| Background:In recent years,the widespread use and emission of tetracycline,as well as the inability of conventional treatment to completely remove it,have led to its frequent detection in the environment.Photocatalytically coupled persulfate activation systems are widely used in the field of environmental governance as a fast,efficient and green method to degrade organic pollutants by synergistic action of two advanced oxidation technologies.Covalent Organic Polymers(COPs)are a class of highly crosslinked porous materials.Due to their large conjugated system,covalent organic polymers(COPS)are gradually attracting the attention of many researchers due to their advantages of structural diversity and photoelectric chemical properties.Objective:The main objective of this experiment is to construct a photocatalytic coupled persulfate activation system for the efficient degradation of tetracycline pollutants based on D-A COPs photocatalyst and to elucidate the related mechanism.Methods:Two kinds of D-A COPs photocatalysts with different internal electric fields were synthesized using the construction units containing strong electron acceptor and weak electron acceptor groups.The molecular structure,photoelectric performance and photocatalytic coupling of persulfate activation and degradation of tetracycline were analyzed,and the intrinsic relationship between the donor-acceptor structure,photocatalytic performance and persulfate activation ability were discussed.The mechanism of enhancing the high charge separation/transport efficiency and photocatalytic degradation efficiency was studied,and the catalytic and degradation mechanism of photocatalysis coupled persulfate activated tetracycline was studied based on strong D-A COPs.Results:The t-COP(strong)and b-COP(weak)were prepared by ultrasonic polycondensation of amine aldehydes.The structure characterization was used to analyze the structure and the synthesis was confirmed successfully.The study of photoelectric properties shows that the reduction ability and migration ability of photogenerated electrons of t-COP are stronger,the recombination rate of photogenerated carriers is smaller and the number of photogenerated carriers is larger,and the efficiency of internal charge transfer and separation is better.The theoretical calculation shows that t-COP is less prone to electron-hole pair recombination.Degradation performance experiments showed that:(1)The t-COP has a good degradation effect on tetracycline at low,medium and high concentrations.The t-COP has a good degradation effect in wide pH range.(2)The catalytic performance of t-COP in photocatalysis and photocatalysis coupled persulfate activation system is higher than that of b-COP.(3)The photocatalytic coupled persulfate activation system of "t-COP+KPS+visible light" was finally selected.The degradation efficiency of tetracycline reached 86.66%after 30 min of light exposure,and 95.03%after 90 min of light exposure.(4)The main active factors in the system is 1O2,followed by h+,·OH,SO4·and O2·-has a smaller role.(5)After repeated use for 5 times,the degradation efficiency of the system is maintained at more than 80%,and it has excellent applicability in the actual water samples and the degradation of other kinds of tetracycline antibiotics.Finally,the possible degradation paths were analyzed using UPLC-HRMS.Conclusions:In this study,a photocatalytic coupled persulfate activation tetracycline degradation system of D-A COPs photocatalyst was successfully constructed,and the structure-activity relationship between the donor-receptor structure,photocatalytic performance and persulfate activation ability was studied.The mechanism of enhanced photocatalytic degradation efficiency was revealed,and the catalytic and degradation mechanisms were clarified.It provides a new idea and theoretical basis for the design and synthesis of COPs photocatalysts for photocatalysed persulfate activation system. |
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