MOF/Polydopamine-modified MXene based mixed matrix membrane for per- and polyfluoroalkyl substances removal from real wastewater

Per- and poly-fluoroalkyl substances (PFAS) are persistent emerging water contaminants and their removal from water bodies is a rigorous challenge. In this work, the removal of long and short chain PFAS from synthetic and real wastewater is examined by using advanced cellulose acetate (CA) based mixed-matrix membranes (MMMs). The membranes incorporate engineered nanofillers (DMMIL) consisting of iron-based metal–organic framework (MOF), in-situ grown in polydopamine-coated MXene nanosheets (PD@Ti₃C₂T_x). The nanofillers and membranes are thoroughly characterized with an array of microscopy and spectroscopy techniques. These include SEM, EDX, XRD, FTIR, XPS, AFM, water contact angle, and zeta potential measurements to examine the properties of nanomaterials and the effect of nanofiller loading on the microscopic morphology, surface texture, wettability, and ionization properties of membranes. The membrane with optimal nanofiller loading (50%DMMIL/CA) exhibited 1.42-fold enhanced water flux and 1.65-fold enhanced perfluorooctanoic acid (PFOA) rejection compared to the pristine CA membrane in the synthetic wastewater system. The fouling test was run for cycles of PFOA filtration followed by cleaning with DI water, and the produced membranes showed up to 68% flux recovery, with 54% shown by the 50%DMMIL/CA membrane after 5 cycles. The membrane's effectiveness in removing both long- and short-chain PFAS was tested in synthetic and real wastewater. In real wastewater samples, the 50%DMMIL/CA membrane removed 60% of PFOA, 57% of perfluoroheptanoic acid (PFHpA), and 55% of perfluorohexanoic acid (PFHxA), as well as other organic and inorganic pollutants.