CO₂ separation by supported liquid membranes synthesized with natural deep eutectic solvents

Area of Science:

• Green chemistry and materials science
• Separation technologies
• Carbon capture and utilization

Background:

• Natural deep eutectic solvents (NADESs) offer a sustainable alternative to traditional solvents.
• Immobilizing NADESs into porous supports creates supported liquid membranes (SLMs) for gas separation.
• Polyvinylidene fluoride (PVDF) is a common polymer support material for membrane applications.

Purpose of the Study:

• To synthesize and characterize betaine-based NADESs using malic acid and tartaric acid as hydrogen bond donors (HBDs).
• To fabricate NADES-based-supported liquid membranes (NADES-SLMs) using a PVDF support.
• To evaluate the performance of NADES-SLMs for CO2 separation from CO2/N2 and CO2/CH4 mixtures.

Main Methods:

• Synthesis of NADESs by mixing betaine (HBA) with malic acid or tartaric acid (HBDs).
• Characterization of NADESs using FTIR, Raman spectroscopy, and thermogravimetric analysis.
• Fabrication of NADES-SLMs and evaluation of gas permeation for CO2/N2 and CO2/CH4 mixtures.

Main Results:

• NADES-SLMs exhibited enhanced CO2 permeability (25.55 to 29.33 Barrer) and CO2/CH4 selectivity (51.1 to 56.4) when malic acid replaced tartaric acid as the HBD.
• The NADES-SLMs demonstrated comparable gas separation performance to imidazolium-based supported ionic liquid membranes.
• The thermal stability of the NADESs was confirmed via thermogravimetric analysis.

Conclusions:

• Betaine-based NADESs immobilized on PVDF membranes are effective for CO2 separation.
• The choice of HBD significantly influences membrane performance, with malic acid showing superior results.
• NADES-SLMs present a promising, green alternative for industrial CO2 separation applications.