The Construction And Photocatalysis Performance Research Of Anatase-B Mixed Phase TiO₂-BiOCl_xI_1-x Ternary Heterojunction

The acceleration of the process of industrialization has greatly improved people’s living standards,but at the same time it has also produced varying degrees of pollution to the ecological environment.Photocatalytic technology is recognized as one of the ideal means to solve environmental pollution problems,and the development of high-efficiency,low-cost photocatalysts has always been the core issue of photocatalytic technology.Among the many known photocatalysts,TiO2 has the characteristics of low price,high photocatalytic activity,stable chemical properties,non-toxic and harmless,etc.It is a star photocatalyst that has attracted much attention,but its photo-generated electrons and holes have a relatively high probability of recombination.High,and the band gap is too wide,so it only responds to ultraviolet light.The mixed-phase TiO2 formed by anatase and B-phase titanium dioxide can expand the light absorption range to a certain extent,effectively promote the separation of photogenerated carriers,and thus help to improve the photocatalytic performance of titanium dioxide.BiOCl,which has attracted much attention in recent years,although its special layered structure is conducive to the transmission of photogenerated carriers,its band gap（3.2 e V）is relatively low,and the utilization rate of sunlight is low,while BiOI has a band gap.Narrow（1.8 e V）,but poor stability.Therefore,the introduction of I-into BiOCl to form BiOClx I1-x solid solution can not only narrow the band gap,but also effectively improve the absorption and utilization efficiency of visible light.In this paper,anatase-B mixed phase TiO2（denoted as M-TiO2）is combined with BiOClx I1-x,and under the action of the surfactant polyvinylpyrrolidone（PVP）,M-TiO2/BiOCl0.7I0.3-P ternary heterojunction high-efficiency composite photocatalyst,and its performance under visible light degradation of acetaminophen and the herbicide fomesafen was investigated.The specific research work is as follows:（1）Preparation of M-TiO₂ and study of its photocatalytic performance:M-TiO2（anatase-B mixed phase TiO2）was prepared by alkaline heating method,and its crystal structure and light absorption ability were obtained by XRD,UV-vis,SEM.The photocatalytic degradation performance of anatase phase titanium dioxide（A-TiO2）,P25 and M-TiO2 were investigated.The results showed that the photocatalytic degradation performance of M-TiO2 was the best.（2）Preparation of BiOCl_xI_1-xcatalyst and study on its photocatalytic performance:The glycerol solution of potassium chloride,potassium iodide and bismuth nitrate pentahydrate in different proportions was treated with ammonia water by the water bath method to prepare BiOClx I1-x with different doping ratios.The samples were characterized by XRD,SEM and BET for their crystal structure,morphology and surface properties.The photocatalytic performance of the catalyst was evaluated by photocatalytic degradation of phenol,and the molar ratio of Cl to I was selected as 7:3 BiOCl0.7I0.3 catalyst.（3）Preparation of M-TiO₂/BiOCl_0.7I_0.3-P ternary heterojunction and photocatalytic performance study:Under water bath conditions,mix M-TiO2 and BiOCl0.7I0.3,and add 0.5 g of polymer at the same time.Vinylpyrrolidone（PVP,abbreviated as P）to control the dispersion of the sample,successfully prepared a ternary heterojunction M-TiO2/BiOCl0.7I0.3-P photocatalyst.Through XRD,UV-vis,SEM,TEM,BET,the crystal structure,light absorption capacity,morphological structure and surface properties were characterized,and the photocatalyst photocatalyst of M-TiO2/BiOCl0.7I0.3-P heterostructure was discussed.Catalytic degradation of acetaminophen and fomesafen,99.81%of acetaminophen can be degraded in 30 minutes,and the degradation rate of fomesafen can reach 99.94%after90 minutes,and the photocatalyst after 5 cycles of experiments The activity remained basically unchanged.The intermediate products of photocatalytic degradation of acetaminophen and fomesafen by M-TiO2/BiOCl0.7I0.3-P were analyzed by HPLC-HRMS.The environment of the degraded organic pollutants was evaluated through environmental toxicity test and TOC.Toxicity and salinity,a possible photocatalytic mechanism is proposed.