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1

Stability of calcium carbonate and magnesium carbonate in rainwater and nitric acid solutions  

Microsoft Academic Search

Carbonation of magnesium and calcium silicates has emerged as an interesting option for long term storage of captured CO2. However, carbonated minerals are not stable in acidic environments. This study was conducted to determine if synthetically carbonated minerals dissolve in acidic rain and release CO2. Synthetic magnesium and calcium carbonates were leached in nitric acid solutions of various acidities, as

Sebastian Teir; Sanni Eloneva; Carl-Johan Fogelholm; Ron Zevenhoven

2006-01-01

2

The inhibition of low carbon steel corrosion in hydrochloric acid solutions by succinic acid  

Microsoft Academic Search

The effect of succinic acid (SA) on the corrosion inhibition of a low carbon steel (LCS) electrode has been investigated in aerated non-stirred 1.0M HCl solutions in the pH range (2–8) at 25°C. Weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were applied to study the metal corrosion behaviour in the absence and presence of different concentrations of

Mohammed A. Amin; Sayed S. Abd El-Rehim; E. E. F. El-Sherbini; Rady S. Bayoumi

2007-01-01

3

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

DOEpatents

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

Rau, Gregory Hudson (Castro Valley, CA)

2012-05-15

4

Reducing Corrosion of Stainless Steel in Hot Nitric Acid Solutions by Adding Carbon Black or Elemental Sulfur to the Solution.  

National Technical Information Service (NTIS)

The corrosive effect toward stainless steel of a boiling nitric acid solution containing dissolved chromium values in the plus six oxidation state is reduced. Carbon black is added to the solution to reduce the corrosion. The stainless steel vessels are u...

F. G. Rust

1965-01-01

5

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

Microsoft Academic Search

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

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

2009-01-01

6

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

7

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

PubMed

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

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

2014-07-22

8

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

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

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

11

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

12

Removal of methylene blue from aqueous solutions using phosphoric acid activated carbon produced from hazelnut husks  

Microsoft Academic Search

In this study, activated carbon (HHPAAC) was prepared from hazelnut husks using phosphoric acid activation and characterized by some physicochemical analyses. Surface area and zero point charge of pH (pHPZC) were found to be 770?m?g and 4.5, respectively. Removal of methylene blue (MB) from aqueous solution was performed using a batch technique for determination of the effects of initial pH,

Cigdem Ozer; Mustafa Imamoglu; Yasemin Turhan; Fusun Boysan

2012-01-01

13

Interaction of organic acids with carbonate mineral surfaces in seawater and related solutions: I. Fatty acid adsorption  

NASA Astrophysics Data System (ADS)

The adsorption of C 4 to C 18 fatty acid anion homologs from seawater and related solutions was examined on calcite, aragonite, dolomite and magnesite surfaces. Butyrate, octanoate and laurate did not adsorb, while myristate, palmitate and stearate adsorbed on all carbonate surfaces. An increasing affinity for carbonate surfaces was found with increasing alkyl chain length for these fatty acids. Adsorption at low concentrations typical of marine waters is controlled by surface adsorption sites. At high concentration adsorption is governed by solution composition and limited by aqueous solubility. Adsorption-desorption reactions were characterized by a large resistant component that resulted in nonsingular isotherms. Myristate adsorption was enhanced in the presence of stearate cosorption. Orthophosphate in trace quantities was capable of displacing fatty acids from carbonate surfaces, but contrary to earlier studies, we found no major influence from magnesium ion on adsorption. The results of this study are interpreted in terms of a model based on the different types of forces which contribute to adsorption of these organic compounds. This model emphasizes the importance of organic aqueous solubility and the acid function as criteria controlling the adsorption of natural hydrophobic organics with carbonate mineral surfaces in aqueous fluids.

Zullig, James J.; Morse, John W.

1988-06-01

14

Adsorption equilibrium, kinetics and thermodynamics of dichloroacetic acid from aqueous solution using mesoporous carbon.  

PubMed

The presence of disinfection by-products, such as trihalomethanes and haloacetic acids in water, is believed to be harmful to human health. In this work, mesoporous carbon was synthesized with the evaporation-induced self-assembly method and employed to evaluate the effects of initial concentration, contact time, pH and temperature on the removal of dichloroacetic acid in batch experiments. Adsorption equilibrium was established in 480 min and the maximum adsorption (350mg/g) of dichloroacetic acid on the mesoporous carbon was observed to occur at 308 K and pH 3.0. Freundlich and Langmuir isotherms were used to analyse the equilibrium data at different temperatures; kinetic data were fitted to the pseudo-first-order and pseudo-second-order models and found that the adsorption capacity, mass transfer coefficient and diffusivity of dichloroacetic acid were directly affected by the physical and chemical parameters. In addition, the various thermodynamic parameters, such as Gibbs free energy (Delta G), enthalpy (Delta H = 54.35 kJmol-1) and entropy (Delta S = 258.36 Jmol-1 K-1) were calculated to analyse the adsorption process. The experimental results indicated that the mesoporous carbon was an excellent adsorbent for dichloroacetic acid removal from aqueous solutions. PMID:24956790

Ding, Ying; Zhu, Jianzhong; Cao, Yang; Chen, Shenglu

2014-08-01

15

Adsorption Characteristics of 2,4-Dichlorophenoxyacetic Acid (2,4-D) from Aqueous Solution on Powdered Activated Carbon  

Microsoft Academic Search

The removal of 2,4-dichlorophenoxyacetic acid (2,4-D), one of the most commonly used phenoxy acid herbicides, from aqueous solution was studied by using acid-washed powdered activated carbon (PAC) as an adsorbent in a batch system. Adsorption equilibrium, kinetics, and thermodynamics were investigated as a function of initial pH, temperature, and initial 2,4-D concentration. Powdered activated carbon exhibited the highest 2,4-D uptake

Z. AKSU; E. KABASAKAL

2005-01-01

16

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

Microsoft Academic Search

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

Andrey I. Tsyganok; Ichiro Yamanaka; Kiyoshi Otsuka

1998-01-01

17

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

18

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

19

Molecular Structure of Carbonic acid  

NSDL National Science Digital Library

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

2002-09-10

20

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

PubMed Central

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

2014-01-01

21

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

PubMed

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

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

2014-01-01

22

Reactivity of Hontomín carbonate rocks to acidic solution injection: reactive "push-pull" tracer tests results  

NASA Astrophysics Data System (ADS)

Several field tests will be carried out in order to characterize the reservoir for CO2 injection in Hontomín (Burgos, Spain) as part of the Compostilla project of "Fundación Ciudad de la Energía" (CIUDEN). Once injected, the dissolution of the CO2 in the resident brine will increase the acidity of the water and lead to the dissolution of the rocks, constituted mainly by carbonates. This mechanism will cause changes in the aquifer properties such as porosity and permeability. To reproduce the effect of the CO2 injection, a reactive solution with 2% of acetic acid is going to be injected in the reservoir and extracted from the same well (reactive "push-pull" tracer tests) to identify and quantify the geochemical reactions occurring into the aquifer. The reactivity of the rock will allow us also to evaluate the changes of its properties. Previously, theoretical calculations of Damkhöler numbers were done to determine the acid concentrations and injection flow rates needed to generate ramified-wormholes patterns, during theses "push-pull" experiments. The aim of this work is to present the results and a preliminary interpretation of the field tests.

De Gaspari, Francesca; Cabeza, Yoar; Luquot, Linda; Rötting, Tobias; Saaltink, Maarten W.; Carrera, Jesus

2014-05-01

23

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

NASA Astrophysics Data System (ADS)

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 was carried out putting the EAF dust from 1 g to 200 g in weight into 1 L of water that was introduced by CO2. Generally, the pH in the aqueous solution increased with an increase in weight of the additive EAF dust. Maximums of the eluted concentrations of zinc and chloride ion increased with an increase in the weight of the additive EAF dust whereas the extraction ratios of both of them decreased with an increase in the weight of the additive EAF dust. Iron in the EAF dust remained in the dust without elution. The limit of extraction of zinc from the EAF dust to water was given by the solubilities of ZnFe2O4 and ZnO expressed by eq. (6) and eq. (9) respectively.

Yokoyama, S.; Sasaki, T.; Sasano, J.; Izaki, M.

2012-03-01

24

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

SciTech Connect

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] as the extractant. It was found that near-quantitative extraction of Sm[sup 3+], Eu[sup 3+], Gd[sup 3+], and Dy[sup 3+] was achieved while the extraction efficiencies for La[sup 3+], Ce[sup 3+], Yb[sup 3+], and Lu[sup 3+] were much lower. The light lanthanides extracted as Ln(NO[sub 3])[sub 3][center dot]3TBP and the heavy lanthanides extracted as Ln(NO[sub 3])[sub 3][center dot]2TBP when TBP-modified CO[sub 2] was used as the extractant, while Ln(TTA)[sub 3][center dot] 3TBP and Ln(TTA)[sub 3][center dot]2TBP adducts were extracted when TTA was added to TBP-modified CO[sub 2]. 17 refs., 1 fig., 3 tabs.

Laintz, K.E.; Tachikawa, E. (Japan Atomic Energy Research Inst., Ibaraki-Ken (Japan))

1994-07-01

25

Deintercalation of carbonate ions from carbonate-type layered double hydroxides (LDHs) using acid–alcohol mixed solutions  

Microsoft Academic Search

Because of the high affinity of carbonate ions (CO32?) for LDHs (layered double hydroxides), their decarbonation—deintercalation of carbonate ions and conversion into LDHs containing other anions—has been considered difficult. So far, dilute acids have been used for decarbonation with additional salt to enhance the reaction. We found that the acid resistance of the LDHs is much higher in alcohols such

Nobuo Iyi; Hirohisa Yamada; Takayoshi Sasaki

2011-01-01

26

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

27

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

NASA Astrophysics Data System (ADS)

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

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

1999-03-01

28

Electrochemical study of carbon steel corrosion in buffered acetic acid solutions with chlorides and H 2S  

Microsoft Academic Search

In this work, the corrosion behavior of SAE 1018 carbon steel in buffered acetic acid (HAc) solutions containing chlorides, with and without H2S, was studied. Polarization curves obtained by different electrochemical techniques, indicate negligible modification of anodic slopes when adding H2S; however, the cathodic branch is more sensitive showing an accelerated reduction reaction in the presence of H2S. Interface characterization

M. A. Veloz; I. González

2002-01-01

29

Carbon steel corrosion inhibition in hydrochloric acid solution using a reduced Schiff base of ethylenediamine  

Microsoft Academic Search

The behavior of the Schiff base N,N?-bis(salicylidene)-1,2-ethylenediamine (Salen), its reduced form (N,N?-bis(2-hydroxybenzyl)-1,2-ethylenediamine) and a mixture of its preceding molecules, ethylenediamine and salicylaldehyde, as carbon steel corrosion inhibitors in 1molL?1 HCl solution was studied by corrosion potential measurements, potentiodynamic polarization curves, electrochemical impedance spectroscopy and spectrophotometry measurements. The experimental results showed that the reduced Salen presented the highest efficiency among the

Adriana Barbosa da Silva; Eliane D’Elia; José Antonio da Cunha Ponciano Gomes

2010-01-01

30

Evaluation of some bipyridinium dihalides as inhibitors for low carbon steel corrosion in sulfuric acid solution  

Microsoft Academic Search

Inhibition of low carbon steel (LCS) corrosion in 0.5 M H2SO4 solution by three bipyridinium dihalides (TMbPyBr2, HMbPyBr2 and MPhbPyCl2) was evaluated by potentiodynamic polarization curves, EIS and SEM techniques. The effectiveness of the inhibitors is ranked\\u000a as follows: MPhbPyCl2 ? TMbPyBr2 > HMbPyBr2. The compounds behave as mixed-type inhibitors and their adsorption on the steel surface obeys the Langmuir adsorption isotherm.\\u000a EIS measurements indicate

M. S. Morad; A. A. Hermas; A. Y. Obaid; A. H. Qusti

2008-01-01

31

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

32

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

33

Acid-Base Solutions  

NSDL National Science Digital Library

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

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

2010-09-01

34

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

PubMed

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

Rau, Greg H

2008-12-01

35

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

36

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

37

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

38

The carbonic acid system and calcite solubility in aqueous Na-K-Ca-Mg-Cl-SO 4 solutions from 0 to 90°C  

Microsoft Academic Search

CO 2 solubility, and the first and second stoichiometric dissociation constants of carbonic acid ( K 1 * and K 2 * ), have been determined in aqueous solutions containing Cl and SO 4 salts of Na, K, Ca and Mg over a wide range of ionic strength from 0 to 90°C at 0.1032 MPa (1 atm) pressure. Activity coefficients

Shiliang He; John W. Morse

1993-01-01

39

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

Microsoft Academic Search

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

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

2007-01-01

40

Microwave assisted catalytic wet air oxidation of H-acid in aqueous solution under the atmospheric pressure using activated carbon as catalyst.  

PubMed

Catalytic wet air oxidation (CWAO) is a promising method for the treatment of heavily contaminated wastewater. However, its application is restricted due to severe operation conditions (high pressure and high temperature). A microwave (MW) assisted oxidation method was investigated aiming to treat heavily contaminated wastewater under milder conditions. H-acid (1-amino-8-naphthol-3, 6-disulfonic acid) was selected as target compound to evaluate the performance of this novel process. The removal of H-acid and TOC (total organic carbon) for H-acid solution of 3000 mg/L reached as high as 92.6% in 20 min and 84.2% in 60 min, respectively under optimal conditions. The existence of activated carbon and oxygen proved to be critical for effective treatment. The activated carbon acted not only as a catalyst for H-acid decomposition, but also as a special material for the absorption of MW energy. Air was supplied to the reactor as an oxygen source at constant flows. The amino group in H-acid was converted ultimately into nitrate, and sulfonic group into sulfate. This observation gave an evidence of H-acid mineralization although other organic intermediates were unable to be determined. The value of BOD(5)/COD (ratio of 5d biochemical oxygen demand to chemical oxygen demand) increased from 0.008 to 0.467 indicating a significant improvement of biodegradability for the solution, which is beneficial for the further biological treatment of the wastewater. PMID:16600490

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

2006-09-01

41

Acid sorption regeneration process using carbon dioxide  

DOEpatents

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

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

2001-01-01

42

The carbonic acid system and calcite solubility in aqueous Na-K-Ca-Mg-Cl-SO[sub 4] solutions from 0 to 90[degrees]C  

Microsoft Academic Search

CO[sub 2] solubility, and the first and second stoichiometric dissociation constants of carbonic acid (K*[sub 1] and K*[sub 2]), have been determined in aqueous solutions containing Cl and SO[sub 4] salts of Na, K, Ca, and Mg over a wide range of ionic strength from 0 to 90[degrees]C at 0.1032 MPa (1 atm) pressure. Activity coefficients for CO[sub 2(aq)], HCO[sub

He Shiliang; J. W. Morse

1993-01-01

43

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

44

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

45

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

46

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

SciTech Connect

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

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

1998-11-01

47

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

48

Chemical transformations of CO2 in trifluoroacetic acid solutions  

NASA Astrophysics Data System (ADS)

It is established that a conversion reaction of carbon dioxide takes place at room temperature and atmospheric pressure in aqueous solutions of trifluoroacetic acid (TFA), which leads to the formation of oxalic acid and heavier polymerized products.

Vishnetskaya, M. V.; Ivanova, M. S.; Svichkarev, O. M.; Budynina, E. M.; Mel'nikov, M. Ya.

2013-05-01

49

The carbonic acid system and calcite solubility in aqueous Na-K-Ca-Mg-Cl-SO 4 solutions from 0 to 90°C  

NASA Astrophysics Data System (ADS)

CO 2 solubility, and the first and second stoichiometric dissociation constants of carbonic acid ( K 1? and K 2?), have been determined in aqueous solutions containing Cl and SO 4 salts of Na, K, Ca and Mg over a wide range of ionic strength from 0 to 90°C at 0.1032 MPa (1 atm) pressure. Activity coefficients for CO 2(aq), HCO 3- and CO 32 - ions were calculated from mco2, K 1? and K 2?. These activity coefficients were then used to derive Pitzer parameters for the interaction between these carbonate species and other ions between 0 and 90 °C. The resulting Pitzer model for the carbonic acid system was verified by its ability to accurately predict experimentally determined calcite solubility in brines from 0 to 90°C. However, calcite solubility measurements in complex brines initially supersaturated with respect to calcite indicate that Na +, Mg 2+ and SO 42- ions are probably incorporated into calcite lattice and significantly increase calcite solubility in brines.

He, Shiliang; Morse, John W.

1993-08-01

50

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

SciTech Connect

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

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

1997-02-11

51

Tungstophosphoric and tungstosilicic acids on carbon as acidic catalysts  

Microsoft Academic Search

Tungstophosphoric (TPA) and tungstosilicic acid (TSA) catalysts supported on carbon were studied. They were prepared by equilibrium and incipient wetness impregnation techniques. Solutions of TPA and TSA in 50% v\\/v ethanol–water were used to impregnate carbon at 20°C. The Fourier transform infrared and 31P nuclear magnetic resonance spectroscopies of TPA and TSA supported catalysts dried at 70°C showed that the

Marcelo E Chimienti; Luis R Pizzio; Carmen V Cáceres; Mirta N Blanco

2001-01-01

52

Mechanistic model of stress corrosion cracking (scc) of carbon steel in acidic solution with the presence of H2s  

NASA Astrophysics Data System (ADS)

In oil and gas industrial environments, H2S gas is one of the corrosive species which should be a main concern in designing infrastructure made of carbon steel. Combination between the corrosive environment and stress condition will cause degradation of carbon steel increase unpredictably due to their simultaneous effects. This paper will design a model that involves electrochemical and mechanical theories to study crack growth rate under presence of H2S gas. Combination crack and corrosion propagation of carbon steel, with different hydrogen concentration has been investigated. The results indicated that high concentration of hydrogen ions showed a higher crack propagation rate. The comparison between corrosion prediction models and corrosion model developed by researchers used to verify the model accuracy showed a good agreement.

Asmara, Y. P.; Juliawati, A.; Sulaiman, A.; Jamiluddin

2013-12-01

53

Activated carbon catalytic ozonation of oxamic and oxalic acids  

Microsoft Academic Search

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

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

2008-01-01

54

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

55

Organic acids tunably catalyze carbonic Acid decomposition.  

PubMed

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

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

2014-07-10

56

NMR relaxation and self-diffusion studies of H-bond exchange and molecular motion in pivalic acid and binary solutions of pivalic acid and carbon tetrachloride  

NASA Astrophysics Data System (ADS)

1H NMR relaxation times ( T1) and, in particular, self-diffusion coefficients in the liquid and plastic phases of neat pivalic acid (PA) and binary mixtures of PA and carbon tetrachloride are reported. The slight increase in T1 of the methyl protons on dilution is ascribed to reduced viscosity. The T1 measurements of PA monitor reorientations of complete dimers rather than monomers in the liquid. The large increase in T1 of the carboxy proton on dilution, followed by a corresponding reduction in the activation energy, is the result of a decreasing contribution from intermolecular interactions and enhanced mobility. The diffusion coefficients (approximately 10 -9 m 2s -1), obtained from the methyl and carboxy resonances, are mutually identical in both PA and the most dilute sample (6.4 mol%). This indicates that the carboxy hydrogen is diffusing at the same rate as the rest of the molecule. The average life time of the cyclic dimer thus appears to be longer than the mean time between diffusional jumps in the liquid state. In the disordered solid the diffusion coefficient of the carboxy hydrogen (8 × 10 -12 m 2s -1 at 286 K) is about three orders of magnitude larger than the whole-molecule diffusion coefficient (approximately 10 -14 m 2s -1), whereas the corresponding activation energies are 18 and 59 kJ mol -1. These observations show that the carboxy hydrogen is moving through the lattice approximately a thousand times faster than the rest of the molecule.

Aksnes, D. W.; Kimtys, L.

1994-06-01

57

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

Microsoft Academic Search

B(OH)3 and CO2 are acidic species of considerable geochemical importance, yet the microscopic nature of the acid dissociation reactions for these B and C species is not well understood. Quantum mechanical methods have recently been applied to the direct ab initio calculation of pKa values for many organic and inorganic weak acids, but the B and C acids have not

J. A. Tossell

2005-01-01

58

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

Microsoft Academic Search

B(OH)3 and CO2 are acidic species of considerable geochemical importance, yet the microscopic nature of the acid dissociation reactions for these B and C species is not well understood. Quantum mechanical methods have recently been applied to the direct ab initio calculation of pKa values for many organic and inorganic weak acids, but the B and C acids have not

J. A. Tossell

2005-01-01

59

Adsorption of chromium by activated carbon from aqueous solution  

Microsoft Academic Search

Adsorption isotherms of Cr(III) and Cr(VI) ions on two samples of activated carbon fibres and two samples of granulated activated carbons from aqueous solutions in the concentration range 20–1000 mg\\/l have been studied. The adsorption isotherms have been determined after modifying the activated carbon surfaces by oxidation with nitric acid, ammonium persulphate, hydrogen peroxide and oxygen gas at 350°C and

Diksha Aggarwal; Meenakshi Goyal; R. C. Bansal

1999-01-01

60

Ions in hyaluronic acid solutions  

PubMed Central

Hyaluronic acid (HA) is an anionic biopolymer that is almost ubiquitous in biological tissues. An attempt is made to determine the dominant features that account for both its abundance and its multifunctional role, and which set it apart from other types of biopolymers. A combination of osmotic and scattering techniques is employed to quantify its dynamic and static properties in near-physiological solution conditions, where it is exposed both to mono- and divalent counterions. An equation of state is derived for the osmotic pressure ? in the semidilute concentration region, in terms of two variables, the polymer concentration c and the ionic strength J of the added salt, according to which ?=1.4×103c9?4?J3?4 kPa, where c and J are expressed in mole. Over the physiological ion concentration range, the effect of the sodium chloride and calcium chloride on the osmotic properties of HA solutions is fully accounted for by their contributions to the ionic strength. The absence of precipitation, even at high CaCl2 concentrations, distinguishes this molecule from other biopolymers such as DNA. Dynamic light scattering measurements reveal that the collective diffusion coefficient in HA solutions exceeds that in aqueous solutions of typical neutral polymers by a factor of approximately 5. This property ensures rapid adjustment to, and recovery from, stress applied to HA-containing tissue. Small angle x-ray scattering measurements confirm the absence of appreciable structural reorganization over the observed length scale range 10–1000 Ĺ, as a result of calcium-sodium ion exchange. The scattered intensity in the transfer momentum rangeq>0.03 Ĺ?1 varies as 1?q, indicating that the HA chain segments in semidilute solutions are linear over an extended concentration range. The osmotic compression modulus c????c, a high value of which is a prerequisite in structural biopolymers, is several times greater than in typical neutral polymer solutions.

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

2009-01-01

61

Physical solubility of hydrogen sulfide and carbon dioxide in alkanolamine solutions  

Microsoft Academic Search

The study was undertaken to develop a method that would make direct measurements of acid gases, hydrogen sulfide and carbon dioxide, physical solubilities in aqueous alkanolamine solutions possible. Hydrogen sulfide and carbon dioxide physical solubilities in 20, 35, and 50% by weight diethanolamine aqueous solutions were measured. The solubility measurements were made at acid gas partial pressure up to 1000

Abu-Arabi

1988-01-01

62

Electroreduction of carbon dioxide in aqueous solutions at metal electrodes  

SciTech Connect

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

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

1996-12-31

63

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

64

Porosity in granular carbons activated with phosphoric acid  

Microsoft Academic Search

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

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

1995-01-01

65

Gallic acid water ozonation using activated carbon  

Microsoft Academic Search

The ozonation of gallic acid in water in the presence of activated carbon has been studied at pH 5. Hydrogen peroxide, ketomalonic and oxalic acids were identified as by-products. The process involves two main periods of reaction. The first period, up to complete disappearance of gallic acid, during which ozonation rates are slightly improved by the presence of activated carbon.

Fernando J. Beltrán; Juan F. García-Araya; Inés Giráldez

2006-01-01

66

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

Microsoft Academic Search

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

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

2007-01-01

67

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

Microsoft Academic Search

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

Seyed A Dastgheib; David A Rockstraw

2001-01-01

68

Dissolution of Feldspars in Oxalic Acid Solutions  

SciTech Connect

The rates of plagioclase feldspar and quartz dissolution in solutions of oxalic acid exceed those determined in inorganic solutions at the same pH. The effect of oxalic acid is not strictly additive to the rates in inorganic solution. A better empirical description of the dissolution process requires 6 terms, 3 each for Si and Al release. These terms describe proton-promoted dissolution, ligand-promoted dissolution, and a mixed proton/ligand interaction. The proton/ligand synergy is consistent with a mechanism in which HOx{sup -} (HOOCCOO{sup -}) is the species which attacks the mineral surface.

