| In recent years,wastewater caused by dye pollution is dangerous for the water environment and human health,which leads to wide attention of the society.The heterogeneous Fenton technology has been widely applied to degrade organic pollutants due to its high oxidation efficiency and easy-recycling catalyst.Nevertheless,most heterogeneous catalysts have the disadvantages of low activity and stability.The spinel ferrite materials,such as Fe3O4 and CuFe2O4,show advantages as low cost,environmentally friendly and excellent magnetic performances,which can be used as catalysts in heterogeneous Fenton process.Hollow-structured Fe3O4/SiO2 and CuFe2O4/SiO2 composites were synthesized in the present,which the catalytic activity and stability in Fenton process were significantly enhanced.The main works are listed as the following:1.Fe3O4 hollow microspheres with good dispersibility and high saturation magnetization were synthesized through a facile one-step solvothermal method.Effects of the reaction time and urea amount on the hollow structure were studied.The results turned out that when the reaction time was 16 h,and the urea amount was 40 mmol,the sample possessed the most significant hollow morphology,the largest cavity size and specific surface area,and the saturation magnetization reached 115.4 emu/g.The formation mechanism of the hollow structure was analyzed by studying the structure and morphology of the products prepared by different reaction times.RhB was used as the target pollutant,and H2O2 was added into the reaction system to investigate the photo-Fenton activity of hollow-structured Fe3O4.2.Using hollow mesoporous spheres of SiO2 as the template,Fe3O4/SiO2 composite with double-mesoporous-shelled hollow structure was fabricated through a solvothermal method.In this reaction system,soluble silicate ions were formed through the part of the SiO2 dissolved in the alkaline solution.Fe3+ions tend to absorbed at the inner and outer surfaces of the SiO2 hollow spheres,which induced the as-formed Fe3O4 anchored at the SiO2 surfaces.Subsequently,the double-shelled hollow spheres were generated through little by little dissolution of the SiO2.The as-prepared composite showed excellent photo-Fenton catalytic activity.About 97.2%of RhB was degraded under neutral pH,0.2 g/L of catalyst,and 20 mg/L of RhB with visible light irradiation for 180 min.In addition,the catalyst possessed good magnetic properties,so it can be recycled by magnetic separation and revealed excellent reusability.These results indicated that the as-formed Fe3O4/SiO2 double-shelled hollow spheres show great potentiality in Fenton field.3.The magnetic Cu-CuFe2O4/SiO2 double shelled hollow sphere was synthesized by a facile one-pot solvothermal method,which can be used as an excellent Fenton-like catalyst for methylene blue(MB)degradation.The Cu-CuFe2O4/SiO2(P)composite with uniform distribution of Cu was obtained by adding polyethylene glycol.The catalytic performance of Cu-CuFe2O4/SiO2(P)was better than that of Fe3O4/SiO2 and CuFe2O4/SiO2 composites under the same condition.This is because of the synergistic effect between Fe3+/Fe2+and Cu2+/Cu+ redox pairs.Moreover,the existence of Cu0 was beneficial to the transformation from Fe3+to Fe2+,which promoted the regeneration of Fe2+and favored H2O2 decomposition to produce more hydroxyl radicals.Effects of catalyst dosage,H2O2 dosage,MB concentration and pH value on the catalytic performance were also investigated.The results indicated that the optimal conditions for degrading 50 mg/L of MB solution were 0.2 g/L of catalyst,pH=7.05 and 1mL of H2O2.In addition,Cu-CuFe2O4/SiO2(P)showed high stability and good reusability in the repetitive experiments. |
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