Preparation Of Bi₄MO₈Br（M=V、Nb）Photocatalysts And Photodegradation For Organic Pollutants In Water

With the rapid development in science&technology and social economy, the environmentalpollution became progressively worse, especially the organic pollution. Most of the organic pollutants aretoxic and recalcitrant. The removal of the organic pollutants has been a crucial task for environmentalprotection. In Recent years, use photocatalysis technology to eliminate pollution has become the mostactive research fields. At present, many photocatalysts are bandgap semiconductor and can be activatedonly by the UV-light. But the sunlight mainly concentrated in the visible light region, which occupiedabout47%of the total energy. Therefore, developing photocatalysts that can absorb visible light becomethe cornerstone to realize the industrialization application of the technology. The Aurivillius-Sillen phasescompounds is a kind of promising visible light catalysts due to their unique layered structure. Most of thecompounds synthesized by solid state technique which the morphology control is difficult. However, theproperty of catalysts is largely depends on particle size distribution and morphology. Using thehydrothermal method, the components of raw material can well mixed, thus prepared materials withspecific morphology and size.In this context, Bi4VO8Br photocatalyst was prepared by hydrothermal method and characterizedby X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis diffuse reflectancespectroscopy (UV-Vis-DRS). The activity of Bi4VO8Br prepared at different conditions were evaluated bythe degradation of methyl orange under visible light irradiation. It was found that hydrothermal pH3,reaction time15h and reaction temperature160℃was the optimum synthesis condition of the material.The degradation activity of Bi4VO8Br to several pesticides and plasticizer were measured under visiblelight and UV-light irradiation. It was found that Bi4VO8Br has a good degradation efficiency todifficult-to-photolysis organics containing benzene ring under visible light irradiation. The influencefactors during the photocatalytic process was studied by degradation of pentachlorophenol (PCP). Theresults indicated that the photocatalyst exhibited high photocatalytic activity for the degradation of PCPunder both visible and UV-light irradiation. Under the conditions:1.0g/L of catalyst dosage, pH5.8of thesolution and10mg/L of PCP initial concentration, the degradation efficiency of PCP was reach to97%and100%after120min of visible light irradiation and20min of UV-light irradiation respectively. Moreover, Active radicals scavenging experiment confirmed that the hole on the surface of catalyst was responsiblefor the photocatalytic degradation of PCP.Furthermore, Bi4NbO8Br photocatalyst was synthesized by hydrothermal approach andcharacterized by XRD, SEM and UV-Vis-DRS respectively. Photocatalytic degradation for sulfadiazine(SDZ) under visible-light was used to investigate the influence factors during the photocatalytic process.The degradation rate of SDZ by Bi4NbO8Br can get a good result at the conditions of catalyst dosage1.5g/L, solution pH3, SDZ initial concentration5mg/L. The photocalyst can degrade91.4%of SDZ after6hof visible light irradiation. The photocatalytic degradation of other five kinds of antibiotics was toinvestigate the relationship between the photoactivity of Bi4NbO8Br and organic compounds structure. Itwas found that organics containing benzene, oxazole and pyrimidine ring were easy to be degraded byBi4NbO8Br under visible light irradiation as compared with organics containing imidazole ring and morebranched carbon chain. In addition to chloramphenicol and metronidazole, other organic matter can bemineralized completely after35min of UV-light irradiation.