Bi-amine functionalized mesostructured silica nanospheres for enhanced CO2 adsorption performance and fast desorption kinetics

A novel solid bi-amine adsorbent was synthesized by simultaneously impregnating pentaethylenehexamine (PEHA) and aminoethylethanolamine (AEEA) on the surfaces of mesoporous MCM–41 nanospheres. AEEA and PEHA had a synergistic effect during the CO2 adsorption of the bi-amine adsorbent and the highest CO2 adsorption capacity was 4.03 mmol·g−1. The bi-amine adsorbent exhibited the favorable recyclability because its saturated CO2 adsorption capacity decreased by 6.20 % after the initial eight adsorption/desorption cycles while by only 2.23 % in the following seven cycles. The adsorption activation energy and the desorption activation energy were determined to be 12.53 and 16.81 kJ·mol−1, respectively. The low value of the desorption activation energy suggested an inconsiderable energy requirement in the multicycles of the adsorbent. The characterization results indicated that hydrogen bonds were formed between the hydrogen atom in hydroxyl groups of AEEA and the oxygen atom in carbonyl groups of the carbamate. The synergistic effect between AEEA and PEHA was unveiled on the CO2 adsorption of the bi-amine adsorbent. The formed hydrogen bonds facilitated the release of protons from carbamic acids, enhanced the stability of the produced carbamate anions, and thus boosted the CO2 adsorption performance.