(27c) Highly Selective Hollow Fiber Membranes for Carbon Capture Via in-Situ Layer-By-Layer Surface Functionalization

Recent developments in the field of carbon sequestration have generated a renewed effort for efficient separation of CO₂, which can be sent to a aquifers or depleted reservoirs for a long-term storage. However, current CO₂ capture technologies, including absorption and pressure swing adsorption, are expensive and contribute 70-80% to the total cost of overall carbon capture and sequestration process. In the past two decades, cost effective membrane technology for CO₂ separation has gained significant attention because of inherently low energy consumption, small carbon footprint and passive operation.

Homogenous polymeric membranes currently studied for separation of O₂ from air and CO₂ from natural gas possess an intrinsic trade-off between permeability and selectivity [1], while industrial application demands membranes with both high permeability and selectivity. Poly(ethylene oxide) (PEO) is a potential candidate for CO₂ selective membranes owing to the unique interaction of the dipole-quadrupole of polar ether groups. In Our past work, we employed layer-by-layer (LbL) technique to fabricate Polymethacrylic acid (PMAA)/polyethylene oxide (PEO) films on polystyrene which demonstrated high CO₂:N₂ (~ 135) selectivity [2]. However, these membranes had but low CO₂ permeability (0.011 barrer).

This works aims to demonstrate a cost-effective approach of deposition of highly CO₂ selective membranes via LbL route on hollow fibers (HF), provided by our collaborator at NETL. These HFs were first potted inside a set-up and polyelectrolyte solution though the setup to deposit functional thin film. After addition of 20 bi-layers of PEO/PMAA on HF substrate, the selectivity of CO₂ over N₂ increased by 3 orders of magnitude exceeding the Robeson’s upper bound for homogenous polymeric films [3]. This work for the first time reports a thin deposition of membranes on HF with high selectivity (~1000) of CO₂ over N₂ as well as significant permeability (~50 barrer). The LbL technique on low-cost and mass-producible HF substrate has a potential use in carbon dioxide capture in power plants and refinery flue gases.

1. Freeman, B.D., Basis of permeability/selectivity tradeoff relations in polymeric gas separation membranes. Macromolecules, 1999. 32(2): p. 375-380.
2. Song, Y., et al., Highly selective multilayer polymer thin films for CO2/N2 separation. Journal of Polymer Science Part B: Polymer Physics, 2017. 55(23): p. 1730-1737.
3. Robeson, L.M., The upper bound revisited. Journal of Membrane Science, 2008. 320(1-2): p. 390-400.