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1

Simultaneous determination of uric acid and ascorbic acid using glassy carbon electrodes in acetate buffer solution  

Microsoft Academic Search

The present work reports the simultaneous determination of uric acid (UA) and ascorbic acid (AA) in 0.2M, pH 4.0, acetate buffer solution using glassy carbon (GC) electrode by square wave voltammetry. Selective detection of UA in the presence of 200-fold excess of AA is achieved at the GC electrode in acetate buffer solution. The GC electrode separates the voltammetric signal

S. Abraham John

2005-01-01

2

Adsorption of organic acids from dilute aqueous solution onto activated carbon  

SciTech Connect

The radioisotope technique was used to study the removal of organic acid contaminants from dilute aqueous solutions onto activated carbon. Acetic acid, propionic acid, n-butyric acid, n-hexanoic acid and n-heptanoic acid were studied at 278, 298, and 313/sup 0/K. Three bi-solute acid mixtures (acetic and propionic acids, acetic and butanoic acids, and propionic and butanoic acids) were studied at 278 and 298/sup 0/K. Isotherms of the single-solute systems were obtained at three different temperatures in the very dilute concentration region (less than 1% by weight). These data are very important in the prediction of bi-solute equilibrium data. A Polanyi-based competitive adsorption potential theory was used to predict the bi-solute equilibrium uptakes. Average errors between calculated and experimental data ranges from 4% to 14%. It was found that the competitive adsorption potential theory gives slightly better results than the ideal adsorbed solution theory.

Wang, S.W.

1980-06-01

3

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

DOEpatents

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.

Rau, Gregory Hudson (Castro Valley, CA)

2012-05-15

4

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

DOEpatents

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.

Rau, Gregory Hudson

2014-07-01

5

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

SciTech Connect

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%.

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

2007-08-15

6

Visible-light photoconversion of carbon dioxide into organic acids in an aqueous solution of carbon dots.  

PubMed

Carbon "quantum" dots (or carbon dots) have emerged as a new class of optical nanomaterials. Beyond the widely reported bright fluorescence emissions in carbon dots, their excellent photoinduced redox properties that resemble those found in conventional semiconductor nanostructures are equally valuable, with photon-electron conversion applications from photovoltaics to CO2 photocatalytic reduction. In this work we used gold-doped carbon dots from controlled synthesis as water-soluble catalysts for a closer examination of the visible-light photoconversion of CO2 into small organic acids, including acetic acid (for which the reduction requires many more electrons than that for formic acid) and, more interestingly, for the significantly enhanced photoconversion with higher CO2 pressures over an aqueous solution of the photocatalysts. The results demonstrate the nanoscale semiconductor-equivalent nature of carbon dots, with excellent potential in energy conversion applications. PMID:24972094

Sahu, Sushant; Liu, Yamin; Wang, Ping; Bunker, Christopher E; Fernando, K A Shiral; Lewis, William K; Guliants, Elena A; Yang, Fan; Wang, Jinping; Sun, Ya-Ping

2014-07-22

7

Molecular Structure of Carbonic acid  

NSDL National Science Digital Library

The hypothetical acid formed with carbon dioxide and water; it is only in the H2CO3 form when in solution. This acid is found in everyday products, the most prominent of which include carbonated beverages. The conversion of carbonic acid into water and carbon dioxide in sodas is the reason the beverage looses the bubbling.

2002-09-10

8

Synthesis of associating poly(acrylic acid) in supercritical carbon dioxide and its solution properties  

Microsoft Academic Search

Hydrophobically associating polymers have been synthesized in supercritical carbon dioxide by copolymerization of acrylic acid with different amounts of acrylate with hydrocarbon or fluorocarbon groups. It was found that conversion of hydrocarbon comonomers was above 95% whereas that for fluorocarbon comonomers was only about 50%. In addition, large amounts of hydrophobic groups could be easily introduced to poly(acrylic acid) by

Zhang Bin; Hongqi Hu; Mingcai Chen; Weiqu Liu

2004-01-01

9

GENERATION OF SOIL SOLUTION ACID NEUTRALIZING CAPACITY BY ADDITION OF DISSOLVED INORGANIC CARBON  

EPA Science Inventory

A Spodosol B horizon(base saturation of 5.4%) collected at the Watershed Manipulation Project site at Lead Mountain, ME, was used to examine soil solution chemistry in response to increasing solution levels of dissolved inorganic carbon (DIC). cid-neutralizing capacity (ANC), det...

10

Electrochemical synthesis of Cr(II) at carbon electrodes in acidic aqueous solutions  

Microsoft Academic Search

The electrochemical synthesis of Cr(II) has been investigated on a vitreous carbon rotating disc electrode and a graphite felt electrode using cyclic voltammetry, impedance spectroscopy and chronoamperometry. The results show that in 0.1 M Cr(III) + 0.5 M sulphuric acid and in 0.1 M Cr(III) + 1 M hydrochloric acid over an electrode potential range of -0.8 to 0.8 V

Q. Yin; N. P. Brandon; G. H. Kelsall

2000-01-01

11

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

NASA Astrophysics Data System (ADS)

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%.

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

1999-03-01

12

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

SciTech Connect

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.

Peter Zalupski; Rocklan McDowell; Guy Dutech

2014-10-01

13

ELECTROCHEMICAL STUDIES ON THE CORROSION OF CARBON STEEL IN OXALIC ACID CLEANING SOLUTIONS  

SciTech Connect

The Savannah River Site (SRS) will disperse or dissolve precipitated metal oxides as part of radioactive waste tank closure operations. Previously SRS has utilized oxalic acid to accomplish this task. Since the waste tanks are constructed of carbon steel, a significant amount of corrosion may occur. Although the total amount of corrosion may be insignificant for a short contact time, a significant amount of hydrogen may be generated due to the corrosion reaction. Linear polarization resistance and anodic/cathodic polarization tests were performed to investigate the corrosion behavior during the process. The effect of process variables such as temperature, agitation, aeration, sample orientation, light as well as surface finish on the corrosion behavior were evaluated. The results of the tests provided insight into the corrosion mechanism for the iron-oxalic acid system.

Wiersma, B; John Mickalonis, J

2007-10-08

14

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

SciTech Connect

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.

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

1992-02-01

15

Electrochemical splitting of calcium carbonate to increase solution alkalinity: implications for mitigation of carbon dioxide and ocean acidity.  

PubMed

Electrochemical splitting of calcium carbonate (e.g., as contained in limestone or other minerals) is explored as a means of forming dissolve hydroxides for absorbing, neutralizing, and storing carbon dioxide, and for restoring, preserving, or enhancing ocean calcification. While essentially insoluble in water, CaCO3 can be dissolved in the presence of the highly acidic anolyte of a water electrolysis cell. The resulting charged constituents, Ca2+ and C03(2-), migrate to the cathode and anode, respectively, forming Ca(OH)2 on the one hand and H2CO3 (or H2O and CO2) on the other. By maintaining a pH between 6 and 9, subsequent hydroxide reactions with CO2 primarily produce dissolved calcium bicarbonate, Ca(HCO3)2aq. Thus, for each mole of CaCO3 split there can be a net capture of up to 1 mol of CO2. Ca(HCO3)2aq is thus the carbon sequestrant that can be diluted and stored in the ocean, in natural or artificial surface water reservoirs, or underground. The theoretical work requirement for the reaction is 266 kJe per net mole CO2 consumed. Even with inefficiencies, a realized net energy expenditure lower than the preceding quantity appears possible considering energy recovery via oxidation of the H2 produced. The net process cost is estimated to be <$100/tonne CO2 mitigated. An experimental demonstration of the concept is presented, and further implementation issues are discussed. PMID:19192821

Rau, Greg H

2008-12-01

16

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

17

The voltammetry–photocurrent response study of passivation of carbon steel in slightly alkaline solutions containing the corrosion inhibitor phosphor-polymaleic acid–ZnSO 4  

Microsoft Academic Search

The electro-oxidation\\/electro-reduction processes on the surface of a carbon steel electrode were studied in borate buffer solutions (pH=8.4) in the presence and absence of the corrosion inhibitor phosphor-polymaleic acid (PPMA)–ZnSO4 at room temperature by using the voltammetry–photocurrent response method. For the carbon steel electrode in solutions containing the corrosion inhibitor, its voltammograms displayed a smaller oxidation peak current and a

Yi-Jiu Li; Bin Wu; Xin-Ping Zeng; Ya-Fei Liu; Ya-Ming Ni; Guo-Ding Zhou; Hong-Hua Ge

2002-01-01

18

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

PubMed

Calcium carbonate nanoparticles of the vaterite polymorph were synthesized by combining CaCl2 and Na2CO3 in the presence of poly (vinylsulfonic acid) (PVSA). By studying the important experimental parameters we found that controlling PVSA concentration, reaction temperature, and order of reagent addition the particle size, monodispersity, and surface charge can be controlled. By increasing PVSA concentration or by decreasing temperature CCNPs with an average size from ?150 to 500 nm could be produced. We believe the incorporation of PVSA into the reaction plays a dual role to (1) slow down the nucleation rate by sequestering calcium and to (2) stabilize the resulting CCNPs as the vaterite polymorph, preventing surface calcification or aggregation into microparticles. The obtained vaterite nanoparticles were found to maintain their crystal structure and surface charge after storage in aqueous buffer for at least 5 months. The aqueous stable vaterite nanoparticles could be a useful platform for the encapsulation of a large variety of biomolecules for drug delivery or as a sacrificial template toward capsule formation for biosensor applications. PMID:24461857

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

2014-03-15

19

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

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

20

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

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.

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

1988-01-01

21

Supercritical fluid extraction of acidic, polar solutes from aqueous matrices: Partitioning data for pentachlorophenol between carbon dioxide and water  

SciTech Connect

Supercritical fluid technologies as alternative methodologies to conventional procedures are being explored for the direct extraction of acidic and polar contaminants from aqueous matrices. In support of the knowledge required to implement these novel methods, the partitioning of pentachlorophenol between water and liquid and supercritical CO{sub 2} has been characterized by determining distribution coefficients at (18.8, 41.7, and 59.8) C from a saturated water solution (11.6 {times} 10{sup {minus}6} g/g solvent). The partitioning of pentachlorophenol from dilute solution (1.27 {times} 10{sup {minus}6} g/g solvent) was measured at 42.2 and 59.9 C. Distribution coefficients were lower at this reduced concentration. Measurements were made at pressures up to about 280 bar. Comparison of the partitioning data to the solubility ratio of the solute in both phases contributes to the interpretation of relevant interactions in this complex system.

Curren, M.S.; Burk, R.C. [Carleton Univ., Ottawa, Ontario (Canada)] [Carleton Univ., Ottawa, Ontario (Canada)

1998-11-01

22

A systematic study on the effect of acidic, basic and neutral additives on dispersion of multiwalled carbon nanotubes using a dimethylformamide solution  

NASA Astrophysics Data System (ADS)

Presence of acidic, basic and neutral additives on dispersion of multiwalled carbon nanotubes (MWCNTs) in dimethylforamide (DMF) solution has been investigated. The surface charge measurement showed that MWCNTs in the presence of acidic additives in DMF exhibit a higher surface charge (?85 C g?1) than that with the basic additives (?22 C g?1). The stability of the MWCNTs dispersion was visually monitored and it was found that in the presence of acidic and no additives it would be stable and dispersed for more than five days, whereas MWCNTs suspension immediately settle down in the presence of basic and neutral additives. The degree of defects on MWCNTs was determined by analysis of detailed Raman spectra of as-received MWNCTs and MWNCTs dispersed in DMF with different additives. By exploring the correlation between the ID/IG (Raman analysis) ratio and the degree of defects, it was found that the carbon–carbon double bond (C=C) of MWCNTs was slightly damaged by adding additives to the solvent.

Nayak, Sasmita; Bhattacharjee, Sarama; Singh, Bimal P.

2014-12-01

23

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

SciTech Connect

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

Crawford, C.L. [Westinghouse Savannah River Company, AIKEN, SC (United States); Peterson, R. A.

1997-02-11

24

Carbonic Acid Retreatment of Biomass  

SciTech Connect

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.

Baylor university

2003-06-01

25

Carbonic Acid Pretreatment of Biomass  

SciTech Connect

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.

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

2003-05-31

26

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

SciTech Connect

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.

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

2014-01-03

27

NiP? nanosheet arrays supported on carbon cloth: an efficient 3D hydrogen evolution cathode in both acidic and alkaline solutions.  

PubMed

Designing efficient and stable hydrogen evolution catalysts made from earth-abundant elements is essential to the development of solar-driven water-splitting devices. In this communication, we develop a two-step strategy for constructing NiP2 nanosheet arrays on carbon cloth (NiP2 NS/CC). As a novel 3D hydrogen evolution cathode, the NiP2 NS/CC electrode is highly active in acidic solutions and needs an overpotential of 75 and 204 mV to achieve current densities of 10 and 100 mA cm(-2), respectively, and it preserves its catalytic activity for at least 57 h. Moreover, it also operates efficiently under alkaline conditions. PMID:25293654

Jiang, Ping; Liu, Qian; Sun, Xuping

2014-11-21

28

NiP2 nanosheet arrays supported on carbon cloth: an efficient 3D hydrogen evolution cathode in both acidic and alkaline solutions  

NASA Astrophysics Data System (ADS)

Designing efficient and stable hydrogen evolution catalysts made from earth-abundant elements is essential to the development of solar-driven water-splitting devices. In this communication, we develop a two-step strategy for constructing NiP2 nanosheet arrays on carbon cloth (NiP2 NS/CC). As a novel 3D hydrogen evolution cathode, the NiP2 NS/CC electrode is highly active in acidic solutions and needs an overpotential of 75 and 204 mV to achieve current densities of 10 and 100 mA cm-2, respectively, and it preserves its catalytic activity for at least 57 h. Moreover, it also operates efficiently under alkaline conditions.Designing efficient and stable hydrogen evolution catalysts made from earth-abundant elements is essential to the development of solar-driven water-splitting devices. In this communication, we develop a two-step strategy for constructing NiP2 nanosheet arrays on carbon cloth (NiP2 NS/CC). As a novel 3D hydrogen evolution cathode, the NiP2 NS/CC electrode is highly active in acidic solutions and needs an overpotential of 75 and 204 mV to achieve current densities of 10 and 100 mA cm-2, respectively, and it preserves its catalytic activity for at least 57 h. Moreover, it also operates efficiently under alkaline conditions. Electronic supplementary information (ESI) available: Experimental section, supplementary figures, tables and movie. See DOI: 10.1039/c4nr04866k

Jiang, Ping; Liu, Qian; Sun, Xuping

2014-10-01

29

Dissolution of Spent Nuclear Fuel in Carbonate-Peroxide Solution  

SciTech Connect

This study shows that spent UO2 fuel can be completely dissolved in a carbonate-peroxide solution apparently without attacking the metallic Mo-Tc-Ru-Rh-Pd fission product phase. Samples of spent nuclear fuel were pulverized and sieved to a uniform size, then duplicate aliquots were weighed into beakers for analysis. One set was dissolved in near-boiling 10M nitric acid, and the other set was dissolved in a solution of ammonium carbonate and hydrogen peroxide at room temperature. All the resulting fuel solutions were then analyzed for Sr-90, Tc-99, Cs-137, plutonium, and Am-241. For all the samples, the concentrations of Cs-137, Sr-90, plutonium, and Am-241 were the same for both the nitric acid dissolution and the ammonium carbonate-hydrogen peroxide dissolution, but the technetium concentration of the ammonium carbonate-hydrogen peroxide fuel solution was only about 25% of the same fuels dissolved in hot nitric acid.

Soderquist, Chuck Z.; Hanson, Brady D.

2010-01-31

30

A Solution to the Problem of Nonequilibrium Acid\\/Base Gas-Particle Transfer at Long Time Step  

Microsoft Academic Search

A stable numerical solution to the unsolved problem of nonequilibrium growth\\/evaporation at long time step of multiple dissociating acids (e.g., nitric acid, hydrochloric acid, carbonic acid, sulfuric acid, etc.) and a base (ammonia) is discussed. The solution eliminates most oscillatory behavior observed in previous solutions at long time step. The solution is applicable across the entire relative humidity range, both

Mark Z. Jacobson

2005-01-01

31

Reactive solute transport in acidic streams  

USGS Publications Warehouse

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.

Broshears, R.E.

1996-01-01

32

Ions in hyaluronic acid solutions  

PubMed Central

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 ?=1.4×103c9?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 Å, as a result of calcium-sodium ion exchange. The scattered intensity in the transfer momentum rangeq>0.03 Å?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. PMID:19916626

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

2009-01-01

33

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

PubMed

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

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

2013-09-01

34

PREDICTING TEMPERATURE BEHAVIOR IN CARBONATE ACIDIZING TREATMENTS  

E-print Network

for carbonate reservoir, since the acid reacts faster with carbonate than sandstone. For vertical wells in multilayer carbonate formation (Fig. 1.1), the layers with higher permeability accept most of the injected acid, which means the low.... This model works perfectly for both gas and oil wells. Nevertheless, this model can not solve the acid injection problem because no reaction is considered in the work. Medeiros and Trevisan (2006) simulated the temperature profile in the formation...

Tan, Xuehao

2010-01-16

35

Cutting Of Carbon Nanotubes Via Solution Plasma Processing  

Microsoft Academic Search

A simple solution plasma process was developed for cutting multi-wall carbon nanotubes (MWCNTs). During the solution plasma\\u000a processing, defects and oxygen-containing functional groups (hydroxyl or carboxylic acid groups) were introduced onto the\\u000a sidewalls of the MWCNTs via hydroxyl radicals. After being cut for 30 min, short MWCNTs of 100–400 nm in length were obtained.

D. G. Tong; Y. Y. Luo; W. Chu; Y. C. Guo; W. Tian

2010-01-01

36

Experiment 2. 1. Preparing Standard Acid Solution  

E-print Network

indicator Concentrated (37 wt%) HCl Primary standard: sodium tetraborate Na2B4O7Ã?10 H2O ("borax"). FW 381.1 M HCl and prepare this solution. b. Prepare primary standard grade sodium tetraborate. c. Weigh fourExperiment 2. 1. Preparing Standard Acid Solution Hydrochloric acid and sodium hydroxide

Nazarenko, Alexander

37

Method for extracting lanthanides and actinides from acid solutions  

DOEpatents

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.

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

1985-01-01

38

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...

39

Solution nonideality related to solute molecular characteristics of amino acids.  

PubMed Central

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

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

1995-01-01

40

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

SciTech Connect

The Savannah River Site has enriched uranium (EU) solution which has been stored for almost 10 years since being purified in the second uranium cycle of the H area solvent extraction process. The concentrations in solution are approximately 6 g/L U and about 0.1 M nitric acid. Residual tributylphosphate in the solutions has slowly hydrolyzed to form dibutyl phosphoric acid (HDBP) at concentrations averaging 50 mg/L. Uranium is known to form compounds with the dibutylphosphate ion (DBP) which have limited solubility. The potential to form uranium-DBP solids raises a nuclear criticality safety issue. Prior SRTC tests (WSRC-TR-98-00188) showed that U-DBP solids precipitate at concentrations potentially attainable during the storage of enriched uranium solutions. Furthermore, evaporation of the existing EUS solution without additional acidification could result in the precipitation of U-DBP solids if the DBP concentration in the resulting solution exceeds 110 mg/L at ambient temperature. The same potential exists for evaporation of unwashed 1CU solutions. As a follow-up to the earlier studies, SRTC studied the solubility limits for solutions containing acid concentrations above 0.5M HNO3. The data obtained in these tests reveals a shift to higher levels of DBP solubility above 0.5M HNO3 for both 6 g/L and 12 g/L uranium solutions. Analysis of U-DBP solids from the tests identified a mixture of different molecular structures for the solids created. The analysis distinguished UO2(DBP)2 as the dominant compound present at low acid concentrations. As the acid concentration increases, the crystalline UO2(DBP)2 shows molecular substitutions and an increase in amorphous content. Further analysis by methods not available at SRS will be needed to better identify the specific compounds present. This data indicates that acidification prior to evaporation can be used to increase the margin of safety for the storage of the EUS solutions. Subsequent experimentation evaluated options for absorbing HDBP from solution using either activated carbon or anion exchange resin. The activated carbon outperformed the anion exchange resin. Activated carbon absorbs DBP rapidly and has demonstrated the capability of absorbing 15 mg of DBP per gram of activated carbon. Analytical results also show that activated carbon absorbs uranium up to 17 mg per gram of carbon. It is speculated that the uranium absorbed is part of a soluble U-DBP complex that has been absorbed. Additional testing must still be performed to 1) establish absorption limits for uranium for anion exchange resin, 2) evaluate desorption characteristics of uranium and DBP, and 3) study the possibility of re-using the absorbent.

Pierce, R.A.

1998-10-02

41

Plutonium recovery from carbonate wash solutions  

SciTech Connect

Periodically higher than expected levels of plutonium are found in carbonate solutions used to wash second plutonium cycle solvent. The recent accumulation of plutonium in carbonate wash solutions has led to studies to determine the cause of that plutonium accumulation, to evaluate the quality of all canyon solvents, and to develop additional criteria needed to establish when solvent quality is acceptable. Solvent from three canyon solvent extraction cycles was used to evaluate technology required to measure tributyl phosphate (TBP) degradation products and was used to evaluate solvent quality criteria during the development of plutonium recovery processes. 1 fig.

Gray, J.H.; Reif, D.J.; Chostner, D.F.; Holcomb, H.P.

1991-12-31

42

Ionization of carbon acids in liquid ammonia.  

PubMed

The acidities of various carbon acids in liquid ammonia (LNH(3)) at room temperature were determined by NMR and rates of D-exchange. There is a reasonable linear correlation of the pK(a)s in LNH(3) with those in water and DMSO of slope 0.7 and 0.8, respectively. Carbon acids with an aqueous pK(a) of less than 12 are fully ionized in liquid ammonia. Nucleophilic substitution of benzyl chloride by carbanions in liquid ammonia generates a Brønsted ?(nuc) = 0.38. PMID:22026552

Ji, Pengju; Powles, Nicholas T; Atherton, John H; Page, Michael I

2011-11-18

43

Sonophotocatalysis of oxalic acid solution.  

PubMed

Sonophotocatalysis of oxalic acid was performed in various atmospheric conditions. Sonophotocatalysis means a coupled reaction of sonolysis and photocatalysis. CO(2), CO and H(2) were obtained. The yield of CO(2) was twice larger than the sum of yields of photocatalysis and sonolysis in an Ar atmosphere. Namely, synergistic effect was observed. Further improvement was observed after pre-sonication. Hydrogen peroxide produced during sonication is a key material for the synergistic effect. In surroundings including O(2), however, synergistic effect could not be observed. The role of ultrasonic waves on the sonophotocatalysis of organic compounds was investigated. PMID:16793102

Harada, Hisashi; Tanaka, Hisashi

2006-12-22

44

Experimental equilibrium between acid gases and ethanolamine solutions  

SciTech Connect

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.

Bhairi, A.M.

1984-01-01

45

Reference electrode for strong oxidizing acid solutions  

DOEpatents

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.

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

46

Aqueous solution dispersement of carbon nanotubes  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

47

Fabrication of carbon-aerogel electrodes for use in phosphoric acid fuel cells  

E-print Network

An experiment was done to determine the ability to fabricate carbon aerogel electrodes for use in a phosphoric acid fuel cell (PAFC). It was found that the use of a 25% solution of the surfactant Cetyltrimethylammonium ...

Tharp, Ronald S

2005-01-01

48

[Investigation on mechanism of pyrite oxidation in acidic solutions].  

PubMed

The mechanism of pyrite oxidation in acidic solutions was investigated by electrochemical analysis methods, such as open-circuit potential, cyclic voltammetry, Tafel polarization curve and anodic polarization curve, using a pyrite-carbon paste electrode as working electrode. The results showed that the oxidation process of pyrite in acidic solutions was via a two-step reaction: the first step was the dissolution of iron moiety and formation of a passivation film composed of elemental sulphur, metal-deficient sulfide and polysulfide; the second step was the further oxidation of these intermediate products to SO4(2-). The final reaction products of pyrite oxidation were Fe3+ and SO4(2-) in acidic solutions. In addition, the open-circuit potential and corrosion potential were positively shifted, the peak current and the corrosion current were increased with the increase in concentration of H2SO4 solutions. This indicated that increased acidity of the system was advantageous to the oxidation of pyrite. PMID:23323425

Wang, Nan; Yi, Xiao-Yun; Dang, Zhi; Liu, Yun

2012-11-01

49

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

PubMed Central

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

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

2014-01-01

50

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

PubMed

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

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

2014-01-01

51

Reactions of rare earth flourides with sodium carbonate and hydroxide solutions  

Microsoft Academic Search

Exchange interactions of sparingly soluble rare earth (RE) compounds such as fluorides, carbonates, and hydroxides in aqueous media are studied. The starting materials were fluorides of individual RE, obtained by precipitation with hydrofluoric acid from solutions of RE nitrates, which were prepared from the corresponding oxides of 99.9% and taken to the air-dry state, and also cp sodium carbonate and

E. L. Chuviliana; N. V. Baryshnikov; I. F. Poletaev

1986-01-01

52

Acidities of Water and Methanol in Aqueous Solution and DMSO  

ERIC Educational Resources Information Center

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

Gao, Daqing

2009-01-01

53

40 CFR 721.10715 - Carbonic acid, dialkyl ester (generic).  

Code of Federal Regulations, 2014 CFR

...2014-07-01 false Carbonic acid, dialkyl ester (generic...Substances § 721.10715 Carbonic acid, dialkyl ester (generic...identified generically as carbonic acid, dialkyl ester (PMN P-13-346...721.80(f), (j), and (s) (100,000 kilograms)....

2014-07-01

54

Alkaline earth cation extraction from acid solution  

DOEpatents

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

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

2003-01-01

55

Simultaneous determination of tryptophan, uric acid and ascorbic acid at iron(III) doped zeolite modified carbon paste electrode  

Microsoft Academic Search

A new chemically modified electrode is constructed based on iron(III) doped zeolite modified carbon paste electrode (Fe3+Y\\/ZCME). The electrode was evaluated as a sensor for sub-micromolar determination of tryptophan (Trp), uric acid (UA) and ascorbic acid (AA) in aqueous solutions. The measurements were carried out by application of the differential pulse voltammetry (DPV) method in phosphate buffer solution with pH

Ali Babaei; Mojgan Zendehdel; Balal Khalilzadeh; Alireza Taheri

2008-01-01

56

Solution influence on biomolecular equilibria - Nucleic acid base associations  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

57

Influences of pyrolysis condition and acid treatment on properties of durian peel-based activated carbon.  

PubMed

Durian peel was used for the synthesis of activated carbon used for adsorption of Basic Green 4 dye. Activated carbon was synthesised under either nitrogen (N(2)) atmospheric or vacuum pyrolysis, followed by carbon dioxide (CO(2)) activation. The synthesised activated carbon then was treated with hydrochloric acid (HCl) solution. The results showed that activated carbon synthesised under vacuum pyrolysis exhibited better properties and adsorption capacities than that under nitrogen atmospheric pyrolysis. The HCl treatment improved properties and adsorption capacities of activated carbons. Pseudo-second-order kinetics well described the adsorption of Basic Green 4. PMID:19695874

Nuithitikul, Kamchai; Srikhun, Sarawut; Hirunpraditkoon, Samorn

2010-01-01

58

Process for the extraction of strontium from acidic solutions  

DOEpatents

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.

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

1994-01-01

59

Containment of nitric acid solutions of Plutonium-238  

NASA Astrophysics Data System (ADS)

The corrosion of various metals that could be used to contain nitric acid solutions of Pu-238 has been studied. Tantalum and tantalum/2.5% tungsten resisted the test solvent better than 304L stainless steel and several INCONEL alloys. The solvent used to imitate nitric acid solutions of Pu-238 contained 70% nitric acid, hydrofluoric acid, and ammonium hexanitratocerate.

Reimus, M. A. H.; Silver, G. L.; Pansoy-Hjelvik, L.; Ramsey, K. B.

1999-01-01

60

Containment of Nitric Acid Solutions of Plutonium-238  

SciTech Connect

The corrosion of various metals that could be used to contain nitric acid solutions of Pu-238 has been studied. Tantalum and tantalum/2.5% tungsten resisted the test solvent better than 304L stainless steel and several INCONEL alloys. The solvent used to imitate nitric acid solutions of Pu-238 contained 70% nitric acid, hydrofluoric acid, and ammonium hexanitratocerate.

Reimus, M.A.H.; Silver, G.L.; Pansoy-Hjelvik, L.; Ramsey, K.

1999-01-31

61

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

Microsoft Academic Search

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.

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

1995-01-01

62

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

Microsoft Academic Search

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

J Behar; M Hitchings; R D Smyth

1977-01-01

63

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

PubMed Central

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

2010-01-01

64

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

PubMed

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

Rohwerder, Thore; Müller, Roland H

2010-01-01

65

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

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

66

Removal of Cu and Ag from aqueous solution on a chemically-carbonized sorbent from date palm leaflets  

Microsoft Academic Search

A chemically-carbonized sorbent was prepared from date palm leaflets by sulphuric acid treatment at 170°C. Carbonization took place via the dehydration effect of the hot sulphuric acid producing a carbon with reduction property. Sorption of Cu and Ag from aqueous solution was investigated in terms of pH, contact time, metal concentration and temperature. A peculiar behaviour was found for the

El-Said Ibrahim El-Shafey; Salma Muhammed Zahran Al-Kindy

2012-01-01

67

Investigating the Effect of Oil Saturation on Acid Propagation during Matrix Acidization of Carbonate Rocks  

E-print Network

affects carbonate acidizing. This study demonstrates the impact of oil saturation on wormholing characteristics while acidizing field and outcrop cores under reservoir conditions (200°F). Knowledge of the effect of different saturation conditions on acid...

Kumar, Rahul Pradeep

2014-01-02

68

Isotope composition of carbon in amino acids of solid bitumens  

NASA Astrophysics Data System (ADS)

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).

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

2014-06-01

69

Stimulation of Carbonate Reservoirs Using a New Emulsified Acid System  

E-print Network

calcite and dolomite formations, measuring the reaction rate and diffusion coefficient when the new emulsified acid systems react with both calcite and dolomite, and testing the new emulsified acid using core samples obtained from carbonate reservoirs...

Sayed, Mohammed Ali Ibrahim

2013-05-15

70

Functionalized carbon nanofibers as solid-acid catalysts for transesterification.  

PubMed

Carbon nanofibers (CNFs) were functionalized with aryl sulfonic acid groups using in situ diazonium coupling. The use of diazonium coupling yielded an acidic carbon material, in which the introduced acidic groups are readily accessible to the triglyceride substrate. The material is an efficient catalyst for the transesterification of triolein and methanol, outperforming conventional sulfonated carbons in both stability and activity per acid site. Upon comparing CNFs with varying degrees of functionalization, a linear correlation between sulfonic acid sites and catalytic performance was found. PMID:23908100

Stellwagen, Daniel R; van der Klis, Frits; van Es, Daan S; de Jong, Krijn P; Bitter, Johannes H

2013-09-01

71

Mechanism of adsorption and electrosorption of bentazone on activated carbon cloth in aqueous solutions.  

PubMed

An electrochemical technique has been applied to enhance the removal of a common herbicide (bentazone) from aqueous solutions using an activated carbon cloth as electrode. A pH increase from acidic to basic reduces the uptake, with capacities going from 127 down to 80 mg/g at pH 2 and 7, respectively. Increasing the oxygen content of the carbon cloth causes a decrease in the bentazone loading capacity at all pH values. This indicates that adsorption is governed by both dispersive and electrostatic interactions, the extent of which is controlled by the solution pH and the nature of the adsorbent. Anodic polarization of the carbon cloth noticeably enhances the adsorption of bentazone, to an extent depending on the current applied to the carbon electrode. The electrosorption is promoted by a local pH decrease provoked by anodic decomposition of water in the pores of the carbon cloth. PMID:17490705

Ania, Conchi O; Béguin, François

2007-08-01

72

Physical solubility of hydrogen sulfide and carbon dioxide in alkanolamine solutions  

SciTech Connect

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.

Abu-Arabi, M.K.

1988-01-01

73

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

Microsoft Academic Search

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

Elsa M Arce; Ignacio González

2002-01-01

74

Corrosion inhibition of benzyl triethanol ammonium chloride and its ethoxylate on steel in sulphuric acid solution  

Microsoft Academic Search

The inhibitive effect of benzyl triethanol ammonium chloride (BTAC) and ethoxylated benzyl triethanol ammonium chloride (EBTAC) on the corrosion of carbon steel in sulphuric acid solution is measured by the weight loss method. The adsorption of these compounds (surfactants) leads to the formation of a monolayer on the metal surface. The relationships between the concentrations of these inhibitors and their

M. M Osman; A. M. A Omar; A. M Al-Sabagh

1997-01-01

75

Continuous electrolytic decarbonation and recovery of a carbonate salt solution from a metal-contaminated carbonate solution.  

