Effect of calcination temperature on photocatalytic activity of magnetic Fe-based composites recycled from hazardous EAF dust

Abstract

In this study, a Fe-rich solution was obtained from a two-step leaching process on electric arc furnace (EAF) dust. Different magnetic Fe-based composites were synthesized by the co-precipitation technique followed by a calcination process. The calcination temperature effects on different properties and the photocatalytic activity were studied. X-ray diffraction (XRD) results showed that as the calcination temperature exceeded 750 °C, the crystallinity of the synthesized composite increased. Also, at calcination temperatures below 1050 °C, the Ca2Fe2O5 phase was not formed. Field emission scanning electron microscopy (FESEM) results represented various morphologies at different calcination temperatures. The saturation magnetization (MS) was enhanced from 8 to 30 ems/g by the calcination temperature increment from 750 to 1200 °C. Also, the coercivity (HC) was increased from 25 to 60 Oe by calcination temperature growth from 750 to 1050 °C and then dropped to 20 Oe at a higher calcination temperature of 1200 °C. The photoluminescence (PL) results indicated that the calcined composite at 900 °C had the least electron-hole recombination rate. Transmission electron microscopy (TEM) results of the synthesized composite at 900 °C showed a nanostructure consisting of MgFe2O4 and CaFe2O4 particles. The average particle size of the above sample was 30 nm, and this sample showed the best photocatalytic activity under visible light irradiation for degradation of methylene blue (MB) with the kinetics of approximately 2.5 times faster than the calcined composite at 1200 °C. The active species capture experiments reveal that photo-generated holes play the most significant role in the photocatalytic mechanism. The reusability test of the synthesized nanocomposite at 900 °C showed stability after three cycles of photodegradation.