Recovery of lead from the leaching residue derived from zinc production plant: process optimization and kinetic modeling

This study aimed to extract lead from a zinc production plant residue containing 3.67% PbO, 2.79% ZnO, 8.75% SiO2, 24.8% SO2, 2.38% Fe2O3, and 4.46% Al2O3. In this regard, response surface modeling based on the central composite design was utilized to scrutinize and optimize the operating parameters such as NaCl concentration, HCl concentration, pulp mixing rate, solid percentage, and leaching time on the leaching efficiency of lead. Our findings demonstrated that NaCl concentration and solid percentage were the most effective parameters on the leaching of lead, in which higher concentrations of chloride and lower solid contents led to an enhancement in lead recovery. To attain the maximum recovery of lead (75.72%) at room temperature, the optimum conditions were found to be 2 mol/L HCl, 350 g/L NaCl, solid percent 10%, stirring rate 300 rpm, and leaching time 90 min. The leaching kinetics was also examined based on the shrinking core models to realize the process mechanism and develop a new kinetic model. The results exhibited that the kinetics control mechanism was the product layer diffusion model with an activation energy of 16.69 kJ/mol. Finally, a kinetic model is developed based on the diffusion model and effective parameters.