[Photo-chemical decomposition of perfluorooctanoic acids in aqueous periodate].

The influence of reaction atmosphere and TiO2 on photochemical decomposition of perfluorooctanoic acid (PFOA) in aqueous periodate was investigated using a type of low-pressure mercury lamps emitted at 254 nm. PFOA photolysis was slight with 254 nm light irradiation under nitrogen, whereas significant decomposition PFOA obtained with the addition of IO4-. In addition, oxygen restrained photochemical decomposition of PFOA. In UV/TiO2/IO4- system, PFOA degradation ratio was 54%, 15% lower than that for UV/IO4- system. *OH radicals generated from UV/TiO2 system exhausted a lot of IO4-, resulting in lower degree of IO3* production. IO3* was high reactive radical which great excitated PFOA decomposition. The accumulation of short-chain perfluorocarbonxylic acids (PFCAs) as products were identified with HPLC/MS. PFCAs bearing shorter perfluoroalkyl groups were formed in a stepwise way from PFCAs that bear longer perfluoroalkyl groups.