Promotion of copper electrolyte self-purification with antimonic oxides

The promotion of copper electrolyte self-purification with antimonic oxides was studied. It was found that the mixed oxides of Sb(III) and Sb(V) can be used to promote copper electrolyte self-purification. The mixture of Sb2O3·xH2O and Sb2O5·xH2O with Sb(V)/Sb(III) molar ratio 0.05 was used to promote the self- purification of copper electrolyte containing 353.21 g/L H2SO4, 19.38 g/L Cu, 20.88 g/L As, 2.29 g/L Sb and 1.51 g/L Bi. Experimental results show that the removal of impurities As, Sb and Bi from copper electrolyte mainly depends on the ratio of the molar number of arsenic in the electrolyte to the molar number of antimony in the promoter, namely the As/Sb mole ratio. When the promoter was added into the electrolyte with the As/Sb mole ratio 1:0.7 at 60 °C stirring for 0.5 h, the removal efficiencies of As, Sb and Bi are 62.0%, 93.0% and 95.0% respectively. Then the As and Bi were separated from the used promoter by adding it into 2 mol/L Na2CO3 stirring for 0.5 h at above 60 °C in pH 8-9. After filtration, the regenerated promoter was obtained by washing the filter cake with diluted sulfuric acid, and the As and Bi were separated from the regenerated solution by crystallizing Na3AsO4·12H2O at room temperature, and by precipitating Bi2O3·xH2O under the pH above 12, respectively.