Zinc recovery from the water-jacket furnace flue dusts by leaching and electrowinning in a SEC-CCS cell

Abstract

Zinc containing flue dusts generated during a copper matte smelting process in a water-jacket furnace was leached in a zinc electrowinning return solution at 55 °C. Ninety percent of the metal was dissolved after 2 h of treatment. The leaching residues contained near 43 wt.% PbSO 4. Iron was removed from leaching solutions by precipitation using a saturated lime solution at pH 3–4. The precipitate formed mainly consisted of gypsum CaSO 4.2H 2O. Iron and magnesium co-precipitated into a chloro-hydroxide compound. No zinc compound had co-precipitated during iron removal. Copper and germanium contents lower than 10 mg/l were achieved by solvent extraction using 10% LIX 64N and cementation. Cobalt contents lower than 1 mg/l in the solution were achieved by cementation on zinc granules for 2 h at 72 to 82 °C in presence of antimony. Cadmium contents of solutions were reduced to 10 mg/l by cementation on zinc granules at room temperature. Electrons transfer regime was identified as a limiting step during zinc electrolysis in a symmetric electrolysis current–continuous circulating system, SEC-CCS. Electrolysis current efficiency higher than 94% and 3.5 kWh/kg of specific energy consumption was achieved under 500–600 A/m 2 at 35 to 40 °C in the presence of gelatine.