Evaluation of the potassium salts of a series of five linear aliphatic amino acids for direct air capture
Year: 2026
Type: article
Abstract: In the present work, aqueous potassium salt solutions of five common linear amino acids bearing a terminal amino and carboxyl group (glycine, β-alanine, 4-aminobutyric acid, 5-aminovaleric acid, and 6-aminohexanoic acid) have been studied for their potential application as direct air capture (DAC) absorbents. Various characteristics including density, viscosity, overall mass transfer coefficient for carbon dioxide (CO 2 ), CO 2 cyclic capacity, and thermal stability were studied under DAC-relevant conditions. The experimental results demonstrated that, among the studied absorbents and conditions, the aqueous potassium salt of 5-aminovaleric acid (K-APA) showed the most favourable characteristics for use as a DAC absorbent. Moreover, the absorbent showed no precipitation at equilibrium with 101.3 kPa CO2 at room temperature (absorption capacity of 0.85 mol CO 2 /mol amino acid). Furthermore, K-APA containing 0.2 mol CO 2 /mol amino acid of CO 2 and heated at 120 °C for 8 weeks showed no signs of degradation, indicating excellent thermal stability, which was not observed for other absorbents studied in the current work. When reacting with CO 2 , K-APA produced the highest proportion of (bi)carbonate species among the studied absorbents, making it suitable for regeneration using low-temperature stripping technologies such as mineralisation of CO 2 or electrolysis of absorbed CO 2 . The work proposes an absorbent that is versatile and stable enough to be deployed in not only the conventional thermal stripping-based DAC processes but also in non-conventional DAC processes where low-temperature stripping technologies such as mineralisation can be used to regenerate the absorbent.
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,060
OpenAlex ID: W7207749051