Study On Odorous Gas Photocatalytic Degradation With Titanium Dioxide

Photocatalytic technology with titanium dioxide has high application value in the field of air purification, but when it comes to the removal of odorous gas containing sulfur and nitrogen, this technology is faced with many problems, such as rapid deactivation of the catalyst and second pollution of sulfur dioxide and nitrogen oxides. Therefore, to achieve a stable gas purification method, it is necessary to study the titanium dioxide inactivation rate and utilization ratio, and enhance the oxidation, adsorption and catalytic activity of photocatalytic reaction system.In this paper, titanium dioxide film was loaded on compact stainless steel net as photocatalyst, the utilization and deactivation rate of titanium dioxide in the photocatalytic removal of hydrogen sulfide or sulfur dioxide was studied. The mechanism of photocatalytic oxidation was analysed, the catalyst deactivation rate and utilization ratio were defined to measure the stability of photocatalysis. The influence of oxygen volume fraction, the target pollutant initial volume fraction, reaction temperature, relative humidity on the reaction stability was researched. Results shows that:the removal of hydrogen sulfide or sulfur dioxide is unstable under anaerobic conditions, the stability of photocatalysis were increased at first and then decreased with the increase of oxygen volume fraction, while the main oxidation products of hydrogen sulfide changed from elemental sulfur to sulfur dioxide or sulfate. The catalyst utilization rati decreases with the increase of target pollutants initial volume fraction; the optimum humidity for photocatalysis is about 20%.In order to improve the stability of photocatalytic oxidation, ozone is introduced into the photocatalytic system, and the mechanism of ozone-photocatalysis for hydrogen sulfide or sulfur dioxide removal was studied, the stability of ozone-photocatalysis was investigated considering the input ozone amount, reaction temperature and relative humidity. The results show that:with the increase of ozone amount, stability of the system first increased and then decreased; the most stable ozone-photocatalysis would be achieved when the relative humidity is about 40% and the reaction temperature is 70℃.In order to change the morphology of titanium dioxide and further improve the stability of photocatalysis, hydrothermal ion chelating method was applied to prepare modified titanium dioxide, including CuSO4/TiO2 Cu(NO3) 2/TiO2, ZnSO4/TiO2 and NH4VO3/TiO2. The catalyst morphology was analysed by characterization method of X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, etc.The adsorption ability and photocatalytic stability of the modified titanium dioxide in hydrogen sulfide or sulfur dioxide removal were studied respectively. The results show that:the stability of titanium dioxide photocatalysis could be effectively improved by Cu doping at proper molar ratio; under the same conditions, the stability of Cu(NO3)2/TiO2 for hydrogen sulfide or sulfur dioxide removal is higher than ozone-photocatalysis.In order to study the removal effects of ammonia and nitrogen oxides by photocatalysis, ozone-photocatalysis and CuSO/TiO2 photocatalysis, the mechanism of ammonia or nitrogen oxides photocatalytic reaction were discussed, the stability of the three methods above for ammonia and nitrogen oxides removal were compared. The results showed that:under ozone combination or after titanium dioxide modification by CuSO4, emission of nitrogen oxides could be effectively inhibited, and the stability of reaction system would be improved.