Preparation of full-bio-based nanofiltration membranes

Abstract

Cellulose acetate (CA) as polymer, glycerol derivatives (namely triacetin, diacetin, monoacetin or glycerol-formal) as solvents and 2-methyltetrahydrofuran (2-MeTHF) as co-solvent were selected as bio-based ingredients for the preparation of full-bio-based nanofiltration membranes via non-solvent induced phase separation (NIPS). Membrane performance was investigated using an aqueous rose bengal (1017Da) solution (RB/H2O) as feed. Membrane morphologies were characterized using SEM (scanning electron microscopy). Both kinetic and thermodynamic aspects of the phase inversion process were studied in detail to gain more insight in the membrane formation process. When implementing a 90s evaporation step prior to coagulation, rejection increased with increasing 2-MeTHF concentration in the casting solution in the case of diacetin and triacetin solvents. In the case of monoacetin and glycerol-formal based casting solutions, evaporation had a less significant impact on RB rejection even though the same volatile co-solvent was used. The best membranes were finally obtained using diacetin as a solvent and 2-MeTHF as co-solvent with permeances ranging from 5.5 to 12.8 L/m2 h bar for membranes with >90% RB rejections.