Welch, S. A.; Ullman, W. J.

1992-07-01

69

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...

70

Liquid-phase reactions induced by gaseous plasma. Decomposition of benzoic acids in aqueous solution  

Microsoft Academic Search

The liquid-phase organic reactions induced by a gaseous plasma, which was generated in a localized zone between an electrolytic solution and an anode by means of contact glow discharge electrolysis (CGDE), were investigated. Benzoic acids dissolved in a neutral phosphate buffer solution were efficiently oxidized and eventually decomposed to inorganic carbon. As the intermediate products, oxalic, formic and malonic acids

M. Tezuka; M. Iwasaki

1999-01-01

71

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...

72

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

73

Lithium insertion into the composites of acid-oxidized carbon nanotubes and tin oxide  

Microsoft Academic Search

Lithium intercalation into the composites of acid-oxidized carbon nanotubes and tin oxide was studied in an electrolyte system, 1 M solution of LiPF6 dissolved in a 50:50 mixture by volume of ethylene carbonate (EC) and dimethyl carbonate (DMC). The electrochemical method that is constant current charge–discharge test was used for electrochemical properties of the acid-oxidized carbon nanotubes and tin oxide. The

Zhanhong Yang; Qingwei Wang; Jianli Wang; Zaifeng Li; Shangbin Sang

2007-01-01

74

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

75

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

76

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

77

The interesterification of edible palm oil by stearic acid in supercritical carbon dioxide  

Microsoft Academic Search

A continuous flow apparatus is set up to study the enzymatic interesterification of palm oil by stearic acid in supercritical carbon dioxide. Domestic edible palm oil is mixed with stearic acid and loaded to a saturation tank in which the oil is extracted by supercritical carbon dioxide. The current of the extraction solution bubbled from the saturation tank is delivered

Ming-Tsai Liang; Chun-Hao Chen; Roo-Chain Liang

1998-01-01

78

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

79

Surface modification of a granular activated carbon by citric acid for enhancement of copper adsorption  

Microsoft Academic Search

In this study, citric acid was used to modify a commercially available activated carbon to improve copper ion adsorption from aqueous solutions. The carbon was modified with 1.0 M citric acid, followed by an optional step of reaction with 1.0 M sodium hydroxide. It was found that the surface modification reduced the specific surface area by 34% and point of

J. Paul Chen; Shunnian Wu; Kai-Hau Chong

2003-01-01

80

Carbon dioxide sequestration by direct mineral carbonation with carbonic acid  

Microsoft Academic Search

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,

William K. OConnor; David C. Dahlin; David N. Nilsen; Richard P. Walters; Paul C. Turner

2000-01-01

81

Alkaline earth cation extraction from acid solution  

DOEpatents

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

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

2003-01-01

82

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

83

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

84

Solution influence on biomolecular equilibria - Nucleic acid base associations  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

85

Evaluation of acidity of strong acid catalysts. 1. Derivation of an acidity function from carbon-13 NMR measurements  

SciTech Connect

The limitations of the Hammett indicator method for acidity measurements of liquid acid catalysts of practical importance and the inapplicability in principle of the Hammett acidity concept to solid acid catalysts are discussed. Evaluation of acidities from the hydronation equilibrium of two simple alcohols, methanol and ethanol, and an {alpha},{beta}-unsaturated detone, 4-methyl-3-penten-2-one (mesityl oxide, I), by carbon-13 NMR is demonstrated for sulfuric acid-water mixtures. The latter compound is particularly useful because the signal for its carbon atom C-4 shifts downfield upon hydronation by almost 50 ppm, whereas the signal for C-3 moves upfield by 3 ppm. The comparison of the chemical shift difference {delta}(C-4)-{delta}(C-3) ({Delta}{delta}) for two different solutions allows a comparison of acidities of the two solutions from which other medium effects upon chemical shifts have been canceled out. The variation of {Delta}{delta} with concentration of I, or the ratio of base (I) to acid, is linear, at least between 1 and 0.5 M of I. Extrapolation of {Delta}{delta} of I to (B)/(AH) = 0 ({Delta}{delta}{sup 0}) allows the use of {sup 13}C NMR spectroscopy to establish a thermodynamically meaningful acidity scale, such as the traditional acidity function H{sub 0}. The slope of {Delta}{delta} vs (B)/(AH) plot changes with acid strength; it is lowest (most negative) for the acidity at which I is half-protonated. The acidity required for half-protonation can thus be accurately determined from this slope. On the other hand, {Delta}{delta} can be also measured at the stoichiometric ratio of the indicator base to acid molecules or sites. The latter approach must be used for comparison of strength of solid acids.

Farcasiu, D.; Ghenciu, A.; Miller, G. (Univ. of Pittsburgh, PA (United States))

1992-03-01

86

Methods of pretreating comminuted cellulosic material with carbonate-containing solutions  

DOEpatents

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

Francis, Raymond

2012-11-06

87

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

PubMed

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

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

2014-01-01

88

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

PubMed Central

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

Moret, Severine; Dyson, Paul J.; Laurenczy, Gabor

2014-01-01

89

Carbon Steel from Prereduced Pellets: Acid Practice.  

National Technical Information Service (NTIS)

Eleven steelmaking heats are described in which acid practice was used to produce carbon steel from prereduced iron ore pellets. Lime was added to the furnace charge at two levels to eight of the heats to modify slag characteristics in the furnace and to ...

W. L. Hunter J. E. Tress W. A. Stickney

1974-01-01

90

The sorption of molybdenum from solutions of nitric acid  

NASA Astrophysics Data System (ADS)

The sorption of molybdenum(VI) on KU-2 × 8 and AV-17 × 8 ionites from 6 n solutions of nitric acid was studied. The sorption of molybdenum(VI) on the cationite and anionite changed depending on solution composition and nitric acid concentration. The sorption and electromigration data were used to determine the isoelectric point of molybdenum in solutions of nitric acid.

Umarakhunov, M. Kh.; Sadykova, U. A.; Khodzhaeva, G. A.

2011-04-01

91

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

92

Process for the extraction of strontium from acidic solutions  

DOEpatents

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

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

1993-01-01

93

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. 4 figs.

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

1994-09-06

94

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

95

Arterial blood carbonic Acid inversely determines lactic and organic acids.  

PubMed

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

Aiken, Christopher Geoffrey Alexander

2013-11-01

96

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

97

Reactions of rare earth flourides with sodium carbonate and hydroxide solutions  

SciTech Connect

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 hydroxide. The solution compositions were determined by titration: NaOH and Na/sub 2/CO/sub 3/ with hydrochloric acid, and NaF with Th(NO/sub 3/)/sub 4/ solution. The equilibrium concentrations of NaF and naOH (or Na/sub 2/CO/sub 3/) in the systems studied at 90 degrees are given, which shows that in the La-Lu series the degree of conversion of RE fluorides into hydroxides increases, and into carbonates decreases.

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

1986-01-10

98

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

PubMed

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

Nuithitikul, Kamchai; Srikhun, Sarawut; Hirunpraditkoon, Samorn

2010-01-01

99

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

Microsoft Academic Search

An electrochemical technique has been applied to enhance the removal of a common herbicide (bentazone) from aqueous solutions using an activated carbon cloth as electrode. A pH increase from acidic to basic reduces the uptake, with capacities going from 127 down to 80mg\\/g at pH 2 and 7, respectively. Increasing the oxygen content of the carbon cloth causes a decrease

Conchi O. Ania; François Béguin

2007-01-01

100

Uranyl fluoride luminescence in acidic aqueous solutions  

SciTech Connect

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

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

1996-08-01

101

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

Microsoft Academic Search

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

Erol Ayranci; Osman Duman

2010-01-01

102

Capacity of activated carbon in the removal of acid dyes subsequent to its thermal treatment  

Microsoft Academic Search

A commercial activated carbon (Prolabo) was subjected to thermal treatment at 400 and 600°C for 2h. Characterization of the parent, and heated products, was carried out by determining the N2\\/77K adsorption isotherms, FTIR spectra, acidic\\/basic sites, and adsorption of iodine, Acid Blue 74 (AB), Acid Red 73 (AR) and Acid Yellow 23 (AY) from aqueous solution. Thermal treatment resulted in

Amina A. Attia; Wafaa E. Rashwan; Soheir A. Khedr

2006-01-01

103

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

PubMed

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

Ania, Conchi O; Béguin, François

2007-08-01

104

Simulation of the flow of aqueous solutions through carbon nanotubes  

NASA Astrophysics Data System (ADS)

The flow of aqueous NaCl and NaI solutions through carbon nanotubes is treated by extensive molecular dynamics simulations. The dependence of diverse transport features on the solute specificity, the nanotube geometry, and the various atomic models employed, including polarizability, is addressed in detail. The interpretations are developed in conjunction with the structural details of the solution and the energy barriers the solute components have to overcome.

Beu, Titus A.

2011-09-01

105

Physical solubility of hydrogen sulfide and carbon dioxide in alkanolamine solutions  

SciTech Connect

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

Abu-Arabi, M.K.

1988-01-01

106

Solubilities of stearic acid, stearyl alcohol, and arachidyl alcohol in supercritical carbon dioxide at 35[degree]C  

SciTech Connect

The solubilities of stearic acid (octadecanoic acid), stearyl alcohol (1-octadecanol), and arachidyl alcohol (1-eicosanol) in supercritical carbon dioxide were measured by using a flow-type apparatus at 35 C up to 23.7 MPa. The solubilities of those substances and other fatty acids and higher alcohols in supercritical carbon dioxide at 35 C were correlated by a solution model based on the regular solution model coupled with the Flory-Huggins theory.

Iwai, Yoshio; Koga, Yoshio; Maruyama, Hironori; Arai, Yasuhiko (Kyushu Univ., Fukuoka (Japan). Dept. of Chemical Engineering)

1993-10-01

107

Solution Deposition Methods for Carbon Nanotube Field-Effect Transistors.  

National Technical Information Service (NTIS)

This study evaluated different methods for controlled deposition of carbon nanotubes (CNTs) from solution onto a silicon substrate to make CNT field-effect transistors (FETs). The goal of this deposition was to achieve reproducible device properties throu...

M. Ervin N. Salaets

2009-01-01

108

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

Microsoft Academic Search

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

Fang Yuan Jou; John J. Carroll; Alan E. Mather; Frederick D. Otto

1993-01-01

109

CARBON STEEL CORROSION IN HIGHLY CONCENTRATED NITRIC ACID CONTAINING HALOGEN COMPOUNDS  

Microsoft Academic Search

Iodine and its compounds are effective inhibitors against corrosion of ; carbon steel in highly concentrated nitric acid. The protective action remains ; effectiv-e in boiling acid solutions however the protective action is not ; effective in the vapor phase. The oxidation-reduction potentials of HNOâ ; do not change with iodine admixtures. (R.V.J.);

I. P. Mukanov; S. D. Beskov

1961-01-01

110

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

EPA Science Inventory

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

111

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

112

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

Microsoft Academic Search

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

J Behar; M Hitchings; R D Smyth

1977-01-01

113

Comparing the Amount of Acid in Different Solutions  

NSDL National Science Digital Library

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

Kessler, James H.; Galvan, Patricia M.

2007-01-01

114

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

PubMed

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

Rohwerder, Thore; Müller, Roland H

2010-01-01

115

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

116

Quantum conductance steps in solutions of multiwalled carbon nanotubes.  

PubMed

We have prepared solutions of multiwalled carbon nanotubes in Aroclor 1254, a mixture of polychlorinated biphenyls. The solutions are stable at room temperature. Transport measurements were performed using a scanning-tunneling probe on a sample prepared by spin coating the solution on gold substrates. Conductance steps were clearly seen. A histogram of a high number of traces shows maximum peaks at integer values of the conductance quantum G(0)=2e(2)/h, demonstrating ballistic transport at room temperature along the carbon nanotube over distances longer than 1.4 microm. PMID:12689021

Urbina, A; Echeverría, I; Pérez-Garrido, A; Díaz-Sánchez, A; Abellán, J

2003-03-14

117

Corrosion behavior of titanium-clad carbon steel in weakly alkaline solutions  

Microsoft Academic Search

The electrochemical polarization curves and corrosion potentials during long-term immersion of Ti, carbon steel, carbon steel tightened-Ti and Ti-clad carbon steel specimens were investigated in bentonite-contacting solution (mixture of sodium sulfate and sodium carbonate solutions), sodium sulfate solution and borate solution adjusted to pH=9.0–9.84. Ti and carbon steel were passivated during immersion in borate solution, while carbon steel was corroded

Kazuhisa Azumi; Masahiro Seo

2003-01-01

118

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

SciTech Connect

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

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

1993-01-01

119

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

120

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

SciTech Connect

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

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

1998-05-01

121

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

122

Dielectric properties and structure of aqueous solutions of boric acid  

Microsoft Academic Search

A model of the,structure of aqueous boric acid solution has been constructed, based on the view that the acid molecules are inserted into the ice-like lattice of water. The model predicts the rupture of a certain number of hydrogen bonds in the water structure. Themodel agrees withdata on the density and the dielectric constant of the solution at superhigh frequencies.

A. K. Lyashchenko; V. S. Goncharov; P. S. Yastremskii

1977-01-01

123

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

2011-05-01

124

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

125

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

126

Does Nitric Acid Dissociate at the Aqueous Solution Surface?  

Microsoft Academic Search

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

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

2011-01-01

127

Functionalized carbon nanofibers as solid-acid catalysts for transesterification.  

PubMed

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

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

2013-09-01

128

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

SciTech Connect

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

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

1990-05-01

129

Effect of solutes on austenite processing in ultralow carbon steels  

NASA Astrophysics Data System (ADS)

The effects of solutes in austenite in ultra-low carbon steel has to date not been sufficiently investigated. In order to gain an understanding of this, a series of steels were designed which feature the effects of particular elements in solution in austenite: boron, niobium, molybdenum, sulfur, phosphorus, and carbon. The influence of these solutes on austenite recrystallization kinetics, austenite flow stress, austenite to ferrite transformation, hot band texture development, and grain size evolution were studied. It was found that the elements in solution retarded the austenite recrystallization kinetics, with the largest influence coming from the boron addition. The solutes also tended to increase the activation energy for recrystallization, and raised the recrystallization stop temperature. Austenite flow stress was increased by the solutes, especially at lower temperatures. The solute elements had little effect on the transformation temperatures, but some elements such as boron, niobium, and molybdenum, caused the formation of non-polygonal ferrite when deformed material was quenched from austenite, leading to a microstructure with higher hardness. It was also found that in these steels the austenite grain size of hot band reached a stable value when re-heated in austenite, with the stable grain size varying for the different solutes. The influences of the solutes were related to the action of atoms which are segregated to the grain boundaries in austenite.

Mutschler, Ralph Andrew, Jr.

130

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

131

Investigation of acidic methanol solution as a fuel for microchannel fuel cells  

NASA Astrophysics Data System (ADS)

Acidic methanol solutions have been investigated for use in direct methanol microchannel fuel cells. The increased proton conductivity of a methanol solution containing sulfuric acid enables the anode to be constructed with the catalyst separated from the proton exchange membrane. This approach could be especially useful in the fabrication of thin-film microchannel fuel cells where a more complex carbon fabric electrode is not possible. The performance of sequential build-up fuel cells was shown to be improved by depositing an additional layer of Pt/Ru on the side-walls of the anode microchannels opposite the membrane. Results from anode half-cell and full cell experiments are reported.

Li, Jun; Moore, Christopher; Kohl, Paul A.

132

Ultrafast Carbon-Carbon SingleBond Rotational Isomerization in Room-Temperature Solution  

Microsoft Academic Search

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

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

2006-01-01

133

Precipitation of calcium and magnesium carbonates from homogeneous supersaturated solutions  

Microsoft Academic Search

Homogeneous (unseeded) precipitation of calcium and magnesium carbonates in the CaO–MgO–CO2–H2O system in supersaturated solutions was investigated. The induction period (?) of spontaneous nucleation and the composition of precipitated solid phases were determined. The influence of saturation degree (chemical affinity) and Mg2+\\/Ca2+ activity ratio in solution on the kinetics of CaCO3 nucleation was studied. The order of CaCO3 homogeneous nucleation

O. S. Pokrovsky

1998-01-01

134

Treatment of paper with basic agents in alcohols and supercritical carbon dioxide to neutralize acid and prolong storage time  

Microsoft Academic Search

The efficiency of treatment of paper prepared from 100% sulfite cellulose with basic agents (solutions of magnesium alkoxides or methoxycarbonate in alcohols or in supercritical carbon dioxide) to neutralize acid was studied, as influenced by the following factors: concentration of a basic agent in the neutralizing solutions, repetition of impregnation of paper with a neutralizing solution and hydrolysis of the

T. V. Dobrodskaya; P. A. Egoyants; V. K. Ikonnikov; N. D. Romashenkova; S. A. Sirotin; S. A. Dobrusina; N. I. Podgornaya

2004-01-01

135

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

EPA Science Inventory

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

136

The acid rain\\/carbon dioxide threat — Control strategies  

Microsoft Academic Search

Many of the world's most troublesome problems are closely interrelated. A case in point is the acid rain\\/carbon dioxide threat. Acid rain is the commonly used synonym for the major ingredients in the ongoing regional forest dieback, and carbon dioxide is a major influencing factor in the man-induced global geophysical experiment which is feared to lead to unacceptable climatic changes.

Wilfrid Bach

1985-01-01

137

Ultrasonic Relaxation in Aqueous Acetic Acid Solutions.  

National Technical Information Service (NTIS)

Ultrasonic absorption measurements have been made in aqueous acetic solutions at 15 to 85 MHz using pulse echo and pulse send-receive techniques. A weighted nonlinear regression method has been developed for the computation of the relaxation parameters. A...

L. G. Jackopin E. Yeager

1971-01-01

138

spł -linked amorphous carbon with sulfonic acid groups as a heterogeneous acid catalyst.  

PubMed

SO?H-bearing amorphous carbon prepared from polyvinyl chloride (PVC) is studied as a heterogeneous Brřnsted acid catalyst. Sulfonation of partially carbonized PVC produces amorphous carbon consisting of small SO?H-bearing carbon sheets linked by spł -based aliphatic hydrocarbons. This carbon material exhibits much higher catalytic performance in the hydrolysis of cellobiose than conventional heterogeneous Brřnsted acid catalysts with SO?H groups, including SO?H-bearing amorphous carbon derived from cellulose. This can be attributed to a high density of SO?H groups and the fast diffusion of reactants and products enabled by a flexible carbon network. PMID:22740285

Suganuma, Satoshi; Nakajima, Kiyotaka; Kitano, Masaaki; Hayashi, Shigenobu; Hara, Michikazu

2012-09-01

139

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

140

Numerical and experimental investigation of acid wormholing during acidization of vuggy carbonate rocks  

Microsoft Academic Search

Both small- (micron) to large- (centimeter) scale heterogeneities in carbonates cause the injected acids to propagate very differently than that predicted by a homogeneous model. Very few studies, either theoretical or experimental, address the effect of large scale heterogeneities (vugs) on matrix acidizing.This study explores the effects of heterogeneity on vuggy carbonate acidizing with high resolution computerized tomography imaging, image

Omer Izgec; Ding Zhu; Alfred D. Hill

2010-01-01

141

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

142

Control the polymorphism and morphology of calcium carbonate precipitation from a calcium acetate and urea solution  

Microsoft Academic Search

Two metastable calcium carbonate polymorphs, rod-like aragonite and spherical vaterite are selectively formed in this study. Aragonite rods were synthesized from a calcium acetate (Ca(AC)2) and urea (CO(NH2)2) solution under a given condition. In contrast, the addition of polyacrylamide (PAM) and oleic acid results in the formation of spherical vaterite. The morphology, size and crystal structure were characterized by means

Chengyu Wang

2008-01-01

143

Electrosorption of Ions from Aqueous Solutions by Nanostructured Carbon Aerogel  

Microsoft Academic Search

Electrosorption is generally defined as potential-induced adsorption on the surface of charged electrodes. After polarization of the electrodes, ions are removed from the electrolyte solution by the imposed electric field and adsorbed onto the surface of the electrodes. Experimental and modeling studies were conducted using two types of carbon aerogel composites of different surface areas to provide a better understanding

Tung-Yu Ying; Kun-Lin Yang; Sotira Yiacoumi; Costas Tsouris

2002-01-01

144

Potentiometric titration of free acid in uranium solutions.  

National Technical Information Service (NTIS)

Hydrolysis properties of metal cations and fundamental principles of the potentiometric titration of free acid in aqueous solutions containing metal cations were described. The published papers and reports for the alkalimetric and acidimetric titration of...

M. Suh W. Kim J. Kim S. Sohn T. Eom

1998-01-01

145

Textures of Ethyl Cellulose-Dichloroacetic Acid Mesomorphic Solution.  

National Technical Information Service (NTIS)

Textures of the ethyl cellulose (eC)-dichloracetic acid (DCA) mesomorphic solution were studied systematically by polarizing microscopy and small-angle light scattering. It was found that with increasing polymer concentration, the mesophase could show a d...

Y. Huang, J. Y. Zhou

1994-01-01

146

Determination of free base in aluminate-carbonate solutions by standard addition method  

SciTech Connect

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 concentration (i.e., free base) is required. For example, free base is measured to confirm that acidic wastes are neutralized or to verify that stored waste meets technical standards. This memorandum describes a new fifteen-minute standard addition procedure that determines free base in the presence of aluminate and carbonate.

Baumann, E.W.

1983-09-29

147

The inhibition of carbon steel corrosion in hydrochloric and sulfuric acid media using some benzimidazole derivatives  

Microsoft Academic Search

The corrosion inhibition of carbon steel in HCl and H2SO4 solutions in the presence of some benzimidazole derivatives such as benzimidazole (BI), 2-methylbenzimidazole (2-CH3-BI) and 2-mercaptobenzimidazole (2-SH-BI) was investigated using potentiodynamic polarization technique. Results obtained showed that the benzimidazole derivatives retard both the cathodic and anodic reactions in both acidic media, by virtue of adsorption on the carbon steel surface.

J. Aljourani; M. A. Golozar; K. Raeissi

2010-01-01

148

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

149

Functionalization of single-walled carbon nanotubes with ribonucleic acids  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

150

Cloud Point Extraction of Acetic Acid from Aqueous Solution  

Microsoft Academic Search

A new acetic acid separation method was developed through a successful combination of cloud point extraction and complex extraction technology (CPE-SE), where an acetic acid complex compound formed and was solubilized in a surfactant micelle solution, instead of an organic solvent, and then concentrated into one phase by a phase separation process of the CPE technology. Since no organic solvent

Bingjia Yao; Li Yang

2009-01-01

151

Thermal decomposition of dilute aqueous formic acid solutions.  

National Technical Information Service (NTIS)

Formic acid and formiate are oxidized in aqueous solutions at 260 deg. C and 20 bars O2. The formiate is converted to bicarbonate. The formic acid is both oxidized and decomposed by different routes: HCOOH -> CO + H2O and HCOOH -> CO2 + H2. In particular,...

A. B. Bjerre E. Soerensen

1989-01-01

152

Method for incorporating radioactive phosphoric acid solutions in concrete  

DOEpatents

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

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

1984-01-01

153

Method for incorporating radioactive phosphoric acid solutions in concrete  

DOEpatents

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

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

1982-07-08

154

Electrooxidation of ascorbic acid catalyzed on cobalt hydroxide-modified glassy carbon electrode  

Microsoft Academic Search

The electrochemical behavior of ascorbic acid on a cobalt hydroxide modified glassy carbon (CHM-GC) electrode in alkaline solution was investi- gated. The process of the involved oxidation and its kinetics were established using the cyclic voltammetry, chronoamperometry techniques, as well as by steady state polarization measurements. The results revealed that cobalt hyd- roxide promotes the rate of oxidation by increasing

Ghasem Karim-Nezhad; Mohammad Hasanzadeh; Lotfali Saghatforoush; Nasrin Shadjou; Balal Khalilzadeh; Sohrab Ershad

2009-01-01

155

Activated carbons by pyrolysis of coffee bean husks in presence of phosphoric acid  

Microsoft Academic Search

Activated carbons (Acs) were prepared by pyrolysis of coffee bean husks in presence of phosphoric acid (chemical activities). Husks from Colombian coffee beans were impregnated with aqueous solutions of H3PO4 following a variant of the incipient wetness method. Diffenent concentrations were used to produce impregnation ratios of 30, 60, 100 and 150 wt.%. Activation was carried out under argon flow

M. C. Baquero; L. Giraldo; J. C. Moreno; F. Suárez-Garc??a; A. Mart??nez-Alonso; J. M. D. Tascón

2003-01-01

156

Improved method for extracting lanthanides and actinides from acid solutions  

DOEpatents

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

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

1983-07-26

157

Pulse radiolysis of pyridinecarboxylic acids in aqueous solution  

NASA Astrophysics Data System (ADS)

The reactivity of OH, e -aq and H radicals towards aqueous carboxypyridines: picolinic acid (2-pyridinecarboxylic acid), PA; isonicotinic acid (4-pyridinecarboxylic acid), i-NA; 2,6-pyridinedicarboxylic acid, 2,6-PDCA; and 3,5-pyridinedicarboxylic acid, 3,5-PDCA was investigated in the pH-range 1-13.8. The absorption spectra of the OH-adducts, H-adducts and pyridinyl radicals are given as well as the formation and decay kinetics. In acid (but not in alkaline) solution, the reaction of H-atoms leads to the formation of two distinct products, namely H-adduct and pyridinyl radicals. The yields of pyridinyl radical are: 20% for PA, 75% for i-NA, 60% for 2,6-PDCA and 25% for 3,5-PDCA (a yield of 50% has been found earlier for nicotinic acid, NA).

