(79g) Evaluation of a Janus Membrane for Enhanced Rejection of PFAS in Membrane Distillation

Treating per- and poly-fluoroalkyl substances (PFAS) contaminated water is an important research topic due to the potential health risks associated with PFAS exposure. Membrane distillation (MD), which utilizes hydrophobic microporous membranes that prevent the transport of non-volatile solutes, is a promising method for separating PFAS from challenging water matrices such as landfill leachate, wastewater, and reverse osmosis residuals. However, amphiphilic PFAS, such as perfluorooctanoic acid (PFOA), may establish hydrophobic interactions with the membrane surface leading to the adsorption of PFAS onto the membrane surface. PFAS adsorption presents a major challenge in the MD process, as it can result in both surface diffusion and pore wetting, which severely impact the separation efficiency. Here, we hypothesize that controlling hydrophobic-hydrophobic interactions is vital for enhancing the membrane’s resistance to PFAS adsorption and surface diffusion. In order to verify the above, a Janus membrane was fabricated by solution-casting a blend of polyvinyl alcohol (PVA) and sulfosuccinic acid (SSA) onto the hydrophobic MD membrane, giving it both hydrophilic and hydrophobic properties. LC-MS/MS analysis was performed on both the feed and permeate samples to measure the extent of PFAS rejection. The electronic conductivity of the permeate as well as the impedance across the membrane were measured to monitor the progress of the pore wetting. A plate-and-frame membrane cell was employed to evaluate the benefits of a Janus membrane relative to a pristine polytetrafluoroethylene (PTFE) under high concentrations of PFOA and NaCl. The study demonstrated the membrane’s remarkable capability to suppress pore wetting as evidenced by superior salt rejection (>99%) and a steady permeate flux under stressed operating conditions where the membrane retentate was continuously recycled. The current research implies a high potential for functionalized membranes for targeted treatment of PFAS from difficult-to-treat water matrices.