Effect of Viscosity of a Deep Eutectic Solvent on CO2 Capture Performance in an Energy-Efficient Membrane Contactor-Based Process

Zachary Coin, Shailesh Dangwal, Mary Hannah Irwin, Thomas Knight, Ramesh Bhave, Gernot Rother, Robert Sacci, Md Arifuzzaman, Vera Bocharova, Ilia Ivanov, David S. Sholl, Syed Z. Islam

Research output: Contribution to journalArticlepeer-review

Abstract

Greenhouse gas contributions to climate change have driven intense interest in the separation of CO2 from wet flue gas streams. Deep eutectic solvents (DESs) are an emerging class of highly selective CO2 absorbents. A prototypical DES, reline, is a mixture of choline chloride and urea. Reline is a thermally stable, nontoxic, and biodegradable solvent with negligible volatility and is inexpensive. We demonstrate a scalable and energy-efficient hollow fiber membrane contactor (HFMC)-based process using a green solvent for CO2 capture. This process uses reline in HFMC to provide close interfacial interactions and contact between DES and CO2. This approach overcomes the disadvantages associated with direct absorption in DES and could potentially be applied to a variety of solvent-based CO2 capture methods. Commercial, low-cost polymer hollow fiber membranes were evaluated for the capture of CO2 with reline. From a mixed gas containing N2 and CO2, the DES-based HFMC separated CO2 with a purity of 97 mol %. The effect of the viscosity of reline on the CO2 capture performance was investigated by adding water to the reline. The addition of water to reline significantly reduced its viscosity, which led to a permeate flux of 170 mmol/(m2·h) at 35 °C, 4 bar, and 60 wt % water in solvent, which was approximately 8 times higher than that of the pure reline in the membrane contactor system. In situ Fourier transform infrared spectroscopy and nuclear magnetic resonance (NMR) revealed that reline absorbs CO2 by physical absorption without forming new chemical compounds and that CO2 separation by reline occurs via the pressure swing mechanism. This research provides fundamental insights about green physical solvent-based separation processes and a pathway toward industrial deployment.

Original languageEnglish
JournalACS Omega
DOIs
StateAccepted/In press - 2025

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