Recovery of Copper from Ammoniacal Leachates by Ion Flotation

摘要

Sulfidic copper-lead-zinc tailings can pose a significant environmental threat, ranging from generation of acid mine drainage (AMD) to dam failures. On the other hand, they can also be considered as low-grade ore resources for zinc and copper provided that novel economically feasible metal extraction and metal recovery techniques are developed. Due to the low metal concentrations in these resources, the leaching will generate dilute leachates from which metal recovery is a challenge. Ion flotation is a foam separation technique capable of recovering metal ions from dilute aqueous leachates. In this paper, ion flotation was applied to separate copper from ammoniacal leachates of microwave-roasted sulfidic tailings samples. The sulfidic tailings were first roasted at 550 degrees C for 60 min, for the oxidation of sulfide minerals to more easily soluble sulfates using microwave-assisted irradiation as heating source. The microwave-roasted material was then leached with a mixture of ammonia and ammonium carbonate solutions. The optimum leaching efficiencies of zinc (86%) and copper (75%) were obtained under the following conditions: liquid-to-solid ratio = 10 mL g(-1), T = 90 degrees C, [NH3 + NH4+] = 4 mol L-1, NH3:NH4+ = 2:1, t = 5 h. From the generated pregnant leach solution, it was possible to selectively separate 85% of copper to the foam phase by ion flotation, with sodium dodecyl sulfate (SDS) surfactant, as colloidal copper(II) tetraamine dodecyl sulfate under the optimized conditions: [SDS](total) = 5.85 mmol L-1, [EtOH] = 0.5 % (v/v), t(total) = 5 h, flotation stages = 3. The zinc that remained in the solution after ion flotation was recovered by precipitation (95%) as basic zinc carbonate.Graphical AbstractCopper and zinc extraction by ammoniacal leaching from microwave-roasted Cu-Zn-Pb sulfidic tailings followed by recovery of copper and zinc by ion flotation and precipitation.