Photo-Fenton defluoridation of pentafluorobenzoic acid with UV-C light

Photocleavage of CF bond in pentafluorobenzoic acid (PFBA) has been carried out using ferrous sulphate/ferrioxalate with H2O2 and UV light. The defluoridation was monitored by the ionometer with fluoride ion selective electrode. The rate of photodefluoridation is higher with the light of 254 nm than with 365 nm. Ferrioxalate process is more efficient than ferrous photo-Fenton process. The effects of various experimental parameters such as pH, initial H2O2, Fe2+, Fe3+, initial PFBA concentration and airflow rate have been investigated. The addition of TiO2-P25 to these processes strongly influenced the defluoridation of PFBA. The GC–MS analysis of PFBA solution after irradiation with photo-Fenton processes reveals the formation of pentafluorobenzene, pentafluorophenol and tetrafluoroquinone as intermediates. The optimum operating conditions for efficient defluoridation are reported.