Per- and polyfluoroalkyl substance (PFAS) retention by colloidal activated carbon (CAC) using dynamic column...

Area of Science:

• Environmental Chemistry
• Soil Science
• Remediation Technologies

Background:

• Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants found in soil and water.
• Effective remediation strategies are crucial for mitigating PFAS risks to ecosystems and human health.
• Colloidal activated carbon (CAC) shows promise for in-situ stabilization of PFAS in subsurface environments.

Purpose of the Study:

• To evaluate the efficacy of colloidal activated carbon (CAC) in retarding the transport of various PFAS in contaminated soil.
• To investigate the fate and transport mechanisms of different PFAS classes (PFAAs, PFCAs, PFSAs, and fluorotelomer sulfonates) under CAC treatment.
• To quantify PFAS retention, partitioning coefficients, and potential CAC loss during soil column experiments.

Main Methods:

• Dynamic soil column tests were conducted using soil treated with 0.03% w/w CAC.
• The retardation of ten classical perfluoroalkyl acids (PFAAs) and two alternative PFAS was assessed.
• Organic carbon analysis was performed to quantify CAC redistribution and elution.

Main Results:

• CAC treatment significantly enhanced PFAS retardation, achieving 99.7% higher retention than untreated soil.
• Long-chain PFAS exhibited higher retardation rates, with partitioning coefficients (K_d) ranging from 10³-10⁵ L kg^-1.
• A 37% overall retention of total PFAS (∑PFAS) was observed in treated columns, despite a 23% loss of CAC carbon.

Conclusions:

• Colloidal activated carbon (CAC) demonstrates significant potential for immobilizing PFAS in soil, reducing contaminant migration.
• PFAS chain length positively correlates with K_d values, indicating preferential binding of longer-chain compounds.
• Further research is needed to optimize CAC application and address potential limitations like carbon redistribution and elution.