Per- and polyfluorinated alkyl substances (PFAS) are a group of synthetic organic compounds that are both persistent in the environment and highly mobile through soils and aquifers. In situ immobilization using sorbents is often a preferred technique to remediate contaminated soil due to its simplicity and low cost. Changes in soil physicochemical properties such as pH, redox, or salinity can occur over time, and it is important that any sorbent used for in situ remediations is durable to withstand these environmental perturbations.
Therefore, this study aimed to predict the potential release of PFAS from contaminated soils after remediation with a commercially available PFAS sorbent. Two contaminated soils were sampled and amended with 5%w/w (Rembind™, Ziltek Pty Ltd). Amended soils were then exposed to a series of laboratory leaching tests such as Australian Standard Leaching Procedure (ASLP)1, the US EPA Multiple Extraction Procedure (MEP)2 and US EPA LEAF Methods 1313 and 1314 3 to determine the potential release of PFAS. Concentrations of 28 PFAS in the leachates were determined using liquid chromatography-tandem mass spectrometry (LC-MS-MS).
The unremediated soils contained multiple PFAS with different chain-lengths. The leachate from unremeditated soils contained a range of short and long-chain PFAS and concentrations were highest from the soil with the lower clay content. Remediation of the soils using the sorbent reduced concentrations of leachable PFAS significantly and retained PFAS strongly within a pH range of 2 to 12. The presence of competing ions or high salinity did not alter the efficiency of the remediation material. The data show that in-situ remediation of PFAS-contaminated soils with these sorbents could be considered robust and durable with little risk of subsequent PFAS desorption, but long-term field validation data are needed.