PubMed

This work studied the characteristic changes of a continuous electrolytic decarbonation and recovery of a carbonate salt solution from a metal-contaminated carbonate solution with changes of operational variables in an electrolytic system which consisted of a cell-stacked electrolyzer equipped with a cation exchange membrane and a gas absorber. The system could completely recover the carbonate salt solution from a uranyl carbonato complex solution in a continuous operation. The cathodic feed rate could control the carbonate concentration of the recovered solution and it affected the most transient pH drop phenomenon of a well type within the gas absorber before a steady state was reached, which caused the possibility of a CO(2) gas slip from the gas absorber. The pH drop problem could be overcome by temporarily increasing the OH(-) concentration of the cathodic solution flowing down within the gas absorber only during the time required for a steady state to be obtained in the case without the addition of outside NaOH. An overshooting peak of the carbonate concentration in the recovered solution before a steady state was observed, which was ascribed to the decarbonation of the initial solution filled within the stacked cells by a redundant current leftover from the complete decarbonation of the feeding carbonate solution. PMID:19604641

Kim, Kwang-Wook; Kim, Yeon-Hwa; Lee, Se-Yoon; Lee, Eil-Hee; Song, Kyusuk; Song, Kee-Chan

2009-11-15

76

Crystallization characteristics of ammonium uranyl carbonate (AUC) in ammonium carbonate solutions  

NASA Astrophysics Data System (ADS)

Ammonium carbonate solutions with an excessive amount of NH 3 were produced in a commercial AUC (ammonium uranyl carbonate) conversion plant. In this study the AUC crystals, precipitated with uranyl nitrate and ammonium carbonate solutions prepared in the laboratory, were characterized to determine the feasibility of recycling ammonium carbonate solution. The AUC crystals were easily agglomerated with the increasing concentration of CO 32- and mole ratio of {NH 4+}/{CO 32-} in ammonium carbonate solution. Effects of a mixing system for the solution in the AUC crystallizer and the feed location of the solution on the agglomeration of AUC crystals were also studied along with the effects of agglomerated AUC powders on UO 2 powders. Finally, the feasibility of manufacturing UO 2 fuel with a sintered pellet density of 10.52 g/cm 3, using the AUC powders generated in this experiment, was demonstrated.

Tae-Joon, Kim; Kyung-Chai, Jeong; Jin-Ho, Park; In-Soon, Chang; Cheong-Song, Choi

1994-05-01

77

Solubility of Small-Chain Carboxylic Acids in Supercritical Carbon Dioxide  

SciTech Connect

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.

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

2010-07-08

78

Sorption of platinum and rhodium on carbon adsorbents from chloride solutions  

Microsoft Academic Search

Sorption recovery of platinum (II, IV) and rhodium (III) on different carbon adsorbents has been studied using fresh chloride\\u000a model solutions with platinum and rhodium concentrations of 0.25–1.0 and 0.049 mmol\\/L, respectively. The concentration of\\u000a hydrochloric acid in these solutions varied from 0.001 to 1.0 mol\\/L. The maximum recovery of platinum and rhodium was achieved\\u000a with the carbon adsorbent based on charcoal

Olga N. Kononova; Tatiana A. Leyman; Victoriya N. Gavrilova; Sergey G. Konontsev; Dmitry M. Kashirin

2010-01-01

79

ABSORPTION OF CARBON DIOXIDE INTO AQUEOUS DIETHANOLAMINE SOLUTIONS  

Microsoft Academic Search

The rates of absorption of pure carbon dioxide into aqueous diethanolamine solutions were measured at 25C in a liquid-jet column and a wetted-wall column. Experimental results were analyzed with the chemical absorption theory based on the penetration model. Physical solubility of carbon dioxide in aqueous diethanolamine solutions was determined from the absorption rates measured in a near pseudo first-order reaction

H. HIKITA; S. ASAI; H. ISHIKAWA; K. UKU

1980-01-01

80

Removal of lead from aqueous solutions on palm shell activated carbon.  

PubMed

The performance of a commercially available palm shell based activated carbon to remove lead ions from aqueous solutions by adsorption was evaluated. The adsorption experiments were carried out at pH 3.0 and 5.0. The effect of malonic and boric acid presence on the adsorption of lead ions was also studied. Palm shell activated carbon showed high adsorption capacity for lead ions, especially at pH 5 with an ultimate uptake of 95.2mg/g. This high uptake showed palm shell activated carbon as amongst the best adsorbents for lead ions. Boric acid presence did not affect significantly lead uptake, whereas malonic acid decreased it. The diffuse layer surface complexation model was applied to predict the extent of adsorption. The model prediction was found to be in concordance with the experimental values. PMID:16321520

Issabayeva, Gulnaziya; Aroua, Mohamed Kheireddine; Sulaiman, Nik Meriam Nik

2006-12-01

81

Process for the recovery of strontium from acid solutions  

DOEpatents

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.

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

1992-01-01

82

Process for the recovery of strontium from acid solutions  

DOEpatents

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

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

1992-03-31

83

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

SciTech Connect

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

Jou, Fang Yuan; Carroll, J.J.; Mather, A.E.; Otto, F.D. (Univ. of Alberta, Edmonton, Alberta (Canada). Dept. of Chemical Engineering)

1993-01-01

84

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

SciTech Connect

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.

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

85

Electrochemical isolation of Np from circulating carbonate solutions  

SciTech Connect

Continuous electrochemical isolation of Np from aqueous potassium carbonate (0.1-2.0 M) as an insoluble double carbonate of NpO{sub 2}{sup +} that is formed during electrochemical reduction of NpO{sub 2}{sup 2+} at a bulk reticulated vitreous carbon (RVC) electrode in a circulating electrolyzer is demonstrated. The electrochemical reactions of Np in aqueous potassium carbonate are investigated. The process parameters for isolating Np (working electrode potential, starting [Np] and [K{sub 2}CO{sub 3}], solution flow rate through the electrolyzer) are optimized. The maximum extraction of Np reached 99%.

Kosyakov, V.N.; Simirskaya, G.P.

1995-03-01

86

Infrared optical constants of HâO ice, amorphous nitric acid solutions, and nitric acid hydrates  

Microsoft Academic Search

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 HâO ice. They measured the transmission of infrared light through thin films of varying thickness over the frequency range from about 7000

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

1994-01-01

87

Solubility of uranous sulfate in aqueous sulfuric acid solution  

NASA Astrophysics Data System (ADS)

To provide important thermodynamic data for use in uranium hydrometallurgy, solubilities of uranous sulfate were determined as a function of free acid concentration and temperature. Two sets of experiments were performed in this study. One set was the precipitation experiments of uranous sulfate crystals, in which concentrated uranous sulfate solution was mixed with sulfuric acid solution of suitable concentration. The other set was the dissolution experiments of uranous sulfate crystals in aqueous sulfuric acid solutions. It is noteworthy that good agreement exists between the solubilities determined by the two methods. At elevated temperatures, say, 363 K, the presence of free sulfuric acid is required to avoid precipitation of uranous hydroxide resulting from the hydrolysis of uranous sulfate. Generally speaking, however, an increase in free sulfuric acid concentration results in a slight decrease in uranous sulfate solubility. The elevation of solution temperature causes a decrease in solubility of uranous sulfate. It should be noted that the solid uranous sulfates equilibrated with saturated solutions at 298 K were U(SO4)2 2H2O in dilute sulfuric acid solution and U(SO4)2 4H2O in concentrated sulfuric acid solution, while those at 333 K and 363 K were mainly U(SO4)2 4H2O.

Suzuki, Shigeru; Hirono, Shuichiro; Awakura, Yasuhiro; Majima, Hiroshi

1990-10-01

88

Effect of acidic solution viscosity on enamel erosion.  

PubMed

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, Ø = 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

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

2013-03-01

89

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

SciTech Connect

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.

Ketusky, E.; Subramanian, K.

2011-01-20

90

Method for liquid chromatographic extraction of strontium from acid solutions  

DOEpatents

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.

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

1992-01-01

91

The Role of Acidizing in Proppant Fracturing in Carbonate Reservoirs  

E-print Network

was also poor and resulted in difficulties and failures to obtain proppant partial monolayer placement. For carbonate formations, acid fracturing is another effective stimulation method. Simpler operation and lower cost made the technique attractive...

Densirimongkol, Jurairat

2010-10-12

92

Peculiarities of electrostatic interactions between amino acids and salicylic acid in aqueous solution  

Microsoft Academic Search

Based on calorimetric data, the enthalpy of transfer of salicylic acid to aqueous buffer solutions with the addition of different\\u000a amino acids at the constant acidity of medium pH 7.35 was determined. It was shown that the exothermicity of transfer and\\u000a negative enthalpic coefficients for these pairwise interactions of salicylic acid with amino acids considerably increase with\\u000a increasing charge of

V. P. Barannikov; V. G. Badelin; M. B. Berezin

2009-01-01

93

Synthesis of multi-walled carbon nanotube\\/silver nanocomposite powders by chemical reduction in aqueous solution  

Microsoft Academic Search

Carbon nanotube (CNT)\\/silver nanocomposite powders with different volume fractions of CNTs 2.5, 5 and 10?vol.% were prepared by chemical reduction in solution. Multi-walled CNTs underwent surface modifications for functionalisations by acid treatments. The acid-treated CNTs were investigated by FT-IR and X-ray photoelectron spectroscopy. The spectroscopic investigations of the acid-functionalised CNTs detected that several kinds of functional groups attached with the

Walid M. Daoush; Soon H. Hong

2012-01-01

94

Polymerization of beta-amino acids in aqueous solution  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

95

Adsorption studies of phthalic acid esters in aqueous solutions  

E-print Network

ADSORPTION STUDIES OF PHTHALIC ACID ESTERS IN AQUEOUS SOLUTIONS A Thesis by KEVIN FRANCIS SULLIVAN Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE... August 1980 Major Subject: Chemistry ADSORPTION STUDIES OF PHTHALIC ACID ESTERS IN AQUEOUS SOLUTIONS A Thesis by KEVIN FRANCIS SULLIVAN Approved as to style and content by: (Chairman of Committ e) (Head of Department) (Member) (Member)( August...

Sullivan, Kevin Francis

2012-06-07

96

Polymerization of Pu(IV) in aqueous nitric acid solutions  

Microsoft Academic Search

The polymerization of Pu(IV) in aqueous nitric acid solutions has been studied spectrophotometrically both to establish the influence of large UO(NO) concentrations on the polymerization rates and, more generally, to review the influence of the major parameters on the polymer reaction. Typically, experiments have been performed at 50°C and with 0.05 M Pu in nitric acid solutions that vary in

L. M. Toth; H. A. Friedman; M. M. Osborne

1980-01-01

97

Modeling of Acid Fracturing in Carbonate Reservoirs  

E-print Network

The acid fracturing process is a thermal, hydraulic, mechanical, and geochemical (THMG)-coupled phenomena in which the behavior of these variables are interrelated. To model the flow behavior of an acid into a fracture, mass and momentum balance...

Al Jawad, Murtada s

2014-06-05

98

Removal of Pb and Zn from the aqueous solutions by activated carbon prepared from Dates stone  

Microsoft Academic Search

The low-cost activated carbon prepared from Date stone, an agricultural solid waste by-product, were prepared by chemical activation with sulphuric acid for the removal of lead and zinc from aqueous solutions has been studied as a function of pH, contact time, metal concentrations and adsorbent concentrations. Adsorption equilibrium was reached after an equilibration time of 60 min and adsorption kinetics

Lotfi Mouni; Djoudi Merabet; Abdelkarim Bouzaza; Lazhar Belkhiri

2010-01-01

99

Method for incorporating radioactive phosphoric acid solutions in concrete  

DOEpatents

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

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

1984-01-01

100

Method for incorporating radioactive phosphoric acid solutions in concrete  

DOEpatents

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

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

1982-07-08

101

PROTON RESONANCE SHIFTS IN NITRIC ACID SOLUTIONS OF ALUMINUM NITRATE  

Microsoft Academic Search

Proton magnetic resonance spectra were used to measure the dissociation ; of nitric acid between 25 and 80 deg C in solutions that were 0 to 1.5 M in ; aluminum nitrate. The salt repressed the dissociation of the acid markedly. At ; temperatures above room temperature, the salt was even more effective at ; dimintshing the dissociation of the

Robert C. Axtmann; Woodfin E. Shuler; Bruce B. Murray

1960-01-01

102

The interaction of Bromophenol Blue with proteins in acidic solution  

Microsoft Academic Search

The interactions of Bromophenol Blue (BPB) with bovine serum albumin and ?-globulin in acidic solutions were investigated by a spectrophotometric method. It was considered that the electrostatic force is the main binding force, and that the color change during the combination is due to the transformation of dye species of free acidic form into bound basic form as well as

Yong-ju Wei; Ke-an Li; Shen-yang Tong

1996-01-01

103

Phosphorylation of Glyceric Acid in Aqueous Solution Using Trimetaphosphate  

NASA Technical Reports Server (NTRS)

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

Kolb, Vera; Orgel, Leslie E.

1996-01-01

104

Electrochemical removal of CI Acid orange 10 from aqueous solutions  

Microsoft Academic Search

The removal of CI Acid orange 10 from aqueous solutions was studied by electrocoagulation and electrooxidation techniques. For electrocoagulation, metallic iron was used as electrodes whereas graphite and IrO2\\/TaO2\\/RuO2 coated titanium were used in the case of electrooxidation. During electro-coagulation, the CI Acid orange 10 molecule was split into aniline and 1-amino-2-naphthol-6,8-disulfonic acid due to reductive cleavage of azo bond.

M. Muthukumar; M. Thalamadai Karuppiah; G. Bhaskar Raju

2007-01-01

105

Solubility and precipitation of nicotinic acid in supercritical carbon dioxide.  

PubMed

Solubilities of a model compound (nicotinic acid) in pure supercritical carbon dioxide (SC-CO(2)) and SC-CO(2) modified with methanol have been measured in the pressure range of 80-200 bar and between temperatures of 35 and 90 degrees C. On-line ultraviolet detection enabled a simple and relatively fast measurement of very low levels of solubility (10(-7) mol fraction) with good accuracy in pure and modified SC-CO(2). The solute solubility in both pure SC-CO(2) and SC-CO(2) modified with methanol increased with pressure at all investigated temperatures. A retrograde solubility behavior was observed in that, at pressures below 120 bar, a solubility decrease on temperature increase occurred. Solubility data were used to calculate supersaturation values and to define optimum operating conditions to obtain crystalline particles 1-5 microm in diameter using the solution-enhanced dispersion by supercritical fluids (SEDS) process, thereby demonstrating the feasibility of a one-step production process for particulate pharmaceuticals suitable for respiratory drug delivery. PMID:11745715

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

2001-10-01

106

Improved method for extracting lanthanides and actinides from acid solutions  

DOEpatents

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

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

1983-07-26

107

Soil Solution Sampling for Organic Acids in Rice Paddy Soils  

Microsoft Academic Search

Low molecular weight organic acids (OA), which are intermediates in the anaerobic decomposition of straw incorporated into submerged soils, have been implicated in causing toxicity to young rice (Oryza sativa L.) seedlings. The objective of this study was to develop a method for measuring OA in soil solution in field and greenhouse studies. Three methods of soil solution sampling were

Olivyn R. Angeles; Sarah E. Johnson; Roland J. Buresh

2005-01-01

108

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

SciTech Connect

This report presents findings from tests investigating the dissolution of simulated and radioactive Savannah River Site sludges with 4 per cent oxalic acid and mixtures of oxalic and citric acid previously recommended by a Russian team from the Khlopin Radium Institute and the Mining and Chemical Combine (MCC). Testing also included characterization of the simulated and radioactive waste sludges. Testing results showed the following: Dissolution of simulated HM and PUREX sludges with oxalic and citric acid mixtures at SRTC confirmed general trends reported previously by Russian testing. Unlike the previous Russian testing six sequential contacts of a mixture of oxalic acid citric acids at a 2:1 ratio (v/w) of acid to sludge did not produce complete dissolution of simulated HM and PUREX sludges. We observed that increased sludge dissolution occurred at a higher acid to sludge ratio, 50:1 (v/w), compared to the recommended ratio of 2:1 (v/w). We observed much lower dissolution of aluminum in a simulated HM sludge by sodium hydroxide leaching. We attribute the low aluminum dissolution in caustic to the high fraction of boehmite present in the simulated sludge. Dissolution of HLW sludges with 4 per cent oxalic acid and oxalic/citric acid followed general trends observed with simulated sludges. The limited testing suggests that a mixture of oxalic and citric acids is more efficient for dissolving HM and PUREX sludges and provides a more homogeneous dissolution of HM sludge than oxalic acid alone. Dissolution of HLW sludges in oxalic and oxalic/citric acid mixtures produced residual sludge solids that measured at higher neutron poison to equivalent 235U weight ratios than that in the untreated sludge solids. This finding suggests that residual solids do not present an increased nuclear criticality safety risk. Generally the neutron poison to equivalent 235U weight ratios of the acid solutions containing dissolved sludge components are lower than those in the untreated sludge solids. We recommend that these results be evaluated further to determine if these solutions contain sufficient neutron poisons. We observed low general corrosion rates in tests in which carbon steel coupons were contacted with solutions of oxalic acid, citric acid and mixtures of oxalic and citric acids. Wall thinning can be minimized by maintaining short contact times with these acid solutions. We recommend additional testing with oxalic and oxalic/citric acid mixtures to measure dissolution performance of sludges that have not been previously dried. This testing should include tests to clearly ascertain the effects of total acid strength and metal complexation on dissolution performance. Further work should also evaluate the downstream impacts of citric acid on the SRS High-Level Waste System (e.g., radiochemical separations in the Salt Waste Processing Facility and addition of organic carbon in the Saltstone and Defense Waste Processing facilities).

STALLINGS, MARY

2004-07-08

109

Electrochemical Behavior of Epinephrine at a Glassy Carbon Electrode Modified by Electrodeposited Films of Caffeic Acid  

PubMed Central

A stable electroactive thin film of poly(caffeic acid) has been deposited on the surface of a glassy carbon electrode by potentiostatic technique in an aqueous solution containing caffeic acid. The voltammetric behavior of epinephrine (EP) at the poly(caffeic acid) modified glassy carbon electrode was studied by cyclic voltammetry. The poly(caffeic acid) modified electrode exhibited a promotion effect on the oxidation of EP. In a pH 7.4 phosphate buffer, the anodic current increased linearly with the concentration of EP in the range from 2.0 × 10?6 to 3.0 × 10?4 mol L?1 and the detection limit for EP was 6.0 × 10?7 mol L?1. The proposed method can be applied to the determination of EP in practical injection samples with simplicity, rapidness and accurate results.

Ren, Wang; Luo, Hong Qun; Li, Nian Bing

2006-01-01

110

Adsorption of selected herbicides from aqueous solutions on activated carbon  

Microsoft Academic Search

The adsorption of MCPA and 2,4-D on the activated carbon Filtrasorb 300 was studied. The adsorption isotherms of herbicides\\u000a from aqueous solutions were measured over a wide range of solute concentrations and at different temperatures. The experimental\\u000a equilibrium data were analyzed by the Langmuir–Freundlich isotherm taking into account the energetic heterogeneity of adsorption\\u000a system. The effect of temperature and herbicide

A. Derylo-Marczewska; M. Blachnio; A. W. Marczewski; A. Swiatkowski; B. Tarasiuk

2010-01-01

111

Decomposition of pertoluic acid in chlorobenzene solution  

SciTech Connect

The kinetics and composition of the decomposition products of pertoluic acid in chlorobenzene at 353-403 K were studied. The activation energy of the gross decomposition is 82.4 is identical to 6 kJ/mole; the main products are pertoluic acid and CO/sub 2/. On the basis of the dependence of the yields of CO/sub 2/ on the concentration of the peracid (0.01-0.05 M), it was concluded that the peracid undergoes radical breakdown, and induced breakdown with abstraction of a H atom from OOH group occurs. The formation of toluence (conversion product of the CH/sub 3/-C/sub 6/H/sub 4/. radical) and O/sub 2/ was demonstrated.

Ariko, N.G.; Kornilova, N.N.; Mitskevich, N.I.

1985-09-01

112

Characterization of carbon black modified by maleic acid  

NASA Astrophysics Data System (ADS)

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 250°C. 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.

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

2013-09-01

113

REMOVAL OF CHLORIDE FROM ACIDIC SOLUTIONS USING NO2  

SciTech Connect

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.

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

2006-08-22

114

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

PubMed

Polyaspartic acid (PSI) is suitable for the inhibition of inorganic scale deposition. To enhance its scale inhibition efficiency, PSI was modified by reacting aspartic acid with malic acid (MA) using thermal polycondensation polymerization. This reaction resulted in poly(aspartic acid-co-malic acid) (PSI-co-MA) dual polymer. The structural, chemical and thermal properties of the dual polymers were analysed by using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry and gel permeation chromatography. The effectiveness of six different molar ratios of PSI-co-MA dual polymer for calcium carbonate and calcium sulphate scale inhibition at laboratory scale batch experiments was evaluated with synthetic brine solution at selected doses of polymer at 65-70°C by the static scale test method. The performance of PSI-co-MA dual polymer for the inhibition of calcium carbonate and calcium sulphate precipitation was compared with that of a PSI single polymer. The PSI-co-MA exhibited excellent ability to control inorganic minerals, with approximately 85.36% calcium carbonate inhibition and 100% calcium sulphate inhibition at a level of 10?mg/L PSI-co-MA, respectively. Therefore, it may be reasonably concluded that PSI-co-MA is a highly effective scale inhibitor for cooling water treatment applications. PMID:25371160

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

2014-12-01

115

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

NASA Astrophysics Data System (ADS)

This study shows that acidic and alkaline wastes co-disposed with uranium into subsurface sediments have significant impact on changes in uranium retardation, concentration, and mass during downward migration. For uranium co-disposal with acidic wastes, significant rapid (i.e., hours) carbonate and slow (i.e., 100 s of hours) clay dissolution resulted, releasing significant sediment-associated uranium, but the extent of uranium release and mobility change was controlled by the acid mass added relative to the sediment proton adsorption capacity. Mineral dissolution in acidic solutions (pH 2) resulted in a rapid (< 10 h) increase in aqueous carbonate (with Ca2 +, Mg2 +) and phosphate and a slow (100 s 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 (10 s to 100 s of hours) increase in silica concentration, likely from montmorillonite, muscovite, and kaolinite dissolution. Infiltration of uranium with a strong base resulted in not only uranium-silicate precipitation (presumed Na-boltwoodite) but also desorption of natural uranium on the sediment due to the high ionic strength solution, or 60% greater mass with greater retardation compared with groundwater. Overall, these results show that acidic or alkaline co-contaminant disposal with uranium can result in complex depth- and time-dependent changes in uranium dissolution/precipitation reactions and uranium sorption, which alter the uranium migration mass, concentration, and velocity.

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

2013-08-01

116

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

PubMed

This study shows that acidic and alkaline wastes co-disposed with uranium into subsurface sediments have significant impact on changes in uranium retardation, concentration, and mass during downward migration. For uranium co-disposal with acidic wastes, significant rapid (i.e., hours) carbonate and slow (i.e., 100 s of hours) clay dissolution resulted, releasing significant sediment-associated uranium, but the extent of uranium release and mobility change was controlled by the acid mass added relative to the sediment proton adsorption capacity. Mineral dissolution in acidic solutions (pH2) resulted in a rapid (<10 h) increase in aqueous carbonate (with Ca(2+), Mg(2+)) and phosphate and a slow (100 s of hours) increase in silica, Al(3+), and K(+), likely from 2:1 clay dissolution. Infiltration of uranium with a strong acid resulted in significant shallow uranium mineral dissolution and deeper uranium precipitation (likely as phosphates and carbonates) with downward uranium migration of three times greater mass at a faster velocity relative to uranium infiltration in pH neutral groundwater. In contrast, mineral dissolution in an alkaline environment (pH13) resulted in a rapid (<10h) increase in carbonate, followed by a slow (10 s to 100 s of hours) increase in silica concentration, likely from montmorillonite, muscovite, and kaolinite dissolution. Infiltration of uranium with a strong base resulted in not only uranium-silicate precipitation (presumed Na-boltwoodite) but also desorption of natural uranium on the sediment due to the high ionic strength solution, or 60% greater mass with greater retardation compared with groundwater. Overall, these results show that acidic or alkaline co-contaminant disposal with uranium can result in complex depth- and time-dependent changes in uranium dissolution/precipitation reactions and uranium sorption, which alter the uranium migration mass, concentration, and velocity. PMID:23851265

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

2013-08-01

117

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

SciTech Connect

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.

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

2013-08-01

118

Probing Electrostatic Potentials in Solution with Carbon Nanotube  

E-print Network

Probing Electrostatic Potentials in Solution with Carbon Nanotube Transistors Lisa Larrimore the electrostatic potential sensed by the nanotube, which in turn shifts the gate-voltage dependence of the nanotube of the electrostatic ( ) and chemical (µi) potentials: Amperometric techniques (i.e., measurements of current) provide

McEuen, Paul L.

119

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

E-print Network

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...

Izgec, Omer

2010-07-14

120

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

DOEpatents

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.

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

1986-01-01

121

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

DOEpatents

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.

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

1986-03-04

122

The action spectrum for folic acid photodegradation in aqueous solutions.  

PubMed

Folate is essential for cell division and growth. Deficiency is linked to birth defects, magaloblastic anaemia, cardiovascular disease, etc. Folic acid is a synthetic form of folate and is used to fortify food and in supplements. In aqueous solutions, in blood and even in human skin, folic acid may be degraded by ultraviolet radiation. Consequently, photodegradation of folic acid in human blood may lead to folate deficiency. However, the degree and the health consequences of such photodegradation are unknown. It is not clear which spectral region plays the most important role in the photodegradation of folic acid. In this study the photodegradation of folic acid in aqueous solution under different wavelengths of ultraviolet radiation (260-400nm) was investigated by fluorescence spectroscopy. The photodegradation rate of folic acid was dependent on wavelength. Action spectrum for 1?M folic acid photodegradation was determined. Its action spectrum is not identical to its absorption or fluorescence excitation spectra. The action spectrum demonstrated that UVB and UVA degrade folic acid. Protecting skin against UVB and UVA radiation by sunscreens may help to protect folic acid in human blood under intense solar radiation. PMID:23892004

Juzeniene, Asta; Thu Tam, Tran Thi; Iani, Vladimir; Moan, Johan

2013-09-01

123

Particulate, carbon monoxide, and acid emission factors for residential wood burn stoves  

SciTech Connect

Emissions from residential wood burning stoves are of increasing concern in many areas. This concern is due to the magnitude of the emissions and the toxic and chemical characteristics of the pollutants. Recent testing of standard and new technology woodstoves has provided data for developing a family of particulate and carbon monoxide emission factor curves. This testing has also provided data illustrating the acidity of woodstove emissions. The particulate and carbon monoxide curves relate the actual stove emissions to the stove size and operating parameters of burn rate, fuel loading, and fuel moisture. Curves relating stove types to the acidity of emissions have also been constructed. Test data show actual emissions vary from 3 to 50 grams per kilogram for particles and from 50 to 300 grams per kilogram for carbon monoxide. Since woodstove emissions are the largest single category of particulate emissions in many area, it is essential that these emissions be quantified specifically for geographic regions, allowing meaningful impact analysis modeling to be accomplished. Emission factors for particles and carbon monoxide are presented from several stove sizes and burn rates. The acidic nature of woodstove emissions has been clearly demonstrated. Tests indicate woodstove flue gas condensate solutions to be predominantly in the 2.8 to 4.2 pH range. Condensate solutions from conventional woodstoves exhibited the characteristic buffering capacity of carboxylic acids when titrations were performed with a strong base. The environmental impact of buffered acidic woodstove emissions is not currently well understood; however, it is possible with the data presented here to make semi-quantitative estimates of acid emission from particulate and carbon monoxide emission factors and wood use inventories.

Burnet, P.G.; Edmisten, N.G.; Tiegs, P.E.; Houck, J.E.; Yoder, R.A.

1986-09-01

124

Does Nitric Acid Dissociate at the Aqueous Solution Surface?  

SciTech Connect

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.

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

2011-11-03

125

Oxidative desulfurization of askale coal by nitric acid solution  

SciTech Connect

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.

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

2007-07-01

126

The hydration structure of aqueous carbonic acid from X-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Despite much effort, aqueous carbonic acid (H2CO3) remains poorly characterized because it is very short-lived. We describe the detection and characterization of aqueous H2CO3 by X-ray absorption spectroscopy, wherein protonation of a bicarbonate solution continuously generates the acid under ambient conditions. Accompanying first principles calculations of the carbon K-edge transitions facilitate spectral assignment and interpretation in terms of the H2CO3 ?* orbital, which exhibits a small (0.2 eV), systematic blueshift relative to that of bicarbonate. These results establish the detailed hydration properties of this short-lived molecule and will thereby facilitate future studies of carbonate chemistry in biological and geological system.

Lam, Royce K.; England, Alice H.; Sheardy, Alex T.; Shih, Orion; Smith, Jacob W.; Rizzuto, Anthony M.; Prendergast, David; Saykally, Richard J.

2014-10-01

127

Electrokinetic Properties of Aluminum Nanopowders in Citric Acid Solution  

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

128

Application of vibrational spectroscopy in the in vitro studies of carbon fiber-polylactic acid composite degradation.  

NASA Astrophysics Data System (ADS)

Vibrational spectroscopy was used for assessment of new material for stomatology, for guided tissue regeneration (GTR) techniqe.Implants applied in the healing of periodontal defects using GTR technique have to meet stringent requirements concerning their chemical as well physical properties.At present the implants prepared from two layers membranes differing in porosity in their outer and inner layers are studied clinically. Composite plates prepared by us consist of three layers: polylactic acid film, carbon fibres coated with polylactic acid and carbon fabric.Vibrational spectroscopic studies of the material; polylactic acid- carbon fiber have made it possible to analyse chemical reactions occurring between the polymer and carbon surface. Analysis of the IR spectra of samples treated in Ringer solution allowed to describe the phenomena resulting from the composite degradation. It was shown that material biostability is related to the presence of carbon fibers.

Blazewicz, Marta; Gajewska, Maria Chomyszyn; Paluszkiewicz, Czeslawa

1999-05-01

129

Simultaneous leaching and carbon sequestration in constrained aqueous solutions  

SciTech Connect

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.

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

2011-01-01

130

Polymerization of Pu(IV) in aqueous nitric acid solutions  

SciTech Connect

The polymerization of Pu(IV) in aqueous nitric acid solutions has been studied spectrophotometrically both to establish the influence of large UO{sub 2}(NO{sub 3}){sub 2} concentrations on the polymerization rates and, more generally, to review the influence of the major parameters on the polymer reaction. Typically, experiments have been performed at 50{sup 0}C and with 0.05 M Pu in nitric acid solutions that vary in acidity from 0.07 to 0.4 M. An induction period usually precedes the polymer growth stage during which time nucleation of primary hydrolysis products occurs. Uranyl nitrate retards the polymerization reaction by approximately 35% in spite of the counteracting influence of the nitrate ions associated with this solute. The rate of polymer formation, expressed as d(percent polymer)/dt, has been shown to depend on the total plutonium concentration in reactions where the Pu(IV) concentration remained constant; and it is therefore suggested that the polymer reaction rate is not first order with respect to the concentration of plutonium as was previously thought. It has been shown further that accurate acid determinations on stock reagents are essential in order to obtain reliable polymerization experiments. Satisfactory procedures for these analyses did not exist, so appropriate modifications to the iodate precipitation methods were developed. The most ideal plutonium reagent material has been shown to be crystalline Pu(IV) nitrate because it can be added directly to acid solutions without the occurrence of unintentional hydrolysis reactions.

Toth, L.M.; Friedman, H.A.; Osborne, M.M.

1980-10-01

131

Modeling Sucrose Hydrolysis in Dilute Sulfuric Acid Solutions at Pretreatment Conditions for Lignocellulosic Biomass  

SciTech Connect

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 25 g/l sucrose with 0.1-2.0% (w/w) sulfuric acid concentrations were treated at temperatures of 160-200 C for 3-12 min. Sucrose was observed to completely hydrolyze at all treatment conditions. However, appreciable concentrations of fructose and glucose were detected and glucose was found to be significantly more stable than fructose. Different mathematical approaches were used to fit the kinetic parameters for acid-catalyzed thermal degradation of these sugars. Since both sugars may survive dilute acid pretreatment, they could provide an additional carbon source for production of ethanol and other bio-based products.

Bower, S.; Wickramasinghe, R.; Nagle, N. J.; Schell, D. J.

2008-01-01

132

Radiolysis of aqueous solutions of acetic acid in the presence of Na-montmorillonite  

NASA Technical Reports Server (NTRS)

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.

Navarro-Gonzalez, R.; Negron-Mendoza, A.; Ramos, S.; Ponnamperuma, C.

1990-01-01

133

Study on the electrochemical behavior of dopamine with poly(sulfosalicylic acid) modified glassy carbon electrode  

Microsoft Academic Search

A glassy carbon electrode was modified with electropolymerized films of sulfosalicylic acid in pH 5.5 phosphate buffer solution (PBS) by cyclic voltammetry. The modified electrode showed an excellent electrocatalytical effect on the oxidation of dopamine (DA). In PBS of pH 7.4, the oxidation current increased linearly with two concentration intervals of dopamine, one is 5.5×10?7 to 2.2×10?5M, the other is

Hong Zhao; Yuzhong Zhang; Zhuobin Yuan

2001-01-01

134

Corrosion inhibition of carbon steel in hydrochloric acid by some polyethylene glycols  

Microsoft Academic Search

The inhibition effect of some PEGs on carbon steel corrosion at 25°C in 0.5N hydrochloric acid as corroding solution was evaluated by weight loss method and polarization and electrochemical impedance spectroscopy (EIS) techniques. In order to study the effect of polyethylene glycols’ structure on the inhibition efficiency, different molecular weights (400, 1000, 4000, and 10,000gmol?1) were selected. This work has

H. Ashassi-Sorkhabi; N. Ghalebsaz-Jeddi; F. Hashemzadeh; H. Jahani

2006-01-01

135

Roentgenoluminescence of hexahydrate of uranyl nitrate in phosphoric acid solution  

NASA Astrophysics Data System (ADS)

The fluorescence (FL) and roentgenoluminescence (XRL) spectra of yellow aqueous solution of hexahydrate of uranyl nitrate phosphoric acid solution have been measured. The XRL spectrum was compared with the XRL of the green alkali alumino-phosphate glasses doped with uranium. It was shown that both the FL and XRL were due to uranyl groups. The radiative transitions are ascribed to3?1u ?1?{g/+}.

Ožvoldová, M.

