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.