Polymeric loose nanofiltration membranes based on water-soluble carbon nitride for efficient organics/salts separation

• Published in: Journal of membrane science 2025-03, Vol.718, p.123687, Article 123687
• Main Authors: Tang, Qingwen, Xia, Lichao, Liu, Lie, An, Xiaoqiang, Lan, Huachun, Liu, Huijuan, Qu, Jiuhui
• Format: Article
• Language: English
• Subjects: Dye/salt separation; Interfacial polymerization; Loose nanofiltration membrane; Negatively charged surface; Water-soluble carbon nitride
• ISSN: 0376-7388
• DOI: 10.1016/j.memsci.2024.123687

Loose nanofiltration (LNF) membranes with a remarkable water permeability are highly promising for the fractionation of organics and salts in the treatment of industrial wastewater. In this study, a novel polymeric membrane with high organics/salts separation efficiency and high water permeability was constructed by interfacial polymerization (IP) between water-soluble cyanocarbon nitride (WCN) and trimesoyl chloride (TMC) monomer. We revealed that the hydrophilic nature of WCN could slow down the polymerization of cyano and chlorine groups by inhibiting the diffusion of WCN into organic phase, forming a thin polymeric membrane with a loose structure on the polyethersulfone (PES) substrates. With a hydrophilic and charged surface, the polymeric membrane exhibited high rejection toward negatively charged organic molecules, while maintained good permeability to salt ions. The membrane demonstrated a high water permeability of 41.6 L m−2 h−1 bar−1, which was 4 times higher than that of conventional polyamide membranes. Additionally, it exhibited a high separation factor (S) of 1418 in the filtration of methyl blue/NaCl mixtures, surpassing the performance of state-of-the-art loose nanofiltration (LNF) membranes reported in the literature. This study provides a new strategy of tailoring the structure of carbon nitride to develop high-performance LNF membranes for water treatment. Modulated interfacial polymerization of large molecular amine monomers yields high performance loose nanofiltration membranes. [Display omitted] •Water-soluble C₃N₄ can be used as an amine monomer to fabricate loose NF membranes.•Surface of WCN-TMC membranes exhibited strong hydrophilicity and electronegativity.•Water permeability of WCN-TMC membranes is 4 times higher than polyamide membranes.•WCN-TMC membranes showed a state-of-the-art separation factor of dyes and salt ions.