Evaluation of physicochemical properties of Type-II deep eutectic solvents/Water mixtures based on choline chloride and calcium/magnesium chloride hexahydrate

Deep Eutectic Solvents (DESs)/water mixtures are widely proposed as unconventional green solvents in a wide range of applications. Here, we report a physicochemical characterization of type-II DESs (made by choline chloride and hexahydrate chloride of calcium or magnesium)/water mixtures, highlighting the potential of the techniques employed and their possible critical points. Viscosity, electrical conductivity, and density were measured at different temperatures and water contents and the data were analyzed to obtain information on the thermal expansibility coefficient, activation energy, and sample ionicity. Nuclear Magnetic Resonance and thermogravimetry provided additional information on the extent of the hydrogen-bond network in the mixtures. In addition, evaluation of microwave (MW) absorption capacity allowed us to classify the samples as suitable media for MW-assisted processes. Together, the information obtained made it possible to characterize the samples from both a structural and an application point of view.