Highly selective CO2 capture over N2 on amine impregnated oxidized granular carbon

The development of efficient and scalable solid sorbents is crucial for advancing CO 2 capture technologies. While commercial activated carbons are inexpensive and porous, they typically exhibit low CO 2 selectivity. This study demonstrates a facile two-step strategy to significantly enhance the CO 2 capture performance of a commercial granulated activated carbon (DGAC). The carbon was first oxidized with nitric acid to create anchoring sites, and then impregnated with the amine-rich polymer polyethylenimine (PEI). Comprehensive characterization like SEM-EDS, XPS, BET confirmed the successful incorporation of PEI onto the oxidized surface. The modified adsorbent (O-DGAC@PEI) achieved a remarkable CO 2 adsorption capacity of 4.67 mmol/g at 273 K and 1 bar, nearly double that of the pristine DGAC (2.6 mmol/g). More importantly, it exhibited exceptional CO 2 /N 2 selectivity of 349 (for a 15/85 CO 2 /N 2 mixture), as calculated by the Ideal Adsorption Solution Theory (IAST). The high isosteric heat of adsorption of 73.63 kJ/mol confirms chemisorption as the dominant mechanism, facilitated by the introduced amine groups. The adsorption process was spontaneous and well-described by the Dual-site Langmuir model. Thus, O-DGAC@PEI offers a favorable balance of high adsorption capacity, strong humidity resistance, and stable cyclic performance, distinguishing it from previously reported systems and demonstrating its potential for practical CO 2 capture applications.