Separation of Cu and As in Cu-As-containing filter cakes by Cu2 +-assisted acid leaching

Abstract

Based on the replacement reaction between As2S3 and Cu2+, the separation of Cu and As in Cu-As-containing filter cakes was investigated using a Cu2+-assisted acid leaching procedure. Initially, the leaching process was thermodynamically analyzed using Eh-pH diagrams of the Cu-As-S-H2O system and leaching chemistry, which indicated that the separation of Cu and As is feasible by this process. The effects of pH, dosage of Cu2+, temperature, liquid-to-solid (L/S) ratio and leaching time on this leaching procedure were then investigated. The results show that the optimal leaching conditions were achieved when the original pH was used with a CuCl2·2H2O dosage of 99mmol/L, a leaching temperature of 85°C, an L/S ratio of 10:1 and a leaching time of 6h. The leaching efficiencies were 97.4% for As and 0.1% for Cu, with final As and Cu concentrations of 17.99g/L and 0.02g/L in the leaching solution, respectively. Further analysis shows that the Cu content in the leach residue increased to 33.05% with CuS as the major Cu phase. Notably, only 0.93% of the As remained in the leach residue. Therefore, the proposed process is a viable method for the effective separation of Cu and As in Cu-As-containing filter cakes. Broadly, the results of this paper provide a reference for the treatment of arsenic sulfide residues from nonferrous metallurgy.