Sample records for carbonic acid solution

  1. Anodic oxidation of 3,4-dihydroxyphenylacetic acid on carbon electrodes in acetic acid solutions

    Microsoft Academic Search

    Slawomir Michalkiewicz; Agata Skorupa

    2010-01-01

    The electrochemical oxidation of 3,4-dihydroxyphenylacetic acid (DOPAC) on a carbon fiber microelectrode (CF) and a glassy carbon macroelectrode (GC) in glacial acetic acid solutions was investigated using voltammetric techniques. Voltammograms recorded at these electrodes show well-defined single waves or peaks. The proposed mechanism of the anodic oxidation of DOPAC consists of two successive one-electron one-proton steps. The loss of the

  2. 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.

  3. 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.

  4. Removal of Acid Dyes from Aqueous Solutions using Chemically Activated Carbon

    Microsoft Academic Search

    zgl Gerel; H. Ferdi Gerel

    2009-01-01

    Textile dyes (Acid Yellow 17 and Acid Orange 7) were removed from its aqueous solution in batch and continuous packed bed adsorption systems by using thermally activated Euphorbia macroclada carbon with respect to contact time, initial dye concentration, and temperature. The activated carbon was prepared using a cheap plant-based material called Euphorbia macroclada, which was chemically modified with K2CO3. Lagergren-first-order

  5. Extraction of palladium from acidic solutions with the use of carbon adsorbents

    SciTech Connect

    O.N. Kononova; N.G. Goryaeva; N.B. Dostovalova; S.V. Kachin; A.G. Kholmogorov [Krasnoyarsk State University, Krasnoyarsk (Russian Federation)

    2007-08-15

    We studied the sorption of palladium(II) on LKAU-4, LKAU-7, and BAU carbon adsorbents from model hydrochloric acid solutions and the solutions of spent palladium-containing catalysts. It was found that sorbents based on charcoal (BAU) and anthracite (LKAU-4) were characterized by high sorption capacities for palladium. The kinetics of the saturation of carbon adsorbents with palladium(II) ions was studied, and it was found that more than 60% of the initial amount of Pd(II) was recovered in a 1-h contact of an adsorbent with a model solution. This value for the solutions of spent catalysts was higher than 35%.

  6. Collagen tissue treated with chitosan solutions in carbonic acid for improved biological prosthetic heart valves.

    PubMed

    Gallyamov, Marat O; Chaschin, Ivan S; Khokhlova, Marina A; Grigorev, Timofey E; Bakuleva, Natalia P; Lyutova, Irina G; Kondratenko, Janna E; Badun, Gennadii A; Chernysheva, Maria G; Khokhlov, Alexei R

    2014-04-01

    Calcification of bovine pericardium dramatically shortens typical lifetimes of biological prosthetic heart valves and thus precludes their choice for younger patients. The aim of the present work is to demonstrate that the calcification is to be mitigated by means of treatment of bovine pericardium in solutions of chitosan in carbonic acid, i.e. water saturated with carbon dioxide at high pressure. This acidic aqueous fluid unusually combines antimicrobial properties with absolute biocompatibility as far as at normal pressure it decomposes spontaneously and completely into H2O and CO2. Yet, at high pressures it can protonate and dissolve chitosan materials with different degrees of acetylation (in the range of 16-33%, at least) without any further pretreatment. Even exposure of the bovine pericardium in pure carbonic acid solution without chitosan already favours certain reduction in calcification, somewhat improved mechanical properties, complete biocompatibility and evident antimicrobial activity of the treated collagen tissue. The reason may be due to high extraction ability of this peculiar compressed fluidic mixture. Moreover, exposure of the bovine pericardium in solutions of chitosan in carbonic acid introduces even better mechanical properties and highly pronounced antimicrobial activity of the modified collagen tissue against adherence and biofilm formation of relevant Gram-positive and Gram-negative strains. Yet, the most important achievement is the detected dramatic reduction in calcification for such modified collagen tissues in spite of the fact that the amount of the thus introduced chitosan is rather small (typically ca. 1wt.%), which has been reliably detected using original tritium labelling method. We believe that these improved properties are achieved due to particularly deep and uniform impregnation of the collagen matrix with chitosan from its pressurised solutions in carbonic acid. PMID:24582232

  7. The effect of phosphoric acid on the absorption of carbon dioxide into solutions of methyldiethanolamine

    E-print Network

    Cordi, Eric Marshall

    1991-01-01

    used for this project was generously donated by Texaco Chemical Company. TABLE OF CONTENTS CHAFER Page I INTRODUCTION II LITERATURE REVIEW Gas Sweetening Technology. Physical Pmperties of MDEA, Chemical Reactions in the MDEA Process... containing acidic impurities, such as carbon dioxide (COz) and hydrogen sulfide (HzS), has continued to evolve over several decades. R. R. Bottoms obtained the first patent in 1930 for the treatment of natural gas with a liquid alkanolamine solution. Since...

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

    SciTech Connect

    Tsyganok, A.I.; Yamanaka, Ichiro; Otsuka, Kiyoshi [Tokyo Inst. of Tech. (Japan). Dept. of Chemical Engineering

    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.

  9. Oleic acid adsorption-desorption isotherms on the surface of high-dispersity ferrites from a solution in carbon tetrachloride

    NASA Astrophysics Data System (ADS)

    Balmasova, O. V.; Korolev, V. V.; Yashkova, V. I.

    2010-01-01

    The equilibrium adsorption method was used to comparatively study the adsorption-desorption isotherms of oleic acid on the surfaces of manganese and copper ferrites from a solution in carbon tetrachloride. The adsorption isotherms of the fatty acid were described in terms of the theory of volume filling of micropores. The theory was used to calculate the limiting adsorption values, characteristic energy, and porous space volumes. The isotherm of oleic acid adsorption on the surface of manganese ferrite from a solution in carbon tetrachloride was similar to the isotherms of fatty acid adsorption from solutions in heptane, whereas the isotherm of adsorption on the surface of copper ferrite was similar to the isotherms of fatty acid adsorption from hexane. The limiting adsorption from carbon tetrachloride was higher on the surface of manganese ferrite than on the surface of copper ferrite. The adsorption-desorption isotherms contained hysteresis loops.

  10. Removal of boron from aqueous solution using magnetic carbon nanotube improved with tartaric acid.

    PubMed

    Zohdi, Nima; Mahdavi, Fariba; Abdullah, Luqman Chuah; Choong, Thomas Sy

    2014-01-01

    Boron removal capacity of multi-walled carbon nanotubes (MWCNTs) modified with tartaric acid was investigated in this study. Modification of MWCNTs with tartaric acid was confirmed by Boehm surface chemistry method and fourier transform infra-red (FT-IR) spectroscopy. Experiments were performed to determine the adsorption isotherm and adsorption thermodynamic parameters of boron adsorption on tartaric acid modified MWCNTs (TA-MWCNTs). The effect of variables including initial pH, dosage of adsorbent, contact time and temperature was investigated. Analysis of data showed that adsorption equilibrium could be better described by Freundlich isotherm and the maximum adsorption capacities obtained at the pH of 6.0 was 1.97mg/g. The estimated thermodynamic values of free energy (?G), entropy (?S) and enthalpy (?H) indicated a spontaneous and an endothermic process. Furthermore, the TA-MWCNTs was magnetized for separation of boron-contaminated adsorbent from aqueous solution by applying magnetic field. The results showed that magnetic TA-MWCNTs particles were separated effectively after adsorption from contaminated water. PMID:24393401

  11. Removal of boron from aqueous solution using magnetic carbon nanotube improved with tartaric acid

    PubMed Central

    2014-01-01

    Boron removal capacity of multi-walled carbon nanotubes (MWCNTs) modified with tartaric acid was investigated in this study. Modification of MWCNTs with tartaric acid was confirmed by Boehm surface chemistry method and fourier transform infra-red (FT-IR) spectroscopy. Experiments were performed to determine the adsorption isotherm and adsorption thermodynamic parameters of boron adsorption on tartaric acid modified MWCNTs (TA-MWCNTs). The effect of variables including initial pH, dosage of adsorbent, contact time and temperature was investigated. Analysis of data showed that adsorption equilibrium could be better described by Freundlich isotherm and the maximum adsorption capacities obtained at the pH of 6.0 was 1.97mg/g. The estimated thermodynamic values of free energy (?G), entropy (?S) and enthalpy (?H) indicated a spontaneous and an endothermic process. Furthermore, the TA-MWCNTs was magnetized for separation of boron-contaminated adsorbent from aqueous solution by applying magnetic field. The results showed that magnetic TA-MWCNTs particles were separated effectively after adsorption from contaminated water. PMID:24393401

  12. Mechanisms of enhanced total organic carbon elimination from oxalic acid solutions by electro-peroxone process.

    PubMed

    Wang, Huijiao; Yuan, Shi; Zhan, Juhong; Wang, Yujue; Yu, Gang; Deng, Shubo; Huang, Jun; Wang, Bin

    2015-09-01

    Electro-peroxone (E-peroxone) is a novel electrocatalytic ozonation process that combines ozonation and electrolysis process to enhance pollutant degradation during water and wastewater treatment. This enhancement has been mainly attributed to several mechanisms that increase O3 transformation to OH in the E-peroxone system, e.g., electro-generation of H2O2 from O2 at a carbon-based cathode and its subsequent peroxone reaction with O3 to OH, electro-reduction of O3 to OH at the cathode, and O3 decomposition to OH at high local pH near the cathode. To get more insight how these mechanisms contribute respectively to the enhancement, this study investigated total organic carbon (TOC) elimination from oxalic acid (OA) solutions by the E-peroxone process. Results show that the E-peroxone process significantly increased TOC elimination rate by 10.2-12.5 times compared with the linear addition of the individual rates of corresponding ozonation and electrolysis process. Kinetic analyses reveal that the electrochemically-driven peroxone reaction is the most important mechanism for the enhanced TOC elimination rate, while the other mechanisms contribute minor to the enhancement by a factor of 1.6-2.5. The results indicate that proper selection of electrodes that can effectively produce H2O2 at the cathode is critical to maximize TOC elimination in the E-peroxone process. PMID:25989593

  13. Resistivity reduction of boron-doped multiwalled carbon nanotubes synthesized from a methanol solution containing boric acid

    NASA Astrophysics Data System (ADS)

    Ishii, Satoshi; Watanabe, Tohru; Ueda, Shinya; Tsuda, Shunsuke; Yamaguchi, Takahide; Takano, Yoshihiko

    2008-05-01

    Boron-doped multiwalled carbon nanotubes (MWNTs) were synthesized using a methanol solution of boric acid as a source material. Accurate measurements of the electrical resistivity of an individual boron-doped MWNT was performed with a four-point contact, which was fabricated using an electron beam lithography technique. The doped boron provides conduction carriers, which reduces the resistivity of the MWNT.

  14. The Adsorption of Gold, Palladium, and Platinum from Acidic Chloride Solutions on Mesoporous Carbons

    SciTech Connect

    Peter R. Zalupski; Rocklan McDowell

    2014-10-01

    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 chloride ions on the ion-exchanging mechanism of metal ions sorption on mesoporous carbon surfaces. The collected acid dependencies illustrate similar adsorption characteristics for CMK-3 and CMK-3/S in 1-5MHCl 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.

  15. 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 ?m with a yield of 90%.

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

    SciTech Connect

    Peter Zalupski; Rocklan McDowell; Guy Dutech

    2014-10-01

    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. 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.

  17. CORROSION TESTING OF CARBON STEEL IN OXALIC ACID CHEMICAL CLEANING SOLUTIONS

    SciTech Connect

    Wiersma, B.; Mickalonis, J.; Subramanian, K.; Ketusky, E.

    2011-10-14

    Radioactive liquid waste has been stored in underground carbon steel tanks for nearly 60 years at the Savannah River Site. The site is currently in the process of removing the waste from these tanks in order to place it into vitrified, stable state for longer term storage. The last stage in the removal sequence is a chemical cleaning step that breaks up and dissolves metal oxide solids that cannot be easily pumped out of the tank. Oxalic acid has been selected for this purpose because it is an effective chelating agent for the solids and is not as corrosive as other acids. Electrochemical and immersion studies were conducted to investigate the corrosion behavior of carbon steel in simulated chemical cleaning environments. The effects of temperature, agitation, and the presence of sludge solids in the oxalic acid on the corrosion rate and the likelihood of hydrogen evolution were determined. The testing showed that the corrosion rates decreased significantly in the presence of the sludge solids. Corrosion rates increased with agitation, however, the changes were less noticeable.

  18. The effect of phosphoric acid on the absorption of carbon dioxide into solutions of methyldiethanolamine

    E-print Network

    Cordi, Eric Marshall

    1991-01-01

    of carbon dioxide in these solutions was slower than predicted, given the amount of free MDEA present. The reduced values of the pseudo-first-order rate constant were tested statistically to cone!ate the rate depression with free MDEA and hydrogen...-away view) . . Page 21 22 4. Two-Film Model of Mass Transfer. . . 32 5. Comparative Arrhenius Plot of Significant CO&/MDEA Research. 6. Pseudo-first-order Rate Constants at 25'C 51 68 7. Free Amine Plot for Pseudo-first-order Rate Constants 69 8...

  19. Effects of impurities on the electroreduction of carbon dioxide on platinum electrodes in acid solutions

    SciTech Connect

    Huang, H. (Dept. of Chemistry, Case-Western Reserve Univ., Cleveland, OH (US))

    1992-02-01

    The electroreduction of carbon dioxide has been studied in this laboratory using electrochemical techniques and in situ Fourier transform infrared reflection absorption spectroscopy (FTIRRAS) on both polycrystalline and single-crystalline platinum electrodes in 0.1M HClO{sub 4} solution. On polycrystalline electrodes and two single-crystalline planes ((110) and (100)), the reduction reaction proceeds in the hydrogen absorption region and gives rise the polycrystalline electrode and Pt(110), and bridge-bonded Co on Pt(100). No. CO was detected on Pt(111). The introduction of CO{sub 2} in solution shows a similar effect on the Butterfly peaks of Pt(111) to that of specifically adsorbed anions, such as bisulfate. The has been attributed tentatively to the absorption of HCO{sub 3} in the potential region between the onset of the butterfly peaks and the formation of oxide. The IR absorption peak between 1418 and 1456 cm{sup {minus}1}, which is assigned to the absorbed HCO{sub 3}{sup {minus}}, shows a large positive shift with increasing potential (127 cm{sup {minus}1}/V). As part of the research on CO{sub 2} reduction, this paper examines the effects of impurities (Cl{sup {minus}}) and electrode rotation rates on Co{sub 2} reduction on polycrystalline Pt electrodes in 0.1M HClO{sub 4} solutions.

  20. The Inhibitory Effect of Some Bipyridine Derivatives on the Corrosion Behavior of N80 Carbon Steel in Sulphuric Acid Solutions

    NASA Astrophysics Data System (ADS)

    Liu, Xia; Okafor, Peter C.; Jiang, Bin; Hu, Hongxiang; Zheng, Yugui

    2015-11-01

    The corrosion inhibition characteristics of 2,2?-bipyridine (BIPY) and 2,2?-bipyridine-3,3?-dicarboxylic acid (BIDA), on carbon steel in sulphuric acid solutions was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques at 20C, 30C and 40C. The results indicate that the organic compounds inhibit the corrosion of mild steel in H2SO4 solutions and the extent of inhibition increases with inhibitor concentration and decreases with temperature. A mixed-inhibition mechanism is proposed for the inhibitive effects of the compounds. The order of inhibition efficiency obtained was BIDA>BIPY. There is a good correlation between the quantum chemical parameters and experimentally determined inhibition efficiency of the inhibitors. The adsorption characteristics of the inhibitor were approximated by Temkin isotherm. Morphological study of the carbon steel electrode surface was undertaken by scanning electron microscope (SEM) and the interfacial species formed on the surface in the presence of inhibitors analyzed by Infrared spectroscopy.

  1. Direct synthesis of H 2O 2 acid solutions on carbon cathode prepared from activated carbon and vapor-growing-carbon-fiber by a H 2\\/O 2 fuel cell

    Microsoft Academic Search

    Ichiro Yamanaka; Toshikazu Hashimoto; Ryo Ichihashi; Kiyoshi Otsuka

    2008-01-01

    Direct synthesis of H2O2 acid solutions was studied using a gas-diffusion cathode prepared from activated carbon (AC), vapor-growing-carbon-fiber (VGCF) and poly-tetra-fluoro-ethylene (PTFE) powders, with a new H2\\/O2 fuel cell reactor. O2 reduction to H2O2 was remarkably enhanced at the three-phase boundary (O2(g)electrode(s)acid(l)) at the [AC+VGCF] cathode. Fast diffusion processes of O2 to the active surface and of H2O2 to the

  2. 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.

  3. Acid sorption regeneration process using carbon dioxide

    DOEpatents

    King, C. Judson (Kensington, CA); Husson, Scott M. (Anderson, SC)

    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.

  4. Study of acid orange 7 removal from aqueous solutions by powdered activated carbon and modeling of experimental results by artificial neural network

    Microsoft Academic Search

    Soheil Aber; Nezameddin Daneshvar; Saeed Mohammad Soroureddin; Ammar Chabok; Karim Asadpour-Zeynali

    2007-01-01

    In this work, removal of acid orange 7 (AO7) by powdered activated carbon, from aqueous solutions with initial concentrations of 150 ppm to 350 ppm and initial pH values of 2.8, 5.8, 8.0 and 10.5 at 25C was studied. Experiments were done in batch mode and the experimental solutions were agitated periodically. All concentrations were measured spectrophotometrically at 483 nm

  5. Adsorption of Gallic Acid from Aqueous Solution Using Fixed Bed Activated Carbon Columns

    Microsoft Academic Search

    Meenakshi Goyal; Rashmi Dhawan; Mamta Bhagat

    2010-01-01

    Naturally occuring matter (NOM), a heterogeneous mixture of complex organic compounds, is invariably present in all surface and ground waters. These materials act as substrate for the growth of bacteria in the distribution system. The disinfection of such water by chlorination produces disinfection by products consisting of several halogenated compounds which are toxic and carcinogenic. As gallic acid is the

  6. 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.

  7. Cu +2 cation+3,5-dimethyl pyrazole mixture as a corrosion inhibitor for carbon steel in sulfuric acid solution

    Microsoft Academic Search

    M Abdallah; M. M El-Naggar

    2001-01-01

    The inhibition effect of [Cu+2 cation+3,5-dimethyl pyrazole] mixture of different molar ratios on the corrosion of carbon steel in a 0.5M H2SO4 solution was studied using both weight loss and galvanostatic polarization techniques. The inhibiting solutions were analyzed using UVvisible spectrophotometric before and after polarization measurements. The results revealed a complex formation between the two components, which was much more

  8. The Perils of Carbonic Acid and Equilibrium Constants.

    ERIC Educational Resources Information Center

    Jencks, William P.; Altura, Rachel A.

    1988-01-01

    Discusses the effects caused by small amounts of carbon dioxide usually present in water and acid-base equilibria of dilute solutions. Notes that dilute solutions of most weak acids and bases undergo significant dissociation or protonation. (MVL)

  9. Corrosion of low-carbon steel in sulphuric acid solution in presence of pyrazolehalides mixture

    Microsoft Academic Search

    Gamal K. Gomma

    1998-01-01

    The corrosion behaviour of steel (0.05% C) in 0.5 M sulphuric acid solution in the presence of pyrazolehalide mixtures was studied. The increase in surface coverage values in the order of I? > Br? > Cl? seems to indicate that the radii and the electronegativity of halides play an important role in the adsorption process. The inhibition efficiency (P%) increases

  10. 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.

  11. Sequential study on reactive blue 29 dye removal from aqueous solution by peroxy acid and single wall carbon nanotubes: experiment and theory

    PubMed Central

    2013-01-01

    The majority of anthraquinone dye released to the environment come from antrapogenic sources. Several techniques are available for dyes' removal. In this study removal of reactive blue 29 (RB29) by an advanced oxidation process sequenced with single wall carbon nanotubes was investigated. Advanced oxidation process was optimized over a period of 60 minutes by changing the ratio of acetic acid to hydrogen peroxide, the compounds which form peroxy acid. Reduction of 20.2% -56.4% of reactive blue 29 was observed when the ratio of hydrogen peroxide/acetic acid/dye changed from 344/344/1 to 344/344/0.08 at different times (60, 120 and 180 min). The optimum ratio of acetic acid/hydrogen peroxide/dye was found to be 344/344/0.16 over 60 min. The resultant then was introduced for further removal by single wall carbon nanotubes(SWCNTs) as adsorbent. The adsorption of reactive blue 29 onto SWCNTs was also investigated. Langmuir, Freundlich and BET isotherms were determined and the results revealed that the adsorption of RB29 onto SWCNTs was well explained by BET model and changed to Freundlich isotherm when SWCNTs was used after the application of peroxy acid. Kinetic study showed that the equilibrium time for adsorption of RB 29 on to SWCNT is 4 h. Experiments were carried out to investigate adsorption kinetics, adsorbent capacity and the effect of solution pH on the removal of reactive blue29. The pseudo-second order kinetic equation could best describe the sorption kinetics. The most efficient pH for color removal (amongst pH=3, 5 and 8) was pH= 5. Further studies are needed to identify the peroxy acid degradation intermediates and to investigate their effects on SWCNTs. PMID:23369540

  12. Activated carbon catalytic ozonation of oxamic and oxalic acids

    Microsoft Academic Search

    P. C. C. Faria; J. J. M. rfo; M. F. R. Pereira

    2008-01-01

    The oxidation of hazardous organic compounds leads to the formation of several by-products, being oxalic acid and oxamic acid final oxidation products refractory to ozonation. The present work aimed to study the ozonation of those carboxylic acids in the presence of activated carbon at different solution pH. For comparative purposes, experiments of adsorption on activated carbon, ozonation, and ozonation in

  13. Carbonic Acid Pretreatment of Biomass

    SciTech Connect

    G. Peter van Walsum; Kemantha Jayawardhana; Damon Yourchisin; Robert McWilliams; Vanessa Castleberry

    2003-05-31

    This project sought to address six objectives, outlined below. The objectives were met through the completion of ten tasks. 1) Solidify the theoretical understanding of the binary CO2/H2O system at reaction temperatures and pressures. The thermodynamics of pH prediction have been improved to include a more rigorous treatment of non-ideal gas phases. However it was found that experimental attempts to confirm theoretical pH predictions were still off by a factor of about 1.8 pH units. Arrhenius experiments were carried out and the activation energy for carbonic acid appears to be substantially similar to sulfuric acid. Titration experiments have not yet confirmed or quantified the buffering or acid suppression effects of carbonic acid on biomass. 2) Modify the carbonic acid pretreatment severity function to include the effect of endogenous acid formation and carbonate buffering, if necessary. It was found that the existing severity functions serve adequately to account for endogenous acid production and carbonate effects. 3) Quantify the production of soluble carbohydrates at different reaction conditions and severity. Results show that carbonic acid has little effect on increasing soluble carbohydrate concentrations for pretreated aspen wood, compared to pretreatment with water alone. This appears to be connected to the release of endogenous acids by the substrate. A less acidic substrate such as corn stover would derive benefit from the use of carbonic acid. 4) Quantify the production of microbial inhibitors at selected reaction conditions and severity. It was found that the release of inhibitors was correlated to reaction severity and that carbonic acid did not appear to increase or decrease inhibition compared to pretreatment with water alone. 5) Assess the reactivity to enzymatic hydrolysis of material pretreated at selected reaction conditions and severity. Enzymatic hydrolysis rates increased with severity, but no advantage was detected for the use of carbonic acid compared to water alone. 6) Determine optimal conditions for carbonic acid pretreatment of aspen wood. Optimal severities appeared to be in the mid range tested. ASPEN-Plus modeling and economic analysis of the process indicate that the process could be cost competitive with sulfuric acid if the concentration of solids in the pretreatment is maintained very high (~50%). Lower solids concentrations result in larger reactors that become expensive to construct for high pressure applications.

  14. Carbonic Acid Retreatment of Biomass

    SciTech Connect

    Baylor university

    2003-06-01

    This project sought to address six objectives, outlined below. The objectives were met through the completion of ten tasks. (1) Solidify the theoretical understanding of the binary CO{sub 2}/H{sub 2}O system at reaction temperatures and pressures. The thermodynamics of pH prediction have been improved to include a more rigorous treatment of non-ideal gas phases. However it was found that experimental attempts to confirm theoretical pH predictions were still off by a factor of about 1.8 pH units. Arrhenius experiments were carried out and the activation energy for carbonic acid appears to be substantially similar to sulfuric acid. Titration experiments have not yet confirmed or quantified the buffering or acid suppression effects of carbonic acid on biomass. (2) Modify the carbonic acid pretreatment severity function to include the effect of endogenous acid formation and carbonate buffering, if necessary. It was found that the existing severity functions serve adequately to account for endogenous acid production and carbonate effects. (3) Quantify the production of soluble carbohydrates at different reaction conditions and severity. Results show that carbonic acid has little effect on increasing soluble carbohydrate concentrations for pretreated aspen wood, compared to pretreatment with water alone. This appears to be connected to the release of endogenous acids by the substrate. A less acidic substrate such as corn stover would derive benefit from the use of carbonic acid. (4) Quantify the production of microbial inhibitors at selected reaction conditions and severity. It was found that the release of inhibitors was correlated to reaction severity and that carbonic acid did not appear to increase or decrease inhibition compared to pretreatment with water alone. (5) Assess the reactivity to enzymatic hydrolysis of material pretreated at selected reaction conditions and severity. Enzymatic hydrolysis rates increased with severity, but no advantage was detected for the use of carbonic acid compared to water alone. (6) Determine optimal conditions for carbonic acid pretreatment of aspen wood. Optimal severities appeared to be in the mid range tested. ASPEN-Plus modeling and economic analysis of the process indicate that the process could be cost competitive with sulfuric acid if the concentration of solids in the pretreatment is maintained very high ({approx}50%). Lower solids concentrations result in larger reactors that become expensive to construct for high pressure applications.

  15. Carbon dioxide sequestration by direct mineral carbonation with carbonic acid

    SciTech Connect

    O'Connor, William K.; Dahlin, David C.; Nilsen, David N.; Walters, Richard P.; Turner, Paul C.

    2000-01-01

    The Albany Research Center (ARC) of the U.S. Dept. of Energy (DOE) has been conducting a series of mineral carbonation tests at its Albany, Oregon, facility over the past 2 years as part of a Mineral Carbonation Study Program within the DOE. Other participants in this Program include the Los Alamos National Laboratory, Arizona State University, Science Applications International Corporation, and the DOE National Energy Technology Laboratory. The ARC tests have focused on ex-situ mineral carbonation in an aqueous system. The process developed at ARC utilizes a slurry of water mixed with a magnesium silicate mineral, olivine [forsterite end member (Mg2SiO4)], or serpentine [Mg3Si2O5(OH)4]. This slurry is reacted with supercritical carbon dioxide (CO2) to produce magnesite (MgCO3). The CO2 is dissolved in water to form carbonic acid (H2CO3), which dissociates to H+ and HCO3 -. The H+ reacts with the mineral, liberating Mg2+ cations which react with the bicarbonate to form the solid carbonate. The process is designed to simulate the natural serpentinization reaction of ultramafic minerals, and for this reason, these results may also be applicable to in-situ geological sequestration regimes. Results of the baseline tests, conducted on ground products of the natural minerals, have been encouraging. Tests conducted at ambient temperature (22 C) and subcritical CO2 pressures (below 73 atm) resulted in very slow conversion to the carbonate. However, when elevated temperatures and pressures are utilized, coupled with continuous stirring of the slurry and gas dispersion within the water column, significant reaction occurs within much shorter reaction times. Extent of reaction, as measured by the stoichiometric conversion of the silicate mineral (olivine) to the carbonate, is roughly 90% within 24 hours, using distilled water, and a reaction temperature of 185?C and a partial pressure of CO2 (PCO2) of 115 atm. Recent tests using a bicarbonate solution, under identical reaction conditions, have achieved roughly 83% conversion of heat treated serpentine and 84% conversion of olivine to the carbonate in 6 hours. The results from the current studies suggest that reaction kinetics can be improved by pretreatment of the mineral, catalysis of the reaction, or some combination of the two. Future tests are intended to examine a broader pressure/temperature regime, various pretreatment options, as well as other mineral groups.

  16. Electrodeposition From Acidic Solutions of Nickel Bis(benzenedithiolate) Produces a Hydrogen-Evolving Ni-S Film on Glassy Carbon

    SciTech Connect

    Fang, Ming; Engelhard, Mark H.; Zhu, Zihua; Helm, Monte L.; Roberts, John A.

    2014-01-03

    Films electrodeposited onto glassy carbon electrodes from acidic acetonitrile solutions of [Bu4N][Ni(bdt)2] (bdt = 1,2-benzenedithiolate) are active toward electrocatalytic hydrogen production at potentials 0.2-0.4 V positive of untreated electrodes. This activity is preserved on rinsing the electrode and transfer to fresh acid solution. X-ray photoelectron spectra indicate that the deposited material contains Ni and S. Correlations between voltammetric and spectroscopic results indicate that the deposited material is active, i.e. that catalysis is heterogeneous rather than homogeneous. Control experiments establish that obtaining the observed catalytic response requires both Ni and the 1,2 benzenedithiolate ligand to be present during deposition. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy. A portion of the research was performed using EMSL, a 17 national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  18. ORGANIC CARBON FRACTIONS IN O AND B HORIZON SOLUTIONS FROM A NEW ENGLAND SPODOSOL: EFFECTS OF ACID TREATMENT

    EPA Science Inventory

    We examined the effects of H2SO4 and HNO3 on dissolved organic carbon (DOC), pH, and DOC fractions in extracts from Spodosol O and B horizon samples of a forest soil from eastern Maine. reliminary work with HNO3 at pH=3(1 to 24h shaking, ionic strength adjustment with NaNO3 (I=0....

  19. Adsorption of chromium by activated carbon from aqueous solution

    Microsoft Academic Search

    Diksha Aggarwal; Meenakshi Goyal; R. C. Bansal

    1999-01-01

    Adsorption isotherms of Cr(III) and Cr(VI) ions on two samples of activated carbon fibres and two samples of granulated activated carbons from aqueous solutions in the concentration range 201000 mg\\/l have been studied. The adsorption isotherms have been determined after modifying the activated carbon surfaces by oxidation with nitric acid, ammonium persulphate, hydrogen peroxide and oxygen gas at 350C and

  20. 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.

  1. Solution properties of polygalacturonic acid

    PubMed Central

    Stoddart, R. W.; Spires, I. P. C.; Tipton, K. F.

    1969-01-01

    1. The specimen of polygalacturonic acid used in these studies was shown to contain very little neutral sugar, methyl ester groups or ash, and only residues of galacturonic acid. Its electrophoretic homogeneity was examined in pyridineacetic acid buffer at pH65 and in borate buffer at pH92. The distribution of effective particle weights was shown to be fairly narrow. 2. The pH-titration curve of the polymer gave a pK value of 37. 3. The interaction of the polymer with Ruthenium Red was studied and titration curves were obtained for the spectral shifts associated with the formation of a complex. 4. Optical-rotatory-dispersion studies showed that the Drude constant, ?c, was dependent on pH. 5. Polygalacturonic acid was shown to display non-Newtonian properties in solution and to have an anomalously high relative specific viscosity at low concentrations. 6. Studies were made of the pH-dependence of the sedimentation coefficient of the polymer. 7. These results are discussed in terms of the structure of the molecule and their relevance to the properties of pectic substances. PMID:5343801

  2. Biosynthesis of 2-hydroxyisobutyric acid (2-HIBA) from renewable carbon

    Microsoft Academic Search

    Thore Rohwerder; Roland H Mller

    2010-01-01

    Nowadays a growing demand for green chemicals and cleantech solutions is motivating the industry to strive for biobased building blocks. We have identified the tertiary carbon atom-containing 2-hydroxyisobutyric acid (2-HIBA) as an interesting building block for polymer synthesis. Starting from this carboxylic acid, practically all compounds possessing the isobutane structure are accessible by simple chemical conversions, e. g. the commodity

  3. Ions in hyaluronic acid solutions

    NASA Astrophysics Data System (ADS)

    Horkay, Ferenc; Basser, Peter J.; Londono, David J.; Hecht, Anne-Marie; Geissler, Erik

    2009-11-01

    Hyaluronic acid (HA) is an anionic biopolymer that is almost ubiquitous in biological tissues. An attempt is made to determine the dominant features that account for both its abundance and its multifunctional role, and which set it apart from other types of biopolymers. A combination of osmotic and scattering techniques is employed to quantify its dynamic and static properties in near-physiological solution conditions, where it is exposed both to mono- and divalent counterions. An equation of state is derived for the osmotic pressure ? in the semidilute concentration region, in terms of two variables, the polymer concentration c and the ionic strength J of the added salt, according to which ? =1.4103c9/4/J3/4 kPa, where c and J are expressed in mole. Over the physiological ion concentration range, the effect of the sodium chloride and calcium chloride on the osmotic properties of HA solutions is fully accounted for by their contributions to the ionic strength. The absence of precipitation, even at high CaCl2 concentrations, distinguishes this molecule from other biopolymers such as DNA. Dynamic light scattering measurements reveal that the collective diffusion coefficient in HA solutions exceeds that in aqueous solutions of typical neutral polymers by a factor of approximately 5. This property ensures rapid adjustment to, and recovery from, stress applied to HA-containing tissue. Small angle x-ray scattering measurements confirm the absence of appreciable structural reorganization over the observed length scale range 10-1000 , as a result of calcium-sodium ion exchange. The scattered intensity in the transfer momentum range q >0.03 -1 varies as 1/q, indicating that the HA chain segments in semidilute solutions are linear over an extended concentration range. The osmotic compression modulus c ??/?c, a high value of which is a prerequisite in structural biopolymers, is several times greater than in typical neutral polymer solutions.

  4. Electrochemical investigations of naphthenic acid corrosion for carbon steel and the inhibitive effect by some ethoxylated fatty acids

    Microsoft Academic Search

    M. A. Deyab; H. A. Abo Dief; E. A. Eissa; A. R. Taman

    2007-01-01

    The electrochemical behavior and corrosion of carbon steel in various types of naphthenic acid solutions have been studied by using cyclic voltammetry technique. The data reveal that the anodic excursion spans of carbon steel in naphthenic acid solution are characterized by the occurrence of a well-defined anodic peak (peak A), followed by a passive region. The passivation may be related

  5. Oligomer distribution in concentrated lactic acid solutions

    Microsoft Academic Search

    Dung T. Vu; Aspi K. Kolah; Navinchandra S. Asthana; Lars Peereboom; Carl T. Lira; Dennis J. Miller

    2005-01-01

    Lactic acid (2-hydroxypropanoic acid) is a significant platform chemical for the biorenewable economy. Concentrated aqueous solutions of lactic acid (>30wt.%) contain a distribution of oligomers that arise via intermolecular esterification. As a result, the titratable acidity changes non-linearly with acid concentration. In this work, the oligomer distribution of lactic acid is characterized using GC, GC\\/MS, and HPLC to extend existing

  6. Prediction of Effective Acid Penetration and Acid Volume for Matrix Acidizing Treatments in Naturally Fractured Carbonates

    Microsoft Academic Search

    Xiong Hongjie

    1994-01-01

    This paper discusses a new method and a corresponding computer model developed to investigate matrix acidizing in naturally fractured carbonates. With this method, the effective acid penetration distance and acid volume needed for acid treatments in naturally fractured carbonates can be predicted. The new model simulates acid flowing in the natural fracture network and the acid\\/rock reaction. During the simulation,

  7. Nucleophilic ?-Carbon Activation of Propionic Acid as a 3-Carbon Synthon by Carbene Organocatalysis.

    PubMed

    Jin, Zhichao; Jiang, Ke; Fu, Zhenqian; Torres, Jaume; Zheng, Pengcheng; Yang, Song; Song, Bao-An; Chi, Yonggui Robin

    2015-06-22

    Direct ?-carbon activation of propionic acid (C2 H5 CO2 H) by carbene organocatalysis has been developed. This activation affords the smallest azolium homoenolate intermediate (without any substituent) as a 3-carbon nucleophile for enantioselective reactions. Propionic acid is an excellent raw material because it is cheap, stable, and safe. This approach provides a much better solution to azolium homoenolate synthesis than the previously established use of acrolein (enal without any substituent), which is expensive, unstable, and toxic. PMID:26013883

  8. Adsorption of lanthanides(III), uranium(VI) and thorium(IV) from nitric acid solutions by carbon inverse opals modified with tetraphenylmethylenediphospine dioxide.

    PubMed

    Turanov, A N; Karandashev, V K; Masalov, V M; Zhokhov, A A; Emelchenko, G A

    2013-09-01

    Carbon inverse opals (C-IOP) were noncovalently modified with tetraphenylmethylenediphospine dioxide (TPMDPDO). The distribution of TPMDPDO between C-IOP and aqueous HNO3 solutions has been studied. The effect of HNO3 concentration in the aqueous phase and that of the TPMDPDO concentration in the sorbent phase on the adsorption of microquantities of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, U, and Th nitrates from HNO3 solutions by C-IOP modified with TPMDPDO is considered. The stoichiometry of the sorbed complexes has been determined by the slope analysis method. The efficiency of lanthanide(III) adsorption from moderate-concentration HNO3 solutions decreases with increasing element atomic number. PMID:23786834

  9. Acylation of peptides by lactic acid solutions.

    PubMed

    Lucke, Andrea; Gpferich, Achim

    2003-01-01

    To simplify the search for effective mechanisms to suppress peptide acylation inside drug delivery devices made of poly(D,L-lactic acid) (PLA) and poly(lactic-co-glycolic acid), we were looking for a suitable model system that would allow screening of strategies for peptide stabilization. With their low pH and the presence of lactic acid oligomers, diluted lactic acid solutions promised to be a suitable test system that mimics the microclimate in degrading PLA devices. We created solutions of 1-50% (w/w) lactic acid by dilution of concentrated lactic acid. Using high performance liquid chromatography (HPLC) and high performance liquid chromatography coupled with mass spectrometry (HPLC-MS) analysis, oligomer hydrolysis was monitored during the equilibration process of the diluted solutions. Their final oligomer content was determined by titration and by calculations based on HPLC data. HPLC-MS analysis of human atrial natriuretic peptide (ANP) stability in different lactic acid solutions at 37 degrees C for 4 weeks demonstrated that ANP underwent acylation even in diluted solutions containing only 0.05% (w/w) lactic acid oligomers. Purity analysis of lactic acid solutions allowed us to compare the conditions in the solution test-system to the microclimate that prevails inside degrading PLA microspheres. PMID:12551701

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

    PubMed

    Mulat, Daniel Girma; Feilberg, Anders

    2015-10-01

    In anaerobic digestion of organic matter, several metabolic pathways are involved during the simultaneous production and consumption of short-chain fatty acids (SCFA) in general and acetate in particular. Understanding the role of each pathway requires both the determination of the concentration and isotope enrichment of intermediates in conjunction with isotope labeled substrates. The objective of this study was to establish a rapid and simple GC/MS method for determining the isotope enrichment of acetate and concentration of underivatized short-chain fatty acids (SCFA) in biogas digester samples by direct liquid injection of acidified aqueous samples. Sample preparation involves only acidification, centrifugation and filtration of the aqueous solution followed by direct injection of the aqueous supernatant solution onto a polar column. With the sample preparation and GC/MS conditions employed, well-resolved and sharp peaks of underivatized SCFA were obtained in a reasonably short time. Good recovery (96.6-102.3%) as well as low detection (4-7mol/L) and quantification limits (14-22mol/L) were obtained for all the 6 SCFA studied. Good linearity was achieved for both concentration and isotope enrichment measurement with regression coefficients higher than 0.9978 and 0.9996, respectively. The method has a good intra- and inter-day precision with a relative standard deviation (RSD) below 6% for determining the tracer-to-tracee ratio (TTR) of both [2-(1)(3)C]acetate and [U-(1)(3)C]acetate. It has also a good intra- and inter-day precision with a RSD below 6% and 5% for determining the concentration of standard solution and biogas digester samples, respectively. Acidification of biogas digester samples with oxalic acid provided the low pH required for the protonation of SCFA and thus, allows the extraction of SCFA from the complex sample matrix. Moreover, oxalic acid was the source of formic acid which was produced in the injector set at high temperature. The produced formic acid prevented the adsorption of SCFA in the column, thereby eliminating peak tailing and ghost peaks. The applicability of the validated GC/MS method for determining the concentration of acetate and its (13)C isotope enrichment in anaerobic digester samples was tested and the results demonstrated the suitability of this method for identifying the metabolic pathways involved in degradation and production of acetate. PMID:26078128

  11. Reduction of the Total Acid Number of Crude Oil with Basic Solution

    Microsoft Academic Search

    R. J. Lu; X. R. Xu; J. Y. Yang; J. S. Gao

    2007-01-01

    Reduction of total acid number (TAN) of crude oil with sodium hydroxide and sodium carbonate solution was investigated. For emulsion emerging in an acid removal process by a sodium hydroxide solution, effects of the volume ratio of sodium hydroxide solution to crude oil and dosage of demulsifiers have been investigated. A model has been engaged to explain the interfacial behavior.

  12. Method for extracting lanthanides and actinides from acid solutions

    DOEpatents

    Horwitz, E. Philip (Naperville, IL); Kalina, Dale G. (Naperville, IL); Kaplan, Louis (Lombard, IL); Mason, George W. (Clarendon Hills, IL)

    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.

  13. Effect of Foams Used During Carbonate Acidizing

    Microsoft Academic Search

    M. G. Bernadiner; K. E. Thompson; H. S. Fogler

    1992-01-01

    Although acidization has been used successfully for many years to increase the productivity of petroleum wells in carbonate formations, demands on the performance and application of the acidizing process are increasing. This paper investigates a method of in-situ foam generation that allows deeper wormhole penetration yet uses less acid than conventional methods. The dissolution patterns were imaged with neutron radiography,

  14. Acylation of peptides by lactic acid solutions

    Microsoft Academic Search

    Andrea Lucke; Achim Gpferich

    2003-01-01

    To simplify the search for effective mechanisms to suppress peptide acylation inside drug delivery devices made of poly(d,l-lactic acid) (PLA) and poly(lactic-co-glycolic acid), we were looking for a suitable model system that would allow screening of strategies for peptide stabilization. With their low pH and the presence of lactic acid oligomers, diluted lactic acid solutions promised to be a suitable

  15. 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...

  16. Pecan shell activated carbon: synthesis, characterization, and application for the removal of copper from aqueous solution

    Microsoft Academic Search

    Seyed A Dastgheib; David A Rockstraw

    2001-01-01

    Activated carbon with a high adsorption capacity for removal of copper ions from aqueous solution is produced from pecan shells. Air and phosphoric acid are used for the oxidation and the modification or development of oxygen- or phosphorus\\/oxygen-containing groups on the carbon surface. It was found that the adsorption capacity of the produced carbon is significantly higher than that of

  17. Sorption of boric acid and borax by activated carbon impregnated with various compounds

    Microsoft Academic Search

    Lj. V. Rajakovi?; M. Dj. Risti?

    1996-01-01

    The separation of boron compounds, boric acid and borax from aqueous solution by activated carbon before and after impregnation with various compounds was studied. A series of activated carbons was prepared from coconut shell impregnated with calcium and barium chlorides, citric and tartaric acids. The examined processes were performed in batch and continuous systems under equilibrium and dynamic conditions. Impregnation

  18. Experimental equilibrium between acid gases and ethanolamine solutions

    SciTech Connect

    Bhairi, A.M.

    1984-01-01

    The general subject area of this study is equilibrium solubility of carbon dioxide and hydrogen sulfide in solutions of some common ethanolamines. The amines studied are most widely used in the area of gas sweetening. They include monoethanolamine, diglycolamine, diethanolamine and methyldiethanolamine. Only limited data are available for some of these amines. The process involved developing simple apparatus and procedure for investigating the equilibrium solubility of carbon dioxide and hydrogen sulfide in aqueous alkanolamine solutions. The procedure uses a single equilibrium cell. No gas chromatograph nor liquid chemical analysis is required. Measurements of the solubility were made in different amine solution concentrations at acid gas partial pressures to 1000 psia and temperatures from 77 to 240{degree}F. The method used was found to be sound as indicated by the consistency and reproducibility of the data.

  19. Reference electrode for strong oxidizing acid solutions

    SciTech Connect

    Rigdon, Lester P. (Livermore, CA); Harrar, Jackson E. (Castro Valley, CA); Bullock, Sr., Jack C. (Pleasanton, CA); McGuire, Raymond R. (Brentwood, CA)

    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.

  20. Increased fracture penetration and productivity using xanthan gelled acid in massive carbonate formations

    SciTech Connect

    Molon, J.P.; Fox, K.B.

    1983-03-01

    A measurable improvement in productivity can be achieved using xanthan gelled acid to stimulate carbonate formations. Well productivity results were compared to conventional acid fracture treatments. The significant improvements over classical acid fracturing techniques are due to the improved control of acid leakoff rates, retarded reaction rate and improved fracture width maintenance. The difficulties involved in acid fracturing massive Middle East carbonate formations are discussed and solutions are proposed using gelled acid technology. Some limitations in computer predictions of acid fracturing results are also discussed.

  1. Acidic properties of aqueous phosphoric acid solutions: a microscopic view.

    PubMed

    Harsnyi, I; Pusztai, L; Jvri, P; Beuneu, B

    2013-11-13

    We report on new neutron and x-ray diffraction data on D2O:D3PO4 solutions at two concentrations, 1:1 and 3:1. The experimental datasets were modelled simultaneously by the reverse Monte Carlo (RMC) method. From the resulting models, partial radial distribution functions (prdf) and coordination numbers were obtained. The acidity was found to decrease with increasing D3PO4 concentration. The ratio of dissociated acidic protons was estimated by dedicated simulation runs using average coordination number constraints. It was found that in the saturated solution the ratio of dissociated protons cannot exceed 20%. PMID:24140599

  2. Adsorption of 6-aminopenicillanic acid on activated carbon

    Microsoft Academic Search

    M. Dutta; R. Baruah; N. N. Dutta

    1997-01-01

    The adsorption and desorption of 6-aminopenicillanic acid (6-APA) in aqueous solution has been studied using activated carbon as the adsorbent. The extent of adsorption was found to be strongly dependent on the aqueous phase pH and this dependence could be interpreted from a model for neutral species adsorption. Desorptionstudies suggest that a small fraction of 6-APA adsorbs irreversibly on activated

  3. Study of Acid Response of Qatar Carbonate Rocks

    E-print Network

    Wang, Zhaohong

    2012-02-14

    reservoirs. Recently papers published from industry discussed the techniques, planning, and optimization of acid stimulation for Qatar carbonate. To the best of authors knowledge, no study has focused on the acid reaction to Qatar carbonates. The lack...