1992-08-01

136

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

PubMed

Aqueous solutions of highly soluble substances such as small amino acids are usually assumed to be essentially homogenous systems with some degree of short range local structuring due to specific interactions on the sub-nanometre scale (e.g. molecular clusters, hydration shells), usually not exceeding several solute molecules. However, recent theoretical and experimental studies have indicated the presence of much larger supramolecular assemblies or mesospecies in solutions of small organic and inorganic molecules as well as proteins. We investigated both supersaturated and undersaturated aqueous solutions of two simple amino acids (glycine and DL-alanine) using Dynamic Light Scattering (DLS), Brownian Microscopy/Nanoparticles Tracking Analysis (NTA) and Cryogenic Transmission Electron Microscopy (Cryo-TEM). Colloidal scale mesospecies (nanodroplets) were previously reported in supersaturated solutions of these amino acids and were implicated as intermediate species on non-classical crystallization pathways. Surprisingly, we have found that the mesospecies are also present in significant numbers in undersaturated solutions even when the solute concentration is well below the solid-liquid equilibrium concentration (saturation limit). Thus, mesopecies can be observed with mean diameters ranging from 100 to 300 nm and a size distribution that broadens towards larger size with increasing solute concentration. We note that the mesospecies are not a separate phase and the system is better described as a thermodynamically stable mesostructured liquid containing solute-rich domains dispersed within bulk solute solution. At a given temperature, solute molecules in such a mesostructured liquid phase are subject to equilibrium distribution between solute-rich mesospecies and the surrounding bulk solution. PMID:24640504

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

2013-01-01

137

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

138

The effects of acid treatment on the thermoelectric power of multiwalled carbon nanotubes synthesized by chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Acid treatment of carbon nanotubes is a post synthesis processing step used to clean carbon nanotubes. We show that exposure of the nanotubes to oxygen rich reagents including nitric and sulfuric acid results in an increase of the thermoelectric power. Improving dispersion through the use of the surfactant triton-x results in a further increase in TEP of up to 21%. Additionally, refluxing in an oxygen rich acidic solution results in improved dispersion and an increased TEP. These results indicate that improved dispersion of the nanotubes by either sonication or reflux leads to increased oxygenation and thermopower.

Hewitt, Corey A.; Carroll, David L.

2013-08-01

139

Pyrite oxidation in carbonate-buffered solution: 1. Experimental kinetics  

Microsoft Academic Search

The kinetic behavior of pyrite oxidation in carbonate-buffered solution was investigated in the laboratory. Oxygen concentration, surface area and temperature were varied while pH values were limited to the range of 6.7-8.5. The rate experiments were performed on crushed and sieved size-fractions of pyrite that were carefully cleaned and mixed with similar-size silica sand. Oxidation occurred in a moisture-suction device

R. V. Nicholson; R. W. Gillham; E. J. Reardon

1988-01-01

140

Insights into non-Fickian solute transport in carbonates  

PubMed Central

[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, 2714–2728, doi:10.1002/wrcr.20238. PMID:24223444

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

2013-01-01

141

Methanol Uptake by Low Temperature Aqueous Sulfuric Acid Solutions  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

142

Comparison of Adsorption Capacity of p-Cresol & pNitrophenol by Activated Carbon in Single and Double Solute  

Microsoft Academic Search

Adsorption of p-Cresol and p-Nitrophenol by untreated activated carbon in single and multisolute solutions was carried out at 301 K and at controlled pH conditions. In acidic conditions, well below the pKa of both solutes, it was observed that the adsorbate solubility and the electron density of aromatic rings influenced the extent of adsorption by affecting the extent of London

Sirous Nouri; Fouad Haghseresht; G. Q. Max Lu

2002-01-01

143

Study of Acid Response of Qatar Carbonate Rocks  

E-print Network

and heterogeneity is believed to be one of the contributors of causing the low field measurements. In this case, acid linear core-flood experiments were conducted with carbonate core samples of different petrophysical properties to study the impact of both...

Wang, Zhaohong

2012-02-14

144

Electrochemical behavior of a covalently modified glassy carbon electrode with aspartic acid and its use for voltammetric differentiation of dopamine and ascorbic acid  

Microsoft Academic Search

Aspartic acid was covalently grafted on to a glassy carbon electrode (GCE) by amine cation radical formation in the electrooxidation of the amino-containing compound. X-ray photoelectron spectroscopic (XPS) measurement and cyclic voltammetric experiments proved the aspartic acid was immobilized as a monolayer on the GCE. Electron transfer to Fe(CN)64? in solution of different pH was studied by cyclic voltammetry. Changes

Lei Zhang; Xiangqin Lin

2005-01-01

145

Cocoa shells for heavy metal removal from acidic solutions.  

PubMed

The development of economic and efficient processes for the removal of heavy metals present in acidic effluents from industrial sources or decontamination technologies has become a priority. The purpose of this work was to study the efficiency with which cocoa shells remove heavy metals from acidic solutions (pH 2) and to investigate how the composition of these solutions influences heavy metal uptake efficiency. Adsorption tests were conducted in agitated flasks with single-metal solutions (0.25 mM Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn), multi-metal solution (comprised of 0.25 mM of each of the cations above) and an effluent obtained from chemical leaching of metal-contaminated soil, in the presence of different cocoa shell concentrations (5-40 g/l). Results from the single-metal solution assays indicated that the fixation capacity of heavy metals by cocoa shells followed a specific order: Pb>Cr>Cd=Cu=Fe>Zn=Co>Mn=Ni=Al. Cocoa shells are particularly efficient in the removal of lead from very acidic solutions (q(max)=6.2 mg Pb/g, pH(i)=2.0 and T=22 degrees C). The presence of other metals and cations in solution did not seem to affect the recovery of lead. It was also observed that the maximum metal uptake was reached in less than 2 h. This research has also demonstrated that the removal of metals caused a decline in solution proton concentration (pH increase) and release of calcium, magnesium, potassium and sodium from the cocoa shells. PMID:14575948

Meunier, N; Laroulandie, J; Blais, J F; Tyagi, R D

2003-12-01

146

Capture of Carbon Dioxide from Ethanol Fermentation by Liquid Absorption for Use in Biological Production of Succinic Acid.  

PubMed

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

Nghiem, Nhuan P; Senske, Gerard E

2014-12-01

147

Anodic dissolution of nickel in acidic chloride solutions  

NASA Astrophysics Data System (ADS)

The anodic dissolution of nickel was studied galvanostatically in hydrochloric acid solutions of various concentrations. The reaction orders of chloride ion and hydrogen ion concentrations were found to be 0.5 and 1.0, respectively. An anodic Tafel slope equal to 120 ± 10 mV · decade-1 was obtained. The dissolution rate of nickel at constant acid concentration was increased with stirring of the solution and increasing temperature. The activation energy, ?H, for the anodic dissolution process was found to be 12 kcal · mol-1. The presence of oxygen in solutions assisted the passivation process. The effect of addition of aniline and some of its derivatives (o-, m-, and p-anisidine) as inhibitors on the dissolution kinetics of Ni in 1 M HCl was also investigated. These compounds inhibited the anodic dissolution of nickel without affecting the Tafel slope, indicating that the adsorption of such inhibitors could not interfere with the mechanism of metal dissolution.

El Aal, E. E. Abd; Zakria, W.; Diab, A.; El Haleem, S. M. Abd

2003-04-01

148

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

PubMed

Preparation of activated carbon from sewage sludge is a promising approach to produce cheap and efficient adsorbent for pollutants removal as well as to dispose of sewage sludge. The first objective of this study was to investigate the physical and chemical properties (BET surface area, ash and elemental content, surface functional groups by Boehm titration and weight loss by thermogravimetric analysis) of the sludge-based activated carbon (SBAC) so as to give a basic understanding of its structure and to compare to those of two commercial activated carbons, PICA S23 and F22. The second and main objective was to evaluate the performance of SBAC for single and competitive adsorption of four substituted phenols (p-nitrophenol, p-chlorophenol, p-hydroxy benzoic acid and phenol) from their aqueous solutions. The results indicated that, despite moderate micropore and mesopore surface areas, SBAC had remarkable adsorption capacity for phenols, though less than PICA carbons. Uptake of the phenolic compound was found to be dependent on both the porosity and surface chemistry of the carbons. Furthermore, the electronegativity and the hydrophobicity of the adsorbate have significant influence on the adsorption capacity. The Langmuir and Freundlich models were used for the mathematical description of the adsorption equilibrium for single-solute isotherms. Moreover, the Langmuir-Freundlich model gave satisfactory results for describing multicomponent system isotherms. The capacity of the studied activated carbons to adsorb phenols from a multi-solute system was in the following order: p-nitrophenol > p-chlorophenol > PHBA > phenol. PMID:21970174

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

2011-01-01

149

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

NASA Astrophysics Data System (ADS)

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 Brønsted acid catalysts such as niobic acid, Nafion ® NR-50, and Amberlyst-15, whereas the carbon catalyst efficiently hydrolyzes cellulose into water-soluble saccharides. The catalytic performance of the carbon catalyst is due to the large adsorption capacity for hydrophilic reactants and the adsorption ability of ?-1,4 glucan, which is not adsorbed to other solid acids.

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

2010-06-01

150

Preparing Standard Acid Solution Hydrochloric acid and sodium hydroxide are the most common strong acids and bases  

E-print Network

. Reagents Methyl Red indicator Concentrated (37 wt%) HCl Primary standard: sodium tetraborate Na2B4O7Ã?10 H2O primary standard grade sodium tetraborate. 3. Weigh four samples, each containing enough Na2B4O7Ã?10 H2OPreparing Standard Acid Solution Hydrochloric acid and sodium hydroxide are the most common strong

Nazarenko, Alexander

151

Separation of glycols from dilute aqueous solutions via complexation with boronic acids  

SciTech Connect

This work examines methods of separating low molecular weight glycols from dilute aqueous solution. Extraction into conventional solvents is generally not economical, since, in the literature reviewed, distribution ratios for the two- to four-carbon glycols are all less than one. Distribution ratios can be increased, however, by incorporating into the organic phase an extracting agent that will complex with the solute of interest. The extracting agent investigated in this work is 3-nitrophenylboronic acid (NPBA). NPBA, a boric acid derivative, reversibly complexes with many glycols. The literature on complexation of borate and related compounds with glycols, including mechanistic data, measurement techniques, and applications to separation processes, provides information valuable for designing experiments with NPBA and is reviewed herein. 88 refs., 15 figs., 24 tabs.

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

1991-07-01

152

tructural membrane glycerolipids of all plant cells contain almost exclusively 16-carbon and 18-carbon fatty acids,  

E-print Network

-carbon fatty acids, with up to three methylene-interrupted double bonds (16:0, 16:1*, 18:0, 18:1, 18:2, 18:3, and in some species 16:3). These fatty acids are often referred to as common fatty acids. In contrast with the conservative fatty acid composition of plant membrane lipids, tremendous fatty acid

Kunst, Ljerka

153

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...

154

A mechanistic study of copper electropolishing in phosphoric acid solutions  

NASA Astrophysics Data System (ADS)

The microelectronics industry is using copper as the interconnect material for microchips. A study of copper electropolishing is important for the process development of a new, low downforce approach, which is being developed to replace chemical mechanical polishing (CMP) of the copper overburden. A promising technology is a combination of electropolishing with conventional CMP. Electropolishing of copper in phosphoric acid has been studied for, more than 70 years. Previous work has shown that the polishing rate, as measured by current density is directly related to the viscosity of the electrolyte. Also, the limiting species is water. In this study, a multidimensional design of experiments was performed to develop an in-depth model of copper electropolishing. Phosphoric acid was mixed with alcohols of different molecular weight and related viscosity to investigate how the solvents' properties affected polishing. The alcohols used were methanol, ethanol, isopropanol, butanol, ethylene glycol, and glycerol. The limiting current densities and electrochemical behavior of each solution was measured by potentiodynamic and potentiostatic experiments. Also, the kinematic viscosity and density were measured to determine the dynamic viscosity to investigate the relationship of current density and viscosity. Water, methanol, ethanol, and isopropanol solutions were also examined at 20°C to 60°C. Next, the relative percentage of dissociated phosphoric acid was measured by Raman spectroscopy for each polishing solution. Raman spectroscopy was also used to measure the relative dissociation of phosphoric acid inside the polishing film. Additionally, wafers were electropolished and electrochemical mechanically polished to investigate the effects of the different solvents, fluid flow, current, and potential. The results of these experiments have shown that the molecular mass and the ability of the solvent to dissociate phosphoric acid are the primary electrolyte properties that control copper electropolishing. The dependence of the polishing rate on viscosity seen in previous studies is purely consequential. Therefore, by controlling the type and concentration of alcohol in the electropolishing solution the polishing rate can be controlled.

Mansson, Andrew

155

Solubility of xenon in amino-acid solutions  

NASA Astrophysics Data System (ADS)

We have measured the Ostwald solubility (L) of 133Xe at 25.0 °C in aqueous solutions of the amino acids: alanine (0-1.8 M), arginine (0-0.9 M), glycine (0-2.1 M), hydroxyproline (0-2.3 M), lysine (0-2.8 M), and proline (0-3.5 M) as well as sucrose (0-2.25 M) and NaCl (0-5.25 M). Over the concentration ranges investigated L decreases, monotonically and approximately linearly, with increasing concentration for amino acids and sucrose. The effect on gas solubility of amino acid in solution can be large, e.g., for 133Xe, we measured L(25.0 °C)=0.1060 in distilled water but L(25.0 °C)=0.055 for a 2.8 M lysine solution. The results can be used to calculate hydration numbers (H), i.e., the number of H2O molecules associated with each solute molecule. The average values of hydration number (H¯) obtained at 25.0 °C are 7.9±0.6 for alanine, 0.2±0.5 for arginine, 8.5±0.6 for glycine, 4.5±0.4 for hydroxyproline, 6.1±1.1 for lysine, 2.0±0.2 for proline, and 3.9±0.7 for sucrose.

Pollack, Gerald L.; Himm, Jeffrey F.

1986-07-01

156

Thermodynamics of pentachlorophenol adsorption from aqueous solutions by oxidized multi-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Chemical modification of MWCNTs via oxidation proved to be a useful tool to improve the suspension stability and solubility of MWCNTs in aqueous solution. Multi-walled carbon nanotubes (MWCNTs) were oxidized using different oxidizing agents and the produced oxidized MWCNTs were characterized using different techniques. IR measurements showed the presence of carboxylic acid function groups especially for the MWCNTs oxidized with nitric acid and hydrogen peroxide. Oxidation of MWCNTs increased their solubility in aqueous solution and hence enhances the contact between the carbon nanotubes and the water and pentachlorophenol molecules. The oxidized MWCNTs were used to study the removal of pentachlorophenol (PCP) from aqueous solutions. The equilibrium adsorption of PCP on the oxidized MWCNTs at various temperatures was studied and the adsorption equilibrium was well described using different adsorption models. The thermodynamic of adsorption was studied at different temperatures and the results showed that the adsorption process was product favored, and becomes more so at higher temperature, since the adsorption is endothermic in general.

Abdel Salam, M.; Burk, R. C.

2008-12-01

157

Interaction of “extremely diluted solutions” with aqueous solutions of hydrochloric acid and sodium hydroxide  

Microsoft Academic Search

The “extremely diluted solutions” (EDS) have revealed a really intriguing behaviour, characterized by multiple independent variables. Because of their behaviour, EDS can be described as far-from-equilibrium systems, capable of auto-organizing as a consequence of little perturbations.We measured the heats of mixing of basic and acid solutions with such EDS and their electrical conductivity, comparing with the analogous heats of mixing

V. Elia; L. Elia; M. Marchese; M. Montanino; E. Napoli; M. Niccoli; L. Nonatelli; F. Savarese

2007-01-01

158

Reconstructing Past Climates using Carbon Isotopes from Fulvic Acids in Cave Sediments  

E-print Network

Ã?Ã? Ã? Ã?Ã?Ã? Ã? Ã?Ã? Reconstructing Past Climates using Carbon Isotopes from Fulvic Acids in Cave Climates using Carbon Isotopes from Fulvic Acids in Cave Sediments, Chemical Geology (2013), doi: 10.1016/j MANUSCRIPT 1 Reconstructing Past Climates using Carbon Isotopes from Fulvic Acids in Cave Sediments *Jason S

Asmerom, Yemane

159

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)

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.

Stefánsson, Andri; Bénézeth, Pascale; Schott, Jacques

2013-11-01

160

Solution Preserves Nucleic Acids in Body-Fluid Specimens  

NASA Technical Reports Server (NTRS)

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.

Pierson, Duane L.; Stowe, Raymond P.

2004-01-01

161

Fluidic delivery of homogeneous solutions through carbon tube bundles  

NASA Astrophysics Data System (ADS)

A wide array of technological applications requires localized high-rate delivery of dissolved compounds (in particular, biological ones), which can be achieved by forcing the solutions or suspensions of such compounds through nano or microtubes and their bundled assemblies. Using a water-soluble compound, the fluorescent dye Rhodamine 610 chloride, frequently used as a model drug release compound, it is shown that deposit buildup on the inner walls of the delivery channels and its adverse consequences pose a severe challenge to implementing pressure-driven long-term fluidic delivery through nano and microcapillaries, even in the case of such homogeneous solutions. Pressure-driven delivery (3-6 bar) of homogeneous dye solutions through macroscopically-long (~1 cm) carbon nano and microtubes with inner diameters in the range 100 nm-1 µm and their bundled parallel assemblies is studied experimentally and theoretically. It is shown that the flow delivery gradually shifts from fast convection-dominated (unobstructed) to slow jammed convection, and ultimately to diffusion-limited transport through a porous deposit. The jamming/clogging phenomena appear to be rather generic: they were observed in a wide concentration range for two fluorescent dyes in carbon nano and microtubes, as well as in comparable transparent glass microcapillaries. The aim of the present work is to study the physics of jamming, rather than the chemical reasons for the affinity of dye molecules to the tube walls.

Srikar, R.; Yarin, A. L.; Megaridis, C. M.

2009-07-01

162

Carbon honeycomb grids for advanced lead-acid batteries. Part I: Proof of concept  

NASA Astrophysics Data System (ADS)

The carbon honeycomb grid is proposed as innovative solution for high energy density lead acid battery. The proof of concept is demonstrated, developing grids suitable for the small capacity, scale of valve-regulated lead acid batteries with 2.5-3 Ah plates. The manufacturing of the grids, includes fast, known and simple processes which can be rescaled for mass production with a minimum, investment costs. The most critical process of green composite carbonisation by heating in inert, atmosphere from 200 to 1000 °C takes about 5 h, guaranteeing the low cost of the grids. An AGM-VRLA, cell with prototype positive plate based on the lead-2% tin electroplated carbon honeycomb grid and, conventional negative plates is cycled demonstrating 191 deep cycles. The impedance spectroscopy, measurements indicate the grid performance remains acceptable despite the evolution of the corrosion, processes during the cycling.

Kirchev, Angel; Kircheva, Nina; Perrin, Marion

2011-10-01

163

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

PubMed

The liquid phase esterification of butyric acid with a series of linear and branched alcohols is examined. Four strong cation exchange resins, Amberlyst™ 15, Amberlyst™ 36, Amberlyst™ BD 20, and Amberlyst™ 70, were used along with para-toluenesulfonic acid as a homogeneous catalyst. The effect of increasing alcohol carbon chain length and branching on esterification rate at 60°C is presented. For all catalysts, the decrease in turnover frequency (TOF) with increasing carbon chain length of the alcohol is described in terms of steric hindrance, alcohol polarity, and hydroxyl group concentration. The kinetics of butyric acid esterification with 2-ethylhexanol using Amberlyst™ 70 catalyst is described with an activity-based, pseudo-homogeneous kinetic model that includes autocatalysis by butyric acid. PMID:23380294

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

2013-02-01

164

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

165

Interaction of Ethyl Alcohol Vapor with Sulfuric Acid Solutions  

NASA Technical Reports Server (NTRS)

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

Leu, Ming-Taun

2006-01-01

166

Solidphase extraction of aminobenzoic acids and aminotoluenesulfonic acids with graphitized carbon black  

Microsoft Academic Search

The extraction of amphoteric aromatic amines from water samples is difficult because of their high polarity. For the enrichment\\u000a of aminobenzoic acids and aminotoluenesulfonic acids with solid-phase extraction, graphitized carbon black (GCB) was investigated.\\u000a With few exceptions, the 12 analytes studied were extracted with recoveries > 60% at neutral or basic pH, whereas at pH 3\\u000a low recoveries were obtained.

C. Böhme; T. C. Schmidt; E. von Löw; G. Stork

1998-01-01

167

Recovery of rhenium from sulfuric acid solutions with activated coals  

SciTech Connect

Equilibrium and kinetic characteristics of rhenium sorption from sulfuric acid solutions (pH 2) by activated coals produced from coal raw materials (China) were studied. Constants of the Henry equation describing isotherms of rhenium sorption by activated coals were calculated. The effective diffusion coefficients of rhenium in the coals were determined. The dynamic characteristics of rhenium sorption and desorption were determined for the activated coal with the best capacity and kinetic characteristics.

Troshkina, I.D.; Naing, K.Z.; Ushanova, O.N.; P'o, V.; Abdusalomov, A.A. [Mendeleev Russian University of Chemical Engineering Moscow (Russian Federation)

2006-09-15

168

Uptake kinetics of three epoxides into sulfuric acid solution  

NASA Astrophysics Data System (ADS)

This work presents a study of the uptake of isoprene epoxide, butadiene epoxide (BMO) and butadiene diepoxide (BDO) into sulfuric acid solutions which helps to understand the reactivity of epoxides existing in the atmosphere toward acidic aerosols. The uptake of these three compounds into 0-30 wt % H2SO4 solutions were measured using a rotated wetted-wall reactor (RWW) coupled to a single-photon ionization time of flight mass spectrometer (SPI-TOFMS). The epoxides were found to be very easily taken up by H2SO4 solutions even in dilute concentrations of pH levels. Isoprene epoxide was found to partition reversibly into solution at pH = 4, whereas irreversible uptake was observed when pH ? 3. We reported the reactive uptake coefficients from 1.87 × 10-5 to 2.67 × 10-3 for pH = 3-20 wt % H2SO4 solutions. A chemical reaction for isoprene epoxide was responsible for the reactive uptake. By means of mass spectrometry, gas chromatography and FTIR spectroscopy, a gas product was identified to be 2-methyl-3-butenal. The uptake behavior of butadiene epoxide was similar with that of isoprene epoxide, while butadiene diepoxide partitioned irreversibly over the whole acidity range of 0-30 wt %, and the reactive uptake coefficients increased slightly (0.849 × 10-4-1.36 × 10-4) from pure water to pH = 1. The reactivity that displayed close dependence on the hydrolysis rates of the three epoxides was analyzed and compared according to their molecular structural differences. The atmospheric lifetimes were calculated and atmospheric implication was discussed based on the corresponding reactive uptake coefficients.

Wang, Tianhe; Liu, Ze; Wang, Weigang; Ge, Maofa

2012-09-01

169

Methanol Uptake By Low Temperature Aqueous Sulfuric Acid Solutions  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

170

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

PubMed

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

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

2014-09-16

171

Nitric acid oxidation of vapor grown carbon nanofibers  

Microsoft Academic Search

Vapor grown carbon nanofibers (Pyrograf III™) with 100–300 nm diameters and ?10–100 ?m lengths were oxidized in 69–71 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 18.3–22.5% for 10–90 min oxidations followed by a drop to 14–15%

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

2004-01-01

172

Organic amendments increase soil solution phosphate concentrations in an acid soil: A controlled environment study  

SciTech Connect

Soil acidification affects at least 4 million hectares of agricultural land in Victoria, Australia. Low soil pH can inhibit plant growth through increased soluble aluminum (Al) concentrations and decreased available phosphorus (P). The addition of organic amendments may increase P availability through competition for P binding sites, solubilization of poorly soluble P pools, and increased solution pH. The effect of two organic amendments (lignite and compost) on P solubility in an acid soil was determined through controlled environment (incubation) studies. Three days after the addition of lignite and compost, both treatments increased orthophosphate and total P measured in soil solution, with the compost treatments having the greatest positive effect. Increased incubation time (26 days) increased soil solution P concentrations in both untreated and amended soils, with the greatest effect seen in total P concentrations. The measured differences in solution P concentrations between the lignite- and compost-amended treatments were likely caused by differences in solution chemistry, predominantly solution pH and cation dynamics. Soil amendment with lignite or compost also increased microbial activity in the incubation systems, as measured by carbon dioxide respiration. Based on the results presented, it is proposed that the measured increase in soil solution P with amendment addition was likely caused by both chemical and biological processes, including biotic and abiotic P solubilization reactions, and the formation of soluble organic-metal complexes.

Schefe, C.R.; Patti, A.F.; Clune, T.S.; Jackson, R. [Rutgers Centre, Rutherglen, Vic. (Australia)

2008-04-15

173

Aquatic photolysis: photolytic redox reactions between goethite and adsorbed organic acids in aqueous solutions  

USGS Publications Warehouse

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.

Goldberg, M.C.; Cunningham, K.M.; Weiner, E.R.

1993-01-01

174

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

PubMed

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

Amiri, Mandana; Imanzadeh, Hamideh; Banaei, Alireza

2015-02-01

175

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

Code of Federal Regulations, 2014 CFR

...cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). 173.195 Section...cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen...consist of passing a piece of Guignard's sodium picrate paper over the...

2014-10-01

176

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

Code of Federal Regulations, 2013 CFR

...cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). 173.195 Section...cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen...consist of passing a piece of Guignard's sodium picrate paper over the...

2013-10-01

177

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

Microsoft Academic Search

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

Yahia Z. Hamada; Wesley R. Harris

2006-01-01

178

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

NASA Astrophysics Data System (ADS)

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

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

1988-05-01

179

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

PubMed

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

Lin, Peter T; Dunn, William A

2014-01-01

180

Metal-free carbon-carbon bond-forming reductive coupling between boronic acids and tosylhydrazones.  

PubMed

The formation of carbon-carbon bonds is a fundamental transformation in organic synthesis. In spite of the myriad methods available, advantageous methodologies in terms of selectivity, availability of starting materials, operational simplicity, functional-group tolerance, environmental sustainability and economy are in constant demand. In this context, the development of new cross-coupling reactions that use catalysts based on inexpensive and non-toxic metals is attracting increasing attention. Similarly, efficient processes that do not require a metal catalyst are of extraordinary interest. Here, we report a new and efficient metal-free carbon-carbon bond-forming coupling between tosylhydrazones and boronic acids. This reaction is very general and functional-group tolerant. As the required tosylhydrazones are easily generated from carbonyl compounds, it can be seen as a reductive coupling of carbonyls, a process of high synthetic relevance that requires several steps using other methodologies. PMID:21378917

Barluenga, José; Tomás-Gamasa, María; Aznar, Fernando; Valdés, Carlos

2009-09-01

181

Comparison of solution and crystal properties of Co(II)substituted human carbonic anhydrase II  

E-print Network

Comparison of solution and crystal properties of Co(II)­substituted human carbonic anhydrase II: Carbonic anhydrase Metalloenzyme Cobalt substitution Crystallography Carbon dioxide a b s t r a c t The visible absorption of crystals of Co(II)­substituted human carbonic anhydrase II (Co(II)­HCA II) were

Tanner, David B.

182

Rate Constants for Peroxidation of Polyunsaturated Fatty Acids and Sterols in Solution and in Liposomes  

PubMed Central

Rate constants for autoxidation propagation of several unsaturated lipids in benzene solution at 37°C and in phosphatidylcholine liposomes were determined by a linoleate radical clock. This radical clock is based on competition between hydrogen atom abstraction by an intermediate peroxyl radical derived from linoleic acid that leads to a trans,cis-conjugated hydroxyoctadecadienoic product and ?–fragmentation of the same peroxyl that gives the trans,trans-product hydroxyoctadecadienoic acid. Rate constants determined by this approach in solution relative to linoleic acid (kp = 62 M?1s?1) were: arachidonic acid (kp = 197 ± 13 M?1s?1), eicosapentaenoic acid (kp = 249 ± 16 M?1s?1), docosahexaenoic acid (kp = 334 ± 37 M?1s?1), cholesterol (kp = 11 ± 2 M?1s?1), and 7-dehydrocholesterol (kp = 2,260 ± 40 M?1s?1). Free radical oxidations of multilamellar and unilamellar liposomes of various mixtures of glycerophosphatidylcholine molecular species were also carried out. In some experiments, cholesterol or 7-dehydrocholesterol was incorporated into the lipid mixture undergoing oxidation. A phosphatidylcholine bearing a linoleate ester at sn-2 was a component of each liposome peroxidation reaction and the ratio of trans,cis/trans,trans (t,c/t,t)-conjugated diene oxidation products formed from this phospholipid was determined for each oxidation reaction. This t,c/t,t-product ratio from linoleate was used to “clock” liposome constituents as hydrogen atom donors in the lipid bilayer. Application of this lipid bilayer radical clock gives relative autoxidation propagation rate constants of arachidonate (20:4), eicosapentaenoate (20:5), docosahexaenoate (22:6), and 7-dehydrocholesterol to be 115 ± 7, 145 ± 8, 172 ± 13, and 832 ± 86, respectively, a reactivity trend that parallels the one in solution. We also conclude from the liposome oxidations that linoleate peroxyl radicals at different positions on the eighteen-carbon chain (at C-9 and C-13) have different kinetic properties. This is in contrast to the results of solution oxidations of linoleate in which the C-9 and C-13 peroxyl radicals have similar reactivities. We suggest that peroxyl radical ?–scission depends on solvent polarity and the polarity of the local environment of peroxyl radicals in liposomal oxidations depends on the position of the peroxyl radical on the eighteen-carbon chain. PMID:19705847

Xu, Libin; Davis, Todd A.; Porter, Ned A.

2013-01-01

183

Poly(lactic acid)/Carbon Nanotube Fibers as Novel Platforms for Glucose Biosensors  

PubMed Central

The focus of this paper is the development and investigation of properties of new nanostructured architecture for biosensors applications. Highly porous nanocomposite fibers were developed for use as active materials in biosensors. The nanocomposites comprised poly(lactic acid)(PLA)/multi-walled carbon nanotube (MWCNT) fibers obtained via solution-blow spinning onto indium tin oxide (ITO) electrodes. The electrocatalytic properties of nanocomposite-modified ITO electrodes were investigated toward hydrogen peroxide (H2O2) detection. We investigated the effect of carbon nanotube concentration and the time deposition of fibers on the sensors properties, viz., sensitivity and limit of detection. Cyclic voltammetry experiments revealed that the nanocomposite-modified electrodes displayed enhanced activity in the electrochemical reduction of H2O2, which offers a number of attractive features to be explored in development of an amperometric biosensor. Glucose oxidase (GOD) was further immobilized by drop coating on an optimized ITO electrode covered by poly(lactic acid)/carbon nanotube nanofibrous mats. The optimum biosensor response was linear up to 800 mM of glucose with a sensitivity of 358 nA·mM?1 and a Michaelis-Menten constant (KM) of 4.3 mM. These results demonstrate that the solution blow spun nanocomposite fibers have great potential for application as amperometric biosensors due to their high surface to volume ratio, high porosity and permeability of the substrate. The latter features may significantly enhance the field of glucose biosensors. PMID:25585633

Oliveira, Juliano Elvis; Mattoso, Luiz Henrique Capparelli; Medeiros, Eliton Souto; Zucolotto, Valtencir

2012-01-01

184

Poly(lactic acid)/Carbon Nanotube Fibers as Novel Platforms for Glucose Biosensors.  

PubMed

The focus of this paper is the development and investigation of properties of new nanostructured architecture for biosensors applications. Highly porous nanocomposite fibers were developed for use as active materials in biosensors. The nanocomposites comprised poly(lactic acid)(PLA)/multi-walled carbon nanotube (MWCNT) fibers obtained via solution-blow spinning onto indium tin oxide (ITO) electrodes. The electrocatalytic properties of nanocomposite-modified ITO electrodes were investigated toward hydrogen peroxide (H2O2) detection. We investigated the effect of carbon nanotube concentration and the time deposition of fibers on the sensors properties, viz., sensitivity and limit of detection. Cyclic voltammetry experiments revealed that the nanocomposite-modified electrodes displayed enhanced activity in the electrochemical reduction of H2O2, which offers a number of attractive features to be explored in development of an amperometric biosensor. Glucose oxidase (GOD) was further immobilized by drop coating on an optimized ITO electrode covered by poly(lactic acid)/carbon nanotube nanofibrous mats. The optimum biosensor response was linear up to 800 mM of glucose with a sensitivity of 358 nA·mM-1 and a Michaelis-Menten constant (KM) of 4.3 mM. These results demonstrate that the solution blow spun nanocomposite fibers have great potential for application as amperometric biosensors due to their high surface to volume ratio, high porosity and permeability of the substrate. The latter features may significantly enhance the field of glucose biosensors. PMID:25585633

Oliveira, Juliano Elvis; Mattoso, Luiz Henrique Capparelli; Medeiros, Eliton Souto; Zucolotto, Valtencir

2012-01-01

185

Oxidation-resistant acidic resins prepared by partial carbonization as cocatalysts in synthesis of adipic acid.  

PubMed

The oxidation-resistant acidic resins are of great importance for the catalytic oxidation systems. In this paper, the oxidatively stable acidic resins are obtained from the cation ion exchange resins (CIERs) through the thermal treatment in N(2) atmosphere. The structure and properties of the thermally treated CIERs were characterized by chemical analysis, Fourier transform infrared (FT-IR) spectra, acid capacity measurement and scanning electron microscope (SEM). The thermally treated CIERs possess high acid capacity up to 4.09 mmol g(-1). A partial carbonization is observed in the thermal treatment process of CIERs, but the morphology of resin spheres maintains well. The as-prepared CIERs are used as solid acids to assist the hydrogen peroxide oxidation of cyclohexene to adipic acid (ADA) with tungstic acid as the catalyst precursor. The improved yields of ADA in the recycling reaction are obtained in the presence of acidic CIERs. Meanwhile, the unproductive decomposition of H(2)O(2) is effectively suppressed. The high yields of ADA (about 81%) are kept by the thermally treated CIERs even after the fifth cycle. The thermally treated CIERs exhibit excellent acid-catalytic performance and possess remarkable oxidation-resistant capability. PMID:22775061

Wei, Huijuan; Li, Hongbian; Liu, Yangqing; Jin, Peng; Wang, Xiangyu; Li, Baojun

2012-08-01

186

Carbon dioxide capture capacity of sodium hydroxide aqueous solution.  

