Synthesis, magnetic properties, biotoxicity and potential mechanism of modified nano zero-valent iron for decolorization of dye wastewater.

SiO₂-coated nano zero-valent iron (nZVI) has emerged as a fine material for the treatment of dye wastewater due to its large specific surface area, high surface activity, and strong reducibility. However, the magnetic properties based on which SiO₂-coated nZVI (SiO₂-nZVI) could effectively separate and recover from treated wastewater, and the biotoxicity analysis of degradation products of the dye wastewater treated by SiO₂-nZVI remain unclear. In this study, SiO₂-nZVI was synthesized using a modified one-step synthesis method. The SiO₂-nZVI nanoparticles were characterized using Transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, Fully automatic specific surface and porosity analyzer, Vibrating sample magnetometer, and Zeta potential analyzer. The removal rate of methyl orange (MO) by SiO₂-nZVI composite reached 98.35% when the degradation performance of SiO₂-nZVI treating MO was optimized. Since SiO₂-nZVI analysed by magnetic hysteresis loops had large saturation magnetization and strong magnetic properties, SiO₂-nZVI exhibited excellent ferromagnetic behaviour. The analysis of the degradation products showed that the MO treated by SiO₂-nZVI was converted into a series of intermediates, resulting in reducing the toxicity of MO. The potential mechanism of MO degradated by SiO₂-nZVI was speculated through degradation process and degradation kinetics analysis. Overall, the SiO₂-nZVI composite may be regarded as a promising catalyst for decolorization of dye wastewater.