are 1:1:0.1, 1:10:0, 1:1:0.4 and 1:1:0.3 for TW, SC, AMIN and NMIN, respectively. The total amount of proton/hydroxyl active surface sites for investigated species ranges from 1 (NMIN) to 9 (SC) mmol/g dry weight. Normalization of these site densities to the area of siliceous skeleton yields values between 0.3 (NMIN) and 0.9 mmol/m 2 (SC) which are an order of magnitude higher than corresponding values for organic-free frustules or amorphous silica. This suggests that the amphoteric properties and possibly the affinity for metal adsorption of diatom cultures are essentially

  1. 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.

  2. Solid-phase extraction of gallium(III) with hydrophobic 8-quinolinol derivatives-impregnated resin from aqueous acidic and alkaline solutions.

    PubMed

    Hatori, Nahoko; Imura, Hisanori; Ohashi, Akira; Ohashi, Kousaburo

    2008-12-01

    Solid-phase extraction (SPE) of gallium(III) with hydrophobic 8-quinolinol derivatives (HQs)-impregnated resin from aqueous acidic and alkaline solutions has been investigated. The HQs used were 7-(4-ethyl-1-methyloctyl)-8-quinolinol (HEMOQ), 5-octyloxymethyl-8-quinolinol (HO(8)Q), 2-methyl-5-octyloxymethyl-8-quinolinol (HMO(8)Q), 5-dioctylaminomethyl-8-quinolinol (HN(8)Q), 7-bromo-5-octyloxymethyl-8-quinolinol (HBrO(8)Q), and 5-(2-ethylhexyloxymethyl)-8-quinolinol (HOEHQ). Various factors affecting the SPE, such as the substituents of the HQs, HCl and NaOH concentrations in the aqueous phase, the HQ concentration in the resin, and the equilibration time were clarified. The extractability for gallium(III) from the aqueous solution became higher in the following order: HBrO(8)Q < HEMOQ < HO(8)Q < HN(8)Q < HMO(8)Q at 3 mol l(-1) HCl; HMO(8)Q < HO(8)Q < HOEHQ < HEMOQ < HN(8)Q < HBrO(8)Q at pH 0.4; HMO(8)Q < HO(8)Q asymptotically equal to HOEHQ < HN(8)Q < HEMOQ at 3 mol l(-1) NaOH.

  3. Excess electron reactivity in amino acid aqueous solution revealed by ab initio molecular dynamics simulation: anion-centered localization and anion-relayed electron transfer dissociation.

    PubMed

    Wu, Xiuxiu; Gao, Liang; Liu, Jinxiang; Yang, Hongfang; Wang, Shoushan; Bu, Yuxiang

    2015-10-28

    Studies on the structure, states, and reactivity of excess electrons (EEs) in biological media are of great significance. Although there is information about EE interaction with desolvated biological molecules, solution effects are hardly explored. In this work, we present an ab initio molecular dynamics simulation study on the interaction and reactivity of an EE with glycine in solution. Our simulations reveal two striking results. Firstly, a pre-solvated EE partially localizes on the negatively charged -COO(-) group of the zwitterionic glycine and the remaining part delocalizes over solvent water molecules, forming an anion-centered quasi-localized structure, due to relative alignment of the lowest unoccupied molecular orbital energy levels of potential sites for EE residence in the aqueous solution. Secondly, after a period of anion-centered localization of an EE, the zwitterionic glycine is induced to spontaneously fragment through the cleavage of the N-Cα bond, losing ammonia (deamination), and leaving a ˙CH2-COO(-) anion radical, in good agreement with experimental observations. Introduction of the same groups (-COO(-) or -NH3(+)) in the side chain (taking lysine and aspartic acid as examples) can affect EE localization, with the fragmentation of the backbone part of these amino acids dependent on the properties of the side chain groups. These findings provide insights into EE interaction mechanisms with the backbone parts of amino acids and low energy EE induced fragmentation of amino acids and even peptides and proteins.

  4. 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

  5. Effect of organic co-solvents on the solvation enthalpies of amino acids and dipeptides in mixed aqueous solutions

    NASA Astrophysics Data System (ADS)

    Badelin, V. G.; Tyunina, E. Yu.

    2011-09-01

    Transition enthalpies (Δtr H o) of substances from water to binary solutions were calculated at 298.15 K on the basis of standard dissolution enthalpies (Δsol H o) for six amino acids and five dipeptides in the mixtures of water with organic solvents of various chemical natures. The enthalpy pair coefficients of interaction h xy for biomolecules with organic component of mixture were estimated within the formalism of the McMillan-Mayer theory. The change in the character of the interaction of the components of solution was demonstrated in dependence on the physicochemical properties of the solvent and nature of the side radical of the dissolved bioorganic substance. Quantitative estimation of the type of interaction of the substance with the solvent was performed on the basis of correlation ratios relating the enthalpy characteristics of bioorganic substances to properties of organic cosolvents. It was shown that in the solutions under study, the effects of both the specific (mainly electron donor) and non-specific solvation of amino acids and peptides are observed.

  6. Performance of mango seed adsorbents in the adsorption of anthraquinone and azo acid dyes in single and binary aqueous solutions.

    PubMed

    Dávila-Jiménez, Martín M; Elizalde-González, María P; Hernández-Montoya, Virginia

    2009-12-01

    In this study the husk of mango seed and two carbonaceous adsorbents prepared from it were used to study the adsorption behavior of eight acid dyes. The adsorbed amount in mmol m(-2) decayed asymptotically as the molecular volume and area increased. The interaction between the studied dyes and the mesoporous carbon was governed by the ionic species in solution and the acidic/basic groups on the surface. Less than 50% of the external surface of the microporous carbon became covered with the dyes molecules, though monolayer formation demonstrating specific interactions only with active sites on the surface and the adsorption magnitudes correlated with the shape parameter of the molecule within a particular dye group. The adsorption behavior in mixtures was determined by the molecular volume of the constituents; the greater the molecular volume difference, the greater the effect on the adsorbed amount. We also demonstrated that the raw husk of the mango seed can be used to remove up to 50% from model 50 mg l(-1) solutions of the studied acid dyes.

  7. Acid titrations of poly(dG-dC).poly(dG-dC) in aqueous solution and in a w/o microemulsion.

    PubMed

    Airoldi, Marta; Boicelli, C Andrea; Gennaro, Guiseppe; Giomini, Marcello; Giuliani, Anna Maria; Giustini, Mauro

    2006-02-01

    The model polynucleotide poly(dG-dC).poly(dG-dC) (polyGC) was titrated with a strong acid (HCl) in aqueous unbuffered solutions and in the quaternary w/o microemulsion CTAB/n-pentanol/n-hexane/water. The titrations, performed at several concentrations of NaCl in the range 0.005 to 0.600 M, were followed by recording the modifications of the electronic absorption and of the CD spectra (210< or = lambda < or =350 nm) upon addition of the acid. In solution, the polynucleotide undergoes two acid-induced transitions, neither of which corresponds to denaturation of the duplex to single coil. The first transition leads to the Hoogsteen type synG.C+ duplex, while the second leads to the C+.C duplex. The initial B-form of polyGC was recovered by back-titration with NaOH. The apparent pKa values were obtained for both steps of the titration, at all salt concentrations. A reasonably linear dependence of pKa1 and pKa2 from p[NaCl] was obtained, with both pKa values decreasing with increasing ionic strength. In microemulsion, at salt concentrations < or = 0.300 M, an acid-induced transition was observed, matching the first conformational transition recorded also in solution. However, further addition of acid led to denaturation of the protonated duplex. Renaturation of polyGC was obtained by back-titration with NaOH. At salt concentrations > 0.300 M, polyGC is present as a mixture of B-form and psi- aggregates, that slowly separate from the microemulsion. The acid titration induces at first a conformational transition similar to the one observed at low salt or in solution, then denaturation occurs, which is however preceded by the appearance of a transient conformation, that has been tentatively classified as a left-handed Z double helix.

  8. Dissociative Binding of Carboxylic Acid Ligand on Nanoceria Surface in Aqueous Solution: A Joint in Situ Spectroscopic Characterization and First-Principles Study

    SciTech Connect

    Lu, Zhou; Karakoti, Ajay S.; Velarde Ruiz Esparza, Luis A.; Wang, Weina; Yang, Ping; Thevuthasan, Suntharampillai; Wang, Hongfei

    2013-11-21

    Carboxylic acid is a common ligand anchoring group to functionalize nanoparticle surfaces. Its binding structures and mechanisms as a function of the oxidation states of metal oxide nanoparticle surfaces are not well characterized experimentally. We present an in situ sum frequency generation vibrational spectroscopy (SFG-VS) study on the binding of deuterated acetic acid on ceria nanoparticles in the aqueous solution. In the SFG experiment, ceria nanoparticles were deposited on the flat surface of a CaF2 hemisphere in contact with acetic acid solutions. While the ceria nanoparticle deprotonated the acetic acid, the CaF2 surface could not. Thus, the binding of the deprotonated acetic acid on ceria can be selectively probed. SFG spectra revealed that the binding modes of the carboxylate group depend on the oxidation states of the ceria surfaces. SFG polarization analysis suggested that the bidentate chelating and bridging binding modes co-exist on the reduced ceria surfaces, while the oxidized ceria surfaces are dominated by the bidentate bridging mode. The direct spectroscopic evidence helps to clarify the binding structures and mechanisms on the ceria nanoparticles. Furthermore, the middle-infrared (IR) transparent CaF2 and its chemical inertness make CaF2 and similar substrate materials good candidates for direct SFG-VS measurement of nanoparticle surface reactions and binding chem-istry.

  9. Non-adiabatic tapered optical fiber sensor for measuring the interaction between α-amino acids in aqueous carbohydrate solution

    NASA Astrophysics Data System (ADS)

    Zibaii, M. I.; Latifi, H.; Karami, M.; Gholami, M.; Hosseini, S. M.; Ghezelayagh, M. H.

    2010-10-01

    A single-mode non-adiabatic tapered optical fiber (NATOF) sensor was utilized for sensing the variation in refractive index (RI) with concentration of d-glucose in deionized water and measurement of the RI of amino acids (AAs) in carbohydrate solutions. This method showed a rewarding ability in understanding the basis of biomolecular interactions in biological systems. Due to high sensitivity, ease of application, low cost and real-time measurement, this method is more efficient in comparison with other techniques, such as calorimetric titration, NMR, UV absorption spectroscopy, x-ray crystallography, computer calculations, kinetic studies and chromatography data. The NATOF is fabricated by the heat pulling method, utilizing a CO2 laser. The limit of detection of the NATOF was 55 ppm for a d-glucose concentration ranging from 0 to 80 mg ml-1, and the limit of detection of the RI measurement corresponding to these concentrations in the range from 1.3330 to 1.3447 was 8.2 × 10-6 as a refractometer sensor. The response of the NATOF shows that different kinds of interactions of various groups of AAs, such as l-alanine, l-leucine and l-cysteine with d-glucose, sucrose and water molecules, depend on functional groups in AAs such as OH, SH, CH2, NH+3 and COO-. These results can be interpreted in terms of solute-solute and solute-solvent interactions and the structure making/breaking ability of solutes in the given solution. Such a study helps in the better understanding of the interactions occurring between AA molecules and entities present in biological matrices.

  10. Bupivacaine salts of diflunisal and other aromatic hydroxycarboxylic acids: aqueous solubility and release characteristics from solutions and suspensions using a rotating dialysis cell model.

    PubMed

    Østergaard, Jesper; Larsen, Susan W; Parshad, Henrik; Larsen, Claus

    2005-11-01

    In the search for poorly soluble bupivacaine salts potentially enabling prolonged postoperative pain relief after local joint administration in the form of suspensions the solubility of bupivacaine salts of diflunisal and other aromatic hydroxycarboxylic acids were investigated together with the release characteristics of selected 1:1 salts from solutions and suspensions using a rotating dialysis cell model. The poorest soluble bupivacaine salts were obtained from the aromatic ortho-hydroxycarboxylic acids diflunisal, 5-iodosalicylic acid, and salicylic acid (aqueous solubilities: 0.6-1.9 mM at 37 degrees C). Diffusant appearance rates in the acceptor phase upon instillation of solutions of various salts in the donor cell applied to first-order kinetics. Calculated permeability coefficients for bupivacaine and the counterions diflunisal, 5-iodosalicylic acid, and mandelic acid were found to be correlated with the molecular size of the diffusants. Release experiments at physiological pH involving suspensions of the bupivacaine-diflunisal salt revealed that at each sampling point the diflunisal concentration exceeded that of bupivacaine in the acceptor phase. However, after an initial lag period, a steady state situation was attained resulting in equal and constant fluxes of the two diffusants controlled by the permeability coefficients in combination with the solubility product of the salt. Due to the fact that the saturation solubility of the bupivacaine-salicylic acid salt in water exceeded that of bupivacaine at pH 7.4, suspensions of the latter salt were unable to provide simultaneous release of the cationic and anionic species at pH 7.4. The release profiles were characterised by a rapid release of salicylate accompanied by a much slower appearance of bupivacaine in the acceptor phase caused by precipitation of bupivacaine base from the solution upon dissolution of the salt in the donor cell.

  11. Stability of cefozopran hydrochloride in aqueous solutions.

    PubMed

    Zalewski, Przemysław; Skibiński, Robert; Paczkowska, Magdalena; Garbacki, Piotr; Talaczyńska, Alicja; Cielecka-Piontek, Judyta; Jelińska, Anna

    2016-01-01

    The influence of pH on the stability of cefozopran hydrochloride (CZH) was investigated in the pH range of 0.44-13.00. Six degradation products were identified with a hybrid ESI-Q-TOF mass spectrometer. The degradation of CZH as a result of hydrolysis was a pseudo-first-order reaction. As general acid-base hydrolysis of CZH was not occurred in the solutions of hydrochloric acid, sodium hydroxide, acetate, borate and phosphate buffers, kobs = kpH because specific acid-base catalysis was observed. Specific acid-base catalysis of CZH consisted of the following reactions: hydrolysis of CZH catalyzed by hydrogen ions (kH+), hydrolysis of dications (k1H2O), monocations (k2H2O) and zwitter ions (k3H2O) and hydrolysis of zwitter ions (k1OH-) and monoanions (k2OH-) of CZH catalyzed by hydroxide ions. The total rate of the reaction was equal to the sum of partial reactions: [Formula: see text]. CZH similarly like other fourth generation cephalosporin was most stable at slightly acidic and neutral pH and less stable in alkaline pH. The cleavage of the β-lactam ring resulting from a nucleophilic attack on the carbonyl carbon in the β-lactam moiety is the preferred degradation pathway of β-lactam antibiotics in aqueous solutions.

  12. ENGINEERING BULLETIN: AIR STRIPPING OF AQUEOUS SOLUTIONS

    EPA Science Inventory

    Air striding is a means to transfer contaminants from aqueous solutions to air. ontaminants are not destroyed by air stripping but are physically separated from the aqueous solutions. ontaminant vapors are transferred into the air stream and, if necessary, can be treated by incin...

  13. SEPARATION OF RUTHENIUM FROM AQUEOUS SOLUTIONS

    DOEpatents

    Beederman, M.; Vogler, S.; Hyman, H.H.

    1959-07-14

    The separation of rathenium from a rathenium containing aqueous solution is described. The separation is accomplished by adding sodium nitrite, silver nitrate and ozone to the ruthenium containing aqueous solution to form ruthenium tetroxide and ihen volatilizing off the ruthenium tetroxide.

  14. Spectrophotometric determination of the protolytic dissociation constants of the new chromogenic reagent "palladiazo"-I Investigations with sodium hydroxide, perchloric acid and different aqueous buffer solutions.

    PubMed

    Pérez-Butsamante, J A; Burriel-Martí, F

    1971-02-01

    The "palladiazo" reagent has been subjected to a detailed spectrophotometric investigation in concentrated perchloric acid, different aqueous buffers and concentrated sodium hydroxide solutions. K(1)-K(10) and (1)-(10) values corresponding to the instability constants of the protolytic equilibria involved and to the molar absorptivities at 540 and 630 run of the different proton complex species of the system have been calculated by a number of analytical and graphical spectrophotometric methods. Special attention has been paid to the study of the complicated phenomena implied by the interaction of the reagent with perchloric acid, which has been shown to give rise to alteration of the initial isomeric composition of the reagent and to the formation of addition and/or oxidation products derived from side-reactions undergone by the reagent with the medium. All the instability constants and molar absorptivities, which have been determined by several methods, are tabulated for comparison.

  15. 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.

  16. Functionalized polymers for binding to solutes in aqueous solutions

    DOEpatents

    Smith, Barbara F.; Robison, Thomas W.

    2006-11-21

    A functionalized polymer for binding a dissolved molecule in an aqueous solution is presented. The polymer has a backbone polymer to which one or more functional groups are covalently linked. The backbone polymer can be such polymers as polyethylenimine, polyvinylamine, polyallylamine, and polypropylamine. These polymers are generally water-soluble, but can be insoluble when cross-linked. The functional group can be for example diol derivatives, polyol derivatives, thiol and dithiol derivatives, guest-host groups, affinity groups, beta-diphosphonic acids, and beta-diamides

  17. Terahertz absorption of dilute aqueous solutions

    NASA Astrophysics Data System (ADS)

    Heyden, Matthias; Tobias, Douglas J.; Matyushov, Dmitry V.

    2012-12-01

    Absorption of terahertz (THz) radiation by aqueous solutions of large solutes reports on the polarization response of their hydration shells. This is because the dipolar relaxation of the solute is dynamically frozen at these frequencies, and most of the solute-induced absorption changes, apart from the expulsion of water, are caused by interfacial water. We propose a model expressing the dipolar response of solutions in terms of a single parameter, the interface dipole moment induced in the interfacial water by electromagnetic radiation. We apply this concept to experimental THz absorption of hydrated sugars, amino acids, and proteins. None of the solutes studied here follow the expectations of dielectric theories, which predict a negative projection of the interface dipole on the external electric field. We find that this prediction is not able to describe the available experimental data, which instead suggests a nearly zero interface dipole for sugars and a more diverse pattern for amino acids. Hydrophobic amino acids, similarly to sugars, give rise to near zero interface dipoles, while strongly hydrophilic ones are best described by a positive projection of the interface dipole on the external field. The sign of the interface dipole is connected to the slope of the absorption coefficient with the solute concentration. A positive slope, implying an increase in the solution polarity relative to water, mirrors results frequently reported for protein solutions. We therefore use molecular dynamics simulations of hydrated glucose and lambda repressor protein to calculate the interface dipole moments of these solutes and the concentration dependence of the THz absorption. The absorption at THz frequencies increases with increasing solute concentration in both cases, implying a higher polarity of the solution compared to bulk water. The structure of the hydration layer, extracted from simulations, is qualitatively similar in both cases, with spatial correlations

  18. Terahertz absorption of dilute aqueous solutions.

    PubMed

    Heyden, Matthias; Tobias, Douglas J; Matyushov, Dmitry V

    2012-12-21

    Absorption of terahertz (THz) radiation by aqueous solutions of large solutes reports on the polarization response of their hydration shells. This is because the dipolar relaxation of the solute is dynamically frozen at these frequencies, and most of the solute-induced absorption changes, apart from the expulsion of water, are caused by interfacial water. We propose a model expressing the dipolar response of solutions in terms of a single parameter, the interface dipole moment induced in the interfacial water by electromagnetic radiation. We apply this concept to experimental THz absorption of hydrated sugars, amino acids, and proteins. None of the solutes studied here follow the expectations of dielectric theories, which predict a negative projection of the interface dipole on the external electric field. We find that this prediction is not able to describe the available experimental data, which instead suggests a nearly zero interface dipole for sugars and a more diverse pattern for amino acids. Hydrophobic amino acids, similarly to sugars, give rise to near zero interface dipoles, while strongly hydrophilic ones are best described by a positive projection of the interface dipole on the external field. The sign of the interface dipole is connected to the slope of the absorption coefficient with the solute concentration. A positive slope, implying an increase in the solution polarity relative to water, mirrors results frequently reported for protein solutions. We therefore use molecular dynamics simulations of hydrated glucose and lambda repressor protein to calculate the interface dipole moments of these solutes and the concentration dependence of the THz absorption. The absorption at THz frequencies increases with increasing solute concentration in both cases, implying a higher polarity of the solution compared to bulk water. The structure of the hydration layer, extracted from simulations, is qualitatively similar in both cases, with spatial correlations

  19. 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.

  20. 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.

  1. Photocatalytic discoloration of Acid Red 14 aqueous solution using titania nanoparticles immobilized on graphene oxide fabricated plate.

    PubMed

    Akerdi, Abdollah Gholami; Bahrami, S Hajir; Arami, Mokhtar; Pajootan, Elmira

    2016-09-01

    Textile industry consumes remarkable amounts of water during various operations. A significant portion of the water discharge to environment is in the form of colored contaminant. The present research reports the photocatalytic degradation of anionic dye effluent using immobilized TiO2 nanoparticle on graphene oxide (GO) fabricated carbon electrodes. Acid Red 14 (AR 14) was used as model compound. Graphene oxide nanosheets were synthesized from graphite powder using modified Hummer's method. The nanosheets were characterized with field emission scanning electron microscope (FESEM) images, X-ray diffraction (XRD) and FTIR spectrum. The GO nanoparticles were deposited on carbon electrode (GO-CE) by electrochemical deposition (ECD) method and used as catalyst bed. TiO2 nanoparticles were fixed on the bed (GO-CE- TiO2) with thermal process. Photocatalytic processes were carried out using a 500 ml solution containing dye in batch mode. Each photocatalytic treatment were carried out for 120 min. Effect of dye concentration (mg/L), pH of solution, time (min) and TiO2 content (g/L) on the photocatalytic decolorization was investigated. PMID:27309674

  2. Indian Jujuba Seed Powder as an Eco-Friendly and a Low-Cost Biosorbent for Removal of Acid Blue 25 from Aqueous Solution

    PubMed Central

    Krishna, L. Sivarama; Reddy, A. Sreenath; Zuhairi, W. Y. Wan; Taha, M. R.; Reddy, A. Varada

    2014-01-01

    Indian jujuba seed powder (IJSP) has been investigated as a low-cost and an eco-friendly biosorbent, prepared for the removal of Acid Blue 25 (AB25) from aqueous solution. The prepared biomaterial was characterized by using FTIR and scanning electron microscopic studies. The effect of operation variables, such as IJSP dosage, contact time, concentration, pH, and temperature on the removal of AB25 was investigated, using batch biosorption technique. Removal efficiency increased with increase of IJSP dosage but decreased with increase of temperature. The equilibrium data were analyzed by the Langmuir and the Freundlich isotherm models. The data fitted well with the Langmuir model with a maximum biosorption capacity of 54.95 mg g−1. The pseudo-second-order kinetics was the best for the biosorption of AB25 by IJSP, with good correlation. Thermodynamic parameters such as standard free energy change (ΔG0), standard enthalpy changes (ΔH0), and standard entropy changes (ΔS0) were analyzed. The removal of AB25 from aqueous solution by IJSP was a spontaneous and exothermic adsorption process. The results suggest that IJSP is a potential low-cost and an eco-friendly biosorbent for the AB25 removal from synthetic AB25 wastewater. PMID:25383360

  3. Preparation of chitosan/poly(acrylic acid) magnetic composite microspheres and applications in the removal of copper(II) ions from aqueous solutions.

    PubMed

    Yan, Han; Yang, Lingyun; Yang, Zhen; Yang, Hu; Li, Aimin; Cheng, Rongshi

    2012-08-30

    In this current work, the magnetic composite microspheres (MCM), consisting of Fe(3)O(4) nanoparticles and poly(acrylic acid) (PAA) blended chitosan (CS), were prepared successfully by a simple method, co-precipitation of the compounds in alkaline solution. SEM, FTIR and TG techniques have been applied to investigate the structures of the MCM materials. The vibrating-sample magnetometer (VSM) measurement illustrated a paramagnetic property as well as a fast magnetic response, which indicated the significant separability of the MCM in the aqueous suspensions. Then, the MCM materials were employed as absorbents for removal of copper(II) (Cu(II)) ions from aqueous solutions. The fundamental adsorption behaviors of MCM were studied also. Experimental results revealed that the CS/PAA-MCM had greater adsorption capacity than CS-MCM, and PAA played an important role for the adsorption of Cu(II) ions. Moreover, the adsorption isotherms were all well described by the Langmuir model, while the adsorption kinetics followed the pseudo-second order equation. Furthermore, the adsorbent could be easily regenerated at lower pH and reused almost without any loss of adsorption capacity. On the contrary, the Cu(II) ions loaded CS-MCM and CS/PAA-MCM were stable enough at pH higher than 4.0, and both exhibited efficient phosphate removal with maximal uptakes around 63.0 and 108.0 mg Pg(-1), respectively. PMID:22749139

  4. Indian jujuba seed powder as an eco-friendly and a low-cost biosorbent for removal of acid blue 25 from aqueous solution.

    PubMed

    Krishna, L Sivarama; Reddy, A Sreenath; Zuhairi, W Y Wan; Taha, M R; Reddy, A Varada

    2014-01-01

    Indian jujuba seed powder (IJSP) has been investigated as a low-cost and an eco-friendly biosorbent, prepared for the removal of Acid Blue 25 (AB25) from aqueous solution. The prepared biomaterial was characterized by using FTIR and scanning electron microscopic studies. The effect of operation variables, such as IJSP dosage, contact time, concentration, pH, and temperature on the removal of AB25 was investigated, using batch biosorption technique. Removal efficiency increased with increase of IJSP dosage but decreased with increase of temperature. The equilibrium data were analyzed by the Langmuir and the Freundlich isotherm models. The data fitted well with the Langmuir model with a maximum biosorption capacity of 54.95 mg g(-1). The pseudo-second-order kinetics was the best for the biosorption of AB25 by IJSP, with good correlation. Thermodynamic parameters such as standard free energy change (ΔG(0)), standard enthalpy changes (ΔH(0)), and standard entropy changes (ΔS(0)) were analyzed. The removal of AB25 from aqueous solution by IJSP was a spontaneous and exothermic adsorption process. The results suggest that IJSP is a potential low-cost and an eco-friendly biosorbent for the AB25 removal from synthetic AB25 wastewater. PMID:25383360

  5. REMOVAL OF CESIUM BY SORPTION FROM AQUEOUS SOLUTIONS

    DOEpatents

    Ames, L.L.

    1962-01-16

    ABS>A process is given for selectively removing cesium from acid aqueous solutions containing cesium in microquantities and other cations in macroquantities by absorption on clinoptilolite. The cesium can be eluted from the clinoptilolite with a solution of ammonia, potassium hydroxide, or rubidium hydroxide. (AEC)

  6. Rapid degradation of p-arsanilic acid with simultaneous arsenic removal from aqueous solution using Fenton process.

    PubMed

    Xie, Xiande; Hu, Yuanan; Cheng, Hefa

    2016-02-01

    Although banned in some developed countries, p-arsanilic acid (p-ASA) is still used widely as a feed additive for swine production in many countries. With little uptake and transformation in animal bodies, nearly all the p-ASA administered to animals is excreted chemically unchanged in animal wastes, which can subsequently release the more toxic inorganic arsenic species upon degradation in the environment. For safe disposal of the animal wastes laden with p-ASA, we proposed a method of leaching the highly water-soluble p-ASA out of the manure first, followed by treatment of the leachate using the Fenton process to achieve fast oxidation of p-ASA and removal of the inorganic arsenic species released (predominantly arsenate) from solution simultaneously. The effects of solution pH, dosages of H2O2 and Fe(2+), and the presence of dissolved organic matter (DOM) on the treatment efficiency were systematically investigated. Under the optimum treatment conditions (0.53 mmol L(-1) Fe(2+), 2.12 mmol L(-1) H2O2, and initial pH of 3.0), p-ASA (10 mg-As L(-1)) could be completely oxidized to As(V) within 30 min in pure water and 4 natural water samples, and at the final pH of 4.0, the residual arsenic levels in solution phase were as low as 1.1 and 20.1-43.4 μg L(-1) in the two types of water matrixes, respectively. The presence of humic acid significantly retarded the oxidation of p-ASA by scavenging HO, and inhibited the As(V) removal through competitive adsorption on ferric hydroxide. Due to the high contents of DOM in the swine manure leachate samples (TOC at ∼500 mg L(-1)), much higher dosages of Fe(2+) (10.0 mmol L(-1)) and H2O2 (40.0 mmol L(-1)) and a longer treatment time (120 min) were required to achieve near complete oxidation of p-ASA (98.0%), while maintaining the levels of residual arsenic in the solution at <70.0 μg L(-1). The degradation pathway of p-ASA in the Fenton process was proposed based on the major degradation products detected

  7. Glucose-Responsive Hybrid Nanoassemblies in Aqueous Solutions: Ordered Phenylboronic Acid within Intermixed Poly(4-hydroxystyrene)-block-poly(ethylene oxide) Block Copolymer.

