Polyamide interlayer supported organically bridged silica membrane for highly selective pervaporation dehydration of N-methyl pyrrolidone

Abstract

Organically bridged hybrid silica, a promising material for energy-efficient molecular separation membranes, is typically prepared on costly ceramic substrates through complex and challenging fabrication processes. This work presents a novel approach for designing hybrid silica membranes by using an ultrathin polyamide (PA) film as the interlayer, replacing the traditional ceramic-based intermediate and transition layers. A flexible, triple-layer hybrid silica composite membrane was fabricated, consisting of an ethylene-bridged hybrid silica layer coated on a poly(ether-ether-ketone) (PEEK) ultrafiltration membrane with a PA interlayer, which was prepared via interfacial polymerization. The smooth, dense, and ultrathin PA interlayer provides favorable conditions for the high-quality deposition of the hybrid silica top layer. This membrane is applied in the pervaporation (PV) dehydration of the polar aprotic solvent N-methyl-2-pyrrolidone (NMP), demonstrating impressive NMP/water separation factor of over 10,000 and competitive permeation flux of ∼0.39 kg/(m² h). In addition, this membrane also demonstrates good solvent tolerance and thermal stability, maintaining stable separation performance during PV dehydration of NMP in a cyclic test lasting up to 50 h, with operating temperatures ranging from 40 to 80 °C. These results show the flexible hybrid silica composite membrane has strong potential for purifying and recovering high-purity NMP via PV dehydration process.