High Performance Thin Film Composite Polyamide Membrane with an Ultrathin Spray-Coated Carbon Nanotubes (CNT) Interlayer

Thin film composite (TFC) polyamide membranes are the current state-of-the-art desalination membranes having superior water permeability, high salt rejection, and excellent mechanical and chemical stability. The formation of highly permeable polyamide active layer with great salt rejection is a key to further improve the perm-selectivity of TFC polyamide membranes. Therefore, we finely tailor the structure and properties of polyamide by creating an ultrathin spray-coated carbon nanotube (CNT) interlayer on the porous support membrane surface and thus optimizing the interfacial polymerization of diamine and TMC. Our results find that the TFC polyamide membranes with the CNT interlayer increase its water permeability more than 6-fold without sacrificing its salt selectivity and achieves the highest A/B value of 39 bar^-1 among the reported forward osmosis membranes. The CNT interlayer is found to provide a favorable interface for the formation of selective polyamide with effective large surface area and inhibit the formation of the polyamide inside the membrane support. Moreover, the removal of polymeric support of TFC membrane, we obtained the CNT supported polyamide membrane (CNTs-PA). Due to the ultrathin and highly porous of CNTs support, the fabricated CNTs-PA membrane exhibits ultralow structure parameter S less than 40 μm, and super high water flux of 150.26 ± 2.56 LMH using DI water as a feed solution (FS) and 1 M NaCl as a draw solution (DS), which is five to ten times as high as the conventional FO membranes (usually around 15–30 LMH). Such a high water flux is almost the highest value reported so far under similar measurement conditions. Our research provides great insights on the structure design and properties optimization of TFC polyamide membrane.