Destruction of Perfluoroalkyl Acids Accumulated in Typha latifolia through Hydrothermal Liquefaction

To investigate whether hydrothermal liquefaction (HTL) could degrade perfluoroalkyl acids (PFAAs) accumulated in plant biomass, we first evaluated degradation of individual and mixed PFAAs in pure aqueous solutions. It was found that all five perfluorocarboxylic acids (PFCAs) were removed completely after 2 h at 300 °C. Three perfluorosulfonic acids (PFSAs) had removal efficiencies of less than 20%. With the amendment of KOH, however, the removal of PFSAs by HTL increased significantly to 85.9 ± 1.2%. HTL also removed PFAAs accumulated in common cattails (Typha latifolia). Regarding PFCAs, nearly 100% disappearance after HTL was observed. Specific to perfluorooctanesulfonic acid (PFOS), one of the PFSAs, the removal of this compound in roots was 98.4%. For shoots, it was 49.7%. These promising results point to the need for further investigation so that HTL can be optimized to handle biomass of plants used for phytoremediation of PFAS.