Perfluorooctanoic acid degradation in the presence of Fe(III) under natural sunlight

• Published in: Journal of hazardous materials 2013-11, Vol.262, p.456-463
• Main Authors: Liu, Dandan, Xiu, Zongming, Liu, Fei, Wu, Gang, Adamson, Dave, Newell, Charles, Vikesland, Peter, Tsai, Ah-Lim, Alvarez, Pedro J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Biological and physicochemical phenomena; Caprylates - chemistry; Caprylates - radiation effects; Chemical engineering; Defluorination; Environmental Restoration and Remediation; Exact sciences and technology; Ferric Compounds - chemistry; Fluorocarbons - chemistry; Fluorocarbons - radiation effects; Hydrogen Peroxide - chemistry; Iron; Natural water pollution; Oxidants - chemistry; PFOA; Photolysis; Pollution; Radical; Reactors; Sodium Compounds - chemistry; Sulfates - chemistry; Sunlight; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - radiation effects; Water treatment and pollution
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2013.09.001

•PFOA was photo-chemically decomposed in the presence of Fe(III) and natural sunlight.•An alternative reaction pathway involves hydroxyl radical as confirmed by EPR.•Common oxidant-persulfate increased PFOA defluorination extent. Due to the high bond dissociation energy (BDE) of CF bonds (116kcal/mol), perfluorooctanoic acid (PFOA) is a highly recalcitrant pollutant. Herein, we demonstrate a novel method to decompose PFOA in the presence of sunlight and ferric iron (Fe(III)). Under such conditions, 97.8±1.7% of 50μM PFOA decomposed within 28 days into shorter-chain intermediates and fluoride (F−), with an overall defluorination extent of 12.7±0.5%. No PFOA was removed under visible light, indicating that UV radiation is required for PFOA decomposition. Spectroscopic analysis indicates that the decomposition reaction is likely initiated by electron-transfer from PFOA to Fe(III), forming Fe(II) and an unstable organic carboxyl radical. An alternative mechanism for the formation of this organic radical involves hydroxyl radicals, detected by electron paramagnetic resonance (EPR). The observation that PFOA can be degraded by Fe(III) under solar irradiation provides mechanistic insight into a possibly overlooked natural attenuation process. Because Fe(III) is abundant in natural waters and sunlight is essentially free, this work represents a potentially important step toward the development of simple and inexpensive remediation strategies for PFOA-contaminated water.