Efficient degradation of imidacloprid in wastewater by a novel p-n heterogeneous Ag2O/BiVO4/diatomite composite under hydrogen peroxide

In this study, Ag 2 O/BiVO 4 /diatomite composite with p-n heterojunction structure was synthesized by simple hydrothermal method with diatomite as carrier. It was found that under the action of hydrogen peroxide (H 2 O 2 ), the imidacloprid (IMD) could be effectively degraded by the composite. Systemic evaluations was conducted on effects of pH value, catalyst dosage, H 2 O 2 concentration, initial IMD concentration, and anion on how effeciently this new photocatalytic composite can degrade IMD. The results show that the p-n heterojunction formed between the two contact surfaces of Ag 2 O nanoparticle and BiVO 4 promotes the charge transfer between the interfaces, inhibits recombination of electrons and holes, and thus significantly improves the catalytic performance. The stability and reusability of Ag 2 O/BiVO 4 /diatomite composites were tested with ICP experiment and cyclic experiment. Active substance capture experiment and ESR reveal the photocatalytic reaction mechanism and confirm that superoxide radical ( O 2 − ), hydroxyl radical ( OH), and h + can promote the degradation of IMD. The degradation products and the intermediates of IMD were identified through LC-MS, on a basis of which the possible transformation pathway was proposed. In situ synthesis of p-type Ag 2 O and n-type BiVO 4 heterojunction composites has opened a new direction for photocatalytic degradation of organic pollutants.