PubMed

The present paper investigates the various features of NaOH aqueous solution when applied as an absorbent to capture carbon dioxide (CO(2)) emitted with relatively high concentration in the flue gas. The overall CO(2) absorption reaction was carried out according to consecutive reaction steps that are generated in the order of Na(2)CO(3) and NaHCO(3). The reaction rate and capture efficiency were strongly dependent on the NaOH concentration in the Na(2)CO(3) production range, but were constant in the NaHCO(3) production step, irrespective of the NaOH concentration. The amount of CO(2) absorbed in the solution was slightly less than the theoretical value, which was ascribed to the low trona production during the reaction and the consequent decrease in CO(2) absorption in the NaOH solution. The mass ratio of absorbed CO(2) that participated in the Na(2)CO(3), NaHCO(3), and trona production reactions was calculated to be 20:17:1, respectively. PMID:23183145

Yoo, Miran; Han, Sang-Jun; Wee, Jung-Ho

2013-01-15

187

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

188

Radiation removal of lead and cadmium complexed with ethylenediamine tetraacetic ACID from aqueous solutions  

NASA Astrophysics Data System (ADS)

The removal of lead (100 mg/L) and cadmium (27 mg/L) complexed with ethylenediamine tetraacetic acid (EDTA) in presence of different scavengers has been investigated. The experiments show that in acidic solutions, the EDTA complexed lead may be reduced at a dose of 40 kGy up to 97% without the addition of typical OH radical scavengers such as Na(K) formate. The addition of OH radical scavengers as 1×10-3 mol/L HCOOK, 2×10-3 mol/L carbonate or 2×10-3 mol/L bicarbonate (wide range of pH) results in no further improvement. The bubbling of the solution with nitrogen or oxygen also exhibits no positive effect. On the contrary, saturation with nitrous oxide in the presence of scavengers has a modest positive influence, whereas in the system which is scavenger-free, high negative effect (30 %) was observed. The presence of nitrate (e aq - scavenger) appears to be important for an effective reduction of complexed lead. The efficient removal of cadmium complexed with EDTA proceeds up to 96 % at a dose of 40 kGy with an addition of 5×10-3 mol/L of carbonate as the OH radical scavenger and simultaneously pH buffer (pH 10.5). After irradiation, the cadmium is present in the final form of CdCO3.

Drtinová, B.; Pospíšil, M.; Mú?ka, V.; ?uba, V.

2006-01-01

189

Metal amides as the simplest acid/base catalysts for stereoselective carbon-carbon bond-forming reactions.  

PubMed

In this paper, new possibilities for metal amides are described. Although typical metal amides are recognized as strong stoichiometric bases for deprotonation of inert or less acidic hydrogen atoms, transition-metal amides, namely silver and copper amides, show interesting abilities as one of the simplest acid/base catalysts in stereoselective carbon-carbon bond-forming reactions. PMID:23775980

Yamashita, Yasuhiro; Kobayashi, Sh?

2013-07-15

190

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...

191

Systems solutions by lactic acid bacteria: from paradigms to practice  

PubMed Central

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

2011-01-01

192

Molecular Structure of Hydrochloric acid (if in aqueous solution)  

NSDL National Science Digital Library

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.

2002-09-10

193

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

NASA Astrophysics Data System (ADS)

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.

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

2006-05-01

194

Effects of acidic solutions on sexual reproduction of Pteridium aquilinum  

SciTech Connect

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% spermatozoids are immobile one min after exposure to pH 6.1 buffer while about an equal percentage remain motile after 30 min exposure to buffer of pH 5.1. Between these two response extremes are two other subpopulations. One is quite sensitive to pH but shows some recovery if pH is between 5.6 and 6.1, while the second subpopulation does not seem to exhibit any motility recovery at all but is more resistant to acidity than the first subpopulation. To complement experiments that evaluate spermatozoid responses, experiments were performed to view the process of fertilization under controlled environmental conditions as well as under the canopy of a forest. Fertilization of gametophytes in uncovered petri dishes under a forest canopy was similar to results in aseptic culture after gametophytes were exposed to various pH levels and 86.6 micrometers sulfate. Fertilization at pH 4.5 and 3.6 was about one-half that occurring at pH 6.1. Fertilization in gametophytes exposed to pH 3.0 was about 10-20% of that occurring at pH 6.1. Addition of 86.6 micrometers sulfate decreased fertilization under all culture conditions. These experimental results suggest that fertilization in p. Aquilinum may be used as a bioindicator of contaminants in rainwater. The results demonstrate that spermatozoid motility (and the process of fertilization) is more acid sensitive than gametophytic and sporophytic tissues.

Evans, L.S.; Conway, C.A.

1980-01-01

195

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

PubMed Central

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

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

2013-01-01

196

GADOLINIUM OXALATE SOLUBILITY MEASUREMENTS IN NITRIC ACID SOLUTIONS  

SciTech Connect

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}.

Pierce, R.

2012-02-22

197

The solvent effect on the acidities of haloacetic acids in aqueous solution. A RISM-SCF study  

NASA Astrophysics Data System (ADS)

The acidities of acetic, fluoracetic and chloroacetic acids in aqueous solution are calculated by means of the ab initio method combined with the reference interaction site method in the statistical mechanics of molecular liquids (the RISM-SCF method). The inversion in the order of acidities experimentally observed when a series of haloacetic acids is immersed into aqueous solution is reproduced. It is shown that the inversion is caused by competition between substitution and solvation effects. The solvation effect is discussed in molecular detail in terms of the charge distribution of the solute and the solute-solvent radial distribution functions.

Kawata, Masaaki; Ten-no, Seiichiro; Kato, Shigeki; Hirata, Fumio

1995-06-01

198

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

SciTech Connect

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.

Elizondo-Villarreal, E.M.

1989-01-01

199

Comparison of the elimination between perfluorinated fatty acids with different carbon chain length in rats  

Microsoft Academic Search

Elimination in urine and feces was compared between four perfluorinated fatty acids (PFCAs) with different carbon chain length. In male rats, perfluoroheptanoic acid (PFHA) was rapidly eliminated in urine with the proportion of 92% of the dose being eliminated within 120 h after an intraperitoneal injection. Perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) was eliminated in urine

Naomi Kudo; Erika Suzuki; Masanori Katakura; Kohtaro Ohmori; Rie Noshiro; Yoichi Kawashima

2001-01-01

200

Modeling of Water-rock interaction in the Mackenzie Basin: competition between sulfuric and carbonic acids  

E-print Network

sulfuric and carbonic acids E. Beaulieu, Y. Godd´eris, D. Labat, C. Roelandt, D. Calmels, J. Gail- lardet in the Mackenzie Basin: competition between sulfuric and carbonic acids. E. Beaulieu1 , Y. Goddéris1 , D. Labat1, a simulation is performed removing the contribution of sulfuric acid to the weathering system. The main

201

Bias-dependent amino-acid-induced conductance changes in short semi-metallic carbon nanotubes  

E-print Network

Bias-dependent amino-acid-induced conductance changes in short semi-metallic carbon nanotubes G the interaction between short semi-metallic carbon nanotubes and different amino acids using molecular dynamics different mechanisms of nanotube-conductance-change upon adsorption of amino acids: one due to the change

Pulfrey, David L.

202

Isotopic fractionations associated with phosphoric acid digestion of carbonate minerals: Insights from first-principles theoretical  

E-print Network

Isotopic fractionations associated with phosphoric acid digestion of carbonate minerals: Insights 27 May 2009; available online 23 June 2009 Abstract Phosphoric acid digestion has been used with phosphoric acid digestion of carbonates at 25 °C are 10.72&, 0.220&, 0.137&, 0.593& for, respectively, 18 O

Goddard III, William A.

203

Stable carbon isotope ratios of methyl-branched fatty acids are different to those of straight-chain fatty acids in dairy products.  

PubMed

Methyl-branched fatty acids (MBFAs) are the dominant form of fatty acid found in many bacteria. They are also found at low levels in a range of foodstuffs, where their presence has been linked to bacterial sources. In this study we evaluated the potential of compound-specific isotope analysis to obtain insights into the stable carbon isotope ratios (delta(13)C values in per thousand) of individual MBFAs and to compare them to the stable carbon isotope ratios of straight-chain fatty acids in food. Due to their low abundance in foodstuffs, the MBFAs were enriched prior to gas chromatography coupled to isotope ratio mass spectrometric (GC-IRMS) analysis. After transesterification, urea complexation was used to suppress the 16:0 and 18:0 methyl esters that were dominant in the samples. Following that, silver-ion high performance liquid chromatography was used to separate the saturated from the unsaturated fatty acids. The resulting solutions of saturated fatty acids obtained from suet, goat's milk, butter, and human milk were studied by GC-IRMS. The delta(13)C values of fatty acids with 12-17 carbons ranged from -25.4 per thousand to -37.6 per thousand. In all samples, MBFAs were most depleted in carbon-13, followed by the odd-chain fatty acids 15:0 and 17:0. 14:0 and 16:0 contained the highest proportions of carbon-13. The results from this study illustrate that MBFAs have distinctive delta(13)C values and must originate from other sources and/or from very different substrates. These measurements support the initial hypothesis that delta(13)C values can be used to attribute MBFAs to particular sources. PMID:17639356

Vetter, Walter; Gaul, Simon; Thurnhofer, Saskia; Mayer, Kathrin

2007-09-01

204

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

USGS Publications Warehouse

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 singlet 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.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 singlet 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.

Goldberg, M.C.; Cunningham, K.M.; Aiken, G.R.; Weiner, E.R.

1992-01-01

205

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

PubMed

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 40°C. 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

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

2012-03-01

206

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

PubMed

Multi-walled carbon nanotubes and powdered activated carbon were used as adsorbents for the successful removal of Reactive Red M-2BE textile dye from aqueous solutions. The adsorbents were characterised by infrared spectroscopy, N(2) adsorption/desorption isotherms and scanning electron microscopy. The effects of pH, shaking time and temperature on adsorption capacity were studied. In the acidic pH region (pH 2.0), the adsorption of the dye was favourable using both adsorbents. The contact time to obtain equilibrium at 298K was fixed at 1h for both adsorbents. The activation energy of the adsorption process was evaluated from 298 to 323K for both adsorbents. The Avrami fractional-order kinetic model provided the best fit to the experimental data compared with pseudo-first-order or pseudo-second-order kinetic adsorption models. For Reactive Red M-2BE dye, the equilibrium data were best fitted to the Liu isotherm model. Simulated dyehouse effluents were used to check the applicability of the proposed adsorbents for effluent treatment. PMID:21724329

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

2011-09-15

207

Microwave Effect for Glycosylation Promoted by Solid Super Acid in Supercritical Carbon Dioxide  

PubMed Central

The effects of microwave irradiation (2.45 GHz, 200 W) on glycosylation promoted by a solid super acid in supercritical carbon dioxide was investigated with particular attention paid to the structure of the acceptor substrate. Because of the symmetrical structure and high diffusive property of supercritical carbon dioxide, microwave irradiation did not alter the temperature of the reaction solution, but enhanced reaction yield when aliphatic acceptors are employed. Interestingly, the use of a phenolic acceptor under the same reaction conditions did not show these promoting effects due to microwave irradiation. In the case of aliphatic diol acceptors, the yield seemed to be dependent on the symmetrical properties of the acceptors. The results suggest that microwave irradiation do not affect the reactivity of the donor nor promoter independently. We conclude that the effect of acceptor structure on glycosylation yield is due to electric delocalization of hydroxyl group and dielectrically symmetric structure of whole molecule. PMID:20054471

Hinou, Hiroshi; Saito, Naohiro; Ogawa, Masato; Maeda, Takahiko; Nishimura, Shin-Ichiro

2009-01-01

208

Electrophoretic deposition of phthalocyanine in organic solutions containing trifluoroacetic acid.  

PubMed

The absorption spectra of copper phthalocyanine (CuPc) 1,2-dichloroethane (DCE) solutions containing trifluoroacetic acid (TFAA) shows that the number of protons coordinating to the CuPc molecule was 1 and 2 for the first and second proton adducts, respectively, which indicates the formations of CuPcH(+) and CuPcH(2)(2+). This CuPc molecule may act as a catalyst to dissociate TFAA into trifluoroacetate anion (A(-)) and H(+) and form the proton adducts. The electrical conductivity dependence of the solution on CuPc concentration also supports this mechanism. A dense film of CuPc was deposited on an indium tin oxide cathode plate by electrophoresis of the solution. Similar dense films of a wide variety of phthalocyanines (MPc; M = Cu, H(2), Fe, Ni, Zn, Pb, VO) were also deposited using this method. Similar films of CuPc were also formed using dichloromethane (DCM) and 1,1,1-trichloroethane (TCE) in place of DCE. Depositions are ascribed to the migration of positively charged monomers (i.e., protonated MPc). Scanning electron microscopy revealed that these films are composed of fibrous crystallites, size of which was found to increase with the electrophoresis time, the strength of the applied electrical field and the concentration of CuPc in the bath. The influence of the dielectric constant of the organic solvent on the film growth is discussed. PMID:20886893

Shrestha, Nabeen K; Kohn, Hideki; Imamura, Mitsuharu; Irie, Kazunobu; Ogihara, Hitoshi; Saji, Tetsuo

2010-11-16

209

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

Microsoft Academic Search

Cellulose carbonate was prepared by the reaction of cellulose pulp and CO2 with treatment reagents, such as aqueous ZnCl2 (20–40 wt%) solution, acetone or ethyl acetate, at ?5–0°C and 30–40 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

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

2002-01-01

210

Carbonic Anhydrase-Inhibitor Binding: From Solution to the Gas Phase  

E-print Network

Carbonic Anhydrase-Inhibitor Binding: From Solution to the Gas Phase Qinyuan Wu,,§ Jinming Gao stabilities of nonco- valent complexes between bovine carbonic anhydrase II (BCAII, EC 4.2.1.1) and para systems due to the stability of carbonic anhydrase (CA) and its well characterized structure and ligand

Gao, Jinming

211

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

E-print Network

Structure Controlled Synthesis of Single-Walled Carbon Nanotubes Using Solution Based Catalyst 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 Thurakitseree1

Mellor-Crummey, John

212

Modeling of dissolution patterns for carbonate acidizing in the porous media  

NASA Astrophysics Data System (ADS)

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.

Samadi, Fereshteh; Esmaeilzadeh, Feridun; Mowla, Dariush

2012-05-01

213

A Simple Demonstration of Carbon Dioxide Fixation and Acid Production in CAM Plants  

ERIC Educational Resources Information Center

Described is an experiment investigating carbon dioxide fixation in the dark and the diurnal rhythm of acid production in plants exhibiting Crassulacean Acid Metabolism. Included are suggestions for four further investigations. (SL)

Walker, John R. L.; McWha, James A.

1976-01-01

214

A New Organic Acid to Stimulate Deep Wells in Carbonate Reservoirs  

E-print Network

Carbonate acidizing has been carried out using HCl-based stimulation fluids for decades. However, at high temperatures, HCl does not produce acceptable results because of its fast reaction, acid penetration, and hence surface dissolution, and its...

Al-Douri, Ahmad F

2014-05-28

215

UPTAKE OF SHORT-CHAIN ALCOHOLS BY SULFURIC ACID SOLUTIONS USING RAMAN AND VIBRATIONAL SUM FREQUENCY  

E-print Network

UPTAKE OF SHORT-CHAIN ALCOHOLS BY SULFURIC ACID SOLUTIONS USING RAMAN AND VIBRATIONAL SUM FREQUENCY-liquid interface of 0 to 96.5 wt% sulfuric acid (SA) solutions has been observed directly using vibrational sum in either the neat methanol or concentrated sulfuric acid spectra. This peak is attributed to the singly

216

Effective Diffusion Coefficients for Methanol in Sulfuric Acid Solutions Measured by Raman Spectroscopy  

E-print Network

Effective Diffusion Coefficients for Methanol in Sulfuric Acid Solutions Measured by Raman % sulfuric acid solutions was followed using Raman spectroscopy. Because methanol reacts to form protonated that the speciation of both methanol and sulfuric acid may be important in determining these transport coefficients

217

GADOLINIUM OXALATE SOLUBILITY MEASUREMENTS IN NITRIC ACID SOLUTIONS  

SciTech Connect

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}. At 25 °C, for 6 M HNO{sub 3}, 11 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 2.5 g/L and 0.8 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}. The solubility of Gd in 4 M HNO{sub 3} with 0.15 M oxalate at 10 °C is about 1.5 g/L. For 6 M HNO{sub 3} with 0.15 M oxalate, the solubility of Gd at 10 °C is about 10 g/L. Gadolinium nitrate is very soluble in HNO{sub 3}. The solubility of Gd is linear as a function of HNO{sub 3} from 343 g/L Gd in 2.88 M HNO{sub 3} to 149 g/L in 8.16 M HNO{sub 3}. Below 2.88 M HNO{sub 3}, the solubility of Gd approaches a limit of about 360 g/L. However, there are no data available below 1.40 M HNO{sub 3}, which has a Gd solubility of 353 g/L.

Pierce, R. A.

2012-03-12

218

Water-soluble organic carbon, dicarboxylic acids, ketoacids, and ?-dicarbonyls in the tropical Indian aerosols  

Microsoft Academic Search

Tropical aerosol (PM10) samples (n = 49) collected from southeast coast of India were studied for water-soluble dicarboxylic acids (C2–C12), ketocarboxylic acids (C2–C9), and ?-dicarbonyls (glyoxal and methylglyoxal), together with analyses of total carbon (TC) and water-soluble organic carbon (WSOC). Their distributions were characterized by a predominance of oxalic acid followed by terephthalic (t-Ph), malonic, and succinic acids. Total concentrations

Chandra Mouli Pavuluri; Kimitaka Kawamura; T. Swaminathan

2010-01-01

219

A method for determining thermophysical properties of organic material in aqueous solutions: Succinic acid  

Microsoft Academic Search

A method for determining evaporation rates and thermodynamic properties of aqueous solution droplets is introduced. The method combines evaporation rate measurements using modified TDMA technique with data evaluation using an accurate evaporation model. The first set of data has been collected and evaluated for succinic acid aqueous solution droplets.Evaporation rates of succinic acid solution droplets have been measured using a

I. Riipinen; B. Svenningsson; M. Bilde; A. Gaman; K. E. J. Lehtinen; M. Kulmala

2006-01-01

220

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

NASA Astrophysics Data System (ADS)

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 planet’s 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.

Rau, G. H.

2010-12-01

221

Isotropic-Nematic Phase Transition of Single-Walled Carbon Nanotubes in Strong Acids  

E-print Network

Isotropic-Nematic Phase Transition of Single-Walled Carbon Nanotubes in Strong Acids Pradeep K. Rai nanotubes (SWNTs) in Brønsted-Lowry acids. We employ a centrifugation technique in conjunction with UV of SWNTs in strong acids. Centrifugation of biphasic dispersions of SWNTs, that is, acid dispersions

Natelson, Douglas

222

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

Microsoft Academic Search

13C NMR spectra of 1,3-dimethylbarbituric acid in aqueous solutions of various acidities and for various solute concentrations have been recorded and interpreted. The spectra recorded at pH=2 and below contain the signals of the neutral solute molecule exclusively, while the ones recorded at pH=7 and above only the signals of the appropriate anion, which has been confirmed by theoretical GIAO-DFT

A. Gryff-Keller; A. Kraska-Dziadecka

223

Bromate removal from aqueous solutions by ordered mesoporous carbon.  

PubMed

We investigated the feasibility of using ordered mesoporous carbon (OMC) for bromate removal from water. Batch experiments were performed to study the influence of various experimental parameters such as the effect of contact time, adsorbent dosage, initial bromate concentration, temperature, pH and effect of competing anions on bromate removal by OMC. The adsorption kinetics indicates that the uptake rate ofbromate was rapid at the beginning: 85% adsorption was completed in 1 h and equilibrium was achieved within 3 h. The sorption process was well described with pseudo-second-order kinetics. The maximum adsorption capacity of OMC for bromate removal was 17.6 mg g(-1) at 298 K. The adsorption data fit the Freundlich model well. The amount of bromate removed was found to be proportional to the influent bromate concentration. The effects of competing anions and solution pH (3-11) were negligible. These limited data suggest that OMC can be effectively utilized for bromate removal from drinking water. PMID:24645482

Xu, Chunhua; Wang, Xiaohong; Shi, Xiaolei; Lin, Sheng; Zhu, Liujia; Che, Yaming

2014-01-01

224

Effects of intravenous solutions on acid-base equilibrium: from crystalloids to colloids and blood components.  

PubMed

Intravenous fluid administration is a medical intervention performed worldwide on a daily basis. Nevertheless, only a few physicians are aware of the characteristics of intravenous fluids and their possible effects on plasma acid-base equilibrium. According to Stewart's theory, pH is independently regulated by three variables: partial pressure of carbon dioxide, strong ion difference (SID), and total amount of weak acids (ATOT). When fluids are infused, plasma SID and ATOT tend toward the SID and ATOT of the administered fluid. Depending on their composition, fluids can therefore lower, increase, or leave pH unchanged. As a general rule, crystalloids having a SID greater than plasma bicarbonate concentration (HCO?-) cause an increase in plasma pH (alkalosis), those having a SID lower than HCO?- cause a decrease in plasma pH (acidosis), while crystalloids with a SID equal to HCO?- leave pH unchanged, regardless of the extent of the dilution. Colloids and blood components are composed of a crystalloid solution as solvent, and the abovementioned rules partially hold true also for these fluids. The scenario is however complicated by the possible presence of weak anions (albumin, phosphates and gelatins) and their effect on plasma pH. The present manuscript summarises the characteristics of crystalloids, colloids, buffer solutions and blood components and reviews their effect on acid-base equilibrium. Understanding the composition of intravenous fluids, along with the application of simple physicochemical rules best described by Stewart's approach, are pivotal steps to fully elucidate and predict alterations of plasma acid-base equilibrium induced by fluid therapy. PMID:25432555

Langer, Thomas; Ferrari, Michele; Zazzeron, Luca; Gattinoni, Luciano; Caironi, Pietro

2014-01-01

225

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

PubMed Central

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

Kurz, Matthias

2008-01-01

226

Equilibrium speciation of select lanthanides in the presence of acidic ligands in homo- and heterogeneous solutions.  

E-print Network

??This dissertation explores lanthanide speciation in liquid solution systems related to separation schemes involving the acidic ligands: bis(2-ethylhexyl) phosphoric acid (HDEHP), lactate, and 8-hydroxyquinoline. Equilibrium… (more)

Robinson, Troy

2011-01-01

227

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

Microsoft Academic Search

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+

D. Aurbach; A. Zaban

1995-01-01

228

Uptake of ozone to mixed sodium bromide/ citric acid solutions  

NASA Astrophysics Data System (ADS)

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).

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

2013-04-01

229

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

SciTech Connect

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.

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

2009-05-26

230

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

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

231

A comparative investigation on adsorption performances of mesoporous activated carbon prepared from waste rubber tire and activated carbon for a hazardous azo dye--Acid Blue 113.  

PubMed

A mesoporous carbon developed from waste tire rubber, characterized by chemical analysis, FTIR, and SEM studies, was used as an adsorbent for the removal and recovery of a hazardous azo dye, Acid Blue 113. Surface area, porosity, and density were determined. The adsorption of the dye over the prepared adsorbent and a commercial activated carbon was achieved under different pH, adsorbate concentration, sieve size, adsorbent dosage, contact time and temperature conditions. Langmuir and Freundlich adsorption isotherm models were applied and thermodynamic parameters were calculated. Kinetic studies indicated that the adsorption process follow first order kinetics and particle diffusion mechanisms are operative. By percolating the dye solution through fixed-bed columns the bulk removal of the Acid Blue 113 was carried out and necessary parameters were determined to find out the percentage saturation of both the columns. Recovery of the dye was made by eluting 0.1 M NaOH through the column. PMID:21163571

Gupta, V K; Gupta, Bina; Rastogi, Arshi; Agarwal, Shilpi; Nayak, Arunima

2011-02-15

232

Large-scale production of anhydrous nitric acid and nitric acid solutions of dinitrogen pentoxide  

DOEpatents

A method and apparatus are disclosed for a large scale, electrochemical production of anhydrous nitric acid and N.sub.2 O.sub.5. The method includes oxidizing a solution of N.sub.2 O.sub.4 /aqueous-HNO.sub.3 at the anode, while reducing aqueous HNO.sub.3 at the cathode, in a flow electrolyzer constructed of special materials. N.sub.2 O.sub.4 is produced at the cathode and may be separated and recycled as a feedstock for use in the anolyte. The process is controlled by regulating the electrolysis current until the desired products are obtained. The chemical compositions of the anolyte and catholyte are monitored by measurement of the solution density and the concentrations of N.sub.2 O.sub.4.

Harrar, Jackson E. (Castro Valley, CA); Quong, Roland (Oakland, CA); Rigdon, Lester P. (Livermore, CA); McGuire, Raymond R. (Brentwood, CA)

2001-01-01

233

Habit modification of calcium carbonate in the presence of malic acid  

SciTech Connect

The ability of malic acid to control calcium carbonate morphology has been investigated by aging calcium chloride solution in the presence of urea in a 90 deg. C bath. Malic acid favors the formation of calcite. A transition from single block to aggregate with special morphology occurs upon increasing malic acid concentration. The morphological development of CaCO{sub 3} crystal obviously depends on the starting pH. CaCO{sub 3} crystal grows from spindle seed to dumbbell in the pH regime from 7 to 11; while it evolves from spindle seed, through peanut, to sphere at pH=11.5. Both dumbbell and sphere consist of rods that are elongated along c-axis and capped with three smooth, well-defined rhombic {l_brace}1 0 4{r_brace} faces. A tentative growth mechanism is proposed based on the fractal model suggested by R. Kniep and S. Busch [Angew. Chem. Int. Ed. Engl. 35 (1996) 2624]. - Graphical abstract: Dumbbell-like CaCO{sub 3} particles obtained in the presence of malic acid.

Mao Zhaofeng [Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Huang Jianhua [Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018 (China)], E-mail: jhhuang@zstu.edu.cn

2007-02-15

234

Hydrogen and carbon in solid solution in oxides and silicates  

NASA Astrophysics Data System (ADS)

The dissolution of H2O and CO2 in structurally dense, nominally anhydrous and non-carbonate oxide matrices such as MgO and CaO is reviewed. H2O and CO2 are treated as gaseous oxide components which enter into solid solution with the refractory oxide hosts. They form anion complexes associated with cation vacancy sites. Evidence is presented that OH- pairs which derive from the dissolution of H2O are subject to a charge transfer (CT) conversion into peroxy moieties and molecular hydrogen, O{2/2-}... H2. Because the O{2/2-}moiety is small (O--O- distance ? 1.5 Å) high pressure probably favors the CT conversion. Mass spectroscopic studies show that molecular H2 may be lost from the solid which retains excess oxygen in the form of O{2/2-}, leading to the release of atomic O. The dissociation of O{2/2-}moieties into a vacancy-bound O- state and an unbound O- state can be followed by measuring the internal redox reactions involving transition metal impurities, the transient paramagnetism of the O- and their effect on the d.c. conductivity. Evidence is presented that CO2 molecules dissolve dissociatively in the structurally dense oxide matrix, as if they were first to dissociate into CO+O and then to form separate solute moieties CO{2/2-}and O{2/2-}, both associated with cation vacancy sites. In the CO{2/2-}moiety (C-O- distance 1.2 1.3 Å, OCO angle ? 130°) the C atom probably sits off center. The transition of the C atom into interstitial sites is accompanied by dissociation of the CO{2/2-}moiety into CO- and O-. This transition can be followed by infrared spectroscopy, using OH- as local probes. Further support derives from magnetic susceptibility, thermal expansion, low frequency dielectric loss and low temperature deformation measurements. The recently observed emission of O and Mg atoms besides a variety of molecules such as CO, CO2, CH4, HCN and other hydrocarbons during impact fracture of MgO single crystals is presented and discussed in the light of the other experimental data.

Freund, Friedemann

1987-10-01

235

Hydrothermal Carbonization: a feasible solution to convert biomass to soil?  

NASA Astrophysics Data System (ADS)

The erosion of fertile soil is a severe problem arising right after peak oil (Myers 1996). That this issue is not only a problem of arid countries is shown by the fact that even the European Commission defined certain milestones to address the problem of soil erosion in Europe (European Commission 2011). The application of bio-char produced by torrefaction or pyrolysis for the remediation, revegetation and restoration of depleted soils started to gain momentum recently (Rillig 2010, Lehmann 2011, Beesley 2011). Hydrothermal carbonization (HTC) is a promising thermo-chemical process that can be applied to convert organic feedstock into fertile soil and water, two resources which are of high value in regions being vulnerable to erosion. The great advantage of HTC is that organic feedstock (e.g. organic waste) can be used without any special pretreatment (e.g. drying) and so far no restrictions have been found regarding the composition of the organic matter. By applying HTC the organic material is processed along a defined pathway in the Van Krevelen plot (Behrendt 2006). By stopping the process at an early stage a nutritious rich material can be obtained, which is known to be similar to terra preta. Considering that HTC-coal is rich in functional groups and can be derived from the process under "wet" conditions, it can be expected that it shall allow soil bacteria to settle more easily compared to the bio-char derived by torrefaction or pyrolysis. In addition, up to 10 tons process water per ton organic waste can be gained (Vorlop 2009). Thus, as organic waste, loss of fertile soil and water scarcity becomes a serious issue within the European Union, hydrothermal carbonization can provide a feasible solution to address these issues of our near future. The presentation reviews the different types of feedstock investigated for the HTC-Process so far and gives an overview on the current stage of development of this technology. References Beesley L., Moreno-Jiménez E., Gomez-Eyles J.L., Harris H., Robinson B., Sizmur T.: A review of biochars' potential role in the remediation, revegetation and restoration of contaminated soils. Environmental Pollution (159), p. 3269 - 3282, 2011. Behrendt F.: Direktverflüssigung von Biomasse - Reaktionsmechanismen und Produktverteilungen Institut für Energietechnik, Technische Universität Berlin Studie im Auftrag der Bundesanstalt für Landwirtschaft und Ernährung; Projektnummer 114-50-10-0337/05-B, 2006. European Commission: "Roadmap to a Resource Efficient Europe", COM(2011) 571. Lehmann J., Rillig M.C., Thies J., Masiello C.A., Hockaday W.C., Crowley D.: Biochar effects on soil biota - A review, Soil Biology & Biochemistry, p. 1-25, 2011. Myers Norman: "Environmental services of biodiversity", Proc. Natl. Acad. Sci. USA Vol 93, pp. 2764 - 2769, 1996. Rillig M.C., Wagner M., Salem M., Antunes P.M., George C., Ramke H.G., Titirici M.M., Antonietti M.: Material derived from hydrothermal carbonization: effects on plant growth and arbuscular mycorrhiza. Applied Soil Ecology (45), p. 238 - 242, 2010. Vorlop K.D., Schuchardt F., Prüße U.: Hydrothermale Carbonisierung Analyse und Ausblicke. FNR-Fachgespräch, Berlin, 2009.

Tesch, Walter; Tesch, Petra; Pfeifer, Christoph

2013-04-01

236

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

PubMed

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

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

2012-06-01

237

Acid-base characteristics of organic carbon in the HUMEX Lake Skjervatjern  

SciTech Connect

The Humic Lake Acidification Experiment (HUMEX) was launched in 1988 to study the role of humic substances in the acidification of surface waters and the impacts of acidic deposition on the chemical and biological properties of humic substances. This subproject was designed to determine the contribution of organic acids to the acidity of Lake Skjervatjern (the HUMEX Lake) and the impacts of the acidification on the characteristics of organic carbon. In order to get an empirical measure for organic acidity, dissolved organic carbon (DOC) was fractionated, isolated, and base-titrated from each half of Lake Skjervatjern. Hydrophobic acids were the dominant organic carbon fraction; the total organic acid content was generally greater than 80% of the DOC. The reliability of the fractionation procedure was tested with synthetic acids and the Nordic Fulvic acid. The DOC fractions did not show high variation over the 1.5-y acidification period. Hydrophilic acids had consistently greater exchange acidities compared to hydrophobic acids, averaging 12.9 [mu]eq/mg DOC vs. 10.9 [mu]eq/mg DOC, respectively. The dissociation of organic acids during acid-base titrations clearly increased with increasing pH. The high organic anion contribution to the ion balances indicates that humic matter is an important acidity source in Lake Skjervatjern. There are slight signs that the contribution of organic acids to overall lake acidity has decreased since acidification was initiated. 22 refs., 5 figs., 1 tab.

Kortelainen, P.; David, M.B.; Roila, T.; Maekinen, I. (National Board of Waters and the Environment, Helsinki (Finland))

1992-01-01

238

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

NASA Astrophysics Data System (ADS)

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.

Fukushima, Kunio; Watanabe, Toshiaki; Umemura, Matome

1986-08-01

239

Simultaneous voltammetric determination of ascorbic acid, dopamine and uric acid using polybromothymol blue film-modified glassy carbon electrode.  

