CO₂ Adsorption Investigation on an Innovative Nanocomposite Material with Hierarchical Porosity

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Developing efficient adsorbents for carbon dioxide (CO₂) capture is crucial for mitigating climate change.
• Zeolites and geopolymers are known for their adsorption properties, but combining them into a monolithic structure with hierarchical porosity presents unique opportunities.

Purpose of the Study:

• To synthesize a NaX nanozeolite-geopolymer monolith using a one-pot hydrothermal method.
• To characterize the microstructural, chemical, and CO₂ adsorption properties of the synthesized monolith.
• To evaluate its potential as a solid adsorbent for industrial CO₂ capture.

Main Methods:

• One-pot hydrothermal synthesis using metakaolin and sodium silicate solution.
• Microstructural and chemical characterization (e.g., BET surface area, porosity, compressive strength).
• CO₂ adsorption capacity measurement using a Sievert-type apparatus at varying temperatures (7, 25, 42 °C) and pressures up to 15 bar.

Main Results:

• The monolith features NaX zeolite nanocrystals embedded in a geopolymer binder, creating a hierarchical pore network.
• It exhibits a BET surface area of 350 m²/g, porosity of ~23.5%, and compressive strength of 16±0.7 MPa.
• Maximum CO₂ uptake reached ~21 wt% at 7 °C, decreasing to 18 wt% at 42 °C. The mesoporosity facilitated faster CO₂ transport compared to pure NaX zeolite.

Conclusions:

• The synthesized NaX nanozeolite-geopolymer monolith offers excellent CO₂ adsorption capacity and improved kinetics due to its hierarchical structure.
• The material's properties suggest its potential as an effective solid adsorbent for industrial carbon capture processes.
• Further research could optimize the synthesis for enhanced performance and scalability.