Degradation of Carbon-Adsorbed PFAS Using Yttrium Ions

This study presents a PFAS in situ remediation process involving the adsorption, degradation, and recycling of rare-earth ions as catalysts. The concern over environmental contamination and toxicity of perfluoroalkyl and polyfluoroalkyl substances (PFAS) has increased the need for effective remediation techniques. The low concentration of PFAS in the environment requires preconcentration. Adsorption of PFAS onto activated carbon (AC) is an effective approach for removing PFAS from water. However, this approach generates PFAS-saturated AC waste. The PFAS-saturated AC was treated with yttrium metal ions in solvents such as N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAc) at 120 °C to break the C–F bonds in PFAS. This results in extraction of fluorine from PFAS to form yttrium fluoride (YF3). The YF3 is then transformed into yttrium hydroxide Y(OH)3 by boiling it in water under basic conditions. This process results in stepwise chemical transformation of PFAS, including formation of partially defluorinated and substituted intermediates, along with recycled activated carbon, recovered yttrium ions, and sodium fluoride. The proposed mechanism for fluorine extraction from perfluorohexanoic acid involves coordination-assisted C–F bond activation, enabling nucleophilic substitution and partial defluorination rather than complete mineralization.