Selective extraction of gold (III) from hydrochloric acid-chlorine gas leach solutions of copper anode slime by tri-butyl phosphate (TBP)

The oxidative leaching causes to dissolve various impurities such as Fe, Cu, Pd, Se in copper anode slime. Organic extractant tri-butyl phosphate (TBP) was used to purify leach solution. Several parameters, such as TBP, HCl and chloride inorganic salt concentrations were chosen in order to determine efficient state for impurities separation. Standard solvent extraction tests for extraction and separation of Au, Pd, Pt, Fe, Cu and Se were conducted with equal volume of aqueous and organic phases in batch experiments. The effect of hydrochloric acid, organic phase and metals initial concentration were examined at ambient temperature. It was found that 0.25 mol/L TBP in the presence of 2.5 mol/L hydrochloric acid can cause high extraction of gold. Meanwhile, in these conditions the extraction of other impurities is negligible. After extraction, pregnant organic phase was scrubbed by distilled water and some impurities were removed. Finally, gold was stripped by sodium thiosulfate solution. The stripping solution does not have any impurities. By adding H2SO4 to stripping solution containing Na2S2O2, SO2 gas is released and Au3+ ions could be reduced.