Facile synthesis of Z-scheme ZnO-nanorod @ BiOBr-nanosheet heterojunction as efficient visible-light responsive photocatalyst: The effect of electrolyte and scavengers

A series of Z-scheme 3D ZnO@BiOBr photocatalysts were prepared by the hydrothermal method. The morphology of BiOBr facing the surface of the ZnO nanorods was controlled under regulating the proper experimental conditions. The photocatalysts were characterized by XRD, FT-IR, FE-SEM, TEM, BET-BJH, UV-vis DRS and PL analyses. The ZnO@BiOBr composites showed the highest photodegradation ability of metronidazole (MTZ), which was about 9.75 and 3.54 times higher than those of the pure ZnO and BiOBr, respectively. In addition, the Z-scheme ZnO@BiOBr photocatalysts indicated high stability after four cycles of MTZ photoreduction. The optimal values of the operating parameters were determined by the Box-Behnken design (BBD) with irradiation time = 112 min, pH = 6, initial MTZ concentration = 20 ppm, and catalyst dose 0.5 g/l. The maximum total organic carbon (TOC) degradation efficiencies in the presence of 3D ZnO@BiOBr reached 76.7% at the optimum conditions. The maximum MTZ removal efficiency was 87.72%. The photodegradation of MTZ by a binary composite followed the first-order kinetics. In addition, the effects of adding inorganic ions at different concentrations on the degradation of MTZ were investigated. Based on the trapping experiments, OH center dot & nbsp;and O2(-center dot) improved the photodegradation process.