Preparation and application of α-Fe ₂ O ₃ @MIL-101(Cr)@TiO ₂ based on metal–organic framework for photocatalytic degradation of paraquat

Abstract

In this study, a new magnetic α-Fe 2 O 3 @MIL-101(Cr)@TiO 2 photocatalyst was successfully synthesized. The material synthesized had been fully characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, vibrating sample magnetometry, transmission electron microscopy, and Brunauer–Emmett–Teller isotherm methods. The X-ray diffraction analysis corroborates that nanoparticles are polycrystalline with rhombohedral and tetragonal crystal structures for Fe 2 O 3 and TiO 2 , respectively. In addition, the photocatalytic degradation of the herbicide paraquat in the presence of α-Fe 2 O 3 @MIL-101(Cr)@TiO 2 under ultraviolet (UV) irradiation was studied. The effect of experimental parameters such as the initial concentration of catalyst, the pH, and the initial paraquat was investigated. The optimal conditions were achieved for concentration of catalyst 0.2 g L −1 , pH 7, and concentration of paraquat 20 mg L −1 . The photocatalytic degradation efficiency was 88.39% after 15 min with α-Fe 2 O 3 @MIL-101(Cr)@TiO 2 under UV irradiation. The pseudo-second-order kinetic model for photocatalytic degradation of paraquat was obtained. The catalysts could be recovered and reused without any loss of efficiency for five times in the consequent reactions. To the best of our knowledge, this is the first report on the photocatalytic degradation of paraquat using new α-Fe 2 O 3 @MIL-101(Cr)@TiO 2 photocatalyst under UV irradiation condition.