Selective recovery of Cu(II) from strongly acidic wastewater by zinc dimethyldithiocarbamate: Affecting factors, efficiency and mechanism.

The selective recovery of copper from strongly acidic wastewater containing mixed metal ions remains a significant challenge. In this study, a novel reagent zinc dimethyldithiocarbamate (Zn(DMDC)) was developed for the selective removal of Cu(II). The removal efficiency of Cu(II) reached 99.6% after 120 min reaction at 30°C when the mole ratio Zn(DMDC)/Cu(II) was 1:1. The mechanism investigation indicates that the Cu(DMDC) products formed as a result of the displacement of Zn(II) from the added Zn(DMDC) by Cu(II) in wastewater, due to the formation of stronger coordination bonds between Cu(II) and the dithiocarbamate groups of Zn(DMDC). Subsequently, we put forward an innovative process of resource recovery for strongly acidic wastewater. Firstly, the selective removal of Cu(II) from actual wastewater using Zn(DMDC), with a removal efficiency of 99.7%. Secondly, high-value CuO was recovered by calcining the Cu(DMDC) at 800°C, with a copper recovery efficiency of 98.3%. Moreover, the residual As(III) and Cd(II) were removed by introducing HS gas, and the purified acidic wastewater was used to dissolve ZnO for preparation of valuable ZnSO·HO. The total economic benefit of resource recovery is estimated to be 11.54 $/m. Accordingly, this study provides a new route for the resource recovery of the treatment of copper-containing acidic wastewater.