(265d) Efficient Photocatalytic PFOA Degradation over Boron Nitride

The strong persistence, pervasiveness, and toxicity of perfluorooctanoic acid (PFOA) makes it a recalcitrant contaminant of emerging concern. The C-F bond is hard to be destroyed by chemical processes or biological degradation, leading to the half-life time of PFOA in water around 50 years at neutral pH.^[1] Industrial PFAS removal is normally conducted by active carbon absorption or reverse osmosis, followed by combustion. The extra energy cost and resultant air pollution drive the finding of more environmentally sustainable PFAS treatment technologies. Photocatalysis is a potential method for degrading PFOA in water with air as the oxidant, and light as the energy source, but identifying photocatalysts is still challenging.^[2] Here we report that hexagonal boron nitride (h-BN) degrades PFOA under UV-C illumination. It exhibited 2× faster initial reaction rate than TiO2 P25 at their optimum dosage. This previously unreported ability of BN to photocatalytically degrade PFOA is unexpected because its bandgap is too large to absorb 254 nm (UVC) light. However, defects allow BN to absorb UVC, leading to little absorbance at 254 nm, as confirmed by UV-vis DRS characterization. The reusability of BN for treating PFOA containing simulated drinking water was also tested, showing no decrease in activity over 3 cycles.

[1] Washington J W, Jenkins T M. Abiotic hydrolysis of fluorotelomer-based polymers as a source of perfluorocarboxylates at the global scale[J]. Environmental science & technology, 2015, 49(24): 14129-14135.

[2] Sahu S P, Qanbarzadeh M, Ateia M, et al. Rapid degradation and mineralization of perfluorooctanoic acid by a new petitjeanite Bi3O (OH)(PO4) 2 microparticle ultraviolet photocatalyst[J]. Environmental Science & Technology Letters, 2018, 5(8): 533-538.