Heavy metal pollution characteristics and environmental risk assessment of the residue after magnetic separation of converter dust in steel plants.

To explore the application pathways of residues after magnetic separation of converter dust (RCD), a comprehensive investigation was conducted on its fundamental properties and environmental risks. The crystalline substances in RCD include KCl, Fe₂O₃, SiO₂, ZnO, and Zn₄Si₂O₇(OH)₂(H₂O), while the organic matter is mainly aromatic compounds with low concentration. The overall order of heavy metal (HM) concentration in RCD is as follows: Zn > Pb > Cr > Ni > Cd > As > Cu > Hg. The results of the improvement of Community Bureau of Reference (BCR) sequential extraction showed that Hg, As, Cd, Cr, Cu, Ni, and Zn in RCD were mainly in the residual fraction. The leaching concentrations of HMs in RCD were far below the identification standards for hazardous waste. Referring to the control limit requirements of HMs (GB 15618-2018), the geological accumulation index (I_geo) of Cd reached 5.27. Meanwhile, the potential ecological hazard coefficient (E_r) values of Hg and Cd were 44.48 and 1740.00, respectively, and the comprehensive potential ecological risk index (RI) value for HMs was 1826.27. This indicated that the ecological risk of HMs in RCD is extremely high and it cannot be used as agricultural land soil. However, the I_geo (< 0), E_r (< 40) and RI (< 150) of HMs of RCD as development land soil were lower, and its ecological risk was slight. RCD had no significant effect on the histopathological changes of mice. The rational use of RCD in production will not cause obvious toxic effects on target animals. Based on risk assessment and safety evaluation, the resource utilization of RCD is controllable, safe and reliable.