Reuse of Fenton sludge as an iron source for NiFe2O4 synthesis and its application in the Fenton-based process.

The potentially hazardous iron-containing sludge from the Fenton process requires proper treatment and disposal, which often results in high treatment cost. In this study, a novel method for the reuse of Fenton sludge as an iron source for the synthesis of nickel ferrite particles (NiFe2O4) is proposed. Through a co-precipitation method followed by sintering at 800°C, magnetic NiFe2O4 particles were successfully synthesized, which was confirmed by powder X-ray diffraction (XRD), scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy. The synthesized NiFe2O4 could be used as an efficient catalyst in the heterogeneous Fenton process. In phenol degradation with H2O2 or NiFe2O4 alone, the phenol removal efficiencies within the reaction time of 330min were as low as 5.9%±0.1% and 13.5%±0.4%, respectively. However, in the presence of both NiFe2O4 and H2O2, phenol removal efficiency as high as 95%±3.4% could be achieved, indicating the excellent catalytic performance of NiFe2O4 in the heterogeneous Fenton process. Notably, a rapid electron exchange between NiII and FeIII ions in the NiFe2O4 structure could be beneficial for the Fenton reaction. In addition, the magnetic catalyst was relatively stable, highly active and recoverable, and has potential applications in the Fenton process for organic pollutant removal.