Separation process for the production of high-purity antimony and bismuth oxides from copper electrorefining circuit wastes: The relevance of the redox control

Abstract

The copper pyrometallurgical industry faces challenges in maintaining copper purity due to increasing impurities in primary resources. Notably, Sb, Bi, and As can form insoluble compounds, compromising copper purity in electrorefining units. To address this, ion-exchange (IX) technology is employed to continually treat copper electrolyte of the electrorefining stage, removing Sb and Bi and ensuring a high copper purity (99.99 %). Upon IX resin saturation, regeneration with 6 M HCl produces a concentrated eluate containing Sb, Bi (7–14 g/L each), and As (1–4 g/L). Currently, lime treatment removes these impurities without valorization, which produces large volumes of waste containing As, Sb and Bi. Recognizing Sb and Bi as critical raw materials, this study aims to develop a valorization route, with the objective of recovering both elements free of As using selective precipitation. Pre-treating the eluate to reduce As and Sb to the (+III) state prevented mixed mineral phases, enabling the recovery of high purity Sb4O5Cl2(s) and BiOCl(s) containing low contents of impurities as As. Further improvement could be achieved with the conversion of the oxychlorides to the oxide forms (M2O3(s)) in alkaline media for potential commercial use. This research contributes to sustainable metal recovery and addresses toxicity concerns associated with As, paving the way for enhanced environmental and economic outcomes in the copper industry.