Electroregeneration of Activated Carbon Filters: Concentrating Short-Chain PFAS

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are persistent fluorinated micropollutants. In recent years, stringent limits have been proposed by regulatory agencies, creating significant challenges for many water utilities. Although activated carbon is widely used for the adsorption and removal of PFAS, its rapid breakthrough, particularly with short-chain PFAS, requires frequent regeneration. This study presents a novel electroregeneration technology for the potential on-site regeneration of activated carbon. PFAS are initially adsorbed onto activated carbon, which is then regenerated in an electrochemical cell with a countercarbon electrode separated by a cation-exchange membrane. The experiments were conducted using a solution with an ionic strength comparable to that of surface water, implying a high concentration of competing ions. For PFPeA, a short-chain PFAS, we achieved effluent concentrations during electroregeneration 130 times higher than initial levels, with most PFPeA successfully desorbed. The method was effective for all short-chain PFAS examined (PFPeA, PFBS, and GenX), which are particularly concerning due to their rapid breakthrough in activated carbon filters. We studied the effect of electronic charge in the electrodes on PFAS adsorption as well as the impact of electrode surface modifications on PFAS electroregeneration performance. Surface modifications increased the presence of positively charged chemical groups, which, in turn, influenced the efficiency of PFAS electroregeneration.