LAUSR

Per- and polyfluoroalkyl substances (PFAS) are persistent, bioaccumulative pollutants found in water resources at concentrations harmful to human health. Whereas current PFAS destruction strategies use nonselective destruction mechanisms, we found that perfluoroalkyl carboxylic acids (PFCAs) could be mineralized through a sodium hydroxide–mediated defluorination pathway. PFCA decarboxylation in polar aprotic solvents produced reactive perfluoroalkyl ion intermediates that degraded to fluoride ions (78 to ~100%) within 24 hours. The carbon-containing intermediates and products were inconsistent with oft-proposed one-carbon-chain shortening mechanisms, and we instead computationally identified pathways consistent with many experiments. Degradation was also observed for branched perfluoroalkyl ether carboxylic acids and might be extended to degrade other PFAS classes as methods to activate their polar headgroups are identified. Description Forever chemicals’ Achilles’ heel Per- and polyfluoroalkyl substances (PFAS) have been referred to as “forever chemicals” because of their resistance to most biological and chemical degradation mechanisms. Most current methods use very harsh conditions to decompose these compounds. Trang et al. found that there is a potential weak spot in carboxylic acid–containing PFAS: Decarboxylation in polar, non-protic solvents yields a carbanion that rapidly decomposes (see the Perspective by Joudan and Lundgren). The authors used computational work and experiments to show that this process involves fluoride elimination, hydroxide addition, and carbon–carbon bond scission. The initial decarboxylation step is rate limiting, and subsequent defluorination and chain shortening steps occur through a series of low barrier steps. The procedure can accommodate perfluoroether carboxylic acids, although sulfonic acids are not currently compatible. —MAF Mechanistic insights into a decarboxylation–defluorination pathway inform methods for perfluorocarboxylic acid mineralization.