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ABSTRACT: The structures of microbial communities in water samples obtained from a landfill site that had been a source of environmental pollution by emitting hydrogen sulfide were elucidated using polymerase chain reaction-denaturing gradient gel electrophoresis. The microbial communities, which consisted of a limited number of major microorganisms, were stable for several months. Microorganisms capable of degrading such chemical compounds as 2-hydroxybenzothiazole and bisphenol A were observed in landfill leachate. Microorganisms responsible for the production of hydrogen sulfide were not the primary microbes detected, even in water samples obtained from the site of gas emission.
Journal of hazardous materials 10/2008; 164(2-3):1503-8. · 4.14 Impact Factor
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ABSTRACT: Magnesium-aluminum oxide (Mg-Al oxide) prepared by the thermal decomposition of a hydrotalcite-like compound was found to have potential for treating NaBF(4) wastewater. The Mg-Al oxide removed the BF(4)(-) and F(-) and H(3)BO(3) from the NaBF(4) solution. With increasing Mg-Al oxide quantity and time, the BF(4)(-) concentration decreased and the degree of BF(4)(-), F(-), and boron removal increased. The decrease in the BF(4)(-) concentration resulted from uptake by the Mg-Al oxide and not hydrolysis. The Mg-Al oxide took up F(-) from the solution preferentially. The Mg-Al oxide also converted the H(3)BO(3) in the aqueous solution into H(2)BO(3)(-), which it took up.
Chemosphere 11/2007; 69(5):832-5. · 3.21 Impact Factor
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ABSTRACT: To reduce the generation of hydrogen sulfide gas from sulfate ions, we synthesized a layered double hydroxide hydrotalcite-like compound intercalated with chloride ions in the interlayer (HT-Cl) using a coprecipitation reaction. The resultant HT-Cl material had a Mg/Al molar ratio of approximately 2, and the molar fraction of the chloride ions on the intercalated anion layer of the HT was 0.90. A higher molar fraction of chloride ions can be inserted into the interlayers of the HT by increasing the initial concentration ratio of chloride ions to aluminum ions [Cl(-)](0)/[Al(3+)](0) in the solution. Approximately 98% of the sulfate ions in the solution were removed within 10 min after adding 1.12 times the stoichiometric quantity of synthesized HT-Cl, which contained a Mg/Al molar ratio of 2 equal to a solution containing a 12 mM calcium sulfate solution.
Journal of Hazardous Materials 06/2007; 143(1-2):582-6. · 4.17 Impact Factor
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ABSTRACT: A new method of supplying radical species to aqueous solutions using a hydrogen-oxygen flame is investigated. When a hydrogen-oxygen flame is directed on the surface of an aqueous solution, hydroxyl radicals (*OH) produced in the flame are extracted into the aqueous phase. The presence of *OH in the aqueous solution was confirmed by electron paramagnetic resonance with spin trapping using 5,5-dimethyl-1-pyrroline-N-oxide. The extraction of *OH into the aqueous solution was monitored using a quantitative analysis of hydrogen peroxide (H2O2). The effects of the hydrogen and oxygen gas flow rates, hydrogen/oxygen ratio, and atmosphere on H2O2 formation were studied. When the hydrogen-oxygen flame blew on a phosphate buffer solution (pH 6.7) under an Ar atmosphere, the concentration of H2O2 increased with the blowing time of the flame and the flow rate of hydrogen gas. Under air, nitrate and nitrite ions were formed in the aqueous phase in addition to H2O2, and the H2O2 concentration was lower than that under argon. The application of this new method to an aqueous solution of Cu(II)-ethylenediaminetetraacetic acid (EDTA) caused a remarkable decrease in the concentration of Cu(II)-EDTA and total organic carbon.
Environmental Science and Technology 09/2005; 39(15):5851-5. · 5.23 Impact Factor
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ABSTRACT: We investigated the removal of Ca(2+) and Cl(-) from CaCl(2) solution at 20-60 degrees C, using magnesium-aluminum oxide, Mg(0.80)Al(0.20)O(1.10), prepared by the thermal decomposition of a hydrotalcite-like compound, Mg(0.80)Al(0.20)(OH)(2)(CO(3))(0.10).0.78 H(2)O. The degree of Ca(2+) and Cl(-) removal from the solution increased with increasing initial CaCl(2) concentration, temperature, and quantity of Mg(0.80)Al(0.20)O(1.10) added. When Mg(0.80)Al(0.20)O(1.10) was added to 0.25 M CaCl(2) solution in a Mg(0.80)Al(0.20)O(1.10)/CaCl(2) molar ratio of 20, the degree of Ca(2+) and Cl(-) removal from the solution at 60 degrees C after 0.5 h was 93.0% and 98.2%, respectively. These results reveal that Mg(0.80)Al(0.20)O(1.10) has the capacity to remove Ca(2+) and Cl(-) simultaneously from aqueous solution.
