Reductive defluorination of perfluorooctanoic acid by titanium(III) citrate with vitamin B12 and copper nanoparticles

• Published in: Journal of hazardous materials 2017-10, Vol.340, p.336-343
• Main Authors: Lee, Yu-Chi, Chen, Yi-Pei, Chen, Meng-Jia, Kuo, Jeff, Lo, Shang-Lien
• Format: Article
• Language: English
• Subjects: Catalytic defluorination; Copper nanoparticles; Perfluorooctanoic acid; Reductive defluorination; Vitamin B12
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2017.06.020

[Display omitted] •Reductive defluorination of PFOA using titanium(III) citrate with vitamin B12 and Cu0 was investigated.•The combination of B12 and Cu0 generate extraordinary reactive radicals for PFOA removal.•The performance of reductants for PFOA removal was titanium(III) citrate≫nano zero-valent Iron>NaBH4.•Mechanisms of PFOA hydrodefluorination through sequential electron transfer pathways were proposed. Perfluorooctanoic acid (PFOA) is widespread in the environment, which causes serious health and safety concerns. A mechanistic study on reductive defluorination of PFOA by titanium(III) citrate in the presence of catalysts was conducted. Vitamin B12 was used to catalyze reduction reactions by shuttling electrons from a reducing agent (electron donor) to PFOA to produce a Co-carbon bond intermediates. In the presence of copper nanoparticles, a precursor complex, B12-C7F14COOH, adsorbed on the metal surface, followed by a hydrogenolytic reaction to form less-fluorinated products. The synergistic effect between vitamin B12 and copper nanoparticles enhances the reductive activities by electron-transfer reactions and hydrogenolysis. The efficient reduction of PFOA to less-noxious compounds was demonstrated with a copper dose of 2gL−1, titanium(III) citrate (45mM), and vitamin B12 (0.2mM) with an initial pH of 9.0 and 70°C. In this anoxic aqueous solution, the biomimetic reductive system effectively removed 65% of PFOA. The mass balance on fluoride matched the observed degradation of PFOA, while no short-chain intermediates were detected.