Sample records for carbonic acid solution

  1. Reduction of Plutonium in Acidic Solutions by Mesoporous Carbons

    DOE PAGES

    Parsons-Moss, Tashi; Jones, Stephen; Wang, Jinxiu; ...

    2015-12-19

    Batch contact experiments with several porous carbon materials showed that carbon solids spontaneously reduce the oxidation state of plutonium in 1-1.5 M acid solutions, without significant adsorption. The final oxidation state and rate of Pu reduction varies with the solution matrix, and also depends on the surface chemistry and surface area of the carbon. It was demonstrated that acidic Pu(VI) solutions can be reduced to Pu(III) by passing through a column of porous carbon particles, offering an easy alternative to electrolysis with a potentiostat.

  2. Electrochemical formation of hydroxide for enhancing carbon dioxide and acid gas uptake by a solution

    DOEpatents

    Rau, Gregory Hudson

    2014-07-01

    A system for forming metal hydroxide from a metal carbonate utilizes a water electrolysis cell having an acid-producing anode and a hydroxyl-producing cathode immersed in a water solution of sufficient ionic content to allow an electric current to pass between the hydroxyl-producing cathode and the acid-producing anode. A metal carbonate is placed in close proximity to the acid-producing anode. A direct current electrical voltage is provided across the acid-producing anode and the hydroxyl-producing cathode sufficient to generate acid at the acid-producing anode and hydroxyl ions at the hydroxyl-producing cathode. The acid dissolves at least part of the metal carbonate into metal and carbonate ions allowing the metal ions to travel toward the hydroxyl-producing cathode and to combine with the hydroxyl ions to form the metal hydroxide. The carbonate ions travel toward the acid-producing anode and form carbonic acid and/or water and carbon dioxide.

  3. Electrochemical formation of hydroxide for enhancing carbon dioxide and acid gas uptake by a solution

    DOEpatents

    Rau, Gregory Hudson [Castro Valley, CA

    2012-05-15

    A system is described for forming metal hydroxide from a metal carbonate utilizing a water electrolysis cell having an acid-producing anode and a hydroxyl-producing cathode immersed in a water solution of sufficient ionic content to allow an electric current to pass between the hydroxyl-producing cathode and the acid-producing anode. A metal carbonate, in particular water-insoluble calcium carbonate or magnesium carbonate, is placed in close proximity to the acid-producing anode. A direct current electrical voltage is provided across the acid-producing anode and the hydroxyl-producing cathode sufficient to generate acid at the acid-producing anode and hydroxyl ions at the hydroxyl-producing cathode. The acid dissolves at least part of the metal carbonate into metal and carbonate ions allowing the metal ions to travel toward the hydroxyl-producing cathode and to combine with the hydroxyl ions to form the metal hydroxide. The carbonate ions travel toward the acid-producing anode and form carbonic acid and/or water and carbon dioxide. Among other uses, the metal hydroxide formed can be employed to absorb acid gases such as carbon dioxide from a gas mixture. The invention can also generate hydrogen and oxidative gases such as oxygen or chlorine.

  4. Kinetics of dodecanoic acid adsorption from caustic solution by activated carbon.

    PubMed

    Pendleton, Phillip; Wu, Sophie Hua

    2003-10-15

    This study examines the influences of adsorbent porosity and surface chemistry and of carbon dosage on dodecanoic acid adsorption kinetics from aqueous and 2 M NaOH solutions as batch adsorption processes. Both adsorbents are steam-activated carbons prepared from either coconut or coal precursors. Prior to use the adsorbents were washed in deionized water or 2 M NaOH. Mass transfer coefficients and effective overall diffusion coefficients indicate a minor contribution from adsorbent porosity. In contrast, high surface oxygen content impedes transport to and into the adsorbent structure. Carbon dosage shows a proportional increase in transport coefficients with increasing mass; these coefficients are constant when normalized per unit mass. Neither water nor NaOH treatment of the adsorbents has a significant influence on dodecanoic acid adsorption kinetics. Molecular and Knudsen diffusion coefficients are defined to demonstrate that the overall effective diffusion coefficient values and the diffusion process are controlled by surface diffusion.

  5. 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.

  6. Pd-loaded carbon felt as the cathode for selective dechlorination of 2,4-dichlorophenoxyacetic acid in aqueous solution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tsyganok, A.I.; Yamanaka, Ichiro; Otsuka, Kiyoshi

    1998-11-01

    Electrocatalytic reductive dehalogenation of 2,4-dichlorophenoxyacetic acid (2,4-D) to phenoxyacetic acid in aqueous solution containing MeOH, trifluoroacetic acid, and tetraalkylammonium salt was studied. A Teflon-made two-compartment flow-through cell with a permeable carbon felt cathode and a platinum foil anode was employed. Several noble metals were tested as electrocatalysts. Palladium-loaded carbon felt was found to be the most suitable significantly enhanced its electrocatalytic activity toward 2,4-D dechlorination. The reaction was hypothesized to proceed at carbon-palladium interface areas through 4-chlorine cleavage to form 2-chlorophenoxyacetic acid as the main reaction intermediate.

  7. Dissolution of spent nuclear fuel in carbonate-peroxide solution

    NASA Astrophysics Data System (ADS)

    Soderquist, Chuck; Hanson, Brady

    2010-01-01

    This study shows that spent UO2 fuel can be completely dissolved in a room temperature carbonate-peroxide solution apparently without attacking the metallic Mo-Tc-Ru-Rh-Pd fission product phase. In parallel tests, identical samples of spent nuclear fuel were dissolved in nitric acid and in an ammonium carbonate, hydrogen peroxide solution. The resulting solutions were analyzed for strontium-90, technetium-99, cesium-137, europium-154, plutonium, and americium-241. The results were identical for all analytes except technetium, where the carbonate-peroxide dissolution had only about 25% of the technetium that the nitric acid dissolution had.

  8. Corrosion control of carbon steel using inhibitor of banana peel extract in acid diluted solutions

    NASA Astrophysics Data System (ADS)

    Komalasari; Utami, S. P.; Fermi, M. I.; Aziz, Y.; Irianti, R. S.

    2018-04-01

    Issues of corrosion happened in pipes, it was used as fluid transportation in the chemical industry. Corrosion cannot be preventing, however it could be controlled or blocked. Inhibitor addition is one of the method to control the corrosion inside the pipe. Corrosion inhibitors consisted of inorganic and organic compound inhibitors. Organic inhibitor is composed from synthetic and natural material. This study focused to evaluate the inhibition’s efficiency from banana peel to carbon steel in different concentration of inhibitor and immersing time in acid solution variation. The research employed inhibitor concentration of 0 gram/liter, 2 gram/liter, 4 gram/liter and 6 gram/liter, immersed time of carbon steel for 2, 4, 6, 8 and 10 hours. It was immersed in chloride acid solution of 0.5 M and 1.5 M. Carbon Steel AISI 4041 was used as specimen steel. Results were analyzed using corrosion rate evaluation for each specimens and inhibitor efficiencies determination. It was found that the specimen without inhibitor yielded fast corrosion rate in long immersing time and high concentration of HCl. However, the specimens with inhibitor gave lowest corrosion rate which was 78.59% for 6 gram/litre and 10 hours in 0.5 M HCl.

  9. Dibutyl Phosphoric Acid Solubility in High-Acid, Uranium-Bearing Solutions at SRS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pierce, R.A.

    1998-10-02

    The Savannah River Site has enriched uranium (EU) solution which has been stored for almost 10 years since being purified in the second uranium cycle of the H area solvent extraction process. The concentrations in solution are approximately 6 g/L U and about 0.1 M nitric acid. Residual tributylphosphate in the solutions has slowly hydrolyzed to form dibutyl phosphoric acid (HDBP) at concentrations averaging 50 mg/L. Uranium is known to form compounds with the dibutylphosphate ion (DBP) which have limited solubility. The potential to form uranium-DBP solids raises a nuclear criticality safety issue. Prior SRTC tests (WSRC-TR-98-00188) showed that U-DBPmore » solids precipitate at concentrations potentially attainable during the storage of enriched uranium solutions. Furthermore, evaporation of the existing EUS solution without additional acidification could result in the precipitation of U-DBP solids if the DBP concentration in the resulting solution exceeds 110 mg/L at ambient temperature. The same potential exists for evaporation of unwashed 1CU solutions. As a follow-up to the earlier studies, SRTC studied the solubility limits for solutions containing acid concentrations above 0.5M HNO3. The data obtained in these tests reveals a shift to higher levels of DBP solubility above 0.5M HNO3 for both 6 g/L and 12 g/L uranium solutions. Analysis of U-DBP solids from the tests identified a mixture of different molecular structures for the solids created. The analysis distinguished UO2(DBP)2 as the dominant compound present at low acid concentrations. As the acid concentration increases, the crystalline UO2(DBP)2 shows molecular substitutions and an increase in amorphous content. Further analysis by methods not available at SRS will be needed to better identify the specific compounds present. This data indicates that acidification prior to evaporation can be used to increase the margin of safety for the storage of the EUS solutions. Subsequent experimentation evaluated

  10. Adsorption of benzene and toluene from aqueous solutions onto activated carbon and its acid and heat treated forms: influence of surface chemistry on adsorption.

    PubMed

    Wibowo, N; Setyadhi, L; Wibowo, D; Setiawan, J; Ismadji, S

    2007-07-19

    The influence of surface chemistry and solution pH on the adsorption of benzene and toluene on activated carbon and its acid and heat treated forms were studied. A commercial coal-based activated carbon F-400 was chosen as carbon parent. The carbon samples were obtained by modification of F-400 by means of chemical treatment with HNO3 and thermal treatment under nitrogen flow. The treatment with nitric acid caused the introduction of a significant number of oxygenated acidic surface groups onto the carbon surface, while the heat treatment increases the basicity of carbon. The pore characteristics were not significantly changed after these modifications. The dispersive interactions are the most important factor in this adsorption process. Activated carbon with low oxygenated acidic surface groups (F-400Tox) has the best adsorption capacity.

  11. Characterization of the International Humic Substances Society standard and reference fulvic and humic acids by solution state carbon-13 (13C) and hydrogen-1 (1H) nuclear magnetic resonance spectrometry

    USGS Publications Warehouse

    Thorn, Kevin A.; Folan, Daniel W.; MacCarthy, Patrick

    1989-01-01

    Standard and reference samples of the International Humic Substances Society have been characterized by solution state carbon-13 and hydrogen-1 nuclear magnetic resonance (NMR) spectrometry. Samples included the Suwannee River, soil, and peat standard fulvic and humic acids, the Leonardite standard humic acid, the Nordic aquatic reference fulvic and humic acids, and the Summit Hill soil reference humic acid. Aqueous-solution carbon-13 NMR analyses included the measurement of spin-lattice relaxation times, measurement of nuclear Overhauser enhancement factors, measurement of quantitative carbon distributions, recording of attached proton test spectra, and recording of spectra under nonquantitative conditions. Distortionless enhancement by polarization transfer carbon-13 NMR spectra also were recorded on the Suwannee River fulvic acid in deuterated dimethyl sulfoxide. Hydrogen-1 NMR spectra were recorded on sodium salts of the samples in deuterium oxide. The carbon aromaticities of the samples ranged from 0.24 for the Suwannee River fulvic acid to 0.58 for the Leonardite humic acid.

  12. Acid sorption regeneration process using carbon dioxide

    DOEpatents

    King, C. Judson; Husson, Scott M.

    2001-01-01

    Carboxylic acids are sorbed from aqueous feedstocks onto a solid adsorbent in the presence of carbon dioxide under pressure. The acids are freed from the sorbent phase by a suitable regeneration method, one of which is treating them with an organic alkylamine solution thus forming an alkylamine-carboxylic acid complex which thermally decomposes to the desired carboxylic acid and the alkylamine.

  13. Methods of pretreating comminuted cellulosic material with carbonate-containing solutions

    DOEpatents

    Francis, Raymond

    2012-11-06

    Methods of pretreating comminuted cellulosic material with an acidic solution and then a carbonate-containing solution to produce a pretreated cellulosic material are provided. The pretreated material may then be further treated in a pulping process, for example, a soda-anthraquinone pulping process, to produce a cellulose pulp. The pretreatment solutions may be extracted from the pretreated cellulose material and selectively re-used, for example, with acid or alkali addition, for the pretreatment solutions. The resulting cellulose pulp is characterized by having reduced lignin content and increased yield compared to prior art treatment processes.

  14. Solubility of small-chain carboxylic acids in supercritical carbon dioxide

    DOE PAGES

    Sparks, Darrell L.; Estevez, L. Antonio; Hernandez, Rafael; ...

    2010-07-08

    The solubility of heptanoic acid and octanoic acid in supercritical carbon dioxide has been determined at temperatures of (313.15, 323.15, and 333.15) K over a pressure range of (8.5 to 30.0) MPa, depending upon the solute. The solubility of heptanoic acid ranged from a solute concentration of (0.08 ± 0.03) kg • m -3 (T = 323.15 K, p = 8.5 MPa) to (147 ± 0.2) kg • m -3 (T = 323.15 K, p = 20.0 MPa). The lowest octanoic acid solubility obtained was a solute concentration of (0.40 ± 0.1) kg • m -3 (T = 333.15 K,more » p = 10.0 MPa), while the highest solute concentration was (151 ± 2) kg • m -3 (T = 333.15 K, p = 26.7 MPa). In addition, solubility experiments were performed for nonanoic acid in supercritical carbon dioxide at 323.15 K and pressures of (10.0 to 30.0) MPa to add to the solubility data previously published by the authors. In general, carboxylic acid solubility increased with increasing solvent density. The results also showed that the solubility of the solutes decreased with increasing molar mass at constant supercritical-fluid density. Additionally, the efficacy of Chrastil's equation and other density-based models was evaluated for each fatty acid.« less

  15. Method for extracting lanthanides and actinides from acid solutions

    DOEpatents

    Horwitz, E. Philip; Kalina, Dale G.; Kaplan, Louis; Mason, George W.

    1985-01-01

    A process for the recovery of actinide and lanthanide values from aqueous acidic solutions with an organic extractant having the formula: ##STR1## where .phi. is phenyl, R.sup.1 is a straight or branched alkyl or alkoxyalkyl containing from 6 to 12 carbon atoms and R.sup.2 is an alkyl containing from 3 to 6 carbon atoms. 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.

  16. Interaction of solid organic acids with carbon nanotube field effect transistors

    NASA Astrophysics Data System (ADS)

    Klinke, Christian; Afzali, Ali; Avouris, Phaedon

    2006-10-01

    A series of solid organic acids were used to p-dope carbon nanotubes. The extent of doping is shown to be dependent on the pKa value of the acids. Highly fluorinated carboxylic acids and sulfonic acids are very effective in shifting the threshold voltage and making carbon nanotube field effect transistors to be more p-type devices. Weaker acids like phosphonic or hydroxamic acids had less effect. The doping of the devices was accompanied by a reduction of the hysteresis in the transfer characteristics. In-solution doping survives standard fabrication processes and renders p-doped carbon nanotube field effect transistors with good transport characteristics.

  17. Dry-spraying of ascorbic acid or acetaminophen solutions with supercritical carbon dioxide

    NASA Astrophysics Data System (ADS)

    Wubbolts, F. E.; Bruinsma, O. S. L.; van Rosmalen, G. M.

    1999-03-01

    Carbon dioxide is a very poor solvent for many organic compounds, which makes it a good anti-solvent. When a solution is sprayed into carbon dioxide vapour the anti-solvent reduces the solubility within several tens of milliseconds and the solute precipitates. Two distinct regions can be identified, below and above the mixture critical pressure. Below this critical pressure the yield remains relatively low and the process is not well controlled. Above the critical pressure small crystals are obtained of about 2 μm with a yield of 90%.

  18. Novel nitrogen doped carbon dots for corrosion inhibition of carbon steel in 1 M HCl solution

    NASA Astrophysics Data System (ADS)

    Cui, Mingjun; Ren, Siming; Zhao, Haichao; Wang, Liping; Xue, Qunji

    2018-06-01

    Nitrogen doped carbon dots (NCDs) were synthesized and used for inhibiting the corrosion of Q235 carbon steel in hydrochloric acid (HCl) solution. Inhibition effectiveness in short- and long-term immersion was examined using electrochemical measurements, weight loss and surface analysis. Results revealed the inhibition efficiency was improved significantly after adding NCDs and strongly dependent on the concentration of NCDs. SVET results showed that the sample immersed in HCl solution with NCDs showed lower anodic current density mapping than that in blank HCl solution. According to the data extracted from the Langmuir adsorption, the absorption of NCDs involved both chemisorption and physisorption.

  19. Heterogeneity of activated carbons in adsorption of aniline from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Podkościelny, P.; László, K.

    2007-08-01

    The heterogeneity of activated carbons (ACs) prepared from different precursors is investigated on the basis of adsorption isotherms of aniline from dilute aqueous solutions at various pH values. The APET carbon prepared from polyethyleneterephthalate (PET), as well as, commercial ACP carbon prepared from peat were used. Besides, to investigate the influence of carbon surface chemistry, the adsorption was studied on modified carbons based on ACP carbon. Its various oxygen surface groups were changed by both nitric acid and thermal treatments. The Dubinin-Astakhov (DA) equation and Langmuir-Freundlich (LF) one have been used to model the phenomenon of aniline adsorption from aqueous solutions on heterogeneous carbon surfaces. Adsorption-energy distribution (AED) functions have been calculated by using an algorithm based on a regularization method. Analysis of these functions for activated carbons studied provides important comparative information about their surface heterogeneity.

  20. Biosorption of formic and acetic acids from aqueous solution using activated carbon from shea butter seed shells

    NASA Astrophysics Data System (ADS)

    Adekola, Folahan A.; Oba, Ismaila A.

    2017-10-01

    The efficiency of prepared activated carbon from shea butter seed shells (SB-AC) for the adsorption of formic acid (FA) and acetic acid (AA) from aqueous solution was investigated. The effect of optimization parameters including initial concentration, agitation time, adsorbent dosage and temperature of adsorbate solution on the sorption capacity were studied. The SB-AC was characterized for the following parameters: bulk density, moisture content, ash content, pH, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The optimal conditions for the adsorption were established and the adsorption data for AA fitted Dubinin-Radushkevich (D-R) isotherm well, whereas FA followed Langmuir isotherm. The kinetic data were examined. It was found that pseudo-second-order kinetic model was found to adequately explain the sorption kinetic of AA and FA from aqueous solution. It was again found that intraparticle diffusion was found to explain the adsorption mechanism. Adsorption thermodynamic parameters were estimated and the negative values of Δ G showed that the adsorption process was feasible and spontaneous in nature, while the negative values of Δ H indicate that the adsorption process was exothermic. It is therefore established that SB-AC has good potential for the removal of AA and FA from aqueous solution. Hence, it should find application in the regular treatment of polluted water in aquaculture and fish breeding system.

  1. The adsorption of gold, palladium and platinum from acidic chloride solutions on mesoporous carbons.

    DOE PAGES

    Zalupski, Peter R.; McDowell, Rocklan; Dutech, Guy

    2014-08-05

    Studies on the adsorption characteristics of gold, palladium and platinum on mesoporous carbon (CMK-3) and sulfur-impregnated mesoporous carbon (CMK-3/S) evaluated the benefits/drawbacks of the presence of a layer of elemental sulfur inside mesoporous carbon structures. Adsorption isotherms collected for Au(III), Pd(II) and Pt(IV) on those materials suggest that sulfur does enhance the adsorption of those metal ions in mildly acidic environment (pH 3). The isotherms collected in 1 M HCl show that the benefit of sulfur disappears due to the competing influence of large concentration of hydrogen ions on the ion-exchanging mechanism of metal ions sorption on mesoporous carbon surfaces.more » The collected acid dependencies illustrate similar adsorption characteristics for CMK-3 and CMK-3/S in 1-5 M HCl concentration range. Sorption of metal ions from diluted aqueous acidic mixtures of actual leached electronic waste demonstrated the feasibility of recovery of gold from such liquors.« less

  2. Solubilities of carbon dioxide in aqueous potassium carbonate solutions mixed with physical solvents

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Park, S.B.; Lee, H.; Lee, K.H.

    1998-09-01

    The removal of acidic gases such as CO{sub 2}, H{sub 2}S, and COS from gas streams is a very important operation for petrochemical, oil refineries, ammonia manufacture, coal gasification, and natural gas purification plants. Here, the solubilities of carbon dioxide in aqueous potassium carbonate (K{sub 2}CO{sub 3}) solutions mixed with physical solvents were measured at 298.2 and 323.2 K with a CO{sub 2} partial-pressure range of 5 kPa to 2 MPa. 1,2-propanediol and propylene carbonate were selected as physical solvents. The aqueous solutions treated in this study were 5 mass% K{sub 2}CO{sub 3}-15 mass% 1,2-propanediol and propylene carbonate were selectedmore » as physical solvents. The aqueous solutions treated in this study were 5 mass% K{sub 2}CO{sub 3}-15 mass% propylene carbonate. The experimental solubility results were presented by the mole ratio of CO{sub 2} and K{sub 2}CO{sub 3} contained in the liquid mixture. The addition of 1,2-propanediol to 5 mass% K{sub 2}CO{sub 3} solution lowered the solubility of CO{sub 2} at constant temperature and pressure conditions when CO{sub 2} partial-pressure range of 5 kPa to 2 MPa. In the case of propylene carbonate the addition of propylene carbonate increased the experimental solubilities in the region of low CO{sub 2} partial pressures and decreased as the CO{sub 2} partial pressure was increased above atmospheric. The solubilities of CO{sub 2} decreased with increasing temperature in the range of 298.2 to 323.2 K.« less

  3. Improvement of the uric acid determination by the carbonate method for serum and urine

    PubMed Central

    Eichhorn, F.; Zelmanowski, S.; Lew, E.; Rutenberg, A.; Fanias, B.

    1961-01-01

    An improved colorimetric procedure for determining uric acid by the carbonate method in serum and urine is described, using a 20% sodium carbonate solution with urea. Reliable results are also obtained in high concentrations of uric acid. PMID:13726059

  4. The molecular properties of biochar carbon released in dilute acidic solution and its effects on maize seed germination.

    PubMed

    Sun, Jingling; Drosos, Marios; Mazzei, Pierluigi; Savy, Davide; Todisco, Daniele; Vinci, Giovanni; Pan, Genxing; Piccolo, Alessandro

    2017-01-15

    It is not yet clear whether the carbon released from biochar in the soil solution stimulates biological activities. Soluble fractions (AQU) from wheat and maize biochars, whose molecular content was thoroughly characterized by FTIR, 13 C and 1 H NMR, and high-resolution ESI-IT-TOF-MS, were separated in dilute acidic solution to simulate soil rhizospheric conditions and their effects evaluated on maize seeds germination activity. Elongation of maize-seeds coleoptile was significantly promoted by maize biochar AQU, whereas it was inhibited by wheat biochar AQU. Both AQU fractions contained relatively small heterocyclic nitrogen compounds, whose structures were accounted by their spectroscopic properties. Point-of-Zero-Charge (PZC) values and van Krevelen plots of identified masses of soluble components suggested that the dissolved carbon from maize biochar behaved as humic-like supramolecular material capable to adhere to seedlings and deliver bioactive molecules. These findings contribute to understand the biostimulation potential of biochars from crop biomasses when applied in agricultural production. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Titration of Monoprotic Acids with Sodium Hydroxide Contaminated by Sodium Carbonate.

    ERIC Educational Resources Information Center

    Michalowski, Tadeusz

    1988-01-01

    Discusses the effects of using carbon dioxide contaminated sodium hydroxide solution as a titrant for a solution of a weak monoprotic acid and the resulting distortion of the titration curve in comparison to one obtained when an uncontaminated titrant is used. (CW)

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2014-06-02

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

  8. Acid neutralizing processes in an alpine watershed front range, Colorado, U.S.A.-1: Buffering capacity of dissolved organic carbon in soil solutions

    USGS Publications Warehouse

    Iggy, Litaor M.; Thurman, E.M.

    1988-01-01

    Soil interstitial waters in the Green Lakes Valley, Front Range, Colorado were studied to evaluate the capacity of the soil system to buffer acid deposition. In order to determine the contribution of humic substances to the buffering capacity of a given soil, dissolved organic carbon (DOC) and pH of the soil solutions were measured. The concentration of the organic anion, Ai-, derived from DOC at sample pH and the concentration of organic anion, Ax- at the equivalence point were calculated using carboxyl contents from isolated and purified humic material from soil solutions. Subtracting Ax- from Ai- yields the contribution of humic substances to the buffering capacity (Aequiv.-). Using this method, one can evaluate the relative contribution of inorganic and organic constituents to the acid neutralizing capacity (ANC) of the soil solutions. The relative contribution of organic acids to the overall ANC was found to be extremely important in the alpine wetland (52%) and the forest-tundra ecotone (40%), and somewhat less important in the alpine tundra sites (20%). A failure to recognize the importance of organic acids in soil solutions to the ANC will result in erroneous estimates of the buffering capacity in the alpine environment of the Front Range, Colorado. ?? 1988.

  9. Efficient optical resolution of amino acid by alanine racemaze chiral analogue supported on mesoporous carbon

    NASA Astrophysics Data System (ADS)

    Jang, D.; Kim, K.; Park, D.; Kim, G.

    2012-09-01

    Optically pure D-amino acids are industrially important chiral building blocks for the synthesis of pharmaceuticals, food ingredients, and drug intermediates. Chemoenzymatic dynamic kinetic-resolution processes have recently been developed for deracemization of amino acids. S-ARCA would be a good candidate for the selective adsorption of D amino acid through the imine formation reaction. The organic phase containing S-ARCA adsorbent, TPPC or Ionic Liquid (as a phase transfer catalyst) in MC were coated on the surfaces of mesoporous carbon C-SBA-15(CMK). The aqueous solution of racemic D/L-amino acid and NaOH were added to the carbon support coated with ARCA. The D/L ratios on ARCA and in solution were determined with increasing reaction time. S-ARCA has a unique property for the selective adsorption of D- amino acid (up to 90% selcetivity) in the racemic mixture. The fixed bed reactor containing ARCA/carbon support was also adopted successfully for the selective separation of amino acid.

  10. Density and viscosity of some partially carbonated aqueous alkanolamine solutions and their blends

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Weiland, R.H.; Dingman, J.C.; Cronin, D.B.

    1998-05-01

    Very little information is available concerning the effect of acid gas loading on the physical properties of amine-treating solutions flowing through the absorption and regeneration columns used in gas processing. The densities and viscosities of partially carbonated monoethanolamine (MEA), diethanolamine (DEA), and N-methyldiethanolamine (MDEA) solutions were measured at 298 K. With increasing carbon dioxide loadings, significant increases in both density and viscosity were observed. These results were combined with literature data to produce correlations for alkanolamine solution density and viscosity as a function of amine concentration, carbon dioxide loading, and temperature. The resulting single-amine correlations were used to predict themore » densities and viscosities of DEA + MDEA and MEA + MDEA blends. Predictions are compared with data measured for these blends.« less

  11. The adsorption of pharmaceutically active compounds from aqueous solutions onto activated carbons.

    PubMed

    Rakić, Vesna; Rac, Vladislav; Krmar, Marija; Otman, Otman; Auroux, Aline

    2015-01-23

    In this study, the adsorption of pharmaceutically active compounds - salicylic acid, acetylsalicylic acid, atenolol and diclofenac-Na onto activated carbons has been studied. Three different commercial activated carbons, possessing ∼650, 900 or 1500m(2)g(-1) surface areas were used as solid adsorbents. These materials were fully characterized - their textural, surface features and points of zero charge have been determined. The adsorption was studied from aqueous solutions at 303K using batch adsorption experiments and titration microcalorimetry, which was employed in order to obtain the heats evolved as a result of adsorption. The maximal adsorption capacities of investigated solids for all target pharmaceuticals are in the range of 10(-4)molg(-1). The obtained maximal retention capacities are correlated with the textural properties of applied activated carbon. The roles of acid/base features of activated carbons and of molecular structures of adsorbate molecules have been discussed. The obtained results enabled to estimate the possibility to use the activated carbons in the removal of pharmaceuticals by adsorption. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Surface coverage and corrosion inhibition effect of Rosmarinus officinalis and zinc oxide on the electrochemical performance of low carbon steel in dilute acid solutions

    NASA Astrophysics Data System (ADS)

    Loto, Roland Tolulope

    2018-03-01

    Electrochemical analysis of the corrosion inhibition and surface protection properties of the combined admixture of Rosmarinus officinalis and zinc oxide on low carbon steel in 1 M HCl and H2SO4 solution was studied by potentiodynamic polarization, open circuit potential measurement, optical microscopy and ATR-FTIR spectroscopy. Results obtained confirmed the compound to be more effective in HCl solution, with optimal inhibition efficiencies of 93.26% in HCl and 87.7% in H2SO4 acid solutions with mixed type inhibition behavior in both acids. The compound shifts the corrosion potential values of the steel cathodically in HCl and anodically in H2SO4 signifying specific corrosion inhibition behavior without applied potential. Identified functional groups of alcohols, phenols, 1°, 2° amines, amides, carbonyls (general), esters, saturated aliphatic, carboxylic acids, ethers, aliphatic amines, alkenes, aromatics, alkyl halides and alkynes within the compound completely adsorbed onto the steel forming a protective covering. Thermodynamic calculations showed physisorption molecular interaction with the steel's surface according to Langmuir and Frumkin adsorption isotherms. Optical microscopy images of the inhibited and uninhibited steels contrast each other with steel specimens from HCl solution showing a better morphology.

  13. Carbonic acid ionization and the stability of sodium bicarbonate and carbonate ion pairs to 200 °C - A potentiometric and spectrophotometric study

    NASA Astrophysics Data System (ADS)

    Stefánsson, Andri; Bénézeth, Pascale; Schott, Jacques

    2013-11-01

    Carbonic acid ionization and sodium bicarbonate and carbonate ion pair formation constants have been experimentally determined in dilute hydrothermal solutions to 200 °C. Two experimental approaches were applied, potentiometric acid-base titrations at 10-60 °C and spectrophotometric pH measurements using the pH indicators, 2-napthol and 4-nitrophenol, at 25-200 °C. At a given temperature, the first and second ionization constants of carbonic acid (K1, K2) and the ion pair formation constants for NaHCO(aq)(K) and NaCO3-(aq)(K) were simultaneously fitted to the data. Results of this study compare well with previously determined values of K1 and K2. The NaHCO(aq) and NaCO3-(aq) ion pair formation constants vary between 25 and 200 °C having values of logK=-0.18 to 0.58 and logK=1.01 to 2.21, respectively. These ion pairs are weak at low-temperatures but become increasingly important with increasing temperature under neutral to alkaline conditions in moderately dilute to concentrated NaCl solutions, with NaCO3-(aq) predominating over CO32-(aq) in ⩾0.1 M NaCl solution at temperatures above 100 °C. The results demonstrate that NaCl cannot be considered as an inert (non-complexing) electrolyte in aqueous carbon dioxide containing solutions at elevated temperatures.

  14. Preparation of iron oxide-impregnated spherical granular activated carbon-carbon composite and its photocatalytic removal of methylene blue in the presence of oxalic acid.

    PubMed

    Kadirova, Zukhra C; Hojamberdiev, Mirabbos; Katsumata, Ken-Ichi; Isobe, Toshihiro; Matsushita, Nobuhiro; Nakajima, Akira; Sharipov, Khasan; Okada, Kiyoshi

    2014-01-01

    The spherical granular activated carbon-carbon composites (GAC-Fe) with different iron oxide contents (Fe mass% = 0.6-10) were prepared by a pore volume impregnation method. The X-ray diffraction (XRD), scanning electron microscopy (SEM), and N2-adsorption results confirm the presence of amorphous iron oxide, pyrolytic carbon, and graphitized globular carbon nanoparticles covered with amorphous carbon in the CAG-Fe. The rate of photodegradation of methylene blue (MB) in aqueous solution under UV light in the presence of oxalic acid correlates with porosity of the prepared materials. The total MB removal includes the combination of adsorption and photodegradation without the addition of H2O2. The results of total organic carbon (TOC) analysis reveal that the decolorization of MB in aqueous solution containing oxalic acid corresponds to the decomposition of organic compounds to CO2 and H2O.

  15. Adsorption of lignite-derived humic acids on coal-based mesoporous activated carbons.

    PubMed

    Lorenc-Grabowska, Ewa; Gryglewicz, Grazyna

    2005-04-15

    The adsorption by a coal-based mesoporous activated carbon of humic acids (HAs) isolated from two Polish lignites was studied. For comparison, a commercial Aldrich humic acid was also included into this study. The differences in chemical structure and functional groups of HAs were determined by elemental analysis and infrared spectroscopy DRIFT. Two activated carbons used differed in terms of mesopore volume, mesopore size distribution, and chemical properties of the surface. The kinetics of adsorption of HAs have been discussed using three kinetic models, i.e., the first-order Lagergren model, the pseudo-second-order model, and the intraparticle diffusion model. It was found that the adsorption of HAs from alkaline solution on mesoporous activated carbon proceeds according to the pseudo-second-order model. The correlation coefficients were close to 1. The intraparticle diffusion of HA molecules within the carbon particle was identified to be the rate-limiting step. Comparing the two activated carbons, the carbon with a higher volume of pores with widths of 10-50 nm showed a greater removal efficiency of HA. An increase in the Freundlich adsorption capacity with decreasing carbon content of HA was observed. Among the HAs studied, S-HA shows characteristics indicating the highest contribution of small-size fraction. The S-HA was removed by both activated carbons to the highest extent. The effect of pH solution on the adsorption of HA was examined over the range pH 5.4-12.2. It was found that the extent of adsorption decreased with decreasing pH of the solution.

  16. Adsorption of 2,4-dichlorophenoxyacetic acid and 4-chloro-2-metylphenoxyacetic acid onto activated carbons derived from various lignocellulosic materials.

    PubMed

    Doczekalska, Beata; Kuśmierek, Krzysztof; Świątkowski, Andrzej; Bartkowiak, Monika

    2018-05-04

    Adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-metylphenoxyacetic acid (MCPA) from aqueous solution onto activated carbons derived from various lignocellulosic materials including willow, miscanthus, flax, and hemp shives was investigated. The adsorption kinetic data were analyzed using two kinetic models: the pseudo-first order and pseudo-second order equations. The adsorption kinetics of both herbicides was better represented by the pseudo-second order model. The adsorption isotherms of 2,4-D and MCPA on the activated carbons were analyzed using the Freundlich and Langmuir isotherm models. The equilibrium data followed the Langmuir isotherm. The effect of pH on the adsorption was also studied. The results showed that the activated carbons prepared from the lignocellulosic materials are efficient adsorbents for the removal of 2,4-D and MCPA from aqueous solutions.

  17. Simple introduction of carboxyl head group with alkyl spacer onto multiwalled carbon nanotubes by solution plasma process

    NASA Astrophysics Data System (ADS)

    Nemoto, Shimpei; Ueno, Tomonaga; Watthanaphanit, Anyarat; Hieda, Junko; Bratescu, Maria Antoaneta; Saito, Nagahiro

    2017-09-01

    A simple method of fabricating carboxyl-terminated multiwalled carbon nanotubes (MWCNTs) with alkyl spacers was developed to improve the dispersion quality of MWCNTs in aqueous solutions using solution plasma (SP) in a 6-aminocaproic acid solution. The formation of SP in the solution led to better dispersion of MWCNTs in aqueous solutions. Fourier transform infrared spectroscopy (FT-IR) results indicate that a carboxyl group with an alkyl spacer can be introduced by SP treatment in the 6-aminocaproic acid solution. Sedimentation tests show that the SP-treated MWCNTs in the 6-aminocaproic acid solution retained their good dispersion quality in aqueous solutions of pHs 5, 6, and 9. The alkyl spacer plays an important role in the preservation of dispersion states particularly at pH 6.

  18. Influence of peracetic acid modification on the physicochemical properties of activated carbon and its performance in the ozone-catalytic oxidation of gaseous benzene

    NASA Astrophysics Data System (ADS)

    Fang, Ruimei; Huang, Haibao; Huang, Wenjun; Ji, Jian; Feng, Qiuyu; Shu, Yajie; Zhan, Yujie; Liu, Gaoyuan; Xie, Ruijie

    2017-10-01

    Coal based activated carbon (AC) was pretreated by peracetic acid solution and used for supporting Mn catalyst towards oxidation of gaseous benzene by catalytic ozonation. The as-obtained activated carbon was characterized by XPS, BET, SEM, and TG technologies. It indicates that peracetic acid solution modification not only raised the quantity of chemisorbed oxygen or water, and hydroxyl group on activated carbon material surface, but also increased the specific surface area and benzene adsorption capacity of activated carbon. Benzene could be completely removed in 300 min and CO2 selectivity reached to 61.9% over Mn/AC-modified catalyst. A possible catalytic ozonation mechanism of activated carbon which was treated by peracetic acid solution supported Mn catalyst for oxidation of benzene was proposed.

  19. Reactive solute transport in acidic streams

    USGS Publications Warehouse

    Broshears, R.E.

    1996-01-01

    Spatial and temporal profiles of Ph and concentrations of toxic metals in streams affected by acid mine drainage are the result of the interplay of physical and biogeochemical processes. This paper describes a reactive solute transport model that provides a physically and thermodynamically quantitative interpretation of these profiles. The model combines a transport module that includes advection-dispersion and transient storage with a geochemical speciation module based on MINTEQA2. Input to the model includes stream hydrologic properties derived from tracer-dilution experiments, headwater and lateral inflow concentrations analyzed in field samples, and a thermodynamic database. Simulations reproduced the general features of steady-state patterns of observed pH and concentrations of aluminum and sulfate in St. Kevin Gulch, an acid mine drainage stream near Leadville, Colorado. These patterns were altered temporarily by injection of sodium carbonate into the stream. A transient simulation reproduced the observed effects of the base injection.

  20. Method for extracting lanthanides and actinides from acid solutions by modification of purex solvent

    DOEpatents

    Horwitz, E. Philip; Kalina, Dale G.

    1986-01-01

    A process for the recovery of actinide and lanthanide values from aqueous solutions with an extraction solution containing an organic extractant having the formula: ##STR1## where .phi. is phenyl, R.sup.1 is a straight or branched alkyl or alkoxyalkyl containing from 6 to 12 carbon atoms and R.sup.2 is an alkyl containing from 3 to 6 carbon atoms and phase modifiers in a water-immiscible hydrocarbon diluent. The addition of the extractant to the Purex process extractant, tri-n-butylphosphate in normal paraffin hydrocarbon diluent, will permit the extraction of multivalent lanthanide and actinide values from 0.1 to 12.0 molar acid solutions.

  1. Development of poly(aspartic acid-co-malic acid) composites for calcium carbonate and sulphate scale inhibition.

    PubMed

    Mithil Kumar, N; Gupta, Sanjay Kumar; Jagadeesh, Dani; Kanny, K; Bux, F

    2015-01-01

    Polyaspartic acid (PSI) is suitable for the inhibition of inorganic scale deposition. To enhance its scale inhibition efficiency, PSI was modified by reacting aspartic acid with malic acid (MA) using thermal polycondensation polymerization. This reaction resulted in poly(aspartic acid-co-malic acid) (PSI-co-MA) dual polymer. The structural, chemical and thermal properties of the dual polymers were analysed by using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry and gel permeation chromatography. The effectiveness of six different molar ratios of PSI-co-MA dual polymer for calcium carbonate and calcium sulphate scale inhibition at laboratory scale batch experiments was evaluated with synthetic brine solution at selected doses of polymer at 65-70°C by the static scale test method. The performance of PSI-co-MA dual polymer for the inhibition of calcium carbonate and calcium sulphate precipitation was compared with that of a PSI single polymer. The PSI-co-MA exhibited excellent ability to control inorganic minerals, with approximately 85.36% calcium carbonate inhibition and 100% calcium sulphate inhibition at a level of 10 mg/L PSI-co-MA, respectively. Therefore, it may be reasonably concluded that PSI-co-MA is a highly effective scale inhibitor for cooling water treatment applications.

  2. In situ synthesis carbonated hydroxyapatite layers on enamel slices with acidic amino acids by a novel two-step method.

    PubMed

    Wu, Xiaoguang; Zhao, Xu; Li, Yi; Yang, Tao; Yan, Xiujuan; Wang, Ke

    2015-09-01

    In situ fabrication of carbonated hydroxyapatite (CHA) remineralization layer on an enamel slice was completed in a novel, biomimetic two-step method. First, a CaCO3 layer was synthesized on the surface of demineralized enamel using an acidic amino acid (aspartic acid or glutamate acid) as a soft template. Second, at the same concentration of the acidic amino acid, rod-like carbonated hydroxyapatite was produced with the CaCO3 layer as a sacrificial template and a reactant. The morphology, crystallinity and other physicochemical properties of the crystals were characterized using field emission scanning electron microscopy (FESEM), Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD) and energy-dispersive X-ray analysis (EDAX), respectively. Acidic amino acid could promote the uniform deposition of hydroxyapatite with rod-like crystals via absorption of phosphate and carbonate ions from the reaction solution. Moreover, compared with hydroxyapatite crystals coated on the enamel when synthesized by a one-step method, the CaCO3 coating that was synthesized in the first step acted as an active bridge layer and sacrificial template. It played a vital role in orienting the artificial coating layer through the template effect. The results show that the rod-like carbonated hydroxyapatite crystals grow into bundles, which are similar in size and appearance to prisms in human enamel, when using the two-step method with either aspartic acid or acidic glutamate (20.00 mmol/L). Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Influence of acidic and alkaline waste solution properties on uranium migration in subsurface sediments.

    PubMed

    Szecsody, Jim E; Truex, Mike J; Qafoku, Nikolla P; Wellman, Dawn M; Resch, Tom; Zhong, Lirong

    2013-08-01

    This study shows that acidic and alkaline wastes co-disposed with uranium into subsurface sediments have significant impact on changes in uranium retardation, concentration, and mass during downward migration. For uranium co-disposal with acidic wastes, significant rapid (i.e., hours) carbonate and slow (i.e., 100 s of hours) clay dissolution resulted, releasing significant sediment-associated uranium, but the extent of uranium release and mobility change was controlled by the acid mass added relative to the sediment proton adsorption capacity. Mineral dissolution in acidic solutions (pH2) resulted in a rapid (<10 h) increase in aqueous carbonate (with Ca(2+), Mg(2+)) and phosphate and a slow (100 s of hours) increase in silica, Al(3+), and K(+), likely from 2:1 clay dissolution. Infiltration of uranium with a strong acid resulted in significant shallow uranium mineral dissolution and deeper uranium precipitation (likely as phosphates and carbonates) with downward uranium migration of three times greater mass at a faster velocity relative to uranium infiltration in pH neutral groundwater. In contrast, mineral dissolution in an alkaline environment (pH13) resulted in a rapid (<10h) increase in carbonate, followed by a slow (10 s to 100 s of hours) increase in silica concentration, likely from montmorillonite, muscovite, and kaolinite dissolution. Infiltration of uranium with a strong base resulted in not only uranium-silicate precipitation (presumed Na-boltwoodite) but also desorption of natural uranium on the sediment due to the high ionic strength solution, or 60% greater mass with greater retardation compared with groundwater. Overall, these results show that acidic or alkaline co-contaminant disposal with uranium can result in complex depth- and time-dependent changes in uranium dissolution/precipitation reactions and uranium sorption, which alter the uranium migration mass, concentration, and velocity. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Dissolution of Simulated and Radioactive Savannah River Site High-Level Waste Sludges with Oxalic Acid & Citric Acid Solutions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    STALLINGS, MARY

    untreated sludge solids. We recommend that these results be evaluated further to determine if these solutions contain sufficient neutron poisons. We observed low general corrosion rates in tests in which carbon steel coupons were contacted with solutions of oxalic acid, citric acid and mixtures of oxalic and citric acids. Wall thinning can be minimized by maintaining short contact times with these acid solutions. We recommend additional testing with oxalic and oxalic/citric acid mixtures to measure dissolution performance of sludges that have not been previously dried. This testing should include tests to clearly ascertain the effects of total acid strength and metal complexation on dissolution performance. Further work should also evaluate the downstream impacts of citric acid on the SRS High-Level Waste System (e.g., radiochemical separations in the Salt Waste Processing Facility and addition of organic carbon in the Saltstone and Defense Waste Processing facilities).« less

  5. Perlwapin, an Abalone Nacre Protein with Three Four-Disulfide Core (Whey Acidic Protein) Domains, Inhibits the Growth of Calcium Carbonate Crystals

    PubMed Central

    Treccani, Laura; Mann, Karlheinz; Heinemann, Fabian; Fritz, Monika

    2006-01-01

    We have isolated a new protein from the nacreous layer of the shell of the sea snail Haliotis laevigata (abalone). Amino acid sequence analysis showed the protein to consist of 134 amino acids and to contain three sequence repeats of ∼40 amino acids which were very similar to the well-known whey acidic protein domains of other proteins. The new protein was therefore named perlwapin. In addition to the major sequence, we identified several minor variants. Atomic force microscopy was used to explore the interaction of perlwapin with calcite crystals. Monomolecular layers of calcite crystals dissolve very slowly in deionized water and recrystallize in supersaturated calcium carbonate solution. When perlwapin was dissolved in the supersaturated calcium carbonate solution, growth of the crystal was inhibited immediately. Perlwapin molecules bound tightly to distinct step edges, preventing the crystal layers from growing. Using lower concentrations of perlwapin in a saturated calcium carbonate solution, we could distinguish native, active perlwapin molecules from denaturated ones. These observations showed that perlwapin can act as a growth inhibitor for calcium carbonate crystals in saturated calcium carbonate solution. The function of perlwapin in nacre growth may be to inhibit the growth of certain crystallographic planes in the mineral phase of the polymer/mineral composite nacre. PMID:16861275

  6. Hydrogen storage and delivery: the carbon dioxide - formic acid couple.

    PubMed

    Laurenczy, Gábor

    2011-01-01

    Carbon dioxide and the carbonates, the available natural C1 sources, can be easily hydrogenated into formic acid and formates in water; the rate of this reduction strongly depends on the pH of the solution. This reaction is catalysed by ruthenium(II) pre-catalyst complexes with a large variety of water-soluble phosphine ligands; high conversions and turnover numbers have been realised. Although ruthenium(II) is predominant in these reactions, the iron(II) - tris[(2-diphenylphosphino)-ethyl]phosphine (PP3) complex is also active, showing a new perspective to use abundant and inexpensive iron-based compounds in the CO2 reduction. In the catalytic hydrogenation cycles the in situ formed metal hydride complexes play a key role, their structures with several other intermediates have been proven by multinuclear NMR spectroscopy. In the other hand safe and convenient hydrogen storage and supply is the fundamental question for the further development of the hydrogen economy; and carbon dioxide has been recognised to be a viable H2 vector. Formic acid--containing 4.4 weight % of H2, that is 53 g hydrogen per litre--is suitable for H2 storage; we have shown that in aqueous solutions it can be selectively decomposed into CO-free (CO < 10 ppm) CO2 and H2. The reaction takes place under mild experimental conditions and it is able to generate high pressure H2 (up to 600 bar). The cleavage of HCOOH is catalysed by several hydrophilic Ru(II) phosphine complexes (meta-trisulfonated triphenylphosphine, mTPPTS, being the most efficient one), either in homogeneous systems or as immobilised catalysts. We have also shown that the iron(II)--hydrido tris[(2-diphenylphosphino)ethyl]phosphine complex catalyses with an exceptionally high rate and efficiency (turnover frequency, TOF = 9425 h(-1)mol(-1); turnover number, TON = 92400) the formic acid cleavage, in environmentally friendly propylene carbonate solution, opening the way to use cheap, non-noble metal based catalysts for this

  7. Method for extracting lanthanides and actinides from acid solutions by modification of Purex solvent

    DOEpatents

    Horwitz, E.P.; Kalina, D.G.

    1986-03-04

    A process is described for the recovery of actinide and lanthanide values from aqueous solutions with an extraction solution containing an organic extractant having the formula as shown in a diagram where [phi] is phenyl, R[sup 1] is a straight or branched alkyl or alkoxyalkyl containing from 6 to 12 carbon atoms and R[sup 2] is an alkyl containing from 3 to 6 carbon atoms and phase modifiers in a water-immiscible hydrocarbon diluent. The addition of the extractant to the Purex process extractant, tri-n-butylphosphate in normal paraffin hydrocarbon diluent, will permit the extraction of multivalent lanthanide and actinide values from 0.1 to 12.0 molar acid solutions. 6 figs.

  8. Toluene nitration in irradiated nitric acid and nitrite solutions

    NASA Astrophysics Data System (ADS)

    Elias, Gracy; Mincher, Bruce J.; Mezyk, Stephen P.; Muller, Jim; Martin, Leigh R.

    2011-04-01

    The kinetics, mechanisms, and stable products produced for the nitration of aryl alkyl mild ortho-para director toluene in irradiated nitric acid and neutral nitrite solutions were investigated using γ and pulse radiolysis. Electron pulse radiolysis was used to determine the bimolecular rate constants for the reaction of toluene with different transient species produced by irradiation. HPLC with UV detection, GC-MS and LC-MS, were used to assess the stable reaction products. Free-radical based nitration reaction products were found in irradiated acidic and neutral media. In 6.0 M HNO3, ring substitution, side chain substitution, and oxidation, produced different nitrated toluene products. For ring substitution, nitrogen oxide radicals were added mainly to cyclohexadienyl radicals, whereas for side chain substitution, these radicals were added to the carbon-centered benzyl radical produced by H-atom abstraction. In neutral nitrite solutions, radiolytically-induced ring nitration products approached a statistically random distribution, suggesting a direct free-radical reaction involving addition of the rad NO2 radical.

  9. Solution influence on biomolecular equilibria - Nucleic acid base associations

    NASA Technical Reports Server (NTRS)

    Pohorille, A.; Pratt, L. R.; Burt, S. K.; Macelroy, R. D.

    1984-01-01

    Various attempts to construct an understanding of the influence of solution environment on biomolecular equilibria at the molecular level using computer simulation are discussed. First, the application of the formal statistical thermodynamic program for investigating biomolecular equilibria in solution is presented, addressing modeling and conceptual simplications such as perturbative methods, long-range interaction approximations, surface thermodynamics, and hydration shell. Then, Monte Carlo calculations on the associations of nucleic acid bases in both polar and nonpolar solvents such as water and carbon tetrachloride are carried out. The solvent contribution to the enthalpy of base association is positive (destabilizing) in both polar and nonpolar solvents while negative enthalpies for stacked complexes are obtained only when the solute-solute in vacuo energy is added to the total energy. The release upon association of solvent molecules from the first hydration layer around a solute to the bulk is accompanied by an increase in solute-solvent energy and decrease in solvent-solvent energy. The techniques presented are expectd to displace less molecular and more heuristic modeling of biomolecular equilibria in solution.

  10. Solubility of mixtures of hydrogen sulfide and carbon dioxide in aqueous N-methyldiethanolamine solutions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jou, Fang Yuan; Carroll, J.J.; Mather, A.E.

    1993-01-01

    Aqueous solutions of alkanolamines are commonly used to strip acid gases (H[sub 2]S and CO[sub 2]) from streams contaminated with these components. The two most widely used amines are monoethanolamine (MEA) and diethanolamine (DEA). The solubilities of mixtures of hydrogen sulfide and carbon dioxide in a 35 wt% (3.04 kmol/m[sup 3]) aqueous solution of N-methyldiethanolamine at 40 and 100C have been measured. Partial pressures of the acid gases ranged from 0.006 to 101 kPa at 40C and from 4 to 530 kPa at 100C.

  11. Quantitative extraction and concentration of synthetic water-soluble acid dyes from aqueous media using a quinine-chloroform solution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kobayashi, F.; Ozawa, N.; Hanai, J.

    Twenty-one water-soluble acid dyes, including eleven azo, five triphenylmethane four xanthene, one naphthol derivatives, used at practical concentrations for food coloration, were quantitatively extracted from water and various carbonated beverages into a 0.1 M quinine-chloroform solution in the presence of 0.5 M boric acid by brief shaking. Quantitative extraction of these dyes was also accomplished by the 0.1 M quinine-chloroform solution made conveniently from chloroform, quinine hydrochloride, and sodium hydroxide added successively to water or beverages containing boric acid. Quinine acted as a countercation on the dyes having sulfonic and/or carboxylic acid group(s) to form chloroform-soluble ion-pair complexes. The diacidicmore » base alkaloid interacted with each acid group of mono-, di-, tri-, and tetrasulfonic acid dyes approximately in the ratio 0.8-0.9 to 1. The dyes in the chloroform solution were quantitatively concentrated into a small volume of sodium hydroxide solution also by brief shaking. The convenient quinine-chloroform method was applicable to the quantitative extraction of a mixture of 12 dyes from carbonated beverages, which are all currently used for food coloration. A high-pressure liquid chromatographic method is also presented for the systematic separation and determination of these 12 dyes following their concentration into the aqueous alkaline solution. The chromatogram was monitored by double-wavelength absorptiometry in the visible and ultraviolet ray regions.« less

  12. ELEMENTAL MERCURY ADSORPTION BY ACTIVATED CARBON TREATED WITH SULFURIC ACID

    EPA Science Inventory

    The paper gives results of a study of the adsorption of elemental mercury at 125 C by a sulfuric-acid (H2S04, 50% w/w/ solution)-treated carbon for the removal of mercury from flue gas. The pore structure of the sample was characterized by nitrogen (N2) at -196 C and the t-plot m...

  13. Removal of gallium (III) ions from acidic aqueous solution by supercritical carbon dioxide extraction in the green separation process.

    PubMed

    Chou, Wei-Lung; Wang, Chih-Ta; Yang, Kai-Chiang; Huang, Yen-Hsiang

    2008-12-15

    Supercritical carbon dioxide extraction, which is a feasible "green" alternative, was applied in this study as a sample pretreatment step for the removal of gallium (III) ions from acidic aqueous solution. The effect of various process parameters, including various chelating agents, extraction pressure and temperature, dimensionless CO(2) volume, the concentration of the chelating agent, and the pH of the solution, governing the efficiency and throughput of the procedure were systematically investigated. The performance of the various chelating agents from different studies indicated that the extraction efficiency of supercritical CO(2) was in the order: thiopyridine (PySH)>thenoyltrifluoroacetone (TTAH)>acetylacetone (AcAcH). The optimal extraction pressure and temperature for the supercritical CO(2) extraction of gallium (III) with chelating agent PySH were found to be 70 degrees C and 3000psi, respectively. The optimum concentration of the chelating agent was found to be 50ppm. A value of 7.5 was selected as the optimum dimensionless CO(2) volume. The optimum pH of the solution for supercritical CO(2) extraction should fall in the range of 2.0-3.0.

  14. Color removal from acid and reactive dye solutions by electrocoagulation and electrocoagulation/adsorption processes.

    PubMed

    Bellebia, S; Kacha, S; Bouberka, Z; Bouyakoub, A Z; Derriche, Z

    2009-04-01

    In this study, electrocoagulation of Marine Blue Erionyl MR (acid dye) and electrocoagulation followed by adsorption of Brilliant Blue Levafix E-BRA (reactive dye) from aqueous solutions were investigated, using aluminum electrodes and granular activated carbon (GAC). In the electrocoagulation and adsorption of dyestuff solutions, the effects of current density, loading charge, pH, conductivity, stirring velocity, contact time, and GAC concentration were examined. The optimum conditions for the electrocoagulation process were identified as loading charges 7.46 and 1.49 F/m3, for a maximum abatement of 200 mg/L reactive and acid dye, respectively. The residual reactive dye concentration was completely removed with 700 mg/L GAC. The results of this investigation provide important data for the development of a combined process to remove significant concentrations of recalcitrant dyes from water, using moderate activated carbon energy and aluminum consumption, and thereby lowering the cost of treatment.

  15. 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.

  16. 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

  17. Soil-solution partitioning of DOC in acid organic soils: Results from a UK field acidification and alkalization experiment

    NASA Astrophysics Data System (ADS)

    Oulehle, Filip; Jones, Timothy; Burden, Annette; Evans, Chris

    2013-04-01

    Dissolved organic carbon (DOC) is an important component of the global carbon (C) cycle and has profound impacts on water chemistry and metabolism in lakes and rivers. Reported increases of DOC concentration in surface waters across Europe and Northern America have been attributed to several drivers; from changing climate and land-use to eutrophication and declining acid deposition. The last of these suggests that acidic deposition suppressed the solubility of DOC, and that this historic suppression is now being reversed by reducing emissions of acidifying pollutants. We studied a set of four parallel acidification and alkalization experiments in organic rich soils which, after three years of manipulation, have shown clear soil solution DOC responses to acidity change. We tested whether these DOC concentration changes were related to changes in the acid/base properties of DOC. Based on laboratory determination of DOC site density (S.D. = amount of carboxylic groups per milligram DOC) and charge density (C.D. = organic acid anion concentration per milligram DOC) we found that the change in DOC soil-solution partitioning was tightly related to the change in degree of dissociation (α = C.D./S.D. ratio) of organic acids (R2=0.74, p<0.01). Carbon turnover in soil organic matter (SOM), determined by soil respiration and β-D-glucosidase enzyme activity measurements, also appears to have some impact on DOC leaching, via constraints on the actual supply of available DOC from SOM; when the turnover rate of C in SOM is low, the effect of α on DOC leaching is reduced. Thus, differences in the magnitude of DOC changes seen across different environments might be explained by interactions between physicochemical restrictions of DOC soil-solution partitioning, and SOM carbon turnover effects on DOC supply.

  18. Effects of humic acid and solution chemistry on the aggregation and dispersion of carboxyl-functionalized carbon black nanoparticles

    NASA Astrophysics Data System (ADS)

    Hwang, G.; Gomez-Flores, A.; Choi, S.; Han, Y., , Dr; Kim, H.

    2017-12-01

    The influence of humic acid, ionic strength and ionic species on the aggregation and dispersion of carboxyl-functionalized carbon black nanoparticles (CB-NPs) was systemically investigated in aqueous media. The experimental conditions of stability tests were selected to the changes in the solution chemistry (0.1-10 mM NaCl and 0.01-1 mM CaCl2) and in the presence/absence of humic acid (1 and 5 mg L-1) in an aquatic environment. The CB-NPs suspension was more rapidly settled in NaCl solution than in CaCl2. Specifically, in the case of NaCl, the aggregation rate of CB-NPs increased with ionic strength. Contrary, CB-NPs dispersed in CaCl2 were insensitive to the aggregation as the ionic strength increased; that was because specific adsorption of the divalent cation Ca2+ occurred since the zeta potential of the CB-NPs is reversed to a positive charge with increasing of the ionic strength. It was confirmed that humic acid greatly influences the stability of the CB-NPs. In particular, the dispersion of CB-NPs was improved in the whole range of ionic strengths of NaCl as well as of CaCl2. To support the results, the interaction energy between CB-NPs was calculated for each condition by using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) and modified-DLVO theories. In the presence of humic acid, the improved stability of CB-NPs is attributed to the steric repulsive force.This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2015R1D1A3A01020766), the Ministry of Education (MOE) and National Research Foundation of Korea (NRF) through the Human Resource Training Project for Regional Innovation (2015H1C1A1035930) and Korea Energy and Mineral Resources Engineering Program (KEMREP).

  19. ELECTROLYTIC REDUCTION OF NITRIC ACID SOLUTIONS

    DOEpatents

    Alter, H.W.; Barney, D.L.

    1958-09-30

    A process is presented for the treatment of radioactivc waste nitric acid solutions. The nitric acid solution is neutralized with an alkali metal hydroxide in an amount sufficient to precipitate insoluble hydroxides, and after separation of the precipitate the solution is electrolyzed to convert the alkali nitrate formed, to alkali hydroxide, gaseous ammonla and oxygen. The solution is then reusable after reducing the volume by evaporating the water and dissolved ammonia.

  20. Competitive adsorption of phenolic compounds from aqueous solution using sludge-based activated carbon.

    PubMed

    Mohamed, E F; Andriantsiferana, C; Wilhelm, A M; Delmas, H

    2011-01-01

    Preparation of activated carbon from sewage sludge is a promising approach to produce cheap and efficient adsorbent for pollutants removal as well as to dispose of sewage sludge. The first objective of this study was to investigate the physical and chemical properties (BET surface area, ash and elemental content, surface functional groups by Boehm titration and weight loss by thermogravimetric analysis) of the sludge-based activated carbon (SBAC) so as to give a basic understanding of its structure and to compare to those of two commercial activated carbons, PICA S23 and F22. The second and main objective was to evaluate the performance of SBAC for single and competitive adsorption of four substituted phenols (p-nitrophenol, p-chlorophenol, p-hydroxy benzoic acid and phenol) from their aqueous solutions. The results indicated that, despite moderate micropore and mesopore surface areas, SBAC had remarkable adsorption capacity for phenols, though less than PICA carbons. Uptake of the phenolic compound was found to be dependent on both the porosity and surface chemistry of the carbons. Furthermore, the electronegativity and the hydrophobicity of the adsorbate have significant influence on the adsorption capacity. The Langmuir and Freundlich models were used for the mathematical description of the adsorption equilibrium for single-solute isotherms. Moreover, the Langmuir-Freundlich model gave satisfactory results for describing multicomponent system isotherms. The capacity of the studied activated carbons to adsorb phenols from a multi-solute system was in the following order: p-nitrophenol > p-chlorophenol > PHBA > phenol.

  1. Decomposition mechanism of chromite in sulfuric acid-dichromic acid solution

    NASA Astrophysics Data System (ADS)

    Zhao, Qing; Liu, Cheng-jun; Li, Bao-kuan; Jiang, Mao-fa

    2017-12-01

    The sulfuric acid leaching process is regarded as a promising, cleaner method to prepare trivalent chromium products from chromite; however, the decomposition mechanism of the ore is poorly understood. In this work, binary spinels of Mg-Al, Mg-Fe, and Mg-Cr in the powdered and lump states were synthesized and used as raw materials to investigate the decomposition mechanism of chromite in sulfuric acid-dichromic acid solution. The leaching yields of metallic elements and the changes in morphology of the spinel were studied. The experimental results showed that the three spinels were stable in sulfuric acid solution and that dichromic acid had little influence on the decomposition behavior of the Mg-Al spinel and Mg-Fe spinel because Mg2+, Al3+, and Fe3+ in spinels cannot be oxidized by Cr6+. However, in the case of the Mg-Cr spinel, dichromic acid substantially promoted the decomposition efficiency and functioned as a catalyst. The decomposition mechanism of chromite in sulfuric acid-dichromic acid solution was illustrated on the basis of the findings of this study.

  2. Synthesis and acid catalysis of cellulose-derived carbon-based solid acid

    NASA Astrophysics Data System (ADS)

    Suganuma, Satoshi; Nakajima, Kiyotaka; Kitano, Masaaki; Yamaguchi, Daizo; Kato, Hideki; Hayashi, Shigenobu; Hara, Michikazu

    2010-06-01

    SO 3H-bearing amorphous carbon, prepared by partial carbonization of cellulose followed by sulfonation in fuming H 2SO 4, was applied as a solid catalyst for the acid-catalyzed hydrolysis of β-1,4 glucan, including cellobiose and crystalline cellulose. Structural analyses revealed that the resulting carbon material consists of graphene sheets with 1.5 mmol g -1 of SO 3H groups, 0.4 mmol g -1 of COOH, and 5.6 mmol g -1 of phenolic OH groups. The carbon catalyst showed high catalytic activity for the hydrolysis of β-1,4 glycosidic bonds in both cellobiose and crystalline cellulose. Pure crystalline cellulose was not hydrolyzed by conventional strong solid Brønsted acid catalysts such as niobic acid, Nafion ® NR-50, and Amberlyst-15, whereas the carbon catalyst efficiently hydrolyzes cellulose into water-soluble saccharides. The catalytic performance of the carbon catalyst is due to the large adsorption capacity for hydrophilic reactants and the adsorption ability of β-1,4 glucan, which is not adsorbed to other solid acids.

  3. 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.

  4. Experimental study of Pb (II) solution sorption behavior onto Coffee Husk Bioactivated Carbon

    NASA Astrophysics Data System (ADS)

    Fona, Z.; Habibah, U.

    2018-04-01

    Coffee husk which is abundantly produced in the coffee plantations is potential to be a challenging adsorbent. The fate of Pb (II) solution in the sorption mechanism onto the adsorbent has been investigated. This paper aimed to study the efficiency of Pb (II) aqueous solution removal using activated carbon from coffee husk (CAC). The sorption characteristics were using two isotherm models, Langmuir and Freundlich, were also reported. The coffee husk from local plantations in Middle Aceh was carbonized and sieved to 120/140 mesh. The charcoal was activated using hydrochloric acid before contacted with the different initial concentrations of Pb (II) solution. The remaining concentrations of the metal in the specified contact times were determined using Atomic Adsorption Spectrophotometer at 283.3 wavelength. The result showed that the equilibrium concentrations were obtained in about 30 minutes which depended on the initial concentration. The sorption mechanism followed Freundlich isotherm model where the adsorption constant and capacity were accordingly 1.353 and 1.195 mgg‑1. The iodine sorption was up to 1,053 mgg‑1. Based on the ash and moisture content, as well as iodine sorption, the activated carbon met the national standard.

  5. Solubility limits of dibutyl phosphoric acid in uranium-nitric acid solutions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pierce, R.A.

    2000-01-04

    The Savannah River Site has enriched uranium (EU) solution that has been stored since being purified in its solvent extraction processes. The concentrations in solution are approximately 6 g/L U and 0.1 M nitric acid. Residual tributylphosphate in solution has slowly hydrolyzed to form dibutyl phosphoric acid (HDBP) at concentrations averaging 30--50 mg/L. Dibutyl phosphoric acid, in turn, is in equilibrium with (HDBP){sub 2} and DBP{sup {minus}}. Uranium can form compounds with the dibutylphosphate ion (DBP{sup {minus}}) which have limited solubility, thereby creating a nuclear criticality safety issue. Literature reports and earlier SRTC tests have shown that it is feasiblemore » to precipitate U-DBP solid during the storage and processing of EU solutions. As a result, a series of solubility experiments were run at nitric acid concentrations from 0--4.0 M HNO{sub 3}, uranium at 0--90 g/L, and temperatures from 0--30 C. The data shows temperature and nitric acid concentration dependence consistent with what would be expected. With respect to uranium concentration, U-DBP solubility passes through a minimum between 6 and 12 g/L U at the acid concentrations and temperatures studied. However, the minimum shows a slight shift toward lower uranium concentrations at lower nitric acid concentrations. The shifts in solubility are strongly dependent upon the overall ionic strength of the solution. The data also reveal a shift to higher DBP solubility above 0.5 M HNO{sub 3} for both 6 g/L and 12 g/L uranium solutions. Analysis of U-DBP solids from the tests identified distinct differences between precipitates from less than 0.5 M solutions and those from greater than 4 M acid. Analyses identified UO{sub 2}(DBP){sub 2} as the dominant compound present at low acid concentrations in accordance with literature reports. As the acid concentration increases, the crystalline UO{sub 2}(DBP){sub 2} shows molecular substitutions and an increase in amorphous content.« less

  6. Partition Coefficients of Organics between Water and Carbon Dioxide Revisited: Correlation with Solute Molecular Descriptors and Solvent Cohesive Properties.

    PubMed

    Roth, Michal

    2016-12-06

    High-pressure phase behavior of systems containing water, carbon dioxide and organics has been important in several environment- and energy-related fields including carbon capture and storage, CO 2 sequestration and CO 2 -assisted enhanced oil recovery. Here, partition coefficients (K-factors) of organic solutes between water and supercritical carbon dioxide have been correlated with extended linear solvation energy relationships (LSERs). In addition to the Abraham molecular descriptors of the solutes, the explanatory variables also include the logarithm of solute vapor pressure, the solubility parameters of carbon dioxide and water, and the internal pressure of water. This is the first attempt to include also the properties of water as explanatory variables in LSER correlations of K-factor data in CO 2 -water-organic systems. Increasing values of the solute hydrogen bond acidity, the solute hydrogen bond basicity, the solute dipolarity/polarizability, the internal pressure of water and the solubility parameter of water all tend to reduce the K-factor, that is, to favor the solute partitioning to the water-rich phase. On the contrary, increasing values of the solute characteristic volume, the solute vapor pressure and the solubility parameter of CO 2 tend to raise the K-factor, that is, to favor the solute partitioning to the CO 2 -rich phase.

  7. Reductive dechlorination of carbon tetrachloride using buffered alkaline ascorbic acid.

    PubMed

    Lin, Ya-Ting; Liang, Chenju

    2015-10-01

    Alkaline ascorbic acid (AA) was recently discovered as a novel in-situ chemical reduction (ISCR) reagent for remediating chlorinated solvents in the subsurface. For this ISCR process, the maintenance of an alkaline pH is essential. This study investigated the possibility of the reduction of carbon tetrachloride (CT) using alkaline AA solution buffered by phosphate and by NaOH. The results indicated that CT was reduced by AA, and chloroform (CF) was a major byproduct at a phosphate buffered pH of 12. However, CT was completely reduced by AA in 2M NaOH without CF formation. In the presence of iron/soil minerals, iron could be reduced by AA and Fe(2+) tends to precipitate on the mineral surface to accelerate CT degradation. A simultaneous transfer of hydrogenolysis and dichloroelimination would occur under phosphate buffered pH 12. This implies that a high alkaline environment is a crucial factor for maintaining the dominant pathway of two electron transfer from dianionic AA to dehydroascorbic acid, and to undergo dichloroelimination of CT. Moreover, threonic acid and oxalic acid were identified to be the major AA decomposition products in alkaline solutions. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Enhanced adsorption of humic acids on ordered mesoporous carbon compared with microporous activated carbon.

    PubMed

    Liu, Fengling; Xu, Zhaoyi; Wan, Haiqin; Wan, Yuqiu; Zheng, Shourong; Zhu, Dongqiang

    2011-04-01

    Humic acids are ubiquitous in surface and underground waters and may pose potential risk to human health when present in drinking water sources. In this study, ordered mesoporous carbon was synthesized by means of a hard template method and further characterized by X-ray diffraction, N2 adsorption, transition electron microscopy, elemental analysis, and zeta-potential measurement. Batch experiments were conducted to evaluate adsorption of two humic acids from coal and soil, respectively, on the synthesized carbon. For comparison, a commercial microporous activated carbon and nonporous graphite were included as additional adsorbents; moreover, phenol was adopted as a small probe adsorbate. Pore size distribution characterization showed that the synthesized carbon had ordered mesoporous structure, whereas the activated carbon was composed mainly of micropores with a much broader pore size distribution. Accordingly, adsorption of the two humic acids was substantially lower on the activated carbon than on the synthesized carbon, because of the size-exclusion effect. In contrast, the synthesized carbon and activated carbon showed comparable adsorption for phenol when the size-exclusion effect was not in operation. Additionally, we verified by size-exclusion chromatography studies that the synthesized carbon exhibited greater adsorption for the large humic acid fraction than the activated carbon. The pH dependence of adsorption on the three carbonaceous adsorbents was also compared between the two test humic acids. The findings highlight the potential of using ordered mesoporous carbon as a superior adsorbent for the removal of humic acids. Copyright © 2011 SETAC.

  9. Synthesis, characterization and study of sorption parameters of multi-walled carbon nanotubes/chitosan nanocomposite for the removal of picric acid from aqueous solutions.

