Green CO2 Capture from Flue Gas Using Potassium Carbonate Solutions Promoted with Amino Acid Salts

CO2 emissions from various anthropogenic activities have led to serious global concerns (climate change and global warming), and, therefore, CO2 capture by sustainable methods is a priority research topic. One of the most widely used and cost-effective technologies for post-combustion CO2 capture (PCC) is the chemical absorption method, where potassium carbonate solution is proposed as a solvent (with or without the addition of promoters, such as amines). An ecological alternative, presented in this study, is the use of amino acids instead of amines as promoters—alanine (Ala), glycine (Gly) and sarcosine (Sar)—in concentrations of 25% by weight of K2CO3 + 5 or 10% by weight of amino acid salt, thus resulting in the so-called green solvents, which do not show high toxicity and inertness to biodegradability. The studies had as a first objective the characterization of the proposed green solvents, in terms of density and viscosity, and then the comparative testing of their efficiency for CO2 retention from gaseous fluxes containing high CO2 concentrations. The experiments were performed at temperatures of 298 K, 313 K, and 333 K at atmospheric pressure. The best performance was observed with K2CO3 + 5% Sar salt at 313 K, reaching an absorption capacity of 2.58 mol CO2/L solvent, which is a promising improvement over the reference solution based on K2CO3. Increasing the amino acid concentration to 10% generally led to a reduced performance, especially for sarcosine, probably due to an increase in solution viscosity or a possible kinetic inhibition. This study provides valuable experimental data supporting the ecological potential of amino acid-promoted potassium carbonate systems, paving the way for further development of chemisorption processes and their implementation on an industrial scale.