Research On Degradation And Mechanism Of Sulfamethoxazole By Dielectric Barrier Discharge Plasma In Collaboration With Fe₃O₄-MnO₂-Cellulose Acetate Film

For the pollution problems induced by the sulfamethoxazole（SMX）existed in the water environment,the Fe₃O₄-MnO₂-cellulose acetate（CA）composite film catalyst was prepared and applied in the ielectric barrier discharge plasma（DBDP）system in this study,and the composite film/DBDP collaborative water treatment system was established.In this collaborative process,the recyclable composite film was used as the catalyst,and ultraviolet light,O₃and H₂O₂produced in the DBDP system were utilized to form multi-effect catalysis,to improve the energy utilization efficiency of the DBDP system as well as the antibiotics degradation in water.In the study,SMX was used as the target pollutant and the catalytic effect of the composite films（MnO₂-CA film and Fe₃O₄-MnO₂-CA film）were verified,and optimal preparation of the film catalyst were determined.The effect of the DBDP in collaboration with the two composite films on the SMX degradation were also investigated.Finally,the synergistic mechanism of Fe₃O₄-MnO₂-CA/DBDP was concluded.The main research results are concluded as follows:（1）Study on the SMX degradation and mechanism in the MnO₂-CA/DBDP system.The successful preparation of the MnO₂-CA composite film catalyst.When the loading of MnO₂was 3%,the degradation rate of SMX could reach 85.54%after60 min treatment.The degradation was better under the alkaline solution condition.When the carrier gas was air,the catalytic effect of MnO₂-CA composite film was more obvious.The results of UV-Vis spectrum analysis proved the synergistic effect induced by the MnO₂-CA composite film addition.The biodegradability and mineralization degree of the SMX solution was were also improved in the MnO₂-CA/DBDP system.The recycle experiments verified the good stability of the MnO₂-CA composite film.The addition of the composite film catalyst can strengthen the changes of the pH and conductivity of the solution,the concentration of O₃and H₂O₂in the liquid phase,and the generated active substances（¹O₂and·OH）.The experiments on different scavengers’addition proved key role of·O₂^-,¹O₂and·OH on the SMX degradation.（2）Study on the SMX degradation and mechanism in the Fe₃O₄-MnO₂-CA/DBDP system.The preparation of Fe₃O₄-MnO₂-CA composite film catalyst was proved by characterization analysis.The catalytic effect of the Fe₃O₄-MnO₂-CA composite film was then confirmed by comparing the SMX degradation.When the molar ratio of the Fe₃O₄and the MnO₂was 3:1 and the loading amount of the Fe₃O₄-MnO₂on the CA was 3%,there was best degradation of the SMX（93.55%）.SMX has high degradation under neutral and alkaline solution conditions in the Fe₃O₄-MnO₂-CA/DBDP system.The results of UV-Vis spectrum analysis proved the synergistic effect induced by the Fe₃O₄-MnO₂-CA composite films addition.The COD and TOC removal rate of the SMX solution could be improved by adding the Fe₃O₄-MnO₂-CA composite film into the DBDP system.The Fe₃O₄-MnO₂-CA composite film still maintained a good catalytic effect after four cycles using.There were more obvious change of the solution pH and conductivity in the Fe₃O₄-MnO₂-CA/DBDP system than those achieved in the sole DBDP system.The concentrations of O₃and H₂O₂obtained in deionized water in the collaborative system were lower,and the ESR results showed that the production of·OH and ¹O₂increased in the collaborative system.The results confirmed the catalysis of the Fe₃O₄-MnO₂-CA composite film in the DBDP system.The different scavengers’addition experiments also proved that·O₂^-,¹O₂and·OH played a key role for the SMX degradation in the Fe₃O₄-MnO₂-CA/DBDP system.（3）Mechanism induction of SMX degradation in the DBDP system combined with the Fe₃O₄-MnO₂-CA composite film catalyst.Nine intermediates of the SMX degradation were identified by LC-MS,and four possible degradation paths were then speculated.The toxicity of the treated SMX solution was reduced.In Fe₃O₄-MnO₂-CA/DBDP system,the main processes responsible for the SMX degradation include:the physical effects and the chemical oxidation effects generated by DBDP itself;photocatalysis and catalytic ozonation of MnO₂in composite film catalyst;catalysis of H₂O₂and O₃in Fe₃O₄.The synergic catalytic action of the Fe₃O₄-MnO₂-CA composite film could improve the energy utilization efficiency of DBDP system and realize the efficient treatment of the SMX solution.