Degradation by hydrothermal liquefaction of fluoroalkylether compounds accumulated in cattails (Typha latifolia)

Per- and polyfluorinated substances with an ether bond (ether-PFAS), such as undecafluoro-2-methyl-3-oxahexanoic acid (GenX), dodecafluoro-3 H-4,8-dioxanonanoate (ADONA) and 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (F-53B), have been widely used to replace conventional PFAS, especially perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). The wide use of ether-PFAS will lead to inevitable release of these chemicals to the environment and cause environmental and human health risks. In this study, we first investigated plant uptake of GenX, ADONA and F-53B by cattails (Typha latifolia), then tested destruction of these chemicals by hydrothermal liquefaction (HTL). The results showed that GenX, ADONA, and F-53B could be taken up and accumulated in cattail tissues. HTL could completely degrade GenX and ADONA in aqueous solutions and in wet cattail biomass at both 250 °C and 300 °C. F-53B, however, was resistant to the thermal treatment. Increasing HTL temperature improved degradation of this chemical by HTL. F-53B in plant biomass had higher removal efficiency, which indicated positive catalytic effect from cattail biomass. With the addition of Ca(OH)2, 100% degradation of F-53B in plant tissues was observed.