Preparation Of Mn Modified Of γ-Fe₂O₃ Coating And Its Photo-assisted Fenton Degradation Performance

Fenton oxidation technology is a commonly used treatment method for the degradation of organic pollutants in wastewater,which has the advantages of green environmental protection and high efficiency of degradation.The application of traditional homogeneous Fenton reaction is limited because of its narrow range of application of p H and the formation of iron mud after degradation.At present,most of the heterogeneous Fenton catalysts are powders,which need to be recovered from the reaction solution by filtration or centrifugation before they can be reused,and the catalytic activity of p H is poor under neutral conditions.Therefore,it is necessary to prepare immobilized Fenton catalysts with high catalytic activity,wide application range of p H and good cycle stability.In this paper,iron oxide catalysts were prepared on titanium alloy surface by micro-arc oxidation technology to improve the difficulty of recovery and utilization of powder catalysts.Manganese was modified by liquid phase doping to further improve the catalytic activity and p H application range of iron oxide catalysts.The surface morphology and composition of the coating were characterized and studied.The photo-Fenton system was used to further improve the catalytic activity and reusability of the catalyst.The photo-Fenton catalytic activity of the coating was prepared by degradation of phenol.The prepared iron oxide coating was mainly composed ofγ-Fe₂O₃ and amorphous Si O₂,because the complex pore structure had a larger specific surface area,which could provide more potential active sites for catalytic reaction.When the concentration of potassium ferricyanide was 20 g/L and the micro-arc oxidation reaction was 15 min,the photo-Fenton performance of the prepared catalyst was the best.97.1%of 35 ppm phenol could be removed in 90 min,and 77%of phenol could be degraded in 120 min after the sixth cycle.The catalytic activity and p H range of manganese modified iron oxide catalysts had been significantly improved.The main components of the coating wereγ-Fe₂O₃,Mn₃O₄,Ti O₂ and amorphous Si O₂;When the manganese source concentration was 6 g/L and the micro-arc oxidation reaction was 20 min,the photo-Fenton performance of the catalyst was the best,96.8%phenol could be degraded in 10 min,99.1%phenol could still be removed in 40 min after six cycles,and the modified catalyst still had effective catalytic activity under neutral and weak alkaline conditions.The photo-Fenton degradation performance of the catalyst was obviously stronger than that of ordinary Fenton degradation,because the photo-Fenton degradation could produce more·OH.γ-Fe₂O₃ was excited by light to form electrons and holes,and electrons and holes reacted with water and H₂O₂ to form·OH.γ-Fe₂O₃,which will also react directly with H₂O₂ to produce·OH.Because of the synergistic effect of iron ion and manganese ion,the formation rate of·OH in manganese modified catalyst was further improved.The addition of free radical scavengers proved that·OH and holes played an important role in the degradation of photo-Fenton.