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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

Effect of organic acids on the determination of carbonate species in solutions  

Microsoft Academic Search

Accurate analysis of carbonate species in natural waters is important for diagenetic modelling and oilfield inorganic chemical scale precipitation estimation. The concentration of carbonate species is often measured by titration. Errors can occur when organic acids are present in the solution due to the titration end points not being clearly identified. In this paper a method is presented for the

Yuping Zhang; Richard Dawe

1996-01-01

3

Removal of Acid Dyes from Aqueous Solutions using Chemically Activated Carbon  

Microsoft Academic Search

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

Özgül Gerçel; H. Ferdi Gerçel

2009-01-01

4

Inhibition of carbon steel corrosion by azathione derivatives in organic acid solutions  

Microsoft Academic Search

Purpose – The purpose of this paper is to investigate the inhibitive effect of azathiones, namely cyclopentyl-tetrahydro-azathione, cyclohexyl-tetrahydro-azathione and isobutyl-methyl-tetrahydro-azathione on the corrosion of carbon steel in formic and acetic acid solution. The effect of inhibitor concentration, immersion time, acid concentration, and solution temperature on the inhibition efficiencies of the selected azathiones were studied systematically. Design\\/methodology\\/approach – The synthesis of

Sadaf Khan; M. Z. A. Rafiquee; Nidhi Saxena; M. A. Quraishi

2009-01-01

5

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

E-print Network

the coabsorption of COz into MDEA solutions. The absorption of carbon dioxide into aqueous MDEA solutions is a mass- transfer process from the gas phase to the liquid phase followed by a chemical reaction. Several researchers, including Tomcej et ah (1989... the carbon dioxide reaction. The objective of this study is to determine whether the addition of small amounts of phosphoric acid (HsPO4) to aqueous MDEA will reduce the rate of CO2 absorption. This will be accomplished by determining comparative kinetic...

Cordi, Eric Marshall

2012-06-07

6

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

PubMed

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

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

2014-04-01

7

Inhibition of the corrosion of low carbon steel in acidic solution by selected polyelectrolytes and polymers  

Microsoft Academic Search

The inhibiting effects of 2,6-ionen and 2,10-ionen type polyvinylbenzyltrimethylammonium chloride, and latex, on low carbon steel in hydrochloric acid solution was investigated by potentiodynamic polarisation measurements and impedance measurement techniques over the temperature range of 20-60°C at different inhibitor concentrations. It was found that the inhibition efficiencies increased with increasing inhibitor concentration. The degree of shift in Ecorr values, together

G. Bereket; A. Yurt; H. Türk

2003-01-01

8

Corrosion Inhibition of Carbon Steel by New Thiophene Azo Dye Derivatives in Acidic Solution  

NASA Astrophysics Data System (ADS)

Inhibition of carbon steel corrosion in 2 M hydrochloric acid (HCl) solution by thiophene azo dye derivatives were studied using weight loss, electrochemical frequency modulation (EFM), and atomic absorption techniques. The experimental data suggest that the inhibition efficiency increases with increasing inhibitors concentration in presence of 103 ?M potassium iodide (KI). This is due to synergistic effect. Thus, the experimental results suggested that the presence of these anions in the solution stabilized the adsorption of inhibitors molecules on the metal surface and improved the inhibition efficiency. The results of EFM experiments are a spectrum of current response as a function of frequency. The corrosion rate and Tafel parameters can be obtained with measurement by analyzing the harmonic frequencies. The adsorption of the inhibitors on metal surface obeys the Langmuir adsorption isotherm. The surface of metal examined using Fourier transform infrared and ultraviolet spectroscopy. Quantum chemical calculations were carried out and relations between computed parameters and experimental inhibition efficiency were discussed.

El-Haddad, Mahmoud N.; Fouda, A. S.; Mostafa, H. A.

2013-08-01

9

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

PubMed Central

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

2014-01-01

10

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...

11

Conductometric determination of carbon in uranium carbide and its solution in nitric acid.  

PubMed

A simple but accurate method has been developed for the determination of carbon in uranium carbide powders/pellets as well as in solutions of uranyl nitrates. The methodology involves quantitative conversion of carbon present in the sample to carbon dioxide that is subsequently absorbed in a dilute solution of barium hydroxide. The conductivity shift of the barium hydroxide solution is monitored on-line continuously using a laboratory-built PC-based conductivity measurement system that has been developed in-house based on the direct conversion of conductance to the digital pulse frequency. A new gas absorption cell has been designed to ensure quantitative absorption during the residence time of the gas in the cell. The method is sensitive, accurate and precise to 1-3% at 600-1000 mug of carbon in samples of uranium carbide. PMID:18968049

Ahmed, M K; Geetha, R; Pandey, N K; Murugesan, S; Koganti, S B; Saha, B; Sahoo, P; Sundararajan, M K

2000-08-16

12

Statistical analysis of a corrosion inhibitor family on three steel surfaces (duplex, super-13 and carbon) in hydrochloric acid solutions  

Microsoft Academic Search

Previous studies have addressed the experimental and theoretical investigation of the inhibition corrosion efficiencies (ICE) of single metal surfaces. Along this line we carried out calculations concerning to 23 compounds on three different single-steel surfaces, duplex, super-13 and the carbon steel in hydrochloric acid (15% w\\/v) solutions. The overall experiment is composed of 69 results of weight loss ICEs at

Ana Luísa de Queiroz Baddini; Sheila Pressentin Cardoso; Eduardo Hollauer; José Antonio da Cunha Ponciano Gomes

2007-01-01

13

CORROSION TESTING OF CARBON STEEL IN OXALIC ACID CHEMICAL CLEANING SOLUTIONS  

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 has been selected for this purpose because it is an effective chelating agent for the solids and is not as corrosive as other acids. Electrochemical and immersion studies were conducted to investigate the corrosion behavior of carbon steel in simulated chemical cleaning environments. The effects of temperature, agitation, and the presence of sludge solids in the oxalic acid on the corrosion rate and the likelihood of hydrogen evolution were determined. The testing showed that the corrosion rates decreased significantly in the presence of the sludge solids. Corrosion rates increased with agitation, however, the changes were less noticeable.

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

2011-10-14

14

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

15

Acid-Base Solutions  

NSDL National Science Digital Library

How do strong and weak acids differ? Use lab tools on your computer to find out! Dip the paper or the probe into solution to measure the pH, or put in the electrodes to measure the conductivity. Then see how concentration and strength affect pH. Can a weak acid solution have the same pH as a strong acid solution?

Simulations, Phet I.; Lancaster, Kelly; Malley, Chris; Loeblein, Patricia; Parson, Robert; Perkins, Kathy

2010-09-01

16

Adsorption removal of acid black 1 from aqueous solution using ordered mesoporous carbon  

NASA Astrophysics Data System (ADS)

A novel ordered mesoporous carbon CMK-3 and synthetic CMK-3 containing nitrogen functional groups by ammonia-treated were applied for acid black 1(AB1) dye adsorption. The ammonia-treated(chemical vapor deposition method) before and after CMK-3 were characterized by using a Micrometitics ASAP 2020 surface area analyzer (ASAP 2020), Fourier transform infrared spectrophotometer (FT-IR), X-ray Photoelectron Spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscope (SEM) and equilibrium studies. This result indicates that the prepared CMK-3 and modified CMK-3 were almost uniform, as rope-like domains and their uniform mesopore with diameter centered at 3.2 nm and 3.7 nm. The FIIR analysis depicted that the presence of a variety of new basic functional groups on the modified CMK-3 surface. Several effect variables of pH, dye concentration and temperature were studied. The pseudo second-order model showed the ?tter well to agree with the kinetic data. The experimental data were analyzed by the Langmuir and Freundlich models, with the latter found to closely the isotherm model. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. The results show that CMK-3 using ammonia gas modified by thermal treatment system is an effective method to improvement capacity as it shows the highest adsorption capacity of AB1, as compared to the unmodified CMK-3 and the bamboo-based carbon, respectively.

Peng, Xiaoming; Hu, Xijun; Fu, Dafang; Lam, Frank L. Y.

2014-03-01

17

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

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

Acid sorption regeneration process using carbon dioxide  

DOEpatents

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

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

2001-01-01

20

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

USGS Publications Warehouse

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

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

1989-01-01

21

The Perils of Carbonic Acid and Equilibrium Constants.  

ERIC Educational Resources Information Center

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

Jencks, William P.; Altura, Rachel A.

1988-01-01

22

Sonolysis of Short-Chain Organic Dicarboxylic Acid Solutions  

NASA Astrophysics Data System (ADS)

Sonolyses of C4 (carbon number 4) dicarboxylic acids (succinic acid, maleic acid, and fumaric acid) were performed in aqueous solution. They changed one into the other during sonication, affording carbon-number-conserving transformations. Maleic acid and fumaric acid were produced from saccinic acid by dehydrogenation. Furthermore, malic acid and tartaric acid were obtained by hydroxylation. The sonochemical reaction processes are discussed in terms of the time dependences of products and the addition of radical scavengers. In addition, mutual isomerization of fumaric acid and maleic acid was observed during sonication without the use of mediators.

Naruke, Yukio; Harada, Hisashi

2011-07-01

23

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

E-print Network

been used to im-3 [26] and boric acid [27,28]. Immersion in the solution is pregnate carbonsCarbon 40 (2002) 1249­1254 Oxidation protection of carbon materials by acid phosphate impregnation Abstract Acid phosphate impregnation, with ozone pre-treatment, improves the oxidation resistance of carbon

Chung, Deborah D.L.

24

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

NASA Astrophysics Data System (ADS)

B(OH) 3 and CO 2 are acidic species of considerable geochemical importance, yet the microscopic nature of the acid dissociation reactions for these B and C species is not well understood. Quantum mechanical methods have recently been applied to the direct ab initio calculation of p Ka values for many organic and inorganic weak acids, but the B and C acids have not yet been considered in detail. In the present study, p Ka values are calculated quantum mechanically for the oxyacids B(OH) 3, H 2CO 3 and HNO 3, which have experimental first p Ka values of 9.2, 6.4 and -1.3, respectively. We calculate the gas-phase reaction free energies at the highly accurate CBS-QB3 ab initio quantum mechanical level and reaction free energies of hydration using a polarizable continuum method. Using a thermodynamic cycle corresponding to the simple dissociation process HA A - + H +, in aqueous solution, we calculate p Ka values of 21.6, 3.8 to 2.2 and -0.8 for the three oxyacids mentioned above, closely matching experiment only for HNO 3. The discrepancies with experiment arise from the more complex nature of the acid dissociation process for B(OH) 3, which involves the addition of H 2O to B(OH) 3 and formation of the B(OH) 4- anion, and from the instability of hypothetical H 2CO 3 compared to the proper hydrated reactant complex CO 2. . . H 2O. When the proper microscopic description of the reactants and products is used the calculated p Ka values for the three acids become 11.1, 7.2 and -0.8, in considerably better agreement with experiment for B(OH) 3 and CO 2. . . H 2O. Thus p Ka calculations using this approach are accurate enough to give information on the actual acid species present in solution and the details of their acid dissociation processes at the microscopic level. 11B and 13C-NMR chemical shifts are also calculated for the various species and compared to experiment. By comparison of our calculations with experiment it is apparent that the 13C-NMR chemical shift has never been measured for an actual H 2CO 3 molecule in solution, consistent with its thermodynamic and kinetic instability with respect to CO 2 + H 2O. By contrast, the good agreement of calculated and experimental NMR shifts for the species B(OH) 3 and B(OH) 4- support their existence in solution. Calculations of the IR spectra of H 2CO 3 and its H-bonded dimer support the idea that spectra previously assigned to condensed phase or surface H 2CO 3 are better interpreted as arising from some type of H-bonded H 2CO 3 oligomer, rather than the monomer. Calculations of the relative free energy for different isotopomers of the B and C oxyacids establish that the partitioning of 13C and 12C between CO 2(aq) and HCO 3- is considerably different from the fractionation between hypothetical H 2CO 3 and HCO 3-. We find a much better match to the experimental CO 2(g) vs. HCO 3-(aq) 13,12C fractionation if the bicarbonate cluster model includes a counter ion, such as Na +. The 11,10B fractionation between B(OH) 3 and the van der Waals complex B(OH) 3. . . H 2O is quite small, while that between gas-phase B(OH) 3 and B(OH) 4- is on the order of 30‰, in qualitative agreement with more rigorous values recently obtained from supermolecule or "water-droplet" calculations.

Tossell, J. A.

2005-12-01

25

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

26

Acetic Acid Catalyzed Carbon Aerogels  

Microsoft Academic Search

We prepared carbon aerogels with a wide range of structural properties and densities using the weak acetic acid as a catalyst. Two series of acetic acid catalyzed carbon aerogels with different dilution of the catalyst and the monomers were investigated accurately. Structural investigation was performed via (U)SAXS, gas sorption and SEM. The pore and particle size can be tailored according

R. Brandt; R. Petricevic; H. Pröbstle; J. Fricke

2003-01-01

27

NiP2 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

2014-10-24

28

Organic acids tunably catalyze carbonic acid decomposition.  

PubMed

Density functional theory calculations predict that the gas-phase decomposition of carbonic acid, a high-energy, 1,3-hydrogen atom transfer reaction, can be catalyzed by a monocarboxylic acid or a dicarboxylic acid, including carbonic acid itself. Carboxylic acids are found to be more effective catalysts than water. Among the carboxylic acids, the monocarboxylic acids outperform the dicarboxylic ones wherein the presence of an intramolecular hydrogen bond hampers the hydrogen transfer. Further, the calculations reveal a direct correlation between the catalytic activity of a monocarboxylic acid and its pKa, in contrast to prior assumptions about carboxylic-acid-catalyzed hydrogen-transfer reactions. The catalytic efficacy of a dicarboxylic acid, on the other hand, is significantly affected by the strength of an intramolecular hydrogen bond. Transition-state theory estimates indicate that effective rate constants for the acid-catalyzed decomposition are four orders-of-magnitude larger than those for the water-catalyzed reaction. These results offer new insights into the determinants of general acid catalysis with potentially broad implications. PMID:24933150

Kumar, Manoj; Busch, Daryle H; Subramaniam, Bala; Thompson, Ward H

2014-07-10

29

The relationship between humic acid (HA) adsorption on and stabilizing multiwalled carbon nanotubes (MWNTs) in water: effects of HA, MWNT and solution properties.  

PubMed

This study was aimed to explore the relationship between humic acid (HA, as a model NOM) adsorption on and stabilizing multiwalled carbon nanotubes (MWNTs) in water with a focus on the effects of HA, MWNT and solution properties. It was found that MWNT-surface area-normalized adsorption of HAs (Q(SA)) increased with increasing outer-diameter of the MWNTs and decreasing polarity of the HAs. However, at low pH values (ca. <4) or high ionic strengths (ca. >1mmolL(-1) Ca(2+)), the HA adsorption decreased with decreasing polarity of the HAs. The MWNT stabilization increased with increasing Q(SA), but the increase leveled off when Q(SA) exceeded a threshold value markedly lower than the maximum Q(SA), especially for the MWNTs with relative large outer-diameters. On the whole, the Q(SA)-normalized MWNT stabilization, presenting the capability of the MWNT-adsorbed HAs for the MWNT stabilization, increased with increasing HA polarity and solution pH, but with decreasing Ca(2+) concentration. However, the stabilized MWNTs by the HAs with greater polarity could be more subject to destabilization by Ca(2+). The results of this study are believed to shed light on predictive understanding the interaction between MWNTs and NOM and the environmental behavior of MWNTs. PMID:23069335

Lin, Daohui; Li, Tingting; Yang, Kun; Wu, Fengchang

2012-11-30

30

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

EPA Science Inventory

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

31

Adsorption of uranium from aqueous solutions using activated carbon  

SciTech Connect

The adsorption of uranium from aqueous solution has been investigated using conventional commercially available activated carbons. It was found that treatment with hot nitric acid oxidized the surface of activated carbon and significantly increased the adsorption capacity for uranium in near-neutral and slightly acidic nitrate solutions. Equilibrium data were fitted to a simplified Freundlich isotherm for the purpose of comparison of oxidized and as-received samples. The decontamination of aqueous solutions was investigated in small column experiments. An ion-exchange mechanism of uranium sorption from aqueous solution is discussed. 43 refs., 11 figs., 1 tab.

Abbasi, W.A. (Pakistan Atomic Energy Commission, Islamabad (Pakistan)); Streat, M. (Loughborough Univ. of Technology, Leicestershire (United Kingdom))

1994-06-01

32

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

33

Process for defoaming acid gas scrubbing solutions and defoaming solutions  

Microsoft Academic Search

The foam in acid gas scrubbing solutions created during an acid gas scrubbing process is reduced or eliminated by the addition of certain polyoxyethylene polyoxypropylene block copolymers as defoaming agents. The defoaming agents are particularly effective when the acid gas scrubbing solution contains an amine having a large hydrophobic moiety.

E. R. Ernst; M. L. Robbins

1980-01-01

34

Process for defoaming acid gas scrubbing solutions and defoaming solutions  

Microsoft Academic Search

The foam in acid gas scrubbing solutions created during an acid gas scrubbing process is reduced or eliminated by the addition of certain polyoxyethylene polyoxypropylene block copolymers as defoaming agents. The defoaming agents are particularly effective when the acid gas scrubbing solution contains an amine having a large hydrophobic moiety. 28 claims.

M. L. Robbins; E. R. Ernst

1980-01-01

35

ELECTROLYTIC REDUCTION OF NITRIC ACID SOLUTIONS  

Microsoft Academic Search

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

H. W. Alter; D. L. Barney

1958-01-01

36

Porosity in granular carbons activated with phosphoric acid  

Microsoft Academic Search

Three series of activated carbon have been prepared by heat treatment of peach stones impregnated with solutions of phosphoric acid, in order to analyze the effect of phosphoric acid on the yield, bulk density and porosity of the resultant activated carbons. The analysis of the adsorption isotherms of N2 at 77 K. CO2 at 273 K and n-C4H10, at 273

M. Molina-Sabio; F. RodRíguez-Reinoso; F. Caturla; M. J. Sellés

1995-01-01

37

Electroreduction of carbon dioxide in aqueous solutions at metal electrodes  

SciTech Connect

The quantities of carbon stored in the form of atmospheric carbon dioxide, CO{sub 2} in the hydrosphere and carbonates in the terrestrial environment substantially exceed those of fossil fuels. In spite of this the industrial use of carbon dioxide as a source of chemical carbon is presently limited to preparation of urea and certain carboxylic acids as well as organic carbonates and polycarbonates. However, the situation is expected to change in the future, if effective catalytic systems allowing to activate carbon dioxide will become available. In this connection, the electrochemical reduction of CO{sub 2}, requiring only an additional input of water and electrical energy, appears as an attractive possibility. For more than 100 years formic acid and formates of alkali metals were considered as the only significant products of the electroreduction of carbon dioxide in aqueous solutions. The highest current efficiencies, exceeding 90 %, were obtained either with mercury or with amalgam electrodes. The only comprehensive study regarding kinetics of CO{sub 2} reduction in aqueous solution has been performed by Eyring et al. using a mercury cathode. This paper describes electrolysis studies.

Augustynski, J.; Jermann, B.; Kedzierzawski, P. [Univ. of Geneva (Switzerland)

1996-12-31

38

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

39

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...

40

Electroreduction of carbon dioxide in aqueous solutions at metal electrodes  

Microsoft Academic Search

The quantities of carbon stored in the form of atmospheric carbon dioxide, COâ in the hydrosphere and carbonates in the terrestrial environment substantially exceed those of fossil fuels. In spite of this the industrial use of carbon dioxide as a source of chemical carbon is presently limited to preparation of urea and certain carboxylic acids as well as organic carbonates

J. Augustynski; B. Jermann; P. Kedzierzawski

1996-01-01

41

Dissolution of hematite in acidic oxalate solutions  

Microsoft Academic Search

The dissolution of hematite in acidic oxalate solutions has been studied under various experimental conditions. The effect of temperature, oxalate concentration and pH on hematite dissolution were studied. In order to study the effect of atmospheric oxygen and light on the dissolution reaction, experiments were carried out in an inert atmosphere (purging with argon), in an ‘oxidising atmosphere’ (without purging),

M. Taxiarchou; D. Panias; I. Douni; I. Paspaliaris; A. Kontopoulos

1997-01-01

42

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

43

[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

44

REACTIONS OF CHLORITE WITH ACTIVATED CARBON AND WITH VANILLIC ACID AND INDAN ADSORBED ON ACTIVATED CARBON  

EPA Science Inventory

The reaction between chlorite (CO2(-1)) and vanillic acid, at pH 6.0 in the presence of granular activated carbon (GAC), yielded several reaction products identifiable by GC/MS; no products were found in the absence of GAC. Indan and ClO2 or ClO2(-1) reacted in aqueous solution a...

45

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

46

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

Microsoft Academic Search

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

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

1996-01-01

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

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.P.; Dietz, M.L.

1993-01-01

49

Adsorption of Pb(II) from aqueous solutions using activated carbon developed from Apricot stone  

Microsoft Academic Search

Low-cost activated carbon was prepared from Apricot stone material by chemical activation with sulphuric acid for the adsorption of Pb(II) from dilute aqueous solution. The activated carbon developed shows substantial capacity to adsorb Pb(II) from dilute aqueous solutions. The parameters studied include physical and chemical properties of adsorbent, pH, adsorbent dose, contact time and initial concentrations. The percent removal increased

Lotfi Mouni; Djoudi Merabet; Abdelkrim Bouzaza; Lazhar Belkhiri

2011-01-01

50

The rate of carbonic acid decomposition in sea water and its oceanographic significance  

E-print Network

with and without the influence of atmospheric carbon dioxide based upon Buch's tables on the carbon dioxide and boric acid system in sea water are compared with exper- imental data obtained by the method of Mitchell and Rakestraw(1933) and Stoddard (1952... Mixtures of weak acids and their salts or of weak bases and their sa3ts are called buffer solutions, since they resist a change in pH upon addit1on oi' sli~ht amounts oi' acid or bases (Kolthoff', 1949). Sea water contairs carbonic and boric acids...

Park, Kilho

2012-06-07

51

Methods of pretreating comminuted cellulosic material with carbonate-containing solutions  

DOEpatents

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

Francis, Raymond

2012-11-06

52

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

53

PREDICTING TEMPERATURE BEHAVIOR IN CARBONATE ACIDIZING TREATMENTS  

E-print Network

in a multilayer carbonate formation and if the low-permeability layer is treated well. This work develops a numerical model to determine the temperature behavior for both injection and flow-back situations. An important phenomenon in this process... wormholes will be created. 4 1.3 Importance We develop a numerical model to determine the temperature profile for both injection and flow back process in an acid stimulation. The method used here is similar as the one presented by previous works...

Tan, Xuehao

2010-01-16

54

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

55

Cathodic Hydrogen Evolution from Aqueous Solutions of Acetic Acid  

Microsoft Academic Search

In continuation of the work on establishing hydrogen donors in the hydrogen evolution reaction from different acid molecules, cathodic evolution of hydrogen on silver is investigated from solutions of monobasic acetic acid with the aim to establish the origin of reduced hydrogen. Solutions of 0.2 M acetic acid with 0.2 M perchloric acid, neutralized to different pH values by NaOH,

V. Marinovi?; A. R. Despi?

2004-01-01

56

Adsorption of aromatic organic acids onto high area activated carbon cloth in relation to wastewater purification  

Microsoft Academic Search

Adsorption of aromatic organic acids: benzoic acid (BA), salicylic acid (SA), p-aminobenzoic acid (pABA) and nicotinic acid (NA), onto high area activated carbon cloth from solutions in 0.4M H2SO4, in water at natural pH, in 0.1M NaOH and also from solutions having pH 7.0 were studied by in situ UV-spectroscopic technique. The first-order rate law was found to be applicable

Erol Ayranci; Osman Duman

2006-01-01

57

Comparing the Amount of Acid in Different Solutions  

NSDL National Science Digital Library

In this activity, learners use detergent solution to compare two solutions containing vinegar and cream of tartar. By comparing the number of drops used to return each solution back to its blue color, learners can discover which solution initially contained more acid. This activity can be used as a follow-up to the activity entitled" Neutralizing Acids and Bases" from the same resource (see related resources).

Kessler, James H.; Galvan, Patricia M.

2007-01-01

58

Multi-walled carbon nanotubes in aqueous phytic acid for enhancing biosensor  

NASA Astrophysics Data System (ADS)

The poor dispersion of carbon based nanomaterials without strong acid pretreatment in aqueous solution is a fundamental problem, limiting its applications in biology-related fields. A good dispersion of multi-walled carbon nanotubes (MWCNTs) in water was realized by 50 wt.% phytic acid (PA) solution. As an application case, the PA-MWCNTs dispersion in aqueous solution was used for the immobilization of horseradish peroxidase (HRP) and its direct electrochemistry was realized. The constructed biosensor has a sound limit of detection, wide linear range, and high affinity for hydrogen peroxide (H2O2) as well as being free from interference of co-existing electro-active species.

Guo, Xiaoyu; Miao, Yun; Ye, Pingping; Wen, Ying; Yang, Haifeng

2014-04-01

59

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

E-print Network

BEHAVIOR OF CARBON ISOTOPES DURING THE HYPERFILTRATION OF CALCIUM CARBONATE SOLUTIONS THROUGH CALCIUM BENTONITES A Thesis DAVID WILLIAM HINZ Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE May 1987 Major Subject: Geology BEHAVIOR OF CARBON ISOTOPES DURING THE HYPERFILTRATION OF CALCIUM CARBONATE SOLUTIONS THROUGH CALCIUM BENTONITES A Thesis by DAVID WILLIAM HINZ Approved as to style and content by...

Hinz, David William

2012-06-07

60

Synthesis of acid-functionalized composite via surface deposition of acid-containing amorphous carbon  

NASA Astrophysics Data System (ADS)

A synthetic procedure, including two steps: a hydrothermal treatment using H2SO4 solution and a thermal treatment with concentrated H2SO4 in Teflon-lined stainless autoclaves was developed to synthesize acid-functionalized composite. In this process, the carbonization of glucose which contributed to the formation of carbon species with acid functional groups occurred on the silica surface. The resultant composite, investigated by powder XRD, low temperature N2 sorption and TEM, possessed well-defined mesostructure. And it was determined by XPS that amorphous carbon was deposited at the silica surface of SBA-15. The presence of multi-functional groups in the composite was confirmed by FT-IR results. Furthermore, carboxylic and sulfonic groups could be incorporated into the composite material via the covalent bond. The composite was employed as the catalyst for the acetalization of carbonyl compounds. It was suggested that acid sites were well dispersed, which was responsible for the good performance in the catalytic test. According to these facts, a synthesis route for mesostructured composite with acid functional groups has been proposed.

Du, Bin; Zhang, Xuan; Lou, Lan-Lan; Dong, Yanling; Liu, Gaixia; Liu, Shuangxi

2012-07-01

61

Corrosion inhibition by polyaniline copolymer of mild steel in hydrochloric acid solution  

Microsoft Academic Search

Purpose – The purpose of this paper is to evaluate the inhibitive effect of a polyaniline copolymer, namely, poly(aniline-co-o-anthranilic acid) solution, on the corrosion of carbon steel in hydrochloric acid. The effect of the different concentrations of the corrosion inhibitor also was investigated. Design\\/methodology\\/approach – Fourier transform infrared spectroscopy was used to characterise the polyaniline copolymer. Weight loss measurements, potentiodynamic

Shi Fuhua; Wang Xiutong; Yu Jianqiang; Hou Baorong

2011-01-01

62

Separation of americium and europium from solutions of nitric and perchloric acid using dipicolinic acid diamides  

Microsoft Academic Search

Extraction of nitric acid, perchloric acid, americium, and europium with dialkyldiarylamides of 2,6-pyridinecarboxylic (dipicolinic)\\u000a acid in polar fluorinated solvents (diluents) was analysed. Among the extractants studied N, N?-diethyl-N, N?-ditolylamide\\u000a dipicolinate is characterized by the best extraction properties. On passing from nitric to perchloric acid solutions extraction\\u000a of metals sharply increases. Extraction of americium from nitric acid solutions is significantly greater

M. Yu. Alyapyshev; V. A. Babain; I. V. Smirnov; A. Yu. Shadrin

2006-01-01

63

Separation of americium and europium from solutions of nitric and perchloric acid using dipicolinic acid diamides  

Microsoft Academic Search

Extraction of nitric acid, perchloric acid, americium, and europium with dialkyldiarylamides of 2,6-pyridinecarboxylic (dipicolinic) acid in polar fluorinated solvents (diluents) was analysed. Among the extractants studied N, N'-diethyl-N, N'-ditolylamide dipicolinate is characterized by the best extraction properties. On passing from nitric to perchloric acid solutions extraction of metals sharply increases. Extraction of americium from nitric acid solutions is significantly greater

M. Yu. Alyapyshev; V. A. Babain; I. V. Smirnov; A. Yu. Shadrin

2006-01-01

64

Process for the recovery of strontium from acid solutions  

SciTech Connect

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.P.; Dietz, M.L.

1990-12-31

65

Acute effect of amino acid peritoneal dialysis solution on vascular  

Microsoft Academic Search

Background: Oral ingestion of proteins or amino acids is associ- ated with endothelial dysfunction. The effect of commercial amino acid peritoneal dialysis solutions on vascular function is unknown. Objective: We compared the acute effect of intraperitoneal amino acid administration with that of intraperitoneal glucose adminis- tration on vascular function in peritoneal dialysis patients. Design: In an open-label randomized, controlled, crossover

Andreas Vychytil; Manuela Födinger; Johannes Pleiner; Marcus Mullner; Peter Konner; Sonja Skoupy; Claudia Röhrer; Michael Wolzt; Gere Sunder-Plassmann

66

Dissolution kinetics of chalcopyrite in acidic potassium dichromate solution  

Microsoft Academic Search

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

S. Aydogan; G. Ucar; M. Canbazoglu

2006-01-01

67

Evaluation of acid neutralizing capacity data for solutions containing natural organic acids  

SciTech Connect

When the acid neutralizing capacity (ANC) of an aqueous solution is measured by an acidimetric titration, the measured parameter (ANC{sub t}) is generally assumed to correspond to the ANC of the sample (ANC{sub i}). This paper demonstrates that ANC{sub t} actually corresponds to ANC{sub i} - ANC{sub e}, where ANC{sub e} is the ANC of the sample at the titration endpoint. This relationship applies whether the endpoint occurs at a fixed pH or is determined by a Gran plot. When the sample contains organic acids, ANC{sub e} is generally non-zero and its neglect can introduce serious errors into the interpretation of ANC titration data. This paper presents computer simulations of ANC titrations in systems containing both carbonate and organic alkalinity, using a realistic thermodynamic model of the acidities of natural organic acids. The necessity of considering ANC{sub e} is demonstrated both computationally and by analysis of published results in which discrepancies between Gran ANC values and anion deficits could not previously be explained.

Cantrell, K.J.; Serkiz, S.M.; Perdue, E.M. (Georgia Institute of Technology, Atlanta (USA))

1990-05-01

68

Citric acid cycle biomimic on a carbon electrode  

Microsoft Academic Search

The citric acid cycle is one of the main metabolic pathways living cells utilize to completely oxidize biofuels to carbon dioxide and water. The overall goal of this research is to mimic the citric acid cycle at the carbon surface of an electrode in order to achieve complete oxidation of ethanol at a bioanode to increase biofuel cell energy density.

Daria Sokic-Lazic; Shelley D. Minteer

2008-01-01

69

Influence of sulfuric acid impregnation on the carbonization of cellulose  

NASA Astrophysics Data System (ADS)

That cellulose, as source of carbon materials, has a low char yield in pyrolysis can present serious difficulties. In this study, we focused on the effect of using sulfuric acid as a dehydration agent and examined the pyrolytic behavior of cellulose impregnated with sulfuric acid by using thermogravimetry and scanning electron microscopy. The mass yield of carbon after an 800 °C treatment in nitrogen was increased by 2-5 times with the addition of small amounts of sulfuric acid. Sample shrinkage during carbonization was also significantly reduced. These effects are interpreted as being the result of facilitated extraction of water from cellulose accompanied by development of extended carbon networks.

Kang, Kyu-Young; Kim, Dae-Young

2012-05-01

70

Effects of acidic solutions on sexual reproduction of Pteridium aquilinum  

Microsoft Academic Search

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%

Lance S. Evans; Christine A. Conway

1980-01-01

71

Separation of americium and europium from solutions of nitric and perchloric acid using dipicolinic acid diamides  

NASA Astrophysics Data System (ADS)

Extraction of nitric acid, perchloric acid, americium, and europium with dialkyldiarylamides of 2,6-pyridinecarboxylic (dipicolinic) acid in polar fluorinated solvents (diluents) was analysed. Among the extractants studied N, N?-diethyl-N, N?-ditolylamide dipicolinate is characterized by the best extraction properties. On passing from nitric to perchloric acid solutions extraction of metals sharply increases. Extraction of americium from nitric acid solutions is significantly greater as compared with europium (separation coefficient reaches 6), whereas extraction of americium and europium from perchloric acid solutions is nearly similar. The effect of diluent on the extraction was analyzed; for different diluents the maximum of extraction from perchloric acid solutions shifts form 3 to 6 M.

Alyapyshev, M. Yu.; Babain, V. A.; Smirnov, I. V.; Shadrin, A. Yu.

2006-01-01

72

Dissociation constants for carbonic acid determined from field measurements  

Microsoft Academic Search

A number of workers have recently shown that the thermodynamic constants for the dissociation of carbonic acid in seawater of Mehrbach et al. are more reliable than measurements made on artificial seawater. These studies have largely been confined to looking at the internal consistency of measurements of total alkalinity (TA), total inorganic carbon dioxide (TCO2) and the fugacity of carbon

Frank J. Millero; Denis Pierrot; Kitack Lee; Rik Wanninkhof; Richard Feely; Christopher L. Sabine; Robert M. Key; Taro Takahashi

2002-01-01

73

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

EPA Science Inventory

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

74

Raman spectra of amino acids and their aqueous solutions  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

75

Copper complexation by tannic acid in aqueous solution.  

