2D materials for improved membrane technology

Abstract

In this work membranes containing 2D materials, namely graphene-like materials, and the most representative polymer of intrinsic microporosity (PIM), PIM-1, were developed for their use in bioalcohol recovery and CO2 gas separation. Graphene-like materials resulting from the alkyl-functionalization of graphene oxide (GO) using octylamine (OA) and octadecylamine (ODA), and their further chemical reduced forms were used as fillers for both applications. The incorporation of graphene-based fillers in freestanding membranes enhanced the separation performance for n-butanol (n-BtOH)/water separation and an average separation factor of 32.9 for n-BtOH/water was obtained with mixed matrix membranes (MMMs) containing 0.1 wt.% reduced alkyl-functionalized GO (OA functionalization), while pristine PIM-1 membranes presented an average separation factor of 13. In order to improve the productivity of the aforementioned membranes, thin film nanocomposite (TFN) membranes were fabricated via dip-coating. Herein, porous polyvinylidene fluoride (PVDF) membranes were used as support layers. The addition graphene-like materials with lateral sizes in the nanometer-range improved the separation performance, in comparison with pristine PIM-1 thin film composite (TFC) membranes. As expected, their fluxes were greater than that for freestanding membranes. Besides that, the incorporation of nanometer-sized fillers also enhanced the total flux of TFN membranes in approximately 40% when compared to PIM-1 TFC membranes. Finally, the addition of graphene-like materials into freestanding PIM-1 polymer matrices and their effect on the physical aging was studied. After 155 days, pristine PIM-1 membranes presented a CO2 permeability of (2.0 ± 0.7) × 10^3 Barrer, corresponding to a reduction in 68% from their initial value. The addition of graphene-based fillers proved to be an efficient way to retard the physical aging of PIM-1; after the same period of 155 days, MMMs containing 0.05 wt.% reduced OA-functionalized GO membranes showed a CO2 permeability of (3.5 ± 0.6) × 10^3 Barrer, i.e., a reduction of 39% relatively to day 0.

Date of Award	31 Dec 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Flor Siperstein (Supervisor) & Patricia Gorgojo (Supervisor)