    PubMed

    Matuszewska, Alicja; Uchman, Mariusz; Adamczyk-Woźniak, Agnieszka; Sporzyński, Andrzej; Pispas, Stergios; Kováčik, Lubomír; Štěpánek, Miroslav

    2015-12-14

    Coassembly behavior of the double hydrophilic block copolymer poly(4-hydroxystyrene)-block-poly(ethylene oxide) (PHOS-PEO) with three amphiphilic phenylboronic acids (PBA) differing in hydrophobicity, 4-dodecyloxyphenylboronic acid (C12), 4-octyloxyphenylboronic acid (C8), and 4-isobutoxyphenylboronic acid (i-Bu) was studied in alkaline aqueous solutions and in mixtures of NaOHaq/THF by spin-echo (1)H NMR spectroscopy, dynamic and electrophoretic light scattering, and SAXS. The study reveals that only the coassembly of C12 with PHOS-PEO provides spherical nanoparticles with intermixed PHOS and PEO blocks, containing densely packed C12 micelles. NMR measurements have shown that spatial proximity of PHOS-PEO and C12 leads to the formation of ester bonds between -OH of PHOS block and hydroxyl groups of -B(OH)2. Due to the presence of PBA moieties, the release of compounds with 1,2- or 1,3-dihydroxy groups loaded in the coassembled PHOS-PEO/PBA nanoparticles by covalent binding to PBA can be triggered by addition of a surplus of glucose that bind to PBA competitively. The latter feature has been confirmed by fluorescence measurements using Alizarin Red as a model compound. Nanoparticles were proved to exhibit swelling in response to glucose as detected by light scattering.

  8. A study of low-energy ion induced radiolysis of thiol-containing amino acid cysteine in the solid and aqueous solution states

    NASA Astrophysics Data System (ADS)

    Ke, Zhigang; Huang, Qing; Dang, Bingrong; Lu, Yilin; Yuan, Hang; Zhang, Shuqing; Yu, Zengliang

    2010-09-01

    The radiolysis of cysteine under plasma discharge and irradiation of low-energy ion beam was investigated. The damage of cysteine in aqueous solution under discharge was assessed via the acid ninhydrin reagent and the yield of cystine produced from the reaction was analyzed by FTIR. In addition, the generation of hydrogen sulfide was also identified. The destruction of solid cysteine under low-energy ion beam irradiation was estimated via monitoring IR bands of different functional groups (-SH, -NH 3, -COO -) of cysteine, and the production of cystine from ion-irradiated solid cysteine after dissolution in water was also verified. These results may help us to understand the inactivation of sulphydryl enzymes under direct and indirect interaction with the low-energy ion irradiation.

  9. Photodegradation of acetone in dilute aqueous solution

    SciTech Connect

    Stefan, M.I.; Bolton, J.R.

    1995-12-31

    Photochemical methods for destroying organic pollutants found in industrial wastewaters and groundwaters are being used successfully in environment treatment systems. This study focuses on acetone photodegradation in aqueous solution by UV irradiation (1 kW medium pressure Hg lamp) in the presence and absence of H{sub 2}O{sub 2}. Intermediates such as acetic and formic acids were detected. The kinetic data were evaluated and the reaction mechanisms were postulated considering the influence of oxygen concentration and pH. The generation of {sm_bullet}OH radicals from the photolysis of H{sub 2}O{sub 2} induces a faster decomposition of acetone (depending on H{sub 2}O{sub 2} concentration) than does direct photolysis.

  10. Photochemical effect of humic acid components separated using molecular imprinting method applying porphyrin-like substances as templates in aqueous solution.

    PubMed

    Yu, Chunyan; Zhang, Yaobin; Quan, Xie; Chen, Shuo; Han, Jianbo; Ou, Xiaoxia; Zhao, Jincai

    2010-08-01

    To elucidate the relationship between photochemical functions with the structure of humic acids (HA), we developed a molecular imprinting method to separate the substances with given structure and investigated their photochemical behavior in aqueous solution. The substances with porphyrin-like core structure, such as chlorophyll or heme, were employed as template substances for preparing molecular imprinting polymers (MIP). The polymers were used to separate the substances with porphyrin-like structure from HA. Photochemical experiments were conducted to evaluate effects of the separated HA fractions on the photodegradation of coexisting organic pollutant. The results showed that all fractions bound by MIP accelerated photochemical degradation of coexisting 2,4-dichlorophenoxyacetic acid (2,4-D) under simulated sunlight (lambda>290 nm) irradiation, indicating that HA with porphyrin-like structure possesses better photoactivity than ones without the structure. The photochemical degradation of 2,4-D was enhanced when Fe(III), the ubiquitous element in natural aquatic systems, was added owing to the formation of Fe(III) complex with the HA. Electron paramagnetic resonance (EPR) spectra indicated that OH* and 1O2 radicals were generated in the solutions of HA fractions bound by MIP under simulated sunlight irradiation, implying that 2,4-D degradation could be related to oxidation reactions caused by reactive oxygen species (ROS).

  11. Preparation and characterization of trihydroxamic acid functionalized carbon materials for the removal of Cu(II) ions from aqueous solution

    NASA Astrophysics Data System (ADS)

    Godino-Salido, M. Luz; Santiago-Medina, Antonio; López-Garzón, Rafael; Gutiérrez-Valero, María D.; Arranz-Mascarós, Paloma; López de la Torre, M. Dolores; Domingo-García, María; López-Garzón, F. Javier

    2016-11-01

    The main objective of this study is to prepare and characterize two functionalizated carbon materials with enhanced adsorptive properties for Cu(II). Thus, two novel hybrid materials have been prepared by a non-covalent functionalization method based on the adsorption of a pyrimidine-desferrioxamine-B conjugate compound (H4L) on two activated carbons, ACs (labelled Merck and F). The adsorption of H4L on the ACs is pH-dependent and highly irreversible. This is due to strong π-π interactions between the arene centers of the ACs and the pyrimidine moiety of H4L. The textural characterization of the AC/H4L hybrids shows large decreases of their surface areas. Thus the values of Merck and F are 1031 and 1426 m2/g respectively, while these of Merck/H4L and F/H4L hybrids are 200 and 322 m2/g. An important decrease in the micropore volumes is also found, due to the blockage of narrow porosity produced by the adsorption of H4L molecules. The ACs/H4L hybrids show larger adsorption capacities for Cu(II) (0.105(4) and 0.13(2) mmol/g, at pH 2.0, and 0.20(3) and 0.242(9) mmol/g, at pH 5.5, for Merck/H4L and F/H4L, respectively) than those of the ACs (0.024(6) and 0.096(9) mmol/g, at pH 2.0, and 0.10(2) and 0.177(8) mmol/g, at pH 5.5, for Merck and F respectively), which is explained on the basis of the complexing ability of the trihydroxamic acid functions. The desorption of Cu(II) from the ACs/H4L/Cu(II) materials in acid solution allows the regeneration of most active sites (78.5% in the case of Merck/H4L/Cu(II) and 83.0% in the case of F/H4L/Cu(II)).

  12. Copper(II) 12-metallacrown-4 complexes of alpha-, beta- and gamma-aminohydroxamic acids: a comparative thermodynamic study in aqueous solution.

    PubMed

    Tegoni, Matteo; Remelli, Maurizio; Bacco, Dimitri; Marchiò, Luciano; Dallavalle, Francesco

    2008-05-28

    A complete thermodynamic study of the protonation and Cu(II) complex formation equilibria of a series of alpha- and beta-aminohydroxamic acids in aqueous solution was performed. The thermodynamic parameters obtained for the protonation of glycine-, (S)-alpha-alanine-, (R,S)-valine-, (S)-leucine-, beta-alanine- and (R)-aspartic-beta-hydroxamic acids were compared with those previously reported for gamma-amino- and (S)-glutamic-gamma-hydroxamic acids. The enthalpy/entropy parameters calculated for the protonation microequilibria of these three types of ligands are in very good agreement with the literature values for simple amines and hydroxamic acids. The pentanuclear complexes [Cu5L4H(-4)]2+ contain the ligands acting as (NH2,N-)-(O,O-) bridging bis-chelating and correspond to 12-metallacrown-4 (12-MC-4) which are formed by self-assembly between pH 4 and 6 with alpha-aminohydroxamates (HL), while those with beta- and gamma-derivatives exist in a wider pH range (4-11). The stability order of these metallomacrocycles is beta- > alpha- > gamma-aminohydroxamates. The formation of 12-MC-4 with alpha-aminohydroxamates is entropy-driven, and that with beta-derivatives is enthalpy-driven, while with gamma-GABAhydroxamate both effects occur. These results are interpreted on the basis of specific enthalpies or entropy contributions related to chelate ring dimensions, charge neutralization and solvation-desolvation effects. The enthalpy/entropy parameters of 12-MC-4 with alpha-aminohydroxamic acids considered are also dependent on the optical purity of the ligands. Actually, that with (R,S)-valinehydroxamic acid presents an higher entropy and a lower enthalpy value than those of enantiopure ligands, although the corresponding stabilities are almost equivalent. Moreover, DFT calculations are in agreement with a more exothermic enthalpy found for metallacrowns with enantiomerically pure ligands.

  13. Kinetic and mechanism of the oxidation of chromium(III) complex with anthranil- N, N-diacetic acid by periodate ion in acidic aqueous solutions

    NASA Astrophysics Data System (ADS)

    Ali, Ismat H.

    2015-06-01

    The kinetics of oxidation of [CrIII(atda)(H2O)2] (atda = anthranil- N, N-diacetato) complex by IO{4/-} was studied spectrophotometrically in aqueous solutions with pH range 2.20-3.34, 0.30 M ionic strength and in 20.0-40.0°C temperature range. The rate law of the reaction exhibited saturation kinetics. Values of the rate constant for the electron transfer process, the equilibrium constant for dissociation of [CrIII (atda)(H2O)2] to [CrIII (atda) (H2O)OH]+ + H+ and the pre-equilibrium formation constant were calculated. The thermodynamic activation parameters are reported. It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of the IVII to chromium(III).

  14. Thermodynamic models of aqueous solutions containing inorganic electrolytes and dicarboxylic acids at 298.15 K. 2. Systems including dissociation equilibria.

    PubMed

    Clegg, Simon L; Seinfeld, John H

    2006-05-01

    Atmospheric aerosols contain a significant fraction of water-soluble organic compounds, including dicarboxylic acids. Pitzer activity coefficient models are developed, using a wide range of data at 298.15 K, for the following systems containing succinic acid (H(2)Succ) and/or succinate salts: [H(+), Li(+), Na(+), K(+), Rb(+), Cs(+)]Cl(-)-H(2)Succ-H(2)O, HNO(3)-H(2)Succ-H(2)O, H(+)-NH(4)(+)-HSucc(-)-Succ(2-)-NH(3)-H(2)Succ-H(2)O, NH(4)Cl-(NH(4))(2)Succ-H(2)O, H(+)-Na(+)-HSucc(-)-Succ(2-)-Cl(-)-H(2)Succ-H(2)O, NH(4)NO(3)-H(2)Succ-H(2)O, and H(2)SO(4)-H(2)Succ-H(2)O. The above compositions are given in terms of ions in the cases where acid dissociation was considered. Pitzer models were also developed for the following systems containing malonic acid (H(2)Malo): H(+)-Na(+)-HMalo(-)-Malo(2-)-Cl(-)-H(2)Malo-H(2)O, and H(2)Malo-H(2)SO(4)-H(2)O. The models are used to evaluate the extended Zdanovskii-Stokes-Robinson (ZSR) model proposed by Clegg and Seinfeld (J. Phys. Chem. A 2004, 108, 1008-1017) for calculating water and solute activities in solutions in which dissociation equilibria occur. The ZSR model yields satisfactory results only for systems that contain moderate to high concentrations of (nondissociating) supporting electrolyte. A practical modeling scheme is proposed for aqueous atmospheric aerosols containing both electrolytes and dissociating (organic) nonelectrolytes.

  15. Thermal-Conductivity Measurements of Aqueous Orthophosphoric Acid Solutions in the Temperature Range from (293 to 400) K and at Pressures up to 15 MPa

    NASA Astrophysics Data System (ADS)

    Guseinov, G. G.; Abdulagatov, I. M.

    2014-02-01

    A new improved guarded parallel-plate thermal-conductivity cell for absolute measurements of corrosive (chemically aggressive) fluids under pressure has been developed. Using the new modified guarded parallel-plate apparatus the thermal conductivity of aqueous orthophosphoric acid solutions was measured over the temperature range from (293 to 400) K and pressures up to 15 MPa. Measurements were made for three compositions of (8 mass%, 15 mass%, and 50 mass%) along three isobars of (0.101, 5, and 15) MPa. The combined expanded uncertainty of the thermal-conductivity measurements at the 95 % confidence level with a coverage factor of is estimated to be 2 %. The uncertainties of the temperature, pressure, and concentration measurements were 15 mK, 0.05 %, and 0.01 %, respectively. The temperature, concentration, and pressure dependences of the thermal conductivity of the solution were studied. The measured values of thermal conductivity were compared with the available reported data and the values calculated from various correlation and prediction models. A new wide-range correlation model (extended Jones-Dole type equation with pressure-dependent coefficients) for the (aq) solution was developed using the present experimental data.

  16. An NMR and ab initio quantum chemical study of acid-base equilibria for conformationally constrained acidic alpha-amino acids in aqueous solution.

    PubMed

    Nielsen, P A; Jaroszewski, J W; Norrby, P O; Liljefors, T

    2001-03-01

    The protonation states of a series of piperidinedicarboxylic acids (PDAs), which are conformationally constrained acidic alpha-amino acids, have been studied by (13)C NMR titration in water. The resulting data have been correlated with theoretical results obtained by HF/6-31+G calculations using the polarizable continuum model (PCM) for the description of water. The PDAs are highly ionizable and contain one or two possible internal hydrogen bonds. In the present study, we show that the PCM model is able to reproduce the relative stabilities of the different protonation states of the PDAs. Furthermore, our results show that prediction of relative pK(a) values for two different types of ionizable functional groups covering a pK(a) range from 1.6 to 12.1 is possible with a high degree of accuracy.

  17. Spatial structure of heptapeptide Glu-Ile-Leu-Asn-His-Met-Lys, a fragment of the HIV enhancer prostatic acid phosphatase, in aqueous and SDS micelle solutions

    NASA Astrophysics Data System (ADS)

    Bloсhin, Dmitri S.; Aganova, Oksana V.; Yulmetov, Aidar R.; Filippov, Andrei V.; Gizatullin, Bulat I.; Afonin, Sergii; Antzutkin, Oleg N.; Klochkov, Vladimir V.

    2013-02-01

    Prostatic acid phosphatase (PAP) is a protein abundantly present in human seminal fluid. PAP plays important role in fertilization. Its 39-amino-acid fragment, PAP(248-286), is effective in enhancing infectivity of HIV virus. In this work, we determined the spatial structure in aqueous solution of a heptapeptide within the PAP fragment, containing amino acid residues 266-272 (Glu-Ile-Leu-Asn-His-Met-Lys). We also report the structure of the complex formed by this heptapeptide with sodium dodecyl sulfate micelles, a model of a biological membrane, as determined by 1H NMR spectroscopy and 2D NMR (TOCSY, HSQC-HECADE, NOESY) spectroscopy. Complex formation was confirmed by chemical shift alterations in the 1H NMR spectra of the heptapeptide, as well as by the signs and values of NOE effects. We also present a comparison of the spatial structure of Glu-Ile-Leu-Asn-His-Met-Lys in water and in complex with sodium dodecyl sulfate.

  18. Mechanism of azo dye degradation in Advanced Oxidation Processes: Degradation of Sulfanilic Acid Azochromotrop and its parent compounds in aqueous solution by ionizing radiation

    NASA Astrophysics Data System (ADS)

    Pálfi, Tamás; Wojnárovits, László; Takács, Erzsébet

    2011-03-01

    Mechanistic studies were made on hydroxyl radical and hydrated electron reaction with Sulfanilic Acid Azochromotrop (SPADNS) as model azo dye in dilute aqueous solution. SPADNS contains 4,5-dihydroxynaphthalene-2,7-disulfonic acid part and 4-sulfophenylazo group. To establish the details of the reaction mechanism the reactions of two simpler molecules without 4-sulfophenylazo part were also studied: one of them contained one (in position 4, II), the other two (in positions 4 and 5, III) -OH groups. Hydroxyl radicals react with these molecules with radical addition to the naphthalene-2,7-disulfonic acid part. The adduct hydroxycyclohexadienyl type radical decays in radical-radical reactions, or undergoes a (pH dependent) water elimination to yield naphthoxy radical. The radical decay takes place on the ms timescale. Degradation efficiencies are 0.6-0.8. Hydrated electron in the case of the two simpler molecules reacts with the rings, while in the case of dye with the azo bond. Electron scavenging is followed by protonation, this reaction in the case of II and III yields cyclohexadienyl, while with the dye hydrazo radical. The efficiency of degradation with II and III is 0.2-0.6, while for SPADNS it is close to 1.

  19. Process for decomposing nitrates in aqueous solution

    DOEpatents

    Haas, Paul A.

    1980-01-01

    This invention is a process for decomposing ammonium nitrate and/or selected metal nitrates in an aqueous solution at an elevated temperature and pressure. Where the compound to be decomposed is a metal nitrate (e.g., a nuclear-fuel metal nitrate), a hydroxylated organic reducing agent therefor is provided in the solution. In accordance with the invention, an effective proportion of both nitromethane and nitric acid is incorporated in the solution to accelerate decomposition of the ammonium nitrate and/or selected metal nitrate. As a result, decomposition can be effected at significantly lower temperatures and pressures, permitting the use of system components composed of off-the-shelf materials, such as stainless steel, rather than more costly materials of construction. Preferably, the process is conducted on a continuous basis. Fluid can be automatically vented from the reaction zone as required to maintain the operating temperature at a moderate value--e.g., at a value in the range of from about 130.degree.-200.degree. C.

  20. Effect of ascorbic acid on the degradation of cyanocobalamin and hydroxocobalamin in aqueous solution: a kinetic study.

    PubMed

    Ahmad, Iqbal; Qadeer, Kiran; Zahid, Saima; Sheraz, Muhammad Ali; Ismail, Tehmina; Hussain, Waqar; Ansari, Izhar Ahmad

    2014-10-01

    The degradation kinetics of 5 × 10(-5) M cyanocobalamin (B12) and hydroxocobalamin (B12b) in the presence of ascorbic acid (AH2) was studied in the pH range of 1.0-8.0. B12 is degraded to B12b which undergoes oxidation to corrin ring cleavage products. B12b alone is directly oxidized to the ring cleavage products. B12 and B12b in degraded solutions were simultaneously assayed by a two-component spectrometric method at 525 and 550 nm without interference from AH2. Both degrade by first-order kinetics and the values of the rate constants at pH 1.0-8.0 range from 0.08 to 1.05 × 10(-5) s(-1) and 0.22-7.62 × 10(-5) s(-1), respectively, in the presence of 0.25 × 10(-3) M AH2. The t 1/2 values of B12 and B12b range from 13.7 to 137.5 h and 2.5-87.5 h, respectively. The second-order rate constants for the interaction of AH2 with B12 and B12b are 0.05-0.28 × 10(-2) and 1.10-30.08 × 10(-2) M(-1) s(-1), respectively, indicating a greater effect of AH2 on B12b compared to that of B12. The k obs-pH profiles for both B12 and B12b show the highest rates of degradation around pH 5. The degradation of B12 and B12b by AH2 is affected by the catalytic effect of phosphate ions on the oxidation of AH2 in the pH range 6.0-8.0. PMID:24920523

  1. Effect of ascorbic acid on the degradation of cyanocobalamin and hydroxocobalamin in aqueous solution: a kinetic study.

    PubMed

    Ahmad, Iqbal; Qadeer, Kiran; Zahid, Saima; Sheraz, Muhammad Ali; Ismail, Tehmina; Hussain, Waqar; Ansari, Izhar Ahmad

    2014-10-01

    The degradation kinetics of 5 × 10(-5) M cyanocobalamin (B12) and hydroxocobalamin (B12b) in the presence of ascorbic acid (AH2) was studied in the pH range of 1.0-8.0. B12 is degraded to B12b which undergoes oxidation to corrin ring cleavage products. B12b alone is directly oxidized to the ring cleavage products. B12 and B12b in degraded solutions were simultaneously assayed by a two-component spectrometric method at 525 and 550 nm without interference from AH2. Both degrade by first-order kinetics and the values of the rate constants at pH 1.0-8.0 range from 0.08 to 1.05 × 10(-5) s(-1) and 0.22-7.62 × 10(-5) s(-1), respectively, in the presence of 0.25 × 10(-3) M AH2. The t 1/2 values of B12 and B12b range from 13.7 to 137.5 h and 2.5-87.5 h, respectively. The second-order rate constants for the interaction of AH2 with B12 and B12b are 0.05-0.28 × 10(-2) and 1.10-30.08 × 10(-2) M(-1) s(-1), respectively, indicating a greater effect of AH2 on B12b compared to that of B12. The k obs-pH profiles for both B12 and B12b show the highest rates of degradation around pH 5. The degradation of B12 and B12b by AH2 is affected by the catalytic effect of phosphate ions on the oxidation of AH2 in the pH range 6.0-8.0.

  2. Probing the general time scale question of boronic acid binding with sugars in aqueous solution at physiological pH.

    PubMed

    Ni, Nanting; Laughlin, Sarah; Wang, Yingji; Feng, You; Zheng, Yujun; Wang, Binghe

    2012-05-01

    The boronic acid group is widely used in chemosensor design due to its ability to reversibly bind diol-containing compounds. The thermodynamic properties of the boronic acid-diol binding process have been investigated extensively. However, there are few studies of the kinetic properties of such binding processes. In this report, stopped-flow method was used for the first time to study the kinetic properties of the binding between three model arylboronic acids, 4-, 5-, and 8-isoquinolinylboronic acids, and various sugars. With all the boronic acid-diol pairs examined, reactions were complete within seconds. The k(on) values with various sugars follow the order of D-fructose>D-tagatose>D-mannose>D-glucose. This trend tracks the thermodynamic binding affinities for these sugars and demonstrates that the 'on' rate is the key factor determining the binding constant.

  3. Oxidation of Purine Nucleotides by Triplet 3,3′,4,4′-Benzophenone Tetracarboxylic Acid in Aqueous Solution: pH-Dependence

    PubMed Central

    2014-01-01

    The photo-oxidation of purine nucleotides adenosine-5′-monophosphate (AMP) and guanosine-5′-monophosphate (GMP) by 3,3′,4,4′-benzophenone tetracarboxylic acid (TCBP) has been investigated in aqueous solutions using nanosecond laser flash photolysis (LFP) and time-resolved chemically induced dynamic nuclear polarization (CIDNP). The pH dependences of quenching rate constants and of geminate polarization are measured within a wide range of pH values. As a result, the chemical reactivity of reacting species in different protonation states is determined. In acidic solution (pH < 4.9), the quenching rate constant is close to the diffusion-controlled limit: kq = 1.3 × 109 M–1 s–1 (GMP), and kq = 1.2 × 109 M–1 s–1 (AMP), whereas in neutral and basic solutions it is significantly lower: kq = 2.6 × 108 M–1 s–1 (GMP, 4.9 < pH < 9.4), kq = 3.5 × 107 M–1 s–1 (GMP, pH > 9.4), kq = 1.0 × 108 M–1 s–1 (AMP, pH > 6.5). Surprisingly, the strong influence of the protonation state of the phosphoric group on the oxidation of adenosine-5′-monophosphate is revealed: the deprotonation of the AMP phosphoric group (6.5) decreases the quenching rate constant from 5.0 × 108 M–1 s–1 (4.9 < pH < 6.5) to 1.0 × 108 M–1 s–1 (pH > 6.5). PMID:24926567

  4. Separation of metal ions from aqueous solutions

    SciTech Connect

    Almon, A.

    1991-12-31

    This invention is comprised of a process and apparatus for quantitatively and selectively separating metal ions from mixtures thereof in aqueous solution. The apparatus includes, in combination, a horizontal electrochemical flowing cell containing flowing bulk electrolyte solution and an aqueous, metal ion-containing solution, the cell containing a metal mesh working electrode, a counter electrode positioned downstream from the working electrode, an independent variable power supply/potentiostat positioned outside of the flowing cell and connected to the electrodes, and optionally a detector such as a chromatographic detector, positioned outside the flowing cell. This apparatus and its operation has significant application where trace amounts of metal ions are to be separated.

  5. Separation of metal ions from aqueous solutions

    DOEpatents

    Almon, Amy C.

    1994-01-01

    A process and apparatus for quantitatively and selectively separating metal ions from mixtures thereof in aqueous solution. The apparatus includes, in combination, a horizontal electrochemical flow cell containing flow bulk electrolyte solution and an aqueous, metal ion-containing solution, the cell containing a metal mesh working electrode, a counter electrode positioned downstream from the working electrode, an independent variable power supply/potentiostat positioned outside of the flow cell and connected to the electrodes, and optionally a detector such as a chromatographic detector, positioned outside the flow cell. This apparatus and its operation has significant application where trace amounts of metal ions are to be separated.

  6. Effective uptake of decontaminating agent (citric acid) from aqueous solution by mesoporous and microporous materials: an adsorption process.

    PubMed

    Gokulakrishnan, Narasimhan; Pandurangan, Arumugam; Sinha, Pradeep Kumar

    2006-04-01

    The presence of citric acid in decontamination waste can cause complexation of the radioactive cations resulting in interferences in their removal by various treatment processes such as chemical precipitation, ion-exchange, etc., which are employed for the removal of radioactivity and may cause potential danger to the environment. Mesoporous Al-MCM-41 (Si/Al=30, 51, 72 and 97) and Si-MCM-41 molecular sieves were synthesized hydrothermally and characterized by XRD, BET (surface area) and FT-IR to evaluate the removal of citric acid through an adsorption process. Adsorption of citric acid over Al-MCM-41 shows the applicability of Freundlich and Langmuir isotherm and follows first order kinetics. The effects of contact time, concentration of citric acid, adsorbents (various Si/Al ratios of Al-MCM-41, Si-MCM-41, Hbeta zeolite and commercial carbon) and pH have been investigated. It has been found that the amount of citric acid adsorbed per unit gram of catalyst followed the order Al-MCM-41 (Si/Al=30)>Al-MCM-41 (Si/Al=51)>activated charcoal>Al-MCM-41 (Si/Al=72)>Al-MCM-41 (Si/Al=97)>Si-MCM-41>Hbeta zeolite.

  7. Freezing temperatures of aqueous iron(III) sulfate solutions and crystallization of a new acidic water-rich sulfate

    NASA Astrophysics Data System (ADS)

    Hennings, E.; Zürner, P.; Schmidt, H.; Voigt, W.

