Study On Magnetic Photo-catalyst Prepared By Dry Particle Coating

A great deal of effort has been devoted in recent years to develop photocatalystswith high activities for practical applications. For water detoxification, mostlyparticles in the nanometer range are used, because of their large specific surface area.In slurry reactors, such materials show excellent performance, but it is difficult andexpensive to separate the catalyst from the treated water. To overcome this drawback,Titania powder has been coated or directly synthesized on supports. Typically, theparticle coating is done by wet-chemical routes. However, wet coating methods havebecome less desirable recently because of environmental concerns over the resultingwaste streams and possible VOC emissions. As an alternative particle coating process,dry particle coating which mechanically coats fine guest onto the surfaces of largerhost particles, without binders or solvents, is investigated.The properties of nano-TiO₂ particles and magnetic fractions were investigated.The influence mechanism of heat treatment and high energy ball mill treatment onnano-TiO₂ particles was analyzed. The physical properties, chemical composition, andelements solubility of magnetic fractions were tested. A novel magnetic photocatalystwas prepared using high energy ball mill as coating device to coat nano-TiO₂ particlesonto the surfaces of magnetic fractions. The surface morphology and elementcomposition of catalyst were investigated by means of Scanning Electron Microscope(SEM), X-ray Photoelectron Spectrograph (XPS). The results show that nano-TiO₂particles can be coated firmly on the supports. Based on the research of the keyparameters affecting the coating, the mechanism of dry particle coating, which coatsnano-guest particles onto the surfaces of micro-guest particles, is discussed.The photocatalytic performance of the composite particles was evaluated in aspecial designed photoreactor. The kinetics of photocatalytic degradation of4-chlorophenol in this step photoreactor was investigated. The photocatalytic activityof magnetic photocatalyst is higher than that of pure crystalline TiO₂. And themagnetic photocatalyst have the advantage of being separated easily from water.Based on the research of this paper, it can concluded that dry particle coating is aviable alternative to wet coating and be used for preparation of photocatalysts whichusing particles as supports. The magnetic photocatalyst, which was prepared by dryparticle coating, has a good prospect for practical application.