Preparation Of Fe₃O₄ Composites And Its Application In Electrochemical Degradation Of Phenol Wastewater

Phenol wastewater is a hazardous wastewater that is difficult to degrade,and it comes from the petrochemical and pharmaceutical industries.Phenol has serious damage to the human body,such as cancer and teratogenesis.Therefore,the treatment of phenol is imminent.However,traditional methods such as physical adsorption,coagulation,chemical oxidation and biological treatment are likely to cause secondary pollution.Electrochemical oxidation technology is faultless in the treatment of organic wastewater.Electrocatalytic oxidation as an important advanced oxidation technology is widely used in wastewater treatment.Electrocatalytic oxidation is a fleet and valid,environmentally friendly technology that produces hydroxyl radicals(·OH)and H2O2.Electrocatalytic oxidation can degrade organic pollutants into carbon dioxide,water and simple organic compounds.The choice of electrodes in electrocatalytic oxidation technology is extremely important.At present,the research on anode materials has been increasingly mature,but the types of cathode materials are still very simple,mainly carbon materials,while the concentration of H2O2 produced using carbon cathodes is not large.Therefore,we urgently need to develop a highly efficient cathode material that can degrade phenol through the double electron oxygen reduction reaction to generate H2O2 and hydroxyl radicals.In the last few years,Fe3O4 has causeed concern as a cathode material,and we can enhance its catalytic activity by adding rare earth oxide or graphene.The presence of Fe3+/Fe2+ redox couples in Fe3O4 promotes the formation of H2O2 by a two-electron oxygen reduction reaction,which further produces ·OH.In this paper,Fe304-CeO2 and Fe304-graphene catalysts with good stability and high catalytic activity were studied.The Ce3+/Ce4+ electron pair in CeO2 has good oxygen storage and oxygen release properties,and Fe304-Ce02 catalyst has an interaction between Fe304 and CeO2.The catalyst has both Ce3+/Ce4+ and Fe3+/Fe2+ electron pairs,which makes it have great catalytic activities.Graphene has good stability and conductivity,high specific surface area and significant electron transfer ability due to its special structural features.The significant catalytic activity increase of Fe304-graphene is due to the electroconductibility of graphene,which forms a connection with Fe3O4,shows strong electrochemical performance,and is more conducive to the production of H2O2 and-OH.In this paper,Fe304-Ce02 and Fe304-graphene were prepared as catalysts,and use electrochemical oxidation method to degrade phenol.The following four parts are the main research contents:1.The Fe304-Ce02 catalyst was produced and characterized.The effects of different preparation conditions on the catalyst were investigated.The optimal preparation conditions were as follows:calcination temperature was 600?,calcination time was 2h,pH was 12,bath temperature was 60 ?and iron to concrete ratio is 1:1.There is some force between Fe3O4 and CeO2 rather than simply mechanical mixing.The oxygen reduction performance(ORR)of the Fe304-CeO2 catalyst was tested.When the calcination temperature is 700°C,the calcination time is 2 h,the material ratio of iron cerium is 1:1 and the pH is 11,the oxygen reduction performance of the composite material is best.Next,we prepared the Fe304-Ce02 catalyst electrode for electrochemical degradation of phenol.Finally,it was concluded that the catalytic activity of the Fe3O4-CeO2 catalyst doped with Ceo2 is greatly enhanced.When the electrolyte concentration is 0.1moL/L,the current density is 50mA/cm,and the pH is 4,the maximum concentration of H2o2 produced by electrolysis is about 5 1mgL-1,degradation efficiency of phenol can reach 93%.Finally we explored the useful life of the electrode and the mechanism of phenol degradation.The stabilization of the electrode was excellent and-OH is the main active species of the degradation reaction.2.The Fe3O4-graphene catalyst was prepared and characterized.When the doping amount of graphene was 60wt.%,the structure of the catalyst was better.The secondary pores are formed between the Fe3O4 nanoparticles and the graphene sheets,and the Fe3O4 nanoparticles are evenly distributed on the graphene sheets and are connected to each other through the graphene network.The oxygen reduction performance of the Fe3O4-graphene composite catalyst was tested.When the addition amount of graphene is 60wt.%,the oxygen reduction performance of the composite material is best.Then the Fe3O4-graphene catalyst electrode was prepared for the electrochemical degradation of phenol.It was concluded that the catalytic activity of the Fe3O4-graphene catalyst after doping with graphene was greatly enhanced.When the electrolyte concentration was 0.1 mol/L,the current density was 30 mA/cm,and the pH was 4,the electrolytically generated H2O2 reached approximately 55mgL-1,degradation efficiency of phenol can reach 90%.Finally we explored the useful life of the electrode and the mechanism of phenol degradation.The stabilization of the electrode was excellent,·OH is the main active species of the degradation reaction.