Environmental Activity and Ecological Assessment of Heavy Metals in the Reductive Leaching Residue from Zinc Hydrometallurgy Industry

Zinc hydrometallurgy residue is one of the main sources of heavy metals in the environment. The chemical components and mineralogical characteristics of the reductive leaching residue was obtained by ICP-AES, XRD and SEM + EDS analysis. The results showed that the main heavy metals in the residue were Pb, Zn, Cd and As. Pb, Zn and Cd in the residue existed as PbSO4, ZnS and CdS, respectively. The three-step sequential extraction procedure study showed that Zn and Cd mainly existed as oxidizable form; Pb and As mainly existed as the residue form. The leaching toxicity results using sulfuric acid and nitric acid method showed that the leaching toxicity of Zn and Cd exceeded the reference values. The potential ecological risk assessment results of heavy metals of the residue showed that the sequence of the environmental activity and ecological risk was Cd > Zn > As > Pb. Cadmium contributed to the potential risk index more greatly than any other heavy metal in the residue and the contribution rate reached 98.9%, which showed that the cadmium in the reductive leaching residue threw the greatest threat to the ecological environment.