Constructing semi-oriented single-walled carbon nanotubes artificial water channels for realized efficient desalination of nanocomposite RO membranes

The application of aquaporin-like structural materials in separation membranes has been developed for several years. Regretfully, the prepared nanocomposite reverse osmosis (RO) membranes exhibited an unsatisfactory separation performance. To obtain highly desirable applied indexes, here we report the use of chopped single-walled carbon nanotubes (SWNTs) with carboxylated ends to construct high-efficiency partially aligned artificial water channels via the “traction” action of external force. The factors affecting the separation performance of artificial water channels were emphatically explored by scientific experiments, demonstrating that only the carbon nanotubes (CNTs) are semi-oriented along the transmembrane direction can truly give play to the transport mechanism of the artificial water channel, thereby achieving high water permeance. Notably, the modification of the polydopamine (PDA) coating can provide physical adhesion to make more SWNTs firmly adhere to the substrate surface, which improved the sieving ability of the SWNTs with a certain size range inner diameter and fortifying the structural stability between the substrate and the polyamide (PA) functional layer. The final PDA-PA-S RO membrane presented extraordinary separation performance with high water permeance of 3.88 L m⁻² h⁻¹ bar⁻¹ and salt rejection of 99.2%, which far surpasses that of the existing CNT-based and aquaporin-based RO membranes.