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1

Stability of carbon nanowalls against chemical attack with acid solutions  

NASA Astrophysics Data System (ADS)

In this paper we report on the stability of CNW layers, synthesized by a radiofrequency plasma jet, against the chemical attack with different acid solutions (sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid). We present the changes of the morphology and structure of the CNW caused by the post-growth chemical treatments. We demonstrate that self-sustaining and transferable CNW layers can be obtained, by chemically dissolving the substrates, while the initial characteristics of the material are well preserved.

Vizireanu, Sorin; Dinescu, Gheorghe; Nistor, Leona Cristina; Baibarac, Mihaela; Ruxanda, Grigore; Stancu, Mihaela; Ciuparu, Dragos

2013-01-01

2

Removal of Cr(VI) from aqueous solution using activated carbon modified with nitric acid  

Microsoft Academic Search

The adsorption processes of Cr(VI) from aqueous solution onto a granular activated carbon (GAC) and a modified activated carbon (MAC) with nitric acid have been investigated. The surface characteristics of these two activated carbons were measured. The results showed that the MAC has a lower surface area, lower pHIEP and more oxygen functional groups compared with the GAC. Adsorption parameters

Guolin Huang; Jeffrey X. Shi; Tim A. G. Langrish

2009-01-01

3

Sorption of uranium from nitric acid solution using TBP-impregnated activated carbons  

SciTech Connect

The concept of extraction chromatography has been used to study the sorption of uranium from nitric acid solutions using tri-n-butyl phosphate (TBP) impregnated activated carbons. Batch equilibrium data and kinetic and breakthrough column behavior of uranium are reported. Wood based activated carbon has shown better capacity and breakthrough characteristics than shell based activated carbon. Sorption rate on impregnated carbons was relatively slow indicating that diffusion is the rate controlling step within the pore structure of the activated carbon. Uranium distribution on impregnated activated carbons is compared with equivalent bulk liquid extraction and a mechanism of uranium sorption is discussed.

Abbasi, W.A. [Pakistan Atomic Energy Commission, Islamabad (Pakistan). Pakistan Inst. of Nuclear Science and Technology; Streat, M. [Loughborough Univ. (United Kingdom). Dept. of Chemical Engineering

1998-08-01

4

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

5

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

SciTech Connect

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

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

2007-08-15

6

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

PubMed

The electrochemical oxidation of 3,4-dihydroxyphenylacetic acid (DOPAC) on a carbon fiber microelectrode (CF) and a glassy carbon macroelectrode (GC) in glacial acetic acid solutions was investigated using voltammetric techniques. Voltammograms recorded at these electrodes show well-defined single waves or peaks. The proposed mechanism of the anodic oxidation of DOPAC consists of two successive one-electron one-proton steps. The loss of the first electron proceeds irreversibly and determines the overall rate of the electrode process. This stage is accompanied by the generation of an unstable phenoxyl radical in position 4 of the aromatic ring. The second stage of the electrode reaction produces substituted orto-quinone as the final product of the electrode process of DOPAC. DOPAC exhibits more antioxidative power than synthetic BHT and can be useful in food protection against reactive oxygen species. The results presented can help to explain biochemical and antioxidative properties of DOPAC in a living cell and can be useful in determination of this compound in real samples. PMID:20004625

Michalkiewicz, Slawomir; Skorupa, Agata

2009-12-03

7

Inhibition Effect of Dodecylamine on Carbon Steel Corrosion in Hydrochloric Acid Solution  

NASA Astrophysics Data System (ADS)

Dodecylamine spontaneously adsorbs on carbon steel via its polar group (-NH2) in hydrochloric acid solution. Furthermore, it forms a monolayer film on carbon steel surface. The inhibition mechanism of dodecylamine for carbon steel is geometric blocking effect. The adsorption of dodecylamine on carbon steel surface follows Arrhenius equation. The adsorption slightly increases activated energy, but greatly reduces pre-exponential factor value. Atomic force microscopy force curves indicate that at the area without adsorbed dodecylamine, no obvious adhere force occurs. At the area with adsorbed dodecylamine, however, an average 1.3 nN adhere force is observed.

Chen, Zhenyu; Huang, Ling; Qiu, Yubing; Guo, Xingpeng

2012-12-01

8

Methylene Blue adsorption from aqueous solution by activated carbon: Effect of acidic and alkaline solution treatments  

Microsoft Academic Search

The removal of Methylene Blue (MB) from aqueous solution using activated carbon (AC) has been investigated. Adsorption experiments were conducted and the maximum adsorption capacity was determined. The effect of experimental parameters such as pH, dye concentration and temperature were studied on the adsorption process. Equilibrium data were mathematically modeled using the Langmuir and Freundlich adsorption models to describe the

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

2010-01-01

9

Elution of zinc in dust discharged from electric arc furnace in carbonic acid solution  

Microsoft Academic Search

The dust discharged from an electric arc furnace (EAF) is a valuable resource of zinc. As a fundamental study of extraction of zinc, iron and chlorine in the EAF dust, the elution behavior of them in carbonic acid solution was studied. The influence of the weight of the EAF dust on the elution behavior was examined in this study. Experiment

S Yokoyama; T Sasaki; J Sasano; M Izaki

2012-01-01

10

Extraction of lanthanides from acidic solution using tributyl phosphate modified supercritical carbon dioxide  

Microsoft Academic Search

The feasibility of using supercritical carbon dioxide as a substitute extraction solvent in nuclear reprocessing was tested by the extraction of lanthanide ions from acidic solution. Lanthanides were extracted from 6 M HNO[sub 3]-3 M LiNO[sub 3] solutions using tributyl phosphate- (TBP-) modified CO[sub 2]. Synergistic effects were also investigated using a combination of thenoyltrifluoroacetone (TTA) and TBP-modified CO[sub 2

K. E. Laintz; E. Tachikawa

1994-01-01

11

Inhibitory mechanism of low-carbon steel corrosion by mimosa tannin in sulphuric acid solutions  

Microsoft Academic Search

Mimosa tannin was investigated as inhibitor of low-carbon steel sulphuric acid corrosion in concentrations from 10-5 to 10-1 mol L-1, at the temperature of 298 K in the solutions of pH 1, 2 and 3. The inhibitor effectiveness increases with increase in concentration. The adsorptive behaviour of mimosa tannin in solutions of pH 1 and 2 may be approximated, both

S. Martinez; I. Štern

2001-01-01

12

Catalytic wet air oxidation of butyric acid solutions using carbon-supported iridium catalysts  

Microsoft Academic Search

Aqueous solutions of butyric acid were treated by catalytic wet air oxidation using carbon-supported iridium catalysts in a stirred reactor. Under the operating conditions of 6.9bar of oxygen partial pressure and 200°C of temperature, conversions up to 52.9% after 2h were obtained depending on the type of catalyst used. The effects of butyric acid initial concentration, loading of catalyst, oxygen

H. T Gomes; J. L Figueiredo; J. L Faria

2002-01-01

13

Analysis of the corrosion of carbon steels in simulated salt repository brines and acid chloride solutions at high temperatures  

Microsoft Academic Search

An analysis of literature data on the corrosion of carbon steels in anoxic brines and acid chloride solutions was performed, and the results were used to assess the expected life of high-level nuclear waste package containers in a salt repository environment. The corrosion rate of carbon steels in moderately acidic aqueous chloride environments obeys an Arrhenius dependence on temperature and

D. R. Diercks; T. F. Kassner

1988-01-01

14

Catalytic Ozonation for the Degradation of P-Chlorobenzoic Acid in Aqueous Solution by Ni Supported Activated Carbon  

Microsoft Academic Search

Catalytic ozonation of p-chlorobenzoic acid (p-CBA) in aqueous solution has been carried out where transitional metal (Ni, Cu, Mn, Co, Fe) supported activated carbon was used as catalysts. Ni supported activated carbon ( Ni\\/AC) catalyst, which is prepared by the dipping method with an aqueous solution of Ni(NO3)2, shows higher catalytic activity. Activated carbon and Ni\\/AC catalyst were characterized by

Xukai Li; Ruihuan Huang; Qiuyun Zhang; Wenqing Yang; Laisheng Li

2010-01-01

15

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

SciTech Connect

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

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

1998-11-01

16

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

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

17

Electrochemical reduction of uranium(VI) in nitric acid-hydrazine solution on glassy carbon electrode  

Microsoft Academic Search

Electrochemical reduction of U(VI) in nitric acid-hydrazine solution is greatly influenced by the concentration of nitric\\u000a acid. In low acidity nitric acid solution such as 0.1M (M=mol\\/dm3) HNO3, U(VI) was firstly reduced to U(V) and then partially reduced to U(IV). In high acidity nitric acid solution, e.g., 3-6M\\u000a HNO3, an electrode process of two-electron transfer was involved in the reduction

Y.-Z. Wei; B. Fang; T. Arai; M. Kumagai

2004-01-01

18

Emulgin as an Inhibitor of Corrosion and Hydrogenation of Carbon Steel in Weakly Acidic H2S-Containing Solutions  

Microsoft Academic Search

The protection effect of emulgin (a technological mixture of some primary and secondary aliphatic amines) in concentrations of 0.078 to 0.625 mmol\\/l from acid, carbon dioxide, and hydrogen sulfide corrosion and hydrogenation of carbon steel St3 was studied. In a 0.005–0.05 M solution of HCl saturated with hydrogen sulfide, the protective value was 97%, no local damage being observed. At

V. I. Vigdorovich; S. E. Sinyutina; L. V. Chivileva

2000-01-01

19

Production of dissolved organic carbon and low-molecular weight organic acids in soil solution driven by recent tree photosynthate  

Microsoft Academic Search

Dissolved organic carbon (DOC) is an important component in the terrestrial carbon cycle. Yet, the relative importance of\\u000a different inputs of DOC to the soil solution remains uncertain. Here, we used a large-scale forest girdling experiment to\\u000a examine how the supply of recent photosynthate to tree roots and their mycorrhizal fungi affects DOC, in particular low-molecular\\u000a weight organic acids (LMWOA).

Reiner Giesler; Mona N. Högberg; Bjarne W. Strobel; Andreas Richter; Anders Nordgren; Peter Högberg

2007-01-01

20

Equilibrium absorption of carbon dioxide by amino acid salt and amine amino acid salt solutions  

Microsoft Academic Search

Experimental vapour liquid equilibrium (VLE) measurements were conducted for an amino acid salt(AAS), 3.5 M potassium sarcosinate and an amine amino acid salt (AAAS), the 5.0 M sarcosinate salt of 3-(methylamino)propylamine.The study was performed in two VLE apparatuses from 40 to 120 °C and for CO2 partial pressures ranging from 0.08 to 995 kPa. Thermodynamic models representing the AAS and AAAS solvent

Ugochukwu E. Aronu; Erik T. Hessen; Tore Haug-Warberg; Karl A. Hoff; Hallvard F. Svendsen

2011-01-01

21

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...

22

Removal of Acid Violet 17 from Aqueous Solutions by Adsorption onto Activated Carbon Prepared from Pistachio Nut Shell  

Microsoft Academic Search

Adsorbents prepared from pistachio nut shell, an agricultural waste biomass, were successfully used to remove Acid Violet 17 from an aqueous solution. The activated carbons PNS1, PNS2, and PNS3 were characterized by scanning electron microscope (SEM), Fourier Transform – Infra Red spectroscopy (FTIR) and (BET). The effect of pH, adsorbent dosage, and temperature on dye removal was studied. Maximum color

P. Vijayalakshmi; V. Sathya Selva Bala; K. V. Thiruvengadaravi; P. Panneerselvam; M. Palanichamy; S. Sivanesan

2010-01-01

23

Thickness effects of a carbon-supported platinum catalyst layer on the electrochemical reduction of oxygen in sulfuric acid solution  

Microsoft Academic Search

The influence of the thickness of a carbon-supported platinum catalyst layer on the oxygen reduction reaction (orr) has been studied in sulfuric acid solution by means of a thin-film rotating disk electrode. Pronounced changes in the Pt utilization, electrode activity and the orr kinetics have been observed upon varying the catalyst layer thickness. The thicker film electrode exhibits a higher

Junhua Jiang; Baolian Yi

2005-01-01

24

Carbonate acidizing  

SciTech Connect

The authors present the first quantitative study and complete model of the wormholing phenomenon, leading to a means of predicting and optimizing carbonate acidizing treatments. Laboratory experiments on a gypsum model system and computer simulations show that for a given geometry, wormholes can be quantified by a unique parameter, their equivalent hydraulic length. The behavior of this quantifying parameter vs. all the system parameters is studied and allows the quantitative prediction of the efficiency of an acidizing treatment. This study highlights the fractal nature of the phenomenon, which is accounted for in the equations, and the strong effect of the sample geometry. Three types of etching can be obtained: compact, wormhole type, or homogeneous. The optimum conditions for achieving the best skin decrease correspond to the creation of wormholes and can then be defined in terms of fluid reactivity and injection rate.

Daccord, G.; Touboul, E.; Lenormand, R.

1989-02-01

25

Intramolecular carbon isotopic analysis of acetic acid by direct injection of aqueous solution  

Microsoft Academic Search

We report an improved method for determining the intramolecular carbon isotopic composition of acetate using direct injection of aqueous samples. The system builds upon prior work that established pyrolytic conditions for online analysis and represents a significant advance in that it requires minimal preparation for samples containing as little as 1mM sodium acetate in aqueous solution. The technique is applicable

Burt Thomas; Katherine H. Freeman; Michael A. Arthur

2009-01-01

26

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

Microsoft Academic Search

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,

B Wiersma; J John Mickalonis

2007-01-01

27

Radiation-induced grafting of multi-walled carbon nanotubes in glycidyl methacrylate–maleic acid binary aqueous solution  

Microsoft Academic Search

With the aim to improve the compatibility between multi-walled carbon nanotubes (MWCNTs) and nylon-6, purified MWCNTs (p-MWCNTs) were grafted successfully with glycidyl methacrylate–maleic acid in aqueous solution using a single-step radiation method. The chemical structure and morphology of grafted p-MWCNTs (g-MWCNTs) was investigated by micro-FTIR, Raman spectroscopy and transmission electron microscopy. The prepared nylon-6\\/g-MWCNTs composite has higher mechanical strength and

Haibo Yu; Xinyue Mo; Jing Peng; Maolin Zhai; Jiuqiang Li; Genshuan Wei; Xiaohong Zhang; Jinliang Qiao

2008-01-01

28

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

29

Analysis of the corrosion of carbon steels in simulated salt repository brines and acid chloride solutions at high temperatures  

SciTech Connect

An analysis of literature data on the corrosion of carbon steels in anoxic brines and acid chloride solutions was performed, and the results were used to assess the expected life of high-level nuclear waste package containers in a salt repository environment. The corrosion rate of carbon steels in moderately acidic aqueous chloride environments obeys an Arrhenius dependence on temperature and a (pH{sub 2}){sup {minus}1/2} dependence on hydrogen partial pressure. The cathodic reduction of water to produce hydrogen is the rate-controlling step in the corrosion process. An expression for the corrosion rate incorporating these two dependencies was used to estimate the corrosion life of several proposed waste package configurations. 42 refs., 11 figs., 2 tabs.

Diercks, D.R.; Kassner, T.F.

1988-04-01

30

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

31

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

Microsoft Academic Search

Potentiometric measurements of the stoichiometric constants for the dissociation of carbonic acid in NaCl solutions (K1?=[H+][HCO3-]\\/[CO2] and K1?=[H+][CO32-]\\/[HCO3-]) have been made as a function of molality (0–6m) and temperature (0–50°C). The results have been fitted to the equationspKi?-pKi=Ai+Bi\\/T+CilnTThe values of pKi in pure water are taken from the literature and the adjustable parameters Ai, Bi and Ci are a function

Frank Millero; Fen Huang; Taylor Graham; Denis Pierrot

2007-01-01

32

Crystal size distributions of induced calcium carbonate crystals in polyaspartic acid and Mytilus edulis acidic organic proteins aqueous solutions  

Microsoft Academic Search

Different concentrations of soluble matrix extracts from Mytilus edulis and polyaspartic acid were mixed with CaCl2 aqueous solutions to produce CaCO3 crystallizations under controlled conditions. The obtained crystals were observed at several intervals of time by optical microscopy and scanning electron microscopy (SEM). Image treatment of the SEM images allowed quantifying the crystal size distribution (CSD) in different crystallization conditions.

Josep Roqué; Judit Molera; Mŕrius Vendrell-Saz; Nativitat Salvadó

2004-01-01

33

Multi-walled carbon nanotubes and poly(lactic acid) nanocomposite fibrous membranes prepared by solution blow spinning.  

PubMed

Nanocomposite fibers based on multi-walled carbon nanotubes (MWCNT) and poly(lactic acid) (PLA) were prepared by solution blow spinning (SBS). Fiber morphology was characterized by scanning electron microscopy (SEM) and optical microscopy (OM). Electrical, thermal, surface and crystalline properties of the spun fibers were evaluated, respectively, by conductivity measurements (4-point probe), thermogravimetric analyses (TGA), differential scanning calorimetry (DSC), contact angle and X-ray diffraction (XRD). OM analysis of the spun mats showed a poor dispersion of MWCNT in the matrix, however dispersion in solution was increased during spinning where droplets of PLA in solution loaded with MWCNT were pulled by the pressure drop at the nozzle, producing PLA fibers filled with MWCNT. Good electrical conductivity and hydrophobicity can be achieved at low carbon nanotube contents. When only 1 wt% MWCNT was added to low-crystalline PLA, surface conductivity of the composites increased from 5 x 10(-8) to 0.46 S/cm. Addition of MWCNT can slightly influence the degree of crystallinity of PLA fibers as studied by XRD and DSC. Thermogravimetric analyses showed that MWCNT loading can decrease the onset degradation temperature of the composites which was attributed to the catalytic effect of metallic residues in MWCNT. Moreover, it was demonstrated that hydrophilicity slightly increased with an increase in MWCNT content. These results show that solution blow spinning can also be used to produce nanocomposite fibers with many potential applications such as in sensors and biosensors. PMID:22755116

Oliveira, Juliano E; Zucolotto, Valtencir; Mattoso, Luiz H C; Medeiros, Eliton S

2012-03-01

34

Analysis of corrosion data for carbon steels in simulated salt repository brines and acid chloride solutions at high temperatures  

SciTech Connect

Carbon steel is currently the leading candidate material for fabrication of a container for isolation of high level nuclear waste in a salt repository. Since brine entrapped in the bedded salt can migrate to the container by several transport processes, corrosion is an important consideration in the long-term performance of the waste package. A detailed literature search was performed to compile relevant corrosion data for carbon steels in anoxic acid chloride solutions, and simulated salt repository brines at temperatures between approx. 20 and 400/sup 0/C. The hydrolysis of Mg/sup 2 +/ ions in simulated repository brines containing high magnesium concentrations causes acidification at temperatures above 25/sup 0/C, which, in turn, influences the protective nature of the magnetite corrosion product layer on carbon steel. The corrosion data for the steels were analyzed, and an analytical model for general corrosion was developed to calculate the amount of penetration (i.e., wall thinning) as a function of time, temperature, and the pressure of corrosion product hydrogen than can build up during exposure in a closed system (e.g., a sealed capsule). Both the temperature and pressure dependence of the corrosion rate of steels in anoxic acid chloride solutions indicate that the rate-controlling partial reaction is the cathodic reduction of water to form hydrogen. Variations in the composition and microstructure of the steels or the concentration of the ionic species in the chloride solutions (provided that they do not change the pH significantly) do not appear to strongly influence the corrosion rate.

Diercks, D.R.; Hull, A.B.; Kassner, T.F.

1988-03-01

35

Nanoporous carbon synthesized from sol–gel template for adsorbing gibberellic acid in aqueous solution  

Microsoft Academic Search

A novel method, based on dynamic carbonization and silica template formed by sol–gel, was developed to prepare nanoporous carbon materials with tailored pore structures. The effects of the sol–gel reaction and carbonization process on the final nanoporous carbon product were investigated by pore features such as specific surface area, the total pore volume, and pore size distribution, which were systemically

Jin Li; Jin-Tong Xia; Hong-Bo Liu; Jiao-Lian He; Jun-Hua Zhang

2011-01-01

36

Adsorption isotherms of linoleic and linolenic acids from solutions in carbon tetrachloride on surfaces of highly dispersed manganese and copper ferrites  

NASA Astrophysics Data System (ADS)

A comparative study of adsorption-desorption isotherms of linoleic and linolenic acids from solutions in carbon tetrachloride on surfaces of manganese and copper ferrites is performed by means of equilibrium adsorption. Adsorption isotherms of fatty acids are described in terms of the theory of volume filling of micropores, and the values of the limiting adsorption, the characteristic adsorption energy, and the pore space volume are calculated. It is established that the limiting adsorption values of linoleic and linolenic acids from solutions in carbon tetrachloride on a copper ferrite surface are higher than on a manganese ferrite surface. It is shown that the adsorption-desorption isotherms have a hysteresis loop.

Balmasova, O. V.; Korolev, V. V.; Ramazanova, A. G.

2012-04-01

37

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

Microsoft Academic Search

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

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

2002-01-01

38

Batch adsorption of 2,4-dichlorophenoxy-acetic acid (2,4-D) from aqueous solution by granular activated carbon  

Microsoft Academic Search

Adsorption equilibrium, kinetics and thermodynamics of 2,4-dichlorophenoxy-acetic acid (2,4-D), one of the most commonly used phenoxy acid herbicides, onto granular activated carbon were studied in aqueous solution in a batch system with respect to pH, temperature and initial 2,4-D concentration. At 600 mg l?1 initial 2,4-D concentration activated carbon exhibited the highest 2,4-D uptake capacity of 518.0 mg g?1 at

Z. Aksu; E. Kabasakal

2004-01-01

39

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

PubMed

Supercritical carbon dioxide extraction, which is a feasible "green" alternative, was applied in this study as a sample pretreatment step for the removal of gallium (III) ions from acidic aqueous solution. The effect of various process parameters, including various chelating agents, extraction pressure and temperature, dimensionless CO(2) volume, the concentration of the chelating agent, and the pH of the solution, governing the efficiency and throughput of the procedure were systematically investigated. The performance of the various chelating agents from different studies indicated that the extraction efficiency of supercritical CO(2) was in the order: thiopyridine (PySH)>thenoyltrifluoroacetone (TTAH)>acetylacetone (AcAcH). The optimal extraction pressure and temperature for the supercritical CO(2) extraction of gallium (III) with chelating agent PySH were found to be 70 degrees C and 3000psi, respectively. The optimum concentration of the chelating agent was found to be 50ppm. A value of 7.5 was selected as the optimum dimensionless CO(2) volume. The optimum pH of the solution for supercritical CO(2) extraction should fall in the range of 2.0-3.0. PMID:18406056

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

2008-02-29

40

Inhibiting properties and adsorption of an amine based fatty acid corrosion inhibitor on carbon steel in aqueous carbon dioxide solutions.  

National Technical Information Service (NTIS)

Carbon dioxide corrosion is a major corrosion problem in oil and gas production systems and many organic inhibitors have been tested and used to protect the substrate from corrosion. This thesis studies the mechanism of interaction of the inhibitor molecu...

J. Buchweishaija

1997-01-01

41

Equilibrium and kinetic studies on the removal of Acid Red 114 from aqueous solutions using activated carbons prepared from seed shells  

Microsoft Academic Search

The use of low-cost and ecofriendly adsorbents has been investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. This paper deals with the removal of Acid Red 114 (AR 114) from aqueous solutions using activated carbons prepared from agricultural waste materials such as gingelly (sesame) (Sp), cotton (Cp) and pongam (Pp) seed shells. Optimum

N. Thinakaran; P. Panneerselvam; P. Baskaralingam; D. Elango; S. Sivanesan

2008-01-01

42

Effect of various chelating agents on supercritical carbon dioxide extraction of indium(III) ions from acidic aqueous solution.  

PubMed

Indium and its compounds have numerous industrial applications in the manufacture of liquid crystal displays and semiconductors. Indium compounds are considered hazardous materials that can be carcinogenic. Supercritical fluid extraction using carbon dioxide was utilized in this research as a sample pretreatment step for extraction of indium(III) ions from the synthetic etching wastewater of the semiconductor and optoelectronic industries. Several parameters, including various chelating agents, pH of solution, molar ratio of chelating agent to indium(III) ions, temperature and pressure were systematically investigated. Indium(III) ions were extracted by supercritical CO2 combined with several various types of chelating agents including beta-diketone (AcAcH), fluorinated beta-diketone (TTAH), thiopyridine (PySH), and piperidinyldithiocarbamic acid (NCS2H) to extract the ions from acidic aqueous solution. The performance of the various chelating agents from different studies indicated that the extraction efficiency by the supercritical CO2 was in the order: NCS2H>or==PySH>TTAH>AcAcH. The optimum pH for supercritical CO2 extraction should fall in the range from 2.0 to 3.0. The optimum molar ratio of chelating agents to indium(III) ions was found to be a ratio of 10:1. It was also revealed that the optimal extraction pressure and temperature for the supercritical CO2 extraction of indium(III) with various chelating agents AcAcH, PySH and NCS2H were 70 degrees C 2000 psi, 60 degrees C 2000 psi, and 60 degrees C 2000 psi, respectively. PMID:18054158

Chou, Wei-Lung; Yang, Kai-Chiang

2007-10-22

43

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

Microsoft Academic Search

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

Meenakshi Goyal; Rashmi Dhawan; Mamta Bhagat

2010-01-01

44

Experimental study on equilibrium solubility (at low partial pressures), density, viscosity and corrosion rate of carbon dioxide in aqueous solutions of ascorbic acid  

Microsoft Academic Search

In this paper, ascorbic acid as a new carbon dioxide (CO2) absorbent was investigated. The equilibrium solubility of CO2 into 0.5, 1 and 1.5moldm?3 (M) aqueous ascorbic acid solutions were measured experimentally with a stirred batch reactor at total atmospheric pressure over the CO2 partial pressure ranging from 0 to 45kPa and temperatures between 298 and 313K. The results of

S. Mazinani; A. Samsami; A. Jahanmiri; A. R. Sardarian

2011-01-01

45

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

Microsoft Academic Search

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

M Abdallah; M. M El-Naggar

2001-01-01

46

Electrochemical behavior of antioxidants: I. Mechanistic study on electrochemical oxidation of gallic acid in aqueous solutions at glassy-carbon electrode  

Microsoft Academic Search

Mechanism of electrochemical oxidation of gallic acid in aqueous phosphate buffer solutions of different pH’s was studied at glassy-carbon electrode. The study was performed using cyclic, convolution–deconvolution sweep voltammetry, chronoamperometry and chronocoulometry. It gives two irreversible diffusion-controlled cyclic voltammetric waves at the entire range of pH. The electrochemical oxidation mechanism was proposed to be an ECEC-first order mechanism in which

Refat Abdel-Hamid; Emad F. Newair

2011-01-01

47

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

48

Acid sorption regeneration process using carbon dioxide  

US Patent & Trademark Office Database

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.

2001-11-13

49

Corrosion of low-carbon steel in sulphuric acid solution in presence of pyrazole—halides mixture  

Microsoft Academic Search

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

Gamal K. Gomma

1998-01-01

50

Solution (sup13)C Nuclear Magnetic Resonance Spectroscopic Analysis of the Amino Acids of Methanosphaera stadtmanae: Biosynthesis and Origin of One-Carbon Units from Acetate and Carbon Dioxide  

PubMed Central

We found that general pathways for amino acid synthesis of Methanosphaera stadtmanae, a methanogen that forms CH(inf4) from H(inf2) and methanol, resembled those of methanogens that form CH(inf4) from CO(inf2) or from the methyl group of acetate. We determined the incorporation of (sup14)C-labeled CO(inf2), formate, methanol, methionine, serine, and acetate into cell macromolecules. Labeling of amino acid carbons was determined by solution nuclear magnetic resonance spectroscopy after growth with (sup13)C-labeled acetate, CO(inf2), serine, and methanol. The (alpha) and (beta) carbons of serine and alanine were formed from carboxyl and methyl carbons of acetate, respectively, and the amino acid carboxyl groups were formed from CO(inf2). This indicates that pyruvate was formed by reductive carboxylation of acetate. Labeling of the methyl carbon of methionine indicated that the major route of synthesis was from the hydroxymethyl carbon of serine that arises from the methyl carbon of acetate. Methanol was a minor source of the methyl of methionine. Unambiguous assignment was made of the sources of all carbons of histidine. Labeling of the histidine 7 position ((epsilon) carbon) was consistent with formation from the C-2 of the purine ring of ATP and the origin of the C-2 from a formyl unit derived from the hydroxymethyl carbon of serine.

Miller, T. L.; Chen, X.; Yan, B.; Bank, S.

1995-01-01

51

Removal of Acid Violet 17 from aqueous solutions by adsorption onto activated carbon prepared from sunflower seed hull  

Microsoft Academic Search

The adsorption of Acid Violet 17 (AV17) was carried out using various activated carbons prepared from sunflower seed hull (SSH), an agricultural solid waste by-product. The effect of parameters such as agitation time, initial dye concentration, adsorbent dosage, pH and temperature were studied. The Langmuir and Freundlich isotherm models were applied and the Langmuir model was found to best report

N. Thinakaran; P. Baskaralingam; M. Pulikesi; P. Panneerselvam; S. Sivanesan

2008-01-01

52

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

USGS Publications Warehouse

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

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

1988-01-01

53

Comparative leaching of spent zinc-manganese-carbon batteries using sulfur dioxide in ammoniacal and sulfuric acid solutions  

Microsoft Academic Search

The non-magnetic fraction of spent zinc-manganese-carbon batteries containing 20.8% Zn, 22.7% Mn, 2.65% Fe, and <0.1% Hg, Ni, Co, Cu and Pb was leached in H2SO4, H2SO4\\/SO2, NH3 and NH3\\/SO2 at 30-60°C. In acid media the complete dissolution of zinc is unaffected by SO2. However, the reductive role of SO2 increases the leaching of manganese in H2SO4 from 25% to

G. Senanayake; S. M. Shin; A. Senaputra; A. Winn; D. Pugaev; J. Avraamides; J. S. Sohn; D. J. Kim

2010-01-01

54

Modeling of wormhole behavior in carbonate acidizing  

SciTech Connect

A mathematical model that describes the growth and competition of wormholes during an acidizing treatment in a carbonate formation is developed. The purpose of the treatment is to remove any near wellbore permeability damage created by drilling or completion fluids so that the production of reservoir fluids is stimulated. Hydrochloric acid is commonly used for this purpose. Since the acid solution tends to flow into the less resistant areas, large pores on the rock surface receive most acid fluid. Pores are enlarged due to the reaction between acid solution and carbonates. The growth of large pores in the formation is referred to as wormholing. Results from the model show that wormholes are formed due to the heterogeneity of carbonate rock and the reaction kinetics between acid and carbonates. Formation of a dominant wormhole is controlled by fluid diffusivity and fluid loss. Model results have good agreement with the results from published papers.

