MECHANISM OF SOLUBILITY ELEVATION IN AQUEOUS MIXED-SOLUTIONS OF LIBR AND CACL2 - DEVELOPMENT OF LIBR-CACL2 MIXTURE ABSORBENT

To develop a high-solubility absorbent, a mechanism of solubility elevation was proposed and experimentally studied on the basis of the "co-hydration" phenomenon. The solute in an aqueous electrolyte solution is ionized and has many water molecules (hydration). Hydration has two regions, the structure-making region (SMR) and the structure-breaking region (SBR). Water vapor pressure depression relates to the hydration number of both regions, while solubility elevation relates to the hydration number of SMR. Solubility tends to increase when the hydration number of the ion, especially in the SMR, decreases. In the proposed solubility elevation mechanism, other ions are added to induce the "co-hydration" phenomenon, the hydration number in the SMR is decreased and the solubility is increased. This mechanism was examined experimentally using aqueous LiBr/CaCl2 solutions and the "co-hydration" phenomenon was confirmed by a compressibility depression seen in density measurements.