An aqueous phase pre-crosslinking modulated nanofiltration membrane preparation process

Nanofiltration (NF) is one of the most promising separation technologies of this century. It plays a major role in the chemical, medical, food, and other fields. The separation and permeation performance of NF membranes is closely related to microstructure. In this study, aqueous phase amine monomers are pre-crosslinked during the preparation of NF membranes. Trimesic acid (TMA) is used as a cross-linking agent with polyethyleneimine (PEI), whereby the resulting aqueous-phase monomer is interfacially polymerized with the organic-phase monomer to form a separation layer with internal lithium-ion permeation channels. The physicochemical structure of nanofiltration membranes is analyzed in detail. The pre-crosslinking process is optimized and the NF membrane performance can achieve 97% rejection of MgCl₂, 15% rejection of LiCl, and 34 L m⁻² h⁻¹ permeate flux. The resulting NF membranes also show stable desalination performance in tests with mixed salt solutions. This study provides a new nanofiltration membrane structure and performance optimization scheme, which is favorable for magnesium-lithium separation systems.