    2013-09-01

    An important question concerning the possibility of life under martian conditions is the existence of liquid water at low temperatures. On the martian surface, the existence of iron(III) sulfate is expected. The influence of iron(III) sulfate salt on ice deposits in respect to the formation of liquid salt brines was not investigated in the past. In this contribution, the investigation of the phase diagram of the system iron(III) sulfate-water and the influence of sulfuric acid to this system are presented. A new crystalline acidic iron(III) sulfate hydrate has been found in the ternary system iron(III) sulfate-water-sulfuric acid, which represents the most water-rich iron salt phase ever detected.

  8. EXTRACTION OF URANYL NITRATE FROM AQUEOUS SOLUTIONS

    DOEpatents

    Furman, N.H.; Mundy, R.J.

    1957-12-10

    An improvement in the process is described for extracting aqueous uranyl nitrate solutions with an organic solvent such as ether. It has been found that the organic phase will extract a larger quantity of uranyl nitrate if the aqueous phase contains in addition to the uranyl nitrate, a quantity of some other soluble nitrate to act as a salting out agent. Mentioned as suitable are the nitrates of lithium, calcium, zinc, bivalent copper, and trivalent iron.

  9. Photochemistry of norharmane in aqueous solution.

    PubMed

    Gonzalez, M Micaela; Salum, M Laura; Gholipour, Yousef; Cabrerizo, Franco M; Erra-Balsells, Rosa

    2009-08-01

    The photochemistry of norharmane (9H-pyrido[3,4-b]indole) in acidic (pH 5.0+/-0.1) and alkaline (pH 10.0+/-0.1) aqueous solutions was studied. The photochemical reactions were monitored by TLC, UV/VIS absorption spectroscopy, high-performance liquid chromatography (HPLC), electronic ionization-mass spectrometry (EI-MS), UV-laser desorption/ionization-time of flight-mass spectrometry (UV-LDI-TOF-MS) and an enzymatic method for H2O2 determination. The neutral (nHoN) and the protonated (nHoH+) forms of norharmane irradiated under Ar atmosphere were photostable, but they suffered a photochemical transformation in the presence of O2, yielding as photoproducts norharmane dimers, trimers and tetramers. nHoN shown to be more photostable than nHoH+. The nHoH+ and nHoN consumption quantum yields were 1.82x10(-3) and 0.51x10(-3), respectively, and the mechanisms involved in its photochemistry are discussed. H2O2 and singlet oxygen (1O2) were also detected and quantified in irradiated solutions of norharmane, and their role in the photochemistry of norharmane is discussed.

  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 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

  12. Precipitation of neptunium dioxide from aqueous solution

    SciTech Connect

    Roberts, K E

    1999-12-01

    Tens of thousands of metric tons of highly radioactive, nuclear waste have been generated in the US. Currently, there is no treatment or disposal facility for these wastes. Of the radioactive elements in high-level nuclear waste, neptunium (Np) is of particular concern because it has a long half-life and may potentially be very mobile in groundwaters associated with a proposed underground disposal site at Yucca Mountain, Nevada. Aqueous Np concentrations observed in previous, short-term solubility experiments led to calculated potential doses exceeding proposed long-term regulatory limits. However, thermodynamic data for Np at 25 C showed that these observed aqueous Np concentrations were supersaturated with respect to crystalline NpO{sub 2}. It was hypothesized that NpO{sub 2} is the thermodynamically stable solid phase in aqueous solution, but it is slow to form in an aqueous solution of NpO{sub 2}{sup +} on the time scale of previous experiments. The precipitation of NpO{sub 2} would provide significantly lower aqueous Np concentrations leading to calculated doses below proposed regulatory limits. To test this hypothesis, solubility experiments were performed at elevated temperature to accelerate any slow precipitation kinetics. Ionic NpO{sub 2}{sup +} (aq) was introduced into very dilute aqueous solutions of NaCl with initial pH values ranging from 6 to 10. The reaction vessels were placed in an oven and allowed to react at 200 C until steady-state aqueous Np concentrations were observed. In all cases, aqueous Np concentrations decreased significantly from the initial value of 10{sup {minus}4} M. The solids that formed were analyzed by x-ray powder diffraction, x-ray absorption spectroscopy, and scanning electron microscopy. The solids were determined to be high-purity crystals of NpO{sub 2}. This is the first time that crystalline NpO{sub 2} has been observed to precipitate from NpO{sub 2}{sup +}(aq) in near-neutral aqueous solutions. The results obtained

  13. Salinity, water hardness, and dissolved organic carbon modulate degradation of peracetic acid (PAA) compounds in aqueous solutions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Peracetic acid (PAA) is used in aquaculture under different conditions for disinfection purposes. However, there is a lack of information about its environmental fate, particularly its persistence in aquatic systems with different chemistries. Therefore, the impact of water hardness, salinity, and d...

  14. Nitric acid recovery from waste solutions

    DOEpatents

    Wilson, A. S.

    1959-04-14

    The recovery of nitric acid from aqueous nitrate solutions containing fission products as impurities is described. It is desirable to subject such solutions to concentration by evaporation since nitric acid is regenerated thereby. A difficulty, however, is that the highly radioactive fission product ruthenium is volatilized together with the nitric acid. It has been found that by adding nitrous acid, ruthenium volatilization is suppressed and reduced to a negligible degree so that the distillate obtained is practically free of ruthenium.

  15. Hydrophobic Solvation: Aqueous Methane Solutions

    ERIC Educational Resources Information Center

    Konrod, Oliver; Lankau, Timm

    2007-01-01

    A basic introduction to concept of a solvation shell around an apolar solute as well as its detection is presented. The hydrophobic solvation of toluene is found to be a good teaching example which connects macroscopic, phenomenological thermodynamic results with an atomistic point of view.

  16. Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution II: Solvent Coordinate-Dependent Reaction Path.

    PubMed

    Daschakraborty, Snehasis; Kiefer, Philip M; Miller, Yifat; Motro, Yair; Pines, Dina; Pines, Ehud; Hynes, James T

    2016-03-10

    The protonation of methylamine base CH3NH2 by carbonic acid H2CO3 within a hydrogen (H)-bonded complex in aqueous solution was studied via Car-Parrinello dynamics in the preceding paper (Daschakraborty, S.; Kiefer, P. M.; Miller, Y.; Motro, Y.; Pines, D.; Pines, E.; Hynes, J. T. J. Phys. Chem. B 2016, DOI: 10.1021/acs.jpcb.5b12742). Here some important further details of the reaction path are presented, with specific emphasis on the water solvent's role. The overall reaction is barrierless and very rapid, on an ∼100 fs time scale, with the proton transfer (PT) event itself being very sudden (<10 fs). This transfer is preceded by the acid-base H-bond's compression, while the water solvent changes little until the actual PT occurrence; this results from the very strong driving force for the reaction, as indicated by the very favorable acid-protonated base ΔpKa difference. Further solvent rearrangement follows immediately the sudden PT's production of an incipient contact ion pair, stabilizing it by establishment of equilibrium solvation. The solvent water's short time scale ∼120 fs response to the incipient ion pair formation is primarily associated with librational modes and H-bond compression of water molecules around the carboxylate anion and the protonated base. This is consistent with this stabilization involving significant increase in H-bonding of hydration shell waters to the negatively charged carboxylate group oxygens' (especially the former H2CO3 donor oxygen) and the nitrogen of the positively charged protonated base's NH3(+). PMID:26876428

  17. Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution II: Solvent Coordinate-Dependent Reaction Path.

    PubMed

    Daschakraborty, Snehasis; Kiefer, Philip M; Miller, Yifat; Motro, Yair; Pines, Dina; Pines, Ehud; Hynes, James T

    2016-03-10

    The protonation of methylamine base CH3NH2 by carbonic acid H2CO3 within a hydrogen (H)-bonded complex in aqueous solution was studied via Car-Parrinello dynamics in the preceding paper (Daschakraborty, S.; Kiefer, P. M.; Miller, Y.; Motro, Y.; Pines, D.; Pines, E.; Hynes, J. T. J. Phys. Chem. B 2016, DOI: 10.1021/acs.jpcb.5b12742). Here some important further details of the reaction path are presented, with specific emphasis on the water solvent's role. The overall reaction is barrierless and very rapid, on an ∼100 fs time scale, with the proton transfer (PT) event itself being very sudden (<10 fs). This transfer is preceded by the acid-base H-bond's compression, while the water solvent changes little until the actual PT occurrence; this results from the very strong driving force for the reaction, as indicated by the very favorable acid-protonated base ΔpKa difference. Further solvent rearrangement follows immediately the sudden PT's production of an incipient contact ion pair, stabilizing it by establishment of equilibrium solvation. The solvent water's short time scale ∼120 fs response to the incipient ion pair formation is primarily associated with librational modes and H-bond compression of water molecules around the carboxylate anion and the protonated base. This is consistent with this stabilization involving significant increase in H-bonding of hydration shell waters to the negatively charged carboxylate group oxygens' (especially the former H2CO3 donor oxygen) and the nitrogen of the positively charged protonated base's NH3(+).

  18. Removal of uranium from aqueous HF solutions

    DOEpatents

    Pulley, Howard; Seltzer, Steven F.

    1980-01-01

    This invention is a simple and effective method for removing uranium from aqueous HF solutions containing trace quantities of the same. The method comprises contacting the solution with particulate calcium fluoride to form uranium-bearing particulates, permitting the particulates to settle, and separting the solution from the settled particulates. The CaF.sub.2 is selected to have a nitrogen surface area in a selected range and is employed in an amount providing a calcium fluoride/uranium weight ratio in a selected range. As applied to dilute HF solutions containing 120 ppm uranium, the method removes at least 92% of the uranium, without introducing contaminants to the product solution.

  19. 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.

  20. Efficient Sorption and Removal of Perfluoroalkyl Acids (PFAAs) from Aqueous Solution by Metal Hydroxides Generated in Situ by Electrocoagulation.

    PubMed

    Lin, Hui; Wang, Yujuan; Niu, Junfeng; Yue, Zhihan; Huang, Qingguo

    2015-09-01

    Removal of environmentally persistent perfluoroalkyl acids (PFAAs), that is, perfluorooctanesulfonate (PFOS) and perfluorocarboxylic acids (PFCAs, C4 ∼ C10) were investigated through sorption on four metal hydroxide flocs generated in situ by electrocoagulation in deionized water with 10 mM NaCl as supporting electrolyte. The results indicated that the zinc hydroxide flocs yielded the highest removal efficiency with a wide range concentration of PFOA/PFOS (1.5 μM ∼ 0.5 mM) at the zinc dosage <150 mg L(-1) with the energy consumption <0.18 Wh L(-1). The sorption kinetics indicated that the zinc hydroxide flocs had an equilibrium adsorbed amount (qe) up to 5.74/7.69 mmol g(-1) (Zn) for PFOA/PFOS at the initial concentration of 0.5 mM with an initial sorption rate (v0) of 1.01 × 10(3)/1.81 × 10(3) mmol g(-1) h(-1). The sorption of PFOA/PFOS reached equilibrium within <10 min. The sorption mechanisms of PFAAs on the zinc hydroxide flocs were proposed based on the investigation of various driving forces. The results indicated that the hydrophobic interaction was primarily responsible for the PFAAs sorption. The electrocoagulation process with zinc anode may have a great potential for removing PFAAs from industrial wastewater as well as contaminated environmental waterbody.

  1. Sorption of organics from aqueous solution onto polymeric resins

    SciTech Connect

    Gusler, G.M.; Browne, T.E.; Cohen, Y. . Dept. of Chemical Engineering)

    1993-11-01

    The uptake of phenol, toluene, chlorobenzene, and benzoic acid by several polymeric resins and activated carbon was investigated experimentally. Presentation of the sorption data in terms of the number of sorbed monolayers and fractional pore volume filled indicated that, for the polymeric resins, solute uptake cannot be viewed as only a surface adsorption phenomenon. It is suggested that the aqueous phase uptake of phenol, toluene, chlorobenzene, and benzoic acid by the polymeric resins is attributable, in part, to solute absorption. The present study also suggests that solute uptake is affected by the swelling of some of the polymeric resins in water.

  2. A new association state of solutes in nanoconfined aqueous solutions

    NASA Astrophysics Data System (ADS)

    Tu, YuSong; Zhao, Liang; Fang, HaiPing

    2016-11-01

    Recently, we have found a reversible transition between the dispersion and aggregation states of solute molecules in aqueous solutions confined in nanoscale geometry, where solutes exhibit distinct behavior in a new association state from that in the dispersion and aggregation states observed usually in macroscopic systems. However, it remains unknown whether this new association state of solute molecules found in nanoconfined systems would vanish with the system size increasing and approaching the macroscopic scale. Here, we achieve the phase diagram of solute association states by making the analyses of Gibbs free energy of solutes in nanoconfined aqueous solutions in detail. In the phase diagram, we observe a closed regime with a finite system size of nanoconfined aqueous solutions and a solute concentration range, only in which there exists the new association state of solutes with the reversible transition between the aggregation and dispersion states, and there indeed exists an upper limit of the system size for the new association state, around several tens nanometers. These findings regarding the intimate connection between the system size and the solute association behavior provides the comprehensive understanding of the association dynamics of solutes in nanoconfined environment.

  3. Reorientation and Allied Dynamics in Water and Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Laage, Damien; Stirnemann, Guillaume; Sterpone, Fabio; Rey, Rossend; Hynes, James T.

    2011-05-01

    The reorientation of a water molecule is important for a host of phenomena, ranging over—in an only partial listing—the key dynamic hydrogen-bond network restructuring of water itself, aqueous solution chemical reaction mechanisms and rates, ion transport in aqueous solution and membranes, protein folding, and enzymatic activity. This review focuses on water reorientation and related dynamics in pure water, and for aqueous solutes with hydrophobic, hydrophilic, and amphiphilic character, ranging from tetra-methylurea to halide ions and amino acids. Attention is given to the application of theory, simulation, and experiment in the probing of these dynamics, in usefully describing them, and in assessing the description. Special emphasis is placed on a novel sudden, large-amplitude jump mechanism for water reorientation, which contrasts with the commonly assumed Debye rotational diffusion mechanism, characterized by small-amplitude angular motion. Some open questions and directions for further research are also discussed.

  4. Adsorption of phthalic acid esters (PAEs) by amphiphilic polypropylene nonwoven from aqueous solution: the study of hydrophilic and hydrophobic microdomain.

    PubMed

    Zhou, Xiangyu; Wei, Junfu; Zhang, Huan; Liu, Kai; Wang, Han

    2014-05-30

    A kind of amphiphilic polypropylene nonwoven with hydrophilic and hydrophobic microdomain was prepared through electron beam induced graft polymerization and subsequent ring opening reaction and then utilized in the adsorption of phthalic acid esters (PAEs). To elucidate the superiority of such amphiphilic microdomain, a unique structure without hydrophilic part was constructed as comparison. In addition, the adsorption behaviors including adsorption kinetics, isotherms and pH effect were systematically investigated. The result indicated that the amphiphilic structure and the synergy between hydrophilic and hydrophobic microdomain could considerably improve the adsorption capacities, rate and affinity. Particularly the existence of hydrophilic microdomain could reduce the diffusion resistance and energy barrier in the adsorption process. These adsorption results showed that the amphiphilic PP nonwoven have the potential to be used in environmental application.

  5. [Study of the removal of Pb2+ from aqueous solution by poly-gamma-glutamic acid coated magnetic nanoparticles].

    PubMed

    Zhang, Juan; Deng, Hui-Ping; Yabutani, Tomoki; Yasuzawa, Mikito

    2011-11-01

    In this study, a novel low cost magnetic adsorbent material prepared by poly-gamma-glutamic acid (gamma-PGA) coating Fe3o4 magnetic particles, which was called coated magnetic namoparticles (PG-M) was developed for the removal of Pb2+ from water by Dr. Yasuzawa. The particle size of PG-M was about 120-320 nm, and there was no significant difference in Fe3O4 and PG-M particle size, Fe3O4 was only as the support of PG-M core and did not directly involve in the reaction. The shape of PG-M was irregular cubic structure. The experiments were applied to quantify adsorptive time, pH, competitive ion and organics on the removal effect of Pb2+. The results showed that PG-M was effective in removal of Pb2+; the equilibrium amount of adsorptive was as high as 93.3 mg/g and the optimized condition of pH value for metal ions removal was 7.0, while contact time was about 45 min. The removal efficiency of Pb2+ was not significantly influenced by Na+ while was reduced with the increasing concentration of Ca2+. The removal of Pb2+ was enhanced with the presence of organic matter (humic acid, HA) when the concentration of HA was below 5 mg/L, and decreased when the concentration of HA exceeded 5 mg/L. Langmuir isotherms fitted the experimental data better compared to Freundlich isotherms. Pseudo second order model well described the sorption kinetics of Pb2+. The used PG-M can be desorbed by 0.1 mol/L HCl and became reusable. PG-M is nontoxic and eco-friendly, which have a good prospect in water treatment. PMID:22295634

  6. Kinetic, equilibrium and thermodynamic studies on sorption of uranium and thorium from aqueous solutions by a selective impregnated resin containing carminic acid.

    PubMed

    Rahmani-Sani, Abolfazl; Hosseini-Bandegharaei, Ahmad; Hosseini, Seyyed-Hossein; Kharghani, Keivan; Zarei, Hossein; Rastegar, Ayoob

    2015-04-01

    In this work, the removal of uranium and thorium ions from aqueous solutions was studied by solid-liquid extraction using an advantageous extractant-impregnated resin (EIR) prepared by loading carminic acid (CA) onto Amberlite XAD-16 resin beads. Batch sorption experiments using CA/XAD-16 beads for the removal of U(VI) and Th(IV) ions were carried out as a function of several parameters, like equilibration time, metal ion concentration, etc. The equilibrium data obtained from the sorption experiments were adjusted to the Langmuir isotherm model and the calculated maximum sorption capacities in terms of monolayer sorption were in agreement with those obtained from the experiments. The experimental data on the sorption behavior of both metal ions onto the EIR beads fitted well in both Bangham and intra-particle diffusion kinetic models, indicating that the intra-particle diffusion is the rate-controlling step. The thermodynamic studies at different temperatures revealed the feasibility and the spontaneous nature of the sorption process for both uranium and thorium ions. PMID:25576783

  7. 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.

  8. Removal of Acid Black 1 and Basic Red 2 from aqueous solutions by electrocoagulation/Moringa oleifera seed adsorption coupling in a batch system.

    PubMed

    de Carvalho, Helder Pereira; Huang, Jiguo; Ni, Jiaheng; Zhao, Meixia; Yang, Xinyu; Wang, Xiansheng

    2015-01-01

    The removal of Acid Black 1 (AB1) and Basic Red 2 (BR2) from aqueous solutions via an electrocoagulation (EC)/Moringa oleifera seeds (MOS) adsorption coupling process by using aluminum and stainless steel electrode in a batch reactor is described in this study. The influences of the operational parameters, i.e. current density, MOS dosage, and dye initial concentration, on degree of color removal were studied, and the unit energy demand, the unit electrode material demand, and the charge loading were calculated and discussed. The amounts of adsorbent and energy consumption were considered as main criteria of process evaluation, and ideal conditions were chosen. The addition of an appropriate MOS dosage (0.6 g/L for AB1 and 5 g/L for BR2) resulted in faster decolorization of dyes especially at lower current densities and was simultaneously accompanied by a significant reduction in contact time compared to the conventional simple EC process. The coupling process achieved degree of removals above 99.3% and 94% for AB1 and BR2, respectively. The EC/MOS coupling technique could be recommended to replace the conventional simple EC because of its high degree of removal, short contact time, and low energy consumption. PMID:26177402

  9. Kinetic, equilibrium and thermodynamic studies on sorption of uranium and thorium from aqueous solutions by a selective impregnated resin containing carminic acid.

    PubMed

    Rahmani-Sani, Abolfazl; Hosseini-Bandegharaei, Ahmad; Hosseini, Seyyed-Hossein; Kharghani, Keivan; Zarei, Hossein; Rastegar, Ayoob

    2015-04-01

    In this work, the removal of uranium and thorium ions from aqueous solutions was studied by solid-liquid extraction using an advantageous extractant-impregnated resin (EIR) prepared by loading carminic acid (CA) onto Amberlite XAD-16 resin beads. Batch sorption experiments using CA/XAD-16 beads for the removal of U(VI) and Th(IV) ions were carried out as a function of several parameters, like equilibration time, metal ion concentration, etc. The equilibrium data obtained from the sorption experiments were adjusted to the Langmuir isotherm model and the calculated maximum sorption capacities in terms of monolayer sorption were in agreement with those obtained from the experiments. The experimental data on the sorption behavior of both metal ions onto the EIR beads fitted well in both Bangham and intra-particle diffusion kinetic models, indicating that the intra-particle diffusion is the rate-controlling step. The thermodynamic studies at different temperatures revealed the feasibility and the spontaneous nature of the sorption process for both uranium and thorium ions.

  10. Oxidation of vanadium(III) by hydrogen peroxide and the oxomonoperoxo vanadium(V) ion in acidic aqueous solutions: a kinetics and simulation study.

    PubMed

    Du, Guodong; Espenson, James H

    2005-07-25

    The reaction between vanadium(III) and hydrogen peroxide in aqueous acidic solutions was investigated. The rate law shows first-order dependences on both vanadium(III) and hydrogen peroxide concentrations, with a rate constant, defined in terms of -d[H(2)O(2)]/dt, of 2.06 +/- 0.03 L mol(-)(1) s(-)(1) at 25 degrees C; the rate is independent of hydrogen ion concentration. The varying reaction stoichiometry, the appreciable evolution of dioxygen, the oxidation of 2-PrOH to acetone, and the inhibition of acetone formation by the hydroxyl radical scavengers, dimethyl sulfoxide and sodium benzoate, point to a Fenton mechanism as the predominant pathway in the reaction. Methyltrioxorhenium(VII) does not appear to catalyze this reaction. A second-order rate constant for the oxidation of V(3+) by OV(O(2))(+) was determined to be 11.3 +/- 0.3 L mol(-)(1) s(-)(1) at 25 degrees C. An overall reaction scheme consisting of over 20 reactions, in agreement with the experimental results and literature reports, was established by kinetic simulation studies.

  11. In situ infrared spectroscopic analysis of the adsorption of aromatic carboxylic acids to TiO 2, ZrO 2, Al 2O 3, and Ta 2O 5 from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Dobson, Kevin D.; McQuillan, A. James

    2000-02-01

    In situ infrared spectroscopy has been used to investigate the adsorption of a range of simple aromatic carboxylic acids from aqueous solution to metal oxides. Thin films of TiO 2, ZrO 2, Al 2O 3 and Ta 2O 5 were prepared by evaporation of aqueous sols on single reflection ZnSe prisms. Benzoic acid adsorbed very strongly to ZrO 2, in a bridging bidentate fashion, but showed only weak adsorption to TiO 2 and Ta 2O 5. Substituted aromatic carboxylic acids; salicylic, phthalic and thiosalicylic, were found to adsorb to each metal oxide. Salicylic and phthalic acids adsorbed to the metal oxides via bidentate interactions, involving coordination through both carboxylate and substituent groups. Thiosalicylic acid adsorbed to the metal oxides as a bridging bidentate carboxylate with no coordination through the thiol substituent group.

  12. Aqueous Solution Chemistry on Mars

    NASA Astrophysics Data System (ADS)

    Quinn, R.; Hecht, M.; Kounaves, S.; Young, S.; West, S.; Fisher, A.; Grunthaner, P.

    2007-12-01

    Currently en route to Mars, the Phoenix mission carries four wet chemistry cells designed to perform basic solution chemistry on martian soil. The measurement objectives are typical of those that would be performed on an unknown sample on Earth, including detection of common anions and cations, total conductivity, pH, redox potential, cyclic voltammetry (CV), etc. Both the challenge and the novelty arise from the necessity to perform these measurements with severely constrained resources in a harsh and (literally) alien environment. Sensors for all measurements are integrated into a common "beaker," with the ability to perform a two-point calibration of some sensors using a pair of low-concentration solutions. Sulfate measurement is performed with a crude titration. While most measurements use ion selective electrodes, halide interferences are resolved by independent chronopotentiometry (CP) measurements. No preconditioning of the soil-water mixture is possible, nor is any physical characterization of the introduced soil sample beyond coarse visual inspection. Among the idiosyncrasies of the measurement is the low external pressure, which requires that the analysis be performed close to the boiling point of water under an atmosphere consisting almost entirely of water vapor. Despite these liabilities, however, extensive laboratory characterization has validated the basic approach, and protocols for both CV and CP have been developed and tested. Enhancing the value of the measurement is the suite of coordinated observations, such as microscopy and evolved gas analysis, to be performed by other Phoenix instruments.

  13. UV-vis and Raman spectroelectrochemical investigation of the redox behavior of poly(5-cyanoindole) in acidic aqueous solutions.

    PubMed

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

    2000-03-01

    Spectroelectrochemical properties of conducting poly(5-cyanoindole) films deposited on indium tin oxide (ITO) and platinum electrodes are investigated using UV-vis and resonant Raman spectroscopies. The transitions from undoped to semi-conducting state of P5CN require the partial oxidation of the polymer to create radical-cations by insertion of charge-neutralizing anions into the polymer. In order to obtain detailed structural information from the vibrational spectra, it is necessary to know the vibrational modes of oxidation-sensitive bands. Vibrational assignments were made on the basis of the results obtained on polyindole and P5CN in acetonitrile solution. The drastic changes in optical absorption and Raman spectra observed at various stage of oxidation were explained by the conversions between at least three different structures. On the basis of the Raman spectra, we have identified the vibrational modes associated with neutral and polaronic segments. The perturbation associated with the coexistence of these polaronic segments has been described as a quinoid structure growing on the expense of the benzoid one. The results obtained indicate that the molecular properties of the conducting polymers at various stages of an oxidation are better revealed by in-situ Raman spectra than by ex-situ studies.

  14. Spontaneous unilamellar polymer vesicles in aqueous solution.

    PubMed

    Kim, Tae-Hwan; Song, Chaeyeon; Han, Young-Soo; Jang, Jong-Dae; Choi, Myung Chul

    2014-01-21

    A unilamellar polymeric vesicle is a self-assembled structure of a block copolymer that forms a spherical single bilayer structure with a hydrophobic interlayer and a hydrophilic surface. Due to their enhanced colloidal stability and mechanical property, controllable surface functionality, or tunable membrane thickness, polymeric vesicles are useful in nano and bio-science, providing potential applications as nanosized carriers for catalysts, drugs, and enzymes. For fabrication of a unilamellar vesicle, however, preparative procedures with a few steps are inherently required. Herein, without complicated preparative procedures, we report spontaneous unilamellar polymeric vesicles with nanometer sizes (<100 nm), which are prepared by simply mixing a triblock copolymer, Pluronic P85 (PEO26PPO40PEO26), and an organic derivative, 5-methyl salicylic acid (5mS), in aqueous solution. Depending on the 5mS concentration and the temperature, the P85-5mS mixtures presented various self-assembled nanostructures such as spherical and cylindrical micelles or vesicles, which were characterized by small angle neutron scattering and cryo-TEM, resulting in a phase diagram drawn as a function of temperature and the 5mS concentration. Interestingly the critical temperature for the micelle-to-vesicle phase transition was easily controlled by varying the 5mS concentration, i.e. it was decreased with increasing the 5mS concentration. PMID:24652418

  15. PHOTOREACTION OF VALEROPHENONE IN AQUEOUS SOLUTION

    EPA Science Inventory

    Kinetics and products of the photoreaction of the phenyl ketone valerophenone were investigated as a function of temperature, pH, and wavelength in aqueous solution. Under these conditions (<10-4M), the photoreactions are pseudo-first-order with respect to valerophenone concentra...

  16. Water & Aqueous Solutions. Final Progress Report

    SciTech Connect

    2002-08-09

    The Gordon Research Conference (GRC) on Water & Aqueous Solutions was held at Holderness School, New Hampshire, 8/4/02 thru 8/9/02. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.

  17. Polyacrylamido-2-methyl-1-propane sulfonic acid-grafted-natural rubber as bio-adsorbent for heavy metal removal from aqueous standard solution and industrial wastewater.

