Techno-economic evaluation of antimony and bismuth upcycling from pyrometallurgical copper wastes

Abstract

The recovery of critical raw materials (CRMs) is important to reduce the supply risk disruption and the dependency on third-countries within the European Union (EU). The present study evaluates the techno-economic implications of antimony (Sb) and bismuth (Bi) recovery from the process stream produced in the polishing stages of the copper electrorefining circuit. The upcycling process was based on the selective precipitation of Sb and Bi from the concentrated hydrochloric acid (HCl) (up to 5–6 M) process stream containing high arsenic (As) concentrations. Four different scenarios were included in the evaluation, in which Sb and Bi were recovered as Sb4O5Cl2(s)/Sb2O3(s) and BiOCl(s)/Bi2O3(s), respectively. The results showed that implementing Bi and Sb upcycling configurations in the copper metallurgical facilities was economically feasible when recovering BiOCl(s)/Sb4O5Cl2(s) and BiOCl(s)/Sb2O3(s) from the eluate stream. Sb recovery was the most cost-intensive process in all the configurations evaluated due to the high chemical requirements needed to neutralize the free HCl excess. The consumption of chemicals represented the most important cost contributor, since high amounts of chemicals are needed for the selective Sb and Bi precipitation. The sensitivity analysis illustrated that recovering these CRMs was economically attractive for all the configurations when achieving Sb and Bi prices above 8.5 and 9.5 €/kg, respectively. Under these CRM prices, the payback period and internal rate of return for the different scenarios range from 4 to 19 years and from 6 to 28 %, respectively. This output highlights that future increase in CRM prices can be an important driver to implement Sb and Bi recovery schemes. Overall, the results of this study highlight the economic potential of implementing Sb and Bi recovery schemes in copper metallurgical plants to align with the ambitious circular economy objectives established by the EU.