(678f) Enhancing PFOS Removal and Membrane Permeability By Functionalizing Polyamide Thin-Film Nanocomposite Hollow Fiber Membranes with Mxene Nanosheets

The prolific use of per- and polyfluoroakyl substances (PFAS) in household product manufacturing has resulted in the contamination of many waterways around the United States. Due to their negative health effects and high chemical stability, PFAS removal is an emerging research area in water purification. In this work, we use MXene nanosheets to functionalize thin-film composite (TFC) hollow fiber nanofiltration (HFN) membranes during the interfacial polymerization (IP) process to enhance the removal of Perfluorooctane sulfonic acid (PFOS) from water. A MXene-polyamide nanofiltration selective layer was fabricated on top of polysulfone hollow fiber support via IP of trimesoyl chloride (TMC) and a mixture of piperazine (PIP) and MXene nanosheets. Incorporating MXene nanosheets during the IP process tuned the morphology and negative surface charge of the selective layer, resulting in an increase in PFOS rejection from 72% (bare TFC) to more than 96% (0.025% (wt.)-MXene-TFC) while the water permeability was also increased from 13.19 (bare TFC) to 29.26 LMH/bar (0.025% (wt.)-MXene-TFC). Our results demonstrate that electrostatic interaction and size exclusion are the two main factors governing PFOS rejection and both are determined by PA selective layer structural and chemical properties. In addition, our results showed that MXene nanosheets tuned the morphology and crosslinking of PA layer by affecting the transport of PIP during the IP process, which resulted in enhanced water permeability and PFAS removal without sacrificing the salt rejection of the TFN membrane.