Sonication-assisted photocatalytic decomposition of perfluorooctanoic acid.
Decomposition of perfluorinated chemicals is of significant interest in both scientific and industrial perspectives. Here, we report the decomposition of perfluorooctanoic acid (PFOA) under sonication-assisted photocatalysis by utilizing commercial TiO(2) (RdH) and home-made TiO(2) (sol-gel) as photocatalysts at ambient temperature, pressure and near neutral pH with the irradiation of 254nm UV light. PFOA was decomposed into fluoride ions and to several perfluorinated carboxylic acids (PFCAs) with a shorter carbon chain length such as perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropropanoic acid (PFPA), and trifluoroacetic acid (TFA). The efficiency of sonication-assisted photocatalysis was found to be 64%. In all the cases, higher efficiencies were obtained when sol-gel TiO(2) was used as a photocatalyst than the commercial RdH TiO(2) catalyst. The specific surface area is three times higher for sol-gel TiO(2) than commercial RdH TiO(2) and appears to be the probable reason for the observed differences in the corresponding efficiencies. It is also interesting to note that pH plays a determining role in the decomposition of PFOA and correspondingly photocatalyses were carried out under different controlled pH. Perfluoroalkyl radicals are presumably oxidized by superoxide and hydroxyl radicals generated during the TiO(2)-mediated photocatalysis at pH 4 and 10, respectively. The role of sonication in sonication-assisted photocatalysis was construed to be an aid to photocatalysis than a tool itself. Sonication enhances photocatalysis through physical dispersion of TiO(2) and eases mass transfer which keeps on rejuvenating the TiO(2) surface.
Panchangam
Sri Chandana
SC
Graduate Institute of Environmental Engineering, National Taiwan University, 71-Chou-shan Road, Taipei 106, Taiwan.
Lin
Angela Yu-Chen
AY
Graduate Institute of Environmental Engineering, National Taiwan University, 71-Chou-shan Road, Taipei 106, Taiwan.
Tsai
Jia-Hong
JH
Graduate Institute of Environmental Engineering, National Taiwan University, 71-Chou-shan Road, Taipei 106, Taiwan.
Lin
Cheng-Fang
CF
Graduate Institute of Environmental Engineering, National Taiwan University, 71-Chou-shan Road, Taipei 106, Taiwan. Electronic address: cflin@ntu.edu.tw.
D002210:Caprylates / Q000032:analysis* / Q000378:metabolism; D002384:Catalysis; D052918:Environmental Restoration and Remediation; D005466:Fluorocarbons / Q000032:analysis* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D010777:Photochemistry / Q000379:methods*; D013010:Sonication; D014025:Titanium / Q000737:chemistry; D014466:Ultraviolet Rays
D002210:Caprylates; D005466:Fluorocarbons; C009495:titanium dioxide; C023036:perfluorooctanoic acid; D014025:Titanium