    PubMed

    Khakpour, Roghayeh; Tahermansouri, Hasan

    2018-04-01

    The modification of carboxylated multi-wall carbon nanotubes (MWCNT-COOH) with chitosan (Chi) has been investigated to prepare a nanocomposite material (MWCNT-Chi) for the removal of picric acid from aqueous solutions. Materials were characterized by FT-IR, TGA, DTG, FESEM, EDX, BET and zeta potential. Batch experiments such as solution pH, dosage of adsorbents, contact time, concentration of the picric acid and temperature were achieved to study sorption process. Kinetic studies were well described by pseudo-second-order kinetic model for both adsorbents. The six isotherm models: Langmuir (four linear forms), Freundlich, Tempkin, Halsey, Harkins-Jura and Dubinin-Radushkevich models were applied to determine the characteristic parameters of the adsorption process. Isotherm studies showed that the Langmuir isotherm for MWCNT-Chi and Freundlich and Halsey models for both adsorbents were found to best represent the measured sorption data. In addition, the results of Dubinin-Radushkevich model confirmed the physical adsorption. Negative ΔG° values for MWCNT-Chi and positive ones for MWCNT-COOH indicated the nature of spontaneous and unspontaneous, respectively for adsorption process in the range of the studied concentrations. In addition, picric acid molecules can be desorbed from MWCNT-Chi up to 90% at pH = 9 and that the consumed MWCNT-Chi could be reutilized up to 5th cycle of regeneration. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Removal of hexavalent chromium in carbonic acid solution by oxidizing slag discharged from steelmaking process in electric arc furnace

    NASA Astrophysics Data System (ADS)

    Yokoyama, Seiji; Okazaki, Kohei; Sasano, Junji; Izaki, Masanobu

    2014-02-01

    Hexavalent chromium (Cr(VI)) is well-known to be a strong oxidizer, and is recognized as a carcinogen. Therefore, it is regulated for drinking water, soil, groundwater and sea by the environmental quality standards all over the world. In this study, it was attempted to remove Cr(VI) ion in a carbonic acid solution by the oxidizing slag that was discharged from the normal steelmaking process in an electric arc furnace. After the addition of the slag into the aqueous solution contained Cr(VI) ion, concentrations of Cr(VI) ion and total chromium (Cr(VI) + trivalent chromium (Cr(III)) ions decreased to lower detection limit of them. Therefore, the used slag could reduce Cr(VI) and fix Cr(III) ion on the slag. While Cr(VI) ion existed in the solution, iron did not dissolve from the slag. From the relation between predicted dissolution amount of iron(II) ion and amount of decrease in Cr(VI) ion, the Cr(VI) ion did not react with iron(II) ion dissolved from the slag. Therefore, Cr(VI) ion was removed by the reductive reaction between Cr(VI) ion and the iron(II) oxide (FeO) in the slag. This reaction progressed on the newly appeared surface of iron(II) oxide due to the dissolution of phase composed of calcium etc., which existed around iron(II) oxide grain in the slag.

  11. The dissociation of carbonic acid in NaCl solutions as a function of concentration and temperature

    NASA Astrophysics Data System (ADS)

    Millero, Frank; Huang, Fen; Graham, Taylor; Pierrot, Denis

    2007-01-01

    Potentiometric measurements of the stoichiometric constants for the dissociation of carbonic acid in NaCl solutions ( K1∗=[H+][HCO3-]/[CO] and K1∗=[H][CO32-]/[HCO3-]) have been made as a function of molality (0-6 m) and temperature (0-50 °C). The results have been fitted to the equations pKi∗-pKi=Ai+Bi/T+CilnT The values of p Ki in pure water are taken from the literature and the adjustable parameters Ai, Bi and Ci are a function of molality A1=35.2911m+0.8491m-0.32m+0.055m B1=-1583.09m C1=-5.4366m A2=38.2746m+1.6057m-0.647m+0.113m B2=-1738.16m C2=-6.0346m ( σ = 0.013 for pK1∗ and σ = 0.020 for pK2∗, N = 603). The values determined in this study are in good agreement with the 25 °C literature values. Our results have been combined with previous measurements to derive equations that are valid from 0 to 250 °C and 0 to 5 m. This large data set has been used to determine the Pitzer parameters ( β(0), β(1) and Cϕ) for the interactions of Na + with HCO 3- and CO 32- from 0 to 250 °C. These results extend the carbonate system Pitzer model to hydrothermal brines containing high concentrations of NaCl.

  12. 197 Au Mössbauer study of the gold species adsorbed on carbon from cyanide solutions

    NASA Astrophysics Data System (ADS)

    Kongolo, K.; Bahr, A.; Friedl, J.; Wagner, F. E.

    1990-04-01

    The gold species present on activated carbon after adsorption from solutions of Au(CN)2 - have been studied by197Au Mössbauer spectroscopy as a function of the pH value of the solution, the loading of the carbon, the coadsorption of polyvalent cations, and the treatment of the samples after adsorption. The gold was found to be adsorbed mainly as Au(CN)2 -. Coadsorbed polyvalent cations (Ca²+, Gd³+) have no influence on the Mössbauer parameters of the adsorbed gold complex. After adsorption from acidic solutions (pH ≲ 4), one finds a substantial amount of adsorbed gold with Mössbauer parameters similar to those of crystalline AuCN. Presumably, this gold is bound in Aux(CN)x+1 oligomers which form during drying. An additional product with Mössbauer parameters close to those of KAu(CN)2Cl2 was observed on dried samples after adsorption at pH 1. A minor gold species with an uncommonly small electric quadrupole splitting was found on wet carbons but disappeared on drying.

  13. The erosion of carbonate stone by acid rain: Laboratory and field investigations

    USGS Publications Warehouse

    Baedecker, P.A.; Reddy, M.M.

    1993-01-01

    One of the goals of research on the effects of acidic deposition on carbonate stone surfaces is to define the incremental impact of acidic deposition relative to natural weathering processes on the rate of carbonate stone erosion. If rain that impacts carbonate stone surfaces is resident on the surface long enough to approach chemical equilibrium, the incremental effect of hydrogen ion is expected to be small (i.e., 6% for a rain of pH 4.0). Under nonequilibrium (i.e., high flow rate) conditions, kinetic considerations suggest that the incremental effect of hydrogen ion deposition could be quite significant. Field run-off experiments involving the chemical analysis of rain collected from inclined stone slabs have been used to evaluate stone dissolution processes under ambient conditions of wet and dry deposition of acidic species. The stoichiometry of the reaction of stone with hydrogen ion is difficult to define from the field data due to scatter in the data attributed to hydrodynamic effects. Laboratory run-off experiments show that the stoichiometry is best defined by a reaction with H+ in which CO2 is released from the system. The baseline effect caused by water in equilibrium with atmospheric CO2 is identical in the field and in laboratory simulation. The experiments show that the solutions are close enough to equilibrium for the incremental effect of hydrogen ion to be minor (i.e., 24% for marble for a rain of pH 4.0) relative to dissolution due to water and carbonic acid reactions. Stone erosion rates based on physical measurement are approximately double the recession rates that are due to dissolution (estimated from the observed calcium content of the run-off solutions). The difference may reflect the loss of granular material not included in recession estimates based on the run-off data. Neither the field nor the laboratory run-off experiments indicate a pH dependence for the grain-removal process.

  14. Enhanced Corrosion Resistance of Carbon Steel in Hydrochloric Acid Solution by Eriobotrya Japonica Thunb. Leaf Extract: Electrochemical Study

    PubMed Central

    Yang, Wenjing; Wang, Qihui; Xu, Ke; Yin, Yanjun; Bao, Hebin; Li, Xueming; Niu, Lidan; Chen, Shiqi

    2017-01-01

    The biodegradable inhibitors, which could effectively reduce the rate of corrosion of carbon steel, were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The mixed-type inhibitors extracted from Eriobotrya japonica Thunb. leaf exhibited excellent inhibition performance, and the inhibition efficiency for carbon steel reached 90.0% at 298 K in hydrochloric acid. Moreover, the adsorption mechanism of the inhibitors on a carbon steel surface is described by the Langmuir adsorption isotherm. Simultaneously, the corrosion morphology of the carbon steel and the inhibitor structure were analyzed by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR), respectively. PMID:28812993

  15. Enhanced Corrosion Resistance of Carbon Steel in Hydrochloric Acid Solution by Eriobotrya Japonica Thunb. Leaf Extract: Electrochemical Study.

    PubMed

    Yang, Wenjing; Wang, Qihui; Xu, Ke; Yin, Yanjun; Bao, Hebin; Li, Xueming; Niu, Lidan; Chen, Shiqi

    2017-08-16

    The biodegradable inhibitors, which could effectively reduce the rate of corrosion of carbon steel, were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The mixed-type inhibitors extracted from Eriobotrya japonica Thunb. leaf exhibited excellent inhibition performance, and the inhibition efficiency for carbon steel reached 90.0% at 298 K in hydrochloric acid. Moreover, the adsorption mechanism of the inhibitors on a carbon steel surface is described by the Langmuir adsorption isotherm. Simultaneously, the corrosion morphology of the carbon steel and the inhibitor structure were analyzed by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR), respectively.

  16. Physical defect formation in few layer graphene-like carbon on metals: influence of temperature, acidity, and chemical functionalization.

    PubMed

    Schumacher, Christoph M; Grass, Robert N; Rossier, Michael; Athanassiou, Evagelos K; Stark, Wendelin J

    2012-03-06

    A systematical examination of the chemical stability of cobalt metal nanomagnets with a graphene-like carbon coating is used to study the otherwise rather elusive formation of nanometer-sized physical defects in few layer graphene as a result of acid treatments. We therefore first exposed the core-shell nanomaterial to well-controlled solutions of altering acidity and temperature. The release of cobalt into these solutions over time offered a simple tool to monitor the progress of particle degradation. The results suggested that the oxidative damage of the graphene-like coatings was the rate-limiting step during particle degradation since only fully intact or entirely emptied carbon shells were found after the experiments. If ionic noble metal species were additionally present in the acidic solutions, the noble metal was found to reduce on the surface of specific, defective particles. The altered electrochemical gradients across the carbon shells were however not found to lead to a faster release of cobalt from the particles. The suggested mechanistic insight was further confirmed by the covalent chemical functionalization of the particle surface with chemically inert aryl species, which leads to an additional thickening of the shells. This leads to reduced cobalt release rates as well as slower noble metal reduction rates depending on the augmentation of the shell thickness.

  17. Interaction of aromatic alcohols, aldehydes and acids with α-hydroxyl-containing carbon-centered radicals: A steady state radiolysis study

    NASA Astrophysics Data System (ADS)

    Samovich, S. N.; Brinkevich, S. D.; Shadyro, O. I.

    2013-01-01

    Benzaldehyde and its derivatives efficaciously oxidize in aqueous solutions α-hydroxyl-containing carbon-centered radicals (α-HCR) of various structures, suppressing thereby the radical recombination and fragmentation reactions. The compounds containing cinnamic moieties are capable of adding α-hydroxyethyl radicals (α-HER) to the carbon-carbon double bonds conjugated with the aromatic system to form molecular products identifiable by mass spectrometry. On radiolysis of aqueous ethanol solutions, reduction of α-HER by aromatic alcohols and acids has been shown to proceed via formation of their adducts with hydrated electron species.

  18. Recovery of organic acids

    DOEpatents

    Verser, Dan W.; Eggeman, Timothy J.

    2009-10-13

    A method is disclosed for the recovery of an organic acid from a dilute salt solution in which the cation of the salt forms an insoluble carbonate salt. A tertiary amine and CO.sub.2 are introduced to the solution to form the insoluble carbonate salt and a complex between the acid and an amine. A water immiscible solvent, such as an alcohol, is added to extract the acid/amine complex from the dilute salt solution to a reaction phase. The reaction phase is continuously dried and a product between the acid and the solvent, such as an ester, is formed.

  19. Recovery of organic acids

    DOEpatents

    Verser, Dan W [Menlo Park, CA; Eggeman, Timothy J [Lakewood, CO

    2011-11-01

    A method is disclosed for the recovery of an organic acid from a dilute salt solution in which the cation of the salt forms an insoluble carbonate salt. A tertiary amine and CO.sub.2 are introduced to the solution to form the insoluble carbonate salt and a complex between the acid and an amine. A water immiscible solvent, such as an alcohol, is added to extract the acid/amine complex from the dilute salt solution to a reaction phase. The reaction phase is continuously dried and a product between the acid and the solvent, such as an ester, is formed.

  20. Nitric acid uptake by sulfuric acid solutions under stratospheric conditions - Determination of Henry's Law solubility

    NASA Technical Reports Server (NTRS)

    Reihs, Christa M.; Golden, David M.; Tolbert, Margaret A.

    1990-01-01

    The uptake of nitric acid by sulfuric acid solutions representative of stratospheric particulate at low temperatures was measured to determine the solubility of nitric acid in sulfuric acid solutions as a function of H2SO4 concentration and solution temperature. Solubilities are reported for sulfuric acid solutions ranging from 58 to 87 wt pct H2SO4 over a temperature range from 188 to 240 K, showing that, in general, the solubility of nitric acid increases with decreasing sulfuric acid concentration and with decreasing temperature. The measured solubilities indicate that nitric acid in the global stratosphere will be found predominantly in the gas phase.

  1. 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.

  2. Influence of dissolved organic carbon content on modelling natural organic matter acid-base properties.

    PubMed

    Garnier, Cédric; Mounier, Stéphane; Benaïm, Jean Yves

    2004-10-01

    Natural organic matter (NOM) behaviour towards proton is an important parameter to understand NOM fate in the environment. Moreover, it is necessary to determine NOM acid-base properties before investigating trace metals complexation by natural organic matter. This work focuses on the possibility to determine these acid-base properties by accurate and simple titrations, even at low organic matter concentrations. So, the experiments were conducted on concentrated and diluted solutions of extracted humic and fulvic acid from Laurentian River, on concentrated and diluted model solutions of well-known simple molecules (acetic and phenolic acids), and on natural samples from the Seine river (France) which are not pre-concentrated. Titration experiments were modelled by a 6 acidic-sites discrete model, except for the model solutions. The modelling software used, called PROSECE (Programme d'Optimisation et de SpEciation Chimique dans l'Environnement), has been developed in our laboratory, is based on the mass balance equilibrium resolution. The results obtained on extracted organic matter and model solutions point out a threshold value for a confident determination of the studied organic matter acid-base properties. They also show an aberrant decreasing carboxylic/phenolic ratio with increasing sample dilution. This shift is neither due to any conformational effect, since it is also observed on model solutions, nor to ionic strength variations which is controlled during all experiments. On the other hand, it could be the result of an electrode troubleshooting occurring at basic pH values, which effect is amplified at low total concentration of acidic sites. So, in our conditions, the limit for a correct modelling of NOM acid-base properties is defined as 0.04 meq of total analysed acidic sites concentration. As for the analysed natural samples, due to their high acidic sites content, it is possible to model their behaviour despite the low organic carbon concentration.

  3. Gas-saturated solution process to obtain microcomposite particles of alpha lipoic acid/hydrogenated colza oil in supercritical carbon dioxide.

    PubMed

    Mishima, Kenji; Honjo, Masatoshi; Sharmin, Tanjina; Ito, Shota; Kawakami, Ryo; Kato, Takafumi; Misumi, Makoto; Suetsugu, Tadashi; Orii, Hideaki; Kawano, Hiroyuki; Irie, Keiichi; Sano, Kazunori; Mishima, Kenichi; Harada, Takunori; Ouchi, Mikio

    2016-09-01

    Alpha lipoic acid (ALA), an active substance in anti-aging products and dietary supplements, need to be masked with an edible polymer to obscure its unpleasant taste. However, the high viscosity of the ALA molecules prevents them from forming microcomposites with masking materials even in supercritical carbon dioxide (scCO2). Therefore, the purpose of this study was to investigate and develop a novel production method for microcomposite particles for ALA in hydrogenated colza oil (HCO). Microcomposite particles of ALA/HCO were prepared by using a novel gas-saturated solution (PGSS) process in which the solid-dispersion method is used along with stepwise temperature control (PGSS-STC). Its high viscosity prevents the formation of microcomposites in the conventional PGSS process even under strong agitation. Here, we disperse the solid particles of ALA and HCO in scCO2 at low temperatures and change the temperature stepwise in order to mix the melted ALA and HCO in scCO2. As a result, a homogeneous dispersion of the droplets of ALA in melted HCO saturated with CO2 is obtained at high temperatures. After the rapid expansion of the saturated solution through a nozzle, microcomposite particles of ALA/HCO several micrometers in diameter are obtained.

  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. Highly biocompatible yogurt-derived carbon dots as multipurpose sensors for detection of formic acid vapor and metal ions

    NASA Astrophysics Data System (ADS)

    Moonrinta, Sasaluck; Kwon, Binhee; In, Insik; Kladsomboon, Sumana; Sajomsang, Warayuth; Paoprasert, Peerasak

    2018-07-01

    Carbon dots are fascinating nanomaterials given their straightforward synthesis, unique optical properties, sensing capabilities, and biocompatibility. In this work, biocompatible carbon dots were prepared from yogurt using a two-step pyrolysis/hydrothermal method. The dots were spherical in shape with an average size of 4.7 nm. They showed blue emission under UV illumination with a quantum yield of 1.5%. Their photoluminescence was stable over three months and in both strong buffer solutions and highly concentrated salt solutions. The optical absorption and photoluminescence properties of the dots were employed for vapor and metal ion sensing, respectively. For the first time, the carbon dots were integrated into an optical electronic nose, and used for the detection of formic acid vapor at room temperature. Sensing was based on monitoring the optical transmission through a carbon dot film upon exposure to vapor, and the results were confirmed by UV-visible spectroscopy. The carbon dot-integrated electronic nose was able to distinguish vapor from formic acid/water solutions at different concentrations, with a detection limit of 7.3% v/v. The sensitivity of the dots to metal ions was tested by measuring the photoluminescence emission intensity at different excitation wavelengths. Principal component analysis was used to differentiate between the ions. The results suggested that interactions between carbon dots and metals ions occurred at a range of binding sites. The biocompability of the dots was demonstrated to be excellent. The study identified carbon dots produced from yogurt as multipurpose fluorescent nanomaterials with potential sensing and biomedical applications.

  6. Reference electrode for strong oxidizing acid solutions

    DOEpatents

    Rigdon, Lester P.; Harrar, Jackson E.; Bullock, Sr., Jack C.; McGuire, Raymond R.

    1990-01-01

    A reference electrode for the measurement of the oxidation-reduction potentials of solutions is especially suitable for oxidizing solutions such as highly concentrated and fuming nitric acids, the solutions of nitrogen oxides, N.sub.2 O.sub.4 and N.sub.2 O.sub.5, in nitric acids. The reference electrode is fabricated of entirely inert materials, has a half cell of Pt/Ce(IV)/Ce(III)/70 wt. % HNO.sub.3, and includes a double-junction design with an intermediate solution of 70 wt. % HNO.sub.3. The liquid junctions are made from Corning No. 7930 glass for low resistance and negligible solution leakage.

  7. Recovery of zinc and manganese, and other metals (Fe, Cu, Ni, Co, Cd, Cr, Na, K) from Zn-MnO2 and Zn-C waste batteries: Hydroxyl and carbonate co-precipitation from solution after reducing acidic leaching with use of oxalic acid

    NASA Astrophysics Data System (ADS)

    Sobianowska-Turek, A.; Szczepaniak, W.; Maciejewski, P.; Gawlik-Kobylińska, M.

    2016-09-01

    The article discusses the current situation of the spent batteries and portable accumulators management. It reviews recycling technologies of the spent batteries and portable accumulators which are used in the manufacturing installations in the world. Also, it presents the authors' research results on the reductive acidic leaching of waste material of the zinc-carbon batteries (Zn-C) and zinc-manganese batteries (alkaline Zn-MnO2) delivered by a company dealing with mechanical treatment of this type of waste stream. The research data proved that the reductive acidic leaching (H2SO4 + C2H2O4) of the battery's black mass allows to recover 85.0% of zinc and 100% of manganese. Moreover, it was found that after the reductive acidic leaching it is possible to recover nearly 100% of manganese, iron, cadmium, and chromium, 98.0% of cobalt, 95.5% of zinc, and 85.0% of copper and nickel from the solution with carbonate method. On the basis of the results, it is possible to assume that the carbonate method can be used for the preparation of manganese-zinc ferrite.

  8. 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.

  9. 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.

  10. Iodide-Photocatalyzed Reduction of Carbon Dioxide to Formic Acid with Thiols and Hydrogen Sulfide.

    PubMed

    Berton, Mateo; Mello, Rossella; González-Núñez, María Elena

    2016-12-20

    The photolysis of iodide anions promotes the reaction of carbon dioxide with hydrogen sulfide or thiols to quantitatively yield formic acid and sulfur or disulfides. The reaction proceeds in acetonitrile and aqueous solutions, at atmospheric pressure and room temperature by irradiation using a low-pressure mercury lamp. This transition-metal-free photocatalytic process for CO 2 capture coupled with H 2 S removal may have been relevant as a prebiotic carbon dioxide fixation. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. 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.

  12. Production of Odd-Carbon Dicarboxylic Acids in Escherichia coli Using an Engineered Biotin-Fatty Acid Biosynthetic Pathway.

    PubMed

    Haushalter, Robert W; Phelan, Ryan M; Hoh, Kristina M; Su, Cindy; Wang, George; Baidoo, Edward E K; Keasling, Jay D

    2017-04-05

    Dicarboxylic acids are commodity chemicals used in the production of plastics, polyesters, nylons, fragrances, and medications. Bio-based routes to dicarboxylic acids are gaining attention due to environmental concerns about petroleum-based production of these compounds. Some industrial applications require dicarboxylic acids with specific carbon chain lengths, including odd-carbon species. Biosynthetic pathways involving cytochrome P450-catalyzed oxidation of fatty acids in yeast and bacteria have been reported, but these systems produce almost exclusively even-carbon species. Here we report a novel pathway to odd-carbon dicarboxylic acids directly from glucose in Escherichia coli by employing an engineered pathway combining enzymes from biotin and fatty acid synthesis. Optimization of the pathway will lead to industrial strains for the production of valuable odd-carbon diacids.

  13. 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.

  14. Effects of EDTA and low molecular weight organic acids on soil solution properties of a heavy metal polluted soil.

    PubMed

    Wu, L H; Luo, Y M; Christie, P; Wong, M H

    2003-02-01

    A pot experiment was conducted to study the effects of EDTA and low molecular weight organic acids (LMWOA) on the pH, total organic carbon (TOC) and heavy metals in the soil solution in the rhizosphere of Brassica juncea grown in a paddy soil contaminated with Cu, Zn, Pb and Cd. The results show that EDTA and LMWOA have no effect on the soil solution pH. EDTA addition significantly increased the TOC concentrations in the soil solution. The TOC concentrations in treatments with EDTA were significantly higher than those in treatments with LMWOA. Adding 3 mmol kg(-1) EDTA to the soil markedly increased the total concentrations of Cu, Zn, Pb and Cd in the soil solution. Compared to EDTA, LMWOA had a very small effect on the metal concentrations. Total concentrations in the soil solution followed the sequence: EDTA > citric acid (CA) approximately oxalic acid (OA) approximately malic acid (MA) for Cu and Pb; EDTA > MA > CA approximately OA for Zn; and EDTA > MA > CA > OA for Cd. The labile concentrations of Cu, Zn, Pb and Cd showed similar trends to the total concentrations.

  15. Adsorptive removal of antibiotics from aqueous solution using carbon materials.

    PubMed

    Yu, Fei; Li, Yong; Han, Sheng; Ma, Jie

    2016-06-01

    Antibiotics, an important type of environmental contamination, have attracted many researchers to the study of their removal from aqueous solutions. Adsorption technology is a fast, efficient, and economical physicochemical method that is extensively used in wastewater treatment. From original activated carbon and carbon nanotubes to the latest graphene-based materials, carbon-based materials have been widely used as highly effective adsorbents for contaminant removal from aqueous solution because of their large specific surface area, high porosity, and high reaction activity. In this article, adsorption removal methods for four major types of antibiotic (tetracyclines, sulfonamides, macrolides, and quinolones) are reviewed. We also provide an overview of the application development of carbon materials as adsorbents for antibiotic removal from aqueous solution. The most promising works are discussed, and the main challenges in preparing high-performance adsorbents and the development tendency of adsorbents are also analyzed. This work provides theoretical guidance for subsequent research in the design and modification of carbon materials for applications in the adsorption removal of antibiotics from aqueous solution. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Production of Odd-Carbon Dicarboxylic Acids in Escherichia coli Using an Engineered Biotin–Fatty Acid Biosynthetic Pathway

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Haushalter, Robert W.; Phelan, Ryan M.; Hoh, Kristina M.

    Dicarboxylic acids are commodity chemicals used in the production of plastics, polyesters, nylons, fragrances, and medications. Bio-based routes to dicarboxylic acids are gaining attention due to environmental concerns about petroleum-based production of these compounds. Some industrial applications require dicarboxylic acids with specific carbon chain lengths, including odd-carbon species. Biosynthetic pathways involving cytochrome P450-catalyzed oxidation of fatty acids in yeast and bacteria have been reported, but these systems produce almost exclusively even-carbon species. Here in this paper we report a novel pathway to odd-carbon dicarboxylic acids directly from glucose in Escherichia coli by employing an engineered pathway combining enzymes from biotinmore » and fatty acid synthesis. Optimization of the pathway will lead to industrial strains for the production of valuable odd-carbon diacids.« less

  17. Surface characterisation of ethylene propylene diene rubber upon exposure to aqueous acidic solution

    NASA Astrophysics Data System (ADS)

    Mitra, Susanta; Ghanbari-Siahkali, Afshin; Kingshott, Peter; Hvilsted, Søren; Almdal, Kristoffer

    2006-07-01

    Two types of pure ethylene propylene diene rubbers were exposed to two different acids for varying period of time. Surface characterisation was carried out using X-ray photoelectron spectroscopy (XPS). Two EPDM rubbers selected for this study were comparable in co-monomer compositions but significantly different with respect to molar mass and the presence of long chain branching. Both rubbers contained 5-ethylidene-2-norbornene (ENB) as diene. Solution cast films of pure EPDM samples were exposed in two different acidic solutions, viz. chromosulphuric (Cr (VI)/H 2SO 4) and sulphuric acid (H 2SO 4) (20%, v/v) at ambient temperature from 1 to 12 weeks. XPS analysis indicated that several oxygenated species were formed on the surface of both rubbers after exposure. It was postulated from the XPS analyses that both aqueous acidic solutions attacked the olefinic double bonds (C dbnd C) of ENB. Furthermore, 20% Cr (VI)/H 2SO 4 also attacked the allylic carbon-hydrogen (C sbnd H) bonds of ENB resulting in more oxygenated species on the surface compared to 20% H 2SO 4 under identical conditions. Cr (VI) in the 20% Cr (VI)/H 2SO 4 was found to play an important role in alteration of surface chemistry. Studies using a model system consisting of EPDM mixed with Cr (VI) and Cr (III) salts revealed that the change of oxidation state from Cr (VI) to Cr (III) as a consequence of direct involvement of Cr (VI) in the chemical alteration of EPDM surfaces. Interestingly, the presence of long chain branching and molar mass did not significantly influence the chemical processes owing to the acid treatment.

  18. Rapid and efficient removal of Pb(II) from aqueous solutions using biomass-derived activated carbon with humic acid in-situ modification.

    PubMed

    Guo, Zizhang; Zhang, Jian; Kang, Yan; Liu, Hai

    2017-11-01

    This study developed an humic acid (HA) in-situ modified activated carbon adsorbent (AC-HA) for the rapid and efficient removal of Pb(II) from aqueous media, and adsorption mechanisms are discussed. The physicochemical characteristics of activated carbons (AC) were investigated via N 2 adsorption/desorption, scanning electron microscopy (SEM), Boehm's titration method and Fourier transform infrared spectroscopy (FTIR). AC-HA exhibited richer oxygen-containing functional groups than the original AC. In addition, the removal performance of AC-HA (250.0mg/g) toward Pb(II) was greatly improved compared with the original AC (166.7mg/g). The batch adsorption study results revealed that the Pb(II) adsorption data were best fit by the pseudo-second-order model of kinetics and Langmuir isotherm of isothermals, and therefore, the effect of the solution pH was studied. The superior performance of AC-HA was attributed to the HA modification, which contains numbers of groups and has a strong π-π interaction binding energy with AC and Pb(II) species. The adsorption mechanisms were confirmed via the XPS study. More importantly, the modified method is simple and has a low cost of production. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. The Degradation of 14C-Glutamic Acid by L-Glutamic Acid Decarboxylase.

    ERIC Educational Resources Information Center

    Dougherty, Charles M; Dayan, Jean

    1982-01-01

    Describes procedures and semi-micro reaction apparatus (carbon dioxide trap) to demonstrate how a particular enzyme (L-Glutamic acid decarboxylase) may be used to determine the site or sites of labeling in its substrate (carbon-14 labeled glutamic acid). Includes calculations, solutions, and reagents used. (Author/SK)

  20. Analytical method for dissolved-organic carbon fractionation

    USGS Publications Warehouse

    Leenheer, Jerry A.; Huffman, Edward W. D.

    1979-01-01

    A standard procedure for analytical-scale dissolved organic carbon fractionation is presented, whereby dissolved organic carbon in water is first fractionated by a nonionic macroreticular resin into acid, base, and neutral hydrophobic organic solute fractions, and next fractionated by ion-exchange resins into acid, base, and neutral hydrophilic solute fractions. The hydrophobic solutes are defined as those sorbed on a nonionic, acrylic-ester macroreticular resin and are differentiated into acid, base, and nautral fractions by sorption/desorption controlled by pH adjustment. The hydrophilic bases are next sorbed on strong-acid ion-exchange resin, followed by sorption of hydrophilic acids on a strong-base ion-exchange resin. Hydrophilic neutrals are not sorbed and remain dissolved in the deionized water at the end of the fractionation procedure. The complete fractionation can be performed on a 200-milliliter filtered water sample, whose dissolved organic carbon content is 5-25 mg/L and whose specific conductance is less than 2,000 μmhos/cm at 25°C. The applications of dissolved organic carbon fractionation analysis range from field studies of changes of organic solute composition with synthetic fossil fuel production, to fundamental studies of the nature of sorption processes.

  1. Effects of dilute substitutional solutes on interstitial carbon in α-Fe: Interactions and associated carbon diffusion from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Liu, Peitao; Xing, Weiwei; Cheng, Xiyue; Li, Dianzhong; Li, Yiyi; Chen, Xing-Qiu

    2014-07-01

    By means of first-principles calculations coupled with the kinetic Monte Carlo simulations, we have systematically investigated the effects of dilute substitutional solutes on the behaviors of carbon in α-Fe. Our results uncover the following. (i) Without the Fe vacancy the interactions between most solutes and carbon are repulsive due to the strain relief, whereas Mn has a weak attractive interaction with its nearest-neighbor carbon due to the local ferromagnetic coupling effect. (ii) The presence of the Fe vacancy results in attractive interactions of all the solutes with carbon. In particular, the Mn-vacancy pair shows an exceptionally large binding energy of -0.81 eV with carbon. (iii) The alloying addition significantly impacts the atomic-scale concentration distributions and chemical potential of carbon in the Fe matrix. Among them, Mn and Cr increase the carbon chemical potential, whereas Al and Si reduce it. (iv) Within the dilute scale of the alloying solution, the solute concentration- and temperature-dependent carbon diffusivities demonstrate that Mn has a little impact on the carbon diffusion, whereas Cr (Al or Si) remarkably retards the carbon diffusion. Our results provide a certain implication for better understanding the experimental observations related with the carbon solubility limit, carbon microsegregation, and carbide precipitations in the ferritic steels.

  2. 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)).

  3. Dissolution profile of dolomite in chloric acid solution: The effect of chloric acid concentration and pulp density

    NASA Astrophysics Data System (ADS)

    Solihin, Indriani, Mubarok, M. Zaki

    2018-05-01

    Dolomite is one of carbonate minerals that contain magnesium. Magnesium is important element used in many aspects of life such as cofactor of many enzymes in human body, nutrient for plants, and raw material in automotive industry. Dolomite can be processed through low temperature process to obtain magnesium and calcium oxide that is needed in important applications such as base material for making drugs, raw material in the synthesize slow release fertilizer, materials for fire retardant, component for catalyst, etc. One of the important step of this low temperature process is dissolution of dolomite. Optimizing the dissolution process determines the % extraction of magnesium and calcium oxide from dolomite. The dissolution of dolomite from Gresik, East Java Provence Indonesia, in chloric acid solution has been conducted. Chloric acid concentration and pulp density are the variables that were observed. The dissolution of magnesium and calcium from Gresik dolomite was found to be very fast. The stable stage of dissolution can be reached for 5-10 seconds. The % extraction is mainly determined by the molar ratio of chloric acid / dolomite. At molar ratio of chloric acid / dolomite equal or above stoichiometric of dolomite dissolution, % extraction of magnesium is almost 100 %.

  4. Determination of the conformation of 2-hydroxy- and 2-aminobenzoic acid dimers using 13C NMR and density functional theory/natural bond order analysis: the central importance of the carboxylic acid carbon.

    PubMed

    Burnette, Ronald R; Weinhold, Frank

    2006-07-20

    The 13C chemical shift for the carboxylic acid carbon provides a powerful diagnostic probe to determine the preferred isomeric dimer structures of benzoic acid derivatives undergoing intra- and intermolecular H-bonding in the gas, solution and crystalline phases. We have employed hybrid density functional calculations and natural bond orbital analysis to elucidate the electronic origins of the observed 13C shieldings and their relationship to isomeric stability. We find that delocalizing interactions from the carbonyl oxygen lone pairs (nO) into vicinal carbon-oxygen and carbon-carbon antibonds (sigmaCO*,sigmaCC*) make critical contributions to the 13C shieldings, and these nO --> sigmaCO*, nO --> sigmaCC* interactions are in turn sensitive to the intramolecular interactions that dictate dimer structure and stability. The carboxyl carbon atom can thus serve as a useful detector of subtle structural and conformational features in this pharmacologically important class of carboxylic acid interactions.

  5. The response of soil solution chemistry in European forests to decreasing acid deposition.

    PubMed

    Johnson, James; Graf Pannatier, Elisabeth; Carnicelli, Stefano; Cecchini, Guia; Clarke, Nicholas; Cools, Nathalie; Hansen, Karin; Meesenburg, Henning; Nieminen, Tiina M; Pihl-Karlsson, Gunilla; Titeux, Hugues; Vanguelova, Elena; Verstraeten, Arne; Vesterdal, Lars; Waldner, Peter; Jonard, Mathieu

    2018-03-31

    Acid deposition arising from sulphur (S) and nitrogen (N) emissions from fossil fuel combustion and agriculture has contributed to the acidification of terrestrial ecosystems in many regions globally. However, in Europe and North America, S deposition has greatly decreased in recent decades due to emissions controls. In this study, we assessed the response of soil solution chemistry in mineral horizons of European forests to these changes. Trends in pH, acid neutralizing capacity (ANC), major ions, total aluminium (Al tot ) and dissolved organic carbon were determined for the period 1995-2012. Plots with at least 10 years of observations from the ICP Forests monitoring network were used. Trends were assessed for the upper mineral soil (10-20 cm, 104 plots) and subsoil (40-80 cm, 162 plots). There was a large decrease in the concentration of sulphate (SO42-) in soil solution; over a 10-year period (2000-2010), SO42- decreased by 52% at 10-20 cm and 40% at 40-80 cm. Nitrate was unchanged at 10-20 cm but decreased at 40-80 cm. The decrease in acid anions was accompanied by a large and significant decrease in the concentration of the nutrient base cations: calcium, magnesium and potassium (Bc = Ca 2+  + Mg 2+  + K + ) and Al tot over the entire dataset. The response of soil solution acidity was nonuniform. At 10-20 cm, ANC increased in acid-sensitive soils (base saturation ≤10%) indicating a recovery, but ANC decreased in soils with base saturation >10%. At 40-80 cm, ANC remained unchanged in acid-sensitive soils (base saturation ≤20%, pHCaCl2 ≤ 4.5) and decreased in better-buffered soils (base saturation >20%, pHCaCl2 > 4.5). In addition, the molar ratio of Bc to Al tot either did not change or decreased. The results suggest a long-time lag between emission abatement and changes in soil solution acidity and underline the importance of long-term monitoring in evaluating ecosystem response to decreases in deposition. © 2018 John Wiley & Sons

  6. 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…

  7. Mineralization of gellan gum hydrogels with calcium and magnesium carbonates by alternate soaking in solutions of calcium/magnesium and carbonate ion solutions.

    PubMed

    Lopez-Heredia, Marco A; Łapa, Agata; Reczyńska, Katarzyna; Pietryga, Krzysztof; Balcaen, Lieve; Mendes, Ana C; Schaubroeck, David; Van Der Voort, Pascal; Dokupil, Agnieszka; Plis, Agnieszka; Stevens, Chris V; Parakhonskiy, Bogdan V; Samal, Sangram Keshari; Vanhaecke, Frank; Chai, Feng; Chronakis, Ioannis S; Blanchemain, Nicolas; Pamuła, Elżbieta; Skirtach, Andre G; Douglas, Timothy E L

    2018-04-27

    Mineralization of hydrogels is desirable prior to applications in bone regeneration. CaCO 3 is a widely used bone regeneration material and Mg, when used as a component of calcium phosphate biomaterials, has promoted bone-forming cell adhesion and proliferation and bone regeneration. In this study, gellan gum (GG) hydrogels were mineralized with carbonates containing different amounts of calcium (Ca) and magnesium (Mg) by alternate soaking in, firstly, a calcium and/or magnesium ion solution and, secondly, a carbonate ion solution. This alternate soaking cycle was repeated five times. Five different calcium and/or magnesium ion solutions, containing different molar ratios of Ca to Mg ranging from Mg-free to Ca-free were compared. Carbonate mineral formed in all sample groups subjected to the Ca:Mg elemental ratio in the carbonate mineral formed was higher than in the respective mineralizing solution. Mineral formed in the absence of Mg was predominantly CaCO 3 in the form of a mixture of calcite and vaterite. Increasing the Mg content in the mineral formed led to the formation of magnesian calcite, decreased the total amount of the mineral formed and its crystallinity. Hydrogel mineralization and increasing Mg content in mineral formed did not obviously improve proliferation of MC3T3-E1 osteoblast-like cells or differentiation after 7 days. This article is protected by copyright. All rights reserved.

  8. Decontamination of adsorbed chemical warfare agents on activated carbon using hydrogen peroxide solutions.

    PubMed

    Osovsky, Ruth; Kaplan, Doron; Nir, Ido; Rotter, Hadar; Elisha, Shmuel; Columbus, Ishay

    2014-09-16

    Mild treatment with hydrogen peroxide solutions (3-30%) efficiently decomposes adsorbed chemical warfare agents (CWAs) on microporous activated carbons used in protective garments and air filters. Better than 95% decomposition of adsorbed sulfur mustard (HD), sarin, and VX was achieved at ambient temperatures within 1-24 h, depending on the H2O2 concentration. HD was oxidized to the nontoxic HD-sulfoxide. The nerve agents were perhydrolyzed to the respective nontoxic methylphosphonic acids. The relative rapidity of the oxidation and perhydrolysis under these conditions is attributed to the microenvironment of the micropores. Apparently, the reactions are favored due to basic sites on the carbon surface. Our findings suggest a potential environmentally friendly route for decontamination of adsorbed CWAs, using H2O2 without the need of cosolvents or activators.

  9. Anaerobic carbon metabolism by the tricarboxylic acid cycle

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vanlerberghe, G.C.; Horsey, A.K.; Weger, H.G.

    Nitrogen-limited cells of Selenastrum minutum (Naeg.) Collins are able to assimilate NH{sub 4}{sup +} in the dark under anaerobic conditions. Addition of NH{sub 4}{sup +} to anaerobic cells results in a threefold increase in tricarboxylic acid cycle (TCAC) CO{sub 2} efflux and an eightfold increase in the rate of anaplerotic carbon fixation via phosphoenspyruvate carboxylase. Both of these observations are consistent with increased TCAC carbon flow to supply intermediates for amino acid biosynthesis. Addition of H{sup 14}CO{sub 3}{sup {minus}} to anaerobic cells assimilating NH{sub 4}{sup +} results in the incorporation of radiolabel into the {alpha}-carboxyl carbon of glutamic acid. Incorporationmore » of radiolabel into glutamic acid is not simply a short-term phenomenon following NH{sub 4}{sup +} addition as the specific activity of glutamic acid increases over time. This indicates that this alga is able to maintain partial oxidative TCAC carbon flow while under anoxia to supply {alpha}ketoglutarate for glutamate production. During dark aerobic NH{sub 4}{sup +} assimilation, no radiolabel appears in fumarate or succinate and only a small amount occurs in malate. During anaerobic NH{sub 4}{sup +} assimilation, these metabolites contain a large proportion of the total radiolabel and radiolabel accumulates in succinate over time. Also, the ratio of dark carbon fixation to NH{sub 4}{sup +} assimilation is much higher under anaerobic than aerobic conditions. These observations suggest the operation of a partial reductive TCAC from oxaloacetic acid to malate, fumarate, and succinate. Such a pathway might contribute to redox balance in an anaerobic cell maintaining partial oxidative TCAC activity.« less

  10. Green preparation of a novel red mud@carbon composite and its application for adsorption of 2,4-dichlorophenoxyacetic acid from aqueous solution.

    PubMed

    Kazak, Omer; Eker, Yasin Ramazan; Akin, Ilker; Bingol, Haluk; Tor, Ali

    2017-10-01

    This study reports the eco-friendly preparation of a novel composite material consisting of red mud and carbon spheres, denoted as red mud@C composite, and its application for the removal of 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) from aqueous solution. The preparation route has a green approach because it follows the low-energy consuming one-step hydrothermal process by using starch as a renewable carbon precursor and red mud as a waste from aluminum production industry. Characterization of the red mud@C composite was performed by FT-IR, TGA, SEM, TEM, BET, XRD, and Raman microscopy analyses. The batch adsorption studies revealed that the red mud@C composite has higher 2,4-D adsorption efficiency than those of the red mud and the naked carbon spheres. The maximum removal at initial pH of 3.0 is explained by considering the pKa of 2,4-D and pH of point of zero charge (pH pzc ) of the composite material. The adsorption equilibrium time was 60 min, which followed the pseudo-second-order kinetic model together with intra-particle diffusion model. The isotherm analysis indicated that Freundlich isotherm model better represented the adsorption data, with isotherm parameters of k [15.849 (mg/g) (mg/L) -1/n ] and n (2.985). The prepared composite is reusable at least 5 cycles of adsorption-desorption with no significant decrease in the adsorption capacity.

  11. Preparation of porous carbon sphere from waste sugar solution for electric double-layer capacitor

    NASA Astrophysics Data System (ADS)

    Hao, Zhi-Qiang; Cao, Jing-Pei; Wu, Yan; Zhao, Xiao-Yan; Zhuang, Qi-Qi; Wang, Xing-Yong; Wei, Xian-Yong

    2017-09-01

    Waste sugar solution (WSS), which contains abundant 2-keto-L-gulonic acid, is harmful to the environment if discharged directly. For value-added utilization of the waste resource, a novel process is developed for preparation of porous carbon spheres by hydrothermal carbonization (HTC) of WSS followed by KOH activation. Additionally, the possible preparation mechanism of carbon spheres is proposed. The effects of hydrothermal and activation parameters on the properties of the carbon sphere are also investigated. The carbon sphere is applied to electric double-layer capacitor and its electrochemical performance is studied. These results show that the carbon sphere obtained by HTC at 180 °C for 12 h with the WSS/deionized water volume ratio of 2/3 possess the highest specific capacitance under identical activation conditions. The specific capacitance of the carbon spheres can reach 296.1 F g-1 at a current density of 40 mA g-1. Besides, excellent cycle life and good capacitance retention (89.6%) are observed at 1.5 A g-1 after 5000 cycles. This study not only provides a facile and potential method for the WSS treatment, but also achieves the high value-added recycling of WSS for the preparation of porous carbon spheres with superior electrochemical properties.

  12. Improvement of oxygen-containing functional groups on olive stones activated carbon by ozone and nitric acid for heavy metals removal from aqueous phase.

    PubMed

    Bohli, Thouraya; Ouederni, Abdelmottaleb

    2016-08-01

    Recently, modification of surface structure of activated carbons in order to improve their adsorption performance toward especial pollutants has gained great interest. Oxygen-containing functional groups have been devoted as the main responsible for heavy metal binding on the activated carbon surface; their introduction or enhancement needs specific modification and impregnation methods. In the present work, olive stones activated carbon (COSAC) undergoes surface modifications in gaseous phase using ozone (O3) and in liquid phase using nitric acid (HNO3). The activated carbon samples were characterized using N2 adsorption-desorption isotherm, SEM, pHpzc, FTIR, and Boehm titration. The activated carbon parent (COSAC) has a high surface area of 1194 m(2)/g and shows a predominantly microporous structure. Oxidation treatments with nitric acid and ozone show a decrease in both specific surface area and micropore volumes, whereas these acidic treatments have led to a fixation of high amount of surface oxygen functional groups, thus making the carbon surface more hydrophilic. Activated carbon samples were used as an adsorbent matrix for the removal of Co(II), Ni(II), and Cu(II) heavy metal ions from aqueous solutions. Adsorption isotherms were obtained at 30 °C, and the data are well fitted to the Redlich-Peterson and Langmuir equation. Results show that oxidized COSACs, especially COSAC(HNO3), are capable to remove more Co(II), Cu(II), and Ni(II) from aqueous solution. Nitric acid-oxidized olive stones activated carbon was tested in its ability to remove metal ions from binary systems and results show an important maximum adsorbed amount as compared to single systems.

  13. Process for the manufacture of carbon or graphite fibers

    NASA Technical Reports Server (NTRS)

    Overhoff, D.; Winkler, E.; Mueller, D.

    1979-01-01

    Carbon or graphite fibers are manufactured by heating polyacrylonitrile fiber materials in various solutions and gases. They are characterized in that the materials are heated to temperatures from 150 to 300 C in a solution containing one or more acids from the group of carbonic acids, sulfonic acids, and/or phenols. The original molecular orientation of the fibers is preserved by the cyclization that occurs before interlacing, which gives very strong and stiff carbon or graphite fibers without additional high temperature stretching treatments.

  14. Calcium leaching behavior of cementitious materials in hydrochloric acid solution.

    PubMed

    Yang, Huashan; Che, Yujun; Leng, Faguang

    2018-06-11

    The calcium leaching behavior of cement paste and silica fume modified calcium hydroxide paste, exposed to hydrochloric acid solution, is reported in this paper. The kinetic of degradation was assessed by the changes of pH of hydrochloric acid solution with time. The changes of compressive strength of specimens in hydrochloric acid with time were tested. Hydration products of leached specimens were also analyzed by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric (TG), and atomic force microscope (AFM). Tests results show that there is a dynamic equilibrium in the supply and consumption of calcium hydroxide in hydrochloric acid solution, which govern the stability of hydration products such as calcium silicate hydrate (C-S-H). The decrease of compressive strength indicates that C-S-H are decomposed due to the lower concentration of calcium hydroxide in the pore solution than the equilibrium concentration of the hydration products. Furthermore, the hydration of unhydrated clinker delayed the decomposition of C-S-H in hydrochloric acid solution due to the increase of calcium hydroxide in pore solution of cementitious materials.

  15. Population and size distribution of solute-rich mesospecies within mesostructured aqueous amino acid solutions.

    PubMed

    Jawor-Baczynska, Anna; Moore, Barry D; Lee, Han Seung; McCormick, Alon V; Sefcik, Jan

    2013-01-01

    Aqueous solutions of highly soluble substances such as small amino acids are usually assumed to be essentially homogenous systems with some degree of short range local structuring due to specific interactions on the sub-nanometre scale (e.g. molecular clusters, hydration shells), usually not exceeding several solute molecules. However, recent theoretical and experimental studies have indicated the presence of much larger supramolecular assemblies or mesospecies in solutions of small organic and inorganic molecules as well as proteins. We investigated both supersaturated and undersaturated aqueous solutions of two simple amino acids (glycine and DL-alanine) using Dynamic Light Scattering (DLS), Brownian Microscopy/Nanoparticles Tracking Analysis (NTA) and Cryogenic Transmission Electron Microscopy (Cryo-TEM). Colloidal scale mesospecies (nanodroplets) were previously reported in supersaturated solutions of these amino acids and were implicated as intermediate species on non-classical crystallization pathways. Surprisingly, we have found that the mesospecies are also present in significant numbers in undersaturated solutions even when the solute concentration is well below the solid-liquid equilibrium concentration (saturation limit). Thus, mesopecies can be observed with mean diameters ranging from 100 to 300 nm and a size distribution that broadens towards larger size with increasing solute concentration. We note that the mesospecies are not a separate phase and the system is better described as a thermodynamically stable mesostructured liquid containing solute-rich domains dispersed within bulk solute solution. At a given temperature, solute molecules in such a mesostructured liquid phase are subject to equilibrium distribution between solute-rich mesospecies and the surrounding bulk solution.

  16. Compatible solute influence on nucleic acids: Many questions but few answers

    PubMed Central

    Kurz, Matthias

    2008-01-01

    Compatible solutes are small organic osmolytes including but not limited to sugars, polyols, amino acids, and their derivatives. They are compatible with cell metabolism even at molar concentrations. A variety of organisms synthesize or take up compatible solutes for adaptation to extreme environments. In addition to their protective action on whole cells, compatible solutes display significant effects on biomolecules in vitro. These include stabilization of native protein and nucleic acid structures. They are used as additives in polymerase chain reactions to increase product yield and specificity, but also in other nucleic acid and protein applications. Interactions of compatible solutes with nucleic acids and protein-nucleic acid complexes are much less understood than the corresponding interactions of compatible solutes with proteins. Although we may begin to understand solute/nucleic acid interactions there are only few answers to the many questions we have. I summarize here the current state of knowledge and discuss possible molecular mechanisms and thermodynamics. PMID:18522725

  17. Reduced carbon sequestration potential of biochar in acidic soil.

    PubMed

    Sheng, Yaqi; Zhan, Yu; Zhu, Lizhong

    2016-12-01

    Biochar application in soil has been proposed as a promising method for carbon sequestration. While factors affecting its carbon sequestration potential have been widely investigated, the number of studies on the effect of soil pH is limited. To investigate the carbon sequestration potential of biochar across a series of soil pH levels, the total carbon emission, CO 2 release from inorganic carbon, and phospholipid fatty acids (PLFAs) of six soils with various pH levels were compared after the addition of straw biochar produced at different pyrolysis temperatures. The results show that the acidic soils released more CO 2 (1.5-3.5 times higher than the control) after the application of biochar compared with neutral and alkaline soils. The degradation of both native soil organic carbon (SOC) and biochar were accelerated. More inorganic CO 2 release in acidic soil contributed to the increased degradation of biochar. Higher proportion of gram-positive bacteria in acidic soil (25%-36%) was responsible for the enhanced biochar degradation and simultaneously co-metabolism of SOC. In addition, lower substrate limitation for bacteria, indicated by higher C-O stretching after the biochar application in the acidic soil, also caused more CO 2 release. In addition to the soil pH, other factors such as clay contents and experimental duration also affected the phsico-chemical and biotic processes of SOC dynamics. Gram-negative/gram-positive bacteria ratio was found to be negatively related to priming effects, and suggested to serve as an indicator for priming effect. In general, the carbon sequestration potential of rice-straw biochar in soil reduced along with the decrease of soil pH especially in a short-term. Given wide spread of acidic soils in China, carbon sequestration potential of biochar may be overestimated without taking into account the impact of soil pH. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Kinetics study of carbon dioxide absorption reaction into the promoted methyldiethanolamine solution

    NASA Astrophysics Data System (ADS)

    Sitorus, Yasmikha Tiurlan Susanti; Taurina, Hanna Sucita; Altway, Ali; Rahmawati, Yeni; Nurkhamidah, Siti

    2017-05-01

    The absorption of carbon dioxide (CO2) is important in the industrial world. In industries, especially petrochemical, oil, and natural gas sectors, separation process of CO2 gas which is a corrosive gas (acid gas) is required. So, the separation process of CO2 gas stream is important, one of the methods used to remove CO2 from the gas stream is reactive absorption process using the promoted methyldiethanolamine (MDEA) solution. Therefore, this study is aimed to obtain the reaction kinetics data of CO2 absorption in MDEA solution using arginine as a promoter. Arginine was chosen because of its amino acid molecule which is reactive, so it can accelerate the reaction rate of MDEA. Moreover, this study also made a comparison between the reactivity of MDEA solution using arginine and MDEA solution using other promoters (glycine and piperazine) for CO2 absorption. The method used is absorption using laboratory scale of Wetted Wall Column (WWC) equipment at 1 atm. This study provides the reaction kinetics data information in order to optimize the separation process of CO2 in the industrialized world. The experimental results show that CO2 absorption rate at 323.15 K without any additon of arginine is 2.33 × 10-7 kmol/sec. By addition of 0.5 and 1 wt% of arginine, the absorption rate becomes 4 × 10-7 kmol/sec (2 times larger) and 6 × 10-7 kmol/sec (3 times larger). These results show that the addition of arginine as a promoter can increase the absorption rate of CO2 in MDEA solution and cover the weaknesses of MDEA solution. Based on the experimental result, the reaction kinetics constant for arginine is 1.91 × 1025 exp (-12296/T) (m3/kmol.s). Although, arginine reaction rate constant is lower than glycine and piperazine.

  19. Rotational Spectrum and Carbon Atom Structure of Dihydroartemisinic Acid

    NASA Astrophysics Data System (ADS)

    Evangelisti, Luca; Seifert, Nathan A.; Spada, Lorenzo; Pate, Brooks

    2016-06-01

    Dihydroartemisinic acid (DHAA, C15H24O2, five chiral centers) is a precursor in proposed low-cost synthetic routes to the antimalarial drug artemisinin. In one reaction process being considered in pharmaceutical production, DHAA is formed from an enantiopure sample of artemisinic acid through hydrogenation of the alkene. This reaction needs to properly set the stereochemistry of the asymmetric carbon for the synthesis to produce artemisinin. A recrystallization process can purify the diastereomer mixture of the hydrogenation reaction if the unwanted epimer is produced in less than 10% abundance. There is a need in the process analytical chemistry to rapidly (less than 1 min) measure the diastereomer excess and current solutions, such a HPLC, lack the needed measurement speed. The rotational spectrum of DHAA has been measured at 300:1 signal-to-noise ratio in a chirped-pulsed Fourier transform microwave spectrometer operating from 2-8 GHz using simple heating of the compound. The 13C isotope analysis provides a carbon atom structure that confirms the diastereomer. This structure is in excellent agreement with quantum chemistry calculations at the B2PLYPD3/ 6-311++G** level of theory. The DHAA spectrum is expected to be fully resolved from the unwanted diastereomer raising the potential for fast diastereomer excess measurement by rotational spectroscopy in the pharmaceutical production process.

  20. Synthesis of seaweed based carbon acid catalyst by thermal decomposition of ammonium sulfate for biodiesel production

    NASA Astrophysics Data System (ADS)

    Ee, Tang Zo; Lim, Steven; Ling, Pang Yean; Huei, Wong Kam; Chyuan, Ong Hwai

    2017-04-01

    Experiment was carried out to study the feasibility of biomass derived solid acid catalyst for the production of biodiesel using Palm Fatty Acid Distillate (PFAD). Malaysia indigenous seaweed was selected as the biomass to be carbonized as the catalyst support. Sulfonation of seaweed based carbon material was carried out by thermal decomposition of ammonium sulfate, (NH4)2SO4. The effects of carbonization temperature at 200 to 600°C on the catalyst physical and chemical properties were studied. The effect of reaction parameters on the fatty acid methyl ester (FAME) yield was studied by varying the concentration of ammonium sulfate (5.0 to 40.0 w/v%) and thermal decomposition time (15 to 90 min). Characterizations of catalyst were carried out to study the catalyst surface morphology with Scanning Electron Microscope (SEM), acid density with back titration and functional group attached with FT-IR. Results showed that when the catalyst sulfonated with 10.0 w/v% ammonium sulfate solution and heated to 235°C for 30 min, the highest FAME yield achieved was 23.7% at the reaction condition of 5.0 wt.% catalyst loading, esterification time of 4 h, methanol to PFAD molar ratio of 20:1 at 100°C reaction temperature.

  1. 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.

  2. Acid pre-treatment method for in situ ore leaching

    DOEpatents

    Mallon, R.G.; Braun, R.L.

    1975-10-28

    An acid leaching method is described for the recovery of a desired element from a subterranean rubblized body of primary ore containing the element and also having associated therewith a carbonate mineral wherein the rubblized ore body is flooded with an aqueous acidic solution in order to release carbon dioxide from the associated carbonate mineral. After a substantial portion of the available carbon dioxide is released and removed from the ore body, as by venting to the atmosphere, an oxidizing gas is introduced into the flooded, rubblized ore to oxidize the ore and form an acid leach solution effective in the presence of the dissolved oxidizing gas to dissolve the ore and cause the desired element to go into solution. The leach solution is then circulated to the surface where the metal values are recovered therefrom.

  3. Sequestering CO(2) by mineral carbonation: stability against acid rain exposure.

    PubMed

    Allen, Daniel J; Brent, Geoff F

    2010-04-01

    Mineral carbonation is a potentially attractive alternative to storage of compressed CO(2) in underground repositories, known as geosequestration. Processes for the conversion of basic ores, such as magnesium silicates, to carbonates have been proposed by various researchers, with storage of the carbonate as backfill in the original mine representing a solid carbon sink. The stability of such carbon sinks against acid rain and other sources of strong acids is examined here. It is acknowledged that in the presence of strong acid, carbonates will dissolve and release carbon dioxide. A sensitivity analysis covering annual average rainfall and pH that may be encountered in industrialized areas of the United States, China, Europe, and Australia was conducted to determine maximum CO(2) rerelease rates from mineral carbonation carbon sinks. This analysis is based on a worst-case premise that is equivalent to assuming infinitely rapid kinetics of dissolution of the carbonate. The analysis shows that under any likely conditions of pH and rainfall, leakage rates of stored CO(2) are negligible. This is illustrated in a hypothetical case study under Australian conditions. It is thus proposed that sequestration by mineral carbonation can be considered to be permanent on practical human time scales. Other possible sources of acid have also been considered.

  4. Activated carbons from potato peels: The role of activation agent and carbonization temperature of biomass on their use as sorbents for bisphenol A uptake from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Arampatzidou, An; Deliyanni, Eleni A.

    2015-04-01

    Activated carbons prepared from potato peels, a solid waste by product, and activated with different activating chemicals, have been studied for the adsorption of an endocrine disruptor (Bisphenol-A) from aqueous solutions. The potato peels biomass was activated with phosphoric acid, KOH and ZnCl2. The different activating chemicals were tested in order the better activation agent to be found. The carbons were carbonized by pyrolysis, in one step procedure, at three different temperatures in order the role of the temperature of carbonization to be pointed out. The porous texture and the surface chemistry of the prepared activated carbons were characterized by Nitrogen adsorption (BET), Scanning Electron Microscope (SEM), thermal analysis (DTA) and Fourier Transform Infrared Spectroscopy (FTIR). Batch experiments were performed to investigate the effect of pH, the adsorbent dose, the initial bisphenol A concentration and temperature. Equilibrium adsorption data were analyzed by Langmuir and Freundlich isotherms. The thermodynamic parameters such as the change of enthalpy (ΔH0), entropy (ΔS0) and Gibb's free energy (ΔG0) of adsorption systems were also evaluated. The adsorption capacity calculated from the Langmuir isotherm was found to be 450 mg g-1 at an initial pH 3 at 25 °C for the phosphoric acid activated carbon, that make the activated carbon a promising adsorbent material.

  5. [Study on solid dispersion of precipitated calcium carbonate-based oleanolic acid].

    PubMed

    Yan, Hong-mei; Zhang, Zhen-hai; Jia, Xiao-bin; Jiang, Yan-rong; Sun, E

    2015-05-01

    Oleanolic acid-precipitated calcium carbonate solid dispersion was prepared by using solvent evaporation method. The microscopic structure and physicochemical properties of solid dispersion were analyzed using differential scanning calorimetry and scanning electron microscopy (SEM). And its in vitro release also was investigated. The properties of the precipitated calcium carbonate was studied which was as a carrier of oleanolic acid solid dispersion. Differential scanning calorimetry analysis suggested that oleanolic acid may be present in solid dispersion as amorphous substance. The in vitro release determination results of oleanolic acid-precipitated calcium carbonate (1: 5) solid dispersion showed accumulated dissolution rate of.oleanolic acid was up to 90% at 45 min. Accelerating experiment showed that content and in vitro dissolution of oleanolic acid solid dispersion did not change after storing over 6 months. The results indicated that in vitro dissolution of oleanolic acid was improved greatly by the solid dispersion with precipitated calcium carbonate as a carrier. The solid dispersion is a stabilizing system which has actual applied value.

  6. Effect of the pH in the adsorption and in the immersion enthalpy of monohydroxylated phenols from aqueous solutions on activated carbons.

    PubMed

    Blanco-Martínez, D A; Giraldo, L; Moreno-Piraján, J C

    2009-09-30

    An activated carbon Carbochem--PS230 was modified by chemical and thermal treatment in flow of H(2) in order to evaluate the influence of the activated carbon chemical surface in the adsorption of the monohydroxylated phenols. The solid-solution interaction was determined by analyzing the adsorption isotherms at 298 K at pH 7, 9 and 11 during 48 h. The adsorption capacity of activated carbons increases when the pH solution decreases. The amount adsorbed increases in the reduced carbon at the maximum adsorption pH and decreases in the oxidized carbon. In the sample of granulated activated carbon, CAG, the monohydroxylated phenols adsorption capacity diminishes in the following order catechol >hydroquinone >resorcinol, at the three pH values. The experimental data are evaluated with Freundlich's and Langmuir's models. The immersion enthalpies are determined and increase with the retained amount, ranging between 21.5 and 45.7 J g(-1). In addition, the immersion enthalpies show more interaction with the reduced activated carbon that has lower total acidity contents.

  7. Anaerobic Carbon Metabolism by the Tricarboxylic Acid Cycle 1

    PubMed Central

    Vanlerberghe, Greg C.; Horsey, Anne K.; Weger, Harold G.; Turpin, David H.

    1989-01-01

    Nitrogen-limited cells of Selenastrum minutum (Naeg.) Collins are able to assimilate NH4+ in the dark under anaerobic conditions. Addition of NH4+ to anaerobic cells results in a threefold increase in tricarboxylic acid cycle (TCAC) CO2 efflux and an eightfold increase in the rate of anaplerotic carbon fixation via phosphoenolpyruvate carboxylase. Both of these observations are consistent with increased TCAC carbon flow to supply intermediates for amino acid biosynthesis. Addition of H14CO3− to anaerobic cells assimilating NH4+ results in the incorporation of radiolabel into the α-carboxyl carbon of glutamic acid. Incorporation of radiolabel into glutamic acid is not simply a short-term phenomenon following NH4+ addition as the specific activity of glutamic acid increases over time. This indicates that this alga is able to maintain partial oxidative TCAC carbon flow while under anoxia to supply α-ketoglutarate for glutamate production. During dark aerobic NH4+ assimilation, no radiolabel appears in fumarate or succinate and only a small amount occurs in malate. During anaerobic NH4+ assimilation, these metabolites contain a large proportion of the total radiolabel and radiolabel accumulates in succinate over time. Also, the ratio of dark carbon fixation to NH4+ assimilation is much higher under anaerobic than aerobic conditions. These observations suggest the operation of a partial reductive TCAC from oxaloacetic acid to malate, fumarate, and succinate. Such a pathway might contribute to redox balance in an anaerobic cell maintaining partial oxidative TCAC activity. PMID:16667215

  8. 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.

  9. Lignin-Derived Carbon Fibers as Efficient Heterogeneous Solid Acid Catalysts for Esterification of Oleic Acid

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Adhikari, Shiba P.; Hood, Zachary D.; Gallego, Nidia C.

    Here, the production of biodiesel by the esterification of oleic acid, as an example of free fatty acid (FFA), was explored by using a new solid acid catalyst derived from lignin, a highly abundant low-cost biomass material. The catalyst was synthesized from lignin-derived carbon fiber by straightforward sulfonation and contains 1.86 mmol/g of sulfonic acid (-SO 3H) groups. The catalyst was characterized by a variety of techniques including PXRD, TGA, TPD-MS, SEM, and XPS to understand the surface chemistry and the result of sulfonation. It was found that the sulfonated lignin-derived carbon fiber (CF-SO 3H) catalyst was very efficient atmore » esterifying oleic acid at 80 oC in 4 hours, with 10 wt. % catalyst (in terms of oleic acid content) and at a 10:1 molar ratio of methanol: oleic acid with a yield of 92%. Furthermore, the catalyst can be reused with no significant loss in activity after 4 cycles. Hence, synthesizing solid acid catalysts from lignin-derived carbon fiber affords a novel strategy for producing biodiesel via ‘green chemistry’.« less

  10. Lignin-Derived Carbon Fibers as Efficient Heterogeneous Solid Acid Catalysts for Esterification of Oleic Acid

    DOE PAGES

    Adhikari, Shiba P.; Hood, Zachary D.; Gallego, Nidia C.; ...

    2018-06-04

    Here, the production of biodiesel by the esterification of oleic acid, as an example of free fatty acid (FFA), was explored by using a new solid acid catalyst derived from lignin, a highly abundant low-cost biomass material. The catalyst was synthesized from lignin-derived carbon fiber by straightforward sulfonation and contains 1.86 mmol/g of sulfonic acid (-SO 3H) groups. The catalyst was characterized by a variety of techniques including PXRD, TGA, TPD-MS, SEM, and XPS to understand the surface chemistry and the result of sulfonation. It was found that the sulfonated lignin-derived carbon fiber (CF-SO 3H) catalyst was very efficient atmore » esterifying oleic acid at 80 oC in 4 hours, with 10 wt. % catalyst (in terms of oleic acid content) and at a 10:1 molar ratio of methanol: oleic acid with a yield of 92%. Furthermore, the catalyst can be reused with no significant loss in activity after 4 cycles. Hence, synthesizing solid acid catalysts from lignin-derived carbon fiber affords a novel strategy for producing biodiesel via ‘green chemistry’.« less

  11. Adsorptive removal of sulfate from acid mine drainage by polypyrrole modified activated carbons: Effects of polypyrrole deposition protocols and activated carbon source.

    PubMed

    Hong, Siqi; Cannon, Fred S; Hou, Pin; Byrne, Tim; Nieto-Delgado, Cesar

    2017-10-01

    Polypyrrole modified activated carbon was used to remove sulfate from acid mine drainage water. The polypyrrole modified activated carbon created positively charged functionality that offered elevated sorption capacity for sulfate. The effects of the activated carbon type, approach of polymerization, preparation temperature, solvent, and concentration of oxidant solution over the sulfate adsorption capacity were studied at an array of initial sulfate concentrations. A hardwood based activated carbon was the more favorable activated carbon template, and this offered better sulfate removal than when using bituminous based activated carbon or oak wood activated carbon as the template. The hardwood-based activated carbon modified with polypyrrole removed 44.7 mg/g sulfate, and this was five times higher than for the pristine hardwood-based activated carbon. Various protocols for depositing the polypyrrole onto the activated carbon were investigated. When ferric chloride was used as an oxidant, the deposition protocol that achieved the most N + atomic percent (3.35%) while also maintaining the least oxygen atomic percent (6.22%) offered the most favorable sulfate removal. For the rapid small scale column tests, when processing the AMD water, hardwood-based activated carbon modified with poly pyrrole exhibited 33 bed volume compared to the 5 bed volume of pristine activated carbons. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Carbonic acid salts at 25 or 45 degrees C to control loquat decay under shelf life conditions.

    PubMed

    Molinu, M G; D'Hallewin, G; Dore, A; Serusi, A; Venditti, T; Agabbio, M

    2005-01-01

    Generally recognised as save compounds (G.R.A.S) are attractive substitutes to synthetic chemicals in postharvest control diseases. They meet safety requirements, are cheap and able to be integrated with other disease control technologies. Among G.R.A.S compounds, carbonic acid salts have been investigated on carrots, bell pepper, melons, sweet cherries and their efficacy was also evaluated when combined with biological control agents. Moreover, the possibility to use sodium carbonate and sodium bicarbonate to prevent P. digitatum an P. italicum spread on Citrus fruit was studied since the begin of the 20th century. We explored the possibility to extend the use of carbonate-bicarbonate salts on loquat fruit in order to control the pathogens and to extend postharvest life. Loquat is a very perishable fruit, susceptible to decay, mechanical damage, moisture and nutritional losses during its postharvest life. We tested the combined effect of temperature and sodium or potassium carbonate-bicarbonate and ammonium carbonate. The fruit was dipped in the salt solutions at variable concentrations (0.5, 1 and 2% w/v) at 25 or 45 degrees C for two minutes and than stored under shelf life conditions (25 degrees C and 70% RH). Decay, weight loss, pH, titrable acidity and sugar content were detected after twelve days. Preliminary data show that the combined treatments were effective in decay control depending on salts. Best results were obtained with 2% potassium and sodium carbonate solution at 25 degrees C. Weight losses were related to treatment temperature and salts concentrations whereas, no differences were detected in the chemical parameters compared to the control.

  13. Amino acids of the Murchison meteorite. II - Five carbon acyclic primary beta-, gamma-, and delta-amino alkanoic acids

    NASA Technical Reports Server (NTRS)

    Cronin, J. R.; Pizzarello, S.; Yuen, G. U.

    1985-01-01

    The five-carbon acyclic primary beta, gamma, and delta amino alkanoic acids of the Murchison meteorite are studied using gas chromatography-mass spectrometry and ion exchange chromatography. The chromatograms reveal that alpha is the most abundant monoamino alkanoic acid followed by gamma and beta, and an exponential increase in the amount of amino acid is observed as the carbon number increases in the homologous series. The influence of frictional heating, spontaneous thermal decomposition, and radiation of the synthesis of amino acids is examined. The data obtained support an amino acid synthesis process involving random combination of single-carbon precursors.

  14. Process for the removal of radium from acidic solutions containing same

    DOEpatents

    Scheitlin, F.M.

    The invention is a process for the removal of radium from acidic aqueous solutions. In one aspect, the invention is a process for removing radium from an inorganic-acid solution. The process comprises contacting the solution with coal fly ash to effect adsorption of the radium on the ash. The radium-containing ash then is separated from the solution. The process is simple, comparatively inexpensive, and efficient. High radium-distribution coefficients are obtained even at room temperature. Coal fly ash is an inexpensive, acid-resistant, high-surface-area material which is available in large quantities throughout the United States. The invention is applicable, for example, to the recovery of /sup 226/Ra from nitric acid solutions which have been used to leach radium from uranium-mill tailings.

  15. Addition of granular activated carbon and trace elements to favor volatile fatty acid consumption during anaerobic digestion of food waste.

    PubMed

    Capson-Tojo, Gabriel; Moscoviz, Roman; Ruiz, Diane; Santa-Catalina, Gaëlle; Trably, Eric; Rouez, Maxime; Crest, Marion; Steyer, Jean-Philippe; Bernet, Nicolas; Delgenès, Jean-Philippe; Escudié, Renaud

    2018-07-01

    The effect of supplementing granular activated carbon and trace elements on the anaerobic digestion performance of consecutive batch reactors treating food waste was investigated. The results from the first batch suggest that addition of activated carbon favored biomass acclimation, improving acetic acid consumption and enhancing methane production. Adding trace elements allowed a faster consumption of propionic acid. A second batch proved that a synergy existed when activated carbon and trace elements were supplemented simultaneously. The degradation kinetics of propionate oxidation were particularly improved, reducing significantly the batch duration and improving the average methane productivities. Addition of activated carbon favored the growth of archaea and syntrophic bacteria, suggesting that interactions between these microorganisms were enhanced. Interestingly, microbial analyses showed that hydrogenotrophic methanogens were predominant. This study shows for the first time that addition of granular activated carbon and trace elements may be a feasible solution to stabilize food waste anaerobic digestion. Copyright © 2018 Elsevier Ltd. All rights reserved.

