Efficient Photocatalytic PFOA Degradation over Boron Nitride
By Lijie Duan, Bo Wang, Kimberly Heck, Sujin Guo, Chelsea A. Clark, Jacob Arredondo, Minghao Wang, Thomas P. Senftle, Paul Westerhoff, Xianghua Wen, Yonghui Song
ES&T L
July 13, 2020
DOI: 10.1021/acs.estlett.0c00434
Concern over water contamination by per/polyfluoroalkyl substances (PFAS) has highlighted the lack of effective treatment approaches. Photocatalysis offers advantages of using ambient conditions for reaction, air as the oxidant, and light as the energy source, but identifying photoactive materials is challenging. Herein, we report that boron nitride (BN) degrades PFOA upon irradiation with 254 nm light. The ability of BN to degrade PFOA photocatalytically has previously been unreported and is unexpected, because its band gap is too large for light absorption. On the basis of scavenger results, we suggest that PFOA degrades in the presence of BN via a hole-initiated reaction pathway similar to the TiO2 case and involves superoxide/hydroperoxyl and hydroxyl radicals. We surmised that defects allow BN to absorb in the UVC range and to photogenerate reactive oxygen species. Sealed batch studies indicated BN was ∼2 and ∼4 times more active than TiO2, before and after ball milling the material, respectively. BN can be reused, showing no decrease in activity over three cycles. BN was active for the photocatalytic degradation of GenX, another PFAS of concern. These findings present fresh opportunities for materials design and for the re-evaluation of other wide band gap semiconductors for PFAS photocatalytic degradation.
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