Synthesis of amine-modified hierarchical porous carbon from high-carbon coal gasification fine slag for coupled CO₂ capture and mineralization

Coal gasification fine slag (CGFS) is a solid waste produced during the gasification process, and its high carbon content limits its large-scale utilization. However, the preparation of amine modified hierarchical porous carbon adsorbents (HPCs) from CGFS not only reduces the production costs of matrix materials but also achieves high-value utilization. In this study, the high-carbon component of CGFS was utilized as the raw material to successfully synthesize an amine-modified HPCs for coupled CO 2 capture and mineralization via pre-impurity removal, chemical activation, and amine impregnation. Results demonstrated that HPCs exhibited excellent CO₂ adsorption performance. Specifically, the CO₂ adsorption capacities of 20 % PEI@HPC and 10 % TEPA@HPC with optimal amine loading reached 2.11 mmol/g and 1.62 mmol/g at 298 K, respectively. Both demonstrated outstanding CO₂ adsorption-desorption cycling performance and stability after 10 cycles. Furthermore, the amine-modified HPCs effectively enhanced the carbonation efficiency of desilicated slag, with 20 % PEI@HPC and 30 % TEPA@HPC increasing the mineralization efficiency of the desilicated slag from 28.68 % to 75.01 % and 82.69 %, respectively. Finally, this study elucidated the mechanism of coupled CO₂ capture and mineralization with amine-modified HPCs. The adsorption isotherm models revealed that CO₂ adsorption on the amine-modified HPCs was influenced not only by physical adsorption but also through chemical adsorption dominated by amine functional groups. In this study, a cost-effective CGFS was used as the raw material to synthesize amine-modified HPCs with excellent CO 2 adsorption performance. This approach was expected to address the issues of single-source and expensive matrix materials and had some potential for industrial- scale utilization.