Toward Sustainable Tackling of Biofouling Implications and Improved Performance of TFC FO Membranes Modified by Ag-MOF Nanorods

Abstract

In this work, nanorods with highly antibacterial properties were synthesized with silver acetate as a metal source and 2-aminoterephthalic acid as an organic linker, and were then embedded into thin-film composite (TFC) membranes to amend their performance as well as to alleviate biofouling. Silver metal-organic frameworks (Ag-MOFs) nanorods with a length smaller than 40 nm were incorporated within the polyamide thin selective layer of the membranes during interfacial polymerization (IP). The interaction of the synthesized nanorods with the polyamide was favored due to the presence of amine-containing functional groups on the nanorodʼs surface. The results of XPS, SEM, EDX spectroscopy, and AFM characterizations proved the presence of Ag-MOFs nanorods in the selective layer of thin-film nanocomposite (TFN) membranes. TFN membranes demonstrated improved water permeance and salt selectivity, and superior antimicrobial properties. Specifically, the increased hydrophilicity and antibacterial activity of the TFN membranes led to a synergetic effect toward biofouling mitigation. The number of live bacteria attached to the surface of the neat TFC membrane decreased by more than 92% when a low amount of Ag-MOFs nanorods (0.2 wt%) was applied. Following contact of the TFN membrane surface with E. coli and S. aureus, full inactivation and degradation of bacteria cells were observed with microscopy, colony-forming unit tests, and disc inhibition zone analyses. This result translated to a negligible amount of biofilm formed on the active layer. Indeed, the incorporation of Ag-MOFs nanorods decreased the metal ion release rate and therefore provided prolonged antibacterial activity.