Co-extraction of Fe, Cr, Ni and Cu from stainless steel dust and copper slag using aluminum dross-based hybrid reductant

An effective and low-carbon method for extracting valuable metals from stainless steel dust (SSD) and copper slag (CS) was developed, using an aluminum dross-based hybrid reductant. The effects of reduction temperature and aluminum dross (AD) proportion in the hybrid reductant on the metal recovery were investigated. High temperature promotes metal oxides reduction, and the recovery degree initially increases before decreasing as the proportion of AD increases. However, excessive addition of AD in the hybrid reductant causes spinel phase to precipitate in the Al₂O₃-CaO-SiO₂-MgO system, which inhibits metal particle aggregation and growth. At 1500℃ and the proportion of 80 % AD in the hybrid reductant, the maximum recovery degrees of Fe, Cr, Ni, and Cu from SSD and CS are 97.52 %, 95.30 %, 97.63 %, and 97.21 %, respectively. The prepared low-carbon ferroalloy contains 72.65 % Fe, 21.29 % Cr, 3.76 % Ni, 1.36 % Cu, and less than 0.94 % carbon content. Furthermore, the secondary slag is primarily composed of the stable phases Ca₂Al₂SiO₇, Ca₂MgSi₂O₇ and MgAl₂O₄, with hazardous concentrations of Cr, Cu, Zn and Pb ranging from 50-76 ppm, 15–23 ppm, 0.37–0.65 ppm and 0.02–0.04 ppm, respectively. This co-extraction process allows for the efficient and low-carbon treatment of multisource metallurgical solid waste.