    PubMed

    Phetphaisit, Chor Wayakron; Yuanyang, Siriwan; Chaiyasith, Wipharat Chuachuad

    2016-01-15

    Bio-adsorbent modified natural rubber (modified NR) was prepared, by placing the sulfonic acid functional group on the isoprene chain. This modification was carried out with the aim to prepare material capable to remove heavy metals from aqueous solution. The structures of modified NR materials were characterized by FT-IR and NMR spectroscopies. Thermal gravimetric analysis of modified NR showed that the initial degradation temperature of rubber decreases with increasing amount of polyacrylamido-2-methyl-1-propane sulfonic acid (PAMPS) in the structure. In addition, water uptake of the rubber based materials was studied as a function of time and content of PAMPS. The influence of the amount of PAMPS grafted onto NR, time, pH, concentration of metal ions, temperature, and regeneration were studied in terms of their influence on the adsorption of heavy metals (Pb(2+), Cd(2+) and Cu(2+)). The adsorption isotherms of Pb(2+) and Cd(2+) were fitted to the Freundlich isotherm model, while Cu(2+) was fitted to the Langmuir isotherm. However, the results from these two isotherms resulted in a similar behavior. The adsorption capacity of the modified NR for the various heavy metals was in the following order: Pb(2+)∼Cd(2+)>Cu(2+). The maximum adsorption capacities of Pb(2+), Cd(2+), and Cu(2+) were 272.7, 267.2, and 89.7 mg/g of modified rubber, respectively. Moreover, the modified natural rubber was used for the removal of metal ions in real samples of industrial effluents where the efficiency and regeneration were also investigated.

  18. Inosylyl(3'-->5')inosine (IpI-). Acid-base and metal ion-binding properties of a dinucleoside monophosphate in aqueous solution.

    PubMed

    Knobloch, Bernd; Okruszek, Andrzej; Sigel, Helmut

    2008-04-01

    The acidity constants of the (N7)H(+) sites of inosylyl(3'-->5')inosine (IpI(-)) were estimated and those of its (N1)H sites were measured by potentiometric pH titrations in aqueous solution (25 degrees C; I = 0.1 M, NaNO3). The same method was used for the determination of the stability constants of the 1:1 complexes formed between Mg(2+), Co(2+), Ni(2+), Zn(2+), or Cd(2+) (= M(2+)) and (IpI - H)(2-) and, in the case of Mg(2+), also of (IpI - 2H)(3-). The stability constants of the M(IpI)(+) complexes were estimated. The acidity constants of H(inosine)(+) and the stability constants of the M(Ino)(2+) and M(Ino - H)(+) complexes were taken from the literature. The comparison of these and related data allows the conclusion that, in the M(IpI - H) species, chelates are formed; most likely they are preferably of an N7/N7 type. For the metal ions Co(2+), Ni(2+), Zn(2+), or Cd(2+), the formation degrees of the chelates are on the order of 60-80%; no chelates could be detected for the Mg(IpI - H) complexes. It is noteworthy that the (N1)H deprotonation, which leads to the M(IpI - H) species, occurs in all M(IpI)(+) complexes in the physiological pH range of about 7.5 or even below.

  19. Polyacrylamido-2-methyl-1-propane sulfonic acid-grafted-natural rubber as bio-adsorbent for heavy metal removal from aqueous standard solution and industrial wastewater.

    PubMed

    Phetphaisit, Chor Wayakron; Yuanyang, Siriwan; Chaiyasith, Wipharat Chuachuad

    2016-01-15

    Bio-adsorbent modified natural rubber (modified NR) was prepared, by placing the sulfonic acid functional group on the isoprene chain. This modification was carried out with the aim to prepare material capable to remove heavy metals from aqueous solution. The structures of modified NR materials were characterized by FT-IR and NMR spectroscopies. Thermal gravimetric analysis of modified NR showed that the initial degradation temperature of rubber decreases with increasing amount of polyacrylamido-2-methyl-1-propane sulfonic acid (PAMPS) in the structure. In addition, water uptake of the rubber based materials was studied as a function of time and content of PAMPS. The influence of the amount of PAMPS grafted onto NR, time, pH, concentration of metal ions, temperature, and regeneration were studied in terms of their influence on the adsorption of heavy metals (Pb(2+), Cd(2+) and Cu(2+)). The adsorption isotherms of Pb(2+) and Cd(2+) were fitted to the Freundlich isotherm model, while Cu(2+) was fitted to the Langmuir isotherm. However, the results from these two isotherms resulted in a similar behavior. The adsorption capacity of the modified NR for the various heavy metals was in the following order: Pb(2+)∼Cd(2+)>Cu(2+). The maximum adsorption capacities of Pb(2+), Cd(2+), and Cu(2+) were 272.7, 267.2, and 89.7 mg/g of modified rubber, respectively. Moreover, the modified natural rubber was used for the removal of metal ions in real samples of industrial effluents where the efficiency and regeneration were also investigated. PMID:26348149

  20. Structure of Hydronium (H3O+)/Chloride (Cl-) Contact Ion Pairs in Aqueous Hydrochloric Acid Solution: A Zundel-like Local Configuration

    SciTech Connect

    Fulton, John L.; Balasubramanian, Mahalingam

    2010-09-15

    Details of the H3O+ and H2O structure in the first solvation shell about Cl- in aqueous HCl solutions are reported from x-ray absorption fine structure (XAFS) measurements. Results show increasing degrees of contact ion pairing between Cl- and H3O+ as the HCl concentration increases from 6.0 m, 10.0 m and finally 16.1 m HCl (concentrated acid). At the highest acid concentration there are on average, approximately 1.6 H3O+ ions and 4.2 H2O’s in the first shell about Cl-. The structure of the Cl-/H3O+ contact ion pair is distinctly different than that of the H2O structure about Cl-. The Cl-O bond length (2.98Å) for Cl-/H3O+ is approximately 0.16 Å shorter than the Cl-/H2O bond. The bridging proton resides at an intermediate position between Cl and O at 1.60 Å from the Cl- and approximately 1.37 Å from the O of the H3O+. The bridging-proton structure of this contact ion pair, [Cl-H-OH2], is similar to structure of the water Zundel ion, [H2O-H-OH2]+. In both cases there is a shortened Cl-O or O-O bond and the intervening proton bond distances are substantially longer than for the covalent bonds of either HCl or H2O. The results further our understanding of the interaction H3O+ with Cl- that is of interest to fundamental physical chemistry and that has consequences in biochemical, geochemical and atmospheric processes.

  1. RECOVERY OF URANIUM FROM AQUEOUS PHOSPHATE-CONTAINING SOLUTIONS

    DOEpatents

    Igelsrud, I.; Stephen, E.F.

    1959-08-11

    ABS>A method is presented for recovering hexavalent uranium from an acidic phosphaie solution. A high molecular weight amine, such as a mixture of cccoanut oil amines, is added to the solution in such amount as to give a ratio of about 2000 parts by weight of amine to 1 part by weight of uranium. The uranium is precipitated with the amines and the whole filtered from the solution. The uranium is leached from the amine mass by washing with aqueous sodium carbonate solution; and the amine mixture is available for reuse.

  2. Hydroxyl radical induced degradation of salicylates in aerated aqueous solution

    NASA Astrophysics Data System (ADS)

    Szabó, László; Tóth, Tünde; Homlok, Renáta; Rácz, Gergely; Takács, Erzsébet; Wojnárovits, László

    2014-04-01

    Ionizing radiation induced degradation of acetylsalicylic acid, its hydrolysis product salicylic acid and a salicylic acid derivative 5-sulpho-salicylic acid, was investigated in dilute aqueous solutions by UV-vis spectrophotometry, HPLC separation and diode-array or MS/MS detection, chemical oxygen demand, total organic carbon content and by Vibrio fischeri toxicity measurements. Hydroxyl radicals were shown to degrade these molecules readily, and first degradation products were hydroxylated derivatives in all cases. Due to the by-products, among them hydrogen peroxide, the toxicity first increased and then decreased with the absorbed dose. With prolonged irradiation complete mineralization was achieved.

  3. Polytungstate-photosensitized formation of hydrogen from aqueous organic solutions

    SciTech Connect

    Muradov, N.Z.; Rustamov, M.I.; Guseinova, A.D.; Ismailov, E.G.; Bazhutin, Yu.V.

    1988-01-01

    When acidic aqueous organic solutions of polytungstates are irradiated by light of wavelength lambda < 400 nm in the photocatalytic evolution of hydrogen takes place, which is accelerated in the presence of colloidal platinum. The dependence of the rate of photoreduction of polytungstates and the photo-induced formation of hydrogen on the reactant concentrations, the amount of Pt, the pH of the solution, temperature, etc., have been determined for aqueous ethanol solutions. Aliphatic alcohols, aldehydes, organic acids, etc., were used as the organic reactants. The photoreduction of the polytungstates was studied by spectrophotometry and by EPR and a conclusion is draw on the mechanism for the photo-induced formation of hydrogen.

  4. Ozone photolysis of paracetamol in aqueous solution.

    PubMed

    Neamţu, Mariana; Bobu, Maria; Kettrup, Antonius; Siminiceanu, Ilie

    2013-01-01

    The degradation of a paracetamol (N-acetil-para-aminofenol) aqueous solution (C (0) P = 5 mmol L(-1)) is studied in a bench-scale setup by means of simple ozonation (O3) and ozonation catalyzed with UV light (O3/UV) in order to quantify the influence of UV light on the degradation process. The results have shown that under the adopted experimental conditions (25°C, applied ozone dose = 9.8 mg L(-1) and gas flow rate of 20 L h(-1)) both oxidative systems are capable of removing the substrate with mineralization degrees up to 51% for ozonation and 53% for O3/UV. HPICE chromatography allowed the detection of nitrate ions and maleic and oxalic acids as ultimate carboxylic acids. The experimental data have been interpreted through 5 indicators: the conversion of paracetamol (XP ), the conversion degree of TOC (XTOC ), the apparent rate constant (kap ), the Hatta number (Ha) and the enhancement factor (E). The main advantage of photo-ozonation compared to simple ozonation was a more advanced conversion (79% vs. 92% after 90 min). The paracetamol decay follows a pseudo-first-order reaction with a superior rate constant (higher by 54%) for the UV catalyzed system in comparison with direct ozonation. Mineralization is slightly accelerated (+4%) in the O3/UV system, due to the additional production of hydroxyl radicals induced by the UV light and a higher Hatta number (+24%). Nevertheless, the process was still in the slow reaction kinetic regime (Ha < 0.3), and the enhancement factor was not significantly increased. The results are useful for the design and scale-up of the gas-liquid processes.

  5. Modeling reactive geochemical transport of concentrated aqueous solutions

    NASA Astrophysics Data System (ADS)

    Zhang, Guoxiang; Zheng, Zuoping; Wan, Jiamin

    2005-02-01

    Aqueous solutions with ionic strength larger than 1 M are usually considered concentrated aqueous solutions. These solutions can be found in some natural systems and are also industrially produced and released into accessible natural environments, and as such, they pose a big environmental problem. Concentrated aqueous solutions have unique thermodynamic and physical properties. They are usually strongly acidic or strongly alkaline, with the ionic strength possibly reaching 30 M or higher. Chemical components in such solutions are incompletely dissociated. The thermodynamic activities of both ionic and molecular species in these solutions are determined by the ionic interactions. In geological media the problem is further complicated by the interactions between the solutions and sediments and rocks. The chemical composition of concentrated aqueous solutions when migrating through the geological media may be drastically altered by these strong fluid-rock interactions. To effectively model reactive transport of concentrated aqueous solutions, we must take into account the ionic interactions. For this purpose we substantially extended an existing reactive transport code, BIO-CORE2D©, by incorporating a Pitzer ion interaction model to calculate the ionic activity. In the present paper, the model and two test cases of the model are briefly introduced. We also simulate a laboratory column experiment in which the leakage of highly alkaline waste fluid stored at Hanford (a U.S. Department of Energy site, located in Washington State) was studied. Our simulation captures the measured pH evolution and indicates that all the reactions controlling the pH evolution, including cation exchanges and mineral dissolution/precipitation, are coupled.

  6. Preparation of thin ceramic films via an aqueous solution route

    DOEpatents

    Pederson, Larry R.; Chick, Lawrence A.; Exarhos, Gregory J.

    1989-01-01

    A new chemical method of forming thin ceramic films has been developed. An aqueous solution of metal nitrates or other soluble metal salts and a low molecular weight amino acid is coated onto a substrate and pyrolyzed. The amino acid serves to prevent precipitation of individual solution components, forming a very viscous, glass-like material as excess water is evaporated. Using metal nitrates and glycine, the method has been demonstrated for zirconia with various levels of yttria stabilization, for lanthanum-strontium chromites, and for yttrium-barium-copper oxide superconductors on various substrates.

  7. The aqueous-polyelectrolyte dye solution as an active laser medium

    SciTech Connect

    Akimov, A I; Saletskii, A M

    2000-11-30

    The spectral, luminescent, and lasing properties of aqueous solutions of a cationic dye rhodamine 6G with additions of anion polyelectrolytes - polyacrylic and polymethacrylic acids - are studied. It is found that the energy and spectral properties of lasing of these solutions depend on the ratio of concentrations of polyelectrolyte and molecules. It is also found that the lasing parameters of aqueous-polyelectrolyte dye solutions can be controlled by changing the structure of the molecular system. The variation in the structure of aqueous-polyelectrolyte dye solutions of rhodamine 6G resulted in an almost five-fold increase in the lasing efficiency compared to that in aqueous dye solutions. (lasers, active media)

  8. A DFT/TDDFT study of the structural and spectroscopic properties of Al(III) complexes with 4-nitrocatechol in acidic aqueous solution

    NASA Astrophysics Data System (ADS)

    Cornard, Jean-Paul; Lapouge, Christine; Merlin, Jean-Claude

    2007-11-01

    The complexation of 4-nitrocatechol in aqueous solution at pH 5 has been studied by molecular spectroscopy combined with quantum chemical calculations. In these physico-chemical conditions, the formation of the two complexes [4ncatAl(H 2O) 4] + and [(4ncat) 2Al(H 2O) 2] - has been highlighted. The electronic absorption spectra of the 1:1 and 1:2 complexes of Al(III) with 4-nitrocatechol have been computed using the time-dependent density functional theory and the polarizable continuum model. It turns out that the 6-311+G(d,p) basis set provides a good agreement between experimental and theoretical absorption spectra. This good agreement has allowed the determination of the preferential conformation of the 1:2 complex in aqueous solution. A complete assignment of the UV-Vis absorption and Raman spectra of the complexes has been proposed.

  9. A novel use of TiO2 fiber for photocatalytic ozonation of 2,4-dichlorophenoxyacetic acid in aqueous solution.

    PubMed

    Giri, Raj Rabindra; Ozaki, Hiroaki; Takanami, Ryohei; Taniguchi, Shogo

    2008-01-01

    More efficient oxidation methods are needed to degrade especially newly emerging recalcitrant organic contaminants at low concentrations in the water environment. Reduced photonic efficiency of immobilized TiO2 is a major challenge in TiO2-assisted advanced oxidation processes (AOP). Mineralization of 2,4-dichllorophenoxyacetic acid (2,4-D) in low aqueous solution by O3/UV/TiO2 using the world's first high-strength TiO2 fiber was investigated and compared with O3, UV/TiO2, and O3/TiO2 in laboratory batch experiments. The 2,4-D degradation and total organic carbon (TOC) removal followed pseudo first-order reaction kinetic, while their rates in O3/UV/TiO2 were respectively about 1.5 and 2.4 times larger than the summation of the values in 03 and UV/TiO2. The O3/UV/TiO2 was characterized by few aromatics with very low abundance, fast disappearance of aliphatics and more than 95% dechlorination. The discrepancies in organic carbon mass balance among the intermediates and 2,4-D were attributed mainly to few apparently major unidentified intermediates. The significantly enhanced 2,4-D mineralization in O3/UV/TiO2 was attributed to increased ozone dissolution followed by its decomposition, and reduced electron-hole recombination in presence of dissolved ozone resulting in a large number of hydroxyl radical (*OH) generation from more than one parallel path. The removal efficiencies of the systems can further be enhanced by optimizing design parameters, and O3/UV/TiO2 with the TiO2 fiber is promising to mineralize recalcitrant organic contaminants in water at low concentrations. PMID:19143323

  10. Pressure Dependence of the Acid/Base Equilibria of Methyl Orange in Aqueous Solutions to 1000 bars at 20°C

    SciTech Connect

    Suleimenov, Oleg M; Boily, Jean F

    2006-07-31

    The pressure dependence on the acid/base equilibria of methyl orange in aqueous solution was measured at 20°C in the 1-1000 bar range with a newly designed flow-through spectrophotometric cell. Combined chemometric and thermodynamic analyses of uv-vis spectrophotometric data were used to extract the dissociation constants as well as the changes in molar volume and isothermal compressibility of methyl orange as a function of pressure. The results show increasing pressure promotes the deprotonation of the methyl orange, with pK values ranging from 3.505 at 1 bar to 3.445 (0.002) at 1000 bars. Increasing pressure also yields small values of negative changes in the molar volume ranging from –6.9 cm3∙mol-1 at 1 bar to –1.7 cm3∙mol-1 at 1000 bars. The isothermal compressibility of methyl orange in this pressure range was estimated using the 2nd derivative of 2nd and 3rd order polynomial fits to the constants and gave rise to a constant value of –48.4x 10-4 cm3∙mol-1∙bar-1 in the former case, and increasing values from -107×10-4 cm3∙mol-1∙bar-1 at 1 bar to 3.43×10-4 cm3∙mol-1∙bar-1 at 1000 bars in the latter case. Molar absorption coefficients for the protonated and deprotonated species were also shown to be only slightly affected by pressure changes and can be used to accurately predict the absorption spectra of methyl orange as a function of pressure.

  11. Effect of acidity on the equilibria of formation of mixed Co2+ complexes with heparin and arginine in aqueous solutions at 37°C

    NASA Astrophysics Data System (ADS)

    Feofanova, M. A.; Frantseva, Yu. V.; Semenov, A. N.; Baranova, N. V.; Zhuravlev, E. V.

    2014-02-01

    Results from studying interactions in the heparin-Co2+ ion-arginine system are presented. The constants of formation of mixed Co2+ complexes with heparin and arginine in aqueous solutions in a broad pH range at 37°C are determined potentiometrically. The chemical equilibria in the system are simulated and the stoichiometry of formation of the complex forms is determined.

  12. Air stripping of aqueous solutions. Engineering bulletin

    SciTech Connect

    Not Available

    1991-10-01

    Air stripping is a means to transfer contaminants from aqueous solutions to air. Contaminants are not destroyed by air stripping but are physically separated from the aqueous solutions. Contaminant vapors are transferred into the air stream and, if necessary, can be treated by incineration, adsorption, or oxidation. Most frequently, contaminants are collected in carbon adsorption systems and then treated or destroyed in this concentrated form. The concentrated contaminants may be recovered, incinerated for waste heat recovery, or destroyed by other treatment technologies. Generally, air stripping is used as one in a series of unit operations and can reduce the overall cost for managing a particular site. Air stripping is applicable to volatile and semivolatile organic compounds. It is not applicable for treating metals and inorganic compounds. The bulletin provides information on the technology applicability, the technology limitations, a description of the technology, the types of residuals produced, site requirements, the latest performance data, the status of the technology, and sources of further information.

  13. Aqueous solution dispersement of carbon nanotubes

    NASA Technical Reports Server (NTRS)

    Kim, Jae-Woo (Inventor); Park, Cheol (Inventor); Choi, Sang H. (Inventor); Lillehei, Peter T. (Inventor); Harrison, Joycelyn S. (Inventor)

    2011-01-01

    Carbon nanotubes (CNTs) are dispersed in an aqueous buffer solution consisting of at least 50 weight percent water and a remainder weight percent that includes a buffer material. The buffer material has a molecular structure defined by a first end, a second end, and a middle disposed between the first and second ends. The first end is a cyclic ring with nitrogen and oxygen heteroatomes, the middle is a hydrophobic alkyl chain, and the second end is a charged group.

  14. Ion-solvent and ion-ion interactions of phosphomolybdic acid in aqueous solution of catechol at 298.15, 308.15, and 318.15 K

    NASA Astrophysics Data System (ADS)

    Roy, M. N.; Sah, R. S.; Pradhan, P. P.; Roy, P. K.

    2009-11-01

    Apparent molar volume ( V Ø) and viscosity B-coefficients were measured for phosphomolybdicacid in aqueous solution of catechol from solution density ( ρ) and viscosity ( η) at 298.15, 308.15, and 318.15 K at various solute concentrations. The experimental density data were evaluated by Masson equation and the derived data were interpreted in terms of ion-solvent and ion-ion interactions. The viscosity data have been analyzed using Jones-Dole equation and the derived parameters, B and A, have been interpreted in terms of ion-solvent and ion-ion interactions respectively. The structure-making or breaking capacity of the solute under investigation has been discussed in terms of sign of ( δ 2 V {Ø/o}/ δT 2) P . The activation parameters of viscous flow were determined and discussed by application of transition state theory.

  15. 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.

  16. Radiation chemistry of aqueous solutions of actinides

    NASA Astrophysics Data System (ADS)

    Pikaev, Alexei K.; Shilov, Vladimir P.; Gogolev, Andrei V.

    1997-09-01

    The data on radiolytic transformations of ions of uranium, neptunium, plutonium, americium, curium and transcurium elements in aqueous solutions are generalised. The results of studies on the kinetics of fast reactions of these ions with primary products of water radiolysis (hydrated electron e-aq, H, OH, and O- radicals and H2O2), many inorganic (Cl2-, NO3, SO4-, CO3-, O3- etc.) and organic free radicals are analysed. The mechanism of γ- and α-radiolysis of solutions of actinide ions is discussed. The bibliography includes 183 references.

  17. Time-resolved FT EPR and optical spectroscopy study on photooxidation of aliphatic alpha-amino acids in aqueous solutions; electron transfer from amino vs carboxylate functional group.

    PubMed

    Tarabek, Peter; Bonifacić, Marija; Beckert, Dieter

    2006-06-01

    Using time-resolved Fourier transform electron paramagnetic resonance, FT EPR, and optical spectroscopy, the photooxidation of glycine, alpha-alanine, alpha-aminoisobutyric acid, and model compounds beta-alanine, methylamine and sodium acetate, by excited triplets of anthraquinone-2,6-disulfonate dianion was studied in aqueous solutions in the pH range 5-13. Anthraquinone radical trianions showing strong emissive spin-polarization (CIDEP) were formed, indicating fast electron transfer from the quenchers to the spin-polarized quinone triplet as the primary reaction. None of the primary radicals formed upon one-electron oxidation of quenchers could be detected at the nanosecond time scale of FT EPR measurements because of their very fast transformation into secondary products. The latter were identified to be decarboxylated alpha-aminoalkyl radicals for alpha-amino acids anions and zwitterions, beta-aminoalkyl radicals for beta-alanine zwitterions, and methyl radicals for acetate anions; corresponding aminyl radicals were the first EPR detectable products from beta-alanine anions and methylamine. Thus, anthraquinone-2,6-disulfonate triplet can take an electron from both NH(2)- and -CO(2)(-) functional groups forming aminium ((+*)NH(2)-) and acyloxyl (-CO(2)(*)) radicals, respectively. Aminium radicals derived from beta-alanine anions and CH(3)-NH(2) stabilize by deprotonation into aminyl radicals, whereas these derived from alpha-amino acids anions are known to suffer ultrafast decarboxylation (tau approximately 10 ps). Analysis of the polarization patterns revealed that decarboxylation from acyloxyl radicals are considerably slower (ns < tau < 0.1 micros). Therefore, in the case of alpha-amino acids, the isoelectronic structures NH(2)-CR(2)-CO(2)(*) and (+*)NH(2)-CR(2)-CO(2)(-) probably do not constitute resonance mesomeric forms of one and the same species and the decarboxylation of aminium radicals is not preceded by the intramolecular carboxylate to amino group

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

    SciTech Connect

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

    1994-04-27

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

  19. Density of aqueous solutions of CO2

    SciTech Connect

    Garcia, Julio E.

    2001-10-10

    In this report, we present a numerical representation for the partial molar volume of CO2 in water and the calculation of the corresponding aqueous solution density. The motivation behind this work is related to the importance of having accurate representations for aqueous phase properties in the numerical simulation of carbon dioxide disposal into aquifers as well as in geothermal applications. According to reported experimental data the density of aqueous solutions of CO2 can be as much as 2-3% higher than pure water density. This density variation might produce an influence on the groundwater flow regime. For instance, in geologic sequestration of CO2, convective transport mixing might occur when, several years after injection of carbon dioxide has stopped, the CO2-rich gas phase is concentrated at the top of the formation, just below an overlaying caprock. In this particular case the heavier CO2 saturated water will flow downward and will be replaced by water with a lesser CO2 content.

  20. Solution nonideality related to solute molecular characteristics of amino acids.

    PubMed Central

    Keener, C R; Fullerton, G D; Cameron, I L; Xiong, J

    1995-01-01

    By measuring the freezing-point depression for dilute, aqueous solutions of all water-soluble amino acids, we test the hypothesis that nonideality in aqueous solutions is due to solute-induced water structuring near hydrophobic surfaces and solute-induced water destructuring in the dipolar electric fields generated by the solute. Nonideality is expressed with a single solute/solvent interaction parameter I, calculated from experimental measure of delta T. A related parameter, I(n), gives a method of directly relating solute characteristics to solute-induced water structuring or destructuring. I(n)-values correlate directly with hydrophobic surface area and inversely with dipolar strength. By comparing the nonideality of amino acids with progressively larger hydrophobic side chains, structuring is shown to increase with hydrophobic surface area at a rate of one perturbed water molecule per 8.8 square angstroms, implying monolayer coverage. Destructuring is attributed to dielectric realignment as described by the Debye-Hückel theory, but with a constant separation of charges in the amino-carboxyl dipole. By using dimers and trimers of glycine and alanine, this destructuring is shown to increase with increasing dipole strength using increased separation of fixed dipolar charges. The capacity to predict nonideal solution behavior on the basis of amino acid characteristics will permit prediction of free energy of transfer to water, which may help predict the energetics of folding and unfolding of proteins based on the characteristics of constituent amino acids. Images FIGURE 6 PMID:7711253

  1. Process for the extraction of strontium from acidic solutions

    DOEpatents

    Horwitz, E. Philip; Dietz, Mark L.

    1994-01-01

    The invention is a process for selectively extracting strontium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant solution is a macrocyclic polyether in an aliphatic hydrocarbon diluent containing a phase modifier. The process will selectively extract strontium values from nitric acid solutions which are up to 6 molar in nitric acid.

  2. Process for the extraction of strontium from acidic solutions

    DOEpatents

    Horwitz, E.P.; Dietz, M.L.

    1993-01-01

    The invention is a process for selectively extracting strontium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant solution is a macrocyclic polyether in an aliphatic hydrocarbon diluent containing a phase modifier. The process will selectively extract strontium values from nitric acid solutions which are up to 6 molar in nitric acid.

  3. Process for the extraction of strontium from acidic solutions

    DOEpatents

    Horwitz, E.P.; Dietz, M.L.

    1994-09-06

    The invention is a process for selectively extracting strontium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant solution is a macrocyclic polyether in an aliphatic hydrocarbon diluent containing a phase modifier. The process will selectively extract strontium values from nitric acid solutions which are up to 6 molar in nitric acid. 4 figs.

