Rapid and Selective Removal of Hg2+ by Copper Sulfides under Strongly Acidic Conditions: Mechanism, Kinetics, and Its Application in Recovering Hg from Waste Acids of Smelters

In this study, CuS x /TiO2 was developed to selectively remove Hg2+ from waste acids. X-ray photoelectron spectroscopy and X-ray diffraction analyses demonstrated that there were two reaction routes for Hg2+ removal by CuS x /TiO2, corresponding to the two types of copper sulfides (i.e., CuS and Cu2S). The CuS route with the product HgS occurred regardless of the presence of Cl–, while the Cu2S route with the product Hg2Cl2 only occurred with Cl–. Therefore, Cl– exhibited a remarkable promotion on Hg2+ removal. Kinetic analysis demonstrated that the CuS route was markedly faster than the Cu2S route, which accounted for the rapid removal of Hg2+. CuS x /TiO2 showed excellent performance for Hg2+ removal at pH 2.0 with an adsorption rate of 16.3 mg g–1 min–1, and removed Hg2+ can be recovered as liquid Hg0 as a co-benefit of Hg0 recovery units in smelters. Therefore, CuS x /TiO2 was a promising sorbent for Hg2+ recovery in waste acids for centralized control.