  16. Porous structure and surface chemistry of phosphoric acid activated carbon from corncob

    NASA Astrophysics Data System (ADS)

    Sych, N. V.; Trofymenko, S. I.; Poddubnaya, O. I.; Tsyba, M. M.; Sapsay, V. I.; Klymchuk, D. O.; Puziy, A. M.

    2012-11-01

    Active carbons have been prepared from corncob using chemical activation with phosphoric acid at 400 °C using varied ratio of impregnation (RI). Porous structure of carbons was characterized by nitrogen adsorption and scanning electron microscopy. Surface chemistry was studied by IR and potentiometric titration method. It has been shown that porosity development was peaked at RI = 1.0 (SBET = 2081 m2/g, Vtot = 1.1 cm3/g), while maximum amount of acid surface groups was observed at RI = 1.25. Acid surface groups of phosphoric acid activated carbons from corncob includes phosphate and strongly acidic carboxylic (pK = 2.0-2.6), weakly acidic carboxylic (pK = 4.7-5.0), enol/lactone (pK = 6.7-7.4; 8.8-9.4) and phenol (pK = 10.1-10.7). Corncob derived carbons showed high adsorption capacity to copper, especially at low pH. Maximum adsorption of methylene blue and iodine was observed for carbon with most developed porosity (RI = 1.0).

  17. Characterization of acid functional groups of carbon dots by nonlinear regression data fitting of potentiometric titration curves

    NASA Astrophysics Data System (ADS)

    Alves, Larissa A.; de Castro, Arthur H.; de Mendonça, Fernanda G.; de Mesquita, João P.

    2016-05-01

    The oxygenated functional groups present on the surface of carbon dots with an average size of 2.7 ± 0.5 nm were characterized by a variety of techniques. In particular, we discussed the fit data of potentiometric titration curves using a nonlinear regression method based on the Levenberg-Marquardt algorithm. The results obtained by statistical treatment of the titration curve data showed that the best fit was obtained considering the presence of five Brønsted-Lowry acids on the surface of the carbon dots with constant ionization characteristics of carboxylic acids, cyclic ester, phenolic and pyrone-like groups. The total number of oxygenated acid groups obtained was 5 mmol g-1, with approximately 65% (∼2.9 mmol g-1) originating from groups with pKa < 6. The methodology showed good reproducibility and stability with standard deviations below 5%. The nature of the groups was independent of small variations in experimental conditions, i.e. the mass of carbon dots titrated and initial concentration of HCl solution. Finally, we believe that the methodology used here, together with other characterization techniques, is a simple, fast and powerful tool to characterize the complex acid-base properties of these so interesting and intriguing nanoparticles.

  18. What does nitric acid really do to carbon nanofibers? [What nitric acid really does to carbon nanofibers

    DOE PAGES

    Sainio, S.; Nordlund, D.; Gandhiraman, R.; ...

    2016-09-15

    Understanding the chemical nature of the surface of carbon nanofibers (CNF) is critical in assessing their fundamental properties and tailoring them for the right application. To gain such knowledge, we present here a detailed X-ray adsorption spectroscopy (XAS) study accompanied by high resolution transmission electron microscopy (TEM) micrographs of two morphologically different CNF pairs (tetrahedral amorphous carbon (ta-C) grown “open structured” fibers and traditional bamboo-like “closed structured” fibers), where the surface chemical properties and structural features of the fibers are investigated in depth and the effects of nitric acid treatment on the fibers are revealed. The morphology of the fibermore » and/or the original seed- and adhesion layers markedly affect the response of the fibers to the acid treatment. Results also show that the nitric acid treatment increases the observed sp 2 intensity and modifies the two types of fibers to become more-alike both structurally and with respect to their oxygen functionalities. Furthermore, the XAS and HRTEM results confirm that a short nitric acid treatment does not remove the Ni catalyst particle but, instead, oxidizes their surfaces, especially in the case of ta-C grown fibers.« less

  19. What does nitric acid really do to carbon nanofibers? [What nitric acid really does to carbon nanofibers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sainio, S.; Nordlund, D.; Gandhiraman, R.

    Understanding the chemical nature of the surface of carbon nanofibers (CNF) is critical in assessing their fundamental properties and tailoring them for the right application. To gain such knowledge, we present here a detailed X-ray adsorption spectroscopy (XAS) study accompanied by high resolution transmission electron microscopy (TEM) micrographs of two morphologically different CNF pairs (tetrahedral amorphous carbon (ta-C) grown “open structured” fibers and traditional bamboo-like “closed structured” fibers), where the surface chemical properties and structural features of the fibers are investigated in depth and the effects of nitric acid treatment on the fibers are revealed. The morphology of the fibermore » and/or the original seed- and adhesion layers markedly affect the response of the fibers to the acid treatment. Results also show that the nitric acid treatment increases the observed sp 2 intensity and modifies the two types of fibers to become more-alike both structurally and with respect to their oxygen functionalities. Furthermore, the XAS and HRTEM results confirm that a short nitric acid treatment does not remove the Ni catalyst particle but, instead, oxidizes their surfaces, especially in the case of ta-C grown fibers.« less

  20. Adsorptive Removal of Nitrate from Aqueous Solution Using Nitrogen Doped Activated Carbon.

    PubMed

    Machida, Motoi; Goto, Tatsuru; Amano, Yoshimasa; Iida, Tatsuya

    2016-01-01

    Activated carbon (AC) has been widely applied for adsorptive removal of organic contaminants from aqueous phase, but not for ionic pollutants. In this study, nitrogen doped AC was prepared to increase the adsorption capacity of nitrate from water. AC was oxidized with (NH 4 ) 2 S 2 O 8 solution to maximize oxygen content for the first step, and then NH 3 gas treatment was carried out at 950°C to aim at forming quaternary nitrogen (N-Q) species on AC surface (Ox-9.5AG). Influence of solution pH was examined so as to elucidate the relationship between surface charge and adsorption amounts of nitrate. The results showed that Ox-9.5AG exhibited about twice higher adsorption capacity than non-treatment AC at any initial nitrate concentration and any equilibrium solution pH (pH e ) investigated. The more decrease in pH e value, the more adsorption amount of negatively charged nitrate ion, because the surface charge of AC and Ox-9.5AG could become more positive in acidic solution. The oxidation and consecutive ammonia treatments lead to increase in nitrogen content from 0.35 to 6.4% and decrease in the pH of the point of zero charge (pH pzc ) from 7.1 to 4.0 implying that positively charged N-Q of a Lewis acid was created on the surface of Ox-9.5AG. Based on a Langmuir data analysis, maximum adsorption capacity attained 0.5-0.6 mmol/g of nitrate and adsorption affinity was 3.5-4.0 L/mmol at pH e 2.5 for Ox-9.5AG.

  1. Thermodynamic Cconstraints on Coupled Carbonate-Pyrite Weathering Dynamics and Carbon Fluxes

    NASA Astrophysics Data System (ADS)

    Winnick, M.; Maher, K.

    2017-12-01

    Chemical weathering within the critical zone regulates global biogeochemical cycles, atmospheric composition, and the supply of key nutrients to terrestrial and aquatic ecosystems. Recent studies suggest that thermodynamic limits on solute production act as a first-order control on global chemical weathering rates; however, few studies have addressed the factors that set these thermodynamic limits in natural systems. In this presentation, we investigate the effects of soil CO2 concentrations and pyrite oxidation rates on carbonate dissolution and associated carbon fluxes in the East River watershed in Colorado, using concentration-discharge relationships and thermodynamic constraints. Within the shallow subsurface, soil respiration rates and moisture content determine the extent of carbonic acid-promoted carbonate dissolution through their modulation of soil pCO2 and the balance of open- v. closed-system weathering processes. At greater depths, pyrite oxidation generates sulfuric acid, which alters the approach to equilibrium of infiltrating waters. Through comparisons of concentration-discharge data and reactive transport model simulations, we explore the conditions that determine whether sulfuric acid reacts to dissolve additional carbonate mineral or instead reacts with alkalinity already in solution - the balance of which determines watershed carbon flux budgets. Our study highlights the importance of interactions between the chemical structure of the critical zone and the hydrologic regulation of flowpaths in determining concentration-discharge relationships and overall carbon fluxes.

  2. Effect of carbon and alloying solute atoms on helium behaviors in α-Fe

    NASA Astrophysics Data System (ADS)

    Zhang, Yange; You, Yu-Wei; Xu, Yichun; Liu, C. S.; Chen, J. L.; Luo, G.-N.

    2017-02-01

    Helium bubbles could strongly degrade the mechanical properties of ferritic steels in fission and fusion systems. The formation of helium bubble is directly affected by the interactions between helium and the compositions in steels, such as solute atoms, carbon and irradiation defects. We thereby performed systematical first-principles calculations to investigate the interactions of solute-helium and carbon-solute-helium. It is found that substitutional helium is more attractive than interstitial helium to all the considered 3p, 4p, 5p and 6p solutes. The attraction between carbon and substitutional helium suggests the carbon-solute-helium complex can be formed stably. By examining the charge density difference and thermal stability, it is found that the ternary complex shows stronger attraction with He than that of solute-helium pair for some solutes (S, Se, In, Te, Pb and Bi) and the complex could existed in iron stably at 700 K. The present theoretical results may be helpful for exploring alloy additions to mitigate the formation of large helium bubbles.

  3. PROCESS FOR RECOVERY OF URANIUM AND VANADIUM FROM CARBONATE SOLUTIONS BY REDUCTION-PRECIPITATION

    DOEpatents

    Ellis, D.A.; Lindblom, R.O.

    1957-09-24

    A process employing carbonate leaching of ores and an advantageous methcd of recovering the uranium and vanadium from the leach solution is described. The uranium and vanadium can be precipitated from carbonate leach solutions by reaction with sodium amalgam leaving the leach solution in such a condition that it is economical to replenish for recycling. Such a carbonate leach solution is treated with a dilute sodium amalgam having a sodium concentration within a range of about 0.01 to 0.5% of sodium. Efficiency of the treatment is dependent on at least three additional factors, intimacy of contact of the amalgam with the leach solution, rate of addition of the amalgam and exclusion of oxygen (air).

  4. Method for the production of dicarboxylic acids

    DOEpatents

    Nghiem, N.P.; Donnelly, M.; Millard, C.S.; Stols, L.

    1999-02-09

    The present invention is an economical fermentation method for the production of carboxylic acids comprising the steps of (a) inoculating a medium having a carbon source with a carboxylic acid-producing organism; (b) incubating the carboxylic acid-producing organism in an aerobic atmosphere to promote rapid growth of the organism thereby increasing the biomass of the organism; (c) controllably releasing oxygen to maintain the aerobic atmosphere; (d) controllably feeding the organism having increased biomass with a solution containing the carbon source to maintain the concentration of the carbon source within the medium of about 0.5 g/l up to about 1 g/l; (e) depriving the aerobic atmosphere of oxygen to produce an anaerobic atmosphere to cause the organism to undergo anaerobic metabolism; (f) controllably feeding the organism having increased biomass a solution containing the carbon source to maintain the concentration of the carbon source within the medium of {>=}1 g/l; and (g) converting the carbon source to carboxylic acids using the anaerobic metabolism of the organism. 7 figs.

  5. Method for the production of dicarboxylic acids

    DOEpatents

    Nghiem, Nhuan Phu; Donnelly, Mark; Millard, Cynthia S.; Stols, Lucy

    1999-01-01

    The present invention is an economical fermentation method for the production of carboxylic acids comprising the steps of a) inoculating a medium having a carbon source with a carboxylic acid-producing organism; b) incubating the carboxylic acid-producing organism in an aerobic atmosphere to promote rapid growth of the organism thereby increasing the biomass of the organism; c) controllably releasing oxygen to maintain the aerobic atmosphere; d) controllably feeding the organism having increased biomass with a solution containing the carbon source to maintain the concentration of the carbon source within the medium of about 0.5 g/L up to about 1 g/L; e) depriving the aerobic atmosphere of oxygen to produce an anaerobic atmosphere to cause the organism to undergo anaerobic metabolism; f) controllably feeding the organism having increased biomass a solution containing the carbon source to maintain the concentration of the carbon source within the medium of .gtoreq.1 g/L; and g) converting the carbon source to carboxylic acids using the anaerobic metabolism of the organism.

  6. Functionalization of Carbon Nanotubes via Electrophilic Substitution Reaction in Polyphosphoric Acid

    DTIC Science & Technology

    2006-07-26

    1 Title of proposed research: Functionalization of Carbon Nanotubes via Electrophilic Substitution Reaction in Polyphosphoric Acid Proposer: Jong...Choi, J.-Y.; Tan, L.-S.; Baek, J.-B. “Functionalization of carbon nanotubes via electrophilic substitution reaction in polyphosphoric acid” AFOSR...2006 4. TITLE AND SUBTITLE Functionalization of carbon nanotubes via electrophilic substitution reaction in polyphosphoric acid 5a. CONTRACT

  7. Modification of carbon fiber surfaces via grafting with Meldrum's acid

    NASA Astrophysics Data System (ADS)

    Cuiqin, Fang; Jinxian, Wu; Julin, Wang; Tao, Zhang

    2015-11-01

    The mechanism of Meldrum's acid modifying carbon fiber surfaces was investigated in this work. The existing carbonyl groups of carbon fibers were grafted with Meldrum's acid to create carboxylic functionalized surfaces. The surface functionalization effect was detected with X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscopy (AFM), and thermogravimetric analysis (TGA). The XPS results showed that the relative content of carboxylic groups on carbon fiber surfaces was increased from initial 1.41% to 7.84%, however, that of carbonyl groups was decreased from 23.11% to 13.28% after grafting reaction. The SEM, AFM and TGA results indicated that the surfaces of carbon fibers neither etched nor generated coating. The tensile strength of carbon fibers was preserved after grafting reaction according to single fiber tensile strength tests. The fibers were well combined with matrix and the maximal interlaminar shear strength (ILSS) of carbon fiber/epoxy resin composites was sharply increased approximately 74% after functionalization. The effects of acetic acid and sonication on the degree of the surface functionalization were also studied.

  8. Solution and shock-induced exsolution of argon in vitreous carbon

    NASA Technical Reports Server (NTRS)

    Gazis, Carey; Ahrens, Thomas J.

    1991-01-01

    To add to the knowledge of noble gas solution and exsolution in carbonaceus material, experiments were performed on vitreous carbon. Ar-rich vitreous carbon samples were prepared under vapor-saturated conditions using argon as the pressurizing medium. Solubility data were obtained for temperatures of 773 to 973 K and pressures of 250 to 1500 bars. Up to 7 wt pct Ar was dissolved in the carbon. The solubility data were compared to a thermodynamic model of argon atoms dissolving into a fixed population of 'holes' in the carbon. Two variations of the model yielded estimates of the enthalpy of solution of Ar in vitreous carbon equal to about -4700 cal/mole. Preliminary shock experiments showed that 28 percent of the total argon was released by driving 4 GPa shocks into the argon-rich carbon. It was demonstrated that shock-induced argon loss is not simply caused by the impact-induced diminution of grain size. The present value of shock pressure required for partial impact devolatilization of Ar from carbon is below the range (5-30 GPa) at which H2O is released from phyllosilicates.

  9. Vibrational studies in aqueous solutions. Part II. The acid oxalate ion and oxalic acid

    NASA Astrophysics Data System (ADS)

    Shippey, T. A.

    1980-08-01

    Assignments for oxalic acid in solution are re-examined. A detailed assignment of the IR and Raman spectra of the acid oxalate ion is presented for the first time. Raman spectroscopy is used to study the first ionization of oxalic acid.

  10. Carboxyl-functionalized nanoparticles with magnetic core and mesopore carbon shell as adsorbents for the removal of heavy metal ions from aqueous solution.

    PubMed

    Wang, Hui; Yu, Yi-Fei; Chen, Qian-Wang; Cheng, Kai

    2011-01-21

    This communication demonstrates superparamagnetic nanosized particles with a magnetic core and a porous carbon shell (thickness of 11 nm), which can remove 97% of Pb(2+) ions from an acidic aqueous solution at a Pb(2+) ion concentration of 100 mg L(-1). It is suggested that a weak electrostatic force of attraction between the heavy metal ions and the nanoparticles and the heavy metal ions adsorption on the mesopore carbon shell contribute most to the superior removal property.

  11. [Adsorbent effect of activated carbon on small molecular uremic toxin and its influence factors].

    PubMed

    Yang, Bo; Jiang, Yun-sheng; Li, Jun

    2003-06-01

    To analyze the adsorbent effect of activated carbon on uremic toxin and its influence factors. Uremic toxins (urea, creatinine and uric acid) were dissolved in the distilled water to obtain uremic toxic solution. Activated carbon was added to the solution, and the concentrations of uremic toxins were measured at different time spots. To determine the influence factors, some possible related materials, such as bile, amino acid, Ringer's, solution of glucose, HCl or NaOH respectively were added simultaneously. The concentrations of toxins in uremic toxic solution decreased 5 min after adding the activated carbon. The concentration of urea was the lowest at 30 min, but it increased after 50 min; while the concentrations of creatinine and uric acid reached the lowest level from 10 to 30 min after adding the activated carbon, and maintained at the same level after that. The bile, amino acid, electrolyte, glucose and pH value did not influence the adsorption of uric acid significantly, but they influenced the adsorption of urea and creatinine. Bile and amino acid influenced the concentration of urea remarkably, following glucose, NaOH and HCl. The effect of pH 2.0 solution on the creatinine concentration was the most significant, following glucose. Activated carbon has adsorptive effect on uremic toxins, but its adsorptive effect decreases as time goes on. Bile, glucose, amino acid, NaOH and HCl can affect the adsorptive effect of activated carbon on uremic toxins to some extent.

  12. Sulfonated mesoporous silica-carbon composites and their use as solid acid catalysts

    NASA Astrophysics Data System (ADS)

    Valle-Vigón, Patricia; Sevilla, Marta; Fuertes, Antonio B.

    2012-11-01

    The synthesis of highly functionalized porous silica-carbon composites made up of sulfonic groups attached to a carbon layer coating the pores of three types of mesostructured silica (i.e. SBA-15, KIT-6 and mesocellular silica) is presented. The synthesis procedure involves the following steps: (a) removal of the surfactant, (b) impregnation of the silica pores with a carbon precursor, (c) carbonization and (d) sulfonation. The resulting silica-carbon composites contain ˜30 wt % of carbonaceous matter with a high density of acidic groups attached to the deposited carbon (i.e.sbnd SO3H, sbnd COOH and sbnd OH). The structural characteristics of the parent silica are retained in the composite materials, which exhibit a high surface area, a large pore volume and a well-ordered porosity made up uniform mesopores. The high density of the sulfonic groups in combination with the mesoporous structure of the composites ensures that a large number of active sites are easily accessible to reactants. These sulfonated silica-carbon composites behave as eco-friendly, active, selective, water tolerant and recyclable solid acids. In this study we demonstrate the usefulness of these composites as solid acid catalysts for the esterification of maleic anhydride, succinic acid and oleic acid with ethanol. These composites exhibit a superior intrinsic catalytic activity to other commercial solid acids such as Amberlyst-15.

  13. Snowmelt controls on concentration-discharge relationships and the balance of oxidative and acid-base weathering fluxes in an alpine catchment, East River, Colorado: ACID-BASE VERSUS OXIDATIVE WEATHERING FLUXES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Winnick, Matthew J.; Carroll, Rosemary W. H.; Williams, Kenneth H.

    Although important for riverine solute and nutrient fluxes, the connections between biogeochemical processes and subsurface hydrology remain poorly characterized. We investigate these couplings in the East River, CO, a high-elevation shale-dominated catchment in the Rocky Mountains, using concentration-discharge (C-Q) relationships for major cations, anions, and organic carbon. Dissolved organic carbon (DOC) displays a positive C-Q relationship with clockwise hysteresis, indicating mobilization and depletion of DOC in the upper soil horizons and emphasizing the importance of shallow flowpaths during snowmelt. Cation and anion concentrations demonstrate that carbonate weathering, which dominates solute fluxes, is promoted by both sulfuric acid derived from pyritemore » oxidation in the shale bedrock and carbonic acid derived from subsurface respiration. Sulfuric acid weathering dominates during baseflow conditions when waters infiltrate below the inferred pyrite oxidation front, whereas carbonic acid weathering plays a dominant role during snowmelt as a result of shallow flowpaths. Differential C-Q relationships between solutes suggest that infiltrating waters approach calcite saturation before reaching the pyrite oxidation front, after which sulfuric acid reduces carbonate alkalinity. This reduction in alkalinity results in CO 2 outgassing when waters equilibrate to surface conditions, and reduces the riverine export of carbon and alkalinity by roughly 33% annually. In conclusion, future changes in snowmelt dynamics that control the balance of carbonic and sulfuric acid weathering may substantially alter carbon cycling in the East River. Ultimately, we demonstrate that differential C-Q relationships between major solutes can provide unique insights into the complex subsurface flow and biogeochemical dynamics that operate at catchment scales.« less

  14. Snowmelt controls on concentration-discharge relationships and the balance of oxidative and acid-base weathering fluxes in an alpine catchment, East River, Colorado: ACID-BASE VERSUS OXIDATIVE WEATHERING FLUXES

    DOE PAGES

    Winnick, Matthew J.; Carroll, Rosemary W. H.; Williams, Kenneth H.; ...

    2017-03-01

    Although important for riverine solute and nutrient fluxes, the connections between biogeochemical processes and subsurface hydrology remain poorly characterized. We investigate these couplings in the East River, CO, a high-elevation shale-dominated catchment in the Rocky Mountains, using concentration-discharge (C-Q) relationships for major cations, anions, and organic carbon. Dissolved organic carbon (DOC) displays a positive C-Q relationship with clockwise hysteresis, indicating mobilization and depletion of DOC in the upper soil horizons and emphasizing the importance of shallow flowpaths during snowmelt. Cation and anion concentrations demonstrate that carbonate weathering, which dominates solute fluxes, is promoted by both sulfuric acid derived from pyritemore » oxidation in the shale bedrock and carbonic acid derived from subsurface respiration. Sulfuric acid weathering dominates during baseflow conditions when waters infiltrate below the inferred pyrite oxidation front, whereas carbonic acid weathering plays a dominant role during snowmelt as a result of shallow flowpaths. Differential C-Q relationships between solutes suggest that infiltrating waters approach calcite saturation before reaching the pyrite oxidation front, after which sulfuric acid reduces carbonate alkalinity. This reduction in alkalinity results in CO 2 outgassing when waters equilibrate to surface conditions, and reduces the riverine export of carbon and alkalinity by roughly 33% annually. In conclusion, future changes in snowmelt dynamics that control the balance of carbonic and sulfuric acid weathering may substantially alter carbon cycling in the East River. Ultimately, we demonstrate that differential C-Q relationships between major solutes can provide unique insights into the complex subsurface flow and biogeochemical dynamics that operate at catchment scales.« less

  15. Interaction Between CO2-Rich Sulfate Solutions and Carbonate Reservoir Rocks from Atmospheric to Supercritical CO2 Conditions: Experiments and Modeling

    NASA Astrophysics Data System (ADS)

    Cama, J.; Garcia-Rios, M.; Luquot, L.; Soler Matamala, J. M.

    2014-12-01

    A test site for CO2 geological storage is situated in Hontomín (Spain) with a reservoir rock that is mainly composed of limestone. During and after CO2 injection, the resulting CO2-rich acid brine gives rise to the dissolution of carbonate minerals (calcite and dolomite) and gypsum (or anhydrite at depth) may precipitate since the reservoir brine contains sulfate. Experiments using columns filled with crushed limestone or dolostone were conducted under different P-pCO2 conditions (atmospheric: 1-10-3.5 bar; subcritical: 10-10 bar; and supercritical: 150-34 bar), T (25, 40 and 60 ºC) and input solution compositions (gypsum-undersaturated and gypsum-equilibrated solutions). We evaluated the effect of these parameters on the coupled reactions of calcite/dolomite dissolution and gypsum/anhydrite precipitation. The CrunchFlow and PhreeqC (v.3) numerical codes were used to perform reactive transport simulations of the experiments. Under the P-pCO2-T conditions, the volume of precipitated gypsum was smaller than the volume of dissolved carbonate minerals, yielding an increase in porosity (Δporosity up to ≈ 4%). A decrease in T favored limestone dissolution regardless of pCO2 owing to increasing undersaturation with decreasing temperature. However, gypsum precipitation was favored at high T and under atmospheric pCO2 conditions but not at high T and under 10 bar of pCO2 conditions. The increase in limestone dissolution with pCO2 was directly attributed to pH, which was more acidic at higher pCO2. Increasing pCO2, carbonate dissolution occurred along the column whereas it was localized in the very inlet under atmospheric conditions. This was due to the buffer capacity of the carbonic acid, which maintains pH at around 5 and keeps the solution undersaturated with respect to calcite and dolomite along the column. 1D reactive transport simulations reproduced the experimental data (carbonate dissolution and gypsum precipitation for different P-pCO2-T conditions). Drawing

  16. Structure-Property Relations in Carbon Nanotube Fibers by Downscaling Solution Processing.

    PubMed

    Headrick, Robert J; Tsentalovich, Dmitri E; Berdegué, Julián; Bengio, Elie Amram; Liberman, Lucy; Kleinerman, Olga; Lucas, Matthew S; Talmon, Yeshayahu; Pasquali, Matteo

    2018-03-01

    At the microscopic scale, carbon nanotubes (CNTs) combine impressive tensile strength and electrical conductivity; however, their macroscopic counterparts have not met expectations. The reasons are variously attributed to inherent CNT sample properties (diameter and helicity polydispersity, high defect density, insufficient length) and manufacturing shortcomings (inadequate ordering and packing), which can lead to poor transmission of stress and current. To efficiently investigate the disparity between microscopic and macroscopic properties, a new method is introduced for processing microgram quantities of CNTs into highly oriented and well-packed fibers. CNTs are dissolved into chlorosulfonic acid and processed into aligned films; each film can be peeled and twisted into multiple discrete fibers. Fibers fabricated by this method and solution-spinning are directly compared to determine the impact of alignment, twist, packing density, and length. Surprisingly, these discrete fibers can be twice as strong as their solution-spun counterparts despite a lower degree of alignment. Strength appears to be more sensitive to internal twist and packing density, while fiber conductivity is essentially equivalent among the two sets of samples. Importantly, this rapid fiber manufacturing method uses three orders of magnitude less material than solution spinning, expanding the experimental parameter space and enabling the exploration of unique CNT sources. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Miniaturized ascorbic acid fuel cells with flexible electrodes made of graphene-coated carbon fiber cloth

    NASA Astrophysics Data System (ADS)

    Hoshi, Kazuki; Muramatsu, Kazuo; Sumi, Hisato; Nishioka, Yasushiro

    2016-04-01

    Ascorbic acid (AA) is a biologically friendly compound and exists in many products such as sports drinks, fruit, and even in human blood. Thus, a miniaturized and flexible ascorbic acid fuel cell (AAFC) is expected be a power source for portable or implantable electric devices. In this study, we fabricated an AAFC with anode and cathode dimensions of 3 × 10 mm2 made of a graphene-coated carbon fiber cloth (GCFC) and found that GCFC electrodes significantly improve the power generated by the AAFC. This is because the GCFC has more than two times the effective surface area of a conventional carbon fiber cloth and it can contain more enzymes. The power density of the AAFC in a phosphate buffer solution containing 100 mM AA at room temperature was 34.1 µW/cm2 at 0.46 V. Technical issues in applying the AAFC to portable devices are also discussed.

  18. Adsorption characteristics of Bisphenol-A on tailored activated carbon in aqueous solutions.

    PubMed

    Yan, Liang; Lv, Di; Huang, Xinwen; Shi, Huixiang; Zhang, Geshan

    2016-10-01

    The adsorption behavior of pharmaceuticals and personal care product, Bisphenol-A (BPA), according to four coal-based and four wood-based granular activated carbons modified using outgassing treatment, acidic treatment or alkaline treatment was studied. The adsorption isotherm results indicated that carbon surface acidity played a very important role in the adsorption of BPA. It was found that increasing surface acidity would increase the hydrogen bonding effects and increase adsorption of BPA on activated carbon. The acidic modified sample (F600-A and OLC-A) represented the best adsorption capacity, and the equilibrium adsorption amounts reached 346.42 and 338.55 mg/g, respectively. Further, effects of surface charge and surface basicity were examined. It was found that the adsorbed amount of BPA decreased with the increase of surface charge. Finally, there appeared to be a significant oligomerization phenomenon with BPA molecules onto the surface of activated carbon. OLC and OLC-OG, which have higher micropore percentages, are very effective in hampering the oligomerization of BPA under oxic conditions.

  19. Solubility of xenon in amino-acid solutions. II. Nine less-soluble amino acids

    NASA Astrophysics Data System (ADS)

    Kennan, Richard P.; Himm, Jeffrey F.; Pollack, Gerald L.

    1988-05-01

    Ostwald solubility (L) of xenon gas, as the radioisotope 133Xe, has been measured as a function of solute concentration, at 25.0 °C, in aqueous solutions of nine amino acids. The amino-acid concentrations investigated covered much of their solubility ranges in water, viz., asparagine monohydrate (0-0.19 M), cysteine (0-1.16 M), glutamine (0-0.22 M), histidine (0-0.26 M), isoleucine (0-0.19 M), methionine (0-0.22 M), serine (0-0.38 M), threonine (0-1.4 M), and valine (0-0.34 M). We have previously reported solubility results for aqueous solutions of six other, generally more soluble, amino acids (alanine, arginine, glycine, hydroxyproline, lysine, and proline), of sucrose and sodium chloride. In general, L decreases approximately linearly with increasing solute concentration in these solutions. If we postulate that the observed decreases in gas solubility are due to hydration, the results under some assumptions can be used to calculate hydration numbers (H), i.e., the number of H2O molecules associated with each amino-acid solute molecule. The average values of hydration number (H¯) obtained at 25.0 °C are 15.3±1.5 for asparagine, 6.8±0.3 for cysteine, 11.5±1.1 for glutamine, 7.3±0.7 for histidine, 5.9±0.4 for isoleucine, 10.6±0.8 for methionine, 11.2±1.3 for serine, 7.7± 1.0 for threonine, and 6.6±0.6 for valine. We have also measured the temperature dependence of solubility L(T) from 5-40 °C for arginine, glycine, and proline, and obtained hydration numbers H¯(T) in this range. Between 25-40 °C, arginine has an H¯ near zero. This may be evidence for an attractive interaction between xenon and arginine molecules in aqueous solution.

  20. Raman spectroscopic study of the conformation of dicarboxylic acid salts in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Fukushima, Kunio; Watanabe, Toshiaki; Umemura, Matome

    1986-08-01

    It is already known that the molecules of long chain monocarboxylic acid salts have a tendency to form micelles in aqueous solutions, the molecular chain taking the all- trans zigzag structure. However it is considered difficult for dicarboxylic acid salts to adopt the same structure as the monocarboxylic acid salts as they have two carboxyl groups, one on each end of the molecular chain. Therefore, a special structure is expected to exist for dicarboxylic acid salts in aqueous solution. In order to examine this, Raman spectra of suberic acid salt and azelaic acid salt in aqueous solution were measured and the normal vibrational calculation carried out, showing that dicarboxylic acid salts have a helical structure in aqueous solution.

  1. Relation Between the Adsorbed Quantity and the Immersion Enthalpy in Catechol Aqueous Solutions on Activated Carbons

    PubMed Central

    Moreno-Piraján, Juan Carlos; Blanco, Diego; Giraldo, Liliana

    2012-01-01

    An activated carbon, CarbochemTM—PS230, was modified by chemical and thermal treatment in flow of H2, in order to evaluate the influence of the activated carbon chemical characteristics in the adsorption of the catechol. The catechol adsorption in aqueous solution was studied along with the effect of the pH solution in the adsorption process of modified activated carbons and the variation of immersion enthalpy of activated carbons in the aqueous solutions of catechol. The interaction solid-solution is characterized by adsorption isotherms analysis, at 298 K and pH 7, 9 and 11 in order to evaluate the adsorption value above and below that of the catechol pKa. The adsorption capacity of carbons increases when the solution pH decreases. The retained amount increases slightly in the reduced carbon to maximum adsorption pH and diminishes in the oxidized carbon. Similar conclusions are obtained from the immersion enthalpies, whose values increase with the solute quantity retained. In granular activated carbon (CAG), the immersion enthalpies obtained are between 21.5 and 45.7 J·g−1 for catechol aqueous solutions in a range of 20 at 1500 mg·L−1. PMID:22312237

  2. Relation between the adsorbed quantity and the immersion enthalpy in catechol aqueous solutions on activated carbons.

    PubMed

    Moreno-Piraján, Juan Carlos; Blanco, Diego; Giraldo, Liliana

    2012-01-01

    An activated carbon, Carbochem(TM)-PS230, was modified by chemical and thermal treatment in flow of H(2), in order to evaluate the influence of the activated carbon chemical characteristics in the adsorption of the catechol. The catechol adsorption in aqueous solution was studied along with the effect of the pH solution in the adsorption process of modified activated carbons and the variation of immersion enthalpy of activated carbons in the aqueous solutions of catechol. The interaction solid-solution is characterized by adsorption isotherms analysis, at 298 K and pH 7, 9 and 11 in order to evaluate the adsorption value above and below that of the catechol pK(a). The adsorption capacity of carbons increases when the solution pH decreases. The retained amount increases slightly in the reduced carbon to maximum adsorption pH and diminishes in the oxidized carbon. Similar conclusions are obtained from the immersion enthalpies, whose values increase with the solute quantity retained. In granular activated carbon (CAG), the immersion enthalpies obtained are between 21.5 and 45.7 J·g(-1) for catechol aqueous solutions in a range of 20 at 1500 mg·L(-1).

  3. Extraction equilibrium of indium(III) from nitric acid solutions by di(2-ethylhexyl)phosphoric acid dissolved in kerosene.

    PubMed

    Tsai, Hung-Sheng; Tsai, Teh-Hua

    2012-01-04

    The extraction equilibrium of indium(III) from a nitric acid solution using di(2-ethylhexyl) phosphoric acid (D2EHPA) as an acidic extractant of organophosphorus compounds dissolved in kerosene was studied. By graphical and numerical analysis, the compositions of indium-D2EHPA complexes in organic phase and stoichiometry of the extraction reaction were examined. Nitric acid solutions with various indium concentrations at 25 °C were used to obtain the equilibrium constant of InR₃ in the organic phase. The experimental results showed that the extraction distribution ratios of indium(III) between the organic phase and the aqueous solution increased when either the pH value of the aqueous solution and/or the concentration of the organic phase extractant increased. Finally, the recovery efficiency of indium(III) in nitric acid was measured.

  4. RECOVERY OF URANIUM AND THORIUM FROM AQUEOUS SOLUTIONS

    DOEpatents

    Calkins, G.D.

    1958-06-10

    >A process is described for the recovery of uranium and thorium from monazite sand, which is frequently processed by treating it with a hot sodium hydroxide solution whereby a precipitate forms consisting mainly of oxides or hydroxides of the rare earths, thorium and uranium. The precipitate is dissolved in mineral acid, and the acid solution is then neutralized to a pH value of between 5.2 and 6.2 whereby both the uranium and thorium precipitate as the hydroxides, while substantially all the rare earth metal values present remain in the solution. The uranium and thoriunn can then be separated by dissolving the precipitate in a solution containing a mixture of alkali carbonate and alkali bicarbonate: and contacting the carbonate solution with a strong-base anion exchange resin whereby the uranium values are adsorbed on the resin while the thorium remains in solution.

  5. Efficiency of cardioplegic solutions containing L-arginine and L-aspartic acid.

    PubMed

    Pisarenko, O I; Shul'zhenko, V S; Studneva, I M

    2006-04-01

    In experiments on rats we studied the effects of cardioplegic solutions with L-aspartic acid or L-arginine on functional recovery and metabolism of isolated working heart after 40-min normothermal global ischemia and 30-min reperfusion. After reperfusion of the hearts preventively protected with cardioplegic solution containing L-aspartic acid or L-arginine, coronary flow decreased in comparison with the initial values. As a component of cardioplegic solution, L-arginine was less efficient in recovery of contractility and cardiac output of the hearts in comparison with L-aspartic acid. In hearts protected with L-aspartic acid, the postischemic levels of ATP and phosphocreatine were significantly higher, and the level of lactate was significantly lower than in hearts protected with L-arginine. In comparison with L-arginine, L-aspartic acid is a more efficient component of cardioplegic solution in protection of the heart from metabolic and functional damages caused by global ischemia and reperfusion.

  6. Uptake of Cr3+ from aqueous solution by lignite-based humic acids.

    PubMed

    Arslan, G; Pehlivan, E

    2008-11-01

    Humic acid (HA) produced from brown coal, a relatively abundant and inexpensive material is currently being investigated as an adsorbent to remove toxic metals from aqueous solution. The influence of five parameters (contact time, solution pH, initial metal concentration, temperature and amount of adsorbent) on the removal at 20+/-1 degrees C was studied. HAs were prepared from lignites by using alkaline extraction, sedimentation and acidic precipitation. Adsorption equilibrium was achieved in about 60 min for Cr3+ ion. The Langmuir adsorption isotherm was used to describe observed sorption phenomena. The maximum adsorption capacity of 0.17 mmol for Ilgin (HA1), 0.29 mmol for Beysehir (HA2) and 0.18 mmol Ermenek (HA3) and 0.17 mmol of Cr3+/g for activated carbon (AC) was achieved, respectively at pH of 4.1. More than 84% of Cr3+ was removed by HA2, 54% by HA3 and 51% by HA1 and 50% by AC from aqueous solution. The adsorption was strongly dependent on pH but independent of ionic strength and metal ions. The adsorption of Cr3+ was higher between pH 4.1 and 5.1 for all HAs and maximum sorption was observed at pH 4.1. The rise in temperature caused a slight decrease in the value of the equilibrium constant (Kc) for the sorption of Cr3+ ion. Complex mechanisms including ion exchange, complexation and adsorption and size exclusion are possible for sorption of Cr3+ ion on HAs.

  7. Hydrogen peroxide generation in a model paediatric parenteral amino acid solution.

    PubMed

    Brawley, V; Bhatia, J; Karp, W B

    1993-12-01

    1. Parenteral amino acid solutions undergo photooxidation, which may be an important factor in total parenteral nutrition-associated hepatic dysfunction. Light-exposed parenteral solutions containing amino acids, in addition to vitamins and trace minerals, generate free radicals, which, in turn, may contribute to this type of injury. This study examined the characteristics of H2O2 production in a parenteral amino acid solution modelled on a commercially available paediatric parenteral amino acid solution. 2. The solution was exposed to light in the presence of riboflavin-5'-monophosphate (riboflavin), and peroxide formation in the presence and absence of catalase (H2O2 formation) was assayed using potassium iodide/molybdate. 3. Peak H2O2 production occurred at a light intensity of 8 microW cm-2 nm-1 in the 425-475 nm waveband and was linear to 2 h of light exposure. H2O2 production reached 500 mumol/l at 24 h. 4. H2O2 was directly related to a riboflavin concentration of up to 20 mumol/l and was maximal at 30 mumol/l. 5. H2O2 production was greatest in the amino acid/riboflavin solution at a pH of between 5 and 6. 6. Under the conditions of light exposure intensity, light exposure time, riboflavin concentration and pH found during the administration of parenteral nutrition in neonatal intensive care units, net H2O2 production occurs in solutions modelled on a paediatric parenteral amino acid preparation.

  8. Effects of acidic deposition on the erosion of carbonate stone - experimental results from the U.S. National Acid Precipitation Assessment Program (NAPAP)

    USGS Publications Warehouse

    Baedecker, P.A.; Reddy, M.M.; Reimann, K.J.; Sciammarella, C.A.

    1992-01-01

    One of the goals of NAPAP-sponsored research on the effects of acidic deposition on carbonate stone has been to quantify the incremental effects of wet and dry deposition of hydrogen ion, sulfur dioxide and nitrogen oxides on stone erosion. Test briquettes and slabs of freshly quarried Indiana limestone and Vermont marble have been exposed to ambient environmental conditions in a long-term exposure program. Physical measurements of the recession of test stones exposed to ambient conditions at an angle of 30?? to horizontal at the five NAPAP materials exposure sites range from ~15 to ~30?? ??m yr-1 for marble, and from ~25 to ~45 ??m yr -1 for limestone, and are approximately double the recession estimates based on the observed calcium content of run-off solutions from test slabs. The difference between the physical and chemical recession measurements is attributed to the loss of mineral grains from the stone surfaces that are not measured in the run-off experiments. The erosion due to grain loss does not appear to be influenced by rainfall acidity, however, preliminary evidence suggests that grain loss may be influenced by dry deposition of sulfur dioxide between rainfall events. Chemical analyses of the run-off solutions and associated rainfall blanks suggest that ~30% of erosion by dissolution can be attributed to the wet deposition of hydrogen ion and the dry deposition of sulfur dioxide and nitric acid between rain events. The remaining ~70% of erosion by dissolution is accounted for by the solubility of carbonate stone in rain that is in equilibrium with atmospheric carbon dioxide ('clean rain'). These results are for marble and limestone slabs exposed at an angle of 30?? from horizontal. The relative contribution of sulfur dioxide to chemical erosion is significantly enhanced for stone slabs having an inclination of 60?? or 85??. The dry deposition of alkaline particulate material has a mitigating effect at the two urban field exposure sites at Washington, DC

  9. 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.

  10. Sorption of lead from aqueous solution by chemically modified carbon adsorbents.

    PubMed

    Nadeem, Muhammad; Mahmood, A; Shahid, S A; Shah, S S; Khalid, A M; McKay, G

    2006-12-01

    An indigenously prepared, steam activated and chemically modified carbon from husk and pods of Moringa oleifera (M. oleifera), an agricultural waste, was comparatively examined as an adsorbent for the removal of lead from aqueous solutions. Studies were conducted as a function of contact time, initial metal concentration, dose of adsorbent, agitation speed, particle size and pH. Maximum uptake capacities were found to be, 98.89, 96.58, 91.8, 88.63, 79.43% for cetyltrimethyl ammonium bromide (CTAB), phosphoric, sulfuric, hydrochloric acid treated and untreated carbon adsorbents, respectively. Bangham, pseudo-first- and second-order, intra-particle diffusion equations were implemented to express the sorption mechanism by utilized adsorbents. Adsorption rate of lead ions was found to be considerably faster for chemically modified adsorbents than unmodified. The results of adsorption were fitted to both the Langmuir and Freundlich models. Satisfactory agreement between the metal uptake capacities by the adsorbents at different time intervals was expressed by the correlation coefficient (R(2)). The Langmuir model represented the sorption process better than the Freundlich one, with R(2) values ranging from 0.994 to 0.998.

  11. Molecular dynamics study on glycolic acid in the physiological salt solution

    NASA Astrophysics Data System (ADS)

    Matsunaga, S.

    2018-05-01

    Molecular dynamics (MD) study on glycolic acid in the physiological salt solution has been performed, which is a model of a biofuel cell. The structure and charge distribution of glycolic acid in aqueous solution used in MD is beforehand optimized by Gaussian09 utilizing the density functional theory. MD is performed in the NTV constant condition, i.e. the number of particles, temperature, and volume of MD cell are definite. The structure difference of the glycolic acid and oxalic acid is detected by the water distribution around the molecules using the pair distribution functions, gij(r), and the frequency dependent diffusion coefficients, Di(ν). The anomalous dielectric constant of the solution, i.e. about 12 times larger than that of water, has been obtained, which may be attributed to the ion pair formation in the solution.

  12. Mechanisms of neptunium redox reactions in nitric acid solutions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chatterjee, Sayandev; Bryan, Samuel A.; Casella, Amanda J.

    First transuranium element neptunium (Np) exhibits complicated behavior in acidic solutions because it can adopt wide range of oxidation states typically from +3 to +6 and coordinate large variety of ligands. In particular, accurate determination of Np redox potentials in nitric acid solutions is challenging due to overlapping chemical and electrochemical reactions leading to significant experimental uncertainties. Furthermore, over past decades spectrophotometry has been extensively applied to identify and characterize Np solution species in different oxidation states. However, relevant spectral database of Np in nitric acid solutions that can serve for the reference purposes has yet to be established duemore » to the experimental difficulty to isolate and stabilize Np species in pure oxidation states without compromising solution optical properties. This work demonstrates that combination of voltammetry and controlled-potential in situ thin-layer spectropotentiometry overcomes these challenges so that Np species in pure +3, +4, +5, or +6 oxidation states were electrochemically generated in the systematically varied 0.1 – 5 M nitric acid solutions, and corresponding vis-NIR spectral signatures were obtained. In situ optical monitoring of the interconversion between adjacent Np oxidation states resulted in elucidation of the mechanisms of the involved redox reactions, in-depth understanding of the relative stability of the Np oxidation states, and allowed benchmarking of the redox potentials of the NpO22+/NpO2+, NpO2+/Np4+ and Np4+/Np3+ couples. Notably, the NpO2+/Np4+ couple was distinguished from the proximal Np4+/Np3+ process overcoming previous concerns and challenges encountered in accurate determination of the respective potentials.« less

  13. [Effects of Low-Molecular-Weight Organic Acids on the Speciation of Pb in Purple Soil and Soil Solution].

    PubMed

    Liu, Jiang; Jiang, Tao; Huang, Rong; Zhang, Jin-zhong; Chen, Hong

    2016-04-15

    Lead (Pb) in purple soil was selected as the research target, using one-step extraction method with 0.01 mol · L⁻¹ sodium nitrate as the background electrolyte to study the release effect of citric acid (CA), tartaric acid (TA) and acetic acid (AC) with different concentrations. Sequential extraction and geochemical model (Visual Minteq v3.0) were applied to analyze and predict the speciation of Pb in soil solid phase and soil solution phase. Then the ebvironmental implications and risks of low-molecule weight organic acid (LMWOA) on soil Pb were analyzed. The results indicated that all three types of LMWOA increased the desorption capacity of Pb in purple soil, and the effect followed the descending order of CA > TA > AC. After the action of LMWOAs, the exchangeable Pb increased; the carbonate-bound Pb and Fe-Mn oxide bound Pb dropped in soil solid phase. Organic bound Pb was the main speciation in soil solution phase, accounting for 45.16%-75.05%. The following speciation of Pb in soil solution was free Pb, accounting for 22.71%-50.25%. For CA and TA treatments, free Pb ions and inorganic bound Pb in soil solution increased with increasing LMWOAs concentration, while organic bound Pb suffered a decrease in this process. An opposite trend for AC treatment was observed compared with CA and TA treatments. Overall, LMWOAs boosted the bioavailability of Pb in purple soil and had a potential risk to contaminate underground water. Among the three LMWOAs in this study, CA had the largest potential to activate soil Pb.

  14. Effect of Acid Oxidation on the Dispersion Property of Multiwalled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Goh, P. S.; Ismail, A. F.; Aziz, M.

    2009-06-01

    A means of dispersion of multiwalled carbon nanotube (MWCNT) via mixed acid (HNO3 and H2SO4) oxidation with different treatment durations was investigated through the solubility study of the treated carbon nanotubes in some common solvents. Fourier transformed infrared (FTIR) characterization of the reaction products revealed that the surface of MWCNTs was successfully functionalized with surface acidic groups. The acid-base titration demonstrated that the amount of surface acidic groups increased in parallel with the refluxing duration. The acid modified MWCNTs were found to be well dispersed in polar solvents, such as ethanol and water due to the presence of the hydrophilic acid functional groups on the surface of raw MWCNTs. Such chemical modification of carbon nanotube properties will pave the way towards the realistic applications in the nanotechnology world.

  15. Adsorption of Reactive Red M-2BE dye from water solutions by multi-walled carbon nanotubes and activated carbon.

    PubMed

    Machado, Fernando M; Bergmann, Carlos P; Fernandes, Thais H M; Lima, Eder C; Royer, Betina; Calvete, Tatiana; Fagan, Solange B

    2011-09-15

    Multi-walled carbon nanotubes and powdered activated carbon were used as adsorbents for the successful removal of Reactive Red M-2BE textile dye from aqueous solutions. The adsorbents were characterised by infrared spectroscopy, N(2) adsorption/desorption isotherms and scanning electron microscopy. The effects of pH, shaking time and temperature on adsorption capacity were studied. In the acidic pH region (pH 2.0), the adsorption of the dye was favourable using both adsorbents. The contact time to obtain equilibrium at 298K was fixed at 1h for both adsorbents. The activation energy of the adsorption process was evaluated from 298 to 323K for both adsorbents. The Avrami fractional-order kinetic model provided the best fit to the experimental data compared with pseudo-first-order or pseudo-second-order kinetic adsorption models. For Reactive Red M-2BE dye, the equilibrium data were best fitted to the Liu isotherm model. Simulated dyehouse effluents were used to check the applicability of the proposed adsorbents for effluent treatment. Copyright © 2011 Elsevier B.V. All rights reserved.

  16. Study of coagulation processes of selected humic acids under copper ions influence*

    NASA Astrophysics Data System (ADS)

    Boguta, Patrycja; Sokolowska, Zofia

    2013-04-01

    Humic acids have limited sorption capacity and big dose of metal or other mineral component which can be sorbed on humic acids, can cause saturation of negative, surface charge of humic acids leading to destabilization of dissolved humic acids compounds. Destabilisation can be observed as coagulation and floculation proces of humic acids. However there are a lot of mechanisms which causing precipitation of humic acids. Thereby, in order to full description of coagulation process, different methods should be applied. Ordinarily, humic acids coagulation is studied by measurement of absorbance, transmittance or carbon loss in solution. Meanwhile, very significant information is also variation of metal content in soil solution and information whether metal goes to precipitate together with humic acids or stays in dissolved form in solution. So, that, from one side, processes of stronger accumulation of metal can lead to soil degradation and micronutrient deficiency for plants. However, there is also possibility to stay metal in solution in toxic and bioavailable form for plants. Main aim of this paper was to study coagulation process of different humic acids extracted from mucking peats under copper ions influence at adjusted pH to 5. In order to this, four peaty-muck soils were taken from selected places in east part of Poland (meadows and river valleys). These soils differed by humification degree, secondary transformation, density and pH. At next step, humic acids were extracted from soils using sodium hydroxide (NaOH) extractant. After exact purification by washing with HF-HCl mixture and water, humic acids were liofilized. Solutions of humic acids were prepared at concentration 40 mg/dm3 with addition of different amount of copper ions to obtain final concentration of Cu(II) ranged from 0-40mg/dm3. After 24 hours solutions were investigated using measurements of absorbance at 470nm (UV-VIS spectrometer Jasco V-530), measurements of organic carbon in solution

  17. Ca-Rich Carbonate Melts: A Regular-Solution Model, with Applications to Carbonatite Magma + Vapor Equilibria and Carbonate Lavas on Venus

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.

    1995-01-01

    A thermochemical model of the activities of species in carbonate-rich melts would be useful in quantifying chemical equilibria between carbonatite magmas and vapors and in extrapolating liquidus equilibria to unexplored PTX. A regular-solution model of Ca-rich carbonate melts is developed here, using the fact that they are ionic liquids, and can be treated (to a first approximation) as interpenetrating regular solutions of cations and of anions. Thermochemical data on systems of alkali metal cations with carbonate and other anions are drawn from the literature; data on systems with alkaline earth (and other) cations and carbonate (and other) anions are derived here from liquidus phase equilibria. The model is validated in that all available data (at 1 kbar) are consistent with single values for the melting temperature and heat of fusion for calcite, and all liquidi are consistent with the liquids acting as regular solutions. At 1 kbar, the metastable congruent melting temperature of calcite (CaCO3) is inferred to be 1596 K, with (Delta)bar-H(sub fus)(calcite) = 31.5 +/- 1 kJ/mol. Regular solution interaction parameters (W) for Ca(2+) and alkali metal cations are in the range -3 to -12 kJ/sq mol; W for Ca(2+)-Ba(2+) is approximately -11 kJ/sq mol; W for Ca(2+)-Mg(2+) is approximately -40 kJ/sq mol, and W for Ca(2+)-La(3+) is approximately +85 kJ/sq mol. Solutions of carbonate and most anions (including OH(-), F(-), and SO4(2-)) are nearly ideal, with W between 0(ideal) and -2.5 kJ/sq mol. The interaction of carbonate and phosphate ions is strongly nonideal, which is consistent with the suggestion of carbonate-phosphate liquid immiscibility. Interaction of carbonate and sulfide ions is also nonideal and suggestive of carbonate-sulfide liquid immiscibility. Solution of H2O, for all but the most H2O-rich compositions, can be modeled as a disproportionation to hydronium (H3O(+)) and hydroxyl (OH(-)) ions with W for Ca(2+)-H3O(+) (approximately) equals 33 kJ/sq mol. The

  18. Competitive effects of humic acid and wastewater on adsorption of Methylene Blue dye by activated carbon and non-imprinted polymers.

    PubMed

    Murray, Audrey; Örmeci, Banu

    2018-04-01

    Natural organic matter (NOM), present in natural waters and wastewater, decreases adsorption of micropollutants, increasing treatment costs. This research investigated mechanisms of competition for non-imprinted polymers (NIPs) and activated carbon with humic acid and wastewater. Three different types of activated carbons (Norit PAC 200, Darco KB-M, and Darco S-51) were used for comparison with the NIP. The lower surface area and micropore to mesopore ratio of the NIP led to decreased adsorption capacity in comparison to the activated carbons. In addition, experiments were conducted for single-solute adsorption of Methylene Blue (MB) dye, simultaneous adsorption with humic acid and wastewater, and pre-loading with humic acid and wastewater followed by adsorption of MB dye using NIP and Norit PAC 200. Both the NIP and PAC 200 showed significant decreases of 27% for NIP (p=0.087) and 29% for PAC 200 (p=0.096) during simultaneous exposure to humic acid and MB dye. There was no corresponding decrease for NIP or PAC 200 pre-loaded with humic acid and then exposed to MB. In fact, for PAC 200, the adsorption capacity of the activated carbon increased when it was pre-loaded with humic acid by 39% (p=0.0005). For wastewater, the NIP showed no significant increase or decrease in adsorption capacity during either simultaneous exposure or pre-loading. The adsorption capacity of PAC 200 increased by 40% (p=0.001) for simultaneous exposure to wastewater and MB. Pre-loading with wastewater had no effect on MB adsorption by PAC 200. Copyright © 2017. Published by Elsevier B.V.

  19. Salicylic acid peels versus Jessner's solution for acne vulgaris: a comparative study.

    PubMed

    Bae, Byung Gi; Park, Chang Ook; Shin, Hyoseung; Lee, Soo Hyun; Lee, Yun Sun; Lee, Sang Ju; Chung, Kee Yang; Lee, Kwang Hoon; Lee, Ju Hee

    2013-02-01

    Salicylic acid was recently formulated in a hydroethanolic vehicle at a concentration of 20% to 30%. Salicylic acid has strong comedolytic effects because of its lipophilic nature. To compare the therapeutic efficacy and tolerability of salicylic acid peels with those of Jessner's solution peels in patients with acne vulgaris. Thirteen patients (13 men; mean age 22.6, range 20-28) with facial acne were enrolled. Jessner's solution was applied to one side of each patient's face and 30% salicylic acid to the other in three sessions at 2-week intervals. A blinded investigator counted noninflammatory and inflammatory lesions before treatment and 2 weeks after each treatment. Inflammatory and noninflammatory acne lesion counts decreased in proportion to the duration of treatment. Inflammatory acne lesion counts did not differ significantly between salicylic acid and Jessner's solution peels, although in terms of noninflammatory acne lesion counts, sites treated with salicylic acid showed significant improvement (p = .04), whereas those treated with Jessner's solution did not. We found that 30% salicylic acid peels were effective for inflammatory acne and more effective than Jessner's solution peels for treating noninflammatory acne. © 2012 by the American Society for Dermatologic Surgery, Inc. Published by Wiley Periodicals, Inc.

  20. Towards Providing Solutions to the Air Quality Crisis in the Mexico City Metropolitan Area: Carbon Sequestration by Succulent Species in Green Roofs.

    PubMed

    Collazo-Ortega, Margarita; Rosas, Ulises; Reyes-Santiago, Jerónimo

    2017-03-31

    In the first months of 2016, the Mexico City Metropolitan Area experienced the worst air pollution crisis in the last decade, prompting drastic short-term solutions by the Mexico City Government and neighboring States. In order to help further the search for long-term sustainable solutions, we felt obliged to immediately release the results of our research regarding the monitoring of carbon sequestration by green roofs. Large-scale naturation, such as the implementation of green roofs, provides a way to partially mitigate the increased carbon dioxide output in urban areas. Here, we quantified the carbon sequestration capabilities of two ornamental succulent plant species, Sedum dendroideum and Sedum rubrotinctum, which require low maintenance, and little or no irrigation. To obtain a detailed picture of these plants' carbon sequestration capabilities, we measured carbon uptake on the Sedum plants by quantifying carbon dioxide exchange and fixation as organic acids, during the day and across the year, on a green roof located in Southern Mexico City. The species displayed their typical CAM photosynthetic metabolism. Moreover, our quantification allowed us to conservatively estimate that a newly planted green roof of Sedum sequesters approximately 180,000,000 ppm of carbon dioxide per year in a green roof of 100 square meters in the short term. The patterns of CAM and carbon dioxide sequestration were highly robust to the fluctuations of temperature and precipitation between seasons, and therefore we speculate that carbon sequestration would be comparable in any given year of a newly planted green roof. Older green roof would require regular trimming to mantain their carbon sink properties, but their carbon sequestration capabilities remain to be quantified. Nevertheless, we propose that Sedum green roofs can be part of the long-term solutions to mitigate the air pollution crisis in the Mexico City Metropolitan area, and other "megacities" with marked seasonal drought.

  1. A comparison of water solubility enhancements of organic solutes by aquatic humic materials and commercial humic acids

    USGS Publications Warehouse

    Chlou, C.T.; Kile, D.E.; Brinton, T.I.; Malcolm, R.L.; Leenheer, J.A.; MacCarthy, P.

    1987-01-01

    Water solubility enhancements of 1,1-bis(p-chloro-phenyl)-2,2,2-trichloroethane (p,p???-DDT), 2,4,5,2???,5???-pentachlorobiphenyl (2,4,5,2???,5???-PCB), and 2,4,4???-tri-chlorobiphenyl (2,4,4???-PCB) by dissolved organic matter have been studied with the following samples: (1) acidic water samples from the Suwannee River, Georgia, and the Sopchoppy River, Florida; (2) a humic extract of a nearly neutral pH water from the Calcasieu River, Louisiana; (3) commercial humic acids from the Aldrich Chemical Co. and Fluka-Tridom Chemical Corp. The calculated partition coefficients on a dissolved organic carbon basis (Kdoc) for organic solutes with water samples and aquatic humic extracts from this and earlier studies indicate that the enhancement effect varies with the molecular composition of the aquatic humic materials. The Kdoc values with water and aquatic humic samples are, however, far less than the observed Kdoc values obtained with the two commercial samples, by factors of about 4-20. In view of this finding, one should be cautious in interpreting the effects of the dissolved organic matter on solubility enhancement of organic solutes on the basis of the use of commercial humic acids.

  2. Effects of acidic deposition on the erosion of carbonate stone — experimental results from the U.S. National Acid Precipitation Assessment Program (NAPAP)

    NASA Astrophysics Data System (ADS)

    Baedecker, Philip A.; Reddy, Michael M.; Reimann, Karl J.; Sciammarella, Cesar A.

    One of the goals of NAPAP-sponsored research on the effects of acidic deposition on carbonate stone has been to quantify the incremental effects of wet and dry deposition of hydrogen ion, sulfur dioxide and nitrogen oxides on stone erosion. Test briquettes and slabs of freshly quarried Indiana limestone and Vermont marble have been exposed to ambient environmental conditions in a long-term exposure program. Physical measurements of the recession of test stones exposed to ambient conditions at an angle of 30° to horizontal at the five NAPAP materials exposure sites range from ˜ 15 to ˜ 30 μm yr -1 for marble, and from ˜ 25 to ˜ 45 μm yr -1 for limestone, and are approximately double the recession estimates based on the observed calcium content of run-off solutions from test slabs. The difference between the physical and chemical recession measurements is attributed to the loss of mineral grains from the stone surfaces that are not measured in the run-off experiments. The erosion due to grain loss does not appear to be influenced by rainfall acidity, however, preliminary evidence suggests that grain loss may be influenced by dry deposition of sulfur dioxide between rainfall events. Chemical analyses of the run-off solutions and associated rainfall blanks suggest that ˜ 30% of erosion by dissolution can be attributed to the wet deposition of hydrogen ion and the dry deposition of sulfur dioxide and nitric acid between rain events. The remaining ˜ 70% of erosion by dissolution is accounted for by the solubility of carbonate stone in rain that is in equilibrium with atmospheric carbon dioxide ("clean rain"). These results are for marble and limestone slabs exposed at an angle of 30° from horizontal. The relative contribution of sulfur dioxide to chemical erosion is significantly enhanced for stone slabs having an inclination of 60° or 85°. The dry deposition of alkaline particulate material has a mitigating effect at the two urban field exposure sites at

  3. L-Lactic acid production from glycerol coupled with acetic acid metabolism by Enterococcus faecalis without carbon loss.

    PubMed

    Murakami, Nao; Oba, Mana; Iwamoto, Mariko; Tashiro, Yukihiro; Noguchi, Takuya; Bonkohara, Kaori; Abdel-Rahman, Mohamed Ali; Zendo, Takeshi; Shimoda, Mitsuya; Sakai, Kenji; Sonomoto, Kenji

    2016-01-01

    Glycerol is a by-product in the biodiesel production process and considered as one of the prospective carbon sources for microbial fermentation including lactic acid fermentation, which has received considerable interest due to its potential application. Enterococcus faecalis isolated in our laboratory produced optically pure L-lactic acid from glycerol in the presence of acetic acid. Gas chromatography-mass spectrometry analysis using [1, 2-(13)C2] acetic acid proved that the E. faecalis strain QU 11 was capable of converting acetic acid to ethanol during lactic acid fermentation of glycerol. This indicated that strain QU 11 restored the redox balance by oxidizing excess NADH though acetic acid metabolism, during ethanol production, which resulted in lactic acid production from glycerol. The effects of pH control and substrate concentration on lactic acid fermentation were also investigated. Glycerol and acetic acid concentrations of 30 g/L and 10 g/L, respectively, were expected to be appropriate for lactic acid fermentation of glycerol by strain QU 11 at a pH of 6.5. Furthermore, fed-batch fermentation with 30 g/L glycerol and 10 g/L acetic acid wholly exhibited the best performance including lactic acid production (55.3 g/L), lactic acid yield (0.991 mol-lactic acid/mol-glycerol), total yield [1.08 mol-(lactic acid and ethanol)]/mol-(glycerol and acetic acid)], and total carbon yield [1.06 C-mol-(lactic acid and ethanol)/C-mol-(glycerol and acetic acid)] of lactic acid and ethanol. In summary, the strain QU 11 successfully produced lactic acid from glycerol with acetic acid metabolism, and an efficient fermentation system was established without carbon loss. Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  4. Surface tensions of solutions containing dicarboxylic acid mixtures

    NASA Astrophysics Data System (ADS)

    Lee, Jae Young; Hildemann, Lynn M.

    2014-06-01

    Organic solutes tend to lower the surface tension of cloud condensation nuclei, allowing them to more readily activate. The surface tension of various dicarboxylic acid aerosol mixtures was measured at 20 °C using the Wilhelmy plate method. At lower concentrations, the surface tension of a solution with equi-molar mixtures of dicarboxylic acids closely followed that of a solution with the most surface-active organic component alone. Measurements of surface tension for these mixtures were lower than predictions using Henning's model and the modified Szyszkowski equation, by ˜1-2%. The calculated maximum surface excess (Γmax) and inverse Langmuir adsorption coefficient (β) from the modified Szyszkowski equation were both larger than measured values for 6 of the 7 mixtures tested. Accounting for the reduction in surface tension in the Köhler equation reduced the critical saturation ratio for these multi-component mixtures - changes were negligible for dry diameters of 0.1 and 0.5 μm, but a reduction from 1.0068 to 1.0063 was seen for the 4-dicarboxylic acid mixture with a dry diameter of 0.05 μm.

  5. Acid-base equilibrium in aqueous solutions of 1,3-dimethylbarbituric acid as studied by 13C NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Gryff-Keller, A.; Kraska-Dziadecka, A.

    2011-12-01

    13C NMR spectra of 1,3-dimethylbarbituric acid in aqueous solutions of various acidities and for various solute concentrations have been recorded and interpreted. The spectra recorded at pH = 2 and below contain the signals of the neutral solute molecule exclusively, while the ones recorded at pH = 7 and above only the signals of the appropriate anion, which has been confirmed by theoretical GIAO-DFT calculations. The signals in the spectra recorded for solutions of pH < 7 show dynamic broadenings. The lineshape analysis of these signals has provided information on the kinetics of the processes running in the dynamic acid-base equilibrium. The kinetic data determined this way have been used to clarify the mechanisms of these processes. The numerical analysis has shown that under the investigated conditions deprotonation of the neutral solute molecules undergoes not only via a simple transfer of the C-H proton to water molecules but also through a process with participation of the barbiturate anions. Moreover, the importance of tautomerism, or association, or both these phenomena for the kinetics of the acid-base transformations in the investigated system has been shown. Qualitatively similar changes of 13C NMR spectra with the solution pH variation have been observed for the parent barbituric acid.

  6. CATALYZED OXIDATION OF URANIUM IN CARBONATE SOLUTIONS

    DOEpatents

    Clifford, W.E.

    1962-05-29

    A process is given wherein carbonate solutions are employed to leach uranium from ores and the like containing lower valent uranium species by utilizing catalytic amounts of copper in the presence of ammonia therein and simultaneously supplying an oxidizing agent thereto. The catalysis accelerates rate of dissolution and increases recovery of uranium from the ore. (AEC)

  7. Determination of polar organic solutes in oil-shale retort water

    USGS Publications Warehouse

    Leenheer, J.A.; Noyes, T.I.; Stuber, H.A.

    1982-01-01

    A variety of analytical methods were used to quantitatively determine polar organic solutes in process retort water and a gas-condensate retort water produced in a modified in situ oil-shale retort. Specific compounds accounting for 50% of the dissolved organic carbon were identified in both retort waters. In the process water, 42% of the dissolved organic carbon consisted of a homologous series of fatty acids from C2 to C10. Dissolved organic carbon percentages for other identified compound classes were as follows: aliphatic dicarboxylic acids, 1.4%; phenols, 2.2%; hydroxypyridines, 1.1%; aliphatic amides, 1.2%. In the gas-condensate retort water, aromatic amines were most abundant at 19.3% of the dissolved organic carbon, followed by phenols (17.8%), nitriles (4.3%), aliphatic alcohols (3.5%), aliphatic ketones (2.4%), and lactones (1.3%). Steam-volatile organic solutes were enriched in the gas-condensate retort water, whereas nonvolatile acids and polyfunctional neutral compounds were predominant organic constituents of the process retort water.

  8. Ozonation of activated carbons: Effect on the adsorption of selected phenolic compounds from aqueous solutions.

    PubMed

    Alvarez, P M; García-Araya, J F; Beltrán, F J; Masa, F J; Medina, F

    2005-03-15

    The impact of ozonation on textural and chemical surface characteristics of two granular activated carbons (GAC), namely F400 and AQ40, and their ability to adsorb phenol (P), p-nitrophenol (PNP), and p-chlorophenol (PCP) from aqueous solutions have been studied. The porous structure of the ozone-treated carbons remained practically unchanged with regard to the virgin GAC. However, important modifications of the chemical surface and hydrophobicity were observed from FTIR spectroscopy, pH titrations, and determination of pH(PZC). As a rule, the ozone treatment at either room temperature (i.e., about 25 degrees C) or 100 degrees C gave rise to acidic surface oxygen groups (SOG). At 25 degrees C primarily carboxylic acids were formed while a more homogeneous distribution of carboxylic, lactonic, hydroxyl, and carbonyl groups was obtained at 100 degrees C. The experimental isotherms for phenolic compounds on both GAC were analyzed using the Langmuir model. Dispersive interactions between pi electrons of the ring of the aromatics and those of the carbon basal planes were thought to be the primary forces responsible for the physical adsorption whereas oxidative coupling of phenolic compounds catalyzed by basic SOG was a major cause of irreversible adsorption. The exposure of both GAC to ozone at room temperature decreased their ability to adsorb P, PNP, and PCP. However, when ozone was applied at 100 degrees C adsorption was not prevented but in some cases (P and PNP on F400) the adsorption process was even enhanced.

  9. Precipitation of Co(2+) carbonates from aqueous solution: insights on the amorphous to crystalline transformation.

    NASA Astrophysics Data System (ADS)

    González-López, Jorge; Fernández-González, Ángeles; Jiménez, Amalia

    2016-04-01

    Cobalt is toxic metal that is present only as a trace in the Earth crust. However, Co might concentrate on specific areas due to both natural and anthropogenic factors and thus, soils and groundwater can be contaminated. It is from this perspective that we are interested in the precipitation of cobalt carbonates, since co-precipitation with minerals phases is a well-known method for metal immobilization in the environment. In particular, the carbonates are widely used due to its reactivity and natural abundance. In order to evaluate the cobalt carbonate precipitation at room temperature, a simple experimental work was carried out in this work. The precipitation occurred via reaction of two common salts: 0.05M of CoCl2 and 0.05M of Na2CO3 in aqueous solution. After reaction, the precipitated solid was kept in the remaining water at 25 oC and under constant stirring for different aging times of 5 min, 1 and 5 hours, 1, 2, 4, 7, 30 and 60 days. In addition to the aging and precipitation experiments, we carried out experiments to determine the solubility of the solids. In these experiments each precipitate was dissolved in Milli-Q water until equilibrium was reached and then the aqueous solution was analyzed regarding Co2+ and total alkalinity. Furthermore, acid solution calorimetry of the products were attained. Finally, we modeled the results using the PHREEQC code. Solid and aqueous phase identification and characterization have been extensively reported in a previous work (González-López et al., 2015). The main results of our investigation were the initial precipitation of an amorphous cobalt carbonate that evolve towards a poorly crystalline cobalt hydroxide carbonate with aging treatment. Solubility of both phases have been calculated under two different approaches: precipitation and dissolution. Values of solubility from each approach were obtained with a general error due to differences in experiment conditions, for instance, ionic strength, temperature and

  10. Malic Acid Carbon Dots: From Super-resolution Live-Cell Imaging to Highly Efficient Separation.

    PubMed

    Zhi, Bo; Cui, Yi; Wang, Shengyang; Frank, Benjamin P; Williams, Denise N; Brown, Richard P; Melby, Eric S; Hamers, Robert J; Rosenzweig, Zeev; Fairbrother, D Howard; Orr, Galya; Haynes, Christy L

    2018-06-15

    As-synthesized malic acid carbon dots are found to possess photoblinking properties that are outstanding and superior compared to those of conventional dyes. Considering their excellent biocompatibility, malic acid carbon dots are suitable for super-resolution fluorescence localization microscopy under a variety of conditions, as we demonstrate in fixed and live trout gill epithelial cells. In addition, during imaging experiments, the so-called "excitation wavelength-dependent" emission was not observed for individual as-made malic acid carbon dots, which motivated us to develop a time-saving and high-throughput separation technique to isolate malic acid carbon dots into fractions of different particle size distributions using C 18 reversed-phase silica gel column chromatography. This post-treatment allowed us to determine how particle size distribution influences the optical properties of malic acid carbon dot fractions, that is, optical band gap energies and photoluminescence behaviors.

