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Membranes having excellent water permeability and high salt rejection are needed for developing nanofiltration technology. In the present work, a modified interfacial polymerization involving low-concentration monomers was utilized to synthesize an ultrathin polyamide (PA) layer. Carboxylated single-walled carbon nanotubes (COOH-SWCNT) were embedded into the ultrathin PA layer. The resultant additional molecular transportation pathways could reduce the trade-off effect. Besides, the morphology of ultrathin PA layer was sensitive to the presence of nanofillers, and contributed to a rougher surface of the thin film nanocomposite (TFN) membrane. As a result, the permeable area was increased, which is beneficial for water permeation. At the optimized COOH-SWCNT dosage of 0.001 wt%, even tubular crumples appeared on the fabricated membranes. Thereby, the membrane achieved an ultrahigh water permeance of 22.67 L·m−2·h−1·bar−1 while maintain a high rejection for divalent salt. For example, the rejection of Na2SO4 and MgSO4 were 95.69% and 90.03%, respectively. These excellent results were achieved using low loadings of nanofillers and under relatively low pressure (3.5 bar). The current work provides a feasible method to adjust the morphologies of NF membrane for improving its performance. And this is a promising approach due to its simplicity, and low consumptions of materials and energy.
•Carboxylated single-walled carbon nanotubes were incorporated into the TFC NF membrane.•A modified interfacial polymerization involving low-concentration monomers was used to form an ultrathin polyamide layer.•Tubular crumples appeared on the membrane surface and improved the available area for water permeation.•The membrane could achieve high water permeation with relatively low pressure which can reduce energy consumption.