Solubility of NaHCO₃ in Systems of Aqueous Glycols (Monoethylene Glycol, Diethylene Glycol, Triethylene Glycol, and Tetraethylene Glycol): The Role of Solvation

Abstract

The solubility and density of NaHCO3 in the systems: monoethylene glycol (MEG)-water, diethylene glycol (DEG)-water, triethylene glycol (TEG)-water, and tetraethylene glycol (TeEG)water have been measured over the entire concentration range from pure water to pure glycol.Experimental measurements have been conducted at the temperatures 5, 20, 40, and 60 °C, and at atmospheric pressure.The solubility of NaHCO3 in all glycol mixtures were increasing with increasing temperatures.Solubility is largest in aqueous MEG and decreases with the higher molecular weights of glycol 2 used. Local minima were observed in all systems in the concentration range 80 to 90 wt% glycol, salt-free. On a mole fraction scale, minima were found at x(glycol, salt-free)=0.5. There is a clear tendency that two solvate mechanisms exist with a 1:1 solvation relation. One type of solvation is formed in NaHCO3-water, and a second type is formed in NaHCO3-glycol.The density results showed a linearly increase up to a glycol concentration ≈ 80 wt%. Above 80 wt% the density seemed to form a minima similar to the solubility phase diagrams.