Selective dissolution of zinc and lead from electric arc furnace dust via oxidative thermolysis with polyvinyl chloride and water-leaching process

Abstract

Electric arc furnace dust (EAFD) is a troublesome metallurgical waste accumulated worldwide in large quantities. In this work, EAFD mixed with polyvinyl chloride (EPVC) was thermally treated at 300 °C under air flow followed by leaching of solid residue in water at pH 5.6 and a temperature of 50 °C. Three sample geometries of EPVC mixtures were considered for thermal treatment stage (loose powder, pelleted thin disks and long cylinder shapes). Oxidative thermal treatment of EPVC mixture has resulted in oxidation of magnetite into hematite and prevented iron chloride formation while both zinc and lead were completely chlorinated. The degree of magnetite oxidation was more pronounced when loose powder was used. The subsequent leaching of the thermal treatment of the loose powder EPVC has resulted in 100% recovery of zinc into leaching solution, while iron recovery was close to 0% at optimal conditions. When the EPVC mixture was pelletized into thin disk or cylindrical shape, the access of oxygen was hindered resulting in incomplete oxidation of magnetite or iron chloride to a non-leachable Fe2O3, which did not completely inhibit iron leaching. Iron recoveries in the post water leaching stage of EPVC residue treated under oxidative environment were found to be 21.6, 8.6 and 0.26% for long cylinder, thin disks, and loose powder, respectively. However, 46% of iron content was leached when a cylindrical shape mixture was thermally treated under inert conditions. These important findings can be utilized for the co-thermal treatment of EAFD and PVC wastes towards sustainable recycling of these wastes.