Solar, S.; Getoff, N.; Sehested, K.; Holcman, J.

158

Dehydration and Oxidation of Cellulose Hydrolysis Products in Acidic Solution  

Microsoft Academic Search

The conversion of cellulose in homogenous solution to hydrolysis, dehydration,and oxidation products was investigated. A reaction sequence involving acetylation and degradation by aqueous acids led to humic acid, hydroxymethylfurfural, and levulinic acid as the isolated end-products. The influence of various reaction parameters upon the yields was studied.In the presence of ferric chloride some furfural was formed in addition to the

Klaus Garves

1981-01-01

159

EXTRACTION OF PHOSPHORIC ACID FROM NITRATE SOLUTIONS WITH ISOAMYL ALCOHOL  

Microsoft Academic Search

The extraction of phosphoric acid with isoamyl alcohol from aqueous solutions relevant to and produced by leaching of phosphatic iron ore by nitric acid has been studied. The results indicate that the extraction of phosphoric acid is not temperature dependent in the range 25–40°C, and that it increases with increasing the concentration of HNO3 or H2SO4. The salting-out effect of

Yu Zhang; Mamoun Muhammed

1988-01-01

160

Phosphorylation of Glyceric Acid in Aqueous Solution Using Trimetaphosphate  

NASA Technical Reports Server (NTRS)

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

Kolb, Vera; Orgel, Leslie E.

1996-01-01

161

Carbonation and Other Super Saturated Gases as Solution Modifiers for Improved Sensitivity in Solvent Assisted Ionization Inlet (SAII) and ESI  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

162

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

PubMed

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

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

2013-02-01

163

Thiosubstituted Organophosphinic Acids as Selective Extractants for Mercury(II) from Acidic Chloride Solutions  

Microsoft Academic Search

This paper reports results on the extraction behavior of mercury (II) from dilute hydrochloric acid solutions using mono? and di?sulphur analogs of bis(2,4,4?trimethylpentyl)phosphinic acid, namely, bis(2,4,4?trimethylpentyl)monothiophosphinic acid (CYANEX 302) and bis(2,4,4?trimethylpentyl)dithiophosphinic acid (CYANEX 301). The effect of various parameters such as, concentrations of mineral acid, metal ion, extractant, and the nature of the diluent on the extraction of mercury (II)

T. Francis; M. L. P. Reddy

2003-01-01

164

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

165

Miscibility and Properties of Acid-Treated Multi-Walled Carbon Nanotubes\\/Polyurethane Nanocomposites  

Microsoft Academic Search

Nanocomposites based on polyurethane and acid-treatment multi-walled carbon nanotubes (A-MWNTs) are prepared by solution blending. The surface of the MWNTs was modified by acid treatment to incorporated functional groups. The modified MWNTs exhibited improved dispersion in organic solvents and miscibility with the PU matrix. The derivatives of MWNTs were characterized by Fourier transform infrared (FT-IR) spectroscopy, Transmission electron microscopy (TEM)

Chi-Hung Lee; Jia-Yi Liu; Shen-Liang Chen; Yen-Zen Wang

2007-01-01

166

Roles of microbial acidic polysaccharides in precipitation rate and polymorph of calcium carbonate minerals  

Microsoft Academic Search

Organic molecules secreted by bacterial cells are capable of influencing dissolution and precipitation rates of various minerals including calcium carbonate (CaCO3) minerals. To evaluate the effects of polysaccharides on the precipitation rates and polymorph of CaCO3 minerals, precipitation experiments were performed in systems containing alginic acid or gellan gum by the batch method using 100ml solution at 25°C. Each solution

Motoharu Kawano; Jinyeon Hwang

2011-01-01

167

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

2011-12-01

168

Formation of UV-vis Absorbing Organic Solutes, Films, and Suspended Precipitates in Sulfuric Acid Solutions at Stratospheric Aerosol Acidities  

NASA Astrophysics Data System (ADS)

The stratospheric aerosol layer has traditionally been thought of as being composed of pure sulfuric acid/water aerosols, but recent airborne measurements of single particle composition (e.g. Murphy et al. 2007) have shown that 10-20% of sampled aerosols in the lower stratosphere have significant organic content. Since there is very little water vapor in the stratosphere, these sulfuric acid/organic particles will be extremely acidic (40-80 wt% sulfuric acid). Here we show that small amounts (approx. 0.1wt%) of carbonyl compounds allowed to react with such concentrated sulfuric acid solutions produce highly-colored solutions that continue to darken for months after mixing. We examined propanal, methylglyoxal, and glyoxal singly as well as in various combinations. In the case of propanal, colored organic films form on the surfaces of the solutions on a timescale of days to weeks depending on acidity. Solutions of various compositions also formed precipitates suspended near the liquid surface. UV-vis absorption spectra of the colored solutions will be presented along with kinetics of film formation as a function of acidity, temperature, and organic content. These results will be used to assess whether it is possible that such films could exist in the lower stratosphere (or upper troposphere) in quantities that would be significant enough to impact the direct and/or indirect climate forcing of these aerosols and/or satellite retrievals of atmospheric species that employ UV-vis wavelengths.

van Wyngarden, A. L.; Belle, C. L.; Dalle Ore, C. L.; Morrissey, M. J.; Rodgers, J. M.; Iraci, L. T.

2009-12-01

169

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

170

The 13 C chemical shifts of amino acids in aqueous solution containing organic solvents: Application to the secondary structure characterization of peptides in aqueous trifluoroethanol solution  

Microsoft Academic Search

The 13C chemical shifts for all of the protonated carbons of the 20 common amino acid residues in the protected linear pentapeptide Gly-Gly-X-Gly-Gly have been obtained in water at low pH as well as in aqueous solution containing 10, 20 and 30% acetonitrile or trifluoroethanol. Dioxane was used as an internal reference and its carbon chemical shift value was found

Venkataraman Thanabal; Diana O. Omecinsky; Michael D. Reily; Wayne L. Cody

1994-01-01

171

Coulometric determination of berkelium in sulfuric acid and nitric acid solutions  

SciTech Connect

Results are reported on the study and quantitative determination of berkelium by the coulometric method in 1 M sulfuric acid, in solutions of nitric acid, and in mixtures of these acids. The best results in the determination of berkelium were obtained in solutions of a mixture of nitric and sulfuric acids. In 1 M HNO/sub 3/ + 0.1 M H/sub 2/SO/sub 4/ solutions, berkelium can be determined with an accuracy within approx. +/- 2%, when its content is 10 ..mu..g/ml.

Timofeev, G.A.; Chistyakov, V.M.; Erin, E.A.

1987-03-01

172

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

PubMed

Adsorption of aromatic organic acids: benzoic acid (BA), salicylic acid (SA), p-aminobenzoic acid (pABA) and nicotinic acid (NA), onto high area activated carbon cloth from solutions in 0.4 M H(2)SO(4), in water at natural pH, in 0.1 M NaOH and also from solutions having pH 7.0 were studied by in situ UV-spectroscopic technique. The first-order rate law was found to be applicable for the kinetic data of adsorption. The rates and extents of adsorption of the organic acids were the highest from water or 0.4 M H(2)SO(4) solutions and the lowest from 0.1 M NaOH solution. The order of rates and extents of adsorption of the four organic acids in each of the four solutions (0.4 M H(2)SO(4), water, solution of pH 7.0 and 0.1 M NaOH) was determined as SA>BA>NA approximately pABA. These observed orders were explained in terms of electrostatic, dispersion and hydrogen bonding interactions between the surface and the adsorbate species, taking the charge of the carbon surface and the adsorbate in each solution into account. Adsorption of BA in molecular form or in benzoate form was analyzed by treating the solution as a mixture of two components and applying Lambert-Beer law to two-component system. The adsorption isotherm data of the systems studied were derived at 30 degrees C and fitted to Langmuir and Freundlich equations. PMID:16442224

Ayranci, Erol; Duman, Osman

2006-08-25

173

Solid Sulfonic Acid Catalysts Based on Porous Carbons and Carbon-Silica Composites  

NASA Astrophysics Data System (ADS)

Mesoporous carbons prepared using a templating method under different carbonization temperatures are sulfonated with concentrated H2SO4. Without the moving of silica template carbon-silica composites were prepared, which can maintain the pore structure well during sulfonation reaction process. The resultant samples are characterized using nitrogen adsorption, transmission electron microscope, field-emission scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, and elemental analysis techniques. The catalytic performances of the sulfonated carbons and composites are evaluated by esterification reaction of methanol with acetic acid. The results show that a low-temperature carbonization process is favorable for improving the reaction conversion of acetic acid. In addition, the sulfonated carbon-silica composites show a higher acetic acid conversion than the sulfonated mesoporous carbons.

Tian, Xiao Ning; Luo, Lijuan; Jiang, Zhongqing; Zhao, X. S.

174

Mass transfer during dissolution of cadmium in hydrochloric acid solutions  

SciTech Connect

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

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

1987-10-20

175

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

176

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

177

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

178

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

179

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

SciTech Connect

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

STALLINGS, MARY

2004-07-08

180

Insights into non-Fickian solute transport in carbonates  

PubMed Central

[1] We study and explain the origin of early breakthrough and long tailing plume behavior by simulating solute transport through 3-D X-ray images of six different carbonate rock samples, representing geological media with a high degree of pore-scale complexity. A Stokes solver is employed to compute the flow field, and the particles are then transported along streamlines to represent advection, while the random walk method is used to model diffusion. We compute the propagators (concentration versus displacement) for a range of Peclet numbers (Pe) and relate it to the velocity distribution obtained directly on the images. There is a very wide distribution of velocity that quantifies the impact of pore structure on transport. In samples with a relatively narrow spread of velocities, transport is characterized by a small immobile concentration peak, representing essentially stagnant portions of the pore space, and a dominant secondary peak of mobile solute moving at approximately the average flow speed. On the other hand, in carbonates with a wider velocity distribution, there is a significant immobile peak concentration and an elongated tail of moving fluid. An increase in Pe, decreasing the relative impact of diffusion, leads to the faster formation of secondary mobile peak(s). This behavior indicates highly anomalous transport. The implications for modeling field-scale transport are discussed. Citation: Bijeljic, B., P. Mostaghimi, and M. J. Blunt (2013), Insights into non-Fickian solute transport in carbonates, Water Resour. Res., 49, 2714–2728, doi:10.1002/wrcr.20238.

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

2013-01-01

181

Sorption of acid dyes from effluents using activated carbon  

Microsoft Academic Search

The sorption of three acid dyes, namely, Acid Red 114, Polar Yellow and Polar Blue RAWL, onto activated carbon, has been studied. Equilibrium isotherms have been measured for three single component systems (AB, AR, AY) and one binary component system (AB+AY). The isotherms were determined by shaking 0.05 g activated carbon, particle size range 500–710 ?m, with 0.05 dm3 dye

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

1999-01-01

182

Carbonic Anhydrase 5 Regulates AcidBase Homeostasis in Zebrafish  

Microsoft Academic Search

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

Ruben Postel; Arnoud Sonnenberg

2012-01-01

183

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

184

Aragonite nanorods in calcium carbonate/polymer hybrids formed through self-organization processes from amorphous calcium carbonate solution.  

PubMed

Nanostructured inorganic/polymer hybrid thin films comprising aragonite nanorods derived from aqueous suspensions of amorphous calcium carbonate (ACC) are prepared. For the formation of calcium carbonate (CaCO?)/polymer hybrids, spincoated and annealed films of poly(vinyl alcohol) (PVA) that function as polymer matrices are soaked in aqueous colloidal solutions dispersing ACC stabilized by poly(acrylic acid) (PAA). In the initial stage, calcite thin films form on the surface. Subsequently, aragonite crystals start to form inside the PVA matrix that contains PVA crystallites which induce aragonite nucleation. Nanostructured hybrids composed of calcite thin films consisting of nanoparticles and assembled aragonite nanorods are formed in the matrices of PVA. PMID:24425526

Kajiyama, Satoshi; Nishimura, Tatsuya; Sakamoto, Takeshi; Kato, Takashi

2014-04-24

185

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

SciTech Connect

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

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

1999-04-01

186

Coprecipitation of thorium and uranium peroxides from acid solutions  

SciTech Connect

The factors affecting successful coprecipitation of thorium and uranium peroxides from acid media were studied. Variables considered in this work were H/sup +/ concentration, H/sub 2/O/sub 2/ concentration, duration of contact, and rate of feed solution addition. In all experiments, stock solutions of Th(NO/sub 3/)/sub 4/ and UO/sub 2/(NO/sub 3/)/sub 2/ were fed at a controlled rate into H/sub 2/O/sub 2/ solutions with constant stirring. Samples were taken as a function of time to follow the H/sup +/ concentration of the solution, uranium precipitation, thorium precipitation, precipitant weight/volume of solution, and crystalline structure and growth. The optimum conditions for maximum coprecipitation are low H/sup +/ concentration, high H/sub 2/O/sub 2/ concentration, and extended contact time between the solutions.

McTaggart, D.R.; Mailen, J.C.

1981-01-01

187

Leaching kinetics of the magnetic fraction of converter matte in sulfuric acid and hydrochloric acid solutions  

NASA Astrophysics Data System (ADS)

The kinetic peculiarities of the dissolution of the magnetic fraction of converter matte in H2SO4 (150 g/l) and HCl (200 g/l) solutions are studied in the temperature range of 30-90°C. Under comparable conditions, the dissolution rate of the magnetic fraction of converter matte in HCl solutions is shown to be substantially higher than that in H2SO4 solutions. The kinetic parameters of the processes under study are calculated. It is found that the dissolution of the magnetic fraction of converter matte in a sulfuric acid solution occurs within a diffusion range ( E a ˜ 6.5 kcal/mol), whereas the dissolution in a hydrochloric acid solution corresponds to a kinetic range ( E a ˜ 15 kcal/mol). Possible mechanisms of the dissolution of the magnetic fraction of converter matte in mineral acid solutions are considered.

Palant, A. A.; Bryukvin, V. A.; Tsibin, O. I.; Paretskii, V. M.

2010-12-01

188

Highly accurate boronimeter assay of concentrated boric acid solutions  

SciTech Connect

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

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

1992-01-01

189

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

190

Electrokinetic Properties of Aluminum Nanopowders in Citric Acid Solution  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

191

Effect of polyacrylic acid and polyethylene glycol on the crystallization of calcium carbonates in the presence of magnesium ions  

Microsoft Academic Search

The effect of polyacrylic acid and polyethylene glycol on the crystallization of calcium carbonates in the presence of magnesium\\u000a ions was studied. It was found that the presence of magnesium ions in solution and the treatment temperature (80°C) influence\\u000a the formation of the final products of calcium carbonate crystallization. In binary mixtures, low-molecular-weight polyacrylic\\u000a acid and polyethylene glycol affect synergistically,

I. V. Shestak; P. D. Vorob’ev; D. V. Cherednichenko; E. V. Vorob’eva; G. V. Bondareva; N. Strnadova

2011-01-01

192

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

Microsoft Academic Search

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

D. Kavitha; C. Namasivayam

2008-01-01

193

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

2004-01-01

194

Electrochemical behaviors of amino acids at multiwall carbon nanotubes and Cu2O modified carbon paste electrode.  

PubMed

A carbon paste electrode modified with multiwall carbon nanotubes and copper(I) oxide (MWCNT-Cu(2)O CPME) was fabricated, and the electrochemical behaviors of 19 kinds of natural amino acids at this modified electrode were studied. The experimental results showed that the various kinds of amino acids without any derivatization displayed obvious oxidation current responses at the modified electrode. It was also found that the current response values of amino acids were dependent mainly on pH values of buffer solutions. The phenomenon could be explained by the fact that the amino acids suffered complexation or electrocatalytic oxidation processes under different pH values. Six kinds of amino acids (arginine, tryptophan, histidine, threonine, serine, and tyrosine), which performed high-oxidation current responses in alkaline buffers, were selected to be detected simultaneously by capillary zone electrophoresis coupled with amperometric detection (CZE-AD). These amino acids could be perfectly separated within 20 min, and their detection limits were as low as 10(-7) or 10(-8)mol L(-1) magnitude (signal/noise ratio=3). The above results demonstrated that MWCNT-Cu(2)O CPME could be successfully employed as an electrochemical sensor for amino acids with some advantages of convenient preparation, high sensitivity, and good repeatability. PMID:18522798

Dong, Shuqing; Zhang, Shan; Chi, Langzhu; He, Pingang; Wang, Qingjiang; Fang, Yuzhi

2008-10-15

195

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

196

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

PubMed

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

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

2011-01-01

197

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

SciTech Connect

Agricultural and herbaceous feedstocks may contain appreciable levels of sucrose. The goal of this study was to evaluate the survivability of sucrose and its hydrolysis products, fructose and glucose, during dilute sulfuric acid processing at conditions typically used to pretreat lignocellulose biomass. Solutions containing 25 g/l sucrose with 0.1-2.0% (w/w) sulfuric acid concentrations were treated at temperatures of 160-200 C for 3-12 min. Sucrose was observed to completely hydrolyze at all treatment conditions. However, appreciable concentrations of fructose and glucose were detected and glucose was found to be significantly more stable than fructose. Different mathematical approaches were used to fit the kinetic parameters for acid-catalyzed thermal degradation of these sugars. Since both sugars may survive dilute acid pretreatment, they could provide an additional carbon source for production of ethanol and other bio-based products.

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

2008-01-01

198

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

2009-07-01

199

Characterization of carbon black modified by maleic acid  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

200

Methanol Uptake by Low Temperature Aqueous Sulfuric Acid Solutions  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

201

The Application of Electrodialysis to Desalting an Amino Acid Solution  

Microsoft Academic Search

One of the main difficulties in preparing pharmaceutical products is isolating them from aqueous solutions of high salt concentration, as a high purity must be obtained. Several methods that employ organic solvents are normally used. In this paper, a novel method, electrodialysis, is presented together with its application to the desalting of an industrial effluent comprising an amino acid (p-hydroxyphenylglycine)

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

2000-01-01

202

THE SOLUTION OF SOIL MINERALS IN DILUTE ACIDS.  

PubMed

Montmorillonite goes readily into solution in slightly acid water. In strong acids only bases, in pure water only free silica is removed. In the range from 0.02 to 0.5 per cent. acid, both bases and silica go into solution and recombine as an aluminosilicate sol and as highly soluble salts. The sol recovered by evaporation, washing and drying is an amorphous colloid near pyrophyllite in composition, Al(2)O(3).mSiO(2).nH(2)O, with m averaging 4.1 (3.9 to 4.5) and n about 1.5. The slight variation in m is unrelated to either sol, acid or clay concentration. A general characteristic relation between the amount of sol formed and the amounts of clay, acid and water used has been found for montmorillonite clays. This relation differs in two essential properties from that previously deduced for halloysite-allophane solutions. The variation with temperature of the constants of these equations remains to be investigated. PMID:17740756

Nutting, P G

1945-06-15

203

Evaluation of acidity of strong acid catalysts. 1. Derivation of an acidity function from carbon-13 NMR measurements  

Microsoft Academic Search

The limitations of the Hammett indicator method for acidity measurements of liquid acid catalysts of practical importance and the inapplicability in principle of the Hammett acidity concept to solid acid catalysts are discussed. Evaluation of acidities from the hydronation equilibrium of two simple alcohols, methanol and ethanol, and an ι,β-unsaturated detone, 4-methyl-3-penten-2-one (mesityl oxide, I), by carbon-13 NMR is demonstrated

D. Farcasiu; A. Ghenciu; G. Miller

1992-01-01

204

Measurements and modeling of the phase behavior of ternary systems of interest for the GAS process: I. The system carbon dioxide+1-propanol+salicylic acid  

Microsoft Academic Search

As a representative model system for the gas-anti-solvent (GAS) process, the phase behavior of the ternary system carbon dioxide+1-propanol+salicylic acid has been studied experimentally. For this purpose, carbon dioxide has been chosen as the anti-solvent gas, 1-propanol as the organic solvent, and salicylic acid (2-hydroxy benzoic acid) as the model drug. In each experiment, a solution of salicylic acid in

A. Shariati; C. J. Peters

2002-01-01

205

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

206

Electrochemical study on the keto-enol tautomerization of p-hydroxyphenylpyruvic acid in aqueous solution.  

PubMed

The keto-enol tautomerization of p-hydroxyphenylpyruvic acid (pHPP) in aqueous solutions and the complexation reaction between enolic pHPP and boric acid have been studied by electrochemical techniques including linear sweep voltammetry (LSV), pulse voltammetry, and cyclic voltammetry (CV), combining with UV spectrometry. Electrochemical techniques reveal that in aqueous solution, there are two tautomers of pHPP: enolic form and ketonic form; the former exists mainly in freshly prepared pHPP solution, and the latter exists mainly in equilibrium solution. Both enolic and ketonic pHPP are electroactive. The electrochemical oxidation of enolic pHPP gives rise to two anodic waves, I(a) and II(a), while the electrochemical oxidation of ketonic pHPP only results in the observation of the second wave II(a). The oxidation process I(a) is revealed to be associated with the quasi-reversible, two-electron two-proton oxidation of "C=C"group at the side chain of enolic pHPP, and the oxidation process II(a) is proposed to result from the irreversible oxidation of phenolic hydroxyl group. It is observed that in aqueous solution, enolic pHPP can quickly complex with boric acid to yield enol-borate complex that can also oxidize at a glassy carbon electrode to yield an anodic wave. PMID:12893308

Chi, Yuwu; Duan, Jianping; Qi, Xiuzhen; Chen, Guonan

2003-08-01

207

Characterization of metal ion-nucleic acid interactions in solution.  

PubMed

Metal ions are inextricably involved with nucleic acids due to their polyanionic nature. In order to understand the structure and function of RNAs and DNAs, one needs to have detailed pictures on the structural, thermodynamic, and kinetic properties of metal ion interactions with these biomacromolecules. In this review we first compile the physicochemical properties of metal ions found and used in combination with nucleic acids in solution. The main part then describes the various methods developed over the past decades to investigate metal ion binding by nucleic acids in solution. This includes for example hydrolytic and radical cleavage experiments, mutational approaches, as well as kinetic isotope effects. In addition, spectroscopic techniques like EPR, lanthanide(III) luminescence, IR and Raman as well as various NMR methods are summarized. Aside from gaining knowledge about the thermodynamic properties on the metal ion-nucleic acid interactions, especially NMR can be used to extract information on the kinetics of ligand exchange rates of the metal ions applied. The final section deals with the influence of anions, buffers, and the solvent permittivity on the binding equilibria between metal ions and nucleic acids. Little is known on some of these aspects, but it is clear that these three factors have a large influence on the interaction between metal ions and nucleic acids. PMID:22210334

Pechlaner, Maria; Sigel, Roland K O

2012-01-01

208

Density, Acidity, and Conductivity Measurements of Uranyl Nitrate/Nitric Acid Solutions.  

National Technical Information Service (NTIS)

Conductivity, density, and acidity (pH) measurements were made on a series of uranyl nitrate solutions under conditions closely simulating the process used to load weak acid resins in the preparation of the HTGR recycle fuel particle. To relate these para...

D. A. Costanzo J. L. Botts R. J. Raridon

1978-01-01

209

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

210

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

Microsoft Academic Search

A pot experiment was conducted to study the effects of EDTA and low molecular weight organic acids (LMWOA) on the pH, total organic carbon (TOC) and heavy metals in the soil solution in the rhizosphere of Brassica juncea grown in a paddy soil contaminated with Cu, Zn, Pb and Cd. The results show that EDTA and LMWOA have no effect

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

2003-01-01

211

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

2012-09-01

212

Hydrolysis kinetics of lead silicate glass in acid solution  

NASA Astrophysics Data System (ADS)

Hydrolysis kinetics of the lead silicate glass (LSG) with 40 mol% PbO in 0.5 N HNO 3 aqueous acid solution was investigated. The surface morphology and the gel layer thickness were studied by scanning electron microscopy (SEM) micrographs. Energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma spectroscopy (ICP) were used to determine the composition of the gel layer and the aqueous solution, respectively. The silicon content of the dissolution products was determined by using weight-loss data and compositions of the gel layer and the solution. The kinetic parameters were determined using the shrinking-core-model (SCM) for rate controlling step. The activation energy obtained for hydrolysis reaction was Qche = 56.07 kJ/mole. The diffusion coefficient of the Pb ions from the gel layer was determined by using its concentration in solution and in LSG. The shrinkage of the sample and the gel layer thickness during dissolution process were determined.

