Tuning the Performance of Composite Membranes by Optimizing PDMS Content and Cross-Linking Time for Solvent Resistant Nanofiltration

Abstract

Herein, a series of composite membranes with optimized solvent permeance and rejection are prepared by combining the advantages of hybridization and cross-linking techniques. Polyethylenimine (PEI) and hydroxyl terminated trifluoride polydimethylsiloxane (PDMS) are cross-linked with trimesoyl chloride as the skin layer, which is isotropic rather than hierarchical. The chain mobility of PEI is inhibited upon hybridization and cross-linking, affording enhanced solvent resistance and thermal/mechanical stabilities. The composite membrane achieves high rejection ability with the rejection of PEG 1000 of about 100%. Additionally, the synergy of hydrophilic PEI and hydrophobic PDMS segments gives acceptable solvent permeances for acetone (up to 2.7 L m −2 h −1 bar −1 ) and ethyl acetate (up to 1.4 L m −2 h −1 bar −1 ). The membrane microstructures are facilely tuned by regulating PDMS content and cross-linking time, allowing the efficient optimization of solvent resistant nanofiltration performances. Moreover, the operational stability and the separation of lotus seedpod proanthocyanidins−ethanol/water mixtures are investigated to evaluate the practical application of the composite membrane.

Recycled Poly(ethylene terephthalate) for High Temperature Solvent Resistant Membranes

“…While some of the newly synthesized polymers can be used in challenging conditions such as temperatures close to 500 °C, commercial polymers would be convenient for membrane fabrication, when considering a faster technology transfer, if the required properties would be addressed. Polyimide, poly­(ether ether ketone), polyvinylidene fluoride, polybenzimidazole, polyamide, and poly­(dimethylsiloxane) − are the most investigated commercial polymers for applications in organic solvents.…”

Production of Composite Membranes by Coupling Coating and Melt Extrusion/Salt Leaching

“…The strong adsorption bands of the LDPE support at 2916 and 2847 cm –1 are associated with C–H stretching vibrations of −CH 3 , −CH 2 , and −CH groups . But these bands disappeared in the FSCM spectra, indicating that the surface was completely covered by the PDMS layer . A peak at 783 cm –1 is attributed to −CH 3 rocking and −Si–C– stretching in −Si–CH 3 .…”

“…30 But these bands disappeared in the FSCM spectra, indicating that the surface was completely covered by the PDMS layer. 31 A peak at 783 cm . The results show that the dissolved C 3 H 8 in the FSCM is 26 and 6 times higher than CH 4 and CO 2 at 70 psi, while the dissolved CO 2 is 42 and 21 times higher than H 2 and N 2 at 290 psi, respectively.…”