Surface fluorination on TiO2 catalyst induced by photodegradation of perfluorooctanoic acid

• Photoabatement of PFOA solutions with TiO2 slurry.
• HPLC–MS analysis to determine the intermediates of PFOA degradation.
• XPS analyses of TiO2 to monitor surface variations induced by fluoride ions.

The photoabatement of perfluorooctanoic acid in aqueous solution has been performed with a commercial nano-sized TiO2-based photocatalyst content of 0.66 g/L under an UV irradiation of 95 W/m2. PFOA degradation intermediates were investigated by HPLC–MS and 19F-NMR analysis. Evidences of a degradation mechanism based on two competitive pathways are discussed: photo-redox and β-scission pathways. Shorter perfluorinated carboxylic acids, CnF2n+1COOH (n = 1–6), as expected degradation intermediates, were identified and their concentration trends over time were determined. The apparent pseudo-first order kinetic constant expressed as rate of PFOA disappearance was also measured: kapp 0.1296 h−1. The influence of fluoride ions on TiO2 surface was analyzed by XPS technique, revealing a surface modification that affects the performances of the catalyst.

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