Electrochemical studies of gold ore processing wastewater containing cyanide, copper, and sulfur compounds

摘要

The electrochemistry of real gold ore processing wastewater solutions from copper sulfide containing gold ore has been investigated. Analysis shows that the wastewater contains a range of sulfur compounds in various oxidation states from sulfide to sulfate. The electrochemical characteristics of the gold ore processing wastewater were evaluated using rotating disk, cyclic voltammetric, polarization and preparative electrolysis studies. The solutions show clear differences versus synthetic alkaline copper cyanide solutions. The copper cyanide/copper oxide catalysis normally seen in synthetic alkaline copper cyanide solutions is strongly inhibited. Two components of the waste-water solution identified as inhibiting the copper cyanide/copper oxide catalysis are copper sulfide complexes and thiocyanate. The inhibition of the copper cyanide/copper oxide catalysis appears to have an initiation time possibly related to the accumulation of copper-sulfur compounds at the electrode surface. The passivated surface is still able to oxidize cyanide, though at a maximum rate that corresponds to the limiting current for free cyanide assuming 1 electron per cyanide. The lack of the copper oxide coating that typically forms during oxidation of synthetic alkaline copper cyanide solutions, plus possibly the presence of various sulfur compounds, results in corrosion at higher anodic potentials when stainless steel is used as an electrode. However, stainless steel can be successfully used as an electrode material to treat the solutions if the potential is carefully controlled.