Sonication-assisted photocatalytic decomposition of perfluorooctanoic acid

Photocatalytic decomposition of perfluorooctanoic acid by iron and niobium co-doped titanium dioxide

“…At pH 6-7, TiO 2 has a neutral or zero point charge and exists in the solution as Ti-OH. TiO 2 assumes the Ti-OH 2 + form in acidic solution; while in alkaline conditions it is present in the form of TiO − [8]. TiO 2 doped with 0.3 mol% of Fe had been reported to have a point of zero charge (pzc) of 7.2 [23].…”

“…While a considerable amount of PFOA was degraded, these methods require extreme reaction conditions such as very low pH or high pressure. TiO 2 -mediated heterogeneous photocatalysis of PFOA and other perfluorinated compounds under relatively mild conditions have been reported using pure TiO 2 and various light sources [7,8], also the investigation on the degradation of a perfluorinated surfactant by gliding arc discharge, with reactive radicals generated by TiO 2 light activation as major agents of decomposition [9]. TiO 2 doped with platinum had been applied to the defluoridation of pentafluorobenzoic acid [10], with the enhanced photo-activity attributed to the electron trapping mechanism of Pt.…”

Effects of pH on photochemical decomposition of perfluorooctanoic acid in different atmospheres by 185nm vacuum ultraviolet

“…Recent studies have demonstrated that high-frequency ultrasonication (Moriwaki et al, 2005;Vecitis et al, 2008;Panchangam et al, 2009a), microwave-induced persulfate (Lee et al, 2009(Lee et al, , 2012, electrochemical method (Guan et al, 2007;Zhuo et al, 2011), and photochemical and photocatalytic methods based on 185 nm VUV or 254 nm UV (Chen et al, 2007;Cho, 2011;Giri et al, 2011aGiri et al, , 2011bGiri et al, , 2012Li et al, 2012;PhanThi et al, 2013;Hori et al, 2004Hori et al, , 2005Dillert et al, 2007;Wang et al, 2008;Wang and Zhang, 2011;Panchangam et al, 2009b;Huang et al, 2007;Park et al, 2009) can degrade PFOA in a stepwise way. In oxidative processes, generally an electron transfers from PFOA to some excited active species, such as sulfate radical anion (SO 4 U− ) (Lee et al, 2009;Hori et al, 2005), carbonate radical anions (CO 3 U− ) (PhanThi et al, 2013), photogenerated holes (Li et al, 2012;Panchangam et al, 2009b) and PFOA complexes (Wang et al, 2008;Wang and Zhang, 2011), and then a perfluoroalkyl radical is formed after decarboxylation of PFOA.…”

The effect of oxygen in the photocatalytic oxidation pathways of perfluorooctanoic acid

“…In particular, the role of oxygen, the concentration trends of the degradation It is commonly recognized that the PFOA degradation mechanism is initiated with the excitation of titanium dioxide caused by the irradiation of UV light [29,36,66]; after being excited by UV radiation (Fig. 5 -Reaction A c c e p t e d M a n u s c r i p t…”

“…It is important to notice that the shorter-chain acids formation during PFOA decomposition observed at the beginning of the reaction and the presence of TFA and PFPrA after 30 minutes (Fig. 2-B) cannot be ascribed to the generally accepted photo-redox consecutive C n → C n-1 chain length decrease mechanism [29].…”