A Nanofiltration Membrane Preparation Process Based on Polyethyleneimine Diffusion Modulation and Surface Modification

Nanofiltration (NF) membranes play a huge role in industrial manufacturing with their unique selective permeability. Membrane material and structure are the main factors affecting the effectiveness of NF separation. Typically, NF membranes are produced by interfacial polymerization (IP). Therefore, control of the IP process is particularly important. This work provides a NF membrane preparation process by combining internal modulation of the separation layer and surface modification. The diffusion of polyethyleneimine (PEI) molecules is accelerated by the introduction of ethanol and cetyltrimethylammonium bromide into the PEI aqueous phase solution, resulting in the formation of a loose interior. In addition, the high selectivity is maintained by high molecular weight PEI modifying. After optimizing the process, the NF membrane permeate flux and selectivity can be increased compared to the blank group (MgCl 2 desalination from 90% to 97%, permeate flux from 17 to 35 L m −2 h −1 ). The resulting PEI/TMC NF membranes also show excellent separation properties in mixed salt applications for magnesium-lithium separation.