A novel 3D hollow magnetic Fe3O4/BiOI heterojunction with enhanced photocatalytic performance for bisphenol A degradation

Abstract

A novel 3D heterojunction photocatalyst Fe3O4/BiOI microsphere with hollow structure was successfully fabricated for the first time via a facile in-situ coprecipitation method. The materials were characterized by a number of techniques including X-ray powder diffraction, scanning electron microscope, transmission electron microscopy, ultraviolet–visible diffuse reflection spectroscopy, Brunauer-Emmett-Teller, X-ray photo-electron spectroscopy, photoluminescence technique, and vibrating sample magnetometer. The photocatalyst was employed to degrade bisphenol A (BPA) in aqueous solution under visible-light irradiation. Among the prepared samples, the Fe3O4/BiOI with molar ratio of 1:4 (FB-4) heterojunction showed the best photocatalytic activity. The optimal dose of FB-4 was 1.0 g/L. The catalytic degradation also showed a dependence on initial pH, and the maximal degradation efficiency was obtained at pH 9.0. The presence of nitrate and bicarbonate stimulated BPA degradation by Fe3O4/BiOI at low concentrations but inhibited the degradation at high concentrations. HA inhibited the degradation at all concentrations. The photogenerated reactive species determined by free radicals trapping experiments revealed that the photodegradation of BPA over Fe3O4/BiOI under visible light was dominated by direct hole and hydroxyl radicals rather than oxidation by superoxide radicals. The disappearance of BPA as well as the formation of its intermediates/products were determined by high-performance liquid chromatography-mass spectroscopy, and possible photocatalytic degradation pathways were proposed. Cycling test showed that the magnetic Fe3O4/BiOI composite could be easily recycled after five cycles and separated well by an external magnetic field, and could maintain an excellent photocatalytic activity on BPA degradation.