Photo-Catalytic Degradation Of Gaseous Pollutant On TiO₂ Film Prepared By Hydrothermal Method

The photo-catalytic technology which developed rapidly recent years has promoted remove of environmental pollutant. It has experimentally proved that the pohoto-catalyzer TiO2 is good at eliminating almost all kind of organic substance when the catalyzer coexisted with ultraviolet radiation. Lots of methods were studied in for TiO2 preparation. Hydrothermal synthesize was one of methods which was developed recently. It is simply with hydrothermal synthesize to produce high quality TiO2 film which was shaped up in liquid phase and not need the crystallizing heat treatment.Inorganic compounds Ti(SO4)2 and urea were employed to preparing TiO2 film grown on glass leptospira with hydrothermal method. Surface image of the film was shown by SEM, crystallogram by XRD, and wavelength of light absorbing by UV-Light spectrophotometer. It was found that the flim was made up of anatase TiO2 particles which was uniformity and compact. TiO2 film combines strongly with glass leptospira. Acid and alkali resistance of the film were tested, and physical and chemical property was stability. It was found that the product (prepared with Ti(SO4)2 0.5mol/L, urea 1.0mol/L, hydrothermal temperature 200℃, and reaction time 2h) had the highest activity using methylic-orange (MO) as the target degradation object. The hydrothermal mechanism was analyzed at last.Used self-designed reaction container which was filled with the catalyzer, the character of toluene degradation was tested in closed circulation system. It was proved ?that many factors such as velocity of airflow, relative humidity, dosage of catalyzer and initial toluene concentration had effect on toluene remove. It was found that toluene remove efficiency reached 97.9% when initial concentration was 345mg/m3, airflow velocity 5L/min, RH 30%, and catalyzer dosage 300g. The middle reaction product was detected by GC/MS and the result showed that no other incomplete reaction product in gas phase was exist. The result was coincided with present conclusion that intermediate reaction product was adsorbed strongly by TiO2. At last, catalyst service life was tested and the result showed that catalyst activity reduced from 58% to 51.2% when it was used repeatedly for toluene which initial concentration is 6.90mg/L in 4 hours.Multi-composed gaseous pollutant, which was made up of formaldehyde, acetone, benzene, and toluene, was also used as degradation object. It was concluded that formaldehyde, benzene, and toluene had the highest degradation efficiency when the airflow velocity was at 5L/min, but acetone at 3L/min. Generally, the degradation rate of many pollutant was higher when they reacted separately than co-exist, except of toluene. It followed that the reaction of TiO2 participated reaction was gas-solid reaction, and it accorded to Langmuir-Hinshelwood kinetic law.