Study On The Performance Of Photocatalytic Removal Of Organic Pollutants By Graphite-Phase Carbon Nitride-Based Flat Membrane

Due to the emergence of antibiotic resistance genes that may cause super bacteria,antibiotics as emerging pollutants have attracted global attention.Moreover,antibiotic wastewater has poor biochemical properties and stable physical and chemical properties,which make it difficult to be degraded,causing serious water pollution,accumulating in the surrounding environment,and seriously endangering human living environment and life and health.Current wastewater treatment technologies cannot fully remove antibiotics in wastewater,so new technologies with high removal rates are needed.The photocatalytic technology has a very good effect on the treatment of difficult-to-degrade organics.Therefore,in this experiment,the photocatalyst is loaded on the PTFE membrane to degrade and remove the organic pollutants in the sewage.The prepared membrane material is not only stable but also has good performance for recyclability.In this thesis,an easy-to-recover PTFE composite membrane material is prepared for the treatment of organic matter in simulated antibiotic wastewater.（1）S-g-C₃N₄,N-TiO₂,S-g-C₃N₄@N-TiO₂are synthesized by hydrothermal method.S-g-C₃N₄/PTFE membrane material,N-TiO₂/PTFE membrane material,and S-g-C₃N₄@N-TiO₂/PTFE film membrane material are prepared by suction filtration,and passed Infrared spectroscopy（FT-IR）,scanning electron microscope（SEM）,X-ray photoelectron spectroscopy（XPS）,fluorescence spectroscopy（PL）and other characterization methods were used to characterize and analyze the three film materials.（2）Tetracycline hydrochloride（TCH）organic matter simulates antibiotic wastewater,and investigates the treatment effects of three membrane materials on target pollutants.（3）Through three kinds of membrane material recycling experiments and electrochemical analysis results,the recyclability and reusability of the materials and the photocatalytic degradation mechanism of the materials are discussed.Research shows:（1）S-g-C₃N₄/PTFE membrane material has good recyclability and photocatalytic performance.Under simulated sunlight,the S-g-C₃N₄/PTFE membrane material has good photocatalytic degradation performance for tetracycline hydrochloride simulated wastewater,and it conforms to the first-order reaction kinetic model.The optimal treatment conditions for tetracycline hydrochloride by S-g-C₃N₄/PTFE membrane material are:the initial concentration of tetracycline hydrochloride is 20 mg/L,the dosage of S-g-C₃N₄material is 0.5 g/L,the loading amount of S-g-C₃N₄material is 50 mg,solution when the p H=5,the photocatalytic degradation rate of S-g-C₃N₄/PTFE membrane material to tetracycline hydrochloride is 98.1%;（2）N-TiO₂/PTFE membrane material also has good recovery and photocatalytic performance.Under simulated sunlight,N-TiO₂/PTFE membrane material has good photocatalytic degradation performance for tetracycline hydrochloride simulated wastewater,and it conforms to the first-order reaction kinetic model.The optimal treatment conditions of N-TiO₂/PTFE membrane material for tetracycline hydrochloride are:the initial concentration of tetracycline hydrochloride is 20 mg/L,the dosage of N-TiO₂material is 0.5 g/L,the loading amount of N-TiO₂material is 50 mg,and the solution when the p H=5,the photocatalytic degradation rate of N-TiO₂/PTFE membrane material to tetracycline hydrochloride is 98.5%;（3）S-g-C₃N₄@N-TiO₂/PTFE membrane material has good recovery and photocatalytic performance.Under simulated sunlight,the S-g-C₃N₄@N-TiO₂/PTFE membrane material has good photocatalytic degradation performance for tetracycline hydrochloride simulated wastewater,and it conforms to the first-order reaction kinetic model.The best treatment conditions for S-g-C₃N₄@N-TiO₂/PTFE membrane material for tetracycline hydrochloride are:the initial concentration of tetracycline hydrochloride is 20 mg/L,the dosage of S-g-C₃N₄@N-TiO₂material is 0.5 g/L,and the ratio of g-C₃N₄and TiO₂is 2:1 as well as the solution p H=5.At this time,the photocatalytic degradation rate of S-g-C₃N₄@N-TiO₂/PTFE membrane material to tetracycline hydrochloride is 99.1%;In addition,repeatability experiments show that S-g-C₃N₄/PTFE membrane material,N-TiO₂/PTFE membrane material,S-g-C₃N₄@N-TiO₂/PTFE membrane material have good recyclability and photocatalytic stability.After 4 cycles,the recovery rate of the three membrane materials can still reach more than 90%,and the degradation rate of the three membrane materials to tetracycline hydrochloride can still reach more than 90%,meeting the needs of recycling and photocatalysis.Afterwards,the photocatalytic degradation mechanism of S-g-C₃N₄/PTFE membrane material,N-TiO₂/PTFE membrane material,S-g-C₃N₄@N-TiO₂/PTFE membrane material was discussed through free radical capture experiments.The experimental results show that the three membrane materials are in superoxide radical(·O^2-)is the main active species in the photocatalytic degradation process.（1）S-g-C₃N₄/PTFE membrane material:S-g-C₃N₄catalyst exhibits agglomeration.Compared with g-C₃N₄,S-g-C₃N₄material shows a slight red shift in the visible light region,the recombination efficiency of electrons and holes is significantly reduced,and the photocurrent response the range increases.（2）N-TiO₂/PTFE film material:TiO₂exists in the form of anatase phase in the N-TiO₂material.Compared with TiO₂,the electron-hole pair recombination efficiency of N-TiO₂/PTFE film material is significantly reduced,and the light increased catalytic activity.（3）S-g-C₃N₄@N-TiO₂/PTFE film material:In S-g-C₃N₄@N-TiO₂/PTFE film material,TiO₂particles are better dispersed on the g-C₃N₄nanosheet layer,compared with monomer materials,composite the material accelerates the electron transfer speed and inhibits the recombination rate of electron-hole pairs,thereby improving the photocatalytic degradation effect of the membrane material on tetracycline hydrochloride.S-g-C₃N₄@N-TiO₂/PTFEmembranematerial:In S-g-C₃N₄@N-TiO₂/PTFE membrane material,TiO₂particles are better dispersed on the g-C₃N₄nanosheets.Compared with the monomer material,the speed of electron transfer in the medium is accelerated,which also inhibits the recombination rate of electron-hole pairs,thereby improving the photocatalytic degradation effect of the membrane material on tetracycline hydrochloride.