Imidacloprid photo-degradation on Ag/AgBr modified TiO2: critical impacts and quantitative study on mechanism

摘要

To improve the visible-light catalytic performance of TiO2 for practical application, Ag/AgBr modified TiO2 was fabricated in ionic liquid-water medium via a facile hydrothermal reduction method. Imidacloprid (IMI) was employed as the target pollutant to evaluate the critical impacts on the catalytic activity of as-prepared Ag/AgBr/TiO2, where the factors relating to the catalyst (composition, dosage, recycle and reuse) and solution chemistry (pH and concentration, simulated wastewater samples and floodwater of rice paddy field) were studied. The results suggested that benefitting from visible-light sensitive Ag/AgBr and high specific surface area TiO2, Ag/AgBr/TiO2 exhibits superior visible-light photocatalytic activity and stability to Ag/AgBr and TiO2. The quenching tests with various scavengers indicate that O-center dot(2)- and h(+), and O-center dot(2)- and (OH)-O-center dot may be the key roles in IMI photo-degradation on Ag/AgBr and on Ag/AgBr/TiO2, respectively. Thus, the photocatalytic performance of Ag/AgBr/TiO2 differs from that of Ag/AgBr. Furthermore, the contribution of such active species is clarified for quantitative mechanisms study. The photo-degradation conducted in the simulated wastewater and the floodwater of rice paddy field proves favorable anti-interference capacity of Ag/AgBr/TiO2. The tests conducted on real wastewater sample verified that Ag/AgBr/TiO2 can mineralize IMI promptly and almost completely.