Preparation Of Iron Oxide Based Magnetic Photo-fenton Catalysts And Their Performance

The development of an efficient,stable and recyclable catalyst at a wide working pH range is crucial for the practical application of heterogeneous Fenton process.Visible light was found to be effective to improve the efficiency of heterogeneous Fenton process and broaden the range of pH.Narrow band gap semiconductors can generate electrons and holes under visible light irradiation.It is well known that the recombination of electrons and holes is very fast in a narrow band gap semiconductor.In order to promote the separation efficiency of electrons and holes,some nanocomposites were developed.Unfortunately,the difficult separation and sophisticated synthetic procedure of these nanomaterials limit their practical application.Therefore,it is highly desirable to develop a low-cost and effective magnetic Fenton catalyst.In this work,magnetic Iron Oxide Based Photo-Fenton Catalysts were synthesized by one-pot and deposition-precipitation methods.Since different Iron Oxides have different structure and optical properties,a synergistic effect between them might be achieved.Organic pollutants in water,such as antibiotic and dye,are effectively removed by the catalysts.The specific studies include the following two parts:?1?In this chapter,magnetic?-FeOOH/?-Fe₂O₃ nanocomposite was one-pot synthesized by a simple pH gradient method.The correlation between its structure and catalytic performance was investigated.The effects of different reaction parameters on the degradation of TC with?-FeOOH/?-Fe₂O₃ were further investigated.The results indicated that?-FeOOH/?-Fe₂O₃ is an efficient and stable magnetic Photo-Fenton catalyst.The magnetization high value(48 emu g^-1)indicates that the samples can be easily separated by a magnet.The obtained sample was found to be an efficient Fenton catalyst for the degradation and mineralization of tetracycline hydrochloride?TC?over a wide pH range?3-10?under visible light irradiation.The removal efficiency was still above 92%after five cycles.It exhibited higher adsorption capacity towards TC at neutral pH,which facilitates the surface reactions of TC with active species.The contribution of homogeneous reactions can be ignored at neutral and alkaline pH,but increased significantly at acidic pH.The mechanism for H₂O₂ activation by?-FeOOH/?-Fe₂O₃ at neutral pH is quite different from that by FeOOH.In the?-FeOOH/?-Fe₂O₃ photo-Fenton process,?-Fe₂O₃ could act as an electron trap and inhibit the reaction between photogenerated electrons and H₂O₂.Consequently,the production of HO·was reduced,whereas more holes were separated and the production of·O₂^-from the reaction of holes with H₂O₂ was significantly enhanced.TC should be degraded by HO·,holes and·O₂^-.Finally,the intermediates were determined by liquid chromatography-mass spectrometry and a possible pathway for TC degradation was proposed.?2?In this paper,Magnetic?-Fe₂O₃ supported on mesoporous ZnFe₂O₄ was synthesized by impregnation and deposition–precipitation methods.The structure,optical property and photo-Fenton performance catalytic performance of the obtained samples were analyzed by different characterization methods.The effects of pH value,the concentrations of H₂O₂ and Orange II on the degradation efficiency of the system were investigated.The results showed that the obtained?-Fe₂O₃/ZnFe₂O₄ was found to be an effective?stable and recyclable catalyst for the degradation and mineralization of Orange II with H₂O₂ under visible light irradiation,which can be attributed to the enhanced production of HO·and particularly·O₂^-.The catalytic mechanism of?-Fe₂O₃/ZnFe₂O₄ for H₂O₂ activation and the degradation pathway of Orange II were investigated.The result indicates that the loaded?-Fe₂O₃ could capture the electrons in the conductive band of ZnFe₂O₄,thus promoting the formation of·O₂^-from the reaction between H₂O₂ and holes.Meanwhile,the formed Fe^III and electrons could react with H₂O₂ to produce HO·.According to the results of liquid chromatography-mass spectrometry,electron paramagnetic resonance and scavenger experiments,Orange II should be mainly degraded by·O₂^-but not HO·due to the destruction of azo bond,while its intermediates were further mineralized by·O₂^-and HO·.