Hung, K.M.

1987-01-01

55

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

56

Removal of Acid Violet 17 from aqueous solutions by adsorption onto activated carbon prepared from sunflower seed hull.  

PubMed

The adsorption of Acid Violet 17 (AV17) was carried out using various activated carbons prepared from sunflower seed hull (SSH), an agricultural solid waste by-product. The effect of parameters such as agitation time, initial dye concentration, adsorbent dosage, pH and temperature were studied. The Langmuir and Freundlich isotherm models were applied and the Langmuir model was found to best report the equilibrium isotherm data. Langmuir adsorption capacity was found to be 116.27 mg/g. Kinetic data followed pseudo-second-order kinetics. Maximum colour removal was observed at pH 2.0. It was observed that the rate of adsorption improves with increasing temperature and the process is endothermic. The adsorbent surface was analysed with a scanning electron microscope. The results indicate that activated sunflower seed hull could be an attractive option for colour removal from dilute industrial effluents. PMID:17689864

Thinakaran, N; Baskaralingam, P; Pulikesi, M; Panneerselvam, P; Sivanesan, S

2007-06-02

57

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

58

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

PubMed Central

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

2013-01-01

59

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

PubMed

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

Jahangiri-Rad, Mahsa; Nadafi, Kazem; Mesdaghinia, Alireza; Nabizadeh, Ramin; Younesian, Masood; Rafiee, Mohammad

2013-01-05

60

Effect of acidic surface functional groups on Cr(VI) removal by activated carbon from aqueous solution  

Microsoft Academic Search

The activated carbon with high surface area was prepared by KOH activation. It was further modified by H2SO4 and HNO3 to introduce more surface functional groups. The pore structure of the activated carbons before and after modification was\\u000a analyzed based on the nitrogen adsorption isotherms. The morphology of those activated carbons was characterized using scanning\\u000a electronic microscopy (SEM). The surface

Hualei Zhou; Yunfa Chen

2010-01-01

61

Dissolution of spent nuclear fuel in carbonate–peroxide solution  

Microsoft Academic Search

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

Chuck Z. Soderquist; Brady D. Hanson

2010-01-01

62

Dissolution of Spent Nuclear Fuel in Carbonate-Peroxide Solution  

SciTech Connect

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

Soderquist, Chuck Z.; Hanson, Brady D.

2010-01-31

63

One-step synthesis of carbon functionalized with sulfonic acid groups using hydrothermal carbonization  

Microsoft Academic Search

Carbon functionalized with sulfonic acid groups has been synthesized using the one-step hydrothermal carbonization of furaldehyde and hydroxyethylsulfonic acid aqueous solution at 180°C for 4h. The carbon exhibited high acidity and comparable activities to sulfuric acid for the traditional acid-catalyzed reactions, which indicated that it has great potential for environment-friendly processes. The copolymerization method provides an efficient procedure for the

Xuezheng Liang; Minfeng Zeng; Chenze Qi

2010-01-01

64

Carbon dioxide sequestration by direct mineral carbonation with carbonic acid  

SciTech Connect

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

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

2000-01-01

65

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....

66

Precipitation of ultrafine benzoic acid by expansion of a supercritical carbon dioxide solution through a porous plate nozzle  

Microsoft Academic Search

A method for the crystallization of ultrafine powders by rapid expansion of a supercritical solution, the RESS process, has been developed using a porous sintered metal plate instead of an orifice or a capillary tube as an expansion nozzle. The effects of the various process parameters on the characteristics of the crystals obtained with this kind of nozzle were investigated

C. Domingo; E. M. Berends; G. M. van Rosmalen

1996-01-01

67

The electrodeposited titanium powders in nonaqueous propylene carbonate solution  

Microsoft Academic Search

Titanium has many good chemical and physical properties. This study investigates the electrodeposition of titanium in nonaqueous propylene carbonate solution at low temperature though the amount of electrodeposited titanium is a little. The amount of electrodeposited titanium increases with an increase of propylene carbonate. The order of electrodeposited titanium amount was at pH 4.5>6.0>3.0 in slightly acidic solution owing to

Chin-Ming Chu

2011-01-01

68

Carbonic Acid Pretreatment of Biomass  

SciTech Connect

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

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

2003-05-31

69

Carbonic Acid Retreatment of Biomass  

SciTech Connect

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

Baylor university

2003-06-01

70

Kinetic study of platinum sorption from solutions by active carbons  

SciTech Connect

The purpose of this work was to study the kinetics of sorption of platinum compounds from hydrochloric acid solutions by active carbons, to identify the controlling step of mass transfer during sorption, and to formulate a mathematical model of the kinetics of the given process. Experimental study of the kinetics of sorption of (PtCl/sub 6/)/sup 2 -/ anions from hydrochloric acid solutions by SKS-3 and SKN-2M artificial active carbons showed that the controlling step is mass transfer by internal diffusion.

Bagreev, A.A.; Tarasenko, Yu.A.; Mardanenko, V.K.; Potyazhenko, I.A.

1988-07-20

71

Ions in hyaluronic acid solutions.  

PubMed

Hyaluronic acid (HA) is an anionic biopolymer that is almost ubiquitous in biological tissues. An attempt is made to determine the dominant features that account for both its abundance and its multifunctional role, and which set it apart from other types of biopolymers. A combination of osmotic and scattering techniques is employed to quantify its dynamic and static properties in near-physiological solution conditions, where it is exposed both to mono- and divalent counterions. An equation of state is derived for the osmotic pressure Pi in the semidilute concentration region, in terms of two variables, the polymer concentration c and the ionic strength J of the added salt, according to which Pi=1.4x10(3)c(9/4)/J(3/4) kPa, where c and J are expressed in mole. Over the physiological ion concentration range, the effect of the sodium chloride and calcium chloride on the osmotic properties of HA solutions is fully accounted for by their contributions to the ionic strength. The absence of precipitation, even at high CaCl(2) concentrations, distinguishes this molecule from other biopolymers such as DNA. Dynamic light scattering measurements reveal that the collective diffusion coefficient in HA solutions exceeds that in aqueous solutions of typical neutral polymers by a factor of approximately 5. This property ensures rapid adjustment to, and recovery from, stress applied to HA-containing tissue. Small angle x-ray scattering measurements confirm the absence of appreciable structural reorganization over the observed length scale range 10-1000 A, as a result of calcium-sodium ion exchange. The scattered intensity in the transfer momentum range q>0.03 A(-1) varies as 1/q, indicating that the HA chain segments in semidilute solutions are linear over an extended concentration range. The osmotic compression modulus c partial differential Pi/partial differential c, a high value of which is a prerequisite in structural biopolymers, is several times greater than in typical neutral polymer solutions. PMID:19916626

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

2009-11-14

72

Root canal irrigation with citric acid solution.  

PubMed

The purpose of this study was to investigate various properties of citric acid and EDTA solution as decalcifying and cleansing agents in root canal irrigation, and antibacterial effects of citric acid and EDTA solution. Powdered dentin-resin mixtures were used for evaluating the decalcifying effect of citric acid and EDTA solution. Twelve bacterial strains isolated from infected root canals, were used to evaluate the antibacterial effects of citric acid and EDTA solution. Powdered dentin-resin mixture was found to be more soluble in a 0.5, 1, and 2 M citric acid solutions than in a 0.5 M EDTA solution. Citric acid solution showed antibacterial effects on all the bacteria used. PMID:8618082

Yamaguchi, M; Yoshida, K; Suzuki, R; Nakamura, H

1996-01-01

73

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

74

A novel Schiff base-based cationic gemini surfactants: Synthesis and effect on corrosion inhibition of carbon steel in hydrochloric acid solution  

Microsoft Academic Search

The corrosion inhibition characteristics of the synthesized cationic gemini surfactants, namely bis(p-(N,N,N-decyldimethylammonium bromide)benzylidene thiourea (10-S-10), bis(p-(N,N,N-dodecyldimethylammonium bromide)benzylidene thiourea (12-S-12) and bis(p-(N,N,N-tetradecyldimethylammonium bromide)benzylidene thiourea (14-S-14) on the carbon steel corrosion in 1M hydrochloric acid have been investigated at 25°C by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The inhibition efficiencies obtained from all methods employed are in good

M. A. Hegazy

2009-01-01

75

ELECTROLYTIC REDUCTION OF NITRIC ACID SOLUTIONS  

DOEpatents

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

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

1958-09-30

76

Plutonium recovery from carbonate wash solutions  

SciTech Connect

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

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

1991-12-31

77

One-step synthesis of a novel carbon-based strong acid catalyst through hydrothermal carbonization  

Microsoft Academic Search

\\u000a Abstract  A novel carbon-based strong acid catalyst was synthesized through the one-step hydrothermal carbonization of furaldehyde and\\u000a p-toluenesulfonic acid (PTSA) in aqueous solution at 180 °C for only 4 h. The novel carbon-based solid acid possessed high\\u000a acidity, and the catalytic activities were investigated by esterification and oxathioketalization. The results showed that\\u000a the novel catalyst demonstrated much greater activity than the traditional solid

Huiquan Xiao; Yingxue Guo; Xuezheng Liang; Chenze Qi

2010-01-01

78

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

Microsoft Academic Search

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

Thore Rohwerder; Roland H Müller

2010-01-01

79

12-Aminododecanoic acid as a corrosion inhibitor for carbon steel  

Microsoft Academic Search

The inhibiting effect of 12-aminododecanoic acid (AA) on corrosion of carbon steel (CS) was investigated in hydrochloric acid of different pH, temperatures and over a prolonged period of time, and also in some other selected corrosive solutions. It was found that AA inhibits both partial corrosion reactions, with a slightly stronger inhibition of the anodic corrosion reaction. The corrosion protection

Saad Ghareba; Sasha Omanovic

2011-01-01

80

Carbon dioxide absorption in glucosamine aqueous solutions  

Microsoft Academic Search

The present paper includes studies related to gas\\/liquid mass transfer process of carbon dioxide in aqueous solutions of glucose and glucosamine. These studies have been carried out employing a cylindrical bubble column, where the gas phase was fed through an only orifice. The absorption process has been characterized taken into account the influence of gas flow-rate and the liquid phase

D. Gómez-Díaz; J. M. Navaza; B. Sanjurjo; L. Vázquez-Orgeira

2006-01-01

81

CATALYZED OXIDATION OF URANIUM IN CARBONATE SOLUTIONS  

DOEpatents

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

Clifford, W.E.

1962-05-29

82

Acylation of peptides by lactic acid solutions.  

PubMed

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

Lucke, Andrea; Göpferich, Achim

2003-01-01

83

Method for extracting lanthanides and actinides from acid solutions  

DOEpatents

A process for the recovery of actinide and lanthanide values from aqueous acidic solutions with an organic extractant having the formula: ##STR1## where .phi. is phenyl, R.sup.1 is a straight or branched alkyl or alkoxyalkyl containing from 6 to 12 carbon atoms and R.sup.2 is an alkyl containing from 3 to 6 carbon atoms. The process is suitable for the separation of actinide and lanthanide values from fission product values found together in high level nuclear reprocessing waste solutions.

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

1985-01-01

84

Processing nitric-phosphoric acid solutions to nitroammophoska  

SciTech Connect

The technology for comprehensive processing of apatite with recovery of all valuable components in the starting material is based on its nitric acid decomposition with crystallization of calcium nitrate tetrahydrate. The results of operation on a pilot installation for complex processing of apatite with production of strontium carbonate, calcium fluoride, a rare earth phosphate concentrate, calcium carbonate and a nitric-phosphoric acid solution (NPAS) are given below. The article presents the data of the operation of the experimental unit for production of complex fertilizers of the nitroammophoska type from the NPAS.

Gol'dinov, A.L.; Abramov, O.B.; Afanasenko, B.P.; Baibakov, P.Y.; Kiselevich, P.V.

1982-12-01

85

Adsorption of phenol from aqueous solutions using mesoporous carbon prepared by two-stage process  

Microsoft Academic Search

Porous carbon prepared from rice husk using phosphoric acid activation through precarbonization and chemical activation has been examined for the adsorption of phenol from aqueous solutions. The method adopted could produce carbons with micro and mesoporous structure. The surface area, pore volume and pore size distribution of carbon samples activated at three different temperatures 700, 800 and 900°C have been

L. John Kennedy; J. Judith Vijaya; K. Kayalvizhi; G. Sekaran

2007-01-01

86

Hydrogen evolution from solutions of citric acids  

Microsoft Academic Search

Hydrogen evolution reaction kinetics were investigated on a rotating silver disc electrode in solutions of citric acid\\/citrate anions and different total concentrations of the organic and different pH. The aim was to establish whether hydrogen atoms bound in the undissociated acid and in the acid anions participate in the reaction as hydrogen donors. The galvanostatic pulse method was used to

V. Marinovi?; A. R. Despi?

1997-01-01

87

Nitric acid vapor removal by activated, impregnated carbons  

SciTech Connect

Laboratory and industrial workers can be exposed to vapors of nitric acid, especially in accidents, such as spills. Nitric acid can also be a product of incineration for energy production or waste (e.g., CW agent) disposal. Activated carbons containing impregnants for enhancing vapor and gas removal have been tested for effectiveness in removing vapors of nitric acid from air. The nitric acid vapor was generated from concentrated acid solutions and detected by trapping in a water bubbler for pH measurements. Both low and moderate relative humidity conditions were used. All carbons were effective at vapor contact times representative of air-purifying respirator use. One surprising observation was the desorption of low levels of ammonia from impregnated carbons. This was apparently due to residual ammonia from the impregnation processes.

Wood, G.O.

1996-12-31

88

Viscosity of aqueous solutions of monocarboxylic acids  

Microsoft Academic Search

An attempt has been undertaken to apply viscosimetric measurements for the examination of incomplete dissociation of symmetric electrolyte solutions. For this purpose precise measurements of the viscosity and density of dilute aqueous solutions of monocarboxylic acids (formic, acetic, propionic and valeric) have been conducted at 298.15 K. Modified Jones–Dole equations have been proposed for incompletely dissociated electrolyte solutions of 1–1 type.

Agnieszka Chmielewska; Anna Wypych-Stasiewicz; Adam Bald

2007-01-01

89

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

SciTech Connect

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

Pierce, R.A.

1998-10-02

90

Degradation of ascorbic acid in ethanolic solutions.  

PubMed

Ascorbic acid occurs naturally in many wine-making fruits. The industry also uses ascorbic acid as an antioxidant and color stabilizer in the making of alcoholic beverages including white wine, wine cooler, alcopop, and fruit liqueur. However, the degradation of ascorbic acid itself may cause browning and the deterioration of color quality. This study was aimed to monitor the degradation of ascorbic acid, the formation of degradation products, and the browning in storage of ascorbic acid containing 0-40% (v/v) ethanolic solutions buffered at pH 3.2 as models of alcoholic beverages. The results show that ascorbic acid degradation in the ethanolic solutions during storage follows first-order reaction, that the degradation and browning rates increase with the increase of ethanol concentration, that the activation energy for the degradation of ascorbic acid is in the range 10.35-23.10 (kcal/mol), that 3-hydroxy-2-pyrone is an indicator and a major product of ascorbic acid degradation, and that aerobic degradation pathway dominants over anaerobic pathway in ascorbic acid degradation in ethanolic solutions. PMID:22994409

Hsu, Hsin-Yun; Tsai, Yi-Chin; Fu, Chi-Chang; Wu, James Swi-Bea

2012-10-11

91

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...

92

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

93

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, and solutions of nitrogen oxides, N{sub 2}O{sub 4} and N{sub 2}N{sub 5}, in nitric acids. The reference electrode is fabricated of entirely inert materials, has a half cell of Pt/Ce(IV)/CE(3)/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. 5 figs.

Ridgon, L.P.; Harrar, J.E.; Bullock, J.C. Sr.; McGuire, R.R.

1989-05-23

94

Amino acid composition of organic matter associated with carbonate and non-carbonate sediments  

Microsoft Academic Search

Amino acids comprise from 15 to 36% by weight of humic substances from carbonate and non-carbonate sediments. Humic and fulvic acids extracted from carbonate sediments are characterized by an amino acid composition consisting primarily of the acidic amino acids, aspartic and glutamic acid. Humic substances from non-carbonate sediments have a distinctly different amino acid composition consisting primarily of glycine and

Paul W. Carter; Richard M. Mitterer

1978-01-01

95

Reactions of rare earth flourides with sodium carbonate and hydroxide solutions  

Microsoft Academic Search

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

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

1986-01-01

96

?-Irradiation of malic acid in aqueous solutions  

NASA Astrophysics Data System (ADS)

The ?-irradiation of malic acid in aqueous solutions was studied under initially oxygenated and oxygen-free conditions in an attempt to determine the possible interconversion of malic acid into other carboxylic acids, specifically those associated with Krebs cycle. The effect of dose on product formation of the system was investigated. Gas-liquid chromatography combined with mass spectrometry was used as the principal means of identification of the non-volatile products. Thin layer chromotography and direct probe mass spectroscopy were also employed. The findings show that a variety of carboxylic acids are formed, with malonic and succinic acids in greatest abundance. These products have all been identified as being formed in the ?-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, Alicia; Graff, Rebecca L.; Ponnamperuma, Cyril

1980-12-01

97

Acid gases partial pressures above a 50 wt% aqueous methyldiethanolamine solution: Experimental work and modeling  

Microsoft Academic Search

Aqueous amine solutions are widely used in the industry for acid gas removal. In order to treat natural gas or refinery process streams, an accurate knowledge of solubility data of carbon dioxide, hydrogen sulfide and other sulfur species in aqueous amine solutions is required. In this paper, new equilibrium measurements on 50wt% aqueous methyldiethanolamine solution with CO2 and H2S have

Moussa Dicko; Christophe Coquelet; Carmen Jarne; Scott Northrop; Dominique Richon

2010-01-01

98

Heterogeneity of activated carbons in adsorption of aniline from aqueous solutions  

NASA Astrophysics Data System (ADS)

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

Podko?cielny, P.; László, K.

2007-08-01

99

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...

100

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.  

National Technical Information Service (NTIS)

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 ful...

K. A. Thorn D. W. Folan P. MacCarthy

1989-01-01

101

Electrical conductivity of acidic chloride solutions  

NASA Astrophysics Data System (ADS)

The electrical conductivities of aqueous solutions in the system HCl-MCln (where M = K, Na, Mg, Ni, or Cd) were measured at different temperatures. The equivalent electrical conductivity of H+ was calculated on the basis of simple assumptions for these solutions, and show an inverse relationship with water activity in these solutions. The results obtained by varying temperatures, solute ratios, and ionic strength on the electrical conductivity were found to be consistent with a proton jump mechanism for the H+ ion, where the activity of water is the most significant parameter affecting its equivalent conductance, and a viscous (Stokes’ law) drag mechanism (i.e., Walden’s rule is obeyed) for other ions found in acidic solutions.

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

1988-02-01

102

Electrical conductivity of acidic sulfate solution  

NASA Astrophysics Data System (ADS)

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

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

1987-03-01

103

Nonequilibrium dynamic modeling of carbon dioxide absorption by partially carbonated ammonia solutions  

Microsoft Academic Search

In this research, a nonequilibrium dynamic stage model has been developed for reactive absorption of carbon dioxide by carbonated ammonia solutions. The model considers mass transfer between gas and liquid phases in both directions employing dynamic film model theory. Experimental data of carbon dioxide reactive absorption by partially carbonated ammonia solution has been used to validate the model. The data

Ahad Ghaemi; Shahrokh Shahhosseini; Mohammad Ghanadi Maragheh

2009-01-01

104

Reactive solute transport in acidic streams  

Microsoft Academic Search

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

Robert E. Broshears

1996-01-01

105

[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

106

Heterogeneity of activated carbons with different surface chemistry in adsorption of phenol from aqueous solutions  

Microsoft Academic Search

The heterogeneity of activated carbons is investigated on the basis of adsorption isotherms of phenol from dilute aqueous solutions at different values of pH in the solution. The original carbon studied was prepared from polyethyleneterephtalate (PET). Its various oxygen surface functionalities were systematically changed by additional nitric acid and heat treatments. The Dubinin–Astakhov adsorption-isotherm equation was used to evaluate the

K. László; P. Podkoscielny; A. Dabrowski

2006-01-01

107

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

108

Effects of acid treatment duration and sulfuric acid molarity on purification of multi-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Multi-walled carbon nanotubes were synthesized using a Fe-Ni bimetallic catalyst supported by MgO using thermal chemical vapor deposition. Purification processes to remove unwanted carbon structures and other metallic impurities were carried out by boiling in sulfuric acid solution. Various analytical techniques such as TGA/DSC, Raman spectroscopy, SEM, HRTEM and EDAX were employed to investigate the morphology, graphitization and quality of the carbon nanotubes. The obtained results reveal the molarity of sulfuric acid and immersed time of the carbon nanotubes in the acid solution is very effective at purifying multi-walled carbon nanotubes. It was also found that 5 M concentration of boiling sulfuric acid for a 3 h treatment duration led to the highest removal of the impurities with the least destructive effect. Moreover, it was observed that acid treatment results in decreasing of CNTs’ diameter.

Mortazavi, Seyedeh Z.; Novinrooz, Abdul J.; Reyhani, Ali; Mirershadi, Soghra

2010-12-01

109

Acidic properties of aqueous phosphoric acid solutions: a microscopic view  

NASA Astrophysics Data System (ADS)

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

Harsányi, I.; Pusztai, L.; Jóvári, P.; Beuneu, B.

2013-11-01

110

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

PubMed

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

Harsányi, I; Pusztai, L; Jóvári, P; Beuneu, B

2013-10-18

111

The removal of low level organics via hydrogen peroxide formed in a reticulated vitreous carbon cathode cell, Part 1. The electrosynthesis of hydrogen peroxide in aqueous acidic solutions  

Microsoft Academic Search

It is demonstrated that hydrogen peroxide can be produced with a current efficiency of 40–70% by the reduction of oxygen at a reticulated vitreous carbon cathode in a divided flow cell using catholytes consisting of aqueous chloride or sulfate media, pH?2. The influence of ferrous salts, potential and electrolyte concentration on the current efficiency and rate of H2O2 production is

Alberto Alvarez-Gallegos; Derek Pletcher

1998-01-01

112

Carbon paste electrode spiked with ferrocene carboxylic acid and its application to the electrocatalytic determination of ascorbic acid  

Microsoft Academic Search

A carbon paste electrode spiked with ferrocene carboxylic acid (FCAMCPE) was constructed by incorporation of ferrocene carboxylic acid in a graphite powder–paraffin oil matrix. It has been shown by direct current cyclic voltammetry and double step chronoamperometry that this electrode can catalyze the oxidation of ascorbic acid in aqueous buffered solution. It has been found that under optimum conditions (pH

Jahan-Bakhsh Raoof; Reza Ojani; Abolfazl Kiani

2001-01-01

113

A laboratory study on pteroyl- l-glutamic acid as a scale prevention inhibitor of calcium carbonate in aqueous solution of synthetic produced water  

Microsoft Academic Search

Oil well scale inhibition with green scale inhibitor is a relatively unexplored area. A huge amount of produced water containing various types and amount of residual scale and corrosion inhibitors is discharged into the environment everyday, which has brought focus of environment regulatory bodies and encourages operators to look for greener chemicals. Pteroyl-l-glutamic acid (PGLU) is a type of water

T. Kumar; S. Vishwanatham; S. S. Kundu

2010-01-01

114

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

115

Pictorial Analogies XI: Concentrations and Acidity of Solutions.  

ERIC Educational Resources Information Center

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

Fortman, John J.

1994-01-01

116

Solution structure of folic acid. Molecular mechanics and NMR investigation  

NASA Astrophysics Data System (ADS)

The structure of folic acid in solution was investigated by nuclear magnetic resonance (NMR) and theoretical calculations. Dynamical information and geometrical constraints were obtained by carbon-13 relaxation study, homo-nuclear NOESY spectra and hetero-nuclear 1H- 13C NOE experiments. This set of experimental data was used for the molecular mechanics and molecular dynamic calculations. The accuracy of the final structure was established by the RNMR factor, which was calculated comparing the experimental NOESY cross-peaks intensities and the corresponding values simulated by using the complete relaxation matrix analysis (CORMA) approach.

Bonechi, C.; Donati, A.; Lampariello, R.; Martini, S.; Picchi, M. P.; Ricci, M.; Rossi, C.

2004-06-01

117

Intercalation of formic acid into carbon fibers and their exfoliation  

Microsoft Academic Search

Intercalation of formic acid in a mesophase-pitch-based fibers was successfully carried out by electrolysis in 50% solution. The formation of intercalation compounds was confirmed by X-ray diffraction (XRD), which showed a broad peak at the interlayer spacing of 0.92nm. By rapid heating of the intercalated compounds of carbon fibers thus produced up to 1000°C, exfoliation was occurred instantaneously. Changes of

M Toyoda; J Sedlacik; M Inagaki

2002-01-01

118

Electrolytic conductivity behaviors and solution conformations of chitosan in different acid solutions  

Microsoft Academic Search

Electrolytic conductivity behavior of chitosan in strong acid solution (0.1M hydrochloric acid) and in weak acid solution (0.1M propionic acid, 0.1M acetic acid and 0.1M formic acid) and its effective factors such as temperature, salt, degree of deacetylation and molecule weight of chitosan were investigated. The inner structure of chitosan films formed from their above different acid solutions were observed

Qiao-xia LI; Bao-zhen SONG; Zhen-qiu YANG; Hong-lei FAN

2006-01-01

119

Acidities of Water and Methanol in Aqueous Solution and DMSO  

ERIC Educational Resources Information Center

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

Gao, Daqing

2009-01-01

120

Effect of foams used during carbonate acidizing  

SciTech Connect

Although acidization has been used successfully for many years to increase the productivity of petroleum wells in carbonate formations, demands on the performance and application of the acidizing process are increasing. This paper investigates a method of in-situ foam generation that allows deeper wormhole penetration yet uses less acid than conventional methods. The dissolution patterns were imaged with neutron radiography, which provided an in-depth understanding of the effects of foam and other critical parameters. Results show that foam is effective in promoting efficient stimulation, even at low acid injection rates.

Bernadiner, M.G. (Mechanical Engineering Dept., New York Polytechnic Univ., Brooklyn, NY (United States)); Thompson, K.E. (Michigan Univ., Ann Arbor, MI (United States)); Fogler, H.S. (Michigan Univ., Ann Arbor, MI (United States). Dept. of Chemical Engineering)

1992-11-01

121

pH-metric determination of ammonium carbonate and bicarbonate in solutions containing ammonium vanadate  

SciTech Connect

Ammonium carbonate and bicarbonate and ammonium carbonate salts used in hydrometallurgy are characterized by low stability both in solid form and in solutions. The frequently used method of acid-base titration in the presence of a pH indicator is unsuitable in the presence of ions in solution that change color within the investigated pH range. The purpose of this paper is to develop a method of rapid determination of the concentration of ammonium carbonate and bicarbonate in solutions containing ammonium vanadate. The authors used a 0.1 M solution of hydrochloric acid, analytical grade ammonium vanadate, and ammonium carbonate salts, the composition of which approximates real technological solutions. An aliquot portion of the test solution (1-2 ml) is transferred to a 50-ml beaker, and 10 ml of distilled water is added. The electrodes of the pH meter are placed in the solution, and it is titrated with 0.1 M hydrochloric acid with constant mixing.

Fofanov, Al.A.; Yuorenko, V.V.; Kharlampieva, T.I.; Potapov, V.I.

1986-07-01

122

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

Microsoft Academic Search

The objective of this study was to determine the effect of wood ash application on soil solution composition of three tropical acid soils. Calcium carbonate was used as a reference amendment. Amended soils and control were incubated for 60 days. To assess soluble nutrients, saturation extracts were analysed at 15 days intervals. Wood ash application affects the soil solution chemistry

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

2002-01-01

123

Carbonic Acid:  From Polyamorphism to Polymorphism  

Microsoft Academic Search

Layers of glassy methanolic (aqueous) solutions of KHCO3 and HCl were deposited sequentially at 78 K on a CsI window, and their reaction on heating in vacuo in steps from 78 to 230 K was followed by Fourier transform infrared (FTIR) spectroscopy. After removal of solvent and excess HCl, IR spectra revealed formation of two distinct states of amorphous carbonic

Katrin Winkel; Wolfgang Hage; Thomas Loerting; Sarah L. Price; Erwin Mayer

2007-01-01

124

Studies on extraction of chromium (VI) from acidic solutions containing various metal ions by emulsion liquid membrane using Alamine 336 as extractant  

Microsoft Academic Search

The extraction of chromium (VI) ions from acidic solutions containing various metal ions by emulsion liquid membrane (ELM) was studied. Liquid membrane consists of a diluent, a surfactant, and an extractant. 0.5M ammonium carbonate solution was used as stripping solution. Effects of acid concentration in feed solution, type and concentration of stripping solution, mixing speed, surfactant concentration, phase ratio and

Recep Ali Kumbasar

2008-01-01

125

Process for the extraction of strontium from acidic solutions  

DOEpatents

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

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

1994-01-01

126

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

PubMed

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

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

2009-06-18

127

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

Microsoft Academic Search

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

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

2012-01-01

128

Containment of nitric acid solutions of Plutonium-238  

NASA Astrophysics Data System (ADS)

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

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

1999-01-01

129

Containment of Nitric Acid Solutions of Plutonium-238  

SciTech Connect

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

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

1999-01-31

130

Kinetics and equilibrium of adsorption of organic solutes on mesoporous carbons  

NASA Astrophysics Data System (ADS)

Static and kinetic studies on adsorption of nitrobenzene, 4-nitrophenol and 4-chlorophenol on two mesoporous carbons are performed. The carbon properties are analyzed by means of nitrogen adsorption. The adsorption experiments are performed in acidic buffer solutions in a wide range of concentrations. The static experiments are analyzed by means of Langmuir Freundlich and Freundlich isotherms. The Lagergren, pseudo-second-order, intraparticle-diffusion and multi-exponent equations are used in the analysis of kinetic equilibria.

Marczewski, Adam W.

2007-04-01

131

Basic Solutions to Carbon/Carbon Oxidation: Science and Technology.  

National Technical Information Service (NTIS)

The goal of this study was to gain a fundamental understanding of the role of boron in carbon oxidation. Boron-doped carbons were synthesized via CVD, ion implantation and high temperature doping are subsequently characterized. It was found that high temp...

