Akhmad Faruq Alhikami, Nurkholis Hamidi, Winarto Winarto, Lilis Yuliati
Effective CO2 adsorbents must combine high capacity, fast kinetics, thermal stability, and energy-efficient regeneration. A critical factor influencing CO2 interaction with silica-based materials is the presence of surface silanol (Si–OH) groups, which serve as active sites through hydrogen bonding and acid–base interactions. This study investigates rice husk-derived nanosilica (nSi) and the effect of silanol modification via NaOH (nSi-NaOH) and APTES (nSi-NH2) treatments on CO2 capture performance. Isoconversional kinetic analysis, CO2 temperature-programmed desorption (CO2-TPD), molecular simulations, and comprehensive surface characterization were employed to elucidate the role of surface chemistry in CO2 desorption energetics. Pristine nSi exhibited high activation and Gibbs free energies in the initial stage, consistent with limited surface reactivity and low CO2 uptake (0.158 mmol/g). Molecular modeling confirmed that functionalization strengthened CO2 interactions by increasing binding energy and electron redistribution. NaOH treatment reduced activation energy and enthalpy by up to 50%, indicating improved thermal response and enhancing CO2 uptake (0.365 mmol/g) via formation of basic Na–O surface sites. Amine functionalization with APTES introduced aminopropyl groups, leading to the highest CO2 capacity (0.863 mmol/g). However, this was accompanied by significantly higher decomposition energy (∆G = 241.39 kJ/mol), reflecting increased thermal resistance of grafted organic layers. These findings highlight the importance of tailored silanol chemistry in balancing between CO2 binding strength and regeneration efficiency, offering valuable design strategies for sustainable silica-based adsorbents in carbon capture applications. © The Author(s), under exclusive licence to Springer Nature B.V. 2025.
Department of Mechanical Engineering, Universitas Brawijaya, Malang, 65145, Indonesia; Department of Mechanical Engineering, Universitas Islam Malang, Malang, 65144, Indonesia