PubMed

A sensitive and selective electrochemical method for simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA) using an electropolymerized bromothymol blue (BTB)-modified glassy carbon electrode (GCE) was developed. The electrochemically synthesized film was investigated using electrochemical impedance spectroscopy and voltammetric methods. The electrochemical behavior of the polymer-modified electrode depends on film thickness, i.e., the electropolymyerization time. The poly-BTB-modified GCE shows excellent electrocatalytic activity toward the oxidation of AA, DA, and UA in phosphate buffer solution (pH 5.0). The voltametric peak separations of AA/DA, DA/UA, and AA/UA on this modified electrode are 118 mV, 298 mV, and 455 mV, respectively. Therefore the voltammetric responses of these three compounds can be resolved well on the polymer-modified electrode, and simultaneous determination of these three compounds can be achieved. In addition, this modified electrode can be successfully applied to determine AA and DA in injection and UA in urine samples without interference. PMID:20522988

Xu, Xiongwei; Lin, Qihuang; Liu, Ailin; Chen, Wei; Weng, Xiuhua; Wang, Changlian; Lin, Xinhua

2010-06-01

240

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

SciTech Connect

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.

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

1999-08-31

241

Corrosion Testing of Carbon Steel in Oxalic Acid that Contains Dissolved Iron  

SciTech Connect

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 (OA) will be used to chemically clean the tanks after waste retrieval is completed. The waste tanks at SRS were constructed from carbon steel materials and thus are vulnerable to corrosion in acidic media. In addition to structural impacts, the impact of corrosion on the hydrogen generated during the process must be assessed. Electrochemical and coupon immersion tests were used to investigate the corrosion mechanism at anticipated process conditions. The testing showed that the corrosion rates were dependent upon the reduction of the iron species that had dissolved in solution. Initial corrosion rates were elevated due to the reduction of the ferric species to ferrous species. At later times, as the ferric species depleted, the corrosion rate decreased. On the other hand, the hydrogen evolution reaction became more dominant.

Wiersma, Bruce J.; Mickalonis, John I.; Subramanian, Karthik H.

2012-10-11

242

Immobilization of high catalytic acid protease on functionalized mesoporous activated carbon particles  

Microsoft Academic Search

The functionalized mesoporous activated carbon (FMAC) was used as support material for immobilization of acid protease (AP). Immobilization of acid protease on functionalized mesoporous activated carbon (AP–FMAC) performs as a suitable enzyme carrier. Under optimized condition pH (6.0) acid protease 150mgg?1 FMAC has been adsorbed. The optimum temperature for both free and immobilized AP activities was 50°C. After incubation at

A. Ganesh Kumar; S. Swarnalatha; P. Kamatchi; G. Sekaran

2009-01-01

243

Anaerobic Mineralization of Quaternary Carbon Atoms: Isolation of Denitrifying Bacteria on Pivalic Acid (2,2-Dimethylpropionic Acid)  

Microsoft Academic Search

The degradability of pivalic acid was established by the isolation of several facultative denitrifying strains belonging to Zoogloea resiniphila ,t oThauera and Herbaspirillum, and to Comamonadaceae, related to (Aquaspi- rillum) and Acidovorax, and of a nitrate-reducing bacterium affiliated with Moraxella osloensis. Pivalic acid was completely mineralized to carbon dioxide. The catabolic pathways may involve an oxidation to dimethyl- malonate or

Christina Probian; Annika Wulfing; Jens Harder

2003-01-01

244

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

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...

Nour, Mohamed

2014-05-06

245

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

PubMed

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

Allen, Daniel J; Brent, Geoff F

2010-04-01

246

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

NASA Astrophysics Data System (ADS)

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.

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

2010-06-01

247

Nonionic Organic Solute Sorption to two Organobentonites as a Function of Organic-Carbon Content  

NASA Astrophysics Data System (ADS)

Sorption of three nonionic organic solutes (benzene, trichloroethene, and 1,2-dichlorobenzene) to hexadecyltrimethylammonium-bentonite (HDTMA-bentonite) and benzyltrimethylammonium-bentonite (BTEA-bentonite) was measured as a function of organic-carbon content at quaternary ammonium cation loadings ranging from 30 to 130% of the clay's cation-exchange capacity. Sorption of all three solutes to HDTMA-bentonite was linear and sorptive capacity of the HDTMA-bentonite increased as the organic-carbon content of the clay increased. 1,2-Dichlorobenzene sorbed most strongly to HDTMA-bentonite, followed by benzene and TCE. The stronger sorption of benzene to HDTMA-bentonite compared to TCE was unexpected based on a partition mechanism of sorption and consideration of solute solubility. This result may be caused by interactions between the pi electrons of benzene and the negatively charged surface of the clay. Log Koc values for all three solutes increased with organic-carbon content. This suggests that the increased organic-carbon content alone may not explain the observed increase in sorption capacity. Sorption of the three solutes to BTEA-bentonite was nonlinear and solute sorption decreased with increasing organic-carbon content. Surface area measurements indicate that the surface area of both organobentonites generally decreased with increasing organic-carbon content. Since nonionic organic solute sorption to BTEA-bentonite occurs by adsorption, the reduced sorption is likely caused by the reduction in surface area corresponding to increased organic cation loading.

Bartelt-Hunt, S. L.; Burns, S. E.; Smith, J. A.

2002-05-01

248

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

249

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

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Chloric acid solution or chlorine dioxide hydrate, frozen. 173.229 Section 173.229...Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the § 172.101 table...

2013-10-01

250

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

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Chloric acid solution or chlorine dioxide hydrate, frozen. 173.229 Section 173.229...Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the § 172.101 table...

2010-10-01

251

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

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Chloric acid solution or chlorine dioxide hydrate, frozen. 173.229 Section 173.229...Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the § 172.101 table...

2011-10-01

252

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

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Chloric acid solution or chlorine dioxide hydrate, frozen. 173.229 Section 173.229...Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the § 172.101 table...

2014-10-01

253

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

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Chloric acid solution or chlorine dioxide hydrate, frozen. 173.229 Section 173.229...Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the § 172.101 table...

2012-10-01

254

Thermodynamic properties of carbon in b.c.c. and f.c.c. iron-silicon-carbon solid solutions.  

NASA Technical Reports Server (NTRS)

The equilibrium between hydrogen-methane gas mixtures and Fe-Si-C solid solutions has been investigated both as a function of temperature and carburizing gas composition. The thermodynamic properties of the carbon atoms in both b.c.c. and f.c.c. solid solution have been derived from the equilibrium measurements. The results found have been compared with those of earlier investigations and with the predictions of recent theoretical models on ternary solid solutions containing both substitutional and interstitial solute atoms.

Chraska, P.; Mclellan, R. B.

1971-01-01

255

Metallocene/carbon hybrids prepared by a solution process for supercapacitor applications  

E-print Network

Efficient and scalable solution-based processes are not generally available to integrate well-studied pseudocapacitive materials (i.e., metal oxides and conducting polymers) with other components such as porous carbon, ...

Mao, Xianwen

256

Temporal variations of organic carbon inputs into the upper Yukon River: Evidence from fatty acids and their  

E-print Network

Temporal variations of organic carbon inputs into the upper Yukon River: Evidence from fatty acids, we tracked the changes in fatty acid con- centrations and their stable carbon isotopic compositions the beginning of snowmelt, while fatty acid contents (normalized to organic carbon in each pool) varied

Guo, Laodong

257

Titanium Implant Osseointegration Problems with Alternate Solutions Using Epoxy/Carbon-Fiber-Reinforced Composite  

PubMed Central

The aim of the article is to present recent developments in material research with bisphenyl-polymer/carbon-fiber-reinforced composite that have produced highly influential results toward improving upon current titanium bone implant clinical osseointegration success. Titanium is now the standard intra-oral tooth root/bone implant material with biocompatible interface relationships that confer potential osseointegration. Titanium produces a TiO2 oxide surface layer reactively that can provide chemical bonding through various electron interactions as a possible explanation for biocompatibility. Nevertheless, titanium alloy implants produce corrosion particles and fail by mechanisms generally related to surface interaction on bone to promote an inflammation with fibrous aseptic loosening or infection that can require implant removal. Further, lowered oxygen concentrations from poor vasculature at a foreign metal surface interface promote a build-up of host-cell-related electrons as free radicals and proton acid that can encourage infection and inflammation to greatly influence implant failure. To provide improved osseointegration many different coating processes and alternate polymer matrix composite (PMC) solutions have been considered that supply new designing potential to possibly overcome problems with titanium bone implants. Now for important consideration, PMCs have decisive biofunctional fabrication possibilities while maintaining mechanical properties from addition of high-strengthening varied fiber-reinforcement and complex fillers/additives to include hydroxyapatite or antimicrobial incorporation through thermoset polymers that cure at low temperatures. Topics/issues reviewed in this manuscript include titanium corrosion, implant infection, coatings and the new epoxy/carbon-fiber implant results discussing osseointegration with biocompatibility related to nonpolar molecular attractions with secondary bonding, carbon fiber in vivo properties, electrical semiconductors, stress transfer, additives with low thermal PMC processing and new coating possibilities. PMID:25635227

Petersen, Richard C.

2014-01-01

258

Genetic and environmental factors involved in increased resistance of brook trout to sulfuric acid solutions and mine acid polluted waters  

Microsoft Academic Search

Several strains of hatchery-reared brook trout, Salvelinus fontinalis (Mitchill), were exposed to low pH in the laboratory (sulfuric acid solutions) and in the field (mine acid polluted waters). Wild brook trout were also used in some field tests. Tests were both acute and chronic (up to 2 mo). Pronounced strain differences in survival ability were detected among embryonic, juvenile, and

FREDERICK A. SWARTS; WILLIAM A. DUNSON; JAMES E. WRIGHT

1978-01-01

259

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

PubMed Central

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

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

2012-01-01

260

Reductive dehalogenation of hexachloroethane, carbon tetrachloride, and bromoform by anthrahydroquinone disulfonate and humic acid  

USGS Publications Warehouse

The reductive dehalogenation of hexachloroethane (C2Cl6), carbon tetrachloride (CCl4), and bromoform (CHBr3) was examined at 50??C in aqueous solutions containing either (1) 500 ??M of 2,6-anthrahydroquinone disulfonate (AHQDS), (2) 250 ??M Fe2+, or (3) 250 ??M HS-. The pH ranged from 4.5 to 11.5 for AHQDS solutions and was 7.2 in the Fe2+ solutions and 7.8 in the HS- solutions. The observed disappearance of C2Cl6 in the presence of AHQDS was pseudo-first-order and fit k??ccl4 = k0[A(OH)2] + k1[A(OH)O-] + k2[A(O)22-] where A(OH)2, A(OH)O-, and A(O)22- represent the concentrations of the three forms of the AHQDS in solution. The values of k0, k1, and k2 were ???0,0.031, and 0.24 M-1 s-1, respectively. The addition of 25 mg of C/L of humic acid or organic matter extracted from Borden aquifer solids to aqueous solutions containing 250 ??M HS- or Fe2+ increased the reduction rate by factors of up to 10. The logarithms of the rate constants for the disappearance of C2Cl6 and CCl4 in seven different experimental systems were significantly correlated; log k???ccl4 = 0-64 log k??? c2cl6 - 0.83 with r2 = 0.80. The observed trend in reaction rates of C2Cl6 > CCl4 > CHBr3 is consistent with a decreasing trend in one-electron reduction potentials. ?? 1994 American Chemical Society.

Curtis, G.P.; Reinhard, M.

1994-01-01

261

Vapor pressure data for potassium carbonate-potassium bicarbonate solutions for application to multiuse power cycles  

Microsoft Academic Search

A novel method of generating electric power based on a gas absorption cycle, rather than a normal Rankine steam power cycle, has been developed. This cycle uses carbon dioxide as the working fluid in the turbine and potassium carbonate solutions as the carrier fluid for the absorption part of the cycle. Thermodynamic calculations for typical operating parameters show a cycle

E. R. Hosler; S. Ghandeharioun

1983-01-01

262

Preparation of activated carbons from Iris tectorum employing ferric nitrate as dopant for removal of tetracycline from aqueous solutions.  

PubMed

Ferric nitrate was employed to modify activated carbon prepared from Iris tectorum during H?PO? activation and ability of prepared activated carbon for removal of tetracycline (TC) was investigated. The properties of the activated carbon samples with or without ferric nitrate, ITAC-Fe and ITAC, were measured by scanning electron microscopy (SEM), N? adsorption/desorption isotherms, Fourier transform infrared spectroscopy (FTIR) and Boehm's titration. The results showed that mixing with iron increased the BET surface area, total pore volume and the adsorption capacity as compared to the original carbon. FTIR and Boehm's titration suggested that ITAC-Fe was characteristic of more acidic functional groups than ITAC. Adsorption of TC on both samples exhibited a strong pH-dependent behavior and adsorption capacity reduced rapidly with the increasing solution pH. The adsorption kinetics agreed well with the pseudo-second-order model and the adsorption isotherms data were well described by Langmuir model with the maximum adsorption capacity of 625.022 mg/g for ITAC and 769.231 mg/g for ITAC-Fe. The present work suggested that ITAC-Fe could be used to remove tetracycline effectively from aqueous solutions. PMID:24021870

Li, Gang; Zhang, Dongsheng; Wang, Man; Huang, Ji; Huang, Lihui

2013-12-01

263

NMR Analyses of Order and Dynamics in Poly(p-Benzamide)/ Sulfuric Acid Solutions  

E-print Network

NMR Analyses of Order and Dynamics in Poly(p-Benzamide)/ Sulfuric Acid Solutions Min Zhou, Veronica sulfuric acid. Quantitative determinations of order in the liquid crystal phases arising in these systems liquid crystalline dopes when dissolved in strong mineral acids at ap- propriate concentrations.10

Frydman, Lucio

264

Reactivity of BrONO2 and HOBr on sulfuric acid solutions at low temperatures  

Microsoft Academic Search

Uptake of BrONO2 onto bulk sulfuric acid solutions and submicron sulfuric acid aerosol particles was studied in laminar flow cylindrical reactors where a chemical ionization mass spectrometer was used to detect products and reactants. Results from measurements at low temperatures and for sulfuric acid content between 70 and 85 wt.% are presented. These measurements suggest that the reaction probability for

D. R. Hanson

2003-01-01

265

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

E-print Network

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

Das, Rhiju

266

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

E-print Network

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

Dietz, Hendrik

267

Direct sensing of fluoride in aqueous solutions using a boronic acid based sensor.  

PubMed

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

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

268

H2SO4 vapor pressure of sulfuric acid and ammonium sulfate solutions  

Microsoft Academic Search

Few measurements of H2SO4 vapor pressure have been made for sulfuric acid in the temperature and concentration ranges of atmospheric interest because of the very low pressures involved (below 10-4Pa, or 10-6torr); no such measurements appear to have been made for sulfuric acid solutions neutralized with ammonia. This work presents measurements of H2SO4 vapor pressure for aqueous sulfuric acid solutions

James J. Marti; Anne Jefferson; Xiao Ping Cai; Chad Richert; Peter H. McMurry; Fred Eisele

1997-01-01

269

CAPD with an amino acid dialysis solution: A long-term, cross-over study  

Microsoft Academic Search

CAPD with an amino acid dialysis solution: A long-term, cross-over study. This prospective cross-over study was undertaken to evaluate the safety and efficacy of a 1% amino acid dialysis solution on the nutritional and metabolic changes, plasma amino acid profiles and peritoneal membrane function of patients on CAPD. Six CAPD patients had one exchange a day with two liters of

Michele Bruno; Cristiana Bagnis; Martino Marangella; Lidia Rovera; Alberto Cantaluppi; Franco Linari

1989-01-01

270

Ultrasonic degradation of oxalic acid in aqueous solutions.  

PubMed

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

Dükkanci, M; Gündüz, G

2006-09-01

271

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

272

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

NASA Astrophysics Data System (ADS)

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

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

2007-07-01

273

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

NASA Technical Reports Server (NTRS)

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.

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

2009-01-01

274

Preparation and characterization of biomass carbon-based solid acid catalyst for the esterification of oleic acid with methanol.  

PubMed

A solid acid catalyst, prepared by sulfonating carbonized corn straw, was proved to be an efficient and environmental benign catalyst for the esterification of oleic acid and methanol. Various synthetic parameters, such as carbonization temperature and time were systematically examined. It was found that the catalyst exhibited the highest acid density of 2.64 mmol/g by NaOH titration. A quantitative yield (98%) of ester was achieved, using the most active sulfonated catalyst at 333 K with a 7 wt.% catalyst/oleic acid ratio for 4h, at a 7:1 M ratio of methanol/oleic acid, while the commercial available Amberlyst-15 only gave 85% yield under the same reaction condition. PMID:23453798

Liu, Tiantian; Li, Zhilong; Li, Wei; Shi, Congjiao; Wang, Yun

2013-04-01

275

Preparation of a carbon-based solid acid catalyst by sulfonating activated carbon in a chemical reduction process.  

PubMed

Sulfonated (SO(3)H-bearing) activated carbon (AC-SO(3)H) was synthesized by an aryl diazonium salt reduction process. The obtained material had a SO(3)H density of 0.64 mmol·g-1 and a specific surface area of 602 m2·g-1. The catalytic properties of AC-SO(3)H were compared with that of two commercial solid acid catalysts, Nafion NR50 and Amberlyst-15. In a 10-h esterification reaction of acetic acid with ethanol, the acid conversion with AC-SO(3)H (78%) was lower than that of Amberlyst-15 (86%), which could be attributed to the fact that the SO(3)H density of the sulfonated carbon was lower than that of Amberlyst-15 (4.60 mmol·g-1). However, AC-SO(3)H exhibited comparable and even much higher catalytic activities than the commercial catalysts in the esterification of aliphatic acids with longer carbon chains such as hexanoic acid and decanoic acid, which may be due to the large specific surface area and mesoporous structures of the activated carbon. The disadvantage of AC-SO(3)H is the leaching of SO(3)H group during the reactions. PMID:20956883

Liu, Xiao-Yan; Huang, Miao; Ma, Hai-Long; Zhang, Zeng-Qiang; Gao, Jin-Ming; Zhu, Yu-Lei; Han, Xiao-Jin; Guo, Xiang-Yun

2010-01-01

276

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

PubMed Central

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 0.1–10 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

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

2010-01-01

277

Inhibitive effects of palm kernel oil on carbon steel corrosion by alkaline solution  

NASA Astrophysics Data System (ADS)

The behavior of carbon steel SAE 1045 in 1 M NaOH solution containing different concentrations of palm kernel oil (PKO) has been studied by weight loss and polarization measurement. Results showed that the corrosion of carbon steel in NaOH solution was considerably reduced in presence of such inhibitors. The inhibition efficiency increases when concentration of inhibitor increase. Maximum inhibition efficiency (? 96.67%) is obtained at PKO concentration 8 v/v %. This result revealed that palm kernel oil can act as a corrosion inhibitor in an alkaline medium. Corrosion rates of carbon steel decrease as the concentration of inhibitor is increased.

Zulkafli, M. Y.; Othman, N. K.; Lazim, A. M.; Jalar, A.

2013-11-01

278

Amino acid synthesis from an amorphous substance composed of carbon, nitrogen, and oxygen  

NASA Astrophysics Data System (ADS)

Hydrogen cyanide, formaldehyde, and ammonia are considered important intermediates in amino acid synthesis by electric discharge. In this study, however, amino acid precursors were synthesized from a CO-N2 mixture free of hydrogen atoms. An amorphous film composed of carbon, nitrogen, and oxygen was given from a highly activated plasma. When exposed to atmospheric moisture, this film incorporated hydrogen atoms to yield amino acid. This is a mechanism for amino acid synthesis without involving hydrogen cyanide, formaldehyde, and ammonia.

Miyakawa, Shin; Tamura, Hideki; Sawaoka, Akira B.; Kobayashi, Kensei

1998-02-01

279

Measurements of the solubilities of derivatized amino acids in supercritical carbon dioxide  

Microsoft Academic Search

The solubilities of phenylalanine and tyrosine in supercritical carbon dioxide (SCCO2) were measured after derivatization as the N-acetyl amino acid ethyl ester, N-carbobenzoxy amino acid and N-acetyl amino acid. Using an SCCO2 flow system, a measuring method of the saturated solubilities of the derivatized amino acids was established in which the contact height of the extraction cell, i.e. a packed

Joerg Freitag; You Yokoyama; Hidetoshi Kuramochi; Katsuya Kawamoto; Kunio Nagahama; Satoru Kato

2007-01-01

280

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

281

Delayed fracture of Ni-Ti superelastic alloys in acidic and neutral fluoride solutions.  

PubMed

Hydrogen-related degradation of the mechanical properties of a Ni-Ti superelastic alloy has been examined by means of delayed fracture tests in acidic and neutral fluoride solutions and hydrogen thermal desorption analysis. Delayed fracture took place in both solutions; the time to fracture was shorter in the acidic solutions than in the neutral solutions with the same fluoride concentration. The time to fracture was reduced in both solutions when applied stress exceeded the critical stress for martensite transformation. In the acidic solutions, Ni-Ti superelastic alloy underwent general corrosion and absorbed substantial amounts of hydrogen. Fractographic features suggested that the delayed fracture in the acidic solutions was attributable to hydrogen embrittlement, whereas in the neutral solutions, a different fracture mode appeared associated with localized corrosion only in the vicinity of the fracture initiation area. In the neutral solutions, the amount of absorbed hydrogen was much less than that in the acidic solutions, and the delayed fracture was likely to be induced by active path corrosion accompanying hydrogen absorption. The results of the present study imply that the hydrogen-related degradation of performance of Ni-Ti superelastic alloys occurs in the presence of fluoride. PMID:14999757

Yokoyama, Ken'ichi; Kaneko, Kazuyuki; Moriyama, Keiji; Asaoka, Kenzo; Sakai, Jun'ichi; Nagumo, Michihiko

2004-04-01

282

Corrosion Behavior of Mild Carbon Steel in Ethanolic Solutions  

NASA Astrophysics Data System (ADS)

Electrochemical evaluation of ASTM A36 steel was performed in ethanolic solutions containing small concentrations of water ranging from 0 to 10 vol.%. Electrochemical techniques such as open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization were utilized to analyze corrosion parameters. A fixed concentration of chloride, as per the ASTM specification for fuel grade ethanol, was added to increase the conductivity of the solutions. The effects of water and oxygen on the corrosion behavior of steel in these solutions have been discussed. Pitting corrosion of the steel specimens in these solutions was evaluated using scanning electron microscopy (SEM) and pitting analysis. This investigation was performed to establish a baseline for the microbiologically influenced corrosion (MIC) of steel in ethanolic solutions.

Bhola, Shaily M.; Bhola, Rahul; Jain, Luke; Mishra, Brajendra; Olson, David L.

2011-04-01

283

Pyrite oxidation in carbonate-buffered solution: 2. Rate control by oxide coatings  

Microsoft Academic Search

The kinetic behavior of pyrite oxidation in the laboratory was studied over a period of about 10,000 hours in reactors through which a carbonate-buffered solution and air (20% Oâ) flowed continuously. Three grain size fractions were monitored. The concentration of sulfate and the mass of the effluent solution were measured periodically to calculate oxidation rates. The results indicate that the

R. V. Nicholson; R. W. Gillham; E. J. Reardon

1990-01-01

284

Special features of humus acids extraction from soils by sodium pyrophosphate solutions of different alkalinity  

NASA Astrophysics Data System (ADS)

The regularities of extracting humus acids from soils of different types with solutions of sodium pyrophosphate at the equilibrium pH values of 5-13 were studied. The increase in the humus acids yield from the soils with the increasing alkalinity of the solution applied is directly related to the capability of acid functional groups (carboxyl and phenol hydroxyl) for dissociation at definite pH values. The regularities of the changes in the chemical nature and degree of humification of humus acids extracted from the soils related to the pH of the solution were revealed. A sodium pyrophosphate solution (pH 10) was suggested for extracting the humus acids most active in the given soil.

Bakina, L. G.; Orlova, N. E.

2012-04-01

285

Particle-induced x-ray emission: Instrumentation, calibration, and application to contact lens solutions and fulvic acid solutions  

SciTech Connect

An expression was derived describing the profile of the proton beam at the PIXE target position. The expression was used to predict the profile for several experimental configurations. The profile was experimentally measured. The PIXE system was calibrated using solutions and commercial foils. Experimental data was adjusted for all absorbers and interferences, and a quadratic relationship was determined relating calibration factor and atomic number for each series of X-ray transitions. Calibration factors were determined for all elements above aluminum, for both a pinhole filter and a 14-mil mylar filter. A group of contact lens solutions was analyzed using PIXE, ICP, and ISE. A digestion method was developed for removal. of chloride ion. Cluster analysis was used to classify the data. A commercial humic acid was separated into three fractions. The fulvic acid was characterized, and separations of metal-fulvic acid complexes from metal ions in solution were attempted using ultrafiltration.

Jenson, D.D.

1989-01-01

286

Chemical evaluation of soil-solution in acid forest soils  

USGS Publications Warehouse

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.

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

1996-01-01

287

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

DOEpatents

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.

Scheitlin, Frank M. (Oak Ridge, TN)

1984-01-01

288

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

PubMed

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

Ma, Jun; Schmidhammer, Uli; Mostafavi, Mehran

2014-09-12

289

Lipase catalyzed resolution of chiral acids or alcohols using mixed carboxylic-carbonic anhydrides  

Microsoft Academic Search

Mixed carboxylic-carbonic anhydrides are efficient irreversible acyl transfer reagents for lipase catalyzed esterification in organic media, and can be used for the resolution of chiral carboxylic acids or alcohols.

Eryka Guibé-Jampel; Zbigniew Chalecki; Mohamed Bassir; Mirjana Gelo-Pujic

1996-01-01

290

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

SciTech Connect

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

Suzuki, Tatsuya; Tachibana, Yu [Department of Nuclear Safety System Engineering, Nagaoka University of Technology, Nagaoka, Niigata 940-2188 (Japan); Koyama, Shi-ichi [O-oarai Research and Development Center, Japan Atomic Energy Agency, Ooarai, Ibaraki 311-1393 (Japan)

2013-07-01

291

Acid Resistance Contributes to the High-Pressure Carbon Dioxide Resistance of Escherichia coli K-12.  

PubMed

Effect of deletion of acid resistant genes of E. coli on the high-pressure carbon dioxide (HPC) resistance was investigated. Genes coding amino acid decarboxylases, such as lysine, arginine, and glutamate decarboxylase, were found to contribute to HPC resistance. Protonophore-treated cells showed hypersensitivity to HPC, confirming that HPC induced cytoplasm acidification and exerted severe damage on cells by intrusion of gaseous carbon dioxide into cytoplasm. PMID:25119308

Furukawa, Soichi; Shimazaki, Junji; Kawaharada, Kazumichi; Matsuda, Tsukasa; Aoyagi, Hiroki; Wakabayashi, Hidekazu; Ogihara, Hirokazu; Yamasaki, Makari; Morinaga, Yasushi

2015-01-01

292

Monomeric metal aqua complexes in the interlayer space of montmorillonites as strong Lewis acid catalysts for heterogeneous carbon-carbon bond-forming reactions.  

PubMed

Montmorillonite-enwrapped copper and scandium catalysts (Cu(2+)- and Sc(3+)-monts) were easily prepared by treating Na(+)-mont with the aqueous solution of the copper nitrate and scandium triflate, respectively. The resulting Cu(2+)- and Sc(3+)-monts showed outstanding catalytic activities for a variety of carbon-carbon bond-forming reactions, such as the Michael reaction, the Sakurai-Hosomi allylation, and the Diels-Alder reaction, under solvent-free or aqueous conditions. The remarkable activity of the mont catalysts is attributable to the negatively charged silicate layers that are capable of stabilizing metal cations. Furthermore, these catalysts were reusable without any appreciable loss in activity and selectivity. The Cu(2+)-mont-catalyzed Michael reaction proceeds via a ternary complex in which both the 1,3-dicarbonyl compound and the enone are coordinated to a Lewis acid Cu(2+) center. PMID:15551316

Kawabata, Tomonori; Kato, Masaki; Mizugaki, Tomoo; Ebitani, Kohki; Kaneda, Kiyotomi

2004-12-17

293

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)

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.

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

2014-06-01

294

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

PubMed

A novel carbon-based solid acid catalyst was prepared by the sulfonation of incompletely carbonized cassava stillage residue (CSR) with concentrated sulfuric acid, and employed to catalyze the esterification of methanol and free fatty acids (FFAs) in waste cooking oil (WCO). The effects of the carbonization and the sulfonation temperatures on the pore structure, acid density and catalytic activity of the CSR-derived catalysts were systematically investigated. Low temperature carbonization and high temperature sulfonation can cause the collapse of the carbon framework, while high temperature carbonization is not conducive to the attachment of SO3H groups on the surface. The catalyst showed high catalytic activity for esterification, and the acid value for WCO is reduced to below 2mg KOH/g after reaction. The activity of catalyst can be well maintained after five cycles. CSR can be considered a promising raw material for the production of a new eco-friendly solid acid catalyst. PMID:24661813

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

2014-04-01

295

Separation of ions in acidic solution by capillary electrophoresis  

SciTech Connect

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.

Thornton, M.

1997-10-08

296

Relay catalysis by a metal-complex/Brønsted acid binary system in a tandem isomerization/carbon-carbon bond forming sequence.  

PubMed

A one-pot tandem isomerization/carbon-carbon bond forming sequence catalyzed by a ruthenium complex/Brønsted acid binary system is demonstrated. The method enables the use of readily available allylamides to deliver reactive imines under relay catalysis using a binary catalytic system. Subsequent Brønsted acid catalyzed carbon-carbon bond forming reactions of the generated imines with nucleophilic components afforded Friedel-Crafts and Mannich products in good yields. PMID:18850704

Sorimachi, Keiichi; Terada, Masahiro

2008-11-01

297

The Effect of Heterogeneity on Matrix Acidizing of Carbonate Rocks  

E-print Network

heterogeneity affects performance. To do this, a coreflood and acidizing apparatus was used to acidize heterogeneous limestone core samples. Rock characterizations and volumetric measurements were considered with the results from these experiments, which made...

Keys, Ryan S.

2010-07-14

298

Precipitation polymerization of hydrophobically modified polyelectrolyte poly(AA-co-ODA) in supercritical carbon dioxide and solution rheology properties  

NASA Astrophysics Data System (ADS)

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.

Zhang, Huaiping; Li, Wei; Cao, Qing; Chen, Mingcai

2014-05-01

299

The effect of fatal carbon monoxide poisoning on the equilibria between cell membranes and the electrolyte solution.  

PubMed

The effect of fatal carbon monoxide poisoning on equilibria between cell membranes and surrounding ions was described using a theoretical four-equilibria model. The model was developed to obtain parameters characterizing the interactions between solution ions and erythrocyte or thrombocyte membrane surface. The parameters are the total surface concentrations of both acidic and basic groups C A, C B and their association constants with solution ions K AH, K BOH. These parameters were used to calculate the theoretical values of surface charge density. The model was validated by comparison of these values to experimental data, which were determined from the electrophoretic mobility measurements of the blood cells. The experimental and theoretical surface charge density values agree at pH 2-8, and at higher pH, the deviation was observed. PMID:25416423

Petelska, Aneta D; Koty?ska, Joanna; Figaszewski, Zbigniew A

2015-02-01

300

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

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.

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

1992-01-01

301

Determination of carbon-centered radicals in aqueous solution by liquid chromatography with fluorescence detection  

SciTech Connect

A simple method to detect subnanomolar to micromolar levels of photochemically generated carbon-centered radicals in aqueous solutions has been developed and optimized. This method is based on the efficient trapping of radicals by a water-soluble amino nitroxide, followed by derivatization of the trapped products with fluorescamine to produce highly fluorescent adducts. These adducts can be separated by reversed-phase high-performance liquid chromatography and detected fluorometrically. The fluorescent derivatives are stable over a period of days. The detection limit, primarily determined by reagent interferences, ranged from 0.3 to 1 nM per analyte for a 500-{mu}L injection at a signal-to-noise ratio of two. The precision of the method for the determination of adduct concentrations in the 1-10 nM range varied from 2.4 to 8.4% relative standard deviation (n = 6). A direct comparison with electron paramagnetic resonance spectroscopy/spin trapping illustrates the advantages of our technique. One important feature of the method is that it permits the simultaneous detection of an array of radicals, as demonstrated through the study of the photochemical production of radicals in a variety of natural water samples and in Suwanee River fulvic acid.

Kieber, D.J.; Blough, N.V. (Woods Hole Oceanographic Institution, MA (USA))

1990-11-01

302

Competitive sorption used to probe strong hydrogen bonding sites for weak organic acids on carbon nanotubes.  

PubMed

We recently proposed that weak acids (AH) adsorb to partially oxidized carbonaceous materials in part by forming strong hydrogen bonds with acidic surface groups, depicted by (A···H···O-surf)(-), known as negative charge-assisted hydrogen bonds, (-)CAHBs. Here we use competition experiments to show that sorption of AH on carbon nanotubes (CNTs) can be described conceptually by a dual specific/nonspecific domain model, where one domain involves (-)CAHB sites that can become saturated. The trends observed in single-solute adsorption, including the stoichiometric release of hydroxide upon sorption of carboxyate or phenolate anions, were consistent with trends in the previous studies and pointed to the formation of (-)CAHB. 3,4-Dinitrophenolate formed (-)CAHBs more efficiently than did 2,6-dichloro-4-nitrophenolate because of alleviation of steric hindrance to approach by the ortho chlorines. Competition against a (-)CAHB-capable target compound was greater when the competitor was also (-)CAHB-capable than when it was not (e.g., benzoate as target vs 3,4-dinitrophenolate or nitrobenzene as competitor; mono-n-butyl phthalate as target vs methyl benzoate or p-tolyl acetate as competitor). Experiments also revealed competition between the nitroaromatic species for ?-? electron donor-acceptor sites. The findings will contribute to a better understanding of the adsorption mechanism of ionizable compounds on carbonaceous materials. PMID:25564729

Li, Xiaoyun; Gámiz, Beatriz; Wang, Yiquan; Pignatello, Joseph J; Xing, Baoshan

2015-02-01

303

Experimental High Velocity Acid Jetting in Limestone Carbonates  

E-print Network

the borehole wall and the formation of wormholes. The purpose of this study is to investigate how the high velocity acid affects the acidizing treatments. The experiments are conducted on 4” diameter by 16” length Indiana limestone cores with acid injected...

