Viscosities and Carbon Dioxide Solubilities of Guanidine Carbonate and Malic Acid-Based Eutectic Solvents

Carbon capture and storage (CCS) is one of the technologies needed to reduce anthropogenic emissions of CO2 in the atmosphere. Protic ionic liquids (PILs) are potential nonaqueous solvents that can combine the benefits of ionic liquids (ILs) and deep eutectic solvents (DESs) to make the carbon capture process more sustainable. In the present study, the viscosities of six eutectic-based solvents have been measured within a temperature range of 303.2–330.2 K and have been modeled using a Vogel–Fulcher–Tammann (VFT)-type equation. The results showed that guanidium malate-based eutectic solvents have significantly lower viscosities than most other deep eutectic solvents. Additionally, CO2 solubilities in three different guanidium-based eutectic solvents have been measured within a temperature range of 313.2–333.2 K and pressures of up to 200 kPa. Henry’s law constants of CO2 in pure solvents were obtained by modeling the solubility in mixed (aqueous) solvents. The values obtained for Henry’s law constants of CO2 in the studied guanidium-based eutectic solvents were found to lie within a range of 1.3–24 MPa. The values of the Gibbs free energy and the dissolution enthalpy and entropy showed that the CO2 absorption is exothermic, and after CO2 absorption, the entropy of the systems decreased.