Study on photocatalytic degradation of several volatile organic compounds

Abstract

The gas-phase photolytic and photocatalytic reactions of several aromatics and chlorohydrocarbons were investigated. The experimental results revealed that chlorohydrocarbons like trichloroethylene, dichloromethane and chloroform could be degraded through either photolysis or photocatalysis under irradiation of germicidal lamp, and the elimination rate of chlorohydrocarbons through photolysis was quicker than that through photocatalysis. UV light from a germicidal lamp could directly lead to degradation of toluene but could hardly act on benzene. The photodegradation rate for these volatile organic compounds (VOCs) through photolysis followed an order: trichloroethylene > chloroform > dichloromethane > toluene > benzene > carbon tetrachloride, and through photocatalysis followed: trichloroethylene > chloroform > toluene > dichloromethane > benzene > carbon tetrachloride. Besides, a series of modified TiO 2 photocatalysts were prepared by depositing noble metal, doping with transition metal ion, recombining with metal oxides and modifying with super strong acid. Activity of these catalysts was examined upon photocatalytic degradation of benzene as a typical compound that was hard to be degraded. It indicated that these modification methods could promote the activity of TiO 2 catalyst to different extent. The apparent zero-order reaction rate constant for degrading benzene over SnO 2/TiO 2 catalyst had the highest value, which was nearly three times as that over P25 TiO 2. But it simultaneously had the lowest rate for mineralizing the objective compound. In spite that Fe 3+/TiO 2 catalyst behaved slightly less active than SnO 2/TiO 2 for degradation of benzene, the mineralization rate over Fe 3+/TiO 2 was the highest one among the prepared catalysts.