Covalent coupling of chitosan-tailored silicas: the effect of interfacial compatibility in pervaporation dehydration of ethanol

Hybrid chitosan-based membranes incorporating covalently integrated mesoporous silicas were developed for selective ethanol dehydration via pervaporation. Amino-functionalized MCF and SBA-15 were first activated with glutaraldehyde (G_MCF or G_SBA) and subsequently incorporated into the chitosan matrix through Schiff-base reaction, enabling polymer-filler coupling and the formation of a chemically integrated network. The resulting membranes were comprehensively characterised in terms of structural, thermal, and hydrophilic properties. During the dehydration of 96 vol% ethanol, pristine chitosan exhibited a separation factor of 4.4 with a permeate flux of 1.89 kg·m⁻²·h⁻¹. Upon incorporation of 10 wt% G_MCF and G_SBA, the separation factor increased dramatically up to 682 and 4850, respectively, while the corresponding fluxes decreased to 1.05 and 0.59 kg·m⁻²·h⁻¹. The substantial enhancement in selectivity was attributed to the preferential sorption of water within the hydrophilic mesoporous silica domains, combined with the suppression of nonselective interfacial defects arising from covalent polymer-filler bonding. In addition, glutaraldehyde-activated silicas acted as multifunctional crosslinking sites, locally reducing polymer chain mobility and stabilizing selective transport pathways, while the overall swelling behaviour depended on the silica type and loading.