Recovery of antimony and bismuth from arsenic-containing waste streams from the copper electrorefining circuit: An example of promoting critical metals circularity from secondary resources

The copper pyrometallurgical industry faces the precipitation of un-soluble slimes containing bismuth, arsenic and antimony that can reduce copper purity. Ion-exchange resins are used to treat the electrolyte to avoid their precipitation. After resin saturation, a regeneration stage with 17%(w/w) hydrochloric acid containing antimony and bismuth (e.g. up to 10 g/L) is currently limed. In this work, a selective precipitation process was developed to recover both elements as pure as possible from the eluate, considering that also high contents of As(V) are present. Results showed that during the precipitation process, As(V) forms insoluble antimony-arsenates. Therefore, the eluate was pre-treated to reduce As(V) and Sb(V) using SO2(g) or NaHSO3(s). In this case, it was possible to obtain sequentially antimony oxychloride (Sb4O5Cl2, purity> 93%) and bismuth oxychloride (BiOCl, purity> 95%) under appropriate pH control using sodium hydroxide, sodium bicarbonate and/or sodium carbonate. The use of calcium hydroxide and calcium carbonate resulted in the precipitation of calcium sulphates (CaSO4:H2O(s) and CaSO4:2H2O(s)), which reduced the by-products purity.