Utilizing silica fume and synthetically produced mesoporous silicas for simulated flue gas CO₂ adsorption

Carbon capture and storage (CCS) is crucial in mitigating greenhouse gas emissions. Solid adsorbents, notable for their reusability and corrosion resistance, are gaining attention in CO₂ gas separation. This study uses Silica fume as an adsorbent and silica source for SiO₂ and MCM-41 silica-based adsorbents. Silica was extracted via an alkaline dissolution method, and adsorbents were synthesized using a CO₂-induced precipitation method, chosen for its shorter synthesis time and CO₂ utilization. The effects of pore volume, average pore diameter, and specific surface area on amine loading and CO₂ adsorption capacity were investigated using CTAB surfactant in SiO₂ synthesis, resulting in MCM-41. The synthesized adsorbents were modified with TEPA and DEA amines due to their high affinity for CO₂. After determining optimal amine loading, the impact of combining TEPA with DEA was examined. The highest CO₂ adsorption capacity under simulated flue gas conditions (15% volume CO₂ and 85% volume N₂) was 198 milligrams per gram of adsorbent for the SiO₂ adsorbent functionalized with 50% by weight amine (28% TEPA and 22% DEA). Variations in CO₂ adsorption over time, the influence of adsorbent quantity on adsorption capacity, the affinity of the adsorbent for N₂ adsorption, and the adsorption-desorption cycle were investigated. The 28%TEPA-22%DEA-SiO₂ adsorbent emerged as the optimal choice due to its large total volume and average pore diameter, absence of a template in its structure, excellent performance in CO₂ adsorption, lack of affinity for N₂, and robust adsorption-desorption stability.