Synergistic mechanism between mineralization and capillary trapping in MSWIFA-based carbon sequestration material

Area of Science:

• Environmental Science
• Geochemistry
• Materials Science

Background:

• Municipal solid waste incineration fly ash (MSWIFA) is a growing urban waste stream.
• MSWIFA's potential for CO2 sequestration via self-foaming is underexplored.
• MSWIFA can improve backfill material porosity and Ca2+ content, enhancing storage capacity.

Purpose of the Study:

• To investigate the coupled mechanisms of CO2 mineralization and capillary trapping in MSWIFA-based backfill.
• To elucidate the effects of in-situ goaf environmental conditions (temperature, pressure) on MSWIFA mineralization.
• To understand how mineral composition, pore structure, and surface properties influence hydrodynamic behavior and CO2 storage.

Main Methods:

• Investigated CO2 mineralization and capillary trapping in MSWIFA backfill under simulated goaf conditions.
• Analyzed the impact of mineral composition, pore structure, and surface properties on hydrodynamic behavior.
• Examined the role of elevated temperature and pressure on mineral transformations and pore architecture.

Main Results:

• A strong synergistic effect between mineral carbonation and capillary trapping significantly enhances CO2 storage.
• Elevated goaf temperature and pressure accelerate calcium silicate hydrate (C-S-H) decomposition, promoting carbonate mineral formation.
• Mineral transformations alter surface properties and pore structure, creating fine pores and large pore segments, optimizing CO2 sequestration.

Conclusions:

• MSWIFA-based backfill materials offer a promising strategy for enhanced CO2 sequestration.
• Optimizing surface characteristics and pore architecture is crucial for maximizing CO2 storage efficiency.
• This research provides a novel approach for high-value utilization of hazardous waste and contributes to greenhouse gas mitigation.