  4. Arterial Blood Carbonic Acid Inversely Determines Lactic and Organic Acids

    PubMed Central

    Aiken, Christopher Geoffrey Alexander

    2013-01-01

    Objective: To establish that arterial blood carbonic acid varies inversely with lactic acid in accordance with bicarbonate exchanging for lactate across cell membranes through the anion exchange mechanism to maintain the Gibbs-Donnan equilibrium. Study Design: Over 5 years, lactate was measured on all blood gases taken from neonatal admissions, as well as organic acid whenever electrolytes were required. Results: Arterial blood gases from 63 infants given high calcium TPN were analyzed. Twenty two needed continuous positive airways pressure (CPAP) only and 31 intermittent positive pressure ventilation (IPPV) and surfactant followed by CPAP to treat respiratory distress syndrome in 51 and meconium aspiration syndrome in 2. All survived and were free of infection. Excluded gases were those with high and falling lactate soon after delivery representing perinatal asphyxia, and those on dexamethasone. Strong inverse relations between carbonic and lactic acids were found at all gestational ages and, independent of glomerular filtration, between carbonic and organic acids. Lactate (mmol/L) = 62.53 X PCO2 -0.96(mmHg) r2 0.315, n 1232, p <0.001. Sixty divided by PCO2 is a convenient measure of physiological lactate at any given PCO2. In the first week, 9.13 2.57% of arterial gases from infants on IPPV had lactates above 120/PCO2, significantly more than 4.74 2.73% on CPAP (p<0.05) and 2.47 2.39% on no support. Conclusion: Changes in arterial blood carbonic acid cause immediate inverse changes in lactic acid, because their anions interchange across cell membranes according to the Gibbs Donnan equilibrium. Increasing PCO2 from 40 to 120 mmHg decreased lactate from 1.5 mmol/L to 0.5 mmol/L, so that the sum of carbonic and lactic acids increased from 2.72 mmol/L to only 4.17 mmol/L. This helps explain the neuroprotective effect of hypercapnoea and highlights the importance of avoiding any degree of hypocapnoea in infants on IPPV. PMID:24392387

  5. Use of activated carbons prepared from sawdust and rice-husk for adsorption of acid dyes: a case study of Acid Yellow 36

    Microsoft Academic Search

    P. K. Malik

    2003-01-01

    Activated carbons, prepared from low-cost mahogany sawdust and rice husk have been utilized as the adsorbents for the removal of acid dyes from aqueous solution. An acid dye, Acid Yellow 36 has been used as the adsorbate. Results show that a pH value of 3 is favourable for the adsorption of acid dye. The isothermal data could be well described

  6. Role of the pericarp of Carya illinoinensis as biosorbent and as precursor of activated carbon for the removal of lead and acid blue 25 in aqueous solutions

    Microsoft Academic Search

    V. Hernndez-Montoya; D. I. Mendoza-Castillo; A. Bonilla-Petriciolet; M. A. Montes-Morn; M. A. Prez-Cruz

    2011-01-01

    The pecan nuts are widely cultivated in states of north of Mexico and the residues generated during nut processing are abundant and not reused. In the present study, the pericarp of pecan (PP) was physicochemically characterized and their use as low cost biosorbent of lead and acid blue 25 was studied in batch systems at different experimental conditions. Also, the

  7. Pictorial Analogies XI: Concentrations and Acidity of Solutions.

    ERIC Educational Resources Information Center

    Fortman, John J.

    1994-01-01

    Presents pictorial analogies of several concepts relating to solutions for chemistry students. These include concentration of solution, strength of solution, supersaturated solution, and conjugate acid-base pairs. Among the examples are comparison of acid strength to percentage of strong soldiers or making supersaturated solution analogous to a

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

    SciTech Connect

    Park, S.B.; Lee, H.; Lee, K.H. [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of)] [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of)

    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 selected 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.

  9. Experimental High Velocity Acid Jetting in Limestone Carbonates

    E-print Network

    Holland, Christopher

    2014-04-30

    Acid jetting is a well stimulation technique that is used in carbonate reservoirs. It typically involves injecting acid down hole at high flow rates through small orifices which cause high velocities of acid to strike the borehole wall...

  10. 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.

  11. Removing of fulvic acids by ozonation and biological active carbon filtration

    Microsoft Academic Search

    Nataliya A. Klymenko; Ivan P. Kozyatnyk; Liudmyla A. Savchyna

    2010-01-01

    It was studied the effect of the content of biodegradable organic carbon (BDOC) after the processes of aeration and ozonation of the fulvic acid (FA) solutions on the efficiency of its adsorption and biofiltration. It was found that the change of free energy of adsorption of the FA oxidation products correlated with the part of biodegradable organic carbon in total

  12. 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.

  13. Process for the extraction of strontium from acidic solutions

    DOEpatents

    Horwitz, E. Philip (Naperville, IL); Dietz, Mark L. (Evanston, IL)

    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.

  14. PERFORMANCE AND MODELING OF A HOT POTASSIUM CARBONATE ACID GAS REMOVAL SYSTEM IN TREATING COAL GAS

    EPA Science Inventory

    The report discusses the performance and modeling of a hot potassium carbonate (K2CO3) acid gas removal system (AGRS) in treating coal gas. Aqueous solutions of K2CO3, with and without amine additive, were used as the acid gas removal solvent in the Coal Gasification/Gas Cleaning...

  15. Polyvinylpyrrolidone and polyethylenimine as inhibitors for the corrosion of a low carbon steel in phosphoric acid

    Microsoft Academic Search

    Y. Jianguo; W. Lin; V. Otieno-Alego; D. P. Schweinsberg

    1995-01-01

    Polarization and weight loss studies showed that both polyvinylpyrrolidonc and polyethylenimine are effective for the inhibition of low carbon steel over a wide concentration range of aqueous phosphoric acid (H3PO4) solutions. Both polymers retard the anodic and cathodic corrosion reactions with emphasis on the former. The results for uninhibited acid confirm the kinetic expression proposed by Mathur and Vasudevan.

  16. 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 (20.00mmol/L). PMID:26046278

  17. Adsorption of cesium (I) from aqueous solution using oxidized multiwall carbon nanotubes

    Microsoft Academic Search

    R. Yavari; Y. D. Huang; S. J. Ahmadi

    2011-01-01

    Multiwall carbon nanotubes (MWCNTs) were modified by nitric acid solution and then used to study the adsorption of cesium\\u000a from aqueous solution using a batch technique under ambient conditions. As produced and oxidized MWCNTs were characterized\\u000a by nitrogen adsorption\\/desorption, Boehms titration method and Fourier transform infrared spectroscopy. The physical properties\\u000a of MWCNTs such as functional groups, total number of acid

  18. Calcium stimulation of gastrin and gastric acid secretion: effect of small doses of calcium carbonate

    Microsoft Academic Search

    J Behar; M Hitchings; R D Smyth

    1977-01-01

    Oral calcium carbonate (0-5 g, pH 9-4) increased serum gastrin and gastric acid output with slight but insignificant change in serum calcium. A similar rise in serum calcium during an intravenous infusion of calcium gluconate failed to increase serum gastrin and gastric acid output. Both intragastric calcium actions were abolished by acidification of the calcium carbonate solution (pH 1-0). The

  19. 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.

  20. Toluene nitration in irradiated nitric acid and nitrite solution

    SciTech Connect

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

    2011-04-01

    The kinetics, mechanisms, and stable products produced for the aryl alkyl mild ortho-para director - toluene, in irradiated nitric acid and neutral nitrite solutions were investigated using ?, 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 was primarily used to assess the stable reaction products. GC-MS and LC-MS were used to confirm the results from HPLC. Free-radical nitration reaction products were found in irradiated acidic and neutral media. In acidic medium, the ring substitution and side chain substitution and oxidation produced different nitro products. In ring substitution, nitrogen oxide radicals were added mainly to hydroxyl radical-produced cyclohexadienyl radical, and in side chain substitution they were added to the carbon-centered benzyl radical produced by H-atom abstraction. In neutral nitrite toluene solution, radiolytic ring nitration products approached a statistically random distribution, suggesting a free-radical reaction involving addition of the NO2 radical.

  1. Biosynthesis of 2-hydroxyisobutyric acid (2-HIBA) from renewable carbon.

    PubMed

    Rohwerder, Thore; Mller, Roland H

    2010-01-01

    Nowadays a growing demand for green chemicals and cleantech solutions is motivating the industry to strive for biobased building blocks. We have identified the tertiary carbon atom-containing 2-hydroxyisobutyric acid (2-HIBA) as an interesting building block for polymer synthesis. Starting from this carboxylic acid, practically all compounds possessing the isobutane structure are accessible by simple chemical conversions, e. g. the commodity methacrylic acid as well as isobutylene glycol and oxide. During recent years, biotechnological routes to 2-HIBA acid have been proposed and significant progress in elucidating the underlying biochemistry has been made. Besides biohydrolysis and biooxidation, now a bioisomerization reaction can be employed, converting the common metabolite 3-hydroxybutyric acid to 2-HIBA by a novel cobalamin-dependent CoA-carbonyl mutase. The latter reaction has recently been discovered in the course of elucidating the degradation pathway of the groundwater pollutant methyl tert-butyl ether (MTBE) in the new bacterial species Aquincola tertiaricarbonis. This discovery opens the ground for developing a completely biotechnological process for producing 2-HIBA. The mutase enzyme has to be active in a suitable biological system producing 3-hydroxybutyryl-CoA, which is the precursor of the well-known bacterial bioplastic polyhydroxybutyrate (PHB). This connection to the PHB metabolism is a great advantage as its underlying biochemistry and physiology is well understood and can easily be adopted towards producing 2-HIBA. This review highlights the potential of these discoveries for a large-scale 2-HIBA biosynthesis from renewable carbon, replacing conventional chemistry as synthesis route and petrochemicals as carbon source. PMID:20184738

  2. 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.

  3. 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. PMID:25912910

  4. Isotope composition of carbon in amino acids of solid bitumens

    NASA Astrophysics Data System (ADS)

    Shanina, S. N.; Bushnev, D. A.

    2014-06-01

    Primary data are presented on the isotope composition of carbon in individual amino acids from solid bitumens and several biological objects. The amino acids of biological objects are characterized by wide variations of the isotope composition of carbon. This fact occurs owing to the difference in biochemical paths of metabolism resulting in the synthesis of individual amino acids. The ?13C values are somewhat decreased for individual amino acids in asphaltenes, varying from -7.7 to -31.7. The carbon of amino acids is weighted in kerits from Bad'el' compared to asphaltenes. All the natural bitumens retain the characteristic trend for natural substances: the isotopically heavy and light amino acids by carbon are glycine and leucine, respectively. The isotope composition of amino-acid carbon is lightened compared to natural bitumens in the samples formed under a pronounced thermal impact (asphalt-like crust and kirishite).

  5. Electrocatalytic oxidation of 3,4-dihydroxyphenylacetic acid at a glassy carbon electrode modified with single-wall carbon nanotubes

    Microsoft Academic Search

    Jianxiu Wang; Meixian Li; Zujin Shi; Nanqiang Li; Zhennan Gu

    2001-01-01

    The voltammetric behavior of 3,4-dihydroxyphenylacetic acid (DOPAC) was studied at a glassy carbon (GC) electrode modified with single-wall carbon nanotubes (SWNTs). In 0.1 M HAcNaAc buffer solution (pH 4.4), the SWNT-modified electrode shows high electrocatalytic activity toward oxidation of DOPAC. One well-defined redox couple is obtained. The peak current increases linearly with the concentration of DOPAC in the range of

  6. The corrosion of aluminum in boric acid solutions

    E-print Network

    Bass, Henry Kinsolving

    1956-01-01

    vs. Time of at 40oC . vs. Time of 40 C . 34 ~ ~ ~ 35 3S Aluminum in Boric ~ ~ ~ 24S Aluminum in Boric Corrosion Rate Acid Solutions vs. Time of at 50oC . 2S Aluminum in Boric 36 Corrosion Rate Acid Solutions vs. Time of at 50oC 3S... Solutions vs. Time of 3S Aluminum in Boric at 70oC 40 Corrosion Rate Acid Solutions vs. Time of at 70oC 24S Aluminum in Boric ~ ~ ~ . a ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ /+1 14. Corrosion Rate Acid Solutions vs. Time of at 90cC 2S Aluminum in Boric 42 15...

  7. Structural effects on the interactions of benzene and naphthalene sulfonates with activated carbon cloth during adsorption from aqueous solutions

    Microsoft Academic Search

    Erol Ayranci; Osman Duman

    2010-01-01

    Interactions of benzene and naphthalene sulfonates with activated carbon cloth (ACC) during adsorption from aqueous solutions were investigated. Systematically chosen sulfonates were sodium salt of benzene sulfonic acid (NaBS), disodium salt of 1,3-benzene disulfonic acid (Na2BDS), sodium salt of 1-naphthalene sulfonic acid (NaNS), disodium salt of 1,5-naphthalene disulfonic acid (Na2NDS) and trisodium salt of 1,3,(6 or 7)-naphthalene trisulfonic acid (Na3NTS).

  8. Uranyl fluoride luminescence in acidic aqueous solutions

    SciTech Connect

    Beitz, J.V.; Williams, C.W. [Argonne National Lab., IL (United States). Chemistry Div.

    1996-08-01

    Luminescence emission spectra and decay rates are reported for uranyl species in acidic aqueous solutions containing HF or added NaF. The longest luminescence lifetime, 0.269 {+-} 0.006 ms, was observed from uranyl in 1 M HF + 1 M HClO{sub 4} at 296 K and decreased with increasing temperature. Based on a luminescence dynamics model that assumes equilibrium among electronically excited uranyl fluoride species and free fluoride ion, this long lived uranyl luminescence in aqueous solution is attributed primarily to UO{sub 2}F{sub 2}. Studies on the effect of added LiNO{sub 3} or Na{sub 2}WO{sub 4}{center_dot}2H{sub 2}O showed relatively weak quenching of uranyl fluoride luminescence which suggests that high sensitivity determination of the UF{sub 6} content of WF{sub 6} gas should be feasible via uranyl luminescence analysis of hydrolyzed gas samples of impure WF{sub 6}.

  9. A comparative study of electrochemical behavior of chalcopyrite, chalcocite and bornite in sulfuric acid solution

    Microsoft Academic Search

    Elsa M Arce; Ignacio Gonzlez

    2002-01-01

    A comparative study of the electrochemical behavior of different copper sulfide minerals (chalcopyrite, bornite and chalcocite) in sulfuric acid solutions was performed. Carbon paste electrodes (CPE) containing mineral particles with nonconducting binder were used. The comparative study shows that the chalcopyrite oxidation process does not produce covellite as claimed by some authors. Chalcopyrite oxidation has been found to produce a

  10. Spectroscopic detection of isolated carbonic acid.

    PubMed

    Mori, Tetsuya; Suma, Kohsuke; Sumiyoshi, Yoshihiro; Endo, Yasuki

    2009-05-28

    Carbonic acid (cis-trans H(2)CO(3)) in the gas phase has been successfully produced in a supersonic jet using a pulsed discharge nozzle, and pure rotational transitions of this molecule have been observed by Fourier-transform microwave spectroscopy. Although the observed cis-trans conformer is not the global minimum structure, it is an important conformer as a starting point of its dissociation to CO(2) and H(2)O. Three deuterated isotopologues of the cis-trans conformer (cis-trans HDCO(3), cis-trans DHCO(3), and cis-trans D(2)CO(3)) have also been observed, yielding the r(0) structure of cis-trans H(2)CO(3). The present result is accurate enough to be used in radio astronomical observations. PMID:19485450

  11. Solubility of Small-Chain Carboxylic Acids in Supercritical Carbon Dioxide

    DOE PAGESBeta

    Sparks, Darrell L.; Estevez, L. Antonio; Hernandez, Rafael; McEwen, Jason; French, Todd

    2010-11-11

    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, p = 10.0 MPa), while the highest solute concentration was (151 2) kg m -3 (T = 333.15 K, p = 26.7 MPa). Additionally, 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.

  12. Solubility of Small-Chain Carboxylic Acids in Supercritical Carbon Dioxide

    DOE PAGESBeta

    Sparks, Darrell L.; Estevez, L. Antonio; Hernandez, Rafael; McEwen, Jason; French, Todd

    2010-11-11

    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,morep = 10.0 MPa), while the highest solute concentration was (151 2) kg m -3 (T = 333.15 K, p = 26.7 MPa). Additionally, 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

  13. Physical solubility of hydrogen sulfide and carbon dioxide in alkanolamine solutions

    SciTech Connect

    Abu-Arabi, M.K.

    1988-01-01

    The study was undertaken to develop a method that would make direct measurements of acid gases, hydrogen sulfide and carbon dioxide, physical solubilities in aqueous alkanolamine solutions possible. Hydrogen sulfide and carbon dioxide physical solubilities in 20, 35, and 50% by weight diethanolamine aqueous solutions were measured. The solubility measurements were made at acid gas partial pressure up to 1000 psia and temperatures of 80, 150, 240 F. The solubility of nitrous oxide in water and in protonated diethanolamine solution was also determined at 80 F. A method that allows for direct measurements of acid gases physical solubilities has been developed. The method eliminates amines reactivity with acid gases by protonating the amines prior to their contact with acid gases. CO{sub 2} physical solubility in aqueous DEA solutions occurs mainly in the water portion of the solution. Therefore, the physical solubility of CO{sub 2} in an aqueous amine solution must be corrected based on the fraction of water in the solution. However, H{sub 2}S physical solubility in aqueous DEA solutions is the same as H{sub 2}S solubility in water. At any acid gas partial pressure, the physical solubility of H{sub 2}S is higher than that of CO{sub 2} for the same solution concentration and for the same temperature. This is also true for their solubilities is pure water. The ratio of CO{sub 2} to H{sub 2}S physical solubility to N{sub 2}O solubility in aqueous DEA solutions is not the same as their ratio in pure water.

  14. Electrode kinetics at a platinum anode in chloroacetic acid solutions

    SciTech Connect

    Lotvin, B.M.; Vasil'ev, Yu.B.

    1987-02-01

    It was shown by direct comparison of kinetic and adsorption data that at platinum in solutions of mono- and trichloroacetic acid, the anodic processes are entirely analogous in character to the processes occurring in acetate solutions. The lack of Kolbe electrosynthesis products in the electrolysis of chloroacetic acids is to the special reaction features of the secondary chloroalkyl radicals.

  15. Binary Diffusion Coefficients for Aqueous Solutions of Lactic Acid

    Microsoft Academic Search

    Ana C. F. Ribeiro; Victor M. M. Lobo; Derek G. Leaist; Joaquim J. S. Natividade; Lus P. Verssimo; Marisa C. F. Barros; Ana M. T. D. P. V. Cabral

    2005-01-01

    Taylor dispersion equipment installed at the University of Coimbra for the measurement of diffusion in liquids has been tested to ensure adequate accuracy and precision by measuring mutual diffusion coefficients for binary aqueous solutions of sucrose, glycine, lithium chloride, potassium chloride, and hydrochloric acid at 298.15 K. In addition, binary mutual diffusion coefficients for aqueous solutions of lactic acid (not

  16. Comparison of Carbonate and Uricase-Carbonate Methods for the Determination of Uric Acid in Serum

    Microsoft Academic Search

    Wendell T. Caraway; Herman Marable

    1965-01-01

    A colorimetric carbonate procedure for the determination of uric acid has been modi- fied to include incubation of serum with uricase to destroy uric acid. Residual non- urate chromogens are subtracted from total chromogens to obtain the concentration of \\

  17. Dissolution kinetics of chalcopyrite in acidic potassium dichromate solution

    Microsoft Academic Search

    S. Aydogan; G. Ucar; M. Canbazoglu

    2006-01-01

    The dissolution of chalcopyrite in acidic potassium dichromate solution has been investigated with respect to the effects of sulphuric acid and potassium dichromate concentrations, by changing stirring speed, leaching temperature and particle size. It was determined that dissolution rate increased with increasing sulphuric acid concentration, potassium dichromate concentration and temperature. A particle size below 75 ?m was required to leach

  18. The effect of acetic acid and acetate on CO2 corrosion of carbon steel

    Microsoft Academic Search

    Dong Liu; ZhenYu Chen; XingPeng Guo

    2008-01-01

    Purpose The purpose of this paper is to consider the effect of acetic acid and acetate on the anodic and cathodic reactions of carbon steel present in CO2 corrosion. Design\\/methodology\\/approach The corrosion behaviour of carbon steel (N80) in CO2-saturated 1% NaCl solution at 50C and 0.1 MPa was investigated by using weight-loss tests, electrochemical methods (polarization curves and

  19. Molecular features of the air/carbonate solution interface.

    PubMed

    Du, Hao; Liu, Jin; Ozdemir, Orhan; Nguyen, Anh V; Miller, Jan D

    2008-02-15

    The nature of the air/carbonate solution interface is considered with respect to water structure by sum-frequency vibrational spectroscopy (SFVS) and molecular dynamics simulations (MDS). Results from this study provide further understating regarding previous observations that the surface tensions of structure making sodium carbonate solutions have been shown to be significantly greater than the surface tensions of structure breaking bicarbonate solutions at equivalent concentrations. This difference in surface tension and its variation with salt concentration is related to the organization of water and ions at the air/solution interface. Spectral results from SFVS show at equivalent concentrations that, for the carbonate solution, the strong water structure signal of 3200 cm(-1) at the air/carbonate solution interface is increased by a factor of 4 when compared to the same signal for the air/bicarbonate solution interface, which spectrum is weaker than the spectrum for the air/water interface in the absence of salt. These results from SFVS are explained by the results from MDS which show that in the case of carbonate solutions the structure making carbonate ions are excluded from the interfacial water region which region is extended in depth. On the other hand, in the case of bicarbonate solutions, the bicarbonate ions are accommodated in the interfacial water region and there is no evidence of an increase in the extent of water structure. These SFVS experimental and MD simulation results provide further information to understand interfacial phenomena of soluble salts at the molecular level. PMID:18035369

  20. Process for the recovery of strontium from acid solutions

    DOEpatents

    Horwitz, E. Philip (Naperville, IL); Dietz, Mark L. (Evanston, IL)

    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.

  1. Process for the recovery of strontium from acid solutions

    SciTech Connect

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

    1990-12-31

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

  2. The Effect of Heterogeneity on Matrix Acidizing of Carbonate Rocks

    E-print Network

    Keys, Ryan S.

    2010-07-14

    In matrix acidizing, the goal is to dissolve minerals in the rock to increase well productivity. This is accomplished by injecting an application-specific solution of acid into the formation at a pressure between the pore ...

  3. Fluorescent Carbon Dots Capped with PEG 200 and Mercaptosuccinic Acid

    Microsoft Academic Search

    Helena Gonalves; Joaquim C. G. Esteves da Silva

    2010-01-01

    The synthesis and functionalization of carbon nanoparticles with PEG200 and mercaptosuccinic acid, rendering fluorescent carbon dots, is described. Fluorescent carbon dots (maximum excitation and\\u000a emission at 320 and 430nm, respectively) with average dimension 267nm were obtained. The lifetime decay of the functionalized\\u000a carbon dots is complex and a three component decay time model originated a good fit with the following

  4. Adsorption of perfluoroalkyl acids by carbonaceous adsorbents: Effect of carbon surface chemistry.

    PubMed

    Zhi, Yue; Liu, Jinxia

    2015-07-01

    Adsorption by carbonaceous sorbents is among the most feasible processes to remove perfluorooctane sulfonic (PFOS) and carboxylic acids (PFOA) from drinking and ground waters. However, carbon surface chemistry, which has long been recognized essential for dictating performance of such sorbents, has never been considered for PFOS and PFOA adsorption. Thus, the role of surface chemistry was systematically investigated using sorbents with a wide range in precursor material, pore structure, and surface chemistry. Sorbent surface chemistry overwhelmed physical properties in controlling the extent of uptake. The adsorption affinity was positively correlated carbon surface basicity, suggesting that high acid neutralizing or anion exchange capacity was critical for substantial uptake of PFOS and PFOA. Carbon polarity or hydrophobicity had insignificant impact on the extent of adsorption. Synthetic polymer-based Ambersorb and activated carbon fibers were more effective than activated carbon made of natural materials in removing PFOS and PFOA from aqueous solutions. PMID:25827692

  5. Infrared optical constants of HO ice, amorphous nitric acid solutions, and nitric acid hydrates

    Microsoft Academic Search

    Owen B. Toon; Margaret A. Tolbert; Birgit G. Koehler; Ann M. Middlebrook; Joseph Jordan

    1994-01-01

    The authors 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. They have also found the infrared optical constants of HO ice. They measured the transmission of infrared light through thin films of varying thickness over the frequency range from about 7000

  6. Functionalization of single-walled carbon nanotubes with ribonucleic acids

    NASA Astrophysics Data System (ADS)

    Park, June; Kim, Sejin; Seong, Maeng-Je; Kim, Yu Jin; Go, Hayoung; Lee, Kangseok

    2013-12-01

    The optical properties of single-walled carbon nanotubes (SWCNTs) dispersed in aqueous solutions of ribonucleic acids (RNA) purified from Escherichia coli were studied using photoluminescence (PL), Raman, and absorption spectroscopy. SWCNT-RNA complexes, down to a single isolated nanotube level, were successfully synthesized. SWCNT signatures in Raman, PL, and absorption spectroscopy were observed from the SWCNT-RNA complexes. Observation of two distinct PL peaks, one at 1.248 eV and the other at 1.392 eV, confirmed the existence of isolated (6,5) and (6,4) SWCNTs, respectively. Atomic force microscope images and height profiles also showed evidence of isolated SWCNT-RNA complex.

  7. Solubility of Pa(V) in solutions of thiocyanic acid

    Microsoft Academic Search

    V. V. Nekrasova; E. S. Palshin; B. F. Myasoedov

    1974-01-01

    The solubility of Pa(V) and Ta(V) hydroxides in HSCN as well as HCl ; solutions containing thiocyanato ions was studied. At equal concentrations of ; the acids the solubility of Pa(V) is higher in HSCN solutions than in HCl ; solutions. In 1M HSCN the Pa(V) solubility is 0.05 g\\/l. (auth);

  8. 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. PMID:24679083

  9. Acid Diversion in Carbonate Reservoirs Using Polymer-Based In-Situ Gelled Acids

    E-print Network

    Gomaa, Ahmed Mohamed Mohamed

    2012-07-16

    Diversion in carbonates is more difficult than in sandstones because of the ability of acid to significantly increase the permeability in carbonates as it reacts in the pore spaces and flow channels of matrix. In-situ gelled acids that are based...

  10. Effect of acidic solution viscosity on enamel erosion.

    PubMed

    Aykut-Yetkiner, A; Wiegand, A; Bollhalder, A; Becker, K; Attin, T

    2013-03-01

    The objective of this in vitro study was to investigate the effects of viscosity changes of different acidic solutions on dental erosion. Bovine enamel samples (n = 240, = 3 mm) were embedded in acrylic resin and were allocated to 30 groups (n = 8). Citric acid (CA) and phosphoric acid (PA) solutions at pH 2.5, 3, and 3.5 were prepared in de-ionized water (titratable acidity to pH 5.5: 31 0.6 mmol OH(-)/l). The kinetic viscosities of the acidic solutions were adjusted to 1.5, 3, 6, 12, and 24 mm(2)/sec by the addition of hydroxypropyl cellulose (HPC) at different concentrations. Solutions were pumped over the enamel surface from a reservoir with a drop rate of 1 mL/min. Each specimen was eroded for 10 min at 20 C. Erosion of enamel surfaces was measured by profilometry. Data were analyzed by analyses of variance and logarithmic regression analyses (p < 0.05). Enamel loss was dependent on viscosity, pH, and the kind of acid. The regression analyses showed that higher viscosity caused lower enamel erosion for both acids and all pH levels. Dental erosion is dependent not only on chemical factors of the acid, like pH and acid type, but also on acid viscosity. PMID:23315475

  11. The influence of cathodic reduction, Fe 2+ and Cu 2+ ions on the electrochemical dissolution of chalcopyrite in acidic solution

    Microsoft Academic Search

    A. E Elsherief

    2002-01-01

    The electrochemical behaviour of chalcopyrite has been studied in sulphuric acid solutions with the carbon paste electrode technique. Cyclic voltammetry were performed and the effect of cathodic scan limit, Fe2+ and Cu2+ ion concentrations were followed. The presence of Cu2+ ions in solutions leads to an increase in both the oxidation and the reduction currents, but in either case further

  12. SAVANNAH RIVER SITE TANK CLEANING: CORROSION RATE FOR ONE VERSUS EIGHT PERCENT OXALIC ACID SOLUTION

    SciTech Connect

    Ketusky, E.; Subramanian, K.

    2011-01-20

    Until recently, the use of oxalic acid for chemically cleaning the Savannah River Site (SRS) radioactive waste tanks focused on using concentrated 4 and 8-wt% solutions. Recent testing and research on applicable dissolution mechanisms have concluded that under appropriate conditions, dilute solutions of oxalic acid (i.e., 1-wt%) may be more effective. Based on the need to maximize cleaning effectiveness, coupled with the need to minimize downstream impacts, SRS is now developing plans for using a 1-wt% oxalic acid solution. A technology gap associated with using a 1-wt% oxalic acid solution was a dearth of suitable corrosion data. Assuming oxalic acid's passivation of carbon steel was proportional to the free oxalate concentration, the general corrosion rate (CR) from a 1-wt% solution may not be bound by those from 8-wt%. Therefore, after developing the test strategy and plan, the corrosion testing was performed. Starting with the envisioned process specific baseline solvent, a 1-wt% oxalic acid solution, with sludge (limited to Purex type sludge-simulant for this initial effort) at 75 C and agitated, the corrosion rate (CR) was determined from the measured weight loss of the exposed coupon. Environmental variations tested were: (a) Inclusion of sludge in the test vessel or assuming a pure oxalic acid solution; (b) acid solution temperature maintained at 75 or 45 C; and (c) agitation of the acid solution or stagnant. Application of select electrochemical testing (EC) explored the impact of each variation on the passivation mechanisms and confirmed the CR. The 1-wt% results were then compared to those from the 8-wt%. The immersion coupons showed that the maximum time averaged CR for a 1-wt% solution with sludge was less than 25-mils/yr for all conditions. For an agitated 8-wt% solution with sludge, the maximum time averaged CR was about 30-mils/yr at 50 C, and 86-mils/yr at 75 C. Both the 1-wt% and the 8-wt% testing demonstrated that if the sludge was removed from the testing, there would be a significant increase in the CR. Specifically, the CR for an agitated 1-wt% pure oxalic acid solution at 45 or 75 C was about 4 to 10 times greater than those for a 1-wt% solution with sludge. For 8-wt% at 50 C, the effect was even larger. The lower CRs suggest that the cathodic reactions were altered by the sludge. For both the 1-wt% and 8-wt% solution, increasing the temperature did not result in an increased CR. Although the CR for a 1-wt% acid with sludge was considered to be non-temperature dependent, a stagnant solution with sludge resulted in a CR that was greater at 45 C than at 75 C, suggesting that the oxalate film formed at a higher temperature was better in mitigating corrosion. For both a 1 and an 8-wt% solution, agitation typically resulted in a higher CR. Overall, the testing showed that the general CR to the SRS carbon steel tanks from 1-wt% oxalic acid solution will remain bounded by those from an 8-wt% oxalic acid solution.

  13. Six Sigma review of root causes of corrosion incidents in hot potassium carbonate acid gas removal plant

    Microsoft Academic Search

    S. J. Harjac; A. Atrens; C. J. Moss

    2008-01-01

    This paper is a summary of a desktop review, using the Six Sigma methodology, of root causes for corrosion incidents in Hot Potassium Carbonate acid gas removal plant. These corrosion incidents involve rapid localised corrosion of carbon steel vessel walls by the CO2 containing process solution. The possible root causes are identified as (1) inadequate concentration of anodic inhibitor, (2)

  14. Conversion of ferulic acid into 4-vinylguaiacol, vanillin and vanillic acid in model solutions of shochu

    Microsoft Academic Search

    Takuya Koseki; Yasurou Ito; Shinji Furuse; Kiyoshi Ito; Kimio Iwano

    1996-01-01

    4-Vinylguaiacol (4-hydroxy-3-methoxystyrene), vanillin (4-hydroxy-3-methoxybenzaldehyde), and vanillic acid (4-hydroxy-3-methoxybenzoic acid) were isolated from distilled and stored model solutions of shochu (MSS) that originally contained only ferulic acid (4-hydroxy-3-methoxycinnamic acid) using a solid-phase extraction technique. These compounds were analyzed by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection. The amounts of the metabolites converted from ferulic acid was affected by pH, alcohol

  15. Solute carbon and carbon segregation in magnesium oxide single crystals a secondary ion mass spectrometry study

    Microsoft Academic Search

    Friedemann Freund

    1986-01-01

    If carbon is to be analyzed by secondary ion mass spectroscopy (SIMS) in an oxide such as MgO, one has to know how the carbon is incorporated in the oxide host structure, before a successful experiment can be planned. If the carbon impurities derive from dissolved CO2 component which form a solid solution while the crystal grew from a melt

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

    DOEpatents

    Horwitz, E. Philip (Naperville, IL); Dietz, Mark L. (Evanston, IL)

    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.

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

    SciTech Connect

    Weiland, R.H.; Dingman, J.C.; Cronin, D.B.; Browning, G.J. [Optimized Gas Treating, Inc., Houston, TX (United States)] [Optimized Gas Treating, Inc., Houston, TX (United States)

    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 the densities and viscosities of DEA + MDEA and MEA + MDEA blends. Predictions are compared with data measured for these blends.

  18. On the texturization of monocrystalline silicon with sodium carbonate solutions

    Microsoft Academic Search

    B. Vallejo; M. Gonzlez-Maas; J. Martnez-Lpez; M. A. Caballero

    2007-01-01

    The texturization of monocrystalline silicon wafers using sodium carbonate solution has been investigated. This etching process has been evaluated in terms of the surface morphology and the reflectance value. The results show that for low concentration of sodium carbonate the increase of texturing time decreases the reflectance value because of the change in morphology from hillocks to pyramidal; on the

  19. Sorption of acid dyes from effluents using activated carbon

    Microsoft Academic Search

    Keith K. H. Choy; Gordon McKay; John F. Porter

    1999-01-01

    The sorption of three acid dyes, namely, Acid Red 114, Polar Yellow and Polar Blue RAWL, onto activated carbon, has been studied. Equilibrium isotherms have been measured for three single component systems (AB, AR, AY) and one binary component system (AB+AY). The isotherms were determined by shaking 0.05 g activated carbon, particle size range 500710 ?m, with 0.05 dm3 dye

  20. Enhanced photochemical loss of organic carbon in acidic waters

    Microsoft Academic Search

    Chad Gennings; Lewis A. Molot; Peter J. Dillon

    2001-01-01

    Previous studies have shown that (a) a large portion of theannual total organic carbon (TOC) inputs to central Ontario lakes iseither lost to sediments or degraded and lost via evasion to theatmosphere, (b) the partitioning of organic carbon between sediments andthe atmosphere appears to be a function of acidity and (c) UVirradiation can account for observed long-term loss of TOC

  1. Effects of acidic solutions on sexual reproduction of Pteridium aquilinum

    Microsoft Academic Search

    Lance S. Evans; Christine A. Conway

    1980-01-01

    Experiments were performed to determine the effects of acidic solutions on spermatozoid motility and fertilization of gametophytes of Pteridium aquilinum. Buffered solutions (approx 0.0025 m) were used to simulate exposures to acidic precipitation for up to a 3.5 hr exposure. Experimental results suggest that the spermatozoid population can be subdivided into several groups with respect to pH sensitivity: About 25%

  2. The Effect of Acid Additives on Carbonate Rock Wettability and Spent Acid Recovery in Low Permeability Gas Carbonates

    E-print Network

    Saneifar, Mehrnoosh

    2012-10-19

    Spent acid retention in the near-wellbore region causes reduction of relative permeability to gas and eventually curtailed gas production. In low-permeability gas carbonate reservoirs, capillary forces are the key parameters that affect the trapping...

  3. Raman spectra of amino acids and their aqueous solutions

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  4. Highly accurate boronimeter assay of concentrated boric acid solutions

    Microsoft Academic Search

    Ball

    1992-01-01

    The Random-Walk Boronimeter has successfully been used as an on-line indicator of boric acid concentration in an operating commercial pressurized water reactor. The principle has been adapted for measurement of discrete samples to high accuracy and to concentrations up to 6000 ppm natural boron in light water. Boric acid concentration in an aqueous solution is a necessary measurement in many

  5. Leaching of copper oxide with different acid solutions

    Microsoft Academic Search

    N. Habbache; N. Alane; S. Djerad; L. Tifouti

    2009-01-01

    In this study, the dissolution of CuO in HCl, H2SO4, HNO3 and citric acid solutions was investigated in a batch reactor employing parameters expected to affect the dissolution rate of copper such as stirring speed, temperature and acid concentration. It was found that 99.95% of copper was dissolved after 14min with inorganic acids at 0.5M, 25C and l\\/s=10ml\\/g while more

  6. Isothermal heat measurements of TBP-nitric acid solutions

    SciTech Connect

    Smith, J.R.; Cavin, W.S. [Westinghouse Savannah River Company, Aiken, SC (United States)

    1995-12-31

    Net heats of reaction were measured in an isothermal calorimeter for TBP/HNO{sub 3} solutions at ambient pressure and temperatures above 100{degrees}C. Carbon and nitrogen balances were performed giving the reaction stoichiometry. Rate expressions were derived and rate constants determined for both the single and two phase systems which included mass lost from the reacting system by evaporation. This mathematical model was fit to the experimental data (including the measured net heat and off-gas rate) gathered over a wide range of conditions. The oxidation rate constant was determined to be 5.4E-4 min{sup -1} at 110{degrees}C for an open {open_quotes}vented{close_quotes} system as compared to >1E-3min{sup -1} in a closed system. The heat released per unit material oxidized was also reduced due to a decrease in dissolved oxidants and an inefficient reduction of HNO{sub 3}. Oxidation in the organic phase was found to be first order in nitric acid and pseudo-zero order in butylnitrate and water.

  7. 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

    2015-05-01

    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 65-70C 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. PMID:25371160

  8. Field evaluation of gelled acid for carbonate formations

    SciTech Connect

    Church, D.C.; Quisenberry, J.L.; Fox, K.B.

    1981-12-01

    A new gelled acid was evaluated in the west Texas, southeast New Mexico, and Oklahoma areas. The purpose of this evaluation was to determine how successful a gelled acid, prepared from xanthan polymer, would be in several carbonate formations. Several types of acidizing techniques were employed. These treatments vary from one to nine stages, with and without diverting agents. More than 20 treatments are summarized. Production figures for the wells treated are discussed, as well as pertinent related information. 5 refs.

  9. MEASUREMENT OF THERMAL NEUTRON SPECTRA IN BORIC ACID SOLUTIONS

    Microsoft Academic Search

    E. Ya. Doilnitsyn; A. G. Novikov

    1962-01-01

    Contradictory data are reported in the literature on the thermal neutron ; spectra of aqueous solutions containing an absorber. This problem was studied by ; exposing boric acid solutions in water to the neutron beam of the GraphiteWater ; Reactor. The experimental results were found to agree well with the as yet ; unpublished theoretical values, calculated by G. I.

  10. Precipitation of plutonium from acidic solutions using magnesium oxide

    SciTech Connect

    Jones, S.A.

    1994-12-05

    Magnesium oxide will be used as a neutralizing agent for acidic plutonium-containing solutions. It is expected that as the magnesium oxide dissolves, the pH of the solution will rise, and plutonium will precipitate. The resulting solid will be tested for suitability to storage. The liquid is expected to contain plutonium levels that meet disposal limit requirements.

  11. Extraction of rare-earth elements from nitric acid solutions with bis(dioctylphosphinylmethyl)phosphinic acid

    Microsoft Academic Search

    A. N. Turanov; V. K. Karandashev; A. N. Yarkevich; Z. V. Safronova

    2006-01-01

    The distribution of microamounts of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y nitrates between aqueous\\u000a HNO3 solutions and solutions of bis(dioctylphosphinylmethyl)phosphinic acid in organic diluents was studied. The stoichiometry\\u000a of the extractable complexes was determined, and the diluent effect on the efficiency of extraction of rare-earth elements\\u000a from nitric acid solutions

  12. 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 ?-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 ?-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

  13. Studies on the Adsorption of Traces of Zirconium on Manganese Dioxide from Acid Solutions

    Microsoft Academic Search

    Syed Moosa Hasany; Ehsan-Ul Haq; Shahid Bilal Butt

    1986-01-01

    The adsorption of zirconium on manganese dioxide from nitric and perchloric acid solutions has been investigated at different concentrations of electrolyte, adsorbent, and adsorbate. The effect of other cations and anions on adsorption has been studied. Fluoride, citrate, oxalate, molybdate, tartrate, carbonate, phosphate, Fe(III), Sr(II), Zn(II), Cr(III), and Mg(II) drastically reduce adsorption. Adsorption of other metal ions on the oxide

  14. Characterization of carbon black modified by maleic acid

    NASA Astrophysics Data System (ADS)

    Asokan, Vijayshankar; Kosinski, Pawel; Skodvin, Tore; Myrseth, Velaug

    2013-09-01

    We present here a method for modifying the surface of carbon black (CB) using a simple heat treatment in the presence of a carboxylic acid as well as water or ethylene glycol as a solvent. CB was mixed with maleic acid and either water or ethylene glycol, and heated at 250C. Unlike the traditional surface modification processes which use heat treatment of carbon with mineral acids the present modification method using a carboxylic acid proved to be simple and time efficient. CB from two different vendors was used, and the modified samples were characterized by TGA, BET surface area measurement, XRD, particle size and zeta potential measurements, and FTIR. It was found that several material properties, including thermal stability and surface area, of the modified CB are significantly altered relative to the parental carbon samples. This method provides a rapid and simple route to tailor new materials with desired properties.

  15. REMOVAL OF CHLORIDE FROM ACIDIC SOLUTIONS USING NO2

    SciTech Connect

    Visser, A; Robert Pierce, R; James Laurinat, J

    2006-08-22

    Chloride (Cl{sup -}) salt processing in strong acids is used to recycle plutonium (Pu) from pyrochemical residues. The Savannah River National Laboratory (SRNL) is studying the potential application of nitrogen dioxide (NO{sub 2}) gas to effectively convert dissolved pyrochemical salt solutions to chloride-free solutions and improve recovery operations. An NO{sub 2} sparge has been shown to effectively remove Cl{sup -} from solutions containing 6-8 M acid (H{sup +}) and up to 5 M Cl{sup -}. Chloride removal occurs as a result of the competition of at least two reactions, one which is acid-dependent. Below 4 M H+, NO2 reacts with Cl- to produce nitrosyl chloride (ClNO). Between 6 M and 8 M H{sup +}, the reaction of hydrochloric acid (HCl) with nitric acid (HNO{sub 3}), facilitated by the presence of NO{sub 2}, strongly affects the rate of Cl{sup -} removal. The effect of heating the acidic Cl{sup -} salt solution without pre-heating the NO{sub 2} gas has minimal effect on Cl{sup -} removal rates when the contact times between NO{sub 2} and the salt solution are on the order of seconds.

  16. Evaluation of localized corrosion of zirconium in acidic chloride solutions

    SciTech Connect

    Fahey, J.; Holmes, D.; Yau, T.L. [Wah Chang, Albany, OR (United States)

    1997-01-01

    Zirconium is prone to localized corrosion in acidic chloride (Cl{sup {minus}}) solutions contaminated by oxidizing ions, such as ferric or cupric ions. This tendency can be reduced by ensuring that the zirconium surface is clean and smooth. The effect of surface condition on localized corrosion of zirconium in acidic chloride solutions was predicted using potentiodynamic polarization scans. Predictions were confirmed by mass-loss tests on various combinations of surface finish and acid concentrations. A real-time indication of localized corrosion was derived by monitoring electrochemical noise produced between two similar electrodes immersed in an acidic chloride solution. Electrochemical noise monitoring correlated well with predictions from the potentiodynamic polarization and mass-loss experiments. Electrochemical noise results showed a more anodic potential caused by ferric ion (Fe{sup 3+}) contamination might be necessary for localized corrosion but that it was not a sufficient condition. A clean zirconium surface reduced localized corrosion of zirconium.

  17. Fluorecently labeled bionanotransporters of nucleic acid based on carbon nanotubes

    E-print Network

    Novopashina, D S; Venyaminova, A G

    2012-01-01

    Here we propose the approach to design of the new type of hybrids of oligonucleotides with fluorescein-functionalized single-walled carbon nanotubes. The approach is based on stacking interactions of functionalized nanotubes with pyrene residues in conjugates of oligonucleotides. The amino- and fluorescein-modified single-walled carbon nanotubes were obtained, and their physico-chemical properties were investigated. The effect of carbon nanotubes functionalization type on the efficacy of sorption of pyrene conjugates of oligonucleotides was examined. Proposed non-covalent hybrids of fluorescein-labeled carbon nanotubes with oligonucleotides may be used for intracellular transport of functional nucleic acids.

  18. Influence of Acidic and Alkaline Waste Solution Properties on Uranium Migration in Subsurface Sediments

    SciTech Connect

    Szecsody, James E.; Truex, Michael J.; Qafoku, Nikolla; Wellman, Dawn M.; Resch, Charles T.; Zhong, Lirong

    2013-08-01

    This study shows that acidic and alkaline wastes co-disposed with uranium into subsurface sediments has 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., 100s 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 (pH 2) resulted in a rapid (< 10 h) increase in aqueous carbonate (with Ca2+, Mg2+) and phosphate and a slow (100s of hours) increase in silica, Al3+, 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 (pH 13) resulted in a rapid (< 10 h) increase in carbonate, followed by a slow (10s to 100s of hours) increase in silica concentration, likely from montmorillonite, muscovite, and kaolinite dissolution. Infiltration of uranium with a strong base resulted in 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.

