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

Area of Science:

• Environmental Science
• Chemical Engineering
• Materials Science

Background:

• Growing concerns about greenhouse gas emissions necessitate effective carbon dioxide (CO2) separation technologies.
• Deep eutectic solvents (DESs) represent a promising class of selective CO2 absorbents due to their favorable properties.
• Reline, a DES composed of choline chloride and urea, is cost-effective, stable, non-toxic, and biodegradable.

Purpose of the Study:

• To demonstrate a scalable and energy-efficient hollow fiber membrane contactor (HFMC) process for CO2 capture using the green solvent reline.
• To investigate the physical absorption mechanism and optimize CO2 capture performance by adjusting solvent properties.

Main Methods:

• Utilized a hollow fiber membrane contactor (HFMC) system with commercial polymer membranes and the reline DES.
• Evaluated CO2 separation from a mixed N2/CO2 gas stream.
• Investigated the effect of water addition on reline viscosity and CO2 capture performance.
• Employed in situ Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) for mechanistic studies.

Main Results:

• Achieved 97 mol% CO2 purity using the reline-based HFMC system.
• Reduced reline viscosity by adding water, significantly increasing CO2 permeate flux by approximately 8 times.
• Demonstrated a permeate flux of 170 mmol/(m²·h) at optimal conditions (35 °C, 4 bar, 60 wt% water).
• Confirmed CO2 absorption via physical absorption and pressure swing mechanism, without chemical compound formation.

Conclusions:

• The HFMC process using reline offers an efficient and scalable method for CO2 capture from wet flue gas.
• Water addition effectively tunes reline viscosity, enhancing CO2 capture performance.
• The findings provide fundamental insights into green physical solvent-based CO2 separation and support industrial deployment.