Magnetic Field Effect On The Process Of Gas-solid Phase Photocatalysis

To improve the low quantum efficiency of TiO₂ is one of the most important questions in the field of photocatalysis research. Our laboratory firstly reported that a magnetic field enhanced the efficiency of photocatalytic degradation of benzene when it was applied on the process of photocatalysis. The paper, on the base of this work, systemically studied the magnetic field effect on photocatalytic degradation of benzene, ethylene and tert-butyl alcohol over Pt/TiO₂ in order to understand for the fundamental reason of the magnetic field effect. Titanium dioxide sol was synthesized by a sol-gel techqique. Platinized titania (Pt/TiO₂) which was used in the study was prepared by an impregnation method and then reduction with NaBH₄. The crystal phase and the average crystal size of the catalyst sample were characterized by XRD. The photoabsorption of the sample was measured by DRS. A fixed bed quartz cylindrical microreactor in a downflow mode, which equipped with an on-line GC, was used to investigate the influence of magnetic field on the degradation reaction of the reactants. In order to make clear the magnetic field effect, the magnetic field intensiy was measured by a Gauss meter; the intensity of UV light by a Nim Sun UV meter, the efficient power of the UV light by digital power meter, and the wavelength distribution of the UV light by a Fulorescence Spectrometer. The results were obtained as following: (1) the effect of magnetic field on the photodegradation of benzene, ethylene and tert-buty alcohol depended on the react apparatus. When the UV lamp was putted nearly to magnetic field or under magnetic field, the applied magnetic field could evidently increase the photocatalytic conversion of benzene and ethylene, and the yield of CO2. However, the effect from magnetic field was no evident when the UV lamp was far away from the magnetic field and light was transmitted by the fiber. (2) The magnetic field strongly affected the photo intensity of UV lamp when it was under a magnetic field. The higher the manetic field, the larger was the effect. But, the distribution of the emitting wavelength of UV lamp didn't depend on magnetic field intensity. (3) The accelerations of magnetic field to photocatalytic degradation of benzene and ethylene was mainly because that magnetic field increase the emitting light intensity of UV lamp. The increase of light intensity, which resulted in both more strong photoabsorption of catalyst and increace of the reaction temperature, made the conversion of the pollutants increase. (4) The effect of temperature was more important than that of light intensity for the magnetic field –photocatalytic process. It is very intresting that the paper found that the acceleration of magnetic field to photocatalytic degradation of benzene and ethylene was mainly because magnetic field enhanced the light intensity.