(285f) Graphene Oxide/Single Walled Carbon Nanotube (GO-SWCNT) Network Restricted Ionic Liquid As a Stable and Effective Membrane for Highly Efficient Carbon Capture

Carbon capture, utilization and storage is considered to be one of the key strategies on alleviating climate change and promoting net removal of carbon dioxide (CO₂) from atmosphere. A significant fraction of CO₂ released into the atmosphere is from flue gas emissions in power plants. It is a challenge to separate CO₂ from these streams due to the low CO₂ partial pressure, leading to lower driving force. Membrane processes may offer a promising solution for low cost, robust and energy efficient CO₂ capture from these power plants. Facilitated transport membranes, although showing strong capability for CO₂ capture at low concentrations and under humid conditions, suffer from the loss of facilitators, such as amines, leading to decline in performance over long-term operation. Ionic liquids (ILs) are chemically and thermally stable and have low vapor pressure, which is ideal to prevent aforementioned losses. However, mechanical stability of supported IL membranes, especially under pressure drop conditions, is a concern. In this work, we report the use of an amino acid IL (containing facilitated carriers), 1-ethyl-3-methylimidazolium glycinate ([EMIM] [GLY]), as the facilitator for CO₂ capture. In order to selectively load and confine [EMIM] [GLY] in a thin selective layer, we fabricated a Single Walled Carbon Nanotubes (SWCNT) intercalated Graphene Oxide (GO) layer (thickness: ~300 nm). The distribution of [EMIM] [GLY] in the GO-SWCNT network is expected to be critical for the formation of a thin selective layer. To understand and optimize this, the ratio of GO to SWCNT was varied in an attempt to adjust the interaction between the network and [EMIM] [GLY]. The negatively charged GO flakes (because of hydroxyl, carboxyl and epoxy groups) act as anchoring sites for [EMIM] [GLY] molecules (due to electrostatic interaction between anions on GO and cations of IL), while the interconnected GO/SWCNT network provides numerous nanochannels for low-resistance gas transport. The influence of IL concentration, temperature, pressure and water on performance of the [EMIM] [GLY] restricted in GO/SWCNT framework was evaluated. The optimized membrane showed a CO₂ permeance of >1,500 GPU and CO₂/N₂ selectivity >300 for simulated flue gas. An attempt has also been made to segregate the contribution of facilitated transport and solution diffusion. It has been found that facilitated transport contributes ~30 times more to transport as compared to solution-diffusion.