Enriched photocatalysis-Fenton synergistic degradation of organic pollutants and coking wastewater via surface oxygen vacancies over Fe-BiOBr composites

Fe-doped three-dimensional flower-like structures BiOBr (Fe-BiOBr) with rich surface oxygen vacancies (OVs) were prepared by a simple microwave method, and the Fe-BiOBr composites completely degraded phenol solution (20 ppm) after 60 min of visible light irradiation in the presence of H2O2. The degradation activity was 12.32 and 1.46 times that of photocatalytic and Fenton reactions, respectively. The catalytic degradation activity was still as high as 90% after five recycles and had good structural stability. Meanwhile, the Fe-BiOBr composites also exhibited good removal efficiency for other phenolics and coking wastewater, and the chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiency of coking wastewater were 63.6% and 53.8%, respectively. Both theoretical calculations and experimental results showed that oxygen vacancies could effectively promote the photocatalytic Fenton synergistic degradation activity, which not only improved the separation efficiency of photogenerated carriers, promoted the transformation of the Fe ion valence state and realized the cycle of the Fenton reaction but also acted as the adsorption and activation site of H2O2 to produce hydroxyl radicals, the most important active species in the synergistic degradation system, which was confirmed by quenching experiments and EPR results. The effects of the Fe doping amount, H2O2 concentration and other factors on the degradation activity were investigated. Based on the results of the experiment and theoretical calculations, the degradation mechanism of the surface oxygen vacancies enhancing the photocatalysis-Fenton degradation activity was proposed.