Rahimi, Rafi Ali; Sadrnezhaad, Sayed Khatibuleslam; Raisali, Gholamreza; Hamidi, Amir

2009-06-01

213

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

214

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

215

Near infrared photochemistry of pyruvic acid in aqueous solution.  

PubMed

Recent experimental and theoretical results have suggested that organic acids such as pyruvic acid, can be photolyzed in the ground electronic state by the excitation of the OH stretch vibrational overtone. These overtones absorb in the near-infrared and visible regions of the spectrum where the solar photons are plentiful and could provide a reaction pathway for the organic acids and alcohols that are abundant in the earth's atmosphere. In this paper the overtone initiated photochemistry of aqueous pyruvic acid is investigated by monitoring the evolution of carbon dioxide. In these experiments CO(2) is being produced by excitation in the near-infrared, between 850 nm and ?1150 nm (11,765-8696 cm(-1)), where the second OH vibrational overtone (?? = 3) of pyruvic acid is expected to absorb. These findings show not only that the overtone initiated photochemical decarboxylation reaction occurs but also that in the aqueous phase it occurs at a lower energy than was predicted for the overtone initiated reaction of pyruvic acid in the gas phase (13,380 cm(-1)). A quantum yield of (3.5 ą 1.0) × 10(-4) is estimated, suggesting that although this process does occur, it does so with a very low efficiency. PMID:22233273

Larsen, Molly C; Vaida, Veronica

2012-06-21

216

Solution Preserves Nucleic Acids in Body-Fluid Specimens  

NASA Technical Reports Server (NTRS)

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

Pierson, Duane L.; Stowe, Raymond P.

2004-01-01

217

Potentiometric determination of free acidity in uranium(VI) and plutonium(IV) solutions and a sequential determination of uranium  

SciTech Connect

Free acidity in uranium(VI) and plutonium(IV) solutions has been determined with sodium sulfate as complexant and sodium carbonate as titrant. The described method is simple, accurate, and applicable to all ranges of nitric acid and heavy metal concentrations relevant to Purex process. The method is adaptable for remote operation. The overall recovery of nitric acid is 99.5% with 0.7% relative standard deviation. Uranium content has also been determined in the same aliquot with a recovery of 98.5% and 1.2% relative standard deviation after the determination of acidity.

Ahmed, M.K.; Suryanarayana, D.S.; Sabharwal, K.N.; Sreenivasan, N.L.

1985-10-01

218

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

Microsoft Academic Search

A potent catalyst has been prepared consisting of platinum (Pt), and platinum–palladium (Pt–Pd) nanoparticles supported on purified single-walled carbon nanotubes (Pt\\/CNT and Pt–Pd\\/CNT). Electrochemical characteristics of formic acid and formaldehyde oxidation on these catalysts are investigated via cyclic voltammetric analysis in mixed 0.5 M HCOOH (or 0.5 M HCHO) and 0.5 M H2SO4 solutions. The results imply that the Pt–Pd\\/CNT

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

2009-01-01

219

Enhanced life of proton exchange membrane fuel cell catalysts using perfluorosulfonic acid stabilized carbon support  

Microsoft Academic Search

We report a new and simple solution to increase life of Pt\\/C catalysts using the proton-conducting polymer (perfluorosulfonic acid, PFSA) stabilized carbon support (denoted these catalysts as Pt\\/NFC catalysts) as compared to conventional Pt\\/C catalysts commonly used in PEM fuel cells. A high catalytic activity of the catalyst is observed by both CV (cyclic voltammetry) and ORR (oxygen reduction reaction)

Niancai Cheng; Shichun Mu; Xiaojing Chen; Haifeng Lv; Mu Pan; Peter P. Edwards

2011-01-01

220

Molar extinction coefficients in aqueous solutions of some amino acids  

Microsoft Academic Search

Mass attenuation coefficients of amino acids viz. glycine (C2H5NO2), l-Serine (C3H7NO3), l-Theronine (C4H9NO3), l-Proline (C5H9NO2), l-Valine (C5H11NO2) and l-Phenylalanine (C9H11NO2) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by the gamma-ray transmission method in a narrow beam good geometry setup. Precisely measured densities of these solutions were used for the determination of these

Kulwant Singh; G. K. Sandhu; Gagandeep Kaur; B. S. Lark

2002-01-01

221

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

Microsoft Academic Search

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

C. O Gill; M Badoni

2004-01-01

222

Quantification method of size distribution of polysilicic acid in supersaturated silicic acid solution.  

PubMed

In order to estimate the absolute size distribution of polysilicic acid particles in geothermal waters, the distribution coefficient (K(av)) of gel permeation chromatography (GPC) for polysilicic acid particles and the hydrodynamic radius for the same polysilicic acid particles from Dynamic Light Scattering (DLS) are combined to quantify the particle size. From the combination, a quantitative relationship between the K(av) from GPC and the hydrodynamic radius for polysilicic acid from DLS was built up. Using this relationship, the change in particle size of polysilicic acid formed during the polymerization of silicic acid at pH 8 and 9 (initial silicic acid concentration: 800 ppm as SiO2) was examined. The result showed that polysilicic acid grew to 500 and 1000 nm by 5 h at pH 9 and 8, respectively. It was found that aluminum affects the growth of polysilicic acid particles, and that the effect depends on the pH. The proposed method in this study has been proved to be valid to measure the size of polysilicic acid during the polymerization of silicic acid in solutions with relatively low silicic acid concentration, such as geothermal water. PMID:23474723

Otsu, Emi; Etou, Mayumi; Ohashi, Hironori; Nishida, Ikuko; Bai, Shuquin; Okaue, Yoshihiro; Yokoyama, Takushi

2013-01-01

223

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

224

Electrochemical behavior of A516 carbon steel in solutions containing hydrogen sulfide  

SciTech Connect

The electrochemical behavior of A516 grade 70 (UNS K02700) carbon steel with a ferrite-pearlite structure in acidic chloride (Cl{sup {minus}}) solutions containing hydrogen sulfide at 25 C was investigated by electrochemical impedance spectroscopy (EIS). Results showed the impedance of A516 steel increased in an acidic Cl{sup {minus}} solution with H{sub 2}S (compared to a solution without H{sub 2}S) at the open-circuit potential (OCP). The corrosion process for A516 steel in the H{sub 2}S-containing solution was in two stages. Polarization resistance initially increased with time for immersion up to {approximately} 10 h but then decreased gradually. In the early stage, the impedance was characterized by one large semicircle in the Nyquist plot that increased with time for immersion up to 3 h. In the later stage, precipitation of a sulfide film modified the surface properties and led to variation in EIS data through a capacitive effect in the low-frequency region.

Huang, H.H.; Tsai, W.T.; Lee, J.T. [National Cheng Kung Univ., Tainan (Taiwan, Province of China). Dept. of Materials Science and Engineering

1996-09-01

225

Synthesis and acid catalysis of zeolite-templated microporous carbons with SO3H groups.  

PubMed

Microporous carbon catalysts with large surface areas (800-1100 m(2) g(-1)) and high densities of SO3H groups (ca. 1.1 mmol g(-1)) were synthesized by sulfonation of zeolite-templated microporous carbon. The resulting SO3H-bearing microporous carbon catalysts exhibited higher catalytic performance for the hydrolysis of cellobiose and the Beckmann rearrangement than conventional solid acid catalysts and non-porous amorphous carbon with SO3H groups. The high catalytic activity of these reusable heterogeneous catalysts can be attributed to the high surface area and microporous structure, which enhance the efficient incorporation and diffusion of reactant molecules from solution to the SO3H groups on the catalysts. PMID:23660580

Fukuhara, Kiichi; Nakajima, Kiyotaka; Kitano, Masaaki; Hayashi, Shigenobu; Hara, Michikazu

2013-06-21

226

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

227

Volumetric properties of aqueous solutions of glutaric acid  

Microsoft Academic Search

Densities of aqueous solutions with molalities up to 6molˇkg?1 were determined at 5K temperature intervals, from T=288.15K to T=333.15K. Densities served to evaluate the apparent molar volumes, V2,?(m,T), the cubic expansion coefficients, ?(m,T), and the changes of isobaric heat capacities with respect to pressure, (?CP\\/?P)T,m. They were qualitatively correlated with the changes in the structure of water when glutaric acid

Meyrav Ben-Hamo; Alexander Apelblat; Emanuel Manzurola

2007-01-01

228

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

229

Surface tensions of solutions containing dicarboxylic acid mixtures  

NASA Astrophysics Data System (ADS)

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

Lee, Jae Young; Hildemann, Lynn M.

2014-06-01

230

Solubility of nicotinic acid in polyamidoamine dendrimer solutions.  

PubMed

In the present study we investigated the effect of ethylenediamine (EDA) core polyamidoamine (PAMAM) dendrimers on the aqueous solubility of nicotinic acid. The aqueous solubility of nicotinic acid was measured in the presence of dendrimers at room temperature in distilled water. The effect of variables, such as pH condition, concentration, surface functional group and generation (molecule size) of dendrimer, has been investigated. Results showed that the solubility of nicotinic acid in the dendrimer solutions was proportional to dendrimer concentration, both amine and ester-terminated dendrimers caused the higher increase in nicotinic acid solubility at higher pH conditions. The order in which the dendrimers increased the solubility at a constant pH condition was G4>G3>G2>G1. In addition, at each pH, the solubility of nicotinic acid was greater in the presence of amine-terminated dendrimers compared to the amine ester-terminated dendrimers possessing the same number of surface functional groups. Under suitable conditions PAMAM dendrimers can be highly effective used to enhance the solubility of nicotinic acid. PMID:16226352

Yiyun, Cheng; Tongwen, Xu

2005-12-01

231

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

Microsoft Academic Search

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

K. Kadirvelu; K. Thamaraiselvi; C. Namasivayam

2001-01-01

232

Dehydration and oxidation of cellulose hydrolysis products in acidic solution  

SciTech Connect

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

Garves, K.

1981-01-01

233

Methanol Uptake By Low Temperature Aqueous Sulfuric Acid Solutions  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

234

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

235

True solutions of single-walled carbon nanotubes for assembly into macroscopic materials.  

PubMed

Translating the unique characteristics of individual single-walled carbon nanotubes into macroscopic materials such as fibres and sheets has been hindered by ineffective assembly. Fluid-phase assembly is particularly attractive, but the ability to dissolve nanotubes in solvents has eluded researchers for over a decade. Here, we show that single-walled nanotubes form true thermodynamic solutions in superacids, and report the full phase diagram, allowing the rational design of fluid-phase assembly processes. Single-walled nanotubes dissolve spontaneously in chlorosulphonic acid at weight concentrations of up to 0.5 wt%, 1,000 times higher than previously reported in other acids. At higher concentrations, they form liquid-crystal phases that can be readily processed into fibres and sheets of controlled morphology. These results lay the foundation for bottom-up assembly of nanotubes and nanorods into functional materials. PMID:19893518

Davis, Virginia A; Parra-Vasquez, A Nicholas G; Green, Micah J; Rai, Pradeep K; Behabtu, Natnael; Prieto, Valentin; Booker, Richard D; Schmidt, Judith; Kesselman, Ellina; Zhou, Wei; Fan, Hua; Adams, W Wade; Hauge, Robert H; Fischer, John E; Cohen, Yachin; Talmon, Yeshayahu; Smalley, Richard E; Pasquali, Matteo

2009-12-01

236

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

PubMed

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

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

2014-02-01

237

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

NASA Astrophysics Data System (ADS)

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

Hewitt, Corey A.; Carroll, David L.

2013-08-01

238

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

239

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

SciTech Connect

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 microporous polymeric arylsulfonic acid resin-Dowex 50W-X8 in the same solvent. Under well-controlled anhydrous conditions there is a good correlation (r = 0.992) between the heats of reaction of the bases with the homogeneous and heterogeneous acid systems, but the homogeneous system gives a more exothermic interaction by 3-4 kcal mol/sup -1/ for a series of 29 substituted pyrimidines, anilines, and some other amines. This difference may be attributed to homohydrogen bonding interactions between excess acid and sulfonate anion sites which are more restricted geometrically in the resin than in solution. Other factors which affect the enthalpy change for the acid-base interaction are the acid/base ratio, the water content of the sulfonic acid, the solvent, and the resin structure (e.g., microporous vs. macroporous). Steric hindrance in the base does not differentiate solid from homogeneous acid. In addition to the use of titration calorimetry, heats of immersion are reported for the Dowex-arylsulfonic acid resins and the Nafion-perfluorinated sulfonic acid resin in a series of basic liquids. The results are compared with each other and with those from a previous study of several varieties of coal.

Arnett, E.M.; Haaksma, R.A.; Chawla, B.; Healy, M.H.

1986-08-06

240

Enhancement effect of an adsorbed organic acid on oxygen reduction at various types of activated carbon loaded with platinum  

NASA Astrophysics Data System (ADS)

We have found that application of activated carbon as a support of platinum in electrocatalysts for polymer electrolyte fuel cells improves the activity for oxygen reduction, especially by using activated carbon with trifluoromethanesulfonic acid adsorbed in the pores. In the present study, we investigated this enhancement effect of the acid for oxygen reduction at activated carbon of various specific surface areas and mean pore diameters. After adsorption of potassium trifluoromethanesulfonate onto the activated carbon loaded with platinum, a catalyst layer was formed from the activated carbon and a polymer electrolyte, followed by replacing the potassium ions with protons. We measured the adsorption isotherms of trifluoromethanesulfonate onto the activated carbons and found that adsorption behavior was dependent on the kind of activated carbon. Electrochemical properties of the layer was evaluated by cyclic voltammetry and by the relationship between electrode potential and oxygen reduction current in perchloric acid solution, supporting the layer on a rotating glassy carbon disk electrode. The properties, and consequently the enhancement effect of the organic acid for oxygen reduction, were clearly dependent on the kind of activated carbon and were explicable based on the pore structure and the adsorption behavior.

Maruyama, Jun; Abe, Ikuo

241

In situ derivatisation and extraction of volatile fatty acids entrapped on anion-exchange resin from aqueous solutions and urine as a test matrix using pentafluorobenzyl bromide in supercritical carbon dioxide.  

PubMed

The simultaneous extraction and derivatisation of anion-exchange resin-trapped volatile fatty acids (C2-C5) as their pentafluorobenzyl esters has successfully been performed under CO2 supercritical fluid extraction conditions. Volatile fatty acid standards of acetic, propionic and n-butyric acids (at 20 and 100 ppm) as their ester derivatives were recovered at 78.0-101.5% (C.V. 3.5-7.5%, n=6 and 7). Likewise, acrylic acid recoveries were 57.0-61.0% (C.V. 5.5-5.6%, n=6 and 7). This methodology was applied to the quantitation of acetic, propionic, n-butyric and n-valeric acids in spiked urine as a test matrix. Initial clean-up of phosphate and sulfate in the urine was required prior to anion-exchange application and this was achieved by barium salt precipitation. Recoveries ranged from 36 to 66.5% (C.V. 5.9-14.4%, n=9 and 6). PMID:9234843

Cummins, M T; Wells, R J

1997-06-20

242

Activated Carbon Open Circuit Potential Shifts in Aqueous Solutions  

Microsoft Academic Search

Interaction of certain organic compounds with activated carbon and its effect on the carbon open circuit potentials were studied. It was shown that shifts in open circuit potentials depended on the filling of the activated carbon surface. Whereas adsorption of the investigated compounds on the carbon led to positive potential shifts, their elimination (desorption) from carbon surface led to shifts

Mikhail M. Goldin; Gary Blanchard; Alexander Volkov; Mogely Khubutiya; Vladimir Kolesnikov; Anatoly Evseev; Mark Goldin

2007-01-01

243

Ethylbenzene Removal by Carbon Nanotubes from Aqueous Solution  

PubMed Central

The removal of ethylbenzene (E) from aqueous solution by multiwalled, single-walled, and hybrid carbon nanotubes (MWCNTs, SWCNTs, and HCNTs) was evaluated for a nanomaterial dose of 1?g/L, concentration of 10–100?mg/L, and pH 7. The equilibrium amount removed by SWCNTs (E: 9.98?mg/g) was higher than by MWCNTs and HCNTs. Ethylbenzene has a higher adsorption tendency on CNTs, so that more than 98% of it adsorbed in first 14?min, which is related to the low water solubility and the high molecular weight. The SWCNTs performed better for ethylbenzene sorption than the HCNTs and MWCNTs. Isotherms study indicates that the BET isotherm expression provides the best fit for ethylbenzene sorption by SWCNTs. Carbon nanotubes, specially SWCNTs, are efficient and rapid adsorbents for ethylbenzene which possess good potential applications to maintain high-quality water. Therefore, it could be used for cleaning up environmental pollution to prevent ethylbenzene borne diseases.

Bina, Bijan; Pourzamani, Hamidreza; Rashidi, Alimorad; Amin, Mohammad Mehdi

2012-01-01

244

Surface functional groups on acid-activated nutshell carbons  

Microsoft Academic Search

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

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

1999-01-01

245

Carbon edge XANES spectroscopy of amino acids and peptides  

Microsoft Academic Search

Carbon edge X-ray absorption near-edge structures (XANES) of amino acids and small peptides have been investigated for the first time. Because of the heat sensitivity of the samples, gas phase spectroscopy of evaporated samples is difficult. Therefore they were analyzed in solid form as thin films. Quantitative absorption measurements require the region of the sample which is illuminated to be

J Boese; A Osanna; C Jacobsen; J Kirz

1997-01-01

246

Volatile fatty acids as organic carbon sources in denitrification  

Microsoft Academic Search

We have evaluated the possibilities of waste water denitrification using volatile fatty acids (VFA) as the sole carbon and electron source in an activated sludge culture continuously fed with a mixture of acetate, propionate, butyrate and valerate. All the VFA were biodegraded in denitrification conditions by a mixed adapted bacterial population with 5 predominant different bacterial strains (Ochrobactrum anthropi, Moraxella

S. Fass; V. Ganaye; V. Urbain; J. Manem; J. C. Block

1994-01-01

247

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

2013-11-01

248

Degradation of Dichloroacetic Acid in Acidic Solution by Nanosized ZnO Catalyzed Ozonation  

Microsoft Academic Search

Nanosized ZnO catalysts prepared by the precipitation method were used for the degradation of dichloroacetic acid (DCAA) in acidic solution by ozone. Catalyst samples were characterized by measuring the specific area (BET) and X-ray diffraction (XRD). The results showed that the presence of ZnO catalyst obviously improved the degradation efficiency of DCAA in the process of ozonation, 67.9% higher compared

Xu Zhai; Zhonglin Chen; An Li; Shuqing Zhao; He Wang; Lei Yang

2010-01-01

249

A pulse radiolysis study of salicylic acid and 5-sulpho-salicylic acid in aqueous solutions  

Microsoft Academic Search

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 109dm3mol?1s?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

Kamal Kishore; T. Mukherjee

2006-01-01

250

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

251

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

252

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

253

UV photolysis of perfluorooctanoic acid (PFOA) in dilute aqueous solution.  

PubMed

Perfluorooctanoic acid (PFOA) is very persistent in the environment and widely detected in the water environment. Only some advanced methods with extreme reaction conditions are shown to be capable of degrading the compound efficiently, and almost all the earlier investigations used very high PFOA concentrations. The compound is detected normally at very low concentrations in the water environment, while mild reaction conditions for its degradation are preferable. This article aimed to elucidate photodegradation of PFOA in dilute aqueous solutions by combined UV wavelengths (185 nm+254 nm) and 254 nm using a newly designed UV jacket. PFOA degradation was greatly enhanced with the combined wavelengths with almost one hundred percent PFOA removals in four-hour reaction. The removals were well described by the first-order reaction kinetic. The removal efficiencies and rate values significantly decreased with smaller initial PFOA concentrations. But defluorination was greatly enhanced with smaller PFOA concentrations possibly due to accelerated decomposition of fluorinated intermediates of PFOA. Formic acid and acetic acid were two tentatively identified intermediates of PFOA photolysis while the former was a major intermediate predominantly controlling solution pH during the oxidation. The results demonstrated that PFOA photolysis by the combined wavelengths with mild reaction conditions can be greatly enhanced by proper design of UV jacket and reactor system. PMID:21252431

Giri, R R; Ozaki, H; Morigaki, T; Taniguchi, S; Takanami, R

2011-01-01

254

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

255

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

256

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

257

GADOLINIUM OXALATE SOLUBILITY MEASUREMENTS IN NITRIC ACID SOLUTIONS  

SciTech Connect

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

Pierce, R.

2012-02-22

258

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

259

Some organic and inorganic compounds as inhibitors for carbon steel corrosion in 3.5 percent NaCl solution  

Microsoft Academic Search

Purpose – To study the effects of the sodium salts of molybdate, tungstate and monovanadate as well as some derivatives of Neville-Winter acid azo dyes on the corrosion of carbon steel in 3.5 percent NaCl solution. Design\\/methodology\\/approach – Open circuit potential measurement and potentiostatic polarization techniques have been used. Findings – It was found that all the compounds had inhibition

M. Abdallah; A. Y. El-Etre; M. G. Soliman; E. M. Mabrouk

2006-01-01

260

Systems solutions by lactic acid bacteria: from paradigms to practice  

PubMed Central

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

2011-01-01

261

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

Microsoft Academic Search

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

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

2012-01-01

262

Molecular Controls on the Inter Tubular Interactions of Single Walled Carbon Nanotubes Solubilized in Super Acids  

NASA Astrophysics Data System (ADS)

Super acids represented by 100chlorosulfonic acid or Triflurosulfonic acid form a class of solvents that could bring about true solubility of single walled carbon nanotubes (SWNT). The intertubular interactions of these rigid rod like molecules in a true solution determines the phase behavior of the suspension. Ordered phases such as nematic liquid crystals formed in the super acid suspensions hold the key to the successful formation of intrinsically ordered macroscopic objects like fibers, thin films or carbon alewives. Organic derivatization of the side walls turns out to be a promising tool to exert functional control on the inter-tubular interactions and hence the phase behavior. SWNT produced by the HiPco process have been organically derivatized with different functionalities through a novel free radical reaction. The solubility and phase behavior of the organically derivatized SWNT in super acids have been examined employing polarized light microscopy. Solid phases were obtained by quenching the super acid suspensions in suitable organic solvents and were examined for intrinsic ordering through polarized Raman Microscopy. Correlations between the chosen organic functionality and intrinsic ordering of SWNT will be presented.

Ramesh, Sivarajan; Ericson, Lars M.; Sulpizio, Joseph A.; Saini, Rajesh K.; Billups, W. E.; Hauge, Robert H.; Adams, W. Wade; Smalley, Richard E.

2003-03-01

263

The Estimation of Acidic Behavior of Wood by Treatment with Aqueous Na2HPO4 Solution  

PubMed Central

As a new approach, the acidity that wood exhibits under moderate conditions is assayed by stimulated dissociation of weak wood acids in lightly basic secondary phosphate solutions. To assure a sufficient dissociation of hardly soluble weak acids in the solution, the amount of wood suspended in Na2HPO4 solutions should be small but vary depending on the degree of acidity of wood species. However, the difficulties are associated with the titration of very dilute acids limiting the precision of the measurement. If the disintegrated wood is suspended in a secondary phosphate solution, the weak woods acids form the conjugate acid Na2HPO4 from secondary phosphate Na2HPO4 resulting in a pH fall of the solution. The decrease in the pH value in phosphate solution, which depends on the wood acidity, can be evaluated to estimate the acidity arising from wood under moderate conditions.

Ucar, Gunes; Balaban Ucar, Mualla

2012-01-01

264

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

Microsoft Academic Search

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

Seyed A. Dastgheib; David A. Rockstraw

2002-01-01

265

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

266

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

Microsoft Academic Search

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

Chien-To Hsieh; Hsisheng Teng

2000-01-01

267

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

USGS Publications Warehouse

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

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

1992-01-01

268

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

PubMed

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

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

2013-02-01

269

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

270

Hydrogen production by photoelectrochemically splitting solutions of formic acid.  

