Leveraging molecular mechanisms of desorption to enhance PFAS bioavailability in contaminated soils

• Rhamnolipids (RL) and acetic acids (AA) led to 60-90% desorption of PFAS from soil. • Oxalic and malic acids hindered the desorption of carboxylic PFAS but enhanced that of sulfonates. • RL and organic acids exhibit distinct desorption kinetics across PFAS compounds. • Desorption efficiency of RL and organic acids is concentration- and time-dependent. • Desorption kinetics revealed that RL and AA accelerated the kinetics of slow desorption. Per- and polyfluoroalkyl substances (PFAS) are known for their strong binding properties to soil matrices owing to their amphiphilic properties. While most studies focus on the search for novel PFAS biodegraders, our knowledge of sustainable biomolecules that could drive PFAS desorption and make them more bioavailable is limited. This study investigated the effectiveness of rhamnolipids and organic acids in desorbing PFAS compounds from contaminated soil. Rhamnolipids (25 mg/L) significantly enhanced the release of PFAS compounds from soil, achieving up to 90% desorption. Acetic acid provided 60-90% desorption efficiency for most of the PFAS studied, except for PFDA and three sulfonic PFAS (L-PFBS, L-PFHxS, and L-PFOS), suggesting acid-induced charge modification and reduced sorption affinity. Increasing the concentration of either additive enhanced desorption across all PFAS types, with acetic acid achieving maximum desorption at 0.5 M. Desorption kinetics revealed that rhamnolipids and acetic acid accelerated the kinetics of slow-desorbing PFAS. While oxalic and malic acids hindered the desorption of carboxylic PFAS, they enhanced the desorption of sulfonates. Considering the higher sorption capacity of sulfonates to sediment and soil, with greater potential for bioconcentration, the sorption reversibility of oxalic and malic acids can be harnessed for enhanced remediation of sulfonic PFAS in situations where rhamnolipids and acetic acids are inapplicable. Our findings will potentially stimulate research aimed at identifying suitable biomolecule-producing plants and microbes for enhanced PFAS desorption. Leveraging eco-friendly molecular mechanisms of desorption will complement the activities of novel microbes and facilitate PFAS biodegradation and site reclamation.