Preparation Of Immobilized TiO₂ Photocatalysts And Study On Their Photocatalytic Activity For Degradation Of VOCs

Photocatalysis as an environment friendly technology has attracted much attention and showed great potential in environmental protect applications, especially in the purification of indoor air pollution. Combined with the charactaristcs of the photocatalysts and the supports, the immobilization of nano-size TiO₂ is an ideal material to photocatalytic degredate the VOCs.In this study, foam nickel was chosen as the support for TiO₂ photocatalysts. First, SiO₂ layers, the mesoporous transition layers with large specific surface area, were coated on foam nickel substrate. Then the nano-size TiO₂ layers were coated on. The composite nano-size TiO₂-SiO₂ photocatalysts loaded on foam nickel substrate have high photocatalytic ability. For higher photocatalytic ability, Pt was loading on the composite photocatalysts. All of the composite photocatalysts were tested in static system and dynamic real-time system. The main content and innovation of this work are presented as follow:1. TiO₂ photocatalysts and SiO₂ layers loaded on pre-oxidized foam nickel substrate prepared by sol-gel processes. The composite TiO₂-SiO₂ photocatalysts were tested in static system. Results showed that when the .wavelength was 253.7nm, the light intensity was 400μW/cm2, and the initial concentration of acetaldehyde was 100ppm, the removal ratio of acetaldehyde by composite photocatalysts was 100% after 1.5 hours under the UV light irradiation. After 7 consecutive runs, the photocatalytic activity of composite photocatalysts reduced almost 40%. The composite photocatalysts can be regenerated easily by two methods: 1) Heating at 300℃in muffle 2) washing under pure water followed by dring at 100℃.2. The noble metal Pt was loaded on the composite TiO₂-SiO₂ photocatalysts. Considering the production in factory, the noble metal Pt nano-particles were deposited on TiO₂-SiO₂ surface by heating reduction method (MTiO₂: MPt=1%). Results showed that the photocatalytic activity was enhanced greatly by Pt deposition; the acetaldehyde removal ratio by Pt/TiO₂-SiO₂ composite photocatalysts was two times higher than that of TiO₂-SiO₂. Test of other photocatalysts under the same work conditions were also made, such as the blue foam photocatalyst produced in Japan and the liquid photocatalyst. Results showed the acetaldehyde removal ratios were much lower than Pt/TiO₂-SiO₂ composite photocatalysts. So the Pt/TiO₂-SiO₂ composite photocatalysts will be tested in dynamic real-time system.3. The composite TiO₂-SiO₂ photocatalysts were tested in static system. The influences of different intensity and wavelength on the degradation activity were investigated. It was found that the bactericidal lamp withλ=253.7nm, and the light intensity between 400-450μW/cm2 has the best degradation activity. Therefore, the ultraviolet lamp used in the nano-photocatalytic air purification equipment has the rationg voltage of 15W, the wavelength of 253.7nm and the light sensitivity more than 400μW/cm2.4. Pt/TiO₂-SiO₂ composite photocatalysts were tested in dynamic real-time experimentation equipments. Results showed the rate of degradation formaldehyde is almost 15% in the wind tunnel. In the test house, the photocatalysts can degrade formaldehyde almost 0.1ppm per hour.The TiO₂-SiO₂ composite photocatalysts loaded on foam nickel substrates showed a good degradation activity. The modified composite photocatalysts will be used in the nano-photocatalytic air purification equipment to create more social and economic profits.