Structural properties of concentrated lithium iodide aqueous solutions at high temperatures and pressures as determined using the method of integral equations

摘要

The structural properties of concentrated LiI : nH(2)O (n = 15, 8, 5) aqueous solutions were studied over a temperature range of 298-623 K at a pressure of 1500 bar. An analysis of its structural characteristics suggests that the LiI : 15H(2)O solution experiences a significant disordering of the water structure as the temperature increases; as a result, the intermolecular H-bond network weakens, and, therefore, the tetrahedral structure of water exists only at temperatures below 373 K. The Li : 8H(2)O and Li : 5H(2)O solutions show no tetrahedral ordering even at 298 K. For all the solutions studied, temperature rise is accompanied by the decrease of the coordination number of the cation and the disruption of the hydrogen bonds between the anion and nearest-neighbor water molecules. As the temperature increases, the concentration of contact ion pairs increases substantially while that of hydrate-separated ion pairs decreases.