One-step and green synthesis of metal doped spinel ferrite (Ni,Zn)Fe2O4 with high magnetic property from Zn-containing electric arc furnace dust

Introduction Zn-containing electric arc furnace dust (EAFD), a solid waste produced during steelmaking process, contains many valuable metals, such as Fe, Zn, Mn, Ca, etc. (Kukurugya et al., 2015; Wang et al., 2016b). And the dust is classified as hazardous wastes according to the US Environmental Protection Agency because of the presence of Cr, Pb, etc. (Ann M. Hagni et al., 1991; Wang et al., 2016a). Therefore, it is becoming increasingly important to find an environmentally friendly solution to treat the EAFD for sustaining a cleaner and greener environment. Up to now, two main methods for treatment of Zn-containing EAFD include solidification/stabilization (S/S) process and recovery of valuable metals. However, the point of the former is the immobilization of hazardous elements, such as Cr, Pb, etc., and the later only pays attention to the pursuit of high added value. Little study has focused on the above two aspects simultaneously. Spinel ferrites such as MFe2O4 (M: Ni, Zn, Mn, Ca, etc.) have attracted considerable interest and efforts due to their stability, novel magnetic/electric properties, and great applications in different fields (Srinivasan et al., 2009). Among them, Ni-Zn spinel ferrite, which has a high saturation magnetization (Ms) and low coercivity (Hc), has been widely used as soft magnetic materials, leading to many studies focused on obtaining high Ms and low Hc. Considering the fact that elements such as Fe, Zn, Cr, and Mn coexisted in the Zn-containing EAFD, it is reasonable to assume that by adjusting the components of the dust, the mole ratio of Fe (Fe, Cr, Al) to M of around 2.0 can be obtained, resulting in the direct synthesis of spinel ferrites from the dusts. In this study, one-step solid state reaction method was proposed for the first time to realize green and simple synthesis of ferrite from Zn-containing EAFD through the addition of NiCl2·6H2O. Single-phase metal doped spinel ferrite (Ni,Zn)Fe2O4 was obtained after the calcined sample was washed by dilute HAc solution. The calcined temperature played an important role in determining the phase structure and magnetic properties of as-prepared MFe2O4. In addition, the hazardous elements were bound to the lattice of the ferrite, realizing the harmless treatment of the EAFD. This work may explore an environmentally friendly and simple pathway for the high value-added utilization of Zn-containing EAFD.