  19. Conversion of carbon dioxide to resorcylic acid under ultrasonication by Kolbe-Schmitt reaction.

    PubMed

    Shanthi, B; Palanivelu, K

    2015-11-01

    The present work focuses on a new approach for the synthesis of ?-resorcylic acid based on Kolbe-Schmitt reaction using carbon dioxide under ultrasonic and mild condition. The Kolbe-Schmitt reaction is a process for the synthesis of ?-resorcylic acid (2,4-dihydroxybenzoic acid) from resorcinol in aqueous potassium hydroxide solution with gaseous CO2. The influences of carbonation time, flow rate of CO2 and the molar ratio of resorcinol/potassium hydroxide on the yield percentage of resorcylic acid were investigated. The study was assessed with the conventional thermal method (non ultrasonic method) for Kolbe-Schmitt reaction and it was observed that applying ultrasound to save more than 95% and 38.6% energy as shown by energy consumption calculations in bath type and horn type sonicator respectively. ?-Resorcylic acid formed was characterized by (1)H NMR, (13)C NMR, DEPT NMR and FTIR spectroscopy. The amount of CO2 utilized in the reaction was evaluated from the yield percentage of ?-resorcylic acid yield. The maximum yield of resorcylic acid of 30% and 65% was obtained at the resorcinol/potassium hydroxide ratio of 1:3, carbonation time of 150min and the CO2 flow rate of 2L/min in bath type and horn type ultrasonicator, respectively. The applicability of the research work was examined in two different positional isomers of resorcinol under optimum conditions. PMID:26186845

  20. Mass transfer during dissolution of cadmium in hydrochloric acid solutions

    SciTech Connect

    Dubynin, A.I.; Duda, B.I.; Berlin, A.A.

    1987-10-20

    This paper reports the dissolution kinetics of cadmium tubes (d = 40, l = 90 mm) in aqueous hydrochloric acid solutions under natural and induced movement at 30/sub 0/C. The external surface and edges were insulated with an acid-resistant lacquer. The hydrochloric acid concentration over the range studied had little effect on the cadmium dissolution rate, the controlling step in the process being desorption of cadmium ions from the anodic sections and hydrogen ions from the cathodic sections. Based on theoretical and experimental studies we postulate a halide passivation of the anodic sections of the metal surface to produce dissolution curve inflections as a result of induced acid movement.

  1. 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.

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

    DOEpatents

    Horwitz, E. Philip (Naperville, IL); Kalina, Dale G. (Naperville, IL)

    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.

  3. Vacuum-jacketed hydrofluoric acid solution calorimeter

    USGS Publications Warehouse

    Robie, R.A.

    1965-01-01

    A vacuum-jacketed metal calorimeter for determining heats of solution in aqueous HF was constructed. The reaction vessel was made of copper and was heavily gold plated. The calorimeter has a cooling constant of 0.6 cal-deg -1-min-1, approximately 1/4 that of the air-jacketed calorimeters most commonly used with HF. It reaches equilibrium within 10 min after turning off the heater current. Measurements of the heat of solution of reagent grade KCl(-100 mesh dried 2 h at 200??C) at a mole ratio of 1 KCl to 200 H2O gave ??H = 4198??11 cal at 25??C. ?? 1965 The American Institute of Physics.

  4. REACTIVE FLOW IN VUGGY CARBONATES: METHODS AND MODELS APPLIED TO MATRIX ACIDIZING OF CARBONATES

    E-print Network

    Izgec, Omer

    2010-07-14

    Carbonates invariably have small (micron) to large (centimeter) scale heterogeneities in flow properties that may cause the effects of injected acids to differ greatly from what is predicted by a model based on a homogenous ...

  5. REACTIVE FLOW IN VUGGY CARBONATES: METHODS AND MODELS APPLIED TO MATRIX ACIDIZING OF CARBONATES

    E-print Network

    Izgec, Omer

    2010-07-14

    Carbonates invariably have small (micron) to large (centimeter) scale heterogeneities in flow properties that may cause the effects of injected acids to differ greatly from what is predicted by a model based on a homogenous formation. To the best...

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

    SciTech Connect

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

    2011-11-03

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

  7. 137Cs desorption from lichen using acid solutions

    NASA Astrophysics Data System (ADS)

    ?u?ulovi?, A. A.; Veselinovi?, D.; Miljani?, S. S.

    2009-09-01

    Desoprtion of 137Cs from samples of Cetraria islandica lichen using HCl ( A) and HNO3 ( B) acid solutions with pH values from 2.00 to 3.75 was investigated. After five consecutive desorptions lasting 24 h it was shown that between 52.2% (solution B pH 3.28) and 72.2% (solution A pH 2.00) of 137Cs was desorbed from the lichen and the initial desorptions were the most successful. Lichen desorbed with the stated solutions did not undergo structural changes. The amount of absorbed water from solutions A and B, used for desorption from lichen, in relation to the starting volume (expressed in %) showed that solution concentration did not take place. Lichen act as neutralizing agents because the pH of the lichen thallus is higher than the pH value of the solution used

  8. Carbonation and other super saturated gases as solution modifiers for improved sensitivity in solvent assisted ionization inlet (SAII) and ESI.

    PubMed

    Pagnotti, Vincent S; Chakrabarty, Shubhashis; McEwen, Charles N

    2013-02-01

    Solvent Assisted Ionization Inlet (SAII) produces ions in a heated inlet to a mass spectrometer from aqueous and aqueous/organic solutions with high sensitivity. However, the use of acid modifiers, which typically aids electrospray ionization, generally results in ion suppression in SAII. Here we demonstrate that the use of carbonation and other super-saturated gases as solution modifiers increases analyte ion abundance and reduces metal cation adduction in SAII. Carbonation is also found to enhance electrospray ionization. The mechanistic and practical utility of carbonation in mass spectrometry is addressed. PMID:23296909

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

    PubMed

    Raki?, 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. PMID:24857621

  10. Behavior of carbon isotopes during the hyperfiltration of calcium carbonate solutions through calcium bentonites

    E-print Network

    Hinz, David William

    1987-01-01

    first by the heavy cement, tne lighter cement will precipitate upstream and adjacent to the early cement. Therefore, a carbon isotopic profile through a cement precipitated by hyperfi ltration will show heavy cement at the sandstone shale contact...BEHAVIOR OF CARBON ISOTOPES DURING THE HYPERFILTRATION OF CALCIUM CARBONATE SOLUTIONS THROUGH CALCIUM BENTONITES A Thesis DAVID WILLIAM HINZ Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirements...

  11. PREDICTING TEMPERATURE BEHAVIOR IN CARBONATE ACIDIZING TREATMENTS

    E-print Network

    Tan, Xuehao

    2010-01-16

    To increase the successful rate of acid stimulation, a method is required to diagnose the effectiveness of stimulation which will help us to improve stimulation design and decide whether future action, such as diversion, ...

  12. Oxidative desulfurization of askale coal by nitric acid solution

    SciTech Connect

    Guru, M. [Gazi University, Ankara (Turkey). Dept. of Chemical Engineering

    2007-07-01

    Efficient use of fossil fuels is of utmost importance in a world that depends on these for the greatest part of its energy needs. Although lignite is a widely used fossil fuel, its sulfur content limits its consumption. This study aims to capture combustible sulfur in the ash by oxidizing it with solution of nitric acid solution. Thus, the combustible sulfur in the coal was converted to sulfate form in the ash. Parameters affecting the conversion of sulfur were determined to be nitric acid concentration, reaction time and mean particle size at constant (near room) temperature and shaking rate. The maximum desulfurization efficiency reached was 38.7% of the original combustible sulfur with 0.3 M nitric acid solution, 16 h of reaction time and 0.1 mm mean particle size.

  13. 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.

  14. Analysis of the stable carbon isotope composition of formic and acetic acids.

    PubMed

    Lee, Xinqing; Zhang, Like; Huang, Daikuan; An, Ning; Yang, Fang; Jiang, Wei; Fang, Bin

    2013-05-15

    Formic and acetic acids are ubiquitous in the environment and in many biological processes. Analysis of the stable carbon isotope composition (?(13)C) of formic and acetic acids is important to understanding their biogeochemical cycles. However, it has been faced with poor accuracy and high detection limits due to their low carbon number, high hydrophilicity, and semi-volatility. Here we developed an analytical technique by needle trap and gas chromatography-isotope ratio mass spectrometry (GC-IRMS). The organic acids in aqueous solution were extracted using a NeedlEx needle through purge-and-trap and were analyzed by GC-IRMS for ?(13)C. The procedures incur no isotope fractionation. Defined as the point at which the mean ?(13)C is statistically the same as the given value and the analytical error starts rising, the method's detection limits are 200 and 100 mg/L for formic and acetic acids, respectively, with an uncertainty of approximately 0.5 in direct extraction and analysis. They were lowered to 1 mg/L with precision of 0.9 after samples were subjected to preconcentration. The method was successfully applied to natural samples as diverse as precipitation, vinegars, ant plasma, and vehicle exhaust, which vary considerably in concentration and matrix of the organic acids. It is applicable to the organic acids in not only aqueous solution but also gaseous phase. PMID:23395975

  15. Alkali Treatment of Acidic Solution from Hanford K Basin Sludge Dissolution

    SciTech Connect

    AA Bessonov; AB Yusov; AM Fedoseev; AV Gelis; AY Garnov; CH Delegard; GM Plavnik; LN Astafurova; MS Grigoriev; NA Budantseva; NN Krot; SI Nikitenko; TP Puraeva; VP Perminov; VP Shilov

    1998-12-22

    Nitric acid solutions will be created from the dissolution of Hanford K Basin sludge. These acidic dissolver solutions must be made alkaline by treatment with NaOH solution before they are disposed to ~ the Tank Waste Remediation System on the Hanford Site. During the alkali treatments, sodium diuranate, hydroxides of iron and aluminum, and radioelements (uranium, plutonium, and americium) will precipitate from the dissolver solution. Laboratory tests, discussed here, were pefiormed to provide information on these precipitates and their precipitation behavior that is important in designing the engineering flowsheet for the treatment process. Specifically, experiments were conducted to determine the optimum precipitation conditions; the completeness of uranium, plutonium, and americium precipitation; the rate of sedimentation; and the physico-chemical characteristics of the solids formed by alkali treatment of simulated acidic dissolver solutions. These experiments also determined the redistribution of uranium, plutonium, and americium flom the sodium di~ate and iron and al&inurn hydroxide precipitates upon contact with carbonate- and EDTA-bearing simulated waste solutions. Note: EDTA is the tetrasodium salt of ethylenediaminetetraacetate.

  16. Buffer behavior of brucite in removing copper from acidic solution

    Microsoft Academic Search

    L. Shao; Y. Zhou; J. F. Chen; W. Wu; S. C. Lu

    2005-01-01

    Brucite was employed as a natural adsorbent to explore its capacity of removing Cu2+ from an acidic solution. Experimental results indicate that brucite has a good neutralization capacity for acidity. The final pH of brucite suspensions rises to 3.47 and 7.91 respectively with initial pH of 1.49 and 2.09, and Cu2+ adsorption on brucite is 1.85% and 96.31% accordingly. The

  17. Electrokinetic Properties of Aluminum Nanopowders in Citric Acid Solution

    NASA Astrophysics Data System (ADS)

    Karepina, E.; Godymchuk, A.; Kuznetsov, D.; Senatova, S.

    2013-05-01

    Electrical conductivity of aqueous suspensions based on aluminum nanopowder and citric acid solution (20 g/l). The correlation between nanoparticles concentration and abating conductivity of suspensions has been demonstrated during the agglomeration of the aluminum nanoparticles. For the studied suspensions with different concentrations of nanoparticles the smallest conductivity was found after which the particles aggregates begin to deagglomerate due to the high diffusion mobility of the carboxyl groups in the acid medium.

  18. Highly accurate boronimeter assay of concentrated boric acid solutions

    SciTech Connect

    Ball, R.M. (Babcock and Wilcox Co., Lynchburg, VA (United States))

    1992-01-01

    The Random-Walk Boronimeter has successfully been used as an on-line indicator of boric acid concentration in an operating commercial pressurized water reactor. The principle has been adapted for measurement of discrete samples to high accuracy and to concentrations up to 6000 ppm natural boron in light water. Boric acid concentration in an aqueous solution is a necessary measurement in many nuclear power plants, particularly those that use boric acid dissolved in the reactor coolant as a reactivity control system. Other nuclear plants use a high-concentration boric acid solution as a backup shutdown system. Such a shutdown system depends on rapid injection of the solution and frequent surveillance of the fluid to ensure the presence of the neutron absorber. The two methods typically used to measure boric acid are the chemical and the physical methods. The chemical method uses titration to determine the ionic concentration of the BO[sub 3] ions and infers the boron concentration. The physical method uses the attenuation of neutrons by the solution and infers the boron concentration from the neutron absorption properties. This paper describes the Random-Walk Boronimeter configured to measure discrete samples to high accuracy and high concentration.

  19. Pseudo-capacitance on exfoliated carbon fiber in sulfuric acid electrolyte

    NASA Astrophysics Data System (ADS)

    Soneda, Y.; Yamashita, J.; Kodama, M.; Hatori, H.; Toyoda, M.; Inagaki, M.

    2006-03-01

    The specific capacitance of exfoliated carbon fibers (ExCF) which were synthesized from pitch-based carbon fibers showed a strong dependence with the concentration of sulfuric acid electrolyte and reached 1.4 F/m2 in 18 M H2SO4 solution. Since the capacitance value is quite large compared with the case of conventional activated carbons, faradic reactions (charge transfer reactions) are the cause of pseudo-capacitance. ExCF, however, gave a featureless cyclic voltammogram in 18 M H2SO4 solution. In the case of exfoliated natural graphite, the intercalation of H2SO4 molecules is evidenced by redox peaks observed in the voltammograms in the same conditions. Therefore, a strong interaction between the H2SO4 molecules and the ExCF surface might be the reason for the origin of pseudo-capacitance with ExCF in H2SO4 electrolyte.

  20. Thiosubstituted Organophosphorus Acids as Selective Extractants for Ag(I) from Acidic Thiourea Solutions

    Microsoft Academic Search

    Z. Gamino Arroyo; M. Stambouli; D. Pareau; A. Buch; G. Durand; M. Avila Rodriguez

    2008-01-01

    This paper deals with the solvent extraction of silver from thiourea leaching Ag ore liquors as an alternative to the traditional process involving cyanide. The investigation of the extraction mechanism of silver from acidic thiourea solution had not been clearly established to date.The extraction behavior of silver using di(2?ethylhexyl)dithiophosphoric acid (D2EHDTPA) and di(2,4,4?trimethylpentyl) thiophosphinic acid (CYANEX 302) was studied. The

  1. Anaerobic carbon metabolism by the tricarboxylic acid cycle

    SciTech Connect

    Vanlerberghe, G.C.; Horsey, A.K.; Weger, H.G.; Turpin, D.H. (Queen's Univ., Kingston, Ontario (Canada))

    1989-12-01

    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. Incorporation 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.

  2. Surface Layers on Chromium in Sulfuric Acid Solutions of Organic Substances: An X-ray Photoelectron Spectroscopy Study

    Microsoft Academic Search

    V. A. Safonov; E. N. Lubnin; L. N. Vykhodtseva; G. E. Chusova; Yu. M. Polukarov

    2001-01-01

    Surface layers formed at a contact of chromium with sulfuric acid solutions containing some organic substances (sodium oxalate, dimethylformamide, methanol) are analyzed by the X-ray photoelectron spectroscopy method. The layers are shown to contain products of deep destruction of organic molecules, i.e. carbon species and those containing functional groups. The data obtained point to the electrocatalytic activity of chromium in

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

    SciTech Connect

    Kobayashi, F.; Ozawa, N.; Hanai, J.; Isobe, M.; Watabe, T.

    1986-12-01

    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 diacidic 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.

  4. 137 Cs desorption from lichen using acid solutions

    Microsoft Academic Search

    A. A. ?u?ulovi?; D. Veselinovic; S. S. Miljanic

    2009-01-01

    Desoprtion of 137Cs from samples of Cetraria islandica lichen using HCl (A) and HNO3 (B) acid solutions with pH values from 2.00 to 3.75 was investigated. After five consecutive desorptions lasting 24 h it was\\u000a shown that between 52.2% (solution B pH 3.28) and 72.2% (solution A pH 2.00) of 137Cs was desorbed from the lichen and the initial desorptions

  5. Electrochemical oxidation of WC in acidic sulphate solution

    Microsoft Academic Search

    Benedetto Bozzini; Gian Pietro De Gaudenzi; Ameriga Fanigliulo; Claudio Mele

    2004-01-01

    The electrochemical oxidation of WC in aqueous solutions is critical for the functional stability of hardmetals in aggressive environments. The oxidation of WC and the nature of the oxides formed in 0.1 M sulphuric acid under electrochemical polarisation have been studied by electrochemical methods (cyclic voltammetry, chronoamperometry). The structure and composition of the electrochemically treated surfaces has been analysed by

  6. Capture of carbon dioxide from ethanol fermentation by liquid absorption for use in biological production of succinic acid.

    PubMed

    Nghiem, Nhuan P; Senske, Gerard E

    2015-02-01

    Previously, it was shown that the gas produced in an ethanol fermentor using either corn or barley as feedstock could be sparged directly into an adjacent fermentor as a feedstock for succinic acid fermentation using Escherichia coli AFP184. In the present investigation, it was demonstrated that the CO2 produced in a corn ethanol fermentor could be absorbed in a base solution and the resultant carbonate solution used both for pH control and supply of the CO2 requirement in succinic acid fermentation. Thus, the CO2 produced in a 5-L corn mash containing 30 wt% total solids was absorbed in a packed column containing 2 L of either 5 M NaOH, 5 M KOH, or 15 wt% NH4OH, and the resultant carbonate solutions were used for pH control in a succinic acid fermentor. The results obtained indicated no significant differences between succinic acid production in these experiments and when 2.5 M solutions of Na2CO3, K2CO3, and (NH4)2CO3 from commercial sources were used. In a commercial setting, the demonstrated capture of CO2 in liquid form will allow transportation of the carbonate solutions to locations not in the immediate vicinity of the ethanol plant, and excess carbonate salts can also be recovered as value-added products. PMID:25448631

  7. Surface functional groups on acid-activated nutshell carbons

    Microsoft Academic Search

    Christopher A. Toles; Wayne E. Marshall; Mitchell M. Johns

    1999-01-01

    Nutshells from agriculturally important nut crops (almond, black walnut, English walnut, macadamia nut and pecan) were converted to granular activated carbon using phosphoric acid activation in nitrogen or air. Surface functional groups (carbonyl, phenols, lactones, carboxyl) were quantified by titration with bases of different ionization potential. The degree of copper uptake was correlated with the presence of various functional groups

  8. Adsorption of Pb(II) From Aqueous Solutions by Chemically Modified Zeolite Supported Carbon Nanotubes: Equilibrium, Kinetic and Thermodynamic Studies

    Microsoft Academic Search

    D. K. Venkata Ramana; D. Harikishore Kumar Reddy; B. Naresh Kumar; K. Seshaiah; G. Purna Chandra Rao; Chungsying Lu

    2012-01-01

    Zeolite supported carbon nanotubes (ZCNTs) were synthesized by the catalytic chemical vapor deposition (CCVD) method. The physical and chemical properties such as surface area, pore diameter, surface functional groups and total acidic and basic sites of the ZCNTs were studied. They were employed as adsorbent to study the adsorption characteristics of Pb(II) in aqueous solution. The adsorption of Pb(II), increase

  9. 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 ?-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 ?-1,4 glycosidic bonds in both cellobiose and crystalline cellulose. Pure crystalline cellulose was not hydrolyzed by conventional strong solid Brnsted 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 ?-1,4 glucan, which is not adsorbed to other solid acids.

  10. CARBON CONTRIBUTION AND CHARACTERISTICS OF HUMIC ACID, FULVIC ACID, PARTICULATE ORGANIC MATTER AND GLOMALIN IN DIVERSE ECOSYSTEMS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Global climate change and soil carbon sequestration issues are entering the forefront of public policy, and emphasis is growing for research on carbon sinks and long-term terrestrial carbon stabilization. Humic acid (HA), fulvic acid (FA), humin and particulate organic matter (POM) have traditionall...

  11. Coprecipitation of asiatic acid and poly( l -lactide) using rapid expansion of subcritical solutions into liquid solvents

    Microsoft Academic Search

    Amporn Sane; Jumras Limtrakul

    Poly(l-lactide) (PLLA) nanoparticles loaded with asiatic acid (AA) were successfully produced by rapid expansion of a subcritical\\u000a solution into an aqueous receiving solution containing a dispersing agent. A mixture of carbon dioxide (CO2) and ethanol (EtOH) with a weight ratio of 1:1 was used as the solvent for AA and PLLA. Two surfactants, Pluronic F127 and\\u000a sodium dodecyl sulfate were

  12. Photoinduced Transformation of Carbon Monoxide in Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Park, Hyoung Ryun; Getoff, Nikola

    1988-05-01

    The photoinduced conversion of CO in aqueous solution under the influence of vacuum-uv radiation at ? = 185 nm has been investigated at pH values ranging from 2 to 13. Formaldehyde, glyoxal, carboxylic acids and small amounts of glycol were determined as final products. Initial quantum yields for product formation have been determined. A probable reaction mechanism is presented.

  13. Diluent effect on the extraction of uranium(VI) from hydrochloric acid solutions by trioctylamine

    SciTech Connect

    Sato, T.; Nakamura, T.; Kuwahara, M.

    1985-01-01

    The extraction of uranium(VI) and divalent metals (copper, zinc and cadmium) from hydrochloric acid solutions by trioctylamine (TOA) has been examined using various toluene, m-xylene, nitrobenzene, carbon tetrachloride, chloroform and 1,2-dichloroethane. It is found that a parabolic dependence of the distribution coefficient on the solubility parameter of diluent is not observed in these extraction systems. The results obtained are investigated in comparison with the extraction of uranium(VI) and divalent metals by trioctylmethylammonium chloride (TOMAC) in organic solvents in which the distribution coefficient and the enthalpy change associated with the metal extraction can be expressed in terms of the solubility parameter of extractant, diluent and the complex formed in the organic phase and their molar volume by assuming a regular solution. Consequently, since the solutions of TOA x HCl in organic solvents are not regarded as regular solutions, it is expected that the extraction of uranium(VI) from hydrochloric acid solutions by TOA is not always explained in the view point of a regular solution therapy. 16 references, 7 figures, 9 tables.

  14. Simultaneous leaching and carbon sequestration in constrained aqueous solutions.

    PubMed

    Moon, Ji-Won; Cho, Kyu-Seong; Moberly, James G; Roh, Yul; Phelps, Tommy J

    2011-12-01

    The behavior of metal ions' leaching and precipitated mineral phases of metal-rich fly ash (FA) was examined in order to evaluate microbial impacts on carbon sequestration and metal immobilization. The leaching solutions consisted of aerobic deionized water (DW) and artificial eutrophic water (AEW) that was anaerobic, organic- and mineral-rich, and higher salinity as is typical of bottom water in eutrophic algae ponds. The Fe- and Ca-rich FAs were predominantly composed of quartz, mullite, portlandite, calcite, hannebachite, maghemite, and hematite. After 86days, only Fe and Ca contents exhibited a decrease in leaching solutions while other major and trace elements showed increasing or steady trends in preference to the type of FA and leaching solution. Ca-rich FA showed strong carbon sequestration efficiency ranging up to 32.3g CO(2)/kg FA after 86days, corresponding to almost 65% of biotic carbon sequestration potential under some conditions. Variations in the properties of FAs such as chemical compositions, mineral constituents as well as the type of leaching solution impacted CO(2) capture. Even though the relative amount of calcite increased sixfold in the AEW and the relative amount of mineral phase reached 37.3 wt% using Ca-rich FA for 86days, chemical sequestration did not accomplish simultaneous precipitation and sequestration of several heavy metals. PMID:21246259

  15. Simultaneous leaching and carbon sequestration in constrained aqueous solutions

    SciTech Connect

    Phelps, Tommy Joe [ORNL; Moon, Ji Won [ORNL; Roh, Yul [Chonnam National University, Gwangju; Cho, Kyu Seong [ORNL

    2011-01-01

    The behavior of metal ions leaching and precipitated mineral phases of metal-rich fly ash (FA) was examined in order to evaluate microbial impacts on carbon sequestration and metal immobilization. The leaching solutions consisted of aerobic deionized water (DW) and artificial eutrophic water (AEW) that was anaerobic, organic- and mineral-rich, and higher salinity as is typical of bottom water in eutrophic algae ponds. The Fe- and Ca-rich FAs were predominantly composed of quartz, mullite, portlandite, calcite, hannebachite, maghemite, and hematite. After 86 days, only Fe and Ca contents exhibited a decrease in leaching solutions while other major and trace elements showed increasing or steady trends in preference to the type of FA and leaching solution. Ca-rich FA showed strong carbon sequestration efficiency ranging up to 32.3 g CO(2)/kg FA after 86 days, corresponding to almost 65% of biotic carbon sequestration potential under some conditions. Variations in the properties of FAs such as chemical compositions, mineral constituents as well as the type of leaching solution impacted CO(2) capture. Even though the relative amount of calcite increased sixfold in the AEW and the relative amount of mineral phase reached 37.3 wt% using Ca-rich FA for 86 days, chemical sequestration did not accomplish simultaneous precipitation and sequestration of several heavy metals.

  16. CORROSION INHIBITION OF CARBON STEEL DURING ACID CLEANING PROCESS BY A NEW SYNTHESIZED POLYAMIDE BASED ON THIOUREA

    Microsoft Academic Search

    A. M. Al-Sabagh; M. A. Migahed; M. Abd El-Raouf

    2012-01-01

    In this work, a new polyamide (PA) based on thiourea and tartaric acid was synthesized and characterized by FT-IR spectroscopy. The efficiency of the new synthesized compound was evaluated as a corrosion inhibitor for carbon steel in 1M HCl solution using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques (EIS). The results show that PA is a good corrosion

  17. Active dissolution and natural passivation of carbon steel in carbon dioxide-loaded alkanolamine solutions

    SciTech Connect

    Tomoe, Y.; Shimizu, M.; Kaneta, H. [Teikoku Oil Co., Ltd., Tokyo (Japan)

    1996-08-01

    Corrosion rates of carbon steel specimens were measured in carbon dioxide(CO{sub 2})-loaded alkanolamine(amine) solutions by weight-loss tests and by the polarization resistance method. In dilute amine solutions, lower than 10{sup {minus}2} M, corrosion rates were controlled by the formation of protective FeCO{sub 3} scale as in hot, CO{sub 2}-H{sub 2}O environments. Tested amines inhibited CO{sub 2} induced corrosion in the concentration range between 10{sup {minus}2} and 2M. In concentrated amine solutions, higher than 3M, primary and tertiary amines showed markedly different effects on carbon steel corrosion. The corrosion rates of carbon steel rose with the increase in primary amine concentration, whereas the corrosion rates of carbon steel stayed low in tertiary amine solutions even at 6M, due to the formation of protective FeCO{sub 3} scale. Tertiary amines absorb CO{sub 2} as HCO{sub 3}{sup {minus}} in the presence of water. On the contrary, primary amines absorb CO{sub 2} by two ways. One is as HCO{sub 3}{sup {minus}} like tertiary amines, and the other is direct absorption of CO{sub 2} without water, producing amine-carbamate. The chemical substances produced due to the absorption of CO{sub 2} by amines are considered to play important roles not only on corrosion rates but also on the morphology and protectiveness of corrosion products.

  18. 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)

    Stefnsson, Andri; Bnzeth, 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.

  19. 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.

  20. ZnO/carbon nano composite: Effective catalyst for the photo degradation of Acid Blue 113

    NASA Astrophysics Data System (ADS)

    Sunitha, S.; Rao, A. Nageswara; Karthikeyan, J.; Krithiga, T.

    2013-06-01

    Zinc oxide carbon composite (ZnO/C) was synthesized by self - propagating solution combustion method. This method enabled the addition of carbon insitu to the metal oxide. The composite synthesized were characterised by XRD, SEM and BET analysis. This composite was used for the removal of organic pollutants such as the dye Acid blue 113 by UV irradiation performed in a batch reactor. The influence of various experimental parameters such as the initial concentration of the dye, Concentration of the photocatalyst and the pH on the photo catalytic degradation under UV irradiation was studied. It has been observed that the degradation of the dye to be more pronounced in neutral medium. The degradation of acid blue 113 was found to increase with ZnO/C composites loading and decreases with decrease in concentration of the composite.

  1. Effect of citric acid to carbon nanotube growth

    NASA Astrophysics Data System (ADS)

    Jiang, Q.; He, Z. W.; Du, B.; Zhao, X. F.; Zhao, Y.

    2009-03-01

    Carbon nanotube (CNT) was synthesized by catalytic chemical vapor deposition using LaNiO3 as the catalyst precursor, where LaNiO3 was prepared by citric acid complexometry. The results show that the catalyst precursors prepared with different citric acid dosages could all grow CNT, but the CNT yield and patterns obtained with these catalyst precursors were different. Different citric acid dosages could result in different (111) crystal face contents of Ni particle in the catalysts (the products obtained from catalyst precursors reduced by the H2) and thus affected the CNT yield and patterns, which is the result of the complexation between the carboxyl (came from citric acid) and metal ions in lower temperature (80C) during the catalyst precursor preparation.

  2. Nanostructure modification to carbon nanowall surface employing hydrogen peroxide solution

    NASA Astrophysics Data System (ADS)

    Shimoeda, Hironao; Kondo, Hiroki; Ishikawa, Kenji; Hiramatsu, Mineo; Sekine, Makoto; Hori, Masaru

    2014-04-01

    Carbon nanowalls (CNWs), which are three-dimensional carbon nanomaterials consisting of stacks of graphene sheets vertically standing on substrates, possess a mazelike architecture containing high-density graphene edges and large-area plane surfaces. A selective morphological modification technique for the surfaces of CNWs after their growth has been developed employing hydrogen peroxide (H2O2) solution. It was found that oxidative radicals in H2O2 solution formed characteristic nanometer-scale asperities on the CNW surface without etching from the top edges. Photoelectron spectra indicate that hydroxyl adsorption and subsequent reactions at the edge and plane of graphene contribute to the selective morphological change on the CNW surface.

  3. 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.

  4. Poly(carbonate ester)s Based on Units of 6-Hydroxyhexanoic Acid and Glycerol

    E-print Network

    Poly(carbonate ester)s Based on Units of 6-Hydroxyhexanoic Acid and Glycerol Jesse B. Wolinsky materials. These include linear polyesters based on amino acids,9,10 sugars,11,12 or modified hydroxy acids(glycolic acid) and poly(lactic acid).26 Herein we report new copolymers based on 6-hydroxyhexanoic acid

  5. Insights into non-Fickian solute transport in carbonates

    PubMed Central

    Bijeljic, Branko; Mostaghimi, Peyman; Blunt, Martin J

    2013-01-01

    [1] We study and explain the origin of early breakthrough and long tailing plume behavior by simulating solute transport through 3-D X-ray images of six different carbonate rock samples, representing geological media with a high degree of pore-scale complexity. A Stokes solver is employed to compute the flow field, and the particles are then transported along streamlines to represent advection, while the random walk method is used to model diffusion. We compute the propagators (concentration versus displacement) for a range of Peclet numbers (Pe) and relate it to the velocity distribution obtained directly on the images. There is a very wide distribution of velocity that quantifies the impact of pore structure on transport. In samples with a relatively narrow spread of velocities, transport is characterized by a small immobile concentration peak, representing essentially stagnant portions of the pore space, and a dominant secondary peak of mobile solute moving at approximately the average flow speed. On the other hand, in carbonates with a wider velocity distribution, there is a significant immobile peak concentration and an elongated tail of moving fluid. An increase in Pe, decreasing the relative impact of diffusion, leads to the faster formation of secondary mobile peak(s). This behavior indicates highly anomalous transport. The implications for modeling field-scale transport are discussed. Citation: Bijeljic, B., P. Mostaghimi, and M. J. Blunt (2013), Insights into non-Fickian solute transport in carbonates, Water Resour. Res., 49, 27142728, doi:10.1002/wrcr.20238. PMID:24223444

  6. CORROSION BEHAVIOR OF SOME TITANIUM BASE ALLOYS IN ACID SOLUTIONS

    Microsoft Academic Search

    M. V. Popa; E. Vasilescu; P. Drob; C. Vasilescu; J. Mirza-Rosca; A. Santana Lopez

    2005-01-01

    Corrosion and passivation behavior of new, ternary titanium alloys Ti-10Mo-10Al and Ti-15Mo-5Al in nitric acid solutions of different concentrations (20% and 60%) and temperatures (25, 50, and 75C) is presented in this paper. Electrochemical impedance spectroscopy (EIS) data were obtained at different potentials as Bode plots. The spectra show some deviations from the ideal behavior, which demonstrate the necessity to

  7. Passive and transpassive anodic behavior of chalcopyrite in acid solutions

    Microsoft Academic Search

    G. W. Warren; M. E. Wadsworth; S. M. El-Raghy

    1982-01-01

    The electrochemical oxidation of CuFeS2 in various acid solutions was studied using electrodes made from massive samples. The primary techniques employed were potentiodynamic\\u000a polarization and constant potential experiments supplemented by capacitance measurements. It was the purpose of this study\\u000a to investigate the behavior of: (1) several sources of CuFeS2 in H2SO4 electrolytes, and (2) a single source of CuFeS2 in

  8. Acid mine drainage: An economic total resource recovery solution

    SciTech Connect

    Clarke, R.L.; Clarke, S.R.; Brackenbury, D.R. [Electrochemical Design Associates, Inc., Orinda, CA (United States)] [and others

    1995-12-31

    A common feature of abandoned hard rock mines and subterranean coal mines is the creation of toxic and acidic solution often containing iron, copper, zinc, lead, cadmium, manganese and alkaline earth and alkali metals. A process is described which sequentially removes heavy metals using electrochemical ion exchange and rotating cylinder electrodes. Studies summarized indicate recovery of copper, zinc, iron, and aluminum oxide; selective stripping of arsenic, cadmium, chromium, and lead; and recovery of water acceptable for drinking after removal of heavy metals.

  9. Corrosion of Iron in Acid Solutions with Hydrogen Sulfide

    Microsoft Academic Search

    X. L. Cheng; H. Y. Ma; X. L. Chen; H. Q. Yang; S. H. Chen; J. P. Zhang

    1998-01-01

    The influence of pH and the concentration of hydrogen sulfide (HS) on corrosion of iron in acid solutions was studied using a potentiostatic polarization method. The alternating current (AC) impedance technique also was used to characterize the active dissolution process of iron. Results showed the dissolution process was accelerated by HS. The anodic dissolution current (i{sub a}) increased with pH

  10. Acetylene-mediated alkylation of monoalkyl carbonates and carbamic acids with tert-amines

    SciTech Connect

    Sasaki, Yoshiyuki [National Institute for Resources and Environment, Onogawa, Tsukuba-shi (Japan)

    1996-12-31

    Carbonic acid diesters and carbamic acid esters are useful organic substances as intermediates for the syntheses of several chemicals. They are currently synthesized in industry using the processes based on phosgene or carbon monoxide. On the other hand, since carbon dioxide is an abundant and cheap carbonyl carbon source, and is much less toxic than those raw materials, substantial efforts have been focused on its fixation into carbonyl compounds including carbonic acid diesters and carbamic acid esters. However, their syntheses based on carbon dioxide reported so far require rather expensive substrates like alkyl halides, and are not competitive with the currently adopted industrial processes.

  11. Dehydration and oxidation of cellulose hydrolysis products in acidic solution

    SciTech Connect

    Garves, K.

    1981-01-01

    The dehydration of cotton cellulose in aqueous solutions in the presence of Ac/sub 2/O, AcOH, HCl, H/sub 2/SO/sub 4/ or HBr proceeded by hydrolysis to carbohydrates with acetate groups, followed by conversion to 5-(hydroxymethyl)furfural (I) and then, to levulinic acid (II) accompanied by humic acids. For the formation of I, HCl was a more efficient and selective catalyst than H/sub 2/SO/sub 4/, and the formation of II was promoted by high acid and H/sub 2/O concentrations in the medium. The addition of FeCl/sub 3/ to the dehydration mixture with HCl and continuous distillation led to the isolation of furfural.

  12. Experimental Investigation for the Effect of the Core Length on the Optimum Acid Flux in Carbonate Acidizing

    E-print Network

    Dong, Kai

    2012-10-19

    Matrix acidizing is commonly used to stimulate wells in carbonate reservoirs. Large amounts of lab tests indicate an optimum acid interstitial velocity (Vi-opt, injection rate over flow area and porosity) exists, which ...

  13. Cryogenic-temperature electron microscopy direct imaging of carbon nanotubes and graphene solutions in superacids.

    PubMed

    Kleinerman, O; Parra-Vasquez, A Nicholas G; Green, M J; Behabtu, N; Schmidt, J; Kesselman, E; Young, C C; Cohen, Y; Pasquali, M; Talmon, Y

    2015-07-01

    Cryogenic electron microscopy (cryo-EM) is a powerful tool for imaging liquid and semiliquid systems. While cryogenic transmission electron microscopy (cryo-TEM) is a standard technique in many fields, cryogenic scanning electron microscopy (cryo-SEM) is still not that widely used and is far less developed. The vast majority of systems under investigation by cryo-EM involve either water or organic components. In this paper, we introduce the use of novel cryo-TEM and cryo-SEM specimen preparation and imaging methodologies, suitable for highly acidic and very reactive systems. Both preserve the native nanostructure in the system, while not harming the expensive equipment or the user. We present examples of direct imaging of single-walled, multiwalled carbon nanotubes and graphene, dissolved in chlorosulfonic acid and oleum. Moreover, we demonstrate the ability of these new cryo-TEM and cryo-SEM methodologies to follow phase transitions in carbon nanotube (CNT)/superacid systems, starting from dilute solutions up to the concentrated nematic liquid-crystalline CNT phases, used as the 'dope' for all-carbon-fibre spinning. Originally developed for direct imaging of CNTs and graphene dissolution and self-assembly in superacids, these methodologies can be implemented for a variety of highly acidic systems, paving a way for a new field of nonaqueous cryogenic electron microscopy. PMID:25818279

  14. Amino-acid-based peritoneal dialysis solution improves amino-acid transport into skeletal muscle

    Microsoft Academic Search

    M Asola; K Virtanen; K Ngren; S Helin; M Taittonen; H Kastarinen; B Anderstam; J Knuuti; K Metsrinne; P Nuutila

    2008-01-01

    Abnormalities of amino-acid (AA) and protein metabolism are known to occur in chronic kidney disease (CKD). Protein malnutrition may contribute to impaired prognosis of dialysis patients. A crucial step in protein metabolism is AA transport into the cells. We compared the effects of an AA-containing peritoneal dialysis (PD) solution to glucose-based solutions on skeletal muscle AA uptake. Thirteen nondiabetic PD

  15. The Application of Electrodialysis to Desalting an Amino Acid Solution

    NASA Astrophysics Data System (ADS)

    Garca-Garca, Vicente; Montiel, Vicente; Gonzlez-Garca, Jos; Expsito, Eduardo; Iniesta, Jess; Bonete, Pedro; Ingls, Marina

    2000-11-01

    One of the main difficulties in preparing pharmaceutical products is isolating them from aqueous solutions of high salt concentration, as a high purity must be obtained. Several methods that employ organic solvents are normally used. In this paper, a novel method, electrodialysis, is presented together with its application to the desalting of an industrial effluent comprising an amino acid (p-hydroxyphenylglycine) with a high salt content (ammonium sulfate and sodium dihydrogenphosphate). It was possible to remove more than 70% of the initial salt content. From this solution with a low salt content, it is possible to isolate the amino acid with a higher purity. This experiment will enable the student to gain a useful knowledge of this technique and to work with typical figures of merit of electrodialysis such as current efficiency, electrical energy consumption, production of the process, removal of salt, and loss of amino acid. In addition the student learns the use of chromatographic techniques applied to the analysis of amino acids (HPLC) and salts (IC).

  16. Stability constants and multinuclear NMR measurements of phosphonic acid derivatives with aluminum in aqueous solutions

    Microsoft Academic Search

    Yahia Z. Hamada; Wesley R. Harris

    2006-01-01

    We are reporting the stability constants of the different complexes between phosphonoacetic acid (PAA), phosphonoformic acid (PFA), aminomethylphosphonic acid (AMPA), aminoethylphosphonic acid (AEPA) and methylenediphosphonic acid (MDP) with the aluminum metal ion in aqueous solutions. (In this study the term aluminum is reserved for the 3+ ion.) The affinity of the phosphonic acid derivatives to chelate aluminum has been tested

  17. Synergistic inhibition of corrosion of steel in sulfuric acid solutions

    SciTech Connect

    Gordeeva, I.I.; Efimov, I.V.; Legin, G.Y.

    1985-07-01

    The authors have studied synergism in compositions of sodium chloride with simple aliphatic compounds containing the neutral phosphate AF-1, the neutral phosphonate AF-10, and the trialkylphosphine oxide AF-13. In contrast with the amines, all the substances have extremely low basicity and are almost incapable of forming cations in an acidic medium. The substances exhibit marked synergism with chloride ions. For comparison, the authors caused the inhibition of steel Stl with carbonyl compounds similar in structure to the three substances, namely diethyl carbonate, butyl acetate, and 2-octanone. The carbonyl compounds are weaker inhibitors, but in compositions with sodium chloride, their qualitative effects are similar to those of phosphoryl compounds.

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

    SciTech Connect

    Reihs, C.M.; Golden, D.M.; Tolbert, M.A. (SRI International, Menlo Park, CA (USA))

    1990-09-20

    A Knudsen cell flow reactor is used to study the uptake of nitric acid by sulfuric acid solutions representative of stratospheric particulate. Henry's law solubility constants are determined using the time dependence of the measured nitric acid uptake efficiencies. Solubilities are reported for sulfuric acid solutions ranging from 58 to 87 weight percent sulfuric acid over a temperature range from 188 to 240 K. In general, the solubility of nitric acid increases with decreasing sulfuric acid concentration and decreasing temperature. Over the reported temperature range the solubilities are cast in the form H* = A exp(B/T), where A = 7.47 {times} 10{sup {minus}8} M/atm, B = 7.16 {times} 10{sup 3}K for 58% H{sub 2}SO{sub 4}; A = 0.202 M/atm, B = 3.19 {times} 10{sup 3}K for 66% H{sub 2}SO{sub 4}; A = 8.54 {times} 10{sup {minus}3} M/atm, B = 3.55 {times} 10{sup 3} K for 74% H{sub 2}SO{sub 4}; and A = 3.56 {times} 10{sup {minus}3} M/atm, B = 3.32 {times} 10{sup 3} K for 87% H{sub 2}SO{sub 4}. The measured solubilities indicate that nitric acid in the global stratosphere will be found predominantly in the gas phase. The ratio of condensed to gas phase nitric acid is less than 10{sup {minus}4} even under conditions of highly elevated sulfuric acid loading.

  19. 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.

  20. Karstification without carbonic acid: bedrock dissolution by gypsum- driven dedolomitization

    USGS Publications Warehouse

    Bischoff, J.L.; Julia, R.; Shanks, Wayne C.; Rosenbauer, R.J.

    1994-01-01

    The primary karst-forming process at Lake Banyoles is dedolomitization of basement rocks driven by gypsum dissolution. Karstification takes place along the subsurface contact between the gypsiferous Beuda Formation and the dolomitic Perafita Formation. This process is here recognized for the first time to cause karstification on a large scale; this is significant because it proceeds without the addition of soil-generated carbonic acid. -from Authors

  1. Nitric acid oxidation of vapor grown carbon nanofibers

    Microsoft Academic Search

    Priya V. Lakshminarayanan; Hossein Toghiani; Charles U. Pittman Jr.

    2004-01-01

    Vapor grown carbon nanofibers (Pyrograf III) with 100300 nm diameters and ?10100 ?m lengths were oxidized in 6971 wt.% nitric acid (115 C) for various times (10 min to 24 h). These fibers were remarkably oxidation-resistant. XPS (O1s) showed that the surface atomic oxygen percent increased from 6.3 to 18.322.5% for 1090 min oxidations followed by a drop to 1415%

  2. Carbon nanoparticles with tosyl functional group for distinguishing voltammetric peaks of ascorbic acid and uric acid.

    PubMed

    Amiri, Mandana; Imanzadeh, Hamideh; Banaei, Alireza

    2015-02-01

    In this approach, electro-oxidation of a mixture of uric acid and ascorbic acid at the surface of tosyl surface carbon nanoparticles/glassy carbon electrode has been performed. The electro-oxidation of these compounds at bare electrode is sluggish and there is no suitable peak separation between them. However, using functionalized carbon nanoparticles, two well-defined anodic peaks with a considerable enhancement in the peak current and a remarkable peak potential separation near 452 mV is obtained. The porous interfacial layer of the carbon nanoparticles modified electrode with a high specific surface area increases the conductive area; molecules can penetrate through the conductive porous channels onto the electrode more easily so leading to higher sensitivity and selectivity. The dynamic linear ranges of 1.0 10(-5) to 3.0 10(-3)M and 1.0 10(-7) to 1.0 10(-4)M with detection limits 1.0 10(-5)M and 2.0 10(-8)M (for S/N=3) were obtained for ascorbic acid and uric acid, respectively. Analytical utility of the modified electrode has been examined successfully using human urine samples and vitamin C commercial tablets. PMID:25492188

  3. Carbon Isotope Ratios in Crassulacean Acid Metabolism Plants

    PubMed Central

    Szarek, Stan R.; Troughton, John H.

