REACTIONS OF HEXAFLUOROBENZENE AND PENTAFLUOROPHENOL CATALYZED BY IRRADIATED TIO2 IN AQUEOUS SUSPENSIONS

Heavily fluorinated aromatic compounds such as hexafluorobenzene (HFB) and pentafluorophenol (PFP) have been mineralized successfully to CO2 and F- ions by irradiating aqueous air-equilibrated suspensions of ti tanium dioxide. Conversion of PFP to tetrafluorohydroquinone (TFHQ) is relatively faster than the conversion of HFB to PFP, indicating the s lower oxidation of fully halogenated aromatics. Several intermediates have been identified and a mechanistic route is proposed for the photo catalyzed transformation, which ultimately leads to mineralization to fluoride and carbon dioxide. This study calls attention to use caution when determining concentrations of tenaciously adsorbed and/or volati le organics when dealing with investigations which purport to demonstr ate loss or mineralization of a given substrate by photocatalytic meth ods.