An integrated and sustainable process for selective separation of zinc from arsenic-bearing lead smelting residue by solvent extraction

This study focuses on the development of a solvent-extraction-based purification route for the selective separation of zinc and arsenic from the acidic leach solution generated by a lead smelting furnace residue in a metallurgical facility in Zanjan, Iran. The residue contained high levels of zinc (14.75%) alongside lead (7.50%), arsenic (4.00%), and chloride (9.00%), making it a critical target for resource recovery and environmental remediation. This research aims to develop an effective hydrometallurgical route for the selective recovery of zinc and the removal of arsenic from lead smelting furnace residue. The process includes chloride elimination followed by sulfuric acid leaching to obtain an acidic zinc-bearing solution as the feed for downstream purification. Two independent purification approaches were briefly examined to provide process context. A precipitation route using iron-based oxidizing agents enhanced arsenic removal but could not reduce the final concentration to electrowinning-acceptable levels. The primary focus of this study is a D2EHPA-based solvent extraction process applied to the same leach solution in a separate treatment pathway. This method involved four extraction stages, followed by two scrubbing steps and two counter-current stripping stages. The solvent extraction system achieved deep arsenic removal (0.33 mg/L in the final electrolyte) and simultaneously enriched zinc to 51,790 mg/L, fully meeting the requirements for electrowinning. The results demonstrate that solvent extraction provides a highly efficient and technically robust purification route for producing high-purity zinc from complex leach solutions derived from lead smelting furnace residue.