The supporting layer of nanofiltration membranes is critical to the overall nanofiltration performance. However, conventional supports lack efficient surface porosity, which leads to the limited utilization rate of the polyamide (PA) layer. Herein a double-skin-layer nanofiltration membrane with porous organic polymer nanointerlayers prepared via a two-step interfacial polymerization technique is presented to investigate the effect of the interlayers' pore properties on the performance of the thin-film composite. Nanometer interlayers with different pore sizes are fabricated via interfacial azo-coupling polymerization. The pore properties of the nanointerlayer extremely influence the permeance, where a suitable pore size of 4.22 nm promotes pure water permeance of up to 32.2 L m-2 h-1 bar-1, which is ∼3.8-fold greater than the membrane without an interlayer. However, an interlayer with 0.54 nm pores limits the performance (4.7 L m-2 h-1 bar-1), which is even lower than the unmodified membrane (7.5 L m-2 h-1 bar-1), because of the narrow pores and confined transport mode. However, the confined diffusion rate of amino monomers from the support to interface leads to a thinner PA layer of ∼45 nm and results in high flux. This work provides a facial route for the fabrication of interlayers and facilitate the design of high-performance membrane materials with interlayers.
Keywords: desalination; interfacial azo-coupling polymerization; nanofiltration; nanointerlayer; thin-film composite membrane.