Abstract Structured adsorbents offer important advantages over conventional bead- or pellet-shaped materials used in fixed-bed gas separation processes. In particular, monolithic architectures can reduce pressure drop and enhance mass and heat transfer, leading to improved process performance. In this work, an activated carbon honeycomb monolith (ACHM) was produced from rice husk through extrusion, carbonization and CO 2 activation. The material was characterized by N 2 physisorption at 77 K, mercury porosimetry and scanning electron microscopy (SEM), confirming a hierarchical porous structure. Thermogravimetric analysis indicated thermal stability up to 873 K. Adsorption equilibrium isotherms of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrogen (N 2 ) were obtained at 303, 323, 348 and 373 K using a manometric method. The ACHM exhibited a higher affinity towards CO 2 , followed by CH 4 and N 2 . The adsorption equilibrium data were accurately correlated using the Dual-Site Langmuir and Toth models. Dynamic single component breakthrough experiments were performed and the results fitted to a mathematical model to determine mass and heat transfer parameters. These were subsequently used to predict the multicomponent breakthrough curves, which consisted in binary mixtures of CO 2 /N 2 and CO 2 /CH 4 . The CO 2 /N 2 and CO 2 /CH4 selectivities at 1 bar and 303 K were ca. 18 and 4, respectively, demonstrating the good potential of the rice husk-based ACHM for adsorption-based processes targeting CO 2 removal from flue gases and biogas.
Ortega-Ortiz et al. (2026) studied this question.