Characterization of Raw and Decopperized Anode Slimes from a Chilean Refinery

This work characterizes raw and decopperized slimes, with the objective of identifying the phases in these two sub-products. The main phases in copper anodes are metallic copper, including CuO, which are present in free form or associated with the presence of copper selenide or tellurides (Cu₂(Se,Te)) and several Cu-Pb-Sb-As-Bi oxides. During electrorefining, the impurities in the anode release and are not deposited in the cathode, part of them dissolving and concentrated in the electrolyte, and others form a raw anode slime that contains Au, Ag, Cu, As, Se, Te and PGM, depending on the composition of the anode. There are several recovery processes, most of which involve acid leaching in the first step to dissolve copper, whose product is decopperized anode slime. SEM analysis revealed that the mineralogical species present in the raw anode slime under study were mainly eucarite (CuAgSe), naumannite (Ag₂Se), antimony arsenate (SbAsO₄), and lead sulfate (PbSO₄). In the case of decopperized slime, the particles were mainly composed of SbAsO₄ (crystalline appearance), non-stoichiometric silver selenide (Ag_(2−x)Se), and chlorargyrite (AgCl).