Preparation Of Bi_xO_yX_z Catalysts And Their Photocatalytic Degradation Of Organic Pollutants

Along with the increasingly serious environmental pollution problem,pollution control and restoration have become research hotspots in the world today.The extensive use of synthetic organic substances(such as chlorophenols,antibiotics,etc.)has caused serious harm to the environment.Such pollutants have acute toxicity,potential carcinogenicity and bioaccumulation capacity,and are relatively difficult to degrade in the environmental system.Photocatalytic technology has attracted much attention because of its environmental protection,mild reaction conditions,low energy consumption and no secondary pollution.Bismuth oxyhalide(BiOX,where X is Cl,Br and I)has a high hole redox potential and relatively low electron-hole recombination rate due to the internal electric field structure formed between[Bi₂O₂]²⁺and the halogen negative layer.It has a good response in the visible light range,and exhibits good catalytic activity and stability.However,the catalyst has relatively wide band gap and activity range in near ultraviolet light,which inhibits the practical application of this type of catalyst.In this paper,a series of composite materials with BiOX as the main body were prepared by solvothermal method,impregnation method and ultrasonic-hydrothermal combination method,and the structure,morphology and photoelectric properties of the catalyst were characterized;Sulfamethazine(SMT),2,4,6-trichlorophenol(2,4,6-TCP)and norfloxacin(NOR)as target pollutants,the catalytic performance of the prepared composite material was tested,and the effect of external conditions on the degradation of pollutants was also investigated;At the same time,the mechanism of the photocatalytic reaction is preliminary discussed through the trapping agents experiment and the free radical capture experiment.The main research contents include:1.The F-BiOCl_0.4Br_0.3I_0.3 composite material with wool ball-like morphology was prepared by solvothermal method,and its structure was characterized.Taking SMT as the research object,the effects of catalyst composition,light duration,material dosage,initial concentration of pollutants,system p H and material reusability on the degradation effect were discussed.Under the best experimental conditions,the degradation rate can reach99.6%.Its special morphology enhances the light absorption capacity,thereby improving the photocatalytic degradation of SMT.2.The rhodamine B(Rh B)sensitized BiOCl Br composite material was prepared by dipping method.The material presents an irregular sheet-like structure with a certain thickness.Based on the response surface method,taking 2,4,6-TCP as the research object,the effect of the amount of material,the initial concentration of pollutants,and the p H of the system on the degradation effect during the photocatalytic degradation process was studied.Under the best experimental conditions,the degradation rate can reach 92.3%,and the sensitization of Rh B improves the photocatalytic activity of the material.3.The 3D flower-like intercalation Z-type Bi₄O₅I₂/Cd S heterojunction composite material was prepared by the ultrasonic-hydrothermal combination method and used for the photocatalytic degradation of NOR.The influence of a series of external conditions on the degradation rate of target pollutants was studied.Under the best experimental conditions,the degradation rate can reach 95.5%.The formation of the Z-type heterojunction can not only improve the separation and transfer efficiency of electron-hole pairs,but also maintain the high redox ability of the semiconductor,thereby improving the photocatalytic degradation of NOR.