Shape-controlled Synthesis Of ?-Fe₂O₃ And FeWO₄ And Their Photocatalytic Properties For Degradation Of Pollutants

Fenton is one of the advanced oxidation technologies,which has been valued due to high efficiency,low cost and easy operation.However,the classical homogeneous Fenton reaction was limited by some disadvantages,such as outflow of the iron ions and large amount of iron sludge.Heterogeneous iron-based catalysts have wide application prospects because the catalysts are stability and it have the low concentration of the iron leaching.In the study,the burger-like ?-Fe₂O₃ catalysts and FeWO₄ nanosheets with the different percentage of {001} facet exposure were prepared by a simple hydrothermal method,the photo-Fenton catalytic activity of the as-prepared catalysts was evaluated by degrading pollutant under the heterogeneous photo-Fenton system.The main research work is as follows:?1?The well-crystallized burger-like ?-Fe₂O₃ has been successfully synthesized by a simple hydrothermal method.The as-prepared catalyst was analyzed by phase and morphology using a variety of characterization techniques.The results showed that the morphology of ?-Fe₂O₃ was burger and the surface of ?-Fe₂O₃ was rough.Based on the time-dependent hydrothermal synthesis of burger-like ?-Fe₂O₃,the probable formation mechanism of the burger-like ?-Fe₂O₃ was proposed.?2?The burger-like ?-Fe₂O₃ showed the best photo-Fenton catalytic activity for the degradation of ARG in the ?-Fe₂O₃/H₂O₂/visible system.The burger-like ?-Fe₂O₃ have the largest specific surface area and it's beneficial to adsorb pollutant molecules,which exhibited the best photo-Fenton catalytic performance.Under the optimum operating conditions,the burger-like ?-Fe₂O₃ catalyst exhibited 98% degradation efficiency and 62% removal rate of COD for ARG in aqueous solution.In addition,the burger-like ?-Fe₂O₃ catalyst still remained high catalytic activity after six cycling experiments,and the leached iron value accounted for only 0.32 wt‰ of the iron content in the catalyst.The photocatalytic mechanism was analyzed by monitoring the active radicals.?3?The {001} facet exposure percentage of FeWO₄ nanosheets was 97% and 52%have been successfully synthesized by a simple hydrothermal method?the two new samples were correspondingly called FW-97 and FW-52?.The as-prepared catalyst was analyzed by phase and morphology using a variety of characterization techniques.The results showed that the morphology of FeWO₄ was sheets.The degradation experiment showed that FW-97 exhibited the higher degradation ratio of ARG andCr???than FW-52.The higher density of surface Fe atoms on the {001} facet compared to that of the {110} facets,indicating that the {001} facet easily generates more active sites,which was favorable for the reaction rate.The results indicated that the FW-97 have the higher photocatalytic activity than that of FW-52.?4?The photocatalytic activity of FW-97 could still be excellent over a wide p H range from 2.2 to 9.6 in FW-97/oxalic acid/visible system.In addition,FW-97 has good catalytic activity on methyl orange,rhodamine B,4-nitrophenol and tetracycline.What's more,the reduction of Cr???to Cr???occurred in FW-97/oxalic acid/visible system.FW-97 catalysts still remained high catalytic activity after six cycling experiments,and the leached iron value accounted for only 0.2 wt% of the iron content in the catalyst.A photocatalytic mechanism was analyzed by the radical species trapping experiments.The burger-like ?-Fe₂O₃ and FeWO₄ nanosheets were synthesized and used as the heterogeneous catalysts for the degradation of organic contaminants in this study.The reasons for the differences in the catalytic performance between different catalysts were analyzed.The heterogeneous catalysts exhibited good degradation effect of ARG,this study has important reference value for efficient degradation of pollutants.