Immobilization of silver nanoparticles on cellulose nanofibrils incorporated into nanofiltration membrane for enhanced desalination performance

Abstract

Abstract Nanofiltration (NF) membranes circumventing global water scarcity with excellent separation and antibacterial performances are highly desirable for efficient water treatment but remain a great challenge. Herein, a nanofiltration membrane was fabricated by in situ immobilizing silver nanoparticles (AgNPs) on sulfated cellulose nanofibril incorporated during interfacial polymerization. AgNPs were confirmed to be uniformly distributed and in situ grown on sulfated cellulose nanofibril (SCNF) due to its abundant sulfate and hydroxyl groups by mixing them with anhydrous piperazine solution as inorganic phase and homophenyl chloride n-hexane solution as the organic phase on the surface of a polyethersulfone microporous membrane. The attributes of SCNF, excellent hydrophilicity, and highly negative charges enhanced both the rejection and water permeability. As the SCNF charge increased, the roughness of SCNF increased and the contact angle decreased, and the maximum values were 203 nm and 17.67°, respectively. Among all the composite NF membranes, H-SCNF/Ag-0.01 had better rejection of Na2SO4 and NaCl, with a maximum rejection of 97.11% and 32.55%, respectively. Meanwhile, it also maintained high water permeability. Antibacterial experiments indicated that the composite NF membrane had effective inhibition against Escherichia coli and exhibited an expected slow-release capability of Ag+, which made it have long-term antibacterial properties. It was estimated that the antibacterial effect could last for 90 days. This work demonstrated that AgNPs in situ immobilization on SCNF could be used as promising nanofillers for designing advanced functional NF membranes.