C. Pantano I. R. Harrison L. Radovic P. Thrower T. Chung

1998-01-01

132

Thermodynamics of carbon and oxygen solutions in manganese melts  

NASA Astrophysics Data System (ADS)

The thermodynamics of carbon and oxygen solutions in manganese melts is studied. An equation for the temperature dependence of the activity coefficient of carbon in liquid manganese is obtained (?{C(Mn)/0}= -1.5966 + (1.0735 × 10-3) T). The temperature dependence of the Gibbs energy of the reaction of carbon dissolved in liquid manganese with the oxygen of manganese oxide is shown to be described by the equation ? G {T/0}= 375264 - 184.66 T(J/mol). This reaction can noticeably be developed depending on the carbon content at temperatures of 1700 1800°C. The deoxidation ability of carbon in manganese melts is shown to be much lower than that in iron and nickel melts due to the higher affinity of manganese to both oxygen and carbon. Although the deoxidation ability of carbon in manganese melts increases with temperature, the process develops at rather high carbon contents in all cases.

Dashevskii, V. Ya.

2007-12-01

133

Flow of Aqueous Solutions in Carbon Nanotubes  

Microsoft Academic Search

\\u000a We conduct simulations of water flowing inside carbon nanotubes using non-equilibrium molecular dynamics simulations. A new\\u000a adaptive forcing scheme is proposed to enforce a mean center of mass velocity. This scheme is compared to the non-adaptive,\\u000a constant body\\/gravity force for the flow of methane in a carbon nanotube. The two schemes produce similar streaming velocity\\u000a profiles and practically identical slip

S. C. Kassinos; J. H. Walther; E. Kotsalis; P. Koumoutsakos

134

CORROSION OF CARBON STEEL IN WASTE SOLUTIONS CONTAINING MERCURY  

Microsoft Academic Search

The corosion behavior of A-285, A-135, A-l06, and A-53 carbon steel was ;\\u000a studied in multicomponent simulated waste solutions containing mercury. In the ;\\u000a liquid phase, the carbon steels corroded at a very low rate; mercury did not ;\\u000a increase the corrosion rate in any of the solutions tested. In the vapor phase ;\\u000a and at the vapor-liquid interface, pitting

Kranzlein

1959-01-01

135

Comparing the Amount of Acid in Different Solutions  

NSDL National Science Digital Library

In this activity students will use a similar process to compare the amount of acid in two different indicator + acid solutions. The teacher demonstrates this process using laundry detergent solution to neutralize two solutions containing 1 and 3 drops of vinegar. Students will then use the same 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, students can discover which solution initially contained more acid.

2010-01-01

136

Toluene nitration in irradiated nitric acid and nitrite solution  

SciTech Connect

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

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

2011-04-01

137

Heterogeneity of active carbons in adsorption of phenol aqueous solutions  

Microsoft Academic Search

Energetic heterogeneity of activated carbons prepared from bituminous coals is investigated on the basis of adsorption isotherms of phenol from the dilute aqueous solutions. The Langmuir–Freundlich (L–F) equation has been used to estimate the monolayer capacity values of carbons studied. Adsorption energy distribution functions have been calculated by using algorithm INTEG based on a regularization method. Analysis of these functions

P. Podkoscielny; A. D; O. V. Marijuk

2003-01-01

138

Effects of mineral loading methods on carbon solution reaction of coal-derived carbon material  

Microsoft Academic Search

11 oxides (MgO, CaO, BaO, TiO2, V2O5, MnO2, Fe2O3, CuO, ZnO, PbO2 and B2O3), often found in coal-derived carbon materials, were loaded into the coal-derived carbon material by two methods such as adsorbing oxides through solution onto the surface of coke and adding oxides into the coal before carbonization. The effects of oxides on carbon solution reaction of carbon material

Jun-he YANG; Xia WANG; Shu-hui CHENG; Xiao-rong LIU; Yong-zheng FANG

2006-01-01

139

Effect of inhibitors on corrosion rate of carbon steels in CO 2 -saturated potassium carbonate solutions  

Microsoft Academic Search

St3 carbon steel [low-carbon steel] manifests corosion resistance under conditions of treating hydrogen-rich gas with potassium carbonate to remove C02 [I]. However, because of the high velocity of the absorbent solution and the presence of suspended solid particles in the solution, equipment made of this steel is subject to local damage in the form of point corrosion, pitting, and corrosion

A. K. Nikitina; V. P. Khvatkova; V. M. Umnyashkina; L. P. Vershinina

1984-01-01

140

Electrochemical isolation of Np from circulating carbonate solutions  

SciTech Connect

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

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

1995-03-01

141

Prediction of effective acid penetration and acid volume for matrix acidizing treatments in naturally fractured carbonates  

SciTech Connect

This paper discusses a new method and a corresponding computer model developed to investigate matrix acidizing in naturally fractured carbonates. With this method, the effective acid penetration distance and acid volume needed for acid treatments in naturally fractured carbonates can be predicted. The new model simulates acid flowing in the natural fracture network and the acid/rock reaction. During the simulation, the model considers the influence of formation temperature, reaction heat, and common ion effect on acid penetration. A set of graphs showing the relationship between acid penetration and the acid volume needed in different formations was developed from numerical simulation results. From these plots, the acid volume that should be used to remove the formation damage can be determined easily when the formation temperature and the damage radius are known or can be estimated.

Xiong, H. (S.A. Holditch and Associates, Inc., College Station, TX (United States))

1994-08-01

142

Calcium, carbonic anhydrase and gastric acid secretion.  

PubMed

Previous data concerning the action of calcium (Ca) on gastric acid secretion (GAS) indicated that calcium ions increase GAS elicited by gastrin released through a vagal mechanism, and also by a direct effect on parietal cells. Our research showed that the stimulating effect of calcium on gastric acid secretion can be antagonized by verapamil administration, which reduces gastric acid secretion . In the present study we followed the effect induced by administration of calcium and Ca-chelating agents (disodium EDTA) on gastric acid secretion and on carbonic anhydrase (CA) activity. We selected two groups of healthy volunteers: Group I (n=21) received a single i.v. dose of CaCl2 (15 mg/kg b.w.), whereas Group II (n=22) received a single i.v. dose of disodium EDTA (5 mg/kg b.w.). We determined blood calcium before and after treatment, gastric acid secretion at 2 hours. erythrocyte CA II activity, and CA IV activity in membrane parietal cells, which were isolated from gastric mucosa obtained by endoscopic biopsy. Assessment of carbonic anhydrase activity was achieved by the stopped-flow method. In Group I calcium administration increased blood calcium, HCl output, CA II and CA IV activity as compared to initial values. In Group II, disodium EDTA reduced blood calcium, HCl output, CA II and CA IV activity as compared to initial values. The results demonstrated that increased blood calcium and GAS values after calcium administration correlated with the increase of erythrocyte CA II and parietal cell CA IV activity, while disodium EDTA induced a reversed process. Our results also show that cytosolic CA II and membrane CA IV values are sensitive to calcium changes and they directly depend on these levels. Our data suggest that intra- and extracellular pH changes induced by carbonic anhydrase might account for the modulation of the physiological and pathological secretory processes in the organism. PMID:11551141

Puscas, I; Coltau, M; Baican, M; Domuta, G; Hecht, A

2001-01-01

143

Kinetics of hydrogen peroxide decomposition in aqueous sulfuric acid over palladium\\/carbon: effcet of acid concentration  

Microsoft Academic Search

Decomposition of H2O2 over Pd (5%)\\/carbon in an aqueous sulfuric acid solution at different acid concentrations (0-10 mol\\/L) and temperatures (281-313\\u000a K) in a magnetically stirred glass reactor has been investigated. The catalytic activity, activation energy and frequency\\u000a factor for the decomposition decrease with increasing acid concentration; the decrease in the activation energy is, however,\\u000a very small.

Vasant R. Choudhary; Abaji G. Gaikwad

2003-01-01

144

Anomalous distribution in atom map of solute carbon in steel.  

PubMed

The distribution of carbon in atom probe tomography maps was investigated in various phases of steel. Carbon atoms in 3D atom maps of martensite and cementite phases showed an almost uniform distribution. On the other hand, carbon atoms in ferrite were consistently enriched along the zone line joining the (0 0 2) and the (2 2 2) poles, and in the depth direction of analysis, which was different from the actual distribution. The width and concentration of the enriched regions remained unchanged at a specimen temperature ranging from 90 to 30K. Moreover, the ratio of molecular carbon ions to total carbon ions decreased with decreasing temperature, but did not change between the enriched and diluted regions. Based on the results, the reason for the anomalous distribution of solute carbon atoms in atom maps is discussed. PMID:21292398

Kobayashi, Y; Takahashi, J; Kawakami, K

2011-01-18

145

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

Microsoft Academic Search

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

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

1995-01-01

146

Removal of Sulfamic Acid from Plutonium Sulfamate--Sulfamic Acid Solution.  

National Technical Information Service (NTIS)

Plutonium metal can be readily dissolved in aqueous solutions of sulfamic acid. When the plutonium sulfamate--sulfamic acid solutions are added to normal purex process streams, the sulfamate ion is oxidized by addition of sodium nitrite. This generates so...

L. W. Gray

1978-01-01

147

Influence of acidic atmospheric deposition on soil solution ...  

Treesearch

Description: Acid atmosperic depositoin may enter an environmental ecosystem ... Given these conditions, long-term changes in soil solution chemistry from acid ... Acrobat reader or Acrobat Reader for Windows with Search and Accessibility.

148

One-step synthesis of novel sulfuric acid groups' functionalized carbon via hydrothermal carbonization  

Microsoft Academic Search

The novel sulfuric acid groups' functionalized carbon has been synthesized via one-step hydrothermal carbonization of polyvinyl alcohol and hydroxyethylsulfuric acid. The novel carbon exhibited high acidity and comparable activities to sulfonic acid for the traditional acid-catalyzed reactions, which indicated that it has great potential for the environmental-friendly processes. The copolymerization method provides an efficient procedure for the synthesis of various

Xuezheng Liang; Huiquan Xiao; Yongmiao Shen; Chenze Qi

2010-01-01

149

Acid yellow 9 as a dispersing agent for carbon nanotubes: Preparation of redox polymer–carbon nanotube composite film and its sensing application towards ascorbic acid and dopamine  

Microsoft Academic Search

In this study, we show that acid yellow 9 (4-amino-1-1?-azobenzene-3,4?-disulfonicacid, AY) is a good stabilizing agent for multi-walled carbon nanotubes (MWCNTs). MWCNTs dispersed in AY solution was remained stable about three months and even remained stable after centrifugation at 10,000rpm for 30min. Using MWCNTs\\/AY dispersion, thin-films were prepared on indium tin oxide coated glass electrode and glassy carbon electrodes. Further,

S. Ashok Kumar; Sea-Fue Wang; Thomas C.-K. Yang; Chun-Ting Yeh

2010-01-01

150

A comparative study of solid carbon acid catalysts for the esterification of free fatty acids for biodiesel production. Evidence for the leaching of colloidal carbon.  

PubMed

The preparation of a variety of sulfonated carbons and their use in the esterification of oleic acid is reported. All sulfonated materials show some loss in activity associated with the leaching of active sites. Exhaustive leaching shows that a finite amount of activity is lost from the carbons in the form of colloids. Fully leached catalysts show no loss in activity upon recycling. The best catalysts; 1, 3, and 6; show initial TOFs of 0.07s(-1), 0.05s(-1), and 0.14s(-1), respectively. These compare favorably with literature values. Significantly, the leachate solutions obtained from catalysts 1, 3, and 6, also show excellent esterification activity. The results of TEM and catalyst poisoning experiments on the leachate solutions associate the catalytic activity of these solutions with carbon colloids. This mechanism for leaching active sites from sulfonated carbons is previously unrecognized. PMID:24021721

Deshmane, Chinmay A; Wright, Marcus W; Lachgar, Abdessadek; Rohlfing, Matthew; Liu, Zhening; Le, James; Hanson, Brian E

2013-08-20

151

A MODEL FOR THE DISTRIBUTION OF ACID GASES BETWEEN AN AQUEOUS ALKANOLAMINE SOLUTION AND LPG  

Microsoft Academic Search

The model of Deshmukh and Mather (1981) is a popular method for correlating and predicting the vapor-liquid equilibria in systems containing acid gases (hydrogen sulfide and carbon dioxide) and aqueous solutions of alkanolamines. The model includes phase equilibrium between an aqueous liquid and a gas as well as chemical equilibrium in the aqueous phase. A recent review by Weiland et

J. J. CARROLL; A. E. MATHER

1996-01-01

152

Catalytic decomposition of aqueous solutions of formic acid by the platinum metals, 4.  

National Technical Information Service (NTIS)

In a series of earlier reports it was shown that the decomposition of aqueous solutions of formic acid into carbon dioxide and hydrogen at 100(degrees)C can be effected by all platinum metals. Certainly its rate, if the finished metals prepared in any mat...

E. Mueller W. Loerpabel

1991-01-01

153

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

PubMed Central

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

2010-01-01

154

Adsorption of phenol and reactive dye from aqueous solution on activated carbons derived from solid wastes.  

PubMed

Activated carbons were produced from several solid wastes, namely, waste PET, waste tires, refuse derived fuel and wastes generated during lactic acid fermentation from garbage. Activated carbons having various pore size distributions were obtained by the conventional steam-activation method and via the pre-treatment method (i.e., mixture of raw materials with a metal salt, carbonization and acid treatment prior to steam-activation) that was proposed by the authors. The liquid-phase adsorption characteristics of organic compounds from aqueous solution on the activated carbons were determined to confirm the applicability of these carbons, where phenol and a reactive dye, Black5, were employed as representative adsorbates. The hydrophobic surface of the carbons prepared was also confirmed by water vapor adsorption. The characteristics of a typical commercial activated carbon were also measured and compared. It was found that the activated carbons with plentiful mesopores prepared from PET and waste tires had quite high adsorption capacity for large molecules. Therefore they are useful for wastewater treatment, especially, for removal of bulky adsorbates. PMID:15026233

Nakagawa, Kyuya; Namba, Akio; Mukai, Shin R; Tamon, Hajime; Ariyadejwanich, Pisit; Tanthapanichakoon, Wiwut

2004-04-01

155

Removal of Pb(II) from aqueous solutions using activated carbon from Sea-buckthorn stones by chemical activation  

Microsoft Academic Search

Two series of activated carbon have been prepared by chemical activation of Sea-buckthorn stones with phosphoric acid and zinc chloride for the removal of Pb(II) ions from aqueous solutions. To characterize the adsorptive characteristics of produced active carbon, surface area was calculated using the standard Brunauer–Emmet–Teller method. The microstructures of the resultant activated carbon were observed by scanning electron micrographs.

Sayed Zia Mohammadi; Mohammad Ali Karimi; Daryoush Afzali; Fatemeh Mansouri

2010-01-01

156

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

157

Effects of acid treatment duration and sulfuric acid molarity on purification of multi-walled carbon nanotubes  

Microsoft Academic Search

Multi-walled carbon nanotubes were synthesized using a Fe-Ni bimetallic catalyst supported by MgO using thermal chemical vapor\\u000a deposition. Purification processes to remove unwanted carbon structures and other metallic impurities were carried out by\\u000a boiling in sulfuric acid solution. Various analytical techniques such as TGA\\/DSC, Raman spectroscopy, SEM, HRTEM and EDAX\\u000a were employed to investigate the morphology, graphitization and quality of

Seyedeh Z. Mortazavi; Abdul J. Novinrooz; Ali Reyhani; Soghra Mirershadi

2010-01-01

158

Separation of fission and corrosion products from boric acid solutions by solvent extraction  

Microsoft Academic Search

Extractive purification of boric acid from radioactive corrosion and fission products dissolved in aqueous solutions modelling\\u000a nuclear reactor coolants has been studied. Aliphatic 1,3-diols containing 8 and 9 carbon atoms per molecule were used as extractants\\u000a fro boric acid. The behaviour of some representative corrosion and fission products as well as various factors affecting their\\u000a distribution between the organic and

J. Narbutt; J. Olza; Z. Przyby?owicz; S. Siekierski

1979-01-01

159

Acid-treated soy hull carbon structure and adsorption performance  

Microsoft Academic Search

The objective of this study was to evaluate the effect of 14 N phosphoric acid and 12 N hydrochloric acid treatments on soy\\u000a hull carbon structure and adsorption performance. Scanning electron micrographs showed that acid treatments disrupted the\\u000a carbon structure whereas X-ray diffraction data indicated that hydrochloric acid had a greater effect than phosphoric acid\\u000a in creating a more amorphous

Yan Hong; Andrew Proctor; John Shultz

2000-01-01

160

Adsorption of selected herbicides from aqueous solutions on activated carbon  

Microsoft Academic Search

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

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

2010-01-01

161

Synthesis of a Novel Carbon Based Strong Acid Catalyst Through Hydrothermal Carbonization  

Microsoft Academic Search

A novel carbon based strong acid catalyst has been synthesized through the sulfonation of the carbon materials from glucose.\\u000a The novel acid catalyst was obtained through the hydrothermal carbonization instead of the traditional heat treatment, which\\u000a made the carbonization process under much milder condition with higher yield. The novel heterogeneous catalyst owned the advantages\\u000a of high acidity as much as

Xuezheng Liang; Jianguo Yang

2009-01-01

162

Electrode kinetics at a platinum anode in chloroacetic acid solutions  

SciTech Connect

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

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

1987-02-01

163

Method for detecting corrosion inhibitor in aqueous acid solutions  

Microsoft Academic Search

A method is presented for simply and inexpensively determining the presence of a corrosion inhibitor in an aqueous acid solution. Gas evolving from a material which will react with uninhibited aqueous acid solutions to evolve such a gas causing a small first container to rise to the surface of a liquid in a larger second container, thus indicating the absence

Keeney

1973-01-01

164

Cocoa shells for heavy metal removal from acidic solutions  

Microsoft Academic Search

The development of economic and efficient processes for the removal of heavy metals present in acidic effluents from industrial sources or decontamination technologies has become a priority. The purpose of this work was to study the efficiency with which cocoa shells remove heavy metals from acidic solutions (pH 2) and to investigate how the composition of these solutions influences heavy

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

2003-01-01

165

Wet-spinning of neat single-walled carbon nanotube fiber from 100+% sulfuric acid  

Microsoft Academic Search

Single-Walled Carbon Nanotubes (SWNT) have been found to have excellent solubility in super acids such as 100+% H2SO4, and chlorsulfonic acid. The solutions display liquid crystalline behavior at high concentrations in super acids. Traditional wet-spinning method has been applied to SWNTs to make fibers from SWNTs only with the assistance of 100+% H2SO 4 (neat SWNT fibers). Extensive conditions, including

Fan Hua

2008-01-01

166

An amperometric sensor for uric acid based on ordered mesoporous carbon-modified pyrolytic graphite electrode  

Microsoft Academic Search

A novel amperometric sensor for uric acid based on ordered mesoporous carbon modified pyrolytic graphite electrode was developed.\\u000a Uric acid oxidation was easily catalyzed by this electrode in a phosphate buffer solution at pH 7.0, with an anodic potential\\u000a decrease about 140 mV compared to bare pyrolytic graphite electrode. The uric acid level was determined by the amperometric\\u000a method, at

Yonggen Ma; Guangzhi Hu; Shijun Shao; Yong Guo

2009-01-01

167

Stability of carbon monoxide adsorbed on nanoparticle Pt and Pt\\/Ru electrodes in sulfuric acid media  

Microsoft Academic Search

Pt and Pt\\/Ru nanoparticle electrodes were used as substrates for studies of stability of chemisorbed CO and its interactions (exchange) with carbon monoxide and hydrogen gas admitted to sulfuric acid solution, which served as the supporting electrolyte for these measurements. The surface bound, radioactive CO was obtained after decomposition of 14C labeled methanol or formic acid from the same solution.

M. S. McGovern; P. Waszczuk; A. Wieckowski

2006-01-01

168

Reactions of lime with carbonate-containing solutions  

Microsoft Academic Search

In the Bayer process for refining alumina, lime (either quicklime or slaked lime) is added to the process liquor to precipitate calcium carbonate and restore alkalinity to the solution. The work described in this paper was undertaken to elucidate the mechanism of this precipitation reaction about which surprisingly little is known. In the first part of the study, the composition

B.-A Xu; D. E Giles; I. M Ritchie

1998-01-01

169

Effect of temperature on carbon dioxide absorption in monoethanolamine solutions  

Microsoft Academic Search

The effect of temperature on volumetric mass transfer coefficient was studied during the absorption process of carbon dioxide in monoethanolamine aqueous solutions, using a square bubble column. Our studies provide an empirical correlation type Boltzmann to estimate the temperature operated, at different amine concentrations and gas flow rates. An excellent agreement has been shown between predicted and experimental data (r2>0.991).

Rocío Maceiras; Estrella Álvarez; M. Ángeles Cancela

2008-01-01

170

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

PubMed

Carbon dioxide and the carbonates, the available natural C1 sources, can be easily hydrogenated into formic acid and formates in water; the rate of this reduction strongly depends on the pH of the solution. This reaction is catalysed by ruthenium(II) pre-catalyst complexes with a large variety of water-soluble phosphine ligands; high conversions and turnover numbers have been realised. Although ruthenium(II) is predominant in these reactions, the iron(II) - tris[(2-diphenylphosphino)-ethyl]phosphine (PP3) complex is also active, showing a new perspective to use abundant and inexpensive iron-based compounds in the CO2 reduction. In the catalytic hydrogenation cycles the in situ formed metal hydride complexes play a key role, their structures with several other intermediates have been proven by multinuclear NMR spectroscopy. In the other hand safe and convenient hydrogen storage and supply is the fundamental question for the further development of the hydrogen economy; and carbon dioxide has been recognised to be a viable H2 vector. Formic acid--containing 4.4 weight % of H2, that is 53 g hydrogen per litre--is suitable for H2 storage; we have shown that in aqueous solutions it can be selectively decomposed into CO-free (CO < 10 ppm) CO2 and H2. The reaction takes place under mild experimental conditions and it is able to generate high pressure H2 (up to 600 bar). The cleavage of HCOOH is catalysed by several hydrophilic Ru(II) phosphine complexes (meta-trisulfonated triphenylphosphine, mTPPTS, being the most efficient one), either in homogeneous systems or as immobilised catalysts. We have also shown that the iron(II)--hydrido tris[(2-diphenylphosphino)ethyl]phosphine complex catalyses with an exceptionally high rate and efficiency (turnover frequency, TOF = 9425 h(-1)mol(-1); turnover number, TON = 92400) the formic acid cleavage, in environmentally friendly propylene carbonate solution, opening the way to use cheap, non-noble metal based catalysts for this reaction, too. PMID:22026175

Laurenczy, Gábor

2011-01-01

171

Transformations of tributyl phosphate in contact with acidic aqueous solutions  

SciTech Connect

Investigation of the transformations of tributyl phosphate in contact with fluoridesulfuric acid solutions be means of method /sup 19/F and /sup 31/P NMR spectroscopy and potentiometric titration shows that in the course of time it undergoes processes of hydrolysis and fluorination. In the extracts acid butyl phosphates and phosphoric acid together with products of their fluorination were found. The extent of the breakdown of tributyl phosphate depends on the time and the composition of the aqueous solutions.

Nikolaev, A.I.; Ignatov, M.E.; Shevyreva, E.V.; Zalkind, L.M.; Il'in, E.G.; Buslaev, Y.A.

1986-11-20

172

Process for the recovery of strontium from acid solutions  

DOEpatents

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

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

1992-01-01

173

Activities and vapor pressures of aqueous sulfuric acid solutions  

Microsoft Academic Search

A quantitative interpretation of the conditions leading to the formation of sulfuric acid in whatever system requires the knowledge of the thermodynamic properties of aqueous sulfuric acid solutions under the conditions of temperature and partial pressures at which the liquid phase is likely to nucleate. Surprisingly, in the light of the importance of sulfuric acid in industrial technology, such data

Bolsaitis

1986-01-01

174

Electrochemical determination of tartaric acid at nano gold/nano carbon modified glassy carbon electrode  

NASA Astrophysics Data System (ADS)

Nano gold/nano carbon coating the surface of glassy carbon electrode is prepared. Electrochemical behavior of tartaric acid at nano gold/graphene modified glassy carbon electrode is investigated. A simple, sensitive, and inexpensive method for determination of tartaric acid in drinks is proposed.

Song, Yang; Song, Yuanzhi; Xu, Jiang

2012-09-01

175

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

Microsoft Academic Search

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

Lotfi Mouni; Djoudi Merabet; Abdelkarim Bouzaza; Lazhar Belkhiri

2010-01-01

176

Thermochemical comparisons of homogeneous and heterogeneous acids and bases. 1. Sulfonic acid solutions and resins as prototype Broensted acids  

Microsoft Academic Search

Heats of ionization by thermometric titration for a series of bases (or acids) can be used to compare solid acids (or bases) with liquid analogues bearing the same functionalities in homogeneous solutions. The method is demonstrated for Broensted acids by reacting a series of substituted nitrogen bases with solutions of p-toluenesulfonic acid (PTSA) in acetonitrile and with suspensions of the

Edward M. Arnett; Rebecca A. Haaksma; B. Chawla; Marguerite H. Healy

1986-01-01

177

Process for removing acidic gases from gaseous mixtures using aqueous scrubbing solutions containing heterocyclic nitrogen compounds  

SciTech Connect

A process is described for removing acid gases selected from hydrogen sulfide and carbon dioxide from gaseous feeds. The process comprises: contacting the feed with an aqueous scrubbing solution comprising water and 1 to 11 moles of a heterocyclic nitrogen compound per liter of solution which compound is selected from the group consisting of imidazole, a C/sub 1/-C/sub 3/ alkyl-substituted imidazole where the alkyl groups are bonded to at least one carbon atom, and a C/sub 1/-C/sub 3/ alkyl- or C/sub 1/-C/sub 3/ hydroxayalkyl-substituted piperazine where the alkyl or hydrozyalkyl groups are bonded to both nitrogen atoms of the ring. The compound has a pKa no greater than about 8, at conditions whereby acid gases are absorbed by the scrubbing solution.

Pan, Y.C.; Savage, D.W.

1986-11-25

178

REDUCTION OF ACIDITY OF NITRIC ACID SOLUTIONS BY USE OF FORMALDEHYDE  

DOEpatents

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

Healy, T.V.

1958-05-20

179

Investigation of amine amino acid salts for carbon dioxide absorption  

Microsoft Academic Search

The carbon dioxide capture potential of amine amino acid salts (AAAS), formed by mixing equinormal amounts of amino acids; e.g. glycine, ?-alanine and sarcosine, with an organic base; 3-(methylamino)propylamine (MAPA), was assessed by comparison with monoethanolamine (MEA), and with amino acid salt (AAS) from amino acid neutralized with an inorganic base; potassium hydroxide (KOH). Carbon dioxide absorption and desorption experiments

Ugochukwu E. Aronu; Hallvard F. Svendsen; Karl Anders Hoff

2010-01-01

180

Method for liquid chromatographic extraction of strontium from acid solutions  

DOEpatents

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

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

1992-01-01

181

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

SciTech Connect

In fertilizer manufacture, calcium phosphate in phosphate rock is rendered soluble by sulfuric acid attack. The phosphoric acid obtained in this way usually contains 26%--28% P{sub 2}O{sub 5}. Several novel processes have been developed for the recovery of uranium from wet-process phosphoric acid. Experimental measurements have been made on the batch extraction of uranium from phosphoric acid solutions using various chelating ion-exchange resins (RSPO, Diaion-CRP200, Diphonix, Purolite S940, Duolite ES467, and Lewatit OC 1060) and a solvent containing ion-exchange resins (Actinide-CU). The kinetic performance of ion-exchange resins was compared, and the effect of Fe(II) and Ca(II) ions on the sorption and elution performance has also been examined. The results showed that the resin Actinide-CU containing a diphosphonate extractant was very effective for removing uranium from phosphoric acid solution. However, the elution performance of this resin with both acid and carbonate eluants was poor. It is concluded that the chelating resins Diphonix, Duolite ES467, Lewatit OC 1060, and Purolite S940 give reasonable sorption of uranium in the presence of Fe(II) ions in batch sorption trials. The desorption of uranium has been performed quantitatively using carbonate eluants. Purolite S940 was used in small-scale column extractions of uranium from phosphoric acid solutions, and promising loading/elution profiles were obtained.

Kabay, N.; Demircioglu, M.; Yayh, S.; Guenay, E.; Yueksel, M.; Saglam, M. [Ege Univ., Bornova (Turkey). Dept. of Chemical Engineering; Streat, M. [Loughborough Univ. (United Kingdom). Dept. of Chemical Engineering

1998-05-01

182

The surface chemistry of lithium electrodes in alkyl carbonate solutions  

SciTech Connect

The chemical composition of the surface films formed on lithium in alkyl carbonate solutions was explored using surface sensitive Fourier transform infrared spectroscopy (external reflectance mode). The solvents included propylene carbonate, ethylene carbonate, and dimethyl carbonate. The salts included LiAsF{sub 6}, LiClO{sub 4}, LiBF{sub 4}, and LiPF{sub 6}. The advantages of this work over previous studies are that highly reflective Li surfaces were prepared fresh in solution and that the aging processes of the surface films initially formed could be rigorously investigated. Furthermore these three important solvents were investigated in a single study. This work further proves that the films initially formed on Li surfaces in these solvents consist of ROCO{sub 2}Li as the major constituents. Upon storage, the films initially formed react with trace water to form Li{sub 2}CO{sub 3}, which gradually also becomes a major surface species. It was found that these aging processes also depend on the salts used (for example ROCO{sub 2}Li or Li{sub 2}CO{sub 3} films are not stable in LiPF{sub 6} or LiBF{sub 4} solutions).

Aurbach, D.; Ein-Ely, Y.; Zaban, A. [Bar-Ilan Univ., Ramat Gan (Israel). Dept. of Chemistry

1994-01-01

183

Simultaneous leaching and carbon sequestration in constrained aqueous solutions.  

