Effect of the presence of water-soluble amines on the carbon dioxide (CO₂) adsorption capacity of amine-grafted poly-succinimide (PSI) adsorbent during CO₂ capture

Global climate change is among the major challenges the world is facing today, and can be attributed to enhanced concentrations of Greenhouse Gases (GHG), such as carbon dioxide (CO₂), in the atmosphere. Therefore, there is an urgent need to mitigate CO₂ emissions, and carbon capture and storage (CCS) is amongst the possible options to reduce CO₂ emission. Against this background, this work investigated the synthesis and performance evaluation of a new material for CO₂ capture. In particular, the effect of the presence of water-soluble amines in the amine-grafted poly-succinimide (PSI) (referred to as Polyaspartamide (PAA) adsorbent), was investigated. Methyl Amine (MA) and Mono-Ethanol Amine (MEA) were employed as water-soluble amines and the effect of changes in their concentration on CO₂ adsorption capacity was investigated as well. Water-soluble amines were incorporated to allow water solubility of the adsorbent paving way for freeze-drying to improve the geometric structure (surface area, pore volume and pore size) of the adsorbent. The water-soluble amines were grafted to an already Ethylenediamine (EDA) grafted PSI (PSI-EDA), with the EDA added to improve the chemical surface of the adsorbent for CO₂ capture. The NMR analysis confirmed the presence of MA and MEA amine groups in the PAA, thereby indicating the presence of the grafted amines on the backbone polymer. An increase in adsorption capacity with an increase in MA and MEA concentrations in MA-PAA and MEA-PAA samples was observed. At low amine concentrations (20% amine and 80% EDA grafted), MEA-PAA was observed to exhibit higher adsorption capacity compared to the MA-PAA samples. At high amine (100% amine grafted) concentrations, MA-PAA samples displayed higher adsorption capacity. Three runs were performed on each sample and the results obtained were reproducible. The best adsorption capacity obtained was 44.2 g CO₂/kg Ads. However, the operating conditions during the CO₂ adsorption should be optimized for enhanced CO₂ adsorption capacity.