Aminated Clay-Polymer Composite as Soil Amendment for Stabilizing the Short- and Long-Chain Per- and Poly-Fluoroalkyl Substances in Contaminated Soil

Abstract

Soils contaminated with per- and poly- fluoroalkyl substances (PFAS) require immediate remediation to protect the surrounding environment and human health. A novel animated clay-polymer composite was developed by applying polyethyleneimine (PEI) solution onto a montmorillonite clay-chitosan polymer composite. The resulting product, PEI-modified montmorillonite chitosan beads (MMTCBs) were characterized as an adsorptive soil amendment for immobilizing PFAS contaminants. The MMTCBs exhibited good efficiency to adsorb the PFAS, showing adsorption capacities of 12.2, 16.7, 18.5, and 20.8mgg−1 for PFBA, PFBS, PFOA, and PFOS, respectively, which were higher than those obtained by granular activated carbon (GAC) (i.e., an adsorbent used as a reference). Column leaching tests demonstrated that amending soil with 10% MMTCBs resulted in a substantial decrease in the leaching of PFOA, PFOS, PFBA, and PFBS by 90%, 100%, 64%, and 68%, respectively. These reductions were comparable to the values obtained for GAC-modified soil, particularly for long-chain PFAS. Incorporating MMTCBs into the soil not only preserved the structural integrity of the soil matrix but also enhanced its shear strength (kPa). Conversely, adding GAC to the soil resulted in a reduction of the soil's mechanical properties. Environmental ImplicationPer- and poly-fluoroalkyl (PFASs) are classified as some of the most hazardous substances due to their persistent, bioaccumulative, and toxic traits, posing risks to both the environment and human health. Soils contaminated with PFASs require immediate remediation to protect the surrounding environment and human health. The developed innovative aminated montmorillonite-chitosan composite in this study effectively stabilizes PFAS in contaminated soil, simultaneously inhibiting their leaching into the surrounding environment and groundwater media. This research progress makes a significant contribution to soil remediation efforts, which aim to protect ecosystems and mitigate the negative effects of these hazardous substances.