PubMed

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. PMID:21246259

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

2011-01-19

184

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

Microsoft Academic Search

This study was undertaken to develop an experimental apparatus that would allow direct measurements of gas equilibrium solubility in aqueous alkanolamine solutions at low gas partial pressures. Carbon dioxide and hydrogen sulfide solubility in 20, 35 and 50% by weight diethanolamine aqueous solutions was measured. The measurements were made at acid gas partial pressures between 0.003 and 10.9 psia and

Elizondo-Villarreal

1989-01-01

185

Magnetic-field-enhanced carbon solution in proeutectoid ferrite  

NASA Astrophysics Data System (ADS)

Modification of phase solubility of Fe–C system by magnetic field has been recognized by thermodynamic calculations and indirectly by microstructural examinations. However, there has been no direct experimental verification and the underlying physical mechanism is not fully uncovered. In this work, the enhanced carbon content in proeutectoid ferrite under a 12 T magnetic field is evidenced through wavelength-dispersive spectroscopy using a Shimadzu 1610 electron probe microanalyser measurements. The magnetic-field-enhanced carbon solution reduces the demagnetization energy of the system and makes it energetically more stable.

Zhang, X. X.; Xu, N.; Wang, S. J.; Zhang, Y. D.; Raulot, J.-M.; Esling, C.; Zhao, X.; Zuo, L.

2013-09-01

186

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

SciTech Connect

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

Ketusky, E.; Subramanian, K.

2011-01-20

187

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

188

Electrochemical determination of ferulic acid in Chinese traditional medicine Xiao Yao Pills at electrode modified with carbon nanotube  

Microsoft Academic Search

The electrochemical behaviors of ferulic acid were investigated at the glassy carbon electrode modified with multi-walled\\u000a carbon nanotube. In pH 5.5, 0.1 mol l?1 HAc-NaAc buffer solution, ferulic acid exhibited a pair of stable and sensitive redox signals at the modified electrode.\\u000a The reaction mechanism was explored. Through the cyclic voltammetry, trace amount of ferulic acid was detected quantitatively.\\u000a In

Yan-Yan Yu; Qing-Sheng Wu; Xiao-Gang Wang; Ya-Ping Ding

2009-01-01

189

SYNTHESIS OF NOVEL HYDROPHILIC POLY(ESTER-CARBONATES) CONTAINING PENDENT CARBOXYLIC ACID GROUPS  

Microsoft Academic Search

A functional cyclic carbonate, 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MBC), was utilized in the synthesis of novel poly(ester-carbonates) containing pendent carboxylic acid groups. Copolymers with ?-caprolactone (CL) and L-lactide (LLA) were synthesized by ring-opening polymerization (ROP) using either an Al-alkoxide (solution) or Sn(Oct)2-alcohol (bulk) initiating system. Analysis of the copolymers revealed a random distribution of the comonomer units along the polymer chain. The copolymers

Robson F. Storey; Brian D. Mullen; Kim M. Melchert

2001-01-01

190

Activated carbons prepared from phosphoric acid activation of grain sorghum  

Microsoft Academic Search

The production of activated carbons from grain sorghum with phosphoric acid activation has been studied by means of two processes, i.e., one-stage and two-stage. The former comprises simultaneous carbonization and activation after impregnation; the latter, the carbonization of the precursor at 300 °C for 15 min, followed by the activation of the resultant char after impregnation with phosphoric acid. The

Yulu Diao; W. P Walawender; L. T Fan

2002-01-01

191

Simultaneous leaching and carbon sequestration in constrained aqueous solutions  

Microsoft Academic Search

The behavior of metal ions’ leaching and precipitated mineral phases of metal-rich fly ash (FA) was examined in order to evaluate\\u000a microbial impacts on carbon sequestration and metal immobilization. The leaching solutions consisted of aerobic deionized\\u000a water (DW) and artificial eutrophic water (AEW) that was anaerobic, organic- and mineral-rich, and higher salinity as is typical\\u000a of bottom water in eutrophic

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

2011-01-01

192

Hydrogen and carbon in solid solution in oxides and silicates  

Microsoft Academic Search

The dissolution of H2O and CO2 in structurally dense, nominally anhydrous and non-carbonate oxide matrices such as MgO and CaO is reviewed. H2O and CO2 are treated as gaseous oxide components which enter into solid solution with the refractory oxide hosts. They form anion complexes associated with cation vacancy sites. Evidence is presented that OH- pairs which derive from the

Friedemann Freund

1987-01-01

193

Surface Tensions and Densities of Sulfuric Acid + Dimethylamine + Water Solutions  

Microsoft Academic Search

The surface tensions and densities of aqueous solutions of dimethylamine, (CH3)2NH, and sulfuric acid, H2SO4, were measured at 24.2 °C. Mol fractions of dimethylamine were varied between 0 and 0.21 and of sulfuric acid between 0 and 0.48. The surface tension of the binary dimethylamine + water solution decreased exponentially as dimethylamine was added, from the surface tension of water

Heikki Lihavainen; Kaisa Hautio; Tomi Raatikainen; Ari Laaksonen; Yrjö Viisanen

2004-01-01

194

Fluorescent Carbon Dots Capped with PEG 200 and Mercaptosuccinic Acid  

Microsoft Academic Search

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

Helena Gonçalves; Joaquim C. G. Esteves da Silva

2010-01-01

195

Anchoring metal nanoparticles on hydrofluoric acid treated multiwalled carbon nanotubes as stable electrocatalysts  

Microsoft Academic Search

We attempted the treatment of multiwalled carbon nanotubes (MWCNTs) in hydrofluoric acid (HF) aqueous solution for depositing Pt nanoparticles as catalysts for methanol oxidation for the first time. The preliminary results revealed that the Pt nanoparticles could be well dispersed on HF treated MWCNTs and gave enhanced activity and stability for methanol oxidation. As demonstrated in this study, the Pt

Yongliang Li; Feng Ping Hu; Xin Wang; Pei Kang Shen

2008-01-01

196

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

197

Adsorptive crystallization of benzoic acid in aerogels from supercritical solutions  

Microsoft Academic Search

In this work, adsorption and crystallization of benzoic acid in different porous carriers (silica aerogel, MCM41, Trisopor glass, zeolite) from supercritical CO2 solutions is studied. The main purpose is to reveal the influence of the adsorptive properties of the carrier on the crystallization behavior of the solute. Therefore, both adsorption and crystallization processes are studied as a function of carrier's

B. S. K. Gorle; I. Smirnova; W. Arlt

2010-01-01

198

Quantification of Protein Solutions with Trinitrobenzenesulfonic Acid  

Microsoft Academic Search

solutions of protein. The trinitrophenyl protein-sulfite corn plexes resulting from reaction of TNBS with protein in the presence of sulfite are highly colored and exhibit maximum spectral absorbance at 420 nm. The TNBS protein-sulfite complex is formed by a simple two.stage condensation and complexation reaction. Protein in concentrations as low as 20 JLgmay be detected by the reaction. The method

Jesse F. Goodwin; Siu-Ying Choi

199

Prediction of multicomponent adsorption equilibria in carboxylic acid-activated carbon systems  

SciTech Connect

Binary adsorption equilibria of aqueous acetic and formic acid mixtures on activated carbon were measured. The multicomponent forms of the Langmuir, Langmuir-Freundlich isotherm, and the ideal adsorbed solution theory were used to predict the fluid phase and adsorbed phase concentration of components at equilibrium. Among the models tested, the ideal adsorbed solution theory gave uniformly satisfactory predictions both for liquid phase and for adsorbed phase compositions.

Goswami, A.N.; Nanoti, A.; Ganguly, S.K. [Indian Inst. of Petroleum, Dehradun (India)

1998-08-01

200

Electrochemical removal of CI Acid orange 10 from aqueous solutions  

Microsoft Academic Search

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

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

2007-01-01

201

Phosphorylation of glyceric acid in aqueous solution using trimetaphosphate  

NASA Astrophysics Data System (ADS)

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

Kolb, Vera; Orgel, Leslie E.

1996-02-01

202

Hydration of negative ions of trichloroacetic acid in aqueous solutions  

NASA Astrophysics Data System (ADS)

Mass spectrum of negative ions of trichloroacetic acid (TCA) in aqueous solution was obtained by mass spectrographic method of electrolyte solution electrospray in vacuum (ESESv). The TCA reactivity was neutralized by potassium hydroxide. The mass spectrum of TCA consists of the acid residue ions, (CCl3COO)?, hydrated by different number of water molecules. The (CCl3COO)? ion hydrated by two water molecules has the maximum intensity. The ESESv method can be helpful for determination of the composition electrolyte solutions in ecological studies.

Karpov, G. V.; Morozov, I. I.; Vasiliev, E. S.; Strokova, N. E.; Savilov, S. V.; Lunin, V. V.

2013-10-01

203

Synthesis of calcium carbonate polymorphs in the presence of polyacrylic acid  

Microsoft Academic Search

Calcium carbonate precipitates are prepared from a solution of CaCl2 and K2CO3 in the presence of polyacrilic acid. The effect of polyacrilic acid incorporation in the [25–80°C] temperature range on crystal morphologies and CaCO3 precipitated polymorph concentrations are investigated using scanning electron microscopy and X-ray diffraction quantitative microstructural and phase analysis. Large changes in morphology and phase proportions are observed

S. Ouhenia; D. Chateigner; M. A. Belkhir; E. Guilmeau; C. Krauss

2008-01-01

204

Covalent sidewall functionalization of single-walled carbon nanotubes by amino acids  

Microsoft Academic Search

Single-walled carbon nanotubes (SWNTs) with amino acids covalently attached to their side walls, viz., “nanotube-aminoacids,” have been prepared starting from colloidal solutions of fluorinated SWNTs (F-SWNTs) and amino acids\\u000a in o-dichlorobenzene and heating at 80–150 °C in the presence of pyridine. The syntheses were carried out with the F-SWNTs of\\u000a approximately 2: 1 (C: F) stoichiometry and several natural ?-aino

M. X. Pulikkathara; V. N. Khabashesku

2008-01-01

205

Adsorption of benzoic acid onto high specific area activated carbon cloth  

Microsoft Academic Search

The adsorption of benzoic acid from aqueous solution onto high area carbon cloth at different pH values has been studied. Over a period of 125 min the adsorption process was found to follow a first-order kinetics and the rate constants were determined for the adsorption of benzoic acid at pH 2.0, 3.7, 5.3, 9.1, and 11.0. The extents of adsorption

Erol Ayranci; Numan Hoda; Edip Bayram

2005-01-01

206

REMOVAL OF CHLORIDE FROM ACIDIC SOLUTIONS USING NO2  

SciTech Connect

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

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

2006-08-22

207

Carbon flux and fatty acid synthesis in plants  

Microsoft Academic Search

The de novo synthesis of fatty acids in plants occurs in the plastids through the activity of fatty acid synthetase. The synthesis of the malonyl-coenzyme A that is required for acyl-chain elongation requires the import of metabolites from the cytosol and their subsequent metabolism. Early studies had implicated acetate as the carbon source for plastidial fatty acid synthesis but more

Stephen Rawsthorne

2002-01-01

208

Nature of paramagnetic centers in anodic aluminum oxide formed in a solution of tartaric acid  

NASA Astrophysics Data System (ADS)

Films of anodic aluminum oxide, prepared in an aqueous solution of 0.4 M tartaric acid, are studied by means of electron paramagnetic resonance (EPR) before and after heating at 200-700°C. The presence of a carbon radical is established in the films ( g factor, 2.0027 ± 0.0002). The nature and conditions of its formation during the electrochemical oxidation of aluminum and the heat-treating of anodic aluminum oxide films are discussed.

Chernyakova, K. V.; Ivanovskaya, M. I.; Azarko, I. I.; Vrublevskii, I. A.

2012-10-01

209

Exchange of oxygen isotopes in carbon dioxide-phosphoric [correction of phosporic] acid systems.  

PubMed

The rate of exchange of isotopes of oxygen between solutions of concentrated phosphoric acid and CO2 was measured as a function of temperature, acid strength (pressure of water in equilibrium with the solution), pressure of CO2, and surface area of the reaction vessel. At 75 degrees C, significant exchange was found to occur even for the "anhydrous" phosphoric acids, those in which the nominal percentage of H3PO4 in solution is equal to or exceeds 100%. Exchange is much slower at 25 degrees C, but isotopic shifts as large as 0.1% can be observed in 95% H3PO4 at equilibration times approaching 1000 hr. Rates of exchange were found to be dependent upon the vapor pressure of water in equilibrium with the acid solutions. Exchange was found to occur primarily on the surface of the reaction vessel above the solution, with no dependence on total CO2 pressure. These observations indicate that phosphoric acids with nominal concentrations of H3PO4 approaching 105% are preferable for the minimization of exchange between CO2 samples and acid solutions during phosphorolyses of carbonate materials. Moreover, with such acids, significant time--temperature trade-offs are possible, allowing rapid preparation of CO2 at elevated temperatures. PMID:11542004

Wachter, E A; Hayes, J M

1985-01-01

210

Infrared matrix isolation studies of carbon disulfide and carbon dioxide complexes with nitrous and nitric acids  

Microsoft Academic Search

Argon matrix infrared spectra of carbon disulfide and carbon dioxide complexes with nitrous and nitric acids indicate the formation of hydrogen bonded structures. In all the studied systems, the acidic proton of the hydroxyl group interacted with the terminal atom (S or O) of the base molecule. The observed red shifts of the OH stretching mode were equal to ca.

M. Wierzejewska; M Dziadosz

1999-01-01

211

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

212

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

213

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

214

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

Microsoft Academic Search

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

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

2012-01-01

215

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

Microsoft Academic Search

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

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

1996-01-01

216

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

Code of Federal Regulations, 2010 CFR

...cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). 173.195 Section 173.195 Transportation...cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous,...

2010-10-01

217

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

Code of Federal Regulations, 2010 CFR

...cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). 173.195 Section 173.195 Transportation...cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous,...

2009-10-01

218

Adsorption of cadmium from aqueous solutions on sulfurized activated carbon prepared from nut shells  

Microsoft Academic Search

Low-cost activated carbon, derived from nut shells, and its modified sample have been used as replacements for the current expensive methods of removing cadmium from aqueous solutions and waste waters. Adsorption of cadmium onto four kinds of activated carbons has been studied; prepared activated carbon (PAC), commercial activated carbon (CAC), and the sulfurized ones (SPAC & SCAC). The activated carbon

Amir Fouladi Tajar; Tahereh Kaghazchi; Mansooreh Soleimani

2009-01-01

219

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

220

Fluidic delivery of homogeneous solutions through carbon tube bundles.  

PubMed

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 (approximately 1 cm) carbon nano and microtubes with inner diameters in the range 100 nm-1 microm 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. PMID:19531856

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

2009-06-17

221

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

PubMed

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

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

222

Pseudo-capacitance on exfoliated carbon fiber in sulfuric acid electrolyte  

Microsoft Academic Search

The specific capacitance of exfoliated carbon fibers (ExCF) which were synthesized from pitch-based carbon fibers showed a\\u000a strong dependence with the concentration of sulfuric acid electrolyte and reached 1.4 F\\/m2 in 18 M H2SO4 solution. Since the capacitance value is quite large compared with the case of conventional activated carbons, faradic reactions\\u000a (charge transfer reactions) are the cause of pseudo-capacitance. ExCF, however,

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

2006-01-01

223

Sorption of Zn(II), Cu(II), Fe(III) on carbon adsorbents from manganese sulfate solutions  

Microsoft Academic Search

Sorption of Zn2+, Cu2+, Fe3+\\/Fe2+ on carbon adsorbents under static (batch) and dynamic (columns) conditions from model and industrial MnSO4 solutions has been studied. The industrial solutions were obtained by reducing acidic leaching of manganese and pyrite concentrates. The initial manganese concentration was ?35 mmol\\/l and concentration of Zn2+, Cu2+, Fe3+ ions was ?0.2 mmol\\/l. It was found out that

O. N Kononova; A. G Kholmogorov; A. N Lukianov; S. V Kachin; G. L Pashkov; Y. S Kononov

2001-01-01

224

Interactions of functionalized carbon nanotubes with tethered pyrenes in solution  

NASA Astrophysics Data System (ADS)

Single-wall carbon nanotubes (SWNTs) were functionalized by oligomeric species containing derivatized pyrenes. Absorption and emission properties of the pyrene moieties tethered to the functionalized SWNTs were studied in homogeneous solution. The absorption spectra suggest no significant ground-state complexation between the pyrenes and nanotubes. The fluorescence and fluorescence excitation results show that the tethered pyrenes form "intramolecular" (intra-nanotube) excimers and that the excimer formation is predominantly dynamic in nature. The time-resolved fluorescence results show that the pyrene monomer and excimer emissions are significantly quenched by the attached SWNTs. The quenching is explained in terms of a mechanism in which carbon nanotubes serve as acceptors for excited-state energy transfers from the tethered pyrene moieties.

Qu, Liangwei; Martin, Robert B.; Huang, Weijie; Fu, Kefu; Zweifel, Daniel; Lin, Yi; Sun, Ya-Ping; Bunker, Christopher E.; Harruff, Barbara A.; Gord, James R.; Allard, Lawrence F.

2002-11-01

225

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

226

Influence of solution acidity on the adsorption and charge transfer kinetics of parabanic acid reduction  

Microsoft Academic Search

Parabanic acid reduction has been studied in the ? 1.4 ? H0 ? 0.9 acidity range by the ac impedance technique. Changes in the adsorption of reactant and products with solution acidity lead to protonation equilibrium constants that differ from their bulk values. The observed pKa shifts were consistent with interfacial dielectric saturation. Variation of the charge transfer parameters with

J. J. Calvente; R. Andreu; E. Roldán; M. Domínguez

1995-01-01

227

Spectrophotofluorometric determination of terbium and europium in potassium carbonate solution.  

PubMed

The conditions for the spectrophotofluorometric determination of terbium and europium, in solutions of potassium carbonate, have been established. The apparent excitation and fluorescence wavelengths used, respectively, are 245 mmu and 550 mmu for terbium and 400 mmu and 620 mmu for europium. The fluorescence varies linearly with the concentration of terbium and europium in the range 0.3-70 mug, of terbium/ml and 4-800 mug of europium/ml. Large amounts of gadolinium, lutetium and yttrium do not interfere. Cerium(IV) interferes seriously. PMID:18959977

Taketatsu, T; Carey, M A; Banks, C V

1966-08-01

228

Probing Chemical Potentials in Solution with Carbon Nanotube Transistors  

NASA Astrophysics Data System (ADS)

We have used single-walled carbon nanotube transistors to sense redox-active transition metal complexes in a conducting liquid environment. The molecules shift the gate voltage dependence of the nanotube conductance. This shift depends logarithmically on the ratio of oxidized to reduced molecules, which is changed and measured using traditional electrochemical methods. We attribute this signal primarily to the changing electrostatic potential of the solution as set by the water-gate wire, and not to a local interaction between the molecules and the nanotube.

Larrimore, Lisa; Nad, Suddhasattwa; Zhou, Xinjian; Abruńa, Héctor; McEuen, Paul

2006-03-01

229

Oxidative desulfurization of askale coal by nitric acid solution  

SciTech Connect

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

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

2007-07-01

230

Impact of the condition of storage of tartaric acid solutions on the production and stability of glyoxylic acid  

Microsoft Academic Search

The production and stability of glyoxylic acid was followed during the storage of tartaric acid solutions under various conditions. The solutions were prepared both with and without ethanol. Quantification of glyoxylic acid and other oxidation products, including hydrogen peroxide and formic acid, were performed using ion exclusion chromatography. Glyoxylic acid was only detected in tartaric acid samples that had been

Andrew C. Clark; Paul D. Prenzler; Geoffrey R. Scollary

2007-01-01

231

Cooperative acid-base effects with functionalized mesoporous silica nanoparticles: applications in carbon-carbon bond-formation reactions.  

PubMed

Acid-base bifunctional mesoporous silica nanoparticles (MSN) were prepared by a one-step synthesis by co-condensation of tetraethoxysilane (TEOS) and silanes possessing amino and/or sulfonic acid groups. Both the functionality and morphology of the particles can be controlled. The grafted functional groups were characterized by using solid-state (29)Si and (13)C cross-polarization/magic angle spinning (CP/MAS) NMR spectroscopy, thermal analysis, and elemental analysis, whereas the structural and the morphological features of the materials were evaluated by using XRD and N(2) adsorption-desorption analyses, and SEM imaging. The catalytic activities of the mono- and bifunctional mesoporous hybrid materials were evaluated in carbon-carbon coupling reactions like the nitroaldol reaction and the one-pot deacetalization-nitroaldol and deacetalization-aldol reactions. Among all the catalysts evaluated, the bifunctional sample containing amine and sulfonic acid groups (MSN-NNH(2)-SO(3)H) showed excellent catalytic activity, whereas the homogeneous catalysts were unable to initiate the reaction due to their mutual neutralization in solution. Therefore a cooperative acid-base activation is envisaged for the carbon-carbon coupling reactions. PMID:19569138

Shylesh, Sankaranarayanapillai; Wagner, Alex; Seifert, Andreas; Ernst, Stefan; Thiel, Werner R

2009-07-20

232

Activated carbon sheet prepared from softwood acetic acid lignin  

Microsoft Academic Search

As an example of activated carbon (AC) moldings, AC sheets were prepared from thermoplastic acetic acid lignin by lamination.\\u000a The resulting AC sheets are a new type of product that can be applied as water and air cleaners. Powdered softwood acetic\\u000a acid lignin (SAL) was molded into sheets by a thermal pressing method. When the sheet was carbonized under a

Yasumitsu Uraki; Ryo Taniwatashi; Satoshi Kubo; Yoshihiro Sano

2000-01-01

233

Phosphorylated Mesoporous Carbon as a Solid Acid Catalyst  

SciTech Connect

Mesoporous carbon catalyst supports are attractive due to their wide chemical stability while potentially increasing masstransport through and providing a path for larger molecules to access catalytic sites. Herein we report the synthesis of a 10 phosphorylated mesoporous carbon solid-acid catalyst characterized by NH3-TPD and isopropanol dehydration.

Dai, Sheng [ORNL; Mayes, Richard T [ORNL; Fulvio, Pasquale F [ORNL; Ma, Zhen [ORNL

2011-01-01

234

Electrochemical behavior of carbon steel in carbon dioxide-saturated diglycolamine solutions  

SciTech Connect

The electrochemical behavior of carbon steel in diglycolamine (DGA) solutions saturated with carbon dioxide (CO{sub 2}) under 4.5 MPa pressure was investigated using potentiodynamic polarization and impedance measurements at room temperature (RT) and at 100 C. Electrode equivalent circuits were proposed for interpreting the impedance measured at the higher temperature. Anodic and cathodic reaction mechanisms depended upon DGA concentration, temperature, and potential. At RT, the rate-determining step of the cathodic reduction changed from a diffusion process to an interfacial reaction with increasing DGA concentration. Corrosion rates were relatively low, and varied only slightly with DGA concentration. At 100 C, a tight corrosion product film was formed on the carbon steel surface in 0.1 M and 1.0 M DGA solutions. Anodic dissolution was inhibited strongly by slow ion diffusion in the film, and corrosion rates were much lower than those at RT. The tight corrosion product film did not form in the 5.0 M DGA solution, and the corrosion rate was very high. There were differences in the anodic dissolution mechanisms between the low- and high-concentration DGA solutions. At the high DGA concentration and at 100 C, a surface adsorption and an interfacial intermediate electrochemical reaction played important roles in cathodic reduction and anodic dissolution, respectively.

Guo, X.P.; Tomoe, Y. [Teikoku Oil Co., Tokyo (Japan). Technical Research Center

1998-11-01

235

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

236

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

237

Irradiation stability of folic Acid in powder and aqueous solution.  

PubMed

This study attempts to examine the folic acid stability after irradiation treatment, under different physical states, pH values, and atmosphere conditions. Aqueous folic acid samples, folic acid in powder, and wheat flour fortified with folic acid were irradiated by an electron beam (E-beam) between 0 (control) and 10.0 kGy. It was realized that the physical state of folic acid plays an important role on its stability toward E-beam processing, being largely unstable in solution, no matter the pH and atmosphere conditions assayed. Otherwise, folic acid in powder showed huge irradiation stability, even when mixed in a dry food matrix, such as fortified wheat flour samples. PMID:21275389

Araújo, Michel M; Marchioni, Eric; Bergaentzle, Martine; Zhao, Minjie; Kuntz, Florent; Hahn, Emeline; Villavicencio, Anna Lucia C H

2011-01-28

238

Liquid crystalline solutions of cellulose in phosphoric acid  

Microsoft Academic Search

It was found that anhydrous phosphoric acid is an excellent direct solvent for cellulose. Dissolution is very fast, and liquid crystalline solutions are formed above a cellulose concentration of 7.5% (w\\/w) at room temperature; even solutions containing 38% (w\\/w) cellulose can be prepared. The composition of the solvent is expressed in a P2O5 concentration. Anhydrous conditions are obtained above a

H. Boerstoel; H. Maatman; J. B. Westerink; B. M. Koenders

2001-01-01

239

Roentgenoluminescence of hexahydrate of uranyl nitrate in phosphoric acid solution  

NASA Astrophysics Data System (ADS)

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

Ožvoldová, M.

1992-08-01

240

Roentgenoluminescence of hexahydrate of uranyl nitrate in phosphoric acid solution  

Microsoft Academic Search

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

M. Ozvoldová

1992-01-01

241

Molal volume of aqueous boric acid-sodium chloride solutions  

Microsoft Academic Search

The apparent molal volume ?\\u000a v\\u000a of boric acid has been determined in various sodium chloride solutions at 0 and 25°C from precise density measurements. Similar\\u000a to its behavior in pure water, the ?\\u000a v\\u000a of boric acid in NaCl solutions is a linear function of the concentration. The infinite dilution ?\\u000a \\u000a v\\u000a \\u000a °\\u000a and the slope S\\u000a v\\u000a *

Gary K. Ward; Frank J. Millero

1974-01-01

242

Antimicrobial activity of kaurenoic acid derivatives substituted on carbon-15.  

PubMed

The antibacterial and antifungic activities of two kaurenic acids, ent kaurenoic acid and cinnamoylgrandifloric acid isolated from a hexane extract of aerial parts of Mikania laevigata, were investigated and compared with the activities of other kaurenic acid derivatives substituted on carbon-15. Only acetylgrandifloric acid (ent-kaur-16-en-15 alpha-acetyloxy-19-oic) and its epimer xylopic acid (ent-kaur-16-en-15 beta-acetyloxy-19-oic) displayed significant antibacterial activity at concentrations greater than or equal to 250 micrograms/ml, the 15 alpha epimer being the most active. PMID:2517587

Davino, S C; Giesbrecht, A M; Roque, N F

1989-01-01

243

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

244

A library of IR bands of nucleic acids in solution  

Microsoft Academic Search

This review presents a compilation and discussion of infrared (IR) bands characteristic of nucleic acids in various conformations. The entire spectral range 1800–800 cm?1 relevant for DNA\\/RNA in aqueous solution has been subdivided into four sections. Each section contains descriptions of bands appearing from group specific parts of nucleic acid structure, such as nucleobase, base–sugar, sugar–phosphate and sugar moiety. The

Martina Banyay; Munna Sarkar; Astrid Gräslund

2003-01-01

245

Hafnium extraction from acidic chloride solutions by Cyanex 923  

SciTech Connect

Hafnium extraction from hydrochloric acid/lithium chloride solutions into Cyanex 923 in kerosene has been studied. Variables investigated were hydrochloric acid, total chloride and hafnium concentrations in the aqueous phase, and extractant/modifier (isodecanol) levels in the organic phase. Hafnium is considered to load as the tetrachloride complex forming a disolvate with Cyanex 923. Results are compared with equivalent data for zirconium extraction. 14 refs., 7 figs., 2 tabs.

El-Ammouri, E.; Distin, P.A. [McGill Univ., Montreal (Canada)

1996-08-01

246

Viscosimetric studies of aqueous solutions of salts of carboxylic acids  

Microsoft Academic Search

Viscosities and densities of aqueous solutions of sodium salts of monocarboxylic acids (formic, acetic, propionic, valeric, chloroacetic, trichloroacetic, glycolic, phenylacetic) and dicarboxylic acids (oxalic, malonic, succinic, glutaric, adypic, pimelic, dl-tartaric, dl-malic, maleic, fumaric, o-phthalic) have been measured in the concentration range 0.02–0.1 mol·dm?3 at 298.15 K. The effect of hydrolysis of salts on viscosimetric data describing the objects under study

Agnieszka Chmielewska; Anna Wypych-Stasiewicz; Adam Bald

2005-01-01

247

Radiolysis of aqueous solutions of 2-aminoethanethiosulfuric acid. [Gamma radiation  

SciTech Connect

In the radiolysis products of aerated and deaerated solutions of the 2-aminoethanethiosulfuric acid the authors have identified cystamine monoxide, cystamine, taurine, mercamine, the sulfate ion, the sulfite ion, and the dithionate ion. The yields of these products under different conditions have been determined. Results indicated that the sulfate ion is formed both from the divalent and the hexavalent sulfur atom of the 2-aminoethanethiosulfuric acid moelcule. A possible radiolysis mechanism is discussed.

Grachev, S.A.; Koroleva, I.K.; Kropachev, E.V.; Litvyakova, G.I.

1982-07-10

248

Metabolic carbon fluxes and biosynthesis of polyhydroxyalkanoates in Ralstonia eutropha on short chain fatty acids.  

PubMed

Short chain fatty acids such as acetic, propionic, and butyric acids can be synthesized into polyhydroxyalkanoates (PHAs) by Ralstonia eutropha. Metabolic carbon fluxes of the acids in living cells have significant effect on the yield, composition, and thermomechanical properties of PHA bioplastics. Based on the general knowledge of central metabolism pathways and the unusual metabolic pathways in R. eutropha, a metabolic network of 41 bioreactions is constructed to analyze the carbon fluxes on utilization of the short chain fatty acids. In fed-batch cultures with constant feeding of acid media, carbon metabolism and distribution in R. eutropha were measured involving CO2, PHA biopolymers, and residual cell mass. As the cells underwent unsteady state metabolism and PHA biosynthesis under nitrogen-limited conditions, accumulative carbon balance was applied for pseudo-steady-state analysis of the metabolic carbon fluxes. Cofactor NADP/NADPH balanced between PHA synthesis and the C3/C4 pathway provided an independent constraint for solution of the underdetermined metabolic network. A major portion of propionyl-CoA was directed to pyruvate via the 2-methylcitrate cycle and further decarboxylated to acetyl-CoA. Only a small amount of propionate carbon (<15% carbon) was directly condensed with acetyl-CoA for 3-hydroxyvalerate. The ratio of glyoxylate shunt to TCA cycle varies from 0 to 0.25, depending on the intracellular acetyl-CoA level and acetic acid in the medium. Malate is the node of the C3/C4 pathway and TCA cycle and its decarboxylation to dehydrogenation ranges from 0.33 to 1.28 in response to the demands on NADPH and oxaloacetate for short chain fatty acids utilization. PMID:15296425

Yu, Jian; Si, Yingtao

249

Insights into non-Fickian solute transport in carbonates  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

250

Electrochemical oxidation of biological molecules at carbon paste electrodes pre-treated in guanine solutions.  