PubMed

The speciation of titrated copper in a dissolved tannic acid (TA) solution with an initial concentration of 4 mmol organic carbon (OC)/l was investigated in a nine-step titration experiment (Cu/OC molar ratio=0.0030-0.0567). We differentiated between soluble and insoluble Cu species by 0.45 microm filtration. Measurements with a copper ion selective electrode (ISE) and diffusive gradients in thin films (DGT) were conducted to quantify unbound Cu(II) cations ("free" Cu) and labile soluble Cu complexes. For the DGT measurements, we used an APA hydrogel and a Chelex 100 chelating resin (Na form). Insoluble organic Cu complexes (>0.45 microm) was the dominant Cu species for Cu/OC=0.0030-0.0567 with a maximum fraction of 0.96 of total Cu. At Cu/OC>0.0100, Cu-catalysed degradation of aggregate structures resulted in a strong increase of free Cu and (labile) soluble Cu complexes with a maximum fraction of 0.28 and 0.32 of total Cu, respectively. Labile (i.e. DGT-detectable) soluble Cu complexes had a relatively high averaged diffusion coefficient (D) in the APA hydrogel (3.50 x 10(-6)- 5.58 x 10(-6)cm(2)s(-1)). PMID:16837024

Kraal, Peter; Jansen, Boris; Nierop, Klaas G J; Verstraten, Jacobus M

2006-12-01

76

The Effect of Heterogeneity on Matrix Acidizing of Carbonate Rocks  

E-print Network

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

Keys, Ryan S.

2010-07-14

77

Studies of individual carbon sites of proteins in solution by natural abundance carbon 13 nuclear magnetic resonance spectroscopy. Relaxation behavior.  

PubMed

The aromatic regions in proton-decoupled natural abundance 13C Fourier transform nuclear magnetic resonance spectra (at 14.2 kG) of small native proteins contain broad methine carbon bands and narrow nonprotonated carbon resonances. Some factors that affect the use of natural abundance 13C Fourier transform NMR spectroscopy for monitoring individual nonprotonated aromatic carbon sites of native proteins in solution are discussed. The effect of protein size is evaluated by comparing the 13C NMR spectra of horse heart ferrocytochrome c, hen egg white lysozyme, horse carbon monoxide myoglobin, and human adult carbon monoxide hemoglobin. Numerous single carbon resonances are observed in the aromatic regions of 13C NMR spectra of cytochrome c, lysozyme, and myoglobin. The much larger hemoglobin yields few resolved individual carbon resonances. Theoretical and some experimental values are presented for the natural linewidths (W), spin-lattice relaxation times (T1), and nuclear Overhauser enhancements (NOE) of nonprotonated aromatic carbons and Czeta of arginine residues. In general, the 13C-1H dipolar mechanism dominates the relaxation of these carbons. 13C-14N dipolar relaxation contributes significantly to 1/T1 of C epsilon2 of tryptophan residues and Czeta of arginine residues of proteins in D2O. The NOE of each nonprotonated aromatic carbon is within experimental error of the calculated value of about 1.2. As a result, integrated intensities can be used for making a carbon count. Theoretical results are presented for the effect of internal rotation on W, T1, and the NOE. A comparison with the experimental T1 and NOE values indicates that if there is internal rotation of aromatic amino acid side chains, it is not fast relative to the over-all rotational motion of the protein. PMID:169239

Oldfield, E; Norton, R S; Allerhand, A

1975-08-25

78

The resistance of recent marine carbonate sediments to solution  

E-print Network

to Samples in the a Mater Page 34 11 +e Dissolved Amounts of Mg w Percent NgC03 in Sediment Pairs of Synthetic Sea Wa ith Respect Samples in ter 't 0 the Ion 35 12 Typical Variations in pH for Various Grain Size Carbonate Sediments 37 LIST.... The carbonate ion concentration of the ground carbonate sediments in NgC1 may be beginning to level off according to Figur. e 5, and the ~+ [Ca j [CO ] ion product from Figure 9 has about reached a constant value, ++ The absence of Mg in solution can...

Jansen, John F

2012-06-07

79

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

Microsoft Academic Search

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 2.5–3Ah plates. The manufacturing of the grids, includes fast, known and simple processes which can be rescaled for mass production with a minimum, investment

Angel Kirchev; Nina Kircheva; Marion Perrin

80

137Cs desorption from lichen using acid solutions  

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

81

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

82

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

83

Solution Processed Carbon Nanotube \\/PMMA Nano Composite Infrared Photodetectors  

Microsoft Academic Search

Solution processable nanostructured materials are of great interest for electronic and optical devices because of their enhance functionality, easy processibility, flexibility, and low cost of fabrication. We tested multi walled carbon nanotube networks dispersed in poly (methyl methacrylate) (PMMA) matrix for use as the infrared (IR) photodetectors at room temperature in ambient condition. Our study reveals both negative and positive

Yi Liu; Liwei Liu; Paul Stokes; Qun Huo; Saiful I. Khondaker

2008-01-01

84

Preparation of acid standards for and determination of free acid in concentrated plutonium-uranium solutions  

SciTech Connect

Standard nitric acid solutions containing up to 400 g/L plutonium and/or uranium were prepared and these provide a way of rigorously testing methods for the determination of free acid in concentrated plutonium solutions. These standard solutions were prepared from uranyl nitrate hexahydrate and crystalline plutonium(IV) nitrate which was in turn obtained by vacuum evaporation of nitric acid solutions of Pu(IV). Three methods of free acid determination in plutonium solutions were tested, and the widely accepted iodate precipitation methods was shown to give markedly erroneous results at high plutonium concentrations. An improved oxalate complexing procedure was developed which gives accurate results (bias less than the standard deviation of 0.02 M) up to at least 400 g/L plutonium. 27 references, 2 figures, 2 tables.

Ryan, J.L.; Bryan, G.H.; Burt, M.C.; Costanzo, D.A.

1985-06-01

85

Meldrum's acids and 5-alkylidene Meldrum's acids in catalytic carbon-carbon bond-forming processes.  

PubMed

Meldrum's acid (2,2-dimethyl-1,3-dioxane-4,6-dione) is a molecule with a unique history, owing to its originally misassigned structure, as well as a unique place among acylating agents, owing to its high acidity and remarkable electrophilicity. In this Account, we outline the work of our group and others toward harnessing the reactivity of Meldrum's acid derivatives in catalytic C-C bond-forming reactions. Taking advantage of the ability of Meldrum's acid to decompose to CO(2) and acetone following acyl substitution, we have shown that intramolecular Friedel-Crafts acylations can be performed under mild Lewis acidic conditions to yield a variety of benzocyclic ketones. In a further expansion of this method, a domino Friedel-Crafts acylation/alpha-tert alkylation reaction was used to complete the first total synthesis of (+/-)-taiwaniaquinol B. The unique characteristics of Meldrum's acid extend to its alkylidene derivatives, which have also proven exceptionally useful for the development of new reactions not readily accessible from other unsaturated carbonyl electrophiles. By combining the electrophilicity and dienophilicity of alkylidene Meldrum's acid with our Friedel-Crafts chemistry, we have demonstrated new domino syntheses of coumarin derivatives and tetrahydrofluorenones by conjugate additions, Diels-Alder cycloadditions, and C-H functionalizations. Additionally, we have used these powerful acceptors to allow conjugate alkenylation with functionalized organostannanes, and conjugate allylation under very mild conditions. We have also shown that these molecules permit the asymmetric formation of all-carbon quaternary stereocenters via enantioselective conjugate additions. These reactions employ dialkylzinc nucleophiles, maximizing functional group compatibility, while the presence of a Meldrum's acid moiety in the product allows a variety of postaddition modifications. A full investigation of this reaction has determined the structural factors of the alkylidene that contribute to optimal enantioselectivity. We have also used these acceptors to form tertiary propargylic stereocenters in very high enantiomeric excess by an extremely mild, Rh(I)-catalyzed addition of TMS-acetylene. Overall, we demonstrate that Meldrum's acid and its derivatives provide access to a broad range of reactivities that, combined with their ease of handling and preparation, make them ideal electrophiles. PMID:20000793

Dumas, Aaron M; Fillion, Eric

2010-03-16

86

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

87

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

88

A microalgae residue based carbon solid acid catalyst for biodiesel production.  

PubMed

Biodiesel production from microalgae is recognized as one of the best solutions to deal with the energy crisis issues. However, after the oil extraction from the microalgae, the microalgae residue was generally discarded or burned. Here a novel carbon-based solid acid catalyst derived from microalgae residue by in situ hydrothermal partially carbonization were synthesized. The obtained catalyst was characterized and subjected to both the esterification of oleic acid and transesterification of triglyceride to produce biodiesel. The catalyst showed high catalytic activity and can be regenerated while its activity can be well maintained after five cycles. PMID:23953130

Fu, Xiaobo; Li, Dianhong; Chen, Jie; Zhang, Yuanming; Huang, Weiya; Zhu, Yi; Yang, Jun; Zhang, Chengwu

2013-10-01

89

One carbon metabolism in anaerobic bacteria: Regulation of carbon and electron flow during organic acid production  

Microsoft Academic Search

The project deals with understanding the fundamental biochemical mechanisms that physiologically control and regulate carbon and electron flow in anaerobic chemosynthetic bacteria that couple metabolism of single carbon compounds and hydrogen to the production of organic acids (formic, acetic, butyric, and succinic) or methane. The authors compare the regulation of carbon dioxide and hydrogen metabolism by fermentation, enzyme, and electron

J. G. Zeikus; M. Jain

1993-01-01

90

Photochemical kinetics of pyruvic Acid in aqueous solution.  

PubMed

Pyruvic acid in the atmosphere is found in both the gas and aqueous phases, and its behavior gives insight into that of other ?-keto acids. Photolysis is a significant degradation pathway for this molecule in the environment, and in aqueous solution the major photoproducts are higher-molecular-weight compounds that may contribute to secondary organic aerosol mass. The kinetics of the aqueous-phase photolysis of pyruvic acid under aerobic and anaerobic conditions was investigated in order to calculate the first-order rate constant, Jaq, in solution. Analysis of the exponential decay of pyruvic acid was performed by monitoring both pyruvic acid and its photolytic products over the course of the reaction by (1)H NMR spectroscopy. Detection of major and minor products in the 0.1, 0.05, and 0.02 M pyruvic acid photolyses clearly demonstrates that the primary reaction pathways are highly dependent on the initial pyruvic acid concentration and the presence of dissolved oxygen. The Jaq values were calculated with approximations based on the dominant pathways for limiting cases of the mechanism. Finally, a model study using the calculated rate constants demonstrates the importance of aqueous-phase photolysis as a sink for pyruvic acid in the atmosphere, compared with gas-phase photolysis and OH oxidation. PMID:24725260

Reed Harris, Allison E; Ervens, Barbara; Shoemaker, Richard K; Kroll, Jay A; Rapf, Rebecca J; Griffith, Elizabeth C; Monod, Anne; Vaida, Veronica

2014-09-18

91

Evaluation of Perforated Carbonate Cores Under Acid Stimulation  

E-print Network

Although it has been shown that clean perforation tunnels facilitate the evolution of a single, deeper-penetrating wormhole, there are no reported applications of reactive shaped charges in carbonates prior to acid stimulation. The present study...

Diaz, Nerwing Jose

2011-10-21

92

Study of Acid Response of Qatar Carbonate Rocks  

E-print Network

-scale heterogeneities which may cause the impact of the injected acids to differ from homogenous case. Recent published field data indicate a much smaller number of pore volume to breakthrough compared with experimental measurement with homogeneous carbonate...

Wang, Zhaohong

2012-02-14

93

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

94

Volumetric Properties of Aqueous Solutions of Cyclohexylsulfamic Acid  

Microsoft Academic Search

The mean apparent molar volume of cyclohexylsulfamic acid has been determined from the density data of aqueous solutions up\\u000a to a molality of 0.540 mol?kg?1 and at 293.15, 298.15, 303.15, 313.15, and 323.15 K. The mean apparent molar volume of the acid was divided into contributing\\u000a ionic and molecular apparent molar volumes. The limiting apparent molar volume of the molecular

Cveto Klofutar; Darja Rudan-Tasic

2006-01-01

95

The corrosion of aluminum in boric acid solutions  

E-print Network

THE CORROSION OF ALUMINUM IN BORIC ACID SOLUTIONS A Thesis By HENRI KINSOLVING BASS, JR. Submitted to the Graduate School of the Agricultural and Mechanical College oi' Texas' in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE ~Janua lqq6 Ma ]or Sub)ect Chemical E ineeri ~RARY I At N csLEEOE QF TExAs THE CORROSION OF ALUKBWM IN BORIC ACID SOLUTIONS A Thesis By HENRY KINSOLVINO BASS, JR. Approved as to style and content by: Cha rman of Committee...

Bass, Henry Kinsolving

2012-06-07

96

Highly accurate boronimeter assay of concentrated boric acid solutions  

SciTech Connect

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

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

1992-01-01

97

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

98

Emulsion liquid membrane extraction of lactic acid from aqueous solutions and fermentation broth.  

PubMed

Studies on the batch extraction of lactic acid using an emulsion liquid membrane system are reported. The membrane phase consists of the tertiary amine carrier Alamine 336 and the surfactant Span 80 dissolved in n-heptane/paraffin and aqueous solutions of sodium carbonate in the internal phase. The effects of internal phase reagent, extraction temperature, and initial external phase pH on the extraction efficiency and the emulsion swelling are examined. A statistical factorial experiment on extraction from clarified lactic acid fermentation broth was carried out to obtain knowledge of the performance of the extraction system from a broth. The extraction efficiency from the fermentation broth is found to be lower as compared to aqueous solutions of pure lactic acid. The effect of pH and the presence of other ionic species on selectivity are discussed. PMID:18609647

Schöller, C; Chaudhuri, J B; Pyle, D L

1993-06-01

99

Carbonic Anhydrase 5 Regulates AcidBase Homeostasis in Zebrafish  

Microsoft Academic Search

The regulation of the acid-base balance in cells is essential for proper cellular homeostasis. Disturbed acid-base balance directly affects cellular physiology, which often results in various pathological conditions. In every living organism, the protein family of carbonic anhydrases regulate a broad variety of homeostatic processes. Here we describe the identification, mapping and cloning of a zebrafish carbonic anhydrase 5 (ca5)

Ruben Postel; Arnoud Sonnenberg

2012-01-01

100

Effects of acidic treatment of activated carbons on dye adsorption  

Microsoft Academic Search

The effect of acidic treatments of activated carbons on dye adsorption was investigated. The physico-chemical properties of activated carbons were characterised by N2 adsorption, mass titration, temperature-programmed desorption (TPD), and X-ray photoelectron spectrometry (XPS). It was found that surface chemistry plays an important role in dye adsorption. HNO3 treatment produces more active acidic surface groups such as carboxyl and lactone,

Shaobin Wang; Z. H. Zhu

2007-01-01

101

Electrosynthesis of Poly(azure B) from Sulfuric Acid Solution  

Microsoft Academic Search

Electrochemical polymerization of azure B from sulfuric acid solution was carried out by using cyclic voltammetry. The electrolytic solution consisted of 5.0 mmol · dm azure B and 0.3 mol · dm H2SO4. The temperature for polymerization was controlled at 20°C. A blue film, i.e., poly(azure B) was formed on a platinum foil and had a electrochemical reversibility, stability and a fast charge transfer ability in

Chuanxiang Chen; Yuhua Gao

2007-01-01

102

Region-selective self-assembly of functionalized carbon allotropes from solution.  

PubMed

Approaches for the selective self-assembly of functionalized carbon allotropes from solution are developed and validated for 0D-fullerenes, 1D-carbon nanotubes and 2D-graphene. By choosing the right molecular interaction of self-assembled monolayers (serving the surface) with the functionalization features of carbon materials, which provide the solubility but also serve the driving force for assembly, we demonstrate a region-selective and self-terminating assembly of the materials. Active layers of the carbon allotropes can be selectively deposited in the channel region of thin-film transistor (TFT) devices by this approach. As an example for a 0D system, molecules of C60 functionalized octadecylphosphonic acids are used to realize self-assembled monolayer field-effect transistors (SAMFETs) based on a selective molecular exchange reaction of stearic acid in the channel region. For noncovalently functionalized single-walled carbon nanotubes (SWCNTs) and graphene oxide (GO) flakes, the electrostatic Coulomb interactions between the functional groups of the carbon allotropes and the charged head groups of a SAM dielectric layer are utilized to implement the selective deposition. PMID:24274682

Wang, Zhenxing; Mohammadzadeh, Saeideh; Schmaltz, Thomas; Kirschner, Johannes; Khassanov, Artoem; Eigler, Siegfried; Mundloch, Udo; Backes, Claudia; Steinrück, Hans-Georg; Magerl, Andreas; Hauke, Frank; Hirsch, Andreas; Halik, Marcus

2013-12-23

103

Carbon dioxide-sustained adsorption of lactic acid at pH > pK{sub a} of the acid  

SciTech Connect

Experimental data are presented for batch and fixed-bed adsorption of lactic acid from aqueous sodium lactate solutions onto the tertiary amine sorbents, Dowex MWA-1 and Amberlite IRA-35, in the presence of carbon dioxide. The effects of carbon dioxide pressure and sodium lactate concentration on lactate uptake capacity were measured. A simple complexation model, which includes chemical-equilibria and mass- and charge-balance equations, was developed to describe the system. There are no fitted parameters in the model. The model predictions compare well with batch adsorption data.

Husson, S.M.; King, C.J. [Lawrence Berkeley National Lab., CA (United States)] [Lawrence Berkeley National Lab., CA (United States)

1999-04-01

104

Electrosorption of inorganic salts from aqueous solution using carbon aerogels.  

PubMed

Capacitive deionization (CDI) with carbon aerogels has been shown to remove various inorganic species from aqueous solutions, though no studies have shown the electrosorption behavior of multisolute systems in which ions compete for limited surface area. Several experiments were conducted to determine the ion removal capacity and selectivity of carbon aerogel electrodes, using both laboratory and natural waters. Although carbon aerogel electrodes have been treated as electrical double-layer capacitors, this study showed that ion sorption followed a Langmuir isotherm, indicating monolayer adsorption. The sorption capacity of carbon aerogel electrodes was approximately 1.0-2.0 x 10(-4) equiv/g aerogel, with ion selectivity being based on ionic hydrated radius. Monovalent ions (e.g., sodium) with smaller hydrated radii were preferentially removed from solution over multivalent ions (e.g., calcium) on a percent or molar basis. Because of the relatively small average pore size (4-9 nm) of the carbon aerogel material, only 14-42 m2/g aerogel surface area was available for ion sorption. Natural organic matter may foul the aerogel surface and limit CDI effectiveness in treating natural waters. PMID:12144279

Gabelich, Christopher J; Tran, Tri D; Suffet, I H Mel

2002-07-01

105

Alkali Treatment of Acidic Solution from Hanford K Basin Sludge Dissolution  

SciTech Connect

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

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

1998-12-22

106

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

107

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

E-print Network

??Spent acid retention in the near-wellbore region causes reduction of relative permeability to gas and eventually curtailed gas production. In low-permeability gas carbonate reservoirs, capillary… (more)

Saneifar, Mehrnoosh

2012-01-01

108

137 Cs desorption from lichen using acid solutions  

Microsoft Academic Search

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

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

2009-01-01

109

Capacity of activated carbon in the removal of acid brilliant blue: Determination of equilibrium and kinetic model parameters  

Microsoft Academic Search

The adsorption of acid brilliant blue onto thermally activated coir pith carbon in aqueous solution was studied in a batch system with respect to contact time, pH, and temperature. Acidic pH was favorable for the adsorption of this dye. The surface characterization of thermally activated coir pith carbon was performed using the FT-IR technique. Kinetic studies showed that the adsorption

D. Kavitha; C. Namasivayam

2008-01-01

110

Anodic alumina films formed in sulfamic acid solution  

Microsoft Academic Search

The formation of anodic oxide films on aluminium in 5% aqueous solution of sulfamic acid is investigated. The investigations were carried out in galvanostatic conditions and at different temperatures and durations. The porosity of porous alumina samples grown under different conditions is determined by the pore-filling method and scanning electron microscopy. The effect of the current density, temperature and duration

Alexander Zahariev; Ivan Kanazirski; Assen Girginov

2008-01-01

111

New insight of amino acid-based dialysis solutions  

Microsoft Academic Search

Malnutrition is a major complication of peritoneal dialysis (PD) and is associated with increased morbidity and mortality. Daily losses of proteins and amino acids (AAs) into dialysate contribute to this problem. Previous metabolic balance study demonstrated that treatment with 1.1% AA-based dialysis solution is safe and may improve protein malnutrition in continuous ambulatory peritoneal dialysis (CAPD) patients ingesting low protein

M S Park; S R Choi; Y S Song; S Y Yoon; S Y Lee; D S Han

2006-01-01

112

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

113

Kinetics of reduction of hexavalent neptunium by nitrous acid in solutions of nitric acid  

Microsoft Academic Search

Abstact  Nitrous acid is a key redox controlling factor, affecting the speciation of neptunium in the reprocessing of used nuclear\\u000a fuel by solvent extraction. The kinetics of the reduction of neptunium(VI) by nitrous acid in solutions of nitric acid was\\u000a investigated spectrophotometrically by the method of initial rates. The reaction is of first order with respect to Np(VI)\\u000a while the order

Martin PrecekAlena Paulenova; Alena Paulenova

2010-01-01

114

Extraction of Lanthanides with Diamides of Dipicolinic Acid from Nitric Acid Solutions. I  

Microsoft Academic Search

Three ortho-, meta-, and para-derivates of ethyl(tolyl)diamides of dipicolinic acid were synthesized and tested on their extraction performance from nitric acids solutions. Extraction of americium and lanthanides (Ln) by these compounds as a function of nitric acid concentration was studied. Distribution ratios of studied metals were determined using ICP-OES method and radiotracer Am. Am\\/Ln separation differs among studied diamides, and

A. Paulenova; M. Yu. Alyapyshev; V. A. Babain; R. S. Herbst; J. D. Law

2008-01-01

115

Sorption of cobalt on activated carbons from aqueous solutions  

SciTech Connect

The efficiencies of 15 commercially available activated carbons were tested for the separation of trace cobalt ({sup 60}Co) in buffer solutions at pH 5.0, 6.7, and 9.1. On the basis of the results four carbon products, Diahope-006, Eurocarb TN5, Hydraffin DG47, and Norit ROW Supra, were selected for further study. These carbons represented varying (low, medium and high) cobalt removal efficiencies and were prepared of three typical raw materials: peat, coconut shell, or coal. Study was made of the effects on sorption efficiencies of factors of interest in metal/radionuclide-bearing waste effluents. These factors were pH, sodium ions, borate, and citrate.

Paajanen, A.; Lehto, J.; Santapakka, T.; Morneau, J.P. [Univ. of Helsinki (Finland)

1997-01-01

116

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

117

Regiocontrolled intramolecular cyclizations of carboxylic acids to carbon-carbon triple bonds promoted by acid or base catalyst.  

PubMed

We systematically investigated, for the first time, the relationship between regioselectivity and acid/base effects in the cyclization reactions between carboxylic acids and carbon-carbon triple bonds. We found novel acid- and base-promoted cyclizations to selectively give isocoumarin or pyran-2(2H)-one and phthalide or furan-2(5H)-one skeletons, respectively, and established a catalytic version of regioselective heterocyclic ring synthesis. Density functional theory calculations and application to a short route to thunberginol A were also described. [reaction: see text]. PMID:17107061

Uchiyama, Masanobu; Ozawa, Hiroki; Takuma, Kazuya; Matsumoto, Yotaro; Yonehara, Mitsuhiro; Hiroya, Kou; Sakamoto, Takao

2006-11-23

118

Electrochemical behaviour of lead electrode in sulfuric acid solution containing citric acid  

NASA Astrophysics Data System (ADS)

The electrochemical behaviour of a lead electrode as the positive electrode (in PbO 2 form) and the negative electrode of a lead/acid battery in sulfuric acid solution containing different concentrations of citric acid has been studied by cyclic voltammetry. For the behaviour of lead as a positive electrode, a new layer of PbO 2 is formed in the presence of citric acid. It is difficult for this layer to be reduced and, therefore, the conductivity between the positive grid and the positive active material will be greater than that in pure sulfuric acid solution. The peak currents attributed to the formation and reduction of PbO 2, and to the evolution of oxygen, increase with the concentration of citric acid. The limits of the effects are reached at about 2 g/1 citric acid in 4.5 M H 2SO 4. For the behaviour of lead as a negative electrode, the peak currents attributed to the oxidation of lead to PbSO 4 and to the evolution of hydrogen gas also increase with the concentration of citric acid. In 4.5 M H 2SO 4, the limits of these effects are reached at a citric acid concentration of 2 and 3 g/1, respectively. The observed behaviour is caused by the adsorption of citric acid on the PbO 2, lead and PbSO 4 surfaces.

Wei, Guo-Lin; Wang, Jia-Rong

119

The Effect Of Viscoelastic Surfactants Used In Carbonate Matrix Acidizing On Wettability  

E-print Network

Carbonate reservoirs are heterogeneous; therefore, proper acid placement/diversion is required to make matrix acid treatments effective. Viscoelastic surfactants (VES) are used as diverting agents in carbonate matrix acidizing. However...

Adejare, Oladapo

2012-07-16

120

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

121

Effects of peroxyacetic acid, acidified sodium chlorite or lactic acid solutions on the microflora of chilled beef carcasses  

Microsoft Academic Search

The effects of solutions of 0.02% peroxyacetic acid, acidified 0.16% sodium chlorite, 2% lactic acid and 4% lactic acid on the natural flora of the distal surfaces of pieces of brisket, from chilled beef carcass quarters delivered from two slaughtering plants to a processing plant, were investigated. Peroxyacetic acid and acidified sodium chlorite solutions had little effect on the numbers

C. O Gill; M Badoni

2004-01-01

122

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

SciTech Connect

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

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

1985-01-01

123

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

124

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

Microsoft Academic Search

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

Amporn Sane; Jumras Limtrakul

125

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

126

The electrochemical behaviour of silver sulphide in sulphuric acid solutions  

Microsoft Academic Search

The electrochemical behaviour of synthetic silver sulphide (acanthite) electrodes in sulphuric acid solutions has been investigated using several techniques including cyclic voltammetry, anodic polarization and constant potential experiments. Under anodic polarization the dissolution has been attributed to the reaction Ag2S=2Ag++S+2e which occurs in two sequential, single electron transfer steps. A kinetic model for this stepwise anodic dissolution process at lower

D. W. Price; G. W. Warren; B. Drouven

1986-01-01

127

Corrosion of silicon nitride in sulphuric acid aqueous solution  

Microsoft Academic Search

The corrosion of a hot pressed silicon nitride (produced with the addition of 3 wt.% Y2O3+3 wt.% La2O3 as sintering aids) in 1.8 M sulphuric acid aqueous solution was studied in the temperature range of 25–70°C for times up to 400 h. No reaction products were detected on the exposed surfaces. The corrosion follows a progressive chemical dissolution of the

F Monteverde; C Mingazzini; M Giorgi; A Bellosi

2001-01-01

128

Surface tensions of solutions containing dicarboxylic acid mixtures  

NASA Astrophysics Data System (ADS)

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

Lee, Jae Young; Hildemann, Lynn M.

2014-06-01

129

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

130

The Application of Electrodialysis to Desalting an Amino Acid Solution  

NASA Astrophysics Data System (ADS)

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

García-García, Vicente; Montiel, Vicente; González-García, José; Expósito, Eduardo; Iniesta, Jesús; Bonete, Pedro; Inglés, Marina

2000-11-01

131

Solution-processed soldering of carbon nanotubes for flexible electronics.  

PubMed

We report a simple lithography-free, solution-based method of soldering of carbon nanotubes with Ohmic contacts, by taking specific examples of multi-walled carbon nanotubes (MWNTs). This is achieved by self-assembling a monolayer of soldering precursor, Pd(2+) anchored to 1,10 decanedithiol, onto which MWNTs could be aligned across the gap electrodes via solvent evaporation. The nanosoldering was realized by thermal/electrical activation or by both in sequence. Electrical activation and the following step of washing ensure selective retention of MWNTs spanning across the gap electrodes. The soldered joints were robust enough to sustain strain caused during the bending of flexible substrates as well as during ultrasonication. The estimated temperature generated at the MWNT-Au interface using an electro-thermal model is ?150?°C, suggesting Joule heating as the primary mechanism of electrical activation. Further, the specific contact resistance is estimated from the transmission line model. PMID:23358531

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

2013-02-22

132

carbonate solid solution at high pressures up to 55 GPa  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

133

Physics Division ESH Bulletin 2007-01 Working with Hydrofluoric Acid Solutions  

E-print Network

Physics Division ESH Bulletin 2007-01 Working with Hydrofluoric Acid Solutions The Physics Division has a procedure, Using Hydrofluoric Acid, that must be followed when working with this acid with hydrofluoric acid. Definition: Hydrofluoric acid (HF) is a very corrosive solution of hydrogen fluoride

134

Photosynthesis In Elodea canadensis Michx: Four-Carbon Acid Synthesis.  

PubMed

Experiments to determine the early labeled photosynthetic products in Elodea canadensis show that after 2 seconds of exposure to NaH(14)CO(3), 45% of the (14)C incorporated is located in malate and aspartate. Phosphoglyceric acid and sugars account for 27% of the label during similar exposures. Equivalent amounts of organic acids and C(3) cycle products are present after 8 seconds. Four-carbon acids remain relatively unchanged throughout the first 45 seconds of exposure, while sugars increase in a linear fashion. Enzyme assays indicate that ribulose diphosphate and phosphoenolpyruvate carboxylase enzymes are present in a ratio of approximately 2:1. It appears that E. canadensis is able to synthesize significant amounts of four-carbon acids via beta-carboxylation and this may play a role in maintaining a pH favorable for carboxylation in aquatic plants. PMID:16660008

Degroote, D; Kennedy, R A

1977-06-01

135

Energetic changes in the surface of activated carbons and relationship with Ni(II) adsorption from aqueous solution  

NASA Astrophysics Data System (ADS)

This study investigated Ni(II) ion adsorption from aqueous solution on activated carbons obtained by chemically modifying the surface with the oxidizing agents nitric acid and hydrogen peroxide (CAGoxP and CAGoxN, respectively). The activated carbons were characterized by total acidity and basicity, pH at the point of charge zero determination and IR spectroscopy. Textural parameters such as the BET area and pore volumes were evaluated by gas adsorption. The BET area of the materials was between 816 and 876 m2 g-1. Additionally, the immersion enthalpies of the activated carbons in water and benzene were determined. The experimental results on adsorption in solution were adjusted to the Langmuir and Freundlich models, obtaining values for the monolayer capacity between 29.68 and 50.97 mg g-1, which indicates that the adsorption capacity depends largely on solid surface chemistry.

Rodríguez-Estupiñan, Paola; Giraldo, Liliana; Moreno-Piraján, Juan Carlos

2013-12-01

136

Vanadium(III) Complexes with Picolinic Acid and Dipicolinic Acid in Aqueous Solution  

Microsoft Academic Search

The complex species formed in aqueous solution (25 ?C, I = 3.0 mol-dm?3 KCl ionic medium) between V3+ cation and the ligands: picolinic acid (Hpic, HL) and dipicolinic acid (H2dipic, H2L), have been studied potentiometrically and by spectrophotometric measurements. The application of the least-squares computer program LETAGROP to the experimental emf (H) data, taking into account the hydrolytic species of

Vito Lubes

2005-01-01

137

Ternary Complex Formation between Vanadium(III), Dipicolinic Acid and Picolinic Acid in Aqueous Solution  

Microsoft Academic Search

Ternary complex species formed by the V3+ cation with the picolinic acid (Hpic, HL) and dipicolinic acid (H2dipic, H2L) ligands in aqueous solutions have been studied potentiometrically (25?°C, I=3.0 mol?dm?3 KCl ionic medium) and by spectrophotometric measurements. Application of the least-squares computer program LETAGROP to the\\u000a experimental emf (H) data, taking into account the hydrolytic V(III) species and the binary V3+–picolinic

Giuseppe Lubes; Mildred Rodríguez; Vito Lubes

2010-01-01

138

Removal of organic contaminants from aqueous solution by cattle manure compost (CMC) derived activated carbons  

NASA Astrophysics Data System (ADS)

The activated carbons (ACs) prepared from cattle manure compost (CMC) with various pore structure and surface chemistry were used to remove phenol and methylene blue (MB) from aqueous solutions. The adsorption equilibrium and kinetics of two organic contaminants onto the ACs were investigated and the schematic models for the adsorptive processes were proposed. The result shows that the removal of functional groups from ACs surface leads to decreasing both rate constants for phenol and MB adsorption. It also causes the decrement of MB adsorption capacity. However, the decrease of surface functional groups was found to result in the increase of phenol adsorption capacity. In our schematic model for adsorptive processes, the presence of acidic functional groups on the surface of carbon is assumed to act as channels for diffusion of adsorbate molecules onto small pores, therefore, promotes the adsorption rate of both phenol and MB. In phenol solution, water molecules firstly adsorb on surface oxygen groups by H-bonding and subsequently form water clusters, which cause partial blockage of the micropores, deduce electrons from the ?-electron system of the carbon basal planes, hence, impede or prevent phenol adsorption. On the contrary, in MB solution, the oxygen groups prefer to combine with MB + cations than water molecules, which lead to the increase of MB adsorption capacity.

