摘要
The sorption of AuCL4- ,AuCl2- and Au(S2O3)23- on δ-MnO2 was investigated at pH2-11.6, 0.01 mol/L and 0.1 mol/L NaNO3 solutions. At pH 4 in two electrolyte strength solutions, Au sorption densities on δ-MnO2 are 0. 18-0.21 and 0.28 μmoL/m2 for AuCl4 and Au(S2O3)23- , respectively, and the Au surface coverage is approximate to or lower than 1 % . This adsorption of the two Au complexes decreases as the solution pH increases, which conforms to the sorption regularity of the anion on δ-MnO2. The Au sorption decreases in the sequence of Au(S2O3)23- >AuCl4- > AuCl2- . The intrinsic equilibrium constants (logKint) of the three Au complexes are 1.17-2.7, much higher than those of Cu and Cd. The hydrolysis products of AuCLi are preferentially adsorbed by δ-MnO2 and the inner-sphere Au-surface complexes are formed on the surface.
The sorption of AuCl<sub>4</sub><sup>-</sup>, AuCl<sub>2</sub><sup>-</sup> and Au（S<sub>2</sub>O<sub>3</sub>）<sub>2</sub><sup>3-</sup> on δ-MnO<sub>2</sub> was investigated at pH2—11.6, 0.01 mol/L and 0.1 mol/L NaNO<sub>3</sub> solutions. At pH 4 in two electrolyte strength solutions, Au sorption densities on δ-MnO<sub>2</sub> are 0.18—0.21 and 0.28 μmoL/m<sup>2</sup> for AuGl<sub>4</sub><sup>-</sup> and Au（S<sub>2</sub>O<sub>3</sub>）<sub>2</sub><sup>3-</sup>, respectively, and the Au surface coverage is approximate to or lower than 1%. This adsorption of the two Au complexes decreases as the solution pH increases, which conforms to the sorption regularity of the anion on δ-MnO<sub>2</sub>. The Au sorption decreases in the sequence of Au（S<sub>2</sub>O<sub>3</sub>）<sub>2</sub><sup>3-</sup>>AuCl<sub>4</sub><sup>-</sup>>AuCl<sub>2</sub><sup>-</sup>. The intrinsic equilibrium constants (logK<sup>int</sup>) of the three Au complexes are 1.17—2.7, much higher than those of Cu and Cd. The hydrolysis products of AuCl<sub>4</sub><sup>-</sup> are preferentially adsorbed by δ-MnO<sub>2</sub> and the inner-sphere Au-surface complexes are formed on the surface.
基金
Project supported by the National Studying-abroad Foundation, the National Natural Science Foundation of China (Grant No. 49573200) and the Australian Mining Industry.
