Electrorefining High-Ni, -Sb and -Sn Anodes from a Primary Copper Smelter

Incorporating impurities, particularly from the recycling of e-scrap, may significantly impact the electrorefining process of the anodes from a copper smelter. In this study, commercial anodes were doped with Ni, Sn and Sb to achieve concentrations of 2500–6500 g/t, 300–900 g/t and 450–950 g/t, respectively. Electron microscopy with microprobe analysis revealed that the doped anodes contained NiO, Kupferglimmer and SnO_2, which were not present in the original commercial anodes. Ni, the main impurity, primarily accumulated within the Cu grains, while Sn and Sb tended to form oxidized inclusions. The distribution of Ni in Cu grains was ca. 20% lower in the anodes doped at higher Ni concentrations due to the formation of nickel-bearing inclusions, such as Kupferglimmer and NiO. The doped anodes showed lower quantities of Cu₂O inclusions than the commercial anodes due to the preferential formation of oxides with these added impurities. X-ray diffraction of the slimes collected after electrorefining the doped anodes in a small laboratory cell using commercial electrolyte revealed that new phases generated in the casting process deported to the slimes. These findings highlight potential challenges for Cu electrorefining in a circular economy, as increased Ni, Sb and Sn content will impact the composition of slimes and electrolyte.