Coal gasification fine slag as a precursor to prepare mesoporous carbon materials by an activation-hydrothermal two-step method for CO₂ adsorption

Coal gasification fine slag (CGFS) is a solid waste produced from gasification process, which consists of residual carbon with porous structure and minerals. The capture of CO₂ by porous materials is an effective method for reducing CO₂ emissions from industrial sources. In this work, the effective separation of residual carbon and ash from CGFS was achieved by froth flotation. A mesoporous carbon material for CO₂ adsorption was successfully synthesized using a two-step chemical activation-hydrothermal method. The results showed prepared mesoporous carbon materials with a specific surface area of 670 m²/g. These materials exhibited an adsorption capacity of 29.4 cm³/g for CO₂ in actual adsorption tests, and their performance remained stable after 10 cycles. Silica-aluminum gel material formed around the pores of the mesoporous carbon during hydrothermal synthesis, leading to a 12.3 cm³/g increase in CO₂ adsorption capacity. The mesoporous carbon materials demonstrated a superior CO₂ adsorption rate, and reached the adsorption equilibrium within 2 min. The two-step chemical activation-hydrothermal method is capable of developing high-performance adsorbent materials from low-cost solid wastes and has some potential for practical applications.