Selenium Dissolution from Decopperized Anode Slimes in ClO−/OH− Media

Abstract

About 90% of selenium is obtained from treating copper anode slimes, which are a by-product of copper electrorefining. Selenium has been traditionally obtained by the pyrometallurgic treatment of anode slimes, which has been effective in recovery. However, in pyrometallurgical processes, there are increasingly strict environmental regulations. Hydrometallurgical treatments have been proposed to totally or partially replace conventional methods, some of which are in the developmental stage, while others are being used at the industrial scale. The selenium present in anode slimes is in the form of silver and copper selenides. This article proposes a hydrometallurgy alternative to recover selenium from decopperized anode slimes generated by a copper electrorefining plant in Chile by an alkaline-oxidizing leaching media (ClO−/OH−). The Taguchi experimental design was used to assess the effects of temperature, reagent concentration, and pH over time. The results indicated that the optimal selenium dissolution of 90% was achieved at pH 11.5, 45 °C, and 0.54 M of ClO−. According to the SEM/EDX characterization of the solid leaching residue, the undissolved percentage of selenium is due to the generation of a layer of AgCl around the selenium particles that hinders the effective diffusion of the reagent.