    1976-01-01

    A year round study of photosynthesis and carbon isotope fractionation was conducted with plants of Opuntia phaeacantha Engelm. and Yucca baccata Torr. occurring in natural stands at elevations of 525, 970, 1450 and 1900 m. Plant water potentials and the daytime pattern of 14CO2 photosynthesis were similar for all cacti along the elevational gradient, despite significant differences in temperature regime and soil water status. Carbon isotope ratios of total tissue and soluble extract fractions were relatively constant throughtout the entire year. Additionally, the ?13C values were similar in all plants of the same species along the elevational gradient, i.e. ?12.5 0.86 for O. phaeacantha and ?15.7 0.95 for Y. baccata. The results of this study indicate Crassulacean acid metabolism predominates as the major carbon pathway of these plants, which do not facultatively utilize the reductive pentose phosphate cycle of photosynthesis as the primary carboxylation reaction. PMID:16659680

  4. 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 35mg 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. PMID:24766592

  5. Suicidal carbon monoxide poisoning by combining formic acid and sulfuric acid within a confined space.

    PubMed

    Lin, Peter T; Dunn, William A

    2014-01-01

    Suicide by inhalation of carbon monoxide produced by mixing formic acid and sulfuric acid within a confined space is a rare method of suicide. This method is similar to the so-called "detergent suicide" method where an acid-based detergent is mixed with a sulfur source to produce hydrogen sulfide. Both methods produce a toxic gas that poses significant hazards for death investigators, first responders and bystanders. Carbon monoxide is an odorless gas, while hydrogen sulfide has a characteristic rotten eggs odor, so the risks associated with carbon monoxide are potentially greater due to lack of an important warning signal. While detergent suicides have become increasingly common in the USA, suicide with formic acid and sulfuric acid is rare with only three prior cases being reported. Greater awareness of this method among death investigators is warranted because of the special risks of accidental intoxication by toxic gas and the possibility that this method of suicide will become more common in the future. PMID:24328850

  6. Impact of hydrogen bonds in polyaniline.AMPSA n \\/acid solutions

    Microsoft Academic Search

    Dali Yang; Phillip N. Adams; Lori Brown; Benjamin R. Mattes

    2006-01-01

    Water concentration in polyaniline (PANI)\\/acid solutions containing 2-acrylamido-2-methyl-l-propanesulfonic acid (AMPSA) significantly changes the solubility of PANI and the stability of its solutions. By varying trace amounts of water, we investigated the impact of hydrogen bonds (H-bonds) on PANI chain conformation in solutions of AMPSA\\/dichloroacetic acid (DCAA) or AMPSA\\/orthophosphoric acid. UVvisNIR spectral changes of these PANI solutions reveal that a competition

  7. Carbonate-containing apatite (CAP) synthesis under moderate conditions starting from calcium carbonate and orthophosphoric acid.

    PubMed

    Pham Minh, Doan; Tran, Ngoc Dung; Nzihou, Ange; Sharrock, Patrick

    2013-07-01

    The synthesis of carbonate-containing apatite (CAP) from calcium carbonate and orthophosphoric acid under moderate conditions was investigated. In all cases, complete precipitation of orthophosphate species was observed. The reaction temperature influenced strongly the decomposition of calcium carbonate and therefore the composition of formed products. The reaction temperature of 80 C was found to be effective for the complete decomposition of calcium carbonate particles after 48 h of reaction. Infra-red spectroscopy (IR), nuclear magnetic resonance (NMR), thermogravimetry/mass spectroscopy (TG-MS) coupling, and X-ray diffraction (XRD) characterizations allowed the identification of the composition of formed products. By increasing the reaction temperature from 20 C to 80 C, the content of A-type CAP increased and that of B-type CAP decreased, according to the favorable effect of temperature on the formation of A-type CAP. The total amount of carbonate content incorporated in CAP's structure, which was determined by TG-MS analysis, increased with the reaction temperature and reached up to 4.1% at 80 C. At this temperature, the solid product was mainly composed of apatitic components and showed the typical flat-needle-like structure of CAP particles obtained in hydrothermal conditions. These results show an interesting one-step synthesis of CAP from calcium carbonate and orthophosphoric acid as low cost but high purity starting materials. PMID:23623121

  8. 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...

  9. 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 (?H0), entropy (?S0) and Gibb's free energy (?G0) 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.

  10. 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.

  11. Solution-processed soldering of carbon nanotubes for flexible electronics

    NASA Astrophysics Data System (ADS)

    Rao, K. D. M.; Radha, B.; Smith, K. C.; Fisher, T. S.; Kulkarni, G. U.

    2013-02-01

    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, Pd2+ 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.

  12. carbonate solid solution at high pressures up to 55 GPa

    NASA Astrophysics Data System (ADS)

    Spivak, Anna; Solopova, Natalia; Cerantola, Valerio; Bykova, Elena; Zakharchenko, Egor; Dubrovinsky, Leonid; Litvin, Yuriy

    2014-09-01

    Magnesite, siderite and ferromagnesites Mg1- x Fe x CO3 ( x = 0.05, 0.09, 0.2, 0.4) were characterized using in situ Raman spectroscopy at high pressures up to 55 GPa. For the Mg-Fe-carbonates, the Raman peak positions of six modes (T, L, ?4, ?1, ?3 and 2?2) in the dependence of iron content in the carbonates at ambient conditions are presented. High-pressure Raman spectroscopy shows that siderite undergoes a spin transition at ~40 GPa. The examination of the solid solutions with compositions Mg0.6Fe0.4CO3, Mg0.8Fe0.2CO3, Mg0.91Fe0.09CO3 and Mg0.95Fe0.05CO3 indicates that with increase in the amount of the Fe spin transition pressure increases up to ~45 GPa.

  13. A solution phase fabrication of magnetic nanoparticles encapsulated in carbon

    NASA Astrophysics Data System (ADS)

    Wei, Xian-Wen; Zhu, Guo-Xing; Xia, Chuan-Jun; Ye, Yin

    2006-09-01

    To avoid high energy consumption, intensive use of hardware and high cost in the manufacture of nanoparticles encapsulated in carbon, a simple, efficient and economical solution-phase method for the fabrication of FeNi@C nanostructures has been explored. The reaction to the magnetic metal@C structures here is conducted at a relatively low temperature (160 C) and this strategy can be transferred to prepare other transition metal@C core-shell nanostructures. The saturation magnetization of metal in metal@C nanostructures is similar to those of the corresponding buck metals. Magnetic metal@C nanostructures with magnetic metal nanoparticles inside and a functionalized carbon surface outside may not only provide the opportunity to tailor the magnetic properties for magnetic storage devices and therapeutics but also make possible the loading of other functional molecules (e.g. enzymes, antigens) for clinic diagnostics, molecular biology, bioengineering, and catalysis.

  14. 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. PMID:25133545

  15. Systems solutions by lactic acid bacteria: from paradigms to practice

    PubMed Central

    2011-01-01

    Lactic acid bacteria are among the powerhouses of the food industry, colonize the surfaces of plants and animals, and contribute to our health and well-being. The genomic characterization of LAB has rocketed and presently over 100 complete or nearly complete genomes are available, many of which serve as scientific paradigms. Moreover, functional and comparative metagenomic studies are taking off and provide a wealth of insight in the activity of lactic acid bacteria used in a variety of applications, ranging from starters in complex fermentations to their marketing as probiotics. In this new era of high throughput analysis, biology has become big science. Hence, there is a need to systematically store the generated information, apply this in an intelligent way, and provide modalities for constructing self-learning systems that can be used for future improvements. This review addresses these systems solutions with a state of the art overview of the present paradigms that relate to the use of lactic acid bacteria in industrial applications. Moreover, an outlook is presented of the future developments that include the transition into practice as well as the use of lactic acid bacteria in synthetic biology and other next generation applications. PMID:21995776

  16. Solubilities and vapour pressures of saturated aqueous solutions of sodium tetraborate, sodium carbonate, and magnesium sulfate and freezing-temperature lowerings of sodium tetraborate and sodium carbonate solutions

    Microsoft Academic Search

    Alexander Apelblat; Emanuel Manzurola

    2003-01-01

    Solubilities and vapour pressures of water over saturated solutions of sodium tetraborate, sodium carbonate, and magnesium sulfate and freezing-temperature lowerings of sodium tetraborate and sodium carbonate solutions were determined and compared with the literature data. These results permitted the evaluation of osmotic and activity coefficients and molar enthalpies of vaporization.

  17. Molecular Structure of Hydrochloric acid (if in aqueous solution)

    NSDL National Science Digital Library

    2002-09-10

    Hydrochloric acid (or hydrogen chloride) can be a colorless liquid with a sharp odor or a colorless to slightly yellow gas. It is a strong acid (it ionizes completely in aqueous solution) and highly corrosive. HCl is widely used as a laboratory reagent in the production of chlorides, in organic synthesis, ore reduction, hydrolyzing of starch and proteins, in the preparation of various food products, metal cleaning and pickling, for instance, and pharmaceutics acidifier. HCI is widely used in the manufacture e.g., in the conversion of cornstarch to syrup, in sugar refining, electroplating, soap refining, leather tanning etc. It is also used to remove scale and dust from boilers and heat exchange equipment, to clean membranes in desalination plants, increase oil well output and prepare metals for coatings.

  18. Removal of arsenious acid from sulfuric acidic solution using ultrasound oxidation and goethite

    NASA Astrophysics Data System (ADS)

    Okawa, Hirokazu; Yoshikawa, Tomohiro; Hosokawa, Ryota; Hangui, Shinji; Kawamura, Youhei; Sugawara, Katsuyasu

    2015-07-01

    We investigated the properties of synthetic goethite for the adsorption of As from strongly acidic solutions in ambient atmosphere under ultrasound irradiation. The goethite was successfully synthesized from iron-containing sulfuric acidic solution (1271 ppm) using an autoclave apparatus for 1 h at 0.12 MPa and 121 C. The ratio of the iron eluted from the synthetic goethite to the acidic solution was only 0.58% at pH 2.1. Ultrasound irradiation (200 kHz, 200 W) was applied to oxidize 10 ppm of As(III) to As(V) at pH 2.2 for 60 min under various atmospheric conditions. Remarkably, the oxidation ratio of As(III) to As(V) is quite high (89.7%) at pH 2.2 in ambient atmosphere and is close to those obtained for Ar (95.3%) and O2 (95.9%) atmospheres. The As(III) removal ratio reached 94.5% after 60 min of irradiation. Therefore, goethite is a promising material for As adsorption using ultrasound oxidation in the acidic region in ambient atmosphere.

  19. Colloidal methods for the fabrication of carbon nanotube-manganese dioxide and carbon nanotube-polypyrrole composites using bile acids.

    PubMed

    Ata, M S; Zhitomirsky, I

    2015-09-15

    Nature inspired strategies have been developed for the colloidal processing of advanced composites for supercapacitor applications. New approach was based on the use of commercially available bile acid salts, such as sodium cholate (ChNa) and taurocholic acid sodium salt (TChNa). It was demonstrated that cholic acid (ChH) films can be obtained by electrophoretic deposition (EPD) from ChNa solutions. The analysis of deposition yield, quartz crystal microbalance and cyclic voltammetry data provided an insight into the anodic deposition mechanism. The outstanding suspension stability of multiwalled carbon nanotubes (MWCNT), achieved using bile acids as anionic dispersants, allowed the fabrication of MWCNT films by EPD. The use of ChNa for EPD offered advantages of binding and film forming properties of this material. Composite MnO2-MWCNT films, prepared using ChNa as a dispersant and film forming agent for EPD, showed promising capacitive behavior. In another colloidal strategy, TChNa was used as a dispersant for MWCNT for the fabrication of polypyrrole (PPy) coated MWCNT. The use of PPy coated MWCNT allowed the fabrication of electrodes with high active mass loading, high capacitance and excellent capacitance retention at high charge-discharge rates. PMID:26001135

  20. Experimental equilibrium and modeling for the absorption of acid gases in diethanolamine solutions at low and high partial pressures

    SciTech Connect

    Elizondo-Villarreal, E.M.

    1989-01-01

    This study was undertaken to develop an experimental apparatus that would allow direct measurements of gas equilibrium solubility in aqueous alkanolamine solutions at low gas partial pressures. Carbon dioxide and hydrogen sulfide solubility in 20, 35 and 50% by weight diethanolamine aqueous solutions was measured. The measurements were made at acid gas partial pressures between 0.003 and 10.9 psia and temperatures of 80, 150 and 240{degree}F. The experimental data at low partial pressure were used in a procedure to correlate them with literature data at high partial pressures and establish a model for carbon dioxide-hydrogen sulfide-aqueous diethanolamine systems. An experimental apparatus was developed to measure the equilibrium solubility of acid gas in diethanolamine solutions at low acid gas partial pressures. The experimental procedure does not require that vapor liquid samples be withdrawn for analysis, so equilibrium in the experimental apparatus is never disturbed. A consistency test for evaluation of experimental acid gas-ethanolamine equilibrium data was developed. The test was shown to apply in the full range of partial pressures where chemical reactions dominate. Predictions of acid gas partial pressures were substantially improved and application to model an integrated high pressure natural gas plant gave good results. The experimental apparatus and the consistency test should be used for other amines of industrial interest to improve the modeling.

  1. Preparation of intercalation compounds of carbon fibers through electrolysis using phosphoric acid electrolyte and their exfoliation

    NASA Astrophysics Data System (ADS)

    Toyoda, Masahiro; Yoshinaga, Aya; Amao, Yutaka; Takagi, Hideyuki; Soneda, Yasushi; Inagaki, Michio

    2006-05-01

    Preparation of intercalation compounds using H3PO4 electrolyte solution in mesophase-pitch-based carbon fibers successfully carried out by electrolysis in less than 10 mol/dm3 of its electrolyte solution. Structural changes with preparation of intercalation compounds of carbon fibers were confirmed by a peak appeared around 2?=8 observed after electrolysis, which corresponds to an interlayer spacing of about 0.9 nm through XRD pattern (anticathode: Cu K?). This new peak was reasonably supposed to be due to the intercalation into interspacing of carbon layers. Suitable synthesis condition of the intercalation compounds was determined to be the concentration of electrolyte of 5 mol/dm3 at the electrolysis. It was also confirmed by morphology changes through SEM, that is carbon fibers, which treated low electrolyte concentration synthesized the intercalation compounds easily, and then it revealed markedly morphology changes such as fibrils. It could become exfoliation as well as them treated by other acid treatment through rapid heat-treatment. The formation of graphite oxide was suggested when the kind of intercalate was analyzed with elementary and TPD analysis.

  2. The determination of chlorophenoxy acid herbicides by liquid chromatography using carbon-14 tracers

    SciTech Connect

    Merriweather, R.; Caldwell, W.M.; Maskarinec, M.P.; Caton, J.E.

    1987-01-01

    The extractive recovery of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-(2,4,5-trichloro)phenoxypropionic acid (Silvex) from environmental samples was evaluated using carbon-14 tracers of the acid form of both herbicides. Recoveries using methylene chloride or 1:1 methylene chloride:acetone for solids exceeded 75% when the material being extracted was maintained at an acid pH (pH less than or equal to2). Following extraction, the extract is taken to dryness and then dissolved in the solution being used for HPLC elution. Two slightly different isocratic elutions with reversed phase columns were studied. In the first system studied a heavily loaded (18% carbon by weight), completely endcapped C18 reversed phase column was eluted with an aqueous solution of 30% (v/v) acetonitrile that contained 0.001 M concentration of a pH 4.6 acetate buffer. The effluent from this column was monitored at 280 nm. The minimum amount detected, when monitoring at 280 nm, is 100 ng of either Silvex or 2,4-D in the injected sample. A second isocratic elution system avoided the use of a buffered eluent by utilizing a high performance reversed phase column and an aqueous methanol (20% v/v) eluent. This second column has been monitored at multiple wavelengths with a diode array detector. The sensitivity of detection can be greatly increased at wavelengths below 240 nm; however, any real sample must be very ''clean'' in order to avoid interferences when monitoring below 230 nm. Thus monitoring at 280 nm is probably optimal for real environmental samples. At this wavelength the detectable concentration of either herbicide in the solution being injected is 5 ppM for a 20 ..mu..l injection.

  3. GADOLINIUM OXALATE SOLUBILITY MEASUREMENTS IN NITRIC ACID SOLUTIONS

    SciTech Connect

    Pierce, R.

    2012-02-22

    HB-Line will begin processing Pu solutions during FY2012 that will involve the recovery of Pu using oxalate precipitation and filtration. After the precipitation and filtration processes, the filtrate solution will be transferred from HB-Line to H-Canyon. The presence of excess oxalate and unfiltered Pu oxalate solids in these solutions create a criticality safety issue if they are sent to H-Canyon without controls in H-Canyon. One approach involves H-Canyon receiving the filtrate solution into a tank that is poisoned with soluble gadolinium (Gd). Decomposition of the oxalate will occur within a subsequent H-Canyon vessel. The receipt of excess oxalate into the H-Canyon receipt tanks has the potential to precipitate a portion of the Gd poison in the receipt tanks. Because the amount of Gd in solution determines the maximum amount of Pu solids that H-Canyon can receive, H-Canyon Engineering requested that SRNL determine the solubility of Gd in aqueous solutions of 4-10 M nitric acid (HNO{sub 3}), 4-12 g/L Gd, and 0.15-0.25 M oxalic acid (H{sub 2}C{sub 2}O{sub 4}) at 25 C. The target soluble Gd concentration is 6 g/L. The data indicate that the target can be achieved above 6 M HNO{sub 3} and below 0.25 M H{sub 2}C{sub 2}O{sub 4}. For 6 M HNO{sub 3}, 10.5 g/L and 7 g/L Gd are soluble in 0.15 M and 0.25 M H{sub 2}C{sub 2}O{sub 4}, respectively. In 4 M HNO{sub 3}, the Gd solubility drops significantly to 2 g/L and 0.25 g/L in 0.15 M and 0.25 M H{sub 2}C{sub 2}O{sub 4}, respectively. The solubility of Gd at 8-10 M HNO{sub 3} exceeds the solubility at 6 M HNO{sub 3}. The data for 4 M HNO{sub 3} showed good agreement with data in the literature. To achieve a target of 6 g/L soluble Gd in solution in the presence of 0.15-0.25 M oxalate, the HNO{sub 3} concentration must be maintained at or above 6 M HNO{sub 3}.

  4. Genetic Analysis of Central Carbon Metabolism Unveils an Amino Acid Substitution That Alters Maize NAD-

    E-print Network

    Flint-Garcia, Sherry

    was the NAD-dependent isocitrate dehydrogenase (IDH, E.C. 1.1.1.41), in which we identified a novel amino-acidGenetic Analysis of Central Carbon Metabolism Unveils an Amino Acid Substitution That Alters Maize Carbon Metabolism Unveils an Amino Acid Substitution That Alters Maize NAD-Dependent Isocitrate

  5. Electrochemical Determination of Glycoalkaloids Using a Carbon Nanotubes-Phenylboronic Acid Modified Glassy Carbon Electrode

    PubMed Central

    Wang, Huiying; Liu, Mingyue; Hu, Xinxi; Li, Mei; Xiong, Xingyao

    2013-01-01

    A versatile strategy for electrochemical determination of glycoalkaloids (GAs) was developed by using a carbon nanotubes-phenylboronic acid (CNTs-PBA) modified glassy carbon electrode. PBA reacts with ?-solanine and ?-chaconine to form a cyclic ester, which could be utilized to detect GAs. This method allowed GA detection from 1 ?M to 28 ?M and the detection limit was 0.3 ?M. Affinity interaction of GAs and immobilized PBA caused an essential change of the peak current. The CNT-PBA modified electrodes were sensitive for detection of GAs, and the peak current values were in quite good agreement with those measured by the sensors. PMID:24287539

  6. Solubility limits and phase diagrams for fatty acids in anionic (SLES) and zwitterionic (CAPB) micellar surfactant solutions.

    PubMed

    Tzocheva, Sylvia S; Kralchevsky, Peter A; Danov, Krassimir D; Georgieva, Gergana S; Post, Albert J; Ananthapadmanabhan, Kavssery P

    2012-03-01

    The limiting solubility of fatty acids in micellar solutions of the anionic surfactant sodium laurylethersulfate (SLES) and the zwitterionic surfactant cocamidopropyl betaine (CAPB) is experimentally determined. Saturated straight-chain fatty acids with n=10, 12, 14, 16, and 18 carbon atoms were investigated at working temperatures of 25, 30, 35, and 40C. The rise of the fatty acid molar fraction in the micelles is accompanied by an increase in the equilibrium concentration of acid monomers in the aqueous phase. Theoretically, the solubility limit is explained with the precipitation of fatty acid crystallites when the monomer concentration reaches the solubility limit of the acid in pure water. In agreement with theory, the experiment shows that the solubility limit is proportional to the surfactant concentration. For ideal mixtures, the plot of the log of solubility limit vs. the chainlength, n, must be a straight line, which is fulfilled for n=14, 16, and 18. For the fatty acids of shorter chains, n=10 and 12, a deviation from linearity is observed, which is interpreted as non-ideal mixing due to a mismatch between the chainlengths of the surfactant and acid. The data analysis yields the solubilization energy and the interaction parameter for the fatty acid molecules in surfactant micelles. By using the determined parameter values, phase diagrams of the investigated mixed solutions are constructed. The four inter-domain boundary lines intersect in a quadruple point, whose coordinates have been determined. The results can be applied for the interpretation and prediction of the solubility, and phase behavior of medium- and long-chain fatty acids and other amphiphiles that are solubilizable in micellar surfactant solutions, as well as for determining the critical micellization concentration (CMC) of the respective mixed solution. PMID:22212739

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

    Microsoft Academic Search

    Sedat ztrkcan; R?za Dndar; Hseyin Kat?lm??; Ali Ekber ?lknur; Sinem Akta?; Senem Hac?mero?lu

    2009-01-01

    This study analyzed the ototoxic effects of boric acid solutions. Boric acid solutions have been used as otologic preparations\\u000a for many years. Boric acid is commonly found in solutions prepared with alcohol or distilled water but can also be found in\\u000a a powder form. These preparations are used for both their antiseptic and acidic qualities in external and middle ear

  8. Kinetic studies of dipeptide-based and amino acid-based peritoneal dialysis solutions

    Microsoft Academic Search

    Andrzej Wery?ski; Jacek Waniewski; Tao Wang; Bjrn Anderstam; Bengt Lindholm; Jonas Bergstrm

    2001-01-01

    Kinetic studies of dipeptide-based and amino acid-based peritoneal dialysis solutions.BackgroundDipeptide-based peritoneal dialysis solutions may have potential advantages compared with the glucose or amino acid-based solutions. Dipeptides may hydrolyze in the peritoneal cavity, generating constituent amino acids and thereby increasing the osmolality of the dialysate. Dipeptides can also be a valuable source of amino acids, which are poorly soluble in water,

  9. Adsorption of nickel(II) from aqueous solution onto activated carbon prepared from coirpith

    Microsoft Academic Search

    K. Kadirvelu; K. Thamaraiselvi; C. Namasivayam

    2001-01-01

    Activated carbon has been prepared from coirpith by chemical activation and characterized. Carbonised coirpith is able to adsorb Ni(II) from aqueous solution. It was noted that a decreasing in the carbon concentration with constant Ni concentration, or an increase in the Ni concentration with constant carbon concentration resulted in a higher nickel uptake per unit weight of carbon. The Langmuir

  10. Electrocatalytic hydrogenation of 5-hydroxymethylfurfural in acidic solution.

    PubMed

    Kwon, Youngkook; Birdja, Yuvraj Y; Raoufmoghaddam, Saeed; Koper, Marc T M

    2015-05-22

    Electrocatalytic hydrogenation of 5-hydroxymethylfurfural (HMF) is studied on solid metal electrodes in acidic solution (0.5?M H2 SO4 ) by correlating voltammetry with on-line HPLC product analysis. Three soluble products from HMF hydrogenation are distinguished: 2,5-dihydroxymethylfuran (DHMF), 2,5-dihydroxymethyltetrahydrofuran (DHMTHF), and 2,5-dimethyl-2,3-dihydrofuran (DMDHF). Based on the dominant reaction products, the metal catalysts are divided into three groups: (1)?metals mainly forming DHMF (Fe, Ni, Cu, and Pb), (2)?metals forming DHMF and DMDHF depending on the applied potentials (Co, Ag, Au, Cd, Sb, and Bi), and (3)?metals forming mainly DMDHF (Pd, Pt, Al, Zn, In, and Sb). Nickel and antimony are the most active catalysts for DHMF (0.95?mM?cm(-2) at ca. -0.35?VRHE and -20?mA?cm(-2) ) and DMDHF (0.7?mM?cm(-2) at -0.6?VRHE and -5?mA?cm(-2) ), respectively. The pH of the solution plays an important role in the hydrogenation of HMF: acidic condition lowers the activation energy for HMF hydro-genation and hydrogenates the furan ring further to tetrahydrofuran. PMID:25908308

  11. Formic acid oxidation by carbon-supported palladium catalysts in direct formic acid fuel cell

    Microsoft Academic Search

    Jae Ho Choi; Soon Young Noh; Sam Duck Han; Soo Kyung Yoon; Chang-Soo Lee; Taek-Sung Hwang; Young Woo Rhee

    2008-01-01

    The oxidation of formic acid by the palladium catalysts supported on carbon with high surface area was investigated. Pd\\/C\\u000a catalysts were prepared by using the impregnation method. 30 wt% and 50 wt% Pd\\/C catalysts had a high BET surface area of\\u000a 123.7 m2\\/g and 89.9 m2\\/g, respectively. The fuel cell performance was investigated by changing various parameters such as anode

  12. Tracer Fluid Flow through Porous Media: Theory Applied to Acid Stimulation Treatments in Carbonate Rocks

    E-print Network

    Zakaria Mohamed Reda, Ahmed

    2014-07-29

    Most carbonate rocks are heterogeneous at multiple length scales. These heterogeneities strongly influence the outcome of the acid stimulation treatments which are routinely performed to improve well productivity. At the pore scale, carbonate rocks...

  13. ?-sulfonated fatty acid esters: II. Solution behavior of ?-sulfonated fatty acid polyethylene glycol esters

    Microsoft Academic Search

    Tomomichi Okano; Naoyuki Egawa; Masami Fujiwara; Masahiro Fukuda

    1996-01-01

    Sodium ?-sulfonated, fatty acid polyethylene glycol monoesters [C\\u000a m\\u000a H2m+1CH(SO3Na)COO(C2H4O)\\u000a n\\u000a H] and diesters [C\\u000a m\\u000a H2m+1CH(SO3Na)COO(C2H4O)\\u000a n\\u000a COCH(SO3Na)C\\u000a m\\u000a H2m+1], wherem=1016 andn=135, were prepared by esterification of ?-sulfonated, fatty acids with polyethylene glycols, followed by neutralization\\u000a with NaOH. Crude products were purified by reversed-phase column chromatography on an octadecyl-modified silica gel. Characteristic\\u000a solution behavior of these ?-sulfonated fatty acid

  14. Double thermal transitions of type I collagen in acidic solution.

    PubMed

    Liu, Yan; Liu, Lingrong; Chen, Mingmao; Zhang, Qiqing

    2013-01-01

    Contributed equally to this work. To further understand the origin of the double thermal transitions of collagen in acidic solution induced by heating, the denaturation of acidic soluble collagen was investigated by micro-differential scanning calorimeter (micro-DSC), circular dichroism (CD), dynamic laser light scattering (DLLS), transmission electron microscopy (TEM), and two-dimensional (2D) synchronous fluorescence spectrum. Micro-DSC experiments revealed that the collagen exhibited double thermal transitions, which were located within 31-37?C (minor thermal transition, T(s)???33?C) and 37-55?C (major thermal transition, T(m)???40?C), respectively. The CD spectra suggested that the thermal denaturation of collagen resulted in transition from polyproline II type structure to unordered structure. The DLLS results showed that there were mainly two kinds of collagen fibrillar aggregates with different sizes in acidic solution and the larger fibrillar aggregates (T(p2)?=?40?C) had better heat resistance than the smaller one (T(p1)?=?33?C). TEM revealed that the depolymerization of collagen fibrils occurred and the periodic cross-striations of collagen gradually disappeared with increasing temperature. The 2D fluorescence correlation spectra were also applied to investigate the thermal responses of tyrosine and phenylalanine residues at the molecular level. Finally, we could draw the conclusion that (1) the minor thermal transition was mainly due to the defibrillation of the smaller collagen fibrillar aggregates and the unfolding of a little part of triple helices; (2) the major thermal transition primarily arose from the defibrillation of the larger collagen fibrillar aggregates and the complete denaturation of the majority part of triple helices. PMID:22963008

  15. Mssbauer, vibrational spectroscopic and solution X-ray diffraction studies of the structure of iron(III) complexes formed with indole-3-alkanoic acids in acidic aqueous solutions

    Microsoft Academic Search

    Krisztina Kovcs; Alexander A. Kamnev; Jnos Mink; Csaba Nmeth; Ern? Kuzmann; Tnde Megyes; Tams Grsz; Hedvig Medzihradszky-Schweiger; Attila Vrtes

    2006-01-01

    The chemical reactions between iron(III) and indole-3-acetic (IAA), -propionic (IPA), and -butyric (IBA) acids were studied\\u000a in acidic aqueous solutions. The motivation of this work was that IAA is one of the most powerful natural plant-growth-regulating\\u000a substances (phytohormones of the auxin series). Mssbauer spectra of the frozen aqueous solutions of iron(III) with indole-3-alkanoic\\u000a acids as ligands (L), showed parallel reactions

  16. Preparation and characterization of aligned carbon nanotubes/polylactic acid composite fibers

    NASA Astrophysics Data System (ADS)

    Kong, Yuxia; Yuan, Jie; Qiu, Jun

    2012-07-01

    Aligned functionalized multiwalled carbon nanotubes/polylactic acid (MWNTs-PCL/PLA) composite fibers were successfully prepared by electrospinning processing. The MWNTs bonded with the polycaprolactone chains exhibited excellent uniform dispersion in PLA solution by comparing with the acid-functionalized MWNTs and amino-functionalized MWNTs. Optical microscopy was used to study the aligned degree of the fibers and to investigate the influences of the electrodes distance on the alignment and structure of the fibers, and results showed that the best quality of aligned fibers with dense structure and high aligned degree were obtained at an electrodes distance of 3 cm. Moreover, the MWNTs embedded inside the MWNTs-PCL/PLA fibers displayed well orientation along the axes of the fibers, which was demonstrated by field emission scanning electron microscopy, transmission electron microscopy and Raman spectroscopy.

  17. Carbon nanofiber supported bimetallic PdAu nanoparticles for formic acid electrooxidation

    NASA Astrophysics Data System (ADS)

    Qin, Yuan-Hang; Jiang, Yue; Niu, Dong-Fang; Zhang, Xin-Sheng; Zhou, Xing-Gui; Niu, Li; Yuan, Wei-Kang

    2012-10-01

    Carbon nanofiber (CNF) supported PdAu nanoparticles are synthesized with sodium citrate as the stabilizing agent and sodium borohydride as the reducing agent. High resolution transmission electron microscopy (HRTEM) characterization indicates that the synthesized PdAu particles are well dispersed on the CNF surface and X-ray diffraction (XRD) characterization indicates that the alloying degree of the synthesized PdAu nanoparticles can be improved by adding tetrahydrofuran to the synthesis solution. The results of electrochemical characterization indicate that the addition of Au can promote the electrocatalytic activity of Pd/C catalyst for formic acid oxidation and the CNF supported high-alloying PdAu catalyst possesses better electrocatalytic activity and stability for formic acid oxidation than either the CNF supported low-alloying PdAu catalyst or the CNF supported Pd catalyst.

  18. Precipitation of plutonium from acidic solutions using magnesium oxide

    SciTech Connect

    Jones, S.A.

    1994-09-06

    Plutonium (IV) is only marginally soluble in alkaline solution. Precipitation of plutonium using sodium or potassium hydroxide to neutralize acidic solutions produces a gelatinous solid that is difficult to filter and an endpoint that is difficult to control. If the pH of the solution is too high, additional species precipitate producing an increased volume of solids separated. The use of magnesium oxide as a reagent has advantages. It is added as a solid (volume of liquid waste produced is minimized), the pH is self-limiting (pH does not exceed about 8.5), and the solids precipitated are more granular (larger particle size) than those produced using KOH or NaOH. Following precipitation, the raffinate is expected to meet criteria for disposal to tank farms. The solid will be heated in a furnace to dry it and convert any hydroxide salts to the oxide form. The material will be cooled in a desiccator. The material is expected to meet vault storage criteria.

  19. Carbon composite micro- and nano-tubes-based electrodes for detection of nucleic acids

    PubMed Central

    2011-01-01

    The first aim of this study was to fabricate vertically aligned multiwalled carbon nanotubes (MWCNTs). MWCNTs were successfully prepared by using plasma enhanced chemical vapour deposition. Further, three carbon composite electrodes with different content of carbon particles with various shapes and sizes were prepared and tested on measuring of nucleic acids. The dependences of adenine peak height on the concentration of nucleic acid sample were measured. Carbon composite electrode prepared from a mixture of glassy and spherical carbon powder and MWCNTs had the highest sensitivity to nucleic acids. Other interesting result is the fact that we were able to distinguish signals for all bases using this electrode. PMID:21711910

  20. Carbon composite micro- and nano-tubes-based electrodes for detection of nucleic acids.

    PubMed

    Prasek, Jan; Huska, Dalibor; Jasek, Ondrej; Zajickova, Lenka; Trnkova, Libuse; Adam, Vojtech; Kizek, Rene; Hubalek, Jaromir

    2011-01-01

    The first aim of this study was to fabricate vertically aligned multiwalled carbon nanotubes (MWCNTs). MWCNTs were successfully prepared by using plasma enhanced chemical vapour deposition. Further, three carbon composite electrodes with different content of carbon particles with various shapes and sizes were prepared and tested on measuring of nucleic acids. The dependences of adenine peak height on the concentration of nucleic acid sample were measured. Carbon composite electrode prepared from a mixture of glassy and spherical carbon powder and MWCNTs had the highest sensitivity to nucleic acids. Other interesting result is the fact that we were able to distinguish signals for all bases using this electrode. PMID:21711910

  1. Amino acids of the Murchison meteorite. I - Six carbon acyclic primary alpha-amino alkanoic acids

    NASA Technical Reports Server (NTRS)

    Cronin, J. R.; Gandy, W. E.; Pizzarello, S.

    1981-01-01

    Six of the seven chain isomers of six-carbon acyclic primary alpha-amino alkanoic acids (leucine isomers) have been either identified or confirmed in hot-water extracts of the Murchison meteorite using combined gas chromatography-mass spectrometry (GC-MS) and ion exchange chromatography. 2-Amino-2-ethylbutyric acid, 2-amino-2,3-dimethylbutyric acid, pseudoleucine, and 2-methylnorvaline were positively identified by GC-MS. These amino acids have not been previously reported to occur in natural materials and may be uniquely meteoritic in origin. The presence of leucine and isoleucine (including the diastereoisomer, alloisoleucine) was confirmed. Peaks corresponding to norleucine were seen by ion-exchange and gas chromatography but characteristic mass spectra were not obtained. The alpha-branched chain isomers in this series are quantitatively the most significant. These results are compared with literature data on amino acid synthesis by electrical discharge and Fischer-Tropsch-type catalysis. Neither model system produces an amino acid suite that is completely comparable to that found in the Murchison meteorite.

  2. Adsorption of zinc(II) from an aqueous solution onto activated carbon

    Microsoft Academic Search

    R Leyva Ramos; L. A Bernal Jacome; J Mendoza Barron; L Fuentes Rubio; R. M Guerrero Coronado

    2002-01-01

    Adsorption isotherms were measured experimentally for Zn(II) adsorption from aqueous solution onto commercial activated carbons C, F-400, F-300 and Centaur HSL in a batch adsorber. The effects of carbon type and solution pH on adsorption isotherms were evaluated in this work. Nearly three times as much Zn(II) adsorbed onto C carbon as on the other three carbon types. The adsorption

  3. Extensional Flow of Hyaluronic Acid Solutions in an Optimized Microfluidic Cross-Slot Devicea)

    E-print Network

    1 Extensional Flow of Hyaluronic Acid Solutions in an Optimized Microfluidic Cross-Slot Devicea) S and rheological properties of hyaluronic acid (HA) solutions representative of the synovial fluid (SF) found of Technology, Cambridge, MA 02139, USA #12;2 I. INTRODUCTION Hyaluronic acid (HA) is a naturally occurring

  4. The passivity of 304 stainless steel in propylene carbonate solutions

    SciTech Connect

    Shifler, D.A.; Kruger, J. (Corrosion and Electrochemistry Research Lab., Dept. of Materials Science and Engineering, John Hopkins Univ., Baltimore, MD (US)); Moran, P.J. (Dept. of Mechanical Engineering, United States Naval Academy, Annapolis, MD (US))

    1992-01-01

    This paper reports that the passivation behavior of 304 stainless steel in anhydrous propylene carbonate (PC) containing 0.5M LiAsF{sub 6} or 0.5M LiClO{sub 4} was studied. The air-formed film on 304SS is stable up to the oxidation potential of PC (PC{sub ox}). Scratch tests show that the bared 304SS surface repassivates in the anhydrous PC solutions of either electrolyte by chemisorption of PC molecules below PC{sub ox}. In PC/0.5M LiAsF{sub 6} solutions, the 304SS is not passivated at potentials above PC{sub ox}. This is attributed to the formation of a thin metastable perchlorate salt film or an adsorbed layer of perchlorate anions. When the perchlorate anions oxidize, the passivation becomes unstable and pitting occurs. Small (3-8 volume percent) additions of PC/0.5M LiClO{sub 4} to PC/0.5M LiAsF{sub 6} solutions raised the passive range to the perchlorate oxidation potential. Small quantities of water, propylene glycol, and propylene oxide added to PC lightly improve the passive range of the 304 stainless steel.

  5. The Influence of Temperature on the Heat Effects of AcidBase Interaction in Aqueous Solutions of Citric Acid

    NASA Astrophysics Data System (ADS)

    Kochergina, L. A.; Vasil'ev, V. P.; Krutov, D. V.; Krutova, O. N.

    2008-04-01

    The heat effects of interaction of a solution of citric acid with solutions of HNO3 and KOH at 288.15, 298.15, and 308.15 K and ionic strength values 0.5, 1.0, and 1.5 (KNO3) were measured calorimetrically. The heat effects of acid dissociation were calculated using the HEAT program. The standard thermodynamic characteristics of step dissociation of citric acid were determined.

  6. Modeling of dissolution patterns for carbonate acidizing in the porous media

    NASA Astrophysics Data System (ADS)

    Samadi, Fereshteh; Esmaeilzadeh, Feridun; Mowla, Dariush

    2012-05-01

    Matrix acidizing is a common technique to stimulate wells for improving well inflow performance. In this treatment that is widely used in the oil industry, acid solution is injected into the formation to dissolve some minerals to increase permeability of carbonate near the wellbore. The aim of the treatment is to create empty channels called wormholes. Wormholing in carbonate rocks is a complex 3-D phenomenon. Matrix acidizing generally should be applied when a well has a high skin factor that cannot be attributed to partial penetration, perforation efficiency or other mechanical aspects of the completion. Obviously, it is of extreme importance to quantify the skin factor to evaluate the effectiveness of stimulation treatments. When wormholes extend beyond the damaged zone or connect with natural fissures in the formation, a negative skin effect is obtained. An ideal matrix treatment restores the permeability in the near wellbore region to a value at least as high as the original undamaged permeability; it accomplishes this over the entire completed interval and it leaves the formation in the treated region with high relative permeability to the oil and/or gas phase. Designing a treatment should strive to achieve this ideal at the lowest possible cost, which requires consideration of the many physical and chemical interactions taking place between the injected fluids and the reservoir minerals and fluids. In this work, a threescale continuum model is used to model reactive dissolution of carbonate rocks in radial flow. Both the Darcy and pore scale physics such as mass transfer of acid molecules to the mineral surface and subsequent reaction at the surface, changing pore structure and variations in reservoir permeability are included in this model. Partial differential equations obtained from the model, have been solved by numerical method. The influence of reservoir temperature on optimum injection rate is investigated. Results show that optimum injection rate increases with temperature.

  7. Experimental fractionation of stable carbon isotopes during degassing of carbon dioxide and precipitation of calcite from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Mller, K.; Winde, V.; Escher, P.; von Geldern, R.; Bttcher, M. E.

    2012-04-01

    Processes in the carbonate system of surface waters are in particular sensitive to variations of boundary conditions as, for instance, the partial pressure of carbon dioxide in the atmosphere and the aqueous solution. Examples range from streams, rivers, to coastal marine waters. The flux of carbon dioxide from continental flowing waters was recently included into calculations of the global carbon budget (Butman & Raymond, 2011, Nature Geo.). These solutions, are often supersaturated in carbon dioxide with respect to the atmosphere. The degassing of carbon dioxide is associated with a kinetically controlled fractionation of the stable carbon isotopes, which has to be considered in balancing water-air carbon dioxide fluxes. The degassing process additionally leads to the super-saturation of the aqueous solution with respect to calcium carbonate. Stable isotope fractionation is of particular value to identify and quantify processes at the water-gas phase interface and link these non-equilibrium processes to the formation mechanisms of calcite and the hydrodynamics of surface waters. Experiments were carried out with or without inert N2 gas flow to degas carbon dioxide from initially supersaturated solutions. Natural solutions used are from different stations of the Elbe estuary, the Jade Bay, the backbarrier tidal area of Spiekeroog Island, carbonate springs of Rgen Island, and the Baltic Sea coastline. Results are compared experiments using bottled mineral waters. By following the (physico) chemical changes in the solutions (pH, TA, Ca PHREEQC modeling) it was found, that two evolutionary stages can be differentiated. Reaction progress led to the preferential liberation of carbon dioxide containing the light carbon isotope, following a Rayleigh-type process. After an induction period, where only degassing of carbon dioxide took place, a second stage was observed where calcite began to form from the highly supersaturated solutions. In this stage the carbonate system of the solution was controlled by both, degassing and carbonate precipitation, still leading to an enrichment of the heavier carbon isotope in the residual DIC. The experimental results are evaluated for both periods, and the influence of salinity and pH is extracted. Acknowledgement: Parts of this study were supported by BMBF within the BIOACID project

  8. Preparation, morphology and properties of acid and amine modified multiwalled carbon nanotube\\/polyimide composite

    Microsoft Academic Search

    Siu-Ming Yuen; Chen-Chi M. Ma; Yao-Yu Lin; Hsu-Chiang Kuan

    2007-01-01

    The precursor of polyimide, polyamic acid, was prepared by reacting 4,4?-oxydianiline (ODA) with 3,3?,4,4?-benzophenone tetracarboxylic dianhydride (BTDA). Unmodified, acid-modified and amine-modified multiwall carbon nanotubes (MWCNT) were separately added to the polyamic acid and heated to 300C to produce polyimide\\/carbon nanotube composite. Scanning electron microscopic (SEM) and transmission electron microscopic (TEM) microphotographs reveal that acid-modified MWCNT and amine-modified MWCNT were dispersed

  9. Electrocatalytic oxidation of formic acid and formaldehyde on nanoparticle decorated single walled carbon nanotubes.

    PubMed

    Selvaraj, V; Grace, A Nirmala; Alagar, M

    2009-05-01

    A potent catalyst has been prepared consisting of platinum (Pt), and platinum-palladium (Pt-Pd) nanoparticles supported on purified single-walled carbon nanotubes (Pt/CNT and Pt-Pd/CNT). Electrochemical characteristics of formic acid and formaldehyde oxidation on these catalysts are investigated via cyclic voltammetric analysis in mixed 0.5 M HCOOH (or 0.5 M HCHO) and 0.5 M H(2)SO(4) solutions. The results imply that the Pt-Pd/CNT electrodes exhibit a better activity than the corresponding Pt nanoparticles modified SWCNT electrodes. The modified electrode exhibits significant electrocatalytic activity towards formic acid and formaldehyde oxidation, which may be attributed due to the uniform dispersion of nanoparticles on SWCNTs and the efficacy of Pd species in Pt-Pd system. Such nanoparticles modified CNT electrodes exhibit better catalytic behavior towards formic acid and formaldehyde than the corresponding carbon electrodes, indicating that the system studied in the present work is the more promising system for use in fuel cells. PMID:19243782

  10. A novel ceriaactivated carbon composite for the catalytic ozonation of carboxylic acids

    Microsoft Academic Search

    P. C. C. Faria; J. J. M. rfo; M. F. R. Pereira

    2008-01-01

    Ceria (CeO) and a novel ceriaactivated carbon composite (AC0CeO) were prepared and tested as catalysts in the ozonation of two selected carboxylic acids, oxalic acid and oxamic acid, at acid pH. CeO showed an interesting catalytic effect, especially in the ozonation of oxalic acid. A strong synergic effect was observed for the AC0CeO composite in the case of oxalic acid,

  11. THE KINETICS OF THE CORROSION OF LOW-HAFNIUM ZIRCONIUM IN AQUEOUS SULFURIC ACID SOLUTIONS

    Microsoft Academic Search

    Tennyson Smith

    1960-01-01

    The rates of corrosion of low-hafnium zirconium in aqueous sulfuric acid ; solutions over the concentration range 9 to 97% by weight, were studied. ; Corrosion was detected by measuring the concentration of zirconium in solution ; with a radioactive tracer, Zr⁹⁵. The samples first were etched in an ; aqueous hydrofluoric-nitric acid solution then placed directly into the sulfuric

  12. Solubility Limits of Dibutyl Phosphoric Acid in Uranium Solutions at SRS

    Microsoft Academic Search

    M. C. Thompson; R. A. Pierce; R. J. Ray

    1998-01-01

    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

  13. Electrochromic properties of oxidized tungsten in sulfuric acid solutions

    SciTech Connect

    Yurkinskii, V.P.; Muzdhaba, V.M.; Sidorova, M.A.; Morachevskii, A.G.

    1987-08-01

    The parameters of the electrochromic process taking place on electrochemically oxidized tungsten electrodes were studied by recording current-voltage curves, making coulometric determinations, and investigating electrooptic effects in the oxide film. The electrochromic effect was studied in sulfuric acid solutions of different concentrations. The shape of the cathodic current-voltage curves is shown. The amounts of charge consumed and the contrast ratios as functions of cathodic potential of the tungsten electrode during coloration are presented. Also shown is the anodic and cathodic current as functions of time during bleaching of oxidized tungsten, plotted in different coordinates. High mobility of the protons in tungsten oxide produced by electrochemical oxidation of tungsten, relative to sputtered oxide, is shown to procure faster response of the electrochromic system.

