Solubility of CO₂ in deep eutectic solvents: Experiments and modelling using the Peng-Robinson equation of state

Carbon dioxide capture and sequestration is drawing increasing attention as a potential method for controlling greenhouse gas emissions. Low cost ionic liquid analogues, namely, deep eutectic solvents (DESs), have attracted more attention for use in a diversity of applications. DESs exhibit many favourable properties, such as availability, non-toxicity, biodegradability, recyclability, non-flammability, and low price.In this work, phosphonium- and ammonium-based DESs with different hydrogen bond donors (HBD) have been synthesised. Then, the CO₂ solubility in the synthesised DESs at a fixed pressure and temperature was determined, experimentally. Furthermore, a mathematical model based on the Peng-Robinson (PR) equation of state (EoS) was developed to correlate the CO₂ solubility in these types of DESs. The model was validated with the obtained experimental data and tested with other specific DESs reported in the literature over a wide range of temperature and pressure values. In general, there was a good agreement between the experimental data and the calculated data using PR EoS. The obtained model can be utilised to study the effectiveness of using DES in CO₂ capturing processes or any other separation processes.