銅アノードスライムの浸出残渣からの電解法による銀の回収
1989 年 53 巻 4 号 p. 399-406
詳細
1989 年 53 巻 4 号 p. 399-406
The feasibility of the electrolytic silver recovery process from the oxidative leaching residue of Cu-anode slime was investigated from the electrochemical and kinetic points of view based on the experimental results of the leaching test, the stoichiometry of the electrolytic silver recovery, the determination of the rest potentials and the cathodic polarization curves for the Pt electrode in the Na2S2O3 solution containing Ag(S2O3)23−, Cu(S2O3)25− and Pb(S2O3)22− ions.
The experimental results are summarized as follows:
(1) The leaching rate of Ag component from the oxidative leaching residue of Cu-anode slime in a Na2S2O3 solution is fast, and the fractional leaching ratio of Ag reaches 0.94 for the retention time of 3.6 ks at 313 K. However, the dissolution ratios of Cu and Pb species from the leaching residue are rather small.
(2) The electrochemical reaction for the Ag deposit starts at about −0.1 V and the reaction rate increases with increasing concentration of Ag(S2O3)23− ions in the solution. The reaction rate is controlled by the rate of Ag(S2O3)23− ions from the bulk solution to the solid interface.
(3) Under the optimum electrolytic conditions, the cathodic current efficiency of the Ag deposit is more than 94%, and metallic silver of more than 99.8% purity can be recovered from the thiosulfate solution containing Ag(S2O3)23− ions.
(4) The electrochemical and other observations have proved the effectiveness of the above electrolytic silver recovery process from the oxidative leaching residue of Cu-anode slime.
