Enhancing PFAS removal: feasibility of an integrated electrocoagulation and adsorptive membrane approach

Per- and polyfluoroalkyl substances (PFAS) contamination of water resources has become one of the greatest environmental and public health threats of our time due to its persistence in the environment and living organisms, bioaccumulation potential, and toxicity. Conventional treatment methods have limited success in removing long-chain and even more mobile short-chain PFAS at different environmental conditions. In this review, we discuss the potential of coupling electrocoagulation (EC) with adsorptive membrane technologies to create a tandem system for PFAS remediation. The molecular properties of PFAS impacting removal effectiveness are highlighted: EC has a selective binding towards negatively charged, short-chain PFAS due to destabilization and adsorption onto metal hydroxide flocs formed in-situ while membrane technology enables a proven size cut-off that can be optimized according to membrane cut-off characteristics allowing for fine filtration of longer chain PFAS. It also highlights the potential side degradation of PFAS when EC techniques are deployed, for instance, by stable and porous electrodes that might allow advanced electrochemical oxidation reactions to occur, thus degrading PFAS molecules rather than simply capturing them. The design of the integrated system realizes synergistic interaction between EC and membrane stages to achieve high removal efficiency and reduced secondary pollution. Moreover, a discussion on the treatment and management of waste streams generated by the integrated process is included, addressing such as, the treatment and disposal of PFAS-containing flocs and membrane concentrates, and strategies for waste management. This review summarizes recent developments and outlines specific gaps in understanding the targeting and degradation pathways of both pollutants and the waste, and then highlights the promise and challenges of the future of hybrid EC-membrane systems as a transformative and sustainable approach to PFAS-contaminated water treatment.