Surface fluorination on TiO2 catalyst induced by photodegradation of perfluorooctanoic acid

Author(s): Sara Gatto, Maurizio Sansotera, Federico Persico, Massimo Gola, Carlo Pirola, Walter Panzeri, Walter Navarrini, Claudia L. Bianchi

Source: Catalysis Today
Volume: 241 Pages: 8-14
Published: Mar (2015)
DOI: 10.1016/j.cattod.2014.04.031

ABSTRACT:

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 adegradation mechanism based on two competitive pathways are discussed: photo-redox and beta-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 asurface modification that affects the performances of the catalyst.