Synthesis of magnetic core–shell Fe3O4@TiO2 nanoparticles from electric arc furnace dust for photocatalytic degradation of steel mill wastewater

Abstract

The study was undertaken to design magnetic core–shell Fe₃O₄@TiO₂ nanoparticles from electric arc furnace dust and evaluate its photocatalytic activity on organic pollutant degradation from steel industry wastewater. Different molar ratios of Fe₃O₄ to TiO₂ were tested on Fe₃O₄@TiO₂ nanoparticles. The materials were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform-infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy, and a zeta potential analyzer and vibrating sample magnetometer. The behavior of Fe₃O₄@TiO₂ nanoparticles under different molar ratios of Fe₃O₄ to TiO₂, pH, photocatalyst dose and temperature was investigated. The apparent rate constant of organic pollutant degradation using Fe₃O₄@TiO₂ was found to be pH dependent as it influenced the surface properties and therefore the photocatalytic activity of Fe₃O₄@TiO₂, which was higher under acidic condition. The degradation of organic pollutants was as high as 96% at pH 3, 1 g L⁻¹ photocatalyst dose, 30 °C temperature, after 90 min reaction time, and the apparent rate constant was 0.043 min⁻¹. The thermodynamic parameters of activation, estimated by the Eyring equation and based on transition state theory (TST), indicated a nonspontaneous process in nature with positive Δ^‡G^o values, an endothermic reaction with positive Δ^‡H^o and negative Δ^‡S^o values. High degradation rate and catalyst recovery were maintained after five consecutive recycling cycles.