Qian, Qingrong; Chen, Qinghua; Machida, Motoi; Tatsumoto, Hideki; Mochidzuki, Kazuhiro; Sakoda, Akiyoshi

2009-04-01

139

Carbon quantum dots with photo-generated proton property as efficient visible light controlled acid catalyst  

NASA Astrophysics Data System (ADS)

Developing light-driven acid catalyst will be very meaningful for the controlled-acid catalytic processes towards a green chemical industry. Here, based on scanning electrochemical microscopy (SECM) and ?pH testing, we demonstrate that the 5-10 nm carbon quantum dots (CQDs) synthesized by electrochemical ablation of graphite have strong light-induced proton properties under visible light in solution, which can be used as an acid catalyst. The 5-10 nm CQDs' catalytic activity is strongly dependent on the illumination intensity and the temperature of the reaction system. As an effective visible light driven and controlled acid-catalyst, 5-10 nm CQDs can catalyze a series of organic reactions (esterification, Beckmann rearrangement and aldol condensation) with high conversion (34.7-46.2%, respectively) in water solution under visible light, while the 1-4 nm CQDs and 10-2000 nm graphite do not have such excellent catalytic activity. The use of 5-10 nm CQDs as a light responsive and controllable photocatalyst is truly a novel application of carbon-based nanomaterials, which may significantly push research in the current catalytic industry, environmental pollution and energy issues.Developing light-driven acid catalyst will be very meaningful for the controlled-acid catalytic processes towards a green chemical industry. Here, based on scanning electrochemical microscopy (SECM) and ?pH testing, we demonstrate that the 5-10 nm carbon quantum dots (CQDs) synthesized by electrochemical ablation of graphite have strong light-induced proton properties under visible light in solution, which can be used as an acid catalyst. The 5-10 nm CQDs' catalytic activity is strongly dependent on the illumination intensity and the temperature of the reaction system. As an effective visible light driven and controlled acid-catalyst, 5-10 nm CQDs can catalyze a series of organic reactions (esterification, Beckmann rearrangement and aldol condensation) with high conversion (34.7-46.2%, respectively) in water solution under visible light, while the 1-4 nm CQDs and 10-2000 nm graphite do not have such excellent catalytic activity. The use of 5-10 nm CQDs as a light responsive and controllable photocatalyst is truly a novel application of carbon-based nanomaterials, which may significantly push research in the current catalytic industry, environmental pollution and energy issues. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03996j

Li, Haitao; Liu, Ruihua; Kong, Weiqian; Liu, Juan; Liu, Yang; Zhou, Lei; Zhang, Xing; Lee, Shuit-Tong; Kang, Zhenhui

2013-12-01

140

Efficacy of Carbonic Acid as an Anesthetic for Rainbow Trout  

Microsoft Academic Search

We determined effective concentration ranges for carbonic acid as an anesthetic for rainbow trout Oncorhynchus mykiss across a wide range of water temperatures and alkalinities. Effective concentrations were based on criteria for induction time (<3 min), recovery time (<10 min), and 72-h survival (100%). Induction time decreased and recovery time increased with increasing concentration. Mortalities were associated with high concentrations

Kevin R. Gelwicks; David J. Zafft; Joe P. Bobbitt

1998-01-01

141

Some amino acids as corrosion inhibitors for copper in nitric acid solution  

Microsoft Academic Search

The inhibition effect of five amino acids (AA) on the corrosion of copper in molar nitric solution was studied by using weight loss and electrochemical polarization measurements. Valine (Val) and Glycine (Gly) accelerate the corrosion process; but Arginine (Arg), Lysine (Lys) and Cysteine (Cys) inhibit the corrosion phenomenon. Cysteine is the best inhibitor. Its efficiency increases with the concentration to

K. Barouni; L. Bazzi; R. Salghi; M. Mihit; B. Hammouti; A. Albourine; S. El Issami

2008-01-01

142

Acetic Acid bacteria: physiology and carbon sources oxidation.  

PubMed

Acetic acid bacteria (AAB) are obligately aerobic bacteria within the family Acetobacteraceae, widespread in sugary, acidic and alcoholic niches. They are known for their ability to partially oxidise a variety of carbohydrates and to release the corresponding metabolites (aldehydes, ketones and organic acids) into the media. Since a long time they are used to perform specific oxidation reactions through processes called "oxidative fermentations", especially in vinegar production. In the last decades physiology of AAB have been widely studied because of their role in food production, where they act as beneficial or spoiling organisms, and in biotechnological industry, where their oxidation machinery is exploited to produce a number of compounds such as l-ascorbic acid, dihydroxyacetone, gluconic acid and cellulose. The present review aims to provide an overview of AAB physiology focusing carbon sources oxidation and main products of their metabolism. PMID:24426139

Mamlouk, Dhouha; Gullo, Maria

2013-12-01

143

Polyaniline Doped with Sulphosalicylic, Salicylic and Citric Acid in Solution and Solid-state  

Microsoft Academic Search

Considerable progress has been made in characterizing and understanding the properties of polyaniline doped with some protonic acids . In this work polyaniline was synthesized by chemical method in the presence of HCI, then undoped polyanilinewas obtained with NH3solution. The undoped polyaniline was doped with the protonic acid such as sulphosalicylic acid, salicylic acid and citric acid. The protonic acids

Farideh Ghadimi; Kazem Dindar Safa; Bakhshali Massoumi

144

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

145

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

146

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

147

Amine extraction of chromium(VI) from aqueous acidic solutions  

Microsoft Academic Search

Extraction of chromium (Cr(VI)) from the aqueous acidic solution into a co-existing organic phase containing Alamine 336 (C8?C10 tertiary amine mixture) and diluent (xylene) was studied at isothermal condition (298.2 K). The distribution ratio was measured for two initial aqueous concentrations of Cr(VI), i.e. 0.019 mol\\/dm3 (1 mg\\/ml) and 0.192 mol\\/dm3 (10 mg\\/ml) against various molarities of the aqueous phase

Aynur Senol

2004-01-01

148

Protactinium Extraction from Mixed Mineral Acid Solutions. Separation Methods for Pa, Nb, and Zr  

Microsoft Academic Search

Protactinium is highly extracted by tetraphenylarsonium chloride from hydrochloric acid solutions, but niobium and zirconium are extracted as well. The three elements have rather low extractabilities from hydrobromic acid solutions and sulfuric acid solutions. In mixtures of (HCl + H2SO4) or (HBr + H2SO4), protactinium indicates high distribution coefficients, while niobium and zirconium have again rather low or negligible extractabilities.

N. Souka; R. Shabana; C. Girgis

1976-01-01

149

Adsorption of fluoranthene in surfactant solution on activated carbon: equilibrium, thermodynamic, kinetic studies.  

PubMed

Adsorption of fluoranthene (FLA) in surfactant solution on activated carbon (AC) was investigated. Isotherm, thermodynamic, and kinetic attributes of FLA adsorption in the presence of the surfactant on AC were studied. Effects of AC dosage, initial concentration of TX100, initial concentration of FLA, and addition of fulvic acid on adsorption were studied. The experimental data of both TX100 and FLA fitted the Langmuir isotherm model and the pseudo-second-order kinetic model well. Positive enthalpy showed that adsorption of FLA on AC was endothermic. The efficiency of selective FLA removal generally increased with increasing initial surfactant concentration and decreasing fulvic acid concentration. The surface chemistry of AC may determine the removal of polycyclic aromatic hydrocarbons. The adsorption process may be controlled by the hydrophobic interaction between AC and the adsorbate. The microwave irradiation of AC may be a feasible method to reduce the cost of AC through its regeneration. PMID:23979852

Liu, Jianfei; Chen, Jiajun; Jiang, Lin; Wang, Xingwei

2014-02-01

150

The use of sulphuric acid-carbonization products of sugar beet pulp in Cr(VI) removal  

Microsoft Academic Search

A carbon rich adsorbent prepared from the reaction of sugar beet pulp with sulphuric acid and gas formed during carbonization process have been studied for Cr(VI) removal from aqueous solutions. The SO2 rich gas was shown to be an excellent Cr(VI) reductant. The equilibrium and kinetic studies were conducted by using the carbonaceous adsorbent derived from sugar beet pulp. The

H. Soner Altundogan; Nurdan Bahar; Buket Mujde; Fikret Tumen

2007-01-01

151

Infrared optical constants of H2O ice, amorphous nitric acid solutions, and nitric acid hydrates  

NASA Technical Reports Server (NTRS)

We determined the infrared optical constants of nitric acid trihydrate, nitric acid dihydrate, nitric acid monohydrate, and solid amorphous nitric acid solutions which crystallize to form these hydrates. We have also found the infrared optical constants of H2O ice. We measured the transmission of infrared light throught thin films of varying thickness over the frequency range from about 7000 to 500/cm at temperatures below 200 K. We developed a theory for the transmission of light through a substrate that has thin films on both sides. We used an iterative Kramers-Kronig technique to determine the optical constants which gave the best match between measured transmission spectra and those calculated for a variety of films of different thickness. These optical constants should be useful for calculations of the infrared spectrum of polar stratospheric clouds.

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

1994-01-01

152

Dissolution of hematite in acidic oxalate solutions: the effect of ferrous ions addition  

Microsoft Academic Search

Studies on the dissolution of hematite in acidic oxalate solutions have shown that there is a strong relationship between dissolution rates and ferrous ion generation in the solution. The effects of temperature, pH of the solution, oxalate and ferrous ions concentration on the dissolution of hematite in acidic oxalate solutions containing ferrous ions were studied. It was found that the

D. Panias; M. Taxiarchou; I. Douni; I. Paspaliaris; A. Kontopoulos

1996-01-01

153

Nanomechanical Behavior of Human Molars Soaked in Slight Acid Solutions  

NASA Astrophysics Data System (ADS)

This paper studied the mechanical and chemical properties of hydroxyl apatite (HA) crystal structure in the teeth when human molars were soaked in slight acid solution. First, we soaked the ground and polished molars respectively in the liquor of 30 wt.% H2CO3 and the liquor of 30 wt.% H2O2 for 10, 20, or 60 minutes. Next, we used a nanoindenter to measure the hardness and Young's modulus. Finally, we used a scanning electron microscope (SEM) coupled with energy dispersive spectroscopy (EDS) to analyze the variation of Ca, P and Na in teeth, a high resolution transmitting electron microscope (HRTEM) to observe the arrangement of crystallization phase of HA, and X-ray diffraction (XRD) to analyze the crystallinity of the hexagonal phase of HA. The results showed that the demineralization phenomenon of the calcium-phosphorous compound in teeth made the teeth reduce sharply in hardness and Young's modulus after they were soaked in the two slight acid solutions for 10 minutes, but the re-mineralization phenomenon made the hardness and Young's modulus ascend gradually when the time lasted longer. With the same period of time, the teeth soaked in H2CO3 were lower in the hardness and Young's modulus than that in H2O2.

Fang, Te-Hua; Chang, Win-Jin; Kang, Shao-Hui; Chu, Chia-Chun

154

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

155

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

156

Adaptation of sweeteners in water and in tannic acid solutions.  

PubMed

Repeated exposure to a tastant often leads to a decrease in magnitude of the perceived intensity; this phenomenon is termed adaptation. The purpose of this study was to determine the degree of adaptation of the sweet response for a variety of sweeteners in water and in the presence of two levels of tannic acid. Sweetness intensity ratings were given by a trained panel for 14 sweeteners: three sugars (fructose, glucose, sucrose), two polyhydric alcohols (mannitol, sorbitol), two terpenoid glycosides (rebaudioside-A, stevioside), two dipeptide derivatives (alitame, aspartame), one sulfamate (sodium cyclamate), one protein (thaumatin), two N-sulfonyl amides (acesulfame-K, sodium saccharin), and one dihydrochalcone (neohesperidin dihydrochalcone). Panelists were given four isointense concentrations of each sweetener by itself and in the presence of two concentrations of tannic acid. Each sweetener concentration was tasted and rated four consecutive times with a 30 s interval between each taste and a 2 min interval between each concentration. Within a taste session, a series of concentrations of a given sweetener was presented in ascending order of magnitude. Adaptation was calculated as the decrease in intensity from the first to the fourth sample. The greatest adaptation in water solutions was found for acesulfame-K, Na saccharin, rebaudioside-A, and stevioside. This was followed by the dipeptide sweeteners, alitame and aspartame. The least adaptation occurred with the sugars, polyhydric alcohols, and neohesperidin dihydrochalcone. Adaptation was greater in tannic acid solutions than in water for six sweeteners. Adaptation of sweet taste may result from the desensitization of sweetener receptors analogous to the homologous desensitization found in the beta adrenergic system. PMID:8190776

Schiffman, S S; Pecore, S D; Booth, B J; Losee, M L; Carr, B T; Sattely-Miller, E; Graham, B G; Warwick, Z S

1994-03-01

157

Carbon footprint optimization: game theoretic problems and solutions  

Microsoft Academic Search

We discuss four problems that we have identified under the umbrella of carbon economics problems: carbon credit allocation (CCA), carbon credit buying (CCB), carbon credit selling (CCS), and carbon credit exchange (CCE). Because of the strategic nature of the players involved in these problems, game theory and mechanism design provides a natural way of formulating and solving these problems. We

Deepak Bagchi; Shantanu Biswas; Y. Narahari; P. Suresh; L. Udaya Lakshmi; N. Viswanadham; S. V. Subrahmanya

158

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

159

Radiolysis gases from nitric acid solutions containing HSA and HAN  

SciTech Connect

The concentration of hydrogen (H{sub 2}) in the radiolytically produced off-gas from 2.76-4.25M HNO{sub 3} solutions is greatly reduced by dilution in the presence of HSA (sulfamic acid) and HAN (hydroxylamine nitrate). This dilution continues at a constant rate until the HSA and HAN are exhausted. The generation rate, G(H{sub 2}), was not affected by these two compounds giving a value of 0.201 mol/100 eV for 2.77M NO{sub 3}{sup -}. The other radiolysis gases produced are O{sub 2}, N{sub 2}, and N{sub 2}O, the later two due to reduction of nitrous acid by HSA and HAN respectively. At high nitrate concentrations, >2.8M, and in the presence of HAN the total off-gas production rate is greatly reduced. This may be due to reaction of nitrate and HAN to produce oxygen reactive compounds such as HNO which can react with dissolved O{sub 2} to regenerate nitrate directly, by-passing nitrous acid. The initial reduction in the off-gas rate is lost after destruction of the HAN.

Smith, J.R. [Westinghouse Svannah River Company, Aiken, SC (United States)

1995-12-31

160

Polyelectrolyte and carbon nanotube multilayers made from ionic liquid solutions.  

PubMed

The inevitable contact of substrates with water during the traditional practice of layer-by-layer assembly (LBL) creates problems for multiple potential applications of LBL films in electronics. To resolve this issue, we demonstrate here the possibility of a LBL process using ionic liquids (ILs), which potentially eliminates corrosion and hydration processes related to aqueous media and opens additional possibilities in structural control of LBL films. ILs are also considered to be one of the best "green" processing solvents, and hence, are advantageous in respect to traditional organic solvents. Poly(ethyleneimine) (PEI) and poly(sodium styrenesulfonate) (PSS) were dispersed in a hydrophilic IL and successfully deposited in the LBL fashion. To produce electroactive thin films with significance to electronics, a similar process was realized for PSS-modified single-walled carbon nanotubes (SWNT-PSS) and poly(vinyl alcohol) (PVA). Characterization of the coating using standard spectroscopy and microscopy techniques typical of the multilayer field indicated that there are both similarities and differences in the structure and properties of LBL films build from ILs and aqueous solutions. The films exhibited electrical conductivity of 10(2) S m(-1) with transparency as high as 98% for visible light, which is comparable to similar parameters for many carbon nanotube and graphene films prepared by both aqueous LBL and other methods. PMID:20931147

Nakashima, Takuya; Zhu, Jian; Qin, Ming; Ho, Szushen; Kotov, Nicholas A

2010-10-01

161

Solubility and dissolution rate of silica in acid fluoride solutions  

NASA Astrophysics Data System (ADS)

We performed 57 batch reactor experiments in acidic fluoride solutions to measure the dissolution rate of quartz. These rate data along with rate data from published studies were fit using multiple linear regression to produce the following non-unique rate law for quartz r(mol/m2s)=10-4.53eaHF1.18aH-0.39 where 10 -5.13 < aHF < 10 1.60, -0.28 < pH < 7.18, and 298 < T < 373 K. Similarly, 97 amorphous silica dissolution rate data from published studies were fit by multiple linear regression to produce the following non-unique rate law for amorphous silica ras(mol/m2s)=100.48eaHF1.50aH-0.46 where 10 -2.37 < aHF < 10 1.61, -0.32 < pH < 4.76 and 296 < T < 343 K. Regression of the rates versus other combinations of solution species, e.g. HF2- + H +, F - + H +, HF + HF2-, HF + F -, or HF2- + F -, produced equally good fits. Any of these rate laws can be interpreted to mean that the rate-determining step for silica dissolution in fluoride solutions involves a coordinated attack of a Lewis acid, on the bridging O atom and a Lewis base on the Si atom. This allows a redistribution of electrons from the Si-O bond to form a O-H group and a Si-FH group.

Mitra, Arijit; Rimstidt, J. Donald

2009-12-01

162

Corrosion inhibition of mild steel in sulfamic acid solution by S-containing amino acids  

Microsoft Academic Search

Rp, potentiodynamic polarization curves and EIS techniques were applied to study the effect of five S-containing amino acids\\u000a on the corrosion of mild steel in 5% sulfamic acid solution at 40 °C. The compounds are effective inhibitors and the inhibition\\u000a efficiency follow the order: N-acetylcysteine (ACC) > cysteine (RSH) > S-benzylcysteine (BzC) > cystine (RSSR) ? methionine (CH3SR). The inhibitors affect the anodic dissolution of steel by blocking the

M. S. Morad

2008-01-01

163

The extraction of actinides from nitric acid solutions with diamides of dipicolinic acid  

NASA Astrophysics Data System (ADS)

Diamides of dipicolinic acid (N,N'-diethyl-N,N'-ditolyl-dipicolinamide, EtTDPA) were synthesized and evaluated for their extraction capability for actinides. In this work the extractions of neptunium(V), protactinium(V), and thorium(IV) with EtTDPA in a polar fluorinated diluent from nitric acid were investigated. EtTDPA shows a high affinity for Th(IV) even at millimolar concentrations. Np(V) and Pa(V) are both reasonably extractable with EtTDPA; however, near saturated solutions are required to achieve appreciable distribution ratios. A comparison with previously published actinide extraction data is given.

Lapka, Joseph L.; Paulenova, Alena; Alyapyshev, Mikhail Yu; Babain, Vasiliy A.; Law, Jack D.; Herbst, R. Scott

2010-03-01

164

The catalytic effect of boric acid on polyacrylonitrile-based carbon fibers and the thermal conductivity of carbon\\/carbon composites produced from them  

Microsoft Academic Search

The catalytic effect of boric acid on the graphitization and surface structure of polyacrylonitrile-based carbon fibers was investigated by dipping fibers in boric acid before heating at 2500°C. The thermal conductivity of carbon\\/carbon composites produced from the modified carbon performs by chemical vapor infiltration was also studied. The results show that the treatment by boric acid has a catalytic-graphitization effect

Jie Chen; Xiang Xiong; Peng Xiao; Hong-Bo Zhang

2010-01-01

165

Amino acid adsorption on single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We investigate and discuss the adsorption of a few amino acids on (3,3) carbon nanotubes and on graphite sheets through calculations within density functional theory. Results show weak binding of the biomolecules on both substrates, but through generally favourable adsorption pathways. Zwitterion adsorption through the charged amine and carboxylate groups are bound stronger to the nanotube surface in comparison to their nonionic counterparts, as well as on histidine, phenylalanine, and cysteine side chain groups fixed in specific orientations. Binding strengths on graphite suggest dissimilar trends for amino acid interactions with increasing nanotube diameter.

Roman, T.; Diño, W. A.; Nakanishi, H.; Kasai, H.

2006-04-01

166

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

USGS Publications Warehouse

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

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

1993-01-01

167

Calcium carbonate precipitation along solution-solution interfaces in porous media  

NASA Astrophysics Data System (ADS)

Biogeochemical processes, such as mineral precipitation, microbial growth, or filtration of biological or mineral colloids, can lead to localized solid deposition and changes in flow and permeability in porous media. The coupling between these processes and flow depends on instantaneous flow paths, dispersive or diffusional mixing, localized flow velocities and the kinetics of the biogeochemical reactions themselves. We have conducted experiments to help predict the outcome of this coupling and how solids are, or could intentionally be, spatially distributed. Initial experiments have used calcium carbonate precipitation in packed sand as a model system that has conceptual parallels to other biological and chemical processes that generate mass in porous media. (A second experiment involves precipitate promotion via in situ urea hydrolysis.) Parallel flowstreams of carbonate and calcium produce a mixing zone at the solution-solution interface by diffusion and dispersion. The flowstreams have been created in both an annular geometry in a column, and in a 2-D flow cell. X-ray tomography and color contrast methods are used to visualize the deposition process at the solution-solution interface, and tracer analysis is used to analyze the systems for the evolution of heterogeneities and changes in permeability. For the 2-D flow cell, continuum-scale modeling (using STORM, STOMP and Hydrogeochem codes) is used to simulate the reactant concentration profiles along the interfacial mixing zone behavior prior to precipitation, a saturation index profile, the changes in permeability that are induced as a consequence of precipitate deposition along the interface, and the subsequent changes in how reactive solutes mix along the interface. The modeling goal is to link the continuum-scale simulations to more detailed pore-scale simulations that are capable of representing the coupling between solute concentrations, nucleation kinetics, precipitate growth kinetics, how precipitates fill pore spaces and how flow paths changes with time. Smoothed Particle Hydrodynamics are being used for simulations at the pore scale. The intention is to experimentally observe, and ultimately to control, how precipitates can be distributed in porous matrices.

Redden, G. D.; Fang, Y.; Scheibe, T.; Tartakovsky, A.; Fox, D. T.; White, T. A.; Fujita, Y.; Delwiche, M.

2005-12-01

168

Porosity and surface area of monolithic carbon aerogels prepared using alkaline carbonates and organic acids as polymerization catalysts  

Microsoft Academic Search

Carbon aerogels were prepared by polymerization of a resorcinol–formaldehyde mixture using different polymerization catalysts such as: sodium or potassium carbonates, oxalic acid or para-toluenesulfonic acid. The carbon aerogel obtained with this last acid was further CO2-activated to 8.5% and 22% burn-off. All samples were characterized by N2 and CO2 adsorption at ?196 and 0°C, respectively, and by mercury porosimetry, scanning

D. Fairén-Jiménez; F. Carrasco-Marín; C. Moreno-Castilla

2006-01-01

169

Effects of Lime and Carbonate of Lime on Acid Phosphate.  

E-print Network

phosphate. AcL 0.1 grzm calcium carbonate mixed with the acid phosphate be- fore putting in the soil. One gram sulphate of potash and 1 gram ammonium nitrate added to all pots. Corn pIanted May S, harvested Julv 10-14, 1911. Four stalks. One gram... .................. ' 1,ah. No. 3653 3653 .0004 0015 0 .0433 .0113 4604 1 -AC corn. .................... ........................... 2-AC. 3-ACL ........................... ........................... 4-ACL I-AC sorghum. ........... : .... 2-AC...

Fraps, G. S. (George Stronach)

1917-01-01

170

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

Microsoft Academic Search

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

Andrzej Wery?ski; Jacek Waniewski; Tao Wang; Björn Anderstam; Bengt Lindholm; Jonas Bergström

2001-01-01

171

Conductivity Studies on Aqueous Solutions of Stereoisomers of Tartaric Acids and Tartrates. Part III. Acidic Tartrates  

Microsoft Academic Search

Conductivity measurements on aqueous solutions of sodium hydrogen tartrate and potassium hydrogen tartrate were performed in the temperature range 5–35°C. By including the dissociation equilibria, the experimental conductivities of the acidic salts can be well described using equivalent limiting conductivities of the bitartrate anion ?8(HTar-) and the tartrate anion ?8 (1\\/2 Tar2-) when applying the Quint and Viallard equations for

Marija Bešter-Roga?; Roland Neueder; Josef Barthel; Alexander Apelblat

1998-01-01

172

Carbon Isotope Ratios in Crassulacean Acid Metabolism Plants  

PubMed Central

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

Szarek, Stan R.; Troughton, John H.

1976-01-01

173

Generation of hydroxyl radical in aqueous solution by microwave energy using activated carbon as catalyst and its potential in removal of persistent organic substances  

Microsoft Academic Search

Salicylic acid (SA, hydroxybenzoic acid) was used as molecular probe to determine hydroxyl radical (OH) in aqueous solutions, where microwave (MW) radiation was involved and activated carbon (AC) existed. Rapid reaction of OH with SA produced a stable fluorescence product, 2,3-dihydroxybenzoic acid (2,3-DHBA) as well as its homologue, 2,5-DHBA, which were determined by HPLC. Dose of AC, air supply, and

Xie Quan; Yaobin Zhang; Shuo Chen; Yazhi Zhao; Fenglin Yang

2007-01-01

174

Radiolysis gases from nitric acid solutions containing HSA and HAN  

SciTech Connect

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

Smith, J.R.

1994-10-28

175

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

176

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

NASA Astrophysics Data System (ADS)

Black carbon (BC) in the Northeast Pacific ultrafiltered dissolved organic matter (UDOM) was found to be surprisingly old with a 14C age of 18,000 +/-3,000 14C years (Ziolkowski and Druffel, 2010) using the Benzene Polycarboxylic Acid (BPCA) method, while BC in sedimentary organic carbon (SOC) was found to be 2,400-12,900 14C years older than non-BC SOC (Masiello and Druffel, 1998) with a different method. Using the dichromate-sulfuric acid oxidation method (Wolbach and Anders, 1989), Masiello and Druffel (1998) estimated that 12-31% of SOC in the Northeast Pacific and the Southern Ocean surface sediments was black carbon (BC). However, the dichromate-sulfuric acid oxidation may over-estimate the concentration of BC, because this method is more biased toward modern (char) material (Currie et al., 2002). Alternatively, the BPCA method isolates aromatic components of BC as benzene rings substituted with carboxylic acid groups, and provides structural information about the BC. Recent modifications to the BPCA method by Ziolkowski and Druffel (2009) involve few biases in quantifying BC in the continuum between char and soot in UDOM. Here we use the BPCA method to determine the concentrations and 14C values of BC in sediments from three sites in the Northeast Pacific Ocean. Constraining the difference between non-BC SOC and BC-SOC using the BPCA method allows for a more precise estimate of how much BC is present in the sediments and its 14C age. Presumably, the intermediate reservoir of BC is oceanic dissolved organic carbon (DOC) and is, in part, responsible for DOC’s great 14C age. These results can be utilized to better constrain the oceanic carbon budget as a possible sink of BC. References: Currie, L. A., Benner Jr., B. A., Kessler, J.D., et al (2002), A critical evaluation of interlaboratory data on total, elemental, and isotopic carbon in the carbonaceous particle reference material, nist srm 1649a, J. Res. Natl. Inst. Stand. Technol., 107, 279-298. Masiello, C., and E. R. Druffel (1988), Black carbon in deep-sea sediments, Science, 280, 1911-1913. Wolbach, W., and E. Anders (1989), Elemental carbon in sediments: Determination and isotopic analysis in presence of kerogen, Geochim. Cosmochim. Acta, 53, 1637-1647. Ziolkowski, L. A., and E. R. Druffel (2010), Aged black carbon identified in marine dissolved organic carbon, J. Geophys. Res., 37, L16601, doi: 10.1029/2010GL043963.

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

2010-12-01

177

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

E-print Network

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

Dong, Kai

2012-10-19

178

Habit modification of calcium carbonate in the presence of malic acid  

NASA Astrophysics Data System (ADS)

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 °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 3 crystal obviously depends on the starting pH. CaCO 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 {1 0 4} 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].

Mao, Zhaofeng; Huang, Jianhua

2007-02-01

179

Polyelectrolyte and carbon nanotube multilayers made from ionic liquid solutions  

NASA Astrophysics Data System (ADS)

The inevitable contact of substrates with water during the traditional practice of layer-by-layer assembly (LBL) creates problems for multiple potential applications of LBL films in electronics. To resolve this issue, we demonstrate here the possibility of a LBL process using ionic liquids (ILs), which potentially eliminates corrosion and hydration processes related to aqueous media and opens additional possibilities in structural control of LBL films. ILs are also considered to be one of the best ``green'' processing solvents, and hence, are advantageous in respect to traditional organic solvents. Poly(ethyleneimine) (PEI) and poly(sodium styrenesulfonate) (PSS) were dispersed in a hydrophilic IL and successfully deposited in the LBL fashion. To produce electroactive thin films with significance to electronics, a similar process was realized for PSS-modified single-walled carbon nanotubes (SWNT-PSS) and poly(vinyl alcohol) (PVA). Characterization of the coating using standard spectroscopy and microscopy techniques typical of the multilayer field indicated that there are both similarities and differences in the structure and properties of LBL films build from ILs and aqueous solutions. The films exhibited electrical conductivity of 102 S m-1 with transparency as high as 98% for visible light, which is comparable to similar parameters for many carbon nanotube and graphene films prepared by both aqueous LBL and other methods.The inevitable contact of substrates with water during the traditional practice of layer-by-layer assembly (LBL) creates problems for multiple potential applications of LBL films in electronics. To resolve this issue, we demonstrate here the possibility of a LBL process using ionic liquids (ILs), which potentially eliminates corrosion and hydration processes related to aqueous media and opens additional possibilities in structural control of LBL films. ILs are also considered to be one of the best ``green'' processing solvents, and hence, are advantageous in respect to traditional organic solvents. Poly(ethyleneimine) (PEI) and poly(sodium styrenesulfonate) (PSS) were dispersed in a hydrophilic IL and successfully deposited in the LBL fashion. To produce electroactive thin films with significance to electronics, a similar process was realized for PSS-modified single-walled carbon nanotubes (SWNT-PSS) and poly(vinyl alcohol) (PVA). Characterization of the coating using standard spectroscopy and microscopy techniques typical of the multilayer field indicated that there are both similarities and differences in the structure and properties of LBL films build from ILs and aqueous solutions. The films exhibited electrical conductivity of 102 S m-1 with transparency as high as 98% for visible light, which is comparable to similar parameters for many carbon nanotube and graphene films prepared by both aqueous LBL and other methods. Electronic supplementary information (ESI) available: Aggregation of PEI and PSS in [EMIm][EtSO4], detailed FTIR data, water-contact angle for (PEI/PSS)10 multilayers, and XPS survey spectra. See DOI: 10.1039/b9nr00333a

Nakashima, Takuya; Zhu, Jian; Qin, Ming; Ho, Szushen; Kotov, Nicholas A.

2010-10-01

180

A mathematical model for calculating the shelf life of ascorbic acid solution under given conditions.  

PubMed

The objective of this paper is to calculate the shelf life of ascorbic acid solution under given conditions by using a mathematical model. An antioxidant, sodium metabisulfite, was added to the ascorbic acid solution. The kinetic parameters of the degradation reaction of ascorbic acid and sodium metabisulfite, were investigated, respectively, and then a mathematical model was developed. According to the mathematical model, the calculated shelf lives of ascorbic acid solution were 783, 835, 873, and 885 days for specifications 2, 5, 10, and 20?mL, respectively. The results showed that the obtained mathematical model can be used to calculate the shelf life of ascorbic acid solution under given conditions. PMID:21812540

Feng, Jiafu; Zhana, Xiancheng; Qiaob, Shiwen; Wub, Chaojun; Xiaob, Longxiang

2012-03-01

181

Removal of fluoride in aqueous solution by adsorption on acid activated water treatment sludge  

NASA Astrophysics Data System (ADS)

This paper reports the use of a pellet of adsorbent made from water treatment sludge (S) and acid activated water treatment sludge (SH) for removal of fluoride in the batch equilibration technique. The influence of pH, adsorbent dosage, temperature and effect of other ions were employed to find out the feasibility of acid activated adsorbent to remove fluoride to the permissible concentration of 0.7 mg/L. The results from the adsorption isotherm followed both Langmuir and Freundlich models and the highest fluoride removal was found for adsorbent activated with acetic acid at 2.0 mol/L. The optimum adsorbent dosage was found at 40 g/L, 0.01 mol/L acid activated adsorbent which was able to adsorb fluoride from 10 down to 0.11 mg/L. The adsorption capacity was decreased when the temperature increased. This revealed that the adsorption of fluoride on SH was exothermic. In the presence of nitrate and carbonate ions in the aqueous solution, fluoride removal efficiency of SH decreased from 94.4% to 86.6% and 90.8%, respectively. However, there is no significant effect in the presence of sulfate and chloride ions.

Vinitnantharat, Soydoa; Kositchaiyong, Sriwilai; Chiarakorn, Siriluk

2010-06-01

182

REMOVAL OF METHYLENE BLUE FROM AQUEOUS SOLUTION BY BIOADSORPTION ONTO Ricinus communis EPICARP ACTIVATED CARBON  

Microsoft Academic Search

Carbon prepared from the epicarp of Ricinus communis was used to remove a textile dye (methylene blue (MB)) from an aqueous solution by adsorption technique under varying conditions of agitation time, dye concentration, adsorbent dose and pH. Adsorption depended on solution pH, dye concentration, carbon concen- tration and contact time. Adsorption followed both Langmuir and Freundlich isotherm models. The adsorption

T. Santhi; S. Manonmani

2009-01-01

183

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

184

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

185

Comparison of three buffer solutions for amino acid derivatization and following analysis by liquid chromatography electrospray mass spectrometry.  

PubMed

For reversed phase separation amino acids are usually derivatized. Several derivatization reactions are carried out at basic pH. In the present work, influence of three basic buffer solutions on liquid chromatography electrospray ionization mass-spectrometric (LC-ESI-MS) analysis of amino acid derivatives was studied. Borate buffer--the most common derivatization buffer--was found to influence ESI ionization up to 23 min retention time. For 9-fluorenylmethylmethoxycarbonyl chloride (Fmoc-Cl derivatization) carbonate buffer should be preferred as it provides higher responses. Hexafluoroisopropanol (HFIP) buffer improves chromatographic peak shapes and responses for diethyl ethoxymethylenemalonate (DEEMM) derivatives. PMID:22673814

Rebane, Riin; Herodes, Koit

2012-07-01

186

Electrocatalytic oxidation of some amino acids on a nickel–curcumin complex modified glassy carbon electrode  

Microsoft Academic Search

This study investigated the electrocatalytic oxidation of alanine, l-arginine, l-phenylalanine, l-lysine and glycine on poly-Ni(II)–curcumin film (curcumin: 1,7-bis [4-hydroxy-3-methoxy phenyl]-1,6-heptadiene-3,5-dione) electrodeposited on a glassy carbon electrode in alkaline solution. The process of oxidation and its kinetics were established by using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy techniques. Voltammetric studies indicated that in the presence of amino acids the anodic

S. Majdi; A. Jabbari; H. Heli; A. A. Moosavi-Movahedi

2007-01-01

187

Release of nitrous Acid and nitrogen dioxide from nitrate photolysis in acidic aqueous solutions.  

