Tannic Acid-Functionalized MoS₂ and g-C₃N₄ Thin Film Lamellar Membranes for Improved Permeance and Rejection in Nanofiltration

Design of lamellar membranes using nanomaterials of different dimensions has gained importance as they offer combined and synergetic properties that can significantly enhance the permeance and rejection. Herein, we report the fabrication of a lamellar thin film composite of a polyamide composite membrane via interfacial polymerization using 1T-molybdenum disulfide/graphitic carbon nitride (1T-MoS 2 /g-C 3 N 4 ), synthesized by a one-pot solid state reaction. The developed nanofiller 1T-MoS 2 /g-C 3 N 4 (MC) had unresolved issues, namely, low stability, agglomeration, low processability, and poor compatibility when incorporated into membranes. A sustainable approach to functionalize the MC surface with low-cost, stable, and ecologically friendly tannic acid (TA), a polyphenol derived from plants and rich in –OH functional groups, has significantly addressed the aforementioned issues. The hydrophilic nature and strong negative charge of TA produce a dense network on the membrane surface, inducing nanofiltration ability, in addition to offering efficient permeance. The optimal loading of this functionalized composite in the membrane resulted in an 18.4% NaCl rejection while achieving twice the permeance (17.7 L m –2 h –1 bar –1 ) compared to that of the non-TA-treated membranes. Divalent salts of sodium and magnesium sulfate show rejection up to 97 and 95%, respectively, while dye molecules of Congo red (696.7 Da) and methylene orange (327.3 Da) show >94% rejection, all with very good permeance. The robust and economical technique of one-pot synthesis of nanofillers together with easy functionalization rendered a very strong, tough, high antifouling thin film nanocomposite membrane that could practically be applied in desalination applications.