Advancing Ionic Liquid-Based Membrane Fabrication: Spray-Coating as a Pathway for Mixed-Matrix Membranes

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Technology

Background:

• Developing efficient mixed-matrix membranes (MMMs) is crucial for industrial carbon dioxide (CO2) separation.
• Ionic liquids (ILs) and functionalized silica IL (SiIL) microparticles offer promising properties for membrane applications.
• Fabrication methods significantly influence membrane performance and architecture.

Purpose of the Study:

• To investigate the impact of two distinct fabrication strategies, solvent casting and spray-coating, on the CO2 separation performance of IL-based MMMs.
• To evaluate the role of functionalized silica IL (SiIL) microparticles as fillers in poly(diallyldimethylammonium) bis(trifluoromethylsulfonyl)imide (PIL) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (IL) based membranes.
• To compare the gas transport properties (permeance, permeability, diffusivity, solubility) and selectivity (CO2/N2) of membranes produced by each method.

Main Methods:

• Fabrication of IL-based MMMs using solvent casting and spray-coating techniques with varying SiIL filler loadings.
• Characterization of membrane performance through gas permeation experiments for CO2 and N2.
• Analysis of CO2/N2 selectivity, gas permeance, permeability, diffusivity, and solubility to assess separation efficiency.
• Evaluation of membrane performance under mixed-gas conditions (15% CO2, 85% N2).

Main Results:

• Spray-coated membranes achieved significantly higher CO2 permeances (up to 27 GPU), approximately ten times greater than solvent-cast samples, while maintaining good CO2/N2 selectivity (29-40).
• Solvent-cast membranes exhibited lower CO2 permeances (2-3 GPU) but showed uniform filler dispersion and a 63% increase in CO2 permeability at optimal SiIL loadings.
• Spray-coated membranes demonstrated superior performance under mixed-gas conditions with minimal CO2 permeance loss (5%-9%), whereas solvent-cast membranes maintained selectivity but had lower flux.

Conclusions:

• Membrane fabrication methodology critically dictates membrane architecture and gas transport behavior, more so than filler content alone.
• Spray-coating is a highly effective approach for producing ultrathin, selective layers, leading to high-performance MMMs for scalable CO2 separation.
• The choice of fabrication technique allows for tailoring membrane properties to optimize either flux or selectivity for specific industrial CO2 separation applications.