Development of KOH-impregnated activated carbon from coal for carbon dioxide capture

With increasing globalization and industrialization, reducing carbon dioxide (CO₂) emissions has become a critical global challenge. The objective of this study was to investigate the potential of coal-derived activated carbon (AC) for CO₂ adsorption under environmentally relevant conditions. In the present study, AC derived from peat and lignite coal was synthesized by a chemical activation method using a wide range of KOH with impregnation ratios (1:1, 1:2, 1:4, 1:6, and 1:8), enabling precise control over micropore development. This study identifies the optimum impregnation ratio that maximizes the ultra-micropore volume, which is directly responsible for enhanced CO₂ adsorption. The prepared materials were systematically characterized by proximate and ultimate analyses, Brunauer-Emmett-Teller surface area measurements, thermogravimetric analysis, Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. CO₂ adsorption experiments were conducted by the Autosorb iQ gas sorption analyzer at near-ambient temperature and pressure. The lignite-derived AC at a 1:8 impregnation ratio showed the highest CO₂ uptake (46.27 mg g^-1) with a breakthrough time of 204.7 min. The most important novelty of our work is the productive utilization of low-grade coal, as a viable precursor and aim is to convert such low-grade coal for the production of high-performance and cost-effective CO₂ adsorbents, which aligns with sustainable materials development and carbon management.