Increasing the sustainability of copper electrorefining: Selective electrodeposition of antimony in the presence of bismuth from highly concentrated hydrochloric acid effluents

Recovering critical materials from effluents of copper electrorefining would improve the circularity and sustainability of this industry. In this task, selectivity is crucial to separate metals present in multi-component electrolytes and obtain added value products. Electrodeposition can be used to recover metals individually when their reduction takes place at different potentials. Moreover, the preferential deposition of a specific element can also be modulated under galvanostatic control. In this study, the recovery and separation of antimony and bismuth from highly concentrated hydrochloric acid solutions is investigated by means of voltammetry and electrodeposition. In potentiostatic mode, the preferential deposition of antimony takes place at -0.25 V Ag/AgCl, although a moderate selectivity is achieved. Under galvanostatic mode, at current densities below the limiting value, the deposition of bismuth is almost prevented, and the selectivity factor for antimony reaches the highest values. These results prove the feasibility of a highly selective antimony recovery by electrodeposition. When the limiting current density is exceeded, the selectivity towards antimony drops due to more cathodic potentials activating the deposition of bismuth and hydrogen evolution, thus decreasing the overall electrodeposition current efficiency.