Photodegradation of some Oxygenated Polycyclic Aromatic Hydrocarbons

In order to obtain information about the degradability of oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) in environment, photodegradation in acetonitrile solution was studied on 9,10-phenanthrenequinone, 9-phenanthrenecarbaldehyde (phenanthrene-9-carboxaldehyde) and 1,8-naphthalenedicarboxylic anhydride (1,8-naphthalic anhydride), which are formed by fuel combustion or by photoirradiation of PAHs. A solution of the substrate was irradiated under atmospheric conditions using a xenon lamp. Photodegradation rates and information about products were obtained using HPLC with fluorescence and photodiode array detectors and GC/MS.

9,10-Phenanthrenequinone rapidly degraded by irradiation of light and yielded diphenic acid, diphenic acid anhydride, phthalic acid anhydride and some unknown compounds. Diphenic acid was a main product and it was produced at maximum upon 5-hour irradiation when degradation rate approached 100%. This reaction seems not to obey first-order equation. 9-Phenanthrenecarbaldehyde degraded slower than 9,10-phenanthrenequinone and yielded a polar unknown compound as a main product. While 1,8-naphthalenedicarboxylic anhydride showed quite stable character under irradiation of light.