Incorporation of Silver-Embedded Carbon Nanotubes Coated with Tannic Acid into Polyamide Reverse Osmosis Membranes toward High Permeability, Antifouling, and Antibacterial Properties

In this work, tannic acid (TA)-functionalized carbon nanotubes (CNT@TA) were synthesized by hydrogen bond and π–π stacking interactions. CNT@TA embedded with silver nanoparticles (Ag-CNT@TA) was obtained by in situ reducing silver ammonia ions in the pore channels of CNT@TA. CNT@TA and Ag-CNT@TA were added into the polyamide (PA) layer by interfacial polymerization to fabricate high-performance nanocomposite reverse osmosis membranes. The results show that the functionalized CNTs can be uniformly distributed in the PA matrix with random orientations. A loose PA separation layer was obtained by introducing CNT@TA. Correspondingly, abundant new water channels were formed. Compared with the pure PA membrane, the water permeability (4.81 L m^–2 h^–1 bar^–1) of the nanocomposite membrane is enhanced by 49.8% without any loss in NaCl rejection (99.3%). The membrane exhibits satisfactory chemical- and bio-fouling resistances to bovine serum albumin and Escherichia coli as model foulants. The high bactericidal rate should be ascribed to the formation of the TA coating and confined Ag nanoparticles in CNT channels. The confined structure effectively avoids the leaching out of the Ag nanoparticles and keeps the persistence of the antibacterial property. The excellent compatibility between the CNTs and the polyamide matrix endows the membrane with long-term performance stability.