Physicochemical properties comparison of deep eutectic mixtures of choline chloride with urea, glucose and citric acid

Deep eutectic mixture (DEM) of choline chloride (ChCl) with urea, glucose and citric acid are biodegradable, non-volatile, non-reactive, non-toxic and safe. Its application in the extraction process is not favored since it possesses high viscosity. The viscosity of DEM can be reduced by simply add water as a co-solvent. However, this method causes a dramatic change in their physicochemical properties. In the present work, the physicochemical properties of ChCl:urea, ChCl:glucose and ChCl:citric acid were investigated. A significant change in the viscosity, density and conductivity of the DEM occurred when water is added. The addition of water reduces the viscosity and density of DEM, while the conductivity increases. Viscous DEM is not suitable for the separation process due to the possibility of limitation for molecular diffusion, whereas conductive DEM could be used as an electrolyte.