Polymer-Ti3C2Tx composite membranes to overcome the trade-off in solvent resistant nanofiltration for alcohol-based system

Abstract

© 2016 Elsevier B.V. Solvent resistant nanofiltration (SRNF) technology is an energy efficient and environmentally friendly alternative to purify alcohol-based mixtures, but there exists a challenge in overcoming the trade-off between membrane flux and rejection. Herein, as the representative of the emerging family of MXenes, Ti3C2Tx nanosheets with abundant -OH groups are chosen as nanofillers to prepare SRNF composite membrane after being incorporated into two typical polymer matrixes: hydrophilic polyethyleneimine (PEI) and hydrophobic polydimethylsiloxane (PDMS). Systematic characterizations and measurements suggest that the uniformly dispersed Ti3C2Tx nanosheets enhance the thermal/mechanical stabilities and solvent resistance for both polymer-based membranes through steric effects and/or interfacial interactions. Besides, the horizontally-lied Ti3C2Tx nanosheets give significant promotion on the transfer of alcohol molecules by providing additional pathways along nanosheet surface using -OH as adsorption site. Particularly, they afford improvements of alcohol flux as high as 30% to PEI-based membrane and 162% to PDMS-based membrane. Meanwhile, the rejection abilities are dramatically improved with MWCOs below 200 Da due to the blockage of solute transfer by the nanosheets. These results indicate that the trade-off between alcohol flux and solute rejection is readily overcome. The transfer properties of weak- or non-polar solvents and the long-term operation stability of membranes are also explored.