Efficient photocatalytic degradation of some model perfluoroalkyl substances over a Bi/TiO2 photocatalyst

A Bi/TiO2 catalyst was prepared via hydrothermal synthesis methods and characterised using a range of techniques, which confirmed the synthesis, loading, shape and nature of Bi (both Bi0 and Bi3+), as well as enhanced visible light absorption following Bi incorporation. The photocatalytic performance was evaluated in the degradation of a range of perfluorinated compounds in aqueous solutions. Levels of degradation and defluorination are reported. Bi0 on the material was converted to BiOCl in situ generating a more active catalytic phase and the progress of this conversion has been tracked using XRD. The post-reaction material was reused five times without a decline in efficiency. The generation of shorter-chain carboxylic acid intermediates following degradation of longer chain acid substrates was confirmed while in complementary experiments it was shown that the shorter-chain acids exhibit greater resistance to photocatalytic degradation than the longer chain analogues. Scavenger studies showed that O2•− and h+ act as the predominant reactive species in this reaction.