Cleaning of high lead-bearing zinc leaching residue by recovery of lead with alkaline leaching

In the hydrometallurgical zinc production processes, huge quantities of solid leaching residues containing different metallic compounds threat the environment are continuously generated around the world. Due to increasing demand of metals and the depletion of high grade natural resources, these types of wastes are gaining great importance in the metallurgical industries. In this study, cleaning of zinc leaching residue, containing 19% Pb in the form of anglesite, by recovering of lead with alkaline leaching was investigated. For this purpose; the effects of NaOH concentration, leaching time and temperature on the Pb recovery from the residue were studied. Under the optimum conditions using NaOH concentration of 11%, L/S ratio of 5, temperature of 100 degrees C, and leaching time of 60 min, the leaching ratio of Pb reached up to 99.6%. Kinetic analysis of the experimental data showed that the leaching was ash layer diffusion controlled with activation energy of 2.78 kJ/mol. Pb could be effectively separated from the pregnant leach solution with chemical precipitation by Na2S and CO2. TCLP and EU Directive EC/2003/33 tests applied to the remaining leach residue showed that it was environmentally stable and nonhazardous waste, respectively. (C) 2015 Elsevier B.V. All rights reserved.