Biohydrogen purification by <scp> CO ₂ </scp> capture with deep eutectic solvents

Abstract The presence of CO 2 in biohydrogen limits its industrial applications, particularly in fuel cells. In order to enhance biohydrogen purity and realize its application, a novel biohydrogen purification device with a CO 2 capture chamber and a deep eutectic solvents (DESs) regeneration chamber was used to capture CO 2 in biohydrogen by employing DESs. The key operational parameters such as device stirring rate, reaction temperature, and biohydrogen flow rate were investigated. Optimal conditions were identified as a biohydrogen flow rate of 2 L/min, a reaction temperature of 40°C, and a stirring rate of 500 r/min. Under these conditions, CO 2 capture capacity of 411 g (0.343 g CO 2 /g DESs) was achieved, with purified hydrogen concentrations (≥99.00%) sustained for 183 min. Furthermore, the DESs still demonstrated excellent regeneration and CO 2 capture performance after 4 heating cycles. This research provided a viable solution for efficient CO 2 capture in biohydrogen, facilitating its industrial application.