Effect of pH on the selective separation of metals from acidic wastewater by controlling potential

In the face of difficulties in separating similar metals from acidic wastewater, a new process is proposed to selectively separate metals from acidic wastewater by controlling potential. In this paper, the effect of pH value on precipitation ratio and separation efficiency is investigated. Through thermodynamic calculations, a 3D E-pH diagram of the Me-S-H2O system was plotted. The results reveal that rising pH value is helpful for metal precipitation, but high pH value may cause co-precipitation of metals impurity. The crystallinity and size of precipitates are obviously affected by pH value. Co can be effectively separated from Zn by xanthate precipitation under controlling potential, and the xanthate dosage is dependent on pH value. Mn-inclusions appear in Zn-precipitate due to high Mn2+ concentration. The optimal pH value for Cu2+, Co2+, and Zn2+ precipitation were 1, 2, and 2, respectively. Mn2+ could be recovered by carbonate precipitation from the solution after Zn removal. Cu2+, Co2+, Zn2+, and Mn2+ precipitation ratios reached to 99%.