Applications in photocatalytic purification of air

Semiconductor-mediated photocatalytic oxidation has received wide interest as a promising technique for remediating environmental pollution. The semiconductor mediated gas-solid heterogeneous photocatalytic oxidation technique provides a promising approach for the purification of air and, in conjunction with air stripping, purification of soils and water that are contaminated with volatile organic compounds (VOCs). Compared to liquid–solid photocatalytic reactions, the gas-phase photocatalytic degradation of organic compounds has much higher reaction rates and photoefficiencies. Most efforts to apply the photocatalytic oxidation process for the destruction of environmental contaminants have focused on purification of water. The effect of water vapor on the rates of oxidation in these systems appears to be system specific. However, if a given VOC requires water for its complete oxidation, water vapor must be present in the feed stream or else the reaction rate will eventually decrease to near zero. In general, increasing the reaction temperature increases the rate of oxidation, although some exceptions have been noted. © 1997 Elsevier B.V.