Preparation Of Bi₄O₅I₂-based Composite Photocatalyst And Its Performance Study On Degradation Of Phenolic Pollutants

Due to the serious environmental pollution,water bodies suffer a lot of pollution,photocatalytic degradation of pollutants in water technology has attracted high attention because of its non-toxic products,economic and environmental protection,no secondary pollution,and other advantages.A variety of organic pollutants contained in water can be completely degraded into CO₂,H₂O,and other harmless small molecules,inorganic pollutants are oxidized or reduced to harmless substances.Using solar energy as a light source to activate photocatalysts,economic and environmental protection.Simple structure,easy to control operation,no secondary pollution.Therefore,the application of photocatalysis technology in the treatment of water pollutants has a very broad prospect.Although photocatalysis technology has outstanding advantages in the degradation of pollutants in water,there are still some technical problems in the practical application.Single photocatalytic materials often have problems such as poor absorption capacity of visible light,weak REDOX capacity and low quantum efficiency.Therefore,the selection and design of the leading photocatalyst is particularly important,which is also an important topic to be solved by scholars at home and abroad.The main research contents and conclusions of this paper are as follows:（1）Micron flower ball Bi₄O₅I₂ was synthesized by ionic liquid assisted precipitation and high temperature calcination,and the photocatalyst Bi₄O₅I₂/BiOBr was successfully prepared by in situ assembling nanometer sheet BiOBr through series characterization.The evaluation results of photocatalytic performance showed that:After 70 minutes of simulated lighting,composite photocatalysts of different proportions Bi₄O₅I₂/BiOBr（BiOBr,Bi₄O₅I₂/BiOBr-1,Bi₄O₅I₂/BiOBr-2,Bi₄O₅I₂/BiOBr-3,Bi₄O₅I₂/BiOBr-4,Bi₄O₅I₂/BiOBr-5,Bi₄O₅I₂/BiOBr-6 and Bi₄O₅I₂）showed different activity:degradation rates of OPP in water,and they were 7%,66%,74%,92%,96%,97%,100%and 60%,respectively.Among them,Bi₄O₅I₂/BiOBr-5 showed the best activity,and almost completely degraded after 60 minutes.In addition,the photocatalytic activity of Bi₄O₅I₂/BiOBr was evaluated by the degradation of PTBP,4-CP and p-nitrophenol in water.The active substances produced in the degradation process were studied by the experiment of trapping agent.Based on the experimental results,a possible degradation mechanism was proposed.（2）BiOI/BiPO₄ was first prepared by ionic liquid assisted preparation,and then Bi₄O₅I₂/BiPO₄ was prepared by high-temperature calcination.Series characterization showed that Bi₄O₅I₂/BiPO₄ photocatalyst was prepared successfully.The results of photocatalytic activity evaluation showed that:After 80 minutes of simulated lighting,the composite photocatalysts Bi₄O₅I₂/BiPO₄（Bi₄O₅I₂,BOPI-1,BOPI-2,BOPI-3,BOPI-4,BOPI-5 and BiPO₄）with different proportions showed different activities,and the degradation efficiency of pure BiPO₄ was about 5%.However,the degradation rate of Bi₄O₅I₂ was only 80%,and the most significant one was BOPI-3（the photocatalytic degradation rate was almost 100%after80 min under the same conditions）.It is clear that all the composite photocatalysts have significantly improved degradation efficiency compared with pure Bi₄O₅I₂ and BiPO₄.In addition,the photocatalytic activity of BOPI-3 compounds was evaluated by degradation of Rhodamine B（Rh B）,tert-butylphenol（PTBP）and bisphenol A（BPA）in water.The above activity results showed that the photocatalyst Bi₄O₅I₂/BiOBr had a very good degradation effect on organic pollutants in water.The active substances produced in the degradation process were studied by the experiment of trapping agent.Based on the experimental results,a possible degradation mechanism was proposed.（3）The precursor ZnSnO₃ was prepared by water bath and high temperature calcination,and then BiOI/ZnSnO₃ was assisted by ionic liquid,and finally Bi₄O₅I₂/ZnSnO₃ was prepared by high temperature calcination of BiOI/ZnSnO₃.Bi₄O₅I₂/ZnSnO₃ was successfully prepared by series characterization.The results showed that the pure ZnSnO₃ sample showed no photocatalytic activity due to its wide band gap.However,the hydrolysis efficiency of Bi₄O₅I₂/ZnSnO₃ heterojunction composite photocatalyst for OPP under visible light irradiation is significantly higher than that of pure Bi₄O₅I₂.Compared with other catalysts,ZSBI-2 showed the best catalytic activity.After 90 min of reaction,the degradation rate of OPP reached 100%,while that of pure Bi₄O₅I₂ was only about 64%.Based on the detection of the production of active species and the experiment of trapping agent,the possible degradation mechanism was proposed.Through the selection and design of leading photocatalysts,we have successfully prepared several Bi₄O₅I₂-based composite photocatalysts,and the activity results show that there is a significant improvement compared with pure Bi₄O₅I₂,which is of great significance to provide new ideas and strategies to solve the problems of environmental pollution and energy shortage.