Abstract
The selective leaching of zinc from three different basic oxygen steelmaking (BOS) filter cakes by butyric acid was investigated to compare the leaching behaviors of zinc and further to establish the correlation of the zinc leaching performances and the chemical compositions. The effects of acid concentration and the acid to solid (L/S) stoichiometric ratio were studied, with different optimal leaching conditions obtained. BOS-1 showed the lowest leachability with only less than 10% of zinc removed by 0.5 M acid concentration and 90% of the L/S stoichiometric ratio in 10 h. The best zinc selectivity was achieved with BOS-2 at 51.2% of zinc leaching efficiency, with only 0.47% of iron loss under optimal conditions of 1.5 M acid concentration and a 70% stoichiometric ratio. BOS-3 showed the highest leaching of zinc but the optimal conditions depend on the priority consideration. Using 1.0 M acid and 90% stoichiometric ratio for 10 h, the leaching efficiency of zinc was 84.6% with 20% iron loss. The filter cakes and the leaching residues were characterized. The results indicate different zinc and iron leaching behaviors, which were probably related to the storage conditions, zinc containing phases and the leaching parameters.
Highlights
In the iron and steel industry, over 30 million tonnes of dusts are generated each year [1,2]
The filter cakes and the corresponding leaching residues were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectrometer (SEM/EDS), thermo-gravimetric/differential scanning calorimetry (TG/DSC)
The following conclusions are obtained: 1. Among the three Basic oxygen furnace steelmaking (BOS) filter cakes, BOS-3 showed the highest removal of zinc by butyric acid, while the best selectivity of zinc over iron was achieved with BOS-2
Summary
In the iron and steel industry, over 30 million tonnes of dusts are generated each year [1,2]. The BOS dust contains metal oxides, zinc mostly exists as ZnO and ZnFe2 O4 while iron is mainly found as Fe, FeO, Fe2 O3 , Fe3 O4 and. In a previous study [23], butyric acid was shown to be highly efficient in selective leaching of zinc over iron from a BOS filter cake. This paper compares the leaching behaviors of zinc from three different BOS filter cakes using butyric acid to develop a better understanding of the relations to their chemical, physical, morphological and mineralogical characterization. This is vital to the design of alternative techniques for treating such BOS filter cakes. The filter cakes and the corresponding leaching residues were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectrometer (SEM/EDS), thermo-gravimetric/differential scanning calorimetry (TG/DSC)
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