Recovery of iron from lead-zinc metallurgical slags by bath smelting

The recovery of iron from iron sinking slag and lead smelter slag was investigated by desulfurization-reduction bath smelting. The effects of lead smelter slag(LSS) to iron sinking slag(ISS) mass ratio and temperature were investigated in desulfurization experiments. The X-ray diffraction(XRD) and X-ray fluorescence(XRF) analyses show that the optimum conditions are LSS:ISS of 3:7 and temperature of 1350°C. The composition of desulfurization products is mainly Zn Fe2O4, and the desulfurization rate of 99.66% is obtained under optimum conditions. The thermogravimetric(TG) and differential scanning calorimeter(DSC) analyses demonstrate that reductant is necessary for decomposition and reduction of zinc ferrite in desulfurization product. The effects of reductant, temperature and feeding modes on iron enrichment were investigated in reduction experiments. The scanning electron microscope(SEM) and energy dispersive spectrometer(EDS) determination show that the iron content of reduction product is up to 99.36% under optimum conditions of coke as reductant, reduction temperature of 1450°C and the feeding mode of premixing.

Heavy metal pollution risk of desulfurized steel slag as a soil amendment in cycling use of solid wastes

The by-product of wet flue gas desulfurization,desulfurized steel slag(DS),had chemical characteristics like natural gypsum that can be used to improve saline-sodic soil.However,contamination risk of heavy metals for cycling utilization of DS in agriculturewas concerned mostly.Both pot and field experiments were conducted for evaluating the potential pollution risk of DS as the amendment of saline-sodic soil.Results showed that application of DS decreased the contents of Cd,Cu,Zn,and Pb,while significantly increasing chromium(Cr)content in DS-amended soils.The field experiment demonstrated that the migration of heavy metals(Cd,Zn,Cu,and Pb)in the soil profile was negligible.The application of DS at the dosage of 22.5–225 tons/ha significantly increased the Cr content in alfalfa(Medicago sativa L.)but lower than the national standard for feed in China(GB 13078-2017).DS altered the chemical fraction of heavy metals(Zn,Cu,and Pb),transferred exchangeable,reducible into oxidizable and residual forms in DS-amended soil.Application of DS combined with fulvic acid(FA)could effectively reduce the movement of heavy metals in soil and the accumulation of Cr in alfalfa.Based on our results,DS was a safe and feasible material for agricultural use and presented relatively little pollution risk of heavy metals.However,the results also showed that DS to a certain extent had a potential environmental risk of Cr if larger dosages of DS were used.