Study On The Effect And Mechanism Of Modified Titanium Dioxide In Degrading Penicillin In Water

Every year,more than 50,000 tons of antibiotics are discharged into the water and soil environment in China.With the process of soil erosion,the antibiotics enriched in the soil will further enter the water body along with surface runoff and soil infiltration,increasing antibiotic pollution.Antibiotics(such as penicillin)use a large base,destroy the microbial community structure in the water and soil environment,reduce the environmental carrying capacity,and at the same time induce microorganisms,animals,and humans to produce resistance genes enriched in the body,posing a serious threat to the ecological environment and human health.TiO2 can use sunlight to degrade antibiotics,but the photogenerated electron-holes in TiO2 are very easy to recombine,resulting in limited degradation effect.The composite of semiconductor materials on the surface of TiO2 is used to construct heterostructures to achieve the purpose of delaying the recombination time of photogenerated electrons and holes.At the same time,the green and low-toxicity synthesis of nanomaterials has received widespread attention.In this study,potato extract was used as a substitute for traditional chemical stabilizers and modifiers,and CdS(QDs),ZnS(QDs),CdS(QDs)-TiO2,ZnS(QDs)-TiO2 were synthesized using low-toxic methods designed to improve the photocatalytic performance of composite materials.Explore the optimal synthesis reaction parameters and degradation reaction parameters for penicillin degradation materials,and lay the foundation for the treatment of antibiotic pollution in water bodies.The main conclusions are as follows:(1)Use potato extract as stabilizer and modifier to prepare CdS QDs.The particle size of ZnS QDs was about 5 nm,the fluorescence excitation wavelength was ?=330 nm and ?=290 nm,and the corresponding emission wavelengths were ?=490 nm and ?=435 nm.(2)Potato extract concentration 200 g/L,cadmium and zinc to sulfur molar ratio 1:30,synthesis temperature 120?,synthesis time 20min were the best preparation conditions for CdS/ZnS QDs(3)The loading amount of ZnS(QDs)on TiO2 was 5‰,the synthesis temperature was 120?,the optimal dosage of ZnS(QDs)-TiO2 was 60mg,the penicillin degradation reaction temperature was controlled at 30?,and the initial pH of the solution was 5,made the best degradation effect.After 2 hours,the degradation rate of the penicillin solution with a concentration of 100 mg/L was as high as 92.6%.(4)The loading amount of ZnS(QDs)on TiO2 was 1‰,the synthesis temperature was 120?,the optimal dosage of ZnS(QDs)-TiO2 was 80mg,the penicillin degradation reaction temperature was controlled at 35?,and the initial pH of the solution was 5,made the best degradation effect.After 2 hours,the degradation rate of the penicillin solution with a concentration of 100 mg/L was as high as 95.6%.The degradation of penicillin by CdS(QDs)-TiO2 and ZnS(QDs)-TiO2 was an oxygen-consuming process,and oxygen could be added to the reaction system to significantly improve the degradation efficiency.The EPR test confirmed that the radical group that plays a major role in the degradation process is·O2-.(5)The CdS(QDs)-TiO2 and ZnS(QDs)-TiO2 composite material finally converted penicillin into four organic compounds,and some small molecule compounds were completely decomposed into H2O and CO2.Compared with the traditional process,during the test time,the CdS(QDs)-TiO2 and ZnS(QDs)-TiO2 composite material further oxidative decarboxylation of the degradation reaction,making the degradation reaction more thorough.Finally,the antibacterial experiment proved that the final 4 compounds had no inhibitory effect on Escherichia coli,and significantly reduced the toxicity of penicillin to microorganisms.It has been verified that CdS(QDs)-TiO2 and ZnS(QDs)-TiO2 had good photocatalytic degradation of penicillin,and could be used as a pretreatment agent or degradation agent for antibiotics polluted water bodies represented by penicillin.This method had important practical application value for low-toxicity synthesis of nanomaterials,treatment of antibiotic pollution caused by soil erosion,and protection of watershed ecological safety.