Determination of the optimum porosity for 2-CEES adsorption by activated carbon fiber from various precursors

In this study, we prepared ACFs with a high specific surface area from various precursors (rayon, pitch, and oxidized polyacrylonitrile-based fibers) by a steam-activation technique and investigated the effects of the micropore and mesopore fraction on 2-CEES adsorption behaviors. The activation time was precisely controlled so that the activation yield was in the range of 35–40% to ensure the mechanical properties of the ACFs. The N₂ adsorption isotherm characteristics at 77K were confirmed by Brunauer–Emmett–Teller, Barrett–Joyner–Halenda and non-local density functional theory equations. The adsorption capacities of the ACF were measured by breakthrough experiments in the gas phase (750 μg/mL of 2-CEES in N₂ flow). The removal efficiency of the ACFs was evaluated and compared with that of AC. From the results, specific surface areas and total pore volume of the ACF were determined to be 1380–1670 m²/g and 0.61–0.82 cm³/g, respectively. It was also observed that various pore characteristics of ACF were found to be dependent on crystallite structure of each precursor. The break through time (C/C₀ = 0.10) was in the order of Oxi-Pan-H-9-2 < Saratoga AC < Rayon-H-9-3 < Pitch-H-9-4. This indicates that 2-CEES adsorption capacity could be a function not only of specific surface area or total pore volume, but also of sub-mesopore volume fraction in the range of 1.5–2.5 nm of adsorbents.