Sustainable advancements in hazardous gases capture: Harnessing the potential of deep eutectic solvents

Abstract

Deep eutectic solvents (DESs) represent a promising solution for gas capture within existing industrial frameworks, requiring minimal retrofitting. This review explores the gas absorption and solubility capabilities of diverse DESs, emphasising their tunability through variations in hydrogen bond donors (HBDs), hydrogen bond acceptors (HBAs), and molar mixing ratios. The introduction of water marginally enhances gas absorption, while increased HBD ratios and elevated temperatures lead to decreased gas solubility. Conversely, pressure elevation improves gas solubility in DES. The alkyl chain length of the DES HBA correlates with gas solubility, attributed to an increase in DES free volume. Other factors like ionicity and alkalinity of DESs were reported to enhance gas capture. This review also discusses the selectivity of DESs in capturing distinct gases, unveiling a robust hydrogen-bond supramolecular network as the key determinant for high gas selectivity. Examples include effective NH3 capture within NH3/CO2 mixtures and targeted SO2 capture in CO2/SO2 mixtures. The absorption mechanism of gaseous pollutants using DES is both physical and chemical, with physical absorption playing a dominant role. During the regeneration of DESs, the stability and volatility of DESs are significant factors to consider. These insights underscore the potential of DESs in tailoring selective gas capture strategies, providing avenues for future research and practical applications in environmental and industrial contexts.