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Modification Of Graphitic Carbon Nitride With Aminobenzaldehyde And Its Visible-Light-Driven Photocatalytic Performance For Degradation Of Antibiotics

Posted on:2024-08-18Degree:MasterType:Thesis
Country:ChinaCandidate:Y LiuFull Text:PDF
GTID:2531307115493734Subject:Materials and Chemical Engineering (Chemical Engineering) (Professional Degree)
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With the extensive use and abuse of antibiotics,the residual antibiotics has been detected in various water environments,which has drastically threatened to the ecological environment and human health.Traditional wastewater treatment methods have the characteristics of high cost and low removal efficiency,which is difficult to achieve complete degradation.Solar-driven photocatalysis technology possesses the advantages of mild reaction conditions and environment-friendliness,and has been one of the effective ways to solve the problem of water pollution.Graphitic carbon nitride(GCN)is an organic semiconductor photocatalyst with visible light response.It has the advantages of rich sources,lowcost and simple preparation,which make it possess wide application in photocatalytic fields such as hydrogen production from water photolysis,carbon dioxide reduction and degradation of organic pollutants.However,the limited utilization of visible light,small specific surface area and high recombination rate of photogenerated carriers has severely suppressed its practical applications.At present,GCN has been modified by morphological regulation,element doping,covalent modification and other means to improve its photocatalytic activity.In view of the shortcomings of GCN,p-dimethylaminobenzaldehyde(ABA)modified GCN photocatalysts using different modification strategies were designed and developed to achieve enhanced photocatalytic activity against antibiotics such as moxifloxacin(MOX).The related work of this dissertation is listed as follows:1.The CN/ABA composite photocatalyst was prepared by theπ-πstacking effect of ABA and GCN self-assembly at room temperature.The characterization results confirmed the successful introduction of ABA,and the addition of ABA could broaden the visible light absorption range of GCN and reduce the recombination probability of photogenerated charge carriers.The CN/ABA could achieve 99%MOX removal within 80 min,and the apparent rate constant was 2.4 times higher than that of GCN.The effects of p H,photocatalyst dosage and MOX concentration on the photocatalytic performance were investigated.The modified catalyst had good stability,durability and universality,as well aspossessed considerable potential in practical application scenarios.Through determining the energy band structure and reactive oxygen species(ROS)experiments,we proposed a possibly photocatalytic mechanism.Furthermore,based on the TOC test and LC-MS data,the reaction pathway of MOX degradation was also proposed.2.By post-synthesis modification strategy,ABA-grafted GCN photocatalyst CN-ABA-X was constructed at different temperatures(X=100 oC,150 oC,200 oC,260 oC)based on the Schiff base reaction between the uronic group of ABA and the terminal amino group of GCN.The characterization results indicated the successful grafting of ABA and the reduced terminal amino groups on GCN.According to the photochemical test,ABA grafting could effectively expand theπ-conjugate system of GCN and promote the separation and transfer of photogenerated charge carriers.The best CN-ABA-150 oC could completely remove MOX within 60 min,and the reaction rate constant was 0.087 min-1,which was 3.6 times higher than that of GCN.The CN-ABA photocatalyst was demonstrated to have highly photocatalytic stability,durability and universality,and its excellent photocatalytic activity in practical scenarios was also verified.Combined with the obtained band structure of CN-ABA and the ROS identification of the reaction system,a possible photocatalytic degradation mechanism was proposed.The degradation pathway of MOX was analyzed by LC-MS,and finally the TOC values of the system were analyzed.3.We employed a solid-state copolymerization synthesis route to prepare a novel CNABA photocatalyst through interaction of ABA into the GCN skeleton using the Schiff base reaction.FTIR and XPS characterizations suggested the successful doping of ABA into the GCN framework.The hybrid photocatalyst had narrower band gap,lower photogenerated electron-hole pair recombination rate and higher charge transport speed than the pristine GCN.Using MOX as the model pollutant,the optimized CNABA-3 exhibited the highest rate constant(0.056 min-1),which is 3.1times higher than the GCN(0.018 min-1).This photocatalyst also showed good catalytic performance for different influence factors,multiple antibiotics and practical scenarios.The excellent stability and reusability of the catalyst were confirmed by cycling experiments.Based on the determined band structure and ROS testing,the mechanism of reactive degradation of MOX was proposed.The reaction intermediates were determined by LC-MS and the MOX degradation pathway was proposed.Combined with TOC analysis,it was concluded that the CNABA photocatalyst was a promising photocatalyst for the elimination of antibiotics driven by visible light.Finally,we compared the properties and kinetics of the three photocatalysts and explained the reasons for the differences in photocatalytic activities.This work provides a feasible strategy for the rational design of aromatic system to modify GCN skeleton to enhance photocatalytic activity.
Keywords/Search Tags:graphitic phase carbon nitride, aminobenzaldehyde, photocatalysis, solid phase synthesis, antibiotics
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