Preparation Of Z-type Heterojunction Composite Material And Study On Its Photocatalytic Degradation Of Rhodamine B

At present,the water pollution problem caused by organic pollutants needs to be solved urgently.As a typical water organic pollutant,dyes have been widely studied because of their high toxicity,strong chroma,and difficulty in biodegradation.Compared with traditional technology,photocatalytic technology has lower energy consumption,mild reaction conditions,and no secondary pollution.It is one of the most promising technologies in the field of environmental treatment.As the new type of photocatalysts,graphite-phase carbon nitride（g-C₃N₄）and bismuth tungstate（Bi₂WO₆）have simple preparation process,stable chemical properties,and suitable for the band gap.They are widely used in the field of photocatalysis,but the photocatalytic efficiency of a single photocatalyst is unsatisfactory.Many researchers have modified g-C₃N₄ and Bi₂WO₆ to improve its photocatalytic performance.In this dissertation,g-C₃N₄ and Bi₂WO₆ are used as substrate materials,and the photocatalytic performance are improved by compounding with other materials to form a heterojunction.The materials are comprehensively analyzed by using relevant characterization methods,the photocatalytic activity of the materials is determined by degrading the organic dye Rhodamine B（Rh B）,and the photocatalytic reaction mechanism is explored by free radical trapping experiments.The main research contents and conclusions of this paper are as follows:1.Using g-C₃N₄ as the substrate,WO₃/g-C₃N₄ composites were synthesized by hydrothermal and in-situ precipitation methods.The results showed that among the four kinds of composites with different mass ratios,20%WO₃/g-C₃N₄ composites could degrade Rh B.The effect is the best.After 100 minutes of light,the degradation rate is86.13%.A Z-type heterojunction is formed between WO₃ and g-C₃N₄.·O2^-and h⁺play the main photocatalytic role.2.Using Bi₂WO₆ as the substrate,the conductive polymer polyaniline（PANI）with good visible light absorption properties is used to modify Bi₂WO₆ to prepare PANI/Bi₂WO₆ composite material.The results showed that the addition of PANI significantly enhances the visible light absorption of the composite material.After 40minutes of light,the degradation rate of Rh B by 10%PANI/Bi₂WO₆ composites was89.35%.·O₂^-and h⁺played a major role in the degradation process,and a Z-type heterojunction was formed between PANI and Bi₂WO₆.3.Based on the research in the previous two chapters,WO₃/g-C₃N₄ composite material and Bi₂WO₆ were further coupled,and the ternary composite material WO₃/g-C₃N₄/Bi₂WO₆ was prepared by in-situ precipitation method.The results show that the ternary composite material has a flower cluster-like nanosheet structure,and the specific surface area is significantly increased.The 30%W/g/Bi composite material has the highest degradation rate.The degradation rate reaches 97.20%under 40 minutes of light.The main roles in photocatalysis are·O₂^-and h⁺.WO₃,g-C₃N₄ and Bi₂WO₆ form a double Z-type heterojunction,and photo-generated carriers are effectively transported between WO₃,g-C₃N₄ and Bi₂WO₆.