Study On Photocatalytic Degradation Of The Poisonous Aldehyde Gas In Indoor

Degradation of the poisonous aldehyde gas in indoor is of great significance to protecting human health. In this work, a gas-solid photocatalysis reaction technology was applied to this reaction system. A series of coupled-complexes THAP-x were designed and prepared. The surface configuration, energy band position, optical absorption property, chemisorption ability to the reactants and photocatalytic performance of the materials were systematically investigated.HAP was prepared by the hydrothermal method successfully under proper temperature. THAP-x compounds had been successfully synthesized by hydrothermal and ion-exchange methods with different Ti/(Ti+Ca) atomic ratios (xTi).The characterization results by XRD, FT-Raman, IR, ICP, BET, TEM and UV-vis DRS techniques showed that the surface area of these materials were above 100m2/g. The nano-metered crystalline of TiO2 was dispersed well on the surface of materials and the HAP was coupled with TiO2 by Ti -O- P bond when xT i = 0.2.The optical absorption properties and edge energy of the coupled-complexes were investigated by the UV-vis DRS experiments and K-M functions. The results demonstrated that the coupled-complexes had a larger Eg compared to bulk phase, the optical absorption were also enhanced due to the coupled effect. According to these results, the energy band structures of the active species and the matching principles of the Eg in their position were figured out. The different migration patterns and the related redox abilities of the photo-excited electrons and holes were also discussed.The experimental results studied by the TPD-MS techniques indicated that the HAP displayed better chemisorption and activation ability to aldehyde than the TiO2. Under UV illumination, active state·O2 - was created because of the transfer of photogenerated electrons to adsorbed oxygen molecule and H2O can be chemisorbed to forming dissociative states -OH when xTi = 0.2, then produced·OH by photo-excitation.The photocatalytic reaction results showed that the photocatalytic degradation of aldehyde could be carried out over the THAP-x catalysts under UV irradiation (intensity 0.65 mw/cm2, wavelength 365 nm). The reaction performance was closely related to the optical absorption property, chemisorption ability and reaction conditions. Under the reaction conditions of ambient pressure, 35℃, rest time 1.5 min, V (HCHO or CH 3 CHO) / V (78%N2 + 22%O2 ) = 0.003 and the irradiation of UV light, the HCHO or CH3CHO conversion of 89.2% or 82.7%, and the selectivity for CO2 of 92.1% or 75.2% were obtained respectively over the THAP-x with xTi =0.2. Based on the above experimental results, a probable mechanism of photocatalytic degradation of aldehyde was discussed.