Study On The Preparation,Characterization And Electro-Fenton Oxidation Performance Of Fe₃O₄@ZIF-8 Core-Shell Materials

Antibiotics wastewater and dyeing wastewater without complete treatment were discharged into surface water,causing serious water pollution and threatening human health at the same time.These pollutants have large molecules and high biological toxicity and they are refractory,which means traditional biological method cannot meet the requirement.Therefore,Fenton technology gains a lot of attention due to it can generate H₂O₂ in-situ and produce?OH which can degrade nearly all contaminants.Cathode material is the key to Fenton technology,and porous carbon materials that have low cost,huge specific surface area and good H₂O₂yield,are the excellent choice used as Electro-Fenton cathode.At the same time,instead of adding solution containing ferrous ions directly which may need strict degradation conditions and produce iron mud and so on,solid catalysts which can reduce iron loss and recycle easily is a good choice.And study found that porous MOF can accelerate the oxygen transfer to prompt two-electron oxygen reduction reaction.In this work,Fe₃O₄@ZIF-8/CA was used as a cathode to degrade antibiotics and dye wastewater in Electro-Fenton process.First,carbon aerogels and Fe₃O₄@ZIF-8 catalyst were prepared via a sol-gel method and a hydrothermal method respectively.And the catalyst was loaded on carbon aerogels to form Fe₃O₄@ZIF-8/CA electrode.General material characterization methods including scanning electron microscope?SEM?,transmission electron microscope?TEM?,X-ray powder diffraction?XRD?,automatic physical adsorption apparatus?BET?,X-ray photo-electron spectroscope?XPS?as well as electrochemical measurements such as cyclic voltammetry?CV?,electro-chemical impedance spectroscopy?EIS?and rotating disk electro?RDE?were carried out to characterize the morphology,internal structure,composition and oxygen reduction performance of the electrode.The results showed that the prepared carbon aerogels have a three-dimension net structure,high porosity and huge specific surface area with687.14 cm²/g,which is good for two-electron oxygen reduction reaction.And Fe₃O₄@ZIF-8catalyst had a core-shell structure and the shell is quite even.At the same time,Fe₃O₄@ZIF-8on the surface of carbon aerogel is relatively uniform,and electrode with catalyst calcined at750?had best oxygen reduction performance.Secondly,Fe₃O₄@ZIF-8/CA was used as cathode and carbon bar used as anode in Electro-Fenton process to degrade berberine.The result showed that the degradation rate could be 95.1%when the current density was 5 mA/cm²and catalyst loading was 300 mg and catalyst calcination temperature at 750?.The stability of the electrode is good and with three-time repeated use,the berberine degradation rate could still reach 80%.LC-MS was used to detect intermediates and peaks at m/z 338.13,198.12 and 114.09 were found and a possible degradation pathway was put forward.To explore the reaction mechanism,oxygen titanium sulfate spectrophotometry was used to detect H₂O₂ production and the result exhibited that within120 minutes,the H₂O₂ yield could be 134 mg/L.Moreover,EPR spectrum detected a obvious peak intensity ratio of 1:2:2:1,which was the characteristic peak of?OH.Therefore it was concluded that?OH attacked the berberine molecules,and the main degradation pathway was put forward.Finally,the Fe₃O₄@ZIF-8/CA electrode was also used for the degradation of rhodamine B and the optimum conditionof the experiment was pH=7,current density of 6 mA/cm²,catalyst loading of 200 mg and catalyst calcination temperature at 750?.Under the optimun condition,the decolorization rate of Rhodamine B can reach 95.7%within 60 minutes.And electrode stability test showed that the electrode has a good stability,after three-time recycle,the degradation rate can still reach 91%.?OH was found during degradation process via EPR,but degradation mechanism remains to be further explored.