Research Of Degradation Of Organic Pollutants In Water With H₂O₂ Or K₂S₂O₈ Catalyzed By Reduced CuFe₂O₄

The textile industry produces a large amount of organic dye wastewater,which is harmful to the environment and human beings.Therefore,it is essential to remove organic dyes wastewater effectively.Advanced oxidation processes（AOPs）have shown great potential for the treatment of industrial wastewaters.To facilitate rapid dye removal in oxidation processes,the modified copper ferrite（CuFe₂O₄）was used as catalyst for hydrogen peroxide（H₂O₂）and persulfate（PS）activation to remove methylene blue（MB）and methyl orange（MO）from aqueous solution.Research of the key operating parameters,electron transfering path of the catalyst and the degradation path of organic pollutants can help to understand the catalytic mechanism of R-CuFe₂O₄.It is helpful to enrich the AOPs theoretical foundation and provide an efficient technology for organic plantants removal from wastewater.CuFe₂O₄ was prepared by coprecipitation method and isothermally reduced in a reducing atmosphere（R-CuFe₂O₄）.The physicochemical properties of R-CuFe₂O₄ were characterized with several techniques,including transmission electron microscopy,N₂ adsorption-desorption isotherms,X-ray diffraction,X-ray photoelectron spectroscopy,fourier transform infrared spectroscopy,and magnetometry.The TEM image shows that R-CuFe₂O₄ has a dispersed and fluffy appearance.The specific surface areas of CuFe₂O₄ and R-CuFe₂O₄ are15.6 m²/g and 51.8 m²/g,respectively.The FT-IR spectrum indicates the changes of symmetric stretching vibration peak of Fe-O bonds.It is confirmed by XPS and XRD that the iron and copper in CuFe₂O₄ are reduced to Fe⁰ and Cu⁰.The surface of R-CuFe₂O₄ samples contained 2.2%Fe⁰ and 10.6%Cu⁰ based on XPS analysis.R-CuFe₂O₄ displayed a magnetic property by VSM,which allowed them to be easily separated and collected in practical applications.In the experiments of activating H₂O₂ to degrade MB,the experimental data followed well the first-order kinetic model.The reaction rate of R-CuFe₂O₄/H₂O₂ and CuFe₂O₄/H₂O₂were 0.055 min^-11 and 0.007 min^-1,respectively.The effects of experimental parameters such as pH,catalyst dosage and H₂O₂ concentration were investigated.Quenching experiments and electron spin resonance（ESR）spectroscopy revealed that the main reactive species was hydroxyl radical（·OH）.R-CuFe₂O₄ remained good activity after being recycled five times.The XRD pattern of the catalyst after five cycles showed that crystal phase of the used catalyst was almost the same as that of the fresh catalyst.The characterization and catalytic activity suggested that the enhanced reactivity of R-CuFe₂O₄ was attributed to the high surface area and the presence of Fe⁰/Cu⁰ bimetallic particles on the surface of R-CuFe₂O₄.In the experiments of activating PS to degrade MO,the experimental data followed well the first-order kinetic model,and the reaction rate of R-CuFe₂O₄/PS system was 5.6 times greater than that of CuFe₂O₄/PS system.The key operating parameters such as solution pH,catalyst dosage and PS concentration were investigated.Catalyst stability of R-CuFe₂O₄ was also tested by consecutive reuse cycles.Quenching experiments and ESR spectroscopy revealed that the main reactive species was sulfate radical(SO₄^·-).Intermediate products of MO degradation were determined by liquid chromatography coupled with a high-resolution hybrid quadrupole time-of-flight mass spectrometer（LC-Q-TOF–MS）and the MO degradation pathways were proposed.Based on the analysis of catalytic activity and surface characteristics of R-CuFe₂O₄,the enhanced reactivity of R-CuFe₂O₄ was mainly attributed to rapid corrosion of Fe⁰/Cu⁰ bimetallic nanoparticles by PS.These findings illustrated that the R-CuFe₂O₄/H₂O₂ system or R-CuFe₂O₄/PS system may be an efficient technology for organic plantants removal from wastewater.