Concentration Process of Sea Water Computed Graphically with Phase Diagram at 110°C

Abstract

In their previous paper (This Journal, 25, 141-147 (1971)), the authors wrote a report on the equilibrium values of the five-component system, Na, K, Mg, Cl, SO₄-H₂O saturated with NaCl at 110°C, which were gained by partial modification of the values found in the classical work of D'Ans.
In the present paper, the authors treated graphically the isothermal evaporation of the sea wate at 110°C, and computed the changes of the compositions of solutions and the kinds of crystalls deposited during the process. Also, they calculated the composition of the solution at which the deposition of NaCl began, by the theoretical equation introduced by Amirkhanov (Zhur. Neorg. Khim., 9, 2465 (1964)). Furthermore, the authors discussed the validity of such method by using the data of Harada (This Joumal, 13, 238 (1959)) and of Maeda (J. Chem, Soc. Japan, Ind. Chem. Sec., 23, 1129 (1920)). As the result, the authors reached the following conclusion:
1. When the authors'calculated values were compared with those of Harada which were calculated by using the equilibrium values of D'Ans, they coincided fairly well with the evaporation rate of water and the deposition rate of NaCl, at an early stage. However, at the later stage of evaporation after the beginning of sulphate deposition, they showed a considerable difference at the composition of solution, also, and a slight difference in the Kinds of deposited crystalls.
2. The