| The wastewater discharged by coking, oil refining, ammonia and other chemical production processes usually contain phenol organic contaminants. If it was discharged optionally without any treatment, it would cause serious harm to human health. Currently, photocatalysis technology has a good prospect in all the methods of phenol wastewater purification as it takes a lower cost. But photocatalytic oxidation degradation of phenol is usually tested on nanosized TiO2 suspension in aqueous solutions. So the catalysts are easy to run off and hard to recycle. In recent years, magnetic photocatalysts which were prepared using Fe3O4 magnetic materials as support were widely researched. But there were few reports about photocatalysis activity vs. structure of magnetic photocatalysts.In this paper, the Fe3O4 magnetic nanosized particles were prepared by co-precipitation first, and then the core-shell SiO2@Fe3O4 magnetic nanosized particles were synthesized by sol-gel technique using Fe3O4 as the cores and the Na2SiO3 and TEOS as silica sources successively. In the end, the TiO2/SiO2@γ-Fe2O3 magnetic nanosized photocatalysts were prepared by sol-gel technique using SiO2@Fe3O4 particles as supported, the tetrabutyl titanate as Ti sources, and calcined at 300-700℃. The structure of the photocatalyst was characterized by XRD, TEM, VSM, BET and UV-VIS, and the influence of some factors on the structure of photocatalyst was also studied. The photocatalysis performances of TiO2/SiO2@y-Fe2O3 were evaluated under UV irradiation using phenol solution as stimulant wastewater. The influence of the calcinations temperature of the photocatalysts, TiO2 and SiO2 conten in the photocatalysts, photocatalysts dosage, initial concentration of phenol, solution pH value and aeration on the photocatalytic oxidation degradation of phenol, as well as the activity of the photocatalyst recycling and recovery rate were investigated.The best preparation condition of Fe3O4 particles was educed through orthogonal experimental design and the influence of some preparation conditions on the crystallinity of Fe3O4 particles. The condition was that the Fe2+/Fe3+molar ratio was 5:1, solution pH value was 9.0, aging temperature was 50℃, aging time was 3 h and ammonia concentration was 0.6 mol·L-1. The size of Fe3O4 particles prepared under this preparation conditions was about 23 nm, the saturation magnetization was 83.0 emu·g-1, and the surface area was 54.71 m2·g-1. The SiO2@Fe3O4 particles taken on core-shell structure, and the thickness of SiO2 layer was about 9 nm. Fe3O4 core of the TiO2/SiO2@y-Fe2O3 were transformed intoγ-Fe2O3 when they were calcined at 300-700℃. The activity phase of the TiO2/SiO2@γ-Fe2O3 magnetic nanosized photocatalysts calcined at 500℃was the anatase TiO2 which had exhibited the best photocatalytic activity for the photocatalytic oxidation degradation of phenol. The size of TiO2/SiO2@γ-Fe2O3 particles was about 37-50 nm, and the saturation magnetization was 9.5 emu·g-1. It had a good superparamagnetism.The best photocatalytic oxidation degradation condition of phenol was educed through the study of the influence of TiO2 and SiO2 conten, photocatalyst dosage, initial concentration of phenol, solution pH value and aeration on the activity. The COD removal efficiency of phenol could achieve up to 70.9% when the mass fraction of TiO2 and SiO2 was 70% and 11% respectively, the initial concentration of phenol was 0.2 mmol·L-1, the concentration of photocatalysts was 0.5 g·L-1, the pH value was about 7.0, bubble oxygen, the reaction temperature was room temperature and the UV irradiation time was 180 min.When the photocatalysts were used in the first time under the best photocatalytic oxidation degradation condition of phenol, the COD removal efficiency of phenol could achieve up to 70.9%, and the recovery rate could achieve up to 97.0%. After used eight cycles, the COD removal efficiency of the phenol was decreased by 20.1%, and however, the recovery rate could achieve up to 91.0%. It showed a good recyclable performance to photocatalytic oxidation degradation of phenol, which afforded us reference for the photocatalytic treatment of organic wastewater. In other respects, the TiO2/SiO2@γ-Fe2O3 magnetic nanosized photocatalysts doped by Ni2+ or Cu2+ exhibitioned a certain influence on the photocatalytic degradation of phenol.
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