Water Research 10/2003; 37(16):4045-50. · 4.86 Impact Factor
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ABSTRACT: 2-Bromophenol was reacted in aqueous sodium hydroxide at 200-250 degrees C. The decomposition rate was remarkably faster at 250 degrees C than at 225 or 200 degrees C, and the percentage debromination reached almost 100% in 1M NaOH at 250 degrees C for 4h. The percentage increased with NaOH concentration over the range 0.1-1M. Aliphatic compounds, such as 2,2-dimethoxypropane and 4-hydroxy-4-methyl-2-pentanone, and aromatic compounds, such as phenol and cresol, were formed as decomposition products. The formation of carboxylic acids, such as formic, acetic, and propionic acids, in the presence of oxygen was also confirmed. Under a nitrogen atmosphere, the oxidation caused by oxygen in solution was suppressed and hydrolysis became the dominant reaction in the decomposition of 2-bromophenol.
Journal of Hazardous Materials 09/2003; 101(3):231-8. · 4.17 Impact Factor
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ABSTRACT: Mineral acids, such as H(3)PO(4), H(2)SO(4), HCl, and HNO(3,) were treated with magnesium-aluminum oxide (Mg-Al oxide), which behaved as a neutralizer and fixative of anions. Anion removal increased with increasing Mg-Al oxide quantity, time, Mg/Al molar ratio, and initial acid concentration. Up to 95% removal of anions was achieved in 0.5 N acids using a stoichiometric quantity of Mg(0.80)Al(0.20)O(1.10) for H(3)PO(4), 1.75 stoichiometric quantities for H(2)SO(4), or 2.5 stoichiometric quantities for HCl or HNO(3) at 20 degrees C over a period of 6 h. The final solutions were found to have a pH in the range of 8-12. Selectivity of acid removal was found to follow the following order: H(3)PO(4) > H(2)SO(4) > HCl > HNO(3). The equivalent of acid removal per 1 g of Mg-Al oxide decreased as the Mg/Al molar ratio of Mg-Al oxide increased.
Water Research 05/2003; 37(7):1545-50. · 4.86 Impact Factor
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ABSTRACT: The dissociation constants of monochlorophenols (2-, 3-, 4-chlorophenols) were examined using direct UV-vis spectroscopy at temperatures from 25 to 175C and at saturated vapor pressures in a high-temperature, high-pressure cell. The dissociation constant, K
a increased under experimental temperatures in the order: 2-chlorophenol, 3-chlorophenol, and 4-chlorophenol. The dissociation constant of 4-chlorophenol increased with increasing temperature under experimental conditions, while those of 2- and 3-chlorophenol reached maximum values at around 125C, and then decreased with further increases in temperature. The slope of (log K)/ (1/T) was nonconstant and positive, that is, endothermic, below 150C. The data on dissociation constants were analyzed by simultaneous regression to yield a five-term equation that described the Van't Hoff isobar. The magnitude of enthalpy H increased at 25C in the order: 3-chlorophenol, 4-chlorophenol, and 2-chlorophenol. The decrease in enthalpy at the absolute temperature was larger for 3-chlorophenol than for either 2- or 4-chlorophenol. Considering the equilibrium constant K
b for the isocoulombic reaction of monochlorophenol with OH–, the nearly linear relationship of log K
b
vs. 1/T for temperatures between 25 and 175C indicates that the Cp values for this isocoulombic reaction are low.
Journal of Solution Chemistry 12/2002; 32(1):19-39. · 1.41 Impact Factor
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ABSTRACT: The hydrolysis equilibrum of gallium (III) solutions in aqueous 1 mol-kg–1 NaCl over a range of low pH was measured potentiometrically with a hydrogen ion concentration cell at temperatures from 25 to 100C at 25C intervals. Potentials at temperatures above 100C increased gradually because of further hydrolysis of the gallium(III) ion, followed by precipitation. The results were treated with a nonlinear least-squares computer program to determine the equilibrium constants for gallium(III)–hydroxo complexes using the Debye–Hckel equation. The log K (mol-kg–1) values of the first hydrolysis constant for the reaction, Ga3+ + H2O GaOH2+ + H+ were –2.85 0.03 at 25C, –2.36 0.03 at 50C, –1.98 0.01 at 75C, and –1.45 0.02 at 100C. The computed standard enthalpy and entropy changes for the hydrolysis reaction are presented over the range of experimental temperatures.
