Removal of zinc from basic oxygen steelmaking filter cake by selective leaching with butyric acid

Abstract

Steelmaking dust is a hazardous waste material containing leachable compounds of lead, cadmium, and other environmentally harmful elements. The recycling is hindered by its high zinc content, which causes furnace operation issues due to zinc accumulation. In this study, butyric acid was used as a leaching reagent to selectively remove zinc from a basic oxygen steelmaking filter cake. The effects of acid concentration, acid to filter cake (L/S) stoichiometric ratio and leaching time on the leaching efficiencies of zinc and iron were investigated to determine the optimum leaching conditions, under which 51% of zinc was leached out with less than 1% of iron. The results show that zinc extraction increased with increasing L/S stoichiometric ratio, but no obvious dependence on acid concentration was observed. Iron dissolution, however, decreased with increasing acid concentration. No significant differences in iron dissolution were observed at various L/S stoichiometric ratios especially at high acid concentrations. Lixiviate reuse was demonstrated to be effective in the selective leaching of zinc whilst repeated leaching of the residue had limited effect on the zinc removal. The leaching mechanism was analysed based on these results. The outcomes demonstrate that leaching with butyric acid provides a highly selective technology for the removal of zinc from the metallurgical waste for the recycling of the hazardous material.