  4. Aqueous Solution Vessel Thermal Model Development II

    SciTech Connect

    Buechler, Cynthia Eileen

    2015-10-28

    The work presented in this report is a continuation of the work described in the May 2015 report, “Aqueous Solution Vessel Thermal Model Development”. This computational fluid dynamics (CFD) model aims to predict the temperature and bubble volume fraction in an aqueous solution of uranium. These values affect the reactivity of the fissile solution, so it is important to be able to calculate them and determine their effects on the reaction. Part A of this report describes some of the parameter comparisons performed on the CFD model using Fluent. Part B describes the coupling of the Fluent model with a Monte-Carlo N-Particle (MCNP) neutron transport model. The fuel tank geometry is the same as it was in the May 2015 report, annular with a thickness-to-height ratio of 0.16. An accelerator-driven neutron source provides the excitation for the reaction, and internal and external water cooling channels remove the heat. The model used in this work incorporates the Eulerian multiphase model with lift, wall lubrication, turbulent dispersion and turbulence interaction. The buoyancy-driven flow is modeled using the Boussinesq approximation, and the flow turbulence is determined using the k-ω Shear-Stress-Transport (SST) model. The dispersed turbulence multiphase model is employed to capture the multiphase turbulence effects.

  5. [Adsorption of Congo red from aqueous solution on hydroxyapatite].

    PubMed

    Zhan, Yan-Hui; Lin, Jian-Wei

    2013-08-01

    The adsorption of Congo red (CR) from aqueous solution on hydroxyapatite was investigated using batch experiments. The hydroxyapatite was effective for CR removal from aqueous solution. The adsorption kinetics of CR on hydroxyapatite well followed a pseudo-second-order model. The equilibrium adsorption data of CR on hydroxyapatite could be described by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated and showed that the adsorption of CR on hydroxyapatite was spontaneous and exothermic in nature. The CR adsorption capacity for hydroxyapatite decreased significantly with increasing pH from 8 to 10. Thermal regeneration showed that hydroxyapatite could be used for six desorption-adsorption cycles with high removal efficiency for CR in each cycle. The mechanisms for CR adsorption on hydroxyapatite with pH value below the pH at point of zero charge (pH(PZC)) include electrostatic attraction, hydrogen bonding and Lewis acid-base interaction. The mechanisms for CR adsorption on hydroxyapatite with pH value above its pH(PZC) include hydrogen bonding and Lewis acid-base interaction. Results of this work indicate that hydroxyapatite is a promising adsorbent for CR removal from aqueous solution.

  6. [Adsorption of Congo red from aqueous solution on hydroxyapatite].

    PubMed

    Zhan, Yan-Hui; Lin, Jian-Wei

    2013-08-01

    The adsorption of Congo red (CR) from aqueous solution on hydroxyapatite was investigated using batch experiments. The hydroxyapatite was effective for CR removal from aqueous solution. The adsorption kinetics of CR on hydroxyapatite well followed a pseudo-second-order model. The equilibrium adsorption data of CR on hydroxyapatite could be described by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated and showed that the adsorption of CR on hydroxyapatite was spontaneous and exothermic in nature. The CR adsorption capacity for hydroxyapatite decreased significantly with increasing pH from 8 to 10. Thermal regeneration showed that hydroxyapatite could be used for six desorption-adsorption cycles with high removal efficiency for CR in each cycle. The mechanisms for CR adsorption on hydroxyapatite with pH value below the pH at point of zero charge (pH(PZC)) include electrostatic attraction, hydrogen bonding and Lewis acid-base interaction. The mechanisms for CR adsorption on hydroxyapatite with pH value above its pH(PZC) include hydrogen bonding and Lewis acid-base interaction. Results of this work indicate that hydroxyapatite is a promising adsorbent for CR removal from aqueous solution. PMID:24191561

  7. Diketopiperazine-mediated peptide formation in aqueous solution

    NASA Astrophysics Data System (ADS)

    Nagayama, M.; Takaoka, O.; Inomata, K.; Yamagata, Y.

    1990-05-01

    Though diketopiperazines (DKP) are formed in most experiments concerning the prebiotic peptide formation, the molecules have not been paid attention in the studies of chemical evolution. We have found that triglycine, tetraglycine or pentaglycine are formed in aqueous solution of glycine anhydride (DKP) and glycine, diglycine or triglycine, respectively. A reaction of alanine with DKP resulted in the formation of glycylglycylalanine under the same conditions. These results indicate that the formation of the peptide bonds proceeds through the nucleophilic attack of an amino group of the amino acids or the oligoglycines on the DKP accompanied by the ring-opening. The formation of glycine anhydride, di-, tri- and tetraglycine was also observed in a mixed aqueous solution of urea and glycine in an open system to allow the evaporation of ammonia. A probable pathway is proposed for prebiotic peptide formation through diketopiperazine on the primitive Earth.

  8. Removal of methyl violet from aqueous solution by perlite.

    PubMed

    Doğan, Mehmet; Alkan, Mahir

    2003-11-01

    The use of perlite for the removal of methyl violet from aqueous solutions at different concentration, pH, and temperature has been investigated. Adsorption equilibrium is reached within 1 h. The capacity of perlite samples for the adsorption of methyl violet was found to increase with increasing pH and temperature and decrease with expansion and increasing acid-activation. The adsorption isotherms are described by means of the Langmuir and Freundlich isotherms. The adsorption isotherm was measured experimentally at different conditions and the experimental data were correlated reasonably well by the adsorption isotherm of Langmuir. The order of heat of adsorption corresponds to a physical reaction. It is concluded that the methyl violet is physically adsorbed onto the perlite. The removal efficiency (P) and dimensionless separation factor (R) have shown that perlite can be used for removal of methyl violet from aqueous solutions, but unexpanded perlite is more effective.

  9. Removal of phenols from aqueous solutions by emulsion liquid membranes.

    PubMed

    Reis, M Teresa A; Freitas, Ondina M F; Agarwal, Shiva; Ferreira, Licínio M; Ismael, M Rosinda C; Machado, Remígio; Carvalho, Jorge M R

    2011-09-15

    The present study deals with the extraction of phenols from aqueous solutions by using the emulsion liquid membranes technique. Besides phenol, two derivatives of phenol, i.e., tyrosol (2-(4-hydroxyphenyl)ethanol) and p-coumaric acid (4-hydroxycinnamic acid), which are typical components of the effluents produced in olive oil plants, were selected as the target solutes. The effect of the composition of the organic phase on the removal of solutes was examined. The influence of pH of feed phase on the extraction of tyrosol and p-coumaric was tested for the membrane with Cyanex 923 as an extractant. The use of 2% Cyanex 923 allowed obtaining a very high extraction of phenols (97-99%) in 5-6 min of contact time for either single solute solutions or for their mixtures. The removal efficiency of phenol and p-coumaric acid attained equivalent values by using the system with 2% isodecanol, but the removal rate of tyrosol was found greatly reduced. The extraction of tyrosol and p-coumaric acid from their binary mixture was also analysed for different operating conditions like the volume ratio of feed phase to stripping phase (sodium hydroxide), the temperature and the initial concentration of solute in the feed phase.

  10. Condensation of oligoglycines with trimeta- and tetrametaphosphate in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Yamanaka, Junpei; Inomata, Katsuhiko; Yamagata, Yukio

    1988-09-01

    The dehydration condensation of glycine with trimetaphosphate in aqueous solution has been reinvestigated. Although it has been reported that the condensation of glycine under the alkaline conditions was brought about through the formation of cyclic acylphosphoramidate and hence the condensation of polyglycines could not occur, we found that the condensation of oligoglycines with trimeta- and tetrametaphosphate in aqueous solution are possible through the formation of their acylphosphates under the neutral or weak acidic conditions. Aqueous solutions of 1.0 M glycylglycine and 1.0 M trimetaphosphate in the various pH from 4.0 to 9.0 were incubated at 38 °C. The solutions were analyzed by HPLC with ninhydrin reaction system. Tetraglycine and hexaglycine were detected and their maximum yields were given in the reaction carried out around pH 7. They are approximately 15% and 4% after 30 days, respectively. Analogous experiments were performed with tetrametaphosphate. The results showed a similar pH dependence for the condensation, but the yields were about one-tenth of those of corresponding experiments with trimetaphosphate. Relative rates of dimerization of glycine, diglycine and triglycine in the equimolar concentration were also investigated at pH 6.0 at 38 °C. The rates for digylcine and triglycine were approximately twice and four times as large as that for glycine. Relevance of the experiments to chemical evolution is discussed.

  11. Pulse Radiolysis of Aqueous Thiocyanate Solution

    SciTech Connect

    Milosavljevic, Bratoljub H.; LaVerne, Jay A.

    2005-01-13

    The pulse radiolysis of N2O saturated aqueous solutions of KSCN was studied under neutral pH conditions. The observed optical absorption spectrum of the SCN• radical in solution is more complex than previously reported, but it is in good agreement with that measured in the gas phase. Kinetic traces at 330 nm and 472 nm corresponding to SCN• and (SCN)2•¯, respectively, were fit using a Monte Carlo simulation kinetic model. The rate coefficient for the oxidation of SCN¯ ions by OH radicals, an important reaction used in competition kinetics measurements, was found to be 1.4 ± 0.1 x 1010 M-1 s-1, about 30 % higher than the normally accepted value. A detailed discussion of the reaction mechanism is presented.

  12. Infrared and Raman spectroscopical studies of salicylic and salicylate derivatives in aqueous solution

    NASA Astrophysics Data System (ADS)

    Humbert, B.; Alnot, M.; Quilès, F.

    1998-03-01

    The assignment of vibrations of salicylic acid, salicylate monoanion and salicylate bianion in aqueous solution are discussed with the help of Raman spectroscopy, of attenuated total reflection infrared spectroscopy and of the computational density functional theory (DFT) approach.

  13. Aqueous Solutions of Ionic Liquids: Microscopic Assembly.

    PubMed

    Vicent-Luna, Jose Manuel; Dubbeldam, David; Gómez-Álvarez, Paula; Calero, Sofia

    2016-02-01

    Aqueous solutions of ionic liquids are of special interest, due to the distinctive properties of ionic liquids, in particular, their amphiphilic character. A better understanding of the structure-property relationships of such systems is hence desirable. One of the crucial molecular-level interactions that influences the macroscopic behavior is hydrogen bonding. In this work, we conduct molecular dynamics simulations to investigate the effects of ionic liquids on the hydrogen-bond network of water in dilute aqueous solutions of ionic liquids with various combinations of cations and anions. Calculations are performed for imidazolium-based cations with alkyl chains of different lengths and for a variety of anions, namely, [Br](-), [NO3](-), [SCN](-) [BF4](-), [PF6](-), and [Tf2N](-). The structure of water and the water-ionic liquid interactions involved in the formation of a heterogeneous network are analyzed by using radial distribution functions and hydrogen-bond statistics. To this end, we employ the geometric criterion of the hydrogen-bond definition and it is shown that the structure of water is sensitive to the amount of ionic liquid and to the anion type. In particular, [SCN](-) and [Tf2N](-) were found to be the most hydrophilic and hydrophobic anions, respectively. Conversely, the cation chain length did not influence the results.

  14. Models of globular proteins in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Wentzel, Nathaniel James

    Protein crystallization is a continuing area of research. Currently, there is no universal theory for the conditions required to crystallize proteins. A better understanding of protein crystallization will be helpful in determining protein structure and preventing and treating certain diseases. In this thesis, we will extend the understanding of globular proteins in aqueous solutions by analyzing various models for protein interactions. Experiments have shown that the liquid-liquid phase separation curves for lysozyme in solution with salt depend on salt type and salt concentration. We analyze a simple square well model for this system whose well depth depends on salt type and salt concentration, to determine the phase coexistence surfaces from experimental data. The surfaces, calculated from a single Monte Carlo simulation and a simple scaling argument, are shown as a function of temperature, salt concentration and protein concentration for two typical salts. Urate Oxidase from Asperigillus flavus is a protein used for studying the effects of polymers on the crystallization of large proteins. Experiments have determined some aspects of the phase diagram. We use Monte Carlo techniques and perturbation theory to predict the phase diagram for a model of urate oxidase in solution with PEG. The model used includes an electrostatic interaction, van der Waals attraction, and a polymerinduced depletion interaction. The results agree quantitatively with experiments. Anisotropy plays a role in globular protein interactions, including the formation of hemoglobin fibers in sickle cell disease. Also, the solvent conditions have been shown to play a strong role in the phase behavior of some aqueous protein solutions. Each has previously been treated separately in theoretical studies. Here we propose and analyze a simple, combined model that treats both anisotropy and solvent effects. We find that this model qualitatively explains some phase behavior, including the existence of

  15. Spatial structure of oligopeptide PAP(248-261), the N-terminal fragment of the HIV enhancer prostatic acid phosphatase peptide PAP(248-286), in aqueous and SDS micelle solutions

    NASA Astrophysics Data System (ADS)

    Blokhin, Dmitriy S.; Filippov, Andrei V.; Antzutkin, Oleg N.; Karataeva, Farida Kh.; Klochkov, Vladimir V.

    2014-07-01

    Prostatic acid phosphatase (PAP) is an enzyme that facilitates infection of cells by HIV. Its peptide fragment PAP(248-286) forms amyloid fibrils known as SEVI, which enhance attachment of the virus by viral adhesion to the host cell prior to receptor-specific binding via reducing the electrostatic repulsion between the membranes of the virus and the target cell. The secondary structure of PAP(248-286) in aqueous and SDS solutions can be divided into an N-terminal disordered region, an α-helical central part and an α/310-helical C-terminal region (Nanga et al., 2009). In this work, we used NMR spectroscopy to study the spatial structure of the isolated N-terminal fragment of PAP(248-286), PAP(248-261) (GIHKQKEKSRLQGG), in aqueous and SDS micelle solutions. Formation of a PAP(248-261)-SDS complex was confirmed by chemical shift alterations in the 1H NMR spectra of the peptide, as well as by the signs and values of Nuclear Overhauser Effect (NOE). In addition, the PAP(248-261) peptide does not form any specified secondary structure in either aqueous or SDS solutions.

  16. Stability of ricobendazole in aqueous solutions.

    PubMed

    Wu, Zimei; Tucker, Ian G; Razzak, Majid; Medlicott, Natalie J

    2009-07-12

    The chemical stability of ricobendazole (RBZ) was investigated using a stability-indicating high performance liquid chromatographic (HPLC) assay with ultraviolet detection. The degradation kinetics of RBZ in aqueous solution was evaluated as a function of pH, buffer strength and temperature. The oxidation reaction in hydrogen peroxide solution was also studied. Degradation products were analyzed by mass spectroscopy and degradation pathways are proposed. Degradation of RBZ followed pseudo first-order kinetics and Arrhenius behavior over the temperature range 24-55 degrees C. A V-shaped pH-rate profile over the pH range 2-12 was observed with maximum stability at pH 4.8. The shape of the pH-rate profile was rationalized by catalytic effects of various components in the solution on each RBZ species. At pH 11 the activation energy for hydrolysis was 79.5 kJ/mol, and phosphate catalysis was not observed. Oxidation occurred in hydrogen peroxide solutions and was catalyzed by the presence of copper (Cu(2+)) ions. Ricobendazole amine and albendazole sulfone were identified by MS assay to be the degradation products of hydrolysis and oxidation respectively. PMID:19342190

  17. Phase behavior of DODAB aqueous solution

    SciTech Connect

    Voronov, V. P.; Kuryakov, V. N.; Muratov, A. R.

    2012-12-15

    Phase behavior of DODAB aqueous solution, prepared without sonication, was studied by adiabatic scanning calorimetry. Measurements revealed four phase transitions with the temperatures 35.2, 39.6, 44.6, and 52.4 Degree-Sign C at heating and one transition at the temperature 40.4 Degree-Sign C at cooling. The first three transitions at heating occur in unilamellar vesicles. The first and third transitions correspond to the subgel-gel and gelliquid phase transitions, corresponding enthalpy jumps are equal to 33 and 49 kJ/mol. The second transition appears after some aging and is similar to gel-ripple phase transition in a DPPC solution, with the enthalpy jump under the transition exceeding 7.4 kJ/mol. The transition occurs in unilamellar vesicles. The transition at the temperature 52.4 Degree-Sign C occurs in another subsystem of the solution, which we believe to be multilamellar vesicles. The enthalpy jump at this transition is equal to 97 kJ/mol, and data analysis suggests that this is a subgel-liquid transition. The phase transition at cooling is the liquid-gel transition in unilamellar vesicles. During the measurements, a slow evolution of the solution occurs, consisting in a change of concentrations of unilamellar and multilamellar vesicles. This transformation mainly occurs at low temperatures.

  18. Heterogeneous nucleation of aspartame from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Kubota, Noriaki; Kinno, Hiroaki; Shimizu, Kenji

    1990-03-01

    Waiting times, the time from the instant of quenching needed for a first nucleus to appear, were measured at constant supercoolings for primary nucleation of aspartame (α-L-aspartyl-L-phenylalanine methylester) from aqueous solutions, which were sealed into glass ampoules (solution volume = 3.16 cm 3). Since the waiting time became shorter by filtering the solution prior to quenching, the nucleation was concluded to be heterogeneously induced. The measured waiting time consisted of two parts: time needed for the nucleus to grow to a detactable size (growth time) and stochastic time needed for nucleation (true waiting time). The distribution of the true waiting time, is well explained by a stochastic model, in which nucleation is regarded to occur heterogeneously and in a stochastic manner by two kinds of active sites. The active sites are estimated to be located on foreign particles in which such elements as Si, Al and Mg were contained. The amount of each element is very small in the order of magnitude of ppb (mass basis) of the whole solution. The growth time was correlated with the degree of supercooling.

  19. Dissolution of lead paint in aqueous solutions

    SciTech Connect

    Barnes, G.L.; Davis, A.P.

    1996-07-01

    An analysis of the rate and extent of lead leaching from a lead-based paint was completed. At low-solution pH, dissolution was rapid and approached 80% of the total lead. Residual lead can be estimated based on the predicted solubility of lead carbonate and basic lead carbonate. Release of lead from the paint was slower than that from pure basic lead carbonate due to inhibition by the paint matrix. Although the dissolved concentration of lead in solution at neutral/high pH was low, the paint binder was apparently destroyed at these pH values, releasing colloidal lead pigment particles. The presence of ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) enhanced both the rate and degree of lead dissolution, while benzoic acid had a minimal effect.

  20. Evaluation of a technique to measure tropospheric hydroxyl radicals using an aqueous phase salicylic acid scrubbing solution, HPLCseparation and fluorescence detection

    NASA Astrophysics Data System (ADS)

    Salmon, R. A.; Schiller, C. L.; Harris, G. W.

    2003-04-01

    A novel method for monitoring gas phase hydroxyl radicals was examined using a liquid-phase salicylic acid solution to trap tropospheric OH. Quantification occurred following HPLC seperaration and fluorescence detection of one of the products, 2,5-dihydroxy benzoic acid. Although the sensitivity was sufficient to measure typical daytime OH concentrations, the method was hindered by a number of interferences. While most of these were identified and eliminated, an interference from methylperoxy radicals was discovered that could not be removed. The validity of previous reports of OH detection using this method is therefore brought into question.

  1. Hydrogen production via photolytic oxidation of aqueous sodium sulfite solutions.

    PubMed

    Huang, Cunping; Linkous, Clovis A; Adebiyi, Olawale; T-Raissi, Ali

    2010-07-01

    Sulfur dioxide (SO(2)) emission from coal-burning power plants and refinery operations has been implicated as a cause of acid rain and other air pollution related problems. The conventional treatment of SO(2)-contaminated air consists of two steps: SO(2) absorption using an aqueous sodium hydroxide solution, forming aqueous sodium sulfite (Na(2)SO(3)), and Na(2)SO(3) oxidation via air purging to produce sodium sulfate (Na(2)SO(4)). In this process, the potential energy of SO(2) is lost. This paper presents a novel ultraviolet (UV) photolytic process for production of hydrogen from aqueous Na(2)SO(3) solutions. The results show that the quantum efficiency of hydrogen production can reach 14.4% under illumination from a low pressure mercury lamp. The mechanism occurs via two competing reaction pathways that involve oxidation of SO(3)(2-) to SO(4)(2-) directly and through the dithionate (S(2)O(6)(2-)) ion intermediate. The first route becomes dominant once a photostationary state for S(2)O(6)(2-) is established. The initial pH of Na(2)SO(3) solution plays an important role in determining both the hydrogen production rate and the final products of the photolytic oxidation. At initial solution pH of 9.80 Na(2)SO(3) photo-oxidation generates Na(2)SO(4) as the final reaction product, while Na(2)S(2)O(6) is merely a reaction intermediate. The highest hydrogen production rate occurs when the initial solution pH is 7.55. Reduction in the initial solution pH to 5.93 results in disproportionation of HSO(3)(-) to elemental sulfur and SO(4)(2-) but no hydrogen production.

  2. Rheological properties of aqueous solutions of biopolymeric hyaluronan

    NASA Astrophysics Data System (ADS)

    Szwajczak, Elzbieta

    2004-09-01

    Aqueous solutions of hyaluronic acid (hyaluronan, HA) were studied. The HA compound is a natural polysaccharide, bipolymer. It plays an important role in numerous biological processes as a component of the extracellular matrix, connective tissues and, especially, human and animal synovial joints. Natural and artificial solutions of the HA have demonstrated the viscoelastic nature. These properties are shown to be related to the microstructure parameters (bulk concentration, molecular weight) and external parameters (temperature, stress, shear rate). We emphasize the role of the flow properties of polymeric systems. It is found a liquid crystalline "order" can be "induced" during the material flow. The dynamic properties, such as the elastic shear modulus and viscous shear modulus, are given. These results are discussed in relation to the postulated function of hyaluronic acid in synovial joint and with respect to possibilities o their application in medicine and pharmacology.

  3. Biconical tapered optical fiber biosensor for measuring refractive index of a-amino acids in aqueous D-glucose and sucrose solution

    NASA Astrophysics Data System (ADS)

    Zibaii, M. I.; Latifi, H.; Karami, M.; Gholami, M.; Hosseini, S. M.; Ghezelayagh, M. H.

    2010-04-01

    A single-mode biconical tapered optical fiber (BTOF) sensor was utilized for sensing the variation of refractive index (RI) with concentration of D-glucose in double distilled deionized water and measuring of RI of amino acids (AAs) in carbohydrate solutions. This method showed a rewarding ability in understanding the basis of biomolecular interactions in biological systems. The BTOF is fabricated by heat pulling method, utilizing a CO2 laser. The detection limit of the BTOF was 50 ppb for the D-glucose concentration ranging from 0 to 80 ppm, and RI detection limit corresponding to these concentrations in the range at 1.3333 to 1.3404 was 5.4×10-6 as a refractometer sensor. The response of the BTOF shows that the different kinds of interactions of various groups of AAs such as L-alanine, L-leucine, and L-cystein with D-glucose, sucrose and water molecules depend on functional groups in AAs such as OH, SH;CH2;NH3+ ,COO-. These results can be interpreted in terms of solute-solute and solute-solvent interactions and structure making/breaking ability of solutes in the given solution.

  4. Gas solubilities in aqueous solutions of organic substances

    SciTech Connect

    Rischbieter, E.; Schumpe, A.; Wunder, V.

    1996-07-01

    The solubilities of He, N{sub 2}, O{sub 2}, CH{sub 4}, and CO{sub 2} in aqueous solutions of glycerol, acetic acid, glucose, sucrose, and lactose were measured at 303.2 K. Additional data were generated for CO{sub 2} at 293.2 K and 323.2 K. The present results and literature data were analyzed to develop an empirical model. The parameter set allows predictions for 15 gases and 63 organic substances at temperatures between 273 K and 343 K.

  5. Kinetics of synthesis of monomeric betaines in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Kazantsev, O. A.; Baruta, D. S.; Kamorin, D. M.; Shirshin, K. V.; Shirshin, K. K.; Kolosov, E. S.

    2016-05-01

    In the nucleophilic addition of N-(3-dimethylaminopropyl)methacrylamide to acrylic acid (1 : 1) in aqueous solutions, forming monomeric β-propiobetaine, the dependence of the initial rate on the starting reagent concentration was found to have a pronounced maximum (whose position does not depend on the temperature at 30-70°C). In the case of the addition of N, N-dimethylaminoethyl methacrylate, the dependence was exponential. The dependences of equilibrium conversions on the starting reagent concentrations were of the same type and had a maximum for both systems. The detected concentration effects are related to the peculiarities of the pre-reaction association of the reagents.

  6. Gamma radiolytic degradation of naphthalene in aqueous solution

    NASA Astrophysics Data System (ADS)

    Chu, Libing; Yu, Shaoqing; Wang, Jianlong

    2016-06-01

    The decomposition of naphthalene in aqueous solution was studied using gamma irradiation combined with both H2O2 and TiO2 nanoparticles. Gamma irradiation led to a complete degradation of naphthalene and a partial mineralization. With initial concentration of 5-32 mg/L, more than 98% of naphthalene was removed and TOC reduction reached 28-31% at an absorbed dose of 3.0 kGy. The degradation of naphthalene was faster at neutral pH and the initial degradation rate increased with increasing the initial concentration of naphthalene. Addition of H2O2 and TiO2 nanoparticles all enhanced the degradation and mineralization of naphthalene. TOC removal efficiency increased from 28% (irradiation alone) to 35% with addition of H2O2 (40 mg/L), and to 48% with addition of TiO2 (0.8 g/L). The degradation of naphthalene in aqueous solution by gamma irradiation was mainly through the oxidation by ·OH radicals. The intermediate naphthol and carboxylic acids such as formic acid and oxalic acid were identified by LC-MS and IC.

  7. Effect of temperature on the protonation of N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid in aqueous solutions: Potentiometric and calorimetric studies

    SciTech Connect

    Li, Xingliang; Zhang, Zhicheng; Endrizzi, Francesco; Martin, Leigh R.; Luo, Shunzhong; Rao, Linfeng

    2015-06-01

    The TALSPEAK process (Trivalent Actinide Lanthanide Separations by Phosphorus-reagent Extraction from Aqueous Komplexes) has been demonstrated in several pilot-scale operations to be effective at separating trivalent actinides (An3+) from trivalent lanthanides (Ln3+). However, fundamental studies have revealed undesired aspects of TALSPEAK, such as the significant partitioning of Na+, lactic acid, and water into the organic phase, thermodynamically unpredictable pH dependence, and the slow extraction kinetics. In the modified TALSPEAK process, the combination of the aqueous holdback complexant HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid) with the extractant HEH[EHP] (2-ethyl(hexyl) phosphonic acid mono-2-ethylhexyl ester) in the organic phase has been found to exhibit a nearly flat pH dependence between 2.5 and 4.5 and more rapid phase transfer kinetics for the heavier lanthanides. To help understand the speciation of Ln3+ and An3+ in the modified TALSPEAK, systematic studies are underway on the thermodynamics of major reactions in the HEDTA system under conditions relevant to the process (e.g., higher temperatures). Thermodynamics of the protonation and complexation of HEDTA with Ln3+ were studied at variable temperatures. Equilibrium constants and enthalpies were determined by a combination of techniques including potentiometry and calorimetry. This paper presents the protonation constants of HEDTA at T = (25 to 70) °C. The potentiometric titrations have demonstrated that, stepwise, the first two protonation constants decrease and the third one slightly increases with the increase of temperature. This trend is in good agreement with the enthalpy of protonation directly determined by calorimetry. The results of NMR analysis further confirm that the first two protonation reactions occur on the diamine nitrogen atoms, while the third protonation reaction occurs on the oxygen of a

  8. Adsorption of chromium from aqueous solution on treated sawdust.

    PubMed

    Garg, V K; Gupta, Renuka; Kumar, Rakesh; Gupta, R K

    2004-03-01

    The adsorption of Cr(VI) from aqueous solutions on formaldehyde treated sawdust (SD) and sulphuric acid treated sawdust carbon (SDC) of Indian Rosewood, a timber industry waste, was studied at varying Cr(VI) concentrations, adsorbent dose, pH and agitation time. Similar experiments were conducted with commercially available coconut based activated carbon to compare the results. The Cr(VI) adsorption efficiency on SDC was higher than SD. The adsorption followed first order rate expression and Lagergren equation. An initial pH of 3.0 was most favorable for Cr(VI) removal by both the adsorbents. Maximum Cr(VI) was sequestered from the solution within 60 min after the beginning for every experiment. It is proposed that SDC and SD can be potential adsorbents for Cr(VI) removal from dilute solutions. PMID:14643989

  9. SEPARATION OF POLONIUM, PROTACTINIUM OR MIXTURES THEREOF IN AQUEOUS SOLUTION FROM BISMUTH, LEAD, ZIRCONIUM AND/OR COLUMBIUM VALUES

    DOEpatents

    Van Winkle, Q.; Kraus, K.A.