  14. The aqueous photolysis of ?-pinene in solution with humic acid

    USGS Publications Warehouse

    Goldberg, Marvin C.; Cunningham, Kirkwood M.; Aiken, George R.; Weiner, Eugene R.

    1992-01-01

    Terpenes are produced abundantly by environmental processes but are found in very low concentrations in natural waters. Aqueous photolysis of solutions containing ?-pinene, a representative terpene, in the presence of humic acid resulted in degradation of the pinene. Comparison of this reaction to photolysis of ?-pinene in the presence of methylene blue leads to the conclusion that the reactive pathway for the abiotic degradation of ?-pinene is due to reaction with singlet oxygen produced by irradiation of the humic material. The initial product of single oxygen and ?-pinene is a hydroperoxide. Since humic materials are prevalent in most natural waters, this mechanism of photodecomposition for ?-pinene probably also applies to other terpenes in surface waters and may be reasonably considered to contribute to their low environmental concentration.

  15. Reaction of CO2 and Carbonate Mineral in Seawater for Mitigation of CO2 and Ocean Acidity

    NASA Astrophysics Data System (ADS)

    Rau, G. H.

    2010-12-01

    A lab-scale seawater/mineral carbonate gas scrubber was found to remove up to 97% of CO2 in a simulated flue gas stream at ambient temperature and pressure, with a large fraction of this carbon ultimately converted to dissolved calcium bicarbonate. Contrary to predictions based on classical carbonate chemistry, up to 85% of the captured carbon was retained in solution, i.e., it did not degas or precipitate, even after full equilibration with air. This is because abiotic precipitation of CaCO3 from seawater is chemically inhibited up to dissolved concentrations approaching 20X supersaturation. Thus, above-ground CO2 hydration with seawater, reaction with mineral carbonate, and conversion to dissolved Ca(HCO3)2 may provide a relatively simple point-source CO2 capture and storage scheme at coastal locations. This approach is analogous to wet limestone scrubbing of flue gas that is commonly used for SO2 removal. Such low-tech CO2 mitigation could be especially relevant for retrofitting to existing coastal power plants and for deployment in the developing world, the primary source of future CO2 emissions. An electrochemically powered version of the preceding has been demonstrated for air capture of CO2. In any case, the addition of the resulting alkaline solution to the ocean would benefit marine ecosystems that are currently challenged by acidification. This is indicated by the widespread use of miniature CO2/carbonate mineral/seawater reactors in saltwater aquaria to generate alkalinity for preserving or enhancing coral and shellfish growth. Large-scale applications would thus allow use of the planets largest saline reservoir, the ocean, to safely and effectively store anthropogenic carbon in a form other than molecular CO2 or carbonic acid. This approach in essence hastens Nature's own very effective but slow CO2 mitigation process; carbonate mineral weathering is a major consumer of excess atmospheric CO2 and ocean acidity on geologic times scales.

  16. Carbon Footprint of Telemedicine Solutions - Unexplored Opportunity for Reducing Carbon Emissions in the Health Sector

    PubMed Central

    Holmner, sa; Ebi, Kristie L.; Lazuardi, Lutfan; Nilsson, Maria

    2014-01-01

    Background The healthcare sector is a significant contributor to global carbon emissions, in part due to extensive travelling by patients and health workers. Objectives To evaluate the potential of telemedicine services based on videoconferencing technology to reduce travelling and thus carbon emissions in the healthcare sector. Methods 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 Ume 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. Results Replacing physical visits with telemedicine appointments resulted in a significant 4070 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. Conclusions 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. PMID:25188322

  17. Influence of mesopore volume and adsorbate size on adsorption capacities of activated carbons in aqueous solutions

    Microsoft Academic Search

    Chien-To Hsieh; Hsisheng Teng

    2000-01-01

    Liquid-phase adsorption of phenol, iodine and tannic acid onto commercial grade granular activated carbons and activated carbon fabric was conducted to explore the influence of the mesopore volume and the size of adsorbates on the adsorption capacity. These carbons have different mesopore volumes, while possessing similar surface areas and micropore volumes, which are believed to determine the adsorption capacity in

  18. The resistance of recent marine carbonate sediments to solution

    E-print Network

    Jansen, John F

    1962-01-01

    sediment samples. TABLE 2 Ca ++ and Mg Content o Carbonate Sed f Unground Natural 2/ iments? S amp le Mes h Size CaCO MgCO 3 Sample Mesh Size CaCO 3 Mgco 2 ? 18 X 2 ? 35 X 2-. 60 X 4-10 X 94. 50 93. 82 93. 48 90. 16 4. 39 2. 03 2. 28 6..., Table 1. These analyses were obt. ained after th. e sediments had been in contact with the Figure 2 relates the dissolve NaHCO solution for ei 3 ++ d amounts o f Ca and ght months e+ Mg in mi 11 imo les to the percentage of MgCO in the sediments...

  19. Radiolysis gases from nitric acid solutions containing HSA and HAN

    SciTech Connect

    Smith, J.R.

    1994-10-28

    The concentration of hydrogen (H{sub 2}) in the radiolytically produced off-gas from 2.76-4.25M HNO{sub 3}/PU solutions has been found to be greatly reduced in the presence of sulfamic acid (HSA) and hydroxylamine nitrate (HAN). The H{sub 2} concentration ([H{sub 2}]) is reduced from 35 percent to about 4 percent by dilution caused from an increase in the production rates of nitrogen (N{sub 2}), nitrous oxide (N{sub 2}O), and oxygen (O{sub 2}) gases. The generation rate of H{sub 2} was not affected by HSA or HAN giving a measured radiolytic yield, G(H{sub 2}), value of 0.201 molecules/100 eV for 2.765M NO{sub 3}{sup -} solution (a value of 0.213 is predicted from previous data). The G(H{sub 2}) values are dependent on the solution nitrate concentration ([NO{sub 3}{sup -}]). The generation rates of N{sub 2}, N{sub 2}O, and O{sub 2} are not dependent on the [NO{sub 3}{sup -}] in this narrow range, but are dependent on the presence of HSA and the concentration of HAN. The percentage [H{sub 2}] for the 2.5 to 3.0M NO{sub 3}{sup -} range expected in the off- from the FB-Line Pu{sup +3} Hold Tanks is conservatively estimated to be about 3.5 to 4.5 % for Pu + 3 solutions initially containing 0.023M HAN/0.165M HSA. The upper limit [H{sub 2}] may actually be about 4.1 % (4.3 % at 90 % confidence limits) but more {open_quotes}initial{close_quotes} off-gas rate data is needed at about 2.9M [NO{sub 3}{sup -}] in Pu{sup +3} solution for verification. Addition of ascorbic acid had no effect on the off-gas rate of Pu{sup +3} solutions containing HSA and NO{sub 3}{sup -} concentrations higher than those expected in the hold tanks. The maximum {open_quotes}hold time{close_quotes} for 50 grams/liter Pu{sup +3}/0.165M HSA/0.023M HAN/2.5-3.0M HNO{sub 3} solution is 20.3{+-}2.1 days. After this time the HSA initially present will become exhausted and the [H{sub 2}] will increase to 35 %. This hold time may be longer in [NO{sub 3}{sup -}] < 3.0M, but again more study is needed.

  20. 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 10100?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

  1. Modification of multi-walled carbon nanotubes with tannic acid for the adsorption of La, Tb and Lu ions

    Microsoft Academic Search

    Shanshan Tong; Shujie Zhao; Weihong Zhou; Ruigang Li; Qiong Jia

    We have prepared an environmental friendly sorbent by modifying multi-walled carbon nanotubes with tannic acid. The adsorption\\u000a of La (III), Tb (III) and Lu (III) as a function of contact time, initial solution pH, and quantity of adsorbent was studied\\u000a using a batch technique. Both Langmuir and Freundlich isotherms can be used to describe the process. The major adsorption\\u000a mechanisms

  2. Direct electrochemistry and electrocatalysis of horseradish peroxidase immobilized in hyaluronic acid and single walled carbon nanotubes composite film

    Microsoft Academic Search

    Qi Wang; Jianbin Zheng

    2010-01-01

    Direct electrochemistry and electrocatalysis of horseradish peroxidase (HRP) immobilized on a hyaluronic acid (HA)-single\\u000a walled carbon nanotubes (SCNs) composite film coated glassy carbon electrode (GCE) was studied for the first time. HRP entrapped\\u000a in the SCNs-HA composite film exhibited a pair of well-defined, quasi-reversible cyclic voltammetric peaks in a 0.1 M phosphate\\u000a buffer solution (pH 7.0). Formal potential vs. standard

  3. Proton magnetic resonance studies of the chemical shifts occurring in propionic acid-dioxane solutions

    E-print Network

    Oldham, William J. Bryan

    1958-01-01

    LIB' OF FIQUHRB PIGUBRB 1, Observers ohemi, cal shiftsoccurring in aqueous solutions of propiolLic acid o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 23 2 ~ Chemical shifts occurring in propionic acyl-diarane solull iona...~ted values of the equilibr1um constant for the dimermonomer dissociation in propionic acid&ioxsne solut ious o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 32 4, Calculated values of the shifx occurring 'u propionic acid&hexane solutions at 73 C...

  4. EXAFS Study on the Reactions Between Iron And Fulvic Acid in Acid Aqueous Solutions

    SciTech Connect

    Schaik, J.W.J.van; Persson, I.; Kleja, D.B.; Gustafsson, J.P.

    2009-05-26

    Iron(III) competes with trace metals for binding sites on organic ligands. We used X-ray absorption fine structure (EXAFS) spectroscopy to determine the binding mode and oxidation state of iron in solutions initially containing only iron(III) and fulvic acid at pHs 2 and 4. EXAFS spectra were recorded at different times after sample preparation. Iron was octahedrally configured with inner-sphere Fe-O interactions at 1.98-2.10 {angstrom}, depending on the oxidation state of iron. Iron(III) formed complexes with fulvic acid within 15 min. Iron(III) was reduced to iron(II) with time at pH 2, whereas no significant reduction occurred at pH 4. No signs of dimeric/trimeric hydrolysis products were found in any of the solution samples (<0.45 {mu}m). However, the isolated precipitate of the pH 2 sample (>0.45 {mu}m) showed Fe{hor_ellipsis}Fe distances, indicating the presence of tightly packed iron(III) trimers and/or clusters of corner-sharing octahedra. It is suggested that the binding mode of iron(III) to fulvic acid at low pH may be phase-dependent: in solution mononuclear complexes predominate, whereas in the solid phase hydrolyzed polynuclear iron(III) complexes form, even at very low pH values. The observed pH dependence of iron(III) reduction was consistent with expected results based on thermodynamic calculations for model ligands.

  5. 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.

  6. Removal of nickel(II) from aqueous solution using Citrus Limettioides peel and seed carbon.

    PubMed

    Sudha, R; Srinivasan, K; Premkumar, P

    2015-07-01

    The agricultural wastes like Citrus Limettioides peel and seed to be suitable precursor for the preparation of carbon [Citrus Limettioides peel carbon (CLPC) and seed carbon (CLSC)] has been explored in the present work, utilizing sulfuric acid as the activating agent. Adsorption studies were performed by varying contact time, solution pH, adsorbent dose and temperature. The equilibrium time for Ni(II) ions was determined as 4h and optimal pH was 4-7. Surface morphology and functionality of the CLPC and CLSC were characterized by SEM, EDX and FT-IR. The experimental data were analysed using the Freundlich, Langmuir, Temkin, Redlich-Peterson, Sips and Dubinin-Radushkevich adsorption isotherm equations using nonlinear regression analysis. Equilibrium data were found to fit well in the Langmuir isotherm, which confirmed the monolayer coverage of Ni(II) ions. The Langmuir monolayer adsorption capacity of CLPC and CLSC was found to be 38.46 and 35.54mg/g. The thermodynamic parameters indicated that the adsorption process was spontaneous and exothermic in nature. The kinetic data followed pseudo-second order model with film diffusion process. The adsorbents were tested with Ni(II) plating wastewater in connection with the reuse and selectivity of the adsorbents. PMID:25841067

  7. Perlwapin, an abalone nacre protein with three four-disulfide core (whey acidic protein) domains, inhibits the growth of calcium carbonate crystals.

    PubMed

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

    2006-10-01

    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 approximately 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

  8. Corrosion-resistant Ni?Cr?Mo alloys in hot concentrated sulphuric acid with active carbon

    Microsoft Academic Search

    Yoshio Takizawa; Katsuo Sugahara

    1995-01-01

    Dewpoint corrosion by sulphuric acid has often been observed in the heat exchangers of coal-burning plants. If ashes contain active carbon, corrosion becomes particularly serious. Various nickel-base alloys with high corrosion resistance in such environments have been designed. The corrosion behaviour of these alloys was examined in hot concentrated sulphuric acid with and without active carbon. The corrosion resistance of

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

    Microsoft Academic Search

    Ewa Lorenc-Grabowska; Gra?yna Gryglewicz

    2005-01-01

    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

  10. Cadmium ion adsorption on different carbon adsorbents from aqueous solutions. Effect of surface chemistry, pore texture, ionic strength, and dissolved natural organic matter.

    PubMed

    Moreno-Castilla, C; Alvarez-Merino, M A; Lpez-Ramn, M V; Rivera-Utrilla, J

    2004-09-14

    Adsorption of Cd(II) species at pH = 5 was studied on three carbon adsorbents: granular activated carbon, activated carbon fiber, and activated carbon cloth. As-received and oxidized adsorbents were used. Cd(II) adsorption greatly increased after oxidation due to the introduction of carboxyl groups. The use of a buffer solution to control the pH introduced some changes in the surface chemistry of carbons through the adsorption of one of the compounds used, biphthalate anions. The increase in ionic strength reduced Cd(II) uptake on both as-received and oxidized carbons due to a screening of the electrostatic attractions between the Cd(II) positive species and the negative surface charge, which in the case of as-received carbons derived from the biphthalate anions adsorbed and in the oxidized ones from the carboxyl groups. Tannic acid was used as a model compound for natural organic matter. Its adsorption was greatly reduced after oxidation, and most of the carbon adsorbents preadsorbed with tannic acid showed an increase in Cd(II) uptake. In the case of competitive adsorption between Cd(II) species and tannic acid molecules, there was a decrease in Cd(II) uptake on the as-received carbon whereas the contrary occurred with the oxidized carbons. These results illustrate the great importance of carbon surface chemistry in this competitive adsorption process. Finally, under all experimental conditions used, when the adsorption capacity of carbons was compared under the same conditions it increased in the following order: granular activated carbon < activated carbon fiber < activated carbon cloth. PMID:15350085

  11. Uptake of ozone to mixed sodium bromide/ citric acid solutions

    NASA Astrophysics Data System (ADS)

    Lee, Ming-Tao; Steimle, Emilie; Bartels-Rausch, Thorsten; Kato, Shunsuke; Lampimki, Markus; Brown, Matthew; van Bokhoven, Jeroen; Nolting, Frithjof; Kleibert, Armin; Trler, Andreas; Ammann, Markus

    2013-04-01

    Sea-salt solution - air interfaces play an important role in the chemistry of the marine boundary layer. The reaction of ozone (O3) with bromide is of interest in the context of formation of photolabile halogens (Br2, BrCl) in the marine boundary layer. Recent experiments have suggested that the bromide oxidation rate is related to the surface concentration of bromide [1] and inversely related to the gas phase concentration of O3, an indication for a precursor mediated reaction at the surface [2]. So far, the effect of organics (such as those occurring at the ocean surface or in marine aerosols) on the reaction of O3 with bromide aerosols has not been studied yet. In our study we investigate the uptake kinetics of O3 to a mixed solution of sodium bromide (NaBr) and citric acid (CA), which represents highly oxidized organic compounds present in the environment, with a well-established coated wall flow tube technique, which leads to exposure of the film to O3 allowing the heterogeneous reactions to take place and the loss of O3 being measured. The results indicate that the uptake of O3 to the films with the higher bromide concentrations (0.34M and 4M) is independent of the gas phase concentration and roughly consistent with uptake limited by reaction in the bulk. For the lower bromide concentration (84mM), however, we observe a trend of the uptake coefficient to decrease with increasing O3 concentration, indicating an increasing importance of a surface reaction. In an attempt to constrain the kinetic data, we employed X-ray photoelectron spectroscopy (XPS) to get insight into the surface composition of the aqueous solution - air interface. Previous XPS studies have shown that halide ion concentrations are enhanced at the aqueous solution air interface [3-4], which likely promotes the surface reactions of bromide or iodide with O3. A first XPS study of ternary solutions of KI with butanol indicated the importance of specific interactions of the cation with the alcohol headgroup [5]. In this study we would like to go one step further and look into the effect of a more complex organic compound, CA. We used ambient pressure XPS on a vacuum liquid microjet. The continuously refreshed free-flowing aqueous filament under vacuum permits photoelectron spectroscopy measurements from volatile aqueous interfaces in absence of beam damage [6]. Measurements were made at the SIM beam line of the Swiss Light Source (SLS) at the Paul Scherrer Institute. The ability to tune the photon energy (150-2000 eV) is crucial to get precise component ratios as a function of photoelectron kinetic energy and thus probe depth, thus allowing to determine relative concentrations of citric acid and bromide at the surface and in the bulk, respectively. REFERENCES [1] Clifford and Donaldson, J. Phys. Chem. A, 111, 9809-9814, (2007). [2] Oldridge and Abbatt, J. Phys. Chem. A, 115, 2590-2598, (2011). [3] S. Ghosal et al., Science 307, 563 (2005). [4] M.A. Brown et al., Phys. Chem. Chem. Phys. 10, 4778 (2008). [5] M. Krisch et al., J. Phys. Chem. C 111, 13497 (2007). [6] M.A. Brown et al., J. Phys. Chem. Lett. 3, 231 (2012).

  12. Reactions of aqueous glucose solution over solid-acid Y-zeolite catalyst at 110-160 C

    SciTech Connect

    Lourvanij, K.; Rorrer, G.L. (Oregon State Univ., Corvallis (United States))

    1993-01-01

    Reactions of glucose with solid-acid Y-zeolite catalyst were studied to see if this heterogeneous system could produce oxygenated hydrocarbons by shape-selective, acid-catalyzed processes at fairly low temperatures. Experimentally, aqueous solutions of glucose (12 wt %) were reacted with HY-zeolite powder in a well-mixed batch reactor at temperatures ranging from 110 to 160 C and catalyst concentrations ranging from 2 to 20 g/150 ml. Unreacted glucose and oxygenated hydrocarbon products were measured by HPLC as a function of reaction time (0-24 h) and process conditions. Glucose conversions of 100% were obtained at 160 C after an 8-h reaction time. The apparent activation energy based on glucose conversion was 23.25 [plus minus] 0.40 kcal/mol. Several acid-catalyzed reactions were identified, including isomerization of glucose to fructose, partial dehydration of glucose to 5-(hydroxymethyl)furfural (HMF), rehydration and cleavage of HMF to formic acid and 4-oxo-pentanoic acid, and carbonization . Polymers of HMF and seven minor additional products in the lower molecular weight organic acids/aldehydes/ketones elution range were also isolated by HPLC. High yields of organic acids relative to HMF and lowered selectivity of HMF in the bulk phase relative to the homogeneous acid-catalyzed reaction suggests the possibility of molecular sieving reactions within the Y-zeolite in addition to reactions on the outer surface of the Y-zeolite particle.

  13. Theromdynamics of carbon in nickel-based multicomponent solid solutions

    Microsoft Academic Search

    1978-01-01

    The activity coefficient of carbon in nickel, nickel-titanium, nickel-titanium-chromium, nickel-titanium-molybdenum and nickel-titanium-molybdenum-chromium alloys has been measured at 900, 1100 and 1215°C. The results indicate that carbon obeys Henry's Law over the range studied (0 to 2 at. percent). The literature for the nickel-carbon and iron-carbon systems are reviewed and corrected. For the activity of carbon in iron as a function

  14. Impedance and ellipsometer measurements of lithium electrodes in propylene carbonate solutions

    SciTech Connect

    Schwager, F.; Muller, R.H.

    1983-09-01

    Complex electrode impedance has been measured for lithium after exposure to nitrogen, propylene carbonate and LiClO/sub 4/ solutions in propylene carbonate. Results for zero-field exchange current density and polarization resistance are in agreement with earlier current pulse measurements. Ellipsometer measurements show a different electrode behavior for anodic and cathodic reactions in perchlorate solution.

  15. Structure Controlled Synthesis of Single-Walled Carbon Nanotubes Using Solution Based Catalyst Deposition

    E-print Network

    Mellor-Crummey, John

    and physical properties, single-walled carbon nanotube (SWCNT) has been considered for many applications. We, mechanical application, etc. #12;Structure Controlled Synthesis of Carbon Nanotubes Theerapol Thurakitseree1Structure Controlled Synthesis of Single-Walled Carbon Nanotubes Using Solution Based Catalyst

  16. Electrostatic charge and interactions within carbon-nanotube nematic in electrolyte solution

    NASA Astrophysics Data System (ADS)

    Lee, Choong-Seop; Yakobson, Boris I.

    2004-03-01

    The lyotropic transitions from isotropic solution (I) to nematic liquid crystalline phases (N, N') of single-wall carbon nanotubes (SWNT) are guided by the volumetric fraction together with the electrostatic forces. The latter depends on charge transfer between the SWNT and the solvent-electrolyte, and can be studied in approach similar to Derjaguin-Landau-Verwey-Overbeek. A simple kinetic model for a charging mechanism of SWNT is proposed, which allows analytical treatment. We have explored the optimization of control parameters (equilibrium constants, temperature, pH, etc.) of the model to achieve the separation of densely packed SWNT-bundle (N) into array of spaced individual tubules (N'). Our results explain the observation in recent experiments [1] of the dispersion of SWNT in oleum (overconcentrated sulpheric acid) as well as the sudden collapse of such dispersion with small amount of water added. [1] M. Pasquali et al., Macromolecules (in press).

  17. 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.

  18. Investigating the Effects of Core Length on Pore Volume to Breakthrough (PVBT) Behavior in Carbonate Core Samples during Matrix Acidizing with Hydrochloric Acid

    E-print Network

    Nour, Mohamed

    2014-05-06

    Most literature contains Hydrochloric acid (HCl) carbonate acidizing experiments performed on short (2 - 6 inch) cores. These cores do not accurately represent reservoir conditions, as spent acid is not propagated for any appreciable distance along...

  19. Preparation of regenerated cellulose fiber via carbonation. I. Carbonation and dissolution in an aqueous NaOH solution

    Microsoft Academic Search

    Sang Youn Oh; Dong Il Yoo; Younsook Shin; Wha Seop Lee; Seong Mu Jo

    2002-01-01

    Cellulose carbonate was prepared by the reaction of cellulose pulp and CO2 with treatment reagents, such as aqueous ZnCl2 (2040 wt%) solution, acetone or ethyl acetate, at ?50C and 3040 bar (CO2) for 2 hr. Among the treatment reagents, ethyl acetate was the most effective. Cellulose carbonate was dissolved in 10% sodium\\u000a hydroxide solution containing zinc oxide up to 3

  20. Organic compounds in olive mill wastewater and in solutions resulting from hydrothermal carbonization of the wastewater.

    PubMed

    Poerschmann, J; Weiner, B; Baskyr, I

    2013-09-01

    Organic components in olive mill wastewater (OMW) were analyzed by exhaustive solvent extraction of the lyophilisate followed by pre-chromatographic derivatization techniques and GC/MS-analysis of the extracts. Simple biophenols including tyrosol (Tyr), hydroxytyrosol (OH-Tyr) and homovanillic alcohol as well as complex biophenols including decarbomethoxy ligostride aglycon and decarbomethoxy oleuropein aglycon proved most abundant analytes. Hydroxylated benzoic and cinnamic acids are less abundant, which may indicate a humification process to have occurred. The pattern of organic components obtained from native OMW was compared with that obtained from hydrothermal carbonization (HTC) of the waste product. Former results provided strong evidence that HTC of OMW at 220C for 14h results in an almost complete hydrolysis of complex aglycons. However, simple biophenols were not decomposed on hydrothermal treatment any further. Phenol and benzenediols as well as low molecular weight organic acids proved most abundant analytes which were generated due to HTC. Similarly to aglycons, lipids including most abundant acylglycerines and less abundant wax esters were subjected almost quantitatively to hydrolysis under hydrothermal conditions. Fatty acids (FAs) released from lipids were further decomposed. The pathways of volatile analytes in both native OMW and aqueous HTC solutions were studied by solventless headspace-Solid Phase Micro Extraction. Basically, a wide array low molecular alcohols and ketones occurring in native OMW survived the HTC process. PMID:23648325

  1. Catalytic ozonation of p-chlorobenzoic acid by activated carbon and nickel supported activated carbon prepared from petroleum coke

    Microsoft Academic Search

    Xukai Li; Qiuyun Zhang; Lili Tang; Ping Lu; Fengqiang Sun; Laisheng Li

    2009-01-01

    The aim of this research was to investigate catalytic activity of petroleum coke, activated carbon (AC) prepared from this material, Ni supported catalyst on activated carbon (Ni\\/AC) in the ozonation of aqueous phase p-chlorobenzoic acid (p-CBA). Activated carbon and Ni\\/AC catalyst were characterized by XRD and SEM. The presence of petroleum coke did not improve the degradation of p-CBA compared

  2. A novel amperometric sensor for ascorbic acid based on poly(Nile blue A) and functionalised multi-walled carbon nanotube modified electrodes.

    PubMed

    Kul, Dilek; Ghica, M Emilia; Pauliukaite, Rasa; Brett, Christopher M A

    2013-07-15

    A new type of modified electrode sensor for ascorbic acid has been prepared by deposition of multi-walled carbon nanotubes (MWCNT) and poly(Nile blue A) on the surface of glassy carbon electrodes. Nile blue A was electropolymerised either beneath (directly on glassy carbon) or onto the MWCNT layer by potential cycling in phosphate buffer solution at pH 6.0. Characterisation of the modified electrodes was carried out by cyclic voltammetry and electrochemical impedance spectroscopy. Quantitative determination of ascorbate was achieved by cyclic voltammetry and fixed potential amperometry in phosphate buffer solution at pH 5.3. The modified electrodes exhibited good sensitivity, wide linear range, a detection limit of 1.6 ?M and good stability, showing that they can be used as sensors for ascorbic acid. There is no interference from compounds commonly found in clinical and pharmaceutical samples and the determination of ascorbic acid in commercial tablet samples was successfully performed. PMID:23622528

  3. Adsorption of malachite green from aqueous solution onto carbon prepared from Arundo donax root

    Microsoft Academic Search

    Jian Zhang; Yan Li; Chenglu Zhang; Yuming Jing

    2008-01-01

    Arundo donax root carbon (ADRC), a new adsorbent, was prepared from Arundo donax root by carbonization. The surface area of the adsorbent was determined 158m2\\/g by N2 adsorption isotherm. Batch adsorption experiments were carried out for the removal of malachite green (MG) from aqueous solution using ADRC as adsorbent. The effects of various parameters such as solution pH (310), carbon

  4. Binary diffusion coefficient, partition ratio, and partial molar volume for docosahexaenoic acid, eicosapentaenoic acid and ?-linolenic acid at infinite dilution in supercritical carbon dioxide

    Microsoft Academic Search

    Toshitaka Funazukuri; Chang Yi Kong; Seiichiro Kagei

    2003-01-01

    A tracer response technique with a poly(ethylene glycol) coated capillary column was employed to measure binary diffusion coefficient and partition ratio for the ?3 group of long chain unsaturated fatty acids such as docosahexaenoic acid, eicosapentaenoic acid and ?-linolenic acid at infinite dilution in supercritical (SC) carbon dioxide at temperatures from 308.15 to 343.15K and pressures from 9 to 30MPa.

  5. A model for the adsorption of single metal ion solutes in aqueous solution onto activated carbon produced from pecan shells

    Microsoft Academic Search

    Seyed A. Dastgheib; David A. Rockstraw

    2002-01-01

    Adsorption isotherms for activated carbon made from pecan shells have been obtained at 25C and an approximate pH of 3 for a number of metal ion solutes. It was found that the Slips and Freundlich equations were satisfactory for explaining the experimental data. The correlation of metal ion adsorption with the solute parameters of metal ion electronegativity and first stability

  6. Solubility of carbon dioxide in aqueous solutions of 2-amino-2-methyl-1,3-propanediol

    SciTech Connect

    Baek, J.I.; Yoon, J.H. [Korea Electric Power Research Inst., Taejon (Korea, Republic of). Center for advanced Studies in Energy and the Environment] [Korea Electric Power Research Inst., Taejon (Korea, Republic of). Center for advanced Studies in Energy and the Environment

    1998-07-01

    The equilibrium solubility of carbon dioxide in aqueous solutions of 2-amino-2-methyl-1,3-propanediol (AMPD) has been measured at (30, 40, and 60) C and the partial pressure of carbon dioxide ranging from (0.5 to 3065) kPa. The concentrations of the aqueous solutions were (10 and 30) mass % AMPD. The tendency of the solubility of carbon dioxide in 30 mass % AMPD aqueous solution at 40 C was found to be similar to that in 30 mass % N-methyldiethanolamine aqueous solution.

  7. Novel graphene flowers modified carbon fibers for simultaneous determination of ascorbic acid, dopamine and uric acid.

    PubMed

    Du, Jiao; Yue, Ruirui; Ren, Fangfang; Yao, Zhangquan; Jiang, Fengxing; Yang, Ping; Du, Yukou

    2014-03-15

    A novel and sensitive carbon fiber electrode (CFE) modified by graphene flowers was prepared and used to simultaneously determine ascorbic acid (AA), dopamine (DA) and uric acid (UA). SEM images showed that beautiful and layer-petal graphene flowers homogeneously bloomed on the surface of CFE. Moreover, sharp and obvious oxidation peaks were found at the obtained electrode when compared with CFE and glassy carbon electrode (GCE) for the oxidation of AA, DA and UA. Also, the linear calibration plots for AA, DA and UA were observed, respectively, in the ranges of 45.4-1489.23 ?M, 0.7-45.21 ?M and 3.78-183.87 ?M in the individual detection of each component. By simultaneously changing the concentrations of AA, DA and UA, their oxidation peaks appeared at -0.05 V, 0.16 V and 2.6 V, and the good linear responses ranges were 73.52-2305.53 ?M, 1.36-125.69 ?M and 3.98-371.49 ?M, respectively. In addition, the obtained electrode showed satisfactory results when applied to the determination of AA, DA and UA in urine and serum samples. PMID:24140872

  8. Activated carbon enhanced ozonation of oxalate attributed to HO oxidation in bulk solution and surface oxidation: effect of activated carbon dosage and pH.

    PubMed

    Xing, Linlin; Xie, Yongbing; Minakata, Daisuke; Cao, Hongbin; Xiao, Jiadong; Zhang, Yi; Crittenden, John C

    2014-10-01

    Ozonation of oxalate in aqueous phase was performed with a commercial activated carbon (AC) in this work. The effect of AC dosage and solution pH on the contribution of hydroxyl radicals (HO) in bulk solution and oxidation on the AC surface to the removal of oxalate was studied. We found that the removal of oxalate was reduced by tert-butyl alcohol (tBA) with low dosages of AC, while it was hardly affected by tBA when the AC dosage was greater than 0.3g/L. tBA also inhibited ozone decomposition when the AC dosage was no more than 0.05g/L, but it did not work when the AC dosage was no less than 0.1g/L. These observations indicate that HO in bulk solution and oxidation on the AC surface both contribute to the removal of oxalate. HO oxidation in bulk solution is significant when the dosage of AC is low, whereas surface oxidation is dominant when the dosage of AC is high. The oxalate removal decreased with increasing pH of the solution with an AC dosage of 0.5g/L. The degradation of oxalate occurs mainly through surface oxidation in acid and neutral solution, but through HO oxidation in basic bulk solution. A mechanism involving both HO oxidation in bulk solution and surface oxidation was proposed for AC enhanced ozonation of oxalate. PMID:25288554

  9. Evaluation of carbons derived from Gingelly oil cake for the removal of lead(II) from aqueous solutions.

    PubMed

    Nagashanmugam, K B; Srinivasan, K

    2010-10-01

    The adsorption of lead(II) onto activated carbons prepared from Gingelly Oil Cake (GOC) by using thermal, sulphuric and zinc chloride activations was investigated. The effects of experimental parameters such as pH, initial concentration, contact time and adsorbents dosage on the lead(II) removal were studied. The data were fitted with Langmuir, Freundlich and Temkin models to describe the equilibrium isotherms. The kinetic data fitted well with Lagergren pseudo first order and pseudo second order models. The maximum adsorption capacity for lead(II) on adsorbents calculated from Langmuir isotherm was found to be 105.26 mg/g and 114.94 mg/g for thermally activated and sulphuric acid activated carbons respectively. R2 values show that Langmuir model fits best to sulphuric acid activated carbon and Freundlich model fits best to thermally activated and zinc chloride activated carbons. The kinetic rates were best fitted to pseudo second order model. FT-IR analysis was used to obtain information on the nature of possible interaction between adsorbents and metal ions. SEM images confirmed the adsorption of lead(II) onto GOC adsorbents through morphological observations. Thermodynamic study showed the feasibility of process and spontaneous nature of the adsorption. The adsorbents were also tested for the removal of lead(II) from lead battery synthetic wastewater. The results indicate that carbons derived from GOC could be used to effectively adsorb lead(II) from aqueous solutions and wastewaters. PMID:22312806

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

    PubMed Central

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

    2012-01-01

    An activated carbon, CarbochemTMPS230, 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 Jg?1 for catechol aqueous solutions in a range of 20 at 1500 mgL?1. PMID:22312237

  11. Temperature induced denaturation of collagen in acidic solution.

    PubMed

    Mu, Changdao; Li, Defu; Lin, Wei; Ding, Yanwei; Zhang, Guangzhao

    2007-07-01

    The denaturation of collagen solution in acetic acid has been investigated by using ultra-sensitive differential scanning calorimetry (US-DSC), circular dichroism (CD), and laser light scattering (LLS). US-DSC measurements reveal that the collagen exhibits a bimodal transition, i.e., there exists a shoulder transition before the major transition. Such a shoulder transition can recover from a cooling when the collagen is heated to a temperature below 35 degrees C. However, when the heating temperature is above 37 degrees C, both the shoulder and major transitions are irreversible. CD measurements demonstrate the content of triple helix slowly decreases with temperature at a temperature below 35 degrees C, but it drastically decreases at a higher temperature. Our experiments suggest that the shoulder transition and major transition arise from the defibrillation and denaturation of collagen, respectively. LLS measurements show the average hydrodynamic radius R(h), radius of gyration R(g)of the collagen gradually decrease before a sharp decrease at a higher temperature. Meanwhile, the ratio R(g)/R(h) gradually increases at a temperature below approximately 34 degrees C and drastically increases in the range 34-40 degrees C, further indicating the defibrillation of collagen before the denaturation. PMID:17431891

  12. The secondary structure of ribosomal ribonucleic acid in solution

    PubMed Central

    Cox, R. A.

    1966-01-01

    1. The u.v.-absorption spectrum of ribosomal RNA from rabbit reticulocytes was studied as a function of temperature at different pH values. The changes in the spectrum over the range 220320m? were interpreted on the basis of the assumption that the effect of denaturation and ionization are additive. The results suggest that in neutral salt solutions the secondary structure of the ribosomal RNA samples studied is due to two species of helical segments stabilized principally, if not solely, by complementary base pairs but differing in nucleotide composition: each species appears to be heterogeneous in other respects in view of the breadth of the melting ranges. 2. The number of base pairs per helical segment was estimated to be small (between 4 and 17) on the basis of the relation between melting temperature and chain length previously established by Lipsett and others for model compounds. Small fragments (about 2s) obtained by alkaline hydrolysis appeared to form the same helical segments as the intact molecule in accord with the estimated size of these segments. 3. Specific nucleotide sequences appear necessary to account for the hysteresis observed on titrating ribosomal RNA with acid or alkali within the range pH3070 since this phenomenon was less pronounced for Escherichia coli transfer RNA and for RNA from turnip yellow-mosaic virus. PMID:5330109

  13. 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. PMID:20199068

  14. Carbon Compounds in Pyrolysates and Amino Acids in Extracts of Apollo 14 Lunar Samples

    Microsoft Academic Search

    VINCENT E. MODZELESKI; JUDITH E. MODZELESKI; M. A. JABBAR MOHAMMED; LOIS ANNE NAGY; BARTHOLOMEW NAGY; WILLIAM S. McEWAN; HAROLD C. UREY; PAUL B. HAMILTON

    1973-01-01

    The analysis of seven samples brought back by the Apollo 14 astronauts is described. Carbon was present in the gases evolved to between 76 and 161 p.p.m. Glycine, aspartic acid, glutamic acid and serine were among the most abundant amnio acids found.

  15. THE BEHAVIOR OF AUSTENITIC STAINLESS STEEL CORROSION PRODUCTS IN HIGH TEMPERATURE BORIC ACID SOLUTIONS

    Microsoft Academic Search

    W. D. Fletcher; A. Krieg; P. Cohen

    1960-01-01

    Studies of the behavior of stainless steel corrosion products showed ; that boron, derived from high temperature boric acid solutions, is incorporated ; in synthetic corrosion products and in corrosion films. The extent of boron ; inclusion from high temperature boric acid solutions containing 1000 ppm B is of ; the order of 3 mg B per gram of synthetic

  16. FEATURE ARTICLE Unified Molecular Picture of the Surfaces of Aqueous Acid, Base, and Salt Solutions

    E-print Network

    FEATURE ARTICLE Unified Molecular Picture of the Surfaces of Aqueous Acid, Base, and Salt Solutions inorganic ions. Molecular dynamics calculations show that in salt solutions and bases the positively charged, consequently, these acids (unlike bases and salts) reduce the surface tension of water. The results

  17. Nitroimidazoles adsorption on activated carbon cloth from aqueous solution.

    PubMed

    Ocampo-Prez, R; Orellana-Garcia, F; Snchez-Polo, M; Rivera-Utrilla, J; Velo-Gala, I; Lpez-Ramn, M V; Alvarez-Merino, M A

    2013-07-01

    The objective of this study was to analyze the equilibrium and adsorption kinetics of nitroimidazoles on activated carbon cloth (ACC), determining the main interactions responsible for the adsorption process and the diffusion mechanism of these compounds on this material. The influence of the different operational variables, such as ionic strength, pH, temperature, and type of water (ultrapure, surface, and waste), was also studied. The results obtained show that the ACC has a high capacity to adsorb nitroimidazoles in aqueous solution. Electrostatic interactions play an important role at pH<3, which favors the repulsive forces between dimetridazole or metronidazole and the ACC surface. The formation of hydrogen bonds and dispersive interactions play the predominant role at higher pH values. Modifications of the ACC with NH3, K2S2O8, and O3 demonstrated that its surface chemistry plays a predominant role in nitroimidazole adsorption on this material. The adsorption capacity of ACC is considerably high in surface waters and reduced in urban wastewater, due to the levels of alkalinity and dissolved organic matter present in the different types of water. Finally, the results of applying kinetic models revealed that the global adsorption rate of dimetridazole and metronidazole is controlled by intraparticle diffusion. PMID:23623410

  18. The application of EQCM to the study of the electrochemical behavior of propylene carbonate solutions

    Microsoft Academic Search

    D. Aurbach; A. Zaban

    1995-01-01

    The electrochemical behavior of gold electrodes in propylene carbonate (PC) solutions was investigated using an electrochemical quartz crystal microbalance (EQCM). The solutions studied included uncontaminated LiAsF6 and LiPF6 solutions, and CO2 and H2O-containing LiAsF6 solutions. Surface film formation on the electrodes in these solutions was investigated during a potential scan from the open-circuit potential (OCV) to 0.5 V vs. LiLi+

  19. 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. PMID:25267993

  20. Quantitative prediction of 3D solution shape and flexibility of nucleic acid nanostructures

    E-print Network

    Dietz, Hendrik

    Quantitative prediction of 3D solution shape and flexibility of nucleic acid nanostructures Do designed using nucleic acids. INTRODUCTION Programmable self-assembly of complementary single- stranded nucleic acids is a versatile approach to designing sophisticated nanoscale structures (24). Scaffolded

  1. Probing counterion modulated repulsion and attraction between nucleic acid duplexes in solution

    E-print Network

    Das, Rhiju

    Probing counterion modulated repulsion and attraction between nucleic acid duplexes in solution Yu for review June 22, 2004) Understanding biological and physical processes involving nucleic acids of the ion atmosphere that surrounds nucleic acids. We have used a simple model DNA system to determine how

  2. HOUSEHOLD AND STRUCTURAL INSECTS Laboratory Evaluation of Boric Acid-Sugar Solutions as Baits

    E-print Network

    HOUSEHOLD AND STRUCTURAL INSECTS Laboratory Evaluation of Boric Acid-Sugar Solutions as Baits of boric acid and tend to be less efcacious than other insecticide baits. The purpose of this study and expressed as lethal time90, the time taken to kill 90% of the cockroaches. Results showed that boric acid

  3. VETERINARY ENTOMOLOGY Water Solutions of Boric Acid and Sugar for Management of German

    E-print Network

    VETERINARY ENTOMOLOGY Water Solutions of Boric Acid and Sugar for Management of German Cockroach for alternative control methods. Boric acid dust has long served as an insecticide in urban pest management of this study was to evaluate the efcacy of liquid baits containing boric acid for the control of German

  4. Corrosion control of CuNi alloys in neutral chloride solutions by amino acids

    Microsoft Academic Search

    Waheed A. Badawy; Khaled M. Ismail; Ahlam M. Fathi

    2006-01-01

    The corrosion inhibition of CuNi alloys was investigated in aqueous chloride solutions using amino acids as environmentally safe materials. The corrosion rate was calculated in absence and presence of the corrosion inhibitor using polarization and impedance techniques. The inhibition efficiency of the different amino acids was also calculated.The experimental results have shown that a simple amino acid like glycine can

  5. Effect of activated carbon surface oxygen- and/or nitrogen-containing groups on adsorption of copper(II) ions from aqueous solution

    SciTech Connect

    Biniak, S.; Pakula, M.; Szymanski, G.S.; Swiatkowski, A.

    1999-08-31

    The adsorption properties of a modified activated carbon with various oxygen-and/or nitrogen-containing surface groups toward copper ions was studied. Previously de-ashed and chemically modified commercial activated carbon D-43/1 (carbo-Tech, Essen, Germany) was used. The chemical properties of the modified carbon surface were estimated by standard neutralization titration with HCl, NaOH, and HaOC{sub 2}{sub 5}. The adsorption of Cu{sup 2+} ions on three modified activated carbons from aqueous CuSO{sub 4} solution of various pH was measured. The carbon samples with adsorbed Cu{sup 2+} ions were analyzed by spectroscopic methods (X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy). In addition, an electrochemical measurement (cyclic voltammetry) was performed using powdered activated carbon electrodes. While the modification procedures employed alter the surface only slightly, they strongly influence the surface chemical structure. Basic groups are predominant in the heat-treated samples; acidic functional groups are predominant in the oxidized sample. Both the copper cation adsorption studies and the spectral and electrochemical measurements show that adsorbed ions interact with the carbon surface in different ways. The number of adsorbed ions depends on the nature and quantity of surface acid-base functionalities and on the pH equilibrium in the aqueous solution. The possible mechanisms of interactions between metal ions and carbon surface functionalities are summarized and discussed.

  6. Emergency cooling experiments with aqueous boric acid solution in the REWET-II facility

    Microsoft Academic Search

    T. Kervinen; J. Tuunanen

    1987-01-01

    Although boron is widely used as soluble neutron poison in nuclear reactors (boric acid in pressurized water reactors, sodium pentaborate in boiling water reactors), there is a lack of experimental data about aqueous boron solution behavior during loss-of-coolant accidents. The main aims of the REWET boric acid experiments were to study the behavior of aqueous boric acid solution during long-term

  7. Bicarbonate\\/lactate-based peritoneal dialysis solution increases cancer antigen 125 and decreases hyaluronic acid levels

    Microsoft Academic Search

    Suzanne Jones; Clifford J. Holmes; Raymond T. Krediet; Ruth Mackenzie; Dirk Faict; Anders Tranaeus; John D. Williams; Gerald A. Coles; Nicholas Topley

    2001-01-01

    Bicarbonate\\/lactate peritoneal dialysate increases cancer antigen 125 and decreases hyaluronic acid levels.BackgroundIn a randomized, controlled trial comparing a pH neutral, bicarbonate\\/lactate (B\\/L)-buffered PD solution to conventional acidic, lactate-buffered solution (C), the overnight dialysate levels of markers of inflammation\\/wound healing [hyaluronic acid (HA)], mesothelial cell mass\\/membrane integrity [cancer antigen 125 (CA125)], and fibrosis [transforming growth factor-?1 (TGF-?1) and procollagen I peptides

  8. 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??M), 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

  9. Removal of chlorophenols from wastewater using commercial acid washed activated carbon.

    PubMed

    El-Dars, Farida M S E; Sayed, Said A; Khalifa, Mohammed G; Alotieby, Abdel Rahman M S; Shalabi, Mohamed E H

    2013-07-01

    The presence of chlorophenols in wastewater represents a serious challenge for its treatment and its further reuse. In this study, the use of commercial acid washed activated carbon as sorbent material for the removal of 2 chlorophenol, 2,4 dichlorophenol and 2,4,6 trichlorophenol from synthetic. aqueous solutions is evaluated. Variables affecting the uptake of these compounds (weight of sorbent material, pH, temperature and shaking time) are investigated to achieve the optimum conditions of removal process. The kinetics of the uptake process indicated that the process was best explained using a pseudo-second order model. As well, the adsorption of the studied chlorophenols on commercially available AC followed the Freundlich isotherm. The thermodynamic parameters further indicated the favorability of the process and that the adsorption was primarily physical in nature enhanced by chemisorptions. PMID:25509944

  10. Tannic acid reduces recovery of water-soluble carbon and nitrogen from soil and affects the composition of Bradford-reactive soil protein

    Microsoft Academic Search

    Jonathan J. Halvorson; Javier M. Gonzalez

    2008-01-01

    Tannins are plant-derived polyphenolic compounds that precipitate proteins, bind to metals and complex with other compounds. Solutions of tannic acid, or other phenolic compounds, were added to soil samples to determine if they would affect recovery of soluble soil carbon (WSC) or nitrogen (WSN) or influence the extraction and composition of Bradford-reactive soil protein (BRSP), associated with glomalin. Tannic acid-C

  11. Comparison of CO2 and oxygen DC submerged thermal plasmas for decomposition of carboxylic acid in aqueous solution

    NASA Astrophysics Data System (ADS)

    Safa, S.; Hekmat-Ardakan, A.; Soucy, G.

