Photochemical decomposition of perfluorooctanoic acid mediated by iron in strongly acidic conditions.
The performance of a ferric ion mediated photochemical process for perfluorooctanoic acid (PFOA) decomposition in strongly acidic conditions of pH 2.0 was evaluated in comparison with those in weakly acidic conditions, pH 3.7 or pH 5.0, based on iron species composition and ferric ion regeneration. Complete decomposition of PFOA under UV irradiation was confirmed at pH 2.0, whereas perfluoroheptanoic acid (PFHpA) and other intermediates were accumulated in weakly acidic conditions. Iron states at each pH were evaluated using a chemical equilibrium model, Visual MINTEQ. The main iron species at pH 2.0 is Fe(3+) ion. Although Fe(3+) ion is consumed and is transformed to Fe(2+) ion by photochemical decomposition of PFOA and its intermediates, the produced Fe(2+) ion will change to Fe(3+) ion to restore chemical equilibrium. Continuous decomposition will occur at pH 2.0. However, half of the iron cannot be dissolved at pH 3.7. The main species of dissolved iron is Fe(OH)(2+). At pH 3.7 or higher pH, Fe(3+) ion will only be produced from the oxidation of Fe(2+) ion by hydroxyl radical produced by Fe(OH)(2+) under UV irradiation. These different mechanisms of Fe(3+) regeneration that prevail in strongly and weakly acidic conditions will engender different performances of the ferric ion.
Environmental Research and Management Center, Hiroshima University, 1-5-3 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8513, Japan. Electronic address: mohno@hiroshima-u.ac.jp.
Masaki
M
Ohno
Faculty of Applied Life Sciences, Niigata University of Pharmacy and Applied Life Sciences, 265-1, Higashijima, Akiha-ku, Niigata 956-8603, Japan.
Masataka
M
Ito
Faculty of Applied Life Sciences, Niigata University of Pharmacy and Applied Life Sciences, 265-1, Higashijima, Akiha-ku, Niigata 956-8603, Japan.
Ryouichi
R
Ohkura
Environmental Research and Management Center, Hiroshima University, 1-5-3 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8513, Japan.
Esteban R
ER
Mino A
Faculty of Applied Life Sciences, Niigata University of Pharmacy and Applied Life Sciences, 265-1, Higashijima, Akiha-ku, Niigata 956-8603, Japan.
Tomohiro
T
Kose
Environmental Research and Management Center, Hiroshima University, 1-5-3 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8513, Japan.
Tetsuji
T
Okuda
Department of Chemical Engineering, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan.
Satoshi
S
Nakai
Faculty of Applied Life Sciences, Niigata University of Pharmacy and Applied Life Sciences, 265-1, Higashijima, Akiha-ku, Niigata 956-8603, Japan.
Kuniaki
K
Kawata
Environmental Research and Management Center, Hiroshima University, 1-5-3 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8513, Japan.
Wataru
W
Nishijima
D002210:Caprylates / Q000737:chemistry / Q000302:isolation & purification* / Q000528:radiation effects; D005290:Ferric Compounds / Q000737:chemistry*; D005466:Fluorocarbons / Q000737:chemistry / Q000302:isolation & purification* / Q000528:radiation effects; D006863:Hydrogen-Ion Concentration; D014466:Ultraviolet Rays; D062065:Wastewater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification* / Q000528:radiation effects; D018508:Water Purification / Q000379:methods*
D002210:Caprylates; D005290:Ferric Compounds; D005466:Fluorocarbons; D062065:Wastewater; D014874:Water Pollutants, Chemical; C023036:perfluorooctanoic acid
Acid condition; Decomposition; Ferric ion; Perfluorooctanoic acid; Ultraviolet