Ozone-assisted Photocatalytic Degradation Of Gaseous Acetaldehyde/formaldehyde On TiO₂/ZSM-5 Composite Catalysts Modified By Mn Ion

The relationship between the indoor environment and human health is paid great attention in the world. The research report from World Health Organization (WHO) suggested that indoor pollution had become a worldwide problem especially in developing countries. As we know, formaldehyde and benzene are two major indoor air volatile organic pollutants, which are seriously harmful to human health.The hybrid system of ozonization and photodegradation was studied in the present work. The synergism of'adsorption/enrichment-photodegradation/ozonization'was used to efficiently degrade the target pollutants. H-ZSM-5 has a shape-selective adsorption structure. It was modified with Mn-ion by impregnation and ion-exchange in order to improve acetaldehyde degradation in UV-ozone atmosphere. The influence of catalyst structure and surface properties on catalytic activity were investigated. Meanwhile, various ways for loading TiO₂ (P25) to H-ZSM-5 and active carbon support have been employed. The degradation of formaldehyde and toluene was simulated in a sealed test chamber. Following conclusions have been drawn:TiO₂/MnO₂-ZSM-5 prepared by impregnation showed higher activities of acetaldehyde degradation in UV-ozone than the sum of UV and ozone used separately. MnOx introduced in catalysts increased the utilization rate of ozone because more O₂^- and·OH were produced for the acetaldehyde degradation.TiO₂/Mn-ZSM-5 prepared by ion-exchange showed higher activities of acetaldehyde degradation than TiO₂/ZSM-5 in UV-ozone. Mn as a promoter at the surface of the zeolite has a beneficial effect on the reaction rate of ozone and acetaldehyde. Mn mainly enhanced and stabilizes the BET surface area of zeolite. The high activity of TiO₂/Mn-ZSM-5 is due to the synergistic effect of'adsorption/enrichment-photodegradation/ ozone'.All catalysts supported on the activated carbon were detected for the decomposition of formaldehyde and toluene in a test chamber. The results indicated that the degradation activity by ozone- photodegradation coupling was five to ten times higher than that by general method, and the pollutants could be quickly derogated and reached the relevant national environmental standards.