Photothermal-Assisted Interfacial Polymerization toward Microstructure Regulation of a Polyamide Membrane with Enhanced Separation Performance

A highly permeable thin-film composite (TFC) polyamide membrane with efficient salt rejection is valuable for numerous industrial processes. To achieve this objective, it is essential to innovate the membrane fabrication process to produce an ultrathin polyamide separation layer. In this study, a photothermal-assisted interfacial polymerization (IP) strategy was proposed to fabricate TFC polyamide membranes by incorporating carboxylated carbon nanotubes (CNTs) with exceptional photothermal properties. CNTs absorb solar energy and convert it into heat, significantly elevating the temperature in their microregions, thereby accelerating the reaction between m-phenylenediamine (MPD) and trimesoyl chloride (TMC) during the IP process. Exploiting the self-inhibition characteristics of IP, the preformed polyamide layer suppresses the subsequent diffusion of MPD into the reaction interface, resulting in the formation of an ultrathin polyamide layer. Consequently, the CNTs-modified polyamide membrane with photothermal assistance obtains a thickness of approximately 94 nm, significantly thinner than the control membrane (189 nm). Furthermore, it demonstrates a superior water flux of 54.4 L m^-2 h^-1, higher than that of the pristine TFC membrane without CNTs and the conventional CNTs-modified membrane, while maintaining a NaCl rejection of ∼96%. The photothermal-assisted IP strategy provides some inspiration for engineering high-performance polyamide membranes available in various advanced separations.