Solvation of ions. Some applications. V. Electrolytic recovery of silver from non-aqueous solutions

Abstract

Electrolysis of a dimethyl sulfoxide solution containing AgCl₂^- and CuCl₂^- has been shown to produce high-purity, adherent, non-dendritic cathode silver with a current efficiency of over 80%. At the anode, CuCl₂- was oxidized to Cu²⁺. An optimum electrolyte/solvent system was chosen after a study of the various parameters contributing to the conductivity of the solution. Diffusion coefficients and Tafel slopes were measured, as were the various potentials contributing to the cell voltage. Good silver deposits were obtained by using 0.75 M CaCl₂.2H₂O, 0.5 M AgCl and 0.5 M CuCl in dimethyl sulfoxide at 50ºC at a cathode current density of 5 mA cm^-2. A practical electrolysis cell is proposed for use with a cyclic leach-electrowin process for recovering pure silver from various high-grade secondary residues.