Facilitating the activation of wide bandgap hexagonal boron nitride via 222 nm far UV-C for efficient photocatalytic degradation of recalcitrant PFAS

UV 222 /hBN exhibited 3-fold higher k PFOA than UV 254 /hBN under equal UV fluence. • UV 222 induced relatively higher C hole than UV 254 with strengthened light activity. • Acidic pH enhanced PFOA adsorption and hole utilization particularly under UV 222 . • UV 222 /hBN demonstrated greater robustness against water matrices than UV 254 /hBN. Hydrophobic hexagonal boron nitride (hBN) has attracted attention as a promising material for the UV-C light-driven photocatalysis of aqueous per - and polyfluoroalkyl substances (PFASs). Far UV-C light centered at 222 nm (UV 222 ) could provide a suitable irradiation source for contending wide band gap of hBN, serving as an alternative to conventional 254 nm UV-C (UV 254 ). This study investigated the first application of a KrCl lamp emitting UV 222 in combination with hBN to degrade perfluorooctanoic acid (PFOA) and compared it with UV 254 under equal UV fluence. UV 222 demonstrated superior hBN activation performance, with UV 222 /hBN exhibiting a higher PFOA degradation rate constant and more extensive chain shortening and defluorination than UV 254 /hBN. These enhancements were attributed to the higher light absorbance of hBN under UV 222, supported by the higher photocurrent response, as well as contributions from direct photolysis. Photogenerated holes were identified as the main reactive species, and their concentration was estimated to be 2.7 times higher in UV 222 /hBN than in UV 254 /hBN. Notably, acidic pH conditions enhanced PFOA adsorption, thereby promoting hole utilization, and the photocatalytic promotion effect was more pronounced under UV 222 than under UV 254 . Moreover, the inhibitory effect of natural water matrix components, including inorganic ions and natural organic matters, was also minimal in UV 222 /hBN. This study demonstrated that far UV-C serves as an effective hBN activation source, offering a viable engineering strategy for the photocatalytic treatment of PFASs. Download: Download high-res image (124KB) Download: Download full-size image