Abstract:Sponge cadmium was extracted from zinc-bearing solution with low Cd2+ concentration (Cd2+ 1 g/L, Zn2+ 20 g/L) by microcurrent-assisted replacement method. Effects of current density, agitation speed, H2SO4 concentration and reaction temperature on cadmium extraction efficiency, residual cadmium concentration, zinc consumption, and sponge cadmium purity were investigated. The results show that increasing current density and agitation speed can significantly accelerate the replacement speed and reduce the residual cadmium concentration. The concentration of sulfuric acid and reaction temperature have little effect on cadmium extraction efficiency and residual cadmium concentration, but sulfuric acid in moderate concentration and increasing of reaction temperature are beneficial to improve purity of sponge cadmium. Cadmium extraction efficiency is 99.2%, residual cadmium concentration drops to 20.4 mg/L, and purity of sponge cadmium is 98.2% under the optimum conditions including current density of 1 mA/cm2, agitation speed of 400 r/min, H2SO4 concentration of 10 g/L, temperature of 35 ℃, replacement reaction time of 2 h. Compared with the traditional replacement process, microcurrent-assisted replacement process can accelerate replacement speed, reduce residual cadmium concentration, and improve purity of sponge cadmium.