Pomelo Peel-derived Active Carbon Aerogel for Methane Adsorption: Performance Evaluation and Mechanism Study

Abstract

Methane (CH₄) is a greenhouse gas, as well as a clean energy source. The key to reducing its emissions and enabling its resource utilization lies in the efficient capture of CH₄ from the environment. This study utilized pomelo peel as a raw material to prepare a pomelo peel-derived activated carbon aerogel (PPACA), PPACA was characterized and used as adsorbent for CH₄. Its adsorption capacity and mechanism for CH₄ were investigated, and its CH₄/N₂ selectivity and cyclic stability were also explored. The results indicated that KOH activation significantly optimized the pore structure and improved the surface chemistry of the material, resulting in a high specific surface area, abundant ultramicropores, and an increased content of surface basic groups. The resulting ultramicropore filling effect plays a dominant role in enhancing CH₄ adsorption, while the increased content of surface basic groups plays a secondary auxiliary role. Increased adsorption temperature and higher gas flow rate adversely affected the adsorption, while increasing the adsorption pressure increased the adsorption capacity. The equilibrium adsorption process of CH₄ on PPACA was accurately described by the Sips model and was identified as physisorption. The adsorption kinetics followed the Bangham model, indicating that the adsorption rate is controlled by pore diffusion. Furthermore, at 298 K and 1 bar, the CH₄ adsorption capacity of PPACA achieved 1.92 mmol·g^− 1, and its IAST selectivity (CH₄/N₂, 10/90 v/v) reached 6.41, which is competitive with or better than many other adsorbents. It also exhibited good cyclic stability. These findings provide a reference and theoretical basis for the application of such novel adsorbents in CH₄ adsorption and capture.