Steam activation of pitch-based carbon fibers for increasing CO₂ adsorption behaviors

Activated carbon fibers (ACFs) have attracted considerable interest as versatile adsorbents for gas separation, water treatment, and similar applications due to their high specific surface area, chemical stability, and robust mechanical properties. In this study, we synthesized ACFs using steam activation and systematically evaluated their CO₂ capture performance. The specific surface area of pitch-derived ACFs (SCF-X, where X is the activation temperature) increased significantly, reaching 2564 m² g⁻¹ in SCF-900. Notably, SCF-800 exhibited the highest CO₂ adsorption capacity, emphasizing the role of micropores <0.73 nm in facilitating efficient CO₂ uptake at 273 K (4.32 mmol g⁻¹), while larger micropores <1.1 nm contributed to a maximum adsorption of 3.50 mmol g⁻¹ at 298 K. Additionally, the adsorption kinetics were described by the pseudo-first-order model (R² > 0.99) across all temperatures (303, 313, and 323 K). This indicated that physisorption predominantly governs the process. Moreover, stable cyclic adsorption-desorption tests performed under simulated flue gas conditions (15% CO₂/85% N₂ at 313 K) demonstrated energy-efficient regeneration. These findings suggest that steam-activated ACFs are highly promising for CO₂ capture applications, offering advantages in terms of environmental sustainability, energy efficiency, and scalability.