    2014-11-01

    The feasibility of the carboxylic acid decomposition with two different direct current (DC) thermal plasma torches was investigated. An oxygen DC submerged thermal plasma torch and a newly designed submerged DC plasma torch operating with a mixture of carbon dioxide and methane (CO2/CH4) were used. Sebacic acid was selected as a representative of pollutants in the most wastewater produced by chemical process industries. The effect of different operational conditions including treatment time, the reactor pressure as well as the role of oxidizing agents such as (H2O2) were investigated on the decomposition rate of sebacic acid. Concentration of sebacic acid was quantified by Ion Chromatography/Mass Spectrometry (IC/MS). The oxygen plasma showed higher decomposition rate in basic medium. Adding H2O2 into aqueous solution enhanced the sebacic acid decomposition rate with the CO2/CH4 plasma up to the same decomposition rate of the oxygen plasma. Increasing the pressure also increased the decomposition rate for both plasmas with an increase twice higher for the CO2/CH4 plasma than that of the oxygen plasma. This work therefore presents the conditions in which these plasmas can provide the same decomposition rate for contaminants in aqueous solution.

  12. Isothermal heat measurements of TBP-nitric acid solutions

    SciTech Connect

    Smith, J.R.; Cavin, W.S.

    1994-12-16

    Net heats of reaction were measured in an isothermal calorimeter for both single phase (organic) and two phase (organic and aqueous) TBP/HNO{sub 3} reacting solutions at temperatures above 100 C. The oxidation rate constant was determined to be 5.4E-4 min{sup {minus}1} at 110 C for an open ``vented`` system as compared to 1.33 E-3 min{sup {minus}1} in the closed system. The heat released per unit material oxidized was also reduced. The oxidation in both phases was found to be first order in nitric acid and pseudo-zero order in butylnitrate and water. The hydrolysis (esterification) rate constant determined by Nichols` (1.33E-3 min{sup {minus}1}) fit the experimental data from this work well. Forced evaporation of the volatile components by the product gases from oxidation resulted in a cooling mechanism which more than balanced the heat from the oxidation reaction in the two-phased systems. Rate expressions were derived and rate constants determined for both the single and two phase systems. An approximating mathematical model was developed to fit the experimental data and to extrapolate beyond the experimental conditions. This model shows that one foot of ``reacting`` 14.3M HNO{sub 3} aqueous phase solution at 121 C will transport sufficient water to the organic phase to replace evaporative losses, maintaining endothermicity, for organic layers up to 12.2 + 6.0 feet deep. If the pressure in a reacting system is allowed to increase due to insufficient venting the temperature of the organic phase would increase in temperature to reach a new equilibrium. The rate of oxidation would increase not only due to the increase in temperature but also from the increased concentration of dissolved HNO{sub 3} reduction products. Another important factor is that the cooling system described in this work becomes less effective as the total pressure increases. These factors probably contributed to the explosion at Tomsk.

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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.

  14. 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

    2012-06-01

    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. PMID:22538869

  15. THE SOLAR NEBULA ON FIRE: A SOLUTION TO THE CARBON DEFICIT IN THE INNER SOLAR SYSTEM

    SciTech Connect

    Lee, Jeong-Eun [Department of Astronomy and Space Science, Astrophysical Research Center for the Structure and Evolution of the Cosmos, Sejong University, Seoul 143-747 (Korea, Republic of); Bergin, Edwin A. [Department of Astronomy, The University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States); Nomura, Hideko [Department of Astronomy, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)], E-mail: jelee@sejong.ac.kr, E-mail: ebergin@umich.edu, E-mail: nomura@kusastro.kyoto-u.ac.jp

    2010-02-10

    Despite a surface dominated by carbon-based life, the bulk composition of the Earth is dramatically carbon poor when compared to the material available at formation. Bulk carbon deficiency extends into the asteroid belt representing a fossil record of the conditions under which planets are born. The initial steps of planet formation involve the growth of primitive sub-micron silicate and carbon grains in the Solar Nebula. We present a solution wherein primordial carbon grains are preferentially destroyed by oxygen atoms ignited by heating due to stellar accretion at radii <5 AU. This solution can account for the bulk carbon deficiency in the Earth and meteorites, the compositional gradient within the asteroid belt, and for growing evidence for similar carbon deficiency in rocks surrounding other stars.

  16. Removal of total organic carbon from aqueous solution containing polyvinyl alcohol by electrocoagulation technology

    Microsoft Academic Search

    Wei-Lung Chou; Chih-Ta Wang; Chia-Wei Hsu; Kai-Yu Huang; Te-Chao Liu

    2010-01-01

    The removal of total organic carbon (TOC) from aqueous solution containing polyvinyl alcohol (PVA) using iron electrocoagulation (EC) was investigated. Iron hydroxides generated during EC were used to remove PVA and TOC from the aqueous solution, and the effects of varying current density and solution temperature on PVA and TOC adsorption characteristics were evaluated. The findings indicated that complete PVA

  17. Adsorptive removal of aniline by granular activated carbon from aqueous solutions with catechol and resorcinol

    Microsoft Academic Search

    S. Suresh; V. C. Srivastava; I. M. Mishra

    2012-01-01

    In the present paper, the removal of aniline by adsorption process onto granular activated carbon (GAC) is reported from aqueous solutions containing catechol and resorcinol separately. The Taguchi experimental design was applied to study the effect of such parameters as the initial component concentrations (C0, i) of two solutes (aniline and catechol or aniline and resorcinol) in the solution, temperature

  18. Effect of boric acid on the severity of vapor explosions in pure water and surfactant solutions

    Microsoft Academic Search

    W. T. W. Skelton; M. F. Dowling; S. I. Abdel-Khalik

    1995-01-01

    Four different dilute aqueous solutions of boric acid and surfactant\\/boric acid were tested to determine the impact of these coolant additives on the severity of vapor explosions in small-scale experiments with molten tin. Twelve grams of molten tin at 800C were dropped into 6 l of coolant solution at room temperature; for each solution, the experiment was repeated 20 times.

  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. 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.

  1. Composites of manganese oxide with carbon materials as catalysts for the ozonation of oxalic acid.

    PubMed

    Orge, C A; rfo, J J M; Pereira, M F R

    2012-04-30

    Manganese oxide and manganese oxide-carbon composites were prepared and tested as catalysts for the removal of oxalic acid by ozonation. Their performances were compared with the parent carbon material (activated carbon or carbon xerogel) used to prepare the composites. Oxalic acid degradation by carbon materials is slower than that attained with manganese oxide or manganese oxide-carbon composites. A complete degradation after 90 and 45 min of reaction was obtained for carbon materials and for the catalysts containing manganese, respectively. The ozonation in the presence of the prepared composites are supposed to occur mainly by surface reactions, following a direct oxidation mechanism by molecular ozone and/or surface oxygenated radicals. PMID:22341747

  2. Carbon nanotubes induced gelation of unmodified hyaluronic acid.

    PubMed

    Zamora-Ledezma, Camilo; Buisson, Lionel; Moulton, Simon E; Wallace, Gordon; Zakri, Ccile; Blanc, Christophe; Anglaret, Eric; Poulin, Philippe

    2013-08-13

    This work reports an experimental study of the kinetics and mechanisms of gelation of carbon nanotubes (CNTs)-hyaluronic acid (HA) mixtures. These materials are of great interest as functional biogels for future medical applications and tissue engineering. We show that CNTs can induce the gelation of noncovalently modified HA in water. This gelation is associated with a dynamical arrest of a liquid crystal phase separation, as shown by small-angle light scattering and polarized optical microscopy. This phenomenon is reminiscent of arrested phase separations in other colloidal systems in the presence of attractive interactions. The gelation time is found to strongly vary with the concentrations of both HA and CNTs. Near-infrared photoluminescence reveals that the CNTs remain individualized both in fluid and in gel states. It is concluded that the attractive forces interplay are likely weak depletion interactions and not strong van der Waals interactions which could promote CNT rebundling, as observed in other biopolymer-CNT mixtures. The present results clarify the remarkable efficiency of CNT at inducing the gelation of HA, by considering that CNTs easily phase separate as liquid crystals because of their giant aspect ratio. PMID:23848357

  3. Recovery of uranium from phosphoric acid solutions using chelating ion-exchange resins

    Microsoft Academic Search

    N. Kabay; M. Demircioglu; S. Yayh; E. Guenay; M. Yueksel; M. Saglam; M. Streat

    1998-01-01

    In fertilizer manufacture, calcium phosphate in phosphate rock is rendered soluble by sulfuric acid attack. The phosphoric acid obtained in this way usually contains 26%--28% PO. Several novel processes have been developed for the recovery of uranium from wet-process phosphoric acid. Experimental measurements have been made on the batch extraction of uranium from phosphoric acid solutions using various chelating ion-exchange

  4. Changes in the Morphology and Proliferation of Astrocytes Induced by Two Modalities of Chemically Functionalized Single-Walled Carbon Nanotubes are Differentially Mediated by Glial Fibrillary Acidic Protein

    PubMed Central

    2015-01-01

    Alterations in glial fibrillary acidic protein (GFAP) levels accompany the changes in the morphology and proliferation of astrocytes induced by colloidal solutes and films of carbon nanotubes (CNTs). To determine if GFAP is required for the effects of CNTs on astrocytes, we used astrocytes isolated from GFAP null mice. We find that selected astrocytic changes induced by CNTs are mediated by GFAP, i.e., perimeter, shape, and cell death for solutes, and proliferation for films. PMID:24875845

  5. Biological denitrification of brine: the effect of compatible solutes on enzyme activities and fatty acid degradation.

    PubMed

    Cyplik, Pawe?; Piotrowska-Cyplik, Agnieszka; Marecik, Roman; Czarny, Jakub; Drozdzy?ska, Agnieszka; Chrzanowski, ?ukasz

    2012-09-01

    The effect of the addition of compatible solutes (ectoine and trehalose) on the denitrification process of saline wastewater was studied. In saline wastewater, it was observed that the initial concentration of nitrates was 500 mg N l?. A fatty substance isolated from oiled bleaching earth (waste of vegetable oil refining process) was used as a source of carbon.The consortium, which was responsible for the denitrification process originated from the wastewater of the vegetable oil industry. The consortium of microorganisms was identified by the use of restriction fragment length polymorphism of 16S rRNA gene amplicons and sequencing techniques. It was noted that ectoine affects significantly the activity of lipase and nitrate reductase, and resulted in faster denitrification compared to saline wastewater with the addition of trehalose or control saline wastewater (without compatible solutes). It was observed that relative enzyme activities of lipase and nitrate reductase increased by 32 and 35%, respectively, in the presence of 1 mM ectoine. This resulted in an increase in specific nitrate reduction rate in the presence of 1 mM ectoine to 5.7 mg N g? VSS h?, which was higher than in the absence of ectoine (3.2 mg N g? VSS h?). The addition of trehalose did not have an effect on nitrate removals. Moreover, it was found that trehalose was used up completely by bacteria as a source of carbon in the denitrification process. The fatty acids were biodegraded by 74% in the presence of 1 mM ectoine. PMID:22286267

  6. Oxalic acid complexes: promising draw solutes for forward osmosis (FO) in protein enrichment.

    PubMed

    Ge, Qingchun; Chung, Tai-Shung

    2015-03-21

    Highly soluble oxalic acid complexes (OACs) were synthesized through a one-pot reaction. The OACs exhibit excellent performance as draw solutes in FO processes with high water fluxes and negligible reverse solute fluxes. Efficient protein enrichment was achieved. The diluted OACs can be recycled via nanofiltration and are promising as draw solutes. PMID:25697506

  7. Dynamic Rheological Studies of Poly(p-phenyleneterephthalamide) and Carbon Nanotube Blends in Sulfuric Acid

    PubMed Central

    Cao, Yutong; Liu, Zhaofeng; Gao, Xianghua; Yu, Junrong; Hu, Zuming; Liang, Ziqi

    2010-01-01

    We have studied the dynamic scanning of liquid-crystalline (LC) poly(p-phenyleneterephthalamide) sulfuric acid (PPTA-H2SO4) solution, and its blend with single-walled carbon nanotubes (SWNTs), by using a flat plate rotational rheometer. The effects of weight concentration and molecular weight of PPTA, as well as operating temperature, on dynamic viscoelasticity of the PPTA-H2SO4 LC solution system are discussed. The transition from a biphasic system to a single-phase LC occurs in the weight concentration range of SWNTs from 0.1% to 0.2%, in which complex viscosity reaches the maximum at 0.2 wt% and the minimum at 0.1 wt%, respectively, of SWNTs. With increasing SWNT weight concentration, the endothermic peak temperature increases from 73.6 to 79.9 C. The PPTA/SWNT/H2SO4 solution is in its plateau zone and storage modulus (G?) is a dominant factor within the frequency (?) range of 0.110 rad/s. As ? increases, the G? rises slightly, in direct proportion to the ?. The loss modulus (G?) does not rise as a function of ? when ? < 1 s?1, then when ? > 1 s?1 G? increases faster than G?, yet not in any proportion to the ?. PMID:20480024

  8. Picosecond Pulse Radiolysis of Highly Concentrated Phosphoric Acid Solutions: Mechanism of Phosphate Radical Formation.

    PubMed

    Ma, Jun; Schmidhammer, Uli; Mostafavi, Mehran

    2015-06-18

    Eight solutions containing phosphoric acid with concentrations ranging from 2 mol L(-1) to neat acid have been studied by picosecond pulse radiolysis. The absorbance of the secondary radical H2PO4() formed within 7 ps of the electron pulse is observed using pulse-probe method in the visible. Kinetic analysis shows that the radicals of phosphoric acid are formed via two mechanisms: direct electron detachment and oxidation by the radical cation of water, H2O(+). On the basis of molar extinction coefficient value of 1850 L mol(-1) cm(-1), at 15 ps the radiolytic yield of H2PO4() formation by direct energy absorption is 3.7 0.1 10(-7) mol J(-1) in neat phosphoric acid. In highly concentrated phosphoric acid solutions, the total yield of phosphate radical at 15 ps exhibits an additional contribution that can be explained by electron transfer from phosphoric acid to H2O(+). The efficiency of the electron transfer to this strongly oxidizing species in phosphoric acid solutions is lower compared with the one in sulfuric acid solutions. Two explanations are given to account for a relatively low efficiency of H2O(+) scavenging in concentrated phosphoric acid solutions. PMID:25176139

  9. Acid Solutions for Etching Corrosion-Resistant Metals

    NASA Technical Reports Server (NTRS)

    Simmons, J. R.

    1982-01-01

    New study characterized solutions for etching austenitic stainless steels, nickel-base alloys, and titanium alloys (annealed). Solutions recommended for use remove at least 0.4 mil of metal from surface in less than an hour. Solutions do not cause intergranular attack on metals for which they are effective, when used under specified conditions.

  10. Surface heterogeneity effects of activated carbons on the kinetics of paracetamol removal from aqueous solution

    NASA Astrophysics Data System (ADS)

    Ruiz, B.; Cabrita, I.; Mestre, A. S.; Parra, J. B.; Pires, J.; Carvalho, A. P.; Ania, C. O.

    2010-06-01

    The removal of a compound with therapeutic activity (paracetamol) from aqueous solutions using chemically modified activated carbons has been investigated. The chemical nature of the activated carbon material was modified by wet oxidation, so as to study the effect of the carbon surface chemistry and composition on the removal of paracetamol. The surface heterogeneity of the carbon created upon oxidation was found to be a determinant in the adsorption capability of the modified adsorbents, as well as in the rate of paracetamol removal. The experimental kinetic data were fitted to the pseudo-second order and intraparticle diffusion models. The parameters obtained were linked to the textural and chemical features of the activated carbons. After oxidation the wettability of the carbon is enhanced, which favors the transfer of paracetamol molecules to the carbon pores (smaller boundary layer thickness). At the same time the overall adsorption rate and removal efficiency are reduced in the oxidized carbon due to the competitive effect of water molecules.

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

    DOEpatents

    Scheitlin, Frank M. (Oak Ridge, TN)

    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.

  12. Molten Carbonate and Phosphoric Acid Stationary Fuel Cells: Overview and Gap Analysis

    SciTech Connect

    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.

  13. Solubility of linoleic acid in aqueous solutions and its reaction with water

    Microsoft Academic Search

    Ahmed Fahmy Mabrouk; L. R. Dugan

    1961-01-01

    In a study of stable emulsions of linoleic acid in 0.1M-KH2PO4\\/Na2HPO4 buffer solutions prepared by sonic vibrations, the influence of linoleic acid on pH was manifested in buffer solutions of\\u000a pH 8.00 and decreased gradually till it became negligible in pH 4.50. This change in pH values was due to differences in solubility\\u000a of linoleic acid in the buffer solutions.

  14. Physicochemical properties of carbons prepared from pecan shell by phosphoric acid activation

    Microsoft Academic Search

    Yanping Guo; David A. Rockstraw

    2007-01-01

    Activated carbons were prepared from pecan shell by phosphoric acid activation. The pore structure and acidic surface groups of these carbons were characterized by nitrogen adsorption, Boehm titration and transmittance Fourier infrared spectroscopy (FTIR) techniques. The characterization results demonstrated that the development of pore structure was apparent at temperatures ?250C, and reached 1130m2\\/g and 0.34cm3\\/g, respectively, at 500C. Impregnation ratio

  15. Carbon-supported PdIr catalyst as anodic catalyst in direct formic acid fuel cell

    Microsoft Academic Search

    Xin Wang; Yawen Tang; Ying Gao; Tianhong Lu

    2008-01-01

    It was reported for the first time that the electrocatalytic activity of the Carbon-supported PdIr (PdIr\\/C) catalyst with the suitable atomic ratio of Pd and Ir for the oxidation of formic acid in the direct formic acid fuel cell (DFAFC) is better than that of the Carbon-supported Pd (Pd\\/C) catalyst, although Ir has no electrocatalytic activity for the oxidation of

  16. A model for matrix acidizing of long horizontal well in carbonate reservoirs

    E-print Network

    Mishra, Varun

    2009-06-02

    A MODEL FOR MATRIX ACIDIZING OF LONG HORIZONTAL WELL IN CARBONATE RESERVOIRS A Thesis by VARUN MISHRA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE August 2007 Major Subject: Petroleum Engineering A MODEL FOR MATRIX ACIDIZING OF LONG HORIZONTAL WELL IN CARBONATE RESERVOIRS A Thesis by VARUN MISHRA Submitted to the Office...

  17. Chemical evaluation of soil-solution in acid forest soils

    USGS Publications Warehouse

    Lawrence, G.B.; David, M.B.

    1996-01-01

    Soil-solution chemistry is commonly studied in forests through the use of soil lysimeters.This approach is impractical for regional survey studies, however, because lysimeter installation and operation is expensive and time consuming. To address these problems, a new technique was developed to compare soil-solution chemistry among red spruce stands in New York, Vermont, New Hampshire, Maine. Soil solutions were expelled by positive air pressure from soil that had been placed in a sealed cylinder. Before the air pressure was applied, a solution chemically similar to throughfall was added to the soil to bring it to approximate field capacity. After the solution sample was expelled, the soil was removed from the cylinder and chemically analyzed. The method was tested with homogenized Oa and Bs horizon soils collected from a red spruce stand in the Adirondack Mountains of New York, a red spruce stand in east-central Vermont, and a mixed hardwood stand in the Catskill Mountains of New York. Reproducibility, effects of varying the reaction time between adding throughfall and expelling soil solution (5-65 minutes) and effects of varying the chemical composition of added throughfall, were evaluated. In general, results showed that (i) the method was reproducible (coefficients of variation were generally < 15%), (ii) variations in the length of reaction-time did not affect expelled solution concentrations, and (iii) adding and expelling solution did not cause detectable changes in soil exchange chemistry. Concentrations of expelled solutions varied with the concentrations of added throughfall; the lower the CEC, the more sensitive expelled solution concentrations were to the chemical concentrations of added throughfall. Addition of a tracer (NaBr) showed that the expelled solution was a mixture of added solution and solution that preexisted in the soil. Comparisons of expelled solution concentrations with concentrations of soil solutions collected by zero-tension and tension lysimetry indicated that expelled solution concentrations were higher than those obtained with either type of lysimeter, although there was less difference with tension lysimeters than zero-tension lysimeters. The method used for collection of soil solution should be taken into consideration whenever soil solution data are being interpreted.

  18. Degradation and removal of naphthalenesulphonic acids by means of adsorption and ozonation catalyzed by activated carbon in water

    Microsoft Academic Search

    J. Rivera-Utrilla; M. Snchez-Polo

    2003-01-01

    Studies were conducted on the efficiency of systems based on the use of ozone, activated carbon, and ozone\\/activated carbon in the treatment of waters containing 1-naphthalenesulphonic acid, 1,5-naphthalenedisulphonic acid, and 1,3,6-naphthalenetrisulphonic acid. In the removal of these acids by adsorption on activated carbon the elevated heights of the mass transfer zone columns and the low values of the breakthrough volumes

  19. Carbon 40 (2002) 12491254 Oxidation protection of carbon materials by acid phosphate

    E-print Network

    Chung, Deborah D.L.

    2002-01-01

    materials (polycrystalline graphite and pitch-based carbon fiber), as shown by weight measurement in air up Science Ltd. All rights reserved. Keywords: A. Carbon fibers, Synthetic graphite; B. Oxidation carbon fibers, provides oxidation protection in a lower temperature range carboncarbon composites

  20. High-pressure and high-temperature Raman spectroscopy of carbonate ions in aqueous solution

    Microsoft Academic Search

    Isabelle Martinez; Carmen Sanchez-Valle; Isabelle Daniel; Bruno Reynard

    2004-01-01

    Two aqueous solutions of sodium carbonate (0.5 and 2 m) have been studied by in situ Raman spectroscopy in the 130 GPa, 25400 C pressuretemperature (PT) range, in an externally heated diamond anvil cell. Neither bicarbonate ions nor CO2 species were observed; carbonate ions were found to be the major species in these solutions over the entire PT range investigated,

  1. Electrolytic Recovery of Cadmium from Cyanide Washing Solutions on Filtering Carbon-Graphite Electrodes

    Microsoft Academic Search

    V. K. Varentsov

    2003-01-01

    Electrorecovery of cadmium(II) on filtering carbon-graphite electrodes from washing cyanide solutions formed in cadmium-plating of articles in a cyanide electrolyte was studied. The effect of the dilution factor of the supporting electrolyte on the run of cathodic polarization curves, pH value, and solution resistivity was analyzed. The influence exerted by the efficiency of cadmium(II) recovery on the carbon-graphite electrodes was

  2. Comparison of activated carbon and ion-exchange resins in recovering copper from cyanide leach solutions

    Microsoft Academic Search

    X. Dai; P. L. Breuer; M. I. Jeffrey

    2010-01-01

    The use of activated carbon and ion-exchange resins for recovering copper cyanide from gold leach solutions is compared in detail. When using activated carbon, the overall cyanide-to-copper ratio should be reduced to ?2 to achieve the most effective adsorption. This can be accomplished by dissolving metallic copper into the leach solution. However when using ion-exchange resins to recover the copper,

  3. Effect of acidic solutions on the surface degradation of a micro-hybrid composite resin.

    PubMed

    Mnchow, Eliseu A; Ferreira, Ana Cludia A; Machado, Raissa M M; Ramos, Tatiana S; Rodrigues-Junior, Sinval A; Zanchi, Cesar H

    2014-01-01

    Composite resins may undergo wear by the action of chemical substances (e.g., saliva, alcohol, bacterial acids) of the oral environment, which may affect the material's structure and surface properties. This study evaluated the effect of acidic substances on the surface properties of a micro-hybrid composite resin (Filtek Z-250). Eighty specimens were prepared, and baseline hardness and surface roughness (KMN0 and Ra0, respectively) were measured. The specimens were subjected to sorption (SO) and solubility (SL) tests according to ISO 4049:2009, but using different storage solutions: deionized water; 75/25 vol% ethanol/water solution; lactic acid; propionic acid; and acetic acid. The acids were used in two concentrations: PA and 0.02 N. pH was measured for all solutions and final hardness (KMN1) and surface roughness (Ra1) were measured. Data were analyzed with paired t-tests and one-way ANOVA and Tukey's test (a=5%). All solutions decreased hardness and increased the Ra values, except for the specimens stored in water and 0.02 N lactic acid, which maintained the hardness. All solutions produced similar SO and SL phenomena, except for the 0.02 N lactic acid, which caused lower solubility than the other solutions. Ethanol showed the highest pH (6.6) and the 0.02 N lactic acid the lowest one (2.5). The solutions affected negatively the surface properties of the composite resin; in addition, an acidic pH did not seem to be a significant factor that intensifies the surface degradation phenomena. PMID:25250496

  4. The Breakdown Mechanism of Diamond Like Carbon Coated Nickel in Chloride Solution

    E-print Network

    The Breakdown Mechanism of Diamond Like Carbon Coated Nickel in Chloride Solution R.S. Lillard, D deposited nickel (CVD Ni) coated with 5 micro- meters of diamond like carbon (DLC) produced by plasma source analyzed within the context of an equivalent circuit model which incorporated three time constants

  5. SiC coating on carbon fibres by a solution coating process

    Microsoft Academic Search

    Yu-Qing Wang; Zuo-Ming Wang; Jun-Ying Yang; Feng-Qiu Zhang; Ben-Lian Zhou

    1995-01-01

    One way of overcoming the shortcomings of carbon fibres is to coat them with SiC. In this work, carbon fibres were coated with a polycarbosilane solution and then pyrolysed continuously at high temperature to obtain the SiC coating. Effects of the coating process on the structure of the coating and the properties of the coated fibres were studied in detail.

  6. In vitro effectiveness of acidic and alkline solutions on scolices of hydatid cyst.

    PubMed

    Moazeni, Mohammad; Larki, Sara

    2010-03-01

    The most confident way for treatment of hydatid cyst is surgical operation. Spillage of the cyst contents during the operation is the major cause of recurrence after hydatid cyst surgery. Instillation of scolicidal agent into hydatid cyst is the most commonly employed measure to prevent this complication. In the present study, the scolicidal effect of highly acidic and alkaline solutions is investigated. Protoscoleces were collected aseptically from sheep livers containing hydatid cyst. Acidic solutions with pH 1, 2, 3, and 4 and alkaline solutions with pH 11, 12, 13, and 14 were used for 5,10, and 15 min in the experiments. Viability of protoscoleces was assessed by 0.1% eosin staining. Scolicidal effect of acidic solution with pH 1 after 5 min and with pH 2 and 3 after 10 min was 100%. Scolicidal effect of acidic solution with pH 2 and 3 after 5 min was 99.6% and 98.7%, respectively. Acidic solution with pH 4 after 5, 10, and 15 min killed 15.5%, 21.5%, and 22.6% of protoscoleces, respectively. Alkaline solution with pH 14 after 5 min and with pH 13 after 15 min killed all protoscoleces. The scolicidal effect of alkaline solution with pH 13 after 5 and 10 min was also 97.5% and 99.7%, respectively. These values for alkaline solution with pH 12 were 29.33%, 33.44% and 37.09%, respectively. The scolicidal effect of solution with pH 11 was 24.5%, 30.5%, and 31.3%, respectively. Although the in vitro scolicidal effect of highly acidic or alkaline solutions was satisfactory in our study, in vivo efficacy of these solutions and also possible side effects, remain to be more investigated. PMID:20111875

  7. 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, and Steubenville, OH.

  8. Activated Carbon from Peach Stones Using Phosphoric Acid Activation at Medium Temperatures

    Microsoft Academic Search

    Dong-Su Kim

    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

  9. Chemical modification of carbon fiber surfaces by nitric acid oxidation followed by reaction with tetraethylenepentamine

    Microsoft Academic Search

    C. U. Pittman; G.-R. He; B. Wu; S. D. Gardner

    1997-01-01

    Amino groups react rapidly with both isocyanates and epoxides. Thus, to prepare carbon fibers which might exhibit enhanced adhesion to both polyurethanes and epoxy resin matrices, attempts were made to introduce a high surface amine concentration onto high-strength carbon fibers (derived from PAN) by nitric acid oxidation followed by reaction with excess tetraethylenepentamine (TEPA). Fibers were oxidized with concentrated (70%)

  10. Influence of acidic surface oxides of activated carbon on gas adsorption characteristics

    Microsoft Academic Search

    H. Tamon; M. Okazaki

    1996-01-01

    An activated carbon was oxidized by HNO3 at boiling temperature. The influence of acidic surface oxides of the activated carbon was experimentally studied on the adsorption characteristics of eleven different gases or vapors. In the adsorption of cyclohexane, benzene, 2-propanol and 2-butanol, the adsorption capacity decreased greatly with oxidizing the carbon by 13.2 N HNO3. This was because the surface

  11. The development and characterisation of polyanilinesingle walled carbon nanotube composite fibres using 2-acrylamido-2 methyl-1-propane sulfonic acid (AMPSA) through one step wet spinning process

    Microsoft Academic Search

    Vahid Mottaghitalab; Geoffrey M. Spinks; Gordon G. Wallace

    2006-01-01

    High strength, flexible and conductive polyaniline (PANi)carbon nanotube (SWNT) composite fibres have been produced using wet spinning. The use of dichloroacetic acid (DCAA) containing 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPSA) has been shown to act as an excellent dispersing medium for carbon nanotubes and for dissolution of polyaniline. The viscosity of DCAAAMPSA solution undergoes a transition from Newtonian to non-Newtonian viscoelastic behaviour

  12. The inhibition effect of some amino acids towards PbSbSeAs alloy corrosion in sulfuric acid solution

    Microsoft Academic Search

    Z. Ghasemi; A. Tizpar

    2006-01-01

    The inhibition effect of three amino acids towards the corrosion of PbSbSeAs alloy in 1.28 s.g. H2SO4 solution was investigated with linear polarization and weight loss measurements methods. The results drawn from two different techniques are comparable. The used amino acids were tryptophane, proline and methionine. The effect of inhibitor concentration and temperature against inhibitor action was investigated. It was

  13. Inhibitory effect of some amino acids on corrosion of PbCaSn alloy in sulfuric acid solution

    Microsoft Academic Search

    M. A. Kiani; M. F. Mousavi; S. Ghasemi; M. Shamsipur; S. H. Kazemi

    2008-01-01

    The present article describes the inhibition effect of amino acids cysteine (Cys), methionine (Met) and alanine (Ala), towards the corrosion of lead-alloy (PbCaSn) in H2SO4 solution by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), weight loss measurement and scanning electron microscopy (SEM) methods. The influence of inhibitor concentration, temperature and time on inhibitory behavior of the amino acids was investigated. The

  14. Separation of ions in acidic solution by capillary electrophoresis

    SciTech Connect

    Thornton, M.

    1997-10-08

    Capillary electrophoresis (CE) is an effective method for separating ionic species according to differences in their electrophoretic mobilities. CE separations of amino acids by direct detection are difficult due to their similar electrophoretic mobilities and low absorbances. However, native amino acids can be separated by CE as cations at a low pH by adding an alkanesulfonic acid to the electrolyte carrier which imparts selectivity to the system. Derivatization is unnecessary when direct UV detection is used at 185 nm. Simultaneous speciation of metal cations such as vanadium (IV) and vanadium (V) can easily be performed without complexation prior to analysis. An indirect UV detection scheme for acidic conditions was also developed using guanidine as the background carrier electrolyte (BCE) for the indirect detection of metal cations. Three chapters have been removed for separate processing. This report contains introductory material, references, and general conclusions. 80 refs.

  15. Experimental investigation of detonation of nitric acid solutions

    Microsoft Academic Search

    V. M. Raikova; B. N. Kondrikov; G. D. Kozak

    1998-01-01

    Detonation of mixtures of concentrated (94100%) nitric acid with nitromethane, diethylene glycol dinitrate, nitroglycol,\\u000a trinitrotoluene, dinitrotoluene, acetic anhydride, and dichlorethane was studied experimentally. The detonation failure diameter\\u000a was measured in glass tubes. For mixtures of nitric acid with nitromethane, dinitrotoluene, and trinitrotoluene, its minimum\\u000a values are smaller than 1 mm and correspond to zero oxygen balance of the mixtures (A=0).

  16. Vapor-liquid equilibria for nitric acid-water and plutonium nitrate-nitric acid-water solutions

    SciTech Connect

    Maimoni, A.

    1980-01-01

    The liquid-vapor equilibrium data for nitric acid and nitric acid-plutnonium nitrate-water solutions were examined to develop correlations covering the range of conditions encountered in nuclear fuel reprocessing. The scanty available data for plutonium nitrate solutions are of poor quality but allow an order of magnitude estimate to be made. A formal thermodynamic analysis was attempted initially but was not successful due to the poor quality of the data as well as the complex chemical equilibria involved in the nitric acid and in the plutonium nitrate solutions. Thus, while there was no difficulty in correlating activity coefficients for nitric acid solutions over relatively narrow temperature ranges, attempts to extend the correlations over the range 25/sup 0/C to the boiling point were not successful. The available data were then analyzed using empirical correlations from which normal boiling points and relative volatilities can be obtained over the concentration ranges 0 to 700 g/l Pu, 0 to 13 M nitric acid. Activity coefficients are required, however, if estimates of individual component vapor pressures are needed. The required ternary activity coefficients can be approximated from the correlations.

  17. Perchlorate Sorption\\/Transformation from Solution Using Activated Carbon

    Microsoft Academic Search

    E. L. Pyatt; A. P. Jackman; D. Rolston

    2002-01-01

    Because perchlorate (ClO4-) inhibits iodide uptake it is a contaminant of concern in groundwater. Therefore ClO4- contaminated drinking water must be treated to either remove ClO4- or reduce ClO4- to chloride (Cl-). Batch and column experiments using varying operational conditions with powdered activated carbon (PAC) and granular activated carbon (PAC) were performed to evaluate PAC and GAC capacity to adsorb

  18. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Hydrogen cyanide, anhydrous, stabilized (hydrocyanic...Than Class 1 and Class 7 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized,...

  19. Density, partial, and excess volumes of solutions of methacrylic acid in organic solvents at 293 K

    NASA Astrophysics Data System (ADS)

    Sergeev, V. V.; Van-Chin-Syan, Yu. Ya.

    2015-03-01

    The densities of solutions of methacrylic acid in acetonitrile, benzene, hexane, 1,2-dichloroethane, and acetic acid at a temperature of 293 K and atmospheric pressure are determined by means of pycnometry. The values of the excess molar volume for the studied systems and those of the partial molar volumes of the components are calculated. It is found that the excess molar volume of binary systems of methacrylic acid with benzene, hexane, 1,2-dichloroethane, and acetic acid is positive over the range of concentrations and is negative in the methacrylic acid-acetonitrile system.

  20. Controlled Exposures of Volunteers to Respirable Carbon and Sulf uric Acid Aerosols

    Microsoft Academic Search

    Karen R. Anderson; Edward L. Avol; Scott A. Edwards; Deborah A. Shamoo; Ru-Chuan Peng; William S. Linn; Jack D. Hackney

    1992-01-01

    Respirable carbon or fly ash particles are suspected to increase the respiratory toxicity of coexisting acidic air pollutants, by concentrating acid on their surfaces and so delivering it efficiently to the lower respiratory tract. To investigate this issue, we exposed 15 healthy and 15 asthmatic volunteers in a controlled- environment chamber (21C, 50 percent relative humidity) to four test atmospheres:

  1. Pyruvic Acid Removal from Water by the Simultaneous Action of Ozone and Activated Carbon

    Microsoft Academic Search

    F. J. Beltrn; B. Acedo; F. J. Rivas; O. Gimeno

    2005-01-01

    Activated carbon (AC) has been used to catalyze the ozonation of pyruvic acid in water. Pyruvic acid conversions were found to be 9 and 37% after 90 min of single ozonation and single adsorption with 40 gL AC, respectively, while 82% was reached at the same conditions during the AC catalytic ozonation. Also, for similar conditions, mineralization reached values of

  2. Fracture Toughness of Carbon Nanofiber Reinforced Polylactic Acid at Room and Elevated Temperatures

    Microsoft Academic Search

    Y. Shimamura; Y. Shibata; K. Tohgo; H. Araki

    2008-01-01

    Summary Polylactic acid (PLA) is a biodegradable plastic made from lactic acid, and can be produced by renewable raw materials. The mechanical properties of PLA are, however, not sufficient for structural materials. In our study,carbon nanofiber rein- forced PLA was fabricated to overcome the deficiency of PLA and the mechanical properties were measured at room and elevated temperatures. Vapor grown

  3. Research Paper An Examination of the Carbon Isotope Effects Associated with Amino Acid Biosynthesis

    Microsoft Academic Search

    JAMES H. SCOTT; DIANE M. O'BRIEN; DAVID EMERSON; HENRY SUN; GENE D. McDONALD; ANTONIO SALGADO; MARILYN L. FOGEL

    Stable carbon isotope ratios (? 13C) were determined for alanine, proline, phenylalanine, valine, leucine, isoleucine, aspartate (aspartic acid and asparagine), glutamate (glutamic acid and glu- tamine), 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

  4. Carbonic Acid as a Reserve of Carbon Dioxide on Icy Moons: The Formation of Carbon Dioxide (CO2) in a Polar Environment

    NASA Astrophysics Data System (ADS)

    Jones, Brant M.; Kaiser, Ralf I.; Strazzulla, Giovanni

    2014-06-01

    Carbon dioxide (CO2) has been detected on the surface of several icy moons of Jupiter and Saturn via observation of the ?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 CO2 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 a rather surprising result pertaining to the synthesis of carbon dioxide in a polar environment. Here, carbonic acid was synthesized in a water (H2O)-carbon dioxide (CO2) (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 ?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.

  5. Integrated 3D Acid Fracturing Model for Carbonate Reservoir Stimulation

    E-print Network

    Wu, Xi

    2014-06-23

    . In order to study the effect of this stochastic nature on acid fracturing, a fully 3D acid reaction model was developed based on the geostatistical parameters of the formation. It is possible to describe local conductivity distribution related to acid...

  6. 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. PMID:23993798

  7. Thermal properties of aminopolycarboxylic acid solutions in the temperature range 20 80C

    NASA Astrophysics Data System (ADS)

    Osman, M. B. S.; Dakroury, A. Z.

    1994-07-01

    The thermal properties (thermal conductivity, thermal diffusivity, and volumetric heat capacity) of aminopolycarboxylic acids, nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), diet hylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), 1,2-diaminocyclohexanetetraacetic acid (DCTA), and ethyleneglycol-bis-(2-aminoethylether) tetraacetic acid (EGTA), in dilute solutions of sodium hydroxide were measured in the temperature range 20 80C. The measurements were performed with a hot-wire (strip) technique. The results show that the values of the thermal properties depend on the number of nitrogen atoms and the number of carboxyalkyl groups, which are bounded to the nitrogen atom, of the aminopolycarboxylic acid and also on the concentration of the investigated compounds in the medium and the temperatures. The mechanism of heat transfer is discussed and the role of convection is taken into consideration.

  8. Mass transfer and current efficiency for the electrodeposition of silver in fluorosilicic acid solution

    Microsoft Academic Search

    J.-S. Do; A.-S. Her

    1999-01-01

    The stripping and electrodeposition of silver in fluorosilicic acid solution are irreversible reactions as indicated by cyclic voltammetry. The rate constant for the intrinsic heterogeneous cathodic deposition of silver was obtained as kC0=40.77 exp(1.88-29.43 EC0') and the diffusion coefficient of the silver ion in fluorosilicic acid solution as 5.1710-5 cm2 s-1. Theoretical calculations of the concentration of silver ion correlated

  9. Leaching of boron from wood impregnated with preservative solutions based on boric acid and liquefied wood

    Microsoft Academic Search

    Botjan Lesar; Franc Budija; Polonca Kralj; Marko Petri?; Miha Humar

    Reducing boron leaching from impregnated wood has been one of the most challenging tasks for at least 50 years. In order to\\u000a slow down the leaching of boron, aqueous solutions of boric acid were combined with liquefied spruce wood. The results clearly\\u000a showed that leaching of boron from spruce wood impregnated with preservative solutions based on boric acid and liquefied

  10. Extraction of rare earth elements by high molecular weight amines from nitric acid solutions

    Microsoft Academic Search

    M. S. Milyukova; N. S. Varezhkina; B. F. Myasoedov

    1986-01-01

    Extraction of trivalent rare earth elements by a high molecular weight primary amine \\/decylamine\\/ from 0.53M nitric acid solutions, containing potassium phosphotungstate \\/K10P2W17O61\\/, has been investigated. The effect of nitric acid and potassium phosphotungstate concentration of the organic solvent, and lanthanides ionic radii upon distribution coefficients has been studied. It has been established that decylamine solutions in chloroform can be

  11. Adsorption of quinalizarin from non aqueous solution onto acid activated palygorskite

    Microsoft Academic Search

    N. Frini-Srasra; E. Srasra

    2009-01-01

    In this study, the adsorption of quinalizarin by natural and mesoporous acid activated palygorskite has been examinated in\\u000a order to remove coloured textile dyes from non aqueous solutions. The adsorption of quanilizarin from ethanol solution onto\\u000a acid activated palygorskite was followed by UV-Visible measurement. The adsorption capacity was largely improved when the\\u000a clay was activated by HCl. The high adsorption

  12. Extraction of hydrochloric acid from dilute solutions by the use of organic solvents

    E-print Network

    Pandya, Harishkumar Chandulal

    1967-01-01

    EXTRACTION OF HYDROCHLORIC ACID FROM DILUTE SOLUTIONS BY THE USE OF ORGANIC SOLVENTS A Thesis HARISHKUMAR CHANDULAL PANDYA Submitted to the Graduate College of the Texas ASM University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE May 1967 Major Subject: CHEMICAL ENGINEERING EXTRACTION OF HYDROCHLORIC ACID FROM DILUTE SOLUTIONS BY THE USE OF ORGANIC SOLVENTS A Thesis By HARI SHKUMAR CHANDULAL PANDYA Approved as to style and content by: airman o Committee...

  13. Stress corrosion cracking susceptibility of sensitized type 316 stainless steel in sulphuric acid solution

    Microsoft Academic Search

    Rokuro Nishimura; Achmad Sulaiman; Yasuaki Maeda

    2003-01-01

    The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 316 was investigated as a function of sensitizing temperature (8001300 K) and test temperature (333373 K) in 0.82 kmol\\/m3 sulphuric acid solution by using a constant load method, to compare with that already obtained in 0.82 kmol\\/m3 hydrochloric acid solution. The three parameters (lss, steady state elongation rate,

  14. Antimicrobial and cytotoxic effects of phosphoric acid solution compared to other root canal irrigants

    PubMed Central

    PRADO, Mara; da SILVA, Emmanuel Joo Nogueira Leal; DUQUE, Thais Mageste; ZAIA, Alexandre Augusto; FERRAZ, Caio Cezar Randi; de ALMEIDA, Jos Flvio Affonso; GOMES, Brenda Paula Figueiredo de Almeida

    2015-01-01

    Phosphoric acid has been suggested as an irrigant due to its effectiveness in removing the smear layer. Objectives : The purpose of this study was to compare the antimicrobial and cytotoxic effects of a 37% phosphoric acid solution to other irrigants commonly used in endodontics. Material and Methods : The substances 37% phosphoric acid, 17% EDTA, 10% citric acid, 2% chlorhexidine (solution and gel), and 5.25% NaOCl were evaluated. The antimicrobial activity was tested against Candida albicans, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Actinomyces meyeri, Parvimonas micra, Porphyromonas gingivalis, and Prevotella nigrescens according to the agar diffusion method. The cytotoxicity of the irrigants was determined by using the MTT assay. Results : Phosphoric acid presented higher antimicrobial activity compared to the other tested irrigants. With regard to the cell viability, this solution showed results similar to those with 5.25% NaOCl and 2% chlorhexidine (gel and solution), whereas 17% EDTA and 10% citric acid showed higher cell viability compared to other irrigants. Conclusion : Phosphoric acid demonstrated higher antimicrobial activity and cytotoxicity similar to that of 5.25% NaOCl and 2% chlorhexidine (gel and solution). PMID:26018307

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

    SciTech Connect

    Karadag, E.; Saraydin, D. [Cumhuriyet Univ., Sivas (Turkey); Gueven, O. [Hacettepe Univ., Ankara (Turkey)

    1995-12-01

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

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

    PubMed Central

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

    2015-01-01

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

  17. The Periplasmic Carbonic Anhydrase Activity of Helicobacter pylori Is Essential for Acid Acclimation

    Microsoft Academic Search

    Elizabeth A. Marcus; Amiel P. Moshfegh; George Sachs; David R. Scott

    2005-01-01

    The role of the periplasmic -carbonic anhydrase (-CA) (HP1186) in acid acclimation of Helicobacter pylori was investigated. Urease and urea influx through UreI have been shown to be essential for gastric colonization and for acid survival in vitro. Intrabacterial urease generation of NH3 has a major role in regulation of periplasmic pH and inner membrane potential under acidic conditions, allowing

  18. Stable carbon isotope ratios of fatty acids in seagrass and redhead ducks

    Microsoft Academic Search

    Beth Trust Hammer; Marilyn L. Fogel; Thomas C. Hoering

    1998-01-01

    Fatty acids were extracted from roots and rhizomes of the seagrass, Halodule wrightii, and from subcutaneous fat tissues of eight redhead ducks (Aythya americana) collected either in Texas or South Dakota. Stable carbon isotope ratios (?13C) of individual fatty acids were measured by gas chromatography\\/combustion\\/isotope ratio mass spectrometry (GC\\/C\\/IRMS). In cases where individual fatty acids were not completely resolved by

  19. 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. Photoinduced crystallization of CaCO3 from homogenous solution was demonstrated. 2-(3-benzoylphenyl)propionic acid was used as a photoreactive CO2 generator. Partially hydrolyzed poly(vinyl alcohol) worked as a stabilizer in the solution. Complete conversion of Ca2+ to CaCO3 was achieved by UV irradiation for 50 min. Nanometer-to-micron-sized calcites dispersed in the poly(vinyl alcohol) matrix.

