Photocatalytic degradation of perfluorooctanoic acid with beta-Ga2O3 in anoxic aqueous solution.
Perfluorooctanoic acid (PFOA) is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical (HO*) due to its stable chemical structure and the high electronegativity of fluorine. Photocatalytic reduction of PFOA with beta-Ga2O3 in anoxic aqueous solution was investigated for the first time, and the results showed that the photoinduced electron (e(cb-)) coming from the beta-Ga2O3 conduction band was the major degradation substance for PFOA, and shorter-chain perfluorinated carboxylic acids (PFCAs, CnF2n+i1COOH, 1 < or = n < or = 6) were the dominant products. Furthermore, the concentration of F- was measured by the IC technique and defluorination efficiency was calculated. After 3 hr, the photocatalytic degradation efficiency was 98.8% and defluorination efficiency was 31.6% in the presence of thiosulfate and bubbling N2. The degradation reaction followed first-order kinetics (k = 0.0239 min(-1), t1/2 = 0.48 hr). PFCAs (CnF2n+1COOH, 1 < or = n < or = 7) were detected and measured by LC-MS and LC-MS/MS methods. It was deduced that the probable photocatalytic degradation mechanism involves e(cb-) attacking the carboxyl of CnF2n+1COOH, resulting in decarboxylation and the generation of CnF2n+1*. The produced CnF2n+1* reacted with H2O, forming CnF2n+1OH, then CnF2n+1OH underwent HF loss and hydrolysis to form CnF2n+1COOH.
School of Environmental and Municipal Engineering, Qingdao Technological University, Qingdao 266033, China. zhaobaoxiu@tsinghua.org.cn
Baoxiu
B
Zhao
Mou
M
Lv
Li
L
Zhou
D000693:Anaerobiosis / Q000528:radiation effects; D002210:Caprylates / Q000737:chemistry* / Q000528:radiation effects*; D002384:Catalysis / Q000528:radiation effects; D005466:Fluorocarbons / Q000737:chemistry* / Q000528:radiation effects*; D005708:Gallium / Q000737:chemistry*; D054879:Halogenation / Q000528:radiation effects; D006863:Hydrogen-Ion Concentration / Q000528:radiation effects; D013058:Mass Spectrometry; D010084:Oxidation-Reduction / Q000528:radiation effects; D010782:Photolysis / Q000528:radiation effects; D012996:Solutions; D013997:Time Factors; D014466:Ultraviolet Rays; D014961:X-Ray Diffraction
D002210:Caprylates; D005466:Fluorocarbons; D012996:Solutions; C038863:gallium oxide; C023036:perfluorooctanoic acid; D005708:Gallium