Copper and nickel recovery from acidic polymetallic aqueous solutions

Acidic polymetallic wastewaters are generated during the pyrometallurgical treatment of chalcopyrite for the production of primary copper. The most important wastewater streams originate from the copper refining and the electrolyte regeneration stages, as well as the sulphuric acid and the precious metals plants. These wastewaters are characterized by medium to high concentration of residual sulphuric acid and heavy metals such Cu, Ni, Pb, Zn, Fe, As, Sb, Bi, etc. Taking into account that the outflows of these industrial streams are usually high, a large amount of valuable metals such as copper and nickel are potentially lost. Thus, it is of great importance to treat properly the wastewaters so that the contained valuable metals to be recovered. This paper is dealing with the treatment of synthetic solutions simulating industrial wastewaters from the copper pyrometallurgical plant in Bor, Serbia. The basic concept includes copper electrorecovery followed by nickel precipitation through neutralization. The feasibility of this treatment was proved theoretically with the thermodynamic analysis of electrochemical and precipitation reactions in this system, as well as experimentally under various conditions. The main conclusion is that copper can be recovered electrolytically followed by bismuth and the two metalloids arsenic and antimony that exhibits almost the same electronegativity with copper. The other high electropositive metals Ni, Pb, Zn, Fe remain, as it was expected, in the solution from which nickel can be recovered with neutralization, contaminated with Cu, Fe, Zn and traces of bismuth, arsenic and antimony. The proposed treatment technology has innovative character because it can mitigate environmental impacts and eliminate solid waste generation while at the same time can recover valuable metals.