Project Summary: Per- and polyfluoroalkyl substances (PFAS) are persistent, toxic contaminants widely detected in drinking water, wastewater effluent, and landfill leachate. Adsorption by granular activated carbon (GAC) is the most commonly used technology for PFAS removal due to its proven effectiveness. However, managing PFAS-laden spent GAC presents a growing challenge. Conventional off-site thermal regeneration is energy intensive, costly, and logistically difficult, especially for smaller or remote facilities.
Microwave-assisted regeneration offers a promising alternative, enabling rapid, internal heating of GAC that reduces energy consumption and preserves the carbon structure. Early studies have demonstrated high regeneration efficiencies and even partial PFAS destruction under optimized MW conditions. Yet most existing work has focused on a limited set of legacy PFAS (e.g., PFOA, PFOS) in clean water matrices. Little is known about how microwave regeneration performs in complex matrices such as wastewater and landfill leachate, where high concentrations of dissolved organic matter (DOM) and metals may significantly influence adsorption and regeneration outcomes.
This one-year experimental study will evaluate the effectiveness of microwave regeneration of PFAS laden GAC in complex water matrices. Using synthetic wastewater and leachate formulations, we will systematically investigate how DOM, metals (e.g., Fe3⁺, Ca2⁺), and microwave heating parameters affect the adsorption and regeneration of four representative PFAS: PFOA, PFOS, 5:3 fluorotelomer carboxylic acid (FTCA) and 6:2 fluorotelomer sulfonate (FTS). PFAS removal and degradation will be quantified using combustion ion chromatography (CIC), while the integrity of regenerated GAC will be evaluated through nitrogen physisorption, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis.
The study aims to (1) elucidate the mechanisms governing PFAS fate during microwave regeneration in high-strength waters; (2) identify optimal regeneration conditions that balance PFAS removal with carbon preservation; and (3) provide quantitative data on regeneration efficiency and defluorination for both legacy and precursor PFAS. Results will inform the feasibility and design of on-site regeneration systems at wastewater treatment plants and landfills. Compared to conventional reactivation, microwave regeneration can reduce energy use by 40–70% (2–3 kWh/kg savings) and lower treatment costs by $0.20–$0.30 per kg of GAC. If adopted by just 200 wastewater treatment plants and 300 landfills, this could translate into nationwide savings exceeding $5 million annually.