PubMed

Nitrate (NO3¯) is an abundant component of aerosols, boundary layer surface films, and surface water. Photolysis of NO3¯ leads to NO2 and HONO, both of which play important roles in tropospheric ozone and OH production. Field and laboratory studies suggest that NO3¯ photochemistry is a more important source of HONO than once thought, although a mechanistic understanding of the variables controlling this process is lacking. We present results of cavity-enhanced absorption spectroscopy measurements of NO2 and HONO emitted during photodegradation of aqueous NO3¯ under acidic conditions. Nitrous acid is formed in higher quantities at pH 2-4 than expected based on consideration of primary photochemical channels alone. Both experimental and modeled results indicate that the additional HONO is not due to enhanced NO3¯ absorption cross sections or effective quantum yields, but rather to secondary reactions of NO2 in solution. We find that NO2 is more efficiently hydrolyzed in solution when it is generated in situ during NO3¯ photolysis than for the heterogeneous system where mass transfer of gaseous NO2 into bulk solution is prohibitively slow. The presence of nonchromophoric OH scavengers that are naturally present in the environment increases HONO production 4-fold, and therefore play an important role in enhancing daytime HONO formation from NO3¯ photochemistry. PMID:25271384

Scharko, Nicole K; Berke, Andrew E; Raff, Jonathan D

2014-10-21

188

Carbonic Anhydrase 5 Regulates Acid-Base Homeostasis in Zebrafish  

PubMed Central

The regulation of the acid-base balance in cells is essential for proper cellular homeostasis. Disturbed acid-base balance directly affects cellular physiology, which often results in various pathological conditions. In every living organism, the protein family of carbonic anhydrases regulate a broad variety of homeostatic processes. Here we describe the identification, mapping and cloning of a zebrafish carbonic anhydrase 5 (ca5) mutation, collapse of fins (cof), which causes initially a collapse of the medial fins followed by necrosis and rapid degeneration of the embryo. These phenotypical characteristics can be mimicked in wild-type embryos by acetazolamide treatment, suggesting that CA5 activity in zebrafish is essential for a proper development. In addition we show that CA5 regulates acid-base balance during embryonic development, since lowering the pH can compensate for the loss of CA5 activity. Identification of selective modulators of CA5 activity could have a major impact on the development of new therapeutics involved in the treatment of a variety of disorders. PMID:22745834

Postel, Ruben; Sonnenberg, Arnoud

2012-01-01

189

Maintenance Carbon Cycle in Crassulacean Acid Metabolism Plant Leaves 1  

PubMed Central

The reciprocal relationship between diurnal changes in organic acid and storage carbohydrate was examined in the leaves of three Crassulacean acid metabolism plants. It was found that depletion of leaf hexoses at night was sufficient to account quantitatively for increase in malate in Ananas comosus but not in Sedum telephium or Kalanchoë daigremontiana. Fructose and to a lesser extent glucose underwent the largest changes. Glucose levels in S. telephium leaves oscillated diurnally but were not reciprocally related to malate fluctuations. Analysis of isolated protoplasts and vacuoles from leaves of A. comosus and S. telephium revealed that vacuoles contain a large percentage (>50%) of the protoplast glucose, fructose and malate, citrate, isocitrate, ascorbate and succinate. Sucrose, a major constituent of intact leaves, was not detectable or was at extremely low levels in protoplasts and vacuoles from both plants. In isolated vacuoles from both A. comosus and S. telephium, hexose levels decreased at night at the same time malate increased. Only in A. comosus, however, could hexose metabolism account for a significant amount of the nocturnal increase in malate. We conclude that, in A. comosus, soluble sugars are part of the daily maintenance carbon cycle and that the vacuole plays a dynamic role in the diurnal carbon assimilation cycle of this Crassulacean acid metabolism plant. PMID:16664005

Kenyon, William H.; Severson, Ray F.; Black, Clanton C.

1985-01-01

190

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

191

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

192

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

NASA Astrophysics Data System (ADS)

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

Lee, Choong-Seop; Yakobson, Boris I.

2004-03-01

193

Recovery of sulphuric acid from waste aqueous solutions containing arsenic by ion exchange  

Microsoft Academic Search

Laboratory scale experiments with anion and cation exchange resins aiming to separate arsenic from highly acidic, sulphate-containing solutions were carried out. The data obtained proved that the use of strong acid cation exchangers in the Na form gives the opportunity for arsenic\\/acid separation in two stages. During the period of sulphuric acid accumulation (a period in which the resin is

V. Nenov; N. Dimitrova; I. Dobrevsky

1997-01-01

194

Sulfuric acid as an agent of carbonate weathering constrained by ? 13C DIC: Examples from Southwest China  

Microsoft Academic Search

Rock weathering by carbonic acid is thought to play an important role in the global carbon cycle because it can geologically sequestrate atmospheric CO2. Current model of carbon cycle evolution usually assumes that carbonic acid is the major weathering agent and that other acids are not important. Here, we use carbon isotopic evidence and water chemistry of springs and rivers

Si-Liang Li; Damien Calmels; Guilin Han; Jérôme Gaillardet; Cong-Qiang Liu

2008-01-01

195

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

196

Viscosity B-coefficients and activation parameters for viscous flow of a solution of heptanedioic acid in aqueous sucrose solution  

Microsoft Academic Search

Viscosity and density data for the system of heptanedioic acid dissolved in aqueous sucrose solution at temperature range from 288.15 to 313.15 K have been measured. The viscosity B-coefficients for heptanedioic acid in aqueous sucrose solution has been calculated. The effect of temperature and sucrose concentration on the B-coefficients is discussed. On the basis of the Feakins equation, the activation

Tong-Chun Bai; Guo-Bing Yan

2003-01-01

197

On the black carbon problem and its solutions  

NASA Astrophysics Data System (ADS)

Black carbon (BC) warms air temperatures in at least seven major ways: (a) directly absorbing downward solar radiation, (b) absorbing upward reflected solar radiation when it is situated above bright surfaces, such as snow, sea ice, and clouds, (c) absorbing some infrared radiation, (d) absorbing additional solar and infrared radiation upon obtaining a coating, (e) absorbing radiation multiply reflected within clouds when situated interstitially between cloud drops, (f) absorbing additional radiation when serving as CCN or scavenged inclusions within cloud drops, and (g) absorbing solar radiation when deposited on snow and sea ice, reducing the albedos of both. Modeling of the climate effects of BC requires treatment of all these processes in detail. In particular, treatment of BC absorption interstitially between cloud drops and from multiply-dispersed cloud drop BC inclusions must be treated simultaneously with treatment of cloud indirect effects to determine the net effects of BC on cloud properties. Here, results from several simulations of the effects of BC from fossil fuel and biofuel sources on global and regional climate and air pollution health are summarized. The simulations account for all the processes mentioned. Results are found to be statistically significant relative to chaotic variability in the climate system. Over time and in steady state, fossil-fuel soot plus biofuel soot are found to enhance warming more than methane. The sum of the soots causes less steady-state warming but more short term warming than does carbon dioxide. Thus eliminating soot emissions from both sources may be the fastest method of reducing rapid climate warming and possibly the only method of saving the Arctic ice. Eliminating such emissions may also reduce over 1.5 million deaths worldwide, particularly in developing countries. Short term mitigation options include the targeting of fossil-fuel and biofuel BC sources with particle traps, new stove technologies, and rural electrification. However, the real solution, to be implemented over a 20-40 year period is complete conversion of the combustion infrastructure to electricity and electrolytic hydrogen, where the electricity is all produced by near-zero emitting wind, water, and solar (WWS) based energy technologies. Such a conversion would reduce BC and greenhouse gases simultaneously with cooling aerosol particles. This would ramp down the presence of both warming and cooling agents, but still cause net reduction of global warming, while reducing devastating health impacts that are occurring from both warming and cooling aerosols.

Jacobson, M. Z.

2010-12-01

198

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

PubMed

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

Poerschmann, J; Weiner, B; Baskyr, I

2013-09-01

199

The Intehaction of Aqueous Solutions of Chlorine with Malic Acid, Tartaric Acid, and Various Fruit Juices: A Source of Mutagens  

Microsoft Academic Search

The interactions of aqueous solutions of chlorine with some fruit acids (citric acid, DL-malic acid, arid L-tartaric acid) at different pH values were studied. Diethyl ether extraction followed by GC\\/MS analysis indicated that a number of mutagens (certain chlorinated propanones and chloral hydrate) are present as major products in some of these samples. A number of fruit juices (orange, grape,

Tak-Lung Chang; Robert P. Streicher; Hans Zimmer; J. W. Munch

1988-01-01

200

Method of solubilizing shortened single-walled carbon nanotubes in organic solutions  

US Patent & Trademark Office Database

Naked single-walled nanotube carbon metals and semiconductors were dissolved in organic solutions by derivatization with SOCl.sub.2 and octadecylamine charge. Both ionic (charge transfer) and covalent solution phase chemistry with concomitant modulation of the single-walled carbon nanotubes (SWNT) band structure were demonstrated. Solution phase near-IR spectroscopy was used to study the effects of chemical modifications on the band gaps of the SWNTs. Reaction of solubilized SWNTs with dichlorocarbene led to functionalization of the nanotube walls.

2001-12-18

201

Synthesis of Mixed Acid Anhydrides from Methane and Carbon Dioxide in  

E-print Network

establishes that the primary product is a mixed anhydride of acetic acid and the acid solvent. In sulfuricSynthesis of Mixed Acid Anhydrides from Methane and Carbon Dioxide in Acid Solvents Mark Zerella acid, the overall reaction is CH4 + CO2 + SO3 f CH3C(O)-O-SO3H. Hydrolysis of the mixed anhydride

Bell, Alexis T.

202

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

203

The Carbon Isotopic Content and Concentration of Ambient Formic and Acetic Acid  

Microsoft Academic Search

A direct method for source determination of atmospheric formic and acetic acid, through carbon isotopic analysis of the ambient acids and their potential sources, has been successfully developed and tested. These first carbon isotopic measurements of formic acid in the atmosphere were found to be fairly constant, regardless of location. This is consistent with a single dominating source of formic

Bryan Jay Johnson

1991-01-01

204

Preparation and properties of activated carbons prepared from nitric acid treatment of bituminous coal  

Microsoft Academic Search

The preparation and properties of low-ash activated carbons from a Pennsylvania high volatile bituminous coal have been investigated. The conversion of raw coal to such carbon was carried out in three steps: The oxidation of the raw coal to humic acids by air and nitric acid followed by separation of the mineral matter with solvent extraction of the acids; the

E. S. Tomezko; T. S. Polansky

1961-01-01

205

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

E-print Network

Poly(carbonate ester)s Based on Units of 6-Hydroxyhexanoic Acid and Glycerol Jesse B. Wolinsky(trimethylene carbon- ate), and most notably poly(glycolic acid) and poly(lactic acid), have met wide acceptance- and nanoparticles for drug delivery applications.5-8 When a polymer does not meet the requirements for an intended

206

Activated carbons treated with sulphuric acid: Catalysts for catalytic wet peroxide oxidation  

Microsoft Academic Search

Different liquid phase thermal treatments were applied to a commercial activated carbon (Norit ROX 0.8) in order to produce modified activated carbons with varying surface chemistry and increased acidic character. Chemical characterization of the prepared materials includes determination of the point of zero charge and evaluation of the concentration and nature of acidic and basic surface functionalities by acid\\/base titrations

Helder T. Gomes; Sandra M. Miranda; Maria J. Sampaio; Adrián M. T. Silva; Joaquim L. Faria

2010-01-01

207

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

PubMed

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

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

2014-10-01

208

Boric acid corrosion of carbon and low alloy steels  

SciTech Connect

Leakage of borated water from the reactor coolant system of pressurized water reactors (PWRs) and the resulting corrosion of carbon and low alloy steel components are concerns that have been addressed by utilities for many years. Significant corrosion has been observed in instances where such leakage has gone undetected for several months. In 1990, the B and W Owners Group (B and WOG) sponsored a test program to determine the levels of wastage that are possible when primary water leakage occurs. In this test program, carbon and stainless steel specimens were exposed to borated water at temperatures from 300 F to 550 F. Initial boric acid concentration was controlled within the limits of 13,000 to 15,000 ppm (as H{sub 3}BO{sub 3}) with 1.0--2.0 ppm lithium (as LiOH) added to duplicate the primary water chemistry. Testing was performed to determine the degree of attack caused by a leak traveling along a pipe both with and without insulation. These tests show the importance of temperature and boric acid concentrations on the wastage that can occur from such a leak.

Campbell, C.A.; Fyfitch, S. [B and W Nuclear Technologies, Lynchburg, VA (United States); Martin, D.T. [Babcock and Wilcox, Alliance, OH (United States). Research and Development Division

1994-12-31

209

Electrochemical detection of amino acids at carbon nanotube and nickel-carbon nanotube modified electrodes.  

PubMed

The oxidation and enhanced detection of traditionally 'non-electroactive' amino acids at a single-wall carbon nanotube (SWNT) surface and at a nickel hydroxide film electrochemically deposited and generated upon the SWNT layer is reported. Different CNT are compared, with Nafion-dispersed SWNT offering the most favorable layer for constant-potential amperometric detection. Factors affecting the oxidation process, including the pH or applied potential, are assessed. The response of the SWNT-Nafion coated electrode compares favorably with that of copper and nickel disk electrodes under flow injection analysis (FIA) conditions. The electrodeposition of nickel onto the SWNT-Nafion layer (Ni-CNT) led to a dramatic enhancement of the analytical response (vs. that observed at the SWNT or nickel electrodes alone). The oxidative process at the Ni(OH)(2) layer has been studied and the increase in sensitivity rationalized. In the presence of amino acid the Ni-CNT layer undergoes an electrocatalytic process in which the amino acid reduces the newly formed NiO(OH) species. Furthermore, the attractive response of both the CNT and Ni-CNT layers has allowed these electrodes to be used for constant-potential FIA of various amino acids and indicates great promise for monitoring chromatographic effluents. Once again an improved signal was observed at the Ni-CNT electrode compared to nickel deposited upon a bare glassy carbon electrode (Ni-GC). PMID:15508037

Deo, Randhir P; Lawrence, Nathan S; Wang, Joseph

2004-11-01

210

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

NASA Astrophysics Data System (ADS)

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

Kong, Yuxia; Yuan, Jie; Qiu, Jun

2012-07-01

211

Carbon nanofiber supported bimetallic PdAu nanoparticles for formic acid electrooxidation  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

212

Enhancing decomposition rate of perfluorooctanoic acid by carbonate radical assisted sonochemical treatment.  

PubMed

Perfluorooctanoic acid (PFOA) is a recalcitrant organic pollutant in wastewater because of its wide range of applications. Technologies for PFOA treatment have recently been developed. In this study, PFOA decomposition by sonochemical treatment was investigated to determine the effects of NaHCO3 concentrations, N2 saturation, and pH on decomposition rates and defluorination efficiencies. The results showed that PFOA decomposition by ultrasound treatment only (150 W, 40 kHz), with or without saturated N2, was <25% after 4 h reaction. The extent and rate of PFOA decomposition and defluorination efficiencies of PFOA, however, greatly increased with the addition of carbonate radical reagents. PFOA was completely decomposed after 4h of sonochemical treatment with a carbonate radical oxidant and saturated N2. Without saturated N2, PFOA was also decomposed to a high (98.81%) degree. The highest PFOA decomposition and defluorination efficiencies occurred in N2 saturated solution containing an initial NaHCO3 concentration of 30 mM. Sonodecomposition of PFOA with CO3(-) radical was most favorable in a slightly alkaline environment (pH=8.65). There isn't any shorter-chain perfluorinated carboxylic acids detected except fluorine ions in final reaction solution. PMID:24751291

Phan Thi, Lan-Anh; Do, Huu-Tuan; Lo, Shang-Lien

2014-09-01

213

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

PubMed

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

Nagashanmugam, K B; Srinivasan, K

2010-10-01

214

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

SciTech Connect

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

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

2010-02-10

215

Adsorption of basic dyes from aqueous solution onto activated carbons  

Microsoft Academic Search

The aim of this research is to compare the adsorption capacity of different types of activated carbons produced by steam activation in small laboratory scale and large industrial scale processes. Equilibrium behaviour of the activated carbons was investigated by performing batch adsorption experiments using bottle-point method. Basic dyes (methylene blue (MB), basic red (BR) and basic yellow (BY)) were used

Emad N. El Qada; Stephen J. Allen; Gavin M. Walker

2008-01-01

216

Solution properties and emulsification properties of amino acid-based gemini surfactants derived from cysteine.  

PubMed

Amino acid-based anionic gemini surfactants (2C(n)diCys, where n represents an alkyl chain with a length of 10, 12, or 14 carbons and "di" and "Cys" indicate adipoyl and cysteine, respectively) were synthesized using the amino acid cysteine. Biodegradability, equilibrium surface tension, and dynamic light scattering were used to characterize the properties of gemini surfactants. Additionally, the effects of alkyl chain length, number of chains, and structure on these properties were evaluated by comparing previously reported gemini surfactants derived from cystine (2C(n)Cys) and monomeric surfactants (C(n)Cys). 2C(n)diCys shows relatively higher biodegradability than does C(n)Cys and previously reported sugar-based gemini surfactants. Both critical micelle concentration (CMC) and surface tension decrease when alkyl chain length is increased from 10 to 12, while a further increase in chain length to 14 results in increased CMC and surface tension. This indicates that long-chain gemini surfactants have a decreased aggregation tendency due to the steric hindrance of the bulky spacer as well as premicelle formation at concentrations below the CMC and are poorly packed at the air/water interface. Formation of micelles (measuring 2 to 5 nm in solution) from 2C(n)diCys shows no dependence on alkyl chain length. Further, shaking the mixtures of aqueous 2C(n)diCys surfactant solutions and squalane results in the formation of oil-in-water type emulsions. The highly stable emulsions are formed using 2C??diCys or 2C??diCys solution and squalane in a 1:1 or 2:1 volume ratio. PMID:23985487

Yoshimura, Tomokazu; Sakato, Ayako; Esumi, Kunio

2013-01-01

217

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

218

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

PubMed Central

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

2011-01-01

219

Experimental Study of Zirconium(IV) Extraction from Fluoride-Containing Acid Solutions  

Microsoft Academic Search

Zirconium(IV) extraction from acid solutions was studied, and the optimal parameters of the process were found. Extractants for zirconium(IV) recovery from nitric and sulfuric acid solutions in the presence of fluoride ions were selected. The distribution coefficients of zirconium(IV) and fluoride ion were determined.

I. A. Dibrov; D. E. Chirkst; T. E. Litvinova

2002-01-01

220

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

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

2014-10-01

221

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

SciTech Connect

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

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

1993-01-01

222

Simultaneous determination of ascorbic acid, uric acid and neurotransmitters with a carbon ceramic electrode prepared by sol-gel technique.  

PubMed

A sol-gel carbon composite electrode (CCE) has been prepared by mixing a sol-gel precursor (e.g. methyltrimethoxysilane) and carbon powder without adding any electron transfer mediator or specific reagents. It was demonstrated that this sensor can be used for simultaneous determination ascorbic acid, neurotransmitters (dopamine and adrenaline) and uric acid. Direct electrochemical oxidation of ascorbic acid, uric acid and catecholamines at a carbon composite electrode was investigated. The experimental results were compared with other common carbon based electrodes, specifically, boron doped diamond, glassy carbon, graphite and carbon paste electrodes. It was found that the CCE shows a significantly higher of reversibility for dopamine. In addition, in comparison to the other electrodes used, for CCE the oxidation peaks of uric acid, ascorbic acid and catecholamines in cyclic and square wave voltammetry were well resolved at the low positive potential with good sensitivity. The advantages of this sensor were high sensitivity, inherent stability and simplicity and ability for simultaneous determination of uric acid, catecholamines and ascorbic acid without using any chromatography or separation systems. The analytical performance of this sensor has been evaluated for detection of biological molecules in urine and serum as real samples. PMID:18970846

Salimi, Abdollah; Mamkhezri, Hussein; Hallaj, Rahman

2006-11-15

223

Acid Solutions for Etching Corrosion-Resistant Metals  

NASA Technical Reports Server (NTRS)

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

Simmons, J. R.

1982-01-01

224

Ciprofloxacin adsorption from aqueous solution onto chemically prepared carbon from date palm leaflets.  

PubMed

A chemically prepared carbon was synthesized from date palm leaflets via sulphuric acid carbonization at 160 degrees C. Adsorption of ciprofloxacin (CIP) from aqueous solution was investigated in terms of time, pH, concentration, temperature and adsorbent status (wet and dry). The equilibrium time was found to be 48 hr. The adsorption rate was enhanced by raising the temperature for both adsorbents, with adsorption data fitting a pseudo second-order model well. The activation energy, Ea, was found to be 17 kJ/mol, indicating a diffusion-controlled, physical adsorption process. The maximum adsorption was found at initial pH 6. The wet adsorbent showed faster removal with higher uptake than the dry adsorbent, with increased performance as temperature increased (25-45 degrees C). The equilibrium data were found to fit the Langmuir model better than the Freundlich model. The thermodynamic parameters showed that the adsorption process is spontaneous and endothermic. The adsorption mechanism is mainly related to cation exchange and hydrogen bonding. PMID:23520864

El-Shafey, El-Said Ibrahim; Al-Lawati, Haider; Al-Sumri, Asmaa Soliman

2012-01-01

225

Effect of metal ions on corrosion inhibition of pimeloyl-1,5-di-hydroxamic acid for steel in neutral solution  

Microsoft Academic Search

The influence of metal ions on the adsorption process and corrosion inhibition of pimeloyl-1,5-di-hydroxamic acid (C7) on carbon steel surface in neutral solutions has been investigated by surface analytical and electrochemical techniques. Effective corrosion inhibition given by C7 in the presence of Zn2+ and Ni2+ is believed to be associated with the ability of the hydroxamic acid to form stable

Abdulmajed Alagta; Ilona Felhösi; Judit Telegdi; Imre Bertóti; Erika Kálmán

2007-01-01

226

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

227

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

E-print Network

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

228

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

E-print Network

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

229

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

230

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

231

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

232

Morphology and acid–base properties of porous carbon derived from poly(ethylene terephthalate) by nitric acid treatment  

Microsoft Academic Search

Activated carbon prepared from poly(ethylene terephthalate) was treated with nitric acid at ambient temperature and at the boiling point of the suspension. The morphology of the products was investigated by scanning electron microscopy, nitrogen adsorption observations and by small-angle X-ray scattering. The effect of acidic treatment on acid–base surface properties was studied by quasi-equilibrium potentiometric acid–base titration. It is found

K. László; Katalin Marthi; E. Tombácz; E. Geissler

233

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

Microsoft Academic Search

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

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

2010-01-01

234

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

235

Long-term carbon stabilization through sorption of dissolved aromatic acids to reactive particles (Invited)  

NASA Astrophysics Data System (ADS)

Short-range order minerals are highly reactive soil constituents that are found in all soils and in particularly high quantities in volcanic soils. They retain large quantities of soil carbon, thereby acting as a long-term sink for carbon dioxide, but the main source for this carbon accumulation in soil is not yet known. We evaluated the biochemistry of solid and dissolved organic carbon in horizons containing differing short-range ordered mineral concentrations using solid-state 13C nuclear magnetic resonance spectroscopy, stable isotope measurements and soil column leaching experiments across a well-constrained chronosequence of volcanic soils in Hawai’i. Molecular mixing model results, isotopic and elemental measurements, indicate that the oldest and most persistent C stores across the chronosequence are comprised not of highly microbially processed organic matter (e.g. proteins or lipids), but rather of partially oxidized aromatic plant compounds (up to 62% of the total soil C) preserved through chemical bonding to reactive soil minerals via carboxyl-rich functionalities. NMR spectra obtained from deep soil horizons containing an abundance of SRO minerals, showed strong chemical resemblance to that of DOM derived from plant litter. Solublization and high production rates of recalcitrant DOM controlled substantially by microbial activity were observed in the soil column leaching experiments. When the DOM-rich solution derived from organic horizons was leached through mineral soil horizons, the quantity of DOM sorbed was dependent on the abundance of SRO minerals present in the soil. These results suggest that microbial-driven DOM formation derived from plant litter and the subsequent binding of the aromatic acids in the DOM to reactive mineral surfaces is a dominant source for long-term soil carbon stabilization in these soils. This potentially globally significant carbon sink may be unresponsive to climate change over decadal to centennial timescales due to strong particle sorption via carboxyl-rich functionalities.

Kramer, M. G.; Sanderman, J.; Chadwick, O.; Chorover, J.; Vitousek, P.

2010-12-01

236

Removal of toxic chromium(VI) from aqueous solution by activated carbon using Casuarina equisetifolia  

Microsoft Academic Search

Highly activated carbon from the seed husk of Casuarina Casuarinas equisetifolia, a worldwide famous plant, have been prepared and tested for the removal of toxic Cr(VI) from its aqueous solution. The adsorbent was investigated for influences of initial chromium concentration (75, 100, 125, and 150 mg l), pH, contact time, and quantity of carbon on removal of Cr(VI) from aqueous solution at

A. El Nemr; A. El Sikaily; A. Khaled; O. Abdelwahab

2007-01-01

237

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

PubMed

Removal of textile dyestuffs from aqueous solution by biosorption onto a dead fungal biomass isolated from acidic mine drainage in the Çanakkale Region of Turkey was investigated. The fungus was found to be a promising biosorbent and identified as Paecilomyces sp. The optimal conditions for bioremediation were as follows: pH, 2.0; initial dyestuff concentration, 50 mg?l(-1) for Reactive Yellow 85 and Reactive Orange 12, and 75 mg?l(-1) for Reactive Black 8; biomass dosage, 2 g?l(-1) for Reactive Yellow 85, 3 g?l(-1) for Reactive Orange 12, 4 g?l(-1) for Reactive Black 8; temperature, 25 °C; and agitation rate, 100 rpm. Zeta potential measurements indicated an electrostatic interaction between the binding sites and dye anions. Fourier transform infrared spectroscopy showed that amine, hydroxyl, carbonyl, and amide bonds were involved in the dyestuff biosorption. A toxicity investigation was also carried out before and after the biosorption process. These results showed that the toxicities for the reactive dyestuffs in aqueous solutions after biosorption studies decreased. The Freundlich and Langmuir adsorption models were used for the mathematical description of the biosorption equilibrium, and isotherm constants were evaluated for each dyestuff. Equilibrium data of biosorption of RY85 and RO12 dyestuffs fitted well to both models at the studied concentration and temperature. PMID:23263759

Çabuk, Ahmet; Aytar, P?nar; Gedikli, Serap; Özel, Yasemin Kevser; Kocab?y?k, Erçin

2013-07-01

238

The rheological properties of concentrated solutions of mixtures of polyamides with polyamido acids  

Microsoft Academic Search

solutions and on their processing technology so that an investigation of the solutions of polymer mixöures is'of considerable theoretieal and practical interest. The work described in this communioation consisted of a study of the rheological properties of the eoncentrated solutions of aromatic polyamides and polyamido acids as representatives of the group of heat-resisting polymers with the greatest promise of spinnability.

R. G. Fedorova; G. I. Kudryavtsev; N. S. Krutikova

1972-01-01

239

Determination of nitric acid in highly radioactive solutions by the method of coulometric titration  

Microsoft Academic Search

A procedure, a cell, and an electronic block have been developed for a long-distance determination of nitric acid in highly radioactive industrial solutions by coulometric titration under hot chamber conditions. A solution of a mixture of ammonium and potassium oxalates was used for the background and anoide electrolytes. This solution prevents the hydrolysis of the metal ions and appreciably decreases

V. S. Gromov; A. Ya. Kuperman; Yu. A. Smirnov

1988-01-01

240

Removal of Cu2+ and Ag+ from aqueous solution on a chemically-carbonized sorbent from date palm leaflets.  

PubMed

A chemically-carbonized sorbent was prepared from date palm leaflets by sulphuric acid treatment at 170 degrees C. Carbonization took place via the dehydration effect of the hot sulphuric acid producing a carbon with reduction property. Sorption of Cu2+ and Ag+ from aqueous solution was investigated in terms of pH, contact time, metal concentration and temperature. A peculiar behaviour was found for the sorption of the two metals on the produced carbon. Sorption of Cu2+ was fast, reaching equilibrium within -2 h, whilst Ag+ sorption was slow and required -60 h to reach equilibrium. Activation energy (E(a)) for Cu2+ sorption was -16.1 kJ/mol indicating a diffusion-controlled ion exchange process; however, E(a) for Ag+ sorption was -44.3 kJ/mol indicating a chemically controlled process. Equilibrium sorption data were tested for the Langmuir and Freundlich equations. Sorption capacity appears to be much higher for Ag+ than for Cu2+ with increased uptake, for both metals, when increasing the temperature (25-45 degrees C). Ag+ was reduced to elemental silver on the sorbent surface and this was confirmed using scanning electron microscopy and x-ray powder diffraction; however, no reduction processes were involved in Cu2+ sorption. This paper discusses the sorption mechanism. PMID:23530353

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

2013-01-01

241

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

242

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

PubMed

In this study the husk of mango seed and two carbonaceous adsorbents prepared from it were used to study the adsorption behavior of eight acid dyes. The adsorbed amount in mmol m(-2) decayed asymptotically as the molecular volume and area increased. The interaction between the studied dyes and the mesoporous carbon was governed by the ionic species in solution and the acidic/basic groups on the surface. Less than 50% of the external surface of the microporous carbon became covered with the dyes molecules, though monolayer formation demonstrating specific interactions only with active sites on the surface and the adsorption magnitudes correlated with the shape parameter of the molecule within a particular dye group. The adsorption behavior in mixtures was determined by the molecular volume of the constituents; the greater the molecular volume difference, the greater the effect on the adsorbed amount. We also demonstrated that the raw husk of the mango seed can be used to remove up to 50% from model 50 mg l(-1) solutions of the studied acid dyes. PMID:19692231

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

2009-12-01

243

Extraction of uranium from aqueous solution by phosphonic acid-imbedded polyurethane foam.  

PubMed

Phenylphosphonic acid was imbedded into the matrix of the polyurethane foam during the fabrication process of the polymer. The extraction of uranium by phosphonic acid-imbedded polyurethane foam and blank polyurethane (i.e., foam without phosphonic acid functional groups) was investigated. Phosphonic acid-imbedded foam showed superior extractability of uranium from solutions with pH=7.0+/-1.5 over a wide range of temperature. PMID:18966928

Katragadda, S; Gesser, H D; Chow, A

1997-10-01

244

Extraction of uranium from aqueous solution by phosphonic acid-imbedded polyurethane foam  

Microsoft Academic Search

Phenylphosphonic acid was imbedded into the matrix of the polyurethane foam during the fabrication process of the polymer. The extraction of uranium by phosphonic acid-imbedded polyurethane foam and blank polyurethane (i.e., foam without phosphonic acid functional groups) was investigated. Phosphonic acid-imbedded foam showed superior extractability of uranium from solutions with pH=7.0±1.5 over a wide range of temperature.

S Katragadda; H. D Gesser; A Chow

1997-01-01

245

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

246

Interaction of nucleic acids with carbon nanotubes and dendrimers.  

PubMed

Nucleic acid interaction with nanoscale objects like carbon nanotubes (CNTs) and dendrimers is of fundamental interest because of their potential application in CNT separation, gene therapy and antisense therapy. Combining nucleic acids with CNTs and dendrimers also opens the door towards controllable self-assembly to generate various supra-molecular and nano-structures with desired morphologies. The interaction between these nanoscale objects also serve as a model system for studying DNA compaction, which is a fundamental process in chromatin organization. By using fully atomistic simulations, here we report various aspects of the interactions and binding modes of DNA and small interfering RNA (siRNA) with CNTs, graphene and dendrimers. Our results give a microscopic picture and mechanism of the adsorption of single- and double-strand DNA (ssDNA and dsDNA) on CNT and graphene. The nucleic acid-CNT interaction is dominated by the dispersive van der Waals (vdW) interaction. In contrast, the complexation of DNA (both ssDNA and dsDNA) and siRNA with various generations of poly-amido-amine (PAMAM) dendrimers is governed by electrostatic interactions. Our results reveal that both the DNA and siRNA form stable complex with the PAMAM dendrimer at a physiological pH when the dendrimer is positively charged due to the protonation of the primary amines. The size and binding energy of the complex increase with increase in dendrimer generation. We also give a summary of the current status in these fields and discuss future prospects. PMID:22750983

Nandy, Bidisha; Santosh, Mogurampelly; Maiti, Prabal K

2012-07-01

247

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

EPA Science Inventory

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

248

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

EPA Science Inventory

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

249

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

250

Studies on solution-derived ceramic coatings for oxidation protection of carbon-carbon composites  

Microsoft Academic Search

Carbon-carbon composites have been coated with silica and zircon prepared by sol-gel technique and with methylsilsesquioxane, a preceramic polymer. The effect of processing parameters for preparation of the sols and coating procedure on coating morphology has been studied. Oxidation behaviour of uncoated and coated carbon-carbon composites has been studied. Coatings with continuous and uniform structure, obtained by controlled processing, have

L. M. Manocha; Satish M. Manocha

1995-01-01

251

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

252

On the black carbon problem and its solutions  

Microsoft Academic Search

Black carbon (BC) warms air temperatures in at least seven major ways: (a) directly absorbing downward solar radiation, (b) absorbing upward reflected solar radiation when it is situated above bright surfaces, such as snow, sea ice, and clouds, (c) absorbing some infrared radiation, (d) absorbing additional solar and infrared radiation upon obtaining a coating, (e) absorbing radiation multiply reflected within

M. Z. Jacobson

2010-01-01

253

Kinetic study of pyrite oxidation in basic carbonate solutions  

Microsoft Academic Search

The general goal of this experimental study was to find ways to control the unwanted oxidation of pyrite during the in situ leaching of uranium ores. The authors investigated the effect of particle size, leaching pH, flow rate, total carbonate concentration, and cation type of column leaching rates. The work appears to be the first dealing with pyrite leaching in

Terry R. Guilinger; Robert S. Schechter; Larry W. Lake

1987-01-01

254

Ecological Engineering promotes Carbon Reduction Solutions for a Sustainable Planet  

Microsoft Academic Search

Due to un-prescedented; social, industrial and human reproductive growth, our global society is rapidly approaching peak development, coupling with climate change factors and accelerating Earths current 'melt cycle'. Our challenge is to do more with less; to question the 'way' it has always been done; to develop innovative low carbon engineering tools; to design and mimic natural eco-systems and to

Stephen Bedford Clark

2009-01-01

255

Effect of surfactant structure on the stability of carbon nanotubes in aqueous solution.  