    1959-10-27

    A process is presented for separating polonium, protactinium, or mixtures thereof in aqueous solution from bismuth, zirconium, lead, and niobium values contained in the solution. The method comprises providing hydrochloric acid in the solution in a concentration of at least 5N. contacting the aqueous solution with a substantially waterimmiscible organic solvent such as diisopropyl ketone, and separating the aqueous phase containing the bismuth, zirconium, lead, and niobium from the organic extract phase containing the polonium, protactinium, or mixture thereof.

  10. Synthesis, spectroscopy, and binding constants of ketocatechol-containing iminodiacetic acid and its Fe(III), Cu(II), and Zn(II) complexes and reaction of Cu(II) complex with H₂O₂ in aqueous solution.

    PubMed

    Gao, Jiaojiao; Xing, Feifei; Bai, Yueling; Zhu, Shourong

    2014-06-01

    A new neuromelanin-like ketocatechol-containing iminodiacetic acid ligand, (N-(3,4-dihydroxyl)phenacylimino)diacetic acid (H4L), which is also quite similar to compounds found in insect cuticle, has been synthesized and characterized. The X-ray crystal structure of H4L has been successfully determined. Proton binding and coordination with Fe(III), Cu(II), and Zn(II) have been studied by potentiometric titrations and UV-vis spectrophotometry in aqueous solution. UV spectra of H4L in the absence and presence of different metal ions indicate complexes formed with the catechol moiety of H4L in aqueous solution. Visible spectra and NMR reveal that H4L with Fe(III), Cu(II), and Zn(II) can all give stable mono-(ML) and dinuclear complexes [M(ML)]. Fe(III) can also form {Fe(FeL)2} and {Fe(FeL)3} species with sufficient base. The process is accompanied by a drastic color change from light blue to deep-blue to wine-red. The Fe(III)-Cu(II) heteronuclear complex also exists in aqueous solution whose spectra are similar to the homonuclear Fe(III) complex. However, the spectra of {Fe(CuL)} shifted to a longer wavelength and {Fe(CuL)2} and {Fe(CuL)3} shifted to a shorter wavelength. Keto-enol tautomerism was observed in weak basic aqueous solution as indicated by (1)H NMR spectra. The reaction products of Cu(II) complex with H2O2 depend on the H2O2 concentration and pH value. Low concentrations of H2O2 oxidize H4L to a series of semiquinone and quinone compounds with absorption maxima at 314-400 nm, while a high concentration of H2O2 oxidizes H4L to colorless muconic acid derivatives. NaIO4 gives different oxidase products, but no 2,4,5-trihydroxyphenylalanine quinone (TPQ)-like hydroxyquinone can be found.

  11. Biosorption of metal ions from aqueous solutions

    SciTech Connect

    Chen, Jiaping; Yiacoumi, Sotira

    1997-01-01

    Copper biosorption from aqueous solutions by calcium alginate is reported in this paper. The experimental section includes potentiometric titrations of biosorbents, batch equilibrium and kinetic studies of copper biosorption, as well as fixed-bed biosorption experiments. The potentiometric titration results show that the surface charge increases with decreasing pH. The biosorption of copper strongly depends on solution pH; the metal ion binding increases from 0 to 90 percent in pH ranging from 1.5 to 5.0. In addition, a decrease in ionic strength results in an increase of copper ion removal. Kinetic studies indicate that mass transfer plays an important role in the biosorption rate. Furthermore, a fixed-bed biosorption experiment shows that calcium alginate has a significant capacity for copper ion removal. The two-pK Basic Stem model successfully represents the surface charge and equilibrium biosorption experimental data. The calculation results demonstrate that the copper removal may result from the binding of free copper and its hydroxide with surface functional groups of the biosorbents.

  12. Opto-electrochemical spectroscopy of metals in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Habib, K.

    2016-03-01

    In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the electrical resistance of aluminium samples during the initial stage of anodisation processes in aqueous solution. In fact, because the resistance values in this investigation were obtained by holographic interferometry, electromagnetic method rather than electronic method, the abrupt rate change of the resistance was called electrical resistance-emission spectroscopy. The anodisation process of the aluminium samples was carried out by electrochemical impedance spectroscopy (EIS) in different sulphuric acid concentrations (1.0%-2.5% H2SO4) at room temperature. In the meantime, the real time holographic interferometry was used to determine the difference between the electrical resistance of two subsequent values, dR, as a function of the elapsed time of the EIS experiment for the aluminium samples in 1.0%, 1.5%, 2.0%, and 2.5% H2SO4 solutions. The electrical resistance-emission spectra of the present investigation represent a detailed picture of not only the rate change of the electrical resistance throughout the anodisation processes but also the spectra represent the rate change of the growth of the oxide films on the aluminium samples in different solutions. As a result, a new spectrometer was developed based on the combination of the holographic interferometry and electrochemical impedance spectroscopy for studying in situ the electrochemical behavior of metals in aqueous solutions.

  13. Formation of hydroxyapatite in various aqueous solutions

    NASA Astrophysics Data System (ADS)

    Sturgeon, Jacqueline Lee

    Hydroxyapatite (HAp), Ca10(PO4)6(OH) 2, is important in the field of biomaterials as it is the mineral component of bones and teeth. Biological apatites do not maintain an exact composition and are usually calcium-deficient, represented as Ca(10- x)(HPO 4)x(PO4)(6-x)(OH)(2-x), where x ranges from 0 to 1, with various ion substitutions. Formation of calcium-deficient hydroxyapatites (CDHAp) from solid calcium phosphate precursor materials was performed at physiologic temperature (37°C) in a variety of aqueous solutions. Two cement systems were utilized in these experiments: tetralcium phosphate (TetCP) with dicalcium phosphate anhydrous (DCPA) and beta-tricalcium phosphate (beta-TCP). The kinetics, solution chemistry, phase evolution, and microstructure of the developed apatites were analyzed as appropriate. Reaction of beta-TCP in ammonium fluoride solutions formed HAp substituted with fluoride and calculated to be deficient in calcium. A new ratio of TetCP to DCPA was used with solutions of sodium bicarbonate to form a calcium-deficient carbonate hydroxyapatite. The capacity for sodium dihydrogen phosphate to buffer pH increases and enhance reaction kinetics in this system was also explored. Formation of a highly crystalline CDHAp was achieved by hydrolyzing beta-TCP in water for extended time periods. Lattice parameters were among the features characterized for this apatite. The hydrolysis of beta-TCP in phosphate buffered saline (PBS) and simulated body fluids (SBF) was also investigated; use of SBF was found to completely inhibit formation of HAp in this system while reaction in PBS was slow in comparison to water. The effects of filler materials on the mechanical properties of a calcium phosphate cement were examined using the TetCP/DCPA system. Dense aggregates were not found to decrease compressive strength in comparison to the cement alone. The use of aggregates was found to improve the compressive strength of cement formed using NaHCO3 solution as a

  14. Isothermal and nonisothermal decomposition of famotidine in aqueous solution.

    PubMed

    Junnarkar, G H; Stavchansky, S

    1995-04-01

    The kinetics of hydrolysis of famotidine in aqueous solution was studied by isothermal and nonisothermal method over the pH range of 1.71 to 10.0. Nonisothermal kinetics was studied with the purpose of determining its use in the establishment of the expiration date of pharmaceutical preparations, particularly drugs in solutions and for assessment of stability characteristics of pharmaceutical formulations during the development stage. A comparison of isothermal (55, 70 and 85 degrees C) and nonisothermal kinetics was performed. Aqueous solutions of famotidine were buffered at pH 1.71, 2.24, 2.66, 4.0, 8.5, 9.0 and 10.0 were used. In the nonisothermal studies, the temperature rate of the reaction was continuously varied throughout the experiment. The energies of activation were found to be in close agreement for isothermal and nonisothermal studies, indicating that nonisothermal studies may save considerable amount of time in the early stages of drug development and stability testing. Logk-pH profiles were constructed for 55, 70 and 85 degrees C from the first-order rate constants obtained from isothermal studies at pH values ranging from 1.71 to 10.00. The pH-rate profile indicated that famotidine undergoes specific acid catalysis in the acidic region and general base catalysis in the alkaline region. Hydrolysis in the acidic and alkaline media resulted in the formation of four and five degradation products, respectively. A possible degradation pathway for the acidic and alkaline hydrolysis was discussed. PMID:7596998

  15. Synthesis of linear low-density polyethylene-g-poly (acrylic acid)-co-starch/organo-montmorillonite hydrogel composite as an adsorbent for removal of Pb(ΙΙ) from aqueous solutions.

    PubMed

    Irani, Maryam; Ismail, Hanafi; Ahmad, Zulkifli; Fan, Maohong

    2015-01-01

    The purpose of this work is to remove Pb(II) from the aqueous solution using a type of hydrogel composite. A hydrogel composite consisting of waste linear low density polyethylene, acrylic acid, starch, and organo-montmorillonite was prepared through emulsion polymerization method. Fourier transform infrared spectroscopy (FTIR), Solid carbon nuclear magnetic resonance spectroscopy (CNMR)), silicon(-29) nuclear magnetic resonance spectroscopy (Si NMR)), and X-ray diffraction spectroscope ((XRD) were applied to characterize the hydrogel composite. The hydrogel composite was then employed as an adsorbent for the removal of Pb(II) from the aqueous solution. The Pb(II)-loaded hydrogel composite was characterized using Fourier transform infrared spectroscopy (FTIR)), scanning electron microscopy (SEM)), and X-ray photoelectron spectroscopy ((XPS)). From XPS results, it was found that the carboxyl and hydroxyl groups of the hydrogel composite participated in the removal of Pb(II). Kinetic studies indicated that the adsorption of Pb(II) followed the pseudo-second-order equation. It was also found that the Langmuir model described the adsorption isotherm better than the Freundlich isotherm. The maximum removal capacity of the hydrogel composite for Pb(II) ions was 430mg/g. Thus, the waste linear low-density polyethylene-g-poly (acrylic acid)-co-starch/organo-montmorillonite hydrogel composite could be a promising Pb(II) adsorbent.

  16. Reactions of CO2 with aqueous piperazine solutions: formation and decomposition of mono- and dicarbamic acids/carbamates of piperazine at 25.0 °C.

    PubMed

    Conway, William; Fernandes, Debra; Beyad, Yaser; Burns, Robert; Lawrance, Geoffrey; Puxty, Graeme; Maeder, Marcel

    2013-02-01

    Piperazine (PZ) is widely recognized as a promising solvent for postcombustion capture (PCC) of carbon dioxide (CO(2)). In view of the highly conflicting data describing the kinetic reactions of CO(2)(aq) in piperazine solutions, the present study focuses on the identification of the chemical mechanism, specifically the kinetic pathways for CO(2)(aq) in piperazine solutions that form the mono- and dicarbamates, using the analysis of stopped-flow spectrophotometric kinetic measurements and (1)H NMR spectroscopic data at 25.0 °C. The complete set of rate and equilibrium constants for the kinetic pathways, including estimations for the protonation constants of the suite of piperazine carbamates/carbamic acids, is reported here using an extended kinetic model which incorporates all possible reactions for CO(2)(aq) in piperazine solutions. From the kinetic data determined in the present study, the reaction of CO(2)(aq) with free PZ was found to be the dominant reactive pathway. The superior reactivity of piperazine is confirmed in the kinetic rate constant determined for the formation of piperazine monocarbamic acid (k(7) = 2.43(3) × 10(4) M(-1) s(-1)), which is within the wide range of published values, making it one of the faster reacting amines. The corresponding equilibrium constant for the formation of the monocarbamic acid, K(7), markedly exceeds that of other monoamines. Kinetic and equilibrium constants for the remaining pathways indicate a minor contribution to the overall kinetics at high pH; however, these pathways may become more significant at higher CO(2) loadings and lower pH values where the concentrations of the reactive species are correspondingly higher. PMID:23286883

  17. Reactions of CO2 with aqueous piperazine solutions: formation and decomposition of mono- and dicarbamic acids/carbamates of piperazine at 25.0 °C.

    PubMed

    Conway, William; Fernandes, Debra; Beyad, Yaser; Burns, Robert; Lawrance, Geoffrey; Puxty, Graeme; Maeder, Marcel

    2013-02-01

    Piperazine (PZ) is widely recognized as a promising solvent for postcombustion capture (PCC) of carbon dioxide (CO(2)). In view of the highly conflicting data describing the kinetic reactions of CO(2)(aq) in piperazine solutions, the present study focuses on the identification of the chemical mechanism, specifically the kinetic pathways for CO(2)(aq) in piperazine solutions that form the mono- and dicarbamates, using the analysis of stopped-flow spectrophotometric kinetic measurements and (1)H NMR spectroscopic data at 25.0 °C. The complete set of rate and equilibrium constants for the kinetic pathways, including estimations for the protonation constants of the suite of piperazine carbamates/carbamic acids, is reported here using an extended kinetic model which incorporates all possible reactions for CO(2)(aq) in piperazine solutions. From the kinetic data determined in the present study, the reaction of CO(2)(aq) with free PZ was found to be the dominant reactive pathway. The superior reactivity of piperazine is confirmed in the kinetic rate constant determined for the formation of piperazine monocarbamic acid (k(7) = 2.43(3) × 10(4) M(-1) s(-1)), which is within the wide range of published values, making it one of the faster reacting amines. The corresponding equilibrium constant for the formation of the monocarbamic acid, K(7), markedly exceeds that of other monoamines. Kinetic and equilibrium constants for the remaining pathways indicate a minor contribution to the overall kinetics at high pH; however, these pathways may become more significant at higher CO(2) loadings and lower pH values where the concentrations of the reactive species are correspondingly higher.

  18. Enzymatic characterization of peptidic materials isolated from aqueous solutions of ammonium cyanide (pH 9) and hydrocyanic acid (pH 6) exposed to ionizing radiation.

    PubMed

    Niketic, V; Draganić, Z; Nesković, S; Draganić, I

    1982-01-01

    The enzymatic digestion of some radiolytically produced peptidic materials was examined. The substrates were compounds isolated from 0.1 molar solutions of NH4CN (pH 9) and HCN (pH 6), after their exposure to gamma rays from a 60Co source (15-20 Mrad doses). Commercial proteolytic enzymes pronase and aminopeptidase M were used. The examined materials were of composite nature and proteolytic action was systematically observed after their subsequent purification. In some fractions the effect was found to be positive with up to 30% of peptide bonds cleaved with respect to the amino acid content. These findings support our previous conclusions on the free radical induced formation of peptidic backbones without the intervention of amino acids. Some side effects were also noted which might be of interest in observations on enzymatic cleavage of other composite peptidic materials of abiotic origin. PMID:6124639

  19. Enzymatic characterization of peptidic materials isolated from aqueous solutions of ammonium cyanide (pH 9) and hydrocyanic acid (pH 6) exposed to ionizing radiation.

    PubMed

    Niketic, V; Draganić, Z; Nesković, S; Draganić, I

    1982-01-01

    The enzymatic digestion of some radiolytically produced peptidic materials was examined. The substrates were compounds isolated from 0.1 molar solutions of NH4CN (pH 9) and HCN (pH 6), after their exposure to gamma rays from a 60Co source (15-20 Mrad doses). Commercial proteolytic enzymes pronase and aminopeptidase M were used. The examined materials were of composite nature and proteolytic action was systematically observed after their subsequent purification. In some fractions the effect was found to be positive with up to 30% of peptide bonds cleaved with respect to the amino acid content. These findings support our previous conclusions on the free radical induced formation of peptidic backbones without the intervention of amino acids. Some side effects were also noted which might be of interest in observations on enzymatic cleavage of other composite peptidic materials of abiotic origin.

  20. Uptake measurements of ethanol on ice surfaces and on supercooled aqueous solutions doped with nitric acid between 213 and 243 K.

    PubMed

    Kerbrat, M; Le Calvé, S; Mirabel, Ph

    2007-02-01

    Uptake of ethanol either on pure frozen ice surfaces or supercooled solutions doped with HNO3 (0.63 and 2.49 wt %) has been investigated using a coated wall flow tube coupled to a mass spectrometric detection. The experiments were conducted over the temperature range of 213-243 K. Uptake of ethanol on these surfaces was always found to be totally reversible whatever were the experimental conditions. The number of ethanol molecules adsorbed per surface unit was conventionally plotted as a function of ethanol concentration in the gas phase and subsequently analyzed using Langmuir's model. The amount of ethanol molecules taken up on nitric acid doped-ice surfaces was found to increase largely with increasing nitric acid concentrations. For example at 223 K, and for an ethanol gas-phase concentration of 1x10(13) molecules cm3, the number of adsorbed molecules are (in units of molecules cm-2): approximately 1.3x10(14) on pure ice; approximately 1.4x10(15) on ice doped with HNO3 0.63 wt %; approximately 7.5x10(15) on ice doped with HNO3, 2.49 wt %, i.e. 60 times larger than on pure ice. Since, according to the shape of the isotherms, the adsorption did not proceed beyond monolayer coverage, the enormous increase of ethanol uptake was explained by considering its dissolution in either a supercooled liquid layer (T<230 K) or a liquid solution (T>230 K). The formation of both was indeed favored by the presence of the HNO3. Our experimental results suggest that the amount of ethanol dissolved in such supercooled solutions follows Henry's law and that the Henry's law constants at low temperatures, i.e., 223-243 K, can be estimated by extrapolation from higher temperatures. Such supercooled solutions which exist in the troposphere either in deep convective clouds or in mixed clouds for temperature above 233 K, might be responsible for the scavenging of large amounts of soluble species, such as nitric and sulfuric acids, oxygenated VOCs including alcohols, carboxylic acids, and

  1. Anti-glycation properties of the aqueous extract solutions of dried algae products and effect of lactic acid fermentation on the properties.

    PubMed

    Kuda, Takashi; Eda, Mika; Kataoka, Manami; Nemoto, Maki; Kawahara, Miho; Oshio, Satoshi; Takahashi, Hajime; Kimura, Bon

    2016-02-01

    The antioxidant and anti-glycation properties in aqueous extract solutions (AESs) of 11 dried algae products were investigated. AESs of brown algae Ecklonia kurome (kurome) and Ecklonia stolonifera (tsuruarame) showed a strong DPPH radical-scavenging capacity and Fe-reducing power with high total phenolic compound content. On the other hand, superoxide anion radical-scavenging capacities of Porphyra sp. (iwanori, red alga), sporophyll of Undaria pinnatifida (mekabu, brown alga), and Gelidiaceae sp. (tengusa, red alga) were also high. Anti-glycation activities in BSA-fructose and BSA-methylglyoxal glycation were also high in kurome, while iwanori showed high activity. Results of the BSA-fructose model agreed with those of superoxide anion radical-scavenging. On the other hand, those of the BSA-methylglyoxal model agreed with those of the phenolic content, DPPH radical-scavenging capacity, and Fe-reducing power. Anti-glycation activities of iwanori, U. pinnatifida (wakame), and mekabu in the BSA-fructose model were clearly increased by fermentation with Lactobacillus plantarum AN6. PMID:26304454

  2. Nitrate Concentration near the Surface of Frozen Aqueous Solutions.

    PubMed

    Marrocco, Harley A; Michelsen, Rebecca R H

    2014-12-26

    Photolysis of nitrate plays an important role in the emission of nitrogen oxides from snow and ice, which affects the composition of the overlying atmosphere. In order to quantify these reactions, it is necessary to know how much nitrate is available for photolysis near the surfaces of snow and ice. The concentration of nitrate excluded from frozen solutions of nitric acid, sodium nitrate, and magnesium nitrate was measured with attenuated total reflection infrared spectroscopy. Liquid water and nitrate were observed at and near the bottom surface of frozen aqueous solutions during annealing from -18 to -2 °C. At -2 °C, the nitrate concentration was determined to be ∼1.0 mol/L for frozen NaNO(3) and Mg(NO(3))(2) solutions and ∼0.8 mol/L for frozen HNO(3) solutions. At lower temperatures, nitrate concentration ranged from 1.6 to 3.7 mol/L. Ideal thermodynamics overestimates nitrate concentration at colder temperatures where the brine is highly concentrated for all solutions. The nitrate concentration at ice surfaces is well described by bulk freezing point depression data close to the melting point of ice and for nitric acid at colder temperatures. Effects of temperature and counterions and implications for modeling snow chemistry are discussed. PMID:25495473

  3. Kinetic measurements of the reactivity of hydrogen peroxide and ozone towards small atmospherically relevant aldehydes, ketones and organic acids in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Schöne, L.; Herrmann, H.

    2014-05-01

    Free radical reactions are an important degradation process for organic compounds within the aqueous atmospheric environment. Nevertheless, non-radical oxidants such as hydrogen peroxide and ozone also contribute to the degradation and conversion of these substances (Tilgner and Herrmann, 2010). In this work, kinetic investigations of non-radical reactions were conducted using UV / Vis spectroscopy (dual-beam spectrophotometer and stopped flow technique) and a capillary electrophoresis system applying pseudo-first order kinetics to reactions of glyoxal, methylglyoxal, glycolaldehyde, glyoxylic, pyruvic and glycolic acid as well as methacrolein (MACR) and methyl vinyl ketone (MVK) with H2O2 and ozone at 298 K. The measurements indicate rather small rate constants at room temperature of k2nd < 3 M-1 s-1 (except for the unsaturated compounds exposed to ozone). Compared to radical reaction rate constants the values are about 10 orders of magnitude smaller (kOH • ~109 M-1 s-1). However, when considering the much larger non-radical oxidant concentrations compared to radical concentrations in urban cloud droplets, calculated first-order conversion rate constants change the picture towards H2O2 reactions becoming more important, especially when compared to the nitrate radical. For some reactions mechanistic suggestions are also given.

  4. Kinetic measurements on the reactivity of hydrogen peroxide and ozone towards small atmospherically relevant aldehydes, ketones and organic acids in aqueous solution

    NASA Astrophysics Data System (ADS)

    Schöne, L.; Herrmann, H.

    2013-10-01

    Within the aqueous atmospheric environment free radical reactions are an important degradation process for organic compounds. Nevertheless, non-radical oxidants like hydrogen peroxide and ozone also contribute to the degradation and conversion of this substance group (Tilgner und Herrmann, 2010). In this work kinetic investigations of non-radical reactions were conducted using UV/Vis spectroscopy (dual-beam spectrophotometer and Stopped Flow technique) and a capillary electrophoresis system applying pseudo-first order kinetics of glyoxal, methylglyoxal, glycolaldehyde, glyoxylic, pyruvic and glycolic acids as well as methacrolein (MACR) and methyl vinyl ketone (MVK) towards H2O2 and ozone. The measurements indicate rather small rate constants at room temperature of k2nd < 3 M-1 s-1 (except for the unsaturated compounds exposed to ozone). Compared to radical reaction rate constants the values are about 10 orders of magnitude smaller (kOH· ~ 109 M-1 s-1). However, when considering the much larger non-radical oxidant concentrations compared to radical concentrations in urban cloud droplets, calculated turnovers change the picture to more important H2O2 reactions especially when compared to the nitrate radical. For some reactions also mechanistic suggestions are given.

  5. Modeling solubility and acid-base properties of some amino acids in aqueous NaCl and (CH3)4NCl aqueous solutions at different ionic strengths and temperatures.

    PubMed

    Bretti, Clemente; Giuffrè, Ottavia; Lando, Gabriele; Sammartano, Silvio

    2016-01-01

    New potentiometric experiments have been performed in NaCl and in (CH3)4NCl media, to determine the protonation constants, the protonation enthalpy changes and the solubility of six natural α-amino acids, namely Glycine (Gly), Alanine (Ala), Valine (Val), Leucine (Leu), Serine (Ser) and Phenylalanine (Phe). The aim of the work is the rationalization of the protonation thermodynamics (log [Formula: see text], solubility and [Formula: see text]) in NaCl, determining recommended, tentative or provisional values in selected experimental conditions and to report, for the first time, data in a weak interacting medium, as (CH3)4NCl. Literature data analysis was performed selecting the most reliable values, analyzed together with new data here reported. Significant trends and similarities were observed in the behavior of the six amino acids, and in some cases it was possible to determine common parameters for the ionic strength and temperature dependence. In general, the first protonation step, relative to the amino group, is significantly exothermic (average value is [Formula: see text] = -44.5 ± 0.4 kJ mol(-1) at infinite dilution and T = 298.15 K), and the second, relative to the carboxylate group, is fairly close to zero ([Formula: see text] = -2.5 ± 1.6, same conditions). In both cases, the main contribution to the proton binding reaction is mainly entropic in nature. For phenylalanine and leucine, solubility measurements at different concentrations of supporting electrolyte allowed to determine total and specific solubility values, then used to obtain the Setschenow and the activity coefficients of all the species involved in the protonation equilibria. The values of the first protonation constant in (CH3)4NCl are lower than the corresponding values in NaCl, due to the weak interaction between the deprotonated amino group and (CH3)4N(+). In this light, differences between the protonation functions in NaCl and (CH3)4NCl were used for the quantification

  6. Modeling solubility and acid-base properties of some amino acids in aqueous NaCl and (CH3)4NCl aqueous solutions at different ionic strengths and temperatures.

    PubMed

    Bretti, Clemente; Giuffrè, Ottavia; Lando, Gabriele; Sammartano, Silvio

    2016-01-01

    New potentiometric experiments have been performed in NaCl and in (CH3)4NCl media, to determine the protonation constants, the protonation enthalpy changes and the solubility of six natural α-amino acids, namely Glycine (Gly), Alanine (Ala), Valine (Val), Leucine (Leu), Serine (Ser) and Phenylalanine (Phe). The aim of the work is the rationalization of the protonation thermodynamics (log [Formula: see text], solubility and [Formula: see text]) in NaCl, determining recommended, tentative or provisional values in selected experimental conditions and to report, for the first time, data in a weak interacting medium, as (CH3)4NCl. Literature data analysis was performed selecting the most reliable values, analyzed together with new data here reported. Significant trends and similarities were observed in the behavior of the six amino acids, and in some cases it was possible to determine common parameters for the ionic strength and temperature dependence. In general, the first protonation step, relative to the amino group, is significantly exothermic (average value is [Formula: see text] = -44.5 ± 0.4 kJ mol(-1) at infinite dilution and T = 298.15 K), and the second, relative to the carboxylate group, is fairly close to zero ([Formula: see text] = -2.5 ± 1.6, same conditions). In both cases, the main contribution to the proton binding reaction is mainly entropic in nature. For phenylalanine and leucine, solubility measurements at different concentrations of supporting electrolyte allowed to determine total and specific solubility values, then used to obtain the Setschenow and the activity coefficients of all the species involved in the protonation equilibria. The values of the first protonation constant in (CH3)4NCl are lower than the corresponding values in NaCl, due to the weak interaction between the deprotonated amino group and (CH3)4N(+). In this light, differences between the protonation functions in NaCl and (CH3)4NCl were used for the quantification

  7. Dinuclear complexes of copper and zinc with m-xylene/cyclohexane-linked bis-aspartic acids: synthesis, characterization, dioxygen activation, and catalytic oxidation of nitrobenzene in pure aqueous solution.

