Recovery of Zn as ZnO from Steelmaking Waste Materials by Mechanochemical Leaching, Solvent Extraction, Precipitation, and Thermal Decomposition Route

Abstract

A large amount of electric arc furnace dust (EAFD) is produced as hazardous waste materials during steelmaking in electric arc furnace. EAFD includes a considerable amount of zinc. Recovery of Zn as ZnO from EAFD via mechanochemical leaching, solvent extraction, precipitation, and thermal decomposition route was investigated. Dissolution behavior of Zn, Fe, Mn, Si, Mg, and Ca during the mechanochemical leaching of EAFD in H2SO4 solution was determined. Optimum mechanochemical leaching parameters were considered as 10 g of EAFD, 2 M H2SO4, 240 min of reaction time, ball to the dust weight ratio of 20, and rotational speed of 500 rpm. D2EHPA solution (20%, vv) was used for solvent extraction of Zn from mechanochemical leach solution. McCabe-Thiele diagrams constructed for extraction and stripping stages indicated that 95% of zinc in the leach solution was extracted in three stages at A:O=1:1, while 97% of Zn was stripped from loaded organic phase at operating line of A:O=4:1. ZnC2O4.2H(2)O powder was precipitated from strip solution obtained by solvent extraction by adding oxalic acid solution at pH 4. Thermal properties of ZnC2O4.2H(2)O precipitated were investigated by thermogravimetric-differential thermal analysis technique. High-purity ZnO was obtained by thermal decomposition of ZnC2O4.2H(2)O precipitated