An Ultraviolet/Boron Nitride Photocatalytic Process Efficiently Degrades Poly-/Perfluoroalkyl Substances in Complex Water Matrices

Hexagonal boron nitride (hBN) is among several semiconductorphotocatalystsshown to degrade poly-/perfluoroalkyl substances (PFAS) in aqueoussuspension when excited by ultraviolet-C radiation (UVC; 254 nm);however, only degradation of perfluorooctanoic acid (PFOA) at ppm-rangeconcentrations has been examined in previous reports, showing relativelylow efficiency. Herein, photocatalytic treatment of PFOA and otherPFAS by hBN was found to be much more efficient than other catalystswhen applied to environmentally relevant concentrations in the ppbrange. The unexpected inverse concentration dependence is likely relatedto the contribution of hydrophobic interactions to PFAS adsorptionon hBN, as are the observed wider operational pH and salinity ranges.When excited with vacuum ultraviolet-emitting lamps (185/254 nm),hBN was also able to degrade perfluorooctanesulfonate (PFOS) throughan unconventional mechanism. Treatment of groundwater contaminatedby aqueous film-forming foams was demonstrated in a 5 L hBN+UVC/VUVphotoreactor, achieving >99% degradation of PFOA in 15 min and65%degradation of PFOS in 1 h. Electrical energies per order of destructionfor PFOA and PFOS therein were 2.7 and & SIM;50 kWh & BULL;m(-3), respectively. The strong performance under a realisticwater matrix and operational conditions suggests that hBN photocatalysiswarrants further research and consideration as a treatment tool forPFAS contamination.

Automated summary

Hexagonal boron nitride (hBN) has been found to be more efficient than other catalysts in photocatalytic degradation of per-/polyfluoroalkyl substances (PFAS), especially at environmentally relevant concentrations. The strong performance of hBN under realistic water conditions suggests its potential as a treatment tool for PFAS contamination.