Selective Leaching and Copper Enrichment from Copper–Cadmium slag via a pH‐Controlled Two‐Stage Process with Waste Zinc Electrolyte

Abstract The rise in global Zn production has increased the generation of Cu–Cd slag during Zn purification, highlighting the need for the efficient recovery of valuable metals. In this study, a novel two‐stage leaching process was developed using waste Zn electrolyte to selectively extract Zn, Cd, and Co from Cu–Cd slag while concentrating Cu in the solid slag. Through controlled experiments, we established optimal conditions: sulfuric acid (H 2 SO 4 ) concentration of 130 g/L, temperature of 55 °C, leaching time of 250 min, and liquid‐to‐solid ratio of 5.5:1(mL/g). Under these economically favorable conditions, we achieved leaching efficiencies of 96.84% for Zn, 96.12% for Cd, and 96.37% for Co. This process increased Cu content of the residue from 6.1% to 58.8%, resulting in a low final slag yield of just 7.1%. Although initial Cu leaching reached 18.34% in the first stage, the subsequent pH‐controlled recovery stage reduced Cu concentration in solution to < 1 mg/L, minimizing losses. This integrated approach offers a sustainable strategy for the complete recovery of valuable metals (Zn, Cd, Co, and Cu), simultaneously mitigating the environmental impact of waste electrolytes and increasing the economic value of Cu–Cd slag.