Simulated solar light-driven photocatalytic degradation of trichloroethylene in water using BiOBr promoted by sulfite addition

Background Photodegradation of trichloroethylene (TCE) in aqueous solution under simulated solar light irradiation was studied under different experimental conditions to determine the reaction mechanism and kinetics that control TCE degradation using bismuth oxybromide (BiOBr) in the presence of sulfite. Photocatalysts were synthesized to be more responsive to visible light under simulated solar light and particular attention was focused on the reactive specie formed by reaction of the sulfite on the surface of BiOBr under simulated sunlight. Result Degradation rate of TCE was greatly enhanced by the presence of sulfite, and the enhancement increased with sulfite dose to a maximum that was retained at higher sulfite doses. Degradation rate of TCE was also affected by other factors, such as initial TCE concentration, BiOBr dose, and solution pH. In addition, the cycling performance of BiOBr was examined, and the amount of TCE degraded was almost constant over increasing cycle numbers when initial sulfite concentration was high enough to maintain a suitable sulfite concentration throughout the experiment. When TCE was degraded by BiOBr in the presence of sulfite under simulated sunlight irradiation, the major by-product measured was the non-hazardous chloride ion, and dechlorination efficiency was about 58%. Conclusion This study extended the use of a potential effective photocatalyst (BiOBr) to a semi-volatile organic contaminant (TCE), not limited to mainly focus on organic dyes, and evaluated the use of sulfite as a hole scavenger in order to enhance the degradation of TCE without needing to manipulate the structure of BiOBr. The active species being responsible for TCE degradation in BiOBr/TCE/sulfite system under simulated solar light was the sulfite radical (SO3 center dot-), and the photocatalytic activity of BiOBr did not decrease over a number of treatment cycles when S-IV dose was sufficient.