Holland, Christopher

2014-04-30

304

Integrated 3D Acid Fracturing Model for Carbonate Reservoir Stimulation  

E-print Network

. 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...

Wu, Xi

2014-06-23

305

Alkaline solution absorption of carbon dioxide method and apparatus  

DOEpatents

Disclosed is a method for measuring the concentration of hydroxides (or pH) in alkaline solutions, using the tendency of hydroxides to adsorb CO{sub 2}. The method comprises passing CO{sub 2} over the surface of an alkaline solution in a remote tank before and after measurements of the CO{sub 2} concentration. Comparison of the measurements yields the adsorption fraction from which the hydroxide concentration can be calculated using a correlation of hydroxide or pH to adsorption fraction. A schematic is given of a process system according to a preferred embodiment of the invention. 2 figs.

Hobbs, D.T.

1991-01-01

306

Study of the acid–base equilibria and conformational changes of double stranded polyadenylic–polyuridylic acid in aqueous solution  

Microsoft Academic Search

UV-absorption and circular dichroism (CD) spectroscopy have been applied to the study of the acid–base properties of the heteropolynucleotide ribopolyadenylic–polyuridylic acid (poly(A)–poly(U)) and to the study of the possible interaction of this polynucleotide with 2,2?-bipyridyl (bipy) in aqueous solutions as a function of pH. Using soft modelling chemometric procedures based on factor analysis and multivariate curve resolution, the individual absorption

A Kudrev; R Gargallo; A Izquierdo-Ridorsa; R Tauler; E Casassas

1998-01-01

307

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

PubMed

Nowadays nanomaterials have been widely used to remove heavy metals from water/wastewater due to their large surface area and high reactivity. Humic acid (HA) and fulvic acid (FA) exist ubiquitously in aquatic environments and have a variety of functional groups which allow them to complex with metal ions and interact with nanomaterials. These interactions can not only alter the environmental behavior of nanomaterials, but also influence the removal and transportation of heavy metals by nanomaterials. Thus, the interactions and the underlying mechanisms involved warrant specific investigations. This review outlined the effects of HA/FA on the removal of heavy metals from aqueous solutions by various nanomaterials, mainly including carbon-based nanomaterials, iron-based nanomaterials and photocatalytic nanomaterials. Moreover, mechanisms involved in the interactions were discussed and potential environmental implications of HA/FA to nanomaterials and heavy metals were evaluated. PMID:24095965

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

2014-01-15

308

Effect of extraction solutions on carbonation of cementitious materials in aqueous solutions  

Microsoft Academic Search

Carbonation efficiency was evaluated for three cementitious materials having different CaO-bearing minerals (lime, Portland cement and waste concrete) using various extraction reagents (HCl, CH3COOH, NH4Cl and deionized water). The cementitious materials were subjected to Ca extraction and carbonation tests under ambient pressure and temperature conditions. The Ca extraction efficiency generally decreased in the order lime, Portland cement and waste concrete,

Hwanju Jo; Ho Young Jo; Young-Nam Jang

2011-01-01

309

Effect of extraction solutions on carbonation of cementitious materials in aqueous solutions  

Microsoft Academic Search

Carbonation efficiency was evaluated for three cementitious materials having different CaO-bearing minerals (lime, Portland cement and waste concrete) using various extraction reagents (HCl, CH3COOH, NH4Cl and deionized water). The cementitious materials were subjected to Ca extraction and carbonation tests under ambient pressure and temperature conditions. The Ca extraction efficiency generally decreased in the order lime, Portland cement and waste concrete,

Hwanju Jo; Ho Young Jo; Young-Nam Jang

2012-01-01

310

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

Microsoft Academic Search

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

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

311

Characterization of Solution-Processed Double-Walled Carbon Nanotube/  

E-print Network

on storage modulus, Tc, Tm and Tg of PVDF is studied. Electromechani- cal strain is observed at low actuation polymers by lowering the actuation voltage and increasing strain and stress response. In this work, piezo- electric PVDF and DWNTs are solution- cast into films. SEM of fracture surfaces confirms good dispersion

Ounaies, Zoubeida

312

Oxidation of Fe (II) in sulfuric acid solutions with dissolved molecular oxygen  

Microsoft Academic Search

The oxidation of Fe(II) with dissolved molecular oxygen was studied in sulfuric acid solutions containing 0.2 mol ? dm?3 FeSO4 at temperatures ranging from 343 to 363 K. In solutions of sulfuric acid above 0.4 mol ? dm?3, the oxidation of Fe (II) was found to proceed through two parallel paths. In one path the reaction rate was proportional\\u000a to

Masao Iwai; Hiroshi Majima; Yasuhiro Awakura

1982-01-01

313

Reactive species produced on irradiation at 365 nm of aqueous solutions of humic acids  

Microsoft Academic Search

In order to characterize the reactive species produced on irradiation at 365 nm of humic acid (HA) solutions, the photoinduced transformation of aromatic compounds was studied as a function of several parameters (concentrations of substrates, HA and oxygen, pH of the solution) and in the presence of additives such as isopropanol, ethylenediaminetetraacetic acid (EDTA), H2O2 and Fe2+. No consumption of

J.-P. Aguer; C. Richard

1996-01-01

314

LITERATURE VALUES FOR SELECTED CHEMICAL PHYSICAL PROPERTIES OF AQUEOUS BORIC ACID SOLUTIONS  

Microsoft Academic Search

Data are given for properties of aqueous solutions of boric acid: ; solubility for orthoboric acid (HâBOâ), specific gravity, pH, ionic-; dissociation constants, colligative properties (vapor-pressure lowering, boiling-; point elevation, freezing-point depression), solute volatility, thermal ; conductivity, electric conductivity, corrosion effects, and mistion and dilution). ; An attempt was made to secure complete literature coverage through mid-1957. ; (P.C.H.);

D. E. Byrnes; W. E. Foster

1961-01-01

315

Oxygen-18 incorporation into malic acid during nocturnal carbon dioxide fixation in crassulacean acid metabolism plants: a new approach to estimating in vivo carbonic anhydrase activity  

SciTech Connect

Crassulacean acid metabolism (CAM) plants fix carbon dioxide at night by the carboxylation of phosphoenolpyruvate. If CO2 fixation is conducted with TC YO2, then in the absence of carbonic anhydrase, the malate formed by dark CO2 fixation should also contain high levels of carbon-13 and oxygen-18. Conversely, if carbonic anhydrase is present and highly active, oxygen exchange between CO2 and cellular H2O will occur more rapidly than carboxylation, and the ( TC) malate formed will contain little or no oxygen-18 above the natural abundance level. The presence of oxygen-18 in these molecules can be detected either by nuclear magnetic resonance or by mass spectrometry. Studies of phosphoenolpyruvate carboxylase in the presence and absence of carbonic anhydrase in vitro confirm the validity of the method. When CAM plants are studied by this method, we find that most species show incorporation of a significant amount of oxygen-18. Comparison of these results with results of isotope fractionation and gas exchange studies permits calculation of the in vivo activity of carbonic anhydrase toward HCO3 compared with that of phosphoenolpyruvate carboxylase. The ratio (carbonic anhydrase activity/phosphoenolpyruvate carboxylase activity) is species dependent and varies from a low of about 7 for Ananas comosus to values near 20 for Hoya carnosa and Bryophyllum pinnatum, 40 for Kalanchoee daigremontiana, and 100 or greater for Bryophyllum tubiflorum, Kalanchoee serrata, and Kalanchoae tomentosa. Carbonic anhydrase activity increases relative to phosphoenolpyruvate carboxylase activity at higher temperature. 37 references, 2 figures, 8 tables.

Holtum, J.A.M.; Summons, R.; Roeske, C.A.; Comins, H.N.; O'Leary, M.H.

1984-01-01

316

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

SciTech Connect

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.

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

1995-12-01

317

Defect studies on as-synthesized and purified carbon nanostructures produced by arc-discharge in solution process.  

PubMed

Carbon nanostructures are synthesized using a novel arc-discharge in solution process. A multitude of defects on nanotubes and nanostructures is found. Evidence of these defects in as-synthesized carbon nanostructures is explored using high-resolution transmission electron microscopy (HRTEM). Tri-, tetra-, penta-, hexa-, heptagonal, toroidal, oval, and spherical nanoshells are found in HRTEM investigation along with carbon nanotubes, carbon nanohorns, carbon rods, nanoporous carbon, dislodged graphene sheets, and amorphous carbon. Purifications are carried out through two oxidation methods to eliminate the amorphous carbon. Several different defects caused by oxidations are also found in purified samples. PMID:16736770

Bera, Debasis; Perrault, Jean-Philippe; Heinrich, Helge; Seal, Sudipta

2006-04-01

318

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

PubMed

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

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

2012-04-30

319

Computational and experimental studies of the interaction between single-walled carbon nanotubes and folic acid  

NASA Astrophysics Data System (ADS)

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.

Castillo, John J.; Rozo, Ciro E.; Castillo-León, Jaime; Rindzevicius, Tomas; Svendsen, Winnie E.; Rozlosnik, Noemi; Boisen, Anja; Martínez, Fernando

2013-03-01

320

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

Microsoft Academic Search

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

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

1998-01-01

321

Reductive desorption of sulfuric acid formed on the carbon catalyst in flue gas desulfurization (FGD)  

Microsoft Academic Search

Reductive desorption of sulfuric acid formed on the carbon catalyst in flue gas desulfurization (FGD) by heating with hydrogen at 3: 200°C converted the acid to gas-phase sulfur dioxide with a significant loss of the acid to hydrogen sulfide and elemental sulfur. These side reactions were suppressed and the temperature required for SOâ recovery was reduced by impregnating the charcoal

S. Yoshizawa; A. Karagiri; K. Watanabe

1979-01-01

322

X-ray microtomography of hydrochloric acid propagation in carbonate rocks.  

PubMed

Acid treatments are used in the oil and gas industry, to increase the permeability of the carbonate reservoirs by creating preferential channels, called wormholes. Channels formation is strongly influenced by acid type and injection rate. The aim of this study is to evaluate some characteristics of the microporous system of carbonate rocks, before and after acidizing. For that purpose X-ray high-resolution microtomography was used. The results show that this technique can be used as a reliable method to analyze microstructural characteristics of the wormholes. PMID:25485884

Machado, A C; Oliveira, T J L; Cruz, F B; Lopes, R T; Lima, I

2015-02-01

323

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

E-print Network

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

Shaqfeh, Eric

324

Heterogeneous freezing of single sulfuric acid solution droplets: laboratory experiments utilizing an acoustic levitator  

Microsoft Academic Search

The heterogeneous freezing temperatures of single binary sulfuric acid solution droplets were measured in dependency of acid concentration down to temperatures as low as -50°C. 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,

M. Ettner; S. K. Mitra; S. Borrmann

2004-01-01

325

Heterogeneous freezing of single sulphuric acid solution droplets: laboratory experiments utilising an acoustic levitator  

Microsoft Academic Search

The heterogeneous freezing temperatures of single binary sulphuric acid solution droplets were measured in dependency of acid concentration down to temperatures as low as -70°C. 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

M. Ettner; S. K. Mitra; S. Borrmann

2004-01-01

326

Di-n-butyl carbamoylphosphonate as an extradant of inorganic ions from hydrochloric acid solutions.  

PubMed

The extraction of 33 elements by a 0.1M solution of di-n-butyl carbamoylphosphonate in chloroform has been investigated as a function of hydrochloric acid concentration. The results show that this new extradant readily extracts most of the elements in a high oxidation state, including the trivalent rare earths, from hydrochloric acid at concentrations greater than 6 M. PMID:18960771

Perricos, D C; Tsolis, A K; Belkas, E P

1970-06-01

327

Induction by perfluorinated fatty acids with different carbon chain length of peroxisomal ?-oxidation in the liver of rats  

Microsoft Academic Search

The potency of the induction of peroxisomal ?-oxidation was compared between perfluorinated fatty acids (PFCAs) with different carbon chain lengths in the liver of male and female rats. In male rats, perfluoroheptanoic acid (PFHA) has little effect, although perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) potentially induced the activity. By contrast, PFHA and PFOA did not induce

Naomi Kudo; Naoki Bandai; Erika Suzuki; Masanori Katakura; Yoichi Kawashima

2000-01-01

328

Dissimilation of Carbon Monoxide to Acetic Acid by Glucose-Limited Cultures of Clostridium thermoaceticum  

PubMed Central

Clostridium thermoaceticum was cultivated in glucose-limited media, and the dissimilation of CO to acetic acid was evaluated. We found that cultures catalyzed the rapid dissimilation of CO to acetic acid and CO2, with the stoichiometry obtained for conversion approximating that predicted from the following reaction: 4CO + 2H2O ? CH3CO2H + 2CO2. Growing cultures formed approximately 50 mmol (3 g) of CO-derived acetic acid per liter of culture, with the rate of maximal consumption approximating 9.1 mmol of CO consumed/h per liter of culture. In contrast, resting cells were found not to dissimilate CO to acetic acid. 14CO was incorporated, with equal distribution between the carboxyl and methyl carbons of acetic acid when the initial cultivation gas phase was 100% CO, whereas 14CO2 preferentially entered the carboxyl carbon when the initial gas phase was 100% CO2. Significantly, in the presence of saturating levels of CO, 14CO2 preferentially entered the methyl carbon, whereas saturating levels of CO2 yielded 14CO-derived labeling predominantly in the carboxyl carbon. These findings are discussed in relation to the path of carbon flow to acetic acid. PMID:16346807

Martin, Douglas R.; Misra, Arun; Drake, Harold L.

1985-01-01

329

Spectrophotometric determination of uranium and plutonium present together in nitric acid solutions  

Microsoft Academic Search

A method is described for the spectrophotometric determination of uranium(VI) and plutonium(IV) in nitric acid solutions. Uranium is determined as a light-absorbing complex with arsenazo III in 0.05 M nitric acid at lambda = 654 nm, plutonium as a light-absorbing complex with xylenol orange in 0.1 M nitric acid at lambda = 540 nm. For the determination of uranium, DTPA

B. I. Levakov; V. B. Mishenev; N. Yu. Nezgovorov; G. K. Ryazanova; G. A. Timofeev

1987-01-01

330

Mercury Removal from Acidic Waste Solutions Using a Thiol Functional Organo?ceramic Adsorbent  

Microsoft Academic Search

Removal of mercury from highly acidic (1–2 M acid concentrations) waste solutions using a novel thiol?functionalized organo?ceramic adsorbent (SOL?AD?IV) has been investigated. The viability of mercury extraction was tested by employing Idaho National Engineering and Environmental Laboratory (INEEL) aluminum calcine and sodium bearing waste (SBW) surrogates. A maximum equilibrium uptake capacity of 740 mg\\/g in the 1–2 M acid concentrations was found, indicating

K. H. Nam; L. L. Tavlarides

2003-01-01

331

Phase formation in sodium dodecylsulfate solutions in the presence of salicylic acid for preconcentration purposes  

Microsoft Academic Search

The occurrence of surfactant-rich phases in aqueous sodium dodecylsulfate solutions in the presence of salicylic acid was\\u000a investigated. The effect of acidity, electrolyte and salicylic acid concentrations on the parameters of phase formation were\\u000a studied. Optimal conditions for microcomponent preconcentration were found. The features of solubilization efficiency changes\\u000a of organic substances depending on their charge and hydrophobicity were established. High

Viktoriia S. Starova; Sergey A. Kulichenko

2010-01-01

332

Effect of Mild Nitric Acid Oxidation on Dispersability, Size, and Structure of Single-Walled Carbon Nanotubes  

E-print Network

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

Resasco, Daniel

333

Carbon isotope composition of dissolved humic and fulvic acids in the Tokachi River system.  

PubMed

This study reports carbon isotopic ratios (?(14)C and ?(13)C) of dissolved humic and fulvic acids in the Tokachi River system, northern Japan. These acids have a refractory feature and they represent the largest fraction of dissolved organic matter in aquatic environments. The acids were isolated using the XAD extraction method from river water samples collected at three sites (on the upper and lower Tokachi River, and from one of its tributaries) in June 2004 and 2005. ?(13)C values were -27.8 to -26.9 ‰ for humic and fulvic acids. On the other hand, the ?(14)C values ranged from -247 to +26 ‰ and the average values were -170 ± 79 ‰ for humic acid and -44 ± 73 ‰ for fulvic acid. The difference was attributed to the residence time of fulvic acid in the watershed being shorter than that of humic acid. The large variation suggested that humic substances have a different pathway in each watershed environment. PMID:21515623

Nagao, Seiya; Kodama, Hiroki; Aramaki, Takafumi; Fujitake, Nobuhide; Uchida, Masao; Shibata, Yasuyuki

2011-07-01

334

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...

335

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

SciTech Connect

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

Chia, D.W.; Yoder, T.J.; Reiter, W.D.; Gibson, S.I.

2000-10-01

336

Solution and shock-induced exsolution of argon in vitreous carbon  

NASA Technical Reports Server (NTRS)

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

Gazis, Carey; Ahrens, Thomas J.

1991-01-01

337

Electricity solutions for a carbon-constrained future  

SciTech Connect

A successful response to the threat of climate change will require substantial technical work as well as practical problem solving in the political, regulatory and public areas. EPRI's 2007 Summer Seminar brought together regulatory, industry, academic, and policy leaders to discuss critical issues and delineate the initiating actions required to begin resolving the climate dilemma. Although the global nature of climate change amplifies its complexity and uncertainly, technology must play a leading role in winnowing opportunity from challenge and crafting a viable solution. 6 figs.

Schimmoller, B. [EPRI (United States)

2007-09-30

338

Labradorite dissolution in aqueous organic acid solutions: an experimental study  

E-print Network

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...

Ahmed, MD. Raquib Uddin

2012-06-07

339

Liquid-Liquid Extraction Studies of Trivalent Yttrium from Phosphoric Acid Solutions Using TOPS 99 as an Extractant  

Microsoft Academic Search

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

B. Ramachandra Reddy; S. Radhika; B. Nagaphani Kumar

2010-01-01

340

Determination of ascorbic acid content of some fruit juices and wine by voltammetry performed at pt and carbon paste electrodes.  

PubMed

A method was developed for assessing ascorbic acid concentration in fruit juices and wine by differential pulse voltammetry. The oxidation peak for ascorbic acid occurs at about 530 mV (versus SCE) on a Pt strip working electrode and at about 470 mV on a carbon paste working electrode. The influence of the operational parameters like the pulse amplitude and the pulse period on the analytical signal was investigated. The obtained calibration graph shows a linear dependence between the peak height and ascorbic acid concentration within the range 0.31-20 mM with a Pt working electrode, and within the range 0.07-20 mM with a carbon paste working electrode. The equation of the calibration graph was y = 21.839x + 35.726, r² = 0.9940, when a Pt strip electrode was used (where y represents the value of the current intensity measured for the peak height, expressed as µA and x the analyte concentration, as mM). R.S.D. = 2.09%, n = 10, C(ascorbic acid) = 2.5 mM. The equation of the calibration graph was y = 3.4429x + 5.7334, r² = 0.9971, when a carbon paste electrode was used (where y represents the value of intensity measured for the peak height, expressed as µA and x the analyte concentration, as mM). R.S.D. = 2.35%, n = 10, C(ascorbic acid) = 2.5 mM. The developed method was applied to ascorbic acid assessment in fruit juices and wine. The ascorbic acid content determined ranged between 6.83 mg/100 mL juice for soft drinks (Fanta Madness) and 54.74 mg/100 mL for citrus (lemon) juices obtained by squeezing fruit. Different ascorbic acid concentrations (from standard solutions) were added to the analysed samples, the degree of recovery being comprised between 94.74 and 104.97%. The results of ascorbic acid assessment by differential pulse voltammetry were compared with those obtained by cyclic voltammetry. The results obtained by the two methods were in good agreement. PMID:21285920

Pisoschi, Aurelia Magdalena; Pop, Aneta; Negulescu, Gheorghe Petre; Pisoschi, Aurel

2011-01-01

341

The Solubility of Boric Acid in Electrolyte Solutions  

Microsoft Academic Search

The solubility of boric acid [B] in LiCl, NaCl, KCl, RbCl, and CsCl was determined as a function of ionic strength (0–6 mol ? kg?1) at 25 ?C. The results were examined using the Pitzer equation\\u000a$$\\u000a\\\\ln \\\\{ [{\\\\rm B}]^0 \\/[{\\\\rm B}]\\\\} = \\\\ln \\\\gamma _{\\\\rm B} = (2\\\

Mareva Chanson; Frank J. Millero

2006-01-01

342

Polymerization of murine recombinant prion protein in nucleic acid solution  

Microsoft Academic Search

Summary.  ?Recombinant prion protein has been used earlier to understand the structural properties of cellular prion protein PrPC and to understand conformational change of PrPC to its isoform, PrPSc which is believed to be responsible for the prion disease. Here we report that murine recombinant prion protein, MoPrPC polymerizes in the presence of nucleic acid. The aggregation process and the properties

P. K. Nandi; E. Leclerc

1999-01-01

343

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

USGS Publications Warehouse

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.

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

1987-01-01

344

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

DOEpatents

A process has been developed for the extraction of multivalent lanthanide and actinide values from acidic waste solutions, and for the separation of these values from fission product and other values, which utilizes a new series of neutral bi-functional extractants, the alkyl(phenyl)-N, N-dialkylcarbamoylmethylphosphine oxides, in combination with a phase modifier to form an extraction solution. The addition of the extractant to the Purex process extractant, tri-n-butylphosphate in normal paraffin hydrocarbon diluent, will permit the extraction of multivalent lanthanide and actinide values from 0.1 to 12.0 molar acid solutions.

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

1984-05-21

345

Control and monitoring of the localized corrosion of zirconium in acidic chloride solutions  

SciTech Connect

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.

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

1995-09-01

346

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

PubMed

A molecular-level description of the structural and dynamical aspects that are responsible for the weak acid behaviour of dilute hydrofluoric acid solutions and their unusual increased acidity at near equimolar concentrations continues to elude us. We address this problem by reporting reflection-absorption infrared spectra (RAIRS) of cryogenic HF-H(2)O binary mixtures at various compositions prepared as nanoscopic films using molecular beam techniques. Optical constants for these cryogenic solutions [n(omega) and k(omega)] are obtained by iteratively solving Fresnel equations for stratified media. Modeling of the experimental RAIRS spectra allow for a quantitative interpretation of the complex interplay between multiple reflections, optical interference and absorption effects. The evolution of the strong absorption features in the intermediate 1000-3000 cm(-1) range with increasing HF concentration reveals the presence of various ionic dissociation intermediates that are trapped in the disordered H-bonded network of cryogenic hydrofluoric acid solutions. Our findings are discussed in light of the conventional interpretation of why hydrofluoric acid is a weak acid revealing molecular-level details of the mechanism for HF ionization that may be relevant to analogous elementary processes involved in the ionization of weak acids in aqueous solutions. PMID:18688521

Ayotte, Patrick; Plessis, Sylvain; Marchand, Patrick

2008-08-28

347

Erosion accelerated corrosion of a carbon steel–stainless steel galvanic couple in a chloride solution  

Microsoft Academic Search

In this work, the galvanic corrosion and erosion-accelerated corrosion of a 1020 carbon steel–304L stainless steel galvanic couple were investigated in a chloride solution using various electrochemical measurements and scanning electron microscopy observation. It was found that the average galvanic current density of the galvanic couple increases with the cathode\\/anode area ratio and the flow velocity of the solution. There

C. F. Dong; K. Xiao; X. G. Li; Y. F. Cheng

2010-01-01

348

Kinetics and thermodynamics studies of chromium(VI) ions adsorption onto activated carbon from aqueous solutions  

Microsoft Academic Search

The removal of chromium(VI) from aqueous solutions by activated carbon has been investigated as a function of solution pH, initial chromium concentration C, solid\\/liquid ratio R and temperature T. The Freundlich and the Langmuir models have been applied and the equilibrium adsorption was found to best fit the Langmuir adsorption isotherm, where good correlation between theoretical and experimental equilibrium concentration

M. Barkat; D. Nibou; S. Chegrouche; A. Mellah

2009-01-01

349

Heterogeneous freezing of single sulfuric acid solution droplets: laboratory experiments utilizing an acoustic levitator  

NASA Astrophysics Data System (ADS)

The heterogeneous freezing temperatures of single binary sulfuric acid solution droplets were measured in dependency of acid concentration down to temperatures as low as -50°C. 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, kaolin or montmorillonite in order to study the influence of the presence of such contamination on the freezing temperature. The radii of the suspended droplets spanned the range between 0.4 and 1.1mm and the concentration of the sulfuric acid solution varied between 5 and 14 weight percent. The presence of the particles in the solution raises the freezing temperature with respect to homogeneous freezing of these solution droplets. The pure solution droplets can be supercooled up to 40 degrees below the ice-acid solution thermodynamic equilibrium curve. Depending on the concentration of sulfuric acid and the nature of the impurity the polluted droplets froze between -11°C and -35°C. The new experimental set-up, combining a deep freezer with a movable ultrasonic levitator and suitable optics, proved to be a useful approach for such investigations on individual droplets.

Ettner, M.; Mitra, S. K.; Borrmann, S.

2004-09-01

350

Heterogeneous freezing of single sulphuric acid solution droplets: laboratory experiments utilising an acoustic levitator  

NASA Astrophysics Data System (ADS)

The heterogeneous freezing temperatures of single binary sulphuric acid solution droplets were measured in dependency of acid concentration down to temperatures as low as -70°C. 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 study the influence of the presence of such contamination on the freezing temperature. The radii of the suspended droplets spanned the range between 0,4 and 1,1 mm and the concentration of the sulphuric acid solution varied between 5 and 25 weight percent. The presence of the particles in the solution raises the freezing temperature with respect to homogeneous freezing of these solution droplets. The pure solution droplets can be supercooled up to 40° below the ice-acid solution thermodynamic equilibrium curve. Depending on the concentration of sulphuric acid and the nature of the impurity the polluted droplets froze between -11°C and -35°C. The experimental set-up, combining a deep freezer with a movable ultrasonic levitator and suitable optics, proved to be a useful approach for such investigations on individual droplets.

Ettner, M.; Mitra, S. K.; Borrmann, S.

2004-03-01

351

Production and characterization of methyl ester sophorolipids with 22-carbon-fatty acids.  

PubMed

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

Shin, Jae Dong; Lee, Jeongmi; Kim, Yong Bum; Han, In-Sun; Kim, Eun-Ki

2010-05-01

352

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

USGS Publications Warehouse

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.

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

2013-01-01

353

CO2 adsorption on modified carbon coated monolith: effect of surface modification by using alkaline solutions  

NASA Astrophysics Data System (ADS)

A monolithic column was used to study the feasibility of modified carbon-coated monolith for recovery of CO2 from gaseous mixtures (He/CO2) in a variety of operating conditions. Carbon-coated monolith was prepared by dip-coating method and modified by two alkaline solutions, i.e. NH3 and KOH. The surface properties of the carbon-coated monolith were altered by functional groups via KOH and NH3 treatments. The comparative study of CO2 uptake by two different adsorbents, i.e. unmodified and modified carbon-coated monolith, demonstrated that the applied modification process had improved CO2 adsorption. The presence of nitrogen- and oxygen-containing functional groups on the surface of the carbon led to an improved level of microporosity on the synthesized carbon-coated monolith. The physical parameters such as higher surface area, lower pore diameter, and larger micropore volume of modified monoliths indicated direct influence on the adsorbed amount of CO2. In the present study, the Deactivation Model is applied to analyze the breakthrough curves. The adsorption capacity increased with an increase in pressure and concentration, while a reduction of CO2 adsorption capacity was occurred with increase in temperature. Ammonia (NH3) and potassium hydroxide (KOH)-modified carbon-coated monolith showed an increase of approximately 12 and 27% in CO2 adsorption, respectively, as compared to unmodified carbon-coated monolith.

Hosseini, Soraya; Marahel, Ehsan; Bayesti, Iman; Abbasi, Ali; Chuah Abdullah, L.; Choong, Thomas S. Y.

2015-01-01

354

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

USGS Publications Warehouse

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.

Aiken, G.R.

1979-01-01

355

First Molecular Dynamics simulation insight into the mechanism of organics adsorption from aqueous solutions on microporous carbons  

NASA Astrophysics Data System (ADS)

The results of 84 MD simulations showing the influence of porosity and carbon surface oxidation on adsorption of three organic compounds from aqueous solutions on carbons are reported. Based on a model of 'soft' activated carbon, three carbon structures with gradually changed microporosity were created. Next, different number of surface oxygen groups was introduced. We observe quantitative agreement between simulation and experiment i.e. the decrease in adsorption from benzene down to paracetamol. Simulation results clearly demonstrate that the balance between porosity and carbon surface chemical composition in organics adsorption on carbons, and the pore blocking determine adsorption properties of carbons.

Terzyk, Artur P.; Gauden, Piotr A.; Zieli?ski, Wojciech; Furmaniak, Sylwester; Weso?owski, Rados?aw P.; Klimek, Kamil K.

2011-10-01

356

A facile hydrothermal approach towards photoluminescent carbon dots from amino acids.  

PubMed

A facile one-pot method to fabricate photoluminescent carbon dots (CDs) was developed by the hydrothermal treatment of amino acids at mild temperatures. Derived from three different kinds of amino acids including serine, histidine, and cystine, the resultant CDs show uniform spherical morphology with the diameters in the range of ?2.5-4.7nm. These amino acid derived CDs also manifest excellent photoluminescence behavior with the quantum yields (QYs) of ?7.5% and high stability. More importantly, this method provides the opportunity to modify the sizes, structures, and photoluminescent behavior of CDs by the utilization of diversified amino acids with different structural characteristics. PMID:25463184

Pei, Supeng; Zhang, Jing; Gao, Mengping; Wu, Dongqing; Yang, Yuxing; Liu, Ruili

2015-02-01

357

Degradation of dye solution by an activated carbon fiber electrode electrolysis system  

Microsoft Academic Search

Degradation of 29 dyes by means of an activated carbon fiber (ACF) electrode electrolysis system was performed successfully. Almost all dye solutions tested were decolorized effectively in this ACF electrolysis process. Internal relationships between treatment mechanisms and chemical composition of the dye have been discussed in this paper. Generally, it is shown that higher solubility leads to greater degradation in

Zhemin Shen; Wenhua Wang; Jinping Jia; Jianchang Ye; Xue Feng; An Peng

2001-01-01

358

Radiolysis of Bicarbonate and Carbonate Aqueous Solutions: Product Analysis and Simulation of Radiolytic Processes  

SciTech Connect

An understanding of the radiation-induced effects in groundwater is essential to evaluate the safe geological disposal of spent fuel. In groundwater, the bicarbonate ion is the predominant and common anion; this work investigated radiation-induced chemical reactions of (bi)carbonate aqueous solutions with steady-state irradiation and pulse radiolysis methods. Aqueous solutions of sodium (bi)carbonate as high as 50 mmol.dm{sup -3} were used. The formation of formate, oxalate, and H{sub 2}O{sub 2} were measured under different conditions. A complete set of reaction steps and reliable kinetic data for the radiolysis of (bi)carbonate aqueous solutions at ionic strength close to the groundwater were proposed. Kinetic calculations were completed based on the proposed reaction steps and the kinetic data obtained in the present work. The results from the calculation are in good agreement with the experimental results. With these proposed reaction steps and kinetic data, computer simulation can be performed to predict the yield of radiolytic products of (bi)carbonate aqueous solutions as a function of irradiation time and used to evaluate the safety of geological disposal options of spent fuel.

Cai Zhongli; Li Xifeng; Katsumura, Yosuke; Urabe, Osamu [University of Tokyo (Japan)

2001-11-15

359

Computer simulation of cascade damage in -iron with carbon in solution  

SciTech Connect

Computer simulation of cascade damage in -iron with carbon in solution Original Research Article Journal of Nuclear Materials, Volume 382, Issues 2 3, 1 December 2008, Pages 91-95 Andrew F. Calder, David J. Bacon, Alexander V. Barashev, Yuri N. Osetsky

Calder, Andrew F [ORNL; Bacon, David J [University of Liverpool; Barashev, Aleksandr [University of Liverpool; Osetsky, Nickolai [ORNL

2008-01-01

360

Raman studies of suspensions and solutions of singlewall carbon nanotubes , A. Pnicaud2  

E-print Network

Raman spectroscopy is used to probe the structure and electronic properties of nanotubes dispersed in polar organic solvents [4]. Raman spectroscopy is the most popular technique to characterize samplesRaman studies of suspensions and solutions of singlewall carbon nanotubes N. Izard1 , A. Pénicaud2

Boyer, Edmond

361

Fructose metabolism of the purple non-sulfur bacterium Rhodospirillum rubrum: effect of carbon dioxide on growth, and production of bacteriochlorophyll and organic acids.  

PubMed

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

Rudolf, Christiane; Grammel, Hartmut

2012-04-01

362

[Preparation, characterization and adsorption performance of mesoporous activated carbon with acidic groups].  