PubMed

The suspending behaviors of multiple-wall carbon nanotubes (MWNTs), including pristine MWNTs (p-MWNTs) and acid-mixture-treated MWNTs (MWNTCOOH), stabilized by cationic single-chain surfactant, dodecyltrimethylammonium bromide (DTAB), and cationic gemini surfactant hexyl-alpha,beta-bis(dodecyldimethylammonium bromide) (C 12C 6C 12Br 2) were studied systematically. The surfactant structure influences the suspendability of MWNTs dramatically as well as the surfactant adsorption behavior on the nanotubes. Although both the surfactants can disperse the MWNTs effectively, they actually show different stabilizing ability. DTAB is not capable of stabilizing these two MWNTs below critical micelle concentration (CMC). However, C 12C 6C 12Br 2 can suspend both the nanotubes effectively even well below its CMC. Moreover, the adsorption of these two surfactants reaches equilibrium at twice the CMC with the original MWNT concentration of 2 mg/mL, 2 mM for C 12C 6C 12Br 2, and 30 mM for DTAB. After the adsorption equilibrium, the maximum amounts of the two suspended MWNTs in C 12C 6C 12Br 2 solution are about twice as much as those in DTAB solution. The strong hydrophobic interaction among the C 12C 6C 12Br 2 molecules and between the C 12C 6C 12Br 2 molecules and the nanotubes as well as the high charge capacity of C 12C 6C 12Br 2 lead to its much stronger adsorption ability on the MWNTs and result in its superior stabilizing ability for the MWNTs in aqueous phase. The gemini surfactant provides a possibility to effectively stabilize the MWNTs in aqueous solutions even at very low surfactant concentration well below its CMC. PMID:18491940

Wang, Qi; Han, Yuchun; Wang, Yilin; Qin, Yujun; Guo, Zhi-Xin

2008-06-19

256

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

257

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

258

Multiple-acid equilibria in adsorption of carboxylic acids from dilute aqueous solution  

SciTech Connect

Equilibria were measured for adsorption of carboxylic acids from aqueous, binary-acid mixtures of lactic and succinic acids and acetic and formic acids onto basic polymeric sorbents. The experimentally determined adsorption isotherms compared well with model predictions, confirming that simple extensions from adsorption of individual acids apply. Fixed-bed studies were carried out that establish the efficacy of chromatographic fractionation of lactic and succinic acids using basic polymeric sorbents. Finally, sequential thermal and solvent regeneration of lactic and acetic acid-laden sorbents was investigated as a method to fractionate among coadsorbed volatile and nonvolatile acids. Essentially complete removal of the acetic acid from the acid-laden sorbent was achieved by vaporization under the conditions used; a small amount of loss of lactic acid (about 11%) was observed.

Husson, S.M.; King, C.J. [Lawrence Berkeley National Lab., CA (United States)] [Lawrence Berkeley National Lab., CA (United States)

1999-02-01

259

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

PubMed

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

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

2014-03-15

260

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

261

Discoloration of titanium alloy in acidic saline solutions with peroxide.  

PubMed

The objective of this study was to compare corrosion behavior in several titanium alloys with immersion in acidulated saline solutions containing hydrogen peroxide. Seven types of titanium alloy were immersed in saline solutions with varying levels of pH and hydrogen peroxide content, and resulting differences in color and release of metallic elements determined in each alloy. Some alloys were characterized using Auger electron spectroscopy. Ti-55Ni alloy showed a high level of dissolution and difference in color. With immersion in solution containing hydrogen peroxide at pH 4, the other alloys showed a marked difference in color but a low level of dissolution. The formation of a thick oxide film was observed in commercially pure titanium showing discoloration. The results suggest that discoloration in titanium alloys immersed in hydrogen peroxide-containing acidulated solutions is caused by an increase in the thickness of this oxide film, whereas discoloration of Ti-55Ni is caused by corrosion. PMID:23370866

Takemoto, Shinji; Hattori, Masayuki; Yoshinari, Masao; Kawada, Eiji; Oda, Yutaka

2013-01-01

262

Distribution of dicarboxylic acids and carbon isotopic compositions in aerosols from 1997 Indonesian forest fires  

Microsoft Academic Search

Fine aerosol particles collected in Southeast Asia during 1997 Indonesian forest fires were studied for the concentrations of total carbon (TC), water-soluble organic carbon (WSOC) and low molecular weight dicarboxylic acids (C2-C12) as well as carbon isotopic ratios of TC (delta13CTC). TC and WSOC showed a large increase during the heavy forest fire event. At the same period, dicarboxylic acids,

M. Narukawa; K. Kawamura; N. Takeuchi; T. Nakajima

1999-01-01

263

Sequestration of naphthenic acids from aqueous solution using ?-cyclodextrin-based polyurethanes.  

PubMed

The sorption characteristics of naphthenic acids (NAs) in their anion form with ?-cyclodextrin (?-CD) based polyurethanes, as sorbents, from aqueous solutions that simulate the conditions of oil sands process water (OSPW) are presented. The copolymer sorbents were synthesized at various ?-CD:diisocyanate monomer mole ratios (e.g., 1:1, 1:2, and 1:3) with diisocyanates of variable molecular size and degree of unsaturation. The equilibrium sorption properties of the copolymer sorbents were characterized using sorption isotherms in aqueous solution at pH 9.00 with electrospray ionization mass spectrometry to monitor the equilibrium unbound fraction of anionic NAs in the aqueous phase. The copolymer sorbents were characterized in the solid state using (13)C CP-MAS NMR spectroscopy, IR spectroscopy and elemental analysis. The sorption results of the copolymer sorbents with anion forms of NAs in solution were compared with a commercially available carbonaceous standard: granular activated carbon (GAC). The monolayer sorption capacities of the sorbents (Q(m)) were obtained from either the Langmuir or the Sips isotherm model used to characterize the sorption characteristics of each copolymer sorbent. The estimated sorption capacity for GAC was 142 mg NAs per g sorbent whereas the polymeric materials ranged from 0-75 mg NAs per g sorbent over the experimental conditions investigated. In general, significant differences in the sorption capacities between GAC and the copolymer sorbents were related to the differences in the accessible surface areas and pore structure characteristics of the sorbents. The Sips parameter (K(eq)) for GAC and the copolymer materials reveal differences in the relative binding affinity of NAs to the sorbent framework in accordance with the synthetic ratios and the value of Q(m). The diisocyanate linker plays a secondary role in the sorption mechanism, whereas the ?-CD macrocycle in the copolymer framework is the main sorption site for NAs because of the formation of inclusion complexes with ?-CD. PMID:21076742

Mohamed, Mohamed H; Wilson, Lee D; Headley, John V; Peru, Kerry M

2011-01-21

264

Evaluation of solution-processable carbon-based electrodes for all-carbon solar cells.  

PubMed

Carbon allotropes possess unique and interesting physical, chemical, and electronic properties that make them attractive for next-generation electronic devices and solar cells. In this report, we describe our efforts into the fabrication of the first reported all-carbon solar cell in which all components (the anode, active layer, and cathode) are carbon based. First, we evaluate the active layer, on standard electrodes, which is composed of a bilayer of polymer sorted semiconducting single-walled carbon nanotubes and C(60). This carbon-based active layer with a standard indium tin oxide anode and metallic cathode has a maximum power conversion efficiency of 0.46% under AM1.5 Sun illumination. Next, we describe our efforts in replacing the electrodes with carbon-based electrodes, to demonstrate the first all-carbon solar cell, and discuss the remaining challenges associated with this process. PMID:23113673

Ramuz, Marc P; Vosgueritchian, Michael; Wei, Peng; Wang, Chenggong; Gao, Yongli; Wu, Yingpeng; Chen, Yongsheng; Bao, Zhenan

2012-11-27

265

Simultaneous determination of dopamine, ascorbic acid, and uric acid using carbon ionic liquid electrode.  

PubMed

A recently constructed carbon composite electrode using room temperature ionic liquid as pasting binder was employed as a novel electrode for sensitive, simultaneous determination of dopamine (DA), ascorbic acid (AA), and uric acid (UA). The apparent reversibility and kinetics of the electrochemical reaction for DA, AA, and UA found were improved significantly compared to those obtained using a conventional carbon paste electrode. The results show that carbon ionic liquid electrode (CILE) reduces the overpotential of DA, AA, and UA oxidation, without showing any fouling effect due to the deposition of their oxidized products. In the case of DA, the oxidation and reduction peak potentials appear at 210 and 135mV (vs Ag/AgCl, KCl, 3.0M), respectively, and the CILE shows a significantly better reversibility for dopamine. The oxidation peak due to the oxidation of AA occurs at about 60mV. For UA, a sharp oxidation peak at 340mV and a small reduction peak at 250mV are obtained at CILE. Differential pulse voltammetry was used for the simultaneous determination of ternary mixtures of DA, AA, and UA. Relative standard deviation for DA, AA, and UA determinations were less than 3.0% and DA, AA, and UA can be determined in the ranges of 2.0x10(-6)-1.5x10(-3), 5.0x10(-5)-7.4x10(-3), and 2.0x10(-6)-2.2x10(-4)M, respectively. The method was applied to the determination of DA, AA, and UA in human blood serum and urine samples. PMID:17069745

Safavi, Afsaneh; Maleki, Norouz; Moradlou, Omran; Tajabadi, Fariba

2006-12-15

266

Fate of microbial nitrogen, carbon, hydrolysable amino acids, monosaccharides, and fatty acids in sediment  

NASA Astrophysics Data System (ADS)

The fate of microbial carbon, nitrogen, hydrolysable amino acids (HAAs), monosaccharides, and fatty acids in sediment was investigated experimentally. The microbial community of a tidal flat sediment was labeled with 13C-enriched glucose and 15N-enriched ammonium, and sediment was incubated for up to 371 days. Analysis of total concentrations and 13C- and 15N content of bulk sediment, hydrolysable amino acids (including D-alanine), monosaccharides, total fatty acids (TFAs), and phospholipid-derived fatty acids (PLFAs) allowed us to trace the fate of microbial biomass and -detritus and the major biochemical groups therein (proteins, carbohydrates, and lipids) over intermediate time scales (weeks-months). Moreover, the unidentified fraction of the labeled material (i.e. not analyzed as HAA, FA, or carbohydrate) provided information on the formation and fate of molecularly uncharacterizable organic matter. Loss of 13C and 15N from the sediment was slow (half live of 433 days) which may have been due to the permanently anoxic conditions in the experiment. Loss rates for the different biochemical groups were also low with the following order of loss rate constants: PLFA > TFA > HAA > monosaccharides. The unidentified 13C-pool was rapidly formed (within days) and then decreased relatively slowly, resulting in a gradual relative accumulation of this pool over time. Degradation and microbial reworking of the labeled material resulted in subtle, yet consistent, diagenetic changes within the different biochemical groups. In the HAA pool, glycine, lysine, and proline were lost relatively slowly (i.e. best preserved) while there was no accumulation of D-alanine relative to L-alanine, indicating no relative accumulation of bacterial macromolecules rich in D-alanine. In the fatty acid pool, there was very little difference between PLFAs and TFAs, indicating a very similar lability of these pools. Differences between individual fatty acids included a relatively slow loss of i15:0, ai15:0 and 18:1?7c which likely resulted from production of these bacterial fatty acids during bacterial reworking of the organic matter. Differences between loss rate constants for individual monosaccharides were not significant. An exception was ribose that was produced and lost relatively rapidly, which may be related to ribose being an important component of RNA. Losses of bulk 13C and 15N were closely coupled despite partly being present in different biochemicals and partly being derived from different microbial sources, indicating no selective preservation of either C or N during organic matter diagenesis.

Veuger, Bart; van Oevelen, Dick; Middelburg, Jack J.

2012-04-01

267

A pharmaceutical product as corrosion inhibitor for carbon steel in acidic environments.  

PubMed

A pharmaceutical product, Trimethoprim (TMP), IUPAC name: 5-(3,4,5-trimethoxybenzyl)pyrimidine-2,4-diamine was investigated, as inhibitor to prevent carbon steel corrosion in acidic environments. The study was performed using weight loss and electrochemical measurements, in temperatures ranging between 25-55°C. The surface morphology before and after corrosion of carbon steel in 1.0 M HCl solution in the presence and absence of TMP was evaluated using scanning electron microscopy (SEM). The inhibition efficiency (IE) increased with the increasing of the inhibitor concentration, reaching a maximum value of 92% at 25°C and 0.9 mM TMP, and decreased with increasing temperature. The inhibition of carbon steel corrosion by TMP can be attributed to the adsorption ability of inhibitor molecules onto the reactive sites of the metal surface. The adsorption is spontaneous and it is best described by the Langmuir isotherm. The apparent activation energy (E(a)) for the corrosion process in the absence and presence of TMP was evaluated from Arrhenius equation, to elucidate its inhibitive properties. PMID:23043337

Samide, Adriana

2013-01-01

268

Solution processable carbon nanotube network thin-film transistors operated in electrolytic solutions at various pH  

NASA Astrophysics Data System (ADS)

We investigate the electronic properties of solution-gated carbon nanotube (CNT) thin-film transistors, where the active layer consists of a randomly distributed single-walled CNT network of >90% semiconducting nanotubes, deposited from an aqueous solution by spin-coating. The devices are characterized in different electrolytic solutions, where a reference electrode immersed in the liquid is used to apply the gate potential. We observe a gate-potential shift in the transfer characteristic when the pH and/or ionic strength of the electrolytic solution is changed with a pH sensitivity of ?19 mV/pH. This sensitivity is attributed to a surface charging effect at the CNT/electrolyte interface.

Haeberle, Tobias; Münzer, Alexandra M.; Buth, Felix; Antonio Garrido, Jose; Abdellah, Alaa; Fabel, Bernhard; Lugli, Paolo; Scarpa, Giuseppe

2012-11-01

269

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

270

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

271

The staining of starch gels with Coomassie Brilliant Blue G 250 perchloric acid solution  

Microsoft Academic Search

Summary Coomassie Brilliant Blue G250 dissolved in dilute perchloric acid solution was used to stain protein bands in starch gels. The bands were visible within min, no destaining was required and the gels could be stored indefinitely.

Gail McFarland

1977-01-01

272

Mitigation of surface damage growth by hydrofluoric acid etching combined with carbon dioxide laser treatment  

NASA Astrophysics Data System (ADS)

Damage sites as large as 600 ?m in fused silica surface were successfully mitigated with a new protocol by hydrofluoric acid (HF) etching combined with carbon dioxide laser treatment. The damage sites were first etched in 40% HF solution to blunt the fractures, and then the etched damage sites were smoothed with a CO2 laser. It has been found that the etching rate of damaged material in the lateral direction is larger than in the longitudinal direction; thus, an optimized etching time was chosen to etch the damage sites based on the etching ratio. Three types of damage test methods were used to confirm the mitigation efficiency of the protocol. The results indicate that the damage resistance capability of mitigated sites can recover to the level of pristine substrate.

Jiang, Yong; Yuan, Xiaodong; He, Shaobo; Zheng, Wanguo; Wang, Haijun; Lü, Haibing; Ren, Wei; Luo, Chengsi; Liu, Chunming; Xiang, Xia; Zu, Xiaotao

2012-08-01

273

Electrical Conductance and Volumetric Studies in Aqueous Solutions of Nicotinic Acid  

Microsoft Academic Search

Conductivity measurements of nicotinic acid and sodium nicotinate in dilute aqueous solutions were performed in the (288.15 to 323.15) K temperature range. The limiting equivalent conductances of the nicotinate anion, ?0(Nic?, T), and the dissociation constants of nicotinic acid, K(T), were derived by the use of the Onsager and the Quint and Viallard conductivity equations. Densities of aqueous solutions with

Zoya Orekhova; Meyrav Ben-Hamo; Emanuel Manzurola; Alexander Apelblat

2005-01-01

274

Quantum-chemical calculations of electronic-absorption spectra of aromatic amino acids in aqueous solution  

NASA Astrophysics Data System (ADS)

Quantum-chemical methods are used to calculate electronic-absorption spectra, dipole moments, and atomic-charge distributions of aromatic amino acids in aqueous solutions at various concentrations. The electronic-absorption spectra are analyzed and compared with the spectra that are calculated for gas phase. The bathochromic shift of the spectral position is shown for the long-wavelength absorption peak of the singlet-singlet transition for aqueous solutions of amino acids.

Migovich, M. I.; Kel'man, V. A.

2014-08-01

275

Quantitative description of the behavior of uranium and hydrazine in the electrophoresis of nitric acid solutions  

SciTech Connect

This paper examines the influence of the composition of the solution, current density, temperature, and other factors on the reduction of uranium (VI) and the decomposition of hydrazine in the electrolysis of nitric acid solutions in a cell without a diaphragm. The study was performed by the method of experimental planning. Mathematical dependences describing the experimental data and permitting optimization of the conditions of electroreduction of uranium (VI) in hydrazine-containing nitric acid media were obtained.

Marchenko, V.I.; Konovalov, Y.V.; Polunin, A.K.; Rodyushkin, S.P.; Shopovalov, M.P.

1986-03-01

276

An investigation into the stability and sterility of citric Acid solutions used for cough reflex testing.  

PubMed

Citric acid is used in cough reflex testing in clinical and research settings to assess reflexive cough in patients at risk of swallowing disorders. To address a lack of knowledge in this area, this study investigated the stability and sterility of citric acid solutions. Triplicate solutions of citric acid (0.8 M) in isotonic saline were stored at 4 ± 2 °C for up to 28 days and analysed by high-performance liquid chromatography. Microbiological sterility of freshly prepared samples and bulk samples previously used for 2 weeks within the hospital was determined using a pour plate technique. Microbial survival in citric acid was determined by inoculating Staphylococcus aureus, Escherichia coli, or Candida albicans into citric acid solution and monitoring the number of colony-forming units/mL over 40 min. Citric acid solutions remained stable at 4 °C for 28 days (98.4 ± 1.8 % remained). The freshly prepared and clinical samples tested were sterile. However, viability studies revealed that citric acid solution allows for the survival of C. albicans but not for S. aureus or E. coli. The microbial survival study showed that citric acid kills S. aureus and E. coli but has no marked effect on C. albicans after 40 min. Citric acid samples at 0.8 M remained stable over the 4-week testing period, with viable microbial cells absent from samples tested. However, C. albicans has the ability to survive in citric acid solution if inadvertently introduced in practice. For this reason, in clinical and research practice it is suggested to use single-use aliquots prepared aseptically which can be stored for up to 28 days at 4 °C. PMID:25150508

Falconer, James R; Wu, Zimei; Lau, Hugo; Suen, Joanna; Wang, Lucy; Pottinger, Sarah; Lee, Elaine; Alazawi, Nawar; Kallesen, Molly; Gargiulo, Derryn A; Swift, Simon; Svirskis, Darren

2014-10-01

277

Densities and excess molar volumes of formic acid, acetic acid and propionic acid in pure water and in water?+?Surf Excel solutions at different temperatures  

Microsoft Academic Search

Densities, ? of the systems formic acid, acetic acid and propionic acid in water and in 0.05% and 0.1% Surf Excel (SE) solutions in water were measured at temperatures 303.15, 308.15, 313.15, 318.15 and 323.15?K respectively covering the whole composition range. Excess molar volumes, for the systems were found to be negative and their values were found to increase with

M. A. Motin; M. H. Kabir; E. M. Huque

2005-01-01

278

In situ electron microscopy studies of calcium carbonate precipitation from aqueous solution with and without organic additives.  

PubMed

For the understanding of mineral formation processes from solution it is important to obtain a deeper insight into the dynamics of crystal growth. In this study we applied for this purpose a novel atmospheric scanning electron microscope that allows the investigation of CaCO3 particle formation in solution under atmospheric conditions with a resolution of approximately 10nm. Furthermore it permits the in situ observation of the dynamics of crystal evolution. With this tool the precipitation of CaCO3 was studied in the absence and presence of additives, namely poly(acrylic acid) and poly(styrene sulfonate-co-maleic acid) which are known to influence the crystal growth rate and morphology. We determined particle growth rates and investigated the formation and dissolution dynamics of an observed transient phase, believed to be amorphous calcium carbonate. This technique also enabled us to study the depletion zones, areas of lower intensity due to reduced ion concentrations. Ion flux rates were obtained from the depletion zone width, which amounted to several ?m assuming the formation and dissolution dynamics of amorphous calcium carbonate being the rate determining process. This assumption was confirmed since the obtained fluxes were found to be in good agreement with fluxes derived from the experimentally observed crystal growth rates. PMID:23742840

Verch, Andreas; Morrison, Ian E G; Locht, Renee van de; Kröger, Roland

2013-08-01

279

The dissolution of quartz in dilute aqueous solutions of organic acids at 25 degree C  

SciTech Connect

The dissolution of quartz in dilute aqueous solutions of organic acids at 25{degree}C and standard pressure was investigated by the batch dissolution method. The bulk dissolution rate of quartz in 20 mmole/Kg citrate solutions at pH 7 was 8 to 10 times faster than that in pure water. After 1750 hours the concentration of dissolved silica in the citrate solution was 167 {mu}mole/Kg compared to 50 {mu}mole/Kg in water and a 20 mmole/Kg solution of acetate at pH 7. Solutions of salicylic, oxalic, and humic acids also accelerated the dissolution of quartz in aqueous solution at pH 7. The rate of dissolution in organic acids decreased sharply with decreasing pH. The possibility of a silica-organic acid complex was investigated using UV-difference spectroscopy. Results suggest that dissolved silica is complexed by citrate, oxalate and pyruvate at pH 7 by an electron-donor acceptor complex, whereas no complexation occurs between silica and acetate, lactate, malonate, or succinate. Three models are proposed for the solution and surface complexation of silica by organic acid which result in the accelerated dissolution and increased solubility of quartz in organic rich water.

Bennett, P.C.; Melcer, M.E.; Siegel, D.I.; Hassett, J.P. (Syracuse Univ., NY (USA))

1988-06-01

280

DISTRIBUTION BEHAVIOR OF NEPTUNIUM AND PLUTONIUM BETWEEN ACID SOLUTIONS AND SOME ORGANIC EXTRACTANTS  

Microsoft Academic Search

The extractive properties of some organonitrogen and organophosphorus ; compounds for neptunium and plutoniuin in aqueous acid solutions were ; investigated under the following conditions: (1) The acid was generally HNO\\/sub ; 3\\/ although HâSOâ and HCl were also studied. (2) The valence of . ; neptunium and plutonium was generally (IV) although Np(V) and (VI) and Pu(lIl) ; and

Boyd Weaver; D. E. Horner

1960-01-01

281

Equilibrium studies on reactive extraction of succinic acid from aqueous solutions with tertiary amines  

Microsoft Academic Search

Reactive extraction of succinic acid from aqueous solutions with various tertiary amines dissolved in 1-octanol and n-heptane has been studied as a function of the acid concentration and the chain length of tertiary amine. When 1-octanol was used as diluent, the extractability of the tertiary amine was proportional to the chain length of tertiary amine at the same concentration of

Yeon Ki Hong; Won Hi Hong

2000-01-01

282

Thermal degradation of polyacrylic acid in dilute aqueous solution  

Microsoft Academic Search

The thermal degradation of polyacrylic acid of molecular weight (Mw) 5660 (PAA 5K) has been studied between 180 and 260 °C, representing the heat conditions prevailing at the high pressure heaters (185 °C) and steam generators (260 °C) of the steam-condensate cycle of CANDU nuclear power plants. The degradation does not follow a simple first-order kinetics but probably a rather complex mechanism that

Louis Lépine; Roland Gilbert

2002-01-01

283

Metal-doped carbon aerogels as catalysts during ozonation processes in aqueous solutions  

Microsoft Academic Search

The efficiency of Co(II)-, Mn(II)-, and Ti(IV)-doped carbon aerogels for the transformation of ozone into OH radicals was investigated. The carbon aerogels had a markedly acid surface character (pHPZC?3–4) with very high surface oxygen concentrations (O?20%). X-ray photoelectron spectroscopy (XPS) analyses of the samples showed the oxidation state of the metals was +2 for Co and Mn and +4 for

M. Sánchez-Polo; J. Rivera-Utrilla; U. von Gunten

2006-01-01

284

Solution spectroscopy of dipicolinic acid interaction with nucleic acids: Role in spore heat resistance  

Microsoft Academic Search

The effect of dipicolinic acid (DPA) or its calcium chelate (CaDPA) on the spectral characteristics of nucleic acids was examined. Dipicolinic acid was found to displace ethidium gromide from DNA; this indicates that it may bind by intercalation. On interaction with DNA, the ultraviolet absorption spectrum revealed downfield shifts and caused progressive diminution in both DNA and dipicolinate chromophores. The

James A. Lindsay; William G. Murrell

1986-01-01

285

Conductance of HCl, NaCl, Na acetate, and acetic acid in water-ethylene carbonate solvent mixtures at 25 and 40°C  

Microsoft Academic Search

The molar conductances of solutions of hydrochloric acid, sodium chloride, sodium acetate, and acetic acid were measured in water-ethylene carbonate (EC) solvent mixtures at 25 and 40°C. These solvents have dielectric constants higher than that of water. Four solvent compositions, in which the mole fraction (x2) of EC was 0.2, 0.4, 0.5, and 0.6, were studied at 25°C. For HCl

Barry R. Boerner; Roger G. Bates

1978-01-01

286

The effective dipole moments of isobutyric acid in the liquid state and dilute solutions in methanol  

Microsoft Academic Search

The dipole moments of isobutyric acid (I) were determined in the liquid state (?1) and dilute solutions in methanol (?1) at 20–50C. The permittivity of I in the liquid state was found to increase as the temperature grew, and the permittivity of solutions of I was lower than that of pure methanol; it decreased as the concentration of I and

A. Yu. Osadchev; T. P. Stepanova

2006-01-01

287

Effect of surface acidic oxides of activated carbon on adsorption of ammonia.  

PubMed

The influence of surface acidity of activated carbon (AC) was experimentally studied on adsorption of ammonia (NH(3)). Coconut shell-based AC was modified by various acids at different concentrations. There were five different acids employed to modified AC, which included nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, and acetic acid. Acidic functional groups on the surface of ACs were determined by a Fourier transform infrared spectrograph (FTIR) and by the Boehm titration method. Specific surface area and pore volume of the ACs were measured by a nitrogen adsorption apparatus. Adsorption amounts of NH(3) onto the ACs were measured by a dynamic adsorption system at room temperature according to the principle of the ASTM standard test method. The concentration of NH(3) in the effluent stream was monitored by a gas-detecting tube technique. Experimental results showed that adsorption amounts of NH(3) on the modified ACs were all enhanced. The ammonia adsorption amounts on various activated carbons modified by different acids are in the following order: nitric acid>sulfuric acid>acetic acid approximately phosphoric acid>hydrochloric acid. It is worth to note that the breakthrough capacity of NH(3) is linearly proportional to the amount of acidic functional groups of the ACs. PMID:18403110

Huang, Chen-Chia; Li, Hong-Song; Chen, Chien-Hung

2008-11-30

288

Galvanic Corrosion of a Carbon Steel-Stainless Steel Couple in Sulfide Solutions  

NASA Astrophysics Data System (ADS)

The galvanic corrosion behavior of carbon steel-stainless steel couples with various cathode/anode area ratios was investigated in S 2--containing solutions, which were in equilibrium with air, by electrochemical measurements, immersion test, and surface characterization. It is found that the galvanic corrosion effect on carbon steel anode increases with the cathode/anode area ratios, and decreases with the increasing concentration of S2- in the solution. A layer of sulfide film is formed on carbon steel surface, which protects it from corrosion. When the cathode/anode area ratio is 1:1, the potentiodynamic polarization curve measurement and the weight-loss determination give the identical measurement of the galvanic corrosion effect. With the increase of the cathode/anode area ratio, the electrochemical method may not be accurate to determine the galvanic effect. The anodic dissolution current density of carbon steel cannot be approximated simply with the galvanic current density.

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

2011-12-01

289

Adsorption of Basic Violet 14 in aqueous solutions using KMnO4-modified activated carbon.  

PubMed

In this paper, an activated carbon was prepared from Typha orientalis and then treated with KMnO(4) and used for the removal of Basic Violet 14 from aqueous solutions. KMnO(4) treatment influenced the physicochemical properties of the carbon and improved its adsorption capacity. Adsorption experiments were then conducted with KMnO(4)-modified activated carbon to study the effects of carbon dosage (250-1500 mg/L), pH (2-10), ion strength (0-0.5 mol/L), temperature, and contact time on the adsorption of Basic Violet 14 from aqueous solutions. The equilibrium data were analyzed by the Langmuir and Freundlich isotherms and fitted well with the Langmuir model. The pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to evaluate the kinetic data and the pseudo-second-order kinetics was the best with good correlation. PMID:20036370

Shi, Qianqian; Zhang, Jian; Zhang, Chenglu; Nie, Wei; Zhang, Bo; Zhang, Huayong

2010-03-01

290

Extraction of steroidal glucosideronic acids from aqueous solutions by anionic liquid ion-exchangers.  

PubMed

A pilot study on the extraction of three steroidal glucosiduronic acids from water into organic solutions of liquid ion-exchangers is reported. A single extraction of a 0.5mm aqueous solution of either 11-deoxycorticosterone 21-glucosiduronic acid or cortisone 21-glucosiduronic acid with 0.1m-tetraheptylammonium chloride in chloroform took more than 99% of the conjugate into the organic phase; under the same conditions, the very polar conjugate, beta-cortol 3-glucosiduronic acid, was extracted to the extent of 43%. The presence of a small amount of chloride, acetate, or sulphate ion in the aqueous phase inhibited extraction, but making the aqueous phase 4.0m with ammonium sulphate promoted extraction strongly. An increase in the concentration of ion-exchanger in the organic phase also promoted extraction. The amount of cortisone 21-glucosiduronic acid extracted by tetraheptylammonium chloride over the pH range of 3.9 to 10.7 was essentially constant. Chloroform solutions of a tertiary, a secondary, or a primary amine hydrochloride also will extract cortisone 21-glucosiduronic acid from water. The various liquid ion exchangers will extract steroidal glucosiduronic acid methyl esters from water into chloroform, although less completely than the corresponding free acids. The extraction of the glucosiduronic acids from water by tetraheptylammonium chloride occurs by an ion-exchange process; extraction of the esters does not involve ion exchange. PMID:5075264

Mattox, V R; Litwiller, R D; Goodrich, J E

1972-02-01

291

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

E-print Network

LIB' OF FIQUHRB PIGUBRB 1, Observers ohemi, cal shiftsoccurring in aqueous solutions of propiolLic acid o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 23 2 ~ Chemical shifts occurring in propionic acyl-diarane solull iona... ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 0 ~ ~ ~ 35 LIET OF TABES TAEIR6 l, Chemical shiftsoccurring in aqueous solutions of propionic PAGE ac id ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 21 2, Chemical shifts occurring in propionic ac1d-dioxane solut1ons 22 3. C...

Oldham, William J. Bryan

2012-06-07

292

The use of linear potentiometric titration curves in the determination of alkalinity and acid-base properties of diluted solutions of humic substances.  

PubMed

A critical study of the use of Gran and modified Gran functions for the determination of alkalinity and acid-base properties of diluted solutions containing humic substances is presented. These solutions were composed of 340 muM HCO3(-)(3) in 0, 10, 20.5 and 41 mg/1. of sodium humate in order to simulate natural waters with different levels of dissolved organic carbon. The results showed that the alkalinity may be determined in good agreement with the expected value using both methodologies. The modified Gran functions give information about acid-base speciation in addition to the alkalinity. The application of the modified Gran functions for determination of humic acid pK(a)s and stoichiometry was studied under conditions simulating waters rich in natural organic matter in terms of humic acid concentrations. PMID:18966083

Masini, J C

1994-08-01

293

Phosphate Removal from Aqueous Solution Using Coir-Pith Activated Carbon  

Microsoft Academic Search

The present study deals with the removal of phosphates from aqueous solution using activated carbon developed from coir pith. Batch adsorption experiments were performed to delineate the effect of initial pH, contact time, adsorbent dose and temperature on the removal of phosphates by coir-pith activated carbon (CAC) (activated by H2SO4). The removal was found to be maximum in the pH

Pradeep Kumar; S. Sudha; Shri Chand; Vimal Chandra Srivastava

2010-01-01

294

Computational investigation of carbon dioxide absorption in alkanolamine solutions.  

PubMed

We investigated CO2 absorption in aqueous alkanolamine solutions using density functional theory with dielectric continuum solvation models (SMD/IEF-PCM and COSMO-RS). We varied the alkyl chain length (m?=?2, 3, 4) and the alcohol chain length (n?=?2, 3, 4) in the alkanolamine structures, H(CH2) m NH(CH2) n OH. Using the SMD/IEF-PCM/B3LYP/6-311++G(d,p) and COSMO-RS/BP/TZVP levels of theory, our calculations predict that the product of CO2 absorption (carbamate or bicarbonate) is strongly affected by the alcohol length but does not differ significantly by varying the alkyl chain length. This prediction was confirmed experimentally by (13)C-NMR. The observed sensitivity to the alcohol chain length can be attributed to hydrogen bonding effects. The intramolecular hydrogen bonds of HN · · · HO, NH2 (+) · · · OH, and NCOO(-) · · · HO induce ring structure formation in neutral alkanolamines, protonated alkanolamines, and carbamate anions, respectively. The results from our studies demonstrate that intramolecular hydrogen bonds play a key role in CO2 absorption reactions in aqueous alkanolamine solutions. PMID:23306736

Yamada, Hidetaka; Matsuzaki, Yoichi; Chowdhury, Firoz; Higashii, Takayuki

2013-10-01

295

Removal of copper and cadmium from the aqueous solutions by activated carbon derived from Ceiba pentandra hulls.  

PubMed

Activated carbon prepared from Ceiba pentandra hulls, an agricultural solid waste by-product, for the removal of copper and cadmium from aqueous solutions has been studied. Parameters such as equilibrium time, effect of pH and adsorbent dose on removal were studied. The adsorbent exhibited good sorption potential for copper and cadmium at pH 6.0. C=O and S=O functional groups present on the carbon surface were the adsorption sites to remove metal ions from solution. The experimental data was analysed by both Freundlich and Langmuir isotherm models. The maximum adsorption capacity of copper and cadmium was calculated from Langmuir isotherm and found to be 20.8 and 19.5 mg/g, respectively. The sorption kinetics of the copper and cadmium have been analysed by Lagergren pseudo-first-order and pseudo-second-order kinetic models. The desorption studies were carried out using dilute hydrochloric acid solution and the effect of HCl concentration on desorption was also studied. Maximum desorption of 90% for copper and 88% for cadmium occurred with 0.2 M HCl. PMID:16191464

Rao, M Madhava; Ramesh, A; Rao, G Purna Chandra; Seshaiah, K

2006-02-28

296

High-performance thin-film transistors produced from highly separated solution-processed carbon nanotubes  

NASA Astrophysics Data System (ADS)

Transistors utilizing carbon nanotube (CNT) thin films have exhibited high on-currents and mobilites greater than those of alternative channel materials. One critical problem that has limited the utilization of CNT thin-film transistors (TFTs) is the occurrence of unavoidable parasitic current paths stemming from metallic nanotubes. In this work, we experimentally demonstrate high-yield, high-performance TFTs composed of a highly purified single-walled carbon nanotube (SWNT) network. A solution process for a highly separated 99.9% semiconducting SWNT solution is used to acquire a significant enhancement in transistor performance, such as a high on/off ratio, high mobility, and high yields close to 100%.

Lee, Dongil; Seol, Myeong-Lok; Moon, Dong-Il; Bennett, Patrick; Yoder, Nathan; Humes, Jefford; Bokor, Jeffrey; Choi, Yang-Kyu; Choi, Sung-Jin

2014-04-01

297

Succinic acid in aqueous solution: connecting microscopic surface composition and macroscopic surface tension.  

