Preparation Of Modified Graphitic Carbon Nitride And Its Photocatalytic Sterilization Performance

Hygienic and safe drinking water is the basic need for human survival.As the water pollution has becoming more and more serious,the impact of microbial contamination in drinking water on humans has also become increasingly profound.Due to the complex structure and unique metabolism of microorganisms,the traditional technology,used to eliminate pathogens（such as chlorination,chlorine dioxide and ozone technologies）,would produce a large number of carcinogenic by-products including trihalomethanes（THMs）and others,which have highly pathogenic risks to humans health.As a promising environmental remediation technology,the photocatalytic technology for water disinfection and microbial control has attracted great attention.Among various photocatalysts,graphitic carbon nitride（g-C₃N₄）has attracted great attention due to its advantages such as response to visible light,simple preparation,and good stability.However,g-C₃N₄ has some disadvantages such as low utilization of light,small specific surface area,and easy recombination of photogenerated charges.Therefore,it is very meaningful to develop g-C₃N₄-based photocatalyst that is economical,efficient,environmentally friendly,and has high catalytic acticity.The main research contents and conclusions are as follows:The urea（CH₄N₂O）and Chitin were used as precursors to prepare the chitin-g-C₃N₄ composite（Chitin-CN）by hydrothermal method.The photocatalytic sterilization performance of the microorganism Escherichia coli K-12 in water under simulated sunlight was studied.The results showed that the composites had excellent photocatalytic activity and great stability.Among them,0.2 Chitin-CN（Chitin mass percentage was 50%）had the best photocatalytic activity,degrading 6.5 lg cfu/m L of E.coli K-12 within 2h.The reason could be attributed to the effective separation of photogenerated electron-hole pairs and the fragmented structure exposing more reactive sites.Moreover,the capture experiments showed that superoxide radicals（·O₂^-）and holes（h⁺）were the main active species in the photocatalytic sterilization process.Cadmium sulfide（CdS）was prepared by using cadmium nitrate and sodium sulfide as precursors.The surface of CdS was carboxylated with thioglycolic acid,then in-situ recombined with g-C₃N₄ by high temperature calcination to prepare a series of CdS-CN composites.The photocatalytic sterilization performance of Escherichia coli K-12 in water under visible light irradiation was studied.The results showed that g-C₃N₄ inhibited the photocorrosion of CdS and improved the stability of the composite.Moreover,the heterojunction formed by the amide bond effectively promoted the separation of photogenerated electron-hole pairs,this made CdS-CN composites have excellent photocatalytic bactericidal activity.Under visible light,1.0CdSCN（CdS mass percentage is 50%）was able to degrade 6.5 lgcfu/m L of E.coli K-12 within 4h.