Effect of solution potential on selective separation of metals from acid wastewater by controlling potential

In view of the difficulties in separating similar metals from acidic wastewater, a new process is proposed to selectively separate metals by controlling potential. In this study, the effects of solution potential on precipitation ratio and separation efficiency were investigated. The potential was controlled by adding sodium sulfide or xanthate and was monitored by an MT320-SpH instrument with a Pt electrode and a calomel electrode. E-pH diagrams of Me-S-H2O system were plotted through thermodynamic calculations. The results revealed that with the drop of solution potential, the metal precipitation ratios increased. Cu2+, Co2+, and Zn2+ can be selectively separated and completely precipitated under controlling potential at 330 mV, 125 mV and 30 mV, respectively. Mn2+ could be recovered by carbonate precipitation from the residual solution after Zn removal. The precipitation ratios of Cu2+, Co2+, Zn2+, and Mn2+ were as high as 99%.