Characteristics of electrochemical reactions accompanying chlorinating annealing of copper sulfide concentrates

The mechanism for reactions accompanying the low-temperature roasting of a copper sulfide concentrate with potassium and sodium chlorides without the formation of sulfurous gases and their evolution into the atmosphere is suggested. The obtained cake is leached with water under pH correction in the vicinity of 6. Water-soluble sulfates transfer into the solution, while copper and iron hydroxides remain in the cake. The further leaching of the cake by an aqueous sulfuric acid at the final pH 2.5–3.0 makes it possible to completely transfer copper into the solution, while iron completely remains in the solid phase. The recovery of copper into the solution under the optimal annealing conditions (t = 450°C, τ = 1 h) and the above conditions of double leaching is no lower than 95%. Chlorinating annealing at temperatures below and above 450°C results in a decrease in the recovery of copper into the final product of copper sulfate. The found maximum is explained.