  11. Method for incorporating radioactive phosphoric acid solutions in concrete

    DOEpatents

    Wolf, G.A.; Smith, J.W.; Ihle, N.C.

    1982-07-08

    A method for incorporating radioactive phosphoric acid solutions in concrete is described wherein the phosphoric acid is reacted with Ca(OH)/sub 2/ to form a precipitate of hydroxyapatite and the hydroxyapatite is mixed with Portland cement to form concrete.

  12. Method for incorporating radioactive phosphoric acid solutions in concrete

    DOEpatents

    Wolf, Gary A [Kennewick, WA; Smith, Jeffrey W [Lancaster, OH; Ihle, Nathan C [Walla Walla, WA

    1984-01-01

    A method for incorporating radioactive phosphoric acid solutions in concrete is described wherein the phosphoric acid is reacted with Ca(OH).sub.2 to form a precipitate of hydroxyapatite and the hydroxyapatite is mixed with portland cement to form concrete.

  13. Supramolecular intermediates in the synthesis of polymeric carbon nitride from melamine cyanurate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dante, Roberto C., E-mail: rcdante@yahoo.com; Sánchez-Arévalo, Francisco M.; Chamorro-Posada, Pedro

    The adduct of melamine and cyanuric acid (MCA) was used in past research to produce polymeric carbon nitride and precursors. The reaction yield was considerably incremented by the addition of sulfuric acid. The polymeric carbon nitride formation occurs around 450 °C at temperatures above the sublimation of the adduct components, which occurs around 400 °C. In this report the effect of sulfuric acid on MCA was investigated. It was found that the MCA rosette supramolecular channel structures behave as a solid solvent able to host small molecules, such as sulfuric acid, inside these channels and interact with them. Therefore, themore » sulfuric acid effect was found to be close to that of a solute that causes a temperature increment of the “solvent sublimation” enough to allowing the formation of polymeric carbon nitride to occur. Sulfate ions are presumably hosted in the rosette channels of MCA as shown by simulations. - Graphical abstract: The blend of melamine cyanurate and sulfuric acid behaves like a solution so that melamine cyanurate decomposition is shifted to temperatures high enough to react and form polymeric carbon nitride. - Highlights: • The adduct of melamine and cyanuric acid behaves as a solid solvent. • The blend of sulfuric acid and melamine cyanurate behaves like a solution. • Melamine cyanurate decomposition is shifted to higher temperatures by sulfuric acid. • The formation of polymeric carbon nitride occurs for these higher temperatures.« less

  14. Carbon mineralization in acidic, xeric forest soils: induction of new activities.

    PubMed

    Tate, R L

    1985-08-01

    Carbon mineralization was examined in Lakehurst and Atsion sands collected from the New Jersey Pinelands and in Pahokee muck from the Everglades Agricultural Area. Objectives were (i) to estimate the carbon mineralization capacities of acidic, xeric Pinelands soils in the absence of exogenously supplied carbon substrate (nonamended carbon mineralization rate) and to compare these activities with those of agriculturally developed pahokee muck, and (ii) to measure the capacity for increased carbon mineralization in the soils after carbon amendment. In most cases, nonamended carbon mineralization rates were greater in samples of the acid- and moisture-stressed Pinelands soils than in Pahokee muck collected from a fallow (bare) field. Carbon amendment resulted in augmented catabolic activity in Pahokee muck samples, suggesting that the microbial community was carbon limited in this soil. With many of the substrates, no stimulation of the catabolic rate was detected after amendment of Pinelands soils. This was documented by the observation that amendment of Pahokee muck with an amino acid mixture, glucose, or acetate resulted in a 3.0-, 3.9-, or 10.5-fold stimulation of catabolic activity, respectively, for the added substrate. In contrast, amendment of the Pinelands soils resulted in increased amino acid and acetate catabolic rates in Lakehurst sand and increased acetate metabolism only in Atsion sand. Other activities were unchanged. The increased glucose respiration rates resulted from stimulation of existing microbial activity rather than from microbial proliferation since no change in the microbial growth rate, as estimated by the rate of incorporation of C-labeled acetate into cell membranes, occurred after glucose amendment of the soils. A stimulation of microbial growth rate was recorded with glucose-amended Lakehurst sand collected from the B horizon.

  15. 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.

  16. High-performance oxygen reduction catalysts in both alkaline and acidic fuel cells based on pre-treating carbon material and iron precursor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Song, Ping; Barkholtz, Heather M.; Wang, Ying

    We demonstrate a new and simple method for pre-treating the carbon material and iron precursor to prepare oxygen reduction reaction (ORR) catalysts, which can produce super-high performance and stability in alkaline solution, with high performance in acid solution. This strategy using cheap materials is simply controllable. Moreover, it has achieved smaller uniform nanoparticles to exhibit high stability, and the synergetic effect of Fe and N offered much higher performance in ORR than commercial Pt/C, with high maximum power density in alkaline and acid fuel cell test. So it can make this kind of catalysts be the most promising alternatives ofmore » Pt-based catalysts with best performance/price.« less

  17. Direct carbon-carbon coupling of furanics with acetic acid over Bronsted zeolites

    DOE PAGES

    Gumidyala, Abhishek; Wang, Bin; Crossley, Steven

    2016-09-16

    Effective carbon-carbon coupling of acetic acid to form larger products while minimizing CO 2 emissions is critical to achieving a step change in efficiency for the production of transportation fuels from sustainable biomass. Here, we report the direct acylation of methylfuran with acetic acid in the presence ofwater, all ofwhich can be readily produced from biomass. This direct coupling limits unwanted polymerization of furanics while producing acetyl methylfuran. Reaction kinetics and density functional theory calculations illustrate that the calculated apparent barrier for the dehydration of the acid to form surface acyl species is similar to the experimentally measured barrier, implyingmore » that this step plays a significant role in determining the net reaction rate. Water inhibits the overall rate, but selectivity to acylated products is not affected.We show that furanic species effectively stabilize the charge of the transition state, therefore lowering the overall activation barrier. These results demonstrate a promising new route to C–C bond–forming reactions for the production of higher-value products from biomass.« less

  18. Reprocessing system with nuclide separation based on chromatography in hydrochloric acid solution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Suzuki, Tatsuya; Tachibana, Yu; Koyama, Shi-ichi

    2013-07-01

    We have proposed the reprocessing system with nuclide separation processes based on the chromatographic technique in the hydrochloric acid solution system. Our proposed system consists of the dissolution process, the reprocessing process, the minor actinide separation process, and nuclide separation processes. In the reprocessing and separation processes, the pyridine resin is used as a main separation media. It was confirmed that the dissolution in the hydrochloric acid solution is easily achieved by the plasma voloxidation and by the addition of oxygen peroxide into the hydrochloric acid solution.

  19. The Formation and Stability of Carbonic Acid on Outer Solar System Bodies

    NASA Technical Reports Server (NTRS)

    Peeters, Z.; Hudson, R. L.; Moore, M. H.; Lewis, Ariel

    2009-01-01

    The radiation chemistry, thermal stability, and vapor pressure of solid-phase carbonic acid (H2CO3) have been studied with mid-infrared spectroscopy. A new procedure for measuring this molecule's radiation stability has been used to obtain intrinsic IR band strengths and half-lives for radiolytic destruction. Results are compared to literature values. We report, for the first time, measurements of carbonic acid's vapor pressure and its heat of sublimation. We also report the first observation of a chemical reaction involving solid-phase carbonic acid. Possible applications of these findings are discussed, with an emphasis on the outer Solar System.

  20. 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%.

  1. Differing Daphnia magna assimilation efficiencies for terrestrial, bacterial, and algal carbon and fatty acids.

    PubMed

    Taipale, Sami J; Brett, Michael T; Hahn, Martin W; Martin-Creuzburg, Dominik; Yeung, Sean; Hiltunen, Minna; Strandberg, Ursula; Kankaala, Paula

    2014-02-01

    There is considerable interest in the pathways by which carbon and growth-limiting elemental and biochemical nutrients are supplied to upper trophic levels. Fatty acids and sterols are among the most important molecules transferred across the plant-animal interface of food webs. In lake ecosystems, in addition to phytoplankton, bacteria and terrestrial organic matter are potential trophic resources for zooplankton, especially in those receiving high terrestrial organic matter inputs. We therefore tested carbon, nitrogen, and fatty acid assimilation by the crustacean Daphnia magna when consuming these resources. We fed Daphnia with monospecific diets of high-quality (Cryptomonas marssonii) and intermediate-quality (Chlamydomonas sp. and Scenedesmus gracilis) phytoplankton species, two heterotrophic bacterial strains, and particles from the globally dispersed riparian grass, Phragmites australis, representing terrestrial particulate organic carbon (t-POC). We also fed Daphnia with various mixed diets, and compared Daphnia fatty acid, carbon, and nitrogen assimilation across treatments. Our results suggest that bacteria were nutritionally inadequate diets because they lacked sterols and polyunsaturated omega-3 and omega-6 (omega-3 and omega-6) fatty acids (PUFAs). However, Daphnia were able to effectively use carbon and nitrogen from Actinobacteria, if their basal needs for essential fatty acids and sterols were met by phytoplankton. In contrast to bacteria, t-POC contained sterols and omega-6 and omega-3 fatty acids, but only at 22%, 1.4%, and 0.2% of phytoplankton levels, respectively, which indicated that t-POC food quality was especially restricted with regard to omega-3 PUFAs. Our results also showed higher assimilation of carbon than fatty acids from t-POC and bacteria into Daphnia, based on stable-isotope and fatty acids analysis, respectively. A relatively high (>20%) assimilation of carbon and fatty acids from t-POC was observed only when the proportion of t

  2. Activated carbon from peach stones using phosphoric acid activation at medium temperatures.

    PubMed

    Kim, Dong-Su

    2004-01-01

    In the present study, the activation features of phosphoric acid have been investigated using waste peach stones as the raw material in the production of granular activated carbon. Thermogravimetry/differential thermal analysis was conducted to characterize the thermal behavior of peach stone and titration method was used to evaluate the adsorption capacity of the produced activated carbon. It was observed that the iodine value of the activated carbon increased with activation temperature. However, temperatures higher than 500 degrees C caused a thermal destruction, which resulted in the decrease of the adsorption capacity. Activation longer than 1.5 h at 500 degrees C resulted in thermal degradation of the porous structure of the activated carbon. The adsorption capacity was enhanced with increasing of amounts of phosphoric acid, however, excessive phosphoric acid caused a decrease in the iodine value. In addition, it was found that the carbon yields generally decreased with activation temperature and activation time. Scanning electron microscopy analysis was conducted to observe the changes in the poros structure of the activated carbon produced in different temperatures. Activation of carbon by phosphoric acid was found to be superior to that by CaCl2 and gas activation. The activated carbon produced from peach stone was applied as an adsorbent in the treatment of synthesized wastewater containing cadmium ion and its adsorption capacity was found to be as good as that of the commercial one.

  3. 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. Copyright © 2013 Elsevier Inc. All rights reserved.

  4. Removal of 2,4-dichlorophenoxyacetic acid in aqueous solution by pulsed corona discharge treatment: Effect of different water constituents, degradation pathway and toxicity assay.

    PubMed

    Singh, Raj Kamal; Philip, Ligy; Ramanujam, Sarathi

    2017-10-01

    A multiple pin-plane corona discharge reactor was used to generate plasma for the degradation of 2,4 dichlorophenoxyacetic acid (2,4-D) from the aqueous solution. The 2,4-D of concentration 1 mg/L was completely removed within 6 min of plasma treatment. Almost complete mineralization was achieved after the treatment time of 14 min for a 2,4-D concentration of 10 mg/L. Effects of different water constituents such as carbonates, nitrate, sulphate, chloride ions, natural organic matter (humic acids) and pH on 2,4-D degradation was studied. A significant antagonistic effect of carbonate and humic acid was observed, whereas, the effects of other ions were insignificant. A higher first order rate constant of 1.73 min -1 was observed, which was significantly decreased in the presence of carbonate ions and humic acids. Also, a higher degradation of 2,4-D was observed in acidic pH conditions. Different 2,4-D intermediates were detected and the degradation pathway of 2,4-D in plasma treatment process was suggested. The toxicity of 10 mg/L 2,4-D was completely eradicated after 10 min of plasma treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Ionizing radiation induced degradation of salicylic acid in aqueous solution

    NASA Astrophysics Data System (ADS)

    Albarrán, Guadalupe; Mendoza, Edith

    2018-06-01

    The radiation-induced degradation of salicylic acid (SA-) in aqueous solutions (1.0 and 0.1 mmol dm-3) saturated with N2O or air or without oxygen were studied. Irradiation was carried out using a cobalt-60 source. With a 1 mmol dm-3 solution saturated with N2O a seemingly total degradation occurred at about 18 kGy, although small quantities of 2,3-dihydroxybenzoic acid, catechol and 2,5-dihydroxybenzoic acid were present at that dose at concentrations of 67, 22 and 6 μmol dm-3 respectively. Under air and when free oxygen, the three radiolytic products were present at 18.54 kGy while SA- was destroyed only to 90% and 62%, respectively. In the case of 0.1 mmol dm-3 SA- solutions, the acid was degraded at 3.5 kGy if the solution contained N2O, at 5.8 kGy in air and at 7 kGy without oxygen. The concentration of the radiolytic products increased with increasing dose and after a maximum they decreased. The oxidation was followed by measuring the chemical oxygen demand; the slopes were 0.48 and 0.11, 0.21 and 0.07, 0.15 and 0.03 mmol dm-3 kGy-1 for 1.0 and 0.10 mmol dm-3 solutions saturated with N2O or air or without oxygen, respectively.

  6. RECOVERY OF ACTINIDES FROM AQUEOUS NITRIC ACID SOLUTIONS

    DOEpatents

    Ader, M.

    1963-11-19

    A process of recovering actinides is presented. Tetravalent actinides are extracted from rare earths in an aqueous nitric acid solution with a ketone and back-extracted from the ketone into an aqueous medium. The aqueous actinide solution thus obtained, prior to concentration by boiling, is sparged with steam to reduce its ketone to a maximum content of 3 grams per liter. (AEC)

  7. Interaction between Al3+ and acrylic acid and polyacrylic acid in acidic aqueous solution: a model experiment for the behavior of Al3+ in acidified soil solution.

    PubMed

    Etou, Mayumi; Masaki, Yuka; Tsuji, Yutaka; Saito, Tomoyuki; Bai, Shuqin; Nishida, Ikuko; Okaue, Yoshihiro; Yokoyama, Takushi

    2011-01-01

    From the viewpoint of the phytotoxicity and mobility of Al(3+) released from soil minerals due to soil acidification, the interaction between Al(3+) and acrylic acid (AA) and polyacrylic acid (PAA) as a model compound of fulvic acid was investigated. The interaction was examined at pH 3 so as to avoid the hydrolysis of Al(3+). The interaction between Al(3+) and AA was weak. However, the interaction between Al(3+) and PAA was strong and depended on the initial (COOH in PAA)/Al molar ratio (R(P)) of the solution. For the range of 1/R(P), the interaction between Al(3+) and PAA can be divided into three categories: (1) 1:1 Al-PAA-complex (an Al(3+) combines to a carboxyl group), (2) intermolecular Al-PAA-complex (an Al(3+) combines to more than 2 carboxyl groups of other Al-PAA-complexes) in addition to the 1:1 Al-PAA-complex and (3) precipitation of intermolecular complexes. In conclusion, R(P) is an important factor affecting the behavior of Al(3+) in acidic soil solution.

  8. IN VITRO INTERACTIONS BETWEEN LACTIC ACID SOLUTION AND ART GLASS-IONOMER CEMENTS

    PubMed Central

    Wang, Linda; Cefaly, Daniela Francisca Gigo; dos Santos, Janaína Lima; dos Santos, Jean Rodrigo; Lauris, José Roberto Pereira; Mondelli, Rafael Francisco Lia; Atta, Maria Teresa

    2009-01-01

    Objectives: Production of acids such as lactic acid contributes to establish a cariogenic environment that leads to dental substrate demineralization. Fluoride plays an important role in this case and, as fluoride-releasing materials, glass-ionomer cements are expected to contribute to minimize deleterious reactions. This study evaluated interactions of glass-ionomer cements used in atraumatic restorative treatment (ART-GICs) with an aqueous lactic acid solution, testing the null hypotheses that no changes occur in the pH of the solution or on the surface roughness and mass of the ART-GICs when exposed to lactic acid solution over a 6-week period. Material and Methods: Ketac Molar, Fuji IX, Vitro Molar and Magic Glass were tested, and compared to Filtek Z250 and Ketac Fil Plus as control groups. Six specimens of each material were made according to manufacturers' instructions. The pH of the solution and roughness and mass changes of each specimen were determined over 6 weeks. Each specimen was individually stored in 2 mL of 0.02 M lactic acid solution for 1 week, renewing the solution every week. pH of solution and mass of the specimens were monitored weekly, and surface roughness of the specimens was assessed before and at the end of the 6-week acid challenge. pH and mass data were analyzed statistically by repeated measures using one-way ANOVA and Tukey's post-hoc tests for each material. Paired t-tests were used for roughness analysis. Tukey's post-hoc tests were applied to verify differences of final roughness among the materials. Significance level was set at 5%. Results: The null hypotheses were partially rejected. All materials were able to increase the pH of the lactic acid solution and presented rougher surfaces after immersion, while mass change was minimal and generally not statistically significant. Conclusions: These findings can be helpful to predict the performance of these materials under clinical conditions. A protective action against the carious

  9. 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.

  10. Carbon dioxide therapy and hyaluronic acid for cosmetic correction of the nasolabial folds.

    PubMed

    Nisi, Giuseppe; Cuomo, Roberto; Brandi, Cesare; Grimaldi, Luca; Sisti, Andrea; D'Aniello, Carlo

    2016-06-01

    The main application of hyaluronic acid filling, in esthetic medicine, is the augmentation of soft tissues. The carbon dioxide therapy, instead, improves quality and elasticity of the dermis and increases the oxygen release to the tissue through an enhancing of the Bohr's effect. The aim of the study was to compare the efficacy, tolerability, and effect duration of hyaluronic acid fillers and the use of carbon dioxide therapy plus hyaluronic acid in the cosmetic correction of nasolabial folds. Forty healthy female patients received a blinded and randomized treatment on nasolabial folds (hyaluronic acid in group A and hyaluronic acid plus subcutaneous injections of carbon dioxide in group B) for cosmetic correction of the nasolabial folds. The results were evaluated by two blinded plastic surgeons after the implant (1 week, 4 and 6 months) using a 1-5 graduated scale (GAIS), and at the same time, each patient was asked to express her opinion about the cosmetic result. Any long-term adverse reaction was reported. The blinded evaluation at 4 and 6 months from the implant shows in all patients a maintenance of a good cosmetic result higher for the side treated with carbon dioxide therapy plus hyaluronic acid. At the control visit, 6 months after the treatment, the patients treated with hyaluronic acid plus carbon dioxide therapy maintain a satisfactory esthetic result while the nasolabial fold treated only with hyaluronic acid shows, in almost all patients, a come back to pretreatment appearance. © 2016 Wiley Periodicals, Inc.

  11. The Path of Carbon in Photosynthesis II. Amino Acids

    DOE R&D Accomplishments Database

    Stepka, W.; Benson, A. A.; Calvin, M.

    1948-05-25

    The radioactive amino acid's synthesized from C{sup 14}O{sub 2} by green algae both in the light and in the dark after CO{sub 2}-free preillumination have been separated and identified using paper chromatography and radioautography. The radioactive amino acids identified were aspartic acid, alanine and smaller amounts of 3- and 4-carbon amino acids. This finding as well as the total absence of radioactive glutamic acid substantiates the mechanism for reduction of CO{sub 2} previously postulated by members of this laboratory.

  12. An Examination of the Carbon Isotope Effects Associated with Amino Acid Biosynthesis

    NASA Astrophysics Data System (ADS)

    Scott, James H.; O'Brien, Diane M.; Emerson, David; Sun, Henry; McDonald, Gene D.; Salgado, Antonio; Fogel, Marilyn L.

    2006-12-01

    Stable carbon isotope ratios (δ13C) were determined for alanine, proline, phenylalanine, valine, leucine, isoleucine, aspartate (aspartic acid and asparagine), glutamate (glutamic acid and glutamine), lysine, serine, glycine, and threonine from metabolically diverse microorganisms. The microorganisms examined included fermenting bacteria, organotrophic, chemolithotrophic, phototrophic, methylotrophic, methanogenic, acetogenic, acetotrophic, and naturally occurring cryptoendolithic communities from the Dry Valleys of Antarctica. Here we demonstrated that reactions involved in amino acid biosynthesis can be used to distinguish amino acids formed by life from those formed by nonbiological processes. The unique patterns of δ13C imprinted by life on amino acids produced a biological bias. We also showed that, by applying discriminant function analysis to the δ13C value of a pool of amino acids formed by biological activity, it was possible to identify key aspects of intermediary carbon metabolism in the microbial world. In fact, microorganisms examined in this study could be placed within one of three metabolic groups: (1) heterotrophs that grow by oxidizing compounds containing three or more carbon-to-carbon bonds (fermenters and organotrophs), (2) autotrophs that grow by taking up carbon dioxide (chemolitotrophs and phototrophs), and (3) acetoclastic microbes that grow by assimilation of formaldehyde or acetate (methylotrophs, methanogens, acetogens, and acetotrophs). Furthermore, we demonstrated that cryptoendolithic communities from Antarctica grouped most closely with the autotrophs, which indicates that the dominant metabolic pathways in these communities are likely those utilized for CO2 fixation. We propose that this technique can be used to determine the dominant metabolic types in a community and reveal the overall flow of carbon in a complex ecosystem.

  13. Predicting sorption of organic acids to a wide range of carbonized sorbents

    NASA Astrophysics Data System (ADS)

    Sigmund, Gabriel; Kah, Melanie; Sun, Huichao; Hofmann, Thilo

    2016-04-01

    Many contaminants and infochemicals are organic acids that undergo dissociation under environmental conditions. The sorption of dissociated anions to biochar and other carbonized sorbents is typically lower than that of neutral species. It is driven by complex processes that are not yet fully understood. It is known that predictive approaches developed for neutral compounds are unlikely to be suitable for organic acids, due to the effects of dissociation on sorption. Previous studies on the sorption of organic acids to soils have demonstrated that log Dow, which describes the decrease in hydrophobicity of acids upon dissociation, is a useful alternative to log Kow. The aim of the present study was to adapt a log Dow based approach to describe the sorption of organic acids to carbonized sorbents. Batch experiments were performed with a series of 9 sorbents (i.e., carbonized wood shavings, pig manure, and sewage sludge, carbon nanotubes and activated carbon), and four acids commonly used for pesticidal and biocidal purposes (i.e., 2,4-D, MCPA, 2,4-DB, and triclosan). Sorbents were comprehensively characterized, including by N2 and CO2 physisorption, Fourier transform infrared spectroscopy, and elemental analysis. The wide range of sorbents considered allows (i) discussing the mechanisms driving the sorption of neutral and anionic species to biochar, and (ii) their dependency on sorbate and sorbent properties. Results showed that the sorption of the four acids was influenced by factors that are usually not considered for neutral compounds (i.e., pH, ionic strength). Dissociation affected the sorption of the four compounds, and sorption of the anions ranged over five orders of magnitude, thus substantially contributing to sorption in some cases. For prediction purposes, most of the variation in sorption to carbonized sorbents (89%) could be well described with a two-parameter regression equation including log Dow and sorbent specific surface area. The proposed model

  14. Surface treated carbon catalysts produced from waste tires for fatty acids to biofuel conversion

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hood, Zachary D.; Adhikari, Shiba P.; Wright, Marcus W.

    A method of making solid acid catalysts includes the step of sulfonating waste tire pieces in a first sulfonation step. The sulfonated waste tire pieces are pyrolyzed to produce carbon composite pieces having a pore size less than 10 nm. The carbon composite pieces are then ground to produce carbon composite powders having a size less than 50 .mu.m. The carbon composite particles are sulfonated in a second sulfonation step to produce sulfonated solid acid catalysts. A method of making biofuels and solid acid catalysts are also disclosed.

  15. Anaerobic mineralization of quaternary carbon atoms: isolation of denitrifying bacteria on pivalic acid (2,2-dimethylpropionic acid).

    PubMed

    Probian, Christina; Wülfing, Annika; Harder, Jens

    2003-03-01

    The degradability of pivalic acid was established by the isolation of several facultative denitrifying strains belonging to Zoogloea resiniphila, to Thauera and Herbaspirillum, and to Comamonadaceae, related to [Aquaspirillum] and Acidovorax, and of a nitrate-reducing bacterium affiliated with Moraxella osloensis. Pivalic acid was completely mineralized to carbon dioxide. The catabolic pathways may involve an oxidation to dimethylmalonate or a carbon skeleton rearrangement, a putative 2,2-dimethylpropionyl coenzyme A mutase.

  16. Understanding Function and Performance of Carbon Additives in Lead-Acid Batteries

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Enos, D. G.; Ferreira, S. R.; Barkholtz, H. M.

    While the low cost and strong safety record of lead-acid batteries make them an appealing option compared to lithium-ion technologies for stationary storage, they can be rapidly degraded by the extended periods of high rate, partial state-of-charge operation required in such applications. Degradation occurs primarily through a process called hard sulfation, where large PbSO 4 crystals are formed on the negative battery plates, hindering charge acceptance and reducing battery capacity. Various researchers have found that the addition of some forms of excess carbon to the negative active mass in lead-acid batteries can mitigate hard sulfation, but the mechanism through whichmore » this is accomplished is unclear. In this work, the effect of carbon composition and morphology was explored by characterizing four discrete types of carbon additives, then evaluating their effect when added to the negative electrodes within a traditional valve-regulated lead-acid battery design. The cycle life for the carbon modified cells was significantly larger than an unmodified control, with cells containing a mixture of graphitic carbon and carbon black yielding the greatest improvement. The carbons also impacted other electrochemical aspects of the battery (e.g., float current, capacity, etc.) as well as physical characteristics of the negative active mass, such as the specific surface area.« less

  17. Understanding Function and Performance of Carbon Additives in Lead-Acid Batteries

    DOE PAGES

    Enos, D. G.; Ferreira, S. R.; Barkholtz, H. M.; ...

    2017-10-31

    While the low cost and strong safety record of lead-acid batteries make them an appealing option compared to lithium-ion technologies for stationary storage, they can be rapidly degraded by the extended periods of high rate, partial state-of-charge operation required in such applications. Degradation occurs primarily through a process called hard sulfation, where large PbSO 4 crystals are formed on the negative battery plates, hindering charge acceptance and reducing battery capacity. Various researchers have found that the addition of some forms of excess carbon to the negative active mass in lead-acid batteries can mitigate hard sulfation, but the mechanism through whichmore » this is accomplished is unclear. In this work, the effect of carbon composition and morphology was explored by characterizing four discrete types of carbon additives, then evaluating their effect when added to the negative electrodes within a traditional valve-regulated lead-acid battery design. The cycle life for the carbon modified cells was significantly larger than an unmodified control, with cells containing a mixture of graphitic carbon and carbon black yielding the greatest improvement. The carbons also impacted other electrochemical aspects of the battery (e.g., float current, capacity, etc.) as well as physical characteristics of the negative active mass, such as the specific surface area.« less

  18. Butyric acid esterification kinetics over Amberlyst solid acid catalysts: the effect of alcohol carbon chain length.

    PubMed

    Pappu, Venkata K S; Kanyi, Victor; Santhanakrishnan, Arati; Lira, Carl T; Miller, Dennis J

    2013-02-01

    The liquid phase esterification of butyric acid with a series of linear and branched alcohols is examined. Four strong cation exchange resins, Amberlyst™ 15, Amberlyst™ 36, Amberlyst™ BD 20, and Amberlyst™ 70, were used along with para-toluenesulfonic acid as a homogeneous catalyst. The effect of increasing alcohol carbon chain length and branching on esterification rate at 60°C is presented. For all catalysts, the decrease in turnover frequency (TOF) with increasing carbon chain length of the alcohol is described in terms of steric hindrance, alcohol polarity, and hydroxyl group concentration. The kinetics of butyric acid esterification with 2-ethylhexanol using Amberlyst™ 70 catalyst is described with an activity-based, pseudo-homogeneous kinetic model that includes autocatalysis by butyric acid. Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. Carbonic Acid by Ion Implantation in Water_solarCarbon Dioxide Ice Mixtures

    NASA Astrophysics Data System (ADS)

    Brucato, J. R.; Palumbo, M. E.; Strazzulla, G.

    1997-01-01

    We present the results of experiments performed by keV ion (He and H) bombardment of frozen mixtures of H 2O:CO 2and of pure CO 2ice. Using keV He ions we confirm the already reported measurement of carbonic acid (H 2CO 3) production in an ice mixture of frozen water and carbon dioxide (1:1) after irradiation by 0.7 MeV H ions (Moore, M. H., and R. K. Khanna 1991. Spectrochim. Acta47, 255-262; Moore, M. H., R. K. Khanna, and B. Donn 1991. J. Geophys. Res. E96(2), 17,541-17,545.). Contrary to a previous report (Pirronello, V., W. L. Brown, L. J. Lanzerotti, K. J. Marcantonio, and E. H. Simmons 1982. Astrophys. J.262, 636-640.), formaldehyde (H 2CO), if any, is not a major product. Implantation with hydrogen ions demonstrates that carbonic acid is formed even if the irradiated target is pure CO 2; i.e., the implanted ion is incorporated into the target and forms new bonds. Some possible astrophysical applications on Solar System objects or (pre-solar) interstellar grains are discussed.

  20. Treatment of infectious skin defects or ulcers with electrolyzed strong acid aqueous solution.

    PubMed

    Sekiya, S; Ohmori, K; Harii, K

    1997-01-01

    A chronic ulcer with an infection such as methicillin-resistant Staphylococcus aureus is hard to heal. Plastic and reconstructive surgeons often encounter such chronic ulcers that are resistant to surgical or various conservative treatments. We applied conservative treatment using an electrolyzed strong acid aqueous solution and obtained satisfactory results. The lesion was washed with the solution or soaked in a bowl of the solution for approximately 20 min twice a day. Fresh electrolyzed strong acid aqueous solution is unstable and should be stored in a cool, dark site in a sealed bottle. It should be used within a week after it has been produced. Here we report on 15 cases of infectious ulcers that were treated by electrolyzed strong acid aqueous solution. Of these cases, 7 patients were healed, 3 were granulated, and in 5, infection subsided. In most cases the lesion became less reddish and less edematous. Discharge or foul odor from the lesion was decreased. Electrolyzed strong acid aqueous solution was especially effective for treating a chronic refractory ulcer combined with diabetes melitus or peripheral circulatory insufficiency. This clinically applied therapy of electrolyzed strong acid aqueous solution was found to be effective so that this new therapeutic technique for ulcer treatment can now be conveniently utilized.

  1. Black Carbon in Sedimentary Organic Carbon in the Northeast Pacific using the Benzene Polycarboxylic Acid Method

    NASA Astrophysics Data System (ADS)

    Coppola, A. I.; Ziolkowski, L. A.; Druffel, E. R.

    2010-12-01

    Black carbon (BC) in the Northeast Pacific ultrafiltered dissolved organic matter (UDOM) was found to be surprisingly old with a 14C age of 18,000 +/-3,000 14C years (Ziolkowski and Druffel, 2010) using the Benzene Polycarboxylic Acid (BPCA) method, while BC in sedimentary organic carbon (SOC) was found to be 2,400-12,900 14C years older than non-BC SOC (Masiello and Druffel, 1998) with a different method. Using the dichromate-sulfuric acid oxidation method (Wolbach and Anders, 1989), Masiello and Druffel (1998) estimated that 12-31% of SOC in the Northeast Pacific and the Southern Ocean surface sediments was black carbon (BC). However, the dichromate-sulfuric acid oxidation may over-estimate the concentration of BC, because this method is more biased toward modern (char) material (Currie et al., 2002). Alternatively, the BPCA method isolates aromatic components of BC as benzene rings substituted with carboxylic acid groups, and provides structural information about the BC. Recent modifications to the BPCA method by Ziolkowski and Druffel (2009) involve few biases in quantifying BC in the continuum between char and soot in UDOM. Here we use the BPCA method to determine the concentrations and 14C values of BC in sediments from three sites in the Northeast Pacific Ocean. Constraining the difference between non-BC SOC and BC-SOC using the BPCA method allows for a more precise estimate of how much BC is present in the sediments and its 14C age. Presumably, the intermediate reservoir of BC is oceanic dissolved organic carbon (DOC) and is, in part, responsible for DOC’s great 14C age. These results can be utilized to better constrain the oceanic carbon budget as a possible sink of BC. References: Currie, L. A., Benner Jr., B. A., Kessler, J.D., et al (2002), A critical evaluation of interlaboratory data on total, elemental, and isotopic carbon in the carbonaceous particle reference material, nist srm 1649a, J. Res. Natl. Inst. Stand. Technol., 107, 279-298. Masiello, C

  2. Impacts of dyebath auxiliaries on the reductive discoloration of Acid Orange 7 dye by high-carbon iron filings.

    PubMed

    Kumar, Raja; Sinha, Alok

    This study proposed that the physicochemical effects of common dyebath auxiliaries on the bulk dye solution as well as on the iron surface can influence the reductive discoloration of effluent containing Acid Orange 7 (AO7) dye using high-carbon iron filings. Sodium chloride increased the discoloration rate because of the pitting corrosion on the iron surface, triggered by chloride anion. 'Salting out' effect of ammonium sulfate improved the reaction rate up to a certain concentration, beyond which it could compete with dye molecules for the reactive sites, as revealed by formed sulfite and sulfide. Urea drastically reduced the discoloration rates by its chaotropic effect on the bulk solution and by wrapping around the iron surface. Organic acids, namely acetic acid and citric acid, stimulated iron corrosion to improve the discoloration rates. The discoloration reaction was biphasic with an initial fast reaction phase, where in every case more than 70% discoloration was observed within 5 min of reaction, preceding a slow reaction phase. The experimental data could be well described using biphasic kinetics equation (R(2)> 0.997 in all cases) and a biphasic equation was developed considering the individual impact of co-existing auxiliaries on AO7 discoloration.

  3. Imprinted zeolite modified carbon paste electrode as a potentiometric sensor for uric acid

    NASA Astrophysics Data System (ADS)

    Khasanah, Miratul; Widati, Alfa Akustia; Fitri, Sarita Aulia

    2016-03-01

    Imprinted zeolite modified carbon paste electrode (carbon paste-IZ) has been developed and applied to determine uric acid by potentiometry. The imprinted zeolite (IZ) was synthesized by the mole ratio of uric acid/Si of 0.0306. The modified electrode was manufactured by mass ratio of carbon, IZ and solid paraffin was 40:25:35. The modified electrode had shown the measurement range of 10-5 M to 10-2 M with Nernst factor of 28.6 mV/decade, the detection limit of 5.86 × 10-6 M and the accuracy of 95.3 - 105.0%. Response time of the electrode for uric acid 10-5 M - 10-2 M was 25 - 44 s. The developed electrode showed the high selectivity toward uric acid in the urea matrix. Life time of the carbon paste-IZ electrode was 10 weeks.

  4. USE OF FATTY ACID STABLE CARBON ISOTOPE RATIO TO INDICATE MICROBIAL CARBON SOURCE IN TROPICAL SOILS

    EPA Science Inventory


    We use measurements of the concentration and stable carbon isotope ratio of individual microbial phospholipid fatty acids (PLFAs) in soils as indicators of live microbial biomass levels, broad microbial community structure, and microbial carbon source. For studies of soil o...

  5. Growth behavior of anodic porous alumina formed in malic acid solution

    NASA Astrophysics Data System (ADS)

    Kikuchi, Tatsuya; Yamamoto, Tsuyoshi; Suzuki, Ryosuke O.

    2013-11-01

    The growth behavior of anodic porous alumina formed on aluminum by anodizing in malic acid solutions was investigated. High-purity aluminum plates were electropolished in CH3COOH/HClO4 solutions and then anodized in 0.5 M malic acid solutions at 293 K and constant cell voltages of 200-350 V. The anodic porous alumina grew on the aluminum substrate at voltages of 200-250 V, and a black, burned oxide film was formed at higher voltages. The nanopores of the anodic oxide were only formed at grain boundaries of the aluminum substrate during the initial stage of anodizing, and then the growth region extended to the entire aluminum surface as the anodizing time increased. The anodic porous alumina with several defects was formed by anodizing in malic acid solution at 250 V, and oxide cells were approximately 300-800 nm in diameter.

  6. Changing fluxes of carbon and other solutes from the Mekong River

    PubMed Central

    Li, Siyue; Bush, Richard T.

    2015-01-01

    Rivers are an important aquatic conduit that connects terrestrial sources of dissolved inorganic carbon (DIC) and other elements with oceanic reservoirs. The Mekong River, one of the world’s largest rivers, is firstly examined to explore inter-annual fluxes of dissolved and particulate constituents during 1923–2011 and their associated natural or anthropogenic controls. Over this period, inter-annual fluxes of dissolved and particulate constituents decrease, while anthropogenic activities have doubled the relative abundance of SO42−, Cl− and Na+. The estimated fluxes of solutes from the Mekong decrease as follows (Mt/y): TDS (40.4) > HCO3− (23.4) > Ca2+ (6.4) > SO42− (3.8) > Cl− (1.74)~Na+ (1.7) ~ Si (1.67) > Mg2+ (1.2) > K+ (0.5). The runoff, land cover and lithological composition significantly contribute to dissolved and particulate yields globally. HCO3− and TDS yields are readily predicted by runoff and percent of carbonate, while TSS yield by runoff and population density. The Himalayan Rivers, including the Mekong, are a disproportionally high contributor to global riverine carbon and other solute budgets, and are of course underlined. The estimated global riverine HCO3− flux (Himalayan Rivers included) is 34014 × 109 mol/y (0.41 Pg C/y), 3915 Mt/y for solute load, including HCO3−, and 13553 Mt/y for TSS. Thereby this study illustrates the importance of riverine solute delivery in global carbon cycling. PMID:26522820

  7. Changing fluxes of carbon and other solutes from the Mekong River.

    PubMed

    Li, Siyue; Bush, Richard T

    2015-11-02

    Rivers are an important aquatic conduit that connects terrestrial sources of dissolved inorganic carbon (DIC) and other elements with oceanic reservoirs. The Mekong River, one of the world's largest rivers, is firstly examined to explore inter-annual fluxes of dissolved and particulate constituents during 1923-2011 and their associated natural or anthropogenic controls. Over this period, inter-annual fluxes of dissolved and particulate constituents decrease, while anthropogenic activities have doubled the relative abundance of SO4(2-), Cl(-) and Na(+). The estimated fluxes of solutes from the Mekong decrease as follows (Mt/y): TDS (40.4) > HCO3(-) (23.4) > Ca(2+) (6.4) > SO4(2-) (3.8) > Cl(-) (1.74)~Na(+) (1.7) ~ Si (1.67) > Mg(2+) (1.2) > K(+ 0.5). The runoff, land cover and lithological composition significantly contribute to dissolved and particulate yields globally. HCO3(-) and TDS yields are readily predicted by runoff and percent of carbonate, while TSS yield by runoff and population density. The Himalayan Rivers, including the Mekong, are a disproportionally high contributor to global riverine carbon and other solute budgets, and are of course underlined. The estimated global riverine HCO3(-) flux (Himalayan Rivers included) is 34,014 × 10(9) mol/y (0.41 Pg C/y), 3915 Mt/y for solute load, including HCO3(-), and 13,553 Mt/y for TSS. Thereby this study illustrates the importance of riverine solute delivery in global carbon cycling.

  8. Solubility and precipitation of nicotinic acid in supercritical carbon dioxide.

    PubMed

    Rehman, M; Shekunov, B Y; York, P; Colthorpe, P

    2001-10-01

    Solubilities of a model compound (nicotinic acid) in pure supercritical carbon dioxide (SC-CO(2)) and SC-CO(2) modified with methanol have been measured in the pressure range of 80-200 bar and between temperatures of 35 and 90 degrees C. On-line ultraviolet detection enabled a simple and relatively fast measurement of very low levels of solubility (10(-7) mol fraction) with good accuracy in pure and modified SC-CO(2). The solute solubility in both pure SC-CO(2) and SC-CO(2) modified with methanol increased with pressure at all investigated temperatures. A retrograde solubility behavior was observed in that, at pressures below 120 bar, a solubility decrease on temperature increase occurred. Solubility data were used to calculate supersaturation values and to define optimum operating conditions to obtain crystalline particles 1-5 microm in diameter using the solution-enhanced dispersion by supercritical fluids (SEDS) process, thereby demonstrating the feasibility of a one-step production process for particulate pharmaceuticals suitable for respiratory drug delivery. Copyright 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:1570-1582, 2001

  9. Synthesis of finely divided molybdenum sulfide nanoparticles in propylene carbonate solution

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Afanasiev, Pavel, E-mail: pavel.afanasiev@ircelyon.univ-lyon1.fr

    2014-05-01

    Molybdenum sulfide nanoparticles have been prepared from the reflux solution reaction involving ammonium heptamolybdate and elemental sulfur in propylene carbonate. Addition to the reaction mixture of starch as a natural capping agent leads to lesser agglomeration and smaller size of the particles. Nanoparticles of MoS{sub x} (x≈4) of 10–30 nm size are highly divided and form stable colloidal suspensions in organic solvents. Mo K edge EXAFS of the amorphous materials shows rapid exchange of oxygen to sulfur in the molybdenum coordination sphere during the solution reaction. Thermal treatment of the amorphous sulfides MoS{sub x} under nitrogen or hydrogen flow atmore » 400 °C allows obtaining mesoporous MoS{sub 2} materials with very high pore volume and specific surface area, up to 0.45 cm{sup 3}/g and 190 m{sup 2}/g, respectively. The new materials show good potential for the application as unsupported hydrotreating catalysts. - Graphical abstract: Solution reaction in propylene carbonate allows preparing weakly agglomerated molybdenum sulfide with particle size 20 nm and advantageous catalytic properties. - Highlights: • Solution reaction in propylene carbonate yields MoS{sub x} particles near 20 nm size. • Addition of starch as capping agent reduces particles size and hinder agglomeration. • EXAFS at Mo K edge shows rapid oxygen to sulfur exchange in the solution. • Thermal treatment leads to MoS{sub 2} with very high porosity and surface area.« less

  10. Recovery of fission product palladium from acidic high level waste solutions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rizvi, G.H.; Mathur, J.N.; Murali, M.S.

    1996-07-01

    The recovery of palladium from a synthetic pressurized heavy water reactor high level waste (PHWR-HLW) solution has been carried out, and the best reagents to use for the actual HLW solutions are discussed. The extraction of palladium from nitric acid solutions has been carried out using Cyanex-471X (triisobutylphosphine sulfide, TIPS) as the extractant. The metal ion could be quantitatively extracted from solutions with nitric acid concentrations between 2.0 and 6.0 M. The species extracted into the organic phase was found to be Pd(NO{sub 3}){sub 2}{center_dot}TIPS. Nitric acid in the range of 2.0 to 5.0 M had no effect on TIPSmore » for at least 71 hours. A systematic study of gamma irradiation on loading and stripping of palladium from loaded organic phases using several potential extractants, TIPS, alpha benzoin oxime, dioctylsulfide, and dioctylsulfoxide has been made. A flow sheet for the recovery of palladium from actual HLW solutions using TIPS is proposed.« less

  11. Effect of wood ash application on soil solution chemistry of tropical acid soils: incubation study.

    PubMed

    Nkana, J C Voundi; Demeyer, A; Verloo, M G

    2002-12-01

    The objective of this study was to determine the effect of wood ash application on soil solution composition of three tropical acid soils. Calcium carbonate was used as a reference amendment. Amended soils and control were incubated for 60 days. To assess soluble nutrients, saturation extracts were analysed at 15 days intervals. Wood ash application affects the soil solution chemistry in two ways, as a liming agent and as a supplier of nutrients. As a liming agent, wood ash application induced increases in soil solution pH, Ca, Mg, inorganic C, SO4 and DOC. As a supplier of elements, the increase in the soil solution pH was partly due to ligand exchange between wood ash SO4 and OH- ions. Large increases in concentrations of inorganic C, SO4, Ca and Mg with wood ash relative to lime and especially increases in K reflected the supply of these elements by wood ash. Wood ash application could represent increased availability of nutrients for the plant. However, large concentrations of basic cations, SO4 and NO3 obtained with higher application rates could be a concern because of potential solute transport to surface waters and groundwater. Wood ash must be applied at reasonable rates to avoid any risk for the environment.

  12. The ototoxic effect of boric acid solutions applied into the middle ear of guinea pigs.

    PubMed

    Oztürkcan, Sedat; Dündar, Riza; Katilmis, Hüseyin; Ilknur, Ali Ekber; Aktaş, Sinem; Haciömeroğlu, Senem

    2009-05-01

    This study analyzed the ototoxic effects of boric acid solutions. Boric acid solutions have been used as otologic preparations for many years. Boric acid is commonly found in solutions prepared with alcohol or distilled water but can also be found in a powder form. These preparations are used for both their antiseptic and acidic qualities in external and middle ear infections. We investigated the ototoxic effect of boric acid solutions on guinea pigs. We are unaware of any similar, previously published study of this subject in English. The study was conducted on 28 young albino guinea pigs. Prior to application of the boric acid solution under general anesthesia, an Auditory Brainstem Response (ABRs) test was applied to the right ear of the guinea pigs. Following the test, a perforation was created on the tympanic membrane of the right ear of each guinea pig and small gelfoam pieces were inserted into the perforated area. Test solutions were administered to the middle ear for 10 days by means of a transcanal route. Fifteen days after inserting the gelfoams in all of the guinea pigs, we anasthesized the guinea pigs and removed the gelfoams from the perforated region of the ear and then performed an ABRs on each guinea pig. The ABRs were within the normal range before the applications. After the application, no significant changes were detected in the ABRs thresholds in neither the saline group nor the group administered boric acid and distilled water solution; however, significant changes were detected in the ABRs thresholds of the Gentamicine and boric acid and alcohol solution groups. We believe that a 4% boric acid solution prepared with distilled water can be a more reliable preparation than a 4% boric acid solution prepared with alcohol.

  13. Optimization of preparation of activated carbon from cotton stalk by microwave assisted phosphoric acid-chemical activation.

    PubMed

    Deng, Hui; Zhang, Genlin; Xu, Xiaolin; Tao, Guanghui; Dai, Jiulei

    2010-10-15

    The preparation of activated carbon (AC) from cotton stalk was investigated in this paper. Orthogonal array experimental design method was used to optimize the preparation of AC using microwave assisted phosphoric acid. Optimized parameters were radiation power of 400 W, radiation time of 8 min, concentration of phosphoric acid of 50% by volume and impregnation time of 20 h, respectively. The surface characteristics of the AC prepared under optimized condition were examined by pore structure analysis, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Pore structure analysis shows that mecropores constitute more of the porosity of the prepared AC. Compared to cotton stalk, different functionalities and morphology on the carbon surfaces were formed in the prepared process. The adsorption capacity of the AC was also investigated by removing methylene blue (MB) in aqueous solution. The equilibrium data of the adsorption was well fitted to the Langmuir isotherm. The maximum adsorption capacity of MB on the prepared AC is 245.70 mg/g. The adsorption process follows the pseudo-second-order kinetic model. 2010 Elsevier B.V. All rights reserved.

  14. Towards Providing Solutions to the Air Quality Crisis in the Mexico City Metropolitan Area: Carbon Sequestration by Succulent Species in Green Roofs

    PubMed Central

    Collazo-Ortega, Margarita; Rosas, Ulises; Reyes-Santiago, Jerónimo

    2017-01-01

    INTRODUCTION: In the first months of 2016, the Mexico City Metropolitan Area experienced the worst air pollution crisis in the last decade, prompting drastic short-term solutions by the Mexico City Government and neighboring States. In order to help further the search for long-term sustainable solutions, we felt obliged to immediately release the results of our research regarding the monitoring of carbon sequestration by green roofs. Large-scale naturation, such as the implementation of green roofs, provides a way to partially mitigate the increased carbon dioxide output in urban areas. METHODS: Here, we quantified the carbon sequestration capabilities of two ornamental succulent plant species, Sedum dendroideum and Sedum rubrotinctum, which require low maintenance, and little or no irrigation. To obtain a detailed picture of these plants’ carbon sequestration capabilities, we measured carbon uptake on the Sedum plants by quantifying carbon dioxide exchange and fixation as organic acids, during the day and across the year, on a green roof located in Southern Mexico City. RESULTS: The species displayed their typical CAM photosynthetic metabolism. Moreover, our quantification allowed us to conservatively estimate that a newly planted green roof of Sedum sequesters approximately 180,000,000 ppm of carbon dioxide per year in a green roof of 100 square meters in the short term. DISCUSSION: The patterns of CAM and carbon dioxide sequestration were highly robust to the fluctuations of temperature and precipitation between seasons, and therefore we speculate that carbon sequestration would be comparable in any given year of a newly planted green roof. Older green roof would require regular trimming to mantain their carbon sink properties, but their carbon sequestration capabilities remain to be quantified. Nevertheless, we propose that Sedum green roofs can be part of the long-term solutions to mitigate the air pollution crisis in the Mexico City Metropolitan area, and

  15. PEROXIDE-INHIBITED DECONTAMINATION SOLUTIONS FOR CARBON STEEL AND OTHER METALS IN THE GAS-COOLED REACTOR PROGRAM. Progress Report, November 1959-July 1962

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Meservey, A.B.

    1963-01-01

    A search for solutions suitable for dissolving uranium dioxide powder or lumps and yet noncorrosive enough to be used for decontaminating the carbon steel EGCR charge and service machines resulted in the development of buffered oxalate solutions of controlled temperature and pH, with hydrogen peroxide added to act as corrosion inhibitor, UO/sub 2/ oxidizer, and decontamination aid. Hydrogen peroxide acts either as a corrosion promoter or inhibitor, depending on factors such as its concentration, the ratio to other ingredients, acidity, temperature, the presence of complexing agents, and the ferric ion content of the solution. In general, oxalate-peroxide solutions for fissionmore » product decontamination from metal surfaces were superior to more conventional decontaminating solutions and had attractively low corrosion rates on carbon steel (less than 0.01 mil/hr), Solution instability, initially a serious drawback, was largely overcome. Of nearly a hundred formulations studied, the one having the best combination of long life, low corrosivity, high solvency for UO/sub 2/, decontamination power, safety, and ease of waste disposal was an aqueous solution of 0.4M oxalic acid, 0.18M ammonium citrate, and 0.34M H/sub 2/O/sub 2/, adjusted to pH 4.00 with ammonium hydroxide and used at 85 to 95 deg C. Similar solutions at lower pH, with increased H/sub 2/O/sub 2/ concentration to maintain noncorrosiveness, were successful decontaminants at 60 deg C when contact times were increased to several hours. Contaminated stainless steels heated to 500 deg C in helium resisted decontamination in noncorrosive reagents. Oxalate-peroxide soluttons are currently recommended as UO/sub 2/ solvents and as general decontaminants for mild steel and aluminum surfaces in the GCR program, and for stainless steels which were not strongly heated while contaminated. These solutions may also find application in the decontamination of metals used in the aqueous reprocessing of radioactive

  16. Recent progress in solution plasma-synthesized-carbon-supported catalysts for energy conversion systems

    NASA Astrophysics Data System (ADS)

    Lun Li, Oi; Lee, Hoonseung; Ishizaki, Takahiro

    2018-01-01

    Carbon-based materials have been widely utilized as the electrode materials in energy conversion and storage technologies, such as fuel cells and metal-air batteries. In these systems, the oxygen reduction reaction is an important step that determines the overall performance. A novel synthesis route, named the solution plasma process, has been recently utilized to synthesize various types of metal-based and heteroatom-doped carbon catalysts. In this review, we summarize cutting-edge technologies involving the synthesis and modeling of carbon-supported catalysts synthesized via solution plasma process, followed by current progress on the electrocatalytic performance of these catalysts. This review provides the fundamental and state-of-the-art performance of solution-plasma-synthesized electrode materials, as well as the remaining scientific and technological challenges for this process.

  17. Fabrication and processing of high-strength densely packed carbon nanotube yarns without solution processes.

    PubMed

    Liu, Kai; Zhu, Feng; Liu, Liang; Sun, Yinghui; Fan, Shoushan; Jiang, Kaili

    2012-06-07

    Defects of carbon nanotubes, weak tube-tube interactions, and weak carbon nanotube joints are bottlenecks for obtaining high-strength carbon nanotube yarns. Some solution processes are usually required to overcome these drawbacks. Here we fabricate ultra-long and densely packed pure carbon nanotube yarns by a two-rotator twisting setup with the aid of some tensioning rods. The densely packed structure enhances the tube-tube interactions, thus making high tensile strengths of carbon nanotube yarns up to 1.6 GPa. We further use a sweeping laser to thermally treat as-produced yarns for recovering defects of carbon nanotubes and possibly welding carbon nanotube joints, which improves their Young's modulus by up to ∼70%. The spinning and laser sweeping processes are solution-free and capable of being assembled together to produce high-strength yarns continuously as desired.

  18. Isolation of an acidic protein from cholesterol gallstones, which inhibits the precipitation of calcium carbonate in vitro.

    PubMed Central

    Shimizu, S; Sabsay, B; Veis, A; Ostrow, J D; Rege, R V; Dawes, L G

    1989-01-01

    In seeking to identify nucleating/antinucleating proteins involved in the pathogenesis of cholesterol gallstones, a major acidic protein was isolated from each of 13 samples of cholesterol gallstones. After the stones were extracted with methyl t-butyl ether to remove cholesterol, and methanol to remove bile salts and other lipids, they were demineralized with EDTA. The extracts were desalted with Sephadex-G25, and the proteins separated by PAGE. A protein was isolated, of molecular weight below 10 kD, which included firmly-bound diazo-positive yellow pigments and contained 24% acidic, but only 7% basic amino acid residues. The presence of N-acetyl glucosamine suggested that this was a glycoprotein. This protein at concentrations as low as 2 micrograms/ml, but neither human serum albumin nor its complex with bilirubin, inhibited calcium carbonate precipitation from a supersaturated solution in vitro. This protein could be precipitated from 0.15 M NaCl solution by the addition of 0.5 M calcium chloride. Considering that cholesterol gallstones contain calcium and pigment at their centers, and that small acidic proteins are important regulators in other biomineralization systems, this protein seems likely to play a role in the pathogenesis of cholesterol gallstones. Images PMID:2592569

  19. The enrichment of chlorogenic acid from Eucommia ulmoides leaves extract by mesoporous carbons.

    PubMed

    Qin, Guotong; Ma, Jing; Wei, Wei; Li, Jaja; Yue, Fangqing

    2018-06-15

    Herein, we report an efficient separation and enrichment method for chlorogenic acid from crude extracts of Eucommia ulmoides leaves using carbon adsorbents. The effects of the pore structure of the carbon adsorbents on the adsorption capacity were studied. Of the four adsorbents investigated, mesoporous carbon (MC3) showed the highest adsorption capacity (294 mg/g of carbon) for chlorogenic acid due to its high mesopore volume. The static adsorption of CGA on carbon can be accurately described using the Freundlich equation. The kinetics of adsorption follow a pseudo-second-order process. External mass transfer was the controlling step of the adsorption process. Dynamic adsorption on MC3 demonstrated that chlorogenic acid began to break through after 28 bed volumes of extract was loaded. This mesoporous carbon-treatment procedure is safe, economic and has the potential to be scaled up for commercial application. Copyright © 2018 Elsevier B.V. All rights reserved.

  20. Effect of nitric acid treatment on activated carbon derived from oil palm shell

    NASA Astrophysics Data System (ADS)

    Allwar, Allwar; Hartati, Retno; Fatimah, Is

    2017-03-01

    The primary object of this work is to study the effect of nitric acid on the porous and morphology structure of activated carbon. Production of activated carbon from oil palm shell was prepared with pyrolysis process at temperature 900°C and by introduction of 10 M nitric acid. Determination of surface area, pore volume and pore size distribution of activated carbon was conducted by the N2 adsorption-desorption isotherm at 77 K. Morphology structure and elemental micro-analysis of activated carbon were estimated by Scanning Electron Microscopy (SEM) and energy dispersive X-ray (EDX), respectively. The result shows that activated carbon after treating with nitric acid proved an increasing porous characteristics involving surface area, pore volume and pore size distribution. It also could remove the contaminants including metals and exhibit an increasing of pores and crevices all over the surface.

  1. Removal of radium from acidic solutions containing same by adsorption on coal fly ash

    DOEpatents

    Scheitlin, Frank M.

    1984-01-01

    The invention is a process for the removal of radium from acidic aqueous solutions. In one aspect, the invention is a process for removing radium from an inorganic-acid solution. The process comprises contacting the solution with coal fly ash to effect adsorption of the radium on the ash. The radium-containing ash then is separated from the solution. The process is simple, comparatively inexpensive, and efficient. High radium-distribution coefficients are obtained even at room temperature. Coal fly ash is an inexpensive, acid-resistant, high-surface-area material which is available in large quantities throughout the United States. The invention is applicable, for example, to the recovery of .sup.226 Ra from nitric acid solutions which have been used to leach radium from uranium-mill tailings.

  2. Morphology-dependent Electrochemical Enhancements of Porous Carbon as Sensitive Determination Platform for Ascorbic Acid, Dopamine and Uric Acid

    NASA Astrophysics Data System (ADS)

    Cheng, Qin; Ji, Liudi; Wu, Kangbing; Zhang, Weikang

    2016-02-01

    Using starch as the carbon precursor and different-sized ZnO naoparticles as the hard template, a series of porous carbon materials for electrochemical sensing were prepared. Experiments of scanning electron microscopy, transmission electron microscopy and Nitrogen adsorption-desorption isotherms reveal that the particle size of ZnO has big impacts on the porous morphology and surface area of the resulting carbon materials. Through ultrasonic dispersion of porous carbon and subsequent solvent evaporation, different sensing interfaces were constructed on the surface of glassy carbon electrode (GCE). The electrochemical behaviors of ascorbic acid (AA), dopamine (DA) and uric acid (UA) were studied. On the surface of porous carbon materials, the accumulation efficiency and electron transfer ability of AA, DA and UA are improved, and consequently their oxidation signals enhance greatly. Moreover, the interface enhancement effects of porous carbon are also controlled by the particle size of hard template. The constructed porous carbon interface displays strong signal amplification ability and holds great promise in constructing a sensitive platform for the simultaneous determination of AA, DA and UA.

  3. Effcet of acid stimulation on the photoresponse of single walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Dhall, Shivani; Mehta, B. R.

    2018-04-01

    In this work, we have investigated the effect of acid treatment on the photoresponse of single walled carbon nanotubes (SWCNTs) and silicon (Si) interface. It was found that acid infiltration of SWCNTs proved helpful for the removal of impurities such as amhoporous carbon and improved the photoresponse at room temperature from 20 % to 42%. Raman analysis confirms that, the calculated crystallite size of the acids treated nanotubes is found to increase to 14.11 nm as compared to 13.7 nm for the pristine tubes. Furthermore, acid functionalized SWCNTs/Si interface shows better rectifying behavior as compared to pristine SWCNTs/ Si interface.

  4. Carbon Mineralization in Acidic, Xeric Forest Soils: Induction of New Activities †

    PubMed Central

    Tate, Robert L.

    1985-01-01

    Carbon mineralization was examined in Lakehurst and Atsion sands collected from the New Jersey Pinelands and in Pahokee muck from the Everglades Agricultural Area. Objectives were (i) to estimate the carbon mineralization capacities of acidic, xeric Pinelands soils in the absence of exogenously supplied carbon substrate (nonamended carbon mineralization rate) and to compare these activities with those of agriculturally developed pahokee muck, and (ii) to measure the capacity for increased carbon mineralization in the soils after carbon amendment. In most cases, nonamended carbon mineralization rates were greater in samples of the acid- and moisture-stressed Pinelands soils than in Pahokee muck collected from a fallow (bare) field. Carbon amendment resulted in augmented catabolic activity in Pahokee muck samples, suggesting that the microbial community was carbon limited in this soil. With many of the substrates, no stimulation of the catabolic rate was detected after amendment of Pinelands soils. This was documented by the observation that amendment of Pahokee muck with an amino acid mixture, glucose, or acetate resulted in a 3.0-, 3.9-, or 10.5-fold stimulation of catabolic activity, respectively, for the added substrate. In contrast, amendment of the Pinelands soils resulted in increased amino acid and acetate catabolic rates in Lakehurst sand and increased acetate metabolism only in Atsion sand. Other activities were unchanged. The increased glucose respiration rates resulted from stimulation of existing microbial activity rather than from microbial proliferation since no change in the microbial growth rate, as estimated by the rate of incorporation of 14C-labeled acetate into cell membranes, occurred after glucose amendment of the soils. A stimulation of microbial growth rate was recorded with glucose-amended Lakehurst sand collected from the B horizon. PMID:16346862

  5. Solution Preserves Nucleic Acids in Body-Fluid Specimens

    NASA Technical Reports Server (NTRS)

    Pierson, Duane L.; Stowe, Raymond P.

    2004-01-01

    A solution has been formulated to preserve deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in specimens of blood, saliva, and other bodily fluids. Specimens of this type are collected for diagnostic molecular pathology, which is becoming the method of choice for diagnosis of many diseases. The solution makes it possible to store such specimens at room temperature, without risk of decomposition, for subsequent analysis in a laboratory that could be remote from the sampling location. Thus, the solution could be a means to bring the benefits of diagnostic molecular pathology to geographic regions where refrigeration equipment and diagnostic laboratories are not available. The table lists the ingredients of the solution. The functions of the ingredients are the following: EDTA chelates divalent cations that are necessary cofactors for nuclease activity. In so doing, it functionally removes these cations and thereby retards the action of nucleases. EDTA also stabilizes the DNA helix. Tris serves as a buffering agent, which is needed because minor contaminants in an unbuffered solution can exert pronounced effects on pH and thereby cause spontaneous degradation of DNA. SDS is an ionic detergent that inhibits ribonuclease activity. SDS has been used in some lysis buffers and as a storage buffer for RNA after purification. The use of the solution is straightforward. For example, a sample of saliva is collected by placing a cotton roll around in the subject's mouth until it becomes saturated, then the cotton is placed in a collection tube. Next, 1.5 mL of the solution are injected directly into the cotton and the tube is capped for storage at room temperature. The effectiveness of the solution has been demonstrated in tests on specimens of saliva containing herpes simplex virus. In the tests, the viral DNA, as amplified by polymerase chain reaction, was detected even after storage for 120 days.

  6. Precipitation of calcium carbonate in aqueous solutions in presence of ethylene glycol and dodecane.

    NASA Astrophysics Data System (ADS)

    Natsi, Panagiota D.; Rokidi, Stamatia; Koutsoukos, Petros G.

    2015-04-01

    The formation of calcium carbonate (CaCO3) in aqueous supersaturated solutions has been intensively studied over the past decades, because of its significance for a number of processes of industrial and environmental interest. In the oil and gas production industry the deposition of calcium carbonate affects adversely the productivity of the wells. Calcium carbonate scale deposits formation causes serious problems in water desalination, CO2 sequestration in subsoil wells, in geothermal systems and in heat exchangers because of the low thermal coefficient of the salt. Amelioration of the operational conditions is possible only when the mechanisms underlying nucleation and crystal growth of calcium carbonate in the aqueous fluids is clarified. Given the fact that in oil production processes water miscible and immiscible hydrocarbons are present the changes of the dielectric constant of the fluid phase has serious impact in the kinetics of calcium carbonate precipitation, which remains largely unknown. The problem becomes even more complicated if polymorphism exhibited by calcium carbonate is also taken into consideration. In the present work, the stability of aqueous solutions supersaturated with respect to all calcium carbonate polymorphs and the subsequent kinetics of calcium carbonate precipitation were measured. The measurements included aqueous solutions and solutions in the presence of water miscible (ethylene glycol, MEG) and water immiscible organics (n-dodecane). All measurements were done at conditions of sustained supersaturation using the glass/ Ag/AgCl combination electrode as a probe of the precipitation and pH as the master variable for the addition of titrant solutions with appropriate concentration needed to maintenance the solution supersaturation. Initially, the metastable zone width was determined from measurements of the effect of the solution supersaturation on the induction time preceding the onset of precipitation at free-drift conditions. The

  7. Carbonate precipitation under bulk acidic conditions as a potential biosignature for searching life on Mars

    NASA Astrophysics Data System (ADS)

    Fernández-Remolar, David C.; Preston, Louisa J.; Sánchez-Román, Mónica; Izawa, Matthew R. M.; Huang, L.; Southam, Gordon; Banerjee, Neil R.; Osinski, Gordon R.; Flemming, Roberta; Gómez-Ortíz, David; Prieto Ballesteros, Olga; Rodríguez, Nuria; Amils, Ricardo; Darby Dyar, M.

    2012-10-01

    Recent observations of carbonate minerals in ancient Martian rocks have been interpreted as evidence for the former presence of circumneutral solutions optimal for carbonate precipitation. Sampling from surface and subsurface regions of the low-pH system of Río Tinto has shown, unexpectedly, that carbonates can form under diverse macroscopic physicochemical conditions ranging from very low to neutral pH (1.5-7.0). A multi-technique approach demonstrates that carbonate minerals are closely associated with microbial activity. Carbonates occur in the form of micron-size carbonate precipitates under bacterial biofilms, mineralization of subsurface colonies, and possible biogenic microstructures including globules, platelets and dumbbell morphologies. We propose that carbonate precipitation in the low-pH environment of Río Tinto is a process enabled by microbially-mediated neutralization driven by the reduction of ferric iron coupled to the oxidation of biomolecules in microbially-maintained circumneutral oases, where the local pH (at the scale of cells or cell colonies) can be much different than in the macroscopic environment. Acidic conditions were likely predominant in vast regions of Mars over the last four billion years of planetary evolution. Ancient Martian microbial life inhabiting low-pH environments could have precipitated carbonates similar to those observed at Río Tinto. Preservation of carbonates at Río Tinto over geologically significant timescales suggests that similarly-formed carbonate minerals could also be preserved on Mars. Such carbonates could soon be observed by the Mars Science Laboratory, and by future missions to the red planet.

  8. Hydrophobic interactions between polymethacrylic acid and sodium laureth sulfate in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Yaremko, Z. M.; Fedushinskaya, L. B.; Burka, O. A.; Soltys, M. N.

    2014-09-01

    The role of hydrophobic interaction in the development of associative processes is demonstrated, based on the concentration dependences of the viscosity and pH of binary solutions of polymethacrylic acid as an anionic polyelectrolyte and sodium laureth sulfate as an anionic surfactant. It is found that the inflection point on the dependence of the difference between the pH values of binary solutions of polymethacrylic acid and sodium laureth sulfate on the polyelectrolyte concentration is a criterion for determining the predominant contribution from hydrophobic interaction, as is the inflection point on the dependence of pH of individual solutions of polymethacrylic acid on the polyelectrolyte concentration.

  9. Impact of fluorescent lighting on the browning potential of model wine solutions containing organic acids and iron.

    PubMed

    Grant-Preece, Paris; Barril, Celia; Schmidtke, Leigh M; Clark, Andrew C

    2018-03-15

    Model wine solutions containing organic acids, individually or combined, and iron(III), were exposed to light from fluorescent lamps or stored in darkness for four hours. (-)-Epicatechin was then added, and the solutions incubated in darkness for 10days. Browning was monitored by UV-visible absorption spectrophotometry and UHPLC-DAD. The pre-irradiated solutions containing tartaric acid exhibited increased yellow/brown coloration compared to the dark controls mainly due to reaction of the tartaric acid photodegradation product glyoxylic acid with (-)-epicatechin to form xanthylium cation pigments. In these solutions, browning decreased as the concentrations of organic acids other than tartaric acid increased. Xanthylium cations were also detected in the pre-irradiated malic acid solution. However, in the malic acid, succinic acid, citric acid and lactic acid solutions, any coloration was mainly due to the production of dehydrodiepicatechin A, which was largely independent of prior light exposure, but strongly affected by the organic acid present. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Micro-organization of humic acids in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Klučáková, Martina; Věžníková, Kateřina

    2017-09-01

    The methods of dynamic light scattering and micro-rheology were used to investigate the molecular organization of humic acids in solutions. The obtained results were supplemented by ultraviolet/visible spectrometry and measurement of the zeta potential. Particle tracking micro-rheology was used for the first time as a novel method in humic research. Solutions of humic acids were prepared in three different mediums: NaOH, NaCl, and NaOH neutralized by HCl after dissolution of the humic sample. The molecular organization of humic acids was studied over a wide concentration range (0.01-10 g dm-3). Two breaks were detected in the obtained concentration dependencies. The rearrangements were observed at concentrations around 0.02 g dm-3 and 1 g dm-3. Changes in the measured values observed at around 0.02 g dm-3 were less noticeable and were related to the formation of particles between 100 and 1000 nm in size and the strong bimodal character of humic systems diluted by NaCl. The ;switch-over point; at around 1 g dm-3 indicated changes in the secondary structure of humic acids connected with the increase in colloidal stability (decrease of zeta potential), the decrease in polydispersity, and minimal values of viscosity.

  11. Large discharge capacity from carbon electrodes in sulfuric acid with oxidant

    NASA Astrophysics Data System (ADS)

    Inagaki, M.; Iwashita, N.

    The discharge performance of the graphite intercalation compounds in sulfuric acid containing nitric acid (H 2SO 4-GICs) was studied by focusing on the effects of oxidant and carbon nanotexture. A large discharge capacity from H 2SO 4-GICs synthesized by using an excess amount of HNO 3, more than 150 times of the theoretical value (93 mAh/g carbon), was obtained depending on the amount of oxidant added, the discharge current, and the nanotexture of carbon electrode. The experimental results are explained in terms of competition between the de-intercalation of sulfuric acid due to galvanostatic reduction and the re-intercalation due to chemical oxidation by HN03 during discharging. However, a subsidiary reaction decreases the effective amount of HNO 3 on the discharge by a small current and also on the cycle of chemical charging and electrochemical discharging. The oxidant KMnO 4 gave only a little larger capacity for discharge than the theoretical one, because it was reduced to the manganese oxide precipitates during the oxidation of the carbon electrode.

