Resource utilization of impurity-removed copper anode slime based on two-stage roasting: process optimization for selective separation and high-value recovery of copper and selenium

Abstract

Copper and selenium in copper anode slime are important strategic metals that exhibit favorable economic benefits for recovery and utilization. In this study, impurity-removed copper anode slime was taken as the research object, and a two-stage roasting process was proposed, which involved low-temperature sulfation roasting-water leaching for copper separation in the first stage and roasting for selenium evaporation in the second stage. This process enables the efficient and environmentally friendly separation of Cu and Se from impurity-removed copper anode slime. In the first-stage roasting, ammonium sulfate was utilized as an additive to convert Cu–Se and Cu–Te metal compounds into soluble sulfates, and the selective separation of Cu was achieved through water leaching. Under the conditions of a roasting temperature of 275 °C, 1.2-fold excess of (NH₄)₂SO₄, oxygen-enriched concentration of 50%, and duration of 90 min, the leaching rate of Cu reached 94.07%. For the second-stage roasting of Cu-removed anode slime for selenium volatilization, the volatilization rate of Se reached 93.33% under the experimental conditions of a roasting temperature of 550 °C, oxygen-enriched concentration of 20%, duration of 90 min, and gas flow rate of 100 mL min⁻¹. The two-stage roasting process realizes selective and efficient separation of Cu and Se, while the scattered metal Te is effectively enriched in the residue phase. Additionally, the use of strong acids is avoided throughout the process. The results can provide theoretical basis and technical support for the construction and optimization of a comprehensive recovery and utilization system of copper anode slime.