Polyurea nanofiltration membranes with extreme-pH stability and high separation performance

Development of high-performance nanofiltration membranes with extreme-pH stability is an urgent need for treatment of wastewater from metallurgical and paper industries. In this study, we design a kind of oil phase monomer toluene diisocyanate (TDI) and the aqueous phase monomer polyethyleneimine (PEI) to prepare polyurea nanofiltration membranes . The special bonding type and dense crosslinking structure of polyurea were used to resist the attack of extreme pH conditions. The support-free interface polymerization was employed to minimize the membrane thickness. The TDI-PEI 10000 composite membranes achieved rejection of 97.5% for MgCl 2 , with a corresponding pure water permeance of 20.0 L m -2  h -1 bar -1 . After exposure to H 2 SO 4 solution with pH=1 for 440 h or NaOH solution with pH=13 for 200 h, the MgCl 2 rejection remained above 90%. Our study provides a facile approach to constructing extreme pH-stable separation membranes .