Synthesis of porous SiO₂ materials from steel slag for CO₂ adsorption

Abstract

During carbon capture from steel slag, large amounts of calcium and magnesium are utilized, whereas silica is largely unutilized. In this study, porous SiO₂ materials were synthesized from the silicon in steel slag for use in indirect carbon capturing. The porous SiO₂ materials were synthesized from γ-dicalcium silicate (γ-Ca₂SiO₄ or γ-C₂S), the main silicon-containing phase in steel slag. The phase exhibits moderate reactivity, and the synthesis of the materials was achieved by optimizing the synthesis parameters and minimizing the influence of other elements present in the slag. The effects of synthesis temperature and pH value of the porous SiO₂ materials on their morphologies, structural parameters, and CO₂ sorption performance were investigated. Using cetyltrimethylammonium bromide as a template agent, porous SiO₂ materials with controllable structural properties could be prepared by adjusting their synthesis temperature and pH values. Porous SiO₂ materials with outstanding properties, such as tunable pore diameters and high specific surfaces (~1000 m²/g) were synthesized in an acidic solution via different types of interactions between the organic template and inorganic silica species. The maximum CO₂ sorption capacity of the porous SiO₂ material samples exceeded 70 mg/g. A resource utilization mechanism for transforming silica sources in steel slag into porous SiO₂ materials is proposed in the study. Highly ordered, pure porous SiO₂ materials with large specific surface areas were successfully synthesized from steel slag. The results indicated that steel-slag-based porous SiO₂ materials would be promising candidates for the in situ CO₂ capture in the steel industry.

Keywords

Porous SiO₂ material / Steel slag / CO₂ capture / Resource utilization

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