PubMed

Carbon paste electrodes were modified in guanine solutions under an applied potential of 1.1 V and used for electrochemical detection of NADH, NADPH, uric acid and 8-oxoguanine. Detection limits were 3.3, 3.7, 6.6 and 2.0 x 10(-6) M, respectively, with sensitivity of 0.13, 0.10, 0.26 and 0.40 A mol(-1) l cm(-2), respectively. The electrodes showed high reproducibility and absence of surface poisoning effects. Good analytical performance was attributed to the formation of superficial dimer or trimers species of guanine during the modification process. PMID:14623600

da Silva, Robson Pinho; Serrano, Silvia H P

2003-11-24

251

Studies on the Adsorption of Americium on Alumina from Aqueous Nitric Acid-Oxalic Acid Solutions  

Microsoft Academic Search

This paper reports a study on the adsorption of Am(III) on alumina from oxalic acid-nitric acid solutions. Distribution coefficients for Am(III) on alumina at different oxalic acid-nitric acid concentrations have been determined and optimum conditions for loading and elution of Am from alumina columns have been established. Separation of Am from Pu and the effects of other ions, such as

M. Subba Rao; A. M. Gaikwad; V. K. Rao; P. R. Natarajan

1985-01-01

252

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

253

Ultrafast carbon-carbon single-bond rotational isomerization in room-temperature solution.  

PubMed

Generally, rotational isomerization about the carbon-carbon single bond in simple ethane derivatives in room-temperature solution under thermal equilibrium conditions has been too fast to measure. We achieved this goal using two-dimensional infrared vibrational echo spectroscopy to observe isomerization between the gauche and trans conformations of an ethane derivative, 1-fluoro-2-isocyanato-ethane (1), in a CCl4 solution at room temperature. The isomerization time constant is 43 picoseconds (ps, 10(-12) s). Based on this value and on density functional theory calculations of the barrier heights of 1, n-butane, and ethane, the time constants for n-butane and ethane internal rotation under the same conditions are approximately 40 and approximately 12 ps, respectively. PMID:17008529

Zheng, Junrong; Kwak, Kyungwon; Xie, Jia; Fayer, M D

2006-09-29

254

Ultrafast Carbon-Carbon Single-Bond Rotational Isomerization in Room-Temperature Solution  

NASA Astrophysics Data System (ADS)

Generally, rotational isomerization about the carbon-carbon single bond in simple ethane derivatives in room-temperature solution under thermal equilibrium conditions has been too fast to measure. We achieved this goal using two-dimensional infrared vibrational echo spectroscopy to observe isomerization between the gauche and trans conformations of an ethane derivative, 1-fluoro-2-isocyanato-ethane (1), in a CCl4 solution at room temperature. The isomerization time constant is 43 picoseconds (ps, 10-12 s). Based on this value and on density functional theory calculations of the barrier heights of 1, n-butane, and ethane, the time constants for n-butane and ethane internal rotation under the same conditions are ~40 and ~12 ps, respectively.

Zheng, Junrong; Kwak, Kyungwon; Xie, Jia; Fayer, M. D.

2006-09-01

255

Intramolecular carbon isotope distribution of acetic acid in vinegar.  

PubMed

Compound-specific carbon isotope analysis of acetic acid is useful for origin discrimination and quality control of vinegar. Intramolecular carbon isotope distributions, which are each carbon isotope ratios of the methyl and carboxyl carbons in the acetic acid molecule, may be required to obtain more detailed information to discriminate such origin. In this study, improved gas chromatography-pyrolysis-gas chromatography-combustion-isotope ratio mass spectrometry (GC-Py-GC-C-IRMS) combined with headspace solid-phase microextraction (HS-SPME) was used to measure the intramolecular carbon isotope distributions of acetic acid in 14 Japanese vinegars. The results demonstrated that the methyl carbons of acetic acid molecules in vinegars produced from plants were mostly isotopically depleted in (13)C relative to the carboxyl carbon. Moreover, isotopic differences (?(13)C(carboxyl) - ?(13)C(methyl)) had a wide range from -0.3 to 18.2‰, and these values differed among botanical origins, C3, C4, and CAM plants. PMID:21830825

Hattori, Ryota; Yamada, Keita; Kikuchi, Makiko; Hirano, Satoshi; Yoshida, Naohiro

2011-08-18

256

Purification of wet phosphoric acid using modified activated carbon  

Microsoft Academic Search

Phosphoric acid is very important to the Tunisian economy. A new method has been developed to reduce the concentration of inorganic impurities present in commercial Tunisian phosphoric acid. This method is based on the modification of activated carbon with sodium dodecyl sulphonate to carry out the exchange of ions. The preliminary results with the column used for this purpose was

Lotfi Monser; Mohamed Ben Amor; Mohamed Ksibi

1999-01-01

257

Hydrogen oxidation on gold electrode in perchloric acid solution  

Microsoft Academic Search

The aim of this research is to study the interface gold\\/perchloric acid solution in presence of hydrogen. The reactive is generated by H+ ion reduction and by saturating the electrolyte with the gaseous H2. No evidence of H2 dissociative adsorption is found. In special conditions, a strongly adsorbed layer is formed from the atoms diffusing from inside of the metal.

M. G. Sustersic; N. V. Almeida; A. E. Von Mengershausen

2010-01-01

258

Effects of solution environment on humic acid fouling during microfiltration  

Microsoft Academic Search

Microfiltration is increasingly used in drinking water treatment for the removal of particles, turbidity, and microorganisms to meet more stringent water quality requirements. Fouling by natural organic matter (e.g., humic and fulvic acids) is a critical factor in microfiltration processes. Experiments were performed to evaluate the effects of solution pH, salt concentration, and ionic composition on the extent and mechanisms

Wei Yuan; Andrew L. Zydney

1999-01-01

259

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

260

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

PubMed Central

Oral calcium carbonate (0-5 g, pH 9-4) increased serum gastrin and gastric acid output with slight but insignificant change in serum calcium. A similar rise in serum calcium during an intravenous infusion of calcium gluconate failed to increase serum gastrin and gastric acid output. Both intragastric calcium actions were abolished by acidification of the calcium carbonate solution (pH 1-0). The increase in serum gastrin and gastric acid output after intragastric calcium carbonate was not affected, however, by a simultaneous intraduodenal acid load. Equivalent neutralising doses of magnesium hydroxide (pH 9-4) did not increase serum gastrin and gastric acid output above basal levels, whereas antral acidification with 20 ml 0-1 N HCl resulted in a slight decrease in serum gastrin. Intraduodenal calcium carbonate (pH 3-0) also increased serum gastrin and gastric acid output, whereas an equivalent volume of intraduodenal saline (pH 3-0) had no effect. These findings indicate that calcium increases serum gastrin by local stimulation of antral and duodenal mucosa. They also suggest that the action of calcium on gastric secretion is partly mediated by gastrin.

Behar, J; Hitchings, M; Smyth, R D

1977-01-01

261

The passivity of 304 stainless steel in propylene carbonate solutions  

SciTech Connect

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

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

1992-01-01

262

Carbon dioxide capture capacity of sodium hydroxide aqueous solution.  

PubMed

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

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

2012-11-24

263

Heterogeneity of activated carbons in adsorption of aniline from aqueous solutions  

Microsoft Academic Search

The heterogeneity of activated carbons (ACs) prepared from different precursors is investigated on the basis of adsorption isotherms of aniline from dilute aqueous solutions at various pH values. The APET carbon prepared from polyethyleneterephthalate (PET), as well as, commercial ACP carbon prepared from peat were used. Besides, to investigate the influence of carbon surface chemistry, the adsorption was studied on

P. Podkoscielny; K. László

2007-01-01

264

Field evaluation of gelled acid for carbonate formations  

SciTech Connect

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

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

1981-12-01

265

Osmotic coefficient of aqueous solutions of cyclohexylsulfamic Acid at the freezing point of solutions.  

PubMed

The osmotic coefficient of aqueous solutions of cyclohexylsulfamic acid was determined by freezing point measurements up to the molality 0.65 mol kg-1. The osmotic coefficients were fitted to the Pitzer equation, and ion interaction parameters ?1, ?(0) and ?(1) were evaluated. The mean ion activity coefficient of the solute was calculated, and the non-ideal behaviour of the system investigated was characterized by calculation of the excess Gibbs energy of solution, as well as the respective partial molar functions of solute and solvent. The partial molar excess Gibbs energy of the solute is negative, like the excess Gibbs energy of its solution, while the partial molar excess Gibbs energy of the solvent is positive and increases with increasing concentration of the solute. The solvation ability of water was calculated from the difference between the Gibbs energy of solution of water in solution and that of pure water, and found to be positive and small for the solute investigated, throughout the concentration range studied. PMID:24061887

Bešter-Roga?, Marija; Klofutar, Cveto; Rudan-Tasi?, Darja

2010-12-01

266

Prediction of adsorption from multicomponent solutions by activated carbon using single-solute parameters  

Microsoft Academic Search

The adsorption of 3 barbiturates—phenobarbital, mephobarbital, and primidone—from simulated intestinal fluid (SIF), without\\u000a pancreatin, by activated carbon was studied using the rotating bottle method. The concentrations of each drug remaining in\\u000a solution at equilibrium were determined with the aid of a high-performance liquid chromatography (HPLC) system employing a\\u000a reversed-phase column. The competitive Langmuir-like model, the modified competitive Langmuir-like model, and

Dale Eric Wurster; Khouloud A. Alkhamis; Lloyd E. Matheson

2000-01-01

267

THE NATURE OF EUROPIUM ION IN CARBONATE SOLUTION AND POLAROGRAPHIC DETERMINATION OF MICRO AMOUNTS OF EUROPIUM  

Microsoft Academic Search

The nature of the complex europium carbonate ion in concentrated ; carbonate solution was studied polarographically. A polarographic method for the ; determination of micro amounts of europium ion in the presence of diverse ions ; (and especially lanthanides) was developed. (auth);

Seizo Misumi; Yoshitaka Masuda

1963-01-01

268

The CNG process: Acid gas removal with liquid carbon dioxide  

SciTech Connect

The CNG acid gas removal process has two unique features: the absorption of sulfur-containing compounds and other trace contaminants with liquid carbon dioxide, and the regeneration of pure liquid carbon dioxide by triple-point crystallization. The process is especially suitable for treating gases which contain large amounts of carbon dioxide and much smaller amounts (relative to carbon dioxide) of hydrogen sulfide. Capital and energy costs are lower than conventional solvent processes. Further, products of the CNG process meet stringent purity specifications without undue cost penalties. A process demonstration unit has been constructed and operated to demonstrate the two key steps of the CNG process. Hydrogen sulfide and carbonyl sulfide removal from gas streams with liquid carbon dioxide absorbent to sub-ppm concentrations has been demonstrated. The production of highly purified liquid carbon dioxide (less than 0.1 ppm total contaminant) by triple-point crystallization also has been demonstrated.

Liu, Y.C.; Auyang, L.; Brown, W.R.

1987-01-01

269

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

SciTech Connect

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

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

1986-09-01

270

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

271

Ozonation of trichloroethylene in acetic acid solution with soluble and solid humic acid.  

PubMed

The combined flushing and oxidation process using acetic acid and ozone has been used successfully to remove trichloroethylene (TCE) completely from contaminated soil. In this study, the effects of humic acid, a fraction of the organic matter in soil, over the performance of TCE decomposition was evaluated. TCE decomposition by ozone was enhanced by the presence of humic acid at concentrations lower than 8mgCL(-1) and then inhibited at higher concentrations. It is possible that the presence of the soluble humic acid fraction during the ozonation of TCE in acetic acid solutions produces hydroxyl radicals during the TCE ozonation which appears to be the reason for the enhanced TCE decomposition rate. Solid humic acid reduced TCE decomposition rate by acting as an ozone scavenger. Similarly, sorbed TCE reduced the amount of TCE available for decomposition by ozone in solution. PMID:18511186

Alcántara-Garduńo, Martha E; Okuda, Tetsuji; Nishijima, Wataru; Okada, Mitsumasa

2008-03-30

272

Fragrance material review on carbonic acid, methyl phenylmethyl ester.  

PubMed

A toxicologic and dermatologic review of carbonic acid, methyl phenylmethyl ester when used as a fragrance ingredient is presented. Carbonic acid, methyl phenylmethyl ester is a member of the fragrance structural group Aryl Alkyl Alcohol Simple Acid Esters (AAASAE). The AAASAE fragrance ingredients are prepared by reacting an aryl alkyl alcohol with a simple carboxylic acid (a chain of 1-4 carbons) to generate formate, acetate, propionate, butyrate, isobutyrate and carbonate esters. This review contains a detailed summary of all available toxicology and dermatology papers that are related to this individual fragrance ingredient and is not intended as a stand-alone document. Available data for carbonic acid, methyl phenylmethyl ester were evaluated, then summarized, and includes: physical properties, acute toxicity, skin irritation, and skin sensitization data. A safety assessment of the entire AAASAE will be published simultaneously with this document. Please refer to Belsito et al. (2012) for an overall assessment of the safe use of this material and all AAASAE in fragrances. PMID:22414647

McGinty, D; Letizia, C S; Api, A M

2012-03-04

273

Dispersion and Related Properties of Acid-Treated Carbon Nanotube\\/Epoxy Composites using Electro-Micromechanical, Surface Wetting and Single Carbon Fiber Sensor Tests  

Microsoft Academic Search

Studies of dispersion and related properties, in carbon nanotube\\/epoxy composites, were conducted using electro-micromechanical and wettability tests. Specimens were prepared from neat epoxy as well as composites with untreated and acid-treated carbon nanotube (CNT). The degree of dispersion and its standard deviation were evaluated by turbidity of the dispersing solution, as well as by volumetric electrical resistivity. Acetone was a

Joung-Man Park; Jung-Hoon Jang; Zuo-Jia Wang; Dong-Jun Kwon; Ga-Young Gu; Woo-Il Lee; Jong-Kyoo Park; K. Lawrence Devries

2011-01-01

274

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

275

Pseudo-capacitance on exfoliated carbon fiber in sulfuric acid electrolyte  

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

276

Preparation and characterization of activated carbon from Amygdalus Scoparia shell by chemical activation and its application for removal of lead from aqueous solutions  

Microsoft Academic Search

Two series of activated carbon have been prepared by chemical activation of Amygdalus Scoparia shell with phosphoric acid or zinc chloride for the removal of Pb(II) ions from aqueous solutions. Several methods were employed\\u000a to characterize the active carbon produced. The surface area was calculated using the standard Brunauer-Emmet-Teller method.\\u000a The microstructures of the resultant activated carbon were observed by

Sayed Z. Mohammadi; Mohammad A. Karimi; Daryoush Afzali; Fatemeh Mansouri

2010-01-01

277

Study of the photolysis of folic acid and 6-formylpterin in acid aqueous solutions  

Microsoft Academic Search

Folic acid and 6-formylpterin solutions of pH in the range 4.5–6.0 were photolysed at 350nm at room temperature. The photochemical reactions were followed by UV–VIS spectrophotometry, thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). In the presence of oxygen, folic acid is photochemically cleavaged yielding 6-formylpterin and p-aminobenzoylglutamic acid. As the photolysis proceeds, 6-carboxypterin arises from 6-formylpterin, as

Andrés H. Thomas; Gustavo Suárez; Franco M. Cabrerizo; Raúl Martino; Alberto L. Capparelli

2000-01-01

278

A mechanistic study of copper electropolishing in phosphoric acid solutions  

NASA Astrophysics Data System (ADS)

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

Mansson, Andrew

279

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

NASA Astrophysics Data System (ADS)

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

Müller, K.; Winde, V.; Escher, P.; von Geldern, R.; Böttcher, M. E.

2012-04-01

280

Uranium (VI) sorption by multiwalled carbon nanotubes from aqueous solution  

NASA Astrophysics Data System (ADS)

Sorption of uranium (VI) from aqueous solutions onto Multiwalled Carbon Nanotubes (MWCNTs) has been studied under varying experimental conditions of initial uranium concentration, contact time, pH, and temperature, to assess the kinetic and equilibrium parameters. The optimum pH for sorption of uranium (VI) onto MWCNTs was 5. The kinetic data were fitted with pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. The sorption process was well described by pseudo-second-order kinetics. The uranium sorption data were fitted by the Langmuir, Freundlich, and Dubinin-Radushkevich equilibrium models to obtain the characteristic parameters of each model. The Langmuir isotherm was found to best represent the measured sorption data. According to the evaluation using the Langmuir model, the maximum sorption capacity of uranium (VI) ions onto MWCNTs increased with temperature, from 24.9 to 39.1 mg g-1 when the temperature was increased from 298 to 318 K. The calculated sorption thermodynamic parameters including ?G°, ?H°, and ?S° indicated the spontaneous nature of uranium sorption onto MWCNTs. The results suggest that MWCNTs are suitable materials for preconcentration and solidification of uranium (VI) species from aqueous solutions.

Fasfous, Ismail I.; Dawoud, Jamal N.

2012-10-01

281

Influence of sodium azide on the removal of fulvic acids by activated carbon  

Microsoft Academic Search

The impact of sodium azide, as an inhibitor of biochemical reactions in aqueous solutions, on its interaction with activated\\u000a carbon (AC) and on the characteristics of equilibrium adsorption of fulvic acids (FA) on AC has been studied. It was shown\\u000a that additions of sodium azide during FA adsorption on AC under equilibrium conditions do not completely inhibit the biological\\u000a activity

N. A. Klimenko; T. V. Polyakova; L. A. Savchina

2010-01-01

282

Activated carbon from cotton stalks by impregnation with phosphoric acid  

Microsoft Academic Search

Dried, crushed cotton stalks were impregnated with varying concentrations of phosphoric acid (20–85 wt.%), dried at 383 K and carbonized at 773 K for 2 h. Porosity was determined by analysis of N2\\/77 K adsorption isotherms. High adsorbing carbons with well developed mesoporosity were obtained. Analysis for microporosity, by the ?S-method, proved the presence of minor content in all products.

Badie S Girgis; Mona F Ishak

1999-01-01

283

Multi-walled carbon nanotubes fabricated by electrospinning of acrylonitrile/nylon solution and subsequent carbonization.  

PubMed

The poly(acrylonitrile) (PAN) nanofiber web interpenetrated nylon-6 nanofiber supporters were prepared by electrospinning of an acrylonitrile (AN)/nylon-6 solution. It was realized that the average diameters of PAN and nylon-6 nanofiber were 20 and 100 nm, respectively, and that the PAN nanofibers constructed spider-mat networks which were supported by the robust nylon-6 nanofiber pillars. After stabilization and carbonization above 600 degrees C, both hollow-shaped and bamboo-shaped multi-walled carbon nanotubes (MWCNTs) were formed with the diameter range from 5 to 20 nm. The morphology and structure of MWCNTs had been further investigated by the combination techniques of transmission electron microscopy (TEM), electron diffraction (ED), X-ray diffraction (XRD) and elemental analyzer (EA). PMID:21125878

Park, Soo-Jin; Parajuli, Daman Chandra; Bajagi, Madhab Prasad; Jeong, Kwang-Un; Barakat, Nasser Aly Mohamed; Kim, Hak Yong

2010-08-01

284

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

PubMed

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

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

2013-02-08

285

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

SciTech Connect

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

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

2008-04-15

286

Nanomechanical Behavior of Human Molars Soaked in Slight Acid Solutions  

Microsoft Academic Search

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

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

2009-01-01

287

Corrosion of cold-deformed brass in acid sulphate solution  

Microsoft Academic Search

The corrosion behaviour and the dezincification process of cold-deformed CuZn-42 brass were tested in an acid sulphate solution at pH-value 2 with additional chloride and copper(II) ions by use of the linear polarization method.The measured corrosion potential and densities of corrosion currents were observed as characteristics of the dezincification process and the corrosion resistance of tested samples of cold-deformed CuZn-42

Zoran Avramovic; Milan Antonijevic

2004-01-01

288

NMR solution structures of LNA (locked nucleic acid) modified quadruplexes  

Microsoft Academic Search

We have determined the NMR solution structures of the quadruplexes formed by d(TGLGLT) and d(TL4T), where L denotes LNA (locked nucleic acid) modified G-residues. Both structures are tetrameric, parallel and right-handed and the native global fold of the corresponding DNA quadruplex is retained upon introduction of the LNA nucleotides. However, local structural alterations are observed owing to the locked LNA

Jakob T. Nielsen; Khalil Arar; Michael Petersen

2006-01-01

289

Viscosimetric studies of aqueous solutions of dicarboxylic acids  

Microsoft Academic Search

A method of analysis of viscosimetric data of weak electrolytes of 1–2 type has been elaborated. For this purpose, the precise measurements of density and viscosity of aqueous solutions of dicarboxylic acids (oxalic, malonic, succinic, glutaric, adipic, pimelic, dl-tartaric, dl-malic, maleic, fumaric and o-phthalic) have been conducted at 298.15 K. Modified Jones–Dole equations taking into account all chemical species existing in

Agnieszka Chmielewska; Adam Bald

2008-01-01

290

Uptake kinetics of three epoxides into sulfuric acid solution  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

291

Adsorption of Mercuric Ion from Aqueous Solutions Using Activated Carbon  

Microsoft Academic Search

Activated carbon (AC) was prepared from hazelnut shells using two steps of carbonization followed by steam activation. Methylene blue dye was used as a probe for evaluation of the prepared activated carbon. In order to have a better comparison, a commercial grade of activated carbon (powdered) obtained from the Merck Company has also been used in this research as standard.

R. Ansari Khalkhali; R. Omidvari

292

A selective voltammetric method for uric acid detection at Nafion(R)-coated carbon paste electrodes.  

PubMed

A square-wave voltammetric method together with Nafion(R)-coated carbon paste electrodes were used for the selective determination of uric acid in the presence of a high concentration of ascorbic acid. Since the oxidation potential of uric acid is about 200 mV more positive than that of ascorbic acid at the Nafion(R)-coated carbon paste electrode, the selectivity can be greatly improved simply by applying an electrolysis potential of +0.4 V vs. Ag/AgCl where only ascorbic acid is oxidised. The acceptable tolerance of ascorbic acid concentration for the determination of uric acid is as high as 1.5 mM. With 30 s of electrolysis time, a linear calibration curve is obtained over the 0-50 muM range in 0.05 M citrate buffer solution, pH 4.0, with slope (muA/muM) and correlation coefficient of 0.34 and 0.9984, respectively. The detection limit (3sigma) is 0.25 muM. The practical analytical utility is illustrated by selective measurements of uric acid in human urine without any preliminary treatment. PMID:18967265

Zen, J M; Hsu, C T

1998-08-01

293

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

294

New method for H(2)S removal in acid solutions.  

PubMed

Several different technologies are available for H(2)S removal from the gas stream of medium capacity. Among them, the most widely used is Locat with more than 120 plants worldwide. In the last decade, many new processes, such as Sulfatreat-DO, Crystasulf, Caltech, and UCSR, were proposed to overcome the drawbacks of the state-of-the-art processes (low sulfur purity, chemical degradation, thiosulfate formation). We have developed a new H(2)S conversion method based on acid ferric nitrate solution, co-catalyzed by a heteropolyacid. H(2)S was converted to pure sulfur (>99.9 %), with no traces of organic compounds. Due to the acid pH of the solution, no chelant or surfactant was needed and iron content in the solution could reach very high levels. Keggin heteropolyacid (H(6)PW(9)V(3)O(40)) catalyzed the reoxidation of reduced ferrous solution with air at mild temperature and at very high reaction rate. The undesired side reaction (NO(x) formation) could be avoided by simply increasing the oxygen partial pressure. PMID:20564280

de Angelis, Alberto; Bellussi, Giuseppe; Pollesel, Paolo; Perego, Carlo

2010-07-19

295

Leaching kinetics of malachite in ammonium carbonate solutions  

NASA Astrophysics Data System (ADS)

Leaching of malachite was conducted with ammonium carbonate as lixiviant and with temperature, lixiviant concentration, and particle size as variables. Two stages of reaction were found. In Stage I, the initial dissolution of malachite proceeds rapidly, but after about 10 pct reaction the rate is reduced by surface blockage due to the presence of a needle-structured intermediate, presumably Cu(OH)2. Subsequently, malachite and the intermediate dissolve concurrently. In Stage II, after 90 pct reaction, essentially all of the malachite has dissolved and only the intermediate remains. It dissolves in Stage II. The activation energy is 64 kJ/mole (15.3 kcal/mole) for Stage I and 75 kJ/mole (18 kcal/mole) for Stage II. The rate of reaction in Stage I is proportional to the reciprocal of particle size and is 0.8 order with respect to the concentration of ammonium carbonate. The structures of leaching residues were studied using a scanning electron microscope. The kinetic data (activation energy and entropy), particle size and concentration dependence, residue morphology, and general leaching behavior evident from microscopic monitoring during leaching were used to develop the geometric equation for leaching in Stage I. The equation, based on a heterogeneous reaction with geometric rate control, is: 1 - (1 - ? 1/3 = K01/r0/[(NH4)2C03]0.8 exp(-64,000/RT)t. It was deduced that initial steps in reaction were: (1) release of Cu2+ from malachite; (2) initial complexing with ammonia to form Cu(NH3)2+; and (3) subsequent complexing to produce Cu(NH3){4/2+} which is stable in solution at pH 8.8, the buffered pH of reaction. Stage II appears to be a similar reaction except that the reaction obeys cylindrical geometry instead of spherical geometry as in Stage I.

Oudenne, Paul D.; Olson, Ferron A.

1983-03-01

296

Capacitance of a passive iron electrode in acidic solutions  

SciTech Connect

In the present work the authors measured the capacitance of the electrical double layer on passive Armco iron in acidic solutions with the simultaneous recording of the potentiodynamic curves. The measurements were carried out on an apparatus which is based on the double-pulse variant of the galvanostatic method with a pulse lifetime of 2 microseconds, in which the influence of the faradic processes on the capacitance curves is negligibly small in the case of electrochemical systems with small exchange currents. The experiments were carried out at room temperature in 0.5 M sulfuric acid (pH 0.25) and 0.5 M tartaric acid H/sub 2/C/sub 4/H/sub 4/O/sub 6/ (pH 1.6).

Grilikhes, M.S.; Berezin, M.Yu.; Gorlin, A.V.; Sapelova, E.V.; Sokolov, M.A.; Sukhotin, A.M.

1985-12-01

297

Azole derivatives as inhibitors for the corrosion of irradiated and non-irradiated carbon steel in HNO3 solution  

Microsoft Academic Search

Purpose – The purpose of this paper is to investigate the effects of several azole derivatives on the corrosion inhibition of irradiated and non-irradiated plain carbon steel in 0.5 M nitric acid (HNO3) solutions at 30-60°C and to study the mechanism of their inhibitive action. Design\\/methodology\\/approach – The inhibition efficiency was evaluated by means of weight-loss determinations and polarization techniques

M. Abdallah; S. T. Atwa; N. M. Abd-Allah; A. S. Fouda

2011-01-01

298

Effect of ZnSO4 upon gastric acid secretion and carbonic anhydrase.  

PubMed

Starting from the multiple role zinc holds in the enzymatic processes of the body and from some positive data concerning treatment with zinc sulphate in gastric ulcer, we have studied the effect of ZnSO4 on gastric acid secretion in duodenal ulcer patients, as well as that on purified and gastric mucosa carbonic anhydrase. Gastric secretory testing showed that zinc sulphate administered in doses of 60 ml/day (1% solution) for 10 days reduced basal acid secretion in duodenal ulcer patients by 57.7%. In vitro, concentrations of ZnSO4 ranging between 10(-6) and 10(-2)M, inhibit purified carbonic anhydrase activity in a dose-dependent manner, reaching maximum effect at 10(-2)M, when carbonic anhydrase activity dropped from 2060 +/- 65 IU to 660 +/- 85 IU. A similar dose-dependent inhibition was found with gastric mucosa carbonic anhydrase activity, where ZnSO4 at 10(-2)M reduces enzyme activity from its basal value of 1.58 +/- 0.36 EU/mg to 0.88 +/- 0.21 EU/mg. Besides this effect, zinc sulphate antagonized in vitro the activation of both purified and gastric mucosa carbonic anhydrase by histamine. In conclusion, the mechanism of antisecretory effect of ZnSO4 might well be the inhibition of the carbonic anhydrase in the gastric mucosa. PMID:4077313

Puscas, I; Sturzu, L; Búzás, G

1985-11-01

299

Pressure solution in carbonate source rocks and its control on petroleum generation and migration  

Microsoft Academic Search

Based on detailed geochemical and petrographic studies of conventional cores of a Triassic age carbonate source rock formation from three well sites at increasing maturity stages, it is shown that the effects of carbonate diagenesis, especially pressure solution during relatively shallow burial stages, exercise major controls on the processes of petroleum generation and migration during deeper burial. Pressure solution leads

Rolando di Primio; Matthias Radke; Rainer G. Schaefer

1995-01-01

300

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

SciTech Connect

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

Pierce, R.A.

2000-01-04

301

Unusual stability and carbon acidity of a dicationic carbon species.  

PubMed

1,1'-Methylenebis(pyridinium) dication (MDP) is an unusual ion with two formal positively charged substituents attached to a central carbon, yet it is remarkably stable to hydrolysis at pH < 8. However, above this pH it undergoes a biphasic reaction liberating two equiv of pyridine sequentially. The rate of the first phase is second order in hydroxide ion, while that of the second is pH-independent. The first phase is also accompanied by the generation of a chromophore at 366 nm, which has been identified as a pyridine-ring-opened unsaturated iminoaldehyde formed by an ANRORC-type mechanism. This intermediate then undergoes ring closure to give the second equiv of pyridine and formaldehyde. Below pD 8 there is a very slow alternative pathway for degradation that is first order in hydroxide ion, liberates only one equiv of pyridine, and forms N-(hydroxymethyl)pyridinium ion. Deuterium exchange of the central methylene in D2O is faster than the breakdown of MDP and is predominantly OD(-)-catalyzed with a small amount of buffer catalysis. The estimated pKa of MDP dication in H2O, 21.2 at 25 °C and I = 1.0 M (KCl), is unexpectedly high but is about 9 units lower than that for the monocationic N-methylpyridinium ion. Deuterium exchange also occurs at the 2 and 6 positions of the pyridinium rings, but at a lower rate that is first order in deuteroxide ion and competitive with the breakdown of MDP only below pD 11. PMID:24059810

Mistry, Dharmit; Powles, Nicholas; Page, Michael I

2013-10-10

302

Method to improve matrix acidizing in carbonates  

SciTech Connect

This patent describes a method for increasing the permeability of a formation which formation has a least one zone of lesser permeability and one zone of greater permeability where high energy impulse fracturing is used to combination with an inhibited acid. It comprises: directing into a wellbore within the formation a pumpable solidifiable gel into a zone of the formation having a greater permeability under conditions to selectively close pores in the greater permeability zone.

