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

Abstract

In this study, Ag2O/BiVO4/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 (H2O2), the imidacloprid (IMD) could be effectively degraded by the composite. Systemic evaluations was conducted on effects of pH value, catalyst dosage, H2O2 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 Ag2O nanoparticle and BiVO4 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 Ag2O/BiVO4/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 (O2−), 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 Ag2O and n-type BiVO4 heterojunction composites has opened a new direction for photocatalytic degradation of organic pollutants.