Impact of operational parameters on arsenic impurities in Sb2O3(s) and Bi2O3(s) recovery from copper electrorefining: A viable alternative to refiners?

The copper pyrometallurgical industry faces growing challenges from elevated impurities such as arsenic (As), antimony (Sb), and bismuth (Bi) in primary ores, complicating the production of high-purity copper (>99.99 %). Integrating ion-exchange (IX) polishing stages into electrorefining circuits offers a sustainable approach for selectively removing Sb and Bi, enabling their recovery as Sb₂O₃(s) and Bi₂O₃(s). However, residual arsenic, especially at high concentrations, remains a key obstacle to the direct valorisation of these by-products, requiring further purification. This study investigates several process strategies to reduce arsenic content and improve the purity of the recovered oxides. These strategies include: (i) optimising precipitation conditions across varying Sb/Bi and As molar ratios; (ii) employing iodide as a catalytic reductant; (iii) introducing washing steps to purify intermediate oxychlorides; and (iv) applying chelating agents during the oxide conversion process. Since Sb and Bi are typically recovered in separate industrial processes, their commercial valorisation relies on generating high-purity concentrates suitable for external refining. Following process optimisation, final products exhibited arsenic concentrations below 0.2 % in Sb₂O₃(s) and Bi₂O₃(s) when derived from feeds with high Sb/As and Bi/As molar ratios. For more challenging feed compositions with lower Sb/As and Bi/As ratios, arsenic levels remained below 0.5 % in Sb₂O₃(s) and 1.0 % in Bi₂O₃(s). Although these improvements are significant, impurity levels still exceed the thresholds for most direct-use industrial applications, confirming that additional refining remains necessary. As downstream treatment may reduce product value by up to 50 %, a clear trade-off exists between purity and process complexity that must be carefully considered for industrial application.