Corolliform morphology thin film composite polyamide membrane constructed via Tröger's base PIM for enhancing nanofiltration separation performances

In this study, a kind of Tröger's base (TB) polymer of intrinsic microporosity (PIM) was proposed to adjust both the micro-structure and macro-performance of the thin film composite (TFC) polyamide nanofiltration (NF) membrane. First, a rigidly-contorted Tröger's base (TB) diamine monomer — 2,8-diamino-4,10-dimethyl-6H,12H-5,11-methanodibenzo [1,5]-diazocine (TBDA) was synthesized (Yield: 90.2 %), and then was incorporated with piperazine (PIP) to react with trimesoyl chloride (TMC) monomer via the coupling of phase inversion and interfacial polymerization for constructing the TB-PIM-based polyamide (PA) selective separation layer. Especially, the NF membrane (TFC-TBDA/PIP) fabricated with 1/1 of TBDA/PIP and 0.075 ( w / v ) % TMC exhibited particular “corolla-like” morphology with high microporosity, thinner selective layer <55 nm. Under neutral condition, this membrane surface also is more negatively charged. These features further endowed this membrane superior permeability and selectivity . It showed about 2-fold water flux (87.67 L·m −2 ·h −1 ) of the conventional NF membrane (TFC-PIP) without sacrificing the multivalent sulfate salt rejections of Na 2 SO 4 and MgSO 4 , and meanwhile the MgSO 4 rejection was about 4.3 times as much as MgCl 2 . Moreover, the XPS results also revealed that there was nearly no chemical structure change of TB-PIM-based polyamide after acid soaking. Therefore, this study provides an effective way to fabricate the high-performance TFC nanofiltration membrane.