Journal of Solution Chemistry 01/1998; 27(11):965-978. · 1.41 Impact Factor
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ABSTRACT: The hydrolysis-precipitation equilibrium reaction of aqueous gallium(III) solution was investigated in 0–3 mol-kg-1 NaCl media at low pH at 100°C using a pressure-tight glass vessel. All precipitates were identified as GaOOH. The results
were analyzed with a nonlinear least-squares computer program to obtain the solubility product Kso for gallium(III) oxyhydroxide using a single-parameter type of Debye-Hückel equation. The value of log Kso for GaOOH(s) + 3H+ ⇆ Ga3+ + 2H2O was -0.60 at 100°C. The solubility product calculated from thermodynamic data was compared with the experimental result.
Journal of Solution Chemistry 05/1997; 26(7):699-708. · 1.41 Impact Factor
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ABSTRACT: A new approach to the decomposition of nitrate ion using Pb metal has been developed. Removal of the oxide layer formed on the surface of Pb plate and the production of Pb powder have been achieved by in situ abrasion of Pb plate in NH4NO3 solution with an abrasive buff. NO3− was reduced to NO2− at initial concentrations of NH4NO3 in the range 0.01–0.2 M, rotational speed of buff, 100–800 rpm and temperature, 25–80°C. Complete reduction of NO3− in 0.05–0.2 M NH4NO3 solution was achieved at 80°C within 4 h. As the temperature increases, the reduction rate of NO3− to NO2− increases abruptly. The reduction rate increases gradually with rotational speed. The formation of NO2− is almost independent of the initial NO3− concentration. Reduction of NO3− to NO2− is related to corrosion of Pb in NH4NO3 solution.
Hydrometallurgy 49(3):297-308. · 2.03 Impact Factor
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ABSTRACT: Our results demonstrate that magnesium–aluminum oxide (Mg–Al oxide) can be advantageous in treating hydrochloric acid waste at temperatures between 10 and 30 °C, by acting as both a neutralizer and fixative for Cl−. The Mg–Al oxide was prepared by the thermal decomposition of a hydrotalcite-like compound. The extent of Cl− removal by Mg–Al oxide increased with increases of temperature, oxide quantity and Mg/Al molar ratio. The initial pH had little effect on Cl− removal; the pH increased rapidly from the start of the reaction and attained a nearly constant value. The reaction involved in Cl− removal from HCl by Mg–Al oxide proceeded under surface chemical reaction control, with apparent activation energy of 65.6 kJ mol−1.
Separation and Purification Technology.
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ABSTRACT: We examined the dehydrochlorination of a chloride ion-intercalated hydrotalcite-like compound (Cl−-HT) on thermal treatment under water vapor, and the subsequent recovery of hydrochloric acid. The degree of dehydrochlorination increased with increasing temperature, partial pressure of water vapor, and time, whereas the hydrochloric acid concentration decreased with increasing partial pressure of water vapor and time. Greater than 90% dehydrochlorination and greater than 20 wt.% recovery of hydrochloric acid could be obtained by thermal treatment of Cl−-HT in the conditions as follows; temperature: 550 °C, time: 0.5 h, water vapor: 7%.
Applied Clay Science 37:215-219. · 2.47 Impact Factor
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ABSTRACT: We prepared a chloride ion-intercalated hydrotalcite-like compound (Cl−-HT) in a co-precipitation reaction, and investigated its thermal properties using thermogravimetry-differential thermal analysis (TG–DTA) and simultaneous thermogravimetry-mass spectrometry (TG-MS). In addition, we examined the effects of temperature and atmosphere on the dehydrochlorination of Cl−-HT during thermal treatment. The thermal decomposition of the Cl−-HT was divided into three stages: the evaporation of surface adsorbed water and interlayer water in the Cl−-HT, the dehydroxylation of the brucite-like octahedral layers in the Cl−-HT, and the elimination of HCl from the Cl−-HT. H2O was produced at four steps: the evaporation of surface adsorbed water and interlayer water in the first stage, two steps of H2O production caused by the dehydroxylation of the parts of Cl−-HT with properties similar to Mg(OH)2 and Al(OH)3, respectively, in the second stage, and H2O production due to the dehydroxylation of the part of Cl−-HT with properties similar to Al(OH)3 in the third stage. HCl was produced at two steps: the dehydrochlorination of the parts of Cl−-HT with properties similar to AlOCl and Mg(OH)Cl, respectively, in the third stage. Hydrochloric acid was obtained from the Cl−-HT on thermal treatment. The degree of dehydrochlorination of the Cl−-HT increased with temperature. The degree was greater under water vapor than under nitrogen at all temperatures, indicating that water vapor promoted the dehydrochlorination of Cl−-HT. However, the concentration of hydrochloric acid obtained under water vapor was lower than that under nitrogen.
Applied Clay Science 35:173-179. · 2.47 Impact Factor
