Regulating interfacial polymerization via a multi-functional calcium carbonate based interlayer for a highly permselective nanofiltration membrane

Abstract

Highly permselective nanofiltration (NF) membranes have potential in water treatment applications, but overcoming the permeability–selectivity trade-off is a challenge. We introduce in this work, a highly permselective NF membrane fabricated by regulating interfacial polymerization (IP) with a calcium carbonate (CaCO₃) interlayer. The flexible CaCO₃ interlayer was grown in situ on the surface of a polyketone (PK) membrane through mineralization, which serves as a regulator to mediate the kinetics of IP by inhibiting the amine monomer diffusion across the interface between the aqueous and organic phases, promoting the synthesis of a thinner selective layer. Furthermore, the CaCO₃ interlayer can react with HCl, a byproduct of the IP reaction, to release more heat and CO₂ nanobubbles, resulting in the formation of a rough selective layer with a loose structure. The resultant CaCO₃ interlayer-incorporated a NF membrane which demonstrated a high water permeance of 23.4 L m⁻² h⁻¹ bar⁻¹ (around 3.5 times the permeance of a pristine NF membrane (6.7 L m⁻² h⁻¹ bar⁻¹)) with a Na₂SO₄ rejection of 97.7%. The multi-functional interlayer explored in this current work may provide a new strategy for the preparation of membranes with highly satisfactory NF performance.