PubMed

Mesoporous activated carbons containing acidic groups were prepared with cotton stalk based fiber as raw materials and H3PO4 as activating agent by one step carbonization method. Effects of impregnation ratio, carbonization temperature and heat preservation time on the yield, elemental composition, oxygen-containing acid functional groups and adsorptive capacity of activated carbon were studied. The adsorption capacity of the prepared activated carbon AC-01 for p-nitroaniline and Pb(II) was studied, and the adsorption mechanism was also suggested according to the equilibrium experimental results. The maximum yield of activated carbons prepared from cotton stalk fiber reached 35.5% when the maximum mesoporous volume and BET surface area were 1.39 cm3 x g(-1) and 1 731 m2 x g(-1), respectively. The activated carbon AC-01 prepared under a H3 PO4/precursor ratio of 3:2 and activated at 900 degrees C for 90 min had a total pore volume of 1.02 cm3 x g(-1), a micoporous ratio of 31%, and a mesoporous ratio of 65%. The pore diameter of the mesoporous activated carbon was mainly distributed in the range of 2-5 nm. The Langmuir maximum adsorption capacities of Pb(II) and p-nitroaniline on cotton stalk fiber activated carbon were 123 mg x g(-1) and 427 mg x g(-1), respectively, which were both higher than those for commercial activated carbon fiber ACF-CK. The equilibrium adsorption experimental data showed that mesopore and oxygen-containing acid functional groups played an important role in the adsorption. PMID:23947073

Li, Kun-Quan; Li, Ye; Zheng, Zheng; Zhang, Yu-Xuan

2013-06-01

363

Investigations of optical limiting mechanisms in carbon particle suspensions and fullerene solutions  

NASA Astrophysics Data System (ADS)

Liquid suspensions of carbon act as optical limiters in the presence of high-intensity Q-switched laser pulses. The optical limiting is a result of optical breakdown, which is initiated by absorption in the small carbon particles. We measured the total energy scattered during the breakdown process and the angular distribution of the scattered light as a function of input energy. We also compared the relative scattered energy created during limiting in the carbon suspensions with that generated in solutions of fullerenes in toluene. The ratio of scattered to absorbed energy is different for the suspensions from that for the fullerene solutions, indicating that different mechanisms dominate the limiting processes in the two media.

Nashold, Karen M.; Powell Walter, Diane

1995-07-01

364

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

NASA Astrophysics Data System (ADS)

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

Rajagopal, K.; Jayabalakrishnan, S. S.

2010-12-01

365

Sorption performance and mechanism of a sludge-derived char as porous carbon-based hybrid adsorbent for benzene derivatives in aqueous solution.  

PubMed

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

Kong, Lingjun; Xiong, Ya; Sun, Lianpeng; Tian, Shuanghong; Xu, Xianyan; Zhao, Cunyuan; Luo, Rongshu; Yang, Xin; Shih, Kaimin; Liu, Haiyang

2014-06-15

366

Anomalous viscosity behavior of fatty acid esters in solution  

Microsoft Academic Search

Solution viscosity of oils of melonseed(Colocynthis vulgaris Schrad.), soyabean [Glycine max (L). Merr], and rubberseed [Hevea brasiliensis (Kunth) Muell.] were determined in different solvents at various concentrations. Reduced viscosity(?\\u000a red) vs concentration (C) plots showed three types of behavior:?\\u000a red increased linearly with C (2–30 g\\/dl);?\\u000a red levelled off with C (2–1.2 g\\/dl); and?\\u000a red rose steeply with decrease in

J. A. Ibemesi; I. O. Igwe

1991-01-01

367

Denitrification of nitrate and nitric acid with methanol as carbon source  

Microsoft Academic Search

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.

Giinter Claus; Hans Jiirgen Kutzner

1985-01-01

368

Hydrogen-bonding dynamics in aqueous solutions of amides and acids: monomer, dimer, trimer, and polymer.  

PubMed

Hydrogen-bonding dynamics in aqueous solutions of series of amides and acids have been investigated by means of femtosecond Raman-induced Kerr effect spectroscopy and ab initio quantum chemistry calculation. The amides and acids studied here are acetamide, 1,3-propanedicarboxamide, 1,3,5-pentanetricaroxamide, polyacrylamide with Mw=1500, acetic acid, 1,3-propanedicarboxylic acid, 1,3,5-pentanetricarboxylic acid, and poly(acrylic acid) with Mw=2000. The femtosecond damped transient feature for aqueous amide solutions, which arises from the intermolecular hydrogen bonds of amide and water, becomes clearer with the larger molecular weight of amide. A characteristic vibrational band at about 100 cm(-1) is assigned as the hydrogen-bonding vibrational mode and the ab initio quantum chemistry calculation result indicates that at least two waters, which make up the hydrogen-bonding network with amide, are necessary for this mode. The hydrogen-bonding vibrational mode at about 100 cm(-1) in aqueous amide solutions shifts to the higher frequency with the larger molecular weight amide in consequence of the stronger intermolecular interaction between amide and water. The evidence likely comes from the stronger hydrophobic interaction for polymer than oligomers and monomer. In the picosecond time region, an extra slow relaxation process with a time constant of about 60 ps has been found in the aqueous polymer solutions. The relaxation is assigned as a local motion of the constitutional repeat unit of polymers from comparison with monomer and oligomers. PMID:18841884

Shirota, Hideaki; Ushiyama, Hiroshi

2008-10-30

369

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

E-print Network

of polymer-based in-situ gelled acids reveal that polymer and other additives separate out of the acid when these acids are prepared in high salinity water. In coreflood tests, in-situ gelled acid formed a gel inside 20? long core samples, and the iv... acid changed its direction several times. Unexpectantly, the core?s permeability was reduced at low shear rate. Wormhole length increased as the shear rate was increased; while the diameter of the wormhole increased as the acid cumulative injected...

Gomaa, Ahmed Mohamed Mohamed

2012-07-16

370

Partitioning of Lysolipids, Fatty Acids and Their Mixtures in Aqueous Lipid Bilayers: Solute Concentration / Composition Effects  

PubMed Central

Distribution of lysopalmitoylphosphatidylcholine (LPPC), Palmitic acid (PA) and their 1:1 mixtures between water and dipalmitoylphosphatidylcholine (DPPC) bilayer were determined using a fluorescence probe that selectively detects only the solutes in water. Water solute concentrations were obtained at each of several lipid concentrations. Dynamic Light Scattering experiments confirmed that the lipid/solute aggregates were vesicles in the concentration range investigated. Lipid concentration dependence of the solute component in water was fit to a thermodynamic model of solute distribution between two coexisting solvents. Water/bilayer partition coefficient and the free energy of transfer, for each of these solutes were determined from the fit. Main findings are: (1) Water/bilayer partition coefficient of solute is greater for 2 to 10 % solute mole fraction than for 0 to 2 %, signaling solute induced bilayer perturbation that increases bilayer solubility, beginning at 2 % solute mole fraction. (2) Partition coefficients are in the order LPPCsolute solubility in the bilayer-gel phase and lack of it in the bilayer-liquid phase when LPPC and PA are present together. Implications of the solute concentration / composition and bilayer phase dependences of the partition coefficients to the reported solute induced enhancements in transmembrane permeability are discussed. PMID:24099742

Singh, Jasmeet; Lai, Amy Jo; Alaee, Yasmin; Ranganathan, Radha

2013-01-01

371

The amino acid's backup bone - storage solutions for proteomics facilities.  

PubMed

Proteomics methods, especially high-throughput mass spectrometry analysis have been continually developed and improved over the years. The analysis of complex biological samples produces large volumes of raw data. Data storage and recovery management pose substantial challenges to biomedical or proteomic facilities regarding backup and archiving concepts as well as hardware requirements. In this article we describe differences between the terms backup and archive with regard to manual and automatic approaches. We also introduce different storage concepts and technologies from transportable media to professional solutions such as redundant array of independent disks (RAID) systems, network attached storages (NAS) and storage area network (SAN). Moreover, we present a software solution, which we developed for the purpose of long-term preservation of large mass spectrometry raw data files on an object storage device (OSD) archiving system. Finally, advantages, disadvantages, and experiences from routine operations of the presented concepts and technologies are evaluated and discussed. This article is part of a Special Issue entitled: Computational Proteomics in the Post-Identification Era. Guest Editors: Martin Eisenacher and Christian Stephan. PMID:23722089

Meckel, Hagen; Stephan, Christian; Bunse, Christian; Krafzik, Michael; Reher, Christopher; Kohl, Michael; Meyer, Helmut Erich; Eisenacher, Martin

2014-01-01

372

Roles of oleic acid during micropore dispersing preparation of nano-calcium carbonate particles  

NASA Astrophysics Data System (ADS)

In the present work, nano-calcium carbonate powder was prepared by micropore dispersion method with assistance of oleic acid as surfactant. CO 2 gas was dispersed into the Ca(OH) 2/H 2O slurry via a glass micropore-plate with the diameter of micropore about 20 ?m. To investigate the effect of oleic acid on the size of CaCO 3 particles, different amount of oleic acid was added in Ca(OH) 2/H 2O slurry at 5 °C and 25 °C, respectively. XRD patterns show that cubic calcite is the only crystalline phase in all cases. ZPA data and TEM photo indicate that the average particle size synthesized at 5 °C without oleic acid is of about 40 nm, slightly smaller than that of prepared at 25 °C, and that the dispersity of sample prepared at 5 °C is better than that of 25 °C. When oleic acid is added in both temperatures, the average particle size decreases a little. FT-IR spectra demonstrate that oleic acid interacts with Ca 2+ and carbon-carbon double bond existed on the surface of particle. Consequently, two opposite roles of oleic acid during the process of preparation of nano-CaCO 3 were proposed, namely preventing nanoparticles from growing during reaction and making nanoparticles reunite to a certain extent after reaction.

Jiang, Jiuxin; Liu, Jie; Liu, Chang; Zhang, Gaowen; Gong, Xinghou; Liu, Jianing

2011-06-01

373

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

SciTech Connect

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

Fulvio, Pasquale F [ORNL; Mahurin, Shannon Mark [ORNL; Mayes, Richard T [ORNL; Bauer, Christopher [ORNL; Wang, Xiqing [ORNL; Veith, Gabriel M [ORNL; Dai, Sheng [ORNL

2012-01-01

374

Recovery of organic acids  

DOEpatents

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.

Verser, Dan W. (Golden, CO); Eggeman, Timothy J. (Lakewood, CO)

2009-10-13

375

Recovery of organic acids  

DOEpatents

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.

Verser, Dan W. (Menlo Park, CA); Eggeman, Timothy J. (Lakewood, CO)

2011-11-01

376

Uptake and Surface Reaction of Methanol by Sulfuric Acid Solutions Investigated by Vibrational Sum Frequency Generation and Raman Spectroscopies  

E-print Network

Uptake and Surface Reaction of Methanol by Sulfuric Acid Solutions Investigated by Vibrational Sum and occurred on a much longer time scale. This suggests that uptake of methanol by sulfuric acid solutions Sulfuric acid (H2SO4) is the predominant aerosol component in the free troposphere.18 Flight measurements

377

An oxidative carbon-carbon bond formation system in cycloalkane-based thermomorphic multiphase solution.  

PubMed

A selective anodic oxidation system in which a carbocation intermediate is generated exclusively by use of a temperature-controlled multiphase solution to separate the different stages of the reaction from each other and from the products is described. The formation of a thermomorphic middle layer in an electrolytic solution composed of c-Hex and LPC/MeNO2 results in enhanced interaction between aliphatic alkenes and polar unstable cation. PMID:18376846

Kim, Shokaku; Noda, Satoko; Hayashi, Kanako; Chiba, Kazuhiro

2008-05-01

378

A method for determining thermophysical properties of organic material in aqueous solutions: Succinic acid  

NASA Astrophysics Data System (ADS)

A method for determining evaporation rates and thermodynamic properties of aqueous solution droplets is introduced. The method combines evaporation rate measurements using modified TDMA technique with data evaluation using an accurate evaporation model. The first set of data has been collected and evaluated for succinic acid aqueous solution droplets. Evaporation rates of succinic acid solution droplets have been measured using a TDMA system at controlled relative humidity (65%) and temperature (298 K). A temperature-dependent expression for the saturation vapour pressure of pure liquid phase succinic acid at atmospheric temperatures has been derived by analysing the evaporation rate data with a numerical model. The obtained saturation vapour pressure of liquid phase succinic acid is ln( p) = 118.41 - 16204.8/ T - 12.452ln( T). The vapour pressure is in unit of Pascal and the temperature in Kelvin. A linear expression for the enthalpy of vaporization for liquid state succinic acid is also presented. According to the results presented in the following, a literature expression for the vapour pressure of liquid phase succinic acid defined for temperatures higher than 461 K [Yaws, C.L., 2003. Yaws' Handbook of Thermodynamic and Physical Properties of Chemical Compounds, Knovel] can be extrapolated to atmospheric temperatures with very good accuracy. The results also suggest that at 298 K the mass accommodation coefficient of succinic acid is unity or very close to unity.

Riipinen, I.; Svenningsson, B.; Bilde, M.; Gaman, A.; Lehtinen, K. E. J.; Kulmala, M.

2006-12-01

379

Dispersion of Single-Walled Carbon Nanotubes in Aqueous Solutions of the Anionic Surfactant NaDDBS  

E-print Network

Dispersion of Single-Walled Carbon Nanotubes in Aqueous Solutions of the Anionic Surfactant Na Form: October 2, 2003 The insolubility of single-walled carbon nanotubes (SWNT) in either water to different extents, the exact mechanism by which carbon nanotubes and the different surfactants interact

Resasco, Daniel

380

Examining the Microbial Degradation of Naphthenic Acids Using Stable Isotope Analysis of Carbon and Nitrogen  

Microsoft Academic Search

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

Patricia P. Videla; Andrea J. Farwell; Barbara J. Butler; D. George Dixon

2009-01-01

381

Graphitic carbon nanofibers developed from bundles of aligned electrospun polyacrylonitrile nanofibers containing phosphoric acid  

Microsoft Academic Search

Graphitic carbon nanofibers (GCNFs) with diameters of approximately 300 nm were developed using bundles of aligned electrospun polyacrylonitrile (PAN) nanofibers containing phosphoric acid (PA) as the innovative precursors through thermal treatments of stabilization, carbonization, and graphitization. The morphological, structural, and mechanical properties of GCNFs were systematically characterized and\\/or evaluated. The GCNFs made from the electrospun PAN precursor nanofibers containing 1.5 wt.% of

Zhengping Zhou; Kunming Liu; Chuilin Lai; Lifeng Zhang; Juanhua Li; Haoqing Hou; Darrell H. Reneker; Hao Fong

2010-01-01

382

Stable carbon isotope measurements of atmospheric organic acids in Los Angeles, California  

SciTech Connect

Atmospheric organic acids are ubiquitous constituents of urban smog and haze and are also present in the atmospheres of rural and largely uninhabited areas (e.g., the Amazon Rain Forest Basin). The authors report here source characterization of atmospheric organic acids in Los Angeles by measurements of their stable carbon isotopic ratios, e.g., {sup 13}C/{sup 12}C({delta}{sup 13}C). The study was performed by separating formic and acetic acids using ion chromatography exclusion (ICE) and isolating milligram quantities of individual organic acids from atmospheric rain samples. Authentic reference samples of formic and acetic acids were used to determine that only a negligible isotope fractionation of {delta}{sup 13}C value occurs after the ICE separation. During 1991-1992, rainwaters were collected in Los Angeles to isolate formic and acetic acids for the isotope measurements. Results presented in this paper demonstrate a significant isotopic difference between the mean {delta}{sup 13}C value for acetic acid ({minus}20.5{per_thousand}) and formic acid ({minus}30.1{per_thousand}). The authors conclude from these results that the formic acid is derived from mixing of formic acid from direct emissions with the acid formed by secondary oxidation processes in the atmosphere, most probably from aldehydes, whereas acetic acid originates only from direct source emissions. 26 refs., 1 fig., 2 tabs.

Sakugawa, H. [Hiroshima Univ. (Japan)] [Hiroshima Univ. (Japan); Kaplan, I.R. [Univ. of California, Los Angeles, CA (United States)] [Univ. of California, Los Angeles, CA (United States)

1995-06-15

383

Thermal transformation of trans-5-O-caffeoylquinic acid (trans-5-CQA) in alcoholic solutions.  

PubMed

Chlorogenic acid (CQA), the ester of caffeic acid with quinic acid supplied to human organisms mainly with coffee, tea, fruit and vegetables, has been one of the most studied polyphenols. It is potentially useful in pharmaceuticals, food additives, and cosmetics due to its recently discovered biomedical activity, which revived interest in its properties, isomers and natural occurrence. We found that the heating of the alcoholic solution of trans-5-O-caffeoylquinic acid produced at least twenty compounds (chlorogenic acid derivatives and its reaction products with water and alcohol). The formation of three of them (methoxy, ethoxy and propoxy adducts) has not been reported yet. No reports exist either on methoxy adducts of 3- and 4-O-caffeoylquinic acid appearing in buffered methanol/water mixtures at pH exceeding 7. We observed that the amount of each formed component depended on the heating time, type of alcohol, its concentration in alcoholic/water mixture, and pH. PMID:25148959

Dawidowicz, Andrzej L; Typek, Rafal

2015-01-15

384

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

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

385

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.

386

Glassy carbon electrodes modified with multiwalled carbon nanotubes for the determination of ascorbic acid by square-wave voltammetry  

PubMed Central

Summary Multiwalled carbon nanotubes were used to modify the surface of a glassy carbon electrode to enhance its electroactivity. Nafion served to immobilise the carbon nanotubes on the electrode surface. The modified electrode was used to develop an analytical method for the analysis of ascorbic acid (AA) by square-wave voltammetry (SWV). The oxidation of ascorbic acid at the modified glassy carbon electrode showed a peak potential at 315 mV, about 80 mV lower than that observed at the bare (unmodified) electrode. The peak current was about threefold higher than the response at the bare electrode. Replicate measurements of peak currents showed good precision (3% rsd). Peak currents increased with increasing ascorbic acid concentration (dynamic range = 0.0047–5.0 mmol/L) and displayed good linearity (R 2 = 0.994). The limit of detection was 1.4 ?mol/L AA, while the limit of quantitation was 4.7 ?mol/L AA. The modified electrode was applied to the determination of the amount of ascorbic acid in four brands of commercial orange-juice products. The measured content agreed well (96–104%) with the product label claim for all brands tested. Recovery tests on spiked samples of orange juice showed good recovery (99–104%). The reliability of the SWV method was validated by conducting parallel experiments based on high-performance liquid chromatography (HPLC) with absorbance detection. The observed mean AA contents of the commercial orange juice samples obtained by the two methods were compared statistically and were found to have no significant difference (P = 0.05). PMID:23016143

Kumar, Sushil

2012-01-01

387

Approximate Solutions for a Self-Folding Problem of Carbon Nanotubes  

SciTech Connect

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

Y Mikata

2006-08-22

388

Acetaldehyde stimulation of net gluconeogenic carbon movement from applied malic acid in tomato fruit pericarp tissue  

SciTech Connect

Applied acetaldehyde is known to lead to sugar accumulation in fruit including tomatoes (Lycopersicon esculentum) presumably due to stimulation of gluconeogenesis. This conjecture was examined using tomato fruit pericarp discs as a test system and applied l-(U-{sup 14}C)malic acid as the source for gluconeogenic carbon mobilization. Results indicate that malic and perhaps other organic acids are carbon sources for gluconeogenesis occurring normally in ripening tomatoes. The process is stimulated by acetaldehyde apparently by attenuating the fructose-2,6-biphosphate levels. The mode of the acetaldehyde regulation of fructose-2,6-biphosphate metabolism awaits clarification.

Halinska, A.; Frenkel, C. (Rutgers, The State Univ. of New Jersey, New Brunswick (United States))

1991-03-01

389

Acid gas absorption in aqueous solutions of mixed amines  

SciTech Connect

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.

Rinker, E.B.; Ashour, S.S.; Sandall, O.C. [Univ. of California, Santa Barbara, CA (United States)

1996-12-31

390

Amino acid-functionalized ionic liquid solid sorbents for post-combustion carbon capture.  

PubMed

Amino acid ionic liquids (AAILs) are potential green substitutes of aqueous amine solutions for carbon dioxide (CO2) capture. However, the viscous nature of AAILs greatly hinders their further development in CO2 capture applications. In this contribution, 1-ethyl-3-methylimidazolium lysine ([EMIM][Lys]) was synthesized and immobilized into a porous poly(methyl methacrylate) (PMMA) microsphere support for post-combustion CO2 capture. The [EMIM][Lys] exhibited good thermal stability and could be facilely immobilized into porous microspheres. Significantly, the [EMIM][Lys]-PMMA sorbents retained their porous structure after [EMIM][Lys] loading and exhibited fast kinetics. When exposed to CO2 at 40 °C, [EMIM][Lys]-PMMA sorbent exhibited the highest CO2 capacity compared to other counterparts studied and achieved a capacity of 0.87 mol/(mol AAIL) or 1.67 mmol/(g sorbent). The capture process may be characterized by two stages: CO2 adsorption on the surface of sorbent and CO2 diffusion into sorbent for further adsorption. The calculated activation energies of the two-stage CO2 sorption were 4.1 and 4.3 kJ/mol, respectively, indicating that, overall, the CO2 can easily adsorb onto this sorbent. Furthermore, multiple cycle tests indicated that the developed sorbents had good long-term stability. The developed sorbent may be a promising candidate for post-combustion CO2 capture. PMID:23927685

Wang, Xianfeng; Akhmedov, Novruz G; Duan, Yuhua; Luebke, David; Hopkinson, David; Li, Bingyun

2013-09-11

391

A study of electrochemically-induced corrosion of low carbon steel in a medium modelling acid rain  

NASA Astrophysics Data System (ADS)

Complementary electrochemical, spectrophotometric and electron microsopic investigations were made in addition to the conversion electron Mössbauer spectroscopic (CEMS) measurements to learn more about the mechanism of corrosion of low carbon steel samples in aqueous sulfate and sulfite containing sulfate solutions (pH 3.5, 6.5 and 8.5). Passivation of iron in pure sulfate solution was studied in detail in earlier papers. In the present work, we used a solution containing both sulfate and sulfite anions to obtain more information about the effect of acid rain on low carbon steel samples. The compositions and thicknesses of the passive films formed due to the electrochemical treatments were determined from the CEM spectra. ?-FeOOH was found in each case on the surface of the samples; nevertheless, at pH 3.5 the sextet belonging to Fe3C appears in the CEM spectra, and also FeSO4 · H2O was detected in low concentration after the shortest polarization time (90 min). The results of the applied methods proved that the sulfite ions induce pitting corrosion at pH 3.5 and 6.5, while the measurements referred to suppressed pitting at pH 8.5.

Vértes, Cs.; Lakatos-Varsányi, M.; Vértes, A.; Meisel, W.; Gütlich, P.

1994-12-01

392

Supercritical fluid extraction of uranium and thorium from nitric acid solutions with organophosphorus reagents  

SciTech Connect

Extraction techniques for the recovery of uranium and transuranic elements from acid waste solutions are important in nuclear waste management. This paper examines the feasibility of extracting uranyl and thorium ions from nitric acid solutions with supercritical CO{sub 2} containing the different organophosphorus reagents. In this study, an organophosphorus reagent is dissolved in supercritical CO{sub 2} by passing the fluid through a reagent vessel placed upstream of the sample vessel in the extractor. Using TBPO or TOPO in supercritical CO{sub 2}, effective extraction of uranyl and thorium ions can be achieved even in dilute HNO{sub 3} solutions, thus yielding the possibility of reducing acidic waste volumes in nuclear waste treatment. The results may form the basis of a novel extraction process for the treatment of acidified nuclear wastes, while minimizing the production of secondary wastes. 12 refs., 2 figs., 2 tabs.

Lin, Y.; Wai, C.M. [Univ. of Idaho, Moscow, ID (United States); Smart, N.G. [Univ. of Idaho, Moscow, ID (United States)]|[British Nuclear Fuels plc, Preston (United Kingdom)

1995-10-01

393

A theoretical study of 31P NMR chemical shielding models for concentrated phosphoric acid solution.  

PubMed

Calculations on the hydrates, dimer, and trimer of phosphoric acid were carried out in an effort to obtain a viable model of the phosphorus NMR chemical shielding in 85% phosphoric acid solution. The theoretical approaches used the gauge-including-atomic-orbital (GIAO) 6-311+G(nd,p) basis set at both scaled density functional theory (sB3LYP) and estimated infinite order Møller-Plesset (EMPI) approaches and with the aug-cc-pvtz basis in the sB3LYP approach. Shieldings and hydrogen bonding stabilization energies are similar in the three approaches and indicate that the faster sB3LYP/6-311+G(nd,p) approach can be used with larger systems. The changes in shielding compared to the isolated species are small and suggest that the undissociated acid dihydrate could serve as a model entity for modeling the phosphorus shielding in concentrated phosphoric acid solution. PMID:16366649

Chesnut, D B

2005-12-29

394

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

395

Stable carbon isotopic compositions of organic acids in total suspended particles and dusts from Guangzhou, China  

NASA Astrophysics Data System (ADS)

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.

Ma, Shexia; Peng, Ping'an; Song, Jianzhong; Zhao, Jinping; He, Lulu; Sheng, Guoying; Fu, Jiamo

2010-10-01

396

Carbon isotope fractionation during cis – trans isomerization of unsaturated fatty acids in Pseudomonas putida  

Microsoft Academic Search

The molecular mechanism of the unique cis to trans isomerization of unsaturated fatty acids in the solvent-tolerant bacterium Pseudomonas putida S12 was studied. For this purpose, the carbon isotope fractionation of the cis– trans isomerase was estimated. In resting cell experiments, addition of 3-nitrotoluene for activation of the cis– trans isomerase resulted in the conversion of the cis-unsaturated fatty acids

Hermann J. Heipieper; Grit Neumann; Nadja Kabelitz; Matthias Kastner; Hans Hermann Richnow

2004-01-01

397

Estimating the average carbon chain length of saturated fatty acid esters by infrared spectroscopy  

Microsoft Academic Search

The average carbon chain length of saturated fatty acid esters can be determined by comparing absorption intensities in the\\u000a 3.3 and 5.75 ? infrared regions. Data are presented for triglycerides, monoglycerides, and methyl esters. The method was used\\u000a to follow the fractionation of hydrogenated milk fat from acetone, and the average values for fatty acid chain length were\\u000a in good

P. G. Keeney

1962-01-01

398

Controls of carbonate mineralogy and solid-solution of Mg in calcite: evidence from spelean systems  

SciTech Connect

Precipitation of carbonate minerals in spelean systems occurs under a wide range of fluid chemistry, Mg-Ca ratios, alkalinities, pH and temperatures; thus, spelean systems provide ideal settings to determine factors controlling the mineralogy of precipitated carbonates and solid-solution of Mg in calcite. Cave waters and actively-precipitating carbonate speleothems were collected from Carlsbad Caverns National Park, New Mexico and the Mammoth-Flint Cave System, Kentucky. Carbonate mineralogy of precipitated phases was determined by x-ray diffraction, and major and minor element composition of waters and accompanying minerals were determined by Atomic Absorption Spectrophotometry. Results demonstrate that at a constant CO3 concentration the precipitation threshold for calcite to aragonite is controlled dominantly by the Mg/Ca ratio of the ambient fluid. Aragonite precipitation is favored by high Mg/Ca ratios. Conversely, with increasing CO3 concentration at constant fluid Mg/Ca ratios, calcite is preferentially precipitated. Solid-solution of Mg in calcite is positively correlated with both increased Mg/Ca ratios and CO3 concentrations. These data suggest that Mg contents of calcite can not be defined solely in terms of a homogeneous distribution coefficient. Rather, Mg concentrations can be also be affected by the CO3 concentration and degree of calcite saturation, suggesting that the rate of crystal growth also plays and important role in Mg solid-solution in calcites.

Gonzalez, L.A.; Lohmann, K.C.

1985-01-01

399

Determination of trichloroacetic acid in environmental studies using carbon 14 and chlorine 36.  

PubMed

Radioisotopes carbon 14 and chlorine 36 were used to elucidate the environmental role of trichloroacetic acid (TCA) formerly taken to be a herbicide and a secondary air pollutant with phytotoxic effects. However, use of 14C-labeling posed again known analytical problems, especially in TCA extraction from the sample matrix. Therefore--after evaluation of available methods--a new procedure using decarboxylation of [1,2-14C]TCA combined with extraction of the resultant 14C-chloroform with a non-polar solvent and its subsequent radiometric measurement was developed. The method solves previous difficulties and permits an easy determination of amounts between 0.4 and 20 kBq (10 - 500 ng g(-1)) of carrier-less [1,2-14C]TCA in samples from environmental investigations. The procedure is, however, not suitable for direct [36Cl]TCA determination in chlorination studies with 36Cl. Because TCA might be microbially degraded in soil during extraction and sample storage and its extraction from soil or needles is never complete, the decarboxylation method--i.e. 2 h TCA decomposition to chloroform and CO2 in aqueous solution or suspension in closed vial at 90 degrees C and pH 4.6 with subsequent CHCl3 extraction-is recommended here, estimated V < 7%. Moreover, the influence of pH and temperature on the decarboxylation of TCA in aqueous solution was studied in a broad range and its environmental relevance is shown in the case of TCA decarboxylation in spruce needles which takes place also at ambient temperatures and might amount more than 10-20% after a growing season. A study of TCA distribution in spruce needles after below-ground uptake shows the highest uptake rate into current needles which have, however, a lower TCA content than older needle-year classes, TCA biodegradation in forest soil leads predominatingly to CO2. PMID:16313943

Matucha, Miroslav; Rohlenová, Jana; Forczek, Sándor T; Uhlírová, Hana; Gryndler, Milan; Fuksová, Kvetoslava; Schröder, Peter

2006-06-01

400

Activated Carbon Production from Date Stones Using Phosphoric Acid  

Microsoft Academic Search

The effects of activation time and activation temperature on the yield and the adsorptive capacity towards iodine were studied. The yield and the quality of the activated carbon prepared by using H3PO4 were compared with that prepared from date stones using the same equipment, and under similar conditions by using ZnCl2 as an oxidizing agent. The iodine number for the

F. Al-Qaessi; L. Abu-Farah

2010-01-01

401

Leaching platinum-group metals in a sulfuric acid\\/chloride solution  

Microsoft Academic Search

A leaching process was established based on the ability of platinum-group metals to form stable chloro-complexes in acidic\\u000a chloride solutions. Industrial catalyst losses were examined for the recovery of platinum, palladium, and rhodium by leaching\\u000a with a mixture of sulfuric acid and sodium chloride to avoid using aqua regia or autoclave conditions. Extraction of platinum\\u000a and rhodium in 60% H2SO4

M. H. H. Mahmoud

2003-01-01

402

Leaching platinum-group metals in a sulfuric acid\\/chloride solution  

Microsoft Academic Search

A leaching process was established based on the ability of platinum-group metals to form stable chloro-complexes in acidic chloride solutions. Industrial catalyst losses were examined for the recovery of platinum, palladium, and rhodium by leaching with a mixture of sulfuric acid and sodium chloride to avoid using aqua regia or autoclave conditions. Extraction of platinum and rhodium in 60% H2SO4

M. H. H. Mahmoud

2003-01-01

403

Rheology control by modulating hydrophobic and inclusion associations in modified poly(acrylic acid) solutions  

Microsoft Academic Search

The rheology of modified poly(acrylic acid) (PAA) solutions can be tuned by controlling the inclusion interactions between ?-cyclodextrins and alkyl hydrophobes. We demonstrate three modes of control: (1) using free cyclodextrins (CD) to displace hydrophobe–hydrophobe association in hydrophobically modified poly(acrylic acid) (HMPAA) polymers—which reduces fluid viscosity, (2) using competitive inclusion interactions where stronger SDS:CD binding can be used to ‘unmask’

Xuhong Guo; Ahmed A. Abdala; Bruce L. May; Stephen F. Lincoln; Saad A. Khan; Robert K. Prud'homme

2006-01-01

404

Adsorption of acid dyes from aqueous solutions by the ethylenediamine-modified magnetic chitosan nanoparticles  

Microsoft Academic Search

The adsorption characteristics of Acid Orange 7(AO7) and Acid Orange 10 (AO10) from aqueous solutions onto the ethylenediamine-modified magnetic chitosan nanoparticles (EMCN) have been investigated. The EMCN were essentially monodispersed and had a main particle size distribution of 15–40nm and saturated magnetization of 25.6emu\\/g. The adsorption experiments indicated that the maximum adsorption capacity occurred at pH 4.0 for AO7 and

Limin Zhou; Jieyun Jin; Zhirong Liu; Xizhen Liang; Chao Shang

2011-01-01

405

Oxidation of ascorbic acid by a (salen)ruthenium(vi) nitrido complex in aqueous solution.  

PubMed

The oxidation of ascorbic acid (H2A) by [Ru(VI)(N)(L)(MeOH)](+) in aqueous acidic solutions has the following stoichiometry: 2[Ru(VI)(N)] + 3H2A ? 2[Ru(III)(NH2-HA)](+) + A. Mechanisms involving HAT/N-rebound at low pH (?2) and nucleophilic attack at the nitride at high pH (?5) are proposed. PMID:25372447

Wang, Qian; Man, Wai-Lun; Lam, William W Y; Lau, Tai-Chu

2014-12-25

406

Barrett's esophagus evokes a quantitatively and qualitatively altered response to both acid and hypertonic solutions  

Microsoft Academic Search

OBJECTIVE:The stomach contents become hypertonic after a meal and provide esophageal refluxate that is both acidic and hypertonic. This study examined the symptomatic response to esophageal exposure to hypertonic and acidic solutions in patients with gastroesophageal reflux disease (GERD) and Barrett's esophagus.METHODS:Symptom intensity and character were measured in double-blind fashion during esophageal instillation of water, hypertonic saline (osmolality 1030 mOsm\\/kg),

Jonathan Fletcher; Derek Gillen; Angela Wirz; Kenneth E. L. McColl

2003-01-01

407

Green, effective chemical route for the synthesis of silver nanoplates in tannic acid aqueous solution  

Microsoft Academic Search

Silver nanoplates, with average size tunable from 50 to 500nm, have been synthesized via a simple room-temperature tannic acid (TA) solution-phase chemical reduction method. The synthesis was a seedless process in which tannic acid was used as a reducing as well as a capping agent, and did not need any other surfactant or capping agent to direct the anisotropic growth

Zao Yi; Xibo Li; Xibin Xu; Binchi Luo; Jiangshan Luo; Weidong Wu; Yougen Yi; Yongjian Tang

408

The adsorption of cationic dye from aqueous solution onto acid-activated andesite  

Microsoft Academic Search

The adsorption of cationic dye (i.e., methylene blue) onto acid-activated andesite in aqueous solution was studied in a batch system with respect to its kinetics as a function of agitation speed, initial adsorbate concentration, pH, and adsorbent mass. It was found that the resulting acid-activated adsorbent possessed a mesoporous structure with BET surface areas at around 60m2\\/g. The surface characterization

Wen-Tien Tsai; Hsin-Chieh Hsu; Ting-Yi Su; Keng-Yu Lin; Chien-Ming Lin; Tzong-Hung Dai

2007-01-01

409

High-rate copper dissolution in hydrochloric acid solution  

SciTech Connect

The dissolution of copper in 1 M chloride solution was studied by steady-state (current-potential curves for various disk rotation rates) and transient measurements [frequency analysis of the electrochemical and electrohydrodynamical (EHD) impedance]. The anodic polarization curves present four regions according to the potential: one region of mixed kinetics followed by another of mass-transport control characterized by one plateau, followed by a second mixed kinetics region and a second plateau. The results obtained for the first domain of mixed kinetics and for the first plateau were previously published. In this work, the second mixed kinetics region is considered. From the analysis of the ac and EHD impedance measurements, it was shown that a transition between the presence and the absence of a CuCl salt layer occurs at a critical potential. The value of this critical potential depends on the rotation rate; the higher the rotation rate, the higher the potential value. A model of kinetic dissolution for this transition is presented, and a coupling between the currents corresponding to the two reactions is demonstrated.