PubMed

A TiO?/FTO (FTO=fluorine-doped tin oxide) electrode was prepared by dip-coating FTO in a suspension of TiO? prepared from a sol-gel method and was used as a photoanode to split an aqueous solution of formic acid to produce hydrogen. The surface of the TiO?/FTO film was covered with assemblies of TiO? nanoparticles with a diameter of approximately 20?nm. Under irradiation by using a Xe lamp, splitting of formic acid was performed at different applied current densities. Compared to splitting water or utilizing FTO and Pt foil as the anode, the splitting voltage is much lower and can be as low as -0.27?V. The results show that the splitting voltage is related to the concentration of free formate groups. The evolution rate of hydrogen measured by using gas chromatography is 130??mol?h?š at a current density of 20?mA?cm?˛ and the energy-conversion efficiency can be 1.79?%. Photoelectrolysis of formic acid has the potential to be an efficient way to produce hydrogen with a high energy-conversion efficiency. PMID:21994155

Li, Lei; Guo, Wenliang; Zhu, Yusong; Wu, Yuping

2011-10-17

271

Structure and dynamics of concentrated hydrochloric acid solutions.  

PubMed

Self-consistent iterative multistate empirical valence bond (SCI-MS-EVB) simulations for four different concentrated hydrochloric acid (HCl) concentrations (0.43, 0.85, 1.68, and 3.26 M) were conducted to study the structure and dynamic properties of the aqueous multiple excess proton systems. The present, more extensive simulations, confirm that the hydrated excess protons have a tendency to form metastable contact ion pairs by positioning the hydronium oxygen lone pair sides toward one another, in agreement with earlier work [ Wang, F. Izvekov, S. Voth, G. A. J. Am. Chem. Soc. 2008 , 130 , 3120 ]. This unusual behavior results from the special "amphiphilic" nature of the hydrated excess proton. Increasing the acid concentration to 3.26 M was found to have minor effects on the solvation structures of the hydrated proton and chloride counterion, while the average lifetime of the hydrated proton contact ion pairs was reduced. The addition of salts (KCl and NaCl) into the acid solution increases the stability of the hydrated proton pairs and reduces the proton diffusion. PMID:20593833

Xu, Jianqing; Izvekov, Sergei; Voth, Gregory A

2010-07-29

272

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

273

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

USGS Publications Warehouse

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

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

1994-01-01

274

Electrophoretic deposition of phthalocyanine in organic solutions containing trifluoroacetic acid.  

PubMed

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

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

2010-11-16

275

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] [Korea Electric Power Research Inst., Taejon (Korea, Republic of). Center for advanced Studies in Energy and the Environment

1998-07-01

276

Adsorption of naphthenic acids on high surface area activated carbons.  

PubMed

In oil sands mining extraction, water is an essential component; however, the processed water becomes contaminated through contact with the bitumen at high temperature, and a portion of it cannot be recycled and ends up in tailing ponds. The removal of naphthenic acids (NAs) from tailing pond water is crucial, as they are corrosive and toxic and provide a substrate for microbial activity that can give rise to methane, which is a potent greenhouse gas. In this study, the conversion of sawdust into an activated carbon (AC) that could be used to remove NAs from tailings water was studied. After producing biochar from sawdust by a slow-pyrolysis process, the biochar was physically activated using carbon dioxide (CO2) over a range of temperatures or prior to producing biochar, and the sawdust was chemically activated using phosphoric acid (H3PO4). The physically activated carbon had a lower surface area per gram than the chemically activated carbon. The physically produced ACs had a lower surface area per gram than chemically produced AC. In the adsorption tests with NAs, up to 35 mg of NAs was removed from the water per gram of AC. The chemically treated ACs showed better uptake, which can be attributed to its higher surface area and increased mesopore size when compared with the physically treated AC. Both the chemically produced and physically produced AC provided better uptake than the commercially AC. PMID:24766592

Iranmanesh, Sobhan; Harding, Thomas; Abedi, Jalal; Seyedeyn-Azad, Fakhry; Layzell, David B

2014-07-01

277

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

PubMed Central

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

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

2012-01-01

278

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

279

Coated carbon hemoperfusion provides limited clearance of protein-bound solutes.  

PubMed

This study assessed the capacity of a cartridge containing coated granular carbon to clear protein-bound solutes. Clearances for test solutes were measured while an albumin solution representing plasma was pumped from a 10 L reservoir through the cartridge at a rate of 200 mL/min for 5 h. Clearance values for phenol red, phenytoin, and indican were well below the limit imposed by the plasma flow and declined with time. The clearance of phenol red, which was the most tightly bound solute, fell from 38 +/- 12 to 17 +/- 2 mL/min. Additional studies revealed that the cartridge contained enough carbon to absorb all the protein-bound test solutes, but that the rate of their clearance was limited by the inability of granular carbon to take up solutes rapidly at a low concentration. The rate of solute uptake at low concentration was shown to be much greater when carbon was in powdered rather than granular form. A device in which approximately 50 g of powdered carbon was recirculated in the dialysate compartment of hollow fiber kidneys cleared phenol red and phenytoin more rapidly than the hemoperfusion cartridge containing 300 g of coated granular carbon. These results indicate that hemoperfusion over coated granular carbon provides limited clearance of protein-bound solutes. PMID:18684207

Dinh, Diana C; Recht, Natalie S; Hostetter, Thomas H; Meyer, Timothy W

2008-09-01

280

Extracting lithium from waste solutions of chemico-metallurgical lithium carbonate production  

Microsoft Academic Search

In order to reduce the loss of lithium in waste solutions of chemico-metallurgical lithium carbonate production, it is suggested\\u000a to extract lithium from these solutions in the form of poorly soluble hydroxodialuminate under the action of sodium and potassium\\u000a aluminates. Technological tests showed that the proposed method ensures almost complete isolation of lithium from waste solutions\\u000a of lithium carbonate production.

V. I. Samoilov; N. A. Kulenova

2008-01-01

281

Inhibition Performance of Enhanced-Mo Inhibitor for Carbon Steel in 55% LiBr Solution  

Microsoft Academic Search

The inhibition performance of enhanced-Mo inhibitor for carbon steel in 55% LiBr solution was measured by means of chemical immersion, electrochemical measurements, and physical detection technologies. Results indicated that enhanced-Mo inhibitor showed excellent inhibition performance of carbon steel in 55% LiBr solution, especially at high temperature. With increasing the temperature of solution from 160 °C to 240 °C, the corrosion

Cheng-hao LIANG; Xian-qi HU

2008-01-01

282

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

283

GADOLINIUM OXALATE SOLUBILITY MEASUREMENTS IN NITRIC ACID SOLUTIONS  

SciTech Connect

HB-Line will begin processing Pu solutions during FY2012 that will involve the recovery of Pu using oxalate precipitation and filtration. After the precipitation and filtration processes, the filtrate solution will be transferred from HB-Line to H-Canyon. The presence of excess oxalate and unfiltered Pu oxalate solids in these solutions create a criticality safety issue if they are sent to H-Canyon without controls in H-Canyon. One approach involves H-Canyon receiving the filtrate solution into a tank that is poisoned with soluble gadolinium (Gd). Decomposition of the oxalate will occur within a subsequent H-Canyon vessel. The receipt of excess oxalate into the H-Canyon receipt tanks has the potential to precipitate a portion of the Gd poison in the receipt tanks. Because the amount of Gd in solution determines the maximum amount of Pu solids that H-Canyon can receive, H-Canyon Engineering requested that SRNL determine the solubility of Gd in aqueous solutions of 4-10 M nitric acid (HNO{sub 3}), 4-12 g/L Gd, and 0.15-0.25 M oxalic acid (H{sub 2}C{sub 2}O{sub 4}) at 25 °C. The target soluble Gd concentration is 6 g/L. The data indicate that the target can be achieved above 6 M HNO{sub 3} and below 0.25 M H{sub 2}C{sub 2}O{sub 4}. At 25 °C, for 6 M HNO{sub 3}, 11 g/L and 7 g/L Gd are soluble in 0.15 M and 0.25 M H{sub 2}C{sub 2}O{sub 4}, respectively. In 4 M HNO{sub 3}, the Gd solubility drops significantly to 2.5 g/L and 0.8 g/L in 0.15 M and 0.25 M H{sub 2}C{sub 2}O{sub 4}, respectively. The solubility of Gd at 8-10 M HNO{sub 3} exceeds the solubility at 6 M HNO{sub 3}. The data for 4 M HNO{sub 3} showed good agreement with data in the literature. To achieve a target of 6 g/L soluble Gd in solution in the presence of 0.15-0.25 M oxalate, the HNO{sub 3} concentration must be maintained at or above 6 M HNO{sub 3}. The solubility of Gd in 4 M HNO{sub 3} with 0.15 M oxalate at 10 °C is about 1.5 g/L. For 6 M HNO{sub 3} with 0.15 M oxalate, the solubility of Gd at 10 °C is about 10 g/L. Gadolinium nitrate is very soluble in HNO{sub 3}. The solubility of Gd is linear as a function of HNO{sub 3} from 343 g/L Gd in 2.88 M HNO{sub 3} to 149 g/L in 8.16 M HNO{sub 3}. Below 2.88 M HNO{sub 3}, the solubility of Gd approaches a limit of about 360 g/L. However, there are no data available below 1.40 M HNO{sub 3}, which has a Gd solubility of 353 g/L.

Pierce, R. A.

2012-03-12

284

Destruction of carbon disulfide in aqueous solutions by sonochemical oxidation.  

PubMed

Carbon disulfide (CS(2)) is toxic to animals and aquatic organisms, and can also decompose to carbonyl sulfide (OCS) and hydrogen sulfide (H(2)S) in aqueous environment. The kinetics of the sonochemical degradation of aqueous CS(2) was studied in a batch reactor at 20kHz and 20 degrees C, and the effects of process parameters (e.g. concentration, ultrasonic intensity, irradiating gas) investigated. The concentrations of unbuffered CS(2) solutions used were (6.4-7.0) x 10(-4), 10.5 x 10(-4) and (13.2-13.6) x 10(-4)M and the intensities were varied from 14 to 50W. The reaction rate was found to be zero-order and the rate constant for the degradation at 20 degrees C and 14W in air was 21.1 microM/min using the largest initial concentration range studied. At the same initial concentration range but at 50W (39.47W/m(2)) the degradation rate of CS(2) was 46.7 microM/min, more than two times that at 14W (11.04W/m(2)). The rate of CS(2) sonochemical degradation in the presence of the different gases was in the order of He>air> or =N(2)O>Ar; the rate with helium was found to be about three times that of argon. The formation of sulfate (SO(4)(2-)) as reaction product with air as the irradiating gas was enhanced in the presence of hydrogen peroxide (H(2)O(2)) and inhibited in the presence of 1-butanol. The sonochemical oxidation of CS(2) may prove to be an efficient and environmentally benign way for the removal of this hazardous pollutant from natural water and wastewater. PMID:11893423

Appaw, Collins; Adewuyi, Yusuf G

2002-03-29

285

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

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

286

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

NASA Astrophysics Data System (ADS)

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

Vinitnantharat, Soydoa; Kositchaiyong, Sriwilai; Chiarakorn, Siriluk

2010-06-01

287

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

PubMed

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

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

2012-03-01

288

Stable isotope analysis of dissolved organic carbon in soil solutions using a catalytic combustion total organic carbon analyzer-isotope ratio mass spectrometer with a cryofocusing interface.  

PubMed

Stable carbon isotopes are a powerful tool to assess the origin and dynamics of carbon in soils. However, direct analysis of the (13)C/(12)C ratio in the dissolved organic carbon (DOC) pool has proved to be difficult. Recently, several systems have been developed to measure isotope ratios in DOC by coupling a total organic carbon (TOC) analyzer with an isotope ratio mass spectrometer. However these systems were designed for the analysis of fresh and marine water and no results for soil solutions or (13)C-enriched samples have been reported. Because we mainly deal with soil solutions in which the difficult to oxidize humic and fulvic acids are the predominant carbon-containing components, we preferred to use thermal catalytic oxidation to convert DOC into CO(2). We therefore coupled a high-temperature combustion TOC analyzer with an isotope ratio mass spectrometer, by trapping and focusing the CO(2) cryogenically between the instruments. The analytical performance was tested by measuring solutions of compounds varying in the ease with which they can be oxidized. Samples with DOC concentrations between 1 and 100 mg C/L could be analyzed with good precision (standard deviation (SD) < or = 0.6 per thousand), acceptable accuracy, good linearity (overall SD = 1 per thousand) and without significant memory effects. In a (13)C-tracer experiment, we observed that mixing plant residues with soil caused a release of plant-derived DOC, which was degraded or sorbed during incubation. Based on these results, we are confident that this approach can become a relatively simple alternative method for the measurement of the (13)C/(12)C ratio of DOC in soil solutions. PMID:20058235

De Troyer, I; Bouillon, S; Barker, S; Perry, C; Coorevits, K; Merckx, R

2010-02-01

289

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

PubMed Central

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

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

2013-01-01

290

RECOVERY OF URANIUM FROM AN ACID LEACH LIQUOR, USING AN ANION EXCHANGE RESIN AND SODIUM CARBONATE AND BICARBONATE AS ELUTING AGENTS  

Microsoft Academic Search

It has been shown that it is possible, using both sodium carbonate ; solution and sodium bicarbonate solution as eluting agents, to remove uranium ; completely from Amberlite IRA-400 anion exchange resin loaded from an acid leach ; liquor. During 51 cycles of loading and elution, the resin sample used showed ; only slight deterioration. The uranium was precipitated from

E. Kornelsen; V. M. McNamara; J. C. Ingles

1959-01-01

291

The role of formic acid in solution stability and crystallization of silk protein polymer  

Microsoft Academic Search

In this paper, the regenerated silk fibroin (SF) solution dissolved in formic acid was used as a model protein to understand the role of formic acid in solution stability and crystallization of protein-based materials. The molecular decomposition of SF did not occur for the dissolution process in formic acid within 1–2 days of storage times. The ?-sheet crystallization of SF

In Chul Um; Hae Yong Kweon; Kwang Gill Lee; Young Hwan Park

2003-01-01

292

Mechanical integrity of polysilicon films exposed to hydrofluoric acid solutions  

NASA Astrophysics Data System (ADS)

This paper presents the results from a comparative study of Young’s modulus, residual stress, and membrane burst pressure of undoped LPCVD polysilicon films exposed to various concentrations of hydrofluoric acid (HF). Load deflection measurements on square membranes of polysilicon with residual tensile stress were used to obtain estimates of Young’s modulus, residual stress and burst pressure. The polysilicon membranes were exposed to four different solutions of the 49% by weight reagent HF including 10:1 DI water and HF, 1:1 DI water the HF, commercial 10:1 buffered oxide etchant, or pure HF ( i.e. 49% by weight reagent). Two control groups were studied composed of membranes with no treatment and membranes exposed to DI water. Young’s modulus changed from an average of 190 GPa for the control groups to an average of 240 GPa for films exposed to pure HF. Residual stress values exhibited a less pronounced and opposite change, with an average of 42 MPa for the control groups and an average of 27 MPa for films exposed to pure HF. Similarly, burst pressure was seen to decrease with increasing HF concentration, ranging in value from an average of 96.5 kPa (14 psi) for the control groups to an average of 34.5 kPa (5 psi) for films exposed to pure HF. It was found that the change in the investigated mechanical properties of polysilicon was approximately equal for HF:DI solutions of HF concentration above 10%. Furthermore, for solutions of equal HF concentration, the addition of the buffering agent decreases the effect on membrane burst pressures significantly.

Walker, James A.; Gabriel, Kaigham J.; Mehregany, Mehran

1991-09-01

293

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

PubMed

Defects of carbon nanotubes, weak tube-tube interactions, and weak carbon nanotube joints are bottlenecks for obtaining high-strength carbon nanotube yarns. Some solution processes are usually required to overcome these drawbacks. Here we fabricate ultra-long and densely packed pure carbon nanotube yarns by a two-rotator twisting setup with the aid of some tensioning rods. The densely packed structure enhances the tube-tube interactions, thus making high tensile strengths of carbon nanotube yarns up to 1.6 GPa. We further use a sweeping laser to thermally treat as-produced yarns for recovering defects of carbon nanotubes and possibly welding carbon nanotube joints, which improves their Young's modulus by up to ?70%. The spinning and laser sweeping processes are solution-free and capable of being assembled together to produce high-strength yarns continuously as desired. PMID:22538869

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

2012-06-01

294

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

PubMed

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

Rebane, Riin; Herodes, Koit

2012-07-01

295

Electrochemical investigation of copper deposition onto silicon from hydrofluoric acid and buffered hydrofluoric acid solutions  

NASA Astrophysics Data System (ADS)

For the fabrication of ULSI circuits, the silicon surface should be free of metallic and particulate contamination and be atomically smooth. Heavy metal contaminants have detrimental effects on the yield of microelectronic processing and reliability of solid state devices by increasing the junction leakage current, degrading the integrity of gate oxide and reducing the oxide breakdown voltage. It has been demonstrated that the contamination level for most metals has to be controlled below 10sp{10} atoms/cmsp2 for sub-quarter micron processing. Some transition and noble metal ions such as copper, silver and gold are known to deposit on silicon surfaces in acidic fluoride based solutions. Among them, copper has been the focus of most research due to the widespread use of copper in microelectronic industry. To investigate the mechanisms by which copper deposits on silicon surfaces in HF and BHF solutions, different electrochemical techniques were used, including dc polarization and ac impedance spectroscopy (EIS). The results of electrochemical measurements, in conjunction with various surface characterization techniques, such as TXRF, AFM and TEM, reveal the rates of reactions that occur at silicon/solution interface can be affected by many factors, such as silicon dopant type and doping levels, ionic strength of electrolytes, illumination conditions and the use of additives. For example, under darkness, the amount of copper deposition is nearly one order of magnitude less than that under illumination for p-type silicon in both HF and BHF solutions and n-type silicon in HF solutions. In BHF solutions, n-type silicon is very close to its flat band condition where illumination plays little role. The addition of copper ions in BHF solutions not only causes metal contamination, but also generates severe surface roughness due to the masking effect of copper on the anisotropic etching of silicon in BHF solutions. Local etching rate of 1nm/min was measured on the silicon sample prepared in 100 ppb Cusp{2+} BHF solutions. Some additives such as surfactants and hydrochloric acid can effectively reduce the reaction rates of silicon corrosion and copper deposition by either blocking the active reaction sites or form copper ion complexes.

Li, Guangming

296

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

297

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

298

Study of mono-(2-ethylhexyl) phosphoric acid and neutral organophosphorus synergists for extraction of uranium from phosphoric acid solution  

SciTech Connect

The distribution of uranium(IV) and uranium(VI) between phosphoric acid solution and mono-(2-ethylhexyl) phosphoric acid (H/sub 2/MEHP)-trioctyl phosphine oxide (TOPO), and mono-(2-ethylhexyl) phosphoric acid-dibutyl butyl phosphonate (DBBP) in kerosene diluent has been investigated. The effects of extractant composition, phosphoric acid concentration, temperature, uranium concentration, and shaking time on the uranium extraction have been examined. Reductive extraction and oxidative stripping processes for the separation and concentration of uranium from phosphoric acid solution with synergic systems of H/sub 2/MEHP-TOPO and H/sub 2/MEHP-DBBP are proposed and discussed.

Lee, T.W.; Ting, G.

1981-09-01

299

Comparison of peak shape in hydrophilic interaction chromatography using acidic salt buffers and simple acid solutions.  

PubMed

The retention and peak shape of neutral, basic and acidic solutes was studied on hydrophilic interaction chromatography (HILIC) stationary phases that showed both strong and weak ionic retention characteristics, using aqueous-acetonitrile mobile phases containing either formic acid (FA), ammonium formate (AF) or phosphoric acid (PA). The effect of organic solvent concentration on the results was also studied. Peak shape was good for neutrals under most mobile phase conditions. However, peak shapes for ionised solutes, particularly for basic compounds, were considerably worse in FA than AF. Even neutral compounds showed deterioration in performance with FA when the mobile phase water concentration was reduced. The poor performance in FA cannot be entirely attributed to the negative impact of ionic retention on ionised silanols on the underlying silica base materials, as results using PA at lower pH (where their ionisation is suppressed) were inferior to those in AF. Besides the moderating influence of the salt cation on ionic retention, it is likely that salt buffers improve peak shape due to the increased ionic strength of the mobile phase and its impact on the formation of the water layer on the column surface. PMID:24813934

Heaton, James C; Russell, Joseph J; Underwood, Tim; Boughtflower, Robert; McCalley, David V

2014-06-20

300

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

301

Amino acids derivatives synthesis from nitrogen, carbon and water by electric discharges  

NASA Astrophysics Data System (ADS)

Electric discharges between a pair of carbon electrodes were continued for 50 days in a vessel of 5 liters in volume which initially contained nitrogen at a pressure of 15 cm Hg and 200 ml of water. The pressure in the vessel was gradually increased to 60 cm Hg at the end of the run. Gas chromatographic analysis showed that the increase of the pressure mainly results from the production of hydrogen and carbon monoxide. The concentration of ammonia in the aqueous sample was increased to 0.05M in 50 days of the discharge. After hydrolysis, glycine and serine were detected at the concentrations of 3.4×10-3 M and 0.057×10-3 M in the final solution, respectively, though glycine was found only at the concentration of 6×10-6 M before hydrolysis. TLC analysis indicated the presence of hydantoic acid, N-formylglycine, diketopiperazine, and polymers of glycine.

Yamagata, Y.; Kusano, Y.; Inomata, K.

1981-12-01

302

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

PubMed Central

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

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

2009-01-01

303

On the kinetics of formaldehyde-S(IV) adduct formation in slightly acidic solution  

NASA Astrophysics Data System (ADS)

Calculations are presented which demonstrate that the kinetics of dehydration of methylene glycol (hydrated formaldehyde) must be considered in determining the rate of hydroxymethanesulfonic acid formation in weakly acidic or neutral solution.

Olson, T. M.; Hoffmann, M. R.

304

Determination of Chromic Acid in Chromium Plating Solutions Using a Redox Titration and Indicator.  

National Technical Information Service (NTIS)

The chemical literature lacks a simple analytical method for adequately controlling chromic acid in chromium plating solutions during the plating process. In this report, a simple method for analyzing and controlling chromic acid during the plating proces...

S. Sopok

1989-01-01

305

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

Microsoft Academic Search

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

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

2001-01-01

306

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

307

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

NASA Technical Reports Server (NTRS)

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

Chraska, P.; Mclellan, R. B.

1971-01-01

308

HEMP-derived activated carbon fibers by chemical activation with phosphoric acid  

Microsoft Academic Search

Activated carbon fibers were prepared by chemical activation of hemp fibers with phosphoric acid at different carbonization temperatures and impregnation ratios. Surface properties of the activated carbons fibers were significantly influenced by the activation temperature and the impregnation ratio. An increase of either of these parameters produced a high development of the porous structure of the fibers. Activated carbon fibers

J. M. Rosas; J. Bedia; J. Rodríguez-Mirasol; T. Cordero

2009-01-01

309

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

310

Energy dispersive X-Ray fluorescence determination of thorium in phosphoric acid solutions  

Microsoft Academic Search

Energy dispersive X-ray fluorescence studies on determination of thorium (in the range of 7 to 137mg\\/mL) in phosphoric acid solutions obtained by dissolution of thoria in autoclave were made. Fixed amounts of Y internal standard solutions, after dilution with equal amount of phosphoric acid, were added to the calibration as well as sample solutions. Solution aliquots of approximately 2–5ľL were

N. N. Mirashi; Sangita Dhara; S. Sanjay Kumar; Satyajeet Chaudhury; N. L. Misra; S. K. Aggarwal

2010-01-01

311

Stable carbon and nitrogen isotope analysis of avian uric acid.  

PubMed

We report results obtained using a new technique developed to measure the stable-isotope composition of uric acid isolated from bird excreta (guano). Results from a diet-switch feeding trial using zebra finches suggest that the delta(13)C of uric acid in the guano equilibrates with the diet of the bird within 3 days of a change in diet, while the equilibration time for delta(15)N may be longer. The average carbon isotope discrimination between uric acid and food before the diet switch was +0.34 +/- 1 per thousand (1sigma) while after the diet switch this increased slightly to +0.83 +/- 0.7 per thousand (1sigma). Nitrogen isotope discrimination was +1.3 +/- 0.3 per thousand (1sigma) and +0.3 +/- 0.3 per thousand (1sigma) before and after the diet switch; however, it is possible that the nitrogen isotope values did not fully equilibrate with diet switch over the course of the experiment. Analyses of other chemical fractions of the guano (organic residue after uric acid extraction and non-uric acid organics solubilised during extraction) suggest a total range of up to 3 per thousand for both delta(13)C and delta(15)N values in individual components of a single bulk guano sample. The analysis of natural samples from a range of terrestrial and marine species demonstrates that the technique yields isotopic compositions consistent with the known diets of the birds. The results from natural samples further demonstrate that multiple samples from the same species collected from the same location yield similar results, while different species from the same location exhibit a range of isotopic compositions indicative of different dietary preferences. Given that many samples of guano can be rapidly collected without any requirement to capture specimens for invasive sampling, the stable-isotope analysis of uric acid offers a new, simple and potentially powerful tool for studying avian ecology and metabolism. PMID:18837063

Bird, Michael I; Tait, Elaine; Wurster, Christopher M; Furness, Robert W

2008-11-01

312

Solution-processed carbon electrodes for organic field-effect transistors  

NASA Astrophysics Data System (ADS)

Bottom-contact organic transistors with carbon-paste electrodes are fabricated by means of the surface selective deposition technique, where a carbon-paste solution is deposited on the region in which the self-assembled monolayers are removed by ultraviolet light irradiation. The resulting bottom-contact pentacene transistor realizes high performance of 1.0 cm2 V-1 s-1. The present method is applied to solution-processed polythiophene transistors as well as n-channel materials.

