| Bismuth tungstate（Bi2WO6）,as a simple Aurivillius-type Oxide,responds not only to UV light but also to a certain range of visible light.Due to its special layered structure,unique optical and chemical properties,it shows good promise for the degradation of pollutants.However,the severe recombination of the charge carriers and the unsatisfactory light absorption properties greatly limit its practical application.Therefore,to overcome these drawbacks of Bi2WO6 and improve its photocatalytic efficiency,Fe3+doped TiO2/Bi2WO6,Ag/AgCl/Bi2WO6 and Ag/AgCl/Bi2WO6/ACF composites were prepared in this paper,and the effects of different experimental parameters on the structure,physicochemical and optical properties of the photocatalysts were also investigated..The main studies are as follows.1.A trace Fe3+doped TiO2/Bi2WO6 composite photocatalyst with abundant oxygen vacancies was successfully synthesized via a hydrothermal method and subsequently impregnation treatment.Fe3+doped TiO2/Bi2WO6 were optimized by adjusting the molar ration of TiO2 and Bi2WO6and the amount of iron ion doping.Experiments show that Fe（0.1）-TB2 with 0.1 wt%Fe ions exhibits excellent photocatalytic activity,which has over 90%toluene removal efficiency after 180 min under visible light irradiation.A series of characterizations reveal that the improved photocatalytic activity of Fe doped TiO2/Bi2WO6 can be attributed to synergistic effects between the extension of photogenerated carrier lifetime,the increase of visible light absorption range by narrowing the energy bandgap and the formation of oxygen vacancies.Furthermore,hydroxyl radicals and holes as the key reactive oxygen species（ROS）in the photodegradation reaction were confirmed by electron spin resonance（ESR）experiments.Therefore,introducing Fe-ions into TiO2/Bi2WO6 photocatalysts is an effective way to enhance the photocatalytic activities,and the modified catalysts can be considered as a promising material for decomposing toluene and other VOCs.2.The Ag/AgCl/Bi2WO6 photocatalyst was prepared via a combination of hydrothermal and photoreduction methods,and its degradation efficiency of toluene under visible light was investigated.The results showed that the Ag/AgCl/Bi2WO6photocatalyst exhibited the best photocatalytic performance when the amount of Ag NO3was 1 mmol,and it achieved 99.99%degradation of toluene after 60 min of visible light irradiation,while the pure Bi2WO6 only achieved 18.2%degradation under the same conditions.In addition,after four cycles of testing,the catalyst activity was slightly reduced and the degradation of toluene remained at 96.32%.Based on the ESR results,superoxide radicals,hydroxyl radicals and holes were found to be the main reactive groups and revealed the existence of a Z-scheme charge transfer mechanism in the photodegradation reaction.Meanwhile,Ag nanoparticles facilitate the enhancement of visible light utilization and separation of photogenerated carriers.3.The Ag/AgCl/Bi2WO6 catalyst powder was loaded onto ACF using a physical bonding method and its removal performance for toluene was investigated.The experimental results showed that the complete removal of toluene by Ag/AgCl/Bi2WO6/ACF was achieved within 30 min under visible light irradiation,which was better than the removal rate of toluene by ACF and Ag/AgCl/Bi2WO6.In addition,the Ag/AgCl/Bi2WO6/ACF composite still showed good removal of toluene at different initial concentrations of toluene.Further,the Ag/AgCl/Bi2WO6/ACF composite exhibited 100%removal of toluene after 30 min of natural sunlight exposure.At the same time,robustness testing of the samples showed that the Ag/AgCl/Bi2WO6photocatalysts were strongly bonded to the ACF.Therefore,the Ag/AgCl/Bi2WO6/ACF composite is a promising photocatalytic purification product with great potential for the treatment of VOCs. |
