Abstract: The photocatalytic degradation of several organic compounds in airstreams was studied at room temperature by using a bed reactor packed with the commercial HZSM-5 and operated in a circulating mode. It was found that the raw HZSM-5 shows an unanticipated photocatalytic activity for oxidating ethylene, bromomethane and methyl orange. XRF and AAS analyses reveal that the photocatalytic activity of the ZSM-5 results from the trace amount of iron impurity in the sample, and the photoactivity is positively related with the content of iron. The primary results of characterization by XRD, DRS, XPS and SPVS suggest that the most of Fe existed in the framework of zeolite and in a tetrahedral coordination. The iron species might be excited by UV irradiation to form a charge transfer excited complex along with the ligands and an electron excited state of Fe 3+, which are responsible for the photocatalytic behavior of zeolites.

Key words: Photocatalysis, Oxidation of ethylene, ZSM-5 zeolites, Iron