Recovery of zinc and lead from zinc extraction residue via mechanical activation and leaching in the presence of NaCl

With the increase in global consumption, primary metal resources are rapidly depleting. Therefore, the search for new production processes and alternative sources continues. Wastes are being evaluated as secondary sources. While secondary sources were previously considered as waste or residue, today they are regarded as products with high economic value. Additionally, the utilization of these wastes contributes to the protection of the ecosystem. In this thesis study, the conditions for dissolving zinc and lead from zinc extraction residue—considered a secondary source—into solution were determined by subjecting the residue to fine grinding/mechanical activation followed by a leaching process. The experimental studies conducted for this purpose also aimed to demonstrate the economic importance and recoverability of secondary sources. In the thesis, the effects of sodium chloride addition during the fine grinding/mechanical activation step, the duration of fine grinding/mechanical activation (5–180 minutes), the amount of zinc extraction residue (1–12 g), and the amount of sodium chloride (1–16 g) were investigated. Subsequently, leaching experiments were conducted with and without sodium chloride to examine its effect on extraction efficiency. To determine the optimum parameters, temperature (25–80°C), leaching time (5–200 minutes), and sodium chloride amount (1–20 g) were studied. Additionally, experiments with and without sodium chloride were carried out to investigate the effect of hydrochloric acid addition (0.05–2 M) on extraction efficiency during the leaching process. Throughout various stages of the study, characterization was performed using AAS, XRD, ICP, N₂-BET, zeta particle analysis, and SEM techniques. Under optimum conditions presence of 8 g sodium chloride, 4 g zinc extraction residue, 15 minutes of fine grinding/mechanical activation, a solid-to-liquid ratio of 1:25, 1 M hydrochloric acid, 16 g sodium chloride, leaching temperature of 45°C, stirring speed of 400 rpm, and leaching duration of 2 hours the extraction efficiencies were determined to be 56% for zinc, 100% for lead, and 11% for iron.