Preparation of mesoporous coal-gasification fine slag adsorbent via amine modification and applications in CO2 capture

Here, a novel adsorbent was prepared from coal-gasification fine slag by acid leaching and amine modification and was used for CO2 capture. The fine slag adsorbent (FSA) material was found to have a specific surface area of 541 m2 g−1 and a pore volume of 0.543 cm3 g−1. To improve the CO2 adsorption capacity of the material, the raw FSA was immobilized with amines through physical impregnation. The FSA-based composites were developed using four types of amines: ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA). The optimum formula was found to be the FSA loaded with 20 wt% TEPA (FSA-TEPA-20), whose theoretical maximum adsorption capacity for CO2 was 132.5 mg g−1 (273 K). The partition coefficient values obtained at 100% breakthrough for FSA and FSA-TEPA-20 were determined as 1.4 × 10−4 and 3.3 × 10−4 mol kg−1 Pa−1, respectively, which were far superior to those of other mesoporous materials (e.g., SBA-PEI). The FSA-TEPA-20 showed good cycling stability. The reaction mechanism was investigated, and the thermodynamic/kinetic parameters for CO2 adsorption were derived; the adsorption was demonstrated to follow the Avrami model. The strength of the preparation strategy is it enables the development of a high-performance adsorbent from low-cost solid wastes.