In the smelting and refining of nonferrous metals, a variety of metals are unavoidably admixed into the product as impurities due to the diversity of ores used as raw materials. Among such impurities are Pb, As, Bi, and Sb. In the smelting and refining of copper, it is difficult to remove impurities completely by the pyrometallurgical process. Accordingly, these impurities are always contained in copper anodes and are submitted to a subsequent electrolytic refining process, which is carried out in an aqueous sulfuric acid solution. Most of the arsenic and part of the bismuth and antimony contained in the copper anode are dissolved into the electrolyte during electrolysis, with the result that the concentrations thereof gradually increase. Because their standard reduction potentials are very close to that of Cu, the Bi, Sb, and As may deposit on the Cu cathode and affect cathode quality (grain structure and impurity content) in accordance with an increase in concentration. The concentration of bismuth, antimony, arsenic, and other impurity elements, therefore, must be controlled in tank-house operations.
展开▼
