Study On Photo-oxidative Degradation Of Organic Wastewater By Two Fe-based Nanocomposites

Photocatalytic oxidation technology has a lot of advantages,such as mild reaction conditions,fast reaction,nonselective oxidation,and the complete mineralization of organic compounds into CO2 and H2O.Therefore,photocatalytic oxidation technology has been widely used in wastewater treatment field.However,there are some disadvantages in photocatalytic oxidation technology,such as narrow range of light response and high carrier recombination rate.In order to solve these problems,it is necessary to modify the photocatalyst.Among the modified catalysts,iron based photocatalysts are popular because of their low cost,simple preparation methods,suitable band gap and wide range of light response.In this work,iron based photocatalysts were used as matrix,iron based nanocomposites were prepared by means of semiconductor composite and pillar,which were used for photocatalytic degradation of phenolic and dye wastewater.The main contents and conclusions are as follows:(1)Popcorn balls-like ZnFe2O4-ZrO2 composite microspheres were prepared by solvothermal method.The structure and morphology of the catalysts were characterized by XRD,SEM,TEM,BET and other means;the optical properties of catalysts were characterized by UV-vis DRS,PL and other means,and used to the photodegradation of 2,4-dinitrophenol simulant wastewater.The experimental results showed that under the visible light,the ZnFe2O4-ZrO2 composite microspheres can degrade 10mg/L of 2,4-dinitrophenol completely in 60min and the degradation rate of ZnFe2O4-ZrO2 is 7.4 and 2.4 times higher than those of ZnFe2O4 and ZrO2,respectively.Free radical capture experiments showed that hydroxyl radical was the main active species produced by photocatalysis,and the possible photocatalytic mechanism was studied.In addition,the ZnFe2O4-ZrO2 composite catalyst has a strong magnetic property and can be easily reused.After five times runs,the photocatalytic degradation performance still remained above 90%.(2)Iron phosphotungstic acid pillared montmorillonite composite catalysts(TPAFe-Mt)were synthesized by hydrothermal method,and the structure and morphology of the catalysts were characterized by XRD,SEM,XRF,BET,FTIR,the optical properties of the catalysts were characterized by UV-vis DRS.The wide XRD displayed the presence of TPAFe crystal in TPAFe-Mt catalysts,small angle XRD displayed iron phosphotungstic acid pllared montmorillonite successfully.Under visible light(X,>420nm)and the presence of H2O2,TPAFe-Mt was used for the photo-Fenton degradation of methyl orange and phenolic compounds(phenol and 2,4-dinitrophenol).The results showed that TPAFe-Mt can completely degrade 40mg/L of methyl orange in 40min,the removal TOC rate was 73.3%at 80min,also exhibited a good ability to degrade phenol compound.The effect of visible light on the degradation reaction was studied by OH radical capture experiment,it was found that the amount of OH produced by photo-Fenton was 3 times than that of Fenton reaction,and the mechanism of photo-Fenton catalysis was studied.After five times cycles,the degradation of methyl orange by TPAFe-Mt catalyst was still as high as 99.1%,and the iron ion only lost 1.01wt%.In addition,the catalyst also has the advantages of easy recovery and utilization.