Enhanced removal of cadmium from wastewater by electro-assisted cementation process: A peculiar Cd reduction on Zn anode

Abstract

Cadmium recovery from wastewater is important to prevent water pollution and add value to the circular economy. Cementation is a widely applied method for Cd removal but this process is found less efficient. Herein, a novel electro-assisted cementation process is proposed, which enables effective Cd removal and recovery from Zn processing wastewater. Under optimal conditions, 98.5 % of dissolved Cd was removed and recovered having 94.1 % purity. More importantly, a peculiar Cd reduction on the Zn anode was observed and the mechanism is explained based on the electrochemical test and experimental results. By applying a cell potential of 0.5 V, the negative surface potential of Zn and its localized dissolution facilitated Cd deposition on the Zn anode by suppressing H2 generation. Moreover, in contrast to the conventional cementation process, the formation of Cd dendritic structures on the Zn anode avoided full surface coverage, thus resulting in high cementation efficiency. In summary, this process presents great potential for the efficient removal of Cd from wastewaters and the findings offer new insights into the enhancement mechanism of electro-assisted cementation.