PubMed

The water-vapor interface of aqueous solutions of succinic acid, where pH values and bulk concentrations were varied, has been studied using surface sensitive X-ray photoelectron spectroscopy (XPS) and molecular dynamics (MD) simulations. It was found that succinic acid has a considerably higher propensity to reside in the aqueous surface region than its deprotonated form, which is effectively depleted from the surface due to the two strongly hydrated carboxylate groups. From both XPS experiments and MD simulations a strongly increased concentration of the acid form in the surface region compared to the bulk concentration was found and quantified. Detailed analysis of the surface of succinic acid solutions at different bulk concentrations led to the conclusion that succinic acid saturates the aqueous surface at high bulk concentrations. With the aid of MD simulations the thickness of the surface layer could be estimated, which enabled the quantification of surface concentration of succinic acid as a multiple of the known bulk concentration. The obtained enrichment factors were successfully used to model the surface tension of these binary aqueous solutions using two different models that account for the surface enrichment. This underlines the close correlation of increased concentration at the surface relative to the bulk and reduced surface tension of aqueous solutions of succinic acid. The results of this study shed light on the microscopic origin of surface tension, a macroscopic property. Furthermore, the impact of the results from this study on atmospheric modeling is discussed. PMID:25182698

Werner, Josephina; Julin, Jan; Dalirian, Maryam; Prisle, Nønne L; Öhrwall, Gunnar; Persson, Ingmar; Björneholm, Olle; Riipinen, Ilona

2014-10-21

298

Labradorite dissolution in aqueous organic acid solutions: an experimental study  

E-print Network

H-buffered solutions of 0.07m acetate(pHi=3.5, 4.7, 5.4), 0.07m acetate0.005m oxalate (pHi=4.4), and 0.07m acetate-0.005m citrate (pHi=4.4). Pore fluid flow was essentially constant (25-30 ml/hr) for rate studies and semi-static and slow (0.03-0.3 ml/hr) for solubility...

Ahmed, MD. Raquib Uddin

2012-06-07

299

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

300

Growth behavior of anodic porous alumina formed in malic acid solution  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

301

Biosynthesis of delta-aminolevulinic acid from the intact carbon skeleton of glutamic acid in greening barley.  

PubMed Central

The customary route in animals and bacteria for delta-aminolevulinic acid biosynthesis is from glycine and succinyl CoA, catalyzed by the enzyme delta-aminolevulinic acid synthetase [succinyl-CoA:glycine C-succinyltransferase (decarboxylating), EC 2.3.1.37]. Attempts to demonstrate this route in plants have been unsuccessful. Evidence is given for a new enzymic route of synthesis of delta-aminolevulinic acid in plants. This route involves the incorporation of the intact five-carbon skeleton of glutamic acid into delta-aminolevulinic acid. Demonstration of the new pathway in plants has been made by feeding specifically labeled [14C]glutamic acid to etiolated barley shoots greening in the light. In the presence of levulinate, a competitive inhibitor of delta-aminolevulinic acid dehydrastase [porphobilinogen synthase; delta-aminolevulinate hydro-lyase (adding delta-aminolevulinate and cyclizing); EC 4.2.1.24], delta-aminolevulinate accumulates. The delta-aminolevulinate formed was chemically degraded by periodate to formaldehyde and succinic acid. The C5 (formaldehyde) fragment was separated, as the 5,5-dimethyl-1,3-cyclohexanedione (dimedone) derivative, from the C1-C4 (succinic acid) fragment. The C5 atom contained radioactivity predominantly derived from C1 of glutamic acid. Conversely, the labeled C3 and C4 atoms of glutamic acid were found primarily in the succinic acid (C1-C4) fragment of delta-aminolevulinate. This labeling pattern for delta-aminolevulinic acid is consistent with a biosynthetic route utilizing the intact five-carbon skeleton of alpha-ketoglutarate, glutamate, or glutamine, and is inconsistent with the delta-aminolevulinic acid synthetase pathway utilizing glycine and succinyl CoA as precursors. PMID:1058487

Beale, S I; Gough, S P; Granick, S

1975-01-01

302

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

303

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

304

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

305

The kinetics of oxidation of bilirubin and ascorbic acid in solution  

NASA Astrophysics Data System (ADS)

The results of a comparative study of the oxidation of bilirubin, ascorbic acid, and their mixture in aqueous solutions under the action of air oxygen and hydrogen peroxide are presented. The observed and true rate constants for the oxidation reactions were determined. It was shown that the oxidation of tetrapyrrole pigment occurred under these conditions bypassing the stage of biliverdin formation to monopyrrole products. Simultaneous oxidation of bilirubin and ascorbic acid was shown to be accompanied by the inhibition of ascorbic acid oxidation by bilirubin, whereas ascorbic acid itself activated the oxidation of bilirubin.

Solomonov, A. V.; Rumyantsev, E. V.; Kochergin, B. A.; Antina, E. V.

2012-07-01

306

Surfactant Screening to Alter the Wettability and Aid in Acidizing Carbonate Formations  

E-print Network

Surfactant flooding in carbonate matrix acidizing treatment has been widely used for changing the wettability of the rock and to achieve low IFT values. Optimizing the type of surfactant and concentration for the specific oil field is very important...

Yadhalli Shivaprasad, Arun Kumar

2013-02-26

307

Evaluation of peritoneal dialysis solutions with amino acids and glycerol in a rat model.  

PubMed

In this study a simple rat model for evaluating the ultrafiltration by peritoneal dialysis solutions is described. Anaesthetised male Sprague-Dawley rats were injected intraperitoneally with dialysis solutions. Zero, 1, 3, or 6 h later, the dialysate volume was determined directly: the abdomen was carefully opened, the intraperitoneal liquid was withdrawn with a syringe and its volume was measured. Good recovery of dialysate, highly reproducible results, and the similarity between the ultrafiltration profiles in rats and published profiles in CAPD patients for control solutions, indicate that the model is valid. The model was then used to evaluate peritoneal dialysis solutions containing a mixture of glycerol and amino acids. Both osmotic agents are chemically compatible and these mixtures provide amino acids and carbohydrates in a single solution. For three mixtures, intraperitoneal dialysate volume were determined as a function of dwell time and the formulation with the desired ultrafiltration could be selected. PMID:1857524

Faict, D; Lameire, N; Kesteloot, D; Peluso, F

1991-01-01

308

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

309

Gas-phase preparation of carbonic Acid and its monomethyl ester.  

PubMed

Carbonic acid (H2 CO3 ), an essential molecule of life (e.g., as bicarbonate buffer), has been well characterized in solution and in the solid state, but for a long time, it has eluded its spectral characterization in the gas phase owing to a lack of convenient preparation methods; microwave spectra were recorded only recently. Here we present a novel and general method for the preparation of H2 CO3 and its monomethyl ester (CH3 OCO2 H) through the gas-phase pyrolysis of di-tert-butyl and tert-butyl methyl carbonate, respectively. H2 CO3 and CH3 OCO2 H were trapped in noble-gas matrices at 8?K, and their infrared spectra match those computed at high levels of theory [focal point analysis beyond CCSD(T)/cc-pVQZ] very well. Whereas the spectra also perfectly agree with those of the vapor phase above the ?-polymorph of H2 CO3 , this is not true for the previously reported ?-polymorph. Instead, the vapor phase above ?-H2 CO3 corresponds to CH3 OCO2 H, which sheds new light on the research that has been conducted on molecular H2 CO3 over the last decades. PMID:25196920

Reisenauer, Hans Peter; Wagner, J Philipp; Schreiner, Peter R

2014-10-27

310

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

E-print Network

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

Mishra, Varun

2009-06-02

311

Effective Condition for Purification of Multi-Walled Carbon Nanotubes by Nitric Acid  

Microsoft Academic Search

The multi-walled carbon nanotubes were synthesized on Fe-Ni bimetallic catalysts supported by MgO using thermal chemical vapor deposition. A comparative study on the effect of nitric acid molarity and time duration of acid treatment on purification of multi-walled nanotubes was done. The studies revealed that for finding a suitable condition for purification of multi-walled carbon nanotubes, it is necessary to

S. Mirershadi; S. Z. Mortazavi; A. Reyhani; N. Moniri; A. J. Novinrooz

2009-01-01

312

Effective Condition for Purification of Multi-walled Carbon Nanotubes by Nitric Acid  

Microsoft Academic Search

The multi-walled carbon nanotubes were synthesized on Fe-Ni bimetallic catalysts supported by MgO using thermal chemical vapor deposition. A comparative study on the effect of nitric acid molarity and time duration of acid treatment on purification of multi-walled nanotubes was done. The studies revealed that for finding a suitable condition for purification of multi-walled carbon nanotubes, it is necessary to

S. Mirershadi; S. Z. Mortazavi; A. Reyhani; N. Moniri; A. J. Novinrooz

2009-01-01

313

Properties of carbonized and converted uranium-loaded weak-acid resins  

Microsoft Academic Search

Weak-acid ion-exchange resins have been found to provide a practical method for fabricating uranium-containing HTGR fuel kernels. Two steps, thermal decomposition or carbonization and carbothermic reduction of UO or conversion, are required in the manufacture of these kernels. The property variations during carbonization of uranium-loaded weak-acid resin-derived fuel proceeds in a manner closely analogous to its thermogravimetric characteristics, particularly the

G. W. Weber; R. L. Beatty; V. J. Tennery

1977-01-01

314

Corrosion Phenomenon of Stainless Steel in Boiling Nitric Acid Solution Using Large-Scale Mock-Up of Reduced Pressurized Evaporator  

Microsoft Academic Search

To evaluate the component life in a spent nuclear fuel reprocessing plant, a large-scale mock-up test apparatus of a reduced pressurized thermosiphon evaporator was constructed, and the corrosion mechanism of a heat transfer tube made of ultralow carbon type 304 stainless steel in boiling nitric acid solution was studied. The corrosion tests were conducted for about 36,000 h, and changes

Fumiyoshi UENO; Chiaki KATO; Takafumi MOTOOKA; Shiro ICHIKAWAY; Masahiro YAMAMOTO

2008-01-01

315

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

316

Regeneration of hexamminecobalt(II) catalyzed by activated carbon treated with KOH solutions.  

PubMed

The combined elimination of NO and SO(2) can be realized by hexamminecobalt(II) solution which is formed by adding soluble cobalt(II) salt into the aqueous ammonia solution. Activated carbon is used as a catalyst to regenerate hexamminecobalt(II), Co(NH(3))(6)(2+), so that NO removal efficiency can be maintained at a high level for a long time. In this study, KOH solution has been explored to modify coconut activated carbon to meliorate its catalytic performance in the reduction of hexamminecobalt(III), Co(NH(3))(6)(3+). The experiments have been performed in a batch stirred cell to investigate the effects of KOH concentration, impregnation duration, activation temperature and activation duration on the performance of activated carbon. The results show that the best KOH concentration for the improvement of activated carbon is 0.5 mol l(-1). The optimal impregnation duration is 9h. High temperature is favorable to ameliorating the catalytic performance of activated carbon. The optimum activation duration is 4h. PMID:21555182

Cheng, Jing-yi; Yang, Lin; Dong, Li; Long, Xiang-li; Yuan, Wei-kang

2011-07-15

317

SIMULTANEOUS INHIBITION OF CARBON AND NITROGEN MINERALIZATION IN A FOREST SOIL BY SIMULATED ACID PRECIPITATION  

EPA Science Inventory

Acid Precipitation may alter the rates of microbial processes in soil that are important for forest productivity. Acidification of soil can result in a depression of carbon mineralization. The present study was designed to determine whether the inhibition of carbon mineralization...

318

USE OF THE COMPOSITION AND STABLE CARBONIISOTOPE RATIO OF MICROBIAL FATTY ACIDS TO STUDY CARBON CYCLING  

EPA Science Inventory

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

319

Formic acid oxidation at spontaneously deposited palladium on polyaniline modified carbon fibre paper  

Microsoft Academic Search

Extended reaction zone anodes for formic acid oxidation have been prepared by the spontaneous deposition of Pd on polyaniline coated carbon fibre paper. The PANI supports, deposited on carbon fibre paper either galvanostatically, potentiostatically, or potentiodynamically, were characterized by electron microscopy, cyclic voltammetry and impedance spectroscopy. Pd was deposited on them by spontaneous reduction of Pd(II) by the reduced form

Reza B. Moghaddam; Peter G. Pickup

2011-01-01

320

Production of activated carbon from a new precursor molasses by activation with sulphuric acid  

Microsoft Academic Search

Activated carbon has been prepared from molasses, a natural precursor of vegetable origin resulting from the sugar industry in Morocco. The preparation of the activated carbon from the molasses has been carried out by impregnation of the precursor with sulphuric acid, followed by carbonisation at varying conditions (temperature and gas coverage) in order to optimize preparation parameters. The influence of

K. Legrouri; E. Khouya; M. Ezzine; H. Hannache; R. Denoyel; R. Pallier; R. Naslain

2005-01-01

321

Mutvei's solution: An ideal agent for resolving microgrowth structures of biogenic carbonates  

E-print Network

illumination) and scanning electron microscopy can be used to analyze the microgrowth structures. WeMutvei's solution: An ideal agent for resolving microgrowth structures of biogenic carbonates Bernd as environmental and physiological proxies, and growth increments as calendars. Recognition of growth structures

Schöne, Bernd R.

322

Version 3.0 SOP 14 --Sodium carbonate solutions October 12, 2007 Page 1 of 3  

E-print Network

water (If desired, carbon dioxide can be removed by boiling and allowing to cool in a stream of nitrogen procedure is carried out for each solution prepared: · Weigh out the necessary amount of salt in a small water, filling from the bottom of the flask through a piece of tubing. · Using a funnel, transfer

323

Sorption of metal ions from multicomponent aqueous solutions by activated carbons produced from waste  

SciTech Connect

Activated carbons produced by thermal treatment of a mixture of sunflower husks, low-grade coal, and refinery waste were studied as adsorbents of transition ion metals from aqueous solutions of various compositions. The optimal conditions and the mechanism of sorption, as well as the structure of the sorbents, were studied.

Tikhonova, L.P.; Goba, V.E.; Kovtun, M.F.; Tarasenko, Y.A.; Khavryuchenko, V.D.; Lyubchik, S.B.; Boiko, A.N. [National Academy of Science Ukraine, Kiev (Ukraine). Institute of Coal Chemistry

2008-08-15

324

Partial molar volume reduction of solvent for solute crystallization using carbon dioxide as antisolvent  

Microsoft Academic Search

The gas antisolvent crystallization (GASC) process using dense carbon dioxide (CO2) as antisolvent is particularly useful for purification and micronization of thermo-labile bioactive solid substances. Conventionally, the GASC process is characterized by the relative total volume expansion or the relative molar volume expansion of the solution. A new criterion is proposed in this work in terms of the relative partial

Mamata Mukhopadhyay

2003-01-01

325

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

326

Enhancement of basic dye adsorption uptake from aqueous solutions using chemically modified oil palm shell activated carbon  

Microsoft Academic Search

The effect of hydrochloric acid (HCl) treatment of activated carbon prepared from oil palm shell on methylene blue (MB) adsorption was investigated. The Fourier transform infrared spectroscopy (FTIR) measurements showed that the surface chemistry of the activated carbon was influenced by the acidic treatment. Adsorption equilibrium data were fitted to the Langmuir, Freundlich and Dubinin–Radushkevich isotherm models. The equilibrium data

I. A. W. Tan; A. L. Ahmad; B. H. Hameed

2008-01-01

327

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

328

Catalytic wet air oxidation of acetic acid on carbon-supported ruthenium catalysts  

SciTech Connect

Ruthenium catalysts prepared by ion exchange of active carbons and high-surface-area graphites are active for the wet air oxidation of aqueous solutions of acetic acid (5-20 g/liter). A total conversion into CO{sub 2} can be achieved between 448 and 473 K using air as oxidizing agent. No leaching of ruthenium can be detected which indicates that the reaction proceeds on the heterogeneous catalysts. For the same particle size (1 nm), graphite-supported ruthenium catalysts are much more active (up to 0.4 mol h{sup -1} g{sub RU}{sup -1} at 473 K in a stirred batch reactor pressurized with air at 10 MPa) than active carbon-supported catalysts. The lower activities of the latters could be due to internal diffusion limitation since the 1-nm Ru particles are located inside the micropores. However, graphite-supported catalysts might be intrinsically more active because of an electron transfer from graphite to metal particles which would increase the resistance of ruthenium to oxygen poisoning. It was also shown that the activity of ruthenium is particle size dependent: the smaller the sizes, the lower the activities. This effect could be interpreted by the higher adsorption energy of oxygen on the small particles which produces a poisoning of the metal surface. From measurements of the reaction rates on the Ru/HSAG graphite catalyst at different temperatures, pressures, and acetic acid concentrations, it was established that the reaction orders were zero and 0.65 with respect to the concentration and oxygen pressure, respectively; the activation energy of the reaction was 100.5 kJ mol{sup -1}. An equation describing the reaction kinetics was proposed. 23 refs., 4 figs., 2 tabs.

Gallezot, P.; Chaumet, S.; Perrard, A. [Institut de Recherches sur la Catalyse, Villeurbanne (France)] [and others] [Institut de Recherches sur la Catalyse, Villeurbanne (France); and others

1997-05-01

329

Formation of amino acids by cobalt-60 irradiation of hydrogen cyanide solutions  

NASA Technical Reports Server (NTRS)

Experiments were conducted to study the pathway for the prebiotic origin of amino acids from hydrogen cyanide (HCN) under the action of ionizing radiation considered as an effective source of energy on the primitive earth. The irradiations were performed in a cobalt-60 source with a dose rate of 200,000 rad/hr. Seven naturally occurring amino acids are identified among the products formed by the hydrolysis of gamma-irradiated solutions of HCN: glycine, alanine, valine, serine, threonine, aspartic acid, and glutamic acid. The identity of these amino acids is established by gas chromatography and mass spectrometry. Control experiments provided evidence that the amino acids are not the result of contamination.

Sweeney, M. A.; Toste, A. P.; Ponnamperuma, C.

1976-01-01

330

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

331

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

332

Regeneration of carboxylic acid-amine extracts by back-extraction with an aqueous solution of a volatile amine  

Microsoft Academic Search

Tertiar amines are effective extractants for the recovery of carboxylic acids from aqueous solution. An approach for regeneration and product recovery from such extracts is to back-extract the carboxylic acid with a water-soluble, volatile tertiary amine, such as trimethylamine. The resulting trimethylammonium carboxylate solution can be concentrated and thermally decomposed, yielding the product acid and the volatile amine for recycle.

I. J. Poole; C. Judson King

1991-01-01

333

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

334

Selective removal of cadmium from mixed metal solution by carbonate infusion  

SciTech Connect

The purpose of this study is to develop the technology of selective precipitation of a single metal from a mixed solution by carbonate infusion. Experiments were conducted in Pyrex reactors and jar testers. Synthetic wastewater of cadmium and copper mixed solution was used in this study. Initial cadmium and copper concentrations were 10{sup {minus}5}, 10{sup {minus}4}, 10{sup {minus}3} M, which are the concentrations commonly occurring in electroplating rinsewater. The effects of pH, carbonate concentration, and mixing rate on copper and cadmium hydrolysis were investigated. The optimum conditions of selective precipitation for the cadmium form mixed solutions were around pH 9, and the mixing rate was 100 rpm.

Cho, S.H.; Young, K.K. (Ajou Univ. Suwon (Korea))

1991-01-01

335

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

336

Effects of sulfuric acid rain on two model hardwood forests: throughfall, litter leachate, and soil solution  

SciTech Connect

Simulated sulfuric acid rain (pH 3.0, 3.5, 4.5, and 5.6) was applied to model forests containing either sugar maple (Acer saccharum) or red alder (Alnus rubra). Water samples were collected above and below the canopy, below the litter, and from 20 cm and 1 m below the surface of the soil. While throughfall chemistry was not very different from rain chemistry, the litter leachate (the actual input to the soil) had consistently higher concentrations of calcium and magnesium, and higher pH than the acid rain. For the first 6 months, sulfate absorption by the soil prevented any apparent differences in sulfate, calcium, or magnesium concentrations in the 20-cm soil solution among plots receiving acid or control rain treatments. Sulfate concentrations on plots receiving the most acid rain (pH 3.0) then became increasingly higher than on the other plots until after 3 years, they were approximately equal to sulfate concentrations in the rain. Twenty-cm soil solutions corresponding to the pH 3.5 and 4.0 treatments responded similarly starting respectively 1 year and 2 years after initiation of exposure to acid rain. Increased calcium and magnesium concentrations and lowered pH in 20-cm soil solution occurred simultaneously with increased sulfate concentrations. No acid rain related effects were evident in the 1-m soil solution even after 3.5 years exposure to pH 3.0 sulfuric acid rain. Cation responses to increased anion concentrations followed those predicted by a computer-simulation model. However, sulfate concentrations in 20-cm soil solutions increased considerably faster than predicted by a Langmuir formulation of sulfate absorption.

Lee, J.J.; Weber, D.E.

1980-01-01

337

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-acid adsorption are bias-dependent. PACS number: 72.80.RJ Submitted to: Nanotechnology #12;Bias that is confirmed by calculations for armchair tubes that are not presented in this paper), or semiconducting tubes

Pulfrey, David L.

338

Sulfate Reducing Rate of SRB with Acetic, Propionic, n-Butyric Acids as Carbon Sources  

Microsoft Academic Search

The aim of this work was to determine the kind of short-chain volatile fatty acid, which is apt to be used by sulfate reducing bacteria (SRB). SRB was feed with culture media used sodium lactate as carbon source. Sulfate reducing rate and different short-chain volatile fatty acids (VFA) utilization rate with SRB were studied. Sulfate variation curves were drawn and

Xiulan Song; Zhimin Zhang

2011-01-01

339

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

Microsoft Academic Search

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

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

2006-01-01

340

Seasonal variations of water-soluble organic carbon, dicarboxylic acids, ketocarboxylic acids, and ?-dicarbonyls in Central Himalayan aerosols  

NASA Astrophysics Data System (ADS)

Aerosol samples were collected from a high elevation mountain site (Nainital, India; 1958 m a.s.l.) in the central Himalayas, a location that provides an isolated platform above the planetary boundary layer to better understand the composition of the remote continental troposphere. The samples were analyzed for water-soluble dicarboxylic acids (C2-C12) and related compounds (ketocarboxylic acids and ?-dicarbonyls), as well as organic carbon, elemental carbon and water soluble organic carbon. The contributions of total dicarboxylic acids to total aerosol carbon during wintertime were 1.7% and 1.8%, for day and night, respectively whereas they were significantly smaller during summer. Molecular distributions of diacids revealed that oxalic (C2) acid was the most abundant species followed by succinic (C4) and malonic (C3) acids. The average concentrations of total diacids (433±108 ng m-3), ketoacids (48±23 ng m-3), and ?-dicarbonyls (9±4 ng m-3) were similar to those from large Asian cities such as Tokyo, Beijing and Hong Kong. During summer most of the organic species were several times more abundant than in winter. Phthalic acid, which originates from oxidation of polycyclic aromatic hydrocarbons such as naphthalene, was found to be 7 times higher in summer than winter. This feature has not been reported before in atmospheric aerosols. Based on molecular distributions and air mass backward trajectories, we conclude that dicarboxylic acids and related compounds in Himalayan aerosols are derived from anthropogenic activities in the highly populated Indo-Gangetic plain areas.

Hegde, P.; Kawamura, K.

2012-07-01

341

Extraction of succinic acid with 1-octanol\\/ n -heptane solutions of mixed tertiary amine  

Microsoft Academic Search

The reactive extraction of succinic acid was carried out by mixed tertiary amine which consisted of tripropylamine (TPA) and trioctylamine (TOA) as the extraction agent in 1-octanol\\/n-heptane diluent. Maximum distribution coefficient was obtained at 8:2 weight ratio of TPA\\/TOA. At this ratio, its extraction efficiency is above 90% at the 3.9 wt.% of succinic acid in aqueous solution. Furthermore, the

Y. K. Hong; W. H. Hong

2000-01-01

342

PHASE SEPARATION OF POLY(AMIC ACID-CO-IMIDE) SOLUTION  

Microsoft Academic Search

Poly(amic acid-co-imide) (PA-I) is an intermediate for preparation of polyimide from polyamic acid (PAA). Phase separation does not appear for the solution until a certain imidization degree. The experimental results of a rotation viscometer and FT-IR analysis showed that the critical point of phase separation (CPPS) was related to the imidization methods (thermal or chemical imidization) and the backbone structures

Yan Zhai; Ye Huang; Rongqi Zhu; Yi Gu

2009-01-01

343

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

344

Dissolution of mechanically activated Panzhihua ilmenites in dilute solutions of sulphuric acid  

Microsoft Academic Search

Dissolution of mechanically activated Panzhihua ilmenite was conducted in 5–20% sulphuric acid solutions. With high milling intensity the milling atmosphere significantly affected the dissolution with milling under vacuum almost double the dissolution of ilmenite milled in air. This was due to formation of a lot of acid-resistant pseudorutile and lowering level of the lattice strains, especially in the c-axis direction

Chun Li; Bin Liang; Ling-hong Guo

2007-01-01

345

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

346

Recovery of water and acid from leach solutions using direct contact membrane distillation.  

PubMed

This paper describes for the first time the use of direct contact membrane distillation (DCMD) for acid and water recovery from a real leach solution generated by a hydrometallurgical plant. The leach solutions considered contained H2SO4 or HCl. In all tests the temperature of the feed solution was kept at 60 °C. The test work showed that fluxes were within the range of 18-33 kg/m(2)/h and 15-35 kg/m(2)/h for the H2SO4 and HCl systems, respectively. In the H2SO4 leach system, the final concentration of free acid in the sample solution increased on the concentrate side of the DCMD system from 1.04 M up to 4.60 M. The sulfate separation efficiency was over 99.9% and overall water recovery exceeded 80%. In the HCl leach system, HCl vapour passed through the membrane from the feed side to the permeate. The concentration of HCl captured in the permeate was about 1.10 M leaving behind only 0.41 M in the feed from the initial concentration of 2.13 M. In all the experiments, salt rejection was >99.9%. DCMD is clearly viable for high recovery of high quality water and concentrated H2SO4 from spent sulfuric acid leach solution where solvent extraction could then be applied to recover the sulfuric acid and metals. While HCl can be recovered for reuse using only DCMD. PMID:24569289

Kesieme, Uchenna K; Milne, Nicholas; Cheng, Chu Yong; Aral, Hal; Duke, Mikel

2014-01-01

347

Extraction of chromium (VI) from multicomponent acidic solutions by emulsion liquid membranes using TOPO as extractant.  

PubMed

Experimental results for the extraction of chromium (VI) from multicomponent acidic solutions by emulsion liquid membrane (ELM) using trioctylphosphine oxide (TOPO) as extractant are presented. The membrane phase consists of kerosene as diluent, TOPO as extractant, ECA 4360J (a nonionic polyamine) as surfactant and (NH(4))(2)CO(3) solution as stripping phase. Effects of various parameters such as mixing speed, type and concentration of stripping solution, surfactant and extractant concentrations, and volume ratio of the membrane phase to internal stripping phase on Cr (VI) extraction were studied and optimum conditions were determined. Results show that with proper adjustment of experimental conditions for the extraction of Cr (VI) can be enhanced to a great extent. This study also examined the effects of concentrations of acid and metal ions in the feed phase for the extraction of Cr (VI) ions. The results also showed that by appropriate selection of the extraction and stability conditions, nearly all of the Cr (VI) ions (100-500 mg/L) present in the acidic feed solution containing 1000 mg/L from each of Cu (II), Zn (II), Co (II), Ni (II) and Cd (II) ions were extracted within a few minutes. Concentration variations of Cr (VI) and other ions in the acidic solutions were determined by atomic absorption spectrophotometry. PMID:19250744

Ali Kumbasar, Recep

2009-08-15

348

Fabrication of carbonate apatite blocks from set gypsum based on dissolution-precipitation reaction in phosphate-carbonate mixed solution.  

PubMed

Carbonate apatite (CO3Ap), fabricated by dissolution-precipitation reaction based on an appropriate precursor, is expected to be replaced by bone according to bone remodeling cycle. One of the precursor candidates is gypsum because it shows self-setting ability, which then enables it to be shaped and molded. The aim of this study, therefore, was to fabricate CO3Ap blocks from set gypsum. Set gypsum was immersed in a mixed solution of 0.4 mol/L disodium hydrogen phosphate (Na2HPO4) and 0.4 mol/L sodium hydrogen carbonate (NaHCO3) at 80-200°C for 6-48 h. Powder X-ray diffraction patterns and Fourier transform infrared spectra showed that CO3Ap block was fabricated by dissolution-precipitation reaction in Na2HPO4-NaHCO3 solution using set gypsum in 48 h when the temperature was 100°C or higher. Conversion rate to CO3Ap increased with treatment temperature. CO3Ap block containing a larger amount of carbonate was obtained when treated at lower temperature. PMID:24614998

Nomura, Shunsuke; Tsuru, Kanji; Maruta, Michito; Matsuya, Shigeki; Takahashi, Ichiro; Ishikawa, Kunio

2014-01-01

349

Effect of carbon chain length on esterification of carboxylic acids with methanol using acid catalysis  

Microsoft Academic Search

This paper reports on an investigation into the impact of carboxylic acid chain length on the kinetics of liquid-phase acid-catalyzed esterification. Using sulfuric acid and a commercial Nafion\\/silica composite solid acid catalyst (SAC-13), initial kinetics were measured for the reactions of a series of linear chain carboxylic acids (acetic, propionic, butyric, hexanoic, and caprylic acid) with methanol at 60?°C. It

Yijun Liu; Edgar Lotero; James G. Goodwin

2006-01-01

350

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

351

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

352

Preparation of activated mesoporous carbons for electrosorption of ions from aqueous solutions  

SciTech Connect

Mesoporous carbon with a narrow pore size distribution centered at about 9 nm, which was prepared by self assembly of block copolymer and phloroglucinol-formaldehyde resin via the soft-template method, was activated by CO{sub 2} and potassium hydroxide (KOH). The effects of activation conditions, such as the temperature, activation time, and mass ratio of KOH/C, on the textural properties of the resulting activated mesoporous carbons were investigated. Activated mesoporous carbons exhibit high BET specific surface areas (up to {approx} 2000 m{sup 2} g{sup -1}) and large pore volumes (up to {approx} 1.6 cm{sup 3} g{sup -1}), but still maintain a highly mesoporous structure. Heat treatment of mesoporous carbons by CO{sub 2} generally requires a moderate to high extent of activation in order to increase its BET surface area by 2-3 times, while KOH activation needs a much smaller degree of activation than the former to reach an identical surface area, ensuring high yields of activated mesoporous carbons. In addition, KOH activation allows a controllable degree of activation by adjusting the mass ratio of KOH/C (2-8), as evidenced by the fact that surface area and pore volume increase with the mass ratio of KOH/C. The electrosorption properties of activated mesoporous carbons were investigated by cyclic voltammetry in 0.1 M NaCl aqueous solutions. Upon activation, the electrosorption capacitance of activated mesoporous carbons was greatly enhanced.

Dai, Sheng [ORNL; Lee, Jeseung [ORNL; Tsouris, Costas [ORNL; DePaoli, David W [ORNL; Wang, Xiqing [ORNL

2010-01-01

353

Structural and functional characterization of solute binding proteins for aromatic compounds derived from lignin: p-coumaric acid and related aromatic acids.  

PubMed

Lignin comprises 15-25% of plant biomass and represents a major environmental carbon source for utilization by soil microorganisms. Access to this energy resource requires the action of fungal and bacterial enzymes to break down the lignin polymer into a complex assortment of aromatic compounds that can be transported into the cells. To improve our understanding of the utilization of lignin by microorganisms, we characterized the molecular properties of solute binding proteins of ATP-binding cassette transporter proteins that interact with these compounds. A combination of functional screens and structural studies characterized the binding specificity of the solute binding proteins for aromatic compounds derived from lignin such as p-coumarate, 3-phenylpropionic acid and compounds with more complex ring substitutions. A ligand screen based on thermal stabilization identified several binding protein clusters that exhibit preferences based on the size or number of aromatic ring substituents. Multiple X-ray crystal structures of protein-ligand complexes for these clusters identified the molecular basis of the binding specificity for the lignin-derived aromatic compounds. The screens and structural data provide new functional assignments for these solute-binding proteins which can be used to infer their transport specificity. This knowledge of the functional roles and molecular binding specificity of these proteins will support the identification of the specific enzymes and regulatory proteins of peripheral pathways that funnel these compounds to central metabolic pathways and will improve the predictive power of sequence-based functional annotation methods for this family of proteins. PMID:23606130

Tan, Kemin; Chang, Changsoo; Cuff, Marianne; Osipiuk, Jerzy; Landorf, Elizabeth; Mack, Jamey C; Zerbs, Sarah; Joachimiak, Andrzej; Collart, Frank R

2013-10-01

354

Structural and functional characterization of solute binding proteins for aromatic compounds derived from lignin: p-coumaric acid and related aromatic acids  

PubMed Central

Lignin comprises 15.25% of plant biomass and represents a major environmental carbon source for utilization by soil microorganisms. Access to this energy resource requires the action of fungal and bacterial enzymes to break down the lignin polymer into a complex assortment of aromatic compounds that can be transported into the cells. To improve our understanding of the utilization of lignin by microorganisms, we characterized the molecular properties of solute binding proteins of ATP.binding cassette transporter proteins that interact with these compounds. A combination of functional screens and structural studies characterized the binding specificity of the solute binding proteins for aromatic compounds derived from lignin such as p-coumarate, 3-phenylpropionic acid and compounds with more complex ring substitutions. A ligand screen based on thermal stabilization identified several binding protein clusters that exhibit preferences based on the size or number of aromatic ring substituents. Multiple X-ray crystal structures of protein-ligand complexes for these clusters identified the molecular basis of the binding specificity for the lignin-derived aromatic compounds. The screens and structural data provide new functional assignments for these solute.binding proteins which can be used to infer their transport specificity. This knowledge of the functional roles and molecular binding specificity of these proteins will support the identification of the specific enzymes and regulatory proteins of peripheral pathways that funnel these compounds to central metabolic pathways and will improve the predictive power of sequence-based functional annotation methods for this family of proteins. PMID:23606130

Tan, Kemin; Chang, Changsoo; Cuff, Marianne; Osipiuk, Jerzy; Landorf, Elizabeth; Mack, Jamey C.; Zerbs, Sarah; Joachimiak, Andrzej; Collart, Frank R.

