Greener gas capture in deep eutectic solvents aqueous solutions: Performance in a dynamic condition

The handling of large gas volumes containing low SO₂ concentrations is still a challenge for the industry. Here is possible to identify an opportunity for a cleaner production by using novel solvents such as ionic liquids (ILs) specially biodegradables Deep Eutectic Solvents (DES) as an alternative of amine-based absorbents which are volatile and easily degrades and may produce further contamination and health hazard. The present work analyses the performance of four DESs were under dynamic conditions (in a packed-bed column) for SO₂ absorption. The results were compared with the absorption capacities published for the same DESs under static conditions identifying essential differences to consider in a large-scale implementation. At low SO₂ partial pressure (600 ppm), chemical absorption becomes the most important mechanism, and thus, the chemical nature of the DES determines the absorption capacity. DESs containing amine groups showed superior absorption, and between the thiourea- and urea-containing DESs, the former exhibited the best performance, which was not related to its viscosity nor its initial solution pH but rather to the chemical interaction of functional groups in the DES promoting ionic interaction with generated sulphites.