  20. Solubility of uranyl nitrate in nitric acid solutions of aluminum nitrate

    Microsoft Academic Search

    B. K. Medkov; M. R. Petrov; O. N. Roslyakova

    1988-01-01

    The solubility of uranyl nitrate in nitric acid solutions of aluminum nitrate at 25°C containing 10, 20 and 30 mass % of nitric acid has been studied by the isothermal method. The Schreinemakers method has been used to establish the composition of the solid phases, which has been confirmed by crystallographic and thermographic studies. Data are presented on the viscosity

  1. The effect of confinement on dynamics and rheology of dilute deoxyribose nucleic acid solutions. II. Effective

    E-print Network

    Shaqfeh, Eric

    The effect of confinement on dynamics and rheology of dilute deoxyribose nucleic acid solutions. II the effect of confinement on deoxyribose nucleic acid rheology and chain dynamics. We present results these findings to microchannel flows to study the rhe- ology and chain dynamics of dilute deoxyribose nucleic

  2. Investigation of inhibition effect of some amino acids against steel corrosion in HCl solution

    Microsoft Academic Search

    H. Ashassi-Sorkhabi; M. R Majidi; K. Seyyedi

    2004-01-01

    The inhibition effect of three amino acids against steel corrosion in HCl solutions has been investigated by potentiodynamic polarization method. Corrosion data such as corrosion rate, corrosion potential (Ecorr) and corrosion resistance (Rp) were determined by extrapolation of the cathodic and anodic Tafel region. Adsorption isotherm was investigated by weight-loss measurement. The used amino acids were alanine, glycine and leucine.

  3. Surface Structural Studies of Methanesulfonic Acid at Air /Aqueous Solution Interfaces Using Vibrational Sum Frequency Spectroscopy

    E-print Network

    Richmond, Geraldine L.

    Surface Structural Studies of Methanesulfonic Acid at Air /Aqueous Solution Interfaces Using Form: NoVember 28, 2000 Atmospheric gas phase species such as methanesulfonic acid (MSA) are adsorbed orientation in which the methyl group points away from the liquid surface. The surrounding surface water

  4. Heterogeneous freezing of single sulfuric acid solution droplets: laboratory experiments utilizing an acoustic levitator

    Microsoft Academic Search

    M. Ettner; S. K. Mitra; S. Borrmann

    2004-01-01

    The heterogeneous freezing temperatures of single binary sulfuric acid solution droplets were measured in dependency of acid concentration down to temperatures as low as -50C. In order to avoid influence of supporting substrates on the freezing characteristics, a new technique has been developed to suspend the droplet by means of an acoustic levitator. The droplets contained immersed particles of graphite,

  5. Heterogeneous freezing of single sulphuric acid solution droplets: laboratory experiments utilising an acoustic levitator

    Microsoft Academic Search

    M. Ettner; S. K. Mitra; S. Borrmann

    2004-01-01

    The heterogeneous freezing temperatures of single binary sulphuric acid solution droplets were measured in dependency of acid concentration down to temperatures as low as -70C. In order to avoid influence of supporting substrates on the freezing characteristics, the droplets were suspended by means of an acoustic levitator. The droplets contained immersed particles of graphite, kaolin or montmorillonite in order to

  6. Sustainable technologies for the regeneration of acidic tin stripping solutions used in PCB fabrication

    Microsoft Academic Search

    Charlie Kerr

    2004-01-01

    Electroplated tin deposits are used as etch resists during the processing of printed circuit boards. The tin coating protects the copper tracks during etching but is subsequently removed (stripped) to expose the defined copper circuitry. The commonly used stripping solutions are based on nitric acid and after use they represent a very acidic waste product with a high metal content.

  7. Environmentally safe corrosion inhibition of the CuNi alloys in acidic sulfate solutions

    Microsoft Academic Search

    Waheed A. Badawy; Khaled M. Ismail; Ahlam M. Fathi

    2005-01-01

    The corrosion and passivation behaviors of alloys with different CuNi ratios were investigated in acidic sulfate solutions. The corrosion rate was calculated and the corrosion inhibition process was investigated using different amino acids as corrosion inhibitors. For these investigations conventional electrochemical techniques and electrochemical impedance spectroscopy (EIS) were used. Fitting of the experimental impedance data to theoretical values enables understanding

  8. Removal of insecticide carbofuran from aqueous solutions by banana stalks activated carbon

    Microsoft Academic Search

    J. M. Salman; B. H. Hameed

    2010-01-01

    In this work, activated carbon was prepared from banana stalks (BSAC) waste to remove the insecticide carbofuran from aqueous solutions. The effects of contact time, initial carbofuran concentration, solution pH and temperature (30, 40 and 50C) were investigated. Adsorption isotherm, kinetics and thermodynamics of carbofuran on BSAC were studied. Equilibrium data were fitted to the Langmuir, Freundlich and Temkin isotherm

  9. Computer simulation of cascade damage in ?-iron with carbon in solution

    Microsoft Academic Search

    Andrew F. Calder; David J. Bacon; Alexander V. Barashev; Yuri N. Osetsky

    2008-01-01

    Molecular dynamics simulation method is used to investigate defect production by displacement cascades in iron with carbon (C) in solution. This is the first study of cascade damage in a metal containing interstitial solute. Iron is of particular interest because of the use of ferritic steels in plant for nuclear power generation. Cascades are simulated with energy in the range

  10. Effect of Mild Nitric Acid Oxidation on Dispersability, Size, and Structure of Single-Walled Carbon Nanotubes

    E-print Network

    Resasco, Daniel

    Effect of Mild Nitric Acid Oxidation on Dispersability, Size, and Structure of Single-Walled Carbon) with nitric acid increases their dispersability in water, methanol, and N,N-dimethylformamide. Two oxidation conditions carefully. Nitric acid has been the most frequently utilized agent for oxidation of carbon

  11. Computational and experimental studies of the interaction between single-walled carbon nanotubes and folic acid

    NASA Astrophysics Data System (ADS)

    Castillo, John J.; Rozo, Ciro E.; Castillo-Len, Jaime; Rindzevicius, Tomas; Svendsen, Winnie E.; Rozlosnik, Noemi; Boisen, Anja; Martnez, Fernando

    2013-03-01

    This Letter involved the preparation of a conjugate between single-walled carbon nanotubes and folic acid that was obtained without covalent chemical functionalization using a simple 'one pot' synthesis method. Subsequently, the conjugate was investigated by a computational hybrid method: our own N-layered Integrated Molecular Orbital and Molecular Mechanics (B3LYP(6-31G(d):UFF)). The results confirmed that the interaction occurred via hydrogen bonding between protons of the glutamic moiety from folic acid and ? electrons from the carbon nanotubes. The single-walled carbon nanotube-folic acid conjugate presented herein is believed to lead the way to new potential applications as carbon nanotube-based drug delivery systems.

  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 ? cm.

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

    PubMed

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

    2012-04-30

    This study focused on the environmental risk of steel making slag itself, arsenic removal mechanism and re-leaching possibility of arsenic to aqueous state after the adsorption. The purpose of the study is to promote the use of steel making slag as a low-cost adsorbent for arsenic in aqueous system. Calcium was easily dissolved out from the slag and become the dominant substance in the leachate. Some of the calcium could form amorphous calcium carbonate in alkaline condition, and arsenic in the aqueous solution would be removed by being co-precipitated with or adsorbed onto the amorphous calcium carbonate. Most of the amorphous calcium carbonate containing arsenic would be bound to amorphous iron oxide of the slag. When the slag was used as an adsorbent for arsenic removal, a little amount of toxic chemicals were leached from the slag itself under pH 0.8 to 13.6. Also, 70-80% of arsenic laden on the slag was bound to amorphous iron oxide which would not easily desorb unless given a reducing and complexing condition. Showing 95-100% removal efficiency near initial pH 2, the slag, therefore, could be used as an appropriate adsorbent for eliminating arsenic in acidic aqueous solution. PMID:22349716

  14. Extraction of actinides into aqueous polyethylene glycol solutions from carbonate media in the presence of alizarin complexone

    SciTech Connect

    Molochnikova, N.P.; Frenkel', V.Ya.; Myasoedov, B.F.; Shkinev, V.M.; Spivakov, B.Ya.; Zolotov, Yu.A.

    1987-01-01

    Actinide extraction in a two-phase aqueous system based on polyethylene glycol from carbonate solutions of various compositions in presence of alizarin complexone is studied. It is shown that the nature of the alkali metals affects actinide extraction into the polyethylene glycol phase. Tri- and tetravalent actinides are extracted maximally from sodium carbonate solutions. Separation of actinides in different oxidation states is more effective in potassium carbonate solutions. The behavior of americium in different oxidation states in the system carbonate-polyethylene glycol-complexone is studied. The possibility of extraction separation of microamount of americium(V) from curium in carbonate solutions in presence of alizarin complexone is shown.

  15. In situ electron microscopy studies of calcium carbonate precipitation from aqueous solution with and without organic additives.

    PubMed

    Verch, Andreas; Morrison, Ian E G; Locht, Renee van de; Krger, Roland

    2013-08-01

    For the understanding of mineral formation processes from solution it is important to obtain a deeper insight into the dynamics of crystal growth. In this study we applied for this purpose a novel atmospheric scanning electron microscope that allows the investigation of CaCO3 particle formation in solution under atmospheric conditions with a resolution of approximately 10nm. Furthermore it permits the in situ observation of the dynamics of crystal evolution. With this tool the precipitation of CaCO3 was studied in the absence and presence of additives, namely poly(acrylic acid) and poly(styrene sulfonate-co-maleic acid) which are known to influence the crystal growth rate and morphology. We determined particle growth rates and investigated the formation and dissolution dynamics of an observed transient phase, believed to be amorphous calcium carbonate. This technique also enabled us to study the depletion zones, areas of lower intensity due to reduced ion concentrations. Ion flux rates were obtained from the depletion zone width, which amounted to several ?m assuming the formation and dissolution dynamics of amorphous calcium carbonate being the rate determining process. This assumption was confirmed since the obtained fluxes were found to be in good agreement with fluxes derived from the experimentally observed crystal growth rates. PMID:23742840

  16. Liquid-Liquid Extraction Studies of Trivalent Yttrium from Phosphoric Acid Solutions Using TOPS 99 as an Extractant

    Microsoft Academic Search

    B. Ramachandra Reddy; S. Radhika; B. Nagaphani Kumar

    2010-01-01

    Liquid-liquid extraction studies of trivalent yttrium (Y) from phosphoric acid solutions have been carried out with commercial organophosphoric acid based extractant TOPS 99 (Talcher Organo phosphorus solvent, an equivalent of di-2-ethylhexyl phosphoric acid). The parameters studied include equilibration time, acid concentration, extractant concentration, diluent, metal concentration, temperature, stripping, and regeneration of the extractant. Increase of phosphoric acid concentration in the

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

    Microsoft Academic Search

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

    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

  18. SOME PHYSICOCHEMICAL STUDIES OF BORIC ACID SOLUTIONS AT HIGH TEMPERATURES

    Microsoft Academic Search

    Byrnes

    1962-01-01

    The use of a neutron absorber dissolved in the coolant has been proposed ; as a means of long-term control in large, closed-cycle water reactors, the so-; called chemical shim. Boron appears among the most promising candidates, being ; added as boric acid in this particular control application. It is often found ; advantageous to add a second substance to

  19. Intramolecular Acid-Catalyzed Amide Isomerization in Aqueous Solution

    E-print Network

    Lectka, Thomas

    experimental verification that hydrogen bond donation to the amide nitrogen by charged proton donors may play. Scheme 1. Acid-Catalyzed Isomerization of Amides ORGANIC LETTERS 1999 Vol. 1, No. 5 749-752 10.1021/ol bond donation to the amide nitrogen by charged proton donors may play a significant role

  20. Corrosion behavior of cold rolled steel in peracetic acid solutions

    Microsoft Academic Search

    Qing Qu; Shuan Jiang; Lei Li; Wei Bai; Jun Zhou

    2008-01-01

    The corrosion behavior of cold rolled steel in different concentrations of peracetic acid (PAA) has been studied by electrochemical technique at 0C, 10C, 20C and 30C, respectively. Electrochemical parameters like corrosion potential, corrosion current density and corrosion rate were determined. The results show that concentrations of PAA and test temperatures can affect the corrosion rate obviously. The corrosion rate increases

  1. Electrochemical actuation of gilded polyaniline bilayers in aqueous acid solutions

    Microsoft Academic Search

    Wen Lu; Elisabeth Smela; Benjamin R. Mattes

    2001-01-01

    In this work, we investigated the electrochemical actuation of gilded polyaniline bilayers in acidic aqueous electrolytes. Gilding was found to be a useful method to ensure a uniform potential distribution across polyaniline films so that well-defined electrochemistry and electrochemical actuation could be obtained. Electrochemical actuation of gilded polyaniline bilayers was studied by means of bending and linear actuation. Actuation could

  2. Oligomerization oscillations of L-lactic acid in solution.

    PubMed

    Sajewicz, Mieczys?aw; Dolnik, Milo; Kronenbach, Dorota; Gontarska, Monika; Kowalska, Teresa; Epstein, Irving R

    2011-12-22

    We employ high-performance liquid chromatography with diode array, evaporative light scattering, and mass spectrometric detection to monitor the oligomerization of L-lactic acid in pure acetonitrile and in 70% aqueous ethanol. The production of higher oligomers appears to proceed in an oscillatory fashion. A model is presented that involves the formation of aggregates (micelles), which catalyze the oligomerization. PMID:22054006

  3. 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...

  4. The Nature of Oxide Films on Tungsten in Acidic and Alkaline Solutions

    E-print Network

    The Nature of Oxide Films on Tungsten in Acidic and Alkaline Solutions R.S. Lillard, G.S. Kanner, D for W in alkaline solution are also presented. #12;2 Introduction Thermodynamically, tungsten trioxide mechanism by which this dissolution process occurs remains elusive. While in alkaline environments

  5. Precipitation polymerization of hydrophobically modified polyelectrolyte poly(AA-co-ODA) in supercritical carbon dioxide and solution rheology properties

    NASA Astrophysics Data System (ADS)

    Zhang, Huaiping; Li, Wei; Cao, Qing; Chen, Mingcai

    2014-05-01

    Hydrophobically modified (HM) polyelectrolytes were prepared by using precipitation polymerization of acrylic acid (AA) and octadecyl acrylate (ODA) in various molar ratios in supercritical carbon dioxide. The product was obtained in the form of a white powder and the micrographs show aggregates of primary particles < 1 ?m in size. The effects of polymer concentration, ODA content in polymer, surfactant, shear time, shear rate on the apparent viscosity were investigated. The reason leaded to a significant viscosity enhancement was discussed. Steady-state and oscillatory tests of solution were also investigated. Solution exhibited shear thinning behavior and thixotropy. Polymers contain octadecyl acrylate (3.4 mol%) at 0.2 g/dL behaved as high entanglement structures or association gels, since the modulus G' were being higher than G? throughout the frequency range. The comparison of apparent and complex viscosities confirmed the association gel properties.

  6. The inhibition effect of some amino acids towards Pb Sb Se As alloy corrosion in sulfuric acid solution

    NASA Astrophysics Data System (ADS)

    Ghasemi, Z.; Tizpar, A.

    2006-03-01

    The inhibition effect of three amino acids towards the corrosion of Pb-Sb-Se-As alloy in 1.28 s.g. H 2SO 4 solution was investigated with linear polarization and weight loss measurements methods. The results drawn from two different techniques are comparable. The used amino acids were tryptophane, proline and methionine. The effect of inhibitor concentration and temperature against inhibitor action was investigated. It was found that these inhibitors act as good inhibitors for the corrosion of lead alloy in H 2SO 4 solution. Increasing inhibitor concentration increases the inhibition efficiency. It was found that adsorption of used amino acids on lead alloy surface follows Langmuir isotherm.

  7. ADSORPTION OF LEVODOPA FROM AQUEOUS SOLUTION ON GRANULAR ACTIVATED CARBON

    Microsoft Academic Search

    JULCOUR-LEBIGUE Carine; Centro de Qumica Farmacutica

    Granular activated carbon filtration has been successfully used in wastewater and drinking water treatment plants, for removal of different pollutants and it is the most efficient conventional treatment method for the purification of water contaminated by other pollutants like pesticides. Levodopa is a drug used to treat Parkinson disease, a progressive condition in which the part of the brain responsible

  8. Ecological Engineering promotes Carbon Reduction Solutions for a Sustainable Planet

    Microsoft Academic Search

    Stephen Bedford Clark

    2009-01-01

    Due to un-prescedented; social, industrial and human reproductive growth, our global society is rapidly approaching peak development, coupling with climate change factors and accelerating Earths current 'melt cycle'. Our challenge is to do more with less; to question the 'way' it has always been done; to develop innovative low carbon engineering tools; to design and mimic natural eco-systems and to

  9. Magnesium recovery from magnesite tailings by acid leaching and production of magnesium chloride hexahydrate from leaching solution by evaporation

    Microsoft Academic Search

    Mine zdemir; Dilek ak?r; ?lker K?pak

    2009-01-01

    The recovery of magnesium from magnesite tailings in aqueous hydrochloric acid solutions by acid leaching was studied in a batch reactor using hydrochloric acid solutions. Subsequent, production of magnesium chloride hexahydrate (MgCl2.6H2O) from leaching solution was also investigated. The effects of temperature, acid concentration, solid-to-liquid ratio, particle size and stirring speed on the leaching process were investigated. The pseudo-second-order reaction

  10. Metabolic engineering of yeast to produce fatty acid-derived biofuels: bottlenecks and solutions.

    PubMed

    Sheng, Jiayuan; Feng, Xueyang

    2015-01-01

    Fatty acid-derived biofuels can be a better solution than bioethanol to replace petroleum fuel, since they have similar energy content and combustion properties as current transportation fuels. The environmentally friendly microbial fermentation process has been used to synthesize advanced biofuels from renewable feedstock. Due to their robustness as well as the high tolerance to fermentation inhibitors and phage contamination, yeast strains such as Saccharomyces cerevisiae and Yarrowia lipolytica have attracted tremendous attention in recent studies regarding the production of fatty acid-derived biofuels, including fatty acids, fatty acid ethyl esters, fatty alcohols, and fatty alkanes. However, the native yeast strains cannot produce fatty acids and fatty acid-derived biofuels in large quantities. To this end, we have summarized recent publications in this review on metabolic engineering of yeast strains to improve the production of fatty acid-derived biofuels, identified the bottlenecks that limit the productivity of biofuels, and categorized the appropriate approaches to overcome these obstacles. PMID:26106371

  11. Metabolic engineering of yeast to produce fatty acid-derived biofuels: bottlenecks and solutions

    PubMed Central

    Sheng, Jiayuan; Feng, Xueyang

    2015-01-01

    Fatty acid-derived biofuels can be a better solution than bioethanol to replace petroleum fuel, since they have similar energy content and combustion properties as current transportation fuels. The environmentally friendly microbial fermentation process has been used to synthesize advanced biofuels from renewable feedstock. Due to their robustness as well as the high tolerance to fermentation inhibitors and phage contamination, yeast strains such as Saccharomyces cerevisiae and Yarrowia lipolytica have attracted tremendous attention in recent studies regarding the production of fatty acid-derived biofuels, including fatty acids, fatty acid ethyl esters, fatty alcohols, and fatty alkanes. However, the native yeast strains cannot produce fatty acids and fatty acid-derived biofuels in large quantities. To this end, we have summarized recent publications in this review on metabolic engineering of yeast strains to improve the production of fatty acid-derived biofuels, identified the bottlenecks that limit the productivity of biofuels, and categorized the appropriate approaches to overcome these obstacles.

  12. Recovery of organic acids

    DOEpatents

    Verser, Dan W. (Golden, CO); Eggeman, Timothy J. (Lakewood, CO)

    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.

  13. Recovery of organic acids

    SciTech Connect

    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.

  14. 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.

  15. Modification of carbon ceramic electrode prepared with sol-gel technique by a thin film of chlorogenic acid: application to amperometric detection of NADH.

    PubMed

    Salimi, Abdollah; Hallaj, Rahman; Ghadermazi, Mohammad

    2005-02-28

    The carbon ceramic electrode prepared with sol-gel technique is modified by a thin film of chlorogenic acid (CGA). By immersing the carbon ceramic electrode in aqueous solution of chlorogenic acid at less than 2s a thin film of chlorogenic acid adsorbed strongly and irreversibly on the surface of electrode. The cyclic voltammetry of the resulting modified CCE prepared at optimum conditions shows a well-defined stable reversible redox couple due to hydroquinone/quinone system in both acidic and basic solutions. The modified electrode showed excellent electrocatalytic activity toward NADH oxidation and it also showed a high analytical performance for amperometric detection of NADH. The catalytic rate constant of the modified carbon ceramic electrode for the oxidation of NADH is determined by cyclic voltammetry measurement. Under the optimised conditions the calibration curve is linear in the concentration range 1-120mum. The detection limit (S/N = 3) and sensitivity are 0.2muM and 25nAmuM(-1).The results of six successive measurement-regeneration cycles show relative standard deviations of 2.5% for electrolyte solution containing 1mM NADH, indicating that the electrode renewal gives a good reproducible and antifouling surface. The advantages of this amperometric detector are: high sensitivity, excellent catalytic activity, short response time t < 2s, remarkable long-term stability, simplicity of preparation at short time and good reproducibility. PMID:18969884

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

    PubMed

    Werner, Josephina; Julin, Jan; Dalirian, Maryam; Prisle, Nnne L; hrwall, Gunnar; Persson, Ingmar; Bjrneholm, Olle; Riipinen, Ilona

    2014-10-21

    The water-vapor interface of aqueous solutions of succinic acid, where pH values and bulk concentrations were varied, has been studied using surface sensitive X-ray photoelectron spectroscopy (XPS) and molecular dynamics (MD) simulations. It was found that succinic acid has a considerably higher propensity to reside in the aqueous surface region than its deprotonated form, which is effectively depleted from the surface due to the two strongly hydrated carboxylate groups. From both XPS experiments and MD simulations a strongly increased concentration of the acid form in the surface region compared to the bulk concentration was found and quantified. Detailed analysis of the surface of succinic acid solutions at different bulk concentrations led to the conclusion that succinic acid saturates the aqueous surface at high bulk concentrations. With the aid of MD simulations the thickness of the surface layer could be estimated, which enabled the quantification of surface concentration of succinic acid as a multiple of the known bulk concentration. The obtained enrichment factors were successfully used to model the surface tension of these binary aqueous solutions using two different models that account for the surface enrichment. This underlines the close correlation of increased concentration at the surface relative to the bulk and reduced surface tension of aqueous solutions of succinic acid. The results of this study shed light on the microscopic origin of surface tension, a macroscopic property. Furthermore, the impact of the results from this study on atmospheric modeling is discussed. PMID:25182698

  17. Control and monitoring of the localized corrosion of zirconium in acidic chloride solutions

    SciTech Connect

    Fahey, J.; Holmes, D.; Yau, T.L. [Teledyne Wah Chang, Albany, OR (United States)

    1995-09-01

    Zirconium in acidic chloride solutions which are contaminated with ferric or cupric cations is prone to localized corrosion. This tendency can be reduced by ensuring that the zirconium surface is clean and smooth. In this paper, the effect of surface condition on the localized corrosion of zirconium in acidic chloride solutions is predicted with potentiodynamic scans. These predictions are confirmed by weight loss tests on various combinations of surface finish and acid concentrations. A real time indication of localized corrosion is seen by monitoring the electrochemical noise produced between two similar electrodes immersed in an acidic chloride solutions. Electrochemical noise monitoring correlates well with the predictions from potentiodynamic and weight loss experiments. The electrochemical noise results show that while an elevated (more anodic) potential caused by ferric ion contamination may be a necessary condition for localized corrosion, it is not a sufficient condition: A smooth, clean zirconium surface reduces the localized corrosion of zirconium.

  18. Degradation of carbon tetrachloride in aqueous solution in the thermally activated persulfate system.

    PubMed

    Xu, Minhui; Gu, Xiaogang; Lu, Shuguang; Qiu, Zhaofu; Sui, Qian; Miao, Zhouwei; Zang, Xueke; Wu, Xiaoliang

    2015-04-01

    Thermal activation of persulfate (PS) has been identified to be effective in the destruction of organic pollutants. The feasibility of carbon tetrachloride (CT) degradation in the thermally activated PS system was evaluated. The experimental results showed that CT could be readily degraded at 50 C with a PS concentration of 0.5M, and CT degradation and PS consumption followed the pseudo-first order kinetic model. Superoxide radical anion (O2(*-)) was the predominant radical species responsible for CT degradation and the split of CCl was proposed as the possible reaction pathways for CT degradation. The process of CT degradation was accelerated by higher PS dose and lower initial CT concentration. No obvious effect of the initial pH on the degradation of CT was observed in the thermally activated PS system. Cl(*-), HCO3(*-), and humic acid (HA) had negative effects on CT degradation. In addition, the degradation of CT in the thermally activated PS system could be significantly promoted by the solvents addition to the solution. In conclusion, the thermally activated PS process is a promising option in in-situ chemical oxidation/reduction remediation for degrading highly oxidized organic contaminants such as CT that is widely detected in contaminated sites. PMID:25544995

  19. Production and characterization of methyl ester sophorolipids with 22-carbon-fatty acids.

    PubMed

    Shin, Jae Dong; Lee, Jeongmi; Kim, Yong Bum; Han, In-Sun; Kim, Eun-Ki

    2010-05-01

    In this study, various fatty acids of 18 and 22 carbons were used as substrates to produce sophorolipids in Candida bombicola ATCC 22214. Methyl esterification of erucic acid and C22-enriched rapeseed oil generated mainly acidic sophorolipids with different degrees of saturation in the fatty acid chain, which was demonstrated by structural analysis using HPLC, LC-MS and NMR spectroscopy. Regardless of methyl esterification, the rapeseed oil served as the best substrate for high production of sophorolipids among the tested. Methyl esterification also had no noticeable effect on the interfacial properties of sophorolipids. However, 22 carbons introduced in the fatty acid chain increased the hydrophobicity of sophorolipids, and therefore improved surface-active properties and biodegradability. PMID:20053555

  20. Whole-body nitrogen and tyrosine metabolism in surgical patients receiving branched-chain amino acid solutions

    Microsoft Academic Search

    S. P. Desai; B. R. Bistrian; L. L. Moldawer; G. L. Blackburn

    1985-01-01

    Fifteen patients undergoing gastric bypass surgery for morbid obesity received preoperatively a standard crystalline amino acid solution containing 15.6% branched-chain amino acids. During the first five postoperative days, the patients were randomized to receive one of three amino acid solutions of different branched-chain amino acid content. Whole-body amino acid appearance and oxidation were estimated using a continuous intravenous infusion of

  1. Investigation of inhibition effect of some amino acids against steel corrosion in HCl solution

    NASA Astrophysics Data System (ADS)

    Ashassi-Sorkhabi, H.; Majidi, M. R.; Seyyedi, K.

    2004-03-01

    The inhibition effect of three amino acids against steel corrosion in HCl solutions has been investigated by potentiodynamic polarization method. Corrosion data such as corrosion rate, corrosion potential ( Ecorr) and corrosion resistance ( Rp) were determined by extrapolation of the cathodic and anodic Tafel region. Adsorption isotherm was investigated by weight-loss measurement. The used amino acids were alanine, glycine and leucine. The effect of inhibitor concentration and acid concentration against inhibitor action was investigated. The inhibition efficiency (IE) depended on the type of amino acid and its concentration. The inhibition effect ranged from 28 to 91%. The amino acids act as a corrosion inhibitor in HCl solution through adsorption on the steel surface and adsorption follows Langmuir isotherm.

  2. 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.

  3. Time dependent inhibition of xanthine oxidase in irradiated solutions of folic acid, aminopterin and methotrexate

    SciTech Connect

    Robinson, K.; Pilot, T.F.; Meany, J.E. (Department of Chemistry, Seattle University, WA (USA))

    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 in solution and the ability of these solutions to inhibit xanthine oxidase. The relative potency of the respective photolysis products were estimated.

  4. Stimulation of Carbonate Reservoirs Using a New Emulsified Acid System

    E-print Network

    Sayed, Mohammed Ali Ibrahim

    2013-05-15

    The scope of work can be divided into; the measurement of the rheological properties of a new emulsified acid system that can be suitable for high temperature applications, a study of the performance of the new emulsified acid in stimulating both...

  5. Spectroscopic detection of the most stable carbonic acid, cis-cis H2CO3.

    PubMed

    Mori, Tetsuya; Suma, Kohsuke; Sumiyoshi, Yoshihiro; Endo, Yasuki

    2011-01-28

    Carbonic acid had not been detected by any spectroscopic means for a long period. Recently, we have reported the detection of its second most stable conformer, cis-trans H(2)CO(3), as the first spectroscopic detection of the isolated carbonic acid molecule. In the present work, the most stable conformer of carbonic acid, cis-cis H(2)CO(3), in the gas phase has been successfully produced in a supersonic jet using a pulsed discharge nozzle, and pure rotational transitions of this molecule have been observed by a Fourier-transform microwave spectrometer. In addition to cis-cis H(2)CO(3), its deuterated isotopologue, cis-cis D2CO3, has been observed, yielding the r(0) structure of the cis-cis conformer. Furthermore, hyperfine constants of the deuterated cis-trans conformers were also determined. The two structures for the stable isolated carbonic acid molecule, those of the cis-cis and cis-trans conformers, are considered to provide basic information for the understanding of chemical reactions involving carbonic acid The present result is accurate enough to be used in radio astronomical observations, where the ortho?para ratio of cis-cis H(2)CO(3) may be used as an important probe of interstellar chemistry. PMID:21280737

  6. 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.

  7. Tuning the optical properties of carbon nanotube solutions using amphiphilic self-assembly

    NASA Astrophysics Data System (ADS)

    Arnold, Michael S.; Stupp, Samuel I.; Hersam, Mark C.

    2003-07-01

    Recently it has been shown that aqueous solutions of sodium dodecyl sulfate (SDS) encapsulated and polymer wrapped single-walled carbon nanotubes (SWNTs) fluoresce in the near infrared (NIR) in the regime of the E11 van Hove transitions for semiconducting SWNTs. For bundled SWNTs, fluorescence is observed to be quenched along with a shift and broadening of the absorbance spectrum. Here, we study two other commercially available surfactants, BRIJ-97 and Triton-X-100, by analysis of carbon nanotube fluorescence and absorptivity in the NIR. It is found that changing the surfactant alters the corresponding optical properties of the solubilized carbon nanotubes. The NIR absorbance spectra of BRIJ-97 and Triton-X-100 carbon nanotube solutions are also compared with the absorbance spectrum of NaCl destabilized SDS-SWNT solutions. By controlling the amount of NaCl added to an aqueous solution of SDS-SWNTs, the optical absorbance spectrum can be made to match that of BRIJ-97 and Triton-X-100 solutions. Lastly, a correlation is drawn between the amount of shift in the absorbance spectrum and the fluorescence intensity, independent of surfactant used. This shift and decrease in fluorescence intensity may be due to carbon nanotube bundling.

  8. Labradorite dissolution in aqueous organic acid solutions: an experimental study

    E-print Network

    Ahmed, MD. Raquib Uddin

    1995-01-01

    Experiments were conducted in sand-pack, flow-through reactors to study labradorite solubility and dissolution kinetics at 50' and IOO'C and 13.8 MPa. Labradorite grains were reacted with distilled deionized water, HCI solutions (pHi=3.5, 4.7), p...

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

    USGS Publications Warehouse

    Aiken, G.R.

    1979-01-01

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

  10. An analysis of electrical conductances of aqueous solutions of polybasic organic acids. Benzenehexacarboxylic (mellitic) acid and its neutral and acidic salts.

    PubMed

    Apelblat, Alexander; Bester-Rogac, Marija; Barthel, Josef; Neueder, Roland

    2006-05-01

    A general approach is proposed to analyze electrical conductivities in aqueous solutions of polybasic organic acids. Experimental conductivities are examined in the context of dissociation and hydrolysis reactions by applying the Quint-Viallard conductivity equations and the Debye-Hckel equations for activity coefficients. The proposed numerical procedure is illustrated by the case of benzenehexacarboxylic (mellitic) acid and its neutral and acidic salts. From conductivity measurements of mellitic acid and its salts, performed in dilute aqueous solutions in the 278.15-308.15 K temperature range, the limiting conductances of mellitic anions, lambda(0)(1/jH(6-j)Mel(-j), T), j = 1, 2, 3, 4, 5, 6 are determined. PMID:16640450

  11. Perchlorate Sorption/Transformation from Solution Using Activated Carbon.

    NASA Astrophysics Data System (ADS)

    Pyatt, E. L.; Jackman, A. P.; Rolston, D.

    2002-12-01

    Because perchlorate (ClO4-) inhibits iodide uptake it is a contaminant of concern in groundwater. Therefore ClO4- contaminated drinking water must be treated to either remove ClO4- or reduce ClO4- to chloride (Cl-). Batch and column experiments using varying operational conditions with powdered activated carbon (PAC) and granular activated carbon (PAC) were performed to evaluate PAC and GAC capacity to adsorb ClO4- and/or reduce ClO4- to Cl-, chlorite (ClO2-) and chlorate (ClO3-). Varying operational conditions were particle size, pH, and ClO4- salt cation. ClO4- adsorption was affected by particle size, pH, and cation salt. ClO4- adsorption on PAC and GAC is partially reversible.

  12. Ozone-activated Carbon Mineralization of 17-?-Ethynylestradiol Aqueous Solutions

    Microsoft Academic Search

    F. J. Beltrn; P. Pocostales; P. Alvarez; A. Aguinaco

    2009-01-01

    Ozone and activated carbon (AC) have been used on the removal of 17?-ethynylestradiol (ETOL), a pharmaceutical compound, and its oxidation by-products. Although single ozonation is not able to totally remove the by-products formed from the degradation of the parent compound (about 65% of TOC removal at pH 7 after 2-hour reaction), the ozone\\/AC system led not only to higher TOC

  13. Solution-reactor-produced Mo-99 using activated carbon to remore I-131

    SciTech Connect

    Kitten, S.; Cappiello, C.

    1998-06-01

    The production of {sup 99}Mo in a solution reactor was explored. Activated charcoal was used to filter the {sup 131}I contaminant from an irradiated fuel solution. Gamma spectroscopy confirmed that the activated carbon trapped a significant amount of {sup 131}I, as well as notable amounts of {sup 133}Xe, {sup 105}Rb, and {sup 140}Ba; the carbon trapped a diminutive amount of {sup 99}Mo. The results promote the idea of solution-reactor-produced {sup 99}Mo. Solution reactors are favorable both energetically and environmentally. A solution reactor could provide enough {sup 99}Mo/{sup 99m}Te to support both the current and future radiopharmaceutical needs of the U.S.

  14. Fructose metabolism of the purple non-sulfur bacterium Rhodospirillum rubrum: effect of carbon dioxide on growth, and production of bacteriochlorophyll and organic acids.

    PubMed

    Rudolf, Christiane; Grammel, Hartmut

    2012-04-01

    During fermentative metabolism, carbon dioxide fixation plays a key role in many bacteria regarding growth and production of organic acids. The present contribution, dealing with the facultative photosynthetic bacterium Rhodospirillum rubrum, reveals not only the strong influence of ambient carbon dioxide on the fermentative break-down of fructose but also a high impact on aerobic growth with fructose as sole carbon source. Both growth rates and biomass yield increased with increasing carbon dioxide supply in chemoheterotrophic aerobic cultures. Furthermore, intracellular metabolite concentration measurements showed almost negligible concentrations of the tricarboxylic acid cycle intermediates succinate, fumarate and malate under aerobic growth, in contrast to several metabolites of the glycolysis. In addition, we present a dual phase fed-batch process, where an aerobic growth phase is followed by an anaerobic production phase. The biosynthesis of bacteriochlorophyll and the secretion of organic acids were both affected by the carbon dioxide supply, the pH value and by the cell density at the time of switching from aerobic to anaerobic conditions. The formation of pigmented photosynthetic membranes and the amount of bacteriochlorophyll were inversely correlated to the secretion of succinate. Accounting the high biotechnological potential of R. rubrum, optimization of carbon dioxide supply is important because of the favored application of fructose-containing fermentable feedstock solutions in bio-industrial processes. PMID:22418264

  15. Carbon fiber cloth supported Au nano-textile fabrics as an efficient catalyst for hydrogen peroxide electroreduction in acid medium

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Cheng, Kui; Wang, Guiling; Cao, Dianxue

    2015-09-01

    The size-controlled hierarchical textile-like Au nanostructures supported carbon fiber cloth (Au NTs/CFC) is successfully fabricated through a simple low-cost electrochemical route. The electrodes are characterised by scanning electron microscopy equipped with an energy dispersive X-ray spectrometer, transmission electron microscopy and X-ray diffractometer. Without any conducting carbons and polymer binders, the 3D electrode with unique structure is directly used as the electrocatalyst for H2O2 reduction in acid solution and the catalytic performance is evaluated by voltammetry and chronoamperometry. The Au NTs/CFC electrode exhibits much higher catalytic activity and remarkably improved utilization of Au than Au nanoparticles (Au NPs/CFC) prepared by the same method owing to its unique structure. In the solution of 3.0 mol L-1 H2SO4 + 0.1 mol L-1 H2O2, with the reduction potential of 0 V, the current of -0.72 A cm-2 mg-1 can be obtained on Au NTs/CFC electrode and only a current of -0.09 A cm-2 mg-1 can be achieved on Au NPs/CFC electrode. All these results reveal that the novel Au NTs/CFC electrode exhibits excellent catalytic performance and superior stability for H2O2 electroreduction in acid medium, benefitting from the unique 3D structure which can ensure high utilization of catalyst.

  16. Basic solutions to carbon/carbon oxidation: Science and technology. Final report, 15 April 1993--14 April 1998

    SciTech Connect

    Harrison, I.R.; Chung, T.; Pantano, C.; Radovic, L.; Thrower, P.

    1998-04-14

    The goal of this study was to gain a fundamental understanding of the role of boron in carbon oxidation. Boron-doped carbons were synthesized via CVD, ion implantation and high temperature doping are subsequently characterized. It was found that high temperature doped HOPG carbons were ideal for oxidation studies because their surface could be reproduced, their surface structures were determined and they were able to be characterized by XPS, AFM and SEM. The direct analysis of the chemical structures and atomic arrangements in boron- doped carbon or carbon surfaces by these techniques was critical in determining the effect of boron on carbon oxidation. XPS was utilized in this work to determine the local bonding environment of boron in carbon before an after oxidation. It was necessary to obtain an accurate calibration of the B1s binding energy scale which was accomplished by obtaining photoemission spectra of boron-doped carbons with known structures (local boron bonding environments), such as boron oxide, boron carbide, triphenylboroxine, tourmaline, boric acid, danburite and high temperature boron-doped graphite. All of the aforementioned standards contain boron in a unique bonding environment and thus their spectra formulated a complete conversion of B1s binding energies to boron chemical environments which has not been reported in the past. It was clearly established that a chemical shift for substitutional boron in graphite exists at 186.5 eV with a FWHM of 1.2. The chemical structures of the boron in the standards were related to the binding energy using a Pauling charge distribution model and a modification of the Sanderson electronegativity method. This approach was used to determine whether the B1s binding energy would change depending upon the specific location of boron in the graphite or graphite surface.

  17. Influence of acid functionalization on the cardiopulmonary toxicity of carbon nanotubes and carbon black particles in mice

    SciTech Connect

    Tong Haiyan [Human Studies Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711 (United States)], E-mail: tong.haiyan@epa.gov; McGee, John K. [Experimental Toxicology Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711 (United States); Saxena, Rajiv K. [School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067 (India); Kodavanti, Urmila P. [Experimental Toxicology Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711 (United States); Devlin, Robert B. [Human Studies Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711 (United States); Gilmour, M. Ian [Experimental Toxicology Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711 (United States)

    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, 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 nanotubes. Further experiments are needed to understand the physico-chemical processes involved in this phenomenon.

  18. Degradation and removal of naphthalenesulphonic acids by means of adsorption and ozonation catalyzed by activated carbon in water

    NASA Astrophysics Data System (ADS)

    Rivera-Utrilla, J.; SNchez-Polo, M.

    2003-09-01

    Studies were conducted on the efficiency of systems based on the use of ozone, activated carbon, and ozone/activated carbon in the treatment of waters containing 1-naphthalenesulphonic acid, 1,5-naphthalenedisulphonic acid, and 1,3,6-naphthalenetrisulphonic acid. In the removal of these acids by adsorption on activated carbon the elevated heights of the mass transfer zone columns and the low values of the breakthrough volumes indicated that a system exclusively based on the use of activated carbon is not appropriate for the removal of these pollutants. In the ozonation of these acids the reactivity of naphthalenesulphonic acid with ozone is low. In addition, the initial concentration of total organic carbon (TOC) was not reduced during naphthalenesulphonic acids ozonation. These results indicate that a system exclusively based on the use of ozone is not adequate to decontaminate water where these acids are present. These ozonation processes were also studied in the presence of activated carbon. The presence of activated carbon enhanced the elimination rate, probably by enhancing ozone decomposition in aqueous phase in highly oxidative species. These catalytic properties seem to be favored by both the basicity of the carbon surface and the higher macropore volume. The catalytic properties of activated carbon were reduced by ozonation. New acid groups such as anhydride, lactones, and carboxylic acid were generated on the activated carbon surface during ozone treatment. This effect reduced the reactivity of the activated carbon to ozone and therefore the capacity to enhance ozone decomposition in aqueous phase. The presence of activated carbon during naphthalenesulphonic acid ozonation produced a reduction in the TOC concentration and in the genotoxicity of the degradation products. All these results indicate that this novel combined system is very promising for the treatment of water polluted with organic matter.

  19. Optoelectronically automated system for carbon nanotubes synthesis via arc-discharge in solution

    NASA Astrophysics Data System (ADS)

    Bera, Debasis; Brinley, Erik; Kuiry, Suresh C.; McCutchen, Matthew; Seal, Sudipta; Heinrich, Helge; Kabes, Bradley

    2005-03-01

    The method of arc discharge in the solution is unique and inexpensive route for synthesis of the carbon nanotubes (CNTs), carbon onions, and other carbon nanostructures. Such a method can be used for in situ synthesis of CNTs decorated with nanoparticles. Herein, we report a simple and inexpensive optoelectronically automated system for arc discharge in solution synthesis of CNTs. The optoelectronic system maintains a constant gap between the two electrodes allowing a continuous synthesis of the carbon nanostructures. The system operates in a feedback loop consisting of an electrode-gap detector and an analog electronic unit, as controller. This computerized feeding system of the anode was used for in situ nanoparticles incorporated CNTs. For example, we have successfully decorated CNTs with ceria, silica, and palladium nanoparticles. Characterizations of nanostructures are performed using high-resolution transmission electron microscopy, scanning transmission electron microscopy, energy dispersive spectroscopy, and scanning electron microscopy.

  20. Carbonized material adsorbents for the removal of mercury from aqueous solutions

    SciTech Connect

    Ishihara, S.; Pulido, L.L. [Kyoto Univ. (Japan); Kajimoto, T. [Wakayama Industrial Technology Center (Japan)

    1996-12-31

    Although wood has essentially been excluded as a starting material for the production of granular activated carbon because of the poor strength and friability of the products, powdered wood based activated carbons are still being used in water treatment and other liquid phase applications. However, the capability of powdered wood-based charcoal which in itself porous has not been fully known. Few studies have been conducted in harnessing its potential for adsorption purposes especially in water treatment. This study was conducted to investigate the possibility of using wood based carbonized materials from Sugi (Cryptomeria japonica D. Don) as adsorption materials in aqueous solutions of heavy metals like mercury, zinc, lead, cadmium and arsenic. However, of all the heavy metals investigated, mercury is considered to be the most toxic so this paper describes only the adsorption ability of the carbonized materials in adsorbing this metal from aqueous solutions of different concentrations.

  1. Optoelectronic ally automated system for carbon nanotubes synthesis via arc-discharge in solution

    SciTech Connect

    Bera, Debasis; Brinley, Erik; Kuiry, Suresh C.; McCutchen, Matthew; Seal, Sudipta; Heinrich, Helge; Kabes, Bradley [Surface Engineering and Nanotechnology Facility - SNF, Advanced Materials Processing and Analysis Center - AMPAC, and Mechanical, Materials and Aerospace Engineering - MMAE, University of Central Florida - UCF, 4000 Central Florida Blvd., Eng 1, no. 381, Orlando, Florida 32816 (United States); Advanced Materials Processing and Analysis Center - AMPAC and Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Eng 1, no. 381, Orlando, Florida 32816 (United States); NSF REU Site (UCF), Department of Chemical Engineering, University of Minnesota, Duluth, Minnesota 55803 (United States)

    2005-03-01

    The method of arc discharge in the solution is unique and inexpensive route for synthesis of the carbon nanotubes (CNTs), carbon onions, and other carbon nanostructures. Such a method can be used for in situ synthesis of CNTs decorated with nanoparticles. Herein, we report a simple and inexpensive optoelectronically automated system for arc discharge in solution synthesis of CNTs. The optoelectronic system maintains a constant gap between the two electrodes allowing a continuous synthesis of the carbon nanostructures. The system operates in a feedback loop consisting of an electrode-gap detector and an analog electronic unit, as controller. This computerized feeding system of the anode was used for in situ nanoparticles incorporated CNTs. For example, we have successfully decorated CNTs with ceria, silica, and palladium nanoparticles. Characterizations of nanostructures are performed using high-resolution transmission electron microscopy, scanning transmission electron microscopy, energy dispersive spectroscopy, and scanning electron microscopy.

