Excess Properties of and Simultaneous Effects of Important Parameters on CO₂ Solubility in Binary Mixture of Water-Phosphonium Based-Deep Eutectic Solvents: Response Surface Methodology (RSM) and Taguchi Method

This study provides useful information on the existing interactions in an aqueous solution of deep eutectic solvents (DESs) by studying excess properties namely excess refractive index and excess logarithm viscosity at different concentrations and temperatures. In order to investigate the effects of DES mole fraction and temperature on the refractive index and viscosity of binary mixtures, the response surface methodology (RSM) was applied based on the mixed-level full factorial design. The analysis of variance (ANOVA) results revealed that although both DES mole fraction and temperature are significant, the DES mole fraction has more effect on these thermophysical properties. Results showed that as excess refractive index and excess logarithm viscosity values are positive over the whole composition range and maximum excess data were investigated at the water-reach region. Moreover, the effects of important factors influencing CO₂ solubilities such as pressure, temperature, water content, and molecular weight of DES were determined using the Taguchi L₁₈ method. A regression model was developed based on the Taguchi method for prediction of the prediction of CO₂ solubility. The results disclosed that the pressure is the most significant factor influencing the CO₂ fraction followed by the water content and molecular weight of DESs while the temperature had the lowest effect. The error evaluations indicated that the Taguchi model is an accurate model and had excellent performance in prediction of the CO₂ solubility.