Fabrication of high performance TFN membrane containing NH₂-SWCNTs via interfacial regulation

A high-flux thin film nanocomposite (TFN) nanofiltration (NF) membrane for low pressure operation (3.5 bar) was fabricated by blending purified amino-functionalized single-walled carbon nanotubes (NH₂-SWCNTs) with piperazine (PIP) as aqueous phase monomers through interfacial polymerization (IP). The surface properties and structures of the polyamide (PA) active layer were suitably tailored by introducing different amounts of NH₂-SWCNTs into the PA layer. It was found that the homogeneous incorporation of NH₂-SWCNTs facilitated a more integral PA layer along with improved roughness, hydrophilicity, and surface charge of the modified membranes, which could be validated by membrane characterisation including SEM, AFM, ATR-FTIR, XPS, zeta potential and water contact angle measurements. Based on cross-flow NF tests, the optimized ultra-thin NH₂-SWCNT-TFN membranes with 0.002 wt% of NH₂-SWCNTs exhibited outstanding water permeability of up to 17.8 L m^-2 h^-1 bar^-1, 71.1% higher than that of the pristine membrane, along with high MgSO₄ rejection of 91.0% and Na₂SO₄ rejection of 96.34%. Meanwhile, NH₂-SWCNT-TFN membranes also showed excellent long-term stability and antifouling ability. This work demonstrates a facile strategy to fabricate a scalable, low-pressure and ultra-thin TFN membrane with excellent performance.