Enabling Sustainable Treatment of PFAS Compounds Via Dual-Stage Electrochemical Oxidation and Wafer-Enhanced Electro-Deionization

Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS), the “forever chemical,” can be found in aqueous film forming foams (AFFF) and serve as surfactants that spread the foam to deoxygenate and suppress the fire quicker than alternatives on the market without these fluorosurfactants. The downside to using these substances are the high cost of maintenance/labor to remove them from drinking water and adverse health effects on humans. The predicament that arises from PFAS is that there is not a cost efficient method of degrading the contaminants. The objective is to develop a risk mitigation and remediation technology that utilizes oxidation/reduction and wafer-enhanced electrodeionization (WE-EDI) to remediate PFAS to ensure the safety of military personnel, decrease labor cost, and increase operational uptime of DoD facilities by allowing continued use of stockpiles of legacy aqueous film forming foams (AFFF) while an effective alternative is being developed. This will be done by using synthetic PFAS solution and diluted AFFF, and altering variables such as voltage, catalyst composite, electrode type, and membranes, within the oxidation/reduction and WE-EDI system to determine the most effective at degrading PFAS. The ultimate success of this project will be determined by any consistent percent degradation of PFAS with the end goal of complete desulfonation and decarboyxlation of PFAS compounds to carbon dioxide and fluoride.  Conventional wastewater treatment methods such as reverse osmosis, ion exchange resins, and granular activated carbon are unable to achieve complete degradation of PFASs, and many PFASs are resistant toward the majority of oxidants/reductants used in water treatment, due to the strength of C-F bonds and the high electronegativity of fluorine. Reverse osmosis can efficiently remove long chain PFASs but information is limited on the removal of short chain C3-C5 PFCAs and PFSAs. Ion exchange resins are generally more effective in removing PFSAs than granular activated carbon although both adsorbents have lower adsorption capacities for short chain compared to long chain PFASs. However, all of these nondestructive conventional techniques result in a concentrated PFAS residual which needs further treatment. Thus, the development of sustainable water treatment technologies that can work with tandem nondestructive techniques and are capable of energy-efficient PFAS degradation is a critical challenge to be addressed.   Few other destructive technologies have shown the ability to mineralize the PFASs, namely sonolysis, UV photolysis, UV activation of S2O82-  and KI, photocatalysis, and electrochemical (EC) treatments.  EC treatment systems have the unique ability to completely mineralize PFASs through potential driven electron transfer reactions using a set of high performance electrodes such as mixed metal oxide (MMO), boron doped diamond, and Magneli phase suboxide ceramic anodes.