Preparation Of ZnFe₂O₄ And RGO-ZnFe₂O₄ Composites And Their Photo-Fenton Degradation Properties Towards Pollutants

In recent years,with the continuous improvement of industrialization level,there are more and more environmental pollution problems.As a green and efficient advanced oxidation technology,photo-Fenton can be used for the treatment of refractory pollutants.The study of highly efficient photo-Fenton catalyst has also become a hot spot.It is well known that the light absorption capacity,the number of active sites and the temperature of the reaction system are closely related to the photo-Fenton catalytic degradation performance.Therefore,in view of the above factors,this study focused on ZnFe₂O₄ catalytic materials,using morphological control and rGO composite methods to control the catalyst in order to further improve the photo-Fenton catalytic degradation performance.The main research contents and conclusions are as follows:?1?The magnetic yolk-shell structure ZnFe₂O₄ catalyst was synthesized by solvothermal and calcination methods.The common morphologies of ZnFe₂O₄ and?-Fe2O3 were synthesized by hydrothermal method.Using tetracycline?TC?as the target pollutant,the photo-Fenton degradation properties of ZnFe2O4 catalysts with different morphologies were studied in the catalyst/H2O2/visible light system.The experimental results show that the yolk-shell structure ZnFe₂O₄ catalyst has better photo-Fenton catalytic degradation performance compared with the common morphology ZnFe₂O₄and?-Fe2O3.Various characterization methods were used to analyze the phase composition,morphology structure,optical properties and surface physical properties of the prepared samples.The reasons for the differences in photo-Fenton degradation performance of ZnFe2O4 catalysts with different morphologies were also explored.The results show that the yolk-shell structure ZnFe2O4 catalyst has the advantages of special morphology,stronger optical absorption,larger surface area and higher photo-generated carrier separation efficiency,and thus has the best photo-Fenton reaction activity.?2?The yolk-shell structure ZnFe₂O₄ catalyst not only has good removal rate for many common organic pollutants?TC,CIP,ARG,MO,RhB,etc.?,but also can effectively degrade mixed pollutants of TC and CIP.The optimum concentration of hydrogen peroxide is 20 mmol/L and the optimum pH is 2.The effects of different factors?temperature,initial concentration of pollutants and inorganic salt ions?on photofenton degradation were also investigated.By chemical fluorescence analysis and free radical capture experiments,we determined that?OH and hole are the main active groups in the process of photo-Fenton.The mechanism of photo-Fenton degradation of pollutants was further explained through the analysis of intermediate products and ZnFe₂O₄ band structure.?3?The rGO-ZnFe₂O₄ composite catalyst was successfully prepared by ultrasonic combined method.CIP was used as the target pollutant.The photo-Fenton degradation properties of rGO-ZnFe2O4 catalysts with different weight ratios was investigated under Xenon lamp light source?200-2500 nm?irradiation.The results showed that the rGO-ZnFe₂O₄ catalyst with a rGO compound ratio of 7%had the best degradation performance.The phase composition,morphology structure,optical properties and surface physical properties of the samples were analyzed by means of XRD,SEM,DRS and BET.The reasons for the difference in the catalytic performance of the catalysts were investigated.It was found that the catalysts with the proper composite proportion had stronger optical absorption properties,larger specific surface area,and the photothermal conversion performance of the composite catalysts.Therefore,the photo-Fenton catalytic degradation performance of catalyst was enhanced obviously.?4?The rGO-ZnFe₂O₄ composites not only has good removal effect for various pollutants?TC,CIP,ARG,MO,RhB,etc.?,but also has excellent stability.After five cycles of experiments,the removal rate of pollutants can still reach 95%.Through chemical fluorescence and free radical capture experiments,we determined that_?OH and hole are the main active groups in the process of photo-Fenton degradation.The mechanism of photo-Fenton degradation of pollutants by rGO-ZnFe₂O₄ composites was investigated.In summary,this work provides theoretical and practical reference for the development and modification of high efficient catalyst and the study of the mechanism of photo-Fenton degradation.