EMT-NH2 zeolite interlayer induces the formation of high-performance polyamide membrane

Abstract

Conventional nanofiltration (NF) thin-film composite (TFC) membranes are strongly restricted by the trade-off between their water permeance and selectivity as well as the poor structural stability for desalination and wastewater treatment. Herein, we report an interlayer-based thin-film composite (i-TFC) NF membrane with high performance using amino-functionalized EMT zeolite (EMT-NH2) nanocrystals as the interlayer. By adjusting the distribution density of EMT-NH2 on the substrate, a thin and dense polyamide (PA) layer with heterogeneity multi-level morphology (nanosized nodules and nanoscale stripes) can be formed and regulated. The EMT-NH2 zeolite nanocrystals with numerous hydrophilic groups (hydroxy and amino groups) and internal cavities can provide an additional priority water channel, increase the amine monomer storage on the substrate, and slow down the diffusion of amine monomer, thereby leading to the construction of a dense PA layer with high performance. As a result, the i-TFC-15 membrane depicted a water permeability of 13.82 ± 0.47 L m-2h−1⋅bar−1 (2.5 times that of the controlled one), while maintaining an excellent retention ability for divalent salts (98.55% for Na2SO4, 98.42% for MgSO4 and 97.40% for MgCl2). Additionally, the rigid hydrophilic interlayer containing zeolite nanocrystals endowed the i-TFC-15 membrane with excellent pressure resistance (up to 2.4 MPa), long-term operating stability, and antifouling propensity (flux-recovery ratio, 90.1%). This work provides an approach for fabricating a novel high-performance NF membrane and deepens our understanding of the role of porous interlayer affecting the formation of the PA layer.