Destruction of Per- and Polyfluoroalkyl Substances using UVC and Boron Nitride

Photocatalytic oxidation is a promising method for degrading per- and polyfluoroalkyl substances (PFAS), but few studies have explored its efficacy in processes beyond the laboratory scale. In this study, degradation of both perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in a bench scale reactor using boron nitride (BN) as a photocatalyst is reported. In addition, a potential full-scale model for incorporation into existing water treatment facilities is proposed. Preliminary results indicated a 53% defluorination rate after 48 h. Final analytical testing indicates 98% PFOA degradation and 79% PFOS degradation after 48 h. Final concentrations of short-chain perfluorocarboxylic acid byproducts are consistent with the previously hypothesized stepwise degradation mechanism for PFOA and suggest that PFOS may degrade through a similar pathway, beginning with the loss of the sulfonic acid head group. There was evidence of NH3 byproduct forming between 48 h and 72 h, suggesting some hydrolytic breakdown of BN occurred during the photocatalysis. BN can carry out destruction of PFOA and PFOS and likely other PFAS compounds, but its stability in water needs to be studied further and improved.