Binary carbon dioxide and nitrogen adsorption on pomelo peel-derived porous sorbent

Abstract

The rising concern regarding CO2 emission from fossil fueled-power plants, along with the heightened interest in repurposing biowaste has necessitated the utilization of biowaste as an adsorbent for CO2 capture. In this study, the pomelo peel-derived activated carbon (POM-AC) was investigated as a potential adsorbent for post-combustion CO2 capture application, which involves capturing CO2 from the CO2 and N2 gas mixture. The POM-AC was characterized, revealing a microporous-mesoporous structure that contains various surface functional groups including hydroxyl, carbonyl, carboxyl, and alkene groups. The strong affinity of POM-AC towards CO2 over N2 was demonstrated from the increment in the CO2 and N2 gas mixture uptake with the increase in CO2 gas compositions. The total adsorption capacity of POM-AC at ambient conditions for 100% CO2, 15% CO2, 10% CO2, and 5% CO2 is 127.8 mg/g, 55.7 mg/g, 49.1 mg/g, and 38.3 mg/g, respectively. Notably, POM-AC outperformed the commercial activated carbon (Chemiz-AC) at simulated post-combustion conditions due to POM-AC having smaller pores than Chemiz-AC. The Ideal Adsorbed Solution Theory (IAST) prediction of binary CO2 and N2 adsorption equilibria showed higher CO2 adsorption capacity than N2 at post-combustion gas compositions (5–15% CO2), which further suggests its stronger preferential of CO2 over N2. Furthermore, a relatively high CO2/N2 selectivity of 23.9 was predicted for 15% CO2 gas composition. The adsorption isotherm and kinetic analysis revealed that the surface of POM-AC is heterogenous, and the rate-controlling step of CO2 and N2 adsorption is physisorption. Coupled with the utilization of a zero-cost biowaste as an activated carbon precursor, these findings showed that POM-AC could be a promising adsorbent for post-combustion CO2 capture application.