  12. In vitro toxicity of carbon nanotubes, nano-graphite and carbon black, similar impacts of acid functionalization.

    PubMed

    Figarol, Agathe; Pourchez, Jérémie; Boudard, Delphine; Forest, Valérie; Akono, Céline; Tulliani, Jean-Marc; Lecompte, Jean-Pierre; Cottier, Michèle; Bernache-Assollant, Didier; Grosseau, Philippe

    2015-12-25

    Carbon nanotubes (CNT) and nano-graphite (NG) are graphene-based nanomaterials which share exceptional physicochemical properties, but whose health impacts are unfortunately still not well understood. On the other hand, carbon black (CB) is a conventional and widely studied material. The comparison of these three carbon-based nanomaterials is thus of great interest to improve our understanding of their toxicity. An acid functionalization was carried out on CNT, NG and CB so that, after a thorough characterization, their impacts on RAW 264.7 macrophages could be compared for a similar surface chemistry (15 to 120 μg·mL(-1) nanomaterials, 90-min to 24-h contact). Functionalized nanomaterials triggered a weak cytotoxicity similar to the pristine nanomaterials. Acid functionalization increased the pro-inflammatory response except for CB which did not trigger any TNF-α production before or after functionalization, and seemed to strongly decrease the oxidative stress. The toxicological impact of acid functionalization appeared thus to follow a similar trend whatever the carbon-based nanomaterial. At equivalent dose expressed in surface and equivalent surface chemistry, the toxicological responses from murine macrophages to NG were higher than for CNT and CB. It seemed to correspond to the hypothesis of a platelet and fiber paradigm. Copyright © 2015. Published by Elsevier Ltd.

  13. Grafting of activated carbon cloths for selective adsorption

    NASA Astrophysics Data System (ADS)

    Gineys, M.; Benoit, R.; Cohaut, N.; Béguin, F.; Delpeux-Ouldriane, S.

    2016-05-01

    Chemical functionalization of an activated carbon cloth with 3-aminophthalic acid and 4-aminobenzoic acid groups by the in situ formation of the corresponding diazonium salt in aqueous acidic solution is reported. The nature and amount of selected functions on an activated carbon surface, in particular the grafted density, were determined by potentiometric titration, elemental analysis and X-ray photoelectron spectroscopy (XPS). The nanotextural properties of the modified carbon were explored by gas adsorption. Functionalized activated carbon cloth was obtained at a discrete grafting level while preserving interesting textural properties and a large porous volume. Finally, the grafting homogeneity of the carbon surface and the nature of the chemical bonding were investigated using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) technique.

  14. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Electrochemical Behavior of Biomedical Titanium Alloys Coated with Diamond Carbon in Hanks' Solution

    NASA Astrophysics Data System (ADS)

    Gnanavel, S.; Ponnusamy, S.; Mohan, L.; Radhika, R.; Muthamizhchelvan, C.; Ramasubramanian, K.

    2018-03-01

    Biomedical implants in the knee and hip are frequent failures because of corrosion and stress on the joints. To solve this important problem, metal implants can be coated with diamond carbon, and this coating plays a critical role in providing an increased resistance to implants toward corrosion. In this study, we have employed diamond carbon coating over Ti-6Al-4V and Ti-13Nb-13Zr alloys using hot filament chemical vapor deposition method which is well-established coating process that significantly improves the resistance toward corrosion, wears and hardness. The diamond carbon-coated Ti-13Nb-13Zr alloy showed an increased microhardness in the range of 850 HV. Electrochemical impedance spectroscopy and polarization studies in SBF solution (simulated body fluid solution) were carried out to understand the in vitro behavior of uncoated as well as coated titanium alloys. The experimental results showed that the corrosion resistance of Ti-13Nb-13Zr alloy is relatively higher when compared with diamond carbon-coated Ti-6Al-4V alloys due to the presence of β phase in the Ti-13Nb-13Zr alloy. Electrochemical impedance results showed that the diamond carbon-coated alloys behave as an ideal capacitor in the body fluid solution. Moreover, the stability in mechanical properties during the corrosion process was maintained for diamond carbon-coated titanium alloys.

  16. Redox potentials and kinetics of the Ce 3+/Ce 4+ redox reaction and solubility of cerium sulfates in sulfuric acid solutions

    NASA Astrophysics Data System (ADS)

    Paulenova, A.; Creager, S. E.; Navratil, J. D.; Wei, Y.

    Experimental work was performed with the aim of evaluating the Ce 4+/Ce 3+ redox couple in sulfuric acid electrolyte for use in redox flow battery (RFB) technology. The solubility of cerium sulfates in 0.1-4.0 M sulfuric acid at 20-60 °C was studied. A synergistic effect of both sulfuric acid concentration and temperature on the solubility of cerous sulfate was observed. The solubility of cerous sulfate significantly decreased with rising concentration of sulfuric acid and rising temperature, while the solubility of ceric sulfate goes through a significant maximum at 40 °C. Redox potentials and the kinetics of the cerous/ceric redox reaction were also studied under the same temperature-concentration conditions. The redox potentials were measured using the combined redox electrode (Pt-Ag/AgCl) in equimolar Ce 4+/Ce 3+ solutions (i.e.[Ce 3+]=[Ce 4+]) in sulfuric acid electrolyte. The Ce 3+/Ce 4+ redox potentials significantly decrease (i.e. shift to more negative values) with rising sulfuric acid concentration; a small maximum is observed at 40 °C. Cyclic voltammetric experiments confirmed slow electrochemical kinetics of the Ce 3+/Ce 4+ redox reaction on carbon glassy electrodes (CGEs) in sulfuric acid solutions. The observed dependencies of solubilities, the redox potentials and the kinetics of Ce 3+/Ce 4+ redox reaction on sulfuric acid concentration are thought to be the result of inequivalent complexation of the two redox species by sulfate anions: the ceric ion is much more strongly bound to sulfate than is the cerous ion. The best temperature-concentration conditions for the RFB electrolytes appear to be 40 °C and 1 M sulfuric acid, where the relatively good solubility of both cerium species, the maximum of redox potentials, and the more or less satisfying stability of CGE s were found. Even so, the relatively low solubility of cerium salts in sulfuric acid media and slow redox kinetics of the Ce 3+/Ce 4+ redox reaction at carbon indicate that the Ce 3+/Ce

  17. A wet chemical method for the estimation of carbon in uranium carbides.

    PubMed

    Chandramouli, V; Yadav, R B; Rao, P R

    1987-09-01

    A wet chemical method for the estimation of carbon in uranium carbides has been developed, based on oxidation with a saturated solution of sodium dichromate in 9M sulphuric acid, absorption of the evolved carbon dioxide in a known excess of barium hydroxide solution, and titration of the excess of barium hydroxide with standard potassium hydrogen phthalate solution. The carbon content obtained is in good agreement with that obtained by combustion and titration.

  18. Organic solute changes with acidification in Lake Skjervatjern as shown by 1H-NMR spectroscopy

    USGS Publications Warehouse

    Malcolm, R.L.; Hayes, T.

    1994-01-01

    1H-NMR spectroscopy has been found to be a useful tool to establish possible real differences and trends between all natural organic solute fractions (fulvic acids, humic acids, and XAD-4 acids) after acid-rain additions to the Lake Skjervatjern watershed. The proton NMR technique used in this study determined the spectral distribution of nonexchangeable protons among four peaks (aliphatic protons; aliphatic protons on carbon ?? or attached to electronegative groups; protons on carbons attached to O or N heteroatoms; and aromatic protons). Differences of 10% or more in the respective peak areas were considered to represent a real difference. After one year of acidification, fulvic acids decreased 13% (relative) in Peak 3 protons on carbon attached to N and O heteratoms and exhibited a decrease in aromatic protons between 27% and 31%. Humic acids also exhibited an 11% relative decrease in aromatic protons as a result of acidification. After one year of acidification, real changes were shown in three of the four proton assignments in XAD-4 acids. Peak 1 aliphatic protons increased by 14% (relative), Peak 3 protons on carbons attached to O and N heteroatoms decreased by 13% (relative), and aromatic protons (Peak 4) decreased by 35% (relative). Upon acidification, there was a trend in all solutes for aromatic protons to decrease and aliphatic protons to increase. The natural variation in organic solutes as shown in the Control Side B of the lake from 1990 to 1991 is perhaps a small limitation to the same data interpretations of acid rain changes at the Lake Skjervatjern site, but the proton NMR technique shows great promise as an independent scientific tool to detect and support other chemical techniques in establishing organic solute changes with different treatments (i.e., additions of acid rain).

  19. Cyanuric Acid-Based Organocatalyst for Utilization of Carbon Dioxide at Atmospheric Pressure.

    PubMed

    Yu, Bing; Kim, Daeun; Kim, Seoksun; Hong, Soon Hyeok

    2017-03-22

    A organocatalytic system based on economical and readily available cyanuric acid has been developed for the synthesis of 2-oxazolidinones and quinazoline-2,4(1H,3H)-diones from propargylamines and 2-aminobenzonitriles under atmospheric pressure carbon dioxide. Notably, a low concentration of carbon dioxide in air was directly converted into 2-oxazolidinone in excellent yields without an external base. Through mechanistic investigation by in situ FTIR spectroscopy, cyanuric acid was demonstrated to be an efficient catalyst for carbon dioxide fixation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Method for liquid chromatographic extraction of strontium from acid solutions

    DOEpatents

    Horwitz, E. Philip; Dietz, Mark L.

    1992-01-01

    A method and apparatus for extracting strontium and technetium values from biological, industrial and environmental sample solutions using a chromatographic column is described. An extractant medium for the column is prepared by generating a solution of a diluent containing a Crown ether and dispersing the solution on a resin substrate material. The sample solution is highly acidic and is introduced directed to the chromatographic column and strontium or technetium is eluted using deionized water.

  1. Fumaric acid: an overlooked form of fixed carbon in Arabidopsis and other plant species

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chia, D.W.; Yoder, T.J.; Reiter, W.D.

    2000-10-01

    Photoassimilates are used by plants for production of energy, as carbon skeletons and in transport of fixed carbon between different plant organs. Many studies have been devoted to characterizing the factors that. regulate photoassimilate concentrations in different plant species. Most studies examining photoassimilate concentrations in C{sub 3} plants have focused on analyzing starch and soluble sugars. However, work presented here demonstrates that a number of C{sub 3} plants, including the popular model organism Arabidopsis thaliana (L.) Heynh., and agriculturally important plants, such as soybean [Glycine ma (L.) Merr.], contain significant quantities of furnaric acid. In fact, furnaric acid can accumulatemore » to levels of several mg per g fresh weight in A-abidopsis leaves, often exceeding starch and soluble sugar levels. Furnaric acid is a component of the tricarboxylic acid cycle and, like starch and soluble sugars, can be metabolized to yield energy and carbon skeletons for production of other compounds. Fumaric acid concentrations increase with plant age and light intensity in Arabidopsis leaves. Arabidopsis phloem exudates contain significant quantities of fumaric acid, raising the possibility that fumaric acid may function in carbon transport.« less

  2. Boric Acid Corrosion of Concrete Rebar

    NASA Astrophysics Data System (ADS)

    Pabalan, R. T.; Yang, L.; Chiang, K.–T.

    2013-07-01

    Borated water leakage through spent fuel pools (SFPs) at pressurized water reactors is a concern because it could cause corrosion of reinforcement steel in the concrete structure and compromise the integrity of the structure. Because corrosion rate of carbon steel in concrete in the presence of boric acid is lacking in published literature and available data are equivocal on the effect of boric acid on rebar corrosion, corrosion rate measurements were conducted in this study using several test methods. Rebar corrosion rates were measured in (i) borated water flowing in a simulated concrete crack, (ii) borated water flowing over a concrete surface, (iii) borated water that has reacted with concrete, and (iv) 2,400 ppm boric acid solutions with pH adjusted to a range of 6.0 to 7.7. The corrosion rates were measured using coupled multielectrode array sensor (CMAS) and linear polarization resistance (LPR) probes, both made using carbon steel. The results indicate that rebar corrosion rates are low (~1 μm/yr or less)when the solution pH is ~7.1 or higher. Below pH ~7.1, the corrosion rate increases with decreasing pH and can reach ~100 μm/yr in solutions with pH less than ~6.7. The threshold pH for carbon steel corrosion in borated solution is between 6.8 and 7.3.

  3. 49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Chloric acid solution or chlorine dioxide hydrate... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the.... Fiberboard boxes must be reinforced and insulated and sufficient dry ice must be used to maintain the hydrate...

  4. 49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Chloric acid solution or chlorine dioxide hydrate... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the.... Fiberboard boxes must be reinforced and insulated and sufficient dry ice must be used to maintain the hydrate...

  5. 49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Chloric acid solution or chlorine dioxide hydrate... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the.... Fiberboard boxes must be reinforced and insulated and sufficient dry ice must be used to maintain the hydrate...

  6. 49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Chloric acid solution or chlorine dioxide hydrate... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the.... Fiberboard boxes must be reinforced and insulated and sufficient dry ice must be used to maintain the hydrate...

  7. 49 CFR 173.229 - Chloric acid solution or chlorine dioxide hydrate, frozen.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Chloric acid solution or chlorine dioxide hydrate... Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the.... Fiberboard boxes must be reinforced and insulated and sufficient dry ice must be used to maintain the hydrate...

  8. Approximate Solutions for a Self-Folding Problem of Carbon Nanotubes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Y Mikata

    2006-08-22

    This paper treats approximate solutions for a self-folding problem of carbon nanotubes. It has been observed in the molecular dynamics calculations [1] that a carbon nanotube with a large aspect ratio can self-fold due to van der Waals force between the parts of the same carbon nanotube. The main issue in the self-folding problem is to determine the minimum threshold length of the carbon nanotube at which it becomes possible for the carbon nanotube to self-fold due to the van der Waals force. An approximate mathematical model based on the force method is constructed for the self-folding problem of carbonmore » nanotubes, and it is solved exactly as an elastica problem using elliptic functions. Additionally, three other mathematical models are constructed based on the energy method. As a particular example, the lower and upper estimates for the critical threshold (minimum) length are determined based on both methods for the (5,5) armchair carbon nanotube.« less

  9. USE OF THE COMPOSITION AND STABLE CARBON ISOTOPE RATIO OF MICROBIAL FATTY ACIDS TO STUDY CARBON CYCLING

    EPA Science Inventory

    We use measurements of the concentration and stable carbon isotopic ratio (Gamma 13C) of individual microbial phospholipid fatty acids (PLFAS) in soils and sediments as indicators of live microbial biomass levels and microbial carbon source. For studies of soil organic matter (SO...

  10. USE OF STABLE CARBON ISOTOPE RATIOS OF FATTY ACIDS TO EVALUATE MICROBIAL CARBON SOURCES IN TERRESTRIAL ENVIRONMENTS

    EPA Science Inventory

    We use measurements of the concentration and stable carbon isotopic ratio (D 13C) of individual microbial phospholipid fatty acids (PLFAs) in soils as indicators of live microbial biomass levels and microbial carbon source. We found that intensive sugar cane cultivation leads to ...

  11. Preparation of a novel carbon-based solid acid from cassava stillage residue and its use for the esterification of free fatty acids in waste cooking oil.

    PubMed

    Wang, Lingtao; Dong, Xiuqin; Jiang, Haoxi; Li, Guiming; Zhang, Minhua

    2014-04-01

    A novel carbon-based solid acid catalyst was prepared by the sulfonation of incompletely carbonized cassava stillage residue (CSR) with concentrated sulfuric acid, and employed to catalyze the esterification of methanol and free fatty acids (FFAs) in waste cooking oil (WCO). The effects of the carbonization and the sulfonation temperatures on the pore structure, acid density and catalytic activity of the CSR-derived catalysts were systematically investigated. Low temperature carbonization and high temperature sulfonation can cause the collapse of the carbon framework, while high temperature carbonization is not conducive to the attachment of SO3H groups on the surface. The catalyst showed high catalytic activity for esterification, and the acid value for WCO is reduced to below 2mg KOH/g after reaction. The activity of catalyst can be well maintained after five cycles. CSR can be considered a promising raw material for the production of a new eco-friendly solid acid catalyst. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Chiral acidic amino acids induce chiral hierarchical structure in calcium carbonate

    PubMed Central

    Jiang, Wenge; Pacella, Michael S.; Athanasiadou, Dimitra; Nelea, Valentin; Vali, Hojatollah; Hazen, Robert M.; Gray, Jeffrey J.; McKee, Marc D.

    2017-01-01

    Chirality is ubiquitous in biology, including in biomineralization, where it is found in many hardened structures of invertebrate marine and terrestrial organisms (for example, spiralling gastropod shells). Here we show that chiral, hierarchically organized architectures for calcium carbonate (vaterite) can be controlled simply by adding chiral acidic amino acids (Asp and Glu). Chiral, vaterite toroidal suprastructure having a ‘right-handed' (counterclockwise) spiralling morphology is induced by L-enantiomers of Asp and Glu, whereas ‘left-handed' (clockwise) morphology is induced by D-enantiomers, and sequentially switching between amino-acid enantiomers causes a switch in chirality. Nanoparticle tilting after binding of chiral amino acids is proposed as a chiral growth mechanism, where a ‘mother' subunit nanoparticle spawns a slightly tilted, consequential ‘daughter' nanoparticle, which by amplification over various length scales creates oriented mineral platelets and chiral vaterite suprastructures. These findings suggest a molecular mechanism for how biomineralization-related enantiomers might exert hierarchical control to form extended chiral suprastructures. PMID:28406143

  13. Effect of citric acid on the acidification of artificial pepsin solution for metacercariae isolation from fish.

    PubMed

    Kim, Min-Ki; Pyo, Kyoung-Ho; Hwang, Young-Sang; Chun, Hyang Sook; Park, Ki Hwan; Ko, Seong-Hee; Chai, Jong-Yil; Shin, Eun-Hee

    2013-11-15

    Artificial digestive solution based on pepsin is essential for collecting metacercariae from fish. To promote the enzymatic reactivity of pepsin, the pH of the solution has to be adjusted to pH 1.0-2.0. Hydrochloride (HCl) is usually used for this purpose, but the use of HCl raises safety concerns. The aim of this work was to address the usefulness of citric acid as an alternative for HCl for the acidification of pepsin solution, and to examine its potential to damage metacercariae during in vitro digestion as compared with HCl. Changes in pH after adding 1-9% of citric acid (m/v) to pepsin solution were compared to a 1% HCl (v/v) addition. Digestion of fish muscle was evaluated by measuring released protein concentrations by spectrophotometry. In addition, survival rates of metacercariae in pepsin solution were determined at different citric acid concentrations and were compared that of with 1% HCl. The present study shows that addition of citric acid reduced the pH of pepsin solutions to the required level. Addition of more than 5% of citric acid resulted in the effective digestion of fish muscle over 3h in vitro, and 5% citric acid was less lethal to metacercariae than 1% HCl in pepsin solution. Pepsin solution containing 5% citric acid had digestive capacity superior to pepsin solution containing 1% HCl after 3h incubation with released protein concentrations of 12.0 ng/ml for 5% citric acid and 9.6 ng/ml for 1% HCl. Accordingly, the present study suggests that the addition of 5% citric acid to pepsin solution is a good alternative to 1% HCl in infection studies because citric acid is a stable at room temperature and has a good safety profile. In addition, we suggest that the use of citric acid enables the preparation of commercial digestive solutions for the detection of microorganisms in fish and other vertebrate muscle tissue. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

  14. Citric acid functionalized carbon materials for fuel cell applications

    NASA Astrophysics Data System (ADS)

    Poh, Chee Kok; Lim, San Hua; Pan, Hui; Lin, Jianyi; Lee, Jim Yang

    Carbon materials can be easily functionalized using citric acid (CA) treatment. The CA modification of carbon materials is both simple and effective. It requires no prolonged heating, filtration and washing, and produces more functional groups such as carboxyl and hydroxide on CA-modified carbon nanotubes and XC72 carbon blacks than on HNO 3-H 2SO 4 oxidized carbon nanotubes and as-purchased XC72. Platinum nanoparticles are deposited on these functionalized carbon materials by means of a microwave-assisted polyol process. The investigations using TEM, XRD, FTIR and TGA indicate that CA modification creates more functional groups and thus deposits more Pt nanoparticles with smaller average particle size on the surface of carbon materials. Electrochemical studies of the Pt/C samples for methanol oxidation reveal higher activity for Pt on CA-modified carbon materials. It is therefore considered that this method can find important applications in reducing the cost and improving performance of proton-exchange membrane fuel cells.

  15. Synthesis carbon foams prepared from gelatin (CFG) for cadmium ion adsorption

    NASA Astrophysics Data System (ADS)

    Ulfa, M.; Ulfa, D. K.

    2018-01-01

    In this paper, carbon foam from gelatin (CFG) was synthesized by acid-catalyzed carbonization of gelatin solution on mild condition by the simple method. Gelatin (Ge) were used as sacrificial template and source of carbon. Sulphuric acid was used as acid catalyst. Carbon foam CFG sample were characterized by scanning electron microscope (SEM), nitrogen adsorption desorption and FTIR for knowing textural and structural properties of the sample. Carbon foam CFG sample demonstrated macro pipes-channel like with pore size that varies between 30-40 μ and surface area m 60-100 m2g-1. The carbon foams CFG sample were tested by using adsorption process for obtained their performance for decreasing Cd(II) ions from aqueous solutions. The adsorption capacities for cadmium was 46.7 mg/g obtained by using adsorbent dose 50 mg, initial concentration 50 ppm, contact time, 3 h; room temperature, stirring rate 150 rpm) which reached equilibrium at 55 min. Adsorption process fits using using Lagergren and Ho and McKay equation and measuring data

  16. Sorption of triclosan onto activated carbon, kaolinite and montmorillonite: effects of pH, ionic strength, and humic acid.

    PubMed

    Behera, Shishir Kumar; Oh, Seok-Young; Park, Hung-Suck

    2010-07-15

    Sorption of triclosan on three sorbents, viz., activated carbon, kaolinite and montmorillonite was studied as a function of pH, ionic strength and humic acid (HA) concentration through controlled batch experiments. Triclosan sorption was found to be higher in the acidic pH range, as varying pH showed significant influence on the surface charge of the sorbents and degree of ionization of the sorbate. Sorption capacity of the sorbents increased with an increase in the ionic strength of solution. At low pH (pH 3), the overall increase in triclosan sorption was 1.2, approximately 4 and 3.5 times, respectively for activated carbon, kaolinite and montmorillonite when ionic strength was increased from 1x10(-3) to 5x10(-1) M. Triclosan sorption onto activated carbon decreased from 31.4 to 10.6 mg g(-1) by increasing the HA concentration to 200 mg C L(-1). However, during sorption onto kaolinite and montmorillonite, the effect of HA was very complex probably due to (i) hydrophobicity (log K(ow)=4.76) of triclosan; and (ii) complexation of HA with triclosan. Though triclosan sorption onto activated carbon is higher, the potential of kaolinite and montmorillonite in controlling the transport of triclosan in subsurface environment can still be appreciable. 2010 Elsevier B.V. All rights reserved.

  17. Magnetic activated carbon-Fe3O4 nanocomposites--synthesis and applications in the removal of acid yellow dye 17 from water.

    PubMed

    Ranjithkumar, V; Hazeen, A Nizarul; Thamilselvan, M; Vairam, S

    2014-07-01

    In this work, synthesis of activated carbon-Fe3O4 composites using activated carbon and iron benzoate/oxalate precursors by simple pyrolytic method and its utility for the removal of acid yellow dye from water are presented. Iron carboxylates held up into the pores of carbon dissociate at their decomposition temperatures form dispersed Fe3O4 nanoparticles in carbon matrix. The composites were characterized by FTIR, PXRD, SEM, TEM, EDX and magnetization measurements. The size of the nano iron oxides are in the range of 21-33 nm formed from iron benzoate precursor and 6-11 nm from iron oxalate precursor. The oxides are magnetic and their saturation magnetization in the range of 0.08-0.16 emu/g and Coercivity (H(c)) 474-600, being lower and higher than that of bare bulk Fe3O4 are due to the nano size of oxides. Composites find application in the removal of acid yellow dye 17 from the synthetic aqueous solution at pH 5. The adsorption data are found to fit well for Langmuir adsorption isotherm. Kinetics data of adsorption of dyes indicate that the adsorption follows pseudo-second order kinetic model.

  18. PROCESS OF SECURING PLUTONIUM IN NITRIC ACID SOLUTIONS IN ITS TRIVALENT OXIDATION STATE

    DOEpatents

    Thomas, J.R.

    1958-08-26

    >Various processes for the recovery of plutonium require that the plutonium be obtalned and maintained in the reduced or trivalent state in solution. Ferrous ions are commonly used as the reducing agent for this purpose, but it is difficult to maintain the plutonium in a reduced state in nitric acid solutions due to the oxidizing effects of the acid. It has been found that the addition of a stabilizing or holding reductant to such solution prevents reoxidation of the plutonium. Sulfamate ions have been found to be ideally suitable as such a stabilizer even in the presence of nitric acid.

  19. Removal of nitroimidazole antibiotics from aqueous solution by adsorption/bioadsorption on activated carbon.

    PubMed

    Rivera-Utrilla, J; Prados-Joya, G; Sánchez-Polo, M; Ferro-García, M A; Bautista-Toledo, I

    2009-10-15

    The objective of the present study was to analyse the behaviour of activated carbon with different chemical and textural properties in nitroimidazole adsorption, also assessing the combined use of microorganisms and activated carbon in the removal of these compounds from waters and the influence of the chemical nature of the solution (pH and ionic strength) on the adsorption process. Results indicate that the adsorption of nitroimidazoles is largely determined by activated carbon chemical properties. Application of the Langmuir equation to the adsorption isotherms showed an elevated adsorption capacity (X(m)=1.04-2.04 mmol/g) for all contaminants studied. Solution pH and electrolyte concentration did not have a major effect on the adsorption of these compounds on activated carbon, confirming that the principal interactions involved in the adsorption of these compounds are non-electrostatic. Nitroimidazoles are not degraded by microorganisms used in the biological stage of a wastewater treatment plant. However, the presence of microorganisms during nitroimidazole adsorption increased their adsorption on the activated carbon, although it weakened interactions between the adsorbate and carbon surface. In dynamic regime, the adsorptive capacity of activated carbon was markedly higher in surface water and groundwater than in urban wastewaters.

  20. Structure of polyacrylic acid and polymethacrylic acid solutions : a small angle neutron scattering study

    NASA Astrophysics Data System (ADS)

    Moussaid, A.; Schosseler, F.; Munch, J. P.; Candau, S. J.

    1993-04-01

    The intensity scattered from polyacrylic acid and polymethacrylic acid solutions has been measured by small angle neutron scattering experiemnts. The influence of polymer concentration, ionization degree, temperature and salt content has been investigated. Results are in qualitative agreement with a model which predicts the existence of microphases in the unstable region of the phase diagram. Quantitative comparison with the theory is performed by fitting the theoretical structure factor to the experimental data. For a narrow range of ionizaiton degrees nearly quantitative agreement with the theory is found for the polyacrylic acide system.

  1. Direct carbon-carbon coupling of furanics with acetic acid over Brønsted zeolites

    PubMed Central

    Gumidyala, Abhishek; Wang, Bin; Crossley, Steven

    2016-01-01

    Effective carbon-carbon coupling of acetic acid to form larger products while minimizing CO2 emissions is critical to achieving a step change in efficiency for the production of transportation fuels from sustainable biomass. We report the direct acylation of methylfuran with acetic acid in the presence of water, all of which can be readily produced from biomass. This direct coupling limits unwanted polymerization of furanics while producing acetyl methylfuran. Reaction kinetics and density functional theory calculations illustrate that the calculated apparent barrier for the dehydration of the acid to form surface acyl species is similar to the experimentally measured barrier, implying that this step plays a significant role in determining the net reaction rate. Water inhibits the overall rate, but selectivity to acylated products is not affected. We show that furanic species effectively stabilize the charge of the transition state, therefore lowering the overall activation barrier. These results demonstrate a promising new route to C–C bond–forming reactions for the production of higher-value products from biomass. PMID:27652345

  2. Acid Rain

    USGS Publications Warehouse

    Bricker, Owen P.; Rice, Karen C.

    1995-01-01

    Although acid rain is fading as a political issue in the United States and funds for research in this area have largely disappeared, the acidity of rain in the Eastern United States has not changed significantly over the last decade, and it continues to be a serious environmental problem. Acid deposition (commonly called acid rain) is a term applied to all forms of atmospheric deposition of acidic substances - rain, snow, fog, acidic dry particulates, aerosols, and acid-forming gases. Water in the atmosphere reacts with certain atmospheric gases to become acidic. For example, water reacts with carbon dioxide in the atmosphere to produce a solution with a pH of about 5.6. Gases that produce acids in the presence of water in the atmosphere include carbon dioxide (which converts to carbonic acid), oxides of sulfur and nitrogen (which convert to sulfuric and nitric acids}, and hydrogen chloride (which converts to hydrochloric acid). These acid-producing gases are released to the atmosphere through natural processes, such as volcanic emissions, lightning, forest fires, and decay of organic matter. Accordingly, precipitation is slightly acidic, with a pH of 5.0 to 5.7 even in undeveloped areas. In industrialized areas, most of the acid-producing gases are released to the atmosphere from burning fossil fuels. Major emitters of acid-producing gases include power plants, industrial operations, and motor vehicles. Acid-producing gases can be transported through the atmosphere for hundreds of miles before being converted to acids and deposited as acid rain. Because acids tend to build up in the atmosphere between storms, the most acidic rain falls at the beginning of a storm, and as the rain continues, the acids "wash out" of the atmosphere.

  3. Nitrogen anion-decorated cobalt tungsten disulfides solid solutions on the carbon nanofibers for water splitting.

    PubMed

    Wan, Meng; Li, Jiang; Li, Tao; Zhu, Han; Wu, Weiwei; Du, Mingliang

    2018-06-28

    A facile method to prepared nitrogen anion-decorated cobalt tungsten disulfides solid solutions retaining ultra-thin WS2-like nanosheet structures (The N-CoxW1-xS2) anchored on carbon nanofibers is developed. The synergistic effect of the WS2 nanosheets provides a secure framework for stabilizing the amorphous Co-S clusters, carbon nanofibers (CNFs) substrate and nitrogen anion-decoration significantly enhances the inherent conductivity of the catalyst, resulting in a significantly promoted hydrogen evolution reaction (HER) activity and stable performance compared to pure Co9S8 nanoparticles or ultra-thin WS2 nanosheets. The N-CoxW1-xS2 electrode demonstrates the excellent electrocatalytic performance, with current density of 10 mA cm-2 at a low overpotential of 93 mV and Tafel slope of 85 mV dec-1, as well as the long-term stability in acid electrolyte. The present investigation may provide a feasible strategy for incorporating other heteroatoms into transitional metal disulfides (TMDs) materials to design catalysts with highly active and stable performance for water splitting. © 2018 IOP Publishing Ltd.

  4. Electrochemical and surface analysis of the Fe-Cr-Ru system in non-oxidizing acid solutions

    NASA Astrophysics Data System (ADS)

    Tjong, S. C.

    1990-03-01

    The effect of ruthenium addition on the spontaneous passivation behaviour of Fe-40Cr alloy in 0.5M H 2SO 4 and 0.5M HCl acid solutions has been studied. Auger and XPS techniques were also used to investigate the surface chemistries of the spontaneously passivated film. Electrochemical measurements indicate that the Fe-40Cr-0.1Ru and Fe-40Cr-0.2Ru alloys exhibit spontaneous passivation upon exposing them in both hydrochloric and sulphuric acid solutions from 25 to 85 ° C. However, the transition time for spontaneous passivation reduces dramatically with an increase in the ruthenium content and solution temperature. Furthermore, this transition time also decreases for the investigated alloys exposed in a less aggressive sulphuric acid solution. AES results show that ruthenium and chromium are enriched in the spontaneous passive films formed on the Fe-40Cr-0.1Ru alloy in both hydrochloric and sulphuric acid solutions at 25 °C, and also in the spontaneous passive film formed on the Fe-40Cr-0.2Ru alloy in hydrochloric acid solution at 25 ° C. AES does not detect the presence of ruthenium in the spontaneous passive film formed on the Fe-40Cr-0.2Ru alloy in sulphuric acid solution. However, XPS analysis shows that ruthenium and chromium are incorporated into the spontaneous passive films formed on the Fe-40Cr-0.1Ru and Fe-40Cr-0.2Ru alloys in both hydrochloric and sulphuric acid solutions as Ru 4+ and Cr 3+ species.

  5. Acid-base behavior of the gaspeite (NiCO3(s)) surface in NaCl solutions.

    PubMed

    Villegas-Jiménez, Adrián; Mucci, Alfonso; Pokrovsky, Oleg S; Schott, Jacques

    2010-08-03

    Gaspeite is a low reactivity, rhombohedral carbonate mineral and a suitable surrogate to investigate the surface properties of other more ubiquitous carbonate minerals, such as calcite, in aqueous solutions. In this study, the acid-base properties of the gaspeite surface were investigated over a pH range of 5 to 10 in NaCl solutions (0.001, 0.01, and 0.1 M) at near ambient conditions (25 +/- 3 degrees C and 1 atm) by means of conventional acidimetric and alkalimetric titration techniques and microelectrophoresis. Over the entire experimental pH range, surface protonation and electrokinetic mobility are strongly affected by the background electrolyte, leading to a significant decrease of the pH of zero net proton charge (PZNPC) and the pH of isoelectric point (pH(iep)) at increasing NaCl concentrations. This challenges the conventional idea that carbonate mineral surfaces are chemically inert to background electrolyte ions. Multiple sets of surface complexation reactions (i.e., ionization and ion adsorption) were formulated within the framework of three electrostatic models (CCM, BSM, and TLM) and their ability to simulate proton adsorption and electrokinetic data was evaluated. A one-site, 3-pK, constant capacitance surface complexation model (SCM) reproduces the proton adsorption data at all ionic strengths and qualitatively predicts the electrokinetic behavior of gaspeite suspensions. Nevertheless, the strong ionic strength dependence exhibited by the optimized SCM parameters reveals that the influence of the background electrolyte on the surface reactivity of gaspeite is not fully accounted for by conventional electrostatic and surface complexation models and suggests that future refinements to the underlying theories are warranted.

  6. Effects of the pH and Concentration on the Stability of Standard Solutions of Proteinogenic Amino Acid Mixtures.

    PubMed

    Kato, Megumi; Yamazaki, Taichi; Kato, Hisashi; Yamanaka, Noriko; Takatsu, Akiko; Ihara, Toshihide

    2017-01-01

    To prepare metrologically traceable amino acid mixed standard solutions, it is necessary to determine the stability of each amino acid present in the mixed solutions. In the present study, we prepared amino acid mixed solutions using certified reference standards of 17 proteinogenic amino acids, and examined the stability of each of these amino acids in 0.1 N HCl. We found that the concentration of glutamic acid decreased significantly during storage. LC/MS analysis indicated that the instability of glutamic acid was due to the partial degradation of glutamic acid to pyroglutamic acid in 0.1 N HCl. Using accelerated degradation tests, we investigated several solvent compositions to improve the stability of glutamic acid in amino acid mixed solution, and determined that the change of the pH by diluting the mixed solution improved the stability of glutamic acid.

  7. INTERACTION OF AQUEOUS SOLUTIONS OF CHLORINE WITH MALIC ACID, TARTARIC ACID, AND VARIOUS FRUIT JUICES, A SOURCE OF MUTAGENS

    EPA Science Inventory

    The interactions of aqueous solutions of chlorine with some fruit acids (citric acid, DL-malic acid, and L-tartaric acid) at different pH values were studied. iethyl ether extraction followed by GC/MS analysis indicated that a number of mutagens (certain chlorinated propanones an...

  8. Acid Chlorides as Formal Carbon Dianion Linchpin Reagents in the Aluminum Chloride-Mediated Dieckmann Cyclization of Dicarboxylic Acids.

    PubMed

    Armaly, Ahlam M; Bar, Sukanta; Schindler, Corinna S

    2017-08-04

    The development of acid chlorides as formal dianion linchpin reagents that enable access to cyclic 2-alkyl- and 2-acyl-1,3-alkanediones from dicarboxylic acids is described herein. Mechanistic experiments relying on 13 C-labeling studies confirm the role of acid chlorides as carbon dianion linchpin reagents and have led to a revised reaction mechanism for the aluminum(III)-mediated Dieckmann cyclization of dicarboxylic acids with acid chlorides.

  9. Biocompatibility of a bicarbonate-buffered amino-acid-based solution for peritoneal dialysis.

    PubMed

    Bender, Thorsten O; Witowski, Janusz; Aufricht, Christoph; Endemann, Michaela; Frei, Ulrich; Passlick-Deetjen, Jutta; Jörres, Achim

    2008-09-01

    Amino-acid-based peritoneal dialysis (PD) fluids have been developed to improve the nutritional status of PD patients. As they may potentially exacerbate acidosis, an amino-acid-containing solution buffered with bicarbonate (Aminobic) has been proposed to effectively maintain acid-base balance. The aim of this study was to evaluate the mesothelial biocompatibility profile of this solution in comparison with a conventional low-glucose-based fluid. Omentum-derived human peritoneal mesothelial cells (HPMC) were preexposed to test PD solutions for up to 120 min, then allowed to recover in control medium for 24 h, and assessed for heat-shock response, viability, and basal and stimulated cytokine [interleukin (IL)-6] and prostaglandin (PGE(2)) release. Acute exposure of HPMC to conventional low-glucose-based PD solution resulted in a time-dependent increase in heat-shock protein (HSP-72) expression, impaired viability, and reduced ability to release IL-6 in response to stimulation. In contrast, in cells treated with Aminobic, the expression of HSP-72 was significantly lower, and viability and cytokine-producing capacity were preserved and did not differ from those seen in control cells. In addition, exposure to Aminobic increased basal release of IL-6 and PGE(2). These data point to a favorable biocompatibility profile of the amino-acid-based bicarbonate-buffered PD solution toward HPMC.

  10. Acidic and basic solutions dissolve protein plugs made of lithostathine complicating choledochal cyst/pancreaticobiliary maljunction.

    PubMed

    Kaneko, Kenitiro; Ono, Yasuyuki; Tainaka, Takahisa; Sumida, Wataru; Ando, Hisami

    2009-07-01

    Symptoms of choledochal cysts are caused by protein plugs made of lithostathine, which block the long common channel and increase pancreaticobiliary ductal pressure. Agents that dissolve protein plugs can provide relief from or prevent symptoms. In the present study, drugs reportedly effective for pancreatic and biliary stones were used in dissolution tests. Protein plugs were obtained from choledochal cysts during surgery in two children (5- and 6-year-old girls). Plugs approximately 2 mm in diameter were immersed in citric acid, tartaric acid, dimethadione, bromhexine, dehydrocholic acid, sodium citrate, hydrochloric acid, and sodium hydroxide solutions under observation with a digital microscope. The pH of each solution was measured using a pH meter. Plugs dissolved in citric acid (5.2 mM; pH 2.64), tartaric acid (6.7 mM; pH 2.51), dimethadione (75 mM; pH 3.70), hydrochloric acid (0.5 mM; pH 3.13), and sodium hydroxide (75 mM; pH 12.75) solutions. Plugs did not dissolve in dimethadione (7.5 mM; pH 4.31), bromhexine (0.1%; pH 4.68), dehydrocholic acid (5%; pH 7.45), and sodium citrate (75 mM; pH 7.23) solutions. Protein plugs in choledochal cysts are dissolved in acidic and basic solutions, which may eliminate longitudinal electrostatic interactions of the lithostathine protofibrils.

  11. A new approach to study cadmium complexes with oxalic acid in soil solution.

    PubMed

    Dytrtová, Jana Jaklová; Jakl, Michal; Sestáková, Ivana; Zins, Emilie-Laure; Schröder, Detlef; Navrátil, Tomáš

    2011-05-05

    This study presents a new analytical approach for the determination of heavy metals complexed to low-molecular-weight-organic acids in soil solutions, which combines the sensitivity of differential pulse anodic stripping voltammetry (DPASV) with the molecular insight gained by electrospray ionization mass spectrometry (ESI-MS). The combination of these analytical methods allows the investigation of such complexes in complex matrixes. On the voltammograms of the soil solutions, in addition to the expected complexes of oxalic acid with cadmium and lead, respectively, also peaks belonging to mixed complexes of cadmium, lead, and oxalic acid (OAH(2)) were observed. In order to verify the possible formation of complexes with OAH(2), aqueous solutions of OAH(2) with traces of Cd(II) were investigated as model systems. Signals corresponding to several distinct molecular complexes between cadmium and oxalic acid were detected in the model solutions using negative-ion ESI-MS, which follow the general formula [Cd(n)(X,Y)((2n+1))](-), where n is the number of cadmium atoms, X=Cl(-), and Y=OAH(-). Some of these complexes were also identified in the ESI mass spectra taken from the soil solutions. Copyright © 2011 Elsevier B.V. All rights reserved.

  12. Fermentation process for the production of organic acids

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hermann, Theron; Reinhardt, James; Yu, Xiaohui

    This invention relates to improvements in the fermentation process used in the production of organic acids from biological feedstock using bacterial catalysts. The improvements in the fermentation process involve providing a fermentation medium comprising an appropriate form of inorganic carbon, an appropriate amount of aeration and a biocatalyst with an enhanced ability to uptake and assimilate the inorganic carbon into the organic acids. This invention also provides, as a part of an integrated fermentation facility, a novel process for producing a solid source of inorganic carbon by sequestering carbon released from the fermentation in an alkali solution.

  13. Chemical and biological consequences of using carbon dioxide versus acid additions in ocean acidification experiments

    USGS Publications Warehouse

    Yates, Kimberly K.; DuFore, Christopher M.; Robbins, Lisa L.

    2013-01-01

    Use of different approaches for manipulating seawater chemistry during ocean acidification experiments has confounded comparison of results from various experimental studies. Some of these discrepancies have been attributed to whether addition of acid (such as hydrochloric acid, HCl) or carbon dioxide (CO2) gas has been used to adjust carbonate system parameters. Experimental simulations of carbonate system parameter scenarios for the years 1766, 2007, and 2100 were performed using the carbonate speciation program CO2SYS to demonstrate the variation in seawater chemistry that can result from use of these approaches. Results showed that carbonate system parameters were 3 percent and 8 percent lower than target values in closed-system acid additions, and 1 percent and 5 percent higher in closed-system CO2 additions for the 2007 and 2100 simulations, respectively. Open-system simulations showed that carbonate system parameters can deviate by up to 52 percent to 70 percent from target values in both acid addition and CO2 addition experiments. Results from simulations for the year 2100 were applied to empirically derived equations that relate biogenic calcification to carbonate system parameters for calcifying marine organisms including coccolithophores, corals, and foraminifera. Calculated calcification rates for coccolithophores, corals, and foraminifera differed from rates at target conditions by 0.5 percent to 2.5 percent in closed-system CO2 gas additions, from 0.8 percent to 15 percent in the closed-system acid additions, from 4.8 percent to 94 percent in open-system acid additions, and from 7 percent to 142 percent in open-system CO2 additions.

  14. Formation of molecular complexes of salicylic acid, acetylsalicylic acid, and methyl salicylate in a mixture of supercritical carbon dioxide with a polar cosolvent

    NASA Astrophysics Data System (ADS)

    Petrenko, V. E.; Antipova, M. L.; Gurina, D. L.; Odintsova, E. G.

    2015-08-01

    The solvate structures formed by salicylic acid, acetylsalicylic acid, and methyl salicylate in supercritical (SC) carbon dioxide with a polar cosolvent (methanol, 0.03 mole fractions) at a density of 0.7 g/cm3 and a temperature of 318 K were studied by the molecular dynamics method. Salicylic and acetylsalicylic acids were found to form highly stable hydrogen-bonded complexes with methanol via the hydrogen atom of the carboxyl group. For methyl salicylate in which the carboxyl hydrogen is substituted by a methyl radical, the formation of stable hydrogen bonds with methanol was not revealed. The contribution of other functional groups of the solute to the interactions with the cosolvent was much smaller. An analysis of correlations between the obtained data and the literature data on the cosolvent effect on the solubility of the compounds in SC CO2 showed that the dissolving ability of SC CO2 with respect to a polar organic substance in the presence of a cosolvent increased only when stable hydrogen-bonded complexes are formed between this substance and the cosolvent.

  15. Novel Acid Catalysts from Waste-Tire-Derived Carbon: Application in Waste-to-Biofuel Conversion

    DOE PAGES

    Hood, Zachary D.; Adhikari, Shiba P.; Li, Yunchao; ...

    2017-06-21

    Many inexpensive biofuel feedstocks, including those containing free fatty acids (FFAs) in high concentrations, are typically disposed of as waste due to our inability to efficiently convert them into usable biofuels. Here we demonstrate that carbon derived from waste tires could be functionalized with sulfonic acid (-SO 3H) to effectively catalyze the esterification of oleic acid or a mixture of fatty acids to usable biofuels. Waste tires were converted to hard carbon, then functionalized with catalytically active -SO 3H groups on the surface through an environmentally benign process that involved the sequential treatment with L-cysteine, dithiothreitol, and H 2O 2.more » In conclusion, when benchmarked against the same waste-tire derived carbon material treated with concentrated sulfuric acid at 150 °C, similar catalytic activity was observed. Both catalysts could also effectively convert oleic acid or a mixture of fatty acids and soybean oil to usable biofuels at 65 °C and 1 atm without leaching of the catalytic sites.« less

  16. Investigation on solubility of hydroxy dibasic acids in alkanolamine solutions

    NASA Astrophysics Data System (ADS)

    Du, M.

    2017-12-01

    Solubilities of three hydroxy dibasic (adipic, suberic, and sebacic) acids in alkanolamine solutions were measured within the 30-90℃ temperature range. It is found that solubility of these acids sharply grows with temperature and concentration of alkanolamine solvent. In addition, the study substantiates the adjustment of pH to optimize the CO2 absorption and desorption processes. The precipitation of added acids from alkanolamine solvents by cooling is found to be quite problematic, which makes the recovery of residual acids from lean alkanolamine solvents non-feasible and requires the application of alternative methods.

  17. Photoinduced crystallization of calcium carbonate from a homogeneous precursor solution in the presence of partially hydrolyzed poly(vinyl alcohol)

    NASA Astrophysics Data System (ADS)

    Nishio, Takashi; Naka, Kensuke

    2015-04-01

    Photoinduced crystallization of calcium carbonate (CaCO3) was demonstrated by the photodecarboxylation of ketoprofen (KP, 2-(3-benzoylphenyl)propionic acid) under alkaline conditions (pH 10). In this method, a homogeneous solution comprising KP, calcium chloride, ammonia, and partially hydrolyzed poly(vinyl alcohol) (PVAPS, degree of saponification: 86.5-89.0 mol %) was used as the precursor solution and was exposed to ultraviolet (UV) irradiation for different time periods. Thermogravimetric analysis of the obtained xerogels showed that increasing the UV irradiation time increased the amount of CaCO3 formed and the complete conversion of calcium ions to calcite was achieved after 50 min of UV irradiation. Furthermore, solid phase analyses suggested that nanometer-to-micron-sized calcite crystals were formed and dispersed in the obtained PVAPS matrix.

  18. Modified Carbon Nanotube Paste Electrode for Voltammetric Determination of Carbidopa, Folic Acid, and Tryptophan

    PubMed Central

    Esfandiari Baghbamidi, Sakineh; Beitollahi, Hadi; Karimi-Maleh, Hassan; Soltani-Nejad, Somayeh; Soltani-Nejad, Vahhab; Roodsaz, Sara

    2012-01-01

    A simple and convenient method is described for voltammetric determination of carbidopa (CD), based on its electrochemical oxidation at a modified multiwall carbon nanotube paste electrode. Under optimized conditions, the proposed method exhibited acceptable analytical performances in terms of linearity (over the concentration range from 0.1 to 700.0 μM), detection limit (65.0 nM), and reproducibility (RSD = 2.5%) for a solution containing CD. Also, square wave voltammetry (SWV) was used for simultaneous determination of CD, folic acid (FA), and tryptophan (TRP) at the modified electrode. To further validate its possible application, the method was used for the quantification of CD, FA, and TRP in urine samples. PMID:22666634

  19. Green synthesis of carbon dots from pork and application as nanosensors for uric acid detection

    NASA Astrophysics Data System (ADS)

    Zhao, Chunxi; Jiao, Yang; Hu, Feng; Yang, Yaling

    2018-02-01

    In this work, a green, simple, economical method was developed in the synthesis of fluorescent carbon dots using pork as carbon source. The as-prepared carbon dots exhibit exceptional advantages including high fluorescent quantum yield (17.3%) and satisfactory chemical stability. The fluorescence of carbon dots based nanosensor can be selectively and efficiently quenched by uric acid. This phenomenon was used to develop a fluorescent method for facile detection of uric acid within a linear range of 0.1-100 μM and 100-500 μM, with a detection limit of 0.05 μM (S/N = 3). Finally, the proposed method was successfully applied in the determination of uric acid in human serum and urine samples with satisfactory recoveries, which suggested that the new nanosensors have great prospect toward the detection of uric acid in human fluids.

  20. 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.

  1. Speciation of platinum(IV) in nitric acid solutions.

    PubMed

    Vasilchenko, Danila; Tkachev, Sergey; Baidina, Iraida; Korenev, Sergey

    2013-09-16

    The speciation of platinum(IV) ions in nitric acid (6-15.8 M) solutions of H2[Pt(OH)6] has been studied by (195)Pt NMR and Raman spectroscopy. Series of aqua-hydroxo-nitrato complexes [Pt(L)(x)(NO3)(6-x)] (L = H2O or OH(-); x = 0, ..., 6) were found to exist in such solutions. The pair additivity model of chemical shifts and statistical theory were used to assign signals in NMR spectra to particular [Pt(L)(x)(NO3)(6-x)] species. Mononuclear hexanitratoplatinates(IV) have been isolated in solid state in substantial yield as pyridinium salt (PyH)2[Pt(NO3)6] and characterized by single-crystal X-ray diffraction. Aging of the platinum nitric acid solutions for more than 5-6 h results in oligomerization of [Pt(L)(x)(NO3)(6-x)] species and the formation of oligonuclear aqua-hydroxo-nitrato complexes with OH(-) and NO3(-) bridging ligands. Oligomeric platinum(IV) complexes with two and four nuclei were unambiguously detected by NMR on (195)Pt -enriched samples. Oligomers with even higher nuclearity were also detected. Dimeric anions [Pt2(μ-OH)2(NO3)8](2-) have been isolated as single crystals of tetramethylammonium salt and characterized by X-ray diffraction.

  2. Intricate Conformational Tunneling in Carbonic Acid Monomethyl Ester.

    PubMed

    Linden, Michael M; Wagner, J Philipp; Bernhardt, Bastian; Bartlett, Marcus A; Allen, Wesley D; Schreiner, Peter R

    2018-04-05

    Disentangling internal and external effects is a key requirement for understanding conformational tunneling processes. Here we report the s- trans/ s- cis tunneling rotamerization of carbonic acid monomethyl ester (1) under matrix isolation conditions and make comparisons to its parent carbonic acid (3). The observed tunneling rate of 1 is temperature-independent in the 3-20 K range and accelerates when using argon instead of neon as the matrix material. The methyl group increases the effective half life (τ eff ) of the energetically disfavored s- trans-conformer from 3-5 h for 3 to 11-13 h for 1. Methyl group deuteration slows the rotamerization further (τ eff ≈ 35 h). CCSD(T)/cc-pVQZ//MP2/aug-cc-pVTZ computations of the tunneling probability suggest that the rate should be almost unaffected by methyl substitution or its deuteration. Thus the observed relative rates are puzzling, and they disagree with previous explanations involving fast vibrational relaxation after the tunneling event facilitated by the alkyl rotor.

  3. The dissolution of quartz in dilute aqueous solutions of organic acids at 25°C

    USGS Publications Warehouse

    Bennett, P.C.; Melcer, M.E.; Siegel, D.I.; Hassett, J.P.

    1988-01-01

    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.

  4. On the neutralization of acid rock drainage by carbonate and silicate minerals

    NASA Astrophysics Data System (ADS)

    Sherlock, E. J.; Lawrence, R. W.; Poulin, R.

    1995-02-01

    The net result of acid-generating and-neutralizing reactions within mining wastes is termed acid rock drainage (ARD). The oxidation of sulfide minerals is the major contributor to acid generation. Dissolution and alteration of various minerals can contribute to the neutralization of acid. Definitions of alkalinity, acidity, and buffer capacity are reviewed, and a detailed discussion of the dissolution and neutralizing capacity of carbonate and silicate minerals related to equilibium conditions, dissolution mechanism, and kinetics is provided. Factors that determine neutralization rate by carbonate and silicate minerals include: pH, PCO 2, equilibrium conditions, temperature, mineral composition and structure, redox conditions, and the presence of “foreign” ions. Similar factors affect sulfide oxidation. Comparison of rates shows sulfides react fastest, followed by carbonates and silicates. The differences in the reaction mechanisms and kinetics of neutralization have important implications in the prediction, control, and regulation of ARD. Current static and kinetic prediction methods upon which mine permitting, ARD control, and mine closure plans are based do not consider sample mineralogy or the kinetics of the acid-generating and-neutralizing reactions. Erroneous test interpretations and predictions can result. The importance of considering mineralogy for site-specific interpretation is highlighted. Uncertainty in prediction leads to difficulties for the mine operator in developing satisfactory and cost-effective control and remediation measures. Thus, the application of regulations and guidelines for waste management planning need to beflexible.

  5. 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

  6. 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. © 2013.

  7. Removal of Heavy Metal Ions with Acid Activated Carbons Derived from Oil Palm and Coconut Shells

    PubMed Central

    Rahman, Mokhlesur M.; Adil, Mohd; Yusof, Alias M.; Kamaruzzaman, Yunus B.; Ansary, Rezaul H.

    2014-01-01

    In this work, batch adsorption experiments were carried out to investigate the suitability of prepared acid activated carbons in removing heavy metal ions such as nickel(II), lead(II) and chromium(VI). Acid activated carbons were obtained from oil palm and coconut shells using phosphoric acid under similar activation process while the differences lie either in impregnation condition or in both pretreatment and impregnation conditions. Prepared activated carbons were modified by dispersing hydrated iron oxide. The adsorption equilibrium data for nickel(II) and lead(II) were obtained from adsorption by the prepared and commercial activated carbons. Langmuir and Freundlich models fit the data well. Prepared activated carbons showed higher adsorption capacity for nickel(II) and lead(II). The removal of chromium(VI) was studied by the prepared acid activated, modified and commercial activated carbons at different pH. The isotherms studies reveal that the prepared activated carbon performs better in low concentration region while the commercial ones in the high concentration region. Thus, a complete adsorption is expected in low concentration by the prepared activated carbon. The kinetics data for Ni(II), Pb(II) and Cr(VI) by the best selected activated carbon fitted very well to the pseudo-second-order kinetic model. PMID:28788640

  8. 40 CFR 721.10369 - Carbonic acid, diphenyl ester, polymer with diphenyl P-methylphosphonate and 4,4′-(1...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Carbonic acid, diphenyl ester, polymer... Carbonic acid, diphenyl ester, polymer with diphenyl P-methylphosphonate and 4,4′-(1-methylethylidene) bis... identified as carbonic acid, diphenyl ester, polymer with diphenyl P-methylphosphonate and 4,4′-(1...

  9. DYNAMIC CONDUCTIVITY MEASUREMENTS IN HUMIC AND FULVIC ACID SOLUTIONS. (R828158)

    EPA Science Inventory

    Conductivity changes of dilute aqueous humic and fulvic acids solutions were monitored after the addition of small quantities of Cu, Cd, Pb, and Zn. The solutions were stirred at a constant and reproducible rate, and measurements proceeded until stable conductivities were atta...

  10. An investigation into the surface heterogeneity of nitric acid oxidized carbon fiber

    NASA Astrophysics Data System (ADS)

    Woodhead, Andrea L.; de Souza, Mandy L.; Church, Jeffrey S.

    2017-04-01

    The carbon fiber surface plays a critical role in the performance of carbon fiber composite materials and, thus it is important to have a thorough understanding of the fiber surface. A series of nitric acid treated intermediate modulus carbon fibers with increasing treatment level was prepared and characterized using a range of surface sensitive techniques including Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy. The results, which were found to be consistent with increasing treatment levels, were compared to the literature. Raman spectral mapping has been used to investigate the heterogeneity of the carbon fiber surface after nitric acid oxidation. The mapping enabled the effects of surface treatment on carbon fiber to be investigated at a spatial resolution unattainable by XPS and provided chemical structure information not provided by SEM or AFM. The highest level of treatment resulted in the most heterogeneous surface. Raman mapping, while time consuming, can provide valuable information which can lead to an enhanced understanding of the heterogeneity of the carbon fiber surface.

  11. 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.

  12. Determination of kojic acid based on the interface enhancement effects of carbon nanotube/alizarin red S modified electrode.

    PubMed

    Liu, Jieshu; Zhou, Dazhai; Liu, Xiaopeng; Wu, Kangbing; Wan, Chidan

    2009-04-01

    Based on non-covalent interactions such as pi-pi stacking, van der Waals interactions and strong adsorption, alizarin red S (ARS) interacts with multi-walled carbon nanotubes (MWNT), improving the solubility of MWNT in water and resulting in a stable MWNT/ARS solution. By successive cyclic sweeps between 0.0 and 2.2V in the MWNT/ARS solution, a MWNT/ARS composite film was fabricated on an electrode surface. The electrochemical behaviors of kojic acid at the bare electrode, the ARS film-modified electrode and the MWNT/ARS film-modified electrode were investigated. It was found that the oxidation signal of kojic acid significantly increased at the MWNT/ARS film-modified electrode, which was attributed to the unique properties of MWNT such as large surface area, strong adsorptive ability and subtle electronic character. The effects of pH and cyclic number of electropolymerization were examined. A rapid, sensitive and simple electrochemical method was then developed for the determination of kojic acid. This method exhibits good linearity over the range from 4.0 x 10(-7) to 6.0 x 10(-5)mol L(-1), and the limit of detection is as low as 1.0 x 10(-7)mol L(-1). In order to validate feasibility, the MWNT/ARS film-modified electrode was used for quantitative analysis of kojic acid in food samples.

  13. [Effects of choledochal perfusion with biliary acid solutions on activity of the sphincter of Oddi (author's transl)].

    PubMed

    Bevilacqua, R G; Margarido, N F; Soares, L A; Mansur, R; Koch, V; Gonçalves, E L

    1979-06-01

    The changes of sphincter of Oddi's resistance, induced by choledochal perfusion of conjugated (taurocolic) and non-conjugated (colic) biliary acid solutions, in anesthetized dogs, were studied. The perfusions were made at a constant flow and intracholedochal pressures were registered. The mean number of contractions per minute, the mean maximal pressures and the mean minimal pressures in each study periods were analysed. The choledochal perfusion with the biliary acids solutions induced a slight but significative increase in sphincteric resistance. After 15 minutes, the perfusion with colic acid solution induced maximal pressures significantly more elevated than the ones observed with taurocolic acid solution. The non-conjugated solution induced a pressure tracing significantly distinct from the tracing observed with the conjugated acid solution. No changes in resistance were observed with a 2% NaCl solution. This implies that the observed changes in resistance were not related to osmotic stimulation of the sphincter of Oddi.

  14. Photosensitized Reduction of Carbon Dioxide in Solution Using Noble-Metal Clusters for Electron Transfer

    NASA Astrophysics Data System (ADS)

    Toshima, Naoki; Yamaji, Yumi; Teranishi, Toshiharu; Yonezawa, Tetsu

    1995-03-01

    Carbon dioxide was reduced to methane by visible-light irradiation of a solution composed of tris(bipyridine)ruthenium(III) as photosensitizer, ethylenediaminetetraacetic acid disodium salt as sacrificial reagent, methyl viologen as electron relay, and a colloidal dispersion of polymer-protected noble-metal clusters, prepared by alcohol-reduction, as catalyst. Among the noble-metal clusters examined, Pt clusters showed the highest activity for the formation of methane as well as hydrogen. In order to improve the activity, oxidized clusters and bimetallic clusters were also applied. For example, the CH4 yield in 3-h irradiation increased from 51 x 10-3 μmol with unoxidized Pt clusters to 72 x 10-3 μmol with partially oxidized ones. In the case of Pt/Ru bimetalic systems, the improvement of the catalytic activity by air treatment was much greater than in case of monometallic clusters.

  15. Comparative study of buffered 50% glycolic acid (pH 3.0) + 0.5% salicylic acid solution vs Jessner's solution in patients with acne vulgaris.

    PubMed

    In Jae, Jeong; Dong Ju, Hyun; Dong Hyun, Kim; Yoon, Moon Soo; Lee, Hee Jung

    2017-11-21

    Superficial chemical peels are frequently used in acne vulgaris treatment. Although glycolic acid (GA) has been widely used in clinical practice, its pH ranges from 0.08-2.75 and thus should be neutralized after application to avoid burns. To evaluate treatment efficacy and safety of chemical peeling using buffered 50% GA (pH 3.0) + 0.5% salicylic acid (SA) solution that does not need to be neutralized in the treatment of acne vulgaris compared to the conventional peeling using Jessner's solution. We performed a prospective, randomized, evaluator-blind, split-face clinical trial. Twenty patients were randomized by assigning one side of each patient's face to receive a 50% GA (pH 3.0) + 0.5% SA peel (GA side) and the other side to receive the Jessner's solution (Jessner's solution side). All patients underwent 2 sessions of treatment spaced 2 weeks apart. Lesion count, acne severity, subjective efficacy assessment, and side effects were evaluated. The total lesion count was significantly reduced for the GA and Jessner's solution sides (P < .001). However, there was no significant difference in the total lesion count, acne severity, or subjective efficacy assessment between the 2 sides (P > .05). The GA side had fewer side effects than the Jessner's solution side. The results of this study suggest that chemical peeling using the 50% GA (pH 3.0) + 0.5% SA solution can be as effective and convenient as the conventional peeling using Jessner's solution in the treatment of acne vulgaris and may show fewer adverse events than the conventional peeling. © 2017 Wiley Periodicals, Inc.

  16. Apparatus for extracting and sequestering carbon dioxide

    DOEpatents

    Rau, Gregory H [Castro Valley, CA; Caldeira, Kenneth G [Livermore, CA

    2010-02-02

    An apparatus and method associated therewith to extract and sequester carbon dioxide (CO.sub.2) from a stream or volume of gas wherein said apparatus hydrates CO.sub.2 and reacts the resulting carbonic acid with carbonate. Suitable carbonates include, but are not limited to, carbonates of alkali metals and alkaline earth metals, preferably carbonates of calcium and magnesium. Waste products are metal cations and bicarbonate in solution or dehydrated metal salts, which when disposed of in a large body of water provide an effective way of sequestering CO.sub.2 from a gaseous environment.

  17. Method for extracting and sequestering carbon dioxide

    DOEpatents

    Rau, Gregory H.; Caldeira, Kenneth G.

    2005-05-10

    A method and apparatus to extract and sequester carbon dioxide (CO.sub.2) from a stream or volume of gas wherein said method and apparatus hydrates CO.sub.2, and reacts the resulting carbonic acid with carbonate. Suitable carbonates include, but are not limited to, carbonates of alkali metals and alkaline earth metals, preferably carbonates of calcium and magnesium. Waste products are metal cations and bicarbonate in solution or dehydrated metal salts, which when disposed of in a large body of water provide an effective way of sequestering CO.sub.2 from a gaseous environment.

  18. Carbon Nanotube Dispersion in Solvents and Polymer Solutions: Mechanisms, Assembly, and Preferences.

    PubMed

    Pramanik, Chandrani; Gissinger, Jacob R; Kumar, Satish; Heinz, Hendrik

    2017-12-26

    Debundling and dispersion of carbon nanotubes (CNTs) in polymer solutions play a major role in the preparation of carbon nanofibers due to early effects on interfacial ordering and mechanical properties. A roadblock toward ultrastrong fibers is the difficulty to achieve homogeneous dispersions of CNTs in polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) precursor solutions in solvents such as dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF). In this contribution, molecular dynamics simulations with accurate interatomic potentials for graphitic materials that include virtual π electrons are reported to analyze the interaction of pristine single wall CNTs with the solvents and polymer solutions at 25 °C. The results explain the barriers toward dispersion of SWCNTs and quantify CNT-solvent, polymer-solvent, as well as CNT-polymer interactions in atomic detail. Debundling of CNTs is overall endothermic and unfavorable with dispersion energies of +20 to +30 mJ/m 2 in the pure solvents, + 20 to +40 mJ/m 2 in PAN solutions, and +20 to +60 mJ/m 2 in PMMA solutions. Differences arise due to molecular geometry, polar, van der Waals, and CH-π interactions. Among the pure solvents, DMF restricts CNT dispersion less due to the planar geometry and stronger van der Waals interactions. PAN and PMMA interact favorably with the pure solvents with dissolution energies of -0.7 to -1.1 kcal per mole monomer and -1.5 to -2.2 kcal per mole monomer, respectively. Adsorption of PMMA onto CNTs is stronger than that of PAN in all solvents as the molecular geometry enables more van der Waals contacts between alkyl groups and the CNT surface. Polar side groups in both polymers prefer interactions with the polar solvents. Higher polymer concentrations in solution lead to polymer aggregation via alkyl groups and reduce adsorption onto CNTs. PAN and PMMA solutions in DMSO and dilute solutions in DMF support CNT dispersion more than other

  19. Nonclinical safety evaluation of boric acid and a novel borate-buffered contact lens multi-purpose solution, Biotrue™ multi-purpose solution.

    PubMed

    Lehmann, David M; Cavet, Megan E; Richardson, Mary E

    2010-12-01

    Multipurpose solutions (MPS) often contain low concentrations of boric acid as a buffering agent. Limited published literature has suggested that boric acid and borate-buffered MPS may alter the corneal epithelium; an effect attributed to cytotoxicity induced by boric acid. However, this claim has not been substantiated. We investigated the effect of treating cells with relevant concentrations of boric acid using two cytotoxicity assays, and also assessed the impact of boric acid on corneal epithelial barrier function by measuring TEER and immunostaining for tight junction protein ZO-1 in human corneal epithelial cells. Boric acid was also assessed in an in vivo ocular model when administered for 28 days. Additionally, we evaluated Biotrue multi-purpose solution, a novel borate-buffered MPS, alone and with contact lenses for ocular compatibility in vitro and in vivo. Boric acid passed both cytotoxicity assays and did not alter ZO-1 distribution or corneal TEER. Furthermore, boric acid was well-tolerated on-eye following repeated administration in a rabbit model. Finally, Biotrue multi-purpose solution demonstrated good ocular biocompatibility both in vitro and in vivo. This MPS was not cytotoxic and was compatible with the eye when administered alone and when evaluated with contact lenses. We demonstrate that boric acid and a borate-buffered MPS is compatible with the ocular environment. Our findings provide evidence that ocular effects reported for some borate-buffered MPS may be incorrectly attributed to boric acid and are more likely a function of the unique combination of ingredients in the MPS formulation tested. Copyright © 2010 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  20. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Interaction of Ethyl Alcohol Vapor with Sulfuric Acid Solutions

    NASA Technical Reports Server (NTRS)

    Leu, Ming-Taun

    2006-01-01

    We investigated the uptake of ethyl alcohol (ethanol) vapor by sulfuric acid solutions over the range approx.40 to approx.80 wt % H2SO4 and temperatures of 193-273 K. Laboratory studies used a fast flow-tube reactor coupled to an electron-impact ionization mass spectrometer for detection of ethanol and reaction products. The uptake coefficients ((gamma)) were measured and found to vary from 0.019 to 0.072, depending upon the acid composition and temperature. At concentrations greater than approx.70 wt % and in dilute solutions colder than 220 K, the values approached approx.0.07. We also determined the effective solubility constant of ethanol in approx.40 wt % H2SO4 in the temperature range 203-223 K. The potential implications to the budget of ethanol in the global troposphere are briefly discussed.

  2. Trapping proton transfer intermediates in the disordered hydrogen-bonded network of cryogenic hydrofluoric acid solutions.

    PubMed

    Ayotte, Patrick; Plessis, Sylvain; Marchand, Patrick

    2008-08-28

    A molecular-level description of the structural and dynamical aspects that are responsible for the weak acid behaviour of dilute hydrofluoric acid solutions and their unusual increased acidity at near equimolar concentrations continues to elude us. We address this problem by reporting reflection-absorption infrared spectra (RAIRS) of cryogenic HF-H(2)O binary mixtures at various compositions prepared as nanoscopic films using molecular beam techniques. Optical constants for these cryogenic solutions [n(omega) and k(omega)] are obtained by iteratively solving Fresnel equations for stratified media. Modeling of the experimental RAIRS spectra allow for a quantitative interpretation of the complex interplay between multiple reflections, optical interference and absorption effects. The evolution of the strong absorption features in the intermediate 1000-3000 cm(-1) range with increasing HF concentration reveals the presence of various ionic dissociation intermediates that are trapped in the disordered H-bonded network of cryogenic hydrofluoric acid solutions. Our findings are discussed in light of the conventional interpretation of why hydrofluoric acid is a weak acid revealing molecular-level details of the mechanism for HF ionization that may be relevant to analogous elementary processes involved in the ionization of weak acids in aqueous solutions.

  3. Influence of D-Penicillamine on the Viscosity of Hyaluronic Acid Solutions

    NASA Astrophysics Data System (ADS)

    Liang, Jing; Krause, Wendy E.; Colby, Ralph H.

    2006-03-01

    Polyelectrolyte hyaluronic acid (HA, hyaluronan) is an important component in synovial fluid. Its presence results in highly viscoelastic solutions with excellent lubricating and shock-absorbing properties. In comparison to healthy synovial fluid, diseased fluid has a reduced viscosity. In osteoarthritis this reduction in viscosity results from a decline in both the molecular weight and concentration of hyaluronic acid HA. Initial results indicate that D-penicillamine affects the rheology of bovine synovial fluid, a model synovial fluid solution, and its components, including HA. In order to understand how D-penicillamine modifies the viscosity of these solutions, the rheological properties of sodium hyaluronate (NaHA) in phosphate-buffered saline (PBS) with D-penicillamine were studied as function of time, D-penicillamine concentration (0 -- 0.01 M), and storage conditions. Penicillamine has a complex, time dependent effect on the viscosity of NaHA solutions---reducing the zero shear rate viscosity of a 3 mg/mL NaHA in PBS by ca. 40% after 44 days.

  4. One-Pot synthesis of phosphorylated mesoporous carbon heterogeneous catalysts with tailored surface acidity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fulvio, Pasquale F; Mahurin, Shannon Mark; Mayes, Richard T

    2012-01-01

    Soft-templated phosphorylated mesoporous carbons with homogeneous distributions of phosphate groups were prepared by a 'one-pot' synthesis method using mixtures of phosphoric acid with hydrochloric, or nitric acids in the presence of Pluronic F127 triblock copolymer. Adjusting the various ratios of phosphoric acid used in these mixtures resulted in carbons with distinct adsorption, structural and surface acidity properties. The pore size distributions (PSDs) from nitrogen adsorption at -196 C showed that mesoporous carbons exhibit specific surface areas as high as 551 m{sup 2}/g and mesopores as large as 13 nm. Both structural ordering of the mesopores and the final phosphate contentsmore » were strongly dependent on the ratios of H{sub 3}PO{sub 4} in the synthesis gels, as shown by transmission electron microscopy (TEM), X-ray photoelectron (XPS) and energy dispersive X-ray spectroscopy (EDS). The number of surface acid sites determined from temperature programmed desorption of ammonia (NH{sub 3}-TPD) were in the range of 0.3-1.5 mmol/g while the active surface areas are estimated to comprise 5-54% of the total surface areas. Finally, the conversion temperatures for the isopropanol dehydration were lowered by as much as 100 C by transitioning from the least acidic to the most acidic catalysts surface.« less

  5. Isotherm-Based Thermodynamic Models for Solute Activities of Organic Acids with Consideration of Partial Dissociation.

