Sustainable fabrication of solvent resistant biodegradable cellulose membranes using green solvents

Abstract

The paradigm of the polymer industry is confronting an inevitable transition from fossil-based to bio-derived sources. The membrane-based separation process, generally regarded as a sustainable technology, mostly employs fossil-based polymeric membranes. In order to become an entirely carbon–neutral technology, all of the materials and chemicals employed during membrane fabrication must be scrutinized from a sustainability perspective. In this work, we report a versatile strategy to fabricate solvent-resistant cellulose membranes using bio-derived green solvents. The thermodynamic and kinetic aspects of the membrane fabrication process were systematically investigated. It was found that well-known green solvents such as Cyrene and PolarClean were not suitable due to high dope viscosity, whereas bio-derived methyl lactate and triethyl phosphate exhibited desirable properties to yield excellent cellulose membranes. The membrane performance could be tailored from the ultrafiltration to nanofiltration range by controlling the fabrication parameters. Importantly, the thermal treatment step prior to the deacetylation reaction was necessary to improve the solute rejection profile. The cellulose membranes displayed adequate compression resistance against pressure. However, their shear resistance was insufficient compared to that of commercial membranes. Nevertheless, the prepared cellulose membranes exhibited excellent solvent resistance in strong aprotic solvents such as N-methylpyrrolidone and N,N-dimethylacetamide, potentially allowing them to enter niche membrane markets such as the organic solvent nanofiltration (OSN).