Cadmium complexation with bisulfide
The authors have used in situ dialysis to measure the solubility of CdS(s) in sulfidic solutions. The solubility product for the reaction CdS(s) + H{sup +} {l{underscore}reversible} Cd{sup 2+} + HS{sup {minus}} at 25 C and 1 atm was found to be 10{sup {minus}14.15{+-}0.06} and 10{sup {minus}14.40{+-}0.03} for a crystalline product and to be 10{sup {minus}14.15{+-}0.06} for two precipitates, respectively. They show that the solubility of these three solids at various pH values and sulfide concentrations can be reproduced adequately by the following four bisulfide complexes: CdHS{sup +}, Cd(HS){sub 2}, Cd(HS){sub 3}{sup {minus}}, and Cd(HS){sub 4}{sup 2{minus}}; the log K{sub n} values for the general equation Cd{sup 2+} + nHS{sup {minus}} {r{underscore}reversible} Cd(HS){sub n}{sup 2{minus}n} are 7.38 {+-} 0.68, 14.43 {+-} 0.01, 16026 & 0.58, and 18.43 {+-} 0.05, respectively. The species CdOHS{sup {minus}}, which has been reported previously, does not explain their experimental results. Calculations using estimated concentrations of organic ligands (humic substances and organic thiols) known to be present in natural waters indicate that sulfide complexes largely dominate Cd speciation in natural waters at {Sigma}S(-II) {ge} 10{sup {minus}6} M.
- Research Organization:
- Univ. du Quebec, Sainte-Foy, Quebec (CA)
- OSTI ID:
- 20006155
- Journal Information:
- Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 23 Vol. 33; ISSN ESTHAG; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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