Polydimethylsiloxane based mixed matrix membranes with pretreated fumed silica for efficient CO₂ separation

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Polydimethylsiloxane (PDMS) membranes are promising for CO2 separation but suffer from low selectivity.
• Enhancing CO2/N2 and CO2/CH4 selectivity in PDMS membranes is crucial for efficient gas separation applications.

Purpose of the Study:

• To develop mixed matrix membranes (MMMs) using surface-treated fumed silica (FS) incorporated into a PDMS matrix.
• To improve the CO2 separation performance of PDMS membranes, specifically targeting enhanced selectivity over N2 and CH4.

Main Methods:

• Surface treatment of fumed silica (FS) to reduce hydrophilicity and improve dispersion in PDMS.
• Fabrication of PDMS-FS mixed matrix membranes (MMMs) with varying FS loadings.
• Single gas permeation tests to evaluate CO2, N2, and CH4 permeability and selectivity.

Main Results:

• Surface treatment of FS led to uniform dispersion in PDMS, increasing fractional free volume and enhancing CO2 permeability.
• The optimized MMM with 7.5 wt% FS exhibited a 1.42-fold increase in CO2 permeability and 1.47-fold and 1.39-fold enhancements in CO2/N2 and CO2/CH4 selectivity, respectively.
• Structural and thermal analyses confirmed the integrity of the PDMS matrix with filler incorporation; feed pressure and time showed no significant impact on separation performance.

Conclusions:

• Surface-treated FS incorporation effectively enhances the CO2 separation performance of PDMS-based MMMs.
• The optimized MMMs offer a promising solution for efficient CO2 capture and separation from N2 and CH4.
• The developed MMMs demonstrate robust performance, unaffected by variations in feed pressure or time.