Thermodynamic Assessment of the Feasibility of Copper Reduction from Sulfide Compounds in Alkaline Melts

We consider copper metal formation from copper sulfides with allowance for the nature of the Cu–S coordination bond, confirmed by thermodynamic and experimental studies of reactions between elemental sulfur and sodium hydroxide. A special role in reduction processes is played by a parallel reaction yielding polysulfides (sulfur sulfides), which have high reactivity with the copper being reduced.