Thin Film Polyamide Nanocomposite Membrane Decorated by Polyphenol-Assisted Ti₃C₂T_<i>x</i> MXene Nanosheets for Reverse Osmosis

Abstract

Transition-metal carbides (MXenes), multifunctional 2D materials, have caught the interest of researchers in the fabrication of high-performance nanocomposite membranes. However, several issues regarding MXenes still remain unresolved, including low ambient stability; facile restacking and agglomeration; and poor compatibility and processability. To address the aforementioned challenges, we proposed a facile, green, and cost-efficient approach for coating a stable layer of plant-derived polyphenol tannic acid (TA) on the surface of MXene (Ti₃C₂T_<i>x</i>) nanosheets. Then, high-performance reverse osmosis polyamide thin film nanocomposite (RO-PA-TFN) membranes were fabricated by the incorporation of modified MXene (Ti₃C₂T_<i>x</i>-TA) nanosheets in the polyamide selective layer through interfacial polymerization. The strong negative charge and hydrophilic multifunctional properties of TA not only boosted the chemical compatibility between Ti₃C₂T_<i>x</i> MXene nanosheets and the polyamide matrix to overcome the formation of nonselective voids but also generated a tight network with selective interfacial pathways for efficient monovalent salt rejection and water permeation. In comparison to the neat thin film composite membrane, the optimum TFN (Ti₃C₂T_<i>x</i>-TA) membrane with a loading of 0.008 wt % nanofiller revealed a 1.4-fold enhancement in water permeability, a well-maintained high NaCl rejection rate of 96% in a dead-end process, and enhanced anti-fouling tendency. This research offers a facile way for the development of modified MXene nanosheets to be successfully integrated into the polyamide-selective layer to improve the performance and fouling resistance of TFN membranes.