    PubMed

    Zhu, Shourong; Qiu, Zhixiang; Ni, Tianjun; Zhao, Xiujuan; Yan, Shikai; Xing, Feifei; Zhao, Yongmei; Bai, Yueling; Li, Mingxing

    2013-08-14

    Two new m-xylene/cyclohexane-linked bis-aspartic acid ligands, L(b) and L(c), were synthesized via Michael addition in basic aqueous solution. Their structures were characterized by elemental analysis, NMR and MS spectrometry. Both ligands react with Cu(II) and Zn(II) to form dinuclear complexes, with M2L(OH)(-) the major species in neutral/weak basic aqueous solution. To quantify the relative interaction strength between a Lewis acid and base, a new parameter σ = log K/14 was proposed which compares the stability constant with the binding constant between H(+) and OH(-). The dinuclear copper complexes (L(b)-2Cu and L(c)-2Cu) react with H2O2 in aqueous solution. The reaction in 0.020 M phosphate buffer at pH 7.5 is first-order for [L(c)-2Cu], but second-order for [L(b)-2Cu]. The oxidation products are oxygenated and/or dehydrogenated species. Radical trapping tests indicate that both complexes slightly scavenge the OH˙ radical, but generate the H˙ radical. L(c)-2Cu generates the H˙ radical much more effectively than that of L(b)-2Cu when reacted with H2O2. Both complexes are excellent catalysts for the oxidation of nitrobenzene in the presence of H2O2 in weakly basic aqueous solution. The oxidation follows the rate-law v = k[complex][nitrobenzene][H2O2]. The k values in pH 8.0 phosphate buffer at 25 °C are 211.2 ± 0.3 and 607.9 ± 1.7 mol(-2) L(2) s(-1) for L(b)-2Cu and L(c)-2Cu, respectively. The Arrhenius activation energies are 69.4 ± 2.2 and 70.0 ± 4.3 kJ mol(-1) for L(b)-2Cu and L(c)-2Cu, respectively, while the Arrhenius pre-exponential factors are 2.62 × 10(14) and 1.06 × 10(15), respectively. The larger pre-exponential factor makes L(c)-2Cu more catalytically active than L(b)-2Cu. These complexes are some of the most effective oxidation catalysts known for the oxidation of nitrobenzene.

  8. Partial molar volumes and viscosities of aqueous hippuric acid solutions containing LiCl and MnCl2 · 4H2O at 303.15 K

    NASA Astrophysics Data System (ADS)

    Deosarkar, S. D.; Tawde, P. D.; Zinjade, A. B.; Shaikh, A. I.

    2015-09-01

    Density (ρ) and viscosity (η) of aqueous hippuric acid (HA) solutions containing LiCl and MnCl2 · 4H2O have been studied at 303.15 K in order to understand volumetric and viscometric behavior of these systems. Apparent molar volume (φv) of salts were calculated from density data and fitted to Massons relation and partial molar volumes (φ{v/0}) at infinite dilution were determined. Relative viscosity data has been used to determine viscosity A and B coefficients using Jones-Dole relation. Partial molar volume and viscosity coefficients have been discussed in terms of ion-solvent interactions and overall structural fittings in solution.

  9. REDUCTION OF ACIDITY OF NITRIC ACID SOLUTIONS BY USE OF FORMALDEHYDE

    DOEpatents

    Healy, T.V.

    1958-05-20

    A continuous method is described of concentrating by evaporation and reducing the nitrate ion content of an aqueous solution of metallic salts containing nitric acid not in excess of 8N. It consists of heating the solution and then passing formaldehyde into the heated solution to bring about decomposition of the nitric acid. The evolved gases containing NO are contacted countercurrently with an aqueous metal salt solution containing nitric acid in excess of 8N so as to bring about decomposition of the nitric acid and lower the normality to at least 8N, whereupon it is passed into the body of heated solution.

  10. Structure of aqueous sodium perchlorate solutions.

    PubMed

    General, Ignacio J; Asciutto, Eliana K; Madura, Jeffry D

    2008-12-01

    Salt solutions have been the object of study of many scientists through history, but one of the most important findings came along when the Hofmeister series were discovered. Their importance arises from the fact that they influence the relative solubility of proteins, and solubility is directly related to one of today's holy grails: protein folding. In this work we characterize one of the more-destabilizing salts in the series, sodium perchlorate, by studying it as an aqueous solution at various concentrations ranging from 0.08 to 1.60 mol/L. Molecular dynamics simulations at room temperature permitted a detailed study of the organization of solvent and cosolvent, in terms of its radial distribution functions, along with the study of the structure of hydrogen bonds in the ions' solvation shells. We found that the distribution functions have some variations in their shape as concentration changes, but the position of their peaks is mostly unaffected. Regarding water, the most salient fact is the noticeable (although small) change in the second hydration shell and even beyond, especially for g(O(w)***O(w)), showing that the locality of salt effects should not be restricted to considerations of only the first solvation shell. The perturbation of the second shell also appears in the study of the HB network, where the difference between the number of HBs around a water molecule and around the Na(+) cation gets much smaller as one goes from the first to the second solvation shell, yet the difference is not negligible. Nevertheless, the effect of the ions past their first hydration shell is not enough to make a noticeable change in the global HB network. The Kirkwood-Buff theory of liquids was applied to our system, in order to calculate the activity derivative of the cosolvent. This coefficient, along with a previously calculated preferential binding, allowed us to establish that if a folded AP peptide is immersed in the studied solution, becoming the solute, then

  11. Component dynamics in polyvinylpyrrolidone concentrated aqueous solutions.

    PubMed

    Busselez, Rémi; Arbe, Arantxa; Cerveny, Silvina; Capponi, Sara; Colmenero, Juan; Frick, Bernhard

    2012-08-28

    (2)H-nuclear magnetic resonance (NMR) and neutron scattering (NS) on isotopically labelled samples have been combined to investigate the structure and dynamics of polyvinylpyrrolidone (PVP) aqueous solutions (4 water molecules/monomeric unit). Neutron diffraction evidences the nanosegregation of polymer main-chains and water molecules leading to the presence of water clusters. NMR reveals the same characteristic times and spectral shape as those of the slower process observed by broadband dielectric spectroscopy in this system [S. Cerveny et al., J. Chem. Phys. 128, 044901 (2008)]. The temperature dependence of such relaxation time crosses over from a cooperative-like behavior at high temperatures to an Arrhenius behavior at lower temperatures. Below the crossover, NMR features the spectral shape as due to a symmetric distribution of relaxation times and the underlying motions as isotropic. NS results on the structural relaxation of both components-isolated via H/D labeling-show (i) anomalously stretched and non-Gaussian functional forms of the intermediate scattering functions and (ii) a strong dynamic asymmetry between the components that increases with decreasing temperature. Strong heterogeneities associated to the nanosegregated structure and the dynamic asymmetry are invoked to explain the observed anomalies. On the other hand, at short times the atomic displacements are strongly coupled for PVP and water, presumably due to H-bond formation and densification of the sample upon hydration.

  12. Photochemistry of dihydrobiopterin in aqueous solution.

    PubMed

    Vignoni, Mariana; Cabrerizo, Franco M; Lorente, Carolina; Claparols, Catherine; Oliveros, Esther; Thomas, Andrés H

    2010-02-21

    Dihydrobiopterin (H(2)Bip) and its oxidized analogue, biopterin (Bip), accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder in which the protection against UV radiation fails. The photochemistry of H(2)Bip was studied in neutral aqueous solutions upon UV-A irradiation (320-400 nm) at room temperature. The photochemical reactions were followed by UV/vis spectrophotometry, HPLC and enzymatic methods for hydrogen peroxide (H(2)O(2)) determination. Photoproducts were analyzed by means of electrospray ionization mass spectrometry. Under anaerobic conditions, excitation of H(2)Bip leads to the formation of at least two isomeric dimers with molecular masses equal to exactly twice the molecular mass of the reactant. This reaction takes place from the singlet excited state of the reactant. To the best of our knowledge, this is the first time that the photodimerization of a dihydropterin is reported. In the presence of air, the dimers are again the main photoproducts at the beginning of the reaction, but a small proportion of the reactant is converted into Bip. As the reaction proceeds and enough Bip accumulates in the solution, a photosensitized process starts, where Bip photoinduces the oxidation of H(2)Bip to Bip, and H(2)O(2) is formed. As a consequence, the rates of H(2)Bip consumption and Bip formation increase as a function of irradiation time, resulting in an autocatalytic photochemical process. In this process, Bip in its triplet excited state reacts with the ground state of H(2)Bip. The mechanisms involved are analyzed and the biological implications of the results are discussed.

  13. Application of acidic treated pumice as an adsorbent for the removal of azo dye from aqueous solutions: kinetic, equilibrium and thermodynamic studies.

    PubMed

    Samarghandi, Mohammad Reza; Zarrabi, Mansur; Sepehr, Mohammad Noori; Amrane, Abdeltif; Safari, Gholam Hossein; Bashiri, Saied

    2012-11-05

    Colored effluents are one of the important environment pollution sources since they contain unused dye compounds which are toxic and less-biodegradable. In this work removal of Acid Red 14 and Acid Red 18 azo dyes was investigated by acidic treated pumice stone as an efficient adsorbent at various experimental conditions. Removal of dye increased with increase in contact time and initial dye concentration, while decreased for increment in solution temperature and pH. Results of the equilibrium study showed that the removal of AR14 and AR18 followed Freundlich (r2>0.99) and Langmuir (r2>0.99) isotherm models. Maximum sorption capacities were 3.1 and 29.7 mg/g for AR 14 and AR18, namely significantly higher than those reported in the literature, even for activated carbon. Fitting of experimental data onto kinetic models showed the relevance of the pseudo-second order (r2>0.99) and intra-particle diffusion (r2>0.98) models for AR14 and AR18, respectively. For both dyes, the values of external mass transfer coefficient decreased for increasing initial dye concentrations, showing increasing external mass transfer resistance at solid/liquid layer. Desorption experiments confirmed the relevance of pumice stone for dye removal, since the pH regeneration method showed 86% and 89% regeneration for AR14 and AR18, respectively.

  14. Application of acidic treated pumice as an adsorbent for the removal of azo dye from aqueous solutions: kinetic, equilibrium and thermodynamic studies.

    PubMed

    Samarghandi, Mohammad Reza; Zarrabi, Mansur; Sepehr, Mohammad Noori; Amrane, Abdeltif; Safari, Gholam Hossein; Bashiri, Saied

    2012-01-01

    Colored effluents are one of the important environment pollution sources since they contain unused dye compounds which are toxic and less-biodegradable. In this work removal of Acid Red 14 and Acid Red 18 azo dyes was investigated by acidic treated pumice stone as an efficient adsorbent at various experimental conditions. Removal of dye increased with increase in contact time and initial dye concentration, while decreased for increment in solution temperature and pH. Results of the equilibrium study showed that the removal of AR14 and AR18 followed Freundlich (r2>0.99) and Langmuir (r2>0.99) isotherm models. Maximum sorption capacities were 3.1 and 29.7 mg/g for AR 14 and AR18, namely significantly higher than those reported in the literature, even for activated carbon. Fitting of experimental data onto kinetic models showed the relevance of the pseudo-second order (r2>0.99) and intra-particle diffusion (r2>0.98) models for AR14 and AR18, respectively. For both dyes, the values of external mass transfer coefficient decreased for increasing initial dye concentrations, showing increasing external mass transfer resistance at solid/liquid layer. Desorption experiments confirmed the relevance of pumice stone for dye removal, since the pH regeneration method showed 86% and 89% regeneration for AR14 and AR18, respectively. PMID:23369579

  15. Electrical conductivity of acidic sulfate solution

    NASA Astrophysics Data System (ADS)

    Majima, Hiroshi; Peters, Ernest; Awakura, Yasuhiro; Park, Sung Kook

    1987-03-01

    The electrical conductivities of the aqueous solution system of H2SO4-MSO4 (involving ZnSO4, MgSO4, Na2SO4, and (NH4)2SO4), reported by Tozawa et al., were examined in terms of a (H2O) and H+ ion concentration. The equations to compute the concentrations of various species in aqueous sulfuric acid solutions containing metal sulfates were derived for a typical example of the H2SO4-ZnSO4-MgSO4-(Na2SO4)-H2O system. It was found that the H+ ion concentrations in concentrated sulfuric acid solutions corresponding to practical zinc electrowinning solutions are very high and remain almost constant with or without the addition of metal sulfates. The addition of metal sulfates to aqueous sulfuric acid solution causes a decrease in electrical conductivity, and this phenomenon is attributed to a decrease in water activity, which reflects a decrease in the amount of free water. The relationship between conductivity and water activity at a constant H+ ion concentration is independent of the kind of sulfates added. On the other hand, any increase in H+ ion concentration results in an increase in electrical conductivity. A novel method for the prediction of electrical conductivity of acidic sulfate solution is proposed that uses the calculated data of water activity and the calculated H+ ion concentration. Also, the authors examined an extension of the Robinson-Bower equation to calculate water activity in quarternary solutions based on molarity instead of molality, and found that such calculated values are in satisfactory agreement with those determined experimentally by a transpiration method.

  16. Photoinduced chemical reactions on natural single crystals and synthesized crystallites of mercury(II) sulfide in aqueous solution containing naturally occurring amino acids.

    PubMed

    Pal, Bonamali; Ikeda, Shigeru; Ohtani, Bunsho

    2003-03-10

    Photoirradiation at >300 nm of aqueous suspensions of several natural crystal specimens and synthesized crystallites of mercury(II) sulfide (HgS) induced deaminocyclization of optically active or racemic lysine into pipecolinic acid (PCA) under deaerated conditions. This is the first example, to the best of our knowledge, of photoinduced chemical reactions of natural biological compounds over natural minerals. It was found that the natural HgS crystals had activity higher than those of synthesized ones but lower than those of other sulfides of transition metals, e.g., CdS and ZnS, belonging to the same II-IV chalcogenides. In almost all of the photoreactions, decompostion of HgS occurred to liberate hydrogen sulfide (H(2)S) and Hg(2+), and the latter seemed to have undergone in-situ reductive deposition on HgS as Hg(0) after a certain induction period (24-70 h) during the photoirradiation, as indicated by the darkened color of the suspensions. The formation of PCA, presumably through combination of oxidation of lysine and reduction of an intermediate, cyclic Schiff base, could also be seen after a certain induction time of the Hg(0) formation. This was supported by the fact that the addition of small amount of Hg(2+) (0.5 wt % of HgS) increased the PCA yield by almost 2-fold. We also tried to elucidate certain aspects of the plausible stereochemical reactions in relation to the chiral crystal structure of HgS. Although, in some experiments, slight enantiomeric excess of the product PCA was observed, the excess was below or equal to the experimental error and no other supporting analytical data could not be obtained; we cannot conclude the enantiomeric photoproduction of PCA by the natural chiral HgS specimen. PMID:12611518

  17. Alkaline earth cation extraction from acid solution

    DOEpatents

    Dietz, Mark; Horwitz, E. Philip

    2003-01-01

    An extractant medium for extracting alkaline earth cations from an aqueous acidic sample solution is described as are a method and apparatus for using the same. The separation medium is free of diluent, free-flowing and particulate, and comprises a Crown ether that is a 4,4'(5')[C.sub.4 -C.sub.8 -alkylcyclohexano]18-Crown-6 dispersed on an inert substrate material.

  18. Nanostructured protic ionic liquids retain nanoscale features in aqueous solution while precursor Brønsted acids and bases exhibit different behavior.

    PubMed

    Greaves, Tamar L; Kennedy, Danielle F; Weerawardena, Asoka; Tse, Nicholas M K; Kirby, Nigel; Drummond, Calum J

    2011-03-10

    Small- and wide-angle X-ray scattering (SWAXS) has been used to investigate the effect that water has on the nanoscale structure of protic ionic liquids (PILs) along with their precursor Brønsted acids and bases. The series of PILs consisted of primary, secondary, and tertiary alkylammonium cations in conjunction with formate, nitrate, or glycolate anions. Significant differences were observed for these systems. The nanoscale aggregates present in neat protic ionic liquids were shown to be stable in size on dilution to high concentrations of water, indicating that the water is localized in the ionic region and has little effect on the nonpolar domains. The Brønsted acid-water solutions did not display nanostructure at any water concentration. Primary amine Brønsted bases formed aggregates in water, which generally displayed characteristics of poorly structured microemulsions or a form of bicontinuous phase. Exceptions were butyl- and pentylamine with high water concentrations, for which the SWAXS patterns fitted well to the Teubner-Strey model for microemulsions. Brønsted base amines containing multiple alkyl chains or hydroxyl groups did not display nanostructure at any water concentration. IR spectroscopy was used to investigate the nature of water in the various solutions. For low PIL concentrations, the water was predominately present as bulk water for PIL molar fractions less than 0.4-0.5. At high PIL concentrations, in addition to the bulk water, there was a significant proportion of perturbed water, which is water influenced in some way by the cations and anions. The molecular state of the water in the studied amines was predominately present as bulk water, with smaller contributions from perturbed water than was seen in the PILs. PMID:21319828

  19. Partitioning of U, Np, Th, and Eu between acidic aqueous Al(NO3)3 solutions and various TOPO extraction chromatographic materials

    NASA Astrophysics Data System (ADS)

    Shafer, Jenifer C.; Sulakova, Jana; Ogden, Mark D.; Nash, Kenneth L.

    2010-03-01

    As the Hanford site undergoes remediation, it is noted that significant economies could be realized by minimizing the amount of aluminum deposited in High-Level Waste glass. Though such a step is not planned, an acidic scrub of the Hanford sludge could enhance Al removal. It is likely that the resulting Al(NO3)3 solution would contain measurable amounts of transuranic elements, thus the solution might require some secondary treatment to remove TRU contamination. Thus far, extraction chromatography (EXC) has shown promise [1] as an alternative to a liquid-liquid remediation of the Hanford site. Previous EXC studies have shown >99% of the Eu can be extracted from simulated Al/Cr waste. This study continues an examination of a hypothetical secondary cleanup of the waste by studying the removal of UO22+, NpO2+, NpO22+ and Th4+ from using tri-n-octyl phospine oxide (TOPO) impregnated XAD7 resins. Neptunium was held in the V and VI oxidation states using ascorbic acid and chromate, respectively. Initial results show extraction following classical metal recovery trends, wherein an increased Zeff correlates with increased distribution of the metal into the organic resin phase. The uptake of Eu3+ (representative of An3+) on a column of the same material was also investigated. Uptake kinetics were improved by wetting the TOPO-XAD7 resin with n-dodecane (TOPO-XAD7n). The presence of n-dodecane also provided consistency between batch mode and column mode metal recovery. Preliminary data show >99% recovery of metal ions with a Zeff >= 3 under various simulated conditions.

  20. Stable aqueous colloidal solutions of intact surfactant-free graphene nanoribbons and related graphitic nanostructures.

    PubMed

    Dimiev, Ayrat M; Gizzatov, Ayrat; Wilson, Lon J; Tour, James M

    2013-04-01

    Here we demonstrate a simple, nondestructive method for the preparation of stable aqueous colloidal solutions of graphene nanoribbons and carbon nanotubes. The method includes sonication of carbon nanomaterials in hypophosphorous acid, filtration accompanied by washing the solids with water and dispersion of the solids in a fresh portion of water to form colloidal solutions.

  1. Stable aqueous colloidal solutions of intact surfactant-free graphene nanoribbons and related graphitic nanostructures.

    PubMed

    Dimiev, Ayrat M; Gizzatov, Ayrat; Wilson, Lon J; Tour, James M

    2013-04-01

    Here we demonstrate a simple, nondestructive method for the preparation of stable aqueous colloidal solutions of graphene nanoribbons and carbon nanotubes. The method includes sonication of carbon nanomaterials in hypophosphorous acid, filtration accompanied by washing the solids with water and dispersion of the solids in a fresh portion of water to form colloidal solutions. PMID:23435853

  2. ELECTROCHEMICAL DECHLORINATIONOF 2-CHLOROBIPHENYL IN AQUEOUS SOLUTION

    EPA Science Inventory

    This paper presents electrochemical dechlorination of 2-chlorobiphenyl (2-CI BP) in aqueous environment using palladium modified granular graphite electrodes. 2-CI BP, the PCB congener that requires the highest reduction potential, was effectively dechlorinated in electrochemical...

  3. Acoustic and thermodynamic investigations of aqueous solutions of some carbohydrates

    NASA Astrophysics Data System (ADS)

    Gepert, M.; Moskaluk, A.

    2006-11-01

    Acoustic and thermodynamic properties of aqueous solutions of three carbohydrates: D-glucose, D-fructose and D-saccharose are discussed. D-glucose and D-fructose have different molecular structures; thus they interact in different ways with the surrounding water molecules. Based on our experimental results, we found that the thermodynamic properties of the aqueous solutions of the two monosaccharides are similar, except the limiting apparent molar compressibilities. As anticipated, the thermodynamic properties of an aqueous solution of D-saccharose are mostly the resultant of the properties of both monosaccharides. Any modifications of these properties are probably caused by the specific linkage between two monosaccharide rings.

  4. Oxygen uptake upon photolysis of 1,4-benzoquinones and 1,4-naphthoquinones in air-saturated aqueous solution in the presence of formate, amines, ascorbic acid, and alcohols.

    PubMed

    Görner, Helmut

    2007-04-19

    The effects of oxygen in the photoreduction of 1,4-benzoquinone (BQ), 1,4-naphthoquinone (NQ), and a series of derivatives were studied in aqueous solution in the presence of acetonitrile and formate, aliphatic amines, e.g., EDTA or triethylamine, ascorbic acid, and alcohols, e.g., methanol or 2-propanol. The quinone triplet state is quenched, whereby the semiquinone and donor radicals are formed which react subsequently with oxygen. The overall reaction is oxidation of the donors and conversion of oxygen via the hydroperoxyl/superoxide radical into hydrogen peroxide. The quantum yield (Phi-O2) of this oxygen uptake changes in 2-propanol-water (1:10) from <0.01 for BQ to Phi-O2 = 0.5-0.8 for NQ. Generally Phi-O2 increases with increasing donor concentration. The specific properties of quinone structure, the radical equilibria and reactivity, and the concentration dependences are discussed. PMID:17388578

  5. METHOD OF RECOVERING PLUTONIUM VALUES FROM AQUEOUS SOLUTIONS BY CARRIER PRECIPITATION

    DOEpatents

    James, R.A.; Thompson, S.G.

    1959-11-01

    A process is presented for pretreating aqueous nitric acid- plutonium solutions containing a small quantity of hydrazine that has formed as a decomposition product during the dissolution of neutron-bombarded uranium in nitric acid and that impairs the precipitation of plutonium on bismuth phosphate. The solution is digested with alkali metal dichromate or potassium permanganate at between 75 and 100 deg C; sulfuric acid at approximately 75 deg C and sodium nitrate, oxaiic acid plus manganous nitrate, or hydroxylamine are added to the solution to secure the plutonium in the tetravalent state and make it suitable for precipitation on BiPO/sub 4/.

  6. Atrazine photodegradation in aqueous solution induced by interaction of humic acids and iron: photoformation of iron(II) and hydrogen peroxide.

    PubMed

    Ou, Xiaoxia; Quan, Xie; Chen, Shuo; Zhao, Huimin; Zhang, Yaobin

    2007-10-17

    The photochemical formation of Fe(II) and hydrogen peroxide (H 2O 2) coupled with humic acids (HA) was studied to understand the significance of iron cycling in the photodegradation of atrazine under simulated sunlight. The presence of HA significantly enhanced the formation of Fe(II) and H 2O 2, and their subsequent product, hydroxyl radical ( (*)OH), was the main oxidant responsible for the atrazine photodegradation. During 60 h of irradiation, the fraction of iron presented as Fe(II) (Fe(II)/Fe(t)) decreased from 20-32% in the presence of the Fe(III)-HA complex to 10-22% after adding atrazine. The rate of atrazine photodegradation in solutions containing Fe(III) increased with increasing HA concentration, suggesting that the complexation of Fe(III) with HA accelerated the Fe(III)/Fe(II) cycling. Using fluorescence spectrometry, the quenching constant and the percentage of fluorophores participating in the complexation of HA with Fe(III) were estimated by the modified Stern-Volmer equation. Fourier transform infrared spectroscopy (FTIR) offered the direct evidence that Fe(III)-carboxylate complex could be formed by ligand exchange of HA with Fe(III). Based on all the information, a possible reaction mechanism was proposed.

  7. Influence of acid and alkaline sources on optical, structural and photovoltaic properties of CdSe nanoparticles precipitated from aqueous solution

    NASA Astrophysics Data System (ADS)

    Coria-Monroy, C. Selene; Sotelo-Lerma, Mérida; Hu, Hailin

    2016-06-01

    CdSe is a widely researched material for photovoltaic applications. One of the most important parameters of the synthesis is the pH value, since it determines the kinetics and the mechanism of the reaction and in consequence, the optical and morphological properties of the products. We present the synthesis of CdSe in solution with strict control of pH and the comparison of ammonia and KOH as alkaline sources and diluted HCl as acid medium. CdSe formation was monitored with photoluminescence emission spectra (main peak in 490 nm, bandgap of CdSe nanoparticles). XRD patterns indicated that CdSe nanoparticles are mainly of cubic structure for ammonia and HCl, but the hexagonal planes appear with KOH. Product yield decreases with pH and also decreases with KOH at constant pH value since ammonia has a double function, as complexing agent and alkaline source. Changes in morphology were observed in SEM images as well with the different alkaline source. The effect of alkaline sources on photovoltaic performance of hybrid organic solar cells with CdSe and poly(3-hexylthiophene) as active layers was clearly observed, indicating the importance of synthesis conditions on optoelectronic properties of promising semiconductor nanomaterials for solar cell applications.

  8. Interaction of adenylic acid with alkaline earth metal ions in the crystalline solid and aqueous solution. Evidence for the sugar C'2-endo/anti, C'3-endo/anti and C'4-exon/anti conformational changes.

    PubMed

    Tajmir-Riahi, H A

    1990-09-10

    The reaction of adenosine 5'-monophosphoric acid (H2-AMP) with the alkaline earth metal ions has been investigated in aqueous solution at neutral pH. The solid salts of Mg-AMP.5H2O, Ca-AMP.6H2O, Sr-AMP.7H2O and Ba-AMP.7H2O were isolated and characterized by Fourier transform infrared, 1H-NMR spectroscopy and X-ray powder diffraction measurements. Spectroscopic and other evidence showed that the Sr-AMP.7H2O and Ba-AMP.7H2O are isomorphous, whereas the Mg-AMP.5H2O and Ca-AMP.6H2O are not similar. The Mg2+ binding is through the N-7 (inner-sphere) and the phosphate group (outer-sphere via H2O), while the Ca2+ binds to the phosphate group (inner-sphere) and to the base N-7 site (outer-sphere through H2O). The Sr2+ and Ba2+ bind to H2O molecules, H-bonding to the N-7, N-1 and the phosphate group (outer-sphere). In aqueous solution, an equilibrium between the inner- and outer-sphere metal ion bindings can be established. The sugar moiety exhibited C'2-endo/anti conformation, in the free H2-AMP acid and the magnesium salt, C'3-endo/anti in the calcium salt and unusual C'4-exo/anti, in the strontium and barium salts.

  9. Mg isotope fractionation between inorganic aragonite and aqueous solution

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Zhang, S.; Hu, P.

