Fabrication of a charged PDA/PEI/Al₂O₃ composite nanofiltration membrane for desalination at high temperatures

Ceramic membranes with high thermal and chemical resistances play an important role in nanofiltration process under harsh conditions. However, the application of ceramic membranes for salt filtration is challenging due to the limitation of pore size and surface charge. Herein, composite ceramic nanofiltration membranes were prepared by the codeposition of polydopamine and polyethyleneimine (PDA/PEI), with subsequent cross-linking by glutaraldehyde (GA). Ceramic ultrafiltration membranes served as supports, endowing the composite membranes with high mechanical stabilities and good hydrophilicity. A significant improvement in the rejection of salt solutions was achieved after modification due to the strong positive surface charge and small membrane pore size. The polydopamine/PEI modification layer crosslinked by glutaraldehyde and bonded to the surface of ceramic membrane through covalent bond show good thermal resistance. At high temperatures, the composite ceramic nanofiltration membranes still have a good rejection performance for divalent salt solutions. Overall, this study offers a composite ceramic nanofiltration membrane for desalination at high temperature, allowing a sustainable chemical process.