Mechanism and impacts of inorganic ion addition on photocatalytic degradation of triclosan catalyzed by heterostructured Bi7O9I3/Bi

Abstract Background Triclosan, a broad-spectrum bacteriostatic germicide, is widely used in daily life. Traditional methods for removal of triclosan however suffer from possible secondary pollution. Photocatalytic technology is considered one of the most promising methods because of its low cost and high efficiencies, which removes pollutants through direct utilization of solar energy. Methods Here, a heterostructured composite photocatalyst Bi7O9I3/Bi was prepared through an in situ reduction method for photocatalytic degradation of triclosan, with the degradation mechanism investigated with a free radical trapping experiment and an electron spin resonance (ESR) method. Furthermore, the effects of the presence of inorganic ions on the degradation efficiencies were investigated. Findings Compared with Bi7O9I3, the degradation efficiency of Bi7O9I3/Bi on triclosan was significantly improved. This is mainly attributed to the formation of Bi nanoparticles on the surface of Bi7O9I3, which effectively promotes the light absorption through surface plasmon effects of Bi and separation of photo-generated electron-hole pairs through band structure modulation, thereby greatly improving the photocatalytic performances. The photo-generated electrons (e−) and superoxide radicals (·O2−) were found to be the main active species for triclosan degradation. Furthermore, the presence of NO3−, SO42- and Cl− all hamper the photodegradation of triclosan, whereas HCO3−, Ca2+ and Mg2+ inhibit or promote it depending on their concentrations.