Magnetically separable CdFe2O4/graphene catalyst and its enhanced photocatalytic properties

Abstract

A magnetically separable CdFe₂O₄/graphene (CdFe₂O₄/GR) photocatalyst was prepared using a one-step hydrothermal method. The photocatalytic activity was evaluated by photocatalytic oxidation of methylene blue (MB) under visible-light irradiation. Its photocatalytic activity was improved significantly by introducing graphene into CdFe₂O₄. The first-order kinetic constant of degradation with CdFe₂O₄/GR (0.00543 min⁻¹) was 5 times that with CdFe₂O₄ (0.00145 min⁻¹). The photocatalytic deactivation was investigated in the presence of individual anions (nitrate, sulfate, carbonate, and phosphate). Among the anionic species studied, carbonate exhibited the promotion effect, but others did not considerably affect the photo-degradation process. The mineralization products of MB were detected using High Performance Liquid Chromatography (HPLC) and ion chromatography. Several scavengers, the band structure obtained from UV-Vis diffuse reflectance spectrum, as well as Mott–Schottky measurement, were used to identify the roles of active species in the degradation process. The active species, i.e. holes and hydroxyl radicals, play major roles in the photo-degradation of MB. Note that the fundamental mechanism based on photo-degradation is discussed in detail, and the enhanced photocatalytic performance of CdFe₂O₄/GR was attributed to the improved electron–hole pair separation efficiency. The CdFe₂O₄/GR showed good stability after four cycles and could be easily separated by a magnet and reused, showing great potential for environmental purification of organic pollutants.