  2. Infrared spectra and molar absorption coefficients of the 20 alpha amino acids in aqueous solutions in the spectral range from 1800 to 500 cm -1

    NASA Astrophysics Data System (ADS)

    Wolpert, Martina; Hellwig, Petra

    2006-07-01

    In this work, we present the absorption spectra and molar coefficients of all 20 amino acids in aqueous solutions down to 500 cm -1. The spectral region between 1200 and 500 cm -1 was yet disregarded for protein infrared spectroscopy, mainly due to the strong H 2O absorption. Absorption spectra were obtained mainly for physiological relevant pH region. Intense bands for aromatic amino acids, histidine and such with OH group could clearly be identified throughout the given spectral region. For sulfur-containing amino acids cysteine and methionine some strong bands besides the weak carbon-sulfur stretching vibration was shown. Effects of aqueous solution environment, pH, protonation states were discussed, together with previously reported data from theoretical approaches. With this complete set of spectral information application to proteins in the whole mid infrared region could be described precise and the potential of the lower spectral region to study typical cofactor ligands like histidine, shown.

  3. Solution of the Knapsack Problem by Deoxyribonucleic Acid Computing

    NASA Astrophysics Data System (ADS)

    Aoi, Yohei; Yoshinobu, Tatsuo; Tanizawa, Katsuyuki; Kinoshita, Kozo; Iwasaki, Hiroshi

    1998-10-01

    Deoxyribonucleic acid (DNA) computing is executed to demonstrate that it is capable of solving a simple instance of the knapsack problem, which is known to be NP-complete. DNA molecules with different lengths coding the data are prepared, and the algorithm is implemented as molecular biological processes such as ligation, polymerase chain reaction (PCR), and DNA sequencing. The scheme of encoding, experimental procedures and results are described, and the scalability of the present method is discussed. Reactions between DNA molecules are expected to realize a massively parallel computation of the order of 1023 per mol.

  4. Corrosion of iron in anhydrous acetonitrile solutions of some carboxylic acids

    SciTech Connect

    Aramaki, Kunitsugu; Shimizu, Kiyoshi; Sakakibara, Makoto; Nishihara, Hiroshi (Keio Univ., Yokohama (Japan). Dept. of Chemistry)

    1993-06-01

    Corrosion of iron in anhydrous acetronitrile solutions of some carboxylic acids containing a small amount of water (100 [approximately] 350 ppm) was investigated by polarization measurements. Polarization curves of the iron electrode in aqueous and acetonitrile solutions of carboxylic acids (acetic, chloroacetic, dichloroacetic, and benzoic) are discussed based on the content of water and the concentration of H[sup +] and carboxylate ion. A linear relationship between logarithms of the corrosion current density and proton concentration was established for iron in acetonitrile solutions. The cathodic reaction was first order with respect to the H[sup +] concentration. The cathodic process of iron corrosion in the acetonitrile solutions with a small amount of water seemed to be similar to that in the aqueous solutions.

  5. Evaluation of peritoneal dialysis solutions with amino acids and glycerol in a rat model.

    PubMed

    Faict, D; Lameire, N; Kesteloot, D; Peluso, F

    1991-01-01

    In this study a simple rat model for evaluating the ultrafiltration by peritoneal dialysis solutions is described. Anaesthetised male Sprague-Dawley rats were injected intraperitoneally with dialysis solutions. Zero, 1, 3, or 6 h later, the dialysate volume was determined directly: the abdomen was carefully opened, the intraperitoneal liquid was withdrawn with a syringe and its volume was measured. Good recovery of dialysate, highly reproducible results, and the similarity between the ultrafiltration profiles in rats and published profiles in CAPD patients for control solutions, indicate that the model is valid. The model was then used to evaluate peritoneal dialysis solutions containing a mixture of glycerol and amino acids. Both osmotic agents are chemically compatible and these mixtures provide amino acids and carbohydrates in a single solution. For three mixtures, intraperitoneal dialysate volume were determined as a function of dwell time and the formulation with the desired ultrafiltration could be selected. PMID:1857524

  6. Denitrification of nitrate and nitric acid with methanol as carbon source

    Microsoft Academic Search

    Giinter Claus; Hans Jiirgen Kutzner

    1985-01-01

    A methanol\\/nitrate-medium and anaerobic conditions yielded an enrichment culture which consisted ofHyphomicrobium andParacoccus. This mixed culture proved to be very effective in denitrification of solutions containing high concentrations of nitrate and free nitric acid when grown in a chemostat (D=0.04 h-1). With 0.1 mol\\/l nitric acid solution as feed medium the pH in the culture vessel adjusted itself to 5.8.

  7. Removal of Cr(VI) from aqueous solution by adsorption onto activated carbon

    Microsoft Academic Search

    K. Selvi; S. Pattabhi; K. Kadirvelu

    2001-01-01

    Activated carbon (AC) prepared from coconut tree sawdust was used as an adsorbent for the removal of Cr(VI) from aqueous solution. Batch mode adsorption studies were carried out by varying agitation time, initial Cr(VI) concentration, carbon concentration and pH. Langmuir and Freundlich adsorption isotherms were applied to model the adsorption data. Adsorption capacity was calculated from the Langmuir isotherm and

  8. Field evaluation of gelled acid for carbonate formations

    SciTech Connect

    Church, D.C.; Quisenberry, J.L.; Fox, K.B.

    1981-01-01

    A new gelled acid was evaluated in W. Texas, S.E. New Mexico, and Oklahoma. The evaluation determined how successful a gelled acid, prepared from xanthan polymer, would be in the following formations: Ellenburger, Blinebry, San Andres, Clearfork, Canyon Lime, Strawn Lime, Grayburg, Devonian, Drinkard Dolomite, Viola and Chester. Treatment depths vary from 4000 to 22,000 ft. Treatment temperatures vary from 70 to 310 F. Treatments were performed on both oil and gas wells. The age of the wells stimulated varies from new to 30 yr old. The concentration of gelled acid remained constant at 15% HCl. The concentration of gelling agent remained constant at 60 lb/1000 gal. The size of the treatments varied from 5000 to 80,000 gal of gelled acid. More than 20 treatments are summarized. Production figures for the well treated are summarized. Production figures for the wells treated are discussed, as well as pertinent related information.

  9. Carbon-centric Computing: IT Solutions for Climate Change

    Microsoft Academic Search

    Aditya K. Ghose; Helen M. Hasan; T. Spedding

    2008-01-01

    IT has a role to play in the current debate on climate change. The current discourse on IT and climate change views IT in a negative light, as a polluter. What remains unrecognized is the critical role of IT as a source of solutions to the climate change problem. We live in a massive, inter-connected Planet Earth Supply Chain. IT

  10. 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.

  11. Adsorption of Pyridine from Aqueous Solution by Surface Treated Carbon Nanotubes

    Microsoft Academic Search

    Bo Zhao; Duan Qiu

    2007-01-01

    The surface treatment of multi?walled carbon nanotubes (MWCNTs) with acid, heat, ultrasonic, and polyvinyl alcohol has been examined. The original CNTs and four treated CNTs were first used as adsorbents to remove pyridine from water and the adsorption isotherms of pyridine on CNTs were studied. At the same time, the effect of pH, temperature, and the adsorption kinetics on the

  12. Grafting molecularly imprinted poly(2-acrylamido-2-methylpropanesulfonic acid) onto the surface of carbon microspheres

    NASA Astrophysics Data System (ADS)

    Yang, Yongzhen; Zhang, Yan; Li, Sha; Liu, Xuguang; Xu, Bingshe

    2012-06-01

    Poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) was grafted on the surface of carbon microspheres (CMSs), which were modified in prior by a mixed acid (HNO3 and H2SO4) oxidation and 3-methacryloxypropyl trimethoxysilane silanization. Then, the molecularly imprinting polymerization was carried out towards the macromolecule PAMPS grafted on the surface of CMSs using dibenzothiophene (DBT) as template, ethylene dimethacrylate as cross-linking agent and (NH4)2S2O8 (APS) as initiator to prepare surface molecularly imprinted polymer (MIP-PAMPS/CMSs) for adsorbing DBT. The optimized conditions of grafting PAMPS, including AMPS dosage, APS content, reaction temperature and reaction time, were emphasized in this paper. The morphology of the samples was characterized by field emission scanning electron microscopy. The functional groups were analyzed qualitatively by Fourier transform infrared spectrometry. The grafting degree of PAMPS was investigated by thermogravimetry. The results show that the preferable AMPS dosage, APS content, reaction temperature and time were 5 g, 0.15 g, 70 C and 12 h, respectively, for preparing PAMPS/CMSs composite on the basis of 1.0 g of silanized-CMSs. The absorbing characteristic of MIP-PAMPS/CMSs toward DBT was studied preliminarily with dynamic adsorption. In the experiment of dynamic adsorption, MIP-PAMPS/CMSs and non-imprinted polymer (NIP-PAMPS/CMSs) were compared with respect to their rapid adsorption in 1 mmol/L of DBT solution in n-hexane. When the first 1 mL of 1 mmol/L DBT solution was injected and flowed through a column packed with 0.1 g of MIP-PAMPS/CMSs, the content of DBT reduced to 0.265 mmol/L, that is, decreased significantly from 279 to 74 ppm. When 3 mL of DBT solution was flowed through the packed column, the adsorption of MIP-PAMPS/CMSs toward DBT reached saturation with the maximum adsorption amount of 1.38 10-2 mmol/g and the overall adsorption efficiency of 46%, while NIP-PAMPS/CMSs adsorbed only 1.66 10-3 mmol/g of DBT. It is suggested that the MIP-PAMPS/CMSs had much better adsorption property towards DBT than NIP-PAMPS/CMSs.

  13. J. Chem. Soc., Perkin Trans. 2, 1997 821 Mechanism of the Beckmann rearrangement in sulfuric acid solution

    E-print Network

    Nguyen, Minh Tho

    a Beckmann mixture consists of a solution of acetic acid and acetic anhydride, saturated with gaseous hydrogen chloride, an oleum solution contains sulfuric acid and sulfur trioxide (H2SO4 SO3). An aqueous aqueous solutions of H2SO4, alicyclic oximes undergo hydrolysis rather than BR. In the industrial

  14. Study on high-temperature naphthenic acid corrosion and erosion-corrosion of aluminized carbon steel

    Microsoft Academic Search

    X. Q. Wu; H. M. Jing; Y. G. Zheng; Z. M. Yao; W. Ke

    2004-01-01

    High-temperature naphthenic acid corrosion (NAC) and erosion-corrosion (NAEC) behaviors of pack-aluminized carbon steel have been investigated in laboratory to evaluate the resistance of aluminized layer to the NAC and NAEC. A field erosion-corrosion test of 700 days was also performed in an oil refinery. Parallel tests were carried out for carbon steel. It was found that the aluminized steel exhibited

  15. Examining the Microbial Degradation of Naphthenic Acids Using Stable Isotope Analysis of Carbon and Nitrogen

    Microsoft Academic Search

    Patricia P. Videla; Andrea J. Farwell; Barbara J. Butler; D. George Dixon

    2009-01-01

    Naphthenic acids (NAs) are a complex group of naturally occurring oil sands constituents that constitute a significant portion\\u000a of the dissolved organic carbon (DOC) pool available for microbial degradation in the process-related waste water associated\\u000a with oil sands mine sites. One approach to understanding the biological fate of oil sands process-derived carbon and nitrogen\\u000a in aquatic reclamation of the mine

  16. Covalent functionalization of single walled carbon nanotubes with peptide nucleic acid: Nanocomponents for molecular level electronics

    Microsoft Academic Search

    Krishna V. Singh; Rajeev R. Pandey; Xu Wang; Roger Lake; Cengiz S. Ozkan; Kang Wang; Mihrimah Ozkan

    2006-01-01

    Imparting molecular recognition to carbon nanotubes (CNTs) by conjugating them with bio-molecules has been an area of great interest as the resulting highly functionalized CNT-bioconjugates find their applications in various fields like molecular level electronics, pharmaceuticals, drug delivery, novel materials and many others. In this work we demonstrate the synthesis of functionally engineered single walled carbon nanotubes (SWNTs)-peptide nucleic acid

  17. Labradorite dissolution in aqueous organic acid solutions: an experimental study

    E-print Network

    Ahmed, MD. Raquib Uddin

    1995-01-01

    H-buffered solutions of 0.07m acetate(pHi=3.5, 4.7, 5.4), 0.07m acetate0.005m oxalate (pHi=4.4), and 0.07m acetate-0.005m citrate (pHi=4.4). Pore fluid flow was essentially constant (25-30 ml/hr) for rate studies and semi-static and slow (0.03-0.3 ml/hr) for solubility...

  18. Anodic dissolution of cobalt suicides in sulfuric acid solutions

    Microsoft Academic Search

    A. B. Shein; O. V. Kanaeva

    2000-01-01

    Anodic dissolution of suicides Co2Si, CoSi, and CoSi2 in 0.5 M H2SO4 solutions with and without NaF is studied by polarization methods coupled with an atomic-absorption analysis. In the absence\\u000a of NaF, anodic stability of cobalt silicides is higher than that of cobalt itself by 36 orders of magnitude and increases\\u000a in the series Co2Si 2. Cobalt selectively dissolves from

  19. Catalytic ozonation of oxalic acid using carbon nanofibres on macrostructured supports.

    PubMed

    Restivo, J; rfo, J J M; Pereira, M F R; Vanhaecke, E; Rnning, M; Iouranova, T; Kiwi-Minsker, L; Armenise, S; Garcia-Bordej, E

    2012-01-01

    Carbon nanofibres (CNFs) were grown on different macrostructured supports such as cordierite monoliths, carbon felts and sintered metal fibres. The resulting composites exhibited excellent resistance to attrition/corrosion and its porosity is mainly due to mesoporous structures. The CNF/structured materials were tested in the ozonation of oxalic acid in a conventional semi-batch reactor after being crushed to powder form, and in a newly designed reactor that may operate in semi-batch or continuous operation. The CNFs supported on the different structured materials exhibited high catalytic activity in the mineralization of oxalic acid. PMID:22546802

  20. 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

  1. 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. PMID:23606130

  2. Carbon Cycle: Exchanging Carbon Dioxide between the Atmosphere and Ocean

    NSDL National Science Digital Library

    This lab investigates the exchange of carbon dioxide between the atmosphere and the ocean's surface. It is based on the fact that carbon dioxide dissolves in the ocean and provides the source of that plants and plankton living in the ocean rely on for photosynthesis. Students will discover that the amount of carbon dioxide the ocean can contain depends on the temperature of the water and its salinity (whether it is sea water or fresh water) and that cold water can hold more carbon dioxide in solution than warm water. They will observe that when carbon dioxide dissolves in water, it forms carbonic acid which makes the water acidic, and they will test for the acidity caused by the presence of dissolved carbon dioxide using Universal Indicator, which turns yellow when the solution is acidic. This activity tests whether sea water or fresh water absorbs more carbon dioxide.

  3. Degradation of 17beta-estradiol in aqueous solution by ozonation in the presence of manganese(II) and oxalic acid.

    PubMed

    Jiang, Liying; Zhang, Lu; Chen, Jianmeng; Ji, Hong

    2013-01-01

    Natural estrogens, such as 17beta-estradiol (E2), are the main substances responsible for estrogenic activity found in domestic sewage. In the work described herein, the degradation of E2 has been investigated by single ozonation and catalytic ozonation in the presence of manganese ion (Mn2+) and oxalic acid. The presence of Mn2+ and oxalic acid in the ozonation processes significantly improved the E2 degradation and, hence, the reduction of estrogenic activity in aqueous solution. The addition of Mn2+ and oxalic acid produced many more hydroxyl radicals in the catalytic ozonation system than in the single ozonation system. Oxidation products formed during ozonation of E2 have been identified by means of gas chromatography-mass spectrometry (GC-MS), on the basis of which a possible reaction pathway for E2 degradation by ozonation is proposed. E2 was first oxidized to hydroxyl-semiquinone isomers, and these were subsequently degraded to low molecular weight compounds such as oxalic acid and malonic acid. The latter were easily oxidized by ozone to form carbon dioxide (CO2). The results demonstrate that the ozonation-Mn(2+)-oxalic acid system may serve as a powerful tool for removing E2, and the addition of Mn2+ and oxalic acid is favourable for the complete removal of estrogenic activity induced by steroid estrogens in aqueous solution. PMID:23530323

  4. Catalytic ozonation of p-chlorobenzoic acid by activated carbon and nickel supported activated carbon prepared from petroleum coke.

    PubMed

    Li, Xukai; Zhang, Qiuyun; Tang, Lili; Lu, Ping; Sun, Fengqiang; Li, Laisheng

    2009-04-15

    The aim of this research was to investigate catalytic activity of petroleum coke, activated carbon (AC) prepared from this material, Ni supported catalyst on activated carbon (Ni/AC) in the ozonation of aqueous phase p-chlorobenzoic acid (p-CBA). Activated carbon and Ni/AC catalyst were characterized by XRD and SEM. The presence of petroleum coke did not improve the degradation of p-CBA compared to ozonation alone, but it was advantageous for p-CBA mineralization (total organic carbon, TOC, reduction), indicating the generation of highly oxidant species (*OH) in the medium. The presence of either activated carbon or Ni/AC considerably improves TOC removal during p-CBA ozonation. Ni/AC catalyst shows the better catalytic activity and stability based on five repeated tests during p-CBA ozonation. During the ozonation (50 mg/h ozone flow rate) of a 10 mg/L p-CBA (pH 4.31), it can be more mineralized in the presence of Ni/AC catalyst (5.0 g/L), TOC removal rate is over 60% in 60 min, 43% using activated carbon as catalyst, only 30% with ozonation alone. PMID:18667273

  5. Linking dynamics of soil microbial phospholipid fatty acids to carbon mineralization in a 13C natural abundance experiment: Impact of heavy metals and acid rain

    Microsoft Academic Search

    Michael Stemmer; Andrea Watzinger; Karl Blochberger; Georg Haberhauer; Martin H. Gerzabek

    2007-01-01

    A 13C natural abundance experiment including GC-c-IRMS analysis of phospholipid fatty acids (PLFAs) was conducted to assess the temporal dynamics of the soil microbial community and carbon incorporation during the mineralization of plant residues under the impact of heavy metals and acid rain. Maize straw was incorporated into (i) control soil, (ii) soil irrigated with acid rain, (iii) soil amended

  6. Effect of acid rain on calcium carbonate saturation in the Albemarle sound of North Carolina

    SciTech Connect

    Rudolph, K.A.; Burgess, S.K.; Willey, J.D.; Kieber, R.J. [Univ. of North Carolina, Wilmington, NC (United States)

    1996-10-01

    The effects of acidic rainwater additions on calcium carbonate solubility and alkalinity in the poorly buffered, biologically active and commercially important waters of the Albemarle Sound, NC are reported. Samples collected monthly at four sites were analyzed for salinity, pK total alkalinity, and calcium concentrations. Five percent and 10% dilutions of sulfuric acid at pH 4, mimicking acid rain additions, were added and total alkalinity and calcium concentrations again determined. The addition of acid decreased the alkalinity in the Albemarle samples by as much as 15%, although the magnitude of the impact depended both on site and season. The effects of acid additions on dissolved calcium concentrations were more variable,. and also displayed a site and season dependency. Calcium concentrations, alkalinity, and pH values were also determined during controlled laboratory experiments, where 25 mg/L Callinectes sapidus shells were added to Albemarle Sound water. All three analytes increased significantly upon acid additions relative to controls.

  7. Carbon isotopic fractionation in the biosynthesis of bacterial fatty acids. Ozonolysis of unsaturated fatty acids as a means of determining the intramolecular distribution of carbon isotopes

    NASA Astrophysics Data System (ADS)

    Monson, K. David; Hayes, J. M.

    1982-02-01

    Methods for the determination of 13C abundances at individual olefinic carbon positions have been developed, tested, and shown to perform accurately. (1) The double bond is oxidized with ozone; (2) silver oxide is used to cleave the resulting ozonide quantitatively to carboxylic-acid fragments; (3) a modified Schmidt decarboxylation is used to produce CO 2 quantitatively from the carboxyl groups of the separated cleavage products; (4) the CO 2 is utilized for mass spectrometric analysis. The results of intramolecular isotopic analyses are combined with molecular-average isotopic compositions determined by total combustion in order to show that fatty acids biosynthesized by Escherichia coli grown aerobically with glucose as the sole carbon source and harvested at late log phase are depleted by approximately 3%. in 13C relative to the glucose. This fractionation arises in the formation of acetylcoenzyme A by pyruvate dehydrogenase and is localized at the carboxyl position in the acetyl-CoA product. The isotopic order in that two-carbon subunit is carried through the biosynthesis of fatty acids so that alternate positions in the fatty-acid chains are depleted in 13C by an amount equal to twice the molecular-average depletion. The kinetic isotope effect at C-2 for pyruvate dehydrogenase in vivo is shown to be approximately 2.3%. While it appears that no other fractionation mechanism has controlled the overall depletion of 13C in these fatty acids, a separate process responsible for control of isotopic abundances in the carboxyl groups has been identified and described elsewhere [Monson K.D. and Hayes J.M. (1980) J. Biol. Chem. 255, 11435-11441]. It is concluded that kinetic, rather than thermodynamic, factors have controlled isotopic distributions in these cells and that kinetic factors will be dominant in most biological reactions.

  8. Sorption performance and mechanism of a sludge-derived char as porous carbon-based hybrid adsorbent for benzene derivatives in aqueous solution.

    PubMed

    Kong, Lingjun; Xiong, Ya; Sun, Lianpeng; Tian, Shuanghong; Xu, Xianyan; Zhao, Cunyuan; Luo, Rongshu; Yang, Xin; Shih, Kaimin; Liu, Haiyang

    2014-06-15

    A porous sludge-derived char was prepared by a new one-step pyrolytic process with citric acid-ZnCl2 mixed fabricating-pore agents. The sludge-derived char was confirmed to be a hierarchically porous hybrid adsorbent containing-elemental carbon, -highly carbonized organic species and -inorganic ash with a great surface area of 792.4m(2)g(-1). It was used as a carbon-based hybrid adsorbent for four benzene derivatives including 4-chlorophenol, phenol, benzoic acid and 4-hydroxylbenzoic acid in aqueous solution. Results showed that their sorption isotherms were nonlinear at low concentrations and linear at high concentrations. The sorption performance could be described by a multiple sorption model (QT=QA+KPCe). The order of these partition sorption coefficients (KP) of these benzene derivatives was consistent with their octanol-water partition coefficients (logKow), but those saturated amounts (QA) were inconsistent with their logKow. The inconstancy was found to be considerably dependent on the preferential interaction of benzoic acid with SiO2 in the sludge-derived char. Quantum theoretical calculation confirmed that the preferential interaction was attributed to the formation of hydrogen bonds (1.61 and 1.69?) and new Si-O bonds (1.83 and 1.87?) between the carboxyl of benzoic acid and the SiO2 surface in the sorption process. PMID:24793296

  9. Stable carbon isotopic compositions of organic acids in total suspended particles and dusts from Guangzhou, China

    NASA Astrophysics Data System (ADS)

    Ma, Shexia; Peng, Ping'an; Song, Jianzhong; Zhao, Jinping; He, Lulu; Sheng, Guoying; Fu, Jiamo

    2010-10-01

    Stable carbon isotopic compositions of individual organic acids were determined in total suspended particles and dusts from Guangzhou. The ? 13C values of high molecular weight n-alkanoic acids (C 20-C 28) varied from -34.1 to -32.4 and tended to be heavier in summer and lighter in winter. These ? 13C values indicate that high molecular weight n-alkanoic acids were derived mainly from emission by C 3 plants. Reduced biological synthesis of high molecular weight n-alkanoic acids in winter may be the reason for the light carbon isotopic composition. The ? 13C values of low molecular weight n-alkanoic acids (C 10-C 18) changed from -31.7 to -30.3 and exhibited a reverse seasonal trend, i.e., heavier in winter and lighter in summer. Slightly heavier ? 13C values of low molecular weight n-alkanoic acids than those of high molecular weight n-alkanoic acids suggested that they may be emitted from blended sources, e.g., anthropogenic sources and vegetation waxes. Lighter ? 13C values in summer may be attributed to relatively low anthropogenic sources and high botanic sources in summer. Dicarboxylic acids and aromatic acids have been proposed as secondary products from photochemical degradation. The average ? 13C values of dicarboxylic acids and aromatic acids were heavier, and ranged from -25.2 to -22.9 and from -30.0 to -27.6, respectively. Both dicarboxylic acids and aromatic acids displayed the same temporal variations in the ? 13C values, i.e., negative ? 13C in the summer samples and positive in the winter samples, which may be controlled by photochemical reactions; they are generally severe in winter in Guangzhou under the monsoon weather system. The heaviest ? 13C values were observed in dicarboxylic acids, indicating that dicarboxylic acids were formed by fast and more complete oxidation reactions. These results indicate that the stable carbon isotopic composition of organic acids may provide important information about sources and photochemical reactions of organic matter in the atmosphere.

  10. Total organic carbon concentrations in acidic lakes in southern Norway

    Microsoft Academic Search

    Arne Henriksen; David F. Brakke; Stephen A. Norton

    1988-01-01

    Regional surveys in Norway demonstrate that most of the lakes have low concentrations of total organic carbon (TOC); 60% of the lakes had TOC < 2 mg\\/L and 90% had TOC < 6 mg\\/L. There was no apparent relationship between lake water pH and TOC. For the 1005 lakes sampled throughout Norway in 1986, organic anions represent <10% of the

  11. Structure and dynamics of hyaluronic acid semidilute solutions: A dielectric spectroscopy study T. Vuleti,* S. Dolanski Babi,

    E-print Network

    Podgornik, Rudolf

    Structure and dynamics of hyaluronic acid semidilute solutions: A dielectric spectroscopy study T , ribonucleic acid RNA , polypeptides and polysaccharides such as hyaluronic acid HA are essen- tial for life to investigate fundamental length scales describing the structure of hyalu- ronic acid sodium salt Na

  12. PII S0016-7037(00)00497-X Calculating the acidity of silanols and related oxyacids in aqueous solution

    E-print Network

    Sahai, Nita

    PII S0016-7037(00)00497-X Calculating the acidity of silanols and related oxyacids in aqueous models for estimating metal-oxide surface acidities. The ultimate goal is to predict surface acidities correlates well with experimental pKa in solution, because hydration enthalpies for the acid anions ( Hhyd

  13. Carbon supported PtBi catalysts for direct formic acid fuel cells

    Microsoft Academic Search

    Xingwen Yu; Peter G. Pickup

    2011-01-01

    Carbon supported PtBi bimetallic catalysts (PtBi\\/C) prepared by depositing Bi on a commercial Pt\\/C catalyst and by codeposition of Pt and Bi have been compared for formic acid oxidation in a multi-anode direct formic acid fuel cell. Both types of catalyst gave much higher cell performances than the Pt\\/C, with only low amounts of Bi (Pt to Bi mole ratios

  14. Performance characterization of direct formic acid fuel cell using porous carbon-supported palladium anode catalysts

    Microsoft Academic Search

    Sam Duck Han; Jae Ho Choi; Soon Young Noh; Soo Kyung Yoon; Young Woo Rhee

    2009-01-01

    Palladium particles supported on porous carbon of 20 and 50 nm pore diameters were prepared and applied to the direct formic\\u000a acid fuel cell (DFAFC). Four different anode catalysts with Pd loading of 30 and 50 wt% were synthesized by using impregnation\\u000a method and the cell performance was investigated with changing experimental variables such as anode catalyst loading, formic\\u000a acid

  15. Metabolically engineered Escherichia coli for biotechnological production of four-carbon 1,4-dicarboxylic acids

    Microsoft Academic Search

    Yujin Cao; Yugang Cao; Xiangzhi Lin

    2011-01-01

    Confronted with inescapable exhaustion of the earths fossil energy resources, the bio-based process to produce industrial\\u000a chemicals is receiving significant interest. Biotechnological production of four-carbon 1,4-dicarboxylic acids (C4 diacids)\\u000a from renewable plant biomass is a promising and attractive alternative to conventional chemistry routes. Although the C4 diacids\\u000a pathway is well characterized and microorganisms able to convert biomass to these acids

  16. Corrosion of Carbon Steel in Carbon Dioxide-Saturated Solutions Containing Small Amounts of Hydrogen Sulfide

    Microsoft Academic Search

    K. Videm; J. Kvarekvaal

    1995-01-01

    Carbon steel specimens were exposed in carbon dioxide (CO)-containing brine with different amounts of hydrogen sulfide (HS) at 70 C and 80 C. The addition of 0.02 mmol\\/L sulfide, corresponding to 45 Pa HS partial pressure (P{sub HS}), to brine with 70 kPa CO at pH 4.2 caused rapid formation of a protective corrosion film. After 15 min, the

  17. Optimization of dissolution of metals from Waelz sintering waste (WSW) by hydrochloric acid solutions

    Microsoft Academic Search

    Ay?e Vildan Be?e; Nurcan Borulu; Mehmet opur; Sabri olak; Osman Nuri Ata

    2010-01-01

    In this study Taguchi method was applied to determine the optimum conditions of dissolution of metals in Waelz sintering waste (WSW) in HCl solutions. The effects of solid-to-liquid ratio, reaction temperature, stirring speed, acid concentration, and reaction time on extraction efficiency were investigated. The optimum conditions were determined as follows: solid-to-liquid ratio, 0.1; reaction temperature, 65C; stirring speed, 700rpm; acid

  18. Characterisation of class F fly ash geopolymer pastes immersed in acid and alkaline solutions

    Microsoft Academic Search

    J. Temuujin; A. Minjigmaa; M. Lee; N. Chen-Tan; A. van Riessen

    2011-01-01

    Acid and alkaline resistance of class F fly ash based geopolymer pastes has been investigated. As prepared geopolymers showed high solubility in both strong alkali and acid solutions. Calcination of the fly ash based geopolymers at 600C resulted in a decrease of amorphous component from 63.4 to 61.6wt.%. However, the solubility of the Al, Si and Fe ions in 14M

  19. Iron(III) Extraction from Phosphoric Acid Solutions by Cyanex 301

    Microsoft Academic Search

    A. Ocio; M. P. Elizalde

    2011-01-01

    The extraction of Fe(III) from phosphoric acid solutions of different concentration ranging from 0.4 up to 7.3 M by Cyanex 301 in toluene is presented. The numerical treatment of the experimental data by means of the Letagrop program has allowed to propose the extraction of a single complex of stoichiometry FeR3, HR being bis(2, 4, 4-trimethylpentyl) dithiophosphinic acid, for which

  20. Adsorption Characteristics of Cadmium from Aqueous Solutions by Acid-Treated Oil Shale Ash

    Microsoft Academic Search

    Tong Su; Ai-min Li; Jing-De Luan

    2009-01-01

    A by-product oil shale ash from Huadian was treated with 5 mol\\/L nitric acid in order to enhance its adsorption capacity. The acid-treated oil shale ash was used as a low cost adsorbent to remove of cadmium from aqueous solutions. The adsorption capacity of samples to remove of cadmium was evaluated by a series of experiments, and the test results

  1. Modeling sucrose hydrolysis in dilute sulfuric acid solutions at pretreatment conditions for lignocellulosic biomass

    Microsoft Academic Search

    Shane Bower; Ranil Wickramasinghe; Nicholas J. Nagle; Daniel J. Schell

    2008-01-01

    Agricultural and herbaceous feedstocks may contain appreciable levels of sucrose. The goal of this study was to evaluate the survivability of sucrose and its hydrolysis products, fructose and glucose, during dilute sulfuric acid processing at conditions typically used to pretreat lignocellulose biomass. Solutions containing 25g\\/l sucrose with 0.12.0% (w\\/w) sulfuric acid concentrations were treated at temperatures of 160200C for 312min.

  2. Peptidic compound as corrosion inhibitor for brass in nitric acid solution

    Microsoft Academic Search

    Y Abed; M Kissi; B Hammouti; M Taleb; S Kertit

    2004-01-01

    The study of BocPheMetOCH3 as corrosion inhibitor for 60Cu40Zn in nitric acid solution was performed through weight loss and electrochemical polarisation measurements. The corrosion rate is highly reduced in the inhibited nitric acid. The inhibition efficiency E (%) reached a maximum value of 100% for BocPheMetOCH3. Polarisation measurements indicated that BocPheMetOCH3 acted as cathodic inhibitors without changing the mechanism of

  3. Ferulic Acid Stabilizes a Solution of Vitamins C and E and Doubles its Photoprotection of Skin

    Microsoft Academic Search

    Fu-Hsiung Lin; Jing-Yi Lin; Ravindra D. Gupta; Joshua A. Tournas; James A. Burch; M. Angelica Selim; Nancy A. Monteiro-Riviere; James M. Grichnik; Jan Zielinski; Sheldon R. Pinnell

    2005-01-01

    Ferulic acid is a potent ubiquitous plant antioxidant. Its incorporation into a topical solution of 15% L-ascorbic acid and 1% ?-tocopherol improved chemical stability of the vitamins (C+E) and doubled photoprotection to solar-simulated irradiation of skin from 4-fold to approximately 8-fold as measured by both erythema and sunburn cell formation. Inhibition of apoptosis was associated with reduced induction of caspase-3

  4. Solution processible poly(aniline) via doping with diesters of sulfosuccinic acid

    Microsoft Academic Search

    M Zagorska; I Kulszewicz-Bajer; O Blet; P Zawirska; B Dufour; P Rannou; A Pron

    2003-01-01

    We demonstrate that similarly as in the case of poly(pyrrole), diesters of sulfosuccinic acid containing alkyl or alkoxy substituents can serve as dopants inducing solution processibility of poly(aniline) (PANI). Free-standing films of PANI doped with sulfosuccinates, cast from 2,2?-dichloroacetic acid, show excellent thermal stability and electrical conductivity exceeding 100Scm?1 which in addition is metallic in character down to 230K.

  5. Dissolution of mechanically activated Panzhihua ilmenites in dilute solutions of sulphuric acid

    Microsoft Academic Search

    Chun Li; Bin Liang; Ling-hong Guo

    2007-01-01

    Dissolution of mechanically activated Panzhihua ilmenite was conducted in 520% sulphuric acid solutions. With high milling intensity the milling atmosphere significantly affected the dissolution with milling under vacuum almost double the dissolution of ilmenite milled in air. This was due to formation of a lot of acid-resistant pseudorutile and lowering level of the lattice strains, especially in the c-axis direction

  6. Enantioselective Small Molecule Synthesis by Carbon Dioxide Fixation using a Dual Brnsted Acid/Base Organocatalyst.

    PubMed

    Vara, Brandon A; Struble, Thomas J; Wang, Weiwei; Dobish, Mark C; Johnston, Jeffrey N

    2015-06-17

    Carbon dioxide exhibits many of the qualities of an ideal reagent: it is nontoxic, plentiful, and inexpensive. Unlike other gaseous reagents, however, it has found limited use in enantioselective synthesis. Moreover, unprecedented is a tool that merges one of the simplest biological approaches to catalysis-Brnsted acid/base activation-with this abundant reagent. We describe a metal-free small molecule catalyst that achieves the three component reaction between a homoallylic alcohol, carbon dioxide, and an electrophilic source of iodine. Cyclic carbonates are formed enantioselectively. PMID:26039818

  7. Acid gas absorption in aqueous solutions of mixed amines

    SciTech Connect

    Rinker, E.B.; Ashour, S.S.; Sandall, O.C. [Univ. of California, Santa Barbara, CA (United States)

    1996-12-31

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

  8. Experimental and theoretical investigation of boric acid production through reactive dissolution of oxalic acid crystals in borax aqueous solution

    Microsoft Academic Search

    Bahman ZareNezhad

    2003-01-01

    Reaction of oxalic acid crystals with borax solution was experimentally investigated in a 1.5 L batch reactor at different\\u000a operating conditions. The reaction was fast and took place very near to the surface of solid reactant. The dissolution process\\u000a was found to be bulk diffusion controlled. A surface reaction model considering particle shrinkage was proposed for description\\u000a of the process.

  9. Fluid and Solute Transport from a Conduit to the Matrix in a Carbonate Aquifer System

    Microsoft Academic Search

    Eric W. Peterson; Carol M. Wicks

    2005-01-01

    Within carbonate systems, the working hypothesis suggests that when a conduit is flooded fluid and solute migrate from the\\u000a conduit into the matrix. This flux of fluid and solute into the matrix creates a reservoir that can be slowly released once\\u000a the flooding recedes. Although hypothesized, these fluxes have never been measured. To quantify the distance that a fluid\\u000a and

  10. Solution-processed flexible transparent conductors based on carbon nanotubes and silver grid hybrid films.

    PubMed

    Wang, Jing; Zhang, Jintao; Sundramoorthy, Ashok Kumar; Chen, Peng; Chan-Park, Mary B

    2014-05-01

    In a simple, cost-effective, and solution-based process, a thin-film of single-walled carbon nanotubes is hybridized on a PET film which has been patterned with solution self-assembled Ag nanoparticles. Such a flexible and transparent electrode exhibits a sheet resistance down to ?5.8 ? sq(-1) at ?83.7% optical transmittance. The hybrid films are stable under ambient conditions and offer excellent bendability. PMID:24675812

  11. Sorption of nickel ions from aqueous solutions using activated carbon derived from walnut shell waste

    Microsoft Academic Search

    Gang Wang; Aimin Li; Mingzhi Li

    2010-01-01

    Studies on a batch sorption process using activated carbon derived from walnut shell were investigated to remove Ni(II) ions from aqueous solutions. The infl uence of operational conditions such as contact time (0150 min), solution initial pH (28), Ni(II) initial concentration (1080 mg\\/L), sorbent mass (0.051.0 g\\/100 mL) and temperature (293313 K) on the sorption was studied. Sorption data of

  12. Descriptive sensory analysis of broiler breast fillets marinated in phosphate, salt, and acid solutions.

    PubMed

    Lyon, B G; Smith, D P; Savage, E M

    2005-02-01

    Sensory attributes of fully aged broiler breast fillets marinated in a 6% NaCl solution containing 2% sodium tripolyphosphate (2P), 2% citric acid (2C), 2% acetic acid (2A), 1% citric acid plus 1% phosphate solution (1C), or 1% acetic acid solution plus 1% phosphate (1A) were studied. A 6% NaCl (6S) solution with no additives was used as control. Oven-cooked samples (177C degrees oven; 75 degrees C internal temperature) were evaluated by a 9-member trained descriptive analysis sensory panel that rated the intensities of 26 different flavor and texture attributes using 15-point line scales. Data were analyzed using general linear model SAS procedures to determine significant differences (P < or = 0.05) in individual sensory attributes due to marinade treatment. All sensory attributes were scored in the low intensity range (1.5 to 5.0). Brothy, vinegar, and residual particles were the only individual attributes rated significantly different (P < or = 0.05) due to treatment. Multivariate analyses indicated that all sensory attributes formed 2 dimensions that explained 57% of variation in the data. The low intensity values for texture attributes indicated possible negative consequences due to phosphates, salt, and acids when used with fully aged fillets. PMID:15742973

  13. Distribution of zirconium in petroleum sulfoxides during extraction and sorption from nitric and hydrochloric acid solutions

    SciTech Connect

    Turanov, A.N.

    1988-11-20

    Petroleum sulfoxides (PSO) are effective extractants for several metals. We discussed the distribution of petroleum sulfoxides and zirconium between aqueous solutions of hydrochloric and nitric acid and organic solvents, and also the macroporous sorbent impregnated with PSO. For the investigation we used a macroposous copolymer of styrene with divinylbenzene. Our investigation showed a noticeable decrease in the contamination of the raffinates by petroleum sulfoxides and their more complete utilization as extractant of metals from solutions of acids when PSO is deposited on a macroporous copolymer of styrene with divinylbenzene.

  14. Properties of alkali-solubilized collagen solution crosslinked by N-hydroxysuccinimide activated adipic acid

    Microsoft Academic Search

    Yihui Chen; Min Zhang; Wentao Liu; Guoying Li

    2011-01-01

    The effect of N-hydroxysuccinimide activated adipic acid (NHS-AA) on the properties of alkali-solubilized collagen solutions\\u000a was examined. The residual amino group content in crosslinked collagen, determined by trinitrobenzensulfonic acid (TNBS) assay,\\u000a was decreased with increasing NHS-AA concentration. The results from differential scanning calorimeter (DSC) indicated that\\u000a the maximum denaturation temperature (T\\u000a d) of crosslinked collagen solution was about 4.2C higher

  15. Optimization of carbon-nitrogen ratio for production of gibberellic acid by Pseudomonas sp.

    PubMed

    Ba?iaik Karako, Safak; Aksz, Nilufer

    2004-01-01

    In this study, favorable carbon-nitrogen ratio for high yields of gibberellic acid (GA3) production from Pseudomonas sp. was investigated. First of all, optimum carbon (glucose, maltose, sucrose, fructose, lactose) and nitrogen (KNO3, NH4Cl, NaNO3, urea, glycine) sources among the others were chosen. The highest yield of GA3 productivity was found in growth medium supplemented with fructose (168.5 mg/L). NaNO3 was found as a suitable nitrogen source (141 mg/L). Then, in order to determine the optimum carbon-nitrogen ratio, different concentrations of carbon (from 50 mM to 150 mM) and nitrogen (from 17 mM to 47 mM) sources were added in culture media. As a result, optimum carbon-nitrogen ratio for GA3 production from Pseudomonas sp. was found to be 100:17 mM. PMID:15478357

  16. Emergency cooling experiments with aqueous boric acid solution in the REWET-II facility

    SciTech Connect

    Kervinen, T.; Tuunanen, J.

    1987-01-01

    Although boron is widely used as soluble neutron poison in nuclear reactors (boric acid in pressurized water reactors, sodium pentaborate in boiling water reactors), there is a lack of experimental data about aqueous boron solution behavior during loss-of-coolant accidents. The main aims of the REWET boric acid experiments were to study the behavior of aqueous boric acid solution during long-term cooling of a nuclear reactor and to find out the circumstances in which boric acid crystallization takes place. In the experiments, carried out in the facility of a 19-fuel-rod simulator bundle, boric acid crystallization caused the uncovering of the bundle, which always occurred on the water surface. However, crossflows and backflows in a reactor presumably make the concentrations uniform and thus retard crystallization. Therefore, experimental investigations of aqueous boric acid solution behavior will be carried out for the next 2 yr in a larger scale experimental facility. The new facility will be a simulator of the Loviisa VVER-440 reactor with a scaling factor of 1:349 for power and volumes and 1:1 for elevations. The facility will contain a full-scale rod bundle.

  17. Electrochemical actuation of gilded polyaniline bilayers in aqueous acid solutions

    NASA Astrophysics Data System (ADS)

    Lu, Wen; Smela, Elisabeth; Mattes, Benjamin R.

    2001-07-01

    In this work, we investigated the electrochemical actuation of gilded polyaniline bilayers in acidic aqueous electrolytes. Gilding was found to be a useful method to ensure a uniform potential distribution across polyaniline films so that well-defined electrochemistry and electrochemical actuation could be obtained. Electrochemical actuation of gilded polyaniline bilayers was studied by means of bending and linear actuation. Actuation could be obtained by a number of electrical stimulation modes including cyclic voltammetry (CV), square wave potential (SWP) and square wave current (SWC). Within the potential range of -0.2 ~ 0.6 V (vs Ag/AgCl), the polyaniline films expanded upon oxidation and contracted upon reduction, which corresponds to the first redox process of polyaniline between the leucomeraldine and emaraldine oxidation states. Actuation obtained in this potential range is related to the insertion/deinsertion of the electrolyte anion upon oxidation/reduction of polyaniline. It was found that, due to the thin thickness of the gold layer, not only fast bending actuation but also linear actuation could be achieved for the resulting gilded polyaniline bilayers. Extending the applied potential to more positive potentials, polyaniline degradation and oxidation of gold layer were observed.

  18. Stability of antimicrobial activity of peracetic acid solutions used in the final disinfection process.

    PubMed

    Costa, Solange Alves da Silva; Paula, Olvia Ferreira Pereira de; Silva, Clia Regina Gonalves E; Leo, Mariella Vieira Pereira; Santos, Silvana Solo 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. PMID:25715037

  19. Incorporation of C14 From Carbon Dioxide into Sugar Phosphates, Carboxylic Acids, and Amino Acids by Clostridium thermoaceticum

    PubMed Central

    Ljungdahl, Lars; Wood, Harland G.

    1965-01-01

    Ljungdahl, Lars (Western Reserve University, Cleveland, Ohio), and Harland G. Wood. Incorporation of C14 from carbon dioxide into sugar phosphates, carboxylic acids, and amino acids by Clostridium thermoaceticum. J. Bacteriol. 89:10551064. 1965.The mechanism of synthesis of acetate from carbon dioxide by Clostridium thermoaceticum was investigated by incubating cells with glucose or xylose in the presence of C14O2. Sugar phosphates, amino acids, and carboxylic acids were isolated and the specific radioactivities were determined; the distributions of C14 were also determined in some of the compounds. Only fructose-1,6-diphosphate, formate, and lactate had higher specific activities than the acetate. The specific activities and distribution of C14 in the fructose-6-phosphate and ribose-5-phosphate were such that we conclude that the synthesis of acetate does not occur via a pathway involving the sugar phosphates as direct intermediates. Likewise, it is shown that pathways including lactate, aspartate, serine, glycine, malate, and succinate are not of importance in the synthesis of acetate from CO2. The methyl group of free methionine was unlabeled and is not a precursor of the methyl group of acetate. PMID:14276095

  20. Acidbase and complexation properties of gem -diphosphonic and gem -diphosphinic acids in aqueous solutions and micellar media of surfactants

    Microsoft Academic Search

    L. P. Loginova; I. V. Levin; A. G. Matveeva; S. A. Pisareva; E. E. Nifantev

    2004-01-01

    Acid-base and complexation properties of gem-disubstituted phosphorus acids, viz., methylenediphosphonic, 1-hydroxyethylidene-1,1-diphosphonic, P,P'-diphenylmethylene-diphosphinic, and P, P'-diphenyl-1-hydroxyethylidene-1, 1-diphosphinic acids, were studied in aqueous solutions and in the presence of biomimetics (micelles of ionic surfactants). The dissociation constants of the acids and stability constants of complexes with magnesium(II) and copper(II) ions were determined in aqueous solutions and microheterogeneous media containing sodium dodecyl sulfate,