Synthesis and Performance Evaluation of Covalent Organic Framework Nanofiltration Membrane for Per- and Polyfluoroalkyl Substances Removal

Abstract

Per- and polyfluoroalkyl substances (PFAS) have attracted the attention of many scientists due to their harm to the human body and the challenge in removing them from water. This thesis discusses the synthesis of covalent organic framework (COF) nanofiltration membranes and their PFAS removal performance. COF membranes were prepared by interfacial polymerization on polymer supports. The effects of synthetic parameters including concentration of monomers in the water phase and organic phase, soaking time, and reaction time on membrane structure and separation property were studied in this research. FTIR, SEM, and confocal microscopy were used for membrane characterization. It was found that increasing 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (Tp) monomer concentration and reaction time reduced the number of defects on the membrane surface and increased the membrane thickness. The change in the membrane surface morphology and thickness is less evident when varying the 2,5-dimethyl-1,4-phenylenediamine (Pa-2) concentration and soaking time. Membrane synthesized using a long reaction time of 120 seconds exhibited the lowest pure water flux and highest PFOS rejection.