    2012-12-01

    Recent studies showed δ26Mg values of some species of Scleractinian corals, and aragonitic sponges and Scaphopod are inconsistent with the Mg isotope fractionation calibrated previously between inorganic aragonite and seawater. In this study, we explored Mg isotope fractionation between aragonite and aqueous solution under various experimental conditions, including salinity (mostly in fresh water), Mg/Ca ratio (3-5 in molar), Ca concentration (400-1500 ppm), temperature (25-55oC) and duration of experiments (3-21 days). Precipitation experiments were conducted using 'free-drift' method. The starting solution was made by mixing an appropriate amount of reagent-grade NaHCO3, CaCl2 and MgCl2 in deionized water, flushed with CO2 gas. The mixed solution was filtered after these reagents completely dissolved before any experiment, and then passively-degassed in a water bath kept at a constant temperature. Over the course of the experiments, pH and alkalinity of the aqueous solution were closely monitored. At the end of the experiment, the precipitates were cleaned, characterized by SEM and checked by XRD. The solution and precipitates were treated by acid. The supernatant was passed through two chromatographic columns to extract pure Mg, and measured for their δ26Mg values. In each case, a leaching procedure is employed to clean aragonite before their isotopic compositions were measured. Our preliminary results show that the Mg isotope fractionation between aragonite and solution varies with Ca concentration at a given Mg/Ca ratio, i.e., aragonite are strongly depleted in 26Mg in solution with high and low Ca concentration (e.g., Ca = 400ppm and 2000 ppm), but less depleted in solutions with intermediate Ca concentration (e.g., Ca= 1000 ppm). At a given Ca and Mg/Ca, the fractionation factor is temperature-dependent, defining linear relationship with 1/T (T is temperature in Kelvin) with temperature sensitivity of ~ 0.01‰/oC. These results seem to suggest a kinetic

  10. Natural hydrophobic flocculation of fine coal particles in aqueous solution

    SciTech Connect

    Song, S.; Lu, S.; Trass, O.; Wang, G.; Wang, Z.

    1994-12-31

    The hydrophobic flocculation of fine coal particles with natural hydrophobicity in aqueous solution, which is called natural hydrophobic flocculation, has been studied in this paper. It features no surfactant addition but only high intensity mechanical agitation. The experimental results showed that this flocculation occurred even in the case of {minus}58 mV jet potential of coal particles, that is contrary to the classical DLVO (Derjaguin-LandauVerwey-Overbeek) theory. Wettability of coal particle surface dominates the stability o fine coal particles in aqueous solution. The bigger the contact angle, the more intensive the flocculation of the coal particle suspension. The quantitative theory of natural hydrophobic flocculation is presented in this paper. Using this theory, the authors have calculated the total potential energy of interaction between coal particles in aqueous solution. The results demonstrate that the hydrophobic interaction plays a dominant role in the interaction between coal particles in aqueous solution.

  11. Singlet Oxygen in Aqueous Solution: A Lecture Demonstration

    ERIC Educational Resources Information Center

    Shakhashiri, Bassam Z.; Williams, Lloyd G.

    1976-01-01

    Describes a demonstration that illustrates the red chemiluminescence due to singlet molecular oxygen that can be observed when aqueous solutions of hypochlorite ion and hydrogen peroxide are mixed. (MLH)

  12. "Switchable water": aqueous solutions of switchable ionic strength.

    PubMed

    Mercer, Sean M; Jessop, Philip G

    2010-04-26

    "Salting out" is a standard method for separating water-soluble organic compounds from water. In this method, adding a large amount of salt to the aqueous solution forces the organic compound out of the aqueous phase. However, the method can not be considered sustainable because it creates highly salty water. A greener alternative would be a method that allows reversible salting out. Herein, we describe aqueous solutions of switchable ionic strength. Aqueous solutions of a diamine in water have essentially zero ionic strength but are converted by CO(2) into solutions of high ionic strength. The change is reversible. Application to the reversible salting out of THF from water is described. PMID:20186910

  13. Remote photoacoustic measurements in aqueous solutions using an optical fiber

    SciTech Connect

    Russo, R.E. ); Rojas, D. ); Robouch, P.; Silva, R.J. )

    1990-12-01

    A photoacoustic spectrometer was developed for remote optical absorption measurements in aqueous solutions using an 85-m optical fiber to deliver pulsed tunable dye laser radiation to a sample cuvette located in a glove box. The spectrometer was tested using aqueous solutions of praseodymium ions. Beer's law was verified down to a concentration of 8{times}10{sup {minus}6}M for an equivalent absorptance of 3.2{times}10{sup {minus}5} cm{sup {minus}1}.

  14. Amphipols: Polymers that Keep Membrane Proteins Soluble in Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Tribet, Christophe; Audebert, Roland; Popot, Jean-Luc

    1996-12-01

    Amphipols are a new class of surfactants that make it possible to handle membrane proteins in detergent-free aqueous solution as though they were soluble proteins. The strongly hydrophilic backbone of these polymers is grafted with hydrophobic chains, making them amphiphilic. Amphipols are able to stabilize in aqueous solution under their native state four well-characterized integral membrane proteins: (i) bacteriorhodopsin, (ii) a bacterial photosynthetic reaction center, (iii) cytochrome b6f, and (iv) matrix porin.

  15. Tuning of thermally induced sol-to-gel transitions of moderately concentrated aqueous solutions of doubly thermosensitive hydrophilic diblock copolymers poly(methoxytri(ethylene glycol) acrylate)-b-poly(ethoxydi(ethylene glycol) acrylate-co-acrylic acid).

    PubMed

    Jin, Naixiong; Zhang, Hao; Jin, Shi; Dadmun, Mark D; Zhao, Bin

    2012-03-15

    We report in this article a method to tune the sol-to-gel transitions of moderately concentrated aqueous solutions of doubly thermosensitive hydrophilic diblock copolymers that consist of two blocks exhibiting distinct lower critical solution temperatures (LCSTs) in water. A small amount of weak acid groups is statistically incorporated into the lower LCST block so that its LCST can be tuned by varying solution pH. Well-defined diblock copolymers, poly(methoxytri(ethylene glycol) acrylate)-b-poly(ethoxydi(ethylene glycol) acrylate-co-acrylic acid) (PTEGMA-b-P(DEGEA-co-AA)), were prepared by reversible addition-fragmentation chain transfer polymerization and postpolymerization modification. PTEGMA and PDEGEA are thermosensitive water-soluble polymers with LCSTs of 58 and 9 °C, respectively, in water. A 25 wt % aqueous solution of PTEGMA-b-P(DEGEA-co-AA) with a molar ratio of DEGEA to AA units of 100:5.2 at pH = 3.24 underwent multiple phase transitions upon heating, from a clear, free-flowing liquid (<15 °C) to a clear, free-standing gel (15-46 °C) to a clear, free-flowing hot liquid (47-56 °C), and a cloudy mixture (≥57 °C). With the increase of pH, the sol-to-gel transition temperature (T(sol-gel)) shifted to higher values, while the gel-to-sol transition (T(gel-sol)) and the clouding temperature (T(clouding)) of the sample remained essentially the same. These transitions and the tunability of T(sol-gel) originated from the thermosensitive properties of two blocks of the diblock copolymer and the pH dependence of the LCST of P(DEGEA-co-AA), which were confirmed by dynamic light scattering and differential scanning calorimetry studies. Using the vial inversion test method, we mapped out the C-shaped sol-gel phase diagrams of the diblock copolymer in aqueous buffers in the moderate concentration range at three different pH values (3.24, 5.58, and 5.82, all measured at ~0 °C). While the upper temperature boundaries overlapped, the lower temperature boundary

  16. Extracting alcohols from aqueous solutions. [USDOE patent application

    DOEpatents

    Compere, A.L.; Googin, J.M.; Griffith, W.L.

    1981-12-02

    The objective is to provide an efficient process for extracting alcohols in aqueous solutions into hydrocarbon fuel mixtures, such as gasoline, diesel fuel and fuel oil. This is done by contacting an aqueous fermentation liquor with a hydrocarbon or hydrocarbon mixture containing carbon compounds having 5-18 carbon atoms, which may include gasoline, diesel fuel or fuel oil. The hydrocarbon-aqueous alcohol solution is then mixed with one or more of a group of polyoxyalkylene polymers to extract the alcohol into the hydrocarbon fuel-polyoxyalkylene polymer mixture.

  17. Effects of radical scavengers on aqueous solutions exposed to heavy-ion irradiation using the liquid microjet technique

    NASA Astrophysics Data System (ADS)

    Nomura, Shinji; Tsuchida, Hidetsugu; Furuya, Ryousuke; Miyahara, Kento; Majima, Takuya; Itoh, Akio

    2015-12-01

    The effects of the radical scavenger ascorbic acid on water radiolysis are studied by fast heavy-ion irradiation of aqueous solutions of ascorbic acid, using the liquid microjet technique under vacuum. To understand the reaction mechanisms of hydroxyl radicals in aqueous solutions, we directly measure secondary ions emitted from solutions with different ascorbic acid concentrations. The yield of hydronium secondary ions is strongly influenced by the reaction between ascorbic acid and hydroxyl radicals. From analysis using a simple model considering chemical equilibria, we determine that the upper concentration limit of ascorbic acid with a radical scavenger effect is approximately 70 μM.

  18. Process for the recovery of strontium from acid solutions

    DOEpatents

    Horwitz, E. Philip; Dietz, Mark L.

    1992-01-01

    The invention is a process for selectively extracting strontium and technetium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant is a macrocyclic polyether in a diluent which is insoluble in water, but which will itself dissolve a small amount of water. The process will extract strontium and technetium values from nitric acid solutions which are up to 6 molar in nitric acid.

  19. Process for the recovery of strontium from acid solutions

    DOEpatents

    Horwitz, E.P.; Dietz, M.L.

    1992-03-31

    The invention is a process for selectively extracting strontium and technetium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant is a macrocyclic polyether in a diluent which is insoluble in water, but which will itself dissolve a small amount of water. The process will extract strontium and technetium values from nitric acid solutions which are up to 6 molar in nitric acid. 5 figs.

  20. Process for the recovery of strontium from acid solutions

    SciTech Connect

    Horwitz, E.P.; Dietz, M.L.

    1990-12-31

    The invention is a process for selectively extracting strontium and technetium values from aqueous nitric acid waste solutions containing these and other fission product values. The extractant is a macrocyclic polyether in a diluent which is insoluble in water, but which will itself dissolve a small amount of water. The process will extract strontium and technetium values from nitric acid solutions which are up to 6 molar in nitric acid.

  1. 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.

  2. 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.

  3. Kinetics of photoinduced electron transfer between DNA bases and triplet 3,3',4,4'-benzophenone tetracarboxylic acid in aqueous solution of different pH's: proton-coupled electron transfer?

    PubMed

    Nguyen, Truong X; Kattnig, Daniel; Mansha, Asim; Grampp, Günter; Yurkovskaya, Alexandra V; Lukzen, Nikita

    2012-11-01

    The kinetics of triplet state quenching of 3,3',4,4'-benzophenone tetracarboxylic acid (BPTC) by DNA bases adenine, adenosine, thymine, and thymidine has been investigated in aqueous solution using time-resolved laser flash photolysis. The observation of the BPTC ketyl radical anion at λ(max) = 630 nm indicates that one electron transfer is involved in the quenching reactions. The pH-dependence of the quenching rate constants is measured in detail. As a result, the chemical reactivity of the reactants is assigned. The bimolecular rate constants of the quenching reactions between triplet BPTC and adenine, adenosine, thymine, and thymidine are k(q) = 2.3 × 10(9) (4.7 < pH < 9.9), k(q) = 4.0 × 10(9) (3.5 < pH < 4.7), k(q) = 1.0 × 10(9) (4.7 < pH < 9.9), and k(q) = 4.0 × 10(8) M(-1) s(-1) (4.7 < pH < 9.8), respectively. Moreover, it reveals that in strong basic medium (pH = 12.0) a keto-enol tautomerism of thymine inhibits its reaction with triplet BPTC. Such a behavior is not possible for thymidine because of its deoxyribose group. In addition, the pH-dependence of the apparent electrochemical standard potential of thymine in aqueous solution was investigated by cyclic voltammetry. The ΔE/ΔpH ≈ -59 mV/pH result is characteristic of proton-coupled electron transfer. This behavior, together with the kinetic analysis, leads to the conclusion that the quenching reactions between triplet BPTC and thymine involve one proton-coupled electron transfer. PMID:23038981

  4. 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

  5. Scavenging of SO 4- radical anions by mono- and dicarboxylic acids in the Mn(II)-catalyzed S(IV) oxidation in aqueous solution

    NASA Astrophysics Data System (ADS)

    Grgić, Irena; Podkrajšek, Boštjan; Barzaghi, Paolo; Herrmann, Hartmut

    The rate constants for reactions of the SO 4- radical anion with some low molecular weight monocarboxylic acids (MCAs) and dicarboxylic acids (DCAs) and their anions using the laser flash photolysis-long path laser absorption (LFP-LPLA) technique were determined. The present study contains the first measured rate constants for SO 4- reactions with glycolic, lactic, malic and malonic acid. The rate constants are found to be in the range from 10 5 to 10 7 M -1 s -1, with the lower values found for acids and higher values for their respective anions. In addition, the rate constants for scavenging of SO 4- by all investigated organics in the Mn(II)-catalyzed S(IV) autoxidation at pH 4.5 and T=25 °C were determined by means of the reversed rate method. The comparison between these rate constants and the rate constants obtained by direct measurements confirms the proposed inhibiting mechanism for the Mn(II)-catalyzed S(IV) autoxidation in the presence of monocarboxylic acids. In the case of formic acid, which causes the highest inhibition, this mechanism can explain the second part of kinetic traces (i.e. after the induction period). Surprisingly, although dicarboxylic acids are reactive toward SO 4- they do not contribute to the inhibition of S(IV) oxidation (especially malic and malonic acids).

  6. 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

  7. Interactions of Cl- and OH radical in aqueous solution.

    PubMed

    Valiev, Marat; D'Auria, Raffaella; Tobias, Douglas J; Garrett, Bruce C

    2009-08-01

    There is a considerable controversy surrounding the nature of the Cl-/OH complex in aqueous solution, which appears as a byproduct of the irradiation of salt solutions in nuclear reactor operation, radioactive waste storage, medicine, and environmental problems. In this work, we report results of combined quantum mechanical molecular mechanics calculations of ground-state free-energy surfaces and absorption spectrum through the CCSDT level of theory that are consistent with the experimental data and suggest that hemibonded HOCl- species may indeed exist in bulk aqueous solution. PMID:19591498

  8. SEPARATION OF TECHNETIUM FROM AQUEOUS SOLUTIONS BY COPRECIPITATION WITH MAGNETITE

    DOEpatents

    Rimshaw, S.J.

    1961-10-24

    A method of separating technetium in the 4+ oxidation state from an aqueous basic solution containing products of uranium fission is described. The method consists of contacting the solution with finely divided magnetite and recovering a technetium-bearing precipitate. (AEC)

  9. Antiscalant properties of Spergularia rubra and Parietaria officinalis aqueous solutions

    NASA Astrophysics Data System (ADS)

    Cheap-Charpentier, Hélène; Gelus, Dominique; Pécoul, Nathalie; Perrot, Hubert; Lédion, Jean; Horner, Olivier; Sadoun, Jonathan; Cachet, Xavier; Litaudon, Marc; Roussi, Fanny

    2016-06-01

    The formation of calcium carbonate in water has important implications in industry. Chemical antiscalant is usually used to control scale depositions. Plant extracts have been recently used as new green antiscalant agents, as they can be easily prepared and are environmentally friendly. In this study, stock aqueous solutions of Spergularia rubra and Parietaria officinalis, two plants used in traditional medicine to treat or prevent urolithiasis, were obtained by infusion. The antiscaling properties of these extracts towards CaCO3 formation were tested by using chronoamperometry and Fast Controlled Precipitation methods. The aqueous solution of S. rubra was further fractionated to isolate compounds of lower polarity. Their efficiency towards CaCO3 precipitation was characterized by Fast Controlled Precipitation method. The inhibiting efficiency of this fractionated solution was greater than that of the stock aqueous solution.

  10. Enthalpies and constants of dissociation of several neutral and cationic acids in aqueous and methanol/water solutions at various temperatures.

    PubMed

    Shoghi, Elham; Romero, Lilian; Reta, Mario; Ràfols, Clara; Bosch, Elisabeth

    2009-05-01

    The acidic dissociation enthalpies and constants of anilinium, protonated tris(hydroxymethyl)aminomethane (HTris(+)), benzoic and acetic acids, have been determined at several temperatures in pure water and in methanol/water mixtures by potentiometry and by isothermal titration microcalorimetry (ITC). The pK(a) values determined by both techniques are in accordance when the dissociation process involves large amounts of heat. However, for the neutral acids the ITC technique gave slightly lower pK(a) values than those from potentiometry at the highest temperatures studied due to the small amounts of heat involved in the acidic dissociation. The dissociation enthalpies have been determined directly by calorimetry and the obtained values slightly decrease with the increase of temperature. Therefore, only a rough estimation of the dissociation enthalpies can be obtained from potentiometric pK(a) by means of the Van't Hoff approach.

  11. Enthalpies and constants of dissociation of several neutral and cationic acids in aqueous and methanol/water solutions at various temperatures.

    PubMed

    Shoghi, Elham; Romero, Lilian; Reta, Mario; Ràfols, Clara; Bosch, Elisabeth

    2009-05-01

    The acidic dissociation enthalpies and constants of anilinium, protonated tris(hydroxymethyl)aminomethane (HTris(+)), benzoic and acetic acids, have been determined at several temperatures in pure water and in methanol/water mixtures by potentiometry and by isothermal titration microcalorimetry (ITC). The pK(a) values determined by both techniques are in accordance when the dissociation process involves large amounts of heat. However, for the neutral acids the ITC technique gave slightly lower pK(a) values than those from potentiometry at the highest temperatures studied due to the small amounts of heat involved in the acidic dissociation. The dissociation enthalpies have been determined directly by calorimetry and the obtained values slightly decrease with the increase of temperature. Therefore, only a rough estimation of the dissociation enthalpies can be obtained from potentiometric pK(a) by means of the Van't Hoff approach. PMID:19261425

  12. Experimental determination of the temperature dependence of water activities for a selection of aqueous organic solutions

    NASA Astrophysics Data System (ADS)

    Ganbavale, G.; Marcolli, C.; Krieger, U. K.; Zuend, A.; Stratmann, G.; Peter, T.

    2014-09-01

    This work presents experimental data of the temperature dependence of water activity in aqueous organic solutions relevant for tropospheric conditions (200-273 K). Water activity (aw) at low temperatures (T) is a crucial parameter for predicting homogeneous ice nucleation. We investigated temperature-dependent water activities, ice freezing and melting temperatures of solutions, and vapour pressures of a selection of atmospherically relevant aqueous organic systems. To measure aw over a wide composition range and with a focus on low temperatures, we use various aw measurement techniques and instruments: a dew point water activity meter, an electrodynamic balance (EDB), differential scanning calorimetry (DSC), and a setup to measure the total gas phase pressure at equilibrium over aqueous solutions. Water activity measurements were performed for aqueous multicomponent and multifunctional organic mixtures containing the functional groups typically found in atmospheric organic aerosols, such as hydroxyl, carboxyl, ketone, ether, ester, and aromatic groups. The aqueous organic systems studied at several fixed compositions over a considerable temperature range differ significantly in their temperature dependence. Aqueous organic systems of 1,4-butanediol and methoxyacetic acid show a moderate decrease in aw with decreasing temperature. The aqueous M5 system (a multicomponent system containing five different dicarboxylic acids) and aqueous 2-(2-ethoxyethoxy)ethanol solutions both show a strong increase of water activity with decreasing temperature at high solute concentrations for T < 270 K and T < 260 K, respectively. These measurements show that the temperature trend of aw can be reversed at low temperatures and that linear extrapolations of high-temperature data may lead to erroneous predictions. To avoid this, experimentally determined aw at low temperature are needed to improve thermodynamic models towards lower temperatures and for improved predictions of the ice

  13. Experimental determination of the temperature dependence of water activities for a selection of aqueous organic solutions

    NASA Astrophysics Data System (ADS)

    Ganbavale, G.; Marcolli, C.; Krieger, U. K.; Zuend, A.; Stratmann, G.; Peter, T.

    2014-05-01

    This work presents experimental data of the temperature dependence of water activity in aqueous organic solutions relevant for tropospheric conditions (200-273 K). Water activity (aw) at low temperatures (T) is a crucial parameter for predicting homogeneous ice nucleation. We investigated temperature dependent water activities, ice freezing and melting temperatures of solutions, and vapour pressures of a selection of atmospherically relevant aqueous organic systems. To measure aw over a wide composition range and with a focus on low temperatures, we use various aw measurement techniques and instruments: a dew point water activity meter, an electrodynamic balance (EDB), differential scanning calorimetry (DSC), and a setup to measure the total gas phase pressure at equilibrium over aqueous solutions. Water activity measurements were performed for aqueous multicomponent and multifunctional organic mixtures containing the functional groups typically found in atmospheric organic aerosols, such as hydroxyl, carboxyl, ketone, ether, ester, and aromatic groups. The aqueous organic systems studied at several fixed compositions over a considerable temperature range differ significantly in their temperature dependence. Aqueous organic systems of 1,4-butanediol and methoxyacetic acid show a moderate decrease in aw with decreasing temperature. The aqueous M5 system (a multicomponent system containing five different dicarboxylic acids) and aqueous 2-(2-ethoxyethoxy)ethanol solutions both show a strong increase of water activity with decreasing temperature at high solute concentrations for T<270 K and T<260 K, respectively. These measurements show that the temperature trend of aw can be reversed at low temperatures and that linear extrapolations of high temperature data may lead to erroneous predictions. To avoid this, experimentally determined aw at low temperature are needed to improve thermodynamic models towards lower temperatures and for improved predictions of the ice

  14. Improved method for extracting lanthanides and actinides from acid solutions

    DOEpatents

    Horwitz, E.P.; Kalina, D.G.; Kaplan, L.; Mason, G.W.

    1983-07-26

    A process for the recovery of actinide and lanthanide values from aqueous acidic solutions uses a new series of neutral bi-functional extractants, the alkyl(phenyl)-N,N-dialkylcarbamoylmethylphosphine oxides. The process is suitable for the separation of actinide and lanthanide values from fission product values found together in high-level nuclear reprocessing waste solutions.

  15. Actinide phosphonate complexes in aqueous solutions

    SciTech Connect

    Nash, K.L.

    1993-10-01

    Complexes formed by actinides with carboxylic acids, polycarboxylic acids, and aminopolycarboxylic acids play a central role in both the basic and process chemistry of the actinides. Recent studies of f-element complexes with phosphonic acid ligands indicate that new ligands incorporating doubly ionizable phosphonate groups (-PO{sub 3}H{sub 2}) have many properties which are unique chemically, and promise more efficient separation processes for waste cleanup and environmental restoration. Simple diphosphonate ligands form much stronger complexes than isostructural carboxylates, often exhibiting higher solubility as well. In this manuscript recent studies of the thermodynamics and kinetics of f-element complexation by 1,1 and 1,2 diphosphonic acid ligands are described.

  16. Determination of hydrogen ion by ion chromatography (IC) with sulfonated cation-exchange resin as the stationary phase and aqueous EDTA (ethylenediamine-N,N,N',N'-tetraacetic acid) solution as the mobile phase.

    PubMed

    Hu, W; Iles, A; Hasebe, K; Matsukami, H; Cao, S; Tanaka, K

    2001-05-01

    An ion chromatographic (IC) method has been developed for determination of hydrogen ion (H+). It is based on the use of sulfonated cation-exchange resin as stationary phase, aqueous ethylenediamine-N,N,N',N'-tetraacetic acid (dipotassium salt, EDTA-2K, written as K2H2Y) solution as mobile phase, and conductivity for detection. H+ was separated mainly by cation-exchange, but its elution was accelerated by the presence of EDTA. The order of elution for the model cations was H+ > Li+ > Na+ > NH4+ > Ca2+ > > Mg2+. A sharp and highly symmetrical peak was obtained for H+ and this was attributed to the capacity of H2Y2(2-) to receive and bind H+. H+ was detected conductiometrically and detector response (reduction in conductivity as a result of H+ +H2Y2- --> H3Y-) was linearly proportional to the concentration of H+ in the sample. The detection limit for H+ with this IC system was better than 4.7 micromol L(-1). A significant advantage of this method was the ability to separate and determine, in one step, H+ and other cations. The successful determination of H+ and other cation species in real acid-rain samples demonstrated the usefulness of this method.

  17. EMERGING TECHNOLOGY BULLETIN: REMOVAL OF PHENOL FROM AQUEOUS SOLUTIONS USING HIGH ENERGY ELECTRON BEAM IRRADIATION

    EPA Science Inventory

    Irradiation of aqueous solutions with high-energy electrons results in the formation of the aqueous electron, hydrogen radical, H-, and the hydroxyl radical, OH-. These reactive transient species initiate chemical reactions capable of destroying organic compounds in aqueous solut...

  18. Chemical repair of base lesions, AP-sites, and strand breaks on plasmid DNA in dilute aqueous solution by ascorbic acid

    SciTech Connect

    Hata, Kuniki; Urushibara, Ayumi; Yamashita, Shinichi; Shikazono, Naoya; Yokoya, Akinari; Katsumura, Yosuke

    2013-05-03

    Highlights: •We report a novel mechanism of radiation protection of DNA by chemical activity of ascorbic acid. •The “chemical repair” of DNA damage was revealed using biochemical assay and chemical kinetics analysis. •We found that ascorbic acid significantly repairs precursors of nucleobase lesions and abasic sites. •However, ascorbic acid seldom repairs precursors of DNA-strand breaks. -- Abstract: We quantified the damage yields produced in plasmid DNA by γ-irradiation in the presence of low concentrations (10–100 μM) of ascorbic acid, which is a major antioxidant in living systems, to clarify whether it chemically repairs radiation damage in DNA. The yield of DNA single strand breaks induced by irradiation was analyzed with agarose gel electrophoresis as conformational changes in closed circular plasmids. Base lesions and abasic sites were also observed as additional conformational changes by treating irradiated samples with glycosylase proteins. By comparing the suppression efficiencies to the induction of each DNA lesion, in addition to scavenging of the OH radicals derived from water radiolysis, it was found that ascorbic acid promotes the chemical repair of precursors of AP-sites and base lesions more effectively than those of single strand breaks. We estimated the efficiency of the chemical repair of each lesion using a kinetic model. Approximately 50–60% of base lesions and AP-sites were repaired by 10 μM ascorbic acid, although strand breaks were largely unrepaired by ascorbic acid at low concentrations. The methods in this study will provide a route to understanding the mechanistic aspects of antioxidant activity in living systems.

  19. The anomaly of oxygen diffusion in aqueous xanthan solutions.

    PubMed

    Ho, C S; Ju, L K; Baddour, R F

    1988-06-20

    A membrane-covered polarographic oxygen electrode was used to measure oxygen diffusion coefficients in aqueous polyelectrolyte solutions of xanthan gum, sodium alginate, and sodium carboxymethylcellulose (CMC). In sodium alginate solutions, dilute xanthan solutions, and solutions containing more than 0.3 wt % CMC, oxygen diffusion coefficients decrease with increasing polymer concentrations. Interestingly, in dilute CMC solutions and concentrate xanthan solutions containing more than 0.5 wt % xanthan gum, oxygen diffusion coefficients increase with increasing polymer concentrations, and values exceeding that in pure water are generally observed.

  20. Study of phosphate removal from aqueous solution by zinc oxide.

    PubMed

    Luo, Zhen; Zhu, Suiyi; Liu, Zhongmou; Liu, Jiancong; Huo, Mingxin; Yang, Wu

    2015-09-01

    Zinc oxide (ZnO) was synthesized and used to investigate the mechanism of phosphate removal from aqueous solution. ZnO particles were characterized by X-ray diffraction, scanning electron microscope and Fourier transform infrared spectroscopy before and after adsorption. Batch experiments were carried out to investigate the kinetics, isotherms, effects of initial pH and co-existing anions. The adsorption process was rapid and equilibrium was almost reached within 150 min. The adsorption kinetics were described well by a pseudo-second-order equation, and the maximum phosphate adsorption capacity was 163.4 mg/g at 298 K and pH ∼6.2±0.1. Thermodynamic analysis indicated the phosphate adsorption onto ZnO was endothermic and spontaneous. The point of zero charge of ZnO was around 8.4 according to the pH-drift method. Phosphate adsorption capacity reduced with the increasing initial solution pH values. The ligand exchange and Lewis acid-base interaction dominated the adsorption process in the lower and the higher pH range, respectively. Nitrate, sulfate and chloride ions had a negligible effect on phosphate removal, while carbonate displayed significant inhibition behavior.