    PubMed

    Nandy, Lucy; Ohm, Peter B; Dutcher, Cari S

    2016-06-23

    Organic acids make up a significant fraction of the organic mass in atmospheric aerosol particles. The calculation of gas-liquid-solid equilibrium partitioning of the organic acid is therefore critical for accurate determination of atmospheric aerosol physicochemical properties and processes such as new particle formation and activation to cloud condensation nuclei. Previously, an adsorption isotherm-based statistical thermodynamic model was developed for capturing solute concentration-activity relationships for multicomponent aqueous solutions over the entire concentration range (Dutcher et al. J. Phys. Chem. C/A 2011, 2012, 2013), with model parameters for energies of adsorption successfully related to dipole-dipole electrostatic forces in solute-solvent and solvent-solvent interactions for both electrolytes and organics (Ohm et al. J. Phys. Chem. A 2015). However, careful attention is needed for weakly dissociating semivolatile organic acids. Dicarboxylic acids, such as malonic acid and glutaric acid are treated here as a mixture of nondissociated organic solute (HA) and dissociated solute (H(+) + A(-)). It was found that the apparent dissociation was greater than that predicted by known dissociation constants alone, emphasizing the effect of dissociation on osmotic and activity coefficient predictions. To avoid additional parametrization from the mixture approach, an expression was used to relate the Debye-Hückel hard-core collision diameter to the adjustable solute-solvent intermolecular distance. An improved reference state treatment for electrolyte-organic aqueous mixtures, such as that observed here with partial dissociation, has also been proposed. This work results in predictive correlations for estimation of organic acid and water activities for which there is little or no activity data.

  6. Comparison of the impacts of acid and nitrogen additions on carbon fluxes in European conifer and broadleaf forests.

    PubMed

    Oulehle, Filip; Tahovská, Karolina; Chuman, Tomáš; Evans, Chris D; Hruška, Jakub; Růžek, Michal; Bárta, Jiří

    2018-07-01

    Increased reactive nitrogen (N) loadings to terrestrial ecosystems are believed to have positive effects on ecosystem carbon (C) sequestration. Global "hot spots" of N deposition are often associated with currently or formerly high deposition of sulphur (S); C fluxes in these regions might therefore not be responding solely to N loading, and could be undergoing transient change as S inputs change. In a four-year, two-forest stand (mature Norway spruce and European beech) replicated field experiment involving acidity manipulation (sulphuric acid addition), N addition (NH 4 NO 3 ) and combined treatments, we tested the extent to which altered soil solution acidity or/and soil N availability affected the concentration of soil dissolved organic carbon (DOC), soil respiration (Rs), microbial community characteristics (respiration, biomass, fungi and bacteria abundances) and enzyme activity. We demonstrated a large and consistent suppression of soil water DOC concentration driven by chemical changes associated with increased hydrogen ion concentrations under acid treatments, independent of forest type. Soil respiration was suppressed by sulphuric acid addition in the spruce forest, accompanied by reduced microbial biomass, increased fungal:bacterial ratios and increased C to N enzyme ratios. We did not observe equivalent effects of sulphuric acid treatments on Rs in the beech forest, where microbial activity appeared to be more tightly linked to N acquisition. The only changes in C cycling following N addition were increased C to N enzyme ratios, with no impact on C fluxes (either Rs or DOC). We conclude that C accumulation previously attributed solely to N deposition could be partly attributable to their simultaneous acidification. Copyright © 2018 Elsevier Ltd. All rights reserved.

  7. Matrix isolation studies of carbonic acid--the vapor phase above the β-polymorph.

    PubMed

    Bernard, Jürgen; Huber, Roland G; Liedl, Klaus R; Grothe, Hinrich; Loerting, Thomas

    2013-05-22

    Twenty years ago two different polymorphs of carbonic acid, α- and β-H2CO3, were isolated as thin, crystalline films. They were characterized by infrared and, of late, by Raman spectroscopy. Determination of the crystal structure of these two polymorphs, using cryopowder and thin film X-ray diffraction techniques, has failed so far. Recently, we succeeded in sublimating α-H2CO3 and trapping the vapor phase in a noble gas matrix, which was analyzed by infrared spectroscopy. In the same way we have now investigated the β-polymorph. Unlike α-H2CO3, β-H2CO3 was regarded to decompose upon sublimation. Still, we have succeeded in isolation of undecomposed carbonic acid in the matrix and recondensation after removal of the matrix here. This possibility of sublimation and recondensation cycles of β-H2CO3 adds a new aspect to the chemistry of carbonic acid in astrophysical environments, especially because there is a direct way of β-H2CO3 formation in space, but none for α-H2CO3. Assignments of the FTIR spectra of the isolated molecules unambiguously reveal two different carbonic acid monomer conformers (C(2v) and C(s)). In contrast to the earlier study on α-H2CO3, we do not find evidence for centrosymmetric (C(2h)) carbonic acid dimers here. This suggests that two monomers are entropically favored at the sublimation temperature of 250 K for β-H2CO3, whereas they are not at the sublimation temperature of 210 K for α-H2CO3.

  8. Carbon isotopic patterns of amino acids associated with various microbial metabolic pathways and physiological conditions

    NASA Astrophysics Data System (ADS)

    Wang, P. L.; Hsiao, K. T.; Lin, L. H.

    2017-12-01

    Amino acids represent one of the most important categories of biomolecule. Their abundance and isotopic patterns have been broadly used to address issues related to biochemical processes and elemental cycling in natural environments. Previous studies have shown that various carbon assimilative pathways of microorganisms (e.g. autotrophy, heterotrophy and acetotrophy) could be distinguished by carbon isotopic patterns of amino acids. However, the taxonomic and catabolic coverage are limited in previous examination. This study aims to uncover the carbon isotopic patterns of amino acids for microorganisms remaining uncharacterized but bearing biogeochemical and ecological significance in anoxic environments. To fulfill the purpose, two anaerobic strains were isolated from riverine wetland and mud volcano in Taiwan. One strain is a sulfate reducing bacterium (related to Desulfovibrio marrakechensis), which is capable of utilizing either H2 or lactate, and the other is a methanogen (related to Methanolobus profundi), which grows solely with methyl-group compounds. Carbon isotope analyses of amino acids were performed on cells grown in exponential and stationary phase. The isotopic patterns were similar for all examined cultures, showing successive 13C depletion along synthetic pathways. No significant difference was observed for the methanogen and lactate-utilizing sulfate reducer harvested in exponential and stationary phases. In contrast, the H2-utilizing sulfate reducer harvested in stationary phase depleted and enriched 13C in aspartic acid and glycine, respectively when compared with that harvested in exponential phase. Such variations might infer the change of carbon flux during synthesis of these two amino acids in the reverse TCA cycle. In addition, the discriminant function analysis for all available data from culture studies further attests the capability of using carbon isotope patterns of amino acids in identifying microbial metabolisms.

  9. Effect of sodium metabisulfite on hydrogen peroxide production in light-exposed pediatric parenteral amino acid solutions.

    PubMed

    Brawley, V; Bhatia, J; Karp, W B

    1998-06-15

    The effect of sodium metabisulfite (MBS) on hydrogen peroxide (HP) production in model and commercial amino acid solutions exposed to phototherapy light was studied. Model and commercial pediatric amino acid solutions were prepared such that the amino acid concentration was 1%. MBS concentration, riboflavin concentration, and duration of exposure to phototherapy light were varied to determine the effect on HP production. Control solutions were kept in the dark. HP production was assayed in the model amino acid solutions by using potassium iodide in the presence of ammonium molybdate. In all experiments, HP production was measured at 360 nm in the presence and absence of catalase. In light-exposed solutions, HP production increased linearly for several hours and reached a plateau by eight hours. A mean maximum of 940 microM was produced (data pooled for all solutions). No detectable HP was generated in the solutions kept in the dark. After two hours of light exposure, it was necessary to add at least 10 times more MBS than is typically found in commercial total parenteral nutrient solutions to scavenge all the HP produced. An average of up to 940 microM of HP was produced in model and commercial pediatric parenteral 1% amino acid solutions in the presence of phototherapy light and clinically relevant concentrations of riboflavin and MBS. Light exposure decreased the antioxidant effect of MBS.

  10. Carbonic acid as a reserve of carbon dioxide on icy moons: The formation of carbon dioxide (CO{sub 2}) in a polar environment

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jones, Brant M.; Kaiser, Ralf I.; Strazzulla, Giovanni, E-mail: brantmj@hawaii.edu

    Carbon dioxide (CO{sub 2}) has been detected on the surface of several icy moons of Jupiter and Saturn via observation of the ν{sub 3} band with the Near-Infrared Mapping Spectrometer on board the Galileo spacecraft and the Visible-Infrared Mapping Spectrometer on board the Cassini spacecraft. Interestingly, the CO{sub 2} band for several of these moons exhibits a blueshift along with a broader profile than that seen in laboratory studies and other astrophysical environments. As such, numerous attempts have been made in order to clarify this abnormal behavior; however, it currently lacks an acceptable physical or chemical explanation. We present amore » rather surprising result pertaining to the synthesis of carbon dioxide in a polar environment. Here, carbonic acid was synthesized in a water (H{sub 2}O)-carbon dioxide (CO{sub 2}) (1:5) ice mixture exposed to ionizing radiation in the form of 5 keV electrons. The irradiated ice mixture was then annealed, producing pure carbonic acid which was then subsequently irradiated, recycling water and carbon dioxide. However, the observed carbon dioxide ν{sub 3} band matches almost exactly with that observed on Callisto; subsequent temperature program desorption studies reveal that carbon dioxide synthesized under these conditions remains in solid form until 160 K, i.e., the sublimation temperature of water. Consequently, our results suggest that carbon dioxide on Callisto as well as other icy moons is indeed complexed with water rationalizing the shift in peak frequency, broad profile, and the solid state existence on these relatively warm moons.« less

  11. Robust forests of vertically aligned carbon nanotubes chemically assembled on carbon substrates.

    PubMed

    Garrett, David J; Flavel, Benjamin S; Shapter, Joseph G; Baronian, Keith H R; Downard, Alison J

    2010-02-02

    Forests of vertically aligned carbon nanotubes (VACNTs) have been chemically assembled on carbon surfaces. The structures show excellent stability over a wide potential range and are resistant to degradation from sonication in acid, base, and organic solvent. Acid-treated single-walled carbon nanotubes (SWCNTs) were assembled on amine-terminated tether layers covalently attached to pyrolyzed photoresist films. Tether layers were electrografted to the carbon substrate by reduction of the p-aminobenzenediazonium cation and oxidation of ethylenediamine. The amine-modified surfaces were incubated with cut SWCNTs in the presence of N,N'-dicyclohexylcarbodiimide (DCC), giving forests of vertically aligned carbon nanotubes (VACNTs). The SWCNT assemblies were characterized by scanning electron microscopy, atomic force microscopy, and electrochemistry. Under conditions where the tether layers slow electron transfer between solution-based redox probes and the underlying electrode, the assembly of VACNTs on the tether layer dramatically increases the electron-transfer rate at the surface. The grafting procedure, and hence the preparation of VACNTs, is applicable to a wide range of materials including metals and semiconductors.

  12. Catalytic Decarboxylation of Fatty Acids to Aviation Fuels over Nickel Supported on Activated Carbon

    PubMed Central

    Wu, Jianghua; Shi, Juanjuan; Fu, Jie; Leidl, Jamie A.; Hou, Zhaoyin; Lu, Xiuyang

    2016-01-01

    Decarboxylation of fatty acids over non-noble metal catalysts without added hydrogen was studied. Ni/C catalysts were prepared and exhibited excellent activity and maintenance for decarboxylation. Thereafter, the effects of nickel loading, catalyst loading, temperature, and carbon number on the decarboxylation of fatty acids were investigated. The results indicate that the products of cracking increased with high nickel loading or catalyst loading. Temperature significantly impacted the conversion of stearic acid but did not influence the selectivity. The fatty acids with large carbon numbers tend to be cracked in this reaction system. Stearic acid can be completely converted at 370 °C for 5 h, and the selectivity to heptadecane was around 80%. PMID:27292280

  13. Treated Carbon Nanofibers for Storing Energy in Aqueous KOH

    NASA Technical Reports Server (NTRS)

    Firsich, David W.

    2004-01-01

    A surface treatment has been found to enhance the performances of carbon nanofibers as electrode materials for electrochemical capacitors in which aqueous solutions of potassium hydroxide are used as the electrolytes. In the treatment, sulfonic acid groups are attached to edge plane sites on carbon atoms. The treatment is applicable to a variety of carbon nanofibers, including fibrils and both single- and multiple-wall nanotubes. The reason for choosing nanofibers over powders and other forms of carbon is that nanofibers offer greater power features. In previous research, it was found that the surface treatment of carbon nanofibers increased energy-storage densities in the presence of acid electrolytes. Now, it has been found that the same treatment increases energy-storage densities of carbon nanofibers in the presence of alkaline electrolytes when the carbon is paired with a NiOOH electrode. This beneficial effect varies depending on the variety of carbon substrate to which it is applied. It has been conjectured that the sulfonic acid groups, which exist in a deprotonated state in aqueous KOH solutions, undergo reversible electro-chemical reactions that are responsible for the observed increases in energystorage capacities. The increases can be considerable: For example, in one case, nanofibers exhibited a specific capacitance of 34 Farads per gram before treatment and 172 Farads per gram (an increase of about 400 percent) after treatment. The most promising application of this development appears to lie in hybrid capacitors, which are devices designed primarily for storing energy. These devices are designed to be capable of (1) discharge at rates greater than those of batteries and (2) storing energy at densities approaching those of batteries. A hybrid capacitor includes one electrode like that of a battery and one electrode like that of an electrochemical capacitor. For example, a hybrid capacitor could contain a potassium hydroxide solution as the electrolyte

  14. One-step microwave synthesis of photoluminescent carbon nanoparticles from sodium dextran sulfate water solution

    NASA Astrophysics Data System (ADS)

    Kokorina, Alina A.; Goryacheva, Irina Y.; Sapelkin, Andrei V.; Sukhorukov, Gleb B.

    2018-04-01

    Photoluminescent (PL) carbon nanoparticles (CNPs) have been synthesized by one-step microwave irradiation from water solution of sodium dextran sulfate (DSS) as the sole carbon source. Microwave (MW) method is very simple and cheap and it provides fast synthesis of CNPs. We have varied synthesis time for obtaining high luminescent CNPs. The synthesized CNPs exhibit excitation-dependent photoluminescent. Final CNPs water solution has a blue- green luminescence. CNPs have low cytotoxicity, good photostability and can be potentially suitable candidates for bioimaging, analysis or analytical tests.

  15. Ultrasound assisted cocrystallization from solution (USSC) containing a non-congruently soluble cocrystal component pair: Caffeine/maleic acid.

    PubMed

    Aher, Suyog; Dhumal, Ravindra; Mahadik, Kakasaheb; Paradkar, Anant; York, Peter

    2010-12-23

    Ultrasound assisted solution cocrystallization (USSC) has been studied using a non-congruently soluble pair of caffeine and maleic acid in methanol. USSC was compared with solvent cooling and slurry sonication using different molar ratios of caffeine:maleic acid (1:0.5, 1:1, 1:2, 1:3 and 1:3.5) in solution/slurry. Products were characterized by PXRD and Raman spectroscopy techniques. In USSC trials, the content of cocrystal in the product was observed to increase with increase in amount of maleic acid in solution. Only USSC offered pure caffeine/maleic acid 2:1 cocrystal product when caffeine:maleic acid; 1:3.5 molar ratio was taken in solution. Caffeine/maleic acid 1:1 cocrystal and maleic acid were not obtained in neither of the techniques. Products of solvent cooling and slurry sonication experiments were mixtures of caffeine and caffeine/maleic acid 2:1 cocrystal in varying amounts. In USSC, ultrasound application must have attained simultaneous supersaturation of cocrystal components in solution due to altered supersaturation conditions resulting in cocrystal formation. For this simultaneous attainment of supersaturation, molar ratio of cocrystal components in solution was identified as an important parameter while designing experiments for a non-congruently soluble pair having large solubility difference. Copyright © 2010 Elsevier B.V. All rights reserved.

  16. Theoretical isotopic fractionation between structural boron in carbonates and aqueous boric acid and borate ion

    NASA Astrophysics Data System (ADS)

    Balan, Etienne; Noireaux, Johanna; Mavromatis, Vasileios; Saldi, Giuseppe D.; Montouillout, Valérie; Blanchard, Marc; Pietrucci, Fabio; Gervais, Christel; Rustad, James R.; Schott, Jacques; Gaillardet, Jérôme

    2018-02-01

    The 11B/10B ratio in calcite and aragonite is an important proxy of oceanic water pH. However, the physico-chemical mechanisms underpinning this approach are still poorly known. In the present study, we theoretically determine the equilibrium isotopic fractionation properties of structural boron species in calcium carbonates, BO33-, BO2(OH)2- and B(OH)4- anions substituted for carbonate groups, as well as those of B(OH)4- and B(OH)3 species in vacuum. Significant variability of equilibrium isotopic fractionation properties is observed among these structural species which is related to their contrasted coordination state, Bsbnd O bond lengths and atomic-scale environment. The isotopic composition of structural boron does not only depend on its coordination number but also on its medium range environment, i.e. farther than its first coordination shell. The isotopic fractionation between aqueous species and their counterparts in vacuum are assessed using previous investigations based on similar quantum-mechanical modeling approaches. At 300 K, the equilibrium isotope composition of structural trigonal species is 7-15‰ lighter than that of aqueous boric acid molecules, whereas substituted tetrahedral borate ions are heavier than their aqueous counterparts by 10-13‰. Although significant uncertainties are known to affect the theoretical prediction of fractionation factors between solids and solutions, the usually assumed lack of isotopic fractionation during borate incorporation in carbonates is challenged by these theoretical results. The present theoretical equilibrium fractionation factors between structural boron and aqueous species differ from those inferred from experiments which may indicate that isotopic equilibrium, unlike chemical equilibrium, was not reached in most experiments. Further research into the isotopic fractionation processes at the interface between calcium carbonates and aqueous solution as well as long duration experiments aimed at

  17. Artificial photosynthesis of. beta. -ketocarboxylic acids from carbon dioxide and ketones via enolate complexes of aluminum porphyrin

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hirai, Yasuhiro; Aida, Takuzo; Inoue, Shohei

    1989-04-12

    Photochemical fixation of carbon dioxide is of much interest in connection with biological photosynthesis by green plants as well as from the viewpoint of carbon resource utilization. One of the important steps in the assimilation of carbon dioxide is the carboxylation of a carbonyl compound into ketocarboxylic acid, where the reaction proceeds via an enolate species as reactive intermediate. For example, in four carbon (C{sub 4}) pathway and Crassulacean acid metabolism (CAM) processes, pyruvate is converted with the aid of ATP into phosphoenolpyruvate, which is subsequently carboxylated to give oxaloacetate by the action of pyruvate carboxylase. In relation to thismore » interesting biological process, some artificial systems have been exploited for the synthesis of {beta}-ketocarboxylic acid derivatives from carbon dioxide and ketones using nucleophiles such as metal carbonates, thiazolates, phenolates, alkoxides, and strong organic as well as inorganic basis, which promote the enolization of ketones in the intermediate step. We wish to report here a novel, visible light-induced fixation of carbon dioxide with the enolate complex of aluminum porphyrin, giving {beta}-ketocarboxylic acid under mild conditions.« less

  18. Carbon Isotopic Ratios of Amino Acids in Stardust-Returned Samples

    NASA Technical Reports Server (NTRS)

    Elsila, Jamie E.; Glavin, Daniel P.; Dworkin, Jason P.

    2009-01-01

    NASA's Stardust spacecraft returned to Earth samples from comet 81P/Wild 2 in January 2006. Preliminary examinations revealed the presence of a suite of organic compounds including several amines and amino acids, but the origin of these compounds could not be identified. Here. we present the carbon isotopic ratios of glycine and E-aminocaproic acid (EACH), the two most abundant amino acids observed, in Stardust-returned foil samples measured by gas chromatography-combustion-isotope ratio crass spectrometry coupled with quadrupole mass spectrometry (GC-QMS/IRMS).

  19. Carbon Isotopic Measurements of Amino Acids in Stardust-Returned Samples

    NASA Technical Reports Server (NTRS)

    Elsila, Jamie

    2009-01-01

    NASA's Stardust spacecraft returned to Earth samples from comet 81P/Wild 2 in January 2006. Preliminary examinations revealed the presence of a suite of organic compounds including several amines and amino acids, but the origin of these compounds could not be identified. Here, we present the carbon isotopic ratios of glycine and e-aminocaproic acid (EACA), the two most abundant amino acids, in Stardust-returned foil samples measured by gas chromatography-combustion-isotope ratio mass spectrometry coupled with quadrupole mass spectrometry (GC-CAMS/IRMS).

  20. Late-Stage Functionalization of Arylacetic Acids by Photoredox-Catalyzed Decarboxylative Carbon-Heteroatom Bond Formation.

    PubMed

    Sakakibara, Yota; Ito, Eri; Fukushima, Tomohiro; Murakami, Kei; Itami, Kenichiro

    2018-05-02

    The rapid transformation of pharmaceuticals and agrochemicals enables access to unexplored chemical space and thus has accelerated the discovery of novel bioactive molecules. Because arylacetic acids are regarded as key structures in bioactive compounds, new transformations of these structures could contribute to drug/agrochemical discovery and chemical biology. This work reports carbon-nitrogen and carbon-oxygen bond formation through the photoredox-catalyzed decarboxylation of arylacetic acids. The reaction shows good functional group compatibility without pre-activation of the nitrogen- or oxygen-based coupling partners. Under similar reaction conditions, carbon-chlorine bond formation was also feasible. This efficient derivatization of arylacetic acids makes it possible to synthesize pharmaceutical analogues and bioconjugates of pharmaceuticals and natural products. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Fabrication of carbonate apatite blocks from set gypsum based on dissolution-precipitation reaction in phosphate-carbonate mixed solution.

    PubMed

    Nomura, Shunsuke; Tsuru, Kanji; Maruta, Michito; Matsuya, Shigeki; Takahashi, Ichiro; Ishikawa, Kunio

    2014-01-01

    Carbonate apatite (CO3Ap), fabricated by dissolution-precipitation reaction based on an appropriate precursor, is expected to be replaced by bone according to bone remodeling cycle. One of the precursor candidates is gypsum because it shows self-setting ability, which then enables it to be shaped and molded. The aim of this study, therefore, was to fabricate CO3Ap blocks from set gypsum. Set gypsum was immersed in a mixed solution of 0.4 mol/L disodium hydrogen phosphate (Na2HPO4) and 0.4 mol/L sodium hydrogen carbonate (NaHCO3) at 80-200°C for 6-48 h. Powder X-ray diffraction patterns and Fourier transform infrared spectra showed that CO3Ap block was fabricated by dissolution-precipitation reaction in Na2HPO4-NaHCO3 solution using set gypsum in 48 h when the temperature was 100°C or higher. Conversion rate to CO3Ap increased with treatment temperature. CO3Ap block containing a larger amount of carbonate was obtained when treated at lower temperature.

  2. Catchment-scale redistribution of lithogenic solutes and black carbon over three years following wildfire in the Jemez Mountains, New Mexico, USA

    NASA Astrophysics Data System (ADS)

    Pohlmann, M. A.; Root, R.; Abrell, L.; Schwartz, C. J.; Chorover, J.

    2017-12-01

    Wildfire represents a disturbance that is becoming more prevalent as climate shifts to hotter and drier conditions in the southwestern US. It has profound and potentially long-term effects on the physical, chemical and microbiological properties of soil, including immediate surface deposition of lithogenic elements and incompletely combusted organic matter (i.e., black carbon or BC) previously held in biomass. The long residence time of BC mitigates oxidative release of carbon to the atmosphere and thus has implications for long-term climate forcing. Immediately following the 2013 Thompson Ridge wildfire in the Jemez River Basin Critical Zone Observatory, we sampled 22 soil profiles across a zero order basin at finely resolved depth intervals to 40 cm. Samples were collected again 12 and 24 months following the fire to assess redistribution of solutes and BC in the two years following fire. Water extractable anions, cations and carbon were measured for each sample and maps were generated by geostatistical interpolation. Additionally, the benzene polycarboxylic acid (BPCA) molecular marker method was employed for a selection of samples to quantify and characterize the BC content of the existing soil organic carbon pool as a function of landscape position and time. The `pulsed' deposition of water-soluble ions and BC followed pre-fire vegetation structure as indicated by solution chemistry data for years one and two displaying elevated solute concentrations in surface depths proximal to dense vegetation. Vertical and lateral redistribution of the water extractable elements and BC were consistent with wetting front propagation and topographic trends (driven by erosion, overland flow and lateral subsurface flow). BC depth profiles indicate vertical infiltration and lateral transport with burial, the latter associated with surface erosion of sediment, as mechanisms for redistribution.

  3. Whole-body pharmacokinetics of HDAC inhibitor drugs, butyric acid, valproic acid and 4-phenylbutyric acid measured with carbon-11 labeled analogs by PET

    PubMed Central

    Kim, Sung Won; Hooker, Jacob M.; Otto, Nicola; Win, Khaing; Muench, Lisa; Shea, Colleen; Carter, Pauline; King, Payton; Reid, Alicia E.; Volkow, Nora D.; Fowler, Joanna S.

    2013-01-01

    The fatty acids, n-butyric acid (BA), 4-phenylbutyric acid (PBA) and valproic acid (VPA, 2-propylpentanoic acid) have been used for many years in the treatment of a variety of CNS and peripheral organ diseases including cancer. New information that these drugs alter epigenetic processes through their inhibition of histone deacetylases (HDACs) has renewed interest in their biodistribution and pharmacokinetics and the relationship of these properties to their therapeutic and side effect profile. In order to determine the pharmacokinetics and biodistribution of these drugs in primates, we synthesized their carbon-11 labeled analogues and performed dynamic positron emission tomography (PET) in six female baboons over 90 min. The carbon-11 labeled carboxylic acids were prepared by using 11CO2 and the appropriate Grignard reagents. [11C]BA was metabolized rapidly (only 20% of the total carbon-11 in plasma was parent compound at 5 min post injection) whereas for VPA and PBA 98% and 85% of the radioactivity was the unmetabolized compound at 30 min after their administration respectively. The brain uptake of all three carboxylic acids was very low (<0.006%ID/cc, BA>VPA>PBA), which is consistent with the need for very high doses for therapeutic efficacy. Most of the radioactivity was excreted through the kidneys and accumulated in the bladder. However, the organ biodistribution between the drugs differed. [11C]BA showed relatively high uptake in spleen and pancreas whereas [11C]PBA showed high uptake in liver and heart. Notably, [11C]VPA showed exceptionally high heart uptake possibly due to its involvement in lipid metabolism. The unique biodistribution of each of these drugs may be of relevance in understanding their therapeutic and side effect profile including their teratogenic effects. PMID:23906667

  4. Whole-body pharmacokinetics of HDAC inhibitor drugs, butyric acid, valproic acid and 4-phenylbutyric acid measured with carbon-11 labeled analogs by PET.

    PubMed

    Kim, Sung Won; Hooker, Jacob M; Otto, Nicola; Win, Khaing; Muench, Lisa; Shea, Colleen; Carter, Pauline; King, Payton; Reid, Alicia E; Volkow, Nora D; Fowler, Joanna S

    2013-10-01

    The fatty acids, n-butyric acid (BA), 4-phenylbutyric acid (PBA) and valproic acid (VPA, 2-propylpentanoic acid) have been used for many years in the treatment of a variety of CNS and peripheral organ diseases including cancer. New information that these drugs alter epigenetic processes through their inhibition of histone deacetylases (HDACs) has renewed interest in their biodistribution and pharmacokinetics and the relationship of these properties to their therapeutic and side effect profiles. In order to determine the pharmacokinetics and biodistribution of these drugs in primates, we synthesized their carbon-11 labeled analogues and performed dynamic positron emission tomography (PET) in six female baboons over 90 min. The carbon-11 labeled carboxylic acids were prepared by using (11)CO2 and the appropriate Grignard reagents. [(11)C]BA was metabolized rapidly (only 20% of the total carbon-11 in plasma was parent compound at 5 min post injection) whereas for VPA and PBA 98% and 85% of the radioactivity were the unmetabolized compound at 30 min after their administration respectively. The brain uptake of all three carboxylic acids was very low (<0.006%ID/cc, BA>VPA>PBA), which is consistent with the need for very high doses for therapeutic efficacy. Most of the radioactivity was excreted through the kidneys and accumulated in the bladder. However, the organ biodistribution between the drugs differed. [(11)C]BA showed relatively high uptake in spleen and pancreas whereas [(11)C]PBA showed high uptake in liver and heart. Notably, [(11)C]VPA showed exceptionally high heart uptake possibly due to its involvement in lipid metabolism. The unique biodistribution of each of these drugs may be of relevance in understanding their therapeutic and side effect profile including their teratogenic effects. © 2013.

  5. Adsorption of Salicylhydroxamic Acid on Selected Rare Earth Oxides and Carbonates

    NASA Astrophysics Data System (ADS)

    Galt, Greer Elaine

    Adsorption behavior of the anionic collector salicylhydroxamic acid (SHA) on a selected group of rare earth oxides (REOs) and carbonates (RECs) was studied via experimental methods and modelling software. Synthetic oxide and carbonate powders of the rare earth elements cerium (Ce), praseodymium (Pr), europium (Eu), and terbium (Tb) were tested for this research. Studies were conducted at different pH levels to analyze the kinetics of collector adsorption onto the oxide and carbonate surfaces in attempts to optimize recovery parameters for commercial flotation processes using SHA. In addition, thermodynamic software StabCal was implemented to compare theoretical adsorption behavior of collectors SHA and octylhydroxamic acid (OHA) on these four rare earth oxides and carbonates. Theoretical points of zero charge were also estimated via StabCal and compared to experimental values to establish validity. Results for oxides indicate that both the amount and rate of SHA adsorption are highest for lighter REOs, decreasing as ionic diameter increases, a chelation phenomenon common with hydroxamates. However, results for the carbonates exhibit the opposite trend: strongest SHA adsorption was seen in the heavy RECs. This pattern correlates to the increasing stability of the carbonate such that ionic diameter of the REs becomes more amenable to chelation due to differences in bonding chemistry. Overall, adsorption kinetics appear dependent on pH, coordination chemistry, and cation size.

  6. Nicotinic Acid Metabolism, V. A Cobamide Coenzyme-Dependent Conversion of α-Methyleneglutaric Acid to Dimethylmaleic Acid

    PubMed Central

    Kung, H. F.; Cederbaum, S.; Tsai, L.; Stadtman, T. C.

    1970-01-01

    A new B12-coenzyme-dependent isomerization, catalyzed by extracts of a nicotinate-fermenting clostridium, results in the conversion of α-methyleneglutaric acid to dimethylmaleic acid. These two acids are intermediates in the multistep anaerobic process wherein nicotinate is converted, ultimately, to one mole each of propionate, acetate, carbon dioxide, and ammonia. Dimethylmaleic acid reacts in its anhydride form with 2,4-dinitrophenylhydrazine to form N-2′,4′-dinitrophenyl-anilino-3,4-dimethylmaleimide. The characteristic reddish color exhibited by the latter derivative in alkaline solution serves as a convenient quantitative assay for dimethylmaleic acid. Comparison of the 2,4-dinitrophenylhydrazine derivatives of the product of the enzymic reaction and of synthetic dimethylmaleic anhydride showed them to be identical in every respect. PMID:5266166

  7. Impact of Acid Attack on the Shear Behaviour of a Carbonate Rock Joint

    NASA Astrophysics Data System (ADS)

    Nouailletas, O.; Perlot, C.; Rivard, P.; Ballivy, G.; La Borderie, C.

    2017-06-01

    The mechanical behaviour of structural discontinuities in rock mass is a key element of the stability analysis in civil engineering, petroleum engineering and mining engineering. In this paper, the mechanical analysis is coupled with the acidic attack of a rock joint associated with leakage of CO2 through a geological fault in the context of carbon sequestration. Experiments were conducted at the laboratory scale to assess the shear behaviour of degraded joint: direct shear tests were performed on rock joints that have been previously immersed into water or into an acidic solution (pH 0.2). The shear behaviour of joints is governed by the roughness of its walls: the parameters Z2, Z3, Z4 and RL characterize the rough surfaces. They are calculated from the scans of joint surfaces after and before immersion. Their comparison pointed out a slight impact of the acidic attack. However, the results of the direct shear tests show significant modifications in the shear behaviour for the degraded joints: the tangential stress peak disappears, the tangential stiffness decreases in the stress/displacement curve, and the contraction increases, the dilation angle decreases in the dilation curve. Acid attack has a greater impact on the mechanical properties of the asperities than their geometric characteristics. The results of this study will be used to improve chemo-mechanical modelling to better simulate with higher accuracy the fault stability in different cases of civil engineering, petroleum engineering and mining engineering.

  8. An investigation into the stability and sterility of citric acid solutions used for cough reflex testing.

    PubMed

    Falconer, James R; Wu, Zimei; Lau, Hugo; Suen, Joanna; Wang, Lucy; Pottinger, Sarah; Lee, Elaine; Alazawi, Nawar; Kallesen, Molly; Gargiulo, Derryn A; Swift, Simon; Svirskis, Darren

    2014-10-01

    Citric acid is used in cough reflex testing in clinical and research settings to assess reflexive cough in patients at risk of swallowing disorders. To address a lack of knowledge in this area, this study investigated the stability and sterility of citric acid solutions. Triplicate solutions of citric acid (0.8 M) in isotonic saline were stored at 4 ± 2 °C for up to 28 days and analysed by high-performance liquid chromatography. Microbiological sterility of freshly prepared samples and bulk samples previously used for 2 weeks within the hospital was determined using a pour plate technique. Microbial survival in citric acid was determined by inoculating Staphylococcus aureus, Escherichia coli, or Candida albicans into citric acid solution and monitoring the number of colony-forming units/mL over 40 min. Citric acid solutions remained stable at 4 °C for 28 days (98.4 ± 1.8 % remained). The freshly prepared and clinical samples tested were sterile. However, viability studies revealed that citric acid solution allows for the survival of C. albicans but not for S. aureus or E. coli. The microbial survival study showed that citric acid kills S. aureus and E. coli but has no marked effect on C. albicans after 40 min. Citric acid samples at 0.8 M remained stable over the 4-week testing period, with viable microbial cells absent from samples tested. However, C. albicans has the ability to survive in citric acid solution if inadvertently introduced in practice. For this reason, in clinical and research practice it is suggested to use single-use aliquots prepared aseptically which can be stored for up to 28 days at 4 °C.

  9. Correlation between mesopore volume of carbon supports and the immobilization of laccase from Trametes versicolor for the decolorization of Acid Orange 7.

    PubMed

    Ramírez-Montoya, Luis A; Hernández-Montoya, Virginia; Montes-Morán, Miguel A; Cervantes, Francisco J

    2015-10-01

    Immobilization of laccase from Trametes versicolor was carried out using carbon supports prepared from different lignocellulosic wastes. Enzymes were immobilized by physical adsorption. Taguchi methodology was selected for the design of experiments regarding the preparation of the carbon materials, which included the use of activating agents for the promotion of mesoporosity. A good correlation between the mesopore volumes of the carbon supports and the corresponding laccase loadings attained was observed. Specifically, the chemical activation of pecan nut shell with FeCl3 led to a highly mesoporous material that also behaved as the most efficient support for the immobilization of laccase. This particular laccase/carbon support system was used as biocatalyst for the decolorization of aqueous solutions containing Acid Orange 7. Mass spectrometry coupled to a liquid chromatograph allowed us to identify the products of the dye degradation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Can Thermally Sprayed Aluminum (TSA) Mitigate Corrosion of Carbon Steel in Carbon Capture and Storage (CCS) Environments?

    NASA Astrophysics Data System (ADS)

    Paul, S.; Syrek-Gerstenkorn, B.

    2017-01-01

    Transport of CO2 for carbon capture and storage (CCS) uses low-cost carbon steel pipelines owing to their negligible corrosion rates in dry CO2. However, in the presence of liquid water, CO2 forms corrosive carbonic acid. In order to mitigate wet CO2 corrosion, use of expensive corrosion-resistant alloys is recommended; however, the increased cost makes such selection economically unfeasible; hence, new corrosion mitigation methods are sought. One such method is the use of thermally sprayed aluminum (TSA), which has been used to mitigate corrosion of carbon steel in seawater, but there are concerns regarding its suitability in CO2-containing solutions. A 30-day test was carried out during which carbon steel specimens arc-sprayed with aluminum were immersed in deionized water at ambient temperature bubbled with 0.1 MPa CO2. The acidity (pH) and potential were continuously monitored, and the amount of dissolved Al3+ ions was measured after completion of the test. Some dissolution of TSA occurred in the test solution leading to nominal loss in coating thickness. Potential measurements revealed that polarity reversal occurs during the initial stages of exposure which could lead to preferential dissolution of carbon steel in the case of coating damage. Thus, one needs to be careful while using TSA in CCS environments.

  11. Solution-Processed Carbon Nanotube True Random Number Generator.

    PubMed

    Gaviria Rojas, William A; McMorrow, Julian J; Geier, Michael L; Tang, Qianying; Kim, Chris H; Marks, Tobin J; Hersam, Mark C

    2017-08-09

    With the growing adoption of interconnected electronic devices in consumer and industrial applications, there is an increasing demand for robust security protocols when transmitting and receiving sensitive data. Toward this end, hardware true random number generators (TRNGs), commonly used to create encryption keys, offer significant advantages over software pseudorandom number generators. However, the vast network of devices and sensors envisioned for the "Internet of Things" will require small, low-cost, and mechanically flexible TRNGs with low computational complexity. These rigorous constraints position solution-processed semiconducting single-walled carbon nanotubes (SWCNTs) as leading candidates for next-generation security devices. Here, we demonstrate the first TRNG using static random access memory (SRAM) cells based on solution-processed SWCNTs that digitize thermal noise to generate random bits. This bit generation strategy can be readily implemented in hardware with minimal transistor and computational overhead, resulting in an output stream that passes standardized statistical tests for randomness. By using solution-processed semiconducting SWCNTs in a low-power, complementary architecture to achieve TRNG, we demonstrate a promising approach for improving the security of printable and flexible electronics.

  12. 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.

  13. A Simple Demonstration of Carbon Dioxide Fixation and Acid Production in CAM Plants

    ERIC Educational Resources Information Center

    Walker, John R. L.; McWha, James A.

    1976-01-01

    Described is an experiment investigating carbon dioxide fixation in the dark and the diurnal rhythm of acid production in plants exhibiting Crassulacean Acid Metabolism. Included are suggestions for four further investigations. (SL)

  14. Understanding the dissolution of α-zein in aqueous ethanol and acetic acid solutions.

    PubMed

    Li, Yunqi; Li, Ji; Xia, Qiuyang; Zhang, Boce; Wang, Qin; Huang, Qingrong

    2012-10-04

    Zein is a corn prolamin that has broad industrial applications because of its unique physical properties. Currently, the high cost of extraction and purification, which is directly related to the dispersion of zein in different solvents, is the major bottleneck of the zein industry. Solution behaviors of zein have been studied for a long time. However, the physical nature of zein in different solvents remains unclear. In this study, small-angle X-ray scattering (SAXS), static light scattering (SLS), and rheology were combined to study the structure and protein-solvent interaction of α-zein in both acetic acid and aqueous ethanol solutions. We found that the like-dissolve-like rule, the partial unfolding, and the protonation of zein are all critical to understanding the solution behaviors. Zein holds an elongated conformation (i.e., prolate ellipsoid) in all solutions, as revealed from SAXS data. There is an "aging effect" for zein in aqueous ethanol solutions, as evidenced by the transition of Newtonian rheological profiles for fresh zein solutions to the non-Newtonian shear thinning behavior for zein solutions after storage at room temperature for 24 h. Such shear thinning behavior becomes more pronounced for zein solutions at higher concentrations. The SLS results clearly show that acetic acid is a better solvent to dissolve zein than aqueous ethanol solution, as supported by a more negative second virial coefficient. This is majorly caused by the protonation of the protein, which was further verified by the dissolution of zein in water (a nonsolvent for zein) with the addition of acids.

  15. The kinetics of oxidation of bilirubin and ascorbic acid in solution

    NASA Astrophysics Data System (ADS)

    Solomonov, A. V.; Rumyantsev, E. V.; Kochergin, B. A.; Antina, E. V.

    2012-07-01

    The results of a comparative study of the oxidation of bilirubin, ascorbic acid, and their mixture in aqueous solutions under the action of air oxygen and hydrogen peroxide are presented. The observed and true rate constants for the oxidation reactions were determined. It was shown that the oxidation of tetrapyrrole pigment occurred under these conditions bypassing the stage of biliverdin formation to monopyrrole products. Simultaneous oxidation of bilirubin and ascorbic acid was shown to be accompanied by the inhibition of ascorbic acid oxidation by bilirubin, whereas ascorbic acid itself activated the oxidation of bilirubin.

  16. Adsorption mechanism of 2,4-dichlorophenoxyacetic acid onto nitric-acid-modified activated carbon fiber.

    PubMed

    Li, Qun; Sun, Jie; Ren, Tianhao; Guo, Lin; Yang, Zhilin; Yang, Qi; Chen, Hai

    2018-04-01

    Adsorption by carbon materials is one of the relatively fast methods in present research, which is widely used in emergency events. Activated carbon fiber (ACF) modified by nitric acid (N-ACF) was studied in this research to determine the adsorption performance for 2,4-dichlorophenoxyacetic acid (2,4-D). Subsequently, influence factors, adsorption isotherm models, kinetics and thermodynamic were investigated in a batch system to realize this adsorption. Experimental results showed that ACF modified by 0.1M nitric acid had a better removal ability than 2,4-D. Removal rate of 2,4-D by N-ACF was greatly influenced by pH with the optimum pH at 2. The superiority of the Langmuir isotherm model in describing the adsorption equilibrium was revealed by correlation coefficients R2 (R 2  ≥ 0.997). Furthermore, adsorption kinetics was well described by pseudo-second-order model. The results of thermodynamic showed that adsorption was a spontaneous, endothermic process with randomness increasing. Additionally, surface structure properties of adsorbent were characterized by Scanning electron microscopy, Fourier transform infrared spectroscopy, Specific surface area analysis of Brunauer, Emmett and Teller and Boehm's titration. It turned out that the micropore structure and functional groups on N-ACF all can contribute to the removal of 2,4-D.

  17. 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.

  18. Ginger extract as green corrosion inhibitor of mild steel in hydrochloric acid solution

    NASA Astrophysics Data System (ADS)

    Fidrusli, A.; Suryanto; Mahmood, M.

    2018-01-01

    Ginger extract as corrosion inhibitor from natural resources was studied to prevent corrosion of mild steel in acid media. Ginger rhizome was extracted to produce green corrosion inhibitor (G-1) while ginger powder bought at supermarket was also extract to form green corrosion inhibitor (G-2). Effectiveness of inhibitor in preventing corrosion process of mild steel was studied in 1.0 M of hydrochloric acid. The experiment of weight loss method and polarization technique were conducted to measure corrosion rate and inhibition efficiency of mild steel in solution containing 1.0 M of hydrochloric acid with various concentration of inhibitor at room temperature. The results showed that, the rate of corrosion dropped from 8.09 mmpy in solution containing no inhibitor to 0.72 mmpy in solution containing 150g/l inhibitor while inhibition efficiency up to 91% was obtained. The polarization curve in polarization experiments shows that the inhibition efficiency is 86% with high concentration of inhibitor. The adsorption of ginger extract on the surface of mild steel was observed by using optical microscope and the characterization analysis was done by using pH measurement method. When high concentration of green inhibitor in the acid solution is used, the pH at the surface of steel is increasing.

  19. Influence of acid functionalization on the cardiopulmonary toxicity of carbon nanotubes and carbon black particles in mice

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tong Haiyan; McGee, John K.; Saxena, Rajiv K.

    2009-09-15

    Engineered carbon nanotubes are being developed for a wide range of industrial and medical applications. Because of their unique properties, nanotubes can impose potentially toxic effects, particularly if they have been modified to express functionally reactive chemical groups on their surface. The present study was designed to evaluate whether acid functionalization (AF) enhanced the cardiopulmonary toxicity of single-walled carbon nanotubes (SWCNT) as well as control carbon black particles. Mice were exposed by oropharyngeal aspiration to 10 or 40 {mu}g of saline-suspended single-walled carbon nanotubes (SWCNTs), acid-functionalized SWCNTs (AF-SWCNTs), ultrafine carbon black (UFCB), AF-UFCB, or 2 {mu}g LPS. 24 hours later,more » pulmonary inflammatory responses and cardiac effects were assessed by bronchoalveolar lavage and isolated cardiac perfusion respectively, and compared to saline or LPS-instilled animals. Additional mice were assessed for histological changes in lung and heart. Instillation of 40 {mu}g of AF-SWCNTs, UFCB and AF-UFCB increased percentage of pulmonary neutrophils. No significant effects were observed at the lower particle concentration. Sporadic clumps of particles from each treatment group were observed in the small airways and interstitial areas of the lungs according to particle dose. Patches of cellular infiltration and edema in both the small airways and in the interstitium were also observed in the high dose group. Isolated perfused hearts from mice exposed to 40 {mu}g of AF-SWCNTs had significantly lower cardiac functional recovery, greater infarct size, and higher coronary flow rate than other particle-exposed animals and controls, and also exhibited signs of focal cardiac myofiber degeneration. No particles were detected in heart tissue under light microscopy. This study indicates that while acid functionalization increases the pulmonary toxicity of both UFCB and SWCNTs, this treatment caused cardiac effects only with the AF-carbon

  20. Macrophage Biocompatibility of CoCr Wear Particles Produced under Polarization in Hyaluronic Acid Aqueous Solution

    PubMed Central

    Perez-Maceda, Blanca Teresa; López-Fernández, María Encarnación; Díaz, Iván; Kavanaugh, Aaron; Billi, Fabrizio; Escudero, María Lorenza; García-Alonso, María Cristina; Lozano, Rosa María

    2018-01-01

    Macrophages are the main cells involved in inflammatory processes and in the primary response to debris derived from wear of implanted CoCr alloys. The biocompatibility of wear particles from a high carbon CoCr alloy produced under polarization in hyaluronic acid (HA) aqueous solution was evaluated in J774A.1 mouse macrophages cultures. Polarization was applied to mimic the electrical interactions observed in living tissues. Wear tests were performed in a pin-on-disk tribometer integrating an electrochemical cell in phosphate buffer solution (PBS) and in PBS supplemented with 3 g/L HA, an average concentration that is generally found in synovial fluid, used as lubricant solution. Wear particles produced in 3 g/L HA solution showed a higher biocompatibility in J774A.1 macrophages in comparison to those elicited by particles obtained in PBS. A considerable enhancement in macrophages biocompatibility in the presence of 3 g/L of HA was further observed by the application of polarization at potentials having current densities typical of injured tissues suggesting that polarization produces an effect on the surface of the metallic material that leads to the production of wear particles that seem to be macrophage-biocompatible and less cytotoxic. The results showed the convenience of considering the influence of the electric interactions in the chemical composition of debris detached from metallic surfaces under wear corrosion to get a better understanding of the biological effects caused by the wear products. PMID:29738506

  1. Methanol Uptake By Low Temperature Aqueous Sulfuric Acid Solutions

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  2. Adsorption Behavior of Ferromagnetic Carbon Nanotubes for Methyl Orange from Aqueous Solution.

    PubMed

    Wang, Liping; Zhang, Mingyu; Zhao, Chenxi; Yang, Shan

    2016-03-01

    The ferromagnetic carbon nanotubes which can be easily separated from aqueous solution were prepared and characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Batch experiments were carried out to investigate the adsorption behavior of ferromagnetic carbon nanotubes for removing methyl orange (MO). The results showed that these ferromagnetic carbon nanotubes were richer in surface function groups than the carbon nanotubes did, furthermore, both γ-Fe2O3 and Fe with ferromagnetism were found on the surface of carbon nanotubes. The results also demonstrated that ferromagnetic carbon nanotubes possessed stronger adsorption ability for MO than carbon nanotubes did. The adsorption isotherms followed Langmuir isotherm equation and the adsorption kinetics could be well described with the pseudo second-order kinetic model. The adsorption process involved an intraparticle diffusion, while it was not the only rate-controlling step. The values of AG were negative and the value of ΔH is -12.37 kJ/mol, proving that the adsorption of MO onto ferromagnetic carbon nanotubes was a spontaneous and exothermic process.

  3. Performance evaluation of trimethylamine-carbon dioxide thermolytic draw solution for engineered osmosis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Boo, C; Khalil, YF; Elimelech, M

    We evaluated the performance of trimethylamine-carbon dioxide (TMA-CO2) as a potential thermolytic draw solution for engineered osmosis. Water flux and reverse solute flux with TMA-CO2 draw solution were measured in forward osmosis (FO) and pressure retarded osmosis (PRO) modes using thin-film composite (TFC) and cellulose triacetate (CTA) FO membranes. Water flux with the TMA-CO2 draw solution was comparable to that obtained with the more common ammonia-carbon dioxide (NH3-CO2) thermolytic draw solution at similar (1 M) concentration. Using a TFC-FO membrane, the water fluxes produced by 1 M TMA-CO2 and NH3-CO2 draw solutions with a DI water feed were, respectively, 33.4more » and 35.6 L m(-2) h(-1) in PRO mode and 14.5 and 152 L m(-2) h(-1) in FO mode. Reverse draw permeation of TMA-CO2 was relatively low compared to NH3-CO2, ranging from 0.1 to 0.2 mol m(-2) h(-1) in all experiments, due to the larger molecular size of TMA. Thermal separation and recovery efficiency for TMA-CO2 was compared to NH3-CO2 by modeling low-temperature vacuum distillation utilizing low-grade heat sources. We also discuss possible challenges in the use TMA-CO2, including potential adverse impact on human health and environments. (C) 2014 Elsevier B.V. All rights reserved.« less

  4. Carbon isotope composition of low molecular weight hydrocarbons and monocarboxylic acids from Murchison meteorite

    NASA Technical Reports Server (NTRS)

    Yuen, G.; Blair, N.; Des Marais, D. J.; Chang, S.

    1984-01-01

    Carbon isotopic compositions have been measured for individual hydrocarbons and monocarboxylic acids from the Murchison meteorite, a C2 carbonaceous chondrite which fell in Australia in 1969. With few exceptions, notably benzene, the volatile products are substantially isotopically heavier than their terrestrial counterparts, signifying their extraterrestrial origin. For both classes of compounds, the ratio of C-13 to C-12 decreases with increasing carbon number in a roughly parallel manner, and each carboxylic acid exhibits a higher isotopic ratio than the hydrocarbon containing the same number of carbon atoms. These trends are consistent with the kinetically controlled synthesis of higher homologues from lower ones. The results suggest the possibility that the production mechanisms for hydrocarbons and carboxylic acids may be similar, and impose constraints on the identity of the reactant species.

  5. Extracorporeal Carbon Dioxide Removal Enhanced by Lactic Acid Infusion in Spontaneously Breathing Conscious Sheep.

    PubMed

    Scaravilli, Vittorio; Kreyer, Stefan; Belenkiy, Slava; Linden, Katharina; Zanella, Alberto; Li, Yansong; Dubick, Michael A; Cancio, Leopoldo C; Pesenti, Antonio; Batchinsky, Andriy I

    2016-03-01

    The authors studied the effects on membrane lung carbon dioxide extraction (VCO2ML), spontaneous ventilation, and energy expenditure (EE) of an innovative extracorporeal carbon dioxide removal (ECCO2R) technique enhanced by acidification (acid load carbon dioxide removal [ALCO2R]) via lactic acid. Six spontaneously breathing healthy ewes were connected to an extracorporeal circuit with blood flow 250 ml/min and gas flow 10 l/min. Sheep underwent two randomly ordered experimental sequences, each consisting of two 12-h alternating phases of ALCO2R and ECCO2R. During ALCO2R, lactic acid (1.5 mEq/min) was infused before the membrane lung. Caloric intake was not controlled, and animals were freely fed. VCO2ML, natural lung carbon dioxide extraction, total carbon dioxide production, and minute ventilation were recorded. Oxygen consumption and EE were calculated. ALCO2R enhanced VCO2ML by 48% relative to ECCO2R (55.3 ± 3.1 vs. 37.2 ± 3.2 ml/min; P less than 0.001). During ALCO2R, minute ventilation and natural lung carbon dioxide extraction were not affected (7.88 ± 2.00 vs. 7.51 ± 1.89 l/min, P = 0.146; 167.9 ± 41.6 vs. 159.6 ± 51.8 ml/min, P = 0.063), whereas total carbon dioxide production, oxygen consumption, and EE rose by 12% each (223.53 ± 42.68 vs. 196.64 ± 50.92 ml/min, 215.3 ± 96.9 vs. 189.1 ± 89.0 ml/min, 67.5 ± 24.0 vs. 60.3 ± 20.1 kcal/h; P less than 0.001). ALCO2R was effective in enhancing VCO2ML. However, lactic acid caused a rise in EE that made ALCO2R no different from standard ECCO2R with respect to ventilation. The authors suggest coupling lactic acid-enhanced ALCO2R with active measures to control metabolism.

  6. Portable electrochemical sensor based on 4-aminobenzoic acid-functionalized herringbone carbon nanotubes for the determination of ascorbic acid and uric acid in human fluids.

    PubMed

    Abellán-Llobregat, A; González-Gaitán, C; Vidal, L; Canals, A; Morallón, E

    2018-06-30

    A new portable electrochemical sensor based on 4-aminobenzoic acid-modified herringbone carbon nanotubes (hCNTs-4ABA/Au-IDA) has been developed for the simultaneous determination of ascorbic acid (AA) and uric acid (UA) in physiological fluids. AA and UA were quantified by chronoamperometry at 0.1 and 0.32 V, respectively, in phosphate buffer solution (PBS 0.25 M, pH 7.0). Significant results were obtained for the separate quantification of AA and UA, with a limit of detection (LOD) of 0.65 μM for both analytes, and sensitivities of (9.0 ± 0.4) A g -1 mM -1 and (8.8 ± 0.3) A g -1 mM -1 for AA and UA, respectively. Repeatability was studied at 50 μM for AA and UA, providing relative standard deviations (RSD) lower than 9%. Additions of glucose, dopamine and epinephrine did not interfere with the AA and UA determination. Furthermore, UA did not interfere with AA determination at 0.1 V, although AA additions increased the current recorded at 0.32 V. The method has been successfully applied to human urine, perspiration and serum samples, without significant matrix effects, which allows for the use of an external calibration and the analysis of all the matrices investigated. Copyright © 2018 Elsevier B.V. All rights reserved.

  7. Formic Acid Formation by Clostridium ljungdahlii at Elevated Pressures of Carbon Dioxide and Hydrogen

    PubMed Central

    Oswald, Florian; Stoll, I. Katharina; Zwick, Michaela; Herbig, Sophia; Sauer, Jörg; Boukis, Nikolaos; Neumann, Anke

    2018-01-01

    Low productivities of bioprocesses using gaseous carbon and energy sources are usually caused by the low solubility of those gases (e.g., H2 and CO). It has been suggested that increasing the partial pressure of those gases will result in higher dissolved concentrations and should, therefore, be helpful to overcome this obstacle. Investigations of the late 1980s with mixtures of hydrogen and carbon monoxide showed inhibitory effects of carbon monoxide partial pressures above 0.8 bar. Avoiding any effects of carbon monoxide, we investigate growth and product formation of Clostridium ljungdahlii at absolute process pressures of 1, 4, and 7 bar in batch stirred tank reactor cultivations with carbon dioxide and hydrogen as sole gaseous carbon and energy source. With increasing process pressure, the product spectrum shifts from mainly acetic acid and ethanol to almost only formic acid at a total system pressure of 7 bar. On the other hand, no significant changes in overall product yield can be observed. By keeping the amount of substance flow rate constant instead of the volumetric gas feed rate when increasing the process pressure, we increased the overall product yield of 7.5 times of what has been previously reported in the literature. After 90 h of cultivation at a total pressure of 7 bar a total of 4 g L−1 of products is produced consisting of 82.7 % formic acid, 15.6 % acetic acid, and 1.7 % ethanol. PMID:29484294

  8. Non-catalytic hydrogenation of VO2 in acid solution.

    PubMed

    Chen, Yuliang; Wang, Zhaowu; Chen, Shi; Ren, Hui; Wang, Liangxin; Zhang, Guobin; Lu, Yalin; Jiang, Jun; Zou, Chongwen; Luo, Yi

    2018-02-26

    Hydrogenation is an effective way to tune the property of metal oxides. It can conventionally be performed by doping hydrogen into solid materials with noble-metal catalysis, high-temperature/pressure annealing treatment, or high-energy proton implantation in vacuum condition. Acid solution naturally provides a rich proton source, but it should cause corrosion rather than hydrogenation to metal oxides. Here we report a facile approach to hydrogenate monoclinic vanadium dioxide (VO 2 ) in acid solution at ambient condition by placing a small piece of low workfunction metal (Al, Cu, Ag, Zn, or Fe) on VO 2 surface. It is found that the attachment of a tiny metal particle (~1.0 mm) can lead to the complete hydrogenation of an entire wafer-size VO 2 (>2 inch). Moreover, with the right choice of the metal a two-step insulator-metal-insulator phase modulation can even be achieved. An electron-proton co-doping mechanism has been proposed and verified by the first-principles calculations.

  9. Nanofiltration and granular activated carbon treatment of perfluoroalkyl acids.

    PubMed

    Appleman, Timothy D; Dickenson, Eric R V; Bellona, Christopher; Higgins, Christopher P

    2013-09-15

    Perfluoroalkyl acids (PFAAs) are of concern because of their persistence in the environment and the potential toxicological effects on humans exposed to PFAAs through a variety of possible exposure routes, including contaminated drinking water. This study evaluated the efficacy of nanofiltration (NF) and granular activated carbon (GAC) adsorption in removing a suite of PFAAs from water. Virgin flat-sheet NF membranes (NF270, Dow/Filmtec) were tested at permeate fluxes of 17-75 Lm(-2)h(-1) using deionized (DI) water and artificial groundwater. The effects of membrane fouling by humic acid on PFAA rejection were also tested under constant permeate flux conditions. Both virgin and fouled NF270 membranes demonstrated >93% removal for all PFAAs under all conditions tested. GAC efficacy was tested using rapid small-scale columns packed with Calgon Filtrasorb300 (F300) carbon and DI water with and without dissolved organic matter (DOM). DOM effects were also evaluated with F600 and Siemens AquaCarb1240C. The F300 GAC had <20% breakthrough of all PFAAs in DI water for up to 125,000 bed volumes (BVs). When DOM was present, >20% breakthrough of all PFAAs by 10,000 BVs was observed for all carbons. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. Titanium Implant Osseointegration Problems with Alternate Solutions Using Epoxy/Carbon-Fiber-Reinforced Composite

    PubMed Central

    Petersen, Richard C.

    2014-01-01

    The aim of the article is to present recent developments in material research with bisphenyl-polymer/carbon-fiber-reinforced composite that have produced highly influential results toward improving upon current titanium bone implant clinical osseointegration success. Titanium is now the standard intra-oral tooth root/bone implant material with biocompatible interface relationships that confer potential osseointegration. Titanium produces a TiO2 oxide surface layer reactively that can provide chemical bonding through various electron interactions as a possible explanation for biocompatibility. Nevertheless, titanium alloy implants produce corrosion particles and fail by mechanisms generally related to surface interaction on bone to promote an inflammation with fibrous aseptic loosening or infection that can require implant removal. Further, lowered oxygen concentrations from poor vasculature at a foreign metal surface interface promote a build-up of host-cell-related electrons as free radicals and proton acid that can encourage infection and inflammation to greatly influence implant failure. To provide improved osseointegration many different coating processes and alternate polymer matrix composite (PMC) solutions have been considered that supply new designing potential to possibly overcome problems with titanium bone implants. Now for important consideration, PMCs have decisive biofunctional fabrication possibilities while maintaining mechanical properties from addition of high-strengthening varied fiber-reinforcement and complex fillers/additives to include hydroxyapatite or antimicrobial incorporation through thermoset polymers that cure at low temperatures. Topics/issues reviewed in this manuscript include titanium corrosion, implant infection, coatings and the new epoxy/carbon-fiber implant results discussing osseointegration with biocompatibility related to nonpolar molecular attractions with secondary bonding, carbon fiber in vivo properties, electrical

  11. Corrosion property of 9Cr-ODS steel in nitric acid solution for spent nuclear fuel reprocessing

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Takeuchi, M.; Koizumi, T.; Inoue, M.

    2013-07-01

    Corrosion tests of oxide dispersion strengthened with 9% Cr (9Cr-ODS) steel, which is one of the desirable materials for cladding tube of sodium-cooled fast reactors, in pure nitric acid solution, spent FBR fuel solution, and its simulated solution were performed to understand the corrosion behavior in a spent nuclear fuel reprocessing. In this study, the 9Cr-ODS steel with lower effective chromium content was evaluated to understand the corrosion behavior conservatively. As results, the tube-type specimens of the 9Cr-ODS steels suffered severe weight loss owing to active dissolution at the beginning of the immersion test in pure nitric acid solution inmore » the range from 1 to 3.5 M. In contrast, the weight loss was decreased and they showed a stable corrosion in the higher nitric acid concentration, the dissolved FBR fuel solution, and its simulated solution by passivation. The corrosion rates of the 9Cr-ODS steel in the dissolved FBR fuel solution and its simulated solution were 1-2 mm/y and showed good agreement with each other. The passivation was caused by the shift of corrosion potential to noble side owing to increase in nitric acid concentration or oxidative ions in the dissolved FBR fuel solution and the simulated spent fuel solution. (authors)« less

  12. Fabrication of carbon nanowires by pyrolysis of aqueous solution of sugar within asbestos nanofibers

    NASA Astrophysics Data System (ADS)

    Butko, V. Yu.; Fokin, A. V.; Nevedomskii, V. N.; Kumzerov, Yu. A.

    2015-05-01

    Carbon nanowires have been fabricated by pyrolysis of an aqueous solution of sugar in nanochannels of asbestos fibers. Electron microscopy demonstrates that the diameter of these nanochannels corresponds to the diameter of the thinnest of the carbon nanowires obtained. Some of these nanowires have a graphite crystal lattice and internal pores. After asbestos is etched out, the carbon nanowires can retain the original shape of the asbestos fibers. Heating in an inert atmosphere reduces the electrical resistivity of the carbon nanowires to ˜0.035 Ω cm.

  13. 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.)

  14. High-speed logic integrated circuits with solution-processed self-assembled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Han, Shu-Jen; Tang, Jianshi; Kumar, Bharat; Falk, Abram; Farmer, Damon; Tulevski, George; Jenkins, Keith; Afzali, Ali; Oida, Satoshi; Ott, John; Hannon, James; Haensch, Wilfried

    2017-09-01

    As conventional monolithic silicon technology struggles to meet the requirements for the 7-nm technology node, there has been tremendous progress in demonstrating the scalability of carbon nanotube field-effect transistors down to the size that satisfies the 3-nm node and beyond. However, to date, circuits built with carbon nanotubes have overlooked key aspects of a practical logic technology and have stalled at simple functionality demonstrations. Here, we report high-performance complementary carbon nanotube ring oscillators using fully manufacturable processes, with a stage switching frequency of 2.82 GHz. The circuit was built on solution-processed, self-assembled carbon nanotube arrays with over 99.9% semiconducting purity, and the complementary feature was achieved by employing two different work function electrodes.

  15. High-speed logic integrated circuits with solution-processed self-assembled carbon nanotubes.

    PubMed

    Han, Shu-Jen; Tang, Jianshi; Kumar, Bharat; Falk, Abram; Farmer, Damon; Tulevski, George; Jenkins, Keith; Afzali, Ali; Oida, Satoshi; Ott, John; Hannon, James; Haensch, Wilfried

    2017-09-01

    As conventional monolithic silicon technology struggles to meet the requirements for the 7-nm technology node, there has been tremendous progress in demonstrating the scalability of carbon nanotube field-effect transistors down to the size that satisfies the 3-nm node and beyond. However, to date, circuits built with carbon nanotubes have overlooked key aspects of a practical logic technology and have stalled at simple functionality demonstrations. Here, we report high-performance complementary carbon nanotube ring oscillators using fully manufacturable processes, with a stage switching frequency of 2.82 GHz. The circuit was built on solution-processed, self-assembled carbon nanotube arrays with over 99.9% semiconducting purity, and the complementary feature was achieved by employing two different work function electrodes.

  16. THE KINETICS OF SAPONIFICATION OF IODOACETIC ACID BY SODIUM HYDROXIDE AND BY CERTAIN ALKALINE BUFFER SOLUTIONS.

    PubMed

    Brdicka, R

    1936-07-20

    1. The rate of the saponification of iodoacetic acid in sodium hydroxide and alkaline buffer solutions yielding glycollic acid was measured by means of Heyrovský's polarographic method. 2. From the bimolecular velocity constants, increasing with the ionic strength of the solution, the Brönsted factor, F, which characterizes the primary salt effect, was calculated. 3. In the borate buffer solutions the monomolecular constants of the saponification were determined which, at values above the pH of neutralization of boric acid, show a proportionality to the concentration of hydroxyl anions. Below the pH of neutralization of boric acid, they are proportional to the concentration of borate anions.

  17. Concentration-Discharge Relationships, Nested Reaction Fronts, and the Balance of Oxidative and Acid-Base Weathering Fluxes in an Alpine Catchment, East River, Colorado

    NASA Astrophysics Data System (ADS)

    Winnick, M.; Carroll, R. W. H.; Williams, K. H.; Maxwell, R. M.; Maher, K.

    2016-12-01

    Although important for solute production and transport, the varied interactions between biogeochemical processes and subsurface hydrology remain poorly characterized. We investigate these couplings in the headwaters of the East River, CO, a high-elevation shale-dominated catchment system in the Rocky Mountains, using concentration-discharge (C-Q) relationships for major cations, anions, and organic carbon. Dissolved organic carbon (DOC) displays a positive C-Q relationship with well-defined clockwise hysteresis, indicating the mobilization and depletion of DOC in the upper soil horizons and highlighting the importance of shallow flowpaths through the snowmelt period. Cation and anion concentrations demonstrate that carbonate weathering, which dominates solute fluxes, is promoted by both carbonic acid and sulfuric acid derived from oxidation of pyrite in the shale bedrock. Sulfuric acid weathering in the deep subsurface dominates during base flow conditions when waters have infiltrated below the hypothesized pyrite oxidation front, whereas carbonic acid weathering plays a dominant role during the snowmelt period as a result of shallow flowpaths. Differential C-Q relationships between solutes suggest that infiltrating waters approach calcite saturation before reaching the pyrite oxidation front, after which sulfuric acid reduces carbonate alkalinity. This increase in CO2(aq) at the expense of HCO3- results in outgassing of CO2 when waters equilibrate to surface conditions, and reduces the export of carbon and alkalinity from the East River by roughly 33% annually. Future changes in snowmelt dynamics that control the balance of carbonic and sulfuric acid weathering therefore have the capacity to substantially alter the cycling of carbon in the East River catchment. Ultimately, we demonstrate that differential C-Q relationships between major solutes can provide unique insights into the complex subsurface flow and biogeochemical dynamics that operate at catchment scales.

  18. The effect of organic acids on wettability of sandstone and carbonate rocks

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mwangi, Paulina; Brady, Patrick V.; Radonjic, Mileva

    This paper examines the role of crude oil’s organic acid surface active compounds (SAC) in determining the reservoir wettability over a range of salinities and temperatures. To isolate the effects of individual SACs, this project used model oil mixtures of pure decane and single SACs to represent the oleic phase. Due to the large number of experiments in this study, we used wettability measurement method by the modified flotation technique (MFT) to produce fast, reliable, and quantitative results. The results showed that oil wetting by decane increased with temperature for carbonate rocks. Sandstones oil wetting showed little temperature dependency. Themore » presence of long-chained acids in decane increased oil wetting in sandstone and carbonate rocks as salinity was lowered, while the short-chained acid increased water wetting under the same conditions. The effect of organic acids on wettability was slightly enhanced with increasing temperature for all rock types.« less

  19. The effect of organic acids on wettability of sandstone and carbonate rocks

    DOE PAGES

    Mwangi, Paulina; Brady, Patrick V.; Radonjic, Mileva; ...

    2018-02-21

    This paper examines the role of crude oil’s organic acid surface active compounds (SAC) in determining the reservoir wettability over a range of salinities and temperatures. To isolate the effects of individual SACs, this project used model oil mixtures of pure decane and single SACs to represent the oleic phase. Due to the large number of experiments in this study, we used wettability measurement method by the modified flotation technique (MFT) to produce fast, reliable, and quantitative results. The results showed that oil wetting by decane increased with temperature for carbonate rocks. Sandstones oil wetting showed little temperature dependency. Themore » presence of long-chained acids in decane increased oil wetting in sandstone and carbonate rocks as salinity was lowered, while the short-chained acid increased water wetting under the same conditions. The effect of organic acids on wettability was slightly enhanced with increasing temperature for all rock types.« less

  20. Application of Lactobacillus immobilized by Activated Carbon Fiber in Fermentation of Lactic Acid in Starch Wastewater

    NASA Astrophysics Data System (ADS)

    Xu, Wei; Wang, Peng; Chi, Guoda; Huang, Chenyong

    2010-11-01

    Activated carbon fibers (ACF) as the carrier of Lactobacillus was introduced into fermenting system, and a method of modifying the surface of ACF by HNO3-Fe (III) was established. Factors that affect ACF carrier's effect on immobilization of Lactobacillus were studied. HCl, H2SO4, HNO3 and FeCl3 solutions were respectively used to modify the surface properties of ACF. The amount of Fe (III) carried on ACF surface was 0.1563 mol/kg after ACF surface was modified by HNO3 for 5 h and then by 0.1 mol/L FeCl3 for 4 h, when the thickness of Lactobacillus on a single silk of carrier reached 40 μm. When ACF modified by HNO3-Fe (III) was applied in the fermentation of lactic acid in starch industry wastewater, the fermentation period reduced by 8 h and the output of L-lactic acid was 65.5 g/L, which was 3.3% more than that fermented without the carrier.

  1. Quenching characteristics of bathocuproinedisulfonic acid, disodium salt in aqueous solution and copper sulfate plating solution

    NASA Astrophysics Data System (ADS)

    Koga, Toshiaki; Hirakawa, Chieko; Takeshita, Michinori; Terasaki, Nao

    2018-04-01

    Bathocuproinedisulfonic acid, disodium salt (BCS) is generally used to detect Cu(I) through a color reaction. We newly found BCS fluorescence in the visible blue region in an aqueous solution. However, the fluorescence mechanism of BCS is not well known, so we should investigate its fundamental information. We confirmed that the characteristics of fluorescence are highly dependent on the molecular concentration and solvent properties. In particular, owing to the presence of the copper compound, the fluorescence intensity extremely decreases. By fluorescence quenching, we observed that a copper compound concentration of 10-6 mol/L or less could easily be measured in an aqueous solution. We also observed BCS fluorescence in copper sulfate plating solution and the possibility of detecting monovalent copper by fluorescence reabsorption.

