Efficient photocatalytic degradation of perfluorooctanoic acid by bismuth nanoparticle modified titanium dioxide

Perfluorooctanoic acid (PFOA) is potentially toxic and exceptionally stable attributed to its robust C F bond, which is hard to be removed by UV/TiO 2 systems. In this research, bismuth nanoparticle (Bi NP) modified titanium oxides (Bi/TiO 2 ) were synthesized by a simple photochemical deposition-calcination method and were applied as photocatalysts for the first time to degrade PFOA. The removal rate of 50 mg/L PFOA reached 99.3 % with 58.6 % defluorination rate after 30 min of irradiation via a mercury lamp. Bi/TiO 2 exhibited superior performance in PFOA degradation compared to commercial photocatalysts (TiO 2 , Ga 2 O 3 , Bi 2 O 3 and In 2 O 3 ). In addition, Bi/TiO 2 showed high degradation activity under actual sunlight, achieved 100 % removal rate and 59.3 % defluorination rate within 2 h. Bi NPs increase the light trapping ability of Bi/TiO 2 and promote the separation of photogenerated electron-hole pairs via local surface plasmon resonance (LSPR) effect, which results in more photogenerated holes (h + ) and hydroxyl radicals ( OH). Combined with DFT calculations and intermediate detections, the degradation reaction is initiated from the oxidation of the PFOA carboxyl group via h + , followed by the loss of the CF 2 unit step by step with the participation of OH. This work presents a novel approach for the practical implementation of TiO 2 -based photocatalysts to achieve highly efficient photocatalytic degradation of perfluorocarboxylic acids (PFCAs).