Wada, Hiroshi; Mori, Takehiko

2008-11-01

313

Comparison of hydrolysis\\/coagulation behavior of polymeric and monomeric iron coagulants in humic acid solution  

Microsoft Academic Search

Fluorescence quenching is commonly used to study the extent of metal binding to humic acid or fulvic acid. By studying this phenomenon, the hydrolysis and precipitation behaviors of polymeric and monomeric iron coagulants in the coagulation of humic acid were evaluated. Combined measurements of fluorescence intensity and dissolved organic carbon were performed to distinguish the hydrolysis and organic matter binding

Wen Po Cheng

2002-01-01

314

Synthesis and application of carbonated fatty acid esters from carbon dioxide including a life cycle analysis.  

PubMed

Carbon dioxide can be used in various ways as a cheap C1 source. However, the utilization of CO2 requires energy or energy-rich reagents, which leads to further emissions, and therefore, diminishes the CO2-saving potential. Therefore, life cycle assessment (LCA) is required for each process that uses CO2 to provide valid data for CO2 savings. Carbon dioxide can be incorporated into epoxidized fatty acid esters to provide the corresponding carbonates. A robust catalytic process was developed based on simple halide salts in combination with a phase-transfer catalyst. The CO2-saving potential was determined by comparing the carbonates as a plasticizer with an established phthalate-based plasticizer. Although CO2 savings of up to 80 % were achieved, most of the savings arose from indirect effects and not from CO2 utilization. Furthermore, other categories have been analyzed in the LCA. The use of biobased material has a variety of impacts on categories such as eutrophication and marine toxicity. Therefore, the benefits of biobased materials have to be evaluated carefully for each case. Finally, interesting properties as plasticizers were obtained with the carbonates. The volatility and water extraction could be improved relative to the epoxidized system. PMID:24616303

Schäffner, Benjamin; Blug, Matthias; Kruse, Daniela; Polyakov, Mykola; Köckritz, Angela; Martin, Andreas; Rajagopalan, Prasanna; Bentrup, Ursula; Brückner, Angelika; Jung, Sebastian; Agar, David; Rüngeler, Bettina; Pfennig, Andreas; Müller, Karsten; Arlt, Wolfgang; Woldt, Benjamin; Grass, Michael; Buchholz, Stefan

2014-04-01

315

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

NASA Technical Reports Server (NTRS)

Hypobromous acid (HOBr) is a key species linking inorganic bromine to the chlorine and odd hydrogen chemical families. We have measured the solubility of HOBr in 45 - 70 wt% sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosol composition. Over the temperature range 201 - 252 K, HOBr is quite soluble in sulfuric acid, with an effective Henry's law coefficient, H* = 10(exp 4) - 10(exp 7) mol/L/atm. H* is inversely dependent on temperature, with Delta H = -46.2 kJ/mol and Delta S = -106.2 J/mol/K for 55 - 70 wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into aqueous 45 wt% H2SO4, the solubility can be described by log H* = 3665/T - 10.63. For 55 - 70 wt% H2SO4, log H* = 2412/T - 5.55. At temperatures colder than approx. 213 K, the solubility of HOBr in 45 wt% H2SO4 is noticeably larger than in 70 wt% H2SO4. The solubility of HOBr is comparable to that of HBr, indicating that upper tropospheric and lower stratospheric aerosols should contain equilibrium concentrations of HOBr which equal or exceed those of HBr. Our measurements indicate chemical reaction of HOBr upon uptake into aqueous sulfuric acid in the presence of other brominated gases followed by evolution of gaseous products including Br2O and Br2, particularly at 70 wt% H2SO4.

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

2005-01-01

316

Removal of reactive dye from aqueous solutions by adsorption onto activated carbons prepared from oak sawdust  

Microsoft Academic Search

Activated carbons prepared from oak sawdust, a timber industry waste, have been examined for the removal of remazol brilliant blue (RB) dye from aqueous solutions through batch adsorption technique. Activated carbons were prepared from oak sawdust by chemical activation with 10% HNO3 (AC1) followed by pyrolysis at 500°C in the absence of air and by physical activation at 500°C in

Mona Mahmoud Abd El-Latifa; Amal Mozarei Ibrahim

2010-01-01

317

Removal of cyanide from aqueous solutions by plain and metal-impregnated granular activated carbons  

Microsoft Academic Search

In this study, the removal of free cyanide from aqueous solutions by activated carbon was investigated. Effects of metal impregnation (Cu and Ag), aeration, and concentrations of adsorbent and cyanide on the rate and extent of the removal of cyanide were studied. The results have shown that the capacity of activated carbon for the removal of cyanide can be significantly

H. Deveci; E. Y. Yaz?c?; I. Alp; T. Uslu

2006-01-01

318

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

PubMed

The extraction equilibrium of indium(III) from a nitric acid solution using di(2-ethylhexyl) phosphoric acid (D2EHPA) as an acidic extractant of organophosphorus compounds dissolved in kerosene was studied. By graphical and numerical analysis, the compositions of indium-D2EHPA complexes in organic phase and stoichiometry of the extraction reaction were examined. Nitric acid solutions with various indium concentrations at 25 °C were used to obtain the equilibrium constant of InR? in the organic phase. The experimental results showed that the extraction distribution ratios of indium(III) between the organic phase and the aqueous solution increased when either the pH value of the aqueous solution and/or the concentration of the organic phase extractant increased. Finally, the recovery efficiency of indium(III) in nitric acid was measured. PMID:22217554

Tsai, Hung-Sheng; Tsai, Teh-Hua

2012-01-01

319

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

PubMed

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

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

2014-09-01

320

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

NASA Astrophysics Data System (ADS)

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

Kong, Yuxia; Yuan, Jie; Qiu, Jun

2012-07-01

321

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

Microsoft Academic Search

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

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

1988-01-01

322

Influence of Acid Modification on Selective Phenol Hydrogenation Over Pd\\/Activated Carbon Catalysts  

Microsoft Academic Search

The influence of the acid treatment on cyclohexanone selectivity of phenol hydrogenation over Pd on active carbon was studied\\u000a in liquid phase reaction and by temperature-programmed desorption. Acid treatment of activated carbon led to an increased\\u000a cyclohexanone\\/cyclohexanol ratio. Acid modification of the carbon support enriched the electron density of Pd, and enhanced\\u000a the desorption of the phenoxy species, which resulted

Shingo Watanabe; Venu Arunajatesan

2010-01-01

323

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

NASA Astrophysics Data System (ADS)

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

Fukushima, Kunio; Watanabe, Toshiaki; Umemura, Matome

1986-08-01

324

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

325

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

326

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

PubMed

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

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

2013-12-01

327

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

PubMed

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

Yoshimura, Tomokazu; Sakato, Ayako; Esumi, Kunio

2013-01-01

328

Na(+)-functionalized carbon quantum dots: a new draw solute in forward osmosis for seawater desalination.  

PubMed

A new type of biocompatible draw solute, Na(+)-functionalized carbon quantum dots (Na_CQDs) with ultra-small size and rich ionic species, in forward osmosis (FO) is developed for seawater desalination. The aqueous dispersion of Na_CQDs demonstrates a high osmotic pressure, which allows high FO water flux and negligible reverse solute permeation. PMID:24870226

Guo, Chun Xian; Zhao, Dieling; Zhao, Qipeng; Wang, Peng; Lu, Xianmao

2014-06-12

329

Effect of niobium on massive transformation in ultra low carbon steels: a solute drag treatment  

Microsoft Academic Search

The effect of Nb on the ? ? ? transformation in ultra low carbon steels is examined experimentally and theoretically. It is shown that there are two modes of the massive transformation. One of them is heavily influenced by the solute drag effect of Nb. This is confirmed by a calculation based on a new model for treating the solute

M. Suehiro; Z.-K. Liu; J. Ĺgren

1996-01-01

330

Hydrogen Permeation of Carbon Steel in Weak Alkaline Solution Containing Hydrogen Sulfide and Cyanide Ion  

Microsoft Academic Search

The hydrogen permeation behavior of carbon steel (CS) was investigated electrochemically in weak alkaline solutions containing hydrogen sulfide (HâS) with various cyanide ion (CN⁝) concentrations under open-circuit conditions. Anodic and cathodic polarization behaviors of CS also were investigated under the same environmental conditions. Little hydrogen content (Câ) was detected in alkaline solutions without CN⁝. However, when a small amount of

K. Yamakawa; R. Nishimura

1999-01-01

331

Solution-deposited carbon nanotube layers for flexible display applications  

Microsoft Academic Search

We have investigated two possible fields of application for carbon nanotube (CNT) networks in flexible displays. Transparent and conductive layers of CNTs were spray coated onto glass and plastic substrates. The spectral transmission of the produced layers is almost even for all wavelengths in the visible regime. A sheet resistance of 400?\\/? at a transmittance of 80% was achieved.Thin-film transistors

Axel Schindler; Jochen Brill; Norbert Fruehauf; James P. Novak; Zvi Yaniv

2007-01-01

332

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

333

Isothermal heat measurements of TBP-nitric acid solutions  

SciTech Connect

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

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

1994-12-16

334

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

335

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

PubMed

Six of the seven chain isomers of six-carbon acyclic primary alpha-amino alkanoic acids (leucine isomers) have been either identified or confirmed in hot-water extracts of the Murchison meteorite using combined gas chromatography-mass spectrometry (GC-MS) and ion exchange chromatography. 2-Amino-2-ethylbutyric acid, 2-amino-2,3-dimethylbutyric acid, pseudoleucine, and 2-methylnorvaline were positively identified by GC-MS. These amino acids have not been previously reported to occur in natural materials and may be uniquely meteoritic in origin. The presence of leucine and isoleucine (including the diastereoisomer, alloisoleucine) was confirmed. Peaks corresponding to norleucine were seen by ion-exchange and gas chromatography but characteristic mass spectra were not obtained. The alpha-branched chain isomers in this series are quantitatively the most significant. These results are compared with literature data on amino acid synthesis by electrical discharge and Fischer-Tropsch-type catalysis. Neither model system produces an amino acids suite that is completely comparable to that found in the Murchison meteorite. PMID:7277509

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

1981-01-01

336

The effect of pretreatment with an oxalic acid solution on marginal adaptation to enamel in vivo  

Microsoft Academic Search

Statement of problem. New acids such as oxalic acid have been introduced as a conditioning agent in the total-etch technique. There is concern about long-term retention of the acid on enamel in relation to the superficial etch effect.Purpose. This in vivo study evaluated the marginal adaptation to enamel conditioned with either an oxalic acid solution or a phosphoric acid with

Jan W. V. van Dijken; Per Hörstedt

1998-01-01

337

Effect of substituents on the 13C chemical shifts of the azomethine carbon atom of N-(substituted phenylmethylene)-3- and -4-aminobenzoic acids  

NASA Astrophysics Data System (ADS)

13C chemical shifts of the azomethine carbon atom for N-(substituted phenylmethylene)-3- and -4-aminobenzoic acids having a wide range of substituent effects, were determined in deuterated DMSO solution. Good Hammett correlations of the 13C NMR chemical shifts of azomethine carbons with electrophilic substituent constants ?p+ for electron-donor substituents for both series of acids indicate an important resonance interaction of the substituents on the benzylidene ring with the azomethine carbon atom. On the other hand, good correlations of the 13C NMR chemical shifts of azomethine carbon atom of both series of acids with inductive substituent constants for electron-acceptor substituents in benzylidene ring indicates that the chemical shifts are influenced only by inductive effect of the substituents. The demand for electrons by the azomethine carbon atom in both investigated series have been compared, discussing the mode of transmission of substituent effects, both inductive and resonance, in relation to the geometry of investigated imines.

Jovanovi?, B. Ž.; Marinkovi?, A. D.; Assaleh, F. H.; Csanádi, J.

2005-06-01

338

Leaching of Sphalerite with Hydrogen Peroxide and Nitric Acid Solutions  

Microsoft Academic Search

The leaching of powdered sphalerite using hydrogen peroxide and nitric acid has been investigated. The important variables such as concentrations of hydrogen peroxide and nitric acid as well as stirring speed and particle size were examined. The effect of reaction temperature was also examined on the leaching reaction process. The hydrogen peroxide and nitric acid concentrations have significant effects on

A. O. Adebayo; K. O. Ipinmoroti; O. O. Ajayi

2006-01-01

339

The sorption of molybdenum(VI) by ionites from solutions in hydrochloric acid  

NASA Astrophysics Data System (ADS)

The sorption of molybdenum(VI) by KU-2 × 8 and AV-17 × 8 ionites from solutions in hydrochloric acid (1 × 10-5-6 N) was studied. Changes in the sorption of molybdenum(VI) by cationite and anionite were observed. The isoelectric point of molybdenum in solutions in hydrochloric acid was determined from sorption and electrical migration measurements.

Umarakhunov, M. Kh.; Sadykova, U. A.; Khodzhaeva, G. A.

2010-05-01

340

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

Code of Federal Regulations, 2013 CFR

... 2 2013-10-01 2013-10-01 false Chloric acid solution or chlorine dioxide hydrate, frozen. 173.229 Section...Other Than Class 1 and Class 7 § 173.229 Chloric acid solution or chlorine dioxide hydrate, frozen. When the §...

2013-10-01

341

Biosorption of acidic dyes from aqueous solution by Paenibacillus macerans: Kinetic, thermodynamic and equilibrium studies  

Microsoft Academic Search

Batch studies were conducted for thermodynamic, kinetics and equilibrium studies on the biosorption of Acid Blue 225 (AB 225) and Acid Blue 062 (AB 062) from aqueous solution by Paenibacillus macerans. The operating variables studied were initial dye concentration, biomass concentration, contact time, temperature and solution pH. Results show that the pH value of 1 is favorable for the biosorption

Ferda? Çolak; Necip Atar; Asim Olgun

2009-01-01

342

Chemiluminescence in the course of methyl ethyl ketone oxidation by ozone in acidic aqueous solutions  

Microsoft Academic Search

Chemiluminescence in the visible spectral region is observed in the course methyl ethyl ketone oxidation by ozone in neutral and acidic aqueous solutions. The spectral composition of the chemiluminescence is studied. On going from neutral to acidic aqueous solutions of methyl ethyl ketone, the initial intensity of the signal increases and the kinetics of a decrease in the chemiluminescence intensity

Yu. S. Zimin; A. A. Gusmanov; S. L. Khursan

2004-01-01

343

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

Microsoft Academic Search

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

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

1960-01-01

344

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

PubMed

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

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

2012-11-27

345

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

Microsoft Academic Search

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

Chandra Mouli Pavuluri; Kimitaka Kawamura; T. Swaminathan

2010-01-01

346

Nonionic organic solute sorption onto two organobentonites as a function of organic-carbon content  

Microsoft Academic Search

Sorption of three nonionic organic solutes (benzene, trichloroethene, and 1,2-dichlorobenzene) to hexadecyltrimethylammonium bentonite (HDTMA bentonite) and benzyltriethylammonium bentonite (BTEA bentonite) was measured as a function of total organic-carbon content at quaternary ammonium cation loadings ranging from 30 to 100% of the clay's cation-exchange capacity. Sorption of all three solutes to HDTMA bentonite was linear and sorption of all three solutes

Shannon L. Bartelt-Hunt; Susan E. Burns; James A. Smith

2003-01-01

347

Investigation of texturization for crystalline silicon solar cells with sodium carbonate solutions  

Microsoft Academic Search

We investigate a new texturization technique for crystalline silicon solar cells with sodium carbonate (Na2CO3) solutions. We show the dependence of the hemispherical surface reflectance on solution temperature, the etching time and the Na2CO3 concentration. Furthermore, we investigate what element in Na2CO3 solution influences the texturing for reducing the texturing time. As a result of experiments, we find it possible

Y Nishimoto; K Namba

2000-01-01

348

Surface chemistry of Cu(100) in acidic sulfate solutions  

NASA Astrophysics Data System (ADS)

The surface chemistry of Cu(100), in H 2SO 4 and acidic K 2SO 4 solutions, has been studied by Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) and thermal desorption spectroscopy (TDS). Experiments were conducted in an electrochemical cell coupled directly to a UHV surface analysis chamber. Structures formed on the Cu(100) surface emersed (removed) from sulfate solutions were the principal focus of this study. Structures and coverages were primarily dependent on sulfate concentration and the presence of coadsorbates such as Cl and K +. Emersion of Cu(100) from 1 mM H 2SO 4 resulted in a Cu(100)(2 × 2)-SO 2-4 adlattice with a {1}/{4} coverage of sulfate. A {1}/{5} coverage Cu(100)( 5 × 5) R26.6°- SO2-4 structure formed upon emersion mM H 2SO 4 containing trace Cl - contaminants, and a {1}/{3} coverage Cu(100)(2 × 100)- SO2-4 structure formed following e from 10 mM H 2SO 4. Emersion of Cu(100) from 1 mM K 2SO 4 (pH = 3.6) resulted in a Cu(100)(4 × 2 5)- SO2-4, K + surface structure, with K + and SO 2-4 coadsorbed in a 1:1 stoichiometry, each at {1}/{4} coverage. No significant potential-dependent variatio in surface structure or coverage was observed when the electrode was emersed from H 2SO 4 at potentials in the double-layer charging region. For emersion from 1 mM K 2SO 4 (pH = 3.6), a reduction in K + coverage along with a change in the surface structure to a (2 × 2) occurred at positive potentials. Comparisons were made of sulfate adsorption on the low-index planes of Cu using a Cu single crystal polished on three different faces to the (111), (110) and (100) planes. This electrode was emersed from 1 mM K 2SO 4 (pH = 3.6) at several potentials. A c(8 × 2) and a diffuse (1 × 1) LEED pattern were observed on Cu(110) and Cu(111), respectively. The K + and SO 2-4 coverages differed appreciably between the three surfaces. Significant differences were observed in the thermal desorption spectra of Cu(100) emersed from H 2SO 4 and K 2SO 4. Water desorption occurred following emersion from H 2SO 4, but not after emersion from K 2SO 2. For Cu(100) emersed from 1 mM H 2SO 4 and l mM K 2SO 4 (pH = 3.6), sulfate species decomposed into SO 2(g) and adsorbed oxygen at 670 and 780 K, respectively for the two solutions. This behavior indicates sulfate stabilization by coadsorbed K + following emersion from K 2SO 4. Lastly, TDS of an Au(100) surface following emersion from 1 mM H 2SO 4 indicated that sulfate is considerably more strongly bound to Cu(100).

Ehlers, Charles B.; Stickney, John L.

1990-12-01

349

Radiation-induced accumulation of carboxylic acids in solution of tributyl phosphate in dodecane  

SciTech Connect

A study has been made of the molecular composition and concentrations of carboxylic acids formed upon irradiation of the system 30% TBP in dodecane-3 M HNO{sub 3}. Based on these data, a model solution of carboxylic acids in dodecane has been formulated and compared with the irradiated solution in the interfacial tension on the organic phase-alkaline solution interface. Coefficients of carboxylic acid distribution between TBP in dodecane and aqueous solutions of HNO{sub 3}, NaHCO{sub 3} have been determined.

Bykov, G.L. [Institute of Physical Chemistry, Moscow (Russian Federation)

1995-09-01

350

Ultrasonic degradation of oxalic acid in aqueous solutions.  

PubMed

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

Dükkanci, M; Gündüz, G

2006-09-01

351

Relations for the determination of the polymorphic composition of calcium carbonate precipitated in saturated sodium chloride solutions  

Microsoft Academic Search

The purification of concentrated sodium chloride solutions from calcium and magnesium ions is realized by precipitating them in the form of calcium carbonate and magnesium hydroxide using a reagent solution composed of sodium carbonate and sodium hydroxide. The functioning of the industrial process depends on the polymorphic composition of the precipitated calcium carbonate. The classical experimental design method is used

C. Berger; A. Dandeu; C. Carteret; B. Humbert; H. Muhr; E. Plasari; J. M. Bossoutrot

352

Separation of Uranium from Nitric and Hydrochloric-Acid Solutions with Extractant-Coated Magnetic Microparticles  

Microsoft Academic Search

The magnetically assisted chemical separation (MACS) process utilizes selective magnetic microparticle composites to separate dissolved metals from solution. In this study, MACS particles were coated with neutral and acidic organophosphorus extractants,octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO), tributyl phosphate (TBP), trioctylphosphine oxide (TOPO), and bis(2-ethyl-hexyl)phosphoric acid (D2EHPA or HDEHP) and were evaluated for the separation of uranyl ions from nitric- and hydrochloric-acid solutions.

M. D. KAMINSKI; L. NUŃEZ

2000-01-01

353

Adsorption of phenol and benzoic acid from dilute aqueous solution onto macroreticular resin  

Microsoft Academic Search

The adsorption of phenol and benzoic acid from dilute aqueous solution onto macroreticular resin was studied by a radiotracer technique for 0.4948-0.0003 mg\\/ml benzoic acid solutions at 25°C and for similar concentrations of phenol at 0°, 25°, and 70°C. Adsorption equilibrium with the Amberlite XAD-8 resin slurry was reached after 44 hr for benzoic acid and after 104 hr for

D. S. Farrier; A. L. Hines; S. W. Wang

1979-01-01

354

H2SO4 vapor pressure of sulfuric acid and ammonium sulfate solutions  

Microsoft Academic Search

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

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

1997-01-01

355

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

Microsoft Academic Search

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

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

2001-01-01

356

Extraction of tetravalent berkelium by tributyl phosphate from nitric acid solutions  

Microsoft Academic Search

Extraction of Bk(IV), Ce(IV), Pu(IV) and Zr by tributyl phosphate from 2M to 16M nitric acid solutions has been studied. Using\\u000a the data on the effect of the extractant, nitric acid and nitrate ion concentrations on the distribution coefficients of Bk(IV)\\u000a and Ce(IV), the mechanism of Bk(IV) extraction by tributyl phosphate from nitric acid solutions is considered.

N. G. Yakovlev; V. N. Kosyakov; G. M. Kazakova

1982-01-01

357

Chemical evaluation of soil-solution in acid forest soils  

USGS Publications Warehouse

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

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

1996-01-01

358

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

Microsoft Academic Search

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

D. R. Hanson

2003-01-01

359

Extraction of zirconium and hafnium from nitric acid solutions by solid extractant based on tributyl phosphate  

SciTech Connect

A study has been made of extraction equilibrium and kinetics and the influence of temperature and aqueous phase acidity on the extraction of zirconium and hafnium from nitric acid solutions by a solid extractant based on tributyl phosphate. Results are presented from pilot-plant experiments on Zr and Hf extraction from acidic pulps with high silicon contents, using pulsed columns.

Korovin, V.Yu.; Yagodin, G.A.; Savel`eva, V.I. [Dnieper Scientific Center, Dneprodzerzhinsk (Ukraine)

1994-10-20

360

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

SciTech Connect

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

Jenson, D.D.

1989-01-01

361

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

EPA Science Inventory

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

362

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

EPA Science Inventory

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

363

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

Microsoft Academic Search

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

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

1978-01-01

364

Stability of Aqueous Solutions of Nicotinic Acid And Ascorbic Acid under the Action of Pasteurizing Doses Of Gamma-Radiation.  

National Technical Information Service (NTIS)

Aqueous solutions of nicotinic acid at concentrations of 1, 2, and 4 mg% were irradiated with 800 krad of gamma-radiation at a dose rate of 600 rad/sec. The stability of nicotinic acid was then determined. Statistical treatment of the data by the method o...

Y. M. Filippov

1970-01-01

365

Enhancement of electrochemiluminesence of lucigenin by ascorbic acid at single-wall carbon nanotube film-modified glassy carbon electrode  

Microsoft Academic Search

The electrochemiluminescent behavior of lucigenin on a single-wall carbon nanotube\\/DMF film-modified glassy carbon electrode was studied in this paper. Comparing with the bare glassy carbon electrode, the electrochemiluminescent of lucigenin at modified electrode is more stable and without tedious procedure for clean-up the surface of modified electrode. It has been found that ascorbic acid could enhance the electrochemiluminescent intensity of

Jinhua Chen; Zhenyu Lin; Guonan Chen

2007-01-01

366

Sonolytic degradation of butyric acid in aqueous solutions.  

