In this study, the activated carbon was prepared with superior CO₂ selective adsorption properties using walnut shells, a biomass waste, as a precursor. The activations were conducted at various times using the microwave heating technique in a steam atmosphere. The surface morphology and chemical composition of activated carbon were analyzed using a scanning electron microscope and energy-dispersive X-ray spectroscopy. The textural properties were investigated using the N₂/77K isothermal method, and the structural characteristics were examined using X-ray diffraction analysis. The CO₂ and H₂ adsorption properties of activated carbon were analyzed using a thermogravimetric analyzer and a high-pressure isothermal adsorption apparatus, respectively, under atmospheric and high-pressure conditions. Depending on the activation time, the specific surface area and total pore volume of the activated carbon were 570–690 m²/g and 0.26–0.34 cm³/g, respectively. The adsorption behaviors of CO₂ of the activated carbon were different under atmospheric and high-pressure conditions. At atmospheric pressure, a significant dependence on micropores with diameters less than 0.8 nm was observed, whereas, at high pressure, the micropores and mesopores in the range of 1.6–2.4 nm exhibited a significant dependence. However, H₂ adsorption did not occur at relatively low pressures. Consequently, the prepared activated carbon exhibited superior selective adsorption properties for CO₂.

Evaporative emissions from automobiles, which mainly consist of hydrocarbons, are a major source of air pollutants. As such, prevention means are required to minimize such emissions. Evaporative emissions are collected using adsorbents, where the adsorption capacity is directly influenced by the ratio of oxygen-containing functional groups, which have high polarity. This study investigated the effect of controlling the oxygen functional group (OFG) on the hydrocarbon adsorption/desorption performance of activated carbon fiber (ACF) in adsorbents. We used microwave heating to remove OFG on the ACF surfaces. The removal of surface OFG by microwave heating was analyzed using scanning electron microscopy-energy-dispersive X-ray spectroscope (SEM-EDS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric–infrared gas analysis (TGA-IR), and X-ray photoelectron spectroscopy (XPS). According to microwave heating, textural properties were analyzed using N₂/77K adsorption/desorption isotherms. The hydrocarbon adsorption/desorption performance of the ACF was evaluated according to a modified ASTM D5228. Compared to the untreated ACF, the butane working capacity of the modified (non-polarized) ACF was increased by up to 20% (adsorption capacity 27%).