  2. Carbon Source-Dependent Inducible Metabolism of Veratryl Alcohol and Ferulic Acid in Pseudomonas putida CSV86

    PubMed Central

    Mohan, Karishma

    2017-01-01

    ABSTRACT Pseudomonas putida CSV86 degrades lignin-derived metabolic intermediates, viz., veratryl alcohol, ferulic acid, vanillin, and vanillic acid, as the sole sources of carbon and energy. Strain CSV86 also degraded lignin sulfonate. Cell respiration, enzyme activity, biotransformation, and high-pressure liquid chromatography (HPLC) analyses suggest that veratryl alcohol and ferulic acid are metabolized to vanillic acid by two distinct carbon source-dependent inducible pathways. Vanillic acid was further metabolized to protocatechuic acid and entered the central carbon pathway via the β-ketoadipate route after ortho ring cleavage. Genes encoding putative enzymes involved in the degradation were found to be present at fer, ver, and van loci. The transcriptional analysis suggests a carbon source-dependent cotranscription of these loci, substantiating the metabolic studies. Biochemical and quantitative real-time (qRT)-PCR studies revealed the presence of two distinct O-demethylases, viz., VerAB and VanAB, involved in the oxidative demethylation of veratric acid and vanillic acid, respectively. This report describes the various steps involved in metabolizing lignin-derived aromatic compounds at the biochemical level and identifies the genes involved in degrading veratric acid and the arrangement of phenylpropanoid metabolic genes as three distinct inducible transcription units/operons. This study provides insight into the bacterial degradation of lignin-derived aromatics and the potential of P. putida CSV86 as a suitable candidate for producing valuable products. IMPORTANCE Pseudomonas putida CSV86 metabolizes lignin and its metabolic intermediates as a carbon source. Strain CSV86 displays a unique property of preferential utilization of aromatics, including for phenylpropanoids over glucose. This report unravels veratryl alcohol metabolism and genes encoding veratric acid O-demethylase, hitherto unknown in pseudomonads, thereby providing new insight into the

  3. Time dependent inhibition of xanthine oxidase in irradiated solutions of folic acid, aminopterin and methotrexate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Robinson, K.; Pilot, T.F.; Meany, J.E.

    1990-01-01

    The xanthine oxidase catalyzed oxidation of hypoxanthine was followed by monitoring the formation of uric acid at 290 nm. Inhibition of xanthine oxidase occurs in aqueous solutions of folic acid methotrexate and aminopterin. These compounds are known to dissociate upon exposure to ultraviolet light resulting in the formation of their respective 6-formylpteridine derivatives. The relative rates of dissociation were monitored spectrophotometrically by determining the absorbance of their 2,4-dinitrophenylhydrazine derivatives at 500 nm. When aqueous solutions of folic acid, aminopterin and methotrexate were exposed to uv light, a direct correlation was observed between the concentrations of the 6-formylpteridine derivatives existing inmore » solution and the ability of these solutions to inhibit xanthine oxidase. The relative potency of the respective photolysis products were estimated.« less

  4. Characterization of D-glucaric acid using NMR, x-ray crystal structure, and MM3 molecular modeling analyses

    USDA-ARS?s Scientific Manuscript database

    D-glucaric acid was characterized in solution by comparing NMR spectra from the isotopically unlabeled molecule with those from D-glucaric acid labeled with deuterium or carbon-13 atoms. The NMR studies provided unequivocal assignments for all carbon atoms and non-hydroxyl protons of the molecule. ...

  5. Tunable hole injection of solution-processed polymeric carbon nitride towards efficient organic light-emitting diode

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaowen; Zheng, Qinghong; Tang, Zhenyu; Li, Wanshu; Zhang, Yan; Xu, Kai; Xue, Xiaogang; Xu, Jiwen; Wang, Hua; Wei, Bin

    2018-02-01

    Polymeric carbon nitride (CNxHy) has been facilely synthesized from dicyandiamide and functions as a solution-processed hole injection layer in organic light-emitting diodes (OLEDs). The measurements using X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and impedance spectroscopy elucidate that CNxHy exhibits superior film morphology and extra electric properties such as tailored work function and tunable hole injection. The luminous efficiency of CNxHy-based OLED is found to improve by 76.6% in comparison to the counterpart using favorite solution-processed poly(ethylene dioxythiophene):poly(styrene sulfonate) as the hole injection layer. Our results also pave a way for broadening carbon nitride applications in organic electronics using the solution process.

  6. Seasonal variations, molecular distributions, and stable carbon isotopic compositions of dicarboxylic acids, ketocarboxylic acids, and α-dicarbonyls in PM2.5 from Beijing, China

    NASA Astrophysics Data System (ADS)

    Zhao, W.; Kawamura, K.; Fu, P.

    2016-12-01

    Low molecular weight (LMW) dicarboxylic acids and related polar compounds comprise a significant fraction of atmospheric aerosols. Seasonal variations, molecular distributions, and stable carbon isotopic compositions of dicarboxylic acids, ketocarboxylic acids, and α-dicarbonyls, as well as organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC) and inorganic ionic species, were determined to better understand the sources and photochemical aging processes of carbonaceous aerosols in urban Beijing from Sept. 2013 to Jul. 2014 (n=65). Concentrations of total diacids ranged from 110-2580 ng m-3, while ketoacids (9.5-353 ng m-3) and dicarbonyls (1.5-85.9 ng m-3) were less abundant. Higher ambient concentrations of phthalic (Ph) (37.9±27.3 ng m-3), terephthalic (tPh) (48.7±51.1 ng m-3), and glyoxylic (ωC2) (44.3±69 ng m-3) acids were found in winter than other seasons. The temporal variations of malonic acid to succinic acid (C3/C4) ratios were relatively low throughout the whole year, most of which were less than or equal to unity, even in summer, implying more contributions of dicarboxylic acids from primary emissions, rather than aging processes during long-range atmospheric transport. The δ13C mean values of malonic acid (-18.7% to -17.3%) and succinic acid (-28.6% to -17.1%) were larger than those of oxalic acid (-22.9% to -20.1%) in both seasons, except for δ13C of succinic acid in summer. Lower δ13C values of these compounds in Beijing than those in marine areas may be mainly associated with primary emissions, such as biomass burning, vehicular exhaust, incomplete fossil fuel combustion and plastic wastes.

  7. Direct sensing of fluoride in aqueous solutions using a boronic acid based sensor.

    PubMed

    Wu, Xin; Chen, Xuan-Xuan; Song, Bing-Nan; Huang, Yan-Jun; Ouyang, Wen-Juan; Li, Zhao; James, Tony D; Jiang, Yun-Bao

    2014-11-21

    Binding of the fluoride ion triggers aggregation of a pyreneboronic acid-catechol ensemble in acidic aqueous solutions, giving rise to intense excimer emission, allowing for sensitive fluoride ion sensing at ppm levels, with an apparent fluoride binding constant higher than 10(3) M(-1) which is unprecedented for boronic acid sensors in water.

  8. Ethylbenzene Removal by Carbon Nanotubes from Aqueous Solution

    PubMed Central

    Bina, Bijan; Pourzamani, Hamidreza; Rashidi, Alimorad; Amin, Mohammad Mehdi

    2012-01-01

    The removal of ethylbenzene (E) from aqueous solution by multiwalled, single-walled, and hybrid carbon nanotubes (MWCNTs, SWCNTs, and HCNTs) was evaluated for a nanomaterial dose of 1 g/L, concentration of 10–100 mg/L, and pH 7. The equilibrium amount removed by SWCNTs (E: 9.98 mg/g) was higher than by MWCNTs and HCNTs. Ethylbenzene has a higher adsorption tendency on CNTs, so that more than 98% of it adsorbed in first 14 min, which is related to the low water solubility and the high molecular weight. The SWCNTs performed better for ethylbenzene sorption than the HCNTs and MWCNTs. Isotherms study indicates that the BET isotherm expression provides the best fit for ethylbenzene sorption by SWCNTs. Carbon nanotubes, specially SWCNTs, are efficient and rapid adsorbents for ethylbenzene which possess good potential applications to maintain high-quality water. Therefore, it could be used for cleaning up environmental pollution to prevent ethylbenzene borne diseases. PMID:22187576

  9. On the location of acid-hydrolysable carbon in lunar soil fines

    NASA Technical Reports Server (NTRS)

    Fallick, A. E.; Wright, I. P.; Pillinger, C. T.; Stephenson, A.; Morris, R. V.

    1982-01-01

    Soil fines exposed on the lunar surface accumulate small metallic iron particles and solar wind-derived carbon. In previous work, it has been suggested that an intimate association exists between one particular carbon phase, hydrolysable carbon, and very fine iron droplets, where the carbon is in solid solution in the iron. The earlier hypothesis of a constant carbon in iron concentration across a broad range of droplet sizes is testable by combining hydrolysable carbon determinations with a variety of magnetic measurements sensitive to different droplet diameters. New measurements of ferromagnetic resonance response on density and magnetic separates from size fractions of soil 12023 are interpreted as evidence that hydrolysable carbon is preferentially associated with the larger, magnetically stable single-domain iron particles rather than with the smaller superparamagnetic droplets. For the former, there is a quite uniform ratio of iron to carbon both within a series of separates from a single soil, and among soils of widely varying FeO content.

  10. Acid neutralizing capacity and leachate results for igneous rocks, with associated carbon contents of derived soils, Animas River AML site, Silverton, Colorado

    USGS Publications Warehouse

    Yager, Douglas B.; Stanton, Mark R.; Choate, LaDonna M.; Burchell,

    2009-01-01

    solution from mine waste used in the kinetic reaction vessel test. This finding suggests that mine waste and not ANC rock may generate the majority of leachable metals in a field scenario.
    The organic carbon content of naturally reclaimed soils derived from weathering of propylitically-altered andesite was determined in catchments where ANC studies were initiated. Soils were found to have total carbon concentrations (TOC) that exceed global average soil TOC abundances by as much as 1.5 – 5 times. These data support an environmental management system involving use of ANC rocks as part of life-cycle mine planning to reduce post-mine closure acid mitigation measures. Carbon contents of undisturbed soils in mined catchments can possibly be used to validate post-reclamation success and help quantify carbon sequestration for CO2 emission offset trading as carbon markets mature.

  11. THE KINETICS OF SAPONIFICATION OF IODOACETIC ACID BY SODIUM HYDROXIDE AND BY CERTAIN ALKALINE BUFFER SOLUTIONS

    PubMed Central

    Brdička, R.

    1936-01-01

    1. The rate of the saponification of iodoacetic acid in sodium hydroxide and alkaline buffer solutions yielding glycollic acid was measured by means of Heyrovský's polarographic method. 2. From the bimolecular velocity constants, increasing with the ionic strength of the solution, the Brönsted factor, F, which characterizes the primary salt effect, was calculated. 3. In the borate buffer solutions the monomolecular constants of the saponification were determined which, at values above the pH of neutralization of boric acid, show a proportionality to the concentration of hydroxyl anions. Below the pH of neutralization of boric acid, they are proportional to the concentration of borate anions. PMID:19872968

  12. 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.

  13. Changes in properties of polyacid-modified composite resins (compomers) following storage in acidic solutions.

    PubMed

    Nicholson, J W; Gjorgievska, E; Bajraktarova, B; McKenzie, M A

    2003-06-01

    The interaction of three polyacid-modified composite resins (compomers) with various acidic storage solutions, and also water, over periods of time up to 6 months has been studied and compared with those of a glass-ionomer and a composite resin. This interaction has been shown to vary in a complex way with length of storage and nature of the acid, and citric acid was found to be the most aggressive storage medium for glass-ionomer cement, and also for the compomers. The pure composite resin, by contrast, was relatively unaffected by all of the acid solutions examined. In all acids, the compomers showed a distinct buffering effect, i.e. they increased the pH towards neutral, as did the glass-ionomer. The extent of this also varied with duration of storage and nature of the acid. The biaxial flexure strength was determined and found to be essentially unaffected by the complex chemical interactions with acidic storage solutions. Values obtained for the compomers were lower than those of the composite resin, but above those of the glass-ionomer. Fourier-transform infrared (FT-IR) spectroscopy was employed to study the changes in the compomers following storage in the aqueous media, but bands were broad and no detailed assignments could be made. There were changes in the region of the spectra associated with metal carboxylates however, and this indicates that the secondary acid-base reaction had occurred following water uptake.

  14. The thermochemical characteristics of solution of phenol and benzoic acid in water-dimethylsulfoxide and water-acetonitrile mixtures

    NASA Astrophysics Data System (ADS)

    Zakharov, A. G.; Voronova, M. I.; Batov, D. V.; Smirnova, K. V.

    2011-03-01

    The solution of phenol and benzoic acid in water-dimethylsulfoxide (DMSO) and water-acetonitrile (AN) mixtures was studied. As distinct from benzoic acid, the thermodynamic characteristics of solution of phenol sharply change at concentrations corresponding to a change in the character of cluster formation in water-DMSO and water-AN mixtures. Differences in the solvation of phenol and benzoic acid are explained by different mechanisms of the interaction of the solutes with clusters existing in binary mixtures.

  15. Formation of amino acids by cobalt-60 irradiation of hydrogen cyanide solutions

    NASA Technical Reports Server (NTRS)

    Sweeney, M. A.; Toste, A. P.; Ponnamperuma, C.

    1976-01-01

    Experiments were conducted to study the pathway for the prebiotic origin of amino acids from hydrogen cyanide (HCN) under the action of ionizing radiation considered as an effective source of energy on the primitive earth. The irradiations were performed in a cobalt-60 source with a dose rate of 200,000 rad/hr. Seven naturally occurring amino acids are identified among the products formed by the hydrolysis of gamma-irradiated solutions of HCN: glycine, alanine, valine, serine, threonine, aspartic acid, and glutamic acid. The identity of these amino acids is established by gas chromatography and mass spectrometry. Control experiments provided evidence that the amino acids are not the result of contamination.

  16. Study of stability of methotrexate in acidic solution spectrofluorimetric determination of methotrexate in pharmaceutical preparations through acid-catalyzed degradation reaction.

    PubMed

    Sabry, Suzy M; Abdel-Hady, M; Elsayed, M; Fahmy, Osama T; Maher, Hadir M

    2003-07-14

    Study of the degradation reaction of methotrexate (MTX) in acidic solution was carried out. Optimization of the experimental parameters of MTX acid hydrolysis was investigated. Spectrofluorimetric method for determination of MTX through measurement of its acid-degradation product, 4-amino-4-deoxy-10-methylpteroic acid (AMP), was developed. Stability of the standard solution of MTX prepared in sulfuric acid was discussed in the view of accelerated stability analysis. Two other comparative spectroflourimetric methods based on measuring the fluorescence intensities from either a condensation reaction with acetylacetone-formaldehyde (Hantzsch reaction) or a reaction with fluorescamine were also described. Beer's law validation, accuracy, precision, limits of detection, limits of quantification, and other aspects of analytical merit are presented in the text. The proposed methods were successfully applied for the analysis of MTX in pure drug and tablets dosage form. The sensitivity of the developed methods was favorable, so it was possible to be adopted for determination of MTX in plasma samples for routine use in high-dose MTX therapy.

  17. Roles of sulfuric acid in elemental mercury removal by activated carbon and sulfur-impregnated activated carbon.

    PubMed

    Morris, Eric A; Kirk, Donald W; Jia, Charles Q; Morita, Kazuki

    2012-07-17

    This work addresses the discrepancy in the literature regarding the effects of sulfuric acid (H(2)SO(4)) on elemental Hg uptake by activated carbon (AC). H(2)SO(4) in AC substantially increased Hg uptake by absorption particularly in the presence of oxygen. Hg uptake increased with acid amount and temperature exceeding 500 mg-Hg/g-AC after 3 days at 200 °C with AC treated with 20% H(2)SO(4). In the absence of other strong oxidizers, oxygen was able to oxidize Hg. Upon oxidation, Hg was more readily soluble in the acid, greatly enhancing its uptake by acid-treated AC. Without O(2), S(VI) in H(2)SO(4) was able to oxidize Hg, thus making it soluble in H(2)SO(4). Consequently, the presence of a bulk H(2)SO(4) phase within AC pores resulted in an orders of magnitude increase in Hg uptake capacity. However, the bulk H(2)SO(4) phase lowered the AC pore volume and could block the access to the active surface sites and potentially hinder Hg uptake kinetics. AC treated with SO(2) at 700 °C exhibited a much faster rate of Hg uptake attributed to sulfur functional groups enhancing adsorption kinetics. SO(2)-treated carbon maintained its fast uptake kinetics even after impregnation by 20% H(2)SO(4).

  18. Reductive dehalogenation of hexachloroethane, carbon tetrachloride, and bromoform by anthrahydroquinone disulfonate and humic acid

    USGS Publications Warehouse

    Curtis, G.P.; Reinhard, M.

    1994-01-01

    The reductive dehalogenation of hexachloroethane (C2Cl6), carbon tetrachloride (CCl4), and bromoform (CHBr3) was examined at 50??C in aqueous solutions containing either (1) 500 ??M of 2,6-anthrahydroquinone disulfonate (AHQDS), (2) 250 ??M Fe2+, or (3) 250 ??M HS-. The pH ranged from 4.5 to 11.5 for AHQDS solutions and was 7.2 in the Fe2+ solutions and 7.8 in the HS- solutions. The observed disappearance of C2Cl6 in the presence of AHQDS was pseudo-first-order and fit k??ccl4 = k0[A(OH)2] + k1[A(OH)O-] + k2[A(O)22-] where A(OH)2, A(OH)O-, and A(O)22- represent the concentrations of the three forms of the AHQDS in solution. The values of k0, k1, and k2 were ???0,0.031, and 0.24 M-1 s-1, respectively. The addition of 25 mg of C/L of humic acid or organic matter extracted from Borden aquifer solids to aqueous solutions containing 250 ??M HS- or Fe2+ increased the reduction rate by factors of up to 10. The logarithms of the rate constants for the disappearance of C2Cl6 and CCl4 in seven different experimental systems were significantly correlated; log k???ccl4 = 0-64 log k??? c2cl6 - 0.83 with r2 = 0.80. The observed trend in reaction rates of C2Cl6 > CCl4 > CHBr3 is consistent with a decreasing trend in one-electron reduction potentials. ?? 1994 American Chemical Society.

  19. Removal of mercury (II) from aqueous solution by activated carbon obtained from furfural.

    PubMed

    Yardim, M F; Budinova, T; Ekinci, E; Petrov, N; Razvigorova, M; Minkova, V

    2003-08-01

    The adsorption of Hg(II) from aqueous solution at 293 K by activated carbon obtained from furfural is studied. The carbon is prepared by polymerization of furfural following carbonization and activation of the obtained polymer material with water vapor at 800 degrees C. Adsorption studies of Hg(II) are carried out varying some conditions: treatment time, metal ion concentration, adsorbent amount and pH. It is determined that Hg(II) adsorption follows both Langmuir and Freundlich isotherms. The adsorption capacity of the carbon is 174 mg/g. It is determined that Hg(II) uptake increases with increasing pH. Desorption studies are performed with hot water. The percent recovery of Hg(II) is 6%.

  20. Large-current-controllable carbon nanotube field-effect transistor in electrolyte solution

    NASA Astrophysics Data System (ADS)

    Myodo, Miho; Inaba, Masafumi; Ohara, Kazuyoshi; Kato, Ryogo; Kobayashi, Mikinori; Hirano, Yu; Suzuki, Kazuma; Kawarada, Hiroshi

    2015-05-01

    Large-current-controllable carbon nanotube field-effect transistors (CNT-FETs) were fabricated with mm-long CNT sheets. The sheets, synthesized by remote-plasma-enhanced CVD, contained both single- and double-walled CNTs. Titanium was deposited on the sheet as source and drain electrodes, and an electrolyte solution was used as a gate electrode (solution gate) to apply a gate voltage to the CNTs through electric double layers formed around the CNTs. The drain current came to be well modulated as electrolyte solution penetrated into the sheets, and one of the solution gate CNT-FETs was able to control a large current of over 2.5 A. In addition, we determined the transconductance parameter per tube and compared it with values for other CNT-FETs. The potential of CNT sheets for applications requiring the control of large current is exhibited in this study.

  1. Method for extracting lanthanides and actinides from acid solutions by modification of Purex solvent

    DOEpatents

    Horwitz, E.P.; Kalina, D.G.

    1984-05-21

    A process has been developed for the extraction of multivalent lanthanide and actinide values from acidic waste solutions, and for the separation of these values from fission product and other values, which utilizes a new series of neutral bi-functional extractants, the alkyl(phenyl)-N, N-dialkylcarbamoylmethylphosphine oxides, in combination with a phase modifier to form an extraction solution. The addition of the extractant to the Purex process extractant, tri-n-butylphosphate in normal paraffin hydrocarbon diluent, will permit the extraction of multivalent lanthanide and actinide values from 0.1 to 12.0 molar acid solutions.

  2. Optimization of mesoporous carbons for efficient adsorption of berberine hydrochloride from aqueous solutions.

    PubMed

    Li, Yin; Fu, Jie; Deng, Shuguang; Lu, Xiuyang

    2014-06-15

    Sixteen mesoporous carbon adsorbents were synthesized by varying the ratio of soft to hard templates in order to optimize the pore textural properties of these adsorbents. The mesoporous carbon adsorbents have a high BET specific surface area (1590.3-2193.5 m(2)/g), large pore volume (1.72-2.56 cm(3)/g), and uniform pore size distribution with a median pore diameter ranging from 3.51 nm to 4.52 nm. It was observed that pore textural properties of the carbon adsorbents critically depend on the molar ratio of carbon sources to templates, and the hard template plays a more important role than the soft template in manipulating the pore textures. Adsorption isotherms of berberine hydrochloride at 303 K were measured to evaluate the adsorption efficacy of these adsorbents. The adsorption of berberine hydrochloride from aqueous solutions on the sixteen mesoporous carbon adsorbents synthesized in this work is very efficient, and the adsorption equilibrium capacities on all samples are more than double the adsorption capacities of berberine hydrochloride of the benchmark adsorbents (polymer resins and spherical activated carbons) at similar conditions. It was observed from the adsorption experiments that the equilibrium adsorption amounts of berberine hydrochloride are strongly correlated with the BET specific surface area and pore volume of the adsorbents. The adsorbent with the highest BET of 2193.5 m(2)/g displayed the largest adsorption capacity of 574 mg/g at an equilibrium concentration of 0.10mg/mL of berberine hydrochloride in an aqueous solution. Copyright © 2014 Elsevier Inc. All rights reserved.

  3. Carbon footprint of telemedicine solutions--unexplored opportunity for reducing carbon emissions in the health sector.

    PubMed

    Holmner, Asa; Ebi, Kristie L; Lazuardi, Lutfan; Nilsson, Maria

    2014-01-01

    The healthcare sector is a significant contributor to global carbon emissions, in part due to extensive travelling by patients and health workers. To evaluate the potential of telemedicine services based on videoconferencing technology to reduce travelling and thus carbon emissions in the healthcare sector. A life cycle inventory was performed to evaluate the carbon reduction potential of telemedicine activities beyond a reduction in travel related emissions. The study included two rehabilitation units at Umeå University Hospital in Sweden. Carbon emissions generated during telemedicine appointments were compared with care-as-usual scenarios. Upper and lower bound emissions scenarios were created based on different teleconferencing solutions and thresholds for when telemedicine becomes favorable were estimated. Sensitivity analyses were performed to pinpoint the most important contributors to emissions for different set-ups and use cases. Replacing physical visits with telemedicine appointments resulted in a significant 40-70 times decrease in carbon emissions. Factors such as meeting duration, bandwidth and use rates influence emissions to various extents. According to the lower bound scenario, telemedicine becomes a greener choice at a distance of a few kilometers when the alternative is transport by car. Telemedicine is a potent carbon reduction strategy in the health sector. But to contribute significantly to climate change mitigation, a paradigm shift might be required where telemedicine is regarded as an essential component of ordinary health care activities and not only considered to be a service to the few who lack access to care due to geography, isolation or other constraints.

  4. Radiation-induced degradation of cyclohexanebutyric acid in aqueous solutions by gamma ray irradiation

    NASA Astrophysics Data System (ADS)

    Jia, Wenbao; He, Yanquan; Ling, Yongsheng; Hei, Daqian; Shan, Qing; Zhang, Yan; Li, Jiatong

    2015-04-01

    The radiation-induced degradation of cyclohexanebutyric acid under gamma ray irradiation was investigated. Degradation experiments were performed with 100 mL sealed Pyrex glass vessels loaded with 80 mL of cyclohexanebutyric acid solutions at various initial concentrations of 10, 20, and 40 mg L-1. The absorbed doses were controlled at 0, 0.65, 1.95, 3.25, 6.5, 9.75, and 13 kGy. The results showed that gamma ray irradiation could effectively degrade cyclohexanebutyric acid in aqueous solutions. The removal rate of cyclohexanebutyric acid increased significantly with the increase of absorbed dose and the decrease of its initial concentration. At the same time, the removal of chemical oxygen demand (COD) was as effective as that of cyclohexanebutyric acid. The kinetic studies showed that the degradation of cyclohexanebutyric acid followed pseudo first-order reaction. Above all, the proposed mechanism obtained when NaNO2, NaNO3 and tert-butanol were added showed that the •OH radical played a major role in the gamma degradation process of cyclohexanebutyric acid, while •H and eaq- played a minor role in the gamma degradation process. The degradation products were identified by Fourier transform infrared spectroscopy (FTIR) and gas chromatography/mass spectrometry (GC/MS) during cyclohexanebutyric acid degradation.

  5. Detection Of Uric Acid Based On Multi-Walled Carbon Nanotubes Polymerized With A Layer Of Molecularly Imprinted PMAA

    NASA Astrophysics Data System (ADS)

    Chen, Po-Yen; Lin, Chia-Yu; Ho, Kuo-Chuan

    2009-05-01

    A molecularly imprinted poly-metharylic acid (PMAA), polymerizing on the surface of multi-walled carbon nanotube (MWCNT), was synthesized. The MWCNT was modified by a layer of carboxylic acid and reacted with EDC and NHS to activate the carboxylic acid, which was prepared for the purpose of bonding allyl amine and getting an unsaturated side chain (-C=C). The resultant structure is abbreviated as MWCNTs-CH=CH2. It is well known that the vinyl group side chain provides good attachment between the MWCNTs and the molecularly imprinted polymer (MIP). The MIP based on PMAA was polymerized on the surface of MWCNTs-CH=CH2 with the addition of uric acid (UA). The non-imprinted polymer (NIP) was polymerized without adding UA. The adsorbed amount of UA approached the equilibrium value upon 60 min adsorption. The adsorption isotherm was obtained by immersing 10 mg of MIP or NIP in 5 mL aqueous solution containing different concentrations of UA. The adsorbed amounts were measured via a UV-Vis spectrometer at a wavelength of 292 nm. From the adsorption isotherm, it is seen that the MIP particles possess a good imprinting efficiency of about 4.41.

  6. Comparison of inhibition effects of some benzoic acid derivatives on sheep heart carbonic anhydrase

    NASA Astrophysics Data System (ADS)

    Kiliç, Deryanur; Yildiz, Melike; Şentürk, Murat; Erdoǧan, Orhan; Küfrevioǧlu, Ömer Irfan

    2016-04-01

    Carbonic anhydrase (CA) is a family of metalloenzymes that requires Zn as a cofactor and catalyze the quick conversion of CO2 to HCO3- and H+. Inhibitors of the carbonic anhydrases (CAs) have medical usage of significant diseases such as glaucoma, epilepsy, gastroduodenal ulcers, acid-base disequilibria and neurological disorders. In the present study, inhibition of CA with some benzoic derivatives (1-6) were investigated. Sheep heart CA (shCA) enzyme was isolated by means of designed affinity chromatography gel (cellulose-benzyl-sulfanylamide) 42.45-fold in a yield of 44 % with 564.65 EU/mg. Purified shCA enzyme was used in vitro studies. In the studies, IC50 values were calculated for 3-aminobenzoic acid (1), 4-aminobenzoic acid (2), 2-hydroxybenzoic acid (3), 2-benzoylbenzoic acid (4), 2,3-dimethoxybenzoic acid (5), and 3,4,5-trimethoxybenzoic acid (6), showing the inhibition effects on the purified enzyme. Such molecules can be used as pioneer for discovery of novel effective CA inhibitors for medicinal chemistry applications.

  7. Effects of simulated acid rain on soil and soil solution chemistry in a monsoon evergreen broad-leaved forest in southern China.

    PubMed

    Qiu, Qingyan; Wu, Jianping; Liang, Guohua; Liu, Juxiu; Chu, Guowei; Zhou, Guoyi; Zhang, Deqiang

    2015-05-01

    Acid rain is an environmental problem of increasing concern in China. In this study, a laboratory leaching column experiment with acid forest soil was set up to investigate the responses of soil and soil solution chemistry to simulated acid rain (SAR). Five pH levels of SAR were set: 2.5, 3.0, 3.5, 4.0, and 4.5 (as a control, CK). The results showed that soil acidification would occur when the pH of SAR was ≤3.5. The concentrations of NO₃(-)and Ca(2+) in the soil increased significantly when the pH of SAR fell 3.5. The concentration of SO₄(2-) in the soil increased significantly when the pH of SAR was <4.0. The effects of SAR on soil solution chemistry became increasingly apparent as the experiment proceeded (except for Na(+) and dissolved organic carbon (DOC)). The net exports of NO₃(-), SO₄(2-), Mg(2+), and Ca(2+) increased about 42-86% under pH 2.5 treatment as compared to CK. The Ca(2+) was sensitive to SAR, and the soil could release Ca(2+) through mineral weathering to mitigate soil acidification. The concentration of exchangeable Al(3+) in the soil increased with increasing the acidity of SAR. The releases of soluble Al and Fe were SAR pH dependent, and their net exports under pH 2.5 treatment were 19.6 and 5.5 times, respectively, higher than that under CK. The net export of DOC was reduced by 12-29% under SAR treatments as compared to CK. Our results indicate the chemical constituents in the soil are more sensitive to SAR than those in the soil solution, and the effects of SAR on soil solution chemistry depend not only on the intensity of SAR but also on the duration of SAR addition. The soil and soil solution chemistry in this region may not be affected by current precipitation (pH≈4.5) in short term, but the soil and soil leachate chemistry may change dramatically if the pH of precipitation were below 3.5 and 3.0, respectively.

  8. Stability of antimicrobial activity of peracetic acid solutions used in the final disinfection process.

    PubMed

    Costa, Solange Alves da Silva; Paula, Olívia Ferreira Pereira de; Silva, Célia Regina Gonçalves E; Leão, Mariella Vieira Pereira; Santos, Silvana Soléo Ferreira dos

    2015-01-01

    The instruments and materials used in health establishments are frequently exposed to microorganism contamination, and chemical products are used before sterilization to reduce occupational infection. We evaluated the antimicrobial effectiveness, physical stability, and corrosiveness of two commercial formulations of peracetic acid on experimentally contaminated specimens. Stainless steel specimens were contaminated with Staphylococcus aureus, Escherichia coli, Candida albicans, blood, and saliva and then immersed in a ready peracetic acid solution: 2% Sekusept Aktiv (SA) or 0.25% Proxitane Alpha (PA), for different times. Then, washes of these instruments were plated in culture medium and colony-forming units counted. This procedure was repeated six times per day over 24 non-consecutive days. The corrosion capacity was assessed with the mass loss test, and the concentration of peracetic acid and pH of the solutions were measured with indicator tapes. Both SA and PA significantly eliminated microorganisms; however, the SA solution was stable for only 4 days, whereas PA remained stable throughout the experiment. The concentration of peracetic acid in the SA solutions decreased over time until the chemical was undetectable, although the pH remained at 5. The PA solution had a concentration of 500-400 mg/L and a pH of 2-3. Neither formulation induced corrosion and both reduced the number of microorganisms (p = 0.0001). However, the differences observed in the performance of each product highlight the necessity of establishing a protocol for optimizing the use of each one.

  9. Semicontinuous measurements of organic carbon and acidity during the Pittsburgh air quality study: implications for acid-catalyzed organic aerosol formation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    S. Takahama; C.I. Davidson; S.N. Pandis

    2006-04-01

    Laboratory evidence suggests that inorganic acid seed particles may increase secondary organic aerosol yields secondary organic aerosol (SOA) through heterogeneous chemistry. Additional laboratory studies, however, report that organic acidity generated in the same photochemical process by which SOA is formed may be sufficient to catalyze these heterogeneous reactions. Understanding the interaction between inorganic acidity and SOA mass is important when evaluating emission controls to meet PM2.5 regulations. Semicontinuous measurements of organic carbon (OC), elemental carbon (EC), and inorganic species from the Pittsburgh Air Quality Study were examined to determine if coupling in the variations of inorganic acidity and OC couldmore » be detected. Significant enhancements of SOA production could not be detected due to inorganic acidity in Western Pennsylvania most of the time, but its signal might have been lost in the noise. If a causal relationship between inorganic acidity and OC is assumed, reductions in OC for Western Pennsylvania that might result from drastic reductions in inorganic acidity were estimated to be 2 {+-} 4% by a regression technique, and an upper bound for this geographic area was estimated to be 5 {+-} 8% based on calculations from laboratory measurements. 48 refs., 7 figs., 3 tabs.« less

  10. A 25% tannic acid solution as a root canal irrigant cleanser: a scanning electron microscope study.

    PubMed

    Bitter, N C

    1989-03-01

    A scanning electron microscope was used to evaluate the cleansing properties of a 25% tannic acid solution on the dentinal surface in the pulp chamber of endodontically prepared teeth. This was compared with the amorphous smear layer of the canal with the use of hydrogen peroxide and sodium hypochlorite solution as an irrigant. The tannic acid solution removed the smear layer more effectively than the regular cleansing agent.

  11. Competitive adsorption of ibuprofen and amoxicillin mixtures from aqueous solution on activated carbons.

    PubMed

    Mansouri, Hayet; Carmona, Rocio J; Gomis-Berenguer, Alicia; Souissi-Najar, Souad; Ouederni, Abdelmottaleb; Ania, Conchi O

    2015-07-01

    This work investigates the competitive adsorption under dynamic and equilibrium conditions of ibuprofen (IBU) and amoxicillin (AMX), two widely consumed pharmaceuticals, on nanoporous carbons of different characteristics. Batch adsorption experiments of pure components in water and their binary mixtures were carried out to measure both adsorption equilibrium and kinetics, and dynamic tests were performed to validate the simultaneous removal of the mixtures in breakthrough experiments. The equilibrium adsorption capacities evaluated from pure component solutions were higher than those measured in dynamic conditions, and were found to depend on the porous features of the adsorbent and the nature of the specific/dispersive interactions that are controlled by the solution pH, density of surface change on the carbon and ionization of the pollutant. A marked roll-up effect was observed for AMX retention on the hydrophobic carbons, not seen for the functionalized adsorbent likely due to the lower affinity of amoxicillin towards the carbon adsorbent. Dynamic adsorption of binary mixtures from wastewater of high salinity and alkalinity showed a slight increase in IBU uptake and a reduced adsorption of AMX, demonstrating the feasibility of the simultaneous removal of both compounds from complex water matrices. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Adsorption of naphthenic acids on high surface area activated carbons.

    PubMed

    Iranmanesh, Sobhan; Harding, Thomas; Abedi, Jalal; Seyedeyn-Azad, Fakhry; Layzell, David B

    2014-01-01

    In oil sands mining extraction, water is an essential component; however, the processed water becomes contaminated through contact with the bitumen at high temperature, and a portion of it cannot be recycled and ends up in tailing ponds. The removal of naphthenic acids (NAs) from tailing pond water is crucial, as they are corrosive and toxic and provide a substrate for microbial activity that can give rise to methane, which is a potent greenhouse gas. In this study, the conversion of sawdust into an activated carbon (AC) that could be used to remove NAs from tailings water was studied. After producing biochar from sawdust by a slow-pyrolysis process, the biochar was physically activated using carbon dioxide (CO2) over a range of temperatures or prior to producing biochar, and the sawdust was chemically activated using phosphoric acid (H3PO4). The physically activated carbon had a lower surface area per gram than the chemically activated carbon. The physically produced ACs had a lower surface area per gram than chemically produced AC. In the adsorption tests with NAs, up to 35 mg of NAs was removed from the water per gram of AC. The chemically treated ACs showed better uptake, which can be attributed to its higher surface area and increased mesopore size when compared with the physically treated AC. Both the chemically produced and physically produced AC provided better uptake than the commercially AC.

  13. Carbon Nanotube Formic Acid Sensors Using a Nickel Bis( ortho-diiminosemiquinonate) Selector.

    PubMed

    Lin, Sibo; Swager, Timothy M

    2018-03-23

    Formic acid is corrosive, and a sensitive and selective sensor could be useful in industrial, medical, and environmental settings. We present a chemiresistor for detection of formic acid composed of single-walled carbon nanotubes (CNTs) and nickel bis( ortho-diiminosemiquinonate) (1), a planar metal complex that can act as a ditopic hydrogen-bonding selector. Formic acid is detected in concentrations as low as 83 ppb. The resistance of the material decreases on exposure to formic acid, but slightly increases on exposure to acetic acid. We propose that 1 assists in partial protonation of the CNT by formic acid, but the response toward acetic acid is dominated by inter-CNT swelling. This technology establishes CNT-based chemiresistive discrimination between formic and acetic acid vapors.

  14. Synthesis of nitrogen-containing carbon by solution plasma in aniline with high-repetition frequency discharges

    NASA Astrophysics Data System (ADS)

    Hyun, Koangyong; Ueno, Tomonaga; Saito, Nagahiro

    2016-01-01

    Nitrogen-containing carbon nanoparticles were synthesized in aniline by solution plasma with high-repetition frequency discharges. We developed a bipolar pulsed power supply that can apply high-repetition frequencies ranging from 25 to 200 kHz. By utilizing high-repetition frequencies, conductive carbons were directly synthesized. The crystallinity was increased and H/C ratio of carbon was decreased. Furthermore, nitrogen atoms were simultaneously embedded in the carbon matrix. Due to the presence of nitrogen atoms, the conductivity and electrocatalytic activity of the samples were remarkably improved compared to that of a pure carbon matrix synthesized from a benzene precursor.

  15. The Path of Carbon in Photosynthesis VIII. The Role of Malic Acid

    DOE R&D Accomplishments Database

    Bassham, James A.; Benson, Andrew A.; Calvin, Melvin

    1950-01-25

    Malonate has been found to inhibit the formation of malic acid during short periods of photosynthesis with radioactive carbon dioxide. This result, together with studies which show the photosynthetic cycle to be operating normally at the same time, indicates that malic acid is not an intermediate in photosynthesis but is probably closely related to some intermediate of the cycle. Absence of labeled succinic and fumaric acids in these experiments, in addition to the failure of malonate to inhibit photosynthesis, precludes the participation of these acids as intermediates in photosynthesis.

  16. Activated carbon production from bagasse and banana stem at various times of carbonization

    NASA Astrophysics Data System (ADS)

    Misran, E.; Maulina, S.; Dina, S. F.; Nazar, A.; Harahap, S. A.

    2018-02-01

    The utilization of bagasse and banana stem as activated carbon precursors has been conducted. In this study, the dried samples were impregnated using phosphoric acid (H3PO4) solution as the activator at a ratio of sample to the activator (w/w) was 1:1. The impregnation was conducted at room temperature for 24 hours. The samples then carbonized at 400 °C for 30, 45 and 60 minutes and finally washed and dried to obtain the activated carbon. The research aimed to investigate the effects of time of carbonization on the characteristics of activated carbon produced from bagasse and banana stem. The result showed that yield of activated carbon was in the range of 40.03 - 46.73 % with a high content of carbon as high 90.33 %. The result of BET analysis showed that the highest surface area reached1130.465 m2/g.

  17. Theoretical estimates of equilibrium 13C-18O clumping in carbonates and organic acids

    NASA Astrophysics Data System (ADS)

    Schauble, E. A.; Eiler, J. M.

    2004-12-01

    The development of techniques for measuring small gas-phase molecules containing more than one rare stable isotope (e.g., 13C18O16O) at natural, ppm-level abundances1,2 has made it possible to track sources and sinks of atmospheric gases from a new perspective. Similar measurements of 13C-18O clumping in ancient samples could improve our understanding of ancient climates, if the abundances of `clumped' rare stable isotopes in materials that retain isotopic signatures over geologic time can be measured with sufficient precision. This theoretical study estimates the abundances of such 13C-18O `clumps' in carbonates and organic acids and discusses their potential applications. Accompanying abstracts by Eiler et al. and Ghosh et al. will present the analytical methods and some initial data for carbonate minerals to examine the applicability of our theoretical models. Equilibrium isotopic speciations in carbonate minerals and organic acids are calculated from the reduced partition function ratios of isotopically substituted crystals and molecules. Vibrational frequencies used as input for these calculations come from ab initio force fields, determined using density functional theory. Our calculations indicate that carbonate minerals, including calcite, dolomite, and aragonite, when equilibrated at earth-surface temperatures, will have a slight overabundance of CO32- groups containing both 13C and 18O (i.e., 13C18O16O22-) relative to what would be expected if carbon and oxygen isotopes were distributed randomly in the crystal lattice. Calcite and dolomite crystals are predicted to have 0.4‰ excesses of 13C18O16O22- at 298 K; in aragonite the excess will be about 0.05‰ larger. The excesses are smaller for crystals formed or equilibrated at higher temperatures, decreasing by 0.003\\permil/oC at room temperature and essentially disappearing at temperatures of 1000 K or higher. Similarly, there is an excess of both 13C18O16OH and 13C16O18OH groups in organic acids like

  18. Wolframite Conversion in Treating a Mixed Wolframite-Scheelite Concentrate by Sulfuric Acid

    NASA Astrophysics Data System (ADS)

    Shen, Leiting; Li, Xiaobin; Zhou, Qiusheng; Peng, Zhihong; Liu, Guihua; Qi, Tiangui; Taskinen, Pekka

    2017-12-01

    Complete wolframite conversion in sulfuric acid is significant for expanding the applicability of the sulfuric acid method for producing ammonium paratungstate. In this paper, the conversion of wolframite in treating a mixed wolframite-scheelite concentrate by sulfuric acid was studied systematically. The results show that the conversion of wolframite in sulfuric acid is more difficult than that of scheelite, requiring rigorous reaction conditions. A solid H2WO4 layer forms on the surfaces of the wolframite particles and becomes denser with increasing H2SO4 concentration, thus hindering the conversion. Furthermore, the difficulty in wolframite conversion can be mainly attributed to the accumulation of Fe2+ (and/or Mn2+) in the H2SO4 solution, which can be solved by reducing Fe2+ (and/or Mn2+) concentration through oxidization and/or a two-stage process. Additionally, the solid converted product of the mixed wolframite-scheelite concentrate has an excellent leachability of tungsten in an aqueous ammonium carbonate solution at ambient temperature, with approximately 99% WO3 recovery. This work presents a route for manufacturing ammonium paratungstate by treating the mixed concentrate in sulfuric acid followed by leaching in ammonium carbonate solution.

  19. Wolframite Conversion in Treating a Mixed Wolframite-Scheelite Concentrate by Sulfuric Acid

    NASA Astrophysics Data System (ADS)

    Shen, Leiting; Li, Xiaobin; Zhou, Qiusheng; Peng, Zhihong; Liu, Guihua; Qi, Tiangui; Taskinen, Pekka

    2018-02-01

    Complete wolframite conversion in sulfuric acid is significant for expanding the applicability of the sulfuric acid method for producing ammonium paratungstate. In this paper, the conversion of wolframite in treating a mixed wolframite-scheelite concentrate by sulfuric acid was studied systematically. The results show that the conversion of wolframite in sulfuric acid is more difficult than that of scheelite, requiring rigorous reaction conditions. A solid H2WO4 layer forms on the surfaces of the wolframite particles and becomes denser with increasing H2SO4 concentration, thus hindering the conversion. Furthermore, the difficulty in wolframite conversion can be mainly attributed to the accumulation of Fe2+ (and/or Mn2+) in the H2SO4 solution, which can be solved by reducing Fe2+ (and/or Mn2+) concentration through oxidization and/or a two-stage process. Additionally, the solid converted product of the mixed wolframite-scheelite concentrate has an excellent leachability of tungsten in an aqueous ammonium carbonate solution at ambient temperature, with approximately 99% WO3 recovery. This work presents a route for manufacturing ammonium paratungstate by treating the mixed concentrate in sulfuric acid followed by leaching in ammonium carbonate solution.

  20. Determination of acid ionization constants for weak acids by osmometry and the instrumental analysis self-evaluation feedback approach to student preparation of solutions

    NASA Astrophysics Data System (ADS)

    Kakolesha, Nyanguila

    One focus of this work was to develop of an alternative method to conductivity for determining the acid ionization constants. Computer-controlled osmometry is one of the emerging analytical tools in industrial research and clinical laboratories. It is slowly finding its way into chemistry laboratories. The instrument's microprocessor control ensures shortened data collection time, repeatability, accuracy, and automatic calibration. The equilibrium constants of acetic acid, chloroacetic acid, bromoacetic acid, cyanoacetic acid, and iodoacetic acid have been measured using osmometry and their values compared with the existing literature values obtained, usually, from conductometric measurements. Ionization constant determined by osmometry for the moderately strong weak acids were in reasonably good agreement with literature values. The results showed that two factors, the ionic strength and the osmotic coefficient, exert opposite effects in solutions of such weak acids. Another focus of the work was analytical chemistry students solution preparation skills. The prevailing teacher-structured experiments leave little room for students' ingenuity in quantitative volumetric analysis. The purpose of this part of the study was to improve students' skills in making solutions using instrument feedback in a constructivist-learning model. After making some solutions by weighing and dissolving solutes or by serial dilution, students used the spectrophotometer and the osmometer to compare their solutions with standard solutions. Students perceived the instrument feedback as a nonthreatening approach to monitoring the development of their skill levels and liked to clarify their understanding through interacting with an instructor-observer. An assessment of the instrument feedback and the constructivist model indicated that students would assume responsibility for their own learning if given the opportunity. This study involved 167 students enrolled in Quantitative Chemical

  1. The separation of lanthanides and actinides in supercritical fluid carbon dioxide

    DOE PAGES

    Mincher, Bruce J.; Wai, Chien M.; Fox, Robert V.; ...

    2015-10-28

    Supercritical fluid carbon dioxide presents an attractive alternative to conventional solvents for recovery of the actinides and lanthanides. Carbon dioxide is a good solvent for fluorine and phosphate-containing ligands, including the traditional tributylphosphate ligand used in process-scale uranium separations. Actinide and lanthanide oxides may even be directly dissolved in carbon dioxide containing the complexes formed between these ligands and mineral acids, obviating the need for large volumes of acids for leaching and dissolution, and the corresponding organic liquid–liquid solvent extraction solutions. As a result, examples of the application of this novel technology for actinide and lanthanide separations are presented.

  2. Structural and functional characterization of solute binding proteins for aromatic compounds derived from lignin: p-coumaric acid and related aromatic acids.

    PubMed

    Tan, Kemin; Chang, Changsoo; Cuff, Marianne; Osipiuk, Jerzy; Landorf, Elizabeth; Mack, Jamey C; Zerbs, Sarah; Joachimiak, Andrzej; Collart, Frank R

    2013-10-01

    Lignin comprises 15-25% of plant biomass and represents a major environmental carbon source for utilization by soil microorganisms. Access to this energy resource requires the action of fungal and bacterial enzymes to break down the lignin polymer into a complex assortment of aromatic compounds that can be transported into the cells. To improve our understanding of the utilization of lignin by microorganisms, we characterized the molecular properties of solute binding proteins of ATP-binding cassette transporter proteins that interact with these compounds. A combination of functional screens and structural studies characterized the binding specificity of the solute binding proteins for aromatic compounds derived from lignin such as p-coumarate, 3-phenylpropionic acid and compounds with more complex ring substitutions. A ligand screen based on thermal stabilization identified several binding protein clusters that exhibit preferences based on the size or number of aromatic ring substituents. Multiple X-ray crystal structures of protein-ligand complexes for these clusters identified the molecular basis of the binding specificity for the lignin-derived aromatic compounds. The screens and structural data provide new functional assignments for these solute-binding proteins which can be used to infer their transport specificity. This knowledge of the functional roles and molecular binding specificity of these proteins will support the identification of the specific enzymes and regulatory proteins of peripheral pathways that funnel these compounds to central metabolic pathways and will improve the predictive power of sequence-based functional annotation methods for this family of proteins. Copyright © 2013 Wiley Periodicals, Inc.

  3. Structural and functional characterization of solute binding proteins for aromatic compounds derived from lignin: p-coumaric acid and related aromatic acids

    PubMed Central

    Tan, Kemin; Chang, Changsoo; Cuff, Marianne; Osipiuk, Jerzy; Landorf, Elizabeth; Mack, Jamey C.; Zerbs, Sarah; Joachimiak, Andrzej; Collart, Frank R.

    2013-01-01

    Lignin comprises 15.25% of plant biomass and represents a major environmental carbon source for utilization by soil microorganisms. Access to this energy resource requires the action of fungal and bacterial enzymes to break down the lignin polymer into a complex assortment of aromatic compounds that can be transported into the cells. To improve our understanding of the utilization of lignin by microorganisms, we characterized the molecular properties of solute binding proteins of ATP.binding cassette transporter proteins that interact with these compounds. A combination of functional screens and structural studies characterized the binding specificity of the solute binding proteins for aromatic compounds derived from lignin such as p-coumarate, 3-phenylpropionic acid and compounds with more complex ring substitutions. A ligand screen based on thermal stabilization identified several binding protein clusters that exhibit preferences based on the size or number of aromatic ring substituents. Multiple X-ray crystal structures of protein-ligand complexes for these clusters identified the molecular basis of the binding specificity for the lignin-derived aromatic compounds. The screens and structural data provide new functional assignments for these solute.binding proteins which can be used to infer their transport specificity. This knowledge of the functional roles and molecular binding specificity of these proteins will support the identification of the specific enzymes and regulatory proteins of peripheral pathways that funnel these compounds to central metabolic pathways and will improve the predictive power of sequence-based functional annotation methods for this family of proteins. PMID:23606130

  4. Interfacial electron transfer of glucose oxidase on poly(glutamic acid)-modified glassy carbon electrode and glucose sensing.

    PubMed

    Zhou, Xuechou; Tan, Bingcan; Zheng, Xinyu; Kong, Dexian; Li, Qinglu

    2015-11-15

    The interfacial electron transfer of glucose oxidase (GOx) on a poly(glutamic acid)-modified glassy carbon electrode (PGA/GCE) was investigated. The redox peaks measured for GOx and flavin adenine dinucleotide (FAD) are similar, and the anodic peak of GOx does not increase in the presence of glucose in a mediator-free solution. These indicate that the electroactivity of GOx is not the direct electron transfer (DET) between GOx and PGA/GCE and that the observed electroactivity of GOx is ascribed to free FAD that is released from GOx. However, efficient electron transfer occurred if an appropriate mediator was placed in solution, suggesting that GOx is active. The PGA/GCE-based biosensor showed wide linear response in the range of 0.5-5.5 mM with a low detection limit of 0.12 mM and high sensitivity and selectivity for measuring glucose. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Study of lithium extraction from brine water, Bledug Kuwu, Indonesia by the precipitation series of oxalic acid and carbonate sodium

    NASA Astrophysics Data System (ADS)

    Sulistiyono, Eko; Lalasari, Latifa Hanum; Mayangsari, W.; Prasetyo, A. B.

    2018-05-01

    Lithium is one of the key elements in the development of batteries for electric car applications. Currently, the resources of the world's lithium are derived from brine water and lithium mineral based on spodumene rock. Indonesia which is located in the area of the ring of fire, has potential brine water resources in some area, such as brine water from Bledug Kuwu, Central Java that used in this research. The purposes of this research are to characterize brine water, Bledug Kuwu and to investigate the influence of chemical solvents on Li, Na, K, Ca, Mg, Al, B ion precipitation from brine water. This research was done with 2 times the process of chemical precipitation that runs series as follows: 5 liters of brine water were chemically precipitated using 400 ml of 12.43 N oxalic acid and followed by chemical precipitation using 400 mL of 7.07 N sodium carbonate solutions. Evaporation and filtration processes were also done twice in an effort to separate white precipitate and filtrate. The filtrate was analyzed by ICP-OES and white precipitates (salts) were analyzed by SEM, XRD, and XRF. The result shows that oxalate precipitation process extracted 32.24% Al, 23.42% B, 22.43% Ca, 14.26% Fe, 3.21 % K, 9.86% Na and 14.26% Li, the following process by carbonate precipitation process extracted 98.86% Mg, 73% Ca, 22.53% Li, 82.04% Al, 14.38% B, 12.50% K, 2.27% Na. There is 63.21% lithium is not extracted from the series process. The SEM analysis shows that the structure of granules on the precipitated salts by oxalic acid form gentle cubic-shaped solid. In the other hand, oxalate precipitation followed by sodium carbonate has various particle sizes and the shape of crystals is fragments, prism and cube look like magnesium carbonate, calcium chloride, and calcite's crystal respectively. This is in accordance with XRD analysis that phases of whewellite (CaC2O4.H2O), disodium oxalate (Na2C2O4), magnesite (MgCO3), calcium lithium aluminum (Al1.19 Ca1Li0.81), dolomite (CaCO3

  6. Effects of topical oxiconazole and boric acid in alcohol solutions to rat inner ears.

    PubMed

    Özdemir, Süleyman; Tuncer, Ülkü; Tarkan, Özgür; Akar, Funda; Sürmelioğlu, Özgür

    2013-06-01

    The aim of this study is to evaluate the ototoxicity of topical oxiconazole and boric acid in alcohol solutions. Prospective controlled animal study. Research laboratory. Fifty adult Wistar albino rats were divided into 5 groups consisting of 10 animals each. The right tympanic membranes were perforated, and baseline and posttreatment distortion product otoacoustic emission (DPOAE) measurements were performed. The solutions were applied through the external ear canal to the middle ear twice a day for 14 days. The rats in group I and group II received 0.1 mL of oxiconazole-containing solution drops and 4% boric acid in alcohol solution drops, respectively. Group III received gentamicin solution (40 mg/mL) (ototoxic control), group IV received saline solution, and group V was followed without any medication. The baseline DPOAE results of the right ears of all animals tested were normal. Animals in groups I, II, IV, and V showed no statistically significant change in the DPOAE amplitudes. The rats in the gentamicin group showed a significant decrease. This study demonstrates that topically used oxiconazole and boric acid in alcohol solutions to the middle ear appear to be safe on the inner ear of rats. The safety of these drugs has not yet been confirmed in humans. Caution should be taken when prescribing these drugs, especially to patients who had tympanic membrane perforation. Ear drops should be chosen more carefully in an external ear infection for patients with tympanic membrane perforation to avoid ototoxicity.

  7. Hybrids of Nucleic Acids and Carbon Nanotubes for Nanobiotechnology

    PubMed Central

    Umemura, Kazuo

    2015-01-01

    Recent progress in the combination of nucleic acids and carbon nanotubes (CNTs) has been briefly reviewed here. Since discovering the hybridization phenomenon of DNA molecules and CNTs in 2003, a large amount of fundamental and applied research has been carried out. Among thousands of papers published since 2003, approximately 240 papers focused on biological applications were selected and categorized based on the types of nucleic acids used, but not the types of CNTs. This survey revealed that the hybridization phenomenon is strongly affected by various factors, such as DNA sequences, and for this reason, fundamental studies on the hybridization phenomenon are important. Additionally, many research groups have proposed numerous practical applications, such as nanobiosensors. The goal of this review is to provide perspective on biological applications using hybrids of nucleic acids and CNTs. PMID:28347014

  8. Hybrids of Nucleic Acids and Carbon Nanotubes for Nanobiotechnology.

    PubMed

    Umemura, Kazuo

    2015-03-12

    Recent progress in the combination of nucleic acids and carbon nanotubes (CNTs) has been briefly reviewed here. Since discovering the hybridization phenomenon of DNA molecules and CNTs in 2003, a large amount of fundamental and applied research has been carried out. Among thousands of papers published since 2003, approximately 240 papers focused on biological applications were selected and categorized based on the types of nucleic acids used, but not the types of CNTs. This survey revealed that the hybridization phenomenon is strongly affected by various factors, such as DNA sequences, and for this reason, fundamental studies on the hybridization phenomenon are important. Additionally, many research groups have proposed numerous practical applications, such as nanobiosensors. The goal of this review is to provide perspective on biological applications using hybrids of nucleic acids and CNTs.

  9. Composite Properties of Polyimide Resins Made From "Salt-Like" Solution Precursors

    NASA Technical Reports Server (NTRS)

    Cano, Roberto J.; Weiser, Erik S.; SaintClair, Terry L.; Echigo, Yoshiaki; Kaneshiro, Hisayasu

    1997-01-01

    Recent work in high temperature materials at NASA Langley Research Center (LaRC (trademark)) have led to the development of new polyimide resin systems with very attractive properties. The majority of the work done with these resin systems has concentrated on determining engineering mechanical properties of composites prepared from a poly(amide acid) precursor. Three NASA Langley-developed polyimide matrix resins, LaRC (trademark) -IA, LaRC (trademark) -IAX, and LaRC (trademark) -8515, were produced via a salt-like process developed by Unitika Ltd. The 'salt-like' solutions (sixty-five percent solids in NMP) were prepregged onto Hexcel IM7 carbon fiber using the NASA LaRC Multipurpose Tape Machine. Process parameters were determined and composite panels fabricated. Mechanical properties are presented for these three intermediate modulus carbon fiber/polyimide matrix composites and compared to existing data on the same polyimide resin systems and IM7 carbon fiber manufactured via poly(amide acid) solutions (thirty-five percent solids in NMP). This work studies the effects of varying the synthetic route on the processing and mechanical properties of polyimide composites.

  10. 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.

  11. Potentially bioavailable natural organic carbon and hydrolyzable amino acids in aquifer sediments

    USGS Publications Warehouse

    Thomas, Lashun K.; Widdowson, Mark A.; Novak, John T.; Chapelle, Francis H.; Benner, Ronald; Kaiser, Karl

    2012-01-01

    This study evaluated the relationship between concentrations of operationally defined potentially bioavailable organic -carbon (PBOC) and hydrolyzable amino acids (HAAs) in sediments collected from a diverse range of chloroethene--contaminated sites. Concentrations of PBOC and HAA were measured using aquifer sediment samples collected at six selected study sites. Average concentrations of total HAA and PBOC ranged from 1.96 ± 1.53 to 20.1 ± 25.6 mg/kg and 4.72 ± 0.72 to 443 ± 65.4 mg/kg, respectively. Results demonstrated a statistically significant positive relationship between concentrations of PBOC and total HAA present in the aquifer sediment (p < 0.05). Higher levels of HAA were consistently observed at sites with greater levels of PBOC and first-order decay rates. Because amino acids are known to be readily biodegradable carbon compounds, this relationship suggests that the sequential chemical extraction procedure used to measure PBOC is a useful indicator of bioavailable carbon in aquifer sediments. This, in turn, is consistent with the interpretation that PBOC measurements can be used for estimating the amount of natural organic carbon available for driving the reductive dechlorination of chloroethenes in groundwater systems.

  12. Assessment of Simple Models for Molecular Simulation of Ethylene Carbonate and Propylene Carbonate as Solvents for Electrolyte Solutions.

    PubMed

    Chaudhari, Mangesh I; Muralidharan, Ajay; Pratt, Lawrence R; Rempe, Susan B

    2018-02-12

    Progress in understanding liquid ethylene carbonate (EC) and propylene carbonate (PC) on the basis of molecular simulation, emphasizing simple models of interatomic forces, is reviewed. Results on the bulk liquids are examined from the perspective of anticipated applications to materials for electrical energy storage devices. Preliminary results on electrochemical double-layer capacitors based on carbon nanotube forests and on model solid-electrolyte interphase (SEI) layers of lithium ion batteries are considered as examples. The basic results discussed suggest that an empirically parameterized, non-polarizable force field can reproduce experimental structural, thermodynamic, and dielectric properties of EC and PC liquids with acceptable accuracy. More sophisticated force fields might include molecular polarizability and Buckingham-model description of inter-atomic overlap repulsions as extensions to Lennard-Jones models of van der Waals interactions. Simple approaches should be similarly successful also for applications to organic molecular ions in EC/PC solutions, but the important case of Li[Formula: see text] deserves special attention because of the particularly strong interactions of that small ion with neighboring solvent molecules. To treat the Li[Formula: see text] ions in liquid EC/PC solutions, we identify interaction models defined by empirically scaled partial charges for ion-solvent interactions. The empirical adjustments use more basic inputs, electronic structure calculations and ab initio molecular dynamics simulations, and also experimental results on Li[Formula: see text] thermodynamics and transport in EC/PC solutions. Application of such models to the mechanism of Li[Formula: see text] transport in glassy SEI models emphasizes the advantage of long time-scale molecular dynamics studies of these non-equilibrium materials.

  13. Selective Removal of Lanthanides from Natural Waters, Acidic Streams and Dialysate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yantasee, Wassana; Fryxell, Glen E.; Addleman, Raymond S.

    2009-09-15

    The increased demand for the lanthanides in commercial products result in increased production of lanthanide containing ores, increasing public exposure to the lanthanides, both from various commercial products and from production wastes/effluents. This work investigates lanthanide (La, Ce, Pr, Nd, Eu, Gd, Lu) binding properties of self-assembled monolayers on mesoporous silica supports (SAMMS®) that were functionalized with diphosphonic acid (DiPhos), acetamide phosphonic acid (AcPhos), propionamide phosphonic acid (ProPhos), and 1-hydroxy-2-pyridinone (1,2-HOPO) from natural waters (river, ground, and sea waters), acid solutions (to mimic certain industrial process streams), and dialysate and compares their performance to a high surface area activated carbon.more » The properties include sorption affinity, capacity, and sorption kinetics. Stability and regenerability of SAMMS materials were also investigated. Going from the acid side over to the alkaline side, the AcPhos- and DiPhos-SAMMS maintain their outstanding affinity for lanthanides, which enable the use of the materials in the systems where the pH may fluctuate. While the activated carbon is as effective as 1,2-HOPO-SAMMS for capturing lanthanides in natural (alkaline) waters, it has no affinity in acid solutions (pH 2.4) and low affinity in carbonate-rich dialysate. Over 99% of 100 ug/L of Gd in dialysate was removed by the ProPhos-SAMMS after ten minutes. SAMMS can be regenerated with an acid wash (0.5 M HCl) without losing the binding properties, for a number of regeneration cycles. In acid solutions, PhoPhos- and 1,2-HOPO-SAMMS have differing affinity along the lanthanide series, suggesting their potential for chromatographic lanthanide separations. Thus, SAMMS materials have a great potential to be used as sorbents in large scale treatment of lanthanides, lanthanide separation prior to analytical instruments, and sorbent dialyzers for lanthanide clearances.« less

  14. Liquid Superlubricity of Polyethylene Glycol Aqueous Solution Achieved with Boric Acid Additive.

    PubMed

    Ge, Xiangyu; Li, Jinjin; Zhang, Chenhui; Luo, Jianbin

    2018-03-27

    Boric acid is a weak acid and has been used as a lubrication additive because of its special structure. In this study, we report that boric acid could achieve a robust superlubricity (μ < 0.01) as an additive in polyethylene glycol (PEG) aqueous solution at the Si 3 N 4 /SiO 2 interfaces. The superlow and steady friction coefficient of approximately 0.004-0.006 could be achieved with boric acid under neutral conditions (pH of approximately 6.4), which is different from the acidic conditions leading to superlubricity. The influence of various factors, including boric acid concentration, sliding speed, applied load, PEG molecular weight, and the volume of lubricant on the superlubricity, were investigated. The results reveal that the PEG aqueous solution with the boric acid additive could achieve superlubricity under a wide range of conditions. The surface composition analysis shows that the synergy effect between boric acid and PEG provides sufficient H + ions to realize the running-in process. Moreover, a composite tribochemical film composed of silica and ammonia-containing compounds were formed on the ball surface, contributing to the superlubricity. The film thickness calculation shows that superlubricity was achieved in a mixed lubrication region, and therefore, the superlubricity state was dominated by both the composite tribochemical film formed via the tribochemical reaction on the contact surfaces and the hydrodynamic lubricating film between the contact surfaces. Such a liquid superlubricity achieved under neutral conditions is of importance for both scientific understanding and engineering applications.

  15. High-Yield Production of Levulinic Acid from Pretreated Cow Dung in Dilute Acid Aqueous Solution.

    PubMed

    Su, Jialei; Shen, Feng; Qiu, Mo; Qi, Xinhua

    2017-02-14

    Agricultural waste cow dung was used as feedstock for the production of a high value-added chemical levulinic acid (LA) in dilute acid aqueous solutions. A high LA yield of 338.9 g/kg was obtained from the pretreated cow dung, which was much higher than that obtained from the crude cow dung (135 g/kg), mainly attributed to the breakage of the lignin fraction in the lignocellulose structure of the cow dung by potassium hydroxide (KOH) pretreatment, and thus enhanced the accessibility of cow dung to the acid sites in the catalytic reaction. Meanwhile, another value-added chemical formic acid could be obtained with a yield of ca. 160 g/kg in the process, implying a total production of ca. 500 g/kg yield for LA and formic acid from the pretreated cow dung with the proposed process. The developed process was shown to be tolerant to high initial substrate loading with a satisfied LA yield. This work provides a promising strategy for the value-increment utilization of liglocellulosic agricultural residues.

  16. Co-precipitation of dissolved organic matter by calcium carbonate in Pyramid Lake, Nevada

    USGS Publications Warehouse

    Leenheer, Jerry A.; Reddy, Michael M.

    2008-01-01

    Our previous research has demonstrated that dissolved organic matter (DOM) influences calcium carbonate mineral formation in surface and ground water. To better understand DOM mediation of carbonate precipitation and DOM co-precipitation and/or incorporation with carbonate minerals, we characterized the content and speciation of DOM in carbonate minerals and in the lake water of Pyramid Lake, Nevada, USA. A 400-gram block of precipitated calcium carbonate from the Pyramid Lake shore was dissolved in 8 liters of 10% acetic acid. Particulate matter not dissolved by acetic acid was removed by centrifugation. DOM from the carbonate rock was fractionated into nine portions using evaporation, dialysis, resin adsorption, and selective precipitations to remove acetic acid and inorganic constituents. The calcium carbonate rock contained 0.23% DOM by weight. This DOM was enriched in polycarboxylic proteinaceous acids and hydroxy-acids in comparison with the present lake water. DOM in lake water was composed of aliphatic, alicyclic polycarboxylic acids. These compound classes were found in previous studies to inhibit calcium carbonate precipitation. DOM fractions from the carbonate rock were 14C-age dated at about 3,100 to 3,500 years before present. The mechanism of DOM co-precipitation and/or physical incorporation in the calcium carbonate is believed to be due to formation of insoluble calcium complexes with polycarboxylic proteinaceous acids and hydroxy-acids that have moderately large stability constants at the alkaline pH of the lake. DOM co-precipitation with calcium carbonate and incorporation in precipitated carbonate minerals removes proteinaceous DOM, but nearly equivalent concentrations of neutral and acidic forms of organic nitrogen in DOM remain in solution. Calcium carbonate precipitation during lime softening pretreatment of drinking water may have practical applications for removal of proteinaceous disinfection by-product precursors.

  17. 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.

  18. Molecular dynamics simulation studies of the interactions between ionic liquids and amino acids in aqueous solution.

    PubMed

    Tomé, Luciana I N; Jorge, Miguel; Gomes, José R B; Coutinho, João A P

    2012-02-16

    Although the understanding of the influence of ionic liquids (ILs) on the solubility behavior of biomolecules in aqueous solutions is relevant for the design and optimization of novel biotechnological processes, the underlying molecular-level mechanisms are not yet consensual or clearly elucidated. In order to contribute to the understanding of the molecular interactions established between amino acids and ILs in aqueous media, classical molecular dynamics (MD) simulations were performed for aqueous solutions of five amino acids with different structural characteristics (glycine, alanine, valine, isoleucine, and glutamic acid) in the presence of 1-butyl-3-methylimidazolium bis(trifluoromethyl)sulfonyl imide. The results from MD simulations enable to relate the properties of the amino acids, namely their hydrophobicity, to the type and strength of their interactions with ILs in aqueous solutions and provide an explanation for the direction and magnitude of the solubility phenomena observed in [IL + amino acid + water] systems by a mechanism governed by a balance between competitive interactions of the IL cation, IL anion, and water with the amino acids.

  19. Process optimization and leaching kinetics of zinc and manganese metals from zinc-carbon and alkaline spent batteries using citric acid reagent

    NASA Astrophysics Data System (ADS)

    Yuliusman; Amiliana, R. A.; Wulandari, P. T.; Huda, M.; Kusumadewi, F. A.

    2018-03-01

    Zn-Carbon and Alkaline spent batteries contains heavy metals, such as zinc and manganese, which can causes environmental problem if not handled properly. Usually the recovery of these metals were done by leaching method using strong acid, but the use of strong acids as leaching reagents can be harmful to the environment. This paper concerns the recovery of Zn and Mn metals from Zn-C and alkaline spent batteries with leaching method using citric acid as the environmental friendly leaching reagent. The leaching conditions using citric acid were optimized and the leaching kinetics of Zn and Mn in citric acid solution was investigated. The leaching of 89.62% Zn and 63.26% Mn was achieved with 1.5 M citric acid, 90°C temperature, and 90 minutes stirring time. Kinetics data for the dissolution of Zn showed the best fit to chemical control shrinking core model, while the diffusion controlled model was suitable for the dissolution of Mn kinetics data. The activation energy of 6.12 and 1.73 kcal/mol was acquired for the leaching of Zn and Mn in the temperature range 60°C-90°C.

  20. Arsenic removal from acidic solutions with biogenic ferric precipitates.

    PubMed

    Ahoranta, Sarita H; Kokko, Marika E; Papirio, Stefano; Özkaya, Bestamin; Puhakka, Jaakko A

    2016-04-05

    Treatment of acidic solution containing 5g/L of Fe(II) and 10mg/L of As(III) was studied in a system consisting of a biological fluidized-bed reactor (FBR) for iron oxidation, and a gravity settler for iron precipitation and separation of the ferric precipitates. At pH 3.0 and FBR retention time of 5.7h, 96-98% of the added Fe(II) precipitated (99.1% of which was jarosite). The highest iron oxidation and precipitation rates were 1070 and 28mg/L/h, respectively, and were achieved at pH 3.0. Subsequently, the effect of pH on arsenic removal through sorption and/or co-precipitation was examined by gradually decreasing solution pH from 3.0 to 1.6 (feed pH). At pH 3.0, 2.4 and 1.6, the highest arsenic removal efficiencies obtained were 99.5%, 80.1% and 7.1%, respectively. As the system had ferric precipitates in excess, decreased arsenic removal was likely due to reduced co-precipitation at pH<2.4. As(III) was partially oxidized to As(V) in the system. In shake flask experiments, As(V) sorbed onto jarosite better than As(III). Moreover, the sorption capacity of biogenic jarosite was significantly higher than that of synthetic jarosite. The developed bioprocess simultaneously and efficiently removes iron and arsenic from acidic solutions, indicating potential for mining wastewater treatment. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Adsorption of anionic and cationic dyes on activated carbon from aqueous solutions: equilibrium and kinetics.

    PubMed

    Rodríguez, Araceli; García, Juan; Ovejero, Gabriel; Mestanza, María

    2009-12-30

    Activated carbon was utilized as adsorbent to remove anionic dye, Orange II (OII), and cationic dye, Methylene blue (MB), from aqueous solutions by adsorption. Batch experiments were conducted to study the effects of temperature (30-65 degrees C), initial concentration of adsorbate (300-500 mg L(-1)) and pH (3.0-9.0) on dyes adsorption. Equilibrium adsorption isotherms and kinetics were investigated. The equilibrium experimental data were analyzed by the Langmuir, Freundlich, Toth and Redlich-Peterson models. The kinetic data obtained with different carbon mass were analyzed using a pseudo-first order, pseudo-second order, intraparticle diffusion, Bangham and Chien-Clayton equations. The best results were achieved with the Langmuir isotherm equilibrium model and with the pseudo-second order kinetic model. The activated carbon was found to be very effective as adsorbent for MB and OII from aqueous solutions.

