Abstract
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•Amine-rich SNW-1 nanoparticles embedded into the PA layer of novel TFN membranes.•SNW-1 nanoparticles covalently bonded to the PA layer and improved membrane hydrophilicity.•The hydrogen bond between the SNW-1 nanoparticles and MPD amine groups evenly dispersed the SNW-1 nanoparticles into the PA layer.•The porous structure of the SNW-1 nanoparticles improved the water flux through the modified membranes.•The optimal membrane, TFN0.005, showed higher water flux than the TFC membrane while retaining the membrane selectivity.
In this study, Schiff base network-1 (SNW-1) nanoparticles, which are covalent organic frameworks (COFs), were used as fillers in the polyamide (PA) active layer to elevate the performance of thin-film nanocomposite (TFN) forward osmosis (FO) membranes. The TFN membranes were prepared by interfacial polymerization (IP) of m-phenylenediamine (MPD) and trimesoyl chloride (TMC), and the SNW-1 nanoparticles were dispersed in the MPD aqueous solution at various concentrations. The secondary amine groups of SNW-1 nanoparticles reacted with the acyl chloride groups of TMC during the IP reaction to form strong covalent/amide bonds, which facilitated better interface integration of SNW-1 nanoparticles in the PA layer. Additionally, the incorporation of amine-rich SNW-1 nanoparticles into the TFN membranes improved their surface hydrophilicity, and the porous structure of SNW-1 nanoparticles offered additional channels for transport of water molecules. The TFN0.005 membrane with a SNW-1 nanoparticle loading of 0.005 wt% demonstrated a higher water flux than that of pristine TFC membrane in both AL-FS (12.0 vs. 9.3 L m−2 h−1) and AL-DS (25.2 vs. 19.4 L m−2 h−1) orientations when they were tested with deionized water and 0.5 M NaCl as feed and draw solution, respectively.