Recovery of value metals from copper smelter slag by ammonium chloride treatment

• Recovery of Zn, Cu, and Fe from the copper smelter slag was studied.
• Slag was treated with NH4Cl at 320 °C and product was subjected to water leaching.
• Metal recoveries to the solution were 91.5% Zn, 89.7% Cu, and 88.3% Fe.
• Metals were subsequently precipitated using ammonia water.

Processing possibility of copper smelter slag produced by Balkhash copper plant (Kazakhstan) was investigated. The effect of temperature and treatment duration on the metal recovery to water-soluble form was studied. A technique of copper, zinc, and iron recovery from the slag of the plant was proposed. The mixture of the slag and ammonium chloride (wt ratio 1:2) was treated at 320 °C for 120 min and subjected to water leaching. After separation the solid residue was treated with ammonium chloride (wt ratio 1:2) for 160 min. Recovery of zinc, copper, and iron into solution is, respectively, 91.5, 89.7, and 88.3%. Apparent activation energy, pre-exponential factor and Gibbs free energy of activation for processes of Zn, Cu, and Fe recovery to water-soluble form have been calculated. By adding an ammonia water into solution hydroxides of zinc, copper, iron, calcium and magnesium is selectively precipitated. Process flowsheet for the value metal recovery from copper smelter slag of the copper plant was proposed.