Synthesis And Photocatalytic Performance Of Magnetic Visible-light-induced Nano-Composite Catalyst

In the development and application of solid-liquid photocatalytic systems,two key problems should be paid attention to.One is the enhancement of the photocatalytic activity and the other is the separation,recovery,and reuse of the catalysts.Composites of two metal oxides,which are of metal-to-metal charge transfer character(MMCT),areconsidered to be effective photo absorbent and photo-inducing agents which can be used as catalysts for redox reaction of organic compounds in visible light.It is newly developed hot field to prepare novel catalyststo meet the actual demands of the degradation of organic pollutants by choosing a suitable pair of metals for constructing MMCT.Immobilization of photo-induced catalytic species onto nano-magnetic particles will facilitate the separation of catalysts with the utilization ofmagnetic feature and the recovery of the catalytic activity.On the basis of related literatures,SiO₂-Fe₃O₄ nanoparticle composite with core-shell structure was prepared in Stober way.And Ti⁴⁺/Mⁿ⁺(MMCT)was assembled on the magnetic SiO₂-Fe₃O₄ nanoparticles.The resultant magnetic nanocomposites were characterized with XRD,TEM,UV-Vis spectrum and IR spectrum.The photocatalyticperformance of the resultant materials was investigated by using thedegradation of phenol and methylene blue under visible light as themodel reactions.Concrete contents of this work are as follows:1,This dissertation reviewed the properties and thesynthetic methods of nanoparticles,the developments ofphoto-induced catalytic materials and their applications inthe field of the degradation of organic pollutants.2,SiO₂-Fe₃O₄ nanoparticle composite with core-shell structure was prepared in Stober way.And Ti⁴⁺/Sn²⁺(MMCT)was assembled on the magnetic SiO₂-Fe₃O₄ nanoparticles.The resultantnanocomposite was characterized XRD,TEM,UV-Visspectrum and IR spectrum..The photo-catalyticperformances of the materials were characterized byphenol degradation.The results show that the obtainedcomposites have the nanoparticle morphology(80 nm)and respond well to the magnetic field.Under visiblelight,the composite exhibits relative strong MMCT absorption.When Sn/Ti-SiO₂-Fe₃O₄ composite with Sncontent of 4 wt% was used as catalyst,83.96% of phenolin aqueous solution of pH=4 was degraded whileirradiated with sunlight at room temperature inpresenting of O₂.3,Ti⁴⁺/Ce³⁺ was assembled on the magnetic SiO₂-Fe₃O₄ nanoparticle.The obtained nanocomposites were characterized in the same way as above.The Thephoto-catalytic performances of the materials in theoxidation degradation of phenol under differentconditions were examined.The research shows that the obtained composites respond well to magnetic field andare highly capable to catalyze the oxidation degradationof phenol in aqueous solution under visible light.Byusing Ce/Ti-SiO₂-Fe₃O₄ composite with Ce content of 2wt%,91.43% of phenol in aqueous solution of pH=4 wasdegraded while irradiated with sunlight at room temperature in presenting of O₂.The catalytic activity ofnanocomposites are easy to be recoveried and thus thecatalyst could be reused. 4,The Ce/Ti-SiO₂-Fe₃O₄ nanocomposites was also used as a catalyst in the photodegradation of methylene blue under visible light.The effects of the initial concentration of methylene blue,the concentration of H₂O₂ and the pH value on the photodegradation of methylene blue performance were studied.The results show that theoptimum conditions for the visible light induceddegradation of methylene blue in aqueous solution arepH=8,the initial concentration of methylene blue is 60mg/L,and the concentration of H₂O₂ is 1.5 mL/L.The catalytic activity retained well after the catalyst beingreused for 3 times.