2013-01-01

355

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

SciTech Connect

Although boron is widely used as soluble neutron poison in nuclear reactors (boric acid in pressurized water reactors, sodium pentaborate in boiling water reactors), there is a lack of experimental data about aqueous boron solution behavior during loss-of-coolant accidents. The main aims of the REWET boric acid experiments were to study the behavior of aqueous boric acid solution during long-term cooling of a nuclear reactor and to find out the circumstances in which boric acid crystallization takes place. In the experiments, carried out in the facility of a 19-fuel-rod simulator bundle, boric acid crystallization caused the uncovering of the bundle, which always occurred on the water surface. However, crossflows and backflows in a reactor presumably make the concentrations uniform and thus retard crystallization. Therefore, experimental investigations of aqueous boric acid solution behavior will be carried out for the next 2 yr in a larger scale experimental facility. The new facility will be a simulator of the Loviisa VVER-440 reactor with a scaling factor of 1:349 for power and volumes and 1:1 for elevations. The facility will contain a full-scale rod bundle.

Kervinen, T.; Tuunanen, J.

1987-01-01

356

Influence of carbons on the structure of the negative active material of lead-acid batteries and on battery performance  

Microsoft Academic Search

It has been established that addition of carbon additives to the lead negative active material (NAM) of lead-acid batteries increase battery charge acceptance in hybrid electric vehicle mode of operation. The present work studies three types of activated carbons and two types of carbon blacks with the aim to evaluate their efficiency in improving the charge acceptance of lead-acid batteries.

D. Pavlov; P. Nikolov; T. Rogachev

2011-01-01

357

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

358

Arachidonic and Docosahexaenoic Acids are Biosynthesized from their 18Carbon Precursors in Human Infants  

Microsoft Academic Search

It is becoming clear that an adequate level of long-chain highly unsaturated fatty acids in the nervous system is required for optimal function and development; however, the ability of infants to biosynthesize long-chain fatty acids is unknown. This study explores the capacity of human infants to convert 18-carbon essential fatty acids to their elongated and desaturated forms, in vivo. A

Norman Salem; Brent Wegher; Patricia Mena; Ricardo Uauy

1996-01-01

359

Electrochemical behavior of negative electrode of lead-acid cells based on reticulated vitreous carbon carrier  

Microsoft Academic Search

Reticulated vitreous carbon (RVC®) and RVC® plated with lead were investigated as carriers for the negative electrode of lead-acid cell. The RVC® and Pb\\/RVC® carriers were pasted with active paste (received from JENOX Ltd., Polish producer of lead-acid batteries) and prepared to be used in lead-acid cell. Comparative study of electrodes based on RVC® and Pb\\/RVC® has been done using

A. Czerwi?ski; S. Obr?bowski; J. Kotowski; Z. Rogulski; J. M. Skowro?ski; P. Krawczyk; T. Rozmanowski; M. Bajsert; M. Przysta?owski; M. Buczkowska-Biniecka; E. Jankowska; M. Baraniak

2010-01-01

360

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

361

Structural and luminescence characterization of porous anodic oxide films on aluminum formed in sulfamic acid solution  

NASA Astrophysics Data System (ADS)

Atomic force microscopy (AFM) and luminescence methods (galvanoluminescence and photoluminescence) were used to characterize porous oxide films obtained by aluminum anodization in sulfamic acid solution. For the first time we measured weak galvanoluminescence during aluminum anodization in sulfamic acid and found strong influence of sample's surface pretreatment as well as anodic conditions on luminescence intensity. AFM analysis showed that the pore arrangement of porous oxide films formed in sulfamic acid by two-step anodization process at a constant voltage of 15-30 V is relatively irregular.

Stojadinovic, S.; Vasilic, R.; Belca, I.; Tadic, M.; Kasalica, B.; Zekovic, Lj.

2008-12-01

362

The extraction of actinides from nitric acid solutions with diamides of dipicolinic acid  

Microsoft Academic Search

Diamides of dipicolinic acid (N,N'-diethyl-N,N'-ditolyl-dipicolinamide, EtTDPA) were synthesized and evaluated for their extraction capability for actinides. In this work the extractions of neptunium(V), protactinium(V), and thorium(IV) with EtTDPA in a polar fluorinated diluent from nitric acid were investigated. EtTDPA shows a high affinity for Th(IV) even at millimolar concentrations. Np(V) and Pa(V) are both reasonably extractable with EtTDPA; however, near

Joseph L Lapka; Alena Paulenova; Mikhail Yu Alyapyshev; Vasiliy A Babain; Jack D Law; R Scott Herbst

2010-01-01

363

Removal of Heavy Metal Ions and Diethylenetriamine Species from Solutions by Magnetic Activated Carbon  

NASA Astrophysics Data System (ADS)

Even though activated carbon is widely used in the removal of contaminants from effluents, it is difficult to be completely recovered by screening or classification. In this project, we prepared a magnetic form of activated carbon (M-AC) by co-precipitation of iron oxides onto activated carbon surface. M-AC can be separated from solutions by applying an external magnetic field and regenerated for reuse. The synthesized M-AC was characterized by X-ray diffraction, specific surface area measurement, and scanning electron microscope. Characterization results show that the major phase of coated iron oxides is magnetite (Fe 3O4). Batch adsorption experiments were carried out for single-component and multi-component solutions. M-AC shows a better adsorption capacity for singlecomponent of Cu (II), Ni (II), or diethylenetriamine (DETA) and for multiple-components of Cu-DETA and Ni-DETA complexes in deionized water than activated carbon. M-AC also shows the potential application in carbon-in-pulp process for gold recovery.

Liu, Kaiwen

364

Kinetics of diuron and amitrole adsorption from aqueous solution on activated carbons.  

PubMed

A study was conducted on the adsorption kinetics of diuron and amitrole from aqueous solutions on activated carbons of different particle sizes and on an activated carbon fiber. Different kinetic models were applied to the experimental results obtained. A pseudo-second-order rate equation fitted the adsorption kinetics data better than a pseudo-first-order rate equation. Amitrole showed faster adsorption kinetics compared with diuron because of the smaller size of the former herbicide, despite its lower driving force for adsorption. Both reaction rate constants increased when the particle size decreased. The activated carbon fiber and the activated carbon of smallest particle size (0.03 mm) showed similar adsorption kinetics. The intraparticle diffusion rate constant increased with higher initial concentration of herbicides in solution and with lower particle size of the adsorbent. This is because the rise in initial concentration increased the amount adsorbed at equilibrium, and the reduction in particle size increased the number of collisions between adsorbate and adsorbent particles. Demineralization of the activated carbon with particle size of 0.5mm had practically no effect on the adsorption kinetics. PMID:18241982

Fontecha-Cámara, M A; López-Ramón, M V; Pastrana-Martínez, L M; Moreno-Castilla, C

2008-08-15

365

Stimulation of Carbonate Reservoirs Using a New Emulsified Acid System  

E-print Network

The scope of work can be divided into; the measurement of the rheological properties of a new emulsified acid system that can be suitable for high temperature applications, a study of the performance of the new emulsified acid in stimulating both...

Sayed, Mohammed Ali Ibrahim

2013-05-15

366

Experimental shock chemistry of aqueous amino acid solutions and the cometary delivery of prebiotic compounds.  

PubMed

A series of shock experiments were conducted to assess the feasibility of the delivery of organic compounds to the Earth via cometary impacts. Aqueous solutions containing near-saturation levels of amino acids (lysine, norvaline, aminobutyric acid, proline, and phenylalanine) were sealed inside stainless steel capsules and shocked by ballistic impact with a steel projectile plate accelerated along a 12-m-long gun barrel to velocities of 0.5-1.9 km sec-1. Pressure-temperature-time histories of the shocked fluids were calculated using 1D hydrodynamical simulations. Maximum conditions experienced by the solutions lasted 0.85-2.7 microseconds and ranged from 5.1-21 GPa and 412-870 K. Recovered sample capsules were milled open and liquid was extracted. Samples were analyzed using high performance liquid chromatography (HPLC) and mass spectrometry (MS). In all experiments, a large fraction of the amino acids survived. We observed differences in kinetic behavior and the degree of survivability among the amino acids. Aminobutyric acid appeared to be the least reactive, and phenylalanine appeared to be the most reactive of the amino acids. The impact process resulted in the formation of peptide bonds; new compounds included amino acid dimers and cyclic diketopiperazines. In our experiments, and in certain naturally occurring impacts, pressure has a greater influence than temperature in determining reaction pathways. Our results support the hypothesis that significant concentrations of organic material could survive a natural impact process. PMID:11296518

Blank, J G; Miller, G H; Ahrens, M J; Winans, R E

2001-01-01

367

Experimental Shock Chemistry of Aqueous Amino Acid Solutions and the Cometary Delivery of Prebiotic Compounds  

NASA Astrophysics Data System (ADS)

A series of shock experiments were conducted to assess the feasibility of the delivery of organic compounds to the Earth via cometary impacts. Aqueous solutions containing near-saturation levels of amino acids (lysine, norvaline, aminobutyric acid, proline, and phenylalanine) were sealed inside stainless steel capsules and shocked by ballistic impact with a steel projectile plate accelerated along a 12-m-long gun barrel to velocities of 0.5-1.9 km sec^-1. Pressure-temperature-time histories of the shocked fluids were calculated using 1D hydrodynamical simulations. Maximum conditions experienced by the solutions lasted 0.85-2.7 ?s and ranged from 5.1-21 GPa and 412-870 K. Recovered sample capsules were milled open and liquid was extracted. Samples were analyzed using high performance liquid chromatography (HPLC) and mass spectrometry (MS). In all experiments, a large fraction of the amino acids survived. We observed differences in kinetic behavior and the degree of survivability among the amino acids. Aminobutyric acid appeared to be the least reactive, and phenylalanine appeared to be the most reactive of the amino acids. The impact process resulted in the formation of peptide bonds; new compounds included amino acid dimers and cyclic diketopiperazines. In our experiments, and in certain naturally occurring impacts, pressure has a greater influence than temperature in determining reaction pathways. Our results support the hypothesis that significant concentrations of organic material could survive a natural impact process.

Blank, Jennifer G.; Miller, Gregory H.; Ahrens, Michael J.; Winans, Randall E.

2001-02-01

368

Length Scale Dependence of the Dynamic Properties of Hyaluronic Acid Solutions in the Presence of Salt  

SciTech Connect

In solutions of the charged semirigid biopolymer hyaluronic acid in salt-free conditions, the diffusion coefficient D{sub NSE} measured at high transfer momentum q by neutron spin echo is more than an order of magnitude smaller than that determined by dynamic light scattering, D{sub DLS}. This behavior contrasts with neutral polymer solutions. With increasing salt content, D{sub DLS} approaches D{sub NSE}, which is independent of ionic strength. Contrary to theoretical expectation, the ion-polymer coupling, which dominates the low q dynamics of polyelectrolyte solutions, already breaks down at distance scales greater than the Debye-Hueckel length.

Horkay, Ferenc; Falus, Peter; Hecht, Anne-Marie; Geissler, Erik (CNRS-UMR); (NIH); (ILL)

2010-12-07

369

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

370

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

371

ANALYSIS FOR Np²³⁷ IN NITRIC ACID SOLUTIONS  

Microsoft Academic Search

A method was developed for the analysis of Np²³⁷ in nitric acid ; solutions that contained uranium, plutonium, and fission products. Neptunium was ; extracted with thenoyltrifluoroacetone after reduction to the (IV) state with ; ferrous sulfamate. The alpha activity of the sepa rated neptunium was then ; measured with an alpha pulse height analyzer, and the degree of separation

1958-01-01

372

Hydrolysis of Polylactic Acid (PLA) and Polycaprolactone (PCL) in Aqueous Acetonitrile Solutions: Autocatalysis  

Microsoft Academic Search

Polylactic acid (PLA) is a hydrolytically degradable aliphatic polyester. The rate of polymer hydrolysis increases with time, and that has been attributed to the high reactivity of the terminal ester and the kinetics of autocatalysis. Hydrolysis is carried out in an acetonitrile\\/water solution to eliminate any solid-state contributions such as diffusion and crystallinity to the degradation process. A kinetic equation

Georgette L. Siparsky; Kent J. Voorhees; Fudu Miao

1998-01-01

373

Effect of acid solutions on plants studied by the optical beam deflection method.  

PubMed

The optical beam deflection method was applied to study the effects of acid solution on both a terrestial and aquatic plants Egeria and Cerastium, which are common aquatic plant and terrestial weed respectively. A probe beam from a He-Ne laser was passed through a vicinity of a leaf of the plants, which were put in culture dishes filled with acid solutions. Deflection signals of the probe beam were monitored and compared for acid solutions with different pH values. The results of Egria showed that the deflection signals changed dramatically when pH values of acid solutions were 2.0 and 3.0, while little at pH of 4.0 and 5.0. For Cerastium when pH were below 3.0, deflection signals changed greatly with time at the begining. After a certain period of time, deflection signals changed little with time. When pH value was above 4.0, deflection signals of Cerastium were still changing with time even after 20 hours. The results suggested that the damage threshold of pH was between 3.0 and 4.0 for both the land and aquatic plants. PMID:25078849

Nie, Liangjiao; Kuboda, Mitsutoshi; Inoue, Tomomi; Wu, Xingzheng

2013-12-01

374

Use of peptide nucleic acids (PNAs) for genotyping by solution and surface methods.  

PubMed

Peptide nucleic acids (PNAs) are synthetic oligonucleotide analogues based on a pseudopeptide backbone that bind complementary DNA or RNA with high affinity and specificity. In this chapter, three PNA-based genotyping assays are described: PCR clamping, fluorescence-based recognition, and microarray platform. The first two methods are performed in solution, while the microarray method uses a solid surface. PMID:24297357

Sforza, Stefano; Tedeschi, Tullia; Bencivenni, Mariangela; Tonelli, Alessandro; Corradini, Roberto; Marchelli, Rosangela

2014-01-01

375

THE EXTRACTION OF URANIUM AND PLUTONIUM FROM NITRIC ACID SOLUTIONS BY TERTIARY AMINES  

Microsoft Academic Search

In the extraction of Pu(IV) nitrate from uranium contairing aqueous ; solutions by means of long chain tertiary amines, the partition coefficient of ; Pu(IV) is influenced by the concentration of nitric acid, uranyl nitrate, and by ; the concentration of the amine in the diluent. At high urarium concentration ; extraction of Pu(IV) ceases to be dependent upon the

F. Baroncelli; G. Scibona; M. Zifferero

1963-01-01

376

Cationic surfactant as corrosion inhibitor for aluminum in acidic and basic solutions  

Microsoft Academic Search

Purpose – To investigate the inhibiting effect of the cationic surfactant cetyl trimethylammonium chloride (CTAC) on aluminum (Al). Design\\/methodology\\/approach – Pure aluminum rods were immersed in hydrochloric acid (HCl) and sodium hydroxide (NaOH) solutions for weight-loss tests and potentiostatic polarization measurements. Findings – The inhibition action depends on the concentration of the inhibitor, the concentration of the corrosive media, and

N. A. F. Al-Rawashdeh; A. K. Maayta

2005-01-01

377

Adsorption of fluoride from aqueous solution by acid treated spent bleaching earth  

Microsoft Academic Search

Acid treated spent bleaching earth was studied to assess its capacity for the adsorption of fluoride from aqueous solutions. Adsorption isotherms have been modeled by Langmuir and Freundlich equations and isotherm constants for both isotherms were calculated. The effect of the adsorbent concentration on the adsorption was studied. The dependence of the adsorption of fluoride on the pH of the

M Mahramanlioglu; I Kizilcikli; I. O Bicer

2002-01-01

378

New cationic surfactant as corrosion inhibitor for mild steel in hydrochloric acid solutions  

Microsoft Academic Search

The inhibiting effect of cationic surfactant N, N, N-dimethyl 4-methylbenzyl dodecyl ammonium chloride on mild steel in hydrochloric acid solutions was investigated by surface and thermodynamic measurements, weight loss tests, polarization measurements and EDS techniques. The data obtained from surface and thermodynamic measurements with the inhibitor indicate that the area per molecule slightly increases with increasing temperature and both absorption

Z. Abdel Hamid; T. Y. Soror; H. A. El-Dahan; A. M. A. Omar

1998-01-01

379

Acid-activated carbons from almond shells: physical, chemical and adsorptive properties and estimated cost of production  

Microsoft Academic Search

A series of phosphoric-acid activated carbons were made from almond shells using six different activation or activation\\/oxidation methods. The carbons were compared to each other and to two commercial carbons in an effort to ascertain the relative value of the carbons in terms of yield, surface area, attrition, surface functional groups, organic uptake, metal uptake, as well as estimated cost

Christopher A Toles; Wayne E Marshall; Mitchell M Johns; Lynda H Wartelle; Andrew McAloon

2000-01-01

380

Static and dynamic adsorption of phenol from aqueous solution using spherical carbon  

NASA Astrophysics Data System (ADS)

The objective of this work is to evaluate spherical carbon and modified spherical carbon for the removal of phenol from aqueous solution in static and dynamic studies under various conditions. It explores mainly two adsorbents, that is, activated spherical carbon (ASC) and modified activated spherical carbon (SSC). SEM characterization of both the adsorbents showed a clear change in the physical and chemical properties of the modified adsorbent from its precursor activated carbon. Both the adsorbents are subjected to static mode adsorption studies and after a comparison based on isotherm analysis; more efficient adsorbent is screened for column mode adsorption studies. The phenol removal increased for modified carbon. The aim of carrying out column mode studies will aid in ascertaining the practical applicability of the adsorbent in the real system and therefore, to assess the effect of various process variables, viz., bed height of the adsorbent, flow rate and initial concentration of the adsorbate on breakthrough time and adsorption capacity. The column studies generated data were modeled using the empirical relationship based on Bohart-Adams model. At the end, the option of regenerating the adsorbent was also explored using sodium hydroxide with the aim of minimize the hazardous generated and also to reuse the adsorbent material for many cycles without affecting original properties. Adsorbent regeneration efficiency of 72% was achieved. This investigation reveals that the material used as an adsorbent is very effective with high adsorption capacities and also possible to use in the real contaminated system.

Bhargavi, R.; Kadirvelu, K.; Kumar, N. S.

2013-06-01

381

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

382

Carbon doping of MgB 2 by toluene and malic-acid-in-toluene  

NASA Astrophysics Data System (ADS)

The decomposition of malic acid (C 4H 6O 5) in the presence of Mg and B was studied using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) which revealed that malic acid reacted with Mg but not B. Also, the addition of toluene (C 7H 8) to dissolve malic acid followed by subsequent drying resulted in no reaction with Mg, indicating that the malic acid had decomposed during the dissolution/drying stage. The total carbon contributed by toluene versus a toluene/5 wt.% malic acid mixture was measured using a LECO CS600 carbon analyzer. The toluene sample contained ?0.4 wt.% C while the toluene/malic acid mixture had ?1.5 wt.% C, demonstrating that the toluene contributed a significant amount of carbon to the final product. Resistivity measurements on powder-in-tube MgB 2 monofilamentary wires established that the toluene/malic acid doped sample had the highest B c2. However, the toluene-only sample had the highest transport J c over most of the magnetic field range (0-9 T), equaled only by that of toluene/malic-acid sample in fields above 9 T.

Bohnenstiehl, S. D.; Susner, M. A.; Yang, Y.; Collings, E. W.; Sumption, M. D.; Rindfleisch, M. A.; Boone, R.

2011-02-01

383

Method for separating constituents from solution employing a recyclable Lewis acid metal-hydroxy gel  

SciTech Connect

This invention permits radionuclides, heavy metals, and organics to be extracted from solution by scavenging them with an amorphous gel. In the preferred embodiment, a contaminated solution (e.g. from soil washing, decontamination, or groundwater pumping) is transferred to a reaction vessel. The contaminated solution is contacted by the sequestering reagent which might contain for example, aluminate and EDTA anions in a 2.5 M NaOH solution. The pH of the reagent bearing solution is lowered on contact with the contaminated solution, or for example by bubbling carbon dioxide through it, causing an aluminum hydroxide gel to precipitate as the solution drops below the range of 1.8 to 2.5 molar NaOH (less than pH 14). This precipitating gel scavenges waste contaminants as it settles through solution leaving a clean supernatant which is then separated from the gel residue by physical means such as centrifugation, or simple settling. The gel residue containing concentrated contaminants is then redissolved releasing contaminants for separations and processing. This is a critical point: the stabilized gel used in this invention is readily re-dissolved by merely increasing the pH above the gels phase transition to aqueous anions. Thus, concentrated contaminants trapped in the gel can be released for convenient separation from the sequestering reagent, and said reagent can then be recycled.

Alexander, D.H.

1995-12-31

384

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

SciTech Connect

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 is introduced into the photometric solution to mask the plutonium together with the tetravalent, and some trivalent, elements. The relative mean-square deviation of the results does not exceed 0.03 in the concentration ranges 0.5-5 ..mu..g U/ml, 1-3 ..mu..g Pu/ml.

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

1987-07-01

385

Influence of acid functionalization on the cardiopulmonary toxicity of carbon nanotubes and carbon black particles in mice  

SciTech Connect

Engineered carbon nanotubes are being developed for a wide range of industrial and medical applications. Because of their unique properties, nanotubes can impose potentially toxic effects, particularly if they have been modified to express functionally reactive chemical groups on their surface. The present study was designed to evaluate whether acid functionalization (AF) enhanced the cardiopulmonary toxicity of single-walled carbon nanotubes (SWCNT) as well as control carbon black particles. Mice were exposed by oropharyngeal aspiration to 10 or 40 {mu}g of saline-suspended single-walled carbon nanotubes (SWCNTs), acid-functionalized SWCNTs (AF-SWCNTs), ultrafine carbon black (UFCB), AF-UFCB, or 2 {mu}g LPS. 24 hours later, pulmonary inflammatory responses and cardiac effects were assessed by bronchoalveolar lavage and isolated cardiac perfusion respectively, and compared to saline or LPS-instilled animals. Additional mice were assessed for histological changes in lung and heart. Instillation of 40 {mu}g of AF-SWCNTs, UFCB and AF-UFCB increased percentage of pulmonary neutrophils. No significant effects were observed at the lower particle concentration. Sporadic clumps of particles from each treatment group were observed in the small airways and interstitial areas of the lungs according to particle dose. Patches of cellular infiltration and edema in both the small airways and in the interstitium were also observed in the high dose group. Isolated perfused hearts from mice exposed to 40 {mu}g of AF-SWCNTs had significantly lower cardiac functional recovery, greater infarct size, and higher coronary flow rate than other particle-exposed animals and controls, and also exhibited signs of focal cardiac myofiber degeneration. No particles were detected in heart tissue under light microscopy. This study indicates that while acid functionalization increases the pulmonary toxicity of both UFCB and SWCNTs, this treatment caused cardiac effects only with the AF-carbon nanotubes. Further experiments are needed to understand the physico-chemical processes involved in this phenomenon.

Tong Haiyan [Human Studies Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711 (United States)], E-mail: tong.haiyan@epa.gov; McGee, John K. [Experimental Toxicology Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711 (United States); Saxena, Rajiv K. [School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067 (India); Kodavanti, Urmila P. [Experimental Toxicology Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711 (United States); Devlin, Robert B. [Human Studies Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711 (United States); Gilmour, M. Ian [Experimental Toxicology Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711 (United States)

2009-09-15

386

Light-controlled single-walled carbon nanotube dispersions in aqueous solution.  

PubMed

We have succeeded in dispersing single-walled carbon nanotubes (SWNTs) into an aqueous solution of poly(ethylene glycol)-terminated malachite green derivative (PEG-MG) through simple sonication. It was found that UV exposure caused reaggregation of these predispersed SWNTs in the same aqueous medium, as adsorbed PEG-MG photochromic chains could be effectively photocleavaged from the nanotube surface. The observed light-controlled dispersion and reaggragation of SWNTs in the aqueous solution should facilitate the development of SWNT dispersions with a controllable dispersity for potential applications. PMID:18672920

Chen, Senlin; Jiang, Yugui; Wang, Zhiqiang; Zhang, Xi; Dai, Liming; Smet, Mario

2008-09-01

387

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

E-print Network

). The solvent extraction process depends upon the water solubility characteristics of certain solvents. The solubility of water in secondary and tertiary amines containing five or six carbon atoms is extremely sensitive to temperature. The solubility.... With hydrochloric acid tertiary amines show much higher extractions than primary or secondary amines (12). In a given series of amines the extraction coefficient could increase, decrease or pass through a maximum de- pending on the diluent used. It was noted...

Pandya, Harishkumar Chandulal

2012-06-07

388

InP synthesis by the synthesis, solute diffusion (SSD) method using glassy-carbon crucibles  

SciTech Connect

An Indium Phosphide (InP) Synthesis system by the Synthesis, Solute Diffusion (SSD) method has been built. It provides high purity InP charges with low carrier densities (3 {times} 10{sup 14} to 2 {times} 10{sup 15} cm{sup {minus}3}) to be used as starting material for InP single-crystal Liquid Encapsulated Czochralski (LEC) growth. Glassy-carbon is a refractory material with low vapor pressure that can be moulded in various forms and sizes. Indeed the glassy-carbon crucible is reusable after the synthesis because InP does not stick to its walls. Preliminary electrical characteristics measurements showed residual carrier concentration below 3 {times} 10{sup 15} cm{sup {minus}3}. These results are comparable with those achieved utilizing quartz crucibles. The features denoted makes glassy-carbon an interesting alternative in comparison with quartz and PBN crucibles.

Miskys, C.R.; Oliveira, C.E.M. de; Carvalho, M.M.G. de [UNICAMP-IFGW-DFA-LPD, Campinas, Sao Paulo (Brazil)

1996-12-31

389

Surface-enhanced Raman spectroelectrochemical studies of corrosion films on iron in aqueous carbonate solution  

SciTech Connect

The corrosion films on iron in aqueous carbonate/bicarbonate solutions were studied as a function of concentration, pH, and temperature by using the technique of surface-enhanced Raman spectroscopy with electrodeposited silver. Both Fe(OH){sub 2} and Fe{sub 3}O{sub 4} were detected in the surface oxide film at prepassivation potentials. Iron carbonate (siderite) was observed in the corrosion film in a limited pH, temperature, and applied potential range. At lower carbonate/bicarbonate concentration (e.g., 0.01 M), passivation was lost, and continuous anodic dissolution of the iron occurred. The cathodic reduction of the corrosion film was enhanced at 75 C.

Simpson, L.J.; Melendres, C.A. [Argonne National Lab., IL (United States)

1996-07-01

390

The breakdown mechanism of diamond-like carbon coated nickel in chloride solution  

Microsoft Academic Search

The breakdown mechanism of chemical vapor deposited nickel (CVD Ni) coated with 5 micrometers of diamond-like carbon (DLC) produced by plasma source ion implantation (PSII) in chloride solution was investigated. PSII differs from traditional implantation techniques in that the targets are placed directly in a plasma source and then pulse biased to produce a non-line-of-sight process to complex-shaped targets without

R. S. Lillard; D. P. Butt; T. N. Taylor; K. C. Walter; M. Nastasi

1997-01-01

391

A moving-boundary problem for concrete carbonation: Global existence and uniqueness of weak solutions  

Microsoft Academic Search

This paper deals with a one-dimensional coupled system of semi-linear parabolic equations with a kinetic condition on the moving boundary. The latter furnishes the driving force for the moving boundary. The main result is a global existence and uniqueness theorem of positive weak solutions. The system under consideration is modelled on the so-called carbonation of concrete – a prototypical chemical-corrosion

Adrian Muntean; Michael Böhm

2009-01-01

392

Thermal stability and hydrophobicity enhancement of wood through impregnation with aqueous solutions and supercritical carbon dioxide  

Microsoft Academic Search

A novel process for the thermal stability and hydrophobicity enhancement of wood is proposed. The process concerns the impregnation\\u000a of wood with water-soluble and water-insoluble salts. The salts are synthesized in situ in wood through aqueous solutions\\u000a and supercritical carbon dioxide treatment. To protect salt-treated wood from absorbing large amounts of humidity a polymer\\u000a film is formed upon the surface

Costas Tsioptsias; Costas Panayiotou

2011-01-01

393

Adsorption kinetics of a basic dye from aqueous solutions onto apricot stone activated carbon  

Microsoft Academic Search

The preparation of activated carbon from apricot stone with H2SO4 activation and its ability to remove a basic dye, astrazon yellow 7GL, from aqueous solutions were reported in this study. The adsorbent was characterized by FTIR, BET and SEM, respectively. The effects of various experimental parameters, such as initial dye concentration, pH, adsorbent dosage and temperature were investigated in a

E. Demirbas; M. Kobya; M. T. Sulak

2008-01-01

394

Activated carbon from coconut coirpith as metal adsorbent: adsorption of Cd(II) from aqueous solution  

Microsoft Academic Search

Activated carbon prepared from coirpith, an agricultural solid waste by-product, has been used for the adsorption of Cd(II) from aqueous solution. Parameters such as the agitation time, metal ion concentration, adsorbent dose and pH were studied. The adsorption data fit well with the Langmuir and Freundlich isotherm models. The adsorption capacity (Q0) calculated from the Langmuir isotherm was 93.4 mg

K. Kadirvelu; C. Namasivayam

2003-01-01

395

Synthesis of biodiesel from waste vegetable oil with large amounts of free fatty acids using a carbon-based solid acid catalyst  

Microsoft Academic Search

A carbon-based solid acid catalyst was prepared by the sulfonation of carbonized vegetable oil asphalt. This catalyst was employed to simultaneously catalyze esterification and transesterification to synthesis biodiesel when a waste vegetable oil with large amounts of free fatty acids (FFAs) was used as feedstock. The physical and chemical properties of this catalyst were characterized by a variety of techniques.

Qing Shu; Jixian Gao; Zeeshan Nawaz; Yuhui Liao; Dezheng Wang; Jinfu Wang

2010-01-01

396

Kinetics and reaction engineering of levulinic acid production from aqueous glucose solutions.  

PubMed

We have developed a kinetic model for aqueous-phase production of levulinic acid from glucose using a homogeneous acid catalyst. The proposed model shows a good fit with experimental data collected in this study in a batch reactor. The model was also fitted to steady-state data obtained in a plug flow reactor (PFR) and a continuously stirred tank reactor (CSTR). The kinetic model consists of four key steps: (1) glucose dehydration to form 5-hydroxymethylfurfural (HMF); (2) glucose reversion/degradation reactions to produce humins (highly polymerized insoluble carbonaceous species); (3) HMF rehydration to form levulinic acid and formic acid; and (4) HMF degradation to form humins. We use our model to predict the optimal reactor design and operating conditions for HMF and levulinic acid production in a continuous reactor system. Higher temperatures (180-200 °C) and shorter reaction times (less than 1 min) are essential to maximize the HMF content. In contrast, relatively low temperatures (140-160 °C) and longer residence times (above 100 min) are essential for maximum levulinic acid yield. We estimate that a maximum HMF carbon yield of 14% can be obtained in a PFR at 200 °C and a reaction time of 10 s. Levulinic acid can be produced at 57% carbon yield (68% of the theoretical yield) in a PFR at 149 °C and a residence time of 500 min. A system of two consecutive PFR reactors shows a higher performance than a PFR and CSTR combination. However, compared to a single PFR, there is no distinct advantage to implement a system of two consecutive reactors. PMID:22696262

Weingarten, Ronen; Cho, Joungmo; Xing, Rong; Conner, William Curtis; Huber, George W

2012-07-01

397

Coconut (Cocos Nucifera) Shell Based Activated Carbon for the Removal of Malachite Green Dye From Aqueous Solutions  

Microsoft Academic Search

The adsorption of malachite green (MG) dye using coconut shell based activated carbon (CSAC) was investigated. Operational factors such as effect of pH, initial dye concentration, adsorbent dosage, contact time, and solution temperature on the adsorption process were studied. Solution pH strongly affected the chemistry of both the dye molecule and CSAC in solution. Optimum dye removal was obtained at

Olugbenga Solomon Bello; Mohd Azmier Ahmad

2012-01-01

398

Nature of Non-Fickian Solute Transport in Complex Heterogeneous Porous Media - Carbonates  

NASA Astrophysics Data System (ADS)

Despite the range of significant practical applications of solute transport, including the long-term fate of nuclear waste repositories, secure storage of CO2 and improved oil recovery, even the qualitative behavior of most rocks is uncertain: vast carbonate sedimentary basins contain more than half the world's current oil reserves yet experimental data on transport in carbonates is scant. The relationship between pore structure, velocity field and transport remains unknown, particularly for heterogeneous carbonates. We simulate solute transport through 3D ?-CT images of different rock samples, representing geological media of increasing pore-scale complexity: a sandpack, a Berea sandstone and a Portland limestone. A finite-difference Stokes solver is employed to compute the flow field and transport particles semi-analytically along streamlines to represent advection with a random motion to model diffusion. We predict the propagators measured on similar cores in Nuclear Magnetic Resonance (NMR) experiments. Dispersion coefficient dependence on Peclet number is shown to have different scaling for complex carbonates. The behavior is explained using continuous time random walks with a truncated power-law distribution of travel times: transport is qualitatively different for the complex limestone compared to the sandstone or sandpack, with long tailing, an almost immobile peak concentration and a very slow approach to asymptotic dispersion. We demonstrate the different nature of non-Fickian transport in carbonates by analyzing the transit time probabilities ?(?) of traveling between two neighboring voxels for Portland carbonate that show an approximately power-law dependence of travel times ?(?) ~ ? -1-? with a slope corresponding to ? = 0.7, as shown in Fig.1. The comparison with ?(?) of the sandpack and Berea sandstone for Pe = ? indicates quantitatively different generic behavior, as the sandpack and sandstone have slope corresponding to ? = 1.8 (two solid parallel lines in the insert in Fig.1). This complex non-Fickian behavior at the pore scale has large implications on modeling of field-scale transport.

Bijeljic, B.; Mostaghimi, P.; Blunt, M. J.

2011-12-01

399

Masking effect of copper during anisotropic etching of silicon in buffered hydrofluoric acid solutions  

NASA Astrophysics Data System (ADS)

The etching characteristics of silicon samples of (100) orientation in buffered hydrofluoric acid (BHF) solutions containing different levels of dissolved copper were studied systematically using atomic force microscopy, total reflection x-ray fluorescence, inductively coupled plasma mass spectroscopy and transmission electron microscopy techniques. It was found that the presence of trace amounts of copper ions in BHF solutions can cause not only metallic contamination but also very severe surface roughness. Copper deposits onto the silicon surfaces in the form of submonoatomic layer clusters which act as masks during silicon anisotropic etching in BHF solutions. Surface roughness as high as 12 nm was generated in 30 min of etching in buffered hydrofluoric acid solution containing 100 ppb Cu2+. Cross-sectional TEM micrographs showed that silicon was etched anisotropically in BHF solutions containing Cu2+ ions. Etching rates as high as 1.0 nm/min were obtained on the (100) planes of p-type silicon in the presence of a 100 ppb Cu2+. The size of the etching structures depends on the Cu2+ concentration in solution and the etching time.

