Preparation Of MOFs-derived Photocatalysts And Study On Degradation Of EE2 In Cooperation With Oxidant

As emerging pollutants,endocrine disrupting compounds（EDCs）have received more and more attention in the past few decades because of their potential threats to organisms and human health.However,traditional wastewater treatment technologies cannot effectively remove these trace pollutants,so it is necessary to develop more powerful and effective technologies.Nowadays,semiconductor photocatalysis technology has already become emerging and attractive technology for the treatment of organic pollutants due to its environmental-friendly advantage of using solar energy.In the photocatalytic system,introducing a strong oxidant（sodium persulfate,PS）into the photocatalytic process is one of the effective ways to improve the efficiency of semiconductor photocatalysis.As an electron acceptor,PS can be activated to generate active radicals,which can significantly improve the photocatalytic performance of semiconductors.Therefore,photocatalyst technology and strong oxidizers synergistically remove organic pollutants is a very meaningful research topic.In this paper,a new type of photocatalyst with high activity was synthesized by MOFs derivatization,and the strategy of photocatalyst and strong oxidant was used to remove organic pollutants.The degradation.of EE2 byβ-Bi₂O₃ and Co₃O₄/Bi₅O₇I photocatalysts respectively cooperated with strong oxidant（PS）was investigated.First,XRD,XPS,SEM,HRTEM,TG,UV-vis and PL were used to characterize the microstructure and physicochemical properties of the synthetic materials;optimize the conditions for photocatalytic degradation of EE2,and evaluate the photocatalytic performance of the materials for EE2 degradation.In addition,the catalytic mechanism and main active species were studied through radical quenching experiment and EPR technology.The specific contents are as follows:1.Compared with commercialβ-Bi₂O₃,β-Bi₂O₃ derived from the precursor MOFs（CAU-17）by high-temperature treatment shows better photocatalytic activity for EE2degradation.The photocatalytic performance of the derivedβ-Bi₂O₃ can be significantly improved by adding sodium persulfate（PS）under light excitation.The first order rate constant of EE2 degradation has raised by 6.22 times from 0.0418 min^-1（β-Bi₂O₃/Vis）to 0.260 min^-1（β-Bi₂O₃/PS/Vis）.Increasing the amount of catalyst and PS concentration can increase the photocatalytic activity ofβ-Bi₂O₃ for EE2 degradation,and the photocatalytic efficiency increases with the increase of p H.Superoxide radicals,photogenerated holes,sulfate radicals and hydroxyl radicals are the active substances for EE2 degradation,among which superoxide radicals and photogenerated holes are the most important active substances.In theβ-Bi₂O₃/PS/Vis system,PS can be used as an electron scavenger to enhance the detachment of photogenerated e^-/h⁺pairs and can significantly improve the photocatalytic activity ofβ-Bi₂O₃.It also showed good stability in the 4 cycles test,and can be used as a steady photocatalyst to remove stubborn organic pollutants.2.The Co₃O₄/Bi₅O₇I composite material was prepared from Co-MOFs（ZIF-67）by adsorption-calcination method.Compared with Bi₅O₇I,Co₃O₄/Bi₅O₇I showed better photocatalytic activity for EE2 degradation.The photocatalytic performance of the derivatized Co₃O₄/Bi₅O₇I composite material can be significantly improved by adding sodium persulfate（PS）under visible light irradiation.The first-order rate constant of EE2 degradation has increased by 30 times from 0.0232 min^-1（Co₃O₄/Bi₅O₇I/Vis）to0.7037 min^-1（Co₃O₄/Bi₅O₇I/PS/Vis）.Increasing the amount of catalyst and PS concentration can increase the photocatalytic activity of the Co₃O₄/Bi₅O₇I composite for EE2 degradation,and the photocatalytic efficiency increases with the increase of p H.Superoxide free radicals and photogenerated holes are the main oxidizing substances that degrade EE2.PS can be used as an electron capture agent to boost the separation of photogenerated hole-electron pairs,and can significantly improve the photocatalytic activity of Co₃O₄/Bi₅O₇I.In addition,Co₃O₄/Bi₅O₇I maintained good chemical stability and over 99%EE2 removal efficiency in 4 cycles of testing,which proved the potential of Co₃O₄/Bi₅O₇I composites in practical applications.