A novel visible-light-active BiOCl/BiVO 4 photocatalyst with a p−n heterojunction structure was prepared using a hydrothermal method. The photocatalytic activity of the heterojunction was investigated by monitoring the change in methyl orange (MO) concentration under visible-light irradiation. The results reveal that the composite exhibited markedly improved efficiency for MO photodegradation in comparison with pure BiVO 4 , BiOCl, and Degussa P25. This is ascribed to the Btype heterojunction structure with a strong oxidative ability and efficient charge separation and transfer across the BiOCl/BiVO 4 p−n junction. The highest activity was obtained in the BiOCl/BiVO 4 heterojunction using a composite of 13 mol % BiOCl and 87 mol % BiVO 4 . The removal of MO was mainly initiated by valence-band holes, but dissolved oxygen also played a crucial role in consuming the conductionband electrons. This was verified by the effects of scavengers and N 2 purging.

Fe3O4 magnetic nanoparticles (MNPs) were employed for electro-Fenton (Fe3O4–electro-Fenton) degradation of C.I. Reactive Blue 19 (RB19) in an undivided electrochemical reactor with an activated carbon fiber felt cathode and a platinum anode. On the basis of physicochemical characterization of the Fe3O4 MNPs as well as quantitative measurements of iron leaching and H2O2 generation, it is concluded that the Fe3O4 MNPs facilitated the decomposition of H2O2 to generate hydroxyl radicals (•OH). Moreover, the cathodic electro-Fenton facilitated electro-regeneration of ferrous ion and maintained continuous supply of H2O2. The effect of several operational parameters such as pH, current density, amount of added Fe3O4 MNPs, initial RB19 concentration, and temperature on the removal of total organic carbon was investigated. It was found that the Fe3O4–electro-Fenton degradation of RB19 followed two-stage first-order kinetics with an induction period and a rapid degradation stage. Mineralization of RB19 proceeded rapidly only at pH 3.0. Increasing the current density and the dosage of Fe3O4 MNPs enhanced the rate of RB19 degradation. However, higher current densities and Fe3O4 dosages inhibited the reaction. The rate of RB19 degradation decreased with the increase in initial RB19 concentration and increased with the increase in temperature. The removal efficiency of total organic carbon reached 87.0% after 120 min of electrolysis at an initial pH of 3.0, current density of 3.0 mA/cm2, 1.0 g/L concentration of added Fe3O4 MNPs, 100 mg/L initial dye concentration, and 35 °C temperature. On the basis of the analytical results for the intermediate products and the assumption that •OH radicals are the major reactive species, we propose a possible pathway of RB19 degradation during the cathodic electro-Fenton process using Fe3O4 MNPs as iron source.

In the present work, reduction of Cr(VI) induced by UV–visible light in aqueous solution was investigated. The aqueous medium contained TiO2 nanosheets and no additional reducing agents or hole scavengers. A hydrothermal method was used to synthesize fluorinated TiO2 nanostructures with various percentages of exposed {001} facets and initial F/Ti ratios. Fluorine-free TiO2 nanosheets were obtained by washing the TiO2 samples with NaOH solution. The surface fluorination facilitates the adsorption process by increasing the number of surface OH groups generated. Moreover, fluorination efficiently inhibits the recombination of photogenerated electron–hole pairs. The {001} facets have an indirect role in the photocatalytic reduction of Cr(VI) because oxidative dissolution of H2O occurring on {001} facets and Cr(VI) reduction occurring on {101} facets are simultaneous reactions. The optimal ratio of exposed {001} to {101} was found to be ∼72:18.