D`Elia, E.; Barcia, O.E.; Mattos, O.R. [UFRJ, Rio de Janeiro (Brazil); Pebere, N. [ENSCT, Toulouse (France). Equipe de Metallurgie Physique; Tribollet, B. [Physique des Liquides et Electrochimie, Paris (France)

1996-03-01

410

Phase equilibria in a system of aqueous arginine with an octane solution of sulfonic acid  

NASA Astrophysics Data System (ADS)

The extraction of arginine (Arg) from aqueous salt (0.1 M NaCl) solutions with a sulfo extractant in a wide range of pH values and amino acid concentrations was studied. The 0.1 M solution of dinonylnaphthalenesulfonic acid (HD) in octane was used as an extractant. The degree of extraction was found to be high at pH 0.8-9.0. This can be explained by the effect of additional intermolecular interactions in the extractant phase involving the guanidine group of Arg.

Kuvaeva, Z. I.; Koval'chuk, I. V.; Vodop'yanova, L. A.; Soldatov, V. S.

2013-05-01

411

Complexation of iron by salicylic acid and its effect on atrazine photodegradation in aqueous solution  

Microsoft Academic Search

The photodegradation of atrazine and the photochemical formation of Fe(II) and H2O2 in aqueous solutions containing salicylic acid and Fe(III) were studied under simulated sunlight irradiation. Atrazine photolysis\\u000a followed first-order reaction kinetics, and the rate constant (k) corresponding to the solution of Fe(III)-salicylic acid complex (Fe(III)-SA) was only 0.0153 h?1, roughly one eighth of the k observed in the Fe(III)

Xiaoxia Ou; Chong Wang; Fengjie Zhang; Xie Quan; Yan Ma; He Liu

2010-01-01

412

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

NASA Astrophysics Data System (ADS)

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

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

1995-02-01

413

The rate of carbonic acid decomposition in sea water and its oceanographic significance  

E-print Network

III. EVIDENCE FOR THE UTILIZATION OF BICARBONATE ION BY MARII'Z PHYTOPI Ah%TON IN PHOTOSYNTHESIS General Consider tions Ihprt tl Materials and Apparatus . Procedures and Results . 43 46 Discussion SVMNARY AND CONC LOS IONS B I BI, IO GRAPHY... primary source of carbon fixation in photosynthesis. INTRODUCTIOH The carbon dioxide system in the sea has long been recognized as important to the problems of the formation and solution of calci. um oarbonate in sediments, the ecology of the sea...

Park, Kilho

2012-06-07

414

Synergistic effect of self-assembled carboxylic acid-functionalized carbon nanotubes and carbon fiber for improved electro-activated polymeric shape-memory nanocomposite  

NASA Astrophysics Data System (ADS)

The present work studies the synergistic effect of self-assembled carboxylic acid-functionalized carbon nanotube (CNT) and carbon fiber on the electrical property and electro-activated recovery behavior of shape memory polymer (SMP) nanocomposites. The combination of CNT and carbon fiber results in improved electrical conductivity in the SMP nanocomposites. Carboxylic acid-functionalized CNTs are grafted onto the carbon fibers and then self-assembled by deposition to significantly enhance the reliability of the bonding between carbon fiber and SMP via van der Waals and covalent crosslink. Furthermore, the self-assembled carboxylic acid-functionalized CNTs and carbon fibers enable the SMP nanocomposites for Joule heating triggered shape recovery.

Lu, Haibao; Min Huang, Wei

2013-06-01

415

Effect of Nitric Acid ``Washing'' Procedure on Electrochemical Behavior of Carbon Nanotubes and Glassy Carbon ?-Particles  

NASA Astrophysics Data System (ADS)

The electroanalytic performances of glassy carbon paste electrode (GCPE), multi-walled carbon nanotube (MWCNT)-GCPE and double-walled carbon nanotube (DWCNT)-GCPE, which include HNO3 washed/unwashed materials, were compared by monitoring cyclic voltammograms of potassium ferricyanide and catechol. Electrodes were prepared by introducing proper amount of DWCNT and MWCNT into GCPE. First untreated materials (DWCNT, MWCNT, GC ?-particles) were used in the electrodes and then HNO3-treated materials were utilized for comparing difference in electrochemical performances. The effect of treatment procedure was also examined by applying Raman spectroscopy to treated and untreated materials. Moreover, TEM images were obtained for further investigation of MWCNT and DWCNT.

Anik, Ülkü; Çevik, Serdar; Pumera, Martin

2010-05-01

416

Separation of linear hydrocarbons and carboxylic acids from ethanol and hexane solutions by reverse osmosis  

Microsoft Academic Search

In this study, asymmetric cellulose acetate membranes with moderate NaCl rejection (85.5%) were prepared and used to study the influence of the chemical nature of organic solutes in different organic solvents. The solute rejection and the solvent flux of linear hydrocarbons (Mw=226–563g\\/mol) and linear carboxylic acids (Mw=228–340g\\/mol) in ethanol and hexane were studied as a function of the molecular weight,

G. H. Koops; S. Yamada; S.-I. Nakao

2001-01-01

417

SELECTIVE RECOVERY OF GOLD FROM ACIDIC SOLUTIONS USING RESINS WITH METHYLENEDIPHOSPHONATE AND CARBOXYMETHYLPHOSPHONATE LIGANDS  

Microsoft Academic Search

The polymeric resins with methylenediphosphonate and carboxymethylphosphonate ligands in the ethyl ester form have been synthesized, characterized and used in the removal of Au(III) from hydrochloric acid solutions. It has been found that they are able to adsorb as much as 130–166 mg Au\\/g of the resin at high concentration of the external solutions. At low concentrations affinity of resins

Andrzej W. Trochimczuk

2001-01-01

418

EXTRACTION OF PLUTONIUM INTO 30% TRIBUTYL PHOSPHATE FROM NITRIC ACID SOLUTIONS CONTAINING FLUORIDE, ALUMINUM, AND BORON  

Microsoft Academic Search

The processing of residues left over from the passing of the Cold War presents new challenges. Solvent extraction processing of high-fluoride-content plutonium residues requires some adjustments in order to prevent high losses of plutonium to the waste stream. Process solutions have a fluoride:plutonium ratio of up to 300:1 and contain up to 0.35 M total fluoride in nitric acid solution.

E. A. Kyser

2001-01-01

419

Modeling and optimizing the design of matrix treatments in carbonate reservoirs with self-diverting acid systems  

NASA Astrophysics Data System (ADS)

Application of a self-diverting-acid based on viscoelastic surfactant (SDVA) is a promising technology for improving the efficacy of acid treatment in oil and gas-bearing carbonate reservoirs. In this study, we present a mathematical model for assessing SDVA flow and reaction with carbonate rock using the SDVA rheological characteristics. The model calculates the technological parameters for acidizing operations and the prediction of well productivity after acid treatment, in addition to technical and economic optimization of the acidizing process by modeling different acid treatment options with varying volumes, injection rates, process fluids stages and initial economic scenarios.

Bulgakova, G. T.; Kharisov, R. Ya; Sharifullin, A. R.; Pestrikov, A. V.

2015-01-01

420

The influence of type and concentration of the carbon source on production of citric acid by Aspergillus niger  

Microsoft Academic Search

The influence of various carbon sources and their concentration on the production of citrate by Aspergillus niger has been investigated. The sugars maltose, sucrose, glucose, mannose and fructose (in the given order) were carbon sources giving high yields of citric acid. Optimal yields were observed at sugar concentrations of 10% (w\\/v), with the exception of glucose (7.5%). No citric acid

Ding-Bang Xu; Cynthia P. Madrid; Max Rfihr; Christian P. Kubicek

1989-01-01

421

Acid rain damage to carbonate stone: a quantitative assessment based on the aqueous geochemistry of rainfall runoff from stone  

USGS Publications Warehouse

An onsite experimental procedure was used to identify and quantify acid rain damage to carbonate stone, based on the change in rain runoff chemical composition. Onsite data obtained during the summer and fall of 1984 at three locations in the northeastern United States indicate that carbonate stone surface recession is related to acid deposition. -from Author

Reddy, M.M.

1988-01-01

422

Single wall carbon nanotube fibers extruded from super-acid suspensions: Preferred orientation, electrical, and thermal transport  

E-print Network

Single wall carbon nanotube fibers extruded from super-acid suspensions: Preferred orientation September 2003 Fibers of single wall carbon nanotubes extruded from super-acid suspensions exhibit preferred orientation along their axes. We characterize the alignment by x-ray fiber diagrams and polarized Raman

Natelson, Douglas

423

Whole-body pharmacokinetics of HDAC inhibitor drugs, butyric acid, valproic acid and 4-phenylbutyric acid measured with carbon-11 labeled analogs by PET  

PubMed Central

The fatty acids, n-butyric acid (BA), 4-phenylbutyric acid (PBA) and valproic acid (VPA, 2-propylpentanoic acid) have been used for many years in the treatment of a variety of CNS and peripheral organ diseases including cancer. New information that these drugs alter epigenetic processes through their inhibition of histone deacetylases (HDACs) has renewed interest in their biodistribution and pharmacokinetics and the relationship of these properties to their therapeutic and side effect profile. In order to determine the pharmacokinetics and biodistribution of these drugs in primates, we synthesized their carbon-11 labeled analogues and performed dynamic positron emission tomography (PET) in six female baboons over 90 min. The carbon-11 labeled carboxylic acids were prepared by using 11CO2 and the appropriate Grignard reagents. [11C]BA was metabolized rapidly (only 20% of the total carbon-11 in plasma was parent compound at 5 min post injection) whereas for VPA and PBA 98% and 85% of the radioactivity was the unmetabolized compound at 30 min after their administration respectively. The brain uptake of all three carboxylic acids was very low (<0.006%ID/cc, BA>VPA>PBA), which is consistent with the need for very high doses for therapeutic efficacy. Most of the radioactivity was excreted through the kidneys and accumulated in the bladder. However, the organ biodistribution between the drugs differed. [11C]BA showed relatively high uptake in spleen and pancreas whereas [11C]PBA showed high uptake in liver and heart. Notably, [11C]VPA showed exceptionally high heart uptake possibly due to its involvement in lipid metabolism. The unique biodistribution of each of these drugs may be of relevance in understanding their therapeutic and side effect profile including their teratogenic effects. PMID:23906667

Kim, Sung Won; Hooker, Jacob M.; Otto, Nicola; Win, Khaing; Muench, Lisa; Shea, Colleen; Carter, Pauline; King, Payton; Reid, Alicia E.; Volkow, Nora D.; Fowler, Joanna S.

2013-01-01

424

Acidbase and complexation properties of gem -diphosphonic and gem -diphosphinic acids in aqueous solutions and micellar media of surfactants  

Microsoft Academic Search

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,

L. P. Loginova; I. V. Levin; A. G. Matveeva; S. A. Pisareva; E. E. Nifant’ev

2004-01-01

425

Characterization of calcium carbonate/chitosan composites  

SciTech Connect

The crystal growth of calcium carbonate on a chitosan substrate was achieved using a supersaturated calcium carbonate solution, by using various additives, polyacrylic acid (PAA). Polyacrylic acid modified the chitosan-film surface and promoted the nucleation of calcium carbonate crystals.

Gonsalves, K.E.; Zhang, S. [Univ. of Connecticut, Storrs, CT (United States)

1995-12-31

426

Simultaneous determination of dopamine, ascorbic acid and uric acid at poly (Evans Blue) modified glassy carbon electrode  

Microsoft Academic Search

A sensitive and selective electrochemical method for the determination of dopamine using an Evans Blue polymer film modified on glassy carbon electrode was developed. The Evans blue polymer film modified electrode shows excellent electrocatalytic activity toward the oxidation of dopamine in phosphate buffer solution (pH 4.5). The linear range of 1.0×10?6–3.0×10?5 M and detection limit of 2.5×10?7 M were observed in pH

Liqing Lin; Jinghua Chen; Hong Yao; Yuanzhong Chen; Yanjie Zheng; Xinhua Lin

2008-01-01

427

Carbon Isotopic Ratios of Amino Acids in Stardust-Returned Samples  

NASA Technical Reports Server (NTRS)

NASA's Stardust spacecraft returned to Earth samples from comet 81P/Wild 2 in January 2006. Preliminary examinations revealed the presence of a suite of organic compounds including several amines and amino acids, but the origin of these compounds could not be identified. Here. we present the carbon isotopic ratios of glycine and E-aminocaproic acid (EACH), the two most abundant amino acids observed, in Stardust-returned foil samples measured by gas chromatography-combustion-isotope ratio crass spectrometry coupled with quadrupole mass spectrometry (GC-QMS/IRMS).

Elsila, Jamie E.; Glavin, Daniel P.; Dworkin, Jason P.

2009-01-01

428

Carbon Isotopic Measurements of Amino Acids in Stardust-Returned Samples  

NASA Technical Reports Server (NTRS)

NASA's Stardust spacecraft returned to Earth samples from comet 81P/Wild 2 in January 2006. Preliminary examinations revealed the presence of a suite of organic compounds including several amines and amino acids, but the origin of these compounds could not be identified. Here, we present the carbon isotopic ratios of glycine and e-aminocaproic acid (EACA), the two most abundant amino acids, in Stardust-returned foil samples measured by gas chromatography-combustion-isotope ratio mass spectrometry coupled with quadrupole mass spectrometry (GC-CAMS/IRMS).

Elsila, Jamie

2009-01-01

429

Citric Acid-Modified Fenton's Reaction for the Oxidation of Chlorinated Ethylenes in Soil Solution Systems  

SciTech Connect

Fenton's reagent, a solution of hydrogen peroxide and ferrous iron catalyst, is used for an in-situ chemical oxidation of organic contaminants. Sulfuric acid is commonly used to create an acidic condition needed for catalytic oxidation. Fenton's reaction often involves pressure buildup and precipitation of reaction products, which can cause safety hazards and diminish efficiency. We selected citric acid, a food-grade substance, as an acidifying agent to evaluate its efficiencies for organic contaminant removal in Fenton's reaction, and examined the impacts of using citric acid on the unwanted reaction products. A series of batch and column experiments were performed with varying H{sub 2}O{sub 2} concentrations to decompose selected chlorinated ethylenes. Either dissolved iron from soil or iron sulfate salt was added to provide the iron catalyst in the batch tests. Batch experiments revealed that both citric and sulfuric acid systems achieved over 90% contaminant removal rates, and the presence of iron catalyst was essential for effective decontamination. Batch tests with citric acid showed no signs of pressure accumulation and solid precipitations, however the results suggested that an excessive usage of H{sub 2}O{sub 2} relative to iron catalysts (Fe{sup 2+}/H{sub 2}O{sub 2} < 1/330) would result in lowering the efficiency of contaminant removal by iron chelations in the citric acid system. Column tests confirmed that citric acid could provide suitable acidic conditions to achieve higher than 55% contaminant removal rates.

Seol, Yongkoo; Javandel, Iraj

2008-03-15

430

Carbon isotope composition of low molecular weight hydrocarbons and monocarboxylic acids from Murchison meteorite  

Microsoft Academic Search

Carbon isotopic compositions have been measured for individual hydrocarbons and monocarboxylic acids from the Murchison meteorite, a C2 carbonaceous chondrite which fell in Australia in 1969. With few exceptions, notably benzene, the volatile products are substantially isotopically heavier than their terrestrial counterparts, signifying their extraterrestrial origin. For both classes of compounds, the ratio of C-13 to C-12 decreases with increasing

George Yuen; Neal Blair; D. J. Des Marais; Sherwood Chang

1984-01-01

431

Polymerization of euphorbia oil with Lewis acid in carbon dioxide media  

Technology Transfer Automated Retrieval System (TEKTRAN)

Boron trifluoride diethyl etherate (BF3-OEt2) Lewis acid catalyzed ring-opening polymerization of euphorbia oil (EO), a natural epoxy oil, in liquid carbon dioxide was conducted in an effort to develop useful vegetable oil based polymers. The resulting polymers (RPEO) were characterized by FTIR, 1H-...

432

FATTY ACID STABLE ISOTOPE INDICATORS OF MICROBIAL CARBON SOURCE IN TROPICAL SOILS  

EPA Science Inventory

The soil microbial community plays an important role in tropical ecosystem functioning because of its importance in the soil organic matter (SOM) cycle. We have measured the stable carbon isotopic ratio (delta13C) of individual phospholipid fatty acids (PLFAs) in a variety of tr...

433

Improved Norway spruce somatic embryo development through the use of abscisic acid combined with activated carbon  

Microsoft Academic Search

The combination of abscisic acid (ABA) and activated carbon increased Norway spruce (Picea abies L., Karst.) cotyledonary somatic embryo yields, increased the number of genotypes forming cotyledonary embryos, caused embryos to form that exhibited improved maturation characteristics, and reduced embryo production costs. Somatic embryos increased in size, showed larger apical regions, became more zygotic-like in shape, and showed higher percentages

G. S. Pullman; P. K. Gupta; R. Timmis; C. Carpenter; M. Kreitinger; E. Welty

2005-01-01

434

EFFECT OF ACID TREATMENT ON DISSOLVED ORGANIC CARBON RETENTION BY A SPODIC HORIZON  

EPA Science Inventory

Processes involving the movement of organic substances in forest soils are not well understood. This study was conducted to examine the role of acidic inputs on dissolved organic carbon (DOC) mobility, processes affecting the retention of DOV by a B horizon, and SO2-4 adsorption....

435

Production of fumaric acid by Rhizopus oryzae: role of carbon-nitrogen ratio.  

PubMed

Cytosolic fumarase, a key enzyme for the accumulation of fumaric acid in Rhizopus oryzae, catalyzes the dehydration of L-malic acid to fumaric acid. The effects of carbon-nitrogen ratio on the acid production and activity of cytosolic fumarase were investigated. Under nitrogen limitation stress, the cytosolic fumarase could keep high activity. With the urea concentration decreased from 2.0 to 0.1 g l?¹, the cytosolic fumarase activity increased by 300% and the production of fumaric acid increased from 14.4 to 40.3 g l?¹ and L-malic acid decreased from 2.1 to 0.3 g l?¹. Cytosolic fumarase could be inhibited by substrate analog 3-hydroxybutyric acid. With the addition of 3-hydroxybutyric acid (50 mM) in the fermentation culture, fumaric acid production decreased from 40.3 to 14.1 g l?¹ and L-malic acid increased from 0.3 to 5.4 g l?¹. PMID:21416336

Ding, Yueyue; Li, Shuang; Dou, Chang; Yu, Yang; Huang, He

2011-08-01

436

Retention of silica nanoparticles on calcium carbonate sands immersed in electrolyte solutions.  

PubMed

Understanding nanoparticle-surface adhesion is necessary to develop inert tracers for subsurface applications. Here we show that nanoparticles with neutral surface charge may make the best subsurface tracers, and that it may be possible to used SiO2 nanoparticle retention to measure the fraction of solid surface that has positive charge. We show that silica nanoparticles dispersed in NaCl electrolyte solutions are increasingly retained in calcium carbonate (calcite) sand-packed columns as the solution ionic strength increases, but are not retained if they are injected in pure water or Na2SO4 electrolyte solutions. The particles retained in the NaCl experiments are released when the column is flushed with pure water or Na2SO4 solution. AFM measurements on calcite immersed in NaCl solutions show the initial repulsion of a silica colloidal probe as the surface is approached is reduced as the solution ionic strength increases, and that at high ionic strengths it disappears entirely and only attraction remains. These AFM measurements and their interpretation with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory shows the calcite surface charge is always negative for Na2SO4 solutions, but changes from negative to positive in a patchy fashion as the ionic strength of the NaCl solution increases. Since mixed-charge (patchy) surfaces may be common in the subsurface, nanoparticles with near-zero charge may make the best tracers. PMID:25259754

Li, Yan Vivian; Cathles, Lawrence M

2014-12-15

437

Formic, acetic, oxalic, malonic and succinic acid concentrations and their contribution to organic carbon in cloud water  

NASA Astrophysics Data System (ADS)

The carbon content of cloud water at a continental background site in Austria was studied during two intensive field campaigns in spring 1999 and 2000. Six carboxylic acids, total (TC) and black (BC) carbon as well as major inorganic ions were determined. Organic carbon (OC) was calculated as the difference between TC and BC. The most abundant carboxylic acids were acetic (average: 0.93 ?g ml -1) and formic (0.61) followed by oxalic (0.38), succinic (0.15) and malonic (0.20) acids. Pyruvic acid was below the detection limit (<0.08) in all samples. The BC concentration was 1.15 and OC 4.81 ?g ml -1 on average. Relating carboxylic acid concentrations to OC, the monocarboxylic acids alone represent 9.3% of OC. Adding the dicarboxylic acids, this average value increases to 11%. Although they are major components, no general trend could be seen between carboxylic acid and OC concentrations.

Löflund, M.; Kasper-Giebl, A.; Schuster, B.; Giebl, H.; Hitzenberger, R.; Puxbaum, H.

438

Active-passive corrosion of iron-chromium-nickel alloys in hot concentrated sulphuric acid solutions  

NASA Astrophysics Data System (ADS)

In the manufacture of sulphuric acid more stringent environmental standards and operation economics have forced the industry to improve product utilization, energy efficiency and reliability. A key to improving both the thermal efficiency and reliability is the use and/or development of more corrosion resistance materials including stainless steels, especially in the parts of the plant that handle the condensed acid. Application of more corrosion resistant material requires a better understanding of the corrosion mechanism involved in concentrated H2SO4-H2O (>90 wt.%) solutions. While corrosion kinetics of carbon steel, the traditional material of construction, are relatively well understood, this is much less true in the case of the cyclic active-passive corrosion of stainless steels. Models proposed to explain the cyclic active-passive corrosion involve a periodic formation of either a protective metal sulphate film or an insoluble sulphur layer. To better understand the reactivity and/or passivity of stainless steel in concentrated H2SO4-H2O solutions a study employing immersion and electrochemical techniques, including rotating electrodes, was conducted in order to clarify the following: (1) The state of stainless steel passivity. (2) The conditions in which passivity is stable. (3) The role played by the major alloying elements in establishing and maintaining the passive state. The study involved evaluating the corrosion behaviour of stainless steels S30403 and S43000 along with iron, chromium and nickel in 93.5 wt.% H2SO4 at temperatures between 25--80°C. Major discoveries of the study include: (1) A content of 17--18 wt.% chromium is sufficient to anodically passivate S43000 as the potential is made more noble. Passivity is not stable and requires anodic polarization. (2) Alloyed nickel plays an active role in improving the corrosion resistance of stainless steel. A content of 8 wt.% nickel is sufficient promote a periodic passivation of the base Fe-(17--18)wt.% Cr stainless steel under open-circuit conditions which reduces the corrosion rate by at least an order of magnitude. (3) The electrolysis of concentrated H2SO4-H 2O solutions involves a potential-dependent reduction of H2SO 4 molecules to sulphur-containing species with an oxidation state lower than six (6). The various reduction products have a significant effect on the stainless steel corrosion resistance. (4) Successful modelling of the corrosion of nickel has been accomplished by using a galvanic interaction between a noncontinuous nickel sulphide (NiS) deposit, formed in situ, and the uncovered nickel metal. (5) Successful modelling of the active-passive corrosion of S30403 has been accomplished using a galvanic interaction between NiS(Ni) and S43000.

Kish, Joseph R.

1999-11-01

439

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

E-print Network

of spent acid in the formation. Capillarity is a function of surface tension at the gas-liquid interface and contact angle of the fluids in the rock. To weaken capillary forces, surface tension should be low and contact angle should be large. This work...

Saneifar, Mehrnoosh

2012-10-19

440

Solution Deposition of Thin Carbon Coatings on LiFePO4.  

PubMed

We report the synthesis of ultrathin carbon coatings on polycrystalline LiFePO4 via solution deposition and subsequent annealing. The annealing temperature was systematically investigated with polymer systems on LiFePO4 nanostructures. The crystal structures, sizes, and morphologies were monitored and analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Micro-Raman and TEM were used to interrogate the carbon coatings after heat-treatments. Electrochemical performance of coated materials was investigated by cyclic voltammograms (CVs) and galvanostatic charge-discharge analysis. The olivine structured LiFePO4 remained stable up to 600 °C but underwent a rapid reduction reaction from LiFePO4 to Fe2P above 700 °C. The good compatibility between polyethylene glycol (PEG) and the surface of LiFePO4 enabled the formation of core-shell structure, which was transformed into a thin carbon coating on LiFePO4 after annealing. Both PEG and sucrose carbon-based sources yielded high-quality carbon coatings after annealing, as determined by the graphitic/disordered (G/D) ratios of 1.30 and 1.20, respectively. By producing more uniform and coherent coatings on LiFePO4 particles, batteries with significantly less carbon (i.e., 0.41 wt %) were fabricated and demonstrated comparable performance to traditionally synthesized carbon-coated LiFePO4 with higher carbon loadings (ca. 2.64 wt %). This will enable development of batteries with higher active material loading and therefore significantly larger energy densities. PMID:25387242

Zhu, Jianxin; Yoo, Kevin; El-Halees, Ibrahim; Kisailus, David

2014-12-10

441

An overview of the recovery of acid from spent acidic solutions from steel and electroplating industries.  

PubMed

Every metal and metallurgical industry is associated with the generation of waste, which may be a solid, liquid or gaseous in nature. Their impacts on the ecological bodies are noticeable due to their complex and hazardous nature affecting the living and non-living environment which is an alarming issue to the environmentalist. The increasingly stringent regulations regarding the discharge of acid and metal into the environment, and the increasing stress upon the recycling/reuse of these effluents after proper treatment have focused the interest of the research community on the development of new approaches for the recovery of acid and metals from industrial wastes. This paper is a critical review on the acidic waste streams generated from steel and electroplating industries particularly from waste pickle liquor and spent bleed streams. Various aspects on the generation of these streams and the methods used for their treatment either for the recovery of acid for reuse or disposal are being dealt with. Major stress is laid upon the hydrometallurgical methods such as solvent extraction. PMID:19632040

Agrawal, Archana; Sahu, K K

2009-11-15

442

Solution structure and backbone dynamics of human liver fatty acid binding protein: fatty acid binding revisited.  

PubMed

Liver fatty acid binding protein (L-FABP), a cytosolic protein most abundant in liver, is associated with intracellular transport of fatty acids, nuclear signaling, and regulation of intracellular lipolysis. Among the members of the intracellular lipid binding protein family, L-FABP is of particular interest as it can i), bind two fatty acid molecules simultaneously and ii), accommodate a variety of bulkier physiological ligands such as bilirubin and fatty acyl CoA. To better understand the promiscuous binding and transport properties of L-FABP, we investigated structure and dynamics of human L-FABP with and without bound ligands by means of heteronuclear NMR. The overall conformation of human L-FABP shows the typical ?-clam motif. Binding of two oleic acid (OA) molecules does not alter the protein conformation substantially, but perturbs the chemical shift of certain backbone and side-chain protons that are involved in OA binding according to the structure of the human L-FABP/OA complex. Comparison of the human apo and holo L-FABP structures revealed no evidence for an "open-cap" conformation or a "swivel-back" mechanism of the K90 side chain upon ligand binding, as proposed for rat L-FABP. Instead, we postulate that the lipid binding process in L-FABP is associated with backbone dynamics. PMID:22713574

Cai, Jun; Lücke, Christian; Chen, Zhongjing; Qiao, Ye; Klimtchuk, Elena; Hamilton, James A

2012-06-01

443

Norepinephrine-modified glassy carbon electrode for the simultaneous determination of ascorbic acid and uric acid  

Microsoft Academic Search

The oxidation of norepinephrine (NE) on a preactivated glassy carbon electrode leads to the formation of a deposited layer of about 4.2×10?10molcm?2 at the surface of the electrode. The electron transfer rate constant, ks, and charge transfer coefficient, ?, for electron transfer between the electrode and immobilized NE film were calculated as 44s?1 and 0.46, respectively. The NE-modified glassy carbon

H. R. Zare; F. Memarzadeh; M. Mazloum Ardakani; M. Namazian; S. M. Golabi

2005-01-01

444

Effects of sulfuric acid treatment on the microstructure and electrochemical performance of a polyacrylonitrile (PAN)-based carbon anode  

Microsoft Academic Search

To examine whether acid treatment of a non-graphitizing hard carbon influences positively or negatively its electrochemical anodic performance, this study reports the effects of sulfuric acid treatment on the microstructural changes and electrochemical performance of PAN-based hard carbons prepared at various temperatures. It was found that PAN-based hard carbons heat treated at 900°C (TAN9) exhibit an increased reversible capacity by

Y. J. Kim; H. J. Lee; S. W. Lee; B. W. Cho; C. R. Park

2005-01-01

445

Removal of Lead (II) Ions from Aqueous Solutions onto Activated Carbon Derived from Waste Biomass  

PubMed Central

The removal of lead (II) ions from aqueous solutions was carried out using an activated carbon prepared from a waste biomass. The effects of various parameters such as pH, contact time, initial concentration of lead (II) ions, and temperature on the adsorption process were investigated. Energy Dispersive X-Ray Spectroscopy (EDS) analysis after adsorption reveals the accumulation of lead (II) ions onto activated carbon. The Langmuir and Freundlich isotherm models were applied to analyze equilibrium data. The maximum monolayer adsorption capacity of activated carbon was found to be 476.2?mg?g?1. The kinetic data were evaluated and the pseudo-second-order equation provided the best correlation. Thermodynamic parameters suggest that the adsorption process is endothermic and spontaneous. PMID:23853528

Erdem, Murat; Ucar, Suat; Karagöz, Selhan; Tay, Turgay

2013-01-01

446

Improving stable carbon and oxygen isotope geochemical measurements in dolomite: reference material and acid fractionation factor  

NASA Astrophysics Data System (ADS)

The analysis of stable carbon and oxygen isotope composition is one of the most commonly used techniques in stratigraphic and diagenetic research of carbonate rocks. The wide-spread use and easy access of this long-established method has the side effect that little attention is paid to fundamental calibrations. Dolomite is often measured against a calcite standard (NBS19), and the acid fractionation factor used to calibrate is based on the one for calcite. To date, no reference material exists for dolomite. In this study, which is part of dolomite research in the Qatar Carbonates and Carbon Storage Research Centre project, we focus on two main goals. First, we characterize a current standard of dolomite used for major and minor elemental geochemistry, and assess its suitability as a new dolomite standard for ?18O and ?13C. Second, we attempt to better constrain the acid fractionation factor for dolomite and assess the influence of different dolomite types on this fractionation factor. As only two third of the total oxygen in the carbonate is released in the form of CO2 during acid reaction, a fractionation between the reacting carbonate and the resulting gas will occur. A recent study by Kim et al. (2007) improved on the acid fractionation factors for calcite and aragonite. Often, the acid fractionation factor for dolomite is used to calculate ?18O and ?13C from the values obtained by calibration with the calcite standard. Only two studies (from the 1980’s) have attempted to constrain the acid fractionation factor for dolomite, of which only Rosenbaum and Sheppard (1986) did experiments not only at 25°C, but also at 50 and 100°C. The dataset of the latter authors is, however, very limited and contains only two dolomite samples. We aim at improving the constraints on the acid fractionation factor of dolomite by reacting a wide range of different types of dolomite at a wide range of acid temperature, and compare this to the absolute isotopic composition of the samples measured on a fluorination line.

Vandeginste, V.; John, C. M.; Jourdan, A.; Davis, S.

2010-12-01

447

Synthesis of sulfonated porous carbon nanospheres solid acid by a facile chemical activation route  

NASA Astrophysics Data System (ADS)

Generally, porous carbon nanospheres materials are usually prepared via a template method, which is a multi-steps and high-cost strategy. Here, we reported a porous carbon nanosphere solid acid with high surface area and superior porosity, as well as uniform nanospheical morphology, which prepared by a facile chemical activation with ZnCl2 using resorcinol-formaldehyde (RF) resins spheres as precursor. The activation of RF resins spheres by ZnCl2 at 400 °C brought high surface area and large volume, and simultaneously retained numerous oxygen-containing and hydrogen-containing groups due to the relatively low processing temperature. The presence of these functional groups is favorable for the modification of -SO3H groups by a followed sulfonation treating with sulphuric acid and organic sulfonic acid. The results of N2 adsorption-desorption and electron microscopy clearly showed the preservation of porous structure and nanospherical morphology. Infrared spectra certified the variation of surface functional groups after activation and the successful modification of -SO3H groups after sulfonation. The acidities of catalysts were estimated by an indirect titration method and th