Jennings, A.R. Jr.; Jones, L.G.; Shu, P.

1990-04-17

303

A mechanistic model of wormhole growth in carbonate matrix acidizing and acid fracturing  

SciTech Connect

A mathematical model that describes the growth and competition of wormholes during ann acidizing treatment in a carbonate formation was developed. The model is initialized with the distribution of largest pores. Wormhole characteristics (size, length, and distribution) were found too be controlled by acid-injection, diffusion, and fluid-loss rates.

Hung, K.M.; Hill, A.D.; Sepehrnoorl, K.

1989-01-01

304

A comparative study of synthetic graphite and Li electrodes in electrolyte solutions based on ethylene carbonate-dimethyl carbonate mixtures  

Microsoft Academic Search

This work entails a comparative study of both Li and synthetic graphite electrodes in electrolyte solutions based on ethylene and dimethyl carbonates (EC-DMC) and the impact of the salt used [from the LiAsFâ, LiClOâ, LiPFâ, LiBFâ, and LiN(SOâCFâ)â list]. The presence of some additives in solutions (e.g., LiâCOâ, COâ, tributylamine) and the effect of the particle size of the carbon

D. Aurbach; B. Markovsky; A. Schechter; Y. Ein-Eli; H. Cohen

1996-01-01

305

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

Microsoft Academic Search

Cellulose carbonate was prepared by the reaction of cellulose pulp and CO2 with treatment reagents, such as aqueous ZnCl2 (20–40 wt%) solution, acetone or ethyl acetate, at ?5–0°C and 30–40 bar (CO2) for 2 hr. Among the treatment reagents, ethyl acetate was the most effective. Cellulose carbonate was dissolved in 10% sodium\\u000a hydroxide solution containing zinc oxide up to 3

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

2002-01-01

306

Silver electrocrystallization on vitreous carbon from ammonium hydroxide solutions  

SciTech Connect

Leaching baths with ammonia as a complexing agent offer a good alternative for precious metal (e.g., silver) recovery, since the environmental impact of these kind of leaching baths is considerably lower than the traditional cyanidation. The early stages of the electrolytic deposition of silver onto vitreous carbon electrodes from ammonium hydroxide solutions have been investigated by the potential step technique. The analysis of the experimental current transients according to existing theories indicates that this process occurs by multiple three-dimensional nucleation, followed by diffusion controlled growth of nuclei. It is shown that treatments that involve classifying the process as either instantaneous or progressive nucleation are not always adequate for the quantitative analysis of electrochemical nucleation phenomena. The nucleation kinetics parameters A (nucleation rate constant per site) and No (number density of active sites on the substrate surface) were estimated separately from the current transient maxima by two different approaches. Both quantities were found to vary with the potential and with the concentration of silver ions, except at very high overpotentials for silver deposition. The potential dependence of the nucleation rate A was interpreted according to the atomistic theory and in all cases it was found that the number of atoms in the critical nucleus (n{sub k}) was one over the entire potential range analyzed.

Palomar-Pardave, M.; Ramirez, M.T.; Gonzalez, I. [Univ. Autonoma Metropolitana-Iztapalapa (Mexico). Dept. de Quimica; Serruya, A.; Scharifker, B.R. [Univ. Simon Bolivar, Caracas (Venezuela). Dept. de Quimica

1996-05-01

307

Carbon flux and fatty acid synthesis in plants.  

PubMed

The de novo synthesis of fatty acids in plants occurs in the plastids through the activity of fatty acid synthetase. The synthesis of the malonyl-coenzyme A that is required for acyl-chain elongation requires the import of metabolites from the cytosol and their subsequent metabolism. Early studies had implicated acetate as the carbon source for plastidial fatty acid synthesis but more recent experiments have provided data that argue against this. A range of cytosolic metabolites including glucose 6-phosphate, malate, phosphoenolpyruvate and pyruvate support high rates of fatty acid synthesis by isolated plastids, the relative utilisation of which depends upon the plant species and the organ from which the plastids are isolated. The import of these metabolites occurs via specific transporters on the plastid envelope and recent advances in the understanding of the role of these transporters are discussed. Chloroplasts are able to generate the reducing power and ATP required for fatty acid synthesis by capture of light energy in the reactions of photosynthetic electron transport. Regulation of chloroplast fatty acid synthesis is mediated by the response of acetyl-CoA carboxylase to the redox state of the plastid, which ensures that the carbon metabolism is linked to the energy status. The regulation of fatty acid synthesis in plastids of heterotrophic cells is much less well understood and is of particular interest in the tissues that accumulate large amounts of the storage oil, triacylglycerol. In these heterotrophic cells the plastids import ATP and oxidise imported carbon sources to produce the required reducing power. The sequencing of the genome of Arabidopsis thaliana has now enabled a number of aspects of plant fatty acid synthesis to be re-addressed, particularly those areas in which in vitro biochemical analysis had provided equivocal answers. Examples of such aspects and future opportunities for our understanding of plant fatty acid synthesis are presented and discussed. PMID:11755683

Rawsthorne, Stephen

2002-03-01

308

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

NASA Astrophysics Data System (ADS)

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

Stefánsson, Andri; Bénézeth, Pascale; Schott, Jacques

2013-11-01

309

Laccase-catalyzed carbon–carbon bond formation: oxidative dimerization of salicylic esters by air in aqueous solution  

Microsoft Academic Search

The laccase catalyzed oxidative dimerization of salicylic esters, a rare example of a laccase-catalyzed carbon–carbon bond formation, was studied. This reaction allows the use of air as stoichiometric oxidant and proceeds in aqueous solution. The preparative scope and the mechanism of the method, which provides a new and convenient access to functionalized biaryls under mild conditions, were investigated.

Sabine Ciecholewski; Elke Hammer; Katrin Manda; Gopal Bose; Van T. H. Nguyen; Peter Langer; Frieder Schauer

2005-01-01

310

Electrochemical properties of a tetrabromo- p-benzoquinone modified carbon paste electrode. Application to the simultaneous determination of ascorbic acid, dopamine and uric acid  

Microsoft Academic Search

The electrochemical study of a tetrabromo-p-benzoquinone modified carbon paste electrode (TBQ-MCPE), as well as its efficiency for electrocatalytic oxidation of ascorbic acid, dopamine and uric acid, is described. Cyclic voltammetry was used to investigate the redox properties of this modified electrode at various solution pH values and at various scan rates. Three linear segments were found with slope values of

H. R. Zare; N. Nasirizadeh; M. Mazloum Ardakani

2005-01-01

311

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

Microsoft Academic Search

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

Jeom-In Baek; Ji-Ho Yoon

1998-01-01

312

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

Microsoft Academic Search

Arundo donax root carbon (ADRC), a new adsorbent, was prepared from Arundo donax root by carbonization. The surface area of the adsorbent was determined 158m2\\/g by N2 adsorption isotherm. Batch adsorption experiments were carried out for the removal of malachite green (MG) from aqueous solution using ADRC as adsorbent. The effects of various parameters such as solution pH (3–10), carbon

Jian Zhang; Yan Li; Chenglu Zhang; Yuming Jing

2008-01-01

313

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

SciTech Connect

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

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

1998-07-01

314

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

315

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

USGS Publications Warehouse

Photolysis of mono and di-carboxylic acids that are adsorbed onto the surface of the iron oxyhydroxide (goethite) results in an oxidation of the organic material and a reduction from Fe(III) to Fe(II) in the iron complex. There is a subsequent release of Fe2+ ions into solution. At constant light flux and constant solution light absorption, the factors responsible for the degree of photolytic reaction include: the number of lattice sites that are bonded by the organic acid; the rate of acid readsorption to the surface during photolysis; the conformation and structure of the organic acid; the degree of oxidation of the organic acid; the presence or absence of an ??-hydroxy group on the acid, the number of carbons in the di-acid chain and the conformation of the di-acid. The ability to liberate Fe(III) at pH 6.5 from the geothite lattice is described by the lyotropic series: tartrate>citrate> oxalate > glycolate > maleate > succinate > formate > fumarate > malonate > glutarate > benzoate = butanoate = control. Although a larger amount of iron is liberated, the series is almost the same at pH 5.5 except that oxalate > citrate and succinate > maleate. A set of rate equations are given that describe the release of iron from the goethite lattice. It was observed that the pH of the solution increases during photolysis if the solutions are not buffered. There is evidence to suggest the primary mechanism for all these reactions is an electron transfer from the organic ligand to the Fe(III) in the complex. Of all the iron-oxyhydroxide materials, crystalline goethite is the least soluble in water; yet, this study indicates that in an aqueous suspension, iron can be liberated from the goethite lattice. Further, it has been shown that photolysis can occur in a multiphase system at the sediment- water interface which results in an oxidation of the organic species and release of Fe2+ to solution where it becomes available for further reaction. ?? 1993.

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

1993-01-01

316

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

317

The effect of phosphonic acid substituents on europium(III) complex stability in acidic solutions  

SciTech Connect

The thermodynamics of protonation and europium(III) complex formation with substituted methane diphosphonic acids have been reported recently. These ligands form strong complexes with europium in moderately acidic solutions ((H{sup +}) {ge} 0.1 M), conditions not conducive to complexation by most carboxylate and aminopolycarboxylate ligands. A correlation of log {beta} vs pK{sub a} values for phosphonate and carboxylate ligands is used to explore the effect of ligand structure on complex stability. 5 refs., 1 fig.

Nash, K.L.

1990-01-01

318

Stoichiometric relation for extraction of zirconium and hafnium from acidic chloride solutions with Versatic Acid 10  

Microsoft Academic Search

The stoichiometric relation for the extraction of zirconium and hafnium from acidic chloride solutions was investigated with Versatic Acid 10. Extraction runs were carried out batchwise at ambient temperature in the pH range from 1.4 to 2.3 for zirconium and from 2.3 to 2.9 for hafnium. The results showed that zirconium was extracted in the form of ZrO2+ rather than

Hwa Young Lee; Sung Gyu Kim; Jong Kee Oh

2004-01-01

319

Speciation of platinum(IV) in nitric acid solutions.  

PubMed

The speciation of platinum(IV) ions in nitric acid (6-15.8 M) solutions of H2[Pt(OH)6] has been studied by (195)Pt NMR and Raman spectroscopy. Series of aqua-hydroxo-nitrato complexes [Pt(L)(x)(NO3)(6-x)] (L = H2O or OH(-); x = 0,?..., 6) were found to exist in such solutions. The pair additivity model of chemical shifts and statistical theory were used to assign signals in NMR spectra to particular [Pt(L)(x)(NO3)(6-x)] species. Mononuclear hexanitratoplatinates(IV) have been isolated in solid state in substantial yield as pyridinium salt (PyH)2[Pt(NO3)6] and characterized by single-crystal X-ray diffraction. Aging of the platinum nitric acid solutions for more than 5-6 h results in oligomerization of [Pt(L)(x)(NO3)(6-x)] species and the formation of oligonuclear aqua-hydroxo-nitrato complexes with OH(-) and NO3(-) bridging ligands. Oligomeric platinum(IV) complexes with two and four nuclei were unambiguously detected by NMR on (195)Pt -enriched samples. Oligomers with even higher nuclearity were also detected. Dimeric anions [Pt2(?-OH)2(NO3)8](2-) have been isolated as single crystals of tetramethylammonium salt and characterized by X-ray diffraction. PMID:23978261

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

2013-08-26

320

Standard Addition Method for Free Acid Determination in Solutions with Hydrolyzable Ions.  

National Technical Information Service (NTIS)

The free acid content of solutions containing hydrolyzable ions has been determined potentiometrically by a standard addition method. Two increments of acid are added to the sample in a 1M potassium thiocyanate solution. The sample concentration is calcul...

E. W. Baumann

1981-01-01

321

Sorption of lanthanum and erbium from aqueous solution by activated carbon prepared from rice husk.  

PubMed

A biomass agricultural waste material, rice husk (RH) was used for preparation of activated carbon by chemical activation using phosphoric acid. The effect of various factors, e.g. time, pH, initial concentration and temperature of carbon on the adsorption capacity of lanthanum and erbium was quantitatively determined. It was found that the monolayer capacity is 175.4 mg g(-1) for La(III) and 250 mg g(-1) for Er(III). The calculated activation energy of La(III) adsorption on the activated carbon derived from rice husk was equal to 5.84 kJ/mol while it was 3.6 kJ/mol for Er(III), which confirm that the reaction is mainly particle-diffusion-controlled. The kinetics of sorption was described by a model of a pseudo-second-order. External diffusion and intra-particular diffusion were examined. The experimental data show that the external diffusion and intra-particular diffusion are significant in the determination of the sorption rate. Therefore, the developed sorbent is considered as a better replacement technology for removal of La(III) and Er(III) ions from aqueous solution due to its low-cost and good efficiency, fast kinetics, as well as easy to handle and thus no or small amount of secondary sludge is obtained in this application. PMID:20800456

Awwad, N S; Gad, H M H; Ahmad, M I; Aly, H F

2010-08-10

322

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

PubMed Central

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

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

2013-01-01

323

Adsorption of phenol and reactive dye from aqueous solution on activated carbons derived from solid wastes  

Microsoft Academic Search

Activated carbons were produced from several solid wastes, namely, waste PET, waste tires, refuse derived fuel and wastes generated during lactic acid fermentation from garbage. Activated carbons having various pore size distributions were obtained by the conventional steam-activation method and via the pre-treatment method (i.e., mixture of raw materials with a metal salt, carbonization and acid treatment prior to steam-activation)

Kyuya Nakagawa; Akio Namba; Shin R Mukai; Hajime Tamon; Pisit Ariyadejwanich; Wiwut Tanthapanichakoon

2004-01-01

324

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

Microsoft Academic Search

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

D. Aurbach; A. Zaban

1995-01-01

325

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

326

Controlled exposures of volunteers to respirable carbon and sulfuric acid aerosols  

SciTech Connect

Respirable carbon or fly ash particles are suspected to increase the respiratory toxicity of coexisting acidic air pollutants, by concentrating acid on their surfaces and so delivering it efficiently to the lower respiratory tract. To investigate this issue, the authors exposed 15 healthy and 15 asthmatic volunteers in a controlled-environment chamber to four test atmospheres: (1) clean air; (2) 0.5-{mu}m H{sub 2}SO{sub 4} aerosol at {approx}100 {mu}g/m{sup 3}, generated from water solution; (3) 0.5-{mu}m carbon aerosol at {approx}250 {mu}g/m{sup 3}, generated from highly pure carbon black with specific surface area comparable to ambient pollution particles; and (4) carbon as in (3) plus {approx}100 {mu}g/m{sup 3} of ultrafine H{sub 2}SO{sub 4} aerosol generated from fuming sulfuric acid. Electron microscopy showed that nearly all acid in (4) became attached to carbon particle surfaces, and that most particles remained in the sub-{mu}m size range. Exposures were performed double-blind, 1 week apart. They lasted 1 hr each, with alternate 10-min periods of heavy exercise (ventilation {approx}50 L/min) and rest. Subjects gargled citrus juice before exposure to suppress airway ammonia. Lung function and symptoms were measured pre-exposure, after initial exercise, and at end-exposure. Bronchial reactivity to methacholine was measured after exposure. Statistical analyses tested for effects of H{sub 2}SO{sub 4} or carbon, separate or interactive, on health measures.

Anderson, K.R.; Avol, E.L.; Edwards, S.A.; Shamoo, D.A.; Ruchuan Peng; Linn, W.S.; Hackney, J.D. (Univ. of Southern California, Downey (United States))

1992-06-01

327

Flow injection analysis of ascorbic acid based on its thermoelectrochemistry at disposable screen-printed carbon electrodes  

Microsoft Academic Search

The thermoelectrochemistry of ascorbic acid (AA) at a disposable screen-printed carbon electrode (SPE) was studied in this paper. The response of AA is greatly suppressed at higher temperatures when the electrolyte solution containing AA is directly heated. On the other hand, as a light beam is applied to heat an SPE, it is interesting that the heated electrode is capable

Jyh-Harng Ke; Hsiao-Jing Tseng; Cheng-Teng Hsu; Jyh-Cheng Chen; Govindan Muthuraman; Jyh-Myng Zen

2008-01-01

328

Catalytic Reduction of Np(VI,V) with Formic Acid in Perchloric Acid Solutions  

Microsoft Academic Search

Neptunium(VI) is successively reduced with formic acid to Np(V) and Np(IV) in perchloric acid solutions in the presence of 1% Pt\\/SiO2 catalyst. The kinetic features of Np(VI,V) reduction with formic acid in 0.1-4.0 M HClO4 in the presence of 0.01-0.1 g ml-1 of 1% Pt\\/SiO2 at [HCOOH] = 0.001-1.0 M and T = 40-70°C were studied. The rate-determining steps of

A. V. Anan'ev; V. P. Shilov

2001-01-01

329

The reciprocal influence between ion transport and degradation of PA66 in acid solution  

Microsoft Academic Search

Transport behavior of acid solution through polyamide was studied by measuring element distribution in cross section, pH, and ion concentration. Degree of degradation that related to the decreasing of molecular weight and flexural strength was observed in order to study the influence of acid solution on the polyamide 66 (PA66) degradation. The permeation mechanism of acid solution can be explained:

Abastari; T. Sakai; H. Sembokuya; M. Kubouchi; K. Tsuda

2006-01-01

330

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

331

Nitric acid in dichloromethane solution. Facile preparation from potassium nitrate and sulfuric acid  

Microsoft Academic Search

Pure dry HNO3 can be liberated from KNO3 with 96% H2SO4 directly into CH2Cl2 to yield solutions of variable concentration for use in a number of organic reactions. The present method efficiently replaces the employment of 100% HNO3 in some synthetic applications, avoiding the problems associated in storage and handling the acid.

Paolo Strazzolini; Angelo G Giumanini; Antonio Runcio

2001-01-01

332

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

333

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

Microsoft Academic Search

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

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

2012-01-01

334

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

335

Effect of Carbon4 and Carbon5 Volatile Fatty Acids on Digestion of Plant Cell Wall In Vitro1  

Microsoft Academic Search

When mixed ruminal bacteria were incubated in an artificial medium with isolated plant cell wails, cell wall diges- tion and ammonia utilization were increased by low concentrations (< .30 mM) of carbon-4 and carbon-5 volatile fatty acids (isobutyric, isovaleric, valeric, and 2-methylbutyric). Carbon-4 and carbon-5 acid supplementation also in- creased cell wall digestion of intact forages. No pattern was observed

A. R. Gorosito; J. B. Russell; P. J. Van Soest

1985-01-01

336

Influence of vegetation on low-molecular-weight carboxylic acids in soil solution—a review  

Microsoft Academic Search

Low-molecular-weight (LMW) carboxylic acids found in soils and soil solutions comprise mainly aliphatic mono-, di- and tricarboxylic acids and substituted benzoic and cinnamic acids. This review compiles current information on the content of LMW carboxylic acids in soil solutions collected by centrifugation and in lysimeters, and soil extracts in relation to type of vegetation, soil type and soil depth. Contents

Bjarne W Strobel

2001-01-01

337

Kinetics of the reductive reextraction of neptunium in the TBP-carbon tetrachloride-water-nitric acid-hydroxylamine system  

SciTech Connect

This paper studies the reextraction of neptunium in the TBP-carbon tetrachloride-water-nitric acid-hydroxylamine system. The experiments were carried out in an extractor with a fixed interfacial surface regardless of mixing and in a MTsE-30-1 small-scale one step centrifugal extractor. Changes are shown in neptunium concentration in the aqueous phase upon reextraction with a nitric acid solution of hydroxylamine in the extractor with the fixed interphase surface.

Pushlenko, M.F.; Lyakin, V.V.; Tikhonov, N.S.; Titov, S.L.; Yasnovitskaya, A.L.

1986-03-01

338

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

339

Reduction of hexavalent chromium by ascorbic acid in aqueous solutions.  

PubMed

Hexavalent chromium is a priority pollutant in the USA and many other countries. Reduction of Cr(VI) to Cr(III) is environmentally favorable as the latter species is not toxic to most living organisms and also has a low mobility and bioavailability. Reduction of Cr(VI) by ascorbic acid (vitamin C) as a reductant was studied using potassium dichromate solution as the model pollutant. Effects of concentration of vitamin C, pH, temperature, irradiation and reaction time on the reduction of Cr(VI) were examined. Cr(VI) might be reduced by vitamin C not only in acidic conditions but also in weakly alkaline solutions. The reduction of Cr(VI) by vitamin C might occur not only under irradiation but also in the dark. Vitamin C is an important biological reductant in humans and animals, and not toxic. It is water-soluble and can easily permeate through various types of soils. The results indicate that vitamin C could be used in effective remediation of Cr(VI)-contaminated soils and groundwater in a wide range of pH, with or without sunlight. PMID:15488923

Xu, Xiang-Rong; Li, Hua-Bin; Li, Xiao-Yan; Gu, Ji-Dong

2004-11-01

340

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

341

The Solar Nebula on Fire: A Solution to the Carbon Deficit in the Inner Solar System  

NASA Astrophysics Data System (ADS)

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; Bergin, Edwin A.; Nomura, Hideko

2010-02-01

342

Dissolution rates of carbonated hydroxyapatite in hydrochloric acid.  

PubMed

Osteoclasts have been shown to dissolve efficiently and effectively the mineral phase of bone by locally controlling the environment surrounding the cell. Although this mineral phase has been identified and well characterized as carbonated hydroxyapatite, there is little understanding of the factors that affect the dissolution properties of this mineral phase. Mimicking the mechanism by which osteoclasts dissolve the mineral phase of bone may provide insight into methods for the decalcification of atherosclerotic mineral deposits in the vascular system. Accordingly, a detailed characterization of the effects of various chemical and mechanical parameters on the dissolution of carbonated hydroxyapatite mineral was investigated in this study. Increases in the mineral dissolution rate (2-10 times) were associated with increases in dissolving solution [H+], osmolality, temperature, and flow rate. Mineral dissolution rate increases (5-8 times) were associated with greater surface area of the mineral and mechanical agitation of the dissolving solution. PMID:11771694

Hankermeyer, Christine R; Ohashi, Kevin L; Delaney, David C; Ross, John; Constantz, Brent R

2002-02-01

343

Solubility of carbon dioxide in aqueous solutions of 2-amino-2-ethyl-1,3-propanediol  

Microsoft Academic Search

The solubilities of carbon dioxide in aqueous solutions of 2-amino-2-ethyl-1,3-propanediol (AEPD) were measured at 313.15, 323.15, and 333.15K over the partial pressure range of carbon dioxide from 1 to 3000kPa. The concentrations of aqueous AEPD solutions were 10 and 30mass%. The solubilities of carbon dioxide in aqueous 10mass% AEPD solutions at 313.15K and 30mass% at 333.15K were compared with those

Jung-Yeon Park; Sang Jun Yoon; Huen Lee; Ji-Ho Yoon; Jae-Goo Shim; Jae Keun Lee; Byung-Yeon Min; Hee-Moon Eum; Min Cheol Kang

2002-01-01

344

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

PubMed

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

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

2013-03-23

345

Electrophoretic deposition of phthalocyanine in organic solutions containing trifluoroacetic acid.  

PubMed

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

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

2010-10-01

346

Corrosion behavior of mild steel in acetic acid solutions  

SciTech Connect

The corrosion behavior of mild steel in acetic acid (CH{sub 3}COOH) solutions was studied by weight loss and potentiostatic polarization techniques. The variation in corrosion rate of mild steel with concentrations of CH{sub 3}COOH, evaluated by weight loss and electrochemical techniques, showed marked resemblance. From both techniques, the maximum corrosion rate was observed for 20% CH{sub 3}COOH solution at all three experimental temperatures (25, 35, and 45 C). Anodic polarization curves showed active-passive behavior at each concentration, except at 80% CH{sub 3}COOH. Critical current density (i{sub c}) passive current density (I{sub n}), primary passivation potential (E{sub pp}), and potential for passivity (E{sub p}) had their highest values in 20% CH{sub 3}COOH solution. With an increase in temperature, while the anodic polarization curves shifted toward higher current density region at each concentration, the passive region became progressively less distinguishable. With the addition of sodium acetate (NaCOOCH{sub 3}) as a supporting electrolyte, the passive range was enlarged substantially. However, the transpassive region commenced at more or less the same potential. Cathodic polarization curves were almost identical irrespective of the concentration of CH{sub 3}COOH or temperature.

Singh, M.M.; Gupta, A.

2000-04-01

347

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

Microsoft Academic Search

SO3H-bearing amorphous carbon, prepared by partial carbonization of cellulose followed by sulfonation in fuming H2SO4, was applied as a solid catalyst for the acid-catalyzed hydrolysis of ?-1,4 glucan, including cellobiose and crystalline cellulose. Structural analyses revealed that the resulting carbon material consists of graphene sheets with 1.5 mmol g?1 of SO3H groups, 0.4 mmol g?1 of COOH, and 5.6 mmol g?1 of phenolic OH groups. The

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

2010-01-01

348

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.

Szarek, Stan R.; Troughton, John H.

1976-01-01

349

Studies on the recovery of Pu(IV) from hydrochloric acid-oxalic acid solutions using an anion exchange method  

Microsoft Academic Search

Sorption of Pu(IV) from hydrochloric acid-oxalic acid solutions has been investigated using different anion exchangers, viz., Dowex-1X4, Amberlite XE-270 (MP) and Amberlyst A-26 (MP) for the recovery of plutonium from plutonium oxalate solutions. Distribution ratios of Pu(IV) for its sorption on these anion exchangers have been determined. The sorption of Pu(IV) from hydrochloric acid solutions decreases drastically in the presence

D. R. Ghadse; D. M. Noronha; I. C. Pius; M. M. Charyulu; A. R. Joshi; C. K. Sivaramakrishnan

1996-01-01

350

Optimization of peroxynitrite-luminol chemiluminescence system for detecting peroxynitrite in cell culture solution exposed to carbon disulphide.  

PubMed

We established a peroxynitrite-luminol chemiluminescence system for detecting peroxynitrite in cell culture solution exposed to carbon disulphide (CS(2)). Three factors, including exposure time to ozone (Factor A), volume of peroxynitrite (ONOO(-)) solution (Factor B) and luminol concentrations (Factor C) at three levels were selected and the combinations were in accordance with orthogonal design L(9) (3(4)). Peroxynitrite was generated from the reaction of ozone and 0.01 mol/L sodium azide (NaN(3)) dissolved in carbonic acid buffer solution (pH 11), and it was reacted with luminol to yield chemiluminescence. The peak value, peak time and kinetic curve of the light emission were observed. The selected combination conditions were 50 s ozone, 800 micro L peroxynitrite and 0.001 mol/L luminol solution. Cell culture solution with CS(2) enhanced the emission intensity of chemiluminescence (F = 8.38, p = 0.018) and shortened the peak time to chemiluminescence (F = 139.00, p = 0.0001). The data demonstrated that this luminol chemiluminescence system is suitable for detecting peroxynitrite in cell culture solutions for evaluating the effect of CS(2) on endothelial cells. PMID:14587075

Chen, Shao L; Jian, Le; Lang, Hui Q

351

Activated carbon passes tests for acid-gas cleanup  

Microsoft Academic Search

Use of activated carbon to remove hydrocarbon contaminants from the acid-gas feed to Claus sulfur-recovery units has been successfully pilot tested in Saudi Arabia. Pilot plant results are discussed here along with issues involved in scale-up to commercial size. Heavy hydrocarbons, particularly benzene, toluene, and xylene (BTX) have been linked to coke formation and catalyst deactivation in Claus converters. This

L. G. Harruff; S. J. Bushkuhl

1996-01-01

352

Nitric acid oxidation of vapor grown carbon nanofibers  

Microsoft Academic Search

Vapor grown carbon nanofibers (Pyrograf III™) with 100–300 nm diameters and ?10–100 ?m lengths were oxidized in 69–71 wt.% nitric acid (115 °C) for various times (10 min to 24 h). These fibers were remarkably oxidation-resistant. XPS (O1s) showed that the surface atomic oxygen percent increased from 6.3 to 18.3–22.5% for 10–90 min oxidations followed by a drop to 14–15%

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

2004-01-01

353

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

SciTech Connect

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

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

1996-12-31

354

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

PubMed

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

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

2012-12-20

355

Selective esterification of non-conjugated carboxylic acids in the presence of conjugated or aromatic carboxylic acids over active carbon supported methanesulfonic acid  

Microsoft Academic Search

Non-conjugated carboxylic acids are selectively esterified in good yields in the presence of conjugated or aromatic carboxylic\\u000a acids by stirring over active carbon supported methanesulfonic acid in dichloromethane at room temperature.

ZeWang Feng; XinQi Zhao; Hua Bi

2008-01-01

356

Carbonate-modified siloxanes as solvents of electrolyte solutions for rechargeable lithium cells  

Microsoft Academic Search

Influence of mixing carbonate-modified siloxanes into LiPF6-ethylene carbonate (EC)\\/ethylmethyl carbonate (EMC) (mixing volume ratio=3:7) mixed solvent electrolytes on charge–discharge cycling properties of lithium was examined. As the solute, 1M (M: molL?1) LiPF6 was used. As siloxanes, 4-(2-trimethylsilyloxydimethylsilylethyl)-1,3-dioxolan-2-one and 4-(2-bis(trimethylsilyloxy)methylsilylethyl)-1,3-dioxolan-2-one were investigated. These siloxanes are derivatives of butylene cyclic carbonate or vinyl ethylene carbonate. Charge–discharge cycling efficiencies of lithium metal anodes

Takashi Takeuchi; Satoshi Noguchi; Hideyuki Morimoto; Shin-ichi Tobishima

2010-01-01

357

UV picosecond laser-induced formation of amino acids from aqueous solutions of ammonic salts of dicarboxylic acids  

NASA Astrophysics Data System (ADS)

It is shown for the first time that the irradiation of the ammonic-salt aqueous solutions of the dicarboxylic acids by powerful ultrashort uv pulses provokes the formation of the related amino acids. The amino-acid quantum yield depends on the intensity and for the aspartic acid, in particular, it reaches 40% at the intensity of about 1 GW/cm2.

Letokhov, V. S.; Matveetz, Yu. A.; Semchishen, V. A.; Khoroshilova, E. V.

1981-12-01

358

Interaction of Aqueous Solutions of Chlorine with Malic Acid, Tartaric Acid, and Various Fruit Juices. A Source of Mutagens.  