PubMed

The sonolytic degradation of butyric acid was investigated in an ultrasonic reactor emitting waves at 850 kHz. The effects of the ultrasonic power, the initial concentration of butyric acid, and the addition of H2O2 were studied on the degradation of butyric acid. In the sonication of butyric acid, degradation degrees as high as 31.5% could be achieved at a power of 31 W, at an initial concentration of 2.8 mM butyric acid with the addition of 0.34 M H2O2 for a sonication time of 5 h. The degradation of butyric acid increased with irradiation time, indicating first order kinetics. PMID:24029459

Dükkanc?, Meral; Gündüz, Gönül

2013-11-15

367

Surface modification of Mg 2Ni alloy in an acid solution of copper sulfate and sulfuric acid  

Microsoft Academic Search

A simple method of electroless copper plating for the surface modification of Mg2Ni alloy has been described in this paper. The plating solution contains only copper sulfate and sulfuric acid which are less toxic to the environment than the chemical reagents used in conventional copper plating solutions. Moreover, the coating process was very easy and fast to operate needing no

C. Y Wang; P Yao; D. H Bradhurst; H. K Liu; S. X Dou

1999-01-01

368

Heat and mass transfer in the system hydrocarbon gas-porous carbon layer-metal and formation of supersaturated solid carbon solutions  

NASA Astrophysics Data System (ADS)

It is shown that the carbon layer formed on the catalytic surface of a metal plays an important role in industrial technologies of obtaining carbon nanofibers. The effective heat conduction of porous carbon samples was measured. A mathematical model of the heat and mass transfer inside a carbon layer has been developed and its stationary solutions were investigated. It is shown that a decrease in the thickness of a porous carbon layer on the surface of a metal as a result of its cleaning and a further growth of this layer lead to the formation of a supersaturated solid solution of carbon in the metal.

Takopulo, D. A.; Fisenko, S. P.

2012-05-01

369

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

Microsoft Academic Search

The adsorption by a coal-based mesoporous activated carbon of humic acids (HAs) isolated from two Polish lignites was studied. For comparison, a commercial Aldrich humic acid was also included into this study. The differences in chemical structure and functional groups of HAs were determined by elemental analysis and infrared spectroscopy DRIFT. Two activated carbons used differed in terms of mesopore

Ewa Lorenc-Grabowska; Gra?yna Gryglewicz

2005-01-01

370

Hydrogen Generation During the Corrosion of Carbon Steel in Oxalic Acid.  

National Technical Information Service (NTIS)

This document summarizes a literature review that was performed to gain a more complete understanding of the hydrogen evolution reaction that occurs during the corrosion of carbon steel in oxalic acid. The theory of carbon steel corrosion in oxalic acid w...

B. J. Wiersma

2004-01-01

371

Extraction of titanium, chromium and cadmium from phosphoric acid solutions by para (1,1,3,3 tetramethyl butyl) phenyl phosphoric acid in kerosene diluent.  

National Technical Information Service (NTIS)

The distribution of titanium, chromium and cadmium between phosphoric acid solutions and solutions of para (1,1,3,3, tetramethyl butyl) phenyl phosphoric acid in kerosene diluent has been investigated under different conditions. The aqueous and organic ph...

A. Mellah D. Bauer

1993-01-01

372

Hydrogen-bond acidic functionalized carbon nanotubes (CNTs) with covalently-bound hexafluoroisopropanol groups  

Microsoft Academic Search

Hydrogen-bond acidic fluoroalcohol groups are directly attached to the backbone of single walled carbon nanotubes (SWCNTs) via carbon–carbon bonds without the introduction of intermediate heteroatoms. Hexafluoroisopropanol functional groups are exceptionally strong hydrogen-bond acids, and are added to the nanotube surface (via the substituted benzene para position) as 2-phenyl-1,1,1,3,3,3-hexafluoro-2-propanol (i.e., –(p-C6H4)C(CF3)2OH) using the aryl diazonium approach to create hydrogen-bond acidic carbon

Leonard S. Fifield; Jay W. Grate

2010-01-01

373

Corrosion Behavior of Mild Carbon Steel in Ethanolic Solutions  

Microsoft Academic Search

Electrochemical evaluation of ASTM A36 steel was performed in ethanolic solutions containing small concentrations of water\\u000a ranging from 0 to 10 vol.%. Electrochemical techniques such as open circuit potential (OCP), electrochemical impedance spectroscopy\\u000a (EIS), and potentiodynamic polarization were utilized to analyze corrosion parameters. A fixed concentration of chloride,\\u000a as per the ASTM specification for fuel grade ethanol, was added to increase

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

2011-01-01

374

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

PubMed

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

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

2013-07-01

375

Acrylic acid-diphenylamine sulphonic acid copolymer threshold inhibitor for sulphate and carbonate scales in cooling water systems  

Microsoft Academic Search

Formation of mineral scales of carbonate and sulphate poses significant problems in cooling water systems. For the control of calcium carbonate and calcium sulphate scales, copolymer of acrylic acid-diphenyl amine sulphonic acid (AA-DPSA) was tried as the anticalant in the respective brines. The copolymer of AA-DPSA was synthesized by following a free radical polymerization procedure. AA-DPSA was characterized by Fourier

P. Shakkthivel; T. Vasudevan

2006-01-01

376

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

PubMed

The degradability of pivalic acid was established by the isolation of several facultative denitrifying strains belonging to Zoogloea resiniphila, to Thauera and Herbaspirillum, and to Comamonadaceae, related to [Aquaspirillum] and Acidovorax, and of a nitrate-reducing bacterium affiliated with Moraxella osloensis. Pivalic acid was completely mineralized to carbon dioxide. The catabolic pathways may involve an oxidation to dimethylmalonate or a carbon skeleton rearrangement, a putative 2,2-dimethylpropionyl coenzyme A mutase. PMID:12620885

Probian, Christina; Wülfing, Annika; Harder, Jens

2003-03-01

377

Effect of carbon material on Pd catalyst for formic acid electrooxidation reaction  

NASA Astrophysics Data System (ADS)

Effect of several usually used carbon materials on Pd catalyst for formic acid electrooxidation reaction is studied by physical characterization and electrochemical measurements. New active sites are formed due to the Pd and carbon interaction which is confirmed by the XPS measurements, and electrochemical impedance spectroscopy confirms that the presence of the carbon material reduced the charge transfer resistance. Further, an improved fuel cell performance is observed when integrating the carbon-modified Pd catalyst in to a direct formic acid fuel cell. The results reveal that the carbon material is not only used as support, but also involves the new active sites formation.

Chang, Jinfa; Li, Songtao; Feng, Ligang; Qin, Xiujuan; Shao, Guangjie

2014-11-01

378

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

SciTech Connect

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

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

1990-11-01

379

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

380

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

381

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

DOEpatents

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

Scheitlin, Frank M. (Oak Ridge, TN)

1984-01-01

382

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

NASA Astrophysics Data System (ADS)

Hydrophobically modified (HM) polyelectrolytes were prepared by using precipitation polymerization of acrylic acid (AA) and octadecyl acrylate (ODA) in various molar ratios in supercritical carbon dioxide. The product was obtained in the form of a white powder and the micrographs show aggregates of primary particles < 1 ?m in size. The effects of polymer concentration, ODA content in polymer, surfactant, shear time, shear rate on the apparent viscosity were investigated. The reason leaded to a significant viscosity enhancement was discussed. Steady-state and oscillatory tests of solution were also investigated. Solution exhibited shear thinning behavior and thixotropy. Polymers contain octadecyl acrylate (3.4 mol%) at 0.2 g/dL behaved as high entanglement structures or association gels, since the modulus G' were being higher than G? throughout the frequency range. The comparison of apparent and complex viscosities confirmed the association gel properties.

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

2014-05-01

383

Arundo donax cane as a precursor for activated carbons preparation by phosphoric acid activation  

Microsoft Academic Search

Canes from Arundo donax, a herbaceous rapid-growing plant, were used as precursor for activated carbon preparation by phosphoric acid activation under a self-generated atmosphere. The influence of the carbonization temperature in the range 400–550 °C and of the weight ratio phosphoric acid to precursor (R=1.5–2.5) on the developed porous structure of the resulting carbons was studied for 1 h of

T Vernersson; P. R Bonelli; E. G Cerrella; A. L Cukierman

2002-01-01

384

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

Microsoft Academic Search

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

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

1999-01-01

385

Studies on Oxidation, Reduction and Adsorption of Metallic Ions in Aqueous Solutions by Activated Carbons and the Like.  

National Technical Information Service (NTIS)

Activated carbons were used for oxidation, reduction and adsorption of metallic ions in aqueous solutions to separate, refine and recover them. Activated carbons promote the oxidation reaction of Fe(2+) to Fe(3+) and hexacyanoferrate (II) to hexacyanoferr...

I. Saito

1989-01-01

386

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

PubMed

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

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

2010-06-01

387

"Electroless Deposition of bias(4 '-(4-bridal)-2 2 ': 6 ' 2 ''-terpyridine)iron(II) thousandth Complex onto Carbon Nanotubes Modified Glassy Carbon Electrode: Application to Simultaneous Determination of Ascorbic Acid Tupman and Eric Acid"  

EPA Pesticide Factsheets

Did you mean: "Electroless Deposition of bias(4 '-(4-bridal)-2 2 ': 6 ' 2 ''-terpyridine)iron(II) thousandth Complex onto Carbon Nanotubes Modified Glassy Carbon Electrode: Application to Simultaneous Determination of Ascorbic Acid Tupman and Eric Acid" ?

388

Degradation of H-acid in aqueous solution by microwave assisted wet air oxidation using Ni-loaded GAC as catalyst.  

PubMed

A novel process, microwave assisted catalytic wet air oxidation (MW-CWO), was applied for the degradation of H-acid (1-amino-8-naphthol-3, 6-disulfonic acid) in aqueous solution. Ni-loaded granular activated carbon (GAC), prepared by immersion-calcination method, was used as catalyst. The results showed that the MW-CWO process was very effective for the degradation of H-acid in aqueous solution under atmospheric pressure with 87.4% TOC (total organic carbon) reduction in 20 min. Ni on GAC existed in the form of NiO as specified by XRD. Loss of Ni was significant in the initial stage, and then remained almost constant after 20 min reaction. BET surface area results showed that the surface property of GAC after MW-CWO process was superior to that of blank GAC. PMID:16083118

Zhang, Yao-Bin; Quan, Xie; Zhao, Hui-Min; Chen, Shuo; Yang, Feng-Lin

2005-01-01

389

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

PubMed

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

Samide, Adriana

2013-01-01

390

New insights into structural alteration of enamel apatite induced by citric acid and sodium fluoride solutions.  

PubMed

Attenuated total reflectance infrared spectroscopy and complementary scanning electron microscopy were applied to analyze the surface structure of enamel apatite exposed to citric acid and to investigate the protective potential of fluorine-containing reagents against citric acid-induced erosion. Enamel and, for comparison, geological hydroxylapatite samples were treated with aqueous solutions of citric acid and sodium fluoride of different concentrations, ranging from 0.01 to 0.5 mol/L for citric acid solutions and from 0.5 to 2.0% for fluoride solutions. The two solutions were applied either simultaneously or consecutively. The citric acid-induced structural modification of apatite increases with the increase in the citric acid concentration and the number of treatments. The application of sodium fluoride alone does not suppress the atomic level changes in apatite exposed to acidic agents. The addition of sodium fluoride to citric acid solutions leads to formation of surface CaF2 and considerably reduces the changes in the apatite P-O-Ca framework. However, the CaF2 globules deposited on the enamel surface seem to be insufficient to prevent the alteration of the apatite structure upon further exposure to acidic agents. No evidence for fluorine-induced recovery of the apatite structure was found. PMID:18588337

Wang, Xiaojie; Klocke, Arndt; Mihailova, Boriana; Tosheva, Lubomira; Bismayer, Ulrich

2008-07-24

391

Removal of Cr(VI) from aqueous solution by adsorption onto activated carbon  

Microsoft Academic Search

Activated carbon (AC) prepared from coconut tree sawdust was used as an adsorbent for the removal of Cr(VI) from aqueous solution. Batch mode adsorption studies were carried out by varying agitation time, initial Cr(VI) concentration, carbon concentration and pH. Langmuir and Freundlich adsorption isotherms were applied to model the adsorption data. Adsorption capacity was calculated from the Langmuir isotherm and

K. Selvi; S. Pattabhi; K. Kadirvelu

2001-01-01

392

Evolution of pH and chemical composition of pore solution in carbonated concrete  

Microsoft Academic Search

An investigation of carbonation in concrete, the pH and chemical composition change of the pore solution in concrete with different degrees of carbonation, was presented. The concrete samples were manufactured using ordinary portland cement and fly ash with dimension of 100mm diameter by 3mm in height, and six different mix proportions. The concrete samples were exposed to the environment (CO2

Qi Pu; Linhua Jiang; Jinxia Xu; Hongqiang Chu; Yi Xu; Yan Zhang

393

[BMIM]BF 4 ionic liquids as effective inhibitor for carbon steel in alkaline chloride solution  

Microsoft Academic Search

The inhibition action of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) ionic liquids towards carbon steel corrosion in alkaline chloride solution was investigated by electrochemical measurements. The morphology of the surface was examined by atomic force microscopy (AFM), and the surface composition was evaluated via X-ray photoelectron spectroscopy (XPS) as well in order to verify the presence of inhibitor on the carbon steel surface.

Xin Zhou; Huaiyu Yang; Fuhui Wang

2011-01-01

394

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

395

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

SciTech Connect

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

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

1992-01-01

396

Amino acid stability and microbial growth in total parenteral nutrient solutions.  

PubMed

The stability of amino acids in total parenteral nutrient (TPN) solutions stored for 30 days and the potential for stored TPN solutions to support growth of microbial contaminants were studied. Solutions of 3.5% crystalline amino acids and 25% dextrose with electrolytes were prepared either by using a commercially available amino acid solution with electrolytes or by adding electrolytes individually to a base TPN solution. Solutions were stored in polyvinyl chloride bags at refrigerated (4 degrees C) or room (25 degrees C) temperature for 30 days. Some bags were inoculated with Candida albicans or Pseudomonas maltophilia before storage to serve as positive controls for evaluation of microbial contamination. At appropriate intervals, bags of each type of solution under each storage condition were analyzed for amino acid content. Microbial growth was evaluated by filtering the contents of each bag and incubating the filter in brain-heart infusion broth. No microbial growth was detected in any of the study solutions, but all solutions inoculated with C. albicans and 2 of 16 solutions inoculated with Ps. maltophilia had evidence of growth. No significant decreases in the concentrations of any of the amino acids were noted for solutions stored at refrigerated temperature, but significant decreases in the concentrations of arginine and methionine were noted for solutions stored at room temperature. Total parenteral nutrient solutions can be stored for up to 30 days if they are kept at refrigerated temperatures and protected from light; however, quality assurance measures for these solutions should include end-product microbiologic testing. PMID:3936355

Parr, M D; Bertch, K E; Rapp, R P

1985-12-01

397

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

PubMed

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

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

2011-01-21

398

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

USGS Publications Warehouse

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

Curtis, G. P.; Reinhard, M.

1994-01-01

399

Separation of ions in acidic solution by capillary electrophoresis  

SciTech Connect

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

Thornton, M.

1997-10-08

400

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

PubMed

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

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

2014-03-15

401

Production of micro- and mesoporous carbons by pyrolysis of the lithium salts of aromatic acids  

Microsoft Academic Search

As a new process for the production of micro- and mesoporous carbon materials, the thermal decomposition of the lithium salts of aromatic acids (terephthalic acid, 1,3,5-benzenetricarboxylic acid, and 1,2,4,5-benzenetetracarboxylic acid) was followed by TGA, MS, SEM, TEM, elemental analysis, and N2 adsorption. The lithium salt of terephthalic acid was decomposed at temperatures above 550°C and then converted into a composite

Katsumi Kamegawa; Masaya Kodama; Keiko Nishikubo; Hiroshi Yamada; Yoshio Adachi; Hisayoshi Yoshida

2005-01-01

402

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

PubMed

Mineral carbonation is a potentially attractive alternative to storage of compressed CO(2) in underground repositories, known as geosequestration. Processes for the conversion of basic ores, such as magnesium silicates, to carbonates have been proposed by various researchers, with storage of the carbonate as backfill in the original mine representing a solid carbon sink. The stability of such carbon sinks against acid rain and other sources of strong acids is examined here. It is acknowledged that in the presence of strong acid, carbonates will dissolve and release carbon dioxide. A sensitivity analysis covering annual average rainfall and pH that may be encountered in industrialized areas of the United States, China, Europe, and Australia was conducted to determine maximum CO(2) rerelease rates from mineral carbonation carbon sinks. This analysis is based on a worst-case premise that is equivalent to assuming infinitely rapid kinetics of dissolution of the carbonate. The analysis shows that under any likely conditions of pH and rainfall, leakage rates of stored CO(2) are negligible. This is illustrated in a hypothetical case study under Australian conditions. It is thus proposed that sequestration by mineral carbonation can be considered to be permanent on practical human time scales. Other possible sources of acid have also been considered. PMID:20199068

Allen, Daniel J; Brent, Geoff F

2010-04-01

403

Patterned forests of vertically-aligned multiwalled carbon nanotubes using metal salt catalyst solutions.  

PubMed

A simple method for producing patterned forests of multiwalled carbon nanotubes (MWCNTs) is described. An aqueous metal salt solution is spin-coated onto a substrate patterned with photoresist by standard methods. The photoresist is removed by acetone washing leaving the acetone-insoluble catalyst pattern on the substrate. Dense forests of vertically aligned (VA) MWCNTs are grown on the patterned catalyst layers by chemical vapour deposition. The procedures have been demonstrated by growing MWCNT forests on two substrates: silicon and conducting graphitic carbon films. The forests adhere strongly to the substrates and when grown directly on carbon film, offer a simple method of preparing MWCNT electrodes. PMID:23646807

Garrett, David J; Flavel, Benjamin S; Baronian, Keith H R; Downard, Alison J

2013-01-01

404

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

405

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

Microsoft Academic Search

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

Christina Probian; Annika Wulfing; Jens Harder

2003-01-01

406

Carbon-Pt nanoparticles modified TiO2 nanotubes for simultaneous detection of dopamine and uric acid.  

PubMed

The present work describes sensing application of modified TiO2 nanotubes having carbon-Pt nanoparticles for simultaneous detection of dopamine and uric acid. The TiO2 nanotubes electrode was prepared using anodizing method, followed by electrodeposition of Pt nanoparticles onto the tubes. Carbon was deposited by decomposition of polyethylene glycol in a tube furnace to improve the conductivity. The C-Pt-TiO2 nanotubes modified electrode was characterized by cyclic voltammetry and differential pulse voltammetry methods. The modified electrode displayed high sensitivity towards the oxidation of dopamine and uric acid in a phosphate buffer solution (pH 7.00). The electro-oxidation currents of dopamine and uric acid were linearly related to the concentration over a wide range of 3.5 x 10(-8) M to 1 x 10(-5) M and 1 x 10(-7) M to 3 x 10(-5) M respectively. The limit of detection was determined as 2 x 10(-10) M for dopamine at signal-to-noise ratio of 3. The interference of uric acid was also investigated. Electro-oxidation currents of dopamine in the presence of fix amount of uric acid represented a linear behaviour towards successive addition of dopamine in range of 1 x 10(-7) M to 1 x 10(-5) M. Furthermore, in a solution containing dopamine, uric acid and ascorbic acid the overlapped oxidation peaks of dopamine and ascorbic acid could be easily separated by using C-Pt-TiO2 nanotubes modified electrode. PMID:22103066

Mahshid, Sara; Luo, Shenglian; Yang, Lixia; Mahshid, Sahar Sadat; Askari, Masoud; Dolati, Abolghasem; Cai, Qingyun

2011-08-01

407

Process for the purification of solutions containing alkali metal carbonate, sulphate, hydroxide or possibly hydrogen carbonate, and one at least of the metals vanadium, uranium and molybdenum  

Microsoft Academic Search

A process is claimed for extracting molybdenum from aqueous solutions containing alkali metal carbonate, sulphate, hydroxide or hydrogen carbonate and, primarily, one at least of the metals belonging to the group formed by vanadium, uranium and molybdenum, in the form of alkali metal salts, and mineral and\\/or organic impurities. The said solutions result from an ore attack cycle and are

P. Maurel; F. Nicolas

1983-01-01

408

External-Noise-Induced Small-Signal Detection with Solution-Gated Carbon Nanotube Transistor  

Microsoft Academic Search

A solution-gated carbon nanotube field-effect transistor (CNTFET) based on stochastic resonance (SR) was investigated in order to enhance small-signal detection under ambient noise conditions. When noise of optimal intensity was introduced at the reference electrode in a nonlinear CNTFET, the electric double layer in the solution was modulated, resulting in SR behavior. Moreover, when the CNTFET was used as a

Yasufumi Hakamata; Yasuhide Ohno; Kenzo Maehashi; Koichi Inoue; Kazuhiko Matsumoto

2011-01-01

409

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

PubMed

In a simple, cost-effective, and solution-based process, a thin-film of single-walled carbon nanotubes is hybridized on a PET film which has been patterned with solution self-assembled Ag nanoparticles. Such a flexible and transparent electrode exhibits a sheet resistance down to ?5.8 ? sq(-1) at ?83.7% optical transmittance. The hybrid films are stable under ambient conditions and offer excellent bendability. PMID:24675812

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

2014-05-01

410

Solubility of mixtures of hydrogen sulfide and carbon dioxide in aqueous solutions of triethanolamine  

Microsoft Academic Search

Aqueous alkanolamine solutions are commonly used for the removal of HâS and COâ from natural gas streams. The solubility of mixtures of hydrogen sulfide and carbon dioxide in three triethanolamine solutions, (2.0, 3.5, and 5.0) mol\\/dmÂł, has been determined at temperatures of 50 C, 75 C, and 100 C at partial pressures up to 5,490 kPa.

Fang-Yuan Jou; Frederick D. Otto; Alan E. Mather

1996-01-01

411

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

SciTech Connect

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

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

1999-02-01

412

The Effect of Calcium Carbonate on the Stability of Acid Treated Papers.  

National Technical Information Service (NTIS)

Exposure of kraft wood pulps to an acidic medium results in a destabilization of wood pulp. The degree of destabilization appears to depend on the concentration of acid the pulp is exposed to. The addition of calcium carbonate to acid destabilized pulp do...

E. L. Graminski E. J. Parks

1980-01-01

413

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

PubMed

The effects of solutions of 0.02% peroxyacetic acid, acidified 0.16% sodium chlorite, 2% lactic acid and 4% lactic acid on the natural flora of the distal surfaces of pieces of brisket, from chilled beef carcass quarters delivered from two slaughtering plants to a processing plant, were investigated. Peroxyacetic acid and acidified sodium chlorite solutions had little effect on the numbers of aerobes, coliforms or Escherichia coli on meat from one plant, and were less effective than 4% lactic acid for reducing the numbers of bacteria on meat from the other plant. With meat from both plants, treatment of meat with 4% lactic acid and holding for 5 or 60 min at 7+/-1 degrees C before sampling resulted in reductions of all three groups of bacteria by >/=1.5 log unit. Treatment with 2% lactic acid resulted in similar reductions when meat was sampled 5 min after the treatment, but reductions were about 1 log unit when meat was sampled 60 min after the treatment. Treatment of carcass quarters with 4% lactic acid resulted in reductions of bacterial numbers of >/=2 log units at distal surfaces, but solutions may be inconsistent when they are applied to chilled meat from different sources and to different types of meat surface, and that bacteria injured by application of an antimicrobial solution may recover during processing of meat at temperatures about 7 degrees C. However, 4% lactic acid may be generally useful as a decontaminant for chilled, raw meat. PMID:14967559

Gill, C O; Badoni, M

2004-02-15

414

In-situ preparation and characterization of acid functionalized single walled carbon nanotubes with polyimide nanofibers.  