  2. 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.

  3. Grafting the surface of carbon nanotubes and carbon black with the chemical properties of hyperbranched polyamines

    NASA Astrophysics Data System (ADS)

    Morales-Lara, Francisco; Domingo-García, María; López-Garzón, Rafael; Luz Godino-Salido, María; Peñas-Sanjuán, Antonio; López-Garzón, F. Javier; Pérez-Mendoza, Manuel; Melguizo, Manuel

    2016-01-01

    Controlling the chemistry on the surface of new carbon materials is a key factor to widen the range of their applicability. In this paper we show a grafting methodology of polyalkylamines to the surface of carbon nanomaterials, in particular, carbon nanotubes and a carbon black. The aim of this work is to reach large degrees of covalent functionalization with hyperbranched polyethyleneimines (HBPEIs) and to efficiently preserve the strong chelating properties of the HBPEIs when they are fixed to the surface of these carbon materials. This functionalization opens new possibilities of using these carbon nanotubes-based hybrids. The results show that the HBPEIs are covalently attached to the carbon materials, forming hybrids. These hybrids emerge from the reaction of amine functions of the HBPEIs with carbonyls and carboxylic anhydrides of the carbon surface which become imine and imide bonds. Thus, due to the nature of these bonds, the pre-oxidized samples with relevant number of C=O groups showed an increase in the degree of functionalization with the HBPEIs. Furthermore, both the acid-base properties and the coordination capacity for metal ions of the hybrids are equivalent to that of the free HBPEIs in solution. This means that the chemical characteristics of the HBPEIs have been efficiently transferred to the hybrids. To reach this conclusion we have developed a novel procedure to assess the acid-base and the coordination properties of the hybrids (solids) by means of potentiometric titration. The good agreement of the values obtained for the hybrids and for the free HBPEIs in aqueous solution supports the reliability of the procedure. Moreover, the high capacity of the hybrids to capture Ni2+ by complexation opens new possibilities of using these hybrids to capture high-value metal ions such as Pd2+ and Pt2+.

  4. Grafting the surface of carbon nanotubes and carbon black with the chemical properties of hyperbranched polyamines

    PubMed Central

    Morales-Lara, Francisco; Domingo-García, María; López-Garzón, Rafael; Luz Godino-Salido, María; Peñas-Sanjuán, Antonio; López-Garzón, F. Javier; Pérez-Mendoza, Manuel; Melguizo, Manuel

    2016-01-01

    Abstract Controlling the chemistry on the surface of new carbon materials is a key factor to widen the range of their applicability. In this paper we show a grafting methodology of polyalkylamines to the surface of carbon nanomaterials, in particular, carbon nanotubes and a carbon black. The aim of this work is to reach large degrees of covalent functionalization with hyperbranched polyethyleneimines (HBPEIs) and to efficiently preserve the strong chelating properties of the HBPEIs when they are fixed to the surface of these carbon materials. This functionalization opens new possibilities of using these carbon nanotubes-based hybrids. The results show that the HBPEIs are covalently attached to the carbon materials, forming hybrids. These hybrids emerge from the reaction of amine functions of the HBPEIs with carbonyls and carboxylic anhydrides of the carbon surface which become imine and imide bonds. Thus, due to the nature of these bonds, the pre-oxidized samples with relevant number of C=O groups showed an increase in the degree of functionalization with the HBPEIs. Furthermore, both the acid-base properties and the coordination capacity for metal ions of the hybrids are equivalent to that of the free HBPEIs in solution. This means that the chemical characteristics of the HBPEIs have been efficiently transferred to the hybrids. To reach this conclusion we have developed a novel procedure to assess the acid-base and the coordination properties of the hybrids (solids) by means of potentiometric titration. The good agreement of the values obtained for the hybrids and for the free HBPEIs in aqueous solution supports the reliability of the procedure. Moreover, the high capacity of the hybrids to capture Ni2+ by complexation opens new possibilities of using these hybrids to capture high-value metal ions such as Pd2+ and Pt2+. PMID:27877902

  5. Patterned forests of vertically-aligned multiwalled carbon nanotubes using metal salt catalyst solutions.

    PubMed

    Garrett, David J; Flavel, Benjamin S; Baronian, Keith H R; Downard, Alison J

    2013-01-01

    A simple method for producing patterned forests of multiwalled carbon nanotubes (MWCNTs) is described. An aqueous metal salt solution is spin-coated onto a substrate patterned with photoresist by standard methods. The photoresist is removed by acetone washing leaving the acetone-insoluble catalyst pattern on the substrate. Dense forests of vertically aligned (VA) MWCNTs are grown on the patterned catalyst layers by chemical vapour deposition. The procedures have been demonstrated by growing MWCNT forests on two substrates: silicon and conducting graphitic carbon films. The forests adhere strongly to the substrates and when grown directly on carbon film, offer a simple method of preparing MWCNT electrodes.

  6. ANALYSIS OF THE REACTIVITY OF RADPRO SOLUTION WITH COTTON RAGS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    MARUSICH RM

    Rags containing RadPro{reg_sign} solution will be generated during the decontamination of the Plutonium Finishing Plant (PFP). Under normal conditions, the rags will be neutralized with sodium carbonate prior to placing in the drums. The concern with RadPro solutions and cotton rags is that some of the RadPro solutions contain nitric acid. Under the right conditions, nitric acid and cotton rags exothermically react. The concern is, will RadPro solutions react with cotton rags exothermically? The potential for a runaway reaction for any of the RadPro solutions used was studied in Section 5.2 of PNNL-15410, Thermal Stability Studies of Candidate Decontamination Agentsmore » for Hanford's Plutonium Finishing Plant Plutonium-Contaminated Gloveboxes. This report shows the thermal behavior of cotton rags having been saturated in one of the various neutralized and non-neutralized RadPro solutions. The thermal analysis was performed using thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Accelerating Rate Calorimetry (ARC).« less

  7. Characterization of 1:1 Random Copolymers Obtained from 6-, 7-, 11-, and 12-Carbon Amino Acids.

    DTIC Science & Technology

    1993-10-22

    Random Copolymers Obtained From 6-, 7-, 11-, and 12-Carbon Amino Acids by C. G. Johnson and L. J. Mathias 0 T .... Prepared for Publication r. t in the...NOOOG4-f-j- From 6-, 7-, 11-, and 12-Carbon Amino Acids 1225 ~~~ :: V Co~de 413m(iUK C. G Johnson, and Lo J. Mathias ś RFORMING ORGANIZA7,iCN ;fAMjjS...distribution is unlimited. Copolymers were prepared from the title amino acids by rr ilt condensation under dry nitrogen. The resulting copolymers were

  8. Infrared optical constants of H2O ice, amorphous nitric acid solutions, and nitric acid hydrates

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.; Koehler, Birgit G.; Middlebrook, Ann M.; Tolbert, Margaret A.; Jordon, Joseph

    1994-01-01

    We determined the infrared optical constants of nitric acid trihydrate, nitric acid dihydrate, nitric acid monohydrate, and solid amorphous nitric acid solutions which crystallize to form these hydrates. We have also found the infrared optical constants of H2O ice. We measured the transmission of infrared light throught thin films of varying thickness over the frequency range from about 7000 to 500/cm at temperatures below 200 K. We developed a theory for the transmission of light through a substrate that has thin films on both sides. We used an iterative Kramers-Kronig technique to determine the optical constants which gave the best match between measured transmission spectra and those calculated for a variety of films of different thickness. These optical constants should be useful for calculations of the infrared spectrum of polar stratospheric clouds.

  9. Effects of dietary polyunsaturated fatty acids and nucleotides on tissue fatty acid profiles of rats with carbon tetrachloride-induced liver damage.

    PubMed

    Fontana, L; Moreira, E; Torres, M I; Periago, J L; Sánchez de Medina, F; Gil, A

    1999-04-01

    The deficiency of polyunsaturated fatty acids (PUFA) that occurs in plasma of patients with liver cirrhosis has been assessed in rats with severe steatosis and mild liver necrosis induced by repeated administration of low doses of carbon tetrachloride (CCl(4)). The contribution of both dietary (n-3) long-chain PUFA and nucleotides to the recovery of the altered fatty acid profiles of tissue lipids of these rats has also been studied. Two groups of rats were used. The first was intraperitoneally injected 0.15 ml of a 10% (v/v) CCl(4)solution in paraffin per 100 g of body weight, three times a week for 9 weeks; the second received paraffin alone. After the treatment, six rats of each group were killed. Afterwards, the remaining controls were fed a semipurified diet (SPD) for 3 weeks, and the remaining rats in the CCl(4)group were divided into three new groups: the first was fed the SP diet; the second was fed the SP diet supplemented with 1% (n-3) polyunsaturated fatty acids (PUFA diet); and the third was fed the SP diet supplemented with 250 mg nucleotides per 100 g diet (NT diet). Fatty acids of plasma, erythrocyte membranes and liver microsomes were analyzed. Decreases in linoleic and arachidonic acids in both total plasma lipids and liver microsomal phospholipids were the main findings due to CCl(4)treatment. The rats that received CCl(4)and the PUFA diet showed the lowest levels of (n-6) PUFA and the highest levels of (n-3) PUFA in liver microsomal phospholipids, as well as a significant increase of (n-3) PUFAs in total plasma lipids. The animals that received the NT diet showed no signs of fatty infiltration and exhibited the highest levels of (n-6) PUFAs in liver microsomal phospholipids. These results show that CCl(4)affects fatty acid metabolism which is accordingly reflected in altered tissue fatty acid profiles, and that balanced diets containing PUFA and nucleotides are important for the recovery of the damaged liver in rats. Copyright 1999 Harcourt

  10. Sol-gel thin-film based mesoporous silica and carbon nanotubes for the determination of dopamine, uric acid and paracetamol in urine.

    PubMed

    Canevari, Thiago C; Raymundo-Pereira, Paulo A; Landers, Richard; Benvenutti, Edilson V; Machado, Sérgio A S

    2013-11-15

    This work describes the preparation, characterization and application of a hybrid material composed of disordered mesoporous silica (SiO2) modified with multiwalled carbon nanotubes (MWCNTs), obtained by the sol-gel process using HF as the catalyst. This hybrid material was characterized by N2 adsorption-desorption isotherms, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission microscopy (HR-TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). This new hybrid material was used for the construction of a thin film on a glassy carbon electrode. The modified electrode using this material was designated SiO2/MWCNT/GCE. The electrocatalytic properties of the electrode toward dopamine, uric acid and paracetamol oxidation were studied by differential pulse voltammetry. Well-defined and separated oxidation peaks were observed in phosphate buffer solution at pH 7.0, in contrast with the ill-defined peaks observed with unmodified glassy carbon electrodes. The electrode had high sensitivity for the determination of dopamine, uric acid and paracetamol, with the limits of detection obtained using statistical methods, at 0.014, 0.068 and 0.098 µmol L(-1), respectively. The electrode presented some important advantages, including enhanced physical rigidity, surface renewability by polishing and high sensitivity, allowing the simultaneous determination of these three analytes in a human urine sample. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved.

  11. Assessment of the Effects Exerted by Acid and Alkaline Solutions on Bone: Is Chemistry the Answer?

    PubMed

    Amadasi, Alberto; Camici, Arianna; Porta, Davide; Cucca, Lucia; Merli, Daniele; Milanese, Chiara; Profumo, Antonella; Rassifi, Nabila; Cattaneo, Cristina

    2017-09-01

    The treatment of corpses with extremely acid or basic liquids is sometimes performed in criminal contexts. A thorough characterization by chemical analysis may provide further help to macroscopic and microscopic analysis; 63 porcine bone samples were treated with solutions at different pH (1-14) for immersion periods up to 70 days, as well as in extremely acidic sulfuric acid solutions (9 M/18 M) and extremely basic sodium hydroxide. Inductively coupled optical emission spectrometry (ICP-OES)/plasma mass spectrometry (ICP-MS), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray analysis (EDX), X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM) showed that only the sulfuric acid solution 18 M was able to completely dissolve the sample. In addition, chemical analysis allowed to recognize the contact between bone and substances. Hydrated calcium sulfate arose from extreme pH. The possibility of detecting the presence of human material within the residual solution was demonstrated, especially with FT-IR, ICP-OES, and EDX. © 2017 American Academy of Forensic Sciences.

  12. Thermodynamics of Hydrophobic Amino Acids in Solution: A Combined Experimental–Computational Study

    DOE PAGES

    Song, Lingshuang; Yang, Lin; Meng, Jie; ...

    2016-12-29

    Here, we present a joint experimental-computational study to quantitatively describe the thermodynamics of hydrophobic leucine amino acids in aqueous solution. X-ray scattering data were acquired at a series of solute and salt concentrations to effectively measure inter-leucine interactions, indicating that a major scattering peak is observed consistently at q = 0.83 Å -1. Atomistic molecular dynamics simulations were then performed and compared with the scattering data, achieving high consistency at both small and wider scattering angles (q = 0$-$1.5 Å -1). This experimental-computational consistence enables a first glimpse of the leucineleucine interacting landscape, where two leucine molecules are aligned mostlymore » in a parallel fashion, as opposed to anti-parallel, but also allows us to derive effective leucine-leucine interactions in solution. Collectively, this combined approach of employing experimental scattering and molecular simulation enables a quantitative characterization on effective inter-molecular interactions of hydrophobic amino acids, critical for protein function and dynamics such as protein folding.« less

  13. Thermodynamics of Hydrophobic Amino Acids in Solution: A Combined Experimental–Computational Study

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Song, Lingshuang; Yang, Lin; Meng, Jie

    Here, we present a joint experimental-computational study to quantitatively describe the thermodynamics of hydrophobic leucine amino acids in aqueous solution. X-ray scattering data were acquired at a series of solute and salt concentrations to effectively measure inter-leucine interactions, indicating that a major scattering peak is observed consistently at q = 0.83 Å -1. Atomistic molecular dynamics simulations were then performed and compared with the scattering data, achieving high consistency at both small and wider scattering angles (q = 0$-$1.5 Å -1). This experimental-computational consistence enables a first glimpse of the leucineleucine interacting landscape, where two leucine molecules are aligned mostlymore » in a parallel fashion, as opposed to anti-parallel, but also allows us to derive effective leucine-leucine interactions in solution. Collectively, this combined approach of employing experimental scattering and molecular simulation enables a quantitative characterization on effective inter-molecular interactions of hydrophobic amino acids, critical for protein function and dynamics such as protein folding.« less

  14. Self-assembly of nitrogen-doped carbon nanoparticles: a new ratiometric UV-vis optical sensor for the highly sensitive and selective detection of Hg(2+) in aqueous solution.

    PubMed

    Ruan, Yudi; Wu, Lie; Jiang, Xiue

    2016-05-23

    Water-soluble nitrogen-doped carbon nanoparticles (N-CNPs) prepared by the one-step hydrothermal treatment of uric acid were found to show ratiometric changes in their UV-vis spectra due to Hg(2+)-mediated self-assembly. For the first time, such a property was developed into a UV-vis optical sensor for detecting Hg(2+) in aqueous solutions with high sensitively and selectively (detection limit = 1.4 nM). More importantly, this novel sensor exhibits a higher linear sensitivity over a wider concentration range compared with the fluorescence sensor based on the same N-CNPs. This work opens an exciting new avenue to explore the use of carbon nanoparticles in constructing UV-vis optical sensors for the detection of metal ions and the use of carbon nanoparticles as a new building block to self-assemble into superlattices.

  15. Nanostructural characterization of large-scale porous alumina fabricated via anodizing in arsenic acid solution

    NASA Astrophysics Data System (ADS)

    Akiya, Shunta; Kikuchi, Tatsuya; Natsui, Shungo; Suzuki, Ryosuke O.

    2017-05-01

    Anodizing of aluminum in an arsenic acid solution is reported for the fabrication of anodic porous alumina. The highest potential difference (voltage) without oxide burning increased as the temperature and the concentration of the arsenic acid solution decreased, and a high anodizing potential difference of 340 V was achieved. An ordered porous alumina with several tens of cells was formed in 0.1-0.5 M arsenic acid solutions at 310-340 V for 20 h. However, the regularity of the porous alumina was not improved via anodizing for 72 h. No pore sealing behavior of the porous alumina was observed upon immersion in boiling distilled water, and it may be due to the formation of an insoluble complex on the oxide surface. The porous alumina consisted of two different layers: a hexagonal alumina layer that contained arsenic from the electrolyte and a pure alumina honeycomb skeleton. The porous alumina exhibited a white photoluminescence emission at approximately 515 nm under UV irradiation at 254 nm.

  16. Solution blow spinning: parameters optimization and effects on the properties of nanofibers from poly(lactic) acid/dimethyl carbonate solutions

    USDA-ARS?s Scientific Manuscript database

    Solution blow spinning (SBS) is a process to produce non-woven fiber sheets with high porosity and an extremely large amount of surface area. In this study, a Box-Behnken experimental design (BBD) was used to optimize the processing parameters for the production of nanofibers from polymer solutions ...

  17. A study on lithium/air secondary batteries-Stability of NASICON-type glass ceramics in acid solutions

    NASA Astrophysics Data System (ADS)

    Shimonishi, Y.; Zhang, T.; Johnson, P.; Imanishi, N.; Hirano, A.; Takeda, Y.; Yamamoto, O.; Sammes, N.

    The stability of a NASICON-type lithium ion conducting solid electrolyte, Li 1+ x+ yTi 2- xAl xP 3- ySi yO 12 (LTAP), in acetic acid and formic acid solutions was examined. XRD patterns of the LTAP powders immersed in 100% acetic acid and formic acid at 50 °C for 4 months showed no change as compared to the pristine LTAP. However, the electrical conductivity of LTAP drastically decreased. On the other hand, no significant electrical conductivity change of LTAP immersed in lithium formate saturated formic acid-water solution was observed, and the electrical conductivity of LTAP immersed in lithium acetate saturated acetic acid-water increased. Cyclic voltammogram tests suggested that acetic acid was stable up to a high potential, but formic acid decomposed under the decomposition potential of water. The acetic acid solution was considered to be a candidate for the active material in the air electrode of lithium-air rechargeable batteries. The cell reaction was considered as 2Li + 2 CH 3COOH + 1/2O 2 = 2CH 3COOLi + H 2O. The energy density of this lithium-air system is calculated to be 1477 Wh kg -1 from the weights of Li and CH 3COOH, and an observed open-circuit voltage of 3.69 V.

  18. Mechanistic study of fulvic acid assisted propranolol photodegradation in aqueous solution.

    PubMed

    Makunina, Maria P; Pozdnyakov, Ivan P; Chen, Yong; Grivin, Vyacheslav P; Bazhin, Nikolay M; Plyusnin, Victor F

    2015-01-01

    Laser flash (355 nm) and stationary (365 nm) photolysis were used to study the mechanisms of propranolol photolysis in the presence of fulvic acid in aqueous solutions. The FA-assisted photodegradation of propranolol was observed using UV-A irradiation (where propranolol is stable). Direct evidence indicated that the photodegradation resulted from the static quenching of the FA triplet state by propranolol via the electron transfer mechanism. The triplet state yield (ϕT≈0.6%) and the T-T absorption coefficient (ɛT(620 nm)≈5×10(4) M(-1) cm(-1)) were estimated for the first time by modeling the yields of the FA triplet state in the presence of propranolol. Thus, fulvic acid is a promising agent for accelerating propranolol photodegradation in aqueous solutions under UV-A light irradiation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Rheology and physical-chemical characteristics of the solutions of the medicines

    NASA Astrophysics Data System (ADS)

    Urakov, A.; Urakova, N.

    2015-04-01

    In the laboratory studied the dynamics of rheology of water solutions with plasma- inflammatory and antiseptic funds when mixing them with blood, plasma and pus under the influence of the following physical and chemical factors of local interaction: gravity, specific gravity, temperature, relative viscosity, internal pressure, sparkling water, total concentration of the ingredients, surface activity, volume of acid and osmotic activity of medicines. Found that the rheology of biological liquids improve hyperthermic, highly alkaline and highly carbonated solution medicines. For the dilution of pus, dense festering mass of sulfur plugs and tear stones invited to apply heated to +39 - +42°C with aqueous solution of 0.5 - 3% hydrogen peroxide and 0.5 - 10% sodium bicarbonate saturated with carbon dioxide to excess pressure 0.2 ATM.

  20. Chemical Corrosion of Liquid-Phase Sintered SiC in Acidic/Alkaline Solutions Part 1. Corrosion in HNO3 Solution

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Zhang, Ming; He, Xinnong; Tang, Wenming

    2016-03-01

    The corrosion behavior of the liquid-phase sintered SiC (LPS-SiC) was studied by dipping in 3.53 mol/L HNO3 aqueous solution at room temperature and 70 °C, respectively. The weight loss, strength reduction and morphology evolution of the SiC specimens during corroding were revealed and also the chemical corrosion process and mechanism of the SiC specimens in the acidic solution were clarified. The results show that the corrosion of the LPS-SiC specimens in the HNO3 solution is selective. The SiC particles are almost free from corrosion, but the secondary phases of BaAl2Si2O8 (BAS) and Y2Si2O7 are corroded via an acid-alkali neutralization reaction. BAS has a higher corrosion rate than Y2Si2O7, resulting in the formation of the bamboo-leaf-like corrosion pits. As the SiC specimens etched in the HNO3 solution at room temperature for 75 days, about 80 μm thickness corrosion layer forms. The weight loss and bending strength reduction of the etched SiC specimens are 2.6 mg/cm2 and 52%, respectively. The corrosion of the SiC specimens is accelerated in the 70 °C HNO3 solution with a rate about five times bigger than that in the same corrosion medium at room temperature.

  1. Carbon-11 and Fluorine-18 Labeled Amino Acid Tracers for Positron Emission Tomography Imaging of Tumors

    NASA Astrophysics Data System (ADS)

    Sun, Aixia; Liu, Xiang; Tang, Ganghua

    2017-12-01

    Tumor cells have an increased nutritional demand for amino acids(AAs) to satisfy their rapid proliferation. Positron-emitting nuclide labeled AAs are interesting probes and are of great importance for imaging tumors using positron emission tomography (PET). Carbon-11 and fluorine-18 labeled AAs include the [1-11C] amino acids, labeling alpha-C- amino acids, the branched-chain of amino acids and N-substituted carbon-11 labeled amino acids. These tracers target protein synthesis or amino acid(AA) transport, and their uptake mechanism mainly involves AA transport. AA PET tracers have been widely used in clinical settings to image brain tumors, neuroendocrine tumors, prostate cancer, breast cancer, non–small cell lung cancer (NSCLC) and hepatocellular carcinoma. This review focuses on the fundamental concepts and the uptake mechanism of AAs, AA PET tracers and their clinical applications.

  2. Ion association in water solution of soil and vadose zone of chestnut saline solonetz as a driver of terrestrial carbon sink

    NASA Astrophysics Data System (ADS)

    Batukaev, Abdul-Malik A.; Endovitsky, Anatoly P.; Andreev, Andrey G.; Kalinichenko, Valery P.; Minkina, Tatiana M.; Dikaev, Zaurbek S.; Mandzhieva, Saglara S.; Sushkova, Svetlana N.

    2016-03-01

    The assessment of soil and vadose zone as the drains for carbon sink and proper modeling of the effects and extremes of biogeochemical cycles in the terrestrial biosphere are the key components to understanding the carbon cycle, global climate system, and aquatic and terrestrial system uncertainties. Calcium carbonate equilibrium causes saturation of solution with CaCO3, and it determines its material composition, migration and accumulation of salts. In a solution electrically neutral ion pairs are formed: CaCO30, CaSO40, MgCO30, and MgSO40, as well as charged ion pairs CaHCO3+, MgHCO3+, NaCO3-, NaSO4-, CaOH+, and MgOH+. The calcium carbonate equilibrium algorithm, mathematical model and original software to calculate the real equilibrium forms of ions and to determine the nature of calcium carbonate balance in a solution were developed. This approach conducts the quantitative assessment of real ion forms of solution in solonetz soil and vadose zone of dry steppe taking into account the ion association at high ionic strength of saline soil solution. The concentrations of free and associated ion form were calculated according to analytical ion concentration in real solution. In the iteration procedure, the equations were used to find the following: ion material balance, a linear interpolation of equilibrium constants, a method of ionic pairs, the laws of initial concentration preservation, operating masses of equilibrium system, and the concentration constants of ion pair dissociation. The coefficient of ion association γe was determined as the ratio of ions free form to analytical content of ion γe = Cass/Can. Depending on soil and vadose zone layer, concentration and composition of solution in the ionic pair's form are 11-52 % Ca2+; 22.2-54.6 % Mg2+; 1.1-10.5 % Na+; 3.7-23.8 HCO3-, 23.3-61.6 % SO42-, and up to 85.7 % CO32-. The carbonate system of soil and vadose zone water solution helps to explain the evolution of salted soils, vadose and saturation zones, and

  3. Application of activated carbon modified by acetic acid in adsorption and separation of CO2 and CH4

    NASA Astrophysics Data System (ADS)

    Song, Xue; Wang, Li'ao; Zeng, Yunmin; Zhan, Xinyuan; Gong, Jian; Li, Tong

    2018-03-01

    Compared with the methods to modify the activated carbons by alkalis for gas adsorption, fewer studies of that by organic acids have been reported. The acid modified activated carbons are usually utilized to treat wastewater, whereas the application in the separation of CO2/CH4 has less been studied. In this study, acetic acid was used to modify activated carbon. N2 adsorption/desorption isotherms and FT-IR were adopted to describe the properties of the samples. According to the adsorption data of pure gas component at 298 K, the gas adsorbed amount and the selectivity on the modified samples were larger than that on the raw sample. Besides, the adsorbed amount of CO2 and the selectivity on 15H-AC in the adsorption breakthrough experiments showed better performance. The results confirm that the method to modify the activated carbons with acetic acid is feasible to improve the adsorption capacity and the separation effect of CO2/CH4.

  4. Adsorption of nucleic acid bases and amino acids on single-walled carbon and boron nitride nanotubes: a first-principles study.

    PubMed

    Zheng, Jiaxin; Song, Wei; Wang, Lu; Lu, Jing; Luo, Guangfu; Zhou, Jing; Qin, Rui; Li, Hong; Gao, Zhengxiang; Lai, Lin; Li, Guangping; Mei, Wai Ning

    2009-11-01

    We study the adsorptions of nucleic acid bases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) and four amino acids phenylalanine, tyrosine, tryptophan, alanine on the single-walled carbon nanotubes (SWCNTs) and boron nitride nanotubes (SWBNNTs) by using density functional theory. We find that the aromatic content plays a critical role in the adsorption. The adsorptions of nucleic acid bases and amino acids on the (7, 7) SWBNNT are stronger than those on the (7, 7) SWCNT. Oxidative treatment of SWCNTs favors the adsorption of biomolecules on nanotubes.

  5. An evaluation of MES (2(N-Morpholino)ethanesulfonic acid) and Amberlite IRC-50 as pH buffers for nutrient solution studies

    NASA Technical Reports Server (NTRS)

    Bugbee, B. G.; Salisbury, F. B.

    1985-01-01

    All buffering agents used to stabilize pH in hydroponic research have disadvantages. Inorganic buffers are absorbed and may become phytotoxic. Solid carbonate salts temporarily mitigate decreasing pH but provide almost no protection against increasing pH, and they alter nutrient absorption. Exchange resins are more effective, but we find that they remove magnesium and manganese from solution. We have tested 2(N-Morpholino)ethanesulfonic acid (MES) as a buffering agent at concentrations of 1 and 10 mol m-3 (1 and 10 mM) with beans, corn, lettuce, tomatoes, and wheat. MES appears to be biologically inert and does not interact significantly with other solution ions. Relative growth rates among controls and MES treatments were nearly identical for each species during the trial period. The pH was stabilized by 1 mol m-3 MES. This buffer warrants further consideration in nutrient research.

  6. 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.

  7. A prospective randomized trial of two solutions for intrapartum amnioinfusion: effects on fetal electrolytes, osmolality, and acid-base status.

    PubMed

    Pressman, E K; Blakemore, K J

    1996-10-01

    Our purpose was to compare the effects of intrapartum amnioinfusion with normal saline solution versus lactated Ringer's solution plus physiologic glucose on neonatal electrolytes and acid-base balance. Patients undergoing amnioinfusion for obstetric indications were randomized to receive normal saline solution or lactated Ringer's solution plus physiologic glucose at standardized amnioinfusion rates. Data were collected prospectively on maternal demographics, course of labor, and maternal and neonatal outcome. Arterial cord blood was obtained for analysis of electrolytes, glucose, osmolality, lactic acid, and blood gases. Control subjects with normal fetal heart rate patterns, and clear amniotic fluid not receiving amnioinfusion were studied concurrently. Data were collected on 59 patients (21 normal saline solution, 18 lactated Ringer's solution plus physiologic glucose, and 20 controls). Maternal demographics, course of labor, and neonatal outcome were similar in all three groups. Cesarean sections were performed more often in the amnioinfusion groups (33.3% for normal saline solution, 38.9% for lactated Ringer's solution plus physiologic glucose) than in the control group (5.0%), p < 0.05. Cord arterial electrolytes, glucose, osmolality, lactic acid, and blood gases were not altered by amnioinfusion with either solution. Intrapartum amnioinfusion with normal saline solution or lactated Ringer's solution plus physiologic glucose has no effect on neonatal electrolytes or acid-base balance.

  8. The effectiveness of sodium hydroxide (NaOH) and sodium carbonate (Na2CO3) on the impurities removal of saturated salt solution

    NASA Astrophysics Data System (ADS)

    Pujiastuti, C.; Ngatilah, Y.; Sumada, K.; Muljani, S.

    2018-01-01

    Increasing the quality of salt can be done through various methods such as washing (hydro-extraction), re-crystallization, ion exchange methods and others. In the process of salt quality improvement by re-crystallization method where salt product diluted with water to form saturated solution and re-crystallized through heating process. The quality of the salt produced is influenced by the quality of the dissolved salt and the crystallization mechanism applied. In this research is proposed a concept that before the saturated salt solution is recrystallized added a chemical for removal of the impurities such as magnesium ion (Mg), calcium (Ca), potassium (K) and sulfate (SO4) is contained in a saturated salt solution. The chemical reagents that used are sodium hydroxide (NaOH) 2 N and sodium carbonate (Na2CO3) 2 N. This research aims to study effectiveness of sodium hydroxide and sodium carbonate on the impurities removal of magnesium (Mg), calcium (Ca), potassium (K) and sulfate (SO4). The results showed that the addition of sodium hydroxide solution can be decreased the impurity ions of magnesium (Mg) 95.2%, calcium ion (Ca) 45%, while the addition of sodium carbonate solution can decreased magnesium ion (Mg) 66.67% and calcium ion (Ca) 77.5%, but both types of materials are not degradable sulfate ions (SO4). The sodium hydroxide solution more effective to decrease magnesium ion than sodium carbonate solution, and the sodium carbonate solution more effective to decrease calcium ion than sodium hydroxide solution.

  9. Solution-processed soldering of carbon nanotubes for flexible electronics.

    PubMed

    Rao, K D M; Radha, B; Smith, K C; Fisher, T S; Kulkarni, G U

    2013-02-22

    We report a simple lithography-free, solution-based method of soldering of carbon nanotubes with Ohmic contacts, by taking specific examples of multi-walled carbon nanotubes (MWNTs). This is achieved by self-assembling a monolayer of soldering precursor, Pd(2+) anchored to 1,10 decanedithiol, onto which MWNTs could be aligned across the gap electrodes via solvent evaporation. The nanosoldering was realized by thermal/electrical activation or by both in sequence. Electrical activation and the following step of washing ensure selective retention of MWNTs spanning across the gap electrodes. The soldered joints were robust enough to sustain strain caused during the bending of flexible substrates as well as during ultrasonication. The estimated temperature generated at the MWNT-Au interface using an electro-thermal model is ∼150 °C, suggesting Joule heating as the primary mechanism of electrical activation. Further, the specific contact resistance is estimated from the transmission line model.

  10. First Molecular Dynamics simulation insight into the mechanism of organics adsorption from aqueous solutions on microporous carbons

    NASA Astrophysics Data System (ADS)

    Terzyk, Artur P.; Gauden, Piotr A.; Zieliński, Wojciech; Furmaniak, Sylwester; Wesołowski, Radosław P.; Klimek, Kamil K.

    2011-10-01

    The results of 84 MD simulations showing the influence of porosity and carbon surface oxidation on adsorption of three organic compounds from aqueous solutions on carbons are reported. Based on a model of 'soft' activated carbon, three carbon structures with gradually changed microporosity were created. Next, different number of surface oxygen groups was introduced. We observe quantitative agreement between simulation and experiment i.e. the decrease in adsorption from benzene down to paracetamol. Simulation results clearly demonstrate that the balance between porosity and carbon surface chemical composition in organics adsorption on carbons, and the pore blocking determine adsorption properties of carbons.

  11. Adsorption of Cu(II) from aqueous solution on sulfuric acid treated palygorskite

    NASA Astrophysics Data System (ADS)

    Niu, Yan-Ning; Yuan, Yuan; Gao, Wei-Xin; Qian, Sheng; Sun, Wen

    2018-03-01

    The absorption behavior of Cu2+ from aqueous solution on sulfuric acid treated palygorskite were investigated, the results showed that palygorskite had high absorption ability for Cu2+ from aqueous solution. Effects of the shaking time, pH and the copper ion concentration on the removal rate were discussed. The absorption behavior of Cu2+ could be well imitated by the Langmuir isothermal equation.

  12. Solid-phase extraction using bis(indolyl)methane-modified silica reinforced with multiwalled carbon nanotubes for the simultaneous determination of flavonoids and aromatic organic acid preservatives.

    PubMed

    Wang, Na; Liao, Yuan; Wang, Jiamin; Tang, Sheng; Shao, Shijun

    2015-12-01

    A novel bis(indolyl)methane-modified silica reinforced with multiwalled carbon nanotubes sorbent for solid-phase extraction was designed and synthesized by chemical immobilization of nitro-substituted 3,3'-bis(indolyl)methane on silica modified with multiwalled carbon nanotubes. Coupled with high-performance liquid chromatography analysis, the extraction properties of the sorbent were evaluated for flavonoids and aromatic organic acid compounds. Under optimum conditions, the sorbent can simultaneously extract five flavonoids and two aromatic organic acid preservatives in aqueous solutions in a single-step solid-phase extraction procedure. Wide linear ranges were obtained with correlation coefficients (R(2) ) ranging from 0.9843 to 0.9976, and the limits of detection were in the range of 0.5-5 μg/L for the compounds tested. Compared with the silica modified with multiwalled carbon nanotubes sorbent and the nitro-substituted 3,3'-bis(indolyl)methane-modified silica sorbent, the developed sorbent exhibited higher extraction efficiency toward the selected analytes. The synergistic effect of nitro-substituted 3,3'-bis(indolyl)methane and multiwalled carbon nanotubes not only improved the surface-to-volume ratio but also enhanced multiple intermolecular interactions, such as hydrogen bonds, π-π, and hydrophobic interactions, between the new sorbent and the selected analytes. The as-established solid-phase extraction with high-performance liquid chromatography and diode array detection method was successfully applied to the simultaneous determination of flavonoids and aromatic organic acid preservatives in grape juices with recoveries ranging from 83.9 to 112% for all the selected analytes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. In vitro study of the effect of a dentifrice containing 8% arginine, calcium carbonate, and sodium monofluorophosphate on acid-softened enamel.

    PubMed

    Rege, Aarti; Heu, Rod; Stranick, Michael; Sullivan, Richard J

    2014-01-01

    To investigate the possible mode of action of a dentifrice containing 8% arginine and calcium carbonate (Pro-Argin Technology), and sodium monofluorophosphate in delivering the benefits of preventing acid erosion and rehardening acid-softened enamel. The surfaces of acid-softened bovine enamel specimens were evaluated after application of a dentifrice containing 8% arginine, calcium carbonate, and sodium monofluorophosphate in vitro. Scanning Electron Microscopy (SEM), Electronic Spectrometry for Chemical Analysis (ESCA), and Secondary Ion Mass Spectrometry (SIMS) were used to characterize the enamel surfaces. Exposure of pristine enamel surfaces to citric acid resulted in clear roughening of the surface. Multiple applications of a dentifrice containing 8% arginine, calcium carbonate, and sodium monofluorophosphate to the surface of the enamel resulted in the disappearance of the microscopic voids observed by SEM as a function of treatment applications. The ESCA analysis demonstrated that both the nitrogen and carbonate levels increased as the number of treatments increased, which provides evidence that arginine and calcium carbonate were bound to the surface. Observance of arginine's signature mass fragmentation pattern by SIMS analysis confirmed the identity of arginine on the enamel surface. A series of in vitro experiments has demonstrated a possible mode of action by which a dentifrice containing 8% arginine, calcium carbonate, and sodium monofluorophosphate delivers the benefits of preventing acid erosion and rehardening acid-softened enamel. The combination of arginine and calcium carbonate adheres to the enamel surface and helps to fill the microscopic gaps created by acid, which in turn helps repair the enamel and provides a protective coating against future acid attacks.

  14. 40 CFR 721.10369 - Carbonic acid, diphenyl ester, polymer with diphenyl P-methylphosphonate and 4,4′-(1...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... with diphenyl P-methylphosphonate and 4,4â²-(1-methylethylidene) bis[phenol]. 721.10369 Section 721... Carbonic acid, diphenyl ester, polymer with diphenyl P-methylphosphonate and 4,4′-(1-methylethylidene) bis... identified as carbonic acid, diphenyl ester, polymer with diphenyl P-methylphosphonate and 4,4′-(1...

  15. Reaction of the thermo-labile triazenide Na[tBu3SiNNNSiMe3] with CO2: formation of the imido carbonate (tBu3SiO)(Me3SiO)C[double bond, length as m-dash]N-SitBu3 and carbamine acid (tBu3SiO)CONH2.

    PubMed

    Lerner, H-W; Bolte, M; Wagner, M

    2017-07-11

    The thermo-labile triazenide Na[tBu 3 SiNNNSiMe 3 ] was prepared by the reaction of Me 3 SiN 3 with Na(thf) 2 [SitBu 3 ] in pentane at -78 °C. Treatment of Na[tBu 3 SiNNNSiMe 3 ] with an excess of carbon dioxide in pentane at -78 °C yielded the imido carbonate (tBu 3 SiO)(Me 3 SiO)C[double bond, length as m-dash]N-SitBu 3 and the carbamine acid (tBu 3 SiO)CONH 2 along with other products. From the reaction solution we could isolate the imido carbonate (tBu 3 SiO)(Me 3 SiO)C[double bond, length as m-dash]N-SitBu 3 and carbamine acid (tBu 3 SiO)CONH 2 . At first single crystals of the carbamine acid (tBu 3 SiO)CONH 2 (triclinic, space group P1[combining macron]) were grown from this solution at room temperature. A second crop of crystals were obtained by concentrating the solution. The second charge consisted of the imido carbonate (tBu 3 SiO)(Me 3 SiO)C[double bond, length as m-dash]N-SitBu 3 (monoclinic, space group P2 1 /n).

  16. 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.

  17. Adsorption of metal ions by pecan shell-based granular activated carbons.

    PubMed

    Bansode, R R; Losso, J N; Marshall, W E; Rao, R M; Portier, R J

    2003-09-01

    The present investigation was undertaken to evaluate the adsorption effectiveness of pecan shell-based granular activated carbons (GACs) in removing metal ions (Cu(2+), Pb(2+), Zn(2+)) commonly found in municipal and industrial wastewater. Pecan shells were activated by phosphoric acid, steam or carbon dioxide activation methods. Metal ion adsorption of shell-based GACs was compared to the metal ion adsorption of a commercial carbon, namely, Calgon's Filtrasorb 200. Adsorption experiments were conducted using solutions containing all three metal ions in order to investigate the competitive effects of the metal ions as would occur in contaminated wastewater. The results obtained from this study showed that acid-activated pecan shell carbon adsorbed more lead ion and zinc ion than any of the other carbons, especially at carbon doses of 0.2-1.0%. However, steam-activated pecan shell carbon adsorbed more copper ion than the other carbons, particularly using carbon doses above 0.2%. In general, Filtrasorb 200 and carbon dioxide-activated pecan shell carbons were poor metal ion adsorbents. The results indicate that acid- and steam-activated pecan shell-based GACs are effective metal ion adsorbents and can potentially replace typical coal-based GACs in treatment of metal contaminated wastewater.

  18. Carbon nanotube-templated assembly of regioregular poly(3-alkylthiophene) in solution

    NASA Astrophysics Data System (ADS)

    Zhu, Jiahua; Stevens, Eric; He, Youjun; Hong, Kunlun; Ivanov, Ilia

    2016-09-01

    Control of structural heterogeneity by rationally encoding of the molecular assemblies is a key enabling design of hierarchical, multifunctional materials of the future. Here we report the strategies to gain such control using solution- based assembly to construct a hybrid nano-assembly and a network hybrid structure of regioregular poly(3- alkylthiophene) - carbon nanotube (P3AT-CNT). The opto-electronic performance of conjugated polymer (P3AT) is defined by the structure of the aggregate in solution and in the solid film. Control of P3AT aggregation would allow formation of broad range of morphologies with very distinct electro-optical. We utilize interactive templating to confine the assembly behavior of conjugated polymers, replacing poorly controlled solution processing approach. Perfect crystalline surface of the single-walled and multi-walled carbon nanotube (SWCNT/MWCNT) acts as a template, seeding P3AT aggregation of the surface of the nanotube. The seed continues directional growth through pi-pi stacking leading to the formation of to well-defined P3AT-CNT morphologies, including comb-like nano-assemblies, super- structures and gel networks. Interconnected, highly-branched network structure of P3AT-CNT hybrids is of particular interest to enable efficient, long-range, balanced charge carrier transport. The structure and opto-electionic function of the intermediate assemblies and networks of P3AT/CNT hybrids are characterized by transmission election microscopy and UV-vis absorption.

  19. Beyond temperature: Clumped isotope signatures in dissolved inorganic carbon species and the influence of solution chemistry on carbonate mineral composition

    NASA Astrophysics Data System (ADS)

    Tripati, Aradhna K.; Hill, Pamela S.; Eagle, Robert A.; Mosenfelder, Jed L.; Tang, Jianwu; Schauble, Edwin A.; Eiler, John M.; Zeebe, Richard E.; Uchikawa, Joji; Coplen, Tyler B.; Ries, Justin B.; Henry, Drew

    2015-10-01

    ;Clumped-isotope; thermometry is an emerging tool to probe the temperature history of surface and subsurface environments based on measurements of the proportion of 13C and 18O isotopes bound to each other within carbonate minerals in 13C18O16O22- groups (heavy isotope ;clumps;). Although most clumped isotope geothermometry implicitly presumes carbonate crystals have attained lattice equilibrium (i.e., thermodynamic equilibrium for a mineral, which is independent of solution chemistry), several factors other than temperature, including dissolved inorganic carbon (DIC) speciation may influence mineral isotopic signatures. Therefore we used a combination of approaches to understand the potential influence of different variables on the clumped isotope (and oxygen isotope) composition of minerals. We conducted witherite precipitation experiments at a single temperature and at varied pH to empirically determine 13C-18O bond ordering (Δ47) and δ18O of CO32- and HCO3- molecules at a 25 °C equilibrium. Ab initio cluster models based on density functional theory were used to predict equilibrium 13C-18O bond abundances and δ18O of different DIC species and minerals as a function of temperature. Experiments and theory indicate Δ47 and δ18O compositions of CO32- and HCO3- ions are significantly different from each other. Experiments constrain the Δ47-δ18O slope for a pH effect (0.011 ± 0.001; 12 ⩾ pH ⩾ 7). Rapidly-growing temperate corals exhibit disequilibrium mineral isotopic signatures with a Δ47-δ18O slope of 0.011 ± 0.003, consistent with a pH effect. Our theoretical calculations for carbonate minerals indicate equilibrium lattice calcite values for Δ47 and δ18O are intermediate between HCO3- and CO32-. We analyzed synthetic calcites grown at temperatures ranging from 0.5 to 50 °C with and without the enzyme carbonic anhydrase present. This enzyme catalyzes oxygen isotopic exchange between DIC species and is present in many natural systems. The two

  20. Beyond temperature: Clumped isotope signatures in dissolved inorganic carbon species and the influence of solution chemistry on carbonate mineral composition

    USGS Publications Warehouse

    Tripati, Aradhna K.; Hill, Pamela S.; Eagle, Robert A.; Mosenfelder, Jed L.; Tang, Jianwu; Schauble, Edwin A.; Eiler, John M.; Zeebe, Richard E.; Uchikawa, Joji; Coplen, Tyler B.; Ries, Justin B.; Henry, Drew

    2015-01-01

    “Clumped-isotope” thermometry is an emerging tool to probe the temperature history of surface and subsurface environments based on measurements of the proportion of 13C and 18O isotopes bound to each other within carbonate minerals in 13C18O16O22- groups (heavy isotope “clumps”). Although most clumped isotope geothermometry implicitly presumes carbonate crystals have attained lattice equilibrium (i.e., thermodynamic equilibrium for a mineral, which is independent of solution chemistry), several factors other than temperature, including dissolved inorganic carbon (DIC) speciation may influence mineral isotopic signatures. Therefore we used a combination of approaches to understand the potential influence of different variables on the clumped isotope (and oxygen isotope) composition of minerals.We conducted witherite precipitation experiments at a single temperature and at varied pH to empirically determine 13C-18O bond ordering (Δ47) and δ18O of CO32- and HCO3- molecules at a 25 °C equilibrium. Ab initio cluster models based on density functional theory were used to predict equilibrium 13C-18O bond abundances and δ18O of different DIC species and minerals as a function of temperature. Experiments and theory indicate Δ47 and δ18O compositions of CO32- and HCO3- ions are significantly different from each other. Experiments constrain the Δ47-δ18O slope for a pH effect (0.011 ± 0.001; 12 ⩾ pH ⩾ 7). Rapidly-growing temperate corals exhibit disequilibrium mineral isotopic signatures with a Δ47-δ18O slope of 0.011 ± 0.003, consistent with a pH effect.Our theoretical calculations for carbonate minerals indicate equilibrium lattice calcite values for Δ47 and δ18O are intermediate between HCO3− and CO32−. We analyzed synthetic calcites grown at temperatures ranging from 0.5 to 50 °C with and without the enzyme carbonic anhydrase present. This enzyme catalyzes oxygen isotopic exchange between DIC species and is present in many

  1. Acid-Base Properties of Azo Dyes in Solution Studied Using Spectrophotometry and Colorimetry

    NASA Astrophysics Data System (ADS)

    Snigur, D. V.; Chebotarev, A. N.; Bevziuk, K. V.

    2018-03-01

    Colorimetry and spectrophotometry with chemometric data processing were used to study the acid-base properties of azo dyes in aqueous solution. The capabilities of both methods were compared. Ionization constants of all the functional groups of the azo compounds studied could be determined relative to the change in the specific color difference depending on the acidity of the medium. The colorimetric functions of ion-molecular forms of azo compounds used as an analytical signal allow us to obtain complete information on the acid-base equilibrium in a wide acidity range.

  2. Effect of Boric Acid Versus Conventional Irrigation Solutions on the Bond Strength Between Fiber Post 
and Root Dentin.

    PubMed

    Culhaoglu, Ahmet Kursad; Özcan, Erdal; Kilicarslan, Mehmet Ali; Seker, Emre

    2017-01-01

    To compare the effect of boric acid solutions of different percentages to conventional irrigation solutions on the adhesive bond strength between fiber posts and radicular dentin surface with different cement types. One hundred fifteen extracted human incisors were endodontically instrumented to a length of 14-15 mm, and 12-mm post spaces were prepared with specific drills. Cylindrical fiber posts (Panavia Post) were luted with two different composite cements (Panavia F 2.0, Panavia SA) and cut into 1-mm-thick slices. These specimens were randomly allocated to 5 groups according to the irrigant applied: 1. control, no irrigant; 2. 10 ml of 2% chlorhexidine; 3. 10 ml of 5.25% NaOCl for 5 min and 10 ml of 17% EDTA for 3 min; 4. 10 ml of 5% boric acid solution at a temperature of 55°C for 60 s; 5. 10% boric acid solution, conditions as in group 4. Bond strength was determined using the push-out test. Microscopic assessment and SEM evaluations were performed in combination with push-out tests. The push-out bond strengths of cervical segments were significantly higher than for the middle and apical segments in all groups. The type of irrigation solution used significantly affected the bond strengths of the posts. The 10% boric acid solution and EDTA + NaOCl irrigation solutions provided the highest bond strengths (p < 0.005). SEM analysis showed that the dentin tubules were open and the smear layer was completely removed when EDTA/NaOCl and 10% boric acid were used as irrigation agents. Boric acid solutions, especially at a concentration of 10%, can be a viable alternative to the conventional irrigants used during endodontic treatment. The extent to which the 10% boric acid solution successfully removed the smear layer and the ease of rinsing boric acid from the root surface are advantageous.

  3. Method for the isolation of citric acid and malic acid in Japanese apricot liqueur for carbon stable isotope analysis.

    PubMed

    Akamatsu, Fumikazu; Hashiguchi, Tomokazu; Hisatsune, Yuri; Oe, Takaaki; Kawao, Takafumi; Fujii, Tsutomu

    2017-02-15

    A method for detecting the undeclared addition of acidic ingredients is required to control the authenticity of Japanese apricot liqueur. We developed an analytical procedure that minimizes carbon isotope discrimination for measurement of the δ(13)C values of citric and malic acid isolated from Japanese apricot liqueur. Our results demonstrated that freeze-drying is preferable to nitrogen spray-drying, because it does not significantly affect the δ(13)C values of citric acid and results in smaller isotope discrimination for malic acid. Both 0.1% formic acid and 0.2% phosphoric acid are acceptable HPLC mobile phases for the isolation of citric and malic acid, although the δ(13)C values of malic acid exhibited relatively large variation compared with citric acid following isolation using either mobile phase. The developed procedure allows precise δ(13)C measurements of citric and malic acid isolated from Japanese apricot liqueur. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Large-scale production of anhydrous nitric acid and nitric acid solutions of dinitrogen pentoxide

    DOEpatents

    Harrar, Jackson E.; Quong, Roland; Rigdon, Lester P.; McGuire, Raymond R.

    2001-01-01

    A method and apparatus are disclosed for a large scale, electrochemical production of anhydrous nitric acid and N.sub.2 O.sub.5. The method includes oxidizing a solution of N.sub.2 O.sub.4 /aqueous-HNO.sub.3 at the anode, while reducing aqueous HNO.sub.3 at the cathode, in a flow electrolyzer constructed of special materials. N.sub.2 O.sub.4 is produced at the cathode and may be separated and recycled as a feedstock for use in the anolyte. The process is controlled by regulating the electrolysis current until the desired products are obtained. The chemical compositions of the anolyte and catholyte are monitored by measurement of the solution density and the concentrations of N.sub.2 O.sub.4.

  5. Diffusivity of Carbon Dioxide in Aqueous Solutions under Geologic Carbon Sequestration Conditions.

    PubMed

    Perera, Pradeep N; Deng, Hang; Schuck, P James; Gilbert, Benjamin

    2018-04-26

    Accurate assessment of the long-term security of geologic carbon sequestration requires knowledge of the mobility of carbon dioxide in brines under pressure and temperature conditions that prevail in subsurface aquifers. Here, we report Raman spectroscopic measurements of the rate of CO 2 diffusion in water and brines as a function of pressure, salinity, and concentration of CO 2 . In pure water at 50 ± 2 °C and 90 ± 2 bar, we find the diffusion coefficient, D, to be (3.08 ± 0.03) × 10 -9 m 2 /s, a value that is consistent with a recent microfluidic study but lower than earlier PVT measurements. Under reservoir conditions, salinity affects the mobility of CO 2 significantly and D decreased by 45% for a 4 M solution of NaCl. We find significant differences of diffusivity of CO 2 in brines (0-4 M NaCl), in both the absolute values and the trend compared to the Stokes-Einstein prediction under our experimental conditions. We observe that D decreases significantly at the high CO 2 concentrations expected in subsurface aquifers (∼15% reduction at 0.55 mol/kg of CO 2 ) and provides an empirical correction to the commonly reported D values that assume a tracer concentration dependence on diffusivity.

  6. Solubility Limits of Dibutyl Phosphoric Acid in Uranium Solutions at SRS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Thompson, M.C.; Pierce, R.A.; Ray, R.J.

    1998-06-01

    The Savannah River Site has enriched uranium (EU) solution which has been stored for almost 10 years since being purified in the second uranium cycle of the H area solvent extraction process. The concentrations in solution are {tilde 6} g/L U and about 0.1 M nitric acid. Residual tributylphosphate in the solutions has slowly hydrolyzed to form dibutyl phosphoric acid (HDBP) at concentrations averaging 50 mg/L. Uranium is known to form compounds with DBP which have limited solubility. The potential to form uranium-DBP solids raises a nuclear criticality safety issue. SRTC tests have shown that U-DBP solids will precipitate atmore » concentrations potentially attainable during storage of enriched uranium solutions. Evaporation of the existing EUS solution without additional acidification could result in the precipitation of U-DBP solids if DBP concentration in the resulting solution exceeds 110 ppm at ambient temperature. The same potential exists for evaporation of unwashed 1CU solutions. The most important variables of interest for present plant operations are HNO{sub 3} and DBP concentrations. Temperature is also an important variable controlling precipitation. The data obtained in these tests can be used to set operating and safety limits for the plant. It is recommended that the data for 0 degrees C with 0.5 M HNO{sub 3} be used for setting the limits. The limit would be 80 mg/L which is 3 standard deviations below the average of 86 observed in the tests. The data shows that super-saturation can occur when the DBP concentration is as much as 50 percent above the solubility limit. However, super-saturation cannot be relied on for maintaining nuclear criticality safety. The analytical method for determining DBP concentration in U solutions was improved so that analyses for a solution are accurate to within 10 percent. However, the overall uncertainty of results for periodic samples of the existing EUS solutions was only reduced slightly. Thus, sampling appears

  7. Synthesis of sulfonated porous carbon nanospheres solid acid by a facile chemical activation route

    NASA Astrophysics Data System (ADS)

    Chang, Binbin; Guo, Yanzhen; Yin, Hang; Zhang, Shouren; Yang, Baocheng

    2015-01-01

    Generally, porous carbon nanospheres materials are usually prepared via a template method, which is a multi-steps and high-cost strategy. Here, we reported a porous carbon nanosphere solid acid with high surface area and superior porosity, as well as uniform nanospheical morphology, which prepared by a facile chemical activation with ZnCl2 using resorcinol-formaldehyde (RF) resins spheres as precursor. The activation of RF resins spheres by ZnCl2 at 400 °C brought high surface area and large volume, and simultaneously retained numerous oxygen-containing and hydrogen-containing groups due to the relatively low processing temperature. The presence of these functional groups is favorable for the modification of -SO3H groups by a followed sulfonation treating with sulphuric acid and organic sulfonic acid. The results of N2 adsorption-desorption and electron microscopy clearly showed the preservation of porous structure and nanospherical morphology. Infrared spectra certified the variation of surface functional groups after activation and the successful modification of -SO3H groups after sulfonation. The acidities of catalysts were estimated by an indirect titration method and the modified amount of -SO3H groups were examined by energy dispersive spectra. The results suggested sulfonated porous carbon nanospheres catalysts possessed high acidities and -SO3H densities, which endowed their significantly catalytic activities for biodiesel production. Furthermore, their excellent stability and recycling property were also demonstrated by five consecutive cycles.

  8. Hydrodeoxygenation of phenols as lignin models under acid-free conditions with carbon-supported platinum catalysts.

    PubMed

    Ohta, Hidetoshi; Kobayashi, Hirokazu; Hara, Kenji; Fukuoka, Atsushi

    2011-11-28

    Carbon-supported Pt catalysts are highly active and reusable for the aqueous-phase hydrodeoxygenation of phenols as lignin models without adding any acids. It is suggested that Pt/carbon facilitates the hydrogenation of phenols and the hydrogenolysis of the resulting cyclohexanols.

  9. Effect of adding acid solution on setting time and compressive strength of high calcium fly ash based geopolymer

    NASA Astrophysics Data System (ADS)

    Antoni, Herianto, Jason Ghorman; Anastasia, Evelin; Hardjito, Djwantoro

    2017-09-01

    Fly ash with high calcium oxide content when used as the base material in geopolymer concrete could cause flash setting or rapid hardening. However, it might increase the compressive strength of geopolymer concrete. This rapid hardening could cause problems if the geopolymer concrete is used on a large scale casting that requires a long setting time. CaO content can be indicated by pH values of the fly ash, while higher pH is correlated with the rapid setting time of fly ash-based geopolymer. This study investigates the addition of acid solution to reduce the initial pH of the fly ash and to prolong the setting time of the mixture. The acids used in this study are hydrochloric acid (HCl), sulfuric acid (H2 SO4), nitric acid (HNO3) and acetic acid (CH3 COOH). It was found that the addition of acid solution in fly ash was able to decrease the initial pH of fly ash, however, the initial setting time of geopolymer was not reduced. It was even faster than that of the control mixture. The acid type causes various influence, depending on the fly ash properties. In addition, the use of acid solution in fly ash reduces the compressive strength of geopolymer mortar. It is concluded that the addition of acid solution cannot prolong the rapid hardening of high calcium fly ash geopolymer, and it causes adverse effect on the compressive strength.

  10. Molten Carbonate and Phosphoric Acid Stationary Fuel Cells: Overview and Gap Analysis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Remick, R.; Wheeler, D.

    2010-09-01

    This report describes the technical and cost gap analysis performed to identify pathways for reducing the costs of molten carbonate fuel cell (MCFC) and phosphoric acid fuel cell (PAFC) stationary fuel cell power plants.

  11. Effects Sprayed Solution of Salicylic Acid to Prevent of Wilt Disease Caused by Fussarium oxysporium

    NASA Astrophysics Data System (ADS)

    Yousif, Dina. Y. M.

    2018-05-01

    The current search aimed to detective the effect of sprayed solution of salicylic acid on plant and leaves of sweet green pepper (Capsicum annuum) for control the pathogen Fussarium oxysporium compering with control plant and leaves. Results indicated that, the spray of salicylic acid at concentration 0.5 g/L is effecting the fungal infection through prevent transport fungus F. oxysporum to the neighboring green pepper plant. The number of dead green pepper plant after sprayed with solution of salicylic acid and only water they were (4, 6, and 3) (8, 9, and 10) respectively. While the experimental infection of green pepper leaves after inoculated the fungus as local spot by scorching small spots of these leaves with the aid of hot nail. These spots were then exposed to the 0.5 g/L aqueous solution salicylic acid before and after the inoculation of the fungus. The spray of salicylic acid before 24 and 48 hour prevent the development of disease and make a good protection of the mention leaves from infection with this fungus, the diameter of leaves lesion (1,1.5 cm) respectively. while the ability of fungus to grow after 24 and 48 hour from salicylic acid treatment was markedly reduce as compared with control, such treatment show slow growth of pathogen infect.

  12. Effect of molecular structure of aniline-formaldehyde copolymers on corrosion inhibition of mild steel in hydrochloric acid solution.

    PubMed

    Zhang, Yan; Nie, Mengyan; Wang, Xiutong; Zhu, Yukun; Shi, Fuhua; Yu, Jianqiang; Hou, Baorong

    2015-05-30

    Aniline-formaldehyde copolymers with different molecular structures have been prepared and investigated for the purpose of corrosion control of mild steel in hydrochloric acid. The copolymers were synthesized by a condensation polymerization process with different ratios of aniline to formaldehyde in acidic precursor solutions. The corrosion inhibition efficiency of as-synthesized copolymers for Q235 mild steel was investigated in 1.0 mol L(-1) hydrochloric acid solution by weight loss measurement, potentiodynamic polarization, and electrochemical impedance spectroscopy, respectively. All the results demonstrate that as-prepared aniline-formaldehyde copolymers are efficient mixed-type corrosion inhibitors for mild steels in hydrochloric acid. The corrosion inhibition mechanism is discussed in terms of the role of molecular structure on adsorption of the copolymers onto the steel surface in acid solution. Copyright © 2015. Published by Elsevier B.V.

  13. Activated carbon with excellent chromium(VI) adsorption performance prepared by acid-base surface modification.

    PubMed

    Liu, S X; Chen, X; Chen, X Y; Liu, Z F; Wang, H L

    2007-03-06

    In the present work, activated carbon (AC) with excellent Cr(VI) adsorption performance especially at low concentrations was prepared by an acid-base surface modification method. Raw activated carbon (AC(0)) was first oxidized in boiling HNO(3) (AC(1)), then treated with a mixture of NaOH and NaCl (AC(2)). Batch equilibrium and continuous column adsorption were conducted to evaluate the adsorption performance. Boehm titration, elemental analysis, and N(2)/77K adsorption isotherm methods were used to characterize the surface properties and pore structure of modified ACs. The results revealed that the modified AC exhibited excellent Cr(VI) adsorption performance in terms of adsorption capacity and adsorption rate: AC(2)>AC(1)>AC(0). Modification caused S(BET) to decrease and the total number of surface oxygen acidic groups to increase. HNO(3) oxidization produced positive acid groups, and subsequently NaOH treatment replaced H(+) of surface acid groups by Na(+), and the acidity of AC decreased. The main cause of higher Cr(VI) adsorption capacity and rate for AC(2) was the presence of more oxygen surface acidic groups and suitable surface acidity. HNO(3)-NaOH modification shows potential for the preparation of high quality AC for the effective removal of low concentrations of Cr(VI).

  14. [Analyze nanofiltration separation rule of chlorogenic acid from low concentration ethanol by Donnan effect and solution-diffusion effect].

    PubMed

    Li, Cun-Yu; Liu, Li-Cheng; Jin, Li-Yang; Li, Hong-Yang; Peng, Guo-Ping

    2017-07-01

    To separate chlorogenic acid from low concentration ethanol and explore the influence of Donnan effect and solution-diffusion effect on the nanofiltration separation rule. The experiment showed that solution pH and ethanol volume percent had influences on the separation of chlorogenic acid. Within the pH values from 3 to 7 for chlorogenic acid in 30% ethanol, the rejection rate of chlorogenic acid was changed by 70.27%. Through the response surface method for quadratic regression model, an interaction had been found in molecule weight cut-off, pH and ethanol volume percent. In fixed nanofiltration apparatus, the existence states of chlorogenic acid determinedits separation rules. With the increase of ethanol concentration, the free form chlorogenic acid was easily adsorbed, dissolved on membrane surface and then caused high transmittance due to the solution-diffusion effect. However, at the same time, due to the double effects of Donnan effect and solution-diffusion effect, the ionic state of chlorogenic acid was hard to be adsorbed in membrane surface and thus caused high rejection rate. The combination of Box-Behnken design and response surface analysis can well optimize the concentrate process by nanofiltration, and the results showed that nanofiltration had several big advantages over the traditional vacuum concentrate technology, meanwhile, and solved the problems of low efficiency and serious component lossesin the Chinese medicines separation process for low concentration organic solvent-water solution. Copyright© by the Chinese Pharmaceutical Association.

  15. Morphological changes of olivine grains reacted with amino acid solutions by impact process

    NASA Astrophysics Data System (ADS)

    Umeda, Yuhei; Takase, Atsushi; Fukunaga, Nao; Sekine, Toshimori; Kobayashi, Takamichi; Furukawa, Yoshihiro; Kakegawa, Takeshi

    2017-03-01

    Early oceans on Earth might have contained certain amounts of biomolecules such as amino acids, and they were subjected to meteorite impacts, especially during the late heavy bombardment. We performed shock recovery experiments by using a propellant gun in order to simulate shock reactions among olivine as a representative meteorite component, water and biomolecules in oceans in the process of marine meteorite impacts. In the present study, recovered solid samples were analyzed by using X-ray powder diffraction method, scanning electron microscopy, electron probe microanalysis, and transmission electron microscopy with energy-dispersive X-ray spectrometry. The analytical results on shocked products in the recovered sample showed (1) morphological changes of olivine to fiber- and bamboo shoot-like crystals, and to pulverized grains; and features of lumpy surfaces affected by hot water, (2) the formation of carbon-rich substances derived from amino acids, and (3) the incorporation of metals from container into samples. According to the present results, fine-grained olivine in meteorites might have morphologically changed and shock-induced chemical reactions might have been enhanced so that amino acids related to the origin of life may have transformed to carbon-rich substances by impacts.

  16. Croconic acid - An absorber in the Venus clouds?

    NASA Technical Reports Server (NTRS)

    Hartley, Karen K.; Wolff, Andrew R.; Travis, Larry D.

    1989-01-01

    The absorbing species responsible for the UV cloud features and pale yellow hue of the Venus clouds is presently suggested to be the carbon monoxide-polymer croconic acid, which strongly absorbs in the blue and near-UV. Laboratory absorption-coefficient measurements of a dilute solution of croconic acid in sulfuric acid are used as the bases of cloud-scattering models; the Venus planetary albedo's observed behavior in the blue and near-UV are noted to be qualitatively reproduced. Attention is given to a plausible croconic acid-production mechanism for the Venus cloudtop region.

  17. Capacitively Coupled Plasma Discharge of Ionic Liquid Solutions to Synthesize Carbon Dots as Fluorescent Sensors.

    PubMed

    Ke, Ching-Bin; Lu, Te-Ling; Chen, Jian-Lian

    2018-05-26

    Oxygen and nitrogen capacitively coupled plasma (CCP) was used to irradiate mixtures of aliphatic acids in high boiling point solvents to synthesize fluorescent carbon dots (C-dots). With a high fluorescence intensity, the C-dots obtained from the O₂/CCP radiation of a 1-ethyl-3-methylimidazolium dicyanamide ionic liquid solution of citric acid were characterized with an average diameter of 8.6 nm (σ = 1.1 nm), nitrogen and oxygen bonding functionalities, excitation-independent emissions, and upconversion fluorescence. Through dialysis of the CCP-treated C-dots, two emissive surface states corresponding to their respective functionalities and emissions were identified. The fluorescence spectrum of the CCP-treated C-dots was different from that of the microwave irradiation and possessed higher intensity than that of hydrothermal pyrolysis. By evaluation of the fluorescence quenching effect on flavonoids and metal ions, the CCP-treated C-dots showed a high selectivity for quercetin and sensitivity to Hg 2+ . Based on the Perrin model, a calibration curve ( R ² = 0.9992) was established for quercetin ranging from 2.4 μM to 119 μM with an LOD (limit of detection) = 0.5 μM. The quercetin in the ethanol extract of the sun-dried peel of Citrus reticulata cv. Chachiensis was determined by a standard addition method to be 4.20 ± 0.15 mg/g with a matrix effect of 8.16%.

  18. Effects of inherent/enhanced solid acidity and morphology of diatomite templates on the synthesis and porosity of hierarchically porous carbon.

    PubMed

    Liu, Dong; Yuan, Peng; Tan, Daoyong; Liu, Hongmei; Fan, Mingde; Yuan, Aihua; Zhu, Jianxi; He, Hongping

    2010-12-21

    The inherent or enhanced solid acidity of raw or activated diatomite is found to have significant effects on the synthesis of hierarchically porous diatomite-templated carbon with high surface area and special porous structure. The solid acidity makes raw/activated diatomite a catalyst for the generation of porous carbon, and the porous parameters of the carbon products are strongly dependent on the solid acidity of diatomite templates. The morphology of diatomite also dramatically affects the textural structure of porous carbon. Two types of macroporous structures in the carbon product, the partially solid pillars and the ordered hollow tubes, derive from the replication of the central and the edge pores of diatom shell, respectively. The hierarchically porous carbon shows good capability for the adsorption of solvent naphtha and H(2), enabling potential applications in adsorption and gas storage.

  19. The Formation of Fe/Mg Smectite Under Mildly Acidic Conditions on Early Mars

    NASA Technical Reports Server (NTRS)

    Sutter, Brad; Golden, D. C.; Ming, Douglas W.; Niles, P. B.

    2011-01-01

    The detection of Fe/Mg smectites and carbonate in Noachian and early Hesperian terrain of Mars has been used to suggest that neutral to mildly alkaline conditions prevailed during the early history of Mars. However, if early Mars was neutral to moderately alkaline with a denser CO2 atmosphere than today, then large carbonates deposits should be more widely detected in Noachian terrain. The critical question is: Why have so few carbonate deposits been detected compared to Fe/Mg smectites? We suggest that Fe/Mg smectites on early Mars formed under mildly acidic conditions, which would inhibit the extensive formation of carbonate deposits. The goal of this work is to evaluate the formation of Fe/Mg smectites under mildly acidic conditions. The stability of smectites under mildly acidic conditions is attributed to elevated Fe/Mg activities that inhibit smectite dissolution. Beidelite and saponite have been shown to form from hydrothermal alteration of basaltic glass at pH 3.5-4.0 in seawater solutions. Nontronite is also known to be stable in mildly acidic systems associated with mafic and ultramafic rock. Nontronite was shown to form in acid sulfate soils in the Bangkok Plain, Thailand due to oxidation of Fe-sulfides that transformed saponite to nontronite. Smectite is known to transform to kaolinite in naturally acid soils due to selective leaching of Mg. However, if Mg removal is limited, then based on equilibrium relationships, the dissolution of smectite should be minimized. If Fe and Mg solution activities are sufficiently high, such as might be found in a low water/rock ratio system that is poorly drained, smectite could form and remain stable under mildly acidic conditions on Mars. The sources of mild acidity on early Mars includes elevated atmospheric CO2 levels, Fe-hydrolysis reactions, and the presence of volcanic SO2 aerosols. Equilibrium calculations dictate that water equilibrated with an early Mars CO2 atmosphere at 1 to 4 bar yields a pH of 3.6 to 3

  20. [Effects of carbon and nitrogen sources on 5-keto-gluconic acid production].

    PubMed

    Tan, Zhilei; Wang, Hongcui; Wei, Yuqiao; Li, Yanyan; Zhong, Cheng; Jia, Shiru

    2014-01-01

    Gluconobacter oxydans is known to oxidize glucose to gluconic acid (GA), and subsequently, to 2-keto-gluconic acid (2KGA) and 5-keto-gluconic acid (5KGA), while 5KGA can be converted to L-(+)-tartaric acid. In order to increase the production of 5KGA, Gluconobacter oxydans HGI-1 that converts GA to 5KGA exclusively was chosen in this study, and effects of carbon sources (lactose, maltose, sucrose, amylum and glucose) and nitrogen sources (yeast extract, fish meal, corn steep liquor, soybean meal and cotton-seed meal) on 5KGA production were investigated. Results of experiment in 500 mL shake-flask show that the highest yield of 5KGA (98.20 g/L) was obtained using 100 g/L glucose as carbon source. 5KGA reached 100.20 g/L, 109.10 g/L, 99.83 g/L with yeast extract, fish meal and corn steep liquor as nitrogen source respectively, among which the optimal nitrogen source was fish meal. The yield of 5KGA by corn steep liquor is slightly lower than that by yeast extract. For the economic reason, corn steep liquor was selected as nitrogen source and scaled up to 5 L stirred-tank fermentor, and the final concentration of 5KGA reached 93.80 g/L, with its maximum volumetric productivity of 3.48 g/(L x h) and average volumetric productivity of 1.56 g/(L x h). The result obtained in this study showed that carbon and nitrogen sourses for large-scale production of 5KGA by Gluconobacter oxydans HGI-1 were glucose and corn steep liquor, respectively, and the available glucose almost completely (85.93%) into 5KGA.