Li, Guangming; Jiao, Jun; Seraphin, Supapan; Raghavan, Srini; Jeon, Joong S.

1999-02-01

400

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

401

The removal of U(VI) from aqueous solution by oxidized multiwalled carbon nanotubes.  

PubMed

Multiwalled carbon nanotubes (MWCNTs) have exhibited high sorption capacity for radionuclides due to the unique hollow structure and large surface area. In this study, surface properties of oxidized MWCNTs were characterized by using XRD, SEM, FTIR and potentiometric acid-base titration. The sorption of U(VI) on oxidized MWCNTs as a function of contact time, U(VI) concentration, pH, ionic strength, humic acid/fulvic acid (HA/FA) and carbonate was investigated by using batch technique. The removal of U(VI) by oxidized MWCNTs was strongly dependent on pH and ionic strength. The presence of HA/FA enhanced U(VI) removal on oxidized MWCNTs at low pH while inhibited U(VI) sorption at high pH. The mechanism of U(VI) sorption on oxidized MWCNTs was assumed to be cation exchange/outer-sphere surface complexation in acidic pH and to form precipitation under circum neutral conditions. The oxidized MWCNTs exhibit higher sorption capacity and stronger chemical affinity than pristine MWCNTs. PMID:22230020

Sun, Yubing; Yang, Shitong; Sheng, Guodong; Guo, Zhiqiang; Wang, Xiangke

2012-02-01

402

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

403

Use of Pyrolyzed Iron Ethylenediaminetetraacetic Acid Modified Activated Carbon as Air-Cathode Catalyst in Microbial Fuel Cells  

E-print Network

Use of Pyrolyzed Iron Ethylenediaminetetraacetic Acid Modified Activated Carbon as Air activity of AC cathodes, AC powders were pyrolyzed with iron ethylenediaminetetraacetic acid (Fe MFCs was 50% lower than MFCs with the AC cathodes. Pyridinic nitrogen, quaternary nitrogen and iron

404

Pressure-Activated Microsyringe Composite Scaffold of Poly(L-lactic acid) and Carbon Nanotubes for Bone Tissue Engineering  

E-print Network

Pressure-Activated Microsyringe Composite Scaffold of Poly(L-lactic acid) and Carbon Nanotubes biocompatibility. In this study, we microfabricated three-dimensional (3D) scaffolds by mixing poly(L-lactic acid

Daraio, Chiara

405

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

E-print Network

to titrate each one, dissolve it in ~50mL of distilled water. Add 3 drops of methyl red indicator and titrate. Reagents Methyl Red indicator Concentrated (37 wt%) HCl Primary standard: sodium tetraborate Na2B4O7Ã?10 H2O heated loosing water. Non-hygroscopic. Reacts with acid: NaClBOHOHHClOBNa 2452 332742 +++ Standardizing

Nazarenko, Alexander

406

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

NASA Astrophysics Data System (ADS)

Studies were conducted on the efficiency of systems based on the use of ozone, activated carbon, and ozone/activated carbon in the treatment of waters containing 1-naphthalenesulphonic acid, 1,5-naphthalenedisulphonic acid, and 1,3,6-naphthalenetrisulphonic acid. In the removal of these acids by adsorption on activated carbon the elevated heights of the mass transfer zone columns and the low values of the breakthrough volumes indicated that a system exclusively based on the use of activated carbon is not appropriate for the removal of these pollutants. In the ozonation of these acids the reactivity of naphthalenesulphonic acid with ozone is low. In addition, the initial concentration of total organic carbon (TOC) was not reduced during naphthalenesulphonic acids ozonation. These results indicate that a system exclusively based on the use of ozone is not adequate to decontaminate water where these acids are present. These ozonation processes were also studied in the presence of activated carbon. The presence of activated carbon enhanced the elimination rate, probably by enhancing ozone decomposition in aqueous phase in highly oxidative species. These catalytic properties seem to be favored by both the basicity of the carbon surface and the higher macropore volume. The catalytic properties of activated carbon were reduced by ozonation. New acid groups such as anhydride, lactones, and carboxylic acid were generated on the activated carbon surface during ozone treatment. This effect reduced the reactivity of the activated carbon to ozone and therefore the capacity to enhance ozone decomposition in aqueous phase. The presence of activated carbon during naphthalenesulphonic acid ozonation produced a reduction in the TOC concentration and in the genotoxicity of the degradation products. All these results indicate that this novel combined system is very promising for the treatment of water polluted with organic matter.

Rivera-Utrilla, J.; SáNchez-Polo, M.

2003-09-01

407

Effects of Solution Hydrodynamics on Corrosion Inhibition of Steel by Citric Acid in Cooling Water  

NASA Astrophysics Data System (ADS)

Corrosion is a major problem in cooling water systems, which is often controlled using corrosion inhibitors. Solution hydrodynamics is one of the factors affecting corrosion inhibition of metals in these systems. The present work focuses on the study of the combined effects of citric acid concentration (as a green corrosion inhibitor) and fluid flow on corrosion of steel in simulated cooling water. Electrochemical techniques including Tafel polarization and electrochemical impedance spectroscopy were used for corrosion studies. Laminar flow was simulated using a rotating disk electrode. The effects of solution hydrodynamics on inhibition performance of citric acid were discussed. The citric acid showed low inhibition performance in quiescent solution; however, when the electrode rotated at 200 rpm, inhibition efficiency increased remarkably. It was attributed mainly to the acceleration of inhibitor mass transport toward metal surface. The efficiencies were then decreased at higher rotation speeds due to enhanced wall shear stresses on metal surface and separation of adsorbed inhibitor molecules. This article is first part of authors' attempts in designing green inhibitor formulations for industrial cooling water. Citric acid showed acceptable corrosion inhibition in low rotation rates; thus, it can be used as a green additive to the corrosion inhibitor formulations.

Ashassi-Sorkhabi, H.; Asghari, E.; Mohammadi, M.

2014-08-01

408

Clinical evaluation of an optimized 1.1% amino-acid solution for peritoneal dialysis.  

PubMed

A significant percentage of dialysed patients have inadequate protein intake. One strategy for treating the protein malnutrition in peritoneal dialysis patients is to replace glucose in the dialysis solution by amino acids. A new peritoneal dialysis solution containing 1.1% amino acids in a formulation optimized for renal patients and with a lactate concentration of 40 mmol/l has been evaluated. Fifteen CAPD patients completed a non-randomized prospective 3-month study. Each patient received 2 litres of the optimised 1.1% amino acid solution for the second exchange of the day with a dwell time of 5-6 h. Indicators of efficacy were serum albumin and transferrin. After 3 months of intraperitoneal amino acids, serum albumin levels significantly increased from 32.7 +/- 2.3 to 35.1 +/- 2.2 g/l (mean +/- SD; P < 0.01). This occurred in parallel with a significant increase in transferrin levels from 2.21 +/- 0.26 to 2.39 +/- 0.27 g/l (P < 0.05). As expected, urea rose from 23.7 +/- 6.8 to 29.9 +/- 9.4 mmol/l. Interestingly bicarbonate did not change (25.5 +/- 4.2 versus 25.2 +/- 3.3 mmol/l). These results suggest that the optimized formulation is effective in improving nutritional parameters in CAPD patients while avoiding unwanted side-effects such as acidosis. PMID:8538938

Faller, B; Aparicio, M; Faict, D; De Vos, C; de Précigout, V; Larroumet, N; Guiberteau, R; Jones, M; Peluso, F

1995-01-01

409

The infrared optical constants of sulfuric acid at 250 K. [spectral reflectance measurement of aqueous solutions  

NASA Technical Reports Server (NTRS)

Results are presented for measurements of the IR spectral reflectance at near-normal incidence of aqueous solutions of sulfuric acid with acid concentrations of 75% and 95.6% by weight. Kramers-Kronig analyses of the reflectance data are employed to obtain values of the optical constants n(nu) and k(nu) in the spectral range from 400 to 6000 cm to the -1 power. The optical constants of these solutions at 250 K and 300 K are compared. It is found that in spectral regions remote from strong absorption bands, the values of the n(nu) indices obtained at 250 K agree with the values given by Lorentz-Lorenz correction of the same indices at 300 K. All absorption bands observed at 300 K are found to be present at 250 K with slight shifts in frequency and with significant differences in the k(nu) indices at the band maxima. Based on these results, it is concluded that the clouds of Venus probably consist of droplets of aqueous solutions of sulfuric acid with acid concentrations of about 75% by weight.

Pinkley, L. W.; Williams, D.

1976-01-01

410

Covalent functionalization of single walled carbon nanotubes with peptide nucleic acid: Nanocomponents for molecular level electronics  

Microsoft Academic Search

Imparting molecular recognition to carbon nanotubes (CNTs) by conjugating them with bio-molecules has been an area of great interest as the resulting highly functionalized CNT-bioconjugates find their applications in various fields like molecular level electronics, pharmaceuticals, drug delivery, novel materials and many others. In this work we demonstrate the synthesis of functionally engineered single walled carbon nanotubes (SWNTs)-peptide nucleic acid

Krishna V. Singh; Rajeev R. Pandey; Xu Wang; Roger Lake; Cengiz S. Ozkan; Kang Wang; Mihrimah Ozkan

2006-01-01

411

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

412

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

PubMed

Together with vitamin C, zinc, selenium, manganese, and magnesium play a vital role in the preservation of organs scheduled for transplantation. In the present study, it is shown that addition of 1 mg/l of these elements influences the stability of 0.3 mM ascorbic acid solutions. The solution's stability was estimated using an accelerated stability test. The concentration of vitamin C was measured using a validated spectrophotometric method, which uses the reduction of 2,6-dichlorophenoloindophenol by ascorbic acid. Elevated temperatures, the factor accelerating substances' decomposition reaction rate, were used in the tests. The research was conducted at two temperatures at intervals of 10 °C: 80?±?0.1 and 90?±?0.1 °C. It was stated that the studied substances' decomposition occurred in accordance with the equation for first-order reactions. The function of the logarithmic concentration (log%C) over time was revealed to be rectilinear. This dependence was used to determine the kinetics of decomposition reaction rate parameters. The stabilization of vitamin C solutions was measured as the time in which 10 % of the substance decomposed at 20 and 0 °C. Addition of Se(IV) or Mg(II) ions significantly increase the stability of ascorbic acid solution (?34 and ?16 %, respectively), but Zn(II) causes a significant decrease in stability by ?23 %. Addition of Mn(II) has no significant influence on vitamin C stability. PMID:23099563

Doli?ska, Barbara; Ostró?ka-Cie?lik, Aneta; Caban, Artur; Rimantas, Klimas; Leszczy?ska, Lucyna; Ryszka, Florian

2012-12-01

413

Novel Regenerated Solvent Extraction Processes for the Recovery of Carboxylic Acids or Ammonia from Aqueous Solutions Part I. Regeneration of Amine-Carboxylic Acid Extracts  

SciTech Connect

Two novel regenerated solvent extraction processes are examined. The first process has the potential to reduce the energy costs inherent in the recovery of low-volatility carboxylic acids from dilute aqueous solutions. The second process has the potential for reducing the energy costs required for separate recovery of ammonia and acid gases (e.g. CO{sub 2} and H{sub 2}S) from industrial sour waters. The recovery of carboxylic acids from dilute aqueous solution can be achieved by extraction with tertiary amines. An approach for regeneration and product recovery from such extracts is to back-extract the carboxylic acid with a water-soluble, volatile tertiary amine, such as trimethylamine. The resulting trimethylammonium carboxylate solution can be concentrated and thermally decomposed, yielding the product acid and the volatile amine for recycle. Experimental work was performed with lactic acid, succinic acid, and fumaric acid. Equilibrium data show near-stoichiometric recovery of the carboxylic acids from an organic solution of Alamine 336 into aqueous solutions of trimethylamine. For fumaric and succinic acids, partial evaporation of the aqueous back extract decomposes the carboxylate and yields the acid product in crystalline form. The decomposition of aqueous solutions of trimethylammonium lactates was not carried out to completion, due to the high water solubility of lactic acid and the tendency of the acid to self-associate. The separate recovery of ammonia and acid gases from sour waters can be achieved by combining steam-stripping of the acid gases with simultaneous removal of ammonia by extraction with a liquid cation exchanger. The use of di-2,4,4-trimethylpentyl phosphinic acid as the liquid cation exchanger is explored in this work. Batch extraction experiments were carried out to measure the equilibrium distribution ratio of ammonia between an aqueous buffer solution and an organic solution of the phosphinic acid (0.2N) in Norpar 12. The concentration-based distribution ratios increase from 0.11 to 0.46 as the aqueous phase pH increases from 7.18 to 8.15. Regeneration of the organic extractant solution was carried out by stripping at elevated temperatures to remove the ammonia, with 99% recovery of the ammonia being obtained at 125 C.

Poole, L.J.; King, C.J.

1990-03-01

414

Recovery of calcium carbonate from steelmaking slag and utilization for acid mine drainage pre-treatment.  

PubMed

The conversion of steelmaking slag (a waste product of the steelmaking process) to calcium carbonate (CaCO(3)) was tested using hydrochloric acid, ammonium hydroxide and carbon dioxide via a pH-swing process. Batch reactors were used to assess the technical feasibility of calcium carbonate recovery and its use for pre-treatment of acid mine drainage (AMD) from coal mines. The effects of key process parameters, such as the amount of acid (HCl/calcium molar ratio), the pH and the CO(2) flow rate were considered. It was observed that calcium extraction from steelmaking slag significantly increased with an increase in the amount of hydrochloric acid. The CO(2) flow rate also had a positive effect on the carbonation reaction rate but did not affect the morphology of the calcium carbonate produced for values less than 2 L/min. The CaCO(3) recovered from the bench scale batch reactor demonstrated effective neutralization ability during AMD pre-treatment compared with the commercial laboratory grade CaCO(3). PMID:22643421

Mulopo, J; Mashego, M; Zvimba, J N

2012-01-01

415

Removal of copper and cadmium from aqueous solution using switchgrass biochar produced via hydrothermal carbonization process.  

PubMed

Biochar produced from switchgrass via hydrothermal carbonization (HTC) was used as a sorbent for the removal of copper and cadmium from aqueous solution. The cold activation process using KOH at room temperature was developed to enhance the porous structure and sorption properties of the HTC biochar. The sorption efficiency of HTC biochar and alkali activated HTC biochar (HTCB) for removing copper and cadmium from aqueous solution were compared with commercially available powdered activated carbon (PAC). The present batch adsorption study describes the effects of solution pH, biochar dose, and contact time on copper and cadmium removal efficiency from single metal ion aqueous solutions. The activated HTCB exhibited a higher adsorption potential for copper and cadmium than HTC biochar and PAC. Experiments conducted with an initial metal concentration of 40 mg/L at pH 5.0 and contact time of 24 h resulted in close to 100% copper and cadmium removal by activated HTCB at 2 g/L, far greater than what was observed for HTC biochar (16% and 5.6%) and PAC (4% and 7.7%). The adsorption capacities of activated HTCB for cadmium removal were 34 mg/g (0.313 mmol/g) and copper removal was 31 mg/g (0.503 mmol/g). PMID:22687632

Regmi, Pusker; Garcia Moscoso, Jose Luis; Kumar, Sandeep; Cao, Xiaoyan; Mao, Jingdong; Schafran, Gary

2012-10-30

416

Solution-processed flexible transparent conductors based on carbon nanotubes and silver grid hybrid films  

NASA Astrophysics Data System (ADS)

In a simple, cost-effective, and solution-based process, a thin-film of single-walled carbon nanotubes is hybridized on a PET film which has been patterned with solution self-assembled Ag nanoparticles. Such a flexible and transparent electrode exhibits a sheet resistance down to ~5.8 ? sq-1 at ~83.7% optical transmittance. The hybrid films are stable under ambient conditions and offer excellent bendability.In a simple, cost-effective, and solution-based process, a thin-film of single-walled carbon nanotubes is hybridized on a PET film which has been patterned with solution self-assembled Ag nanoparticles. Such a flexible and transparent electrode exhibits a sheet resistance down to ~5.8 ? sq-1 at ~83.7% optical transmittance. The hybrid films are stable under ambient conditions and offer excellent bendability. Electronic supplementary information (ESI) available: Experimental details, performance of graphene-Ag hybrid and met-SWNT-Ag hybrid films. See DOI: 10.1039/c3nr06386k

Wang, Jing; Zhang, Jintao; Sundramoorthy, Ashok Kumar; Chen, Peng; Chan-Park, Mary B.

2014-04-01

417

Revised black carbon assessment using benzene polycarboxylic acids  

Microsoft Academic Search

Black carbon (BC), the ubiquitous stable product of incomplete combustion, is believed to be a potential sink for atmospheric CO2 and therefore a contributor to the Earth’s radiative heat balance. Nevertheless, analytical procedures to measure BC are inconsistent, giving a non-systematic variation by factors of 14–571 for estimates of its content in soil. We hypothesized that the HCl used to

S. Brodowski; A. Rodionov; L. Haumaier; B. Glaser; W. Amelung

2005-01-01

418

The electrochemical reduction of carbon dioxide to formate/formic acid: engineering and economic feasibility.  

PubMed

The engineering and economic feasibility of large-scale electrochemical reduction of carbon dioxide to formate salts and formic acid is the focus of this Full Paper. In our study we investigated the long-term performance of tin and other proprietary catalysts in the reduction of carbon dioxide to formate/formic acid at a gas/solid/liquid interface, using a flow-through reactor. The overall economics and energy consumption of the process are evaluated through a value chain analysis. The sensitivity of the net present value of the process to various process parameters is examined. PMID:21922681

Agarwal, Arun S; Zhai, Yumei; Hill, Davion; Sridhar, Narasi

2011-09-19

419

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

420

Mouse organic solute transporter ? deficiency enhances renal excretion of bile acids and attenuates cholestasis  

PubMed Central

Organic solute transporter alpha-beta (Ost?-Ost?) is a heteromeric bile acid and sterol transporter that facilitates the entero- and renal-hepatic circulation of bile acids. Hepatic expression of this basolateral membrane protein is increased in cholestasis, presumably to facilitate removal of toxic bile acids from the liver. In this study we show that the cholestatic phenotype induced by common bile duct ligation (BDL) is reduced in mice genetically deficient in Ost?. Although Ost??/? mice have a smaller bile acid pool size which could explain lower serum and hepatic levels of bile acids after BDL, gallbladder bilirubin and urinary bile acid concentrations were significantly greater in Ost??/? BDL mice, suggesting additional alternative adaptive responses. Livers of Ost??/? mice had higher mRNA levels of constitutive androstane receptor (Car) than wild-type BDL mice and increased expression of Phase I enzymes (Cyp7a1, Cyp2b10, Cyp3a11), Phase II enzymes (Sult2a1, Ugt1a1) and Phase III transporters (Mrp2, Mrp3). Following BDL, the bile acid pool size increased in Ost??/? mice and protein levels for the hepatic basolateral membrane export transporters, Mrp3 and Mrp4, and for the apical bilirubin transporter, Mrp2, were all increased. In the kidney of Ost??/? mice after BDL the apical bile acid uptake transporter, Asbt, is further reduced, while apical export transporters, Mrp2 and Mrp4, are increased, resulting in a significant increase in urinary bile acid excretion. Conclusions: These findings indicate that loss of Ost? provides protection from liver injury in obstructive cholestasis through adaptive responses in both the kidney and liver that enhance clearance of bile acids into urine and through detoxification pathways most likely mediated by the nuclear receptor, Car. PMID:19902485

Soroka, Carol J.; Mennone, Albert; Hagey, Lee R.; Ballatori, Nazzareno; Boyer, James L.

2010-01-01

421

PROCESS FOR EXTRACTING NEPTUNIUM AND PLUTONIUM FROM NITRIC ACID SOLUTIONS OF SAME CONTAINING URANYL NITRATE WITH A TERTIARY AMINE  

Microsoft Academic Search

A process of selectively extracting plutonium nitrate and neptunium ; nitrate with an organic solution of a tertiary amine, away from uranyl nitrate ; present in an aqueous solution in a maximum concentration of 1M is described. ; The nitric acid concentration is adjusted to about 4M and nitrous acid is added ; prior to extraction. (AEC)

Sheppard

1962-01-01

422

Studies on the enhancement of solid electrolyte interphase formation on graphitized anodes in LiX-carbonate based electrolytes using Lewis acid additives for lithium-ion batteries  

Microsoft Academic Search

The new electrolyte systems utilizing one type of Lewis acids, the boron based anion receptors (BBARs) with LiF, Li2O, or Li2O2 in carbonate solutions have been developed and reported by us. These systems open up a new approach in developing non-aqueous electrolytes with higher operating voltage and less moisture sensitivity for lithium-ion batteries. However, the formation of a stable solid

L. F. Li; B. Xie; H. S. Lee; H. S. Lee; X. Q. Yang; J. McBreen; X. J. Huang

2009-01-01

423

Carbon dioxide curing of plates for lead--acid batteries  

Microsoft Academic Search

A process for curing lead--acid battery plates by exposing them to COâ in the presence of water is described. Since the cohesion of the active material is improved, a more open grid structure may be employed. The process is of value for both cathodes and anodes. (RWR)

Yarnell

1975-01-01

424

Kinetics of the extraction of succinic acid with tri-n-octylamine in 1-octanol solution.  

PubMed

Kinetic studies for the extraction of succinic acid from aqueous solution with 1-octanol solutions of tri-n-octylamine (TOA) were carried out using a stirred cell with a microporous hydrophobic membrane. The interfacial concentrations of species were correlated and thus the intrinsic kinetics was obtained. The overall extraction process was controlled by the chemical reaction at or near the interface between the aqueous and organic phases. The formation reaction of succinic acid-TOA complex was found to be first order with respect to the concentration of succinic acid in the aqueous phase and the order of 0.5 with respect to that of TOA in the organic phase with a rate constant of (3.14 +/- 0.6) x 10(-8) m(2.5) x mol(-0.5) x s(-1). The dissociation reaction of succinic acid-TOA complex was found to be the second-order with respect to that of succinic acid-TOA complex in the organic phase and the order of -2 with respect to that of TOA in the organic phase with a rate constant of (1.44 +/- 1.4) x 10(-4) mol x m(-2) x s(-1). PMID:16321050

Jun, Young-Si; Huh, Yun Suk; Hong, Won Hi; Hong, Yeon Ki

2005-01-01

425

Influence of the thermodynamic constants of carbonic acid in the current views of the ocean carbon cycle  

SciTech Connect

The recent redetermination of the thermodynamic dissociation constants of carbonic acid (K*[sub 1] and K[sup asterisk][sub 2]) in sea water (Goyet and Poisson; in press), appears to have uncovered some fundamental issues concerning the determination of the parameter of the CO[sub 2]/carbonate system. We use a non-linear curve-fitting procedure to illustrate the importance of small differences in pK*[sub 1] (which generate large errors in the fit of the thermodynamical model to the first points of the curve) in the determination of total alkalinity (TA) and total CO[sub 2] (TCO[sub 2]) from an experimental potentiometric titration curve. This flexible procedure which may also take into account concentrations of unknown protolytes shows that presently the accuracy for titration TA and TCO[sub 2] are [+-] 0.1 [mu]eq.kp[sup -1] and [+-] 0.6 [mu]M.kg[sup -1], respectively. We review the effect this has on the determination of oceanic properties such as CO[sup 2-][sub 3], and possible interfering organic species. This paper also reports the practical implications involved by the improvement of the determination of the dissociation constants of carbonic acid in numerical models used to study the effect of rising carbon dioxide (the most important of the greenhouse gases).

Goyet, C.; Bradshaw, A.L.; Brewer, P.G. (Woods Hole Oceanographic Inst., MA (United States))

1990-01-09

426

Quantification and mass isotopomer profiling of ?-keto acids in central carbon metabolism.  

PubMed

Mass spectrometry has been established as a powerful and versatile technique for studying cellular metabolism. Applications range from profiling of metabolites to accurate quantification and tracing of stable isotopes through the biochemical reaction network. Despite broad coverage of central carbon metabolism, most methods fail to provide accurate assessments of the ?-keto acids oxaloacetic acid, pyruvate, and glyoxylate because these compounds are highly reactive and degraded during sample processing and mass spectrometric measurement. We present a derivatization procedure to chemically stabilize these compounds readily during quenching of cellular metabolism. Stable derivatives were analyzed by ultrahigh pressure liquid chromatography coupled tandem mass spectrometry to accurately quantify the abundance of ?-keto acids in biological matrices. Eventually, we demonstrated that the developed protocol is suited to measure mass isotopomers of these ?-keto acids in tracer studies with stable isotopes. In conclusion, the here described method fills one of the last technical gaps for metabolomics investigations of central carbon metabolism. PMID:24533614

Zimmermann, Michael; Sauer, Uwe; Zamboni, Nicola

2014-03-18

427

Thermodynamic characteristics of the interaction between nicotinic acid and phenylalanine in an aqueous buffer solution at 298 K  

NASA Astrophysics Data System (ADS)

The interaction between L-phenylalanine and nicotinic acid is studied by solution calorimetry in an aqueous buffer solution (pH 7.35) at different ratios of the reagents. Experimental data on the enthalpy of dissolution of amino acid in the buffer solution of nicotinic acid at 298.15 K are calculated. The values of thermodynamic parameters for the complexation of L-phenylalanine with nicotinic acid are calculated. It is shown that the formation of a 1: 2 molecular complex is stabilized by the entropy factor due to the dominant role of the dehydration effect of initial reagents.

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

2013-08-01

428

ATR FT-IR H 2O spectra of acidic aqueous solutions. Insights about proton hydration  

NASA Astrophysics Data System (ADS)

Proton hydration in aqueous solutions has been recently characterised in our laboratory by means of vibrational spectra of HDO isotopically diluted in H 2O [M. ?miechowski, J. Stangret, J. Chem. Phys. 125 (2006) 204508]. Here, we attempt to study quantitatively H 2O spectra of acidic aqueous solutions. In principle, H 2O spectra provide more information about the structural state of water molecules, resulting from oscillator couplings in the system, but they are much more difficult in interpretation, when compared with HDO spectra. The spectra of aqueous solutions of monoprotic acids (HCl, HClO 4, HPF 6) have been measured by Attenuated Total Reflectance (ATR) FT-IR spectroscopy. Spectral data have been analysed in a way that led to removal of the contribution of bulk water, in order to separate the spectra of solute-affected water only. The analysis has been focused on the infinite dilution limit behaviour of the spectrum. Changes induced in the affected spectra by temperature have been studied for HPF 6 solutions at 25-45 °C. The stretching vibration fundamental has been found to be primarily affected by counter-anion. Proton-affected H 2O spectrum shows the presence of very wide absorption bands in the range, where bulk water shows negligible own absorption, rather than "absorption continua". They could be adequately resolved into analytical components. These bands have been unaffected by temperature and loosely correlated with the stretching fundamental, as indicated by 2D IR correlation spectra. All spectral effects of the studied acids on H 2O in solution have been quantitatively evidenced and discussed. They seem to be in accordance with the main conclusions about proton hydration derived from recent studies of HDO spectra mentioned above.

?miechowski, Maciej; Stangret, Janusz

2008-04-01

429

Composition and process for separating cesium ions from an acidic aqueous solution also containing other ions  

DOEpatents

A crown ether cesium ion extractant is disclosed as is its synthesis. The crown ether cesium ion extractant is useful for the selective purification of cesium ions from aqueous acidic media, and more particularly useful for the isolation of radioactive cesium-137 from nuclear waste streams. Processes for isolating cesium ions from aqueous acidic media using the crown ether cesium extractant are disclosed as are processes for recycling the crown ether cesium extractant and processes for recovering cesium from a crown ether cesium extractant solution. 4 figs.

Dietz, M.L.; Horwitz, E.P.; Bartsch, R.A.; Barrans, R.E. Jr.; Rausch, D.

1999-03-30

430

Volumetric properties of aqueous solutions of quinic acid and its sodium salt  

Microsoft Academic Search

\\u000a Abstract  The apparent molar volume of quinic acid and its sodium salt were determined from the density data of aqueous solutions up\\u000a to molality of 0.4 mol kg?1 and in the temperature range from 293.15 to 328.15 K. The apparent molar volume of sodium quinate comprises the ionic and\\u000a the associated ion-pair contributions. From the apparent molar volumes of quinic acid and the quinate

Nataša Poklar Ulrih; Nataša Šegatin

2010-01-01

431

Dynamical properties in uniform and periodic growth modes of ascorbic acid crystal domain from thin solution film  

E-print Network

There exists the threshold-sensitive dynamical transition between the uniform and the periodic growth modes in the domain growth of ascorbic acid crystals from its aqueous supersaturated solution film. The crystal growth induces the solution flow. Humidity controls the fluidity of the solution. The solution flow varies the film thickness. The threshold exists in the thickness of the solution film, and the crystal growth almost stops if the thickness becomes lower than the threshold.

Yoshihiro Yamazaki; Mitsunobu Kikuchi; Akihiko Toda; Jun-ichi Wakita; Mitsugu Matsushita

2013-11-19

432

Investigations on the mechanism of superlubricity achieved with phosphoric acid solution by direct observation  

NASA Astrophysics Data System (ADS)

In this work, the contact region between a Si3N4 ball and a SiO2 plate with the lubrication of phosphoric acid solution is observed directly by an optical microscope combined with a Raman microscope to understand the superlubricity mechanism. It is found that the wear on the friction surfaces mainly occurs at the beginning of the test and nearly disappears after the friction coefficient reduces to 0.05. When the superlubricity appears (? = 0.004), there is only a limited amount of solution available to the contact (forming starvation state), resulting in an "H" distribution surrounding the contact region. Moreover, it is observed that the hydrogen bond effect in the solution is enhanced with time going by, and finally a thin film with hydrogen bond network among H3PO4, H2PO4-, and H2O is formed on the friction surfaces, leading to the superlubricity. By employing this direct observation approach, the structure of the confined solution and the superlubricity mechanism of phosphoric acid solution are finally investigated and discussed.

Li, Jinjin; Ma, Liran; Zhang, Shaohua; Zhang, Chenhui; Liu, Yuhong; Luo, Jianbin

2013-09-01

433

Copper-Sulfate Pentahydrate as a Product of the Waste Sulfuric Acid Solution Treatment  

NASA Astrophysics Data System (ADS)

The aim of this study is synthesis of copper-sulfate pentahydrate from the waste sulfuric acid solution-mother liquor generated during the regeneration process of copper bleed solution. Copper is removed from the mother liquor solution in the process of the electrolytic treatment using the insoluble lead anodes alloyed with 6 mass pct of antimony on the industrial-scale equipment. As the result of the decopperization process, copper is removed in the form of the cathode sludge and is precipitated at the bottom of the electrolytic cell. By this procedure, the content of copper could be reduced to the 20 mass pct of the initial value. Chemical characterization of the sludge has shown that it contains about 90 mass pct of copper. During the decopperization process, the very strong poison, arsine, can be formed, and the process is in that case terminated. The copper leaching degree of 82 mass pct is obtained using H2SO4 aqueous solution with the oxygen addition during the cathode sludge chemical treatment at 80 °C ± 5 °C. Obtained copper salt satisfies the requirements of the Serbian Standard for Pesticide, SRPS H.P1. 058. Therefore, the treatment of waste sulfuric acid solutions is of great economic and environmental interest.

Markovi?, Radmila; Stevanovi?, Jasmina; Avramovi?, Ljiljana; Nedeljkovi?, Dragutin; Jugovi?, Branimir; Staji?-Troši?, Jasna; Gvozdenovi?, Milica

2012-12-01

434

Electro-oxidation of methanol on Pt(111) in acid solutions: effects of electrolyte anions during electrocatalytic reactions  

NASA Astrophysics Data System (ADS)

The electro-oxidation of methanol on a Pt(111) surface in both sulfuric and perchloric acid solutions was investigated by combined apparatus under both ultra-high vacuum and electrochemical environments. In sulfuric acid solution, a strong lateral interaction was observed between adsorbed bisulfate and CO derived from methanol. Coadsorption of CO derived from methanol with bisulfate ion yielded a (?7 × ?7)-R19.1°-CO-bisulfate structure. In perchloric acid solution, however, no lateral interaction between adsorbed CO and perchlorate was seen. The difference in reaction rates of methanol oxidation in both solutions was explained by these specific anion adsorption effects.

Ogasawara, Hirohito; Ito, Masatoki

1995-10-01

435

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

436

Production of monoolein from oleic acid and glycerol in supercritical carbon dioxide media: A kinetic approach  

Microsoft Academic Search

Esterification of free fatty acids (FFA) with glycerol in supercritical carbon dioxide (SC-CO2) media to produce designer monoacylglycerols (MAG) for food, cosmetic, and pharmaceutical industries, was conducted to elucidate the reaction kinetics and provide the reaction mechanism. Reactions were conducted in SC-CO2 at 10–30MPa, 170–250°C in a batch stirred reactor using an anhydrous glycerol to oleic acid initial molar ratio

Paul H. L. Moquin; Feral Temelli

2008-01-01

437

Dissociation of acetic acid in 50 mass % ethylene carbonate-water from 20 to 55°C  

Microsoft Academic Search

The dissociation constant of acetic acid in 50 mass % ethylene carbonate-water solvents has been determined at eight temperatures from 20 to 55°C by emf measurements of cells without liquid-junction containing hydrogen electrodes and silver-silver chloride electrodes. Acetic acid is weaker in the mixed solvent than in pure water. At 25°C, pK is 5.645 as compared with 4.756 in water,

J-C Hallé; Roger G. Bates

1975-01-01

438

Spectral and Acid-Base Properties of Hydroxyflavones in Micellar Solutions of Cationic Surfactants  

NASA Astrophysics Data System (ADS)

It has been shown that the spectral characteristics (intensity, position of the absorption band) and the acid-base properties in a series of structurally similar hydroxyflavones depend on the concentration of the cationic surfactants miramistin and decamethoxin in aqueous solutions, and the extent of their changes is more pronounced for hydrophobic quercetin than for hydrophilic rutin. For the first time, we have determined the apparent dissociation constants of quercetin and rutin in solutions of these cationic surfactants (pKa1) over a broad concentration range and we have established that they decrease in the series water-decamethoxin-miramistin.

Lipkovska, N. A.; Barvinchenko, V. N.; Fedyanina, T. V.; Rugal', A. A.

2014-09-01