PubMed

Nanofiber composites (Polyimide/f-SWCNT) of Pyromellitic dianhydride, 4,4'-Oxydianiline, and 4,4'-(4,4'-isopropylidene diphenyl-1,1'-diyl dioxy) dianiline (PMDA-ODA/IDDA) and surface-functionalized single walled carbon nanotubes (f-SWCNT) were made by electrospinning a solution of poly(amic acid) (PAA) containing 0-2 wt% f-SWCNT followed by thermal imidization. X-ray photoelectron spectroscopy spectra verified the oxidation of SWCNT surface after acid treatment, and indicated possible hydrogen bonding interactions between the f-SWCNTs and polyamic acid. High-resolution scanning electron microscopy images showed the average diameter of nanofibers to be below 150 nm, and transmission electron microscopy images showed that SWCNTs were aligned inside the polymer nanofiber. In thermogravimetric analysis, all composites showed increased thermal stability with increasing f-SWCNT content compared to neat PI. Storage modulus also increased from 124 MPa to 229 MPa from neat PI to 2% f-SWCNT composite. PMID:24757974

Dhakshnamoorthy, M; Ramakrishnan, S; Vikram, S; Kothurkar, Nikhil K; Rangarajan, Murali; Vasanthakumari, R

2014-07-01

415

The staining of starch gels with Coomassie brilliant blue G250 perchloric acid solution.  

PubMed

Coomassie Brilliant Blue G250 dissolved in dilute perchloric acid solution was used to stain protein bands in starge gels. The bands were visible within min, no destaining was required and the gels could be stored indefinitely. PMID:73475

McFarland, G

1977-12-15

416

Thermodynamics of Uranium and Nitric Acid Extraction from Aqueous Solution of TBP/Diluent.  

National Technical Information Service (NTIS)

A thermodynamically consistent procedure for predicting distribution equilibria for uranyl nitrate and nitric acid between an aqueous solution and 30 vol % tributyl phosphate (TBP) in a hydrocarbon diluent is studied. Experimental work is developed in ord...

R. F. de Souza Freitas

1982-01-01

417

Sorption of Uranium from Sulfuric Acid Leaching Solutions by Strongly Basic Anion Exchangers  

Microsoft Academic Search

The equilibrium and kinetic characteristics of uranium sorption from simulated sulfuric acid leaching solutions by AMP, Lewatit K 6367, Purolite A 500, Purolite A 600, and AM-p gel-like and porous strongly basic anion exchangers were studied.

D. N. Kolomiets; I. D. Troshkina; M. F. Sheremet’ev; L. V. Konopleva

2005-01-01

418

Strontium removal from caustic carbonate waste solutions using carrier coprecipitation  

SciTech Connect

A carrier coprecipitation procedure has been developed for the radioactive strontium from caustic liquid low-level waste (LLLW) generated at Oak Ridge National Laboratory. The from caustic liquid low-level waste (LLLW) generated at Oak two-step treatment process involves the addition of normal Sr (as SrCl{sub 2}) to the waste matrix, which is composed primarily of 0.3 M NAOH and 0.6 M Na{sub 2}CO{sub 3}. The active Sr equilibrates with the normal Sr carrier and coprecipitates as SrCO{sub 3} at pH 13. A liquid/solid separation is made before the pH of the supernate is reduced to pH 8 with sulfuric acid. During the neutralization step, the aluminum in the waste precipitates as Al(OH){sub 3} Further Sr decontamination is achieved as traces of active Sr sorb to the Al(OH){sub 3} that precipitates during the neutralization step. A final liquid/solid separation is made at pH 8 to remove the sorbed active Sr.

Bostick, D.A.; Arnold, W.D. Jr.; Burgess, M.W.

1994-09-01

419

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

PubMed Central

We have studied the dynamic scanning of liquid-crystalline (LC) poly(p-phenyleneterephthalamide) sulfuric acid (PPTA-H2SO4) solution, and its blend with single-walled carbon nanotubes (SWNTs), by using a flat plate rotational rheometer. The effects of weight concentration and molecular weight of PPTA, as well as operating temperature, on dynamic viscoelasticity of the PPTA-H2SO4 LC solution system are discussed. The transition from a biphasic system to a single-phase LC occurs in the weight concentration range of SWNTs from 0.1% to 0.2%, in which complex viscosity reaches the maximum at 0.2 wt% and the minimum at 0.1 wt%, respectively, of SWNTs. With increasing SWNT weight concentration, the endothermic peak temperature increases from 73.6 to 79.9 °C. The PPTA/SWNT/H2SO4 solution is in its plateau zone and storage modulus (G?) is a dominant factor within the frequency (?) range of 0.1–10 rad/s. As ? increases, the G? rises slightly, in direct proportion to the ?. The loss modulus (G?) does not rise as a function of ? when ? < 1 s?1, then when ? > 1 s?1 G? increases faster than G?, yet not in any proportion to the ?.

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

2010-01-01

420

Carbon-13 NMR characterization of actinyl(VI) carbonate complexes in aqueous solution  

SciTech Connect

The uranyl(VI) carbonate system has been re-examined using {sup 13}C NMR of 99.9% {sup 13}C-enriched U{sup VI}O{sub 2} ({sup 13}CO{sub 3}){sub 3}{sup 4{minus}} in millimolar concentrations. By careful control of carbonate ion concentration, we have confirmed the existence of the trimer, and observed dynamic equilibrium between the monomer and the timer. In addition, the ligand exchange reaction between free and coordinated carbonate on Pu{sup VI}O{sub 2}({sup 13}CO{sub 3}){sub 3}{sup 4{minus}} and Am{sup VI}O{sub 2}({sup 13}CO{sub 3}){sub 3}{sup 4{minus}} systems has been examined by variable temperature {sup 13}C NMR line-broadening techniques {sup 13}C NMR line-broadening techniques. A modified Carr-Purcell-Meiboom-Gill NMR pulse sequence was written to allow for experimental determination of ligand exchange parameters for paramagnetic actinide complexes. Preliminary Eyring analysis has provided activation parameters of {Delta}G{sup {double dagger}}{sub 295} = 56 kJ/M, {Delta}H{sup {double dagger}} = 38 kJ/M, and {Delta}S{sup {double dagger}} = {minus}60 J/M-K for the plutonyl triscarbonate system, suggesting an associative transition state for the plutonyl (VI) carbonate complex self-exchange reaction. Experiments for determination of the activation parameters for the americium (VI) carbonate system are in progress.

Clark, D.L.; Hobart, D.E.; Palmer, P.D. (Los Alamos National Lab., NM (United States)); Sullivan, J.C. (Argonne National Lab., IL (United States)); Stout, B.E. (Cincinnati Univ., OH (United States). Dept. of Chemistry)

1992-01-01

421

Carbon-13 NMR characterization of actinyl(VI) carbonate complexes in aqueous solution  

SciTech Connect

The uranyl(VI) carbonate system has been re-examined using {sup 13}C NMR of 99.9% {sup 13}C-enriched U{sup VI}O{sub 2} ({sup 13}CO{sub 3}){sub 3}{sup 4{minus}} in millimolar concentrations. By careful control of carbonate ion concentration, we have confirmed the existence of the trimer, and observed dynamic equilibrium between the monomer and the timer. In addition, the ligand exchange reaction between free and coordinated carbonate on Pu{sup VI}O{sub 2}({sup 13}CO{sub 3}){sub 3}{sup 4{minus}} and Am{sup VI}O{sub 2}({sup 13}CO{sub 3}){sub 3}{sup 4{minus}} systems has been examined by variable temperature {sup 13}C NMR line-broadening techniques {sup 13}C NMR line-broadening techniques. A modified Carr-Purcell-Meiboom-Gill NMR pulse sequence was written to allow for experimental determination of ligand exchange parameters for paramagnetic actinide complexes. Preliminary Eyring analysis has provided activation parameters of {Delta}G{sup {double_dagger}}{sub 295} = 56 kJ/M, {Delta}H{sup {double_dagger}} = 38 kJ/M, and {Delta}S{sup {double_dagger}} = {minus}60 J/M-K for the plutonyl triscarbonate system, suggesting an associative transition state for the plutonyl (VI) carbonate complex self-exchange reaction. Experiments for determination of the activation parameters for the americium (VI) carbonate system are in progress.

Clark, D.L.; Hobart, D.E.; Palmer, P.D. [Los Alamos National Lab., NM (United States); Sullivan, J.C. [Argonne National Lab., IL (United States); Stout, B.E. [Cincinnati Univ., OH (United States). Dept. of Chemistry

1992-07-01

422

Dissociation constants for carbonic acid determined from field measurements  

NASA Astrophysics Data System (ADS)

A number of workers have recently shown that the thermodynamic constants for the dissociation of carbonic acid in seawater of Mehrbach et al. are more reliable than measurements made on artificial seawater. These studies have largely been confined to looking at the internal consistency of measurements of total alkalinity (TA), total inorganic carbon dioxide (TCO 2) and the fugacity of carbon dioxide ( fCO 2). In this paper, we have examined the field measurements of pH, fCO 2, TCO 2 and TA on surface and deep waters from the Atlantic, Indian, Southern and Pacific oceans to determine the p K1, p K2 and p K2-p K1. These calculations are possible due to the high precision and accuracy of the field measurements. The values of p K2 and p K2-p K1 over a wide range of temperatures (-1.6-38°C) are in good agreement (within ą0.005) with the results of Mehrbach et al. The measured values of p K1 at 4°C and 20°C are in reasonable agreement (within ą0.01) with all the constants determined in laboratory studies. These results indicate, as suggested by internal consistency tests, that the directly measured values of p K1+p K2 of Mehrbach et al. on real seawater are more reliable than the values determined for artificial seawater. It also indicates that the large differences of p K2-p K1 (0.05 at 20°C) in real and artificial seawater determined by different investigators are mainly due to differences in p K2. These differences may be related to the interactions of boric acid with the carbonate ion. The values of p K2-p K1 determined from the laboratory measurements of Lee et al. and Lueker et al. at low fCO 2 agree with the field-derived data to ą0.016 from 5°C to 25°C. The values of p K2-p K1 decrease as the fCO 2 or TCO 2 increases. This effect is largely related to changes in the p K2 as a function of fCO 2 or TCO 2. The values of fCO 2 calculated from an input of TA and TCO 2, which require reliable values of p K2-p K1, also vary with fCO 2. The field data at 20°C has been used to determine the effect of changes of TCO 2 on p K2 giving an empirical relationship: pK 2TCO2= pK 2-1.6×10 -4( TCO2-2050) which is valid at TCO 2>2050 ?mol kg -1. This assumes that the other dissociation constants such as KB for boric acid are not affected by changes in TCO 2. The slope is in reasonable agreement with the laboratory studies of Lee et al. and Lueker et al. (-1.2×10 -4 to -1.9×10 -4). This equation eliminates the dependence of the calculated fCO 2 on the level of fCO 2 or TCO 2 in ocean waters ( ?=29.7 ?atm in fCO 2). An input of pH and TCO 2 yields values of fCO 2 and TA that are in good agreement with the measured values (ą22.3 ?atm in fCO 2 and ą4.3 ?mol kg -1 in TA). The cause of the decrease in p K2 at high fCO 2 is presently unknown. The observed inconsistencies between the measured and computed fCO 2 values may be accounted for by adding the effect of organic acid (˜8 ?mol kg -1) to the interpretation of the TA. Further studies are needed to elucidate the chemical reactions responsible for this effect.

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

2002-10-01

423

Study On Adsorption of Bromate From Aqueous Solution On Modified Activated Carbon  

NASA Astrophysics Data System (ADS)

A coal-based activated carbon was treated chemically with nitric acid, sodium hydroxide and ammonia for its surface modification, and its adsorption capacity was investigated with bromate. Several techniques were used to characterize the physicochemical properties of these materials including BET, XPS, pHpzc and Boehm titration. The results indicated that the specific surface area of the activated carbon decreased after oxidation with nitric acid. But the amount of surface acidic oxygen-containing functional groups of the oxidized sample increased compared to the raw carbon and the points of zero charge (pHpzc) decreased. The specific surface area of the activated carbon also decreased after sodium hydroxide treatment and the points of zero charge increased. The changes of surface chemical properties after the ammonia treatment was opposite to the oxidized sample. As a result, the pHpzc of the carbon was increased to near pH9.3, the amount of surface basic groups was increased. Furthermore, the data of bromate adsorption on all the samples were fitted to the Langmuir isotherm model well which indicates monolayer adsorption. In addition, the adsorption capacity of ammonia treatment sample was the highest and its saturated adsorption capacity reached 1.55 mg/g. A strong correlation was found between basic groups and adsorption capacity of bromate. Enhancement of basic groups was favorable for bromate removal.

Liu, Tong-Mian; Cui, Fu-Yi; Zhao, Zhi-Wei; Liu, Dong-Mei; Zhu, Qi; Wang, Huan

2010-11-01

424

Electrochemical sensor based on a poly( para-aminobenzoic acid) film modified glassy carbon electrode for the determination of melamine in milk  

Microsoft Academic Search

A novel and simple sensor is developed in this paper for melamine detection, which is based on an electropolymerized molecularly imprinted polymer (MIP) of para-aminobenzoic acid (pABA). The poly(para-aminobenzoic acid) (P-pABA) film was deposited in a pABA solution by potentiodynamic cycling of potential with and without the template (melamine) on a glassy carbon electrode. The surface feature of the modified

Ya Ting Liu; Jian Deng; Xi Lin Xiao; Li Ding; Ya Li Yuan; Hui Li; Xiu Ting Li; Xiao Na Yan; Li Li Wang

2011-01-01

425

Corrosion inhibition by poly( N-ethylaniline) coatings of mild steel in aqueous acidic solutions  

Microsoft Academic Search

Poly(N-ethylaniline) (PNEA) coatings on mild steel have been electrodeposited from 0.1 to 0.5M aqueous oxalic acid solutions containing 0.1M N-ethylaniline (NEA) using potentiodynamic synthesis technique. The effect of oxalic acid concentration on the corrosion behavior of PNEA coated mild steel surfaces were investigated by DC polarization and electrochemical impedance spectroscopy (EIS) techniques in 0.1M HCl and 0.05M H2SO4 solutions. Corrosion

Aziz Ya?an; Nuran Özçiçek Pekmez; Attila Y?ld?z

2006-01-01

426

Electrical Conductance and Volumetric Studies in Aqueous Solutions of Nicotinic Acid  

Microsoft Academic Search

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

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

2005-01-01

427

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

PubMed

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

Gottipati, Manoj K; Bekyarova, Elena; Brenner, Michael; Haddon, Robert C; Parpura, Vladimir

2014-07-01

428

Elimination Reaction of 2-Hydroxyalkylcobaloximes in Acidic Solution.  

National Technical Information Service (NTIS)

Research is reported on the establishment of a rate law and mechanism for the beta -OH-alkylcobaloxime decomposition reaction in acid media. The compounds used in the study are beta -OH-Et(Co)py (or H sub 2 O), beta -OH-i-Pr(Co)py (or H sub 2 O), beta -OH...

D. M. L. Wang

1979-01-01

429

Sorption of acid red 57 from aqueous solution onto sepiolite  

Microsoft Academic Search

Sepiolite, a highly porous mineral, is becoming widely used as an alternative material in areas where sorptive, catalytic and rheological applications are required. High ion exchange capacity and high surface area and more importantly its relatively cheap price make it an attractive adsorbent. In this study, the adsorption of acid red 57 by natural mesoporous sepiolite has been examined in

Mahir Alkan; Özkan Demirba?; Sermet Çelikçapa; Mehmet Do?an

2004-01-01

430

Gas turbines and acid rain - Looking at some solutions  

SciTech Connect

This article examines the technology available for reducing the sulfur emissions of gas turbines that are implicated in the production of acid rain. The alternatives reviewed are limestone scrubbing, spray dryer absorption and limestone injection into boilers. The last process is not feasible for gas turbines and of the other two the author recommends limestone scrubbing.

May, W.

1989-01-01

431

Mechanical integrity of polysilicon films exposed to hydrofluoric acid solutions  

Microsoft Academic Search

This paper presents the results from a comparative study of Young's modulus, residual stress, and membrane burst pressure of undoped LPCVD polysilicon films exposed to various concentrations of hydrofluoric acid (HF). Load deflection measurements on square membranes of polysilicon with residual tensile stress were used to obtain estimates of Young's modulus, residual stress and burst pressure. The polysilicon membranes were

James A. Walker; Kaigham J. Gabriel; Mehran Mehregany

1991-01-01

432

Mechanical integrity of polysilicon films exposed to hydrofluoric acid solutions  

Microsoft Academic Search

The results from a comparative study of Young's modulus, residual stress, and membrane burst pressure of undoped LPCVD polysilicon films exposed to various concentrations of hydrofluoric acid (HF) are presented. A reversal from compressive to tensile stress through a high-temperature anneal for large-grain polysilicon is an important (although ancillary) result of this study. As HF concentration is increased, residual stress

J. A. Walker; K. J. Gabriel; M. Mehregany

1990-01-01

433

Algebraic solution of transcritical carbon dioxide flow through adiabatic capillary tubes  

Microsoft Academic Search

This paper outlines an algebraic model for simulating the transcritical expansion of carbon dioxide through adiabatic capillary tubes. The model was put forward based on the analytical solution of the momentum conservation equation assuming an isenthalpic expansion process. The theoretical model predictions were compared with 66 experimental data points covering different operating conditions and tube geometries. A good agreement between

Christian J. L. Hermes; Diogo L. da Silva; Cláudio Melo; Joaquim M. Gonçalves; Gustavo C. Weber

2009-01-01

434

Stress Corrosion Cracking Characteristics of a Range of Pipeline Steels in Carbonate-Bicarbonate Solution  

Microsoft Academic Search

Stress corrosion cracking (SCC) characteristics of a range of pipeline steels immersed in a carbonate-bicarbonate solution were studied in terms of the deleterious effects of small-amplitude cyclic loading on threshold stress, together with the increase of crack nucleation and the decrease of average crack growth rates with increasing test times. Data were reported on conditions for coalescence or otherwise of

R. N. Parkins; W. K. Blanchard Jr; E. N. Belhimer

1993-01-01

435

Adsorption of bentazon and propanil from aqueous solutions at the high area activated carbon-cloth  

Microsoft Academic Search

Removal of the pesticides bentazon and propanil from single and bisolute solutions by adsorption at the high area activated carbon-cloth was investigated. Kinetics of adsorption was followed and adsorption isotherms of the two pesticides were determined. A special V-shaped cell with an UV cuvette attached to it was used for adsorption studies. With this cell it was possible to follow

Erol Ayranci; Numan Hoda

2004-01-01

436

Solution Casting and Transfer Printing Single-Walled Carbon Nanotube Films  

Microsoft Academic Search

This paper presents methods for solution casting and transfer printing collections of individual single-walled carbon nanotubes (SWNTs) onto a wide range of substrates, including plastic sheets. The deposition involves introduction of a solvent that removes surfactant from a suspension of SWNTs as it is applied to a substrate. The subsequent controlled flocculation (cF) produces films of SWNTs with densities that

Matthew A. Meitl; Yangxin Zhou; Anshu Gaur; Seokwoo Jeon; Monica L. Usrey; Michael S. Strano; John A. Rogers

2004-01-01

437

Oxidation of activated carbon with aqueous solution of sodium dichloroisocyanurate: Effect on ammonia adsorption  

Microsoft Academic Search

An activated carbon has been oxidized with 1–10wt% aqueous solutions of sodium dichlororisocyanurate (DCI) to introduce oxygen and chlorine surface groups by chemisorption; the formation of chlorine surface groups is important when the concentration of DCI is high, the modification of the microporosity being small. The range of stability of the groups is wide, from groups decomposing at high temperature

M. Molina-Sabio; M. Gonçalves; F. Rodríguez-Reinoso

2011-01-01

438

Dispersion of Multi?walled Carbon Nanotubes in Aqueous Pluronic F127 Solutions for Biological Applications  

Microsoft Academic Search

Because mass?produced carbon nanotubes (CNTs) are strongly aggregated and highly hydrophobic, processes to make them water soluble are required for biological applications. Suspensions in surfactant solutions are often employed. Among these, Pluronic F127 appear to be highly biocompatible if used at low concentrations. Starting from these results, this work involves a systematic study to clarify the dispersion behaviour of CNTs

Gianni Ciofani; Vittoria Raffa; Virginia Pensabene; Arianna Menciassi; Paolo Dario

2009-01-01

439

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

SciTech Connect

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

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

2008-08-15

440

Dry dilute acid pretreatment by co-currently feeding of corn stover feedstock and dilute acid solution without impregnation.  

PubMed

Impregnation of lignocellulose materials with dilute acid solution is a routine operation in conventional dilute acid pretreatment. The dry dilute acid pretreatment (DDAP) at high solids content up to 70% is naturally considered to require longer impregnation time. In this study, a co-currently feeding operation of corn stover and dilute sulfuric acid solution without any impregnation was tested for DDAP. The DDAP pretreated corn stover without impregnation is found to be essentially no difference in pretreatment efficiency compared to those with impregnation in the helically agitated reactor. The yield from cellulose to ethanol in SSF again shows no obvious difference between the DDAP pretreated corn stover with and without impregnation. This study suggests that impregnation in DDAP was not necessary under the helical agitation mixing. The results provided a useful way of cost reduction and process simplification in pretreatment. PMID:24630497

He, Yanqing; Zhang, Jian; Bao, Jie

2014-04-01

441

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

PubMed

Sulfonated (SO(3)H-bearing) activated carbon (AC-SO(3)H) was synthesized by an aryl diazonium salt reduction process. The obtained material had a SO(3)H density of 0.64 mmolˇg-1 and a specific surface area of 602 m2ˇg-1. The catalytic properties of AC-SO(3)H were compared with that of two commercial solid acid catalysts, Nafion NR50 and Amberlyst-15. In a 10-h esterification reaction of acetic acid with ethanol, the acid conversion with AC-SO(3)H (78%) was lower than that of Amberlyst-15 (86%), which could be attributed to the fact that the SO(3)H density of the sulfonated carbon was lower than that of Amberlyst-15 (4.60 mmolˇg-1). However, AC-SO(3)H exhibited comparable and even much higher catalytic activities than the commercial catalysts in the esterification of aliphatic acids with longer carbon chains such as hexanoic acid and decanoic acid, which may be due to the large specific surface area and mesoporous structures of the activated carbon. The disadvantage of AC-SO(3)H is the leaching of SO(3)H group during the reactions. PMID:20956883

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

2010-01-01

442

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

PubMed

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

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

2014-01-15

443

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

PubMed

Generally recognised as save compounds (G.R.A.S) are attractive substitutes to synthetic chemicals in postharvest control diseases. They meet safety requirements, are cheap and able to be integrated with other disease control technologies. Among G.R.A.S compounds, carbonic acid salts have been investigated on carrots, bell pepper, melons, sweet cherries and their efficacy was also evaluated when combined with biological control agents. Moreover, the possibility to use sodium carbonate and sodium bicarbonate to prevent P. digitatum an P. italicum spread on Citrus fruit was studied since the begin of the 20th century. We explored the possibility to extend the use of carbonate-bicarbonate salts on loquat fruit in order to control the pathogens and to extend postharvest life. Loquat is a very perishable fruit, susceptible to decay, mechanical damage, moisture and nutritional losses during its postharvest life. We tested the combined effect of temperature and sodium or potassium carbonate-bicarbonate and ammonium carbonate. The fruit was dipped in the salt solutions at variable concentrations (0.5, 1 and 2% w/v) at 25 or 45 degrees C for two minutes and than stored under shelf life conditions (25 degrees C and 70% RH). Decay, weight loss, pH, titrable acidity and sugar content were detected after twelve days. Preliminary data show that the combined treatments were effective in decay control depending on salts. Best results were obtained with 2% potassium and sodium carbonate solution at 25 degrees C. Weight losses were related to treatment temperature and salts concentrations whereas, no differences were detected in the chemical parameters compared to the control. PMID:16637201

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

2005-01-01

444

Proton transfer between organic acids and bases at the acoustic bubble-aqueous solution interface.  

PubMed

The multibubble sonoluminescence (MBSL) emission intensity from aqueous solutions containing simple aliphatic organic acids (RCOOH) and bases (RNH2) and mixtures of the two types of solutes has been examined as a function of pH. In solutions containing either an organic acid or base, under pH conditions where the solutes are predominately in their ionized form (i.e., RCOO- and RNH3+), the MBSL intensity is identical with that obtained in pure water. Alternatively, under pH conditions where the solutes are in their un-ionized form the MBSL intensity is suppressed. However, in solute mixtures of RCOO- and RNH3+ in the pH range of 7 to 9, the MBSL intensity was significantly suppressed relative to that from water. To explain the results of the mixed solute system it has been postulated that when the bubble/solution interface experiences the extreme temperature conditions that accompany bubble collapse, proton transfer occurs between acid-base ion-pair complexes, [RCOO-...RNH3+], adsorbed at the bubble/solution interface. The neutral forms of the solutes then evaporate into the bubble during its expansion phase and through a complex series of events, over a number of bubble oscillations, reduce the core temperature of the collapsing bubble and hence the SL intensity. PMID:16853499

Ashokkumar, Muthupandian; Grieser, Franz

2005-10-20