Article ID Journal Published Year Pages File Type
580765 Journal of Hazardous Materials 2009 9 Pages PDF
Abstract
The binding between heavy metals and corresponding ligands affects their chemical behavior and toxicity in soil environments. The mechanisms of competitive complexation and/or chelation between Cd2+ free cations and preferential concentrations of Cl−, SO42−, and fulvate anions were investigated in simulated soil solutions at pH 4.00, 5.00 and 6.00. The Cd2+ concentrations were calculated by a proposed equation, simulated by MINTEQ software, and directly determined by ion chromatography (IC). When Cl−/Cd or Cl−/Cd with SO42−/Cd molar ratios of 3.18 and 4.05, the differences among Cd2+ concentrations calculated by equation, simulated by MINTEQ software, and directly determined by IC were not significant, but their differences were pH independent for considering Cl−/Cd molar ratio and pH dependent for Cl−/Cd and SO42−/Cd molar ratios. When Cl−/Cd, SO42−/Cd, and additional FA/Cd molar ratios of 3.18 and 4.05, the Cd2+ concentrations calculated by equation were significantly larger than those simulated by MINTEQ and determined by IC because in simulation and determination of Cd2+ concentrations by IC, the complexation of Cd2+ with ligands to form CdCl+, CdSO4, FACd+ and FA2Cd had been considered, whereas in calculation this complexation aspect was ignored. Though IC can be used to determine Cd2+ concentration in rhizosphere soil solutions ion chromatographic peak of Cd2+ in 0.1 M HCl saturation extract of slightly acidic soil and in deionized distilled water saturation extract of acidic soils still may be shielded by the vicinal chromatographic peaks of Mg2+ and Mn2+, respectively. The Cd2+ concentrations in rhizosphere soil solutions of acidic or slightly acidic soils calculated by equation and/or simulated by Model may thus be used as potential alternatives for those determined by IC.
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Physical Sciences and Engineering Chemical Engineering Chemical Health and Safety
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