Study On Photocatalytic Degradation Of Antibiotics By P-TiO₂/G-C₃N₄

China is the largest antibiotic user in world.However,only about 10-20%of antibiotics are metabolized by organisms,and the unmetabolized part is directly or indirectly discharged into the water environment.Therefore,how to effectively remove residual antibiotics has become a research hotspot in life,health and environmental protection.The significant advantages of photocatalytic degradation of antibiotics are high stability,low cost,strong oxidation and high degradation efficiency,etc.,which has attracted widespread attention in environmental governance and restoration.This article selects tetracycline and sulfa antibiotics as the objects.For the purpose of high-efficiency photocatalytic degradation of antibiotics,phosphorus-supported titanium dioxide（P-TiO₂）and graphite phase carbon nitride composite phosphating titanium dioxide（P-TiO₂/g-C₃N₄）were successfully prepared.With the help of a variety of characterization techniques,this article analyzes and discusses the mechanism of photocatalytic materials degradation of antibiotics and the factors affecting the photocatalytic degradation of antibiotics（p H,catalytic material usage,initial antibiotic concentration,etc.）.Provide references and suggestions for more in-depth study of photocatalytic degradation of antibiotics.The main research conclusions are as follows:（1）Phosphor-loaded TiO₂ photocatalytic material（P-TiO₂）was prepared by neutral amine sol-gel technology.Due to the large specific surface area and adsorption capacity of phosphorus doping,it had a good removal effect of tetracycline（99.16%）,but the photocatalytic degradation effect of sulfonamides antibiotics was not good.Photogenerated e^-is the main active substance involved in photocatalytic reaction in the reaction system.At the same time,the recovery experiment showed that the photocatalyst had good stability,and the degradation effect of 5P-TiO₂ on tetracycline remained above 98%after three cycle tests.Response surface analysis（RSM）was used to optimize the photocatalytic degradation of tetracycline.The variance results showed that the illumination time and the concentration of photocatalytic materials were the significant factors affecting the photocatalytic degradation of tetracycline.Under the optimal conditions(P-TiO₂=17.45 wt%,photocatalyst concentration=1.00 g·L^-1,irradiation time=40.39 min,light intensity=5 A,p H=7,tetracycline concentration=29.93 mg·L^-1),the photocatalytic degradation rate of tetracycline was 99.16%,which was in good agreement with the predicted value（100%）.According to the intermediates identified by GC-MS,there were more chain and ring products in the mass spectrum of this study,and a possible photocatalytic degradation pathway of tetracycline was proposed.（2）The prepared P-TiO₂ showed excellent photocatalytic degradation effect on tetracycline,but the photocatalytic degradation effect on sulfonamide antibiotics,especially the four mixed sulfonamides,was poor,only about 50%.Therefore,it is necessary to conduct a further modification study on the degradation performance of P-TiO₂ photocatalytic materials.Under the condition of nitrogen protection and calcination at 500℃,the P-TiO₂ prepared by the gel-sol method was calcined with urea for 2 h to prepare the P-TiO₂/g-C₃N₄ composite photocatalytic material.The study found that the construction of the Z-scheme heterojunction greatly improves the separation efficiency of electron-hole pairs,thereby improving the photocatalytic activity of P-TiO₂/g-C₃N₄.Various characterization methods were used to investigate the performance of the heterojunction photocatalytic degradation of sulfonamide antibiotics.P-TiO₂ particles are uniformly loaded on g-C₃N₄ flakes.DMPO-·O₂^–free radical detection test,XPS energy spectrum shift,valence band position and active material quenching experiments further confirmed the Z-scheme electron transport mechanism.When P-TiO₂ and g-C₃N₄ are combined to form a Z-scheme heterojunction,the effective separation of photo-generated carriers is increased,thereby improving its photocatalytic degradation performance.The P-TiO₂/g-C₃N₄ composite photocatalytic material（CNPT-3）prepared by adding 30 mg of P-TiO₂ to the four sulfonamide antibiotics in a short light irradiation time（30 min）showed good light Catalytic degradation effect,including SD:99.3%,SM2:99.6%,SMM:99.1%,SMZ:99.0%.In the factor influence experiment,the most suitable photocatalytic material concentration,antibiotic concentration and p H are 400 mg/L,5 mg/L and 7,respectively.The quenching experiment proved that·O₂^–,·OH and h⁺played a major role in the photocatalytic degradation of mixed sulfonamide antibiotics by the P-TiO₂/g-C₃N₄composite photocatalytic material.