Gas permeation through nanoporous membranes in the transitional flow region

Area of Science:

• Materials Science
• Chemical Engineering
• Physical Chemistry

Background:

• Nanoporous membranes are crucial for gas separation and filtration.
• Understanding gas transport in the transitional flow regime (Knudsen numbers 0.1-10) is essential for optimizing membrane performance.
• Existing gas permeation models often fail to accurately predict behavior due to molecular interactions.

Purpose of the Study:

• To experimentally investigate gas permeability through anodic alumina and track-etched nanoporous membranes.
• To analyze gas transport behavior in the transitional flow regime.
• To develop and validate new models accounting for molecular collision dynamics and slip flow effects.

Main Methods:

• Experimental measurements of gas permeance across anodic alumina (20-120 nm) and track-etched (30 nm) membranes.
• Varying Knudsen numbers from 0.1 to 10 to explore the transitional flow regime.
• Developing two novel models based on intermolecular collisions and tangential momentum accommodation.

Main Results:

• Observed significant variations (up to 30%) in membrane permeance for different gases at identical Knudsen numbers.
• Identified molecular effective collision area as a key factor influencing permeance, poorly addressed by conventional models.
• Validated proposed models against experimental data for 30 membrane-gas pairs, demonstrating improved predictive capability.

Conclusions:

• Molecular effective collision area significantly impacts gas permeation in nanoporous membranes within the transitional flow regime.
• The proposed models offer a more accurate description of gas transport by incorporating intermolecular collisions and slip flow enhancements.
• This research provides a refined understanding of gas-membrane interactions, crucial for advanced separation technologies.