Decomposition of highly persistent perfluorooctanoic acid by hollow Bi/BiOIF: Synergistic effects of surface plasmon resonance and modified band structures.

Perfluorooctanoic acid (PFOA) is highly stable due to the strong CF bond and extremely difficult to be removed by conventional photocatalysts. In this study, Bi doped BiOIF solid solutions with hollow microsphere structure were prepared through a facile one-step hydrothermal method. Compared with pure BiOI and BiOF, the band gap of the Bi/BiOIF solid solutions was significantly reduced, thus promoting the visible light absorbance. The cavity structure of the BiOIF solid solutions enhanced the surface areas and active sites for reaction. The local electromagnetic field dominated by surface plasmon resonance (SPR) effect of Bi metal on the surface favored the separation of the photoinduced charge pairs. As a consequence, Bi/BiOIF (x = 0.20, the doping amount of fluorine was 20 %) composite displayed the best photocatalytic performance for decomposing PFOA, and 40 mg/L PFOA could be removed within 2 h illumination. The degradation rate constant (k = 0.0375 min) of PFOA by Bi/BiOIF was about tenfold of that by pure BiOI and BiOF. Superoxide radical (·O-) predominated in the degradation of PFOA by Bi/BiOIF, and the possible degradation pathway of PFOA by Bi/BiOIF was proposed. This work provides a highly efficient catalyst for the practical application in removal of highly persistent PFOA.