National Technical Information Service (NTIS)

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

T. L. Chang R. P. Streicher H. Zimmer

1988-01-01

359

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

360

Catalytic Reduction of Pu(IV) with Formic Acid in Nitric Acid Solutions  

Microsoft Academic Search

Pu(IV) is reduced to Pu(III) in nitric acid solutions with formic acid in the presence of urea and 1% Pt\\/SiO2 catalyst. The kinetics of reduction were studied in 0.3-2.3 M HNO3 containing 0.2-1 M HCOOH, 0.1-0.5 M (NH2)2CO, and 0.01-0.1 g ml-1 of 1% Pt\\/SiO2 at 30-60°C. At HNO3 concentration higher than 2 M, the Pu(IV) reduction is reversible because

A. V. Anan'ev; V. P. Shilov

2004-01-01

361

Determination of Free Base in Aluminate-Carbonate Solutions by Standard Addition Method.  

National Technical Information Service (NTIS)

Alkaline waste solutions from the 200-Area separations processes are analyzed for sodium hydroxide, sodium aluminate, and sodium carbonate by a complicated titration procedure that requires about two hours. Frequently, however, only the sodium hydroxide c...

E. W. Baumann

1983-01-01

362

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

363

Hydrolytic decarboxylation of carboxylic acids and the formation of protonated carbonic acid.  

PubMed

Acid-catalyzed decarboxylation reactions of carboxylic acids should avoid formation of protonated carbon dioxide, a very high energy species. A potential alternative route parallels ester hydrolysis, with addition of water to the carboxyl group followed by protonation of the unsaturated leaving group and formation of protonated carbonic acid, a species that had been predicted to be a viable reaction intermediate. The hydrolytic mechanism for the decarboxylation of pyrrole-2-carboxylic acid is consistent with observed (12)C/(13)C kinetic isotope effects (1.010 +/- 0.001 at H(0) = -0.01 and 1.043 +/- 0.001 at H(0) = -2.6), solvent kinetic isotope effects (k(H(2))(O)/k(D(2))(O) = 2 at H(0) = 0.9; k(H(2))(O)/k(D(2))(O) = 1 at H(0) = -2.9), and activation parameters [DeltaH() = 23.5 kcal.mol(-1) and DeltaS() = 5.5 cal.deg(-1).mol(-1) at H(0) = -2.9]. Thus, the specific route for a decarboxylation process is a consequence of the nature of the potential carbanion (or its conjugate acid), the acidity of the medium and avoidance of formation of protonated carbon dioxide. PMID:20121187

Mundle, Scott O C; Lacrampe-Couloume, Georges; Lollar, Barbara Sherwood; Kluger, Ronald

2010-02-24

364

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 CaCO3 crystal obviously depends on the starting pH. CaCO3 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

365

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

366

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

NASA Astrophysics Data System (ADS)

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

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

2006-05-01

367

Americium and europium extraction from carbonate solutions by 1-phenyl-3-methyl-4-benzoylpyrazolone -5  

Microsoft Academic Search

Trivalent TPEs and REEs are extractable from carbonate solutions by 1-pheny-3-methyl-4-benzoylpyrazolone-5 (PMBP). The effect of concentration of KHCOâ and KâCOâ, extractant, metal, and other factors on the extent of extraction of the elements has been clarified. The kinetics of extraction of the elements from carbonate solutions has been studied. It has been shown that in the KHCOâ concentration range 0.2-2.0

Z. K. Karalova; Deviris E. A; L. A. Fedorov; B. F. Myasoedov; M. S. Rukov

1986-01-01

368

Use of activated carbon in removal of some radioisotopes from their waste solutions  

Microsoft Academic Search

Removal of some radioisotopes namely (152+154)Eu and 65Zn from radioactive solutions by activated carbon using both batch and column techniques has been performed. Experimental studies were conducted to evaluate and optimize the various process variables, i.e., equilibrium time, carbon dose, solution pH. Sorption data have been interpreted in terms of both Freündlich and Langmuir isotherms. The fixed-bed results indicate the

H. A. Omar; H. Moloukhia

2008-01-01

369

Electrochemical properties of Zn\\/orange dye aqueous solution\\/carbon cell  

Microsoft Academic Search

An investigation is made of the electrochemical properties of a Zn\\/orange dye aqueous solution\\/carbon cell. In this cell, a solution of 3wt.% orange dye (C17H17N5O2) in distilled water is used as the electrolyte and zinc and carbon rods serve as electrodes. The cell is fabricated in a cylindrical glass vessel and has a length and a diameter of 4 and

Khasan S. Karimov; Muhammad H. Sayyad; Mukhtar Ali; Muhammad N. Khan; Syed A. Moiz; Khurram B. Khan; Humera Farah; Zioda M. Karieva

2006-01-01

370

Effect of surface state of carbon fiber electrode on copper electroplating from sulfate solutions  

Microsoft Academic Search

The effect of the fiber surface state of a carbon fiber fabric on the parameters of copper electro-plating from a sulfate\\u000a solution (the copper current efficiency, the electroplating rate, and the deposit distribution in the depth of electrode)\\u000a is studied. The surface state of fibers was changed by preliminarily polarizing the carbon fiber fabric in electrolyte solutions.\\u000a The change in

V. I. Varentsova; V. K. Varenstov; I. A. Bataev; S. I. Yusin

2011-01-01

371

Anodic polarization behavior of low-carbon steel in concentrated sodium hydroxide and sodium nitrate solutions  

Microsoft Academic Search

High-level radioactive wastes, primarily consisting of concentrated sodium hydroxide (NaOH) and sodium nitrate (NaNO3) solutions, are stored in large underground storage tanks made of low-carbon steel. The anodic polarization behavior of low-carbon steel in concentrated solutions of 10M NaOH and various concentrations of NaNO3 (0.01–2.0M) was determined in order to predict the caustic stress corrosion cracking (CSCC) susceptibility of the

Karthik Subramanian; John Mickalonis

2005-01-01

372

Reduction of patulin in aqueous solution by lactic acid bacteria.  

PubMed

This study aims to investigate the ability of lactic acid bacteria (LAB) to remove patulin (PAT) from aqueous solution with respect to the bacterial viability, initial PAT concentration, incubation time, temperature, and pH. The removal of PAT determined by high-performance liquid chromatography (HPLC) coupled with UV detector. The maximum PAT uptake was achieved by Bifidobacterium bifidum 6071 and Lactobacillus rhamnosus 6149 strains (52.9% and 51.1%) for viable and (54.1% and 52.0%) for nonviable cells after 24 h incubation. The highest removal of PAT was at pH 4.0 and 37 °C and increased with decreasing of toxin levels. The removal ability of selected strains could represent new strategies for a possible application in contaminated food products and animal feed. PMID:22394296

Hatab, Shaimaa; Yue, Tianli; Mohamad, Osama

2012-03-06

373

Coprecipitation of radium with calcium and strontium from acid solutions using crown ether and tungstosilicic acid  

Microsoft Academic Search

The coprecipitation of radium with strontium or calcium, 18C6 and tungstosilicic acid was studied. It was determined that radium is coprecipitated with Ca and Sr and mixed compounds are fomed. It was also find the yield of Ra depends on the ratio of stability constants of metals present in a solution with 18C6. The stability constant of Ra with 18C6

P. Rajec; V. Mikulaj; P. Husar?ik; V. Švec

1997-01-01

374

Catalytic reduction of U(VI) with formic acid in acid solutions on palladium catalysts  

Microsoft Academic Search

The kinetics of catalytic reduction of U(VI) with formic acid in H2SO4 solutions in the presence of Pd\\/SiO2 catalysts differing in the size of nanocrystallites of the active metal was studied. A decrease in the size of supported\\u000a Pd particles leads to a decrease in the specific activity of the catalyst, i.e., the catalytic centers located on large crystallites\\u000a exhibit

M. Yu. Boltoeva; V. P. Shilov; A. V. Anan’ev

2008-01-01

375

Adsorption of boron from aqueous solutions using activated carbon prepared from olive bagasse  

Microsoft Academic Search

In this study, activated carbon was prepared from olive bagasse by physical activation. The pore properties including the BET surface area, pore volume, pore size distribution and average pore diameter were characterized. BET surface area of the activated carbon was determined as 803 mg. In this study, boron removal from aqueous solutions by adsorption was investigated. In the batch mode

T. Ennil Köse; Hakan Demiral; Ne?e Öztürk

2011-01-01

376

Irreversible and reversible adsorption of some heavy transition metals on graphitic carbons from dilute aqueous solutions  

Microsoft Academic Search

The adsorption of various heavy transition metal compounds was studied using two different flow adsorption methodologies: flow injection adsorption and flow equilibrium adsorption analyses. In both cases the determinations were made of the heats of adsorption and the amounts of adsorption from dilute aqueous solutions.The carbons used for the work included two different types of graphitised carbon black and active

A. J. Groszek

1997-01-01

377

Simple Method for Simultaneous Determination of Carbonate, Sulfite and Hydroxide in Solution  

NASA Astrophysics Data System (ADS)

A method is proposed for the simultaneous determination of carbon dioxide and sulphur dioxide in a complex matrices. The method involves salvation of the tow gases in Sodium Hydroxide solution followed by simultaneous determination of the three species (carbonate, sulfite and hydroxide) using conductometric and potentiometric titration. What set this method apart from other determination methods it`s simplicity.

Al-Itawi, Hossam I.; Al-Ebaisat, Hamdan; Al-Garaleh, Mazen

378

Removal of copper (II) and phenol from aqueous solution using porous carbons derived from hydrothermal chars  

Microsoft Academic Search

The feasibility of hydrothermal char (HTC), a byproduct from biomass hydrothermal liquefaction for bio-oil production, as raw material for preparation of porous carbons was investigated in the present study. The resultant HTC-derived porous carbons were characterized and utilized as adsorbents for copper (II) and phenol removal from aqueous solution. Compared with porous carbons using pyrolytic char as precursor, the HTC-derived

Zhengang Liu; Fu-Shen Zhang

2011-01-01

379

ESR study of 13 C-enriched carbonated calciumapatites precipitated from aqueous solutions  

Microsoft Academic Search

The ESR spectrum of X-irradiated carbonated apatites precipitated from aqueous solutions was studied at carbonate contents ranging from approximately 5.4 up to 12.4 wt%. 12C- as well as 13C-enriched samples were prepared and examined with ESR after drying until constant weight at 25°C and 400°C. In these carbonated apatites, two CO33- radicals were detected, one of which is derived from

F. J. Callens; R. M. H. Verbeeck; D. E. Naessens; P. F. A. Matthys; E. R. Boesman

1993-01-01

380

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

DOEpatents

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

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

1957-09-24

381

Fate of Aliphatic Compounds in Nitric Acid Processing Solutions.  

National Technical Information Service (NTIS)

The reaction of hyperazeotropic iodic acid-saturated nitric acid with short chain aliphatic iodides, nitrates, and acids was studied in order to determine the conditions for complete removal of organic materials from nitric acid systems. The aliphatic iod...

W. E. Clark W. B. Howerton

1975-01-01

382

Mechanism of plagioclase dissolution in acid solution at 25°C  

NASA Astrophysics Data System (ADS)

The dissolution kinetics of three plagioclase feldspars (An 13, An 46, and An 76) were studied in flow-through reactors over the pH range 3-7. In accordance with the surface complexation model, dissolution rate was described by the equation Rate= x aA exp( E a/kT)(C sH) n) , where ( Chs) is the concentration of protonated surface sites, xa is the mole fraction of these that are activated, A is the Arrhenius pre-exponential factorand Ea is the activation energy for the reaction. The reaction order with respect to surface charge ( n) at pH < 5 is a function of mineral composition, and increases with increasing anorthite content. Orders of 0.46, 1.2, and 2.0 are obtained for oligoclase, andesine, and bytownite, respectively. This indicates that the reaction intermediate is more highly protonated in feldspars of higher aluminum content. The nonintegral reaction orders obtained demonstrate the importance of several surface species in the dissolution reaction. Reaction rates increase with increasing anorthite content. In acid solution this reflects the linear dependence of Ea on the number of Al-O-Si bonds involved in the rate-determining step. Under conditions of low surface protonation (in near-neutral solutions), dissolution is independent of surface charge. As reaction occurs at neutral alumina sites, the rate is approximately proportional to the anorthite (Al) content of the feldspar.

Oxburgh, Rachel; Drever, James I.; Sun, Yan-Ting

1994-01-01

383

Basic solutions to carbon/carbon oxidation: Science and technology. Annual technical report, 15 April 1993-14 April 1994  

SciTech Connect

The attached report addresses the first year of a program aimed at developing basic solutions to carbon/carbon composite oxidation. In particular, one primary thrust is the development of boron containing carbons through pyrolysis of boron containing polymers. Additionally, a basic understanding of the oxidation mechanisms in carbons and boron containing carbons is being sought. Several new boron containing precursors have been synthesized, which can be converted to B/C materials after pyrolysis. In particular, polyacrylonitrile (PAN) has been copolymerized with a boron-containing monomer (vinylcatecholborane.) Approximately 68% of the original boron is retained after pyrolysis yielding a product with 3.4% boron. 1,4-polybutadiene (PBD) has been hydroborated to contain large amounts of boron. Model compounds have been used to prepare polydiyne with considerable amounts of boron. In the latter two cases, direct analysis for % boron is not yet available. Preliminary TGA data suggests that PBD containing boron results in a more stable structure.

Harrison, T.R.; Chung, T.; Radovic, L.; Pantano, C.; Thrower, P.A.

1994-05-13

384

Recovery of hydrochloric acid from metal pickling solutions by membrane distillation  

Microsoft Academic Search

Membrane distillation (MD) was applied for the concentration of solutions containing hydrochloric acid and salts. It was found that under MD conditions through pores of a hydrophobic membrane both water vapor and hydrogen chloride are transported. This effect was utilized for the recovery of HCl from acidic spent solutions. The experiments were performed using model or real metal pickling solutions

M. Tomaszewska; M. Gryta; A. W. Morawski

2001-01-01

385

Corrosion Behavior of Mild Carbon Steel in Ethanolic Solutions  

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

386

Adsorption of pesticides from aqueous solution onto banana stalk activated carbon  

Microsoft Academic Search

Activated carbon was prepared from banana stalk by potassium hydroxide (KOH) and carbon dioxide (CO2) activation and its ability to remove the pesticides, 2,4-dichlorophenoxyacetic acid (2,4-D) and bentazon was explored. The banana stalk activated carbon (BSAC) was characterized by Fourier transform infrared spectroscopy (FT-IR) analysis. The adsorption kinetic data were analyzed using two kinetic models: the pseudo-first-order and pseudo-second-order models.

J. M. Salman; V. O. Njoku; B. H. Hameed

2011-01-01

387

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

PubMed

Degradation of 29 dyes by means of an activated carbon fiber (ACF) electrode electrolysis system was performed successfully. Almost all dye solutions tested were decolorized effectively in this ACF electrolysis process. Internal relationships between treatment mechanisms and chemical composition of the dye have been discussed in this paper. Generally, it is shown that higher solubility leads to greater degradation in the process. Dyes with many -SO3-, COO-, -SO2NH2, -OH, hydrophilic groups, and azo linkages are susceptible to reduction. However, dyes with many -C=O, -NH-and aromatic groups, and hydrophobic groups, tend to be adsorbed. For dyes with -SO3-, COOH and -OH groups, if their molecules linearly spread in solution and have a significant tendency to form colloids by hydrogenous bonding, they also tend to be adsorbed and flocculated. Typical dynamic electrolysis of dye Acid Red B, Vat Blue BO and Disperse Red E-4B shows how the two major mechanisms, degradation and adsorption, act differently during treatment. Reduction occurs evenly during treatment. During the dominant adsorption process, after certain amount of iron is generated, colloid precipitation occurs and TOC and color are rapidly removed. PMID:11376888

Shen, Z; Wang, W; Jia, J; Ye, J; Feng, X; Peng, A

2001-06-01

388

Adsorption of phenol and dye from aqueous solution using chemically modified date pits activated carbons  

Microsoft Academic Search

The adsorption of phenol and methylene blue (MB) on modified activated carbons has been investigated. The activated carbon was prepared from date pits by physical activation (CO2 as activating agent). Oxidation in the liquid phase with nitric acid and thermal treatment under flowing nitrogen were carried out in order to produce samples with different surface chemical properties but with no

Meriem Belhachemi; Zohra Belala; Driss Lahcene; Fatima Addoun

2009-01-01

389

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

Code of Federal Regulations, 2010 CFR

...Chloric acid solution or chlorine dioxide hydrate, frozen. 173.229 Section 173...Chloric acid solution or chlorine dioxide hydrate, frozen. When the § 172.101...sufficient dry ice must be used to maintain the hydrate or acid in a frozen state during...

2010-10-01

390

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

Code of Federal Regulations, 2010 CFR

...Chloric acid solution or chlorine dioxide hydrate, frozen. 173.229 Section 173...Chloric acid solution or chlorine dioxide hydrate, frozen. When the § 172.101...sufficient dry ice must be used to maintain the hydrate or acid in a frozen state during...

2009-10-01

391

Use of Flow-Injection Conductometry of Strong and Weak Protolytes in Solutions Containing Amino Acids  

Microsoft Academic Search

Based on the results of systematic studies, it was demonstrated that flow-injection conductometry can be used in solutions containing amino acids for the determination of low concentrations of strong and weak acids and bases. For the analysis of aqueous and organic solutions, it was proposed to use protolytic reactions of zwitterionic forms of some amino acids as highly sensitive and

M. S. Piskunova; G. M. Sergeev

2001-01-01

392

Etching characteristics of high-purity aluminum in hydrochloric acid solutions  

Microsoft Academic Search

We investigated the effects of additives to the etching solution of 1M hydrochloric acid on the electrochemical etching behavior for aluminum electrolytic capacitors, using scanning and transmission electron microscopy, and AC impedance spectroscopy. For the addition of 1M sulfuric acid or 5% ethylene glycol to the hydrochloric acid solution, the distribution of etch tunnels was more uniform with high density

Han-Jun Oh; Jong-Ho Lee; Hong-Joo Ahn; Yongsoo Jeong; No-Jin Park; Seong-Su Kim; Choong-Soo Chi

2007-01-01

393

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

Microsoft Academic Search

Sodium ?-sulfonated, fatty acid polyethylene glycol monoesters [C\\u000a m\\u000a H2m+1CH(SO3Na)COO(C2H4O)\\u000a n\\u000a H] and diesters [C\\u000a m\\u000a H2m+1CH(SO3Na)COO(C2H4O)\\u000a n\\u000a COCH(SO3Na)C\\u000a m\\u000a H2m+1], wherem=10–16 andn=1–35, were prepared by esterification of ?-sulfonated, fatty acids with polyethylene glycols, followed by neutralization\\u000a with NaOH. Crude products were purified by reversed-phase column chromatography on an octadecyl-modified silica gel. Characteristic\\u000a solution behavior of these ?-sulfonated fatty acid

Tomomichi Okano; Naoyuki Egawa; Masami Fujiwara; Masahiro Fukuda

1996-01-01

394

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

395

EXTRACTION AND SEPARATION OF ACTINIDES AND LANTHANIDES FROM ALKALINE AND CARBONATE SOLUTIONS  

Microsoft Academic Search

The review generalizes the results on the extraction of actinides, lanthanides and other elements from alkaline and carbonate solutions with the extractants of various classes. It discusses the mechanisms of the processes and practical possibilities of the separation of elements in alkaline solutions.

Z. K. Karalova; B. F. Myasoedov; T. I. Bukina; E. A. Lavrinovich

1988-01-01

396

Adsorption of naphthalene from aqueous solution on activated carbons obtained from bean pods.  

PubMed

The preparation of activated carbons from bean pods waste by chemical (K(2)CO(3)) and physical (water vapor) activation was investigated. The carbon prepared by chemical activation presented a more developed porous structure (surface area 1580 m(2) g(-1) and pore volume 0.809 cm(3) g(-1)) than the one obtained by water vapor activation (258 m(2) g(-1) and 0.206 cm(3) g(-1)). These carbons were explored as adsorbents for the adsorption of naphthalene from water solutions at low concentration and room temperature and their properties are compared with those of commercial activated carbons. Naphthalene adsorption on the carbons obtained from agricultural waste was stronger than that of carbon adsorbents reported in the literature. This seems to be due to the presence of large amounts of basic groups on the bean-pod-based carbons. The adsorption capacity evaluated from Freundlich equation was found to depend on both the textural and chemical properties of the carbons. Naphthalene uptake on biomass-derived carbons was 300 and 85 mg g(-1) for the carbon prepared by chemical and physical activation, respectively. Moreover, when the uptake is normalized per unit area of adsorbent, the least porous carbon displays enhanced naphthalene removal. The results suggest an important role of the carbon composition including mineral matter in naphthalene retention. This issue remains under investigation. PMID:18541368

Cabal, Belen; Budinova, Temenuzhka; Ania, Conchi O; Tsyntsarski, Boyko; Parra, José B; Petrova, Bilyana

2008-05-03

397

Silver particles-modified polysulfonic acid-doped polyaniline layers: electroless deposition of silver in slightly acidic and neutral solutions  

Microsoft Academic Search

Polyaniline layers are produced by electrochemical polymerisation of aniline in the presence of small amounts of poly(2-acryalamido-2-methyl-propane-sulfonic\\u000a acid) in an inorganic acid solution. Electroactivity and in situ conductance of the obtained polysulfonic acid-doped layers\\u000a are studied in slightly acidic and neutral solutions. Electroless deposition of silver particles is carried out in silver-EDTA\\u000a complex ion solutions at pH?=?4.2 and pH?=?6.6 by

Vladimir Lyutov; Vessela Tsakova

398

Carbon nanotubes and nucleic acids: tools and targets  

NASA Astrophysics Data System (ADS)

Nucleic acids are playing an important role in the rapid development of nanotechnologies. Our Editor's Choice [1] discusses the use of nucleic acids to disperse and sort single walled carbon nanotubes (SWNTs). The cover picture shows a two-dimensional photoluminescence (PL) spectrum of highly purified (6,5) SWNT:DNA hybrids. The fine resolution of the PL peaks displays photo-excited intermediates in a range of energies between ES22 and ES11 transitions revealing for the first time specific phonon-assisted optical absorption and energy relaxation mechanisms.The first author, Bibiana Onoa, has been working on carbon nanotubes and nucleic acids in the molecular electronics group of Dupont Central Research and Development. Her current research focuses on the development of nanotechnologies that allow fast and economical detection of pathogens.This special issue of physica status solidi (a) presents representative contributions and main topics on Trends in Nanotechnology from the TNT2005 International Conference in Oviedo (Spain).

Onoa, Bibiana; Zheng, Ming; Dresselhaus, Mildred S.; Diner, Bruce A.

2006-05-01

399

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.

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

1985-01-01

400

Synthesis of calcium carbonate in a pure ethanol and aqueous ethanol solution as the solvent  

NASA Astrophysics Data System (ADS)

The possibility of formation of precipitated calcium carbonate (PCC) in pure ethanol, not as small additives, but as the main solvent, was investigated by precipitating a variety of PCC via a carbonation reaction. During the carbonation in a slaked lime pure ethanol suspension, three morphology types of CaCO3 were also precipitated, including calcite, which was the only type of PCC precipitated in the pure water system, and aragonite and vaterite, which were also precipitated without leaving Ca(OH)2 as the reactants. Their particle size was half of those from pure water. In a pure ethanol system, calcite was first precipitated from the carbonation in bulk solution as in the pure water system, while the aragonite and vaterite might be synthesized via other local carbonation routes occurring in the surface of the Ca(OH)2 grain following the bulk carbonation in the solution. In this local carbonation, there was little variation of electrical conductivity and pH. In the aqueous solution of less than 40 mol% ethanol, the PCC is all calcite; therefore, water has dominant effect as the solvent. On the other hand, in the solution of more than 60 mol% ethanol, the solvent acts as the pure ethanol and calcite, aragonite and vaterite can be precipitated.

Seo, Kang-Seok; Han, Choon; Wee, Jung-Ho; Park, Jin-Koo; Ahn, Ji-Whan

2005-04-01

401

Uptake of hypobromous acid (HOBr) by aqueous sulfuric acid solutions: low-temperature solubility and reaction  

NASA Astrophysics Data System (ADS)

Hypobromous acid (HOBr) is a key species linking inorganic bromine to the chlorine and odd hydrogen chemical families. We have measured the solubility of HOBr in 45-70wt% sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosol composition. Over the temperature range 201-252 K, HOBr is quite soluble in sulfuric acid, with an effective Henry's law coefficient, H*=104-107mol L-1atm-1. H* is inversely dependent on temperature, with ?H=-45.0±5.4 kJ mol-1 and ?S=-101±24 J mol-1K-1 for 55-70wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into 55-70wt% H2SO4, the solubility is described by log H*=(2349±280)/T-(5.27±1.24). At temperatures colder than ~213K, the solubility of HOBr in 45wt% H2SO4 is at least a factor of five larger than in 70wt% H2SO4, with log H*=(3665±270)/T-(10.63±1.23). The solubility of HOBr is comparable to that of HBr, indicating that upper tropospheric and lower stratospheric aerosols should contain equilibrium concentrations of HOBr which equal or exceed those of HBr. Upon uptake of HOBr into aqueous sulfuric acid in the presence of other brominated gases, particularly for 70wt% H2SO4 solution, our measurements demonstrate chemical reaction of HOBr followed by evolution of gaseous products including Br2O and Br2.

Iraci, L. T.; Michelsen, R. R.; Ashbourn, S. F. M.; Rammer, T. A.; Golden, D. M.

2005-06-01

402

Uptake of hypobromous acid (HOBr) by aqueous sulfuric acid solutions: low-temperature solubility and reaction  

NASA Astrophysics Data System (ADS)

Hypobromous acid (HOBr) is a key species linking inorganic bromine to the chlorine and odd hydrogen chemical families. We have measured the solubility of HOBr in 45-70 wt% sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosol composition. Over the temperature range 201-252 K, HOBr is quite soluble in sulfuric acid, with an effective Henry's law coefficient, H*=104-107 mol L-1 atm-1. H* is inversely dependent on temperature, with ?H=-45.0±5.4 kJ mol-1 and ?S=-101±24 J mol-1 K-1 for 55-70 wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into 55-70 wt% H2SO4, the solubility is described by log H*=(2349±280)/T-(5.27±1.24). At temperatures colder than ~213 K, the solubility of HOBr in 45 wt% H2SO4 is at least a factor of five larger than in 70 wt% H2SO4, with log H*=(3665±270)/T-(10.63±1.23). The solubility of HOBr is comparable to that of HBr, indicating that upper tropospheric and lower stratospheric aerosols should contain equilibrium concentrations of HOBr which equal or exceed those of HBr. Upon uptake of HOBr into aqueous sulfuric acid in the presence of other brominated gases, particularly for 70 wt% H2SO4 solution, our measurements demonstrate chemical reaction of HOBr followed by evolution of gaseous products including Br2O and Br2.

Iraci, L. T.; Michelsen, R. R.; Ashbourn, S. F. M.; Rammer, T. A.; Golden, D. M.

2005-03-01

403

Interaction of trace elements in acid mine drainage solution with humic acid.  

PubMed

The release of metal ions from a coal mining tailing area, Lamphun, Northern Thailand, is studied by leaching tests. Considerable amounts of Mn, Fe, Al, Ni and Co are dissolved in both simulated rain water (pH 4) and 10 mg L(-1) humic acid (HA) solution (Aldrich humic acid, pH 7). Due to the presence of oxidizing pyrite and sulfide minerals, the pH in both leachates decreases down to approximately 3 combined with high sulfate concentrations typical to acid mine drainage (AMD) water composition. Interaction of the acidic leachates upon mixing with ground- and surface water containing natural organic matter is simulated by subsequent dilution (1:100; 1:200; 1:300; 1:500) with a 10 mg L(-1) HA solution (ionic strength: 10(-3) mol L(-1)). Combining asymmetric flow field-flow fractionation (AsFlFFF) with UV/Vis and ICP-MS detection allows for the investigation of metal ion interaction with HA colloid and colloid size evolution. Formation of colloid aggregates is observed by filtration and AsFlFFF depending on the degree of the dilution. While the average HA size is initially found to be 2 nm, metal-HA complexes are always found to be larger. Such observation is attributed to a metal induced HA agglomeration, which is found even at low coverage of HA functional groups with metal ions. Increasing the metal ion to HA ratio, the HA bound metal ions and the HA entities are growing in size from <3 to >450 nm. At high metal ion to HA ratios, precipitation of FeOOH phases and HA agglomeration due to colloid charge neutralization by complete saturation of HA complexing sites are responsible for the fact that most of Fe and Al precipitate and are found in a size fraction >450 nm. In the more diluted solutions, HA is more relevant as a carrier for metal ion mobilization. PMID:16631855

Suteerapataranon, Siripat; Bouby, Muriel; Geckeis, Horst; Fanghänel, Thomas; Grudpan, Kate

2006-06-01

404

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

405

Carbon monoxide … the silent killer with an audible solution  

Microsoft Academic Search

Carbon monoxide (CO) is responsible for more poisoning fatalities each year than any other toxic agent. The often insidious nature of the symptom progression and its ability to imitate many common illnesses may result in the failure to diagnose a potentially fatal outcome. CO detectors equipped with an audible alarm can alert potential victims of CO poisoning before toxic sequelae

Edward P Krenzelok; Ronald Roth; Robert Full

1996-01-01

406

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

407

[Denitrification using polylactic acid as solid carbon source].  

PubMed

Polylactic acid (PLA) was used as solid carbon source and biofilm support simultaneously, to investigate the applicability of PLA in the denitrification process. The effect of temperature on denitrification performance was also studied. The IR analysis and SEM observation were performed to investigate the PLA surface structure and biofim morphology. The results showed that when the initial concentration of nitrate nitrogen was 50 mg/L and the temperature was 30 degrees C, the average denitrification rate was 2.6 x 10(-1) mg/(g x h) and nitrate could be completely removed within 13h. Temperature had a significant influence on the denitrification rate. The IR analysis and SEM observation of PLA surface structure confirmed the feasibility of PLA as solid carbon source. The SEM observation of biofim showed that the biofilm was thin and mainly consisted of cocci. PMID:19799294

Fan, Zhen-xing; Wang, Jian-long

2009-08-15

408

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.

Kurz, Matthias

2008-01-01

409

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

410

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

PubMed

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

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

2012-07-20

411

Americium and europium extraction from alkali and carbonate solutions with 2-hydroxy-5-alkylbenzyldiethanolamine  

Microsoft Academic Search

Americium and europium extraction from alkali solutions in presence of tartrate and carbonate ions using 2-hydroxy-5-alkylbenzyldiethanolamine (DEAP) in different diluents as a function of NaOH, NaâCâHâOâ, KâCOâ, extractant and metal concentration, and pH of the medium has been studied. It was found that americium is extracted to the maximum by 1 M DEAP solution in hexane from tartrate solutions with

Z. K. Karalova; T. I. Bukina; E. A. Devirts; Z. Z. Agaev; B. F. Myasoedov

1988-01-01

412

Analysis of solute distribution in dendrites of carbon steel with ?\\/? transformation during solidification  

Microsoft Academic Search

Solute distribution in dendrites during solidification of carbon steel was analyzed by unidirectional solidification experiments\\u000a and mathematical analysis. The characteristic of the mathematical analysis is that diffusion of solutes in solid and redistribution\\u000a of solutes at solid\\/liquid and?\\/? interfaces are taken into consideration. Based on the observed and calculated results, it was found that phosphorus was redistributed\\u000a from?-phase to?-phase, and

Yoshiyuki Ueshima; Shozo Mizoguchi; Tooru Matsumiya; Hiroyuki Kajioka

1986-01-01

413

Spectroscopic and Electrochemical Studies of Selected Lanthanides and Actinides in Concentrated Aqueous Carbonate and Carbonate-Hydroxide Solutions and in Molten Dimethyl Sulfone.  

National Technical Information Service (NTIS)

Electrochemical and spectroscopic studies of neptunium, plutonium, americium, californium, and terbium in concentrated aqueous carbonate and carbonate-hydroxide solutions have been carried out. Changes in the absorption spectra of Np(VII), Np(V), Pu(VI), ...

P. G. Varlashkin

1985-01-01

414

Carbonate interlayered hydrotalcites-enhanced peroxynitrous acid chemiluminescence for high selectivity sensing of ascorbic acid.  

PubMed

In this study, Mg-Al-carbonate layered double hydroxides (denoted as Mg-Al-CO(3) LDHs) were found to catalyze the chemiluminescence (CL) emission from peroxynitrous acid (ONOOH). The enhanced CL signals resulted from the concentration of peroxynitrite (ONOO(-)) onto the LDHs surface by electrostatic attraction, meaning that ONOO(-) can interact with the intercalated carbonate easily and effectively. Moreover, ascorbic acid can react with ONOO(-), or its decomposition products (e.g., ?OH and ?NO(2)), resulting in a decrease in the CL intensity from the Mg-Al-CO(3) LDHs-catalyzed ONOOH reaction. Based on these findings, a sensitive, selective and rapid CL method was developed for the determination of ascorbic acid using Mg-Al-CO(3) LDHs-catalyzed ONOOH as a novel CL system. The CL intensity was proportional to the concentration of ascorbic acid in the range from 5.0 to 5000 nM. The detection limit (S/N = 3) was 0.5 nM and the relative standard deviation (RSD) for nine repeated measurements of 0.1 ?M ascorbic acid was 2.6%. This method has been successfully applied to determine ascorbic acid in commercial liquid fruit juices with recoveries of 97-107%. This work is not only of importance for a better understanding of the unique properties of LDHs-catalyzed CL but also of great potential for extensive applications in many fields, such as luminescence devices, bioanalysis, and labeling probes. PMID:22382556

Wang, Zhihua; Teng, Xu; Lu, Chao

2012-03-02

415

Interactions of Hydrazine, Ferrous Sulfamate, Sodium Nitrite, and Nitric Acid in Nuclear Fuel Processing Solutions.  

National Technical Information Service (NTIS)

Hydrazine and ferrous sulfamate are used as reductants in a variety of nuclear fuel processing solutions. An oxidant, normally sodium nitrite, must frequently be added to these nitric acid solutions before additional processing can proceed. The interactio...

L. W. Gray

1977-01-01

416

The influence of temperature on the heat effects of acid-base interaction in aqueous solutions of citric acid  

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

417

Electrochemical treatment of aqueous oxalic acid solution by using solid polymer electrolyte (SPE) reactor  

Microsoft Academic Search

In this study, the feasibility of electrochemical oxidation of the aqueous oxalic acid solution has been investigated in an electrochemical reactor with SPE and simultaneous hydrogen production has been observed.Experiments were conducted to examine the effects of applied current density, flow rate of solution, pH of the solution, the concentration of supporting electrolyte, the temperature of the solution, types of

Ebru Önder; Ali Sava? Koparal; Ülker Bakir Ö?ütveren

2009-01-01

418

HYDROGEN CHEMISORPTION ON Pt SINGLE CRYSTAL SURFACES IN ACIDIC SOLUTIONS  

SciTech Connect

Hydrogen chemisorption from dilute acidic solution onto Pt single crystal surfaces was examined using an electrochemical cell directly coupled to LEED/Auger analytical system. No pre-anodization was used prior to observing hydrogen adsorption by cyclic voltammetry so that clean surfaces having the ordered structures indicated by LEED were studied. The problem of contributions from non-ordered parts of the electrode like support wires and edges was solved by using a gold evaporation masking technique. The specific contribution of atomic imperfections to the voltammetry curve was deduced from the ordered and countable imperfections occurring on high Miller index single crystal surfaces that have a stepped structure. The H-Pt bond energy Has found to be structure sensitive, and sensitive both to local site geometry and long range order in the surface. The bond strength was found to vary systematically: n(111)x(100) > (100) > n(111)x(111) > (110) > (111). Distinct states for hydrogen at steps versus hydrogen on terraces could be distinguished. The (110) surface is shown to be a (111) vicinal, probably the [3(111) x 2(111)] microfacetted surface. The zero coverage heat of adsorption on the well-ordered (111) surface (48 kJ/mol) in solutions is the same as the value reported by Ertl and co-workers for adsorption on a (111) surface in vacuum. Adsorption Isotherms for hydrogen on the (111) and (100) surfaces is adequately fit by the classical model for immobile adsorption at single sites with nearest neighbor repulsive interaction.

Ross, Jr., Philip N.

1980-04-01

419

Carbon isotope fractionation in phospholipid fatty acid biomarkers of bacteria and fungi native to an acid mine drainage lake  

Microsoft Academic Search

This study identifies isotope signatures associated with autotrophic and heterotrophic microbial communities that may provide a means to determine carbon cycling relationships in situ for acid mine drainage (AMD) sites. Stable carbon isotope ratios (?13C) of carbon sources, bulk cells, and membrane phospholipids (PLFA) were measured for autotrophic and heterotrophic microbial enrichment cultures from a mine tailings impoundment in northern

Benjamin R. Cowie; Gregory F. Slater; Luc Bernier; Lesley A. Warren

2009-01-01

420

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

PubMed

From the viewpoint of the phytotoxicity and mobility of Al(3+) released from soil minerals due to soil acidification, the interaction between Al(3+) and acrylic acid (AA) and polyacrylic acid (PAA) as a model compound of fulvic acid was investigated. The interaction was examined at pH 3 so as to avoid the hydrolysis of Al(3+). The interaction between Al(3+) and AA was weak. However, the interaction between Al(3+) and PAA was strong and depended on the initial (COOH in PAA)/Al molar ratio (R(P)) of the solution. For the range of 1/R(P), the interaction between Al(3+) and PAA can be divided into three categories: (1) 1:1 Al-PAA-complex (an Al(3+) combines to a carboxyl group), (2) intermolecular Al-PAA-complex (an Al(3+) combines to more than 2 carboxyl groups of other Al-PAA-complexes) in addition to the 1:1 Al-PAA-complex and (3) precipitation of intermolecular complexes. In conclusion, R(P) is an important factor affecting the behavior of Al(3+) in acidic soil solution. PMID:21233571

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

2011-01-01

421

Equilibrium sorption of methionine on carboxyl cation exchangers from solutions of various acidities  

NASA Astrophysics Data System (ADS)

The influence of the acidity of solutions of methionine on methionine interaction with KB-2 and KB-4 carboxyl cation exchangers in the protonated and deprotonated forms was studied by the calorimetric, sorption, and spectroscopic methods. It was found that nonexchange methionine absorption occurred from acid solutions, and mixed ion exchange and nonexchange sorption, from alkaline solutions. The enthalpies of sorption of methionine at various external solution pH values were determined.

Ovsyannikova, D. V.; Bondareva, L. P.; Selemenev, V. F.; Karpov, S. I.

2009-05-01

422

Synthesis of silicon\\/carbon, multi-core\\/shell microspheres using solution polymerization for a high performance Li ion battery  

Microsoft Academic Search

In this work, silicon–carbon composite particles were designed and synthesized for the anode materials of a lithium ion battery and synthesized using a simple method that is adaptable for industrial application. The silicon\\/carbon precursor and monomer mixtures were polymerized through solution polymerization in an organic continuous medium and granulated in a polyvinyl alcohol (PVA) aqueous solution. After carbonization of the

Kyomin Shin; Dae-Jin Park; Hyung-Seok Lim; Yang-Kook Sun; Kyung-Do Suh

423

Leaching kinetics of malachite in ammonium carbonate solutions  

Microsoft Academic Search

Leaching of malachite was conducted with ammonium carbonate as lixiviant and with temperature, lixiviant concentration, and particle size as variables. Two stages of reaction were found. In Stage I, the initial dissolution of malachite proceeds rapidly, but after about 10 pct reaction the rate is reduced by surface blockage due to the presence of a needle-structured intermediate, presumably Cu(OH)2. Subsequently,

Paul D. Oudenne; Ferron A. Olson

1983-01-01

424

Leaching kinetics of malachite in ammonium carbonate solutions  

Microsoft Academic Search

Leaching of malachite was conducted with ammonium carbonate as lixiviant and with temperature, lixiviant concentration, and\\u000a particle size as variables. Two stages of reaction were found. In Stage I, the initial dissolution of malachite proceeds rapidly,\\u000a but after about 10 pct reaction the rate is reduced by surface blockage due to the presence of a needle-structured intermediate,\\u000a presumably Cu(OH)2. Subsequently,

Paul D. Oudenne; Ferron A. Olson

1983-01-01

425

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

426

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

2004-08-13

427

Photochemistry of aqueous solutions of kynurenic acid and kynurenine yellow.  

PubMed

The photophysics and photochemistry of kynurenic acid (KNA) and kynurenine yellow (KNY) in neutral aqueous solutions were investigated using time-resolved optical spectroscopy. Both molecules have similar quinoline-like structures, the only difference being the absence of conjugation in the nitrogen containing cycle in KNY. The main channel of S(1) excited state decay in the case of partially-unconjugated KNY is the solvent assisted S(1) ? S(0) radiationless transition via intermolecular hydrogen bonds (?(IC) = 0.96), whereas, in the case of fully-conjugated KNA, it is intersystem crossing to the triplet state (?(T) = 0.82). The major intermediate products of the singlet excited KNY deactivation are the triplet state (?(T) = 0.022) and, most probably, the enol form (?(enol) = 0.012), which decay with the formation of 2,3-dihydro-4-hydroxyquinoline and 4-hydroxyquinoline, respectively. The results obtained show that KNA and KNY, which are products of the decomposition of the UV filter kynurenine, are significantly more photoactive and less photostable than the parent molecule. PMID:23258594

Zelentsova, Ekaterina A; Sherin, Peter S; Snytnikova, Olga A; Kaptein, Robert; Vauthey, Eric; Tsentalovich, Yuri P

2013-03-01

428

Solubility of Boron Compounds in Nitric Acid Solutions  

SciTech Connect

A series of laboratory experiments has been performed to determine flowsheet conditions for formation of boron solids during processing of glovebox floor sweepings (FS) and sand, slag, and crucible (S,S, and C) materials in canyon dissolvers. The precipitation of a boron compound (KBF4) was identified during the flowsheet development work for processing Rocky Flats S,S, and C materials at Savannah River. The subsequent series of laboratory experiments has focused on flowsheet conditions planned for the dissolution of glovebox floor sweepings in S,S, and C solutions.The concentrations of potassium fluoride (KF) and total fluoride were established where precipitation of boron solids would and would not occur during the processing of floor sweepings. Other variables such as changes in nitric acid and iron concentrations were found to have no impact on formation of boron solids. Results presented in Table 1 indicate that boron solids will not form at 0.22 molar KF and 0.30 molar total fluoride during processing of floor sweepings and at 0.22 molar KF and 0.32 molar total fluoride during processing of S,S, and C materials.

Gray, J.H.

1998-12-11

429

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

SciTech Connect

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

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

2009-05-26

430

Hydrothermal fluxes of solutes, carbon, and heat to Himalayan rivers  

Microsoft Academic Search

Hot springs flow along the base of the Himalayan front in the Narayani river basin of central Nepal. The springs flow near the Main Central Thrust (MCT), in a zone characterized by active uplift and high incision and erosion rates. Water-rock interaction at depth results in hydrothermal fluids with high solute loads. Himalayan rivers flowing through the zones of geothermal

Matthew Jared Evans

2003-01-01

431

A pulse radiolysis study of salicylic acid and 5-sulpho-salicylic acid in aqueous solutions  

NASA Astrophysics Data System (ADS)

Reactions of H, OH, eaq- and some one-electron oxidants have been studied with salicylic acid and 5-sulpho-salicylic acid in aqueous solutions. Rate constants for the reaction of eaq- with these compounds were of the order of 109 dm3 mol-1 s-1 and this reaction led to the formation of reducing radicals which could transfer electron to methyl viologen. Other one-electron reductants were not able to reduce these compounds. OH radicals reacted with these compounds by addition pathway with very high rate constants (>1010 dm3 mol-1 s-1) while O- radical anions could oxidize these molecules to give phenoxyl type of radicals. Amongst the one-electron oxidants, only N3 and SO4- could oxidize salicylic acid while 5-sulpho-salicylic acid could be oxidized only by SO4- radicals indicating that while one-electron reduction potential for semi-oxidized SA may be<1.33 V vs. NHE (the Eo1 for N3 radical), it is more than 1.33 V vs. NHE for semi-oxidized SSA species.

Kishore, Kamal; Mukherjee, T.

2006-01-01

432

Solution-reactor-produced Mo-99 using activated carbon to remore I-131  

SciTech Connect

The production of {sup 99}Mo in a solution reactor was explored. Activated charcoal was used to filter the {sup 131}I contaminant from an irradiated fuel solution. Gamma spectroscopy confirmed that the activated carbon trapped a significant amount of {sup 131}I, as well as notable amounts of {sup 133}Xe, {sup 105}Rb, and {sup 140}Ba; the carbon trapped a diminutive amount of {sup 99}Mo. The results promote the idea of solution-reactor-produced {sup 99}Mo. Solution reactors are favorable both energetically and environmentally. A solution reactor could provide enough {sup 99}Mo/{sup 99m}Te to support both the current and future radiopharmaceutical needs of the U.S.

Kitten, S.; Cappiello, C.

1998-06-01

433

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

NASA Astrophysics Data System (ADS)

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

Rau, G. H.

2010-12-01

434

Preparation and Characterization of Poly (1, 3-propylene glycol-hexanedioic acid)-functionalized Carbon Nanotubes  

Microsoft Academic Search

An in situ process was used to prepare poly (1, 3-propylene glycol-hexanedioic acid)-functionalized carbon nanotubes using carboxylate-functionalized multi-walled carbon nanotubes, 1, 3-propylene glycol and hexanedioic acid as reactants. The functionalized carbon nanotubes were characterized using transmission electronic microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. The results indicated that the carboxylate-functionalized carbon nanotubes chemically reacted and were linked with the

Qing-Jie Meng; Xing-Xiang Zhang; Xue-Chen Wang

2007-01-01

435

The effect of carbonic acid on well cements  

NASA Astrophysics Data System (ADS)

Sequestration in abandoned petroleum fields has the potential to reduce atmospheric emissions of CO2 if adopted on a large scale. When CO2 comes in contact with brine in the sequestration formation, it will form carbonic acid. The acid may damage cement that is used to construct and abandon wells in the sequestration formation, allowing the wells to leak. CO2 release from a sequestration formation through abandoned wells to the vadose zone and then from the vadose zone into a residence could cause exposure to high levels of CO2. This study presents the results of two types of experiments that were conducted in order to understand how CO2 will affect well cements. This dissertation also presents a hypothetical risk assessment that examines the risks that a sequestration site may pose. The experiments examine how well cements react when exposed to carbonated brines at 20° and 50°C. Month-long flow-through experiments were conducted on samples made from Class H neat paste and Class H cement containing 6% bentonite under conditions that simulated sandstone (pH 2.4 and 3.7) and limestone (pH 5) sequestration formations. Year-long batch experiments were conducted on composite samples made from Class H well cement and either sandstone or limestone in order to determine how carbonated brine affects the cement-stone interface. The results of the flow-through experiments showed that calcium-containing phases in cement may be completely degraded and the formation of the calcium carbonate layer acts to slow, but not stop, degradation. The results of the batch experiments showed that carbonated brines can degrade cement and damage the integrity of the cement-stone interface. The damage to the cement at the cement-stone interface caused an order-of-magnitude increase in permeability in the sandstone-cement samples. The risk assessment identifies two potential screening levels. The assessment then uses a semianalytical wellfield model coupled with analytical models of diffusion through the vadose zone and foundation walls to establish CO 2 concentrations in residential basements. The results show CO 2 levels may not reach either screening level unless the value of the air-exchange rate in the houses is small.

Duguid, Andrew

436

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

PubMed

Amino acid-based anionic gemini surfactants (2CndiCys, 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 (2CnCys) and monomeric surfactants (CnCys). 2CndiCys shows relatively higher biodegradability than does CnCys 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 2CndiCys shows no dependence on alkyl chain length. Further, shaking the mixtures of aqueous 2CndiCys surfactant solutions and squalane results in the formation of oil-in-water type emulsions. The highly stable emulsions are formed using 2C12diCys or 2C14diCys solution and squalane in a 1:1 or 2:1 volume ratio. PMID:23985487

Yoshimura, Tomokazu; Sakato, Ayako; Esumi, Kunio

2013-01-01

437

Raman spectroscopic study of the phase transition of amorphous to crystalline beta-carbonic acid.  

PubMed

What's the matter? The laboratory Raman spectra for carbonic acid (H(2)CO(3)), both for the beta-polymorph and its amorphous state, are required to detect carbonic acid on the surface of the pole caps of Mars in 2009, when the Mars Microbeam Raman Spectrometer lands on the planet. The picture shows a martian crater with ice of unknown composition, possibly containing carbonic acid (image adapted from DLR, with permission from ESA, DLR, and FU Berlin--G. Neukum). PMID:19212997

Kohl, Ingrid; Winkel, Katrin; Bauer, Marion; Liedl, Klaus R; Loerting, Thomas; Mayer, Erwin

2009-01-01

438

Deterministic modeling of the corrosion of a low-carbon steel by carbon dioxide and the effect of acetic acid  

NASA Astrophysics Data System (ADS)

The current work is carried out with the aim of developing a deterministic model of the corrosion of low-carbon steel by carbon dioxide including the effect of acetic acid. The interaction of acetic acid with the corrosion-products layer is studied and the system is modelled by considering reactions and the transport processes within the boundary layer along with protective film formation and its dissolution. The Point Defect Model (PDM) is used to describe passive film processes using fundamental chemical reactions and physicochemical properties of the metal-film-solution interface. The underlying mechanisms for describing currents, thicknesses, impedances, and structures are based on the defect chemistry of the layers formed on the metallic surface. Ellipsometry Spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Focus Ion Beam (FIB) and Electrochemical Impedance Spectroscopy (EIS) are used to determine the nature of the layers formed on the metallic surface. Transient analysis is carried out to obtain the parameters for the PDM from the impedance analysis under steady state conditions. Ellipsometry, SEM and FIB are applied for a further understanding on the composition and morphology of the film. According to Electrochemical Impedance Spectroscopy (EIS), acetic acid effect is markedly dependent upon the pH of the environment, showing a decrease in the charge transfer resistance at pH=4, and an increase of this parameter at pH=6. Acetic acid decreases the corrosion caused by dissolved carbon dioxide but its presence does not change the mechanisms of corrosion. The PDM accounts for most of the experimental observations on the structure and behavior of the films formed on the metallic surface predicting the dissolution of the oxide layer adjacent to the metal surface when the outer layer resistance is similar in magnitude to the applied potential; this is supported by experimental findings from FIB and SEM. The porosity of the outer layer, the electric field strength across the barrier layer, the polarizability of the barrier layer/outer layer interface and the standard rate constants for the point defect generation and annihilation reactions at the barrier layer interfaces, and other parameters, are found to be independent of the applied potential.

Rosas-Camacho, Omar

439

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

NASA Astrophysics Data System (ADS)

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.

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

2011-05-01

440

OXIDATION OF URONIC ACIDS BY MANGANESE(III) SULFATE IN ACID SOLUTION: A KINETIC AND MECHANISTIC STUDY  

Microsoft Academic Search

The kinetics and mechanism of oxidation of D-glucuronic acid and D-galacturonic acid by manganese(III) sulfate, in aqueous sulfuric acid solution at 30°C, was followed spectrophotometrically at ?max=500 nm. A first-order dependence of the rate each on [Mn(III)] and [uronic acid] was observed. The rate is independent of the concentration of hydrogen ions and the reaction product, Mn(II). Effects of varying

K. S. Rangappa; N. Anitha; M. Ayesha Nikath; K. M. L. Rai; N. M. Made Gowda

2001-01-01

441

Acetic acid and lithium chloride effects on hydrothermal carbonization of lignocellulosic biomass.  

PubMed

As a renewable non-food resource, lignocellulosic biomass has great potential as an energy source or feedstock for further conversion. However, challenges exist with supply logistics of this geographically scattered and perishable resource. Hydrothermal carbonization treats any kind of biomass in 200 to 260°C compressed water under an inert atmosphere to produce a hydrophobic solid of reduced mass and increased fuel value. A maximum in higher heating value (HHV) was found when 0.4 g of acetic acid was added per g of biomass. If 1g of LiCl and 0.4 g of acetic acid were added per g of biomass to the initial reaction solution, a 30% increase in HHV was found compared to the pretreatment with no additives, along with greater mass reduction. LiCl addition also reduces reaction pressure. Addition of acetic acid and/or LiCl to hydrothermal carbonization each contribute to increased HHV and reduced mass yield of the solid product. PMID:21411315

Lynam, Joan G; Coronella, Charles J; Yan, Wei; Reza, Mohammad T; Vasquez, Victor R

2011-02-13

442

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

Microsoft Academic Search

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

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

443

Optoelectronic ally automated system for carbon nanotubes synthesis via arc-discharge in solution  

SciTech Connect

The method of arc discharge in the solution is unique and inexpensive route for synthesis of the carbon nanotubes (CNTs), carbon onions, and other carbon nanostructures. Such a method can be used for in situ synthesis of CNTs decorated with nanoparticles. Herein, we report a simple and inexpensive optoelectronically automated system for arc discharge in solution synthesis of CNTs. The optoelectronic system maintains a constant gap between the two electrodes allowing a continuous synthesis of the carbon nanostructures. The system operates in a feedback loop consisting of an electrode-gap detector and an analog electronic unit, as controller. This computerized feeding system of the anode was used for in situ nanoparticles incorporated CNTs. For example, we have successfully decorated CNTs with ceria, silica, and palladium nanoparticles. Characterizations of nanostructures are performed using high-resolution transmission electron microscopy, scanning transmission electron microscopy, energy dispersive spectroscopy, and scanning electron microscopy.

Bera, Debasis; Brinley, Erik; Kuiry, Suresh C.; McCutchen, Matthew; Seal, Sudipta; Heinrich, Helge; Kabes, Bradley [Surface Engineering and Nanotechnology Facility - SNF, Advanced Materials Processing and Analysis Center - AMPAC, and Mechanical, Materials and Aerospace Engineering - MMAE, University of Central Florida - UCF, 4000 Central Florida Blvd., Eng 1, no. 381, Orlando, Florida 32816 (United States); Advanced Materials Processing and Analysis Center - AMPAC and Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Eng 1, no. 381, Orlando, Florida 32816 (United States); NSF REU Site (UCF), Department of Chemical Engineering, University of Minnesota, Duluth, Minnesota 55803 (United States)

2005-03-01

444

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

445

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

2009-08-19

446

Mechanical degradation of polyacrylamide solutions in core plugs from several carbonate reservoirs  

SciTech Connect

This paper presents results of laboratory studies on mechanical degradation of partially hydrolyzed polyacrylamide (HPAM) solutions in core samples from several different carbonate reservoirs. Studies in carbonates are of particular importance because several of the larger polymer projects are in carbonate reservoirs and because data on carbonate rocks have not previously been available. Much of the data in the literature was obtained with solutions of polymer in brine. Since HPAM polymers are generally more efficient in fresh waters, lower salinity waters were used for the bulk of the present study. Variables investigated included: polymer molecular weight, polymer concentration, and salinity of the aqueous solvent. The HPAM samples used were commercial products of varying molecular weight. Results were compared to correlations previously developed for sandstone core plugs and uncosolidated sands.

Martin, F.D.

1984-04-01

447

Highly efficient procedure for the synthesis of fructone fragrance using a novel carbon based acid.  

PubMed

The novel carbon based acid has been synthesized via one-step hydrothermal carbonization of furaldehyde and hydroxyethylsulfonic acid. A highly efficient procedure for the synthesis of fructone has been developed using the novel carbon based acid. The results showed that the catalyst possessed high activity for the reaction, giving a yield of over 95%. The advantages of high activity, stability, reusability and low cost for a simple synthesis procedure and wide applicability to various diols and beta-keto esters make this novel carbon based acid one of the best choices for the reaction. PMID:20714302

Hu, Baowei; Li, Chunqing; Zhao, Sheng-Xian; Rong, Lin-Mei; Lv, Shao-Qin; Liang, Xuezheng; Qi, Chenze

2010-08-05

448

Kinetics of nitrous acid formation in nitric acid solutions under the effect of power ultrasound.  

PubMed

Sonochemical nitrous acid formation was investigated in 0.1-4.0 mol dm(-3) aqueous nitric acid solutions under the effect of power ultrasound with 20 kHz frequency. HNO2 steady-state concentration was obtained under long-time sonication; the excess HNO2 formed is decomposed and evoluted from the solution as NO and NO2 gases. The HNO2 steady-state concentration and the HNO2 initial formation rate depend linearly on the HNO3 concentration and acoustic intensity (1.8-3.5 W cm(-2)) and decrease with rising temperature in the range 21-50 degrees C. The HNO2 formation rate depends on the type of saturating gas as follows: Ar > N2 > He > air. NO and O2 are the major gaseous products of HNO3 sonication. The NO2 accumulation of in the gas phase is observed only when the decomposition of HNO2 formed becomes noticeable. The gaseous products formation rates depend on the HNO3 concentration, acoustic intensity and the type of saturating gas. The mechanism of HNO2 sonochemical formation is assumed to be the thermal decomposition of HNO3 in the gaseous vicinity of collapsing bubbles or in the overheated liquid reaction zone surrounding the cavitational bubbles. PMID:11237042

Venault, L; Moisy, P H; Nikitenko, S I; Madic, C

1997-04-01

449

Wet-spinning of neat single-walled carbon nanotube fiber from 100+% sulfuric acid  

NASA Astrophysics Data System (ADS)

Single-Walled Carbon Nanotubes (SWNT) have been found to have excellent solubility in super acids such as 100+% H2SO4, and chlorsulfonic acid. The solutions display liquid crystalline behavior at high concentrations in super acids. Traditional wet-spinning method has been applied to SWNTs to make fibers from SWNTs only with the assistance of 100+% H2SO 4 (neat SWNT fibers). Extensive conditions, including concentrations, coagulation, and operation temperature, have been explored with Daca mixer and other custom-designed apparatuses (SBM and Refined Mixer). Fibers' properties have been tremendously improved through the research. Different characterizations have been done and all of them confirmed the neat SWNT fibers have the best alignment to-date among any macroscopic neat SWNT articles, as well as electrical conductivities. Meanwhile, neat SWNT fibers were used for X-ray diffraction study. For the first time, direct evidence has been provided to support the strong intercalation between SWNTs and super acids. Interestingly, for the first time, it has been reported that liquid sulfuric acid forms shell structure while exposed to SWNTs.

Hua, Fan

450

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

451

Removal of heavy metals from aqueous solutions using activated carbon prepared from Cicer arietinum  

Microsoft Academic Search

Removal of Cu, Cd, Pb, and Zn from aqueous solutions by activated carbon prepared from stems and seed hulls of Cicer arietinum, an agricultural solid waste, has been studied. The influence of various parameters, such as pH, contact time, adsorbent dose, and initial concentration of metal ions on removal was evaluated. The activated carbon was characterized by FT-IR spectroscopy, X-ray

D. K. V. Ramana; K. Jamuna; B. Satyanarayana; B. Venkateswarlu; M. Madava Rao; K. Seshaiah

2010-01-01

452

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

Code of Federal Regulations, 2011 CFR

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

2011-10-01

453

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

Code of Federal Regulations, 2012 CFR

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

2012-10-01

454

Phosphorylation of Glyceric Acid in Aqueous Solution Using Trimetaphosphate.  

National Technical Information Service (NTIS)

The phosphorylation of glyceric acid is an interesting prebiotic reaction because it converts a simple, potentially prebiotic organic molecule into phosphate derivatives that are central to carbohydrate metabolism. We find that 0.05 M glyceric acid in the...

V. Kolb L. E. Orgel

1996-01-01

455

Solubility of carbon dioxide in aqueous solutions of 2-amino-2-hydroxymethyl-1,3-propanediol  

Microsoft Academic Search

The solubility of CO2 in aqueous solutions of 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD) was measured for AHPD mass fractions w=0.0015,0.005,0.01?and?0.025 at 283.15, 298.15 and 313.15K and for CO2 partial pressures within 2–75kPa. These ranges were compatible with aqueous solutions in use in a CO2 capture process using human carbonic anhydrase metalloenzyme. The influence of carbonic anhydrase on the solubility of CO2 in AHPD

David Le Tourneux; Ion Iliuta; Maria C. Iliuta; Sylvie Fradette; Faďçal Larachi

2008-01-01

456

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

ERIC Educational Resources Information Center

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

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

1976-01-01

457

Separation of Rare Earths from Solutions of Phosphoric Acid.  

National Technical Information Service (NTIS)

Rare earths are separated from 6M phosphoric acid by adsorption onto cation resin BIORAD AG50W-X8. The phosphoric acid is then washed from the column, and the rare earths are eluted with 4M hydrochloric acid. (Atomindex citation 16:001535)

E. A. Jones

1977-01-01

458

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

PubMed

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

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

2010-11-27

459