Quantitative Zn speciation in zinc-containing steelmaking wastes by X-ray absorption spectroscopy

Abstract

To prevent improper handling of zinc-containing steelmaking wastes and find better solutions for recycling these materials, synchrotron induced X-ray absorption spectroscopy (XAS) was used to determine the chemical form of zinc quantitatively at the atomic scale. Five types of zinc-containing steelmaking wastes generated during the production of carbon steel in blast furnace, basic oxygen furnace and blast furnace were collected. In dust collected from the gas-cleaning system of electric arc furnace (EAFD) and basic oxygen furnace developed by Lurgi and Thyssen companies (BOF LT), zinc existed predominantly as franklinite phase (ZnFe₂O₄). The presence of Zn–O, Zn–Fe, Zn–Zn bonds in the nearest two coordination shells were observed. In off gas sludge generated in basic oxygen furnace (BOF OG), three main types of zinc species were identified: Zn₅(CO₃)₂(OH)₆, ZnFe₂O₄ and ZnSO₄·7H₂O. Zn–O and Zn–Zn bonds occurred in the nearest two coordination shells. Blast furnace dust (BFD) comprised about 39% soluble phase in the form of ZnCl₂ and 61% insoluble phase in the form of ZnFe₂O₄. In blast furnace sludge (BFS), ZnCl₂ was also obtained as the soluble phase and the insoluble phase was zinc silicate possibly in the form of ZnSiO₃. These findings deepened our understanding of zinc speciation contained in zinc-containing steelmaking wastes and provided the fundamental information for better dealing with this kind of metallurgical residues.