Differential precipitation of copper and nickel from acidic polymetallic aqueous solutions

During the pyrometallurgical treatment of copper concentrates several wastes (gaseous, solid and liquid) are generated. Wastewaters produced in a primary copper smelter are acidic polymetallic solutions characterized by intermediate to high sulphuric acid concentration. Additionally, they usually contain large quantities of valuable metals, such as Cu and Ni, as well as impurities, such as Pb, Zn, Fe, As, Sb, Bi, etc. Therefore, recovery of valuable metals from acidic polymetallic aqueous solutions is of great importance for every plant. This paper is dealing with the recovery of copper and nickel from the acidic polymetallic solutions generated in the copper smelter at Bor, Serbia. The process of differential precipitation of metals through neutralization with caustic soda was selected as the treatment alternative that combines simplicity, efficiency and reliability with low capital and maintenance costs. The concept was based on the development of a simple and efficient process that could be more attractive for industries located in countries suffering from economic recession. Theoretical analysis and experimental results showed that copper and nickel can be differentially removed from the acidic polymetallic solutions at pH = 7 and pH = 10, respectively, mainly contaminated by arsenic, which occurs at high concentrations in acidic polymetallic solutions. Both metals were precipitated as hydroxides, although a small portion of copper was removed also as copper sulfate salt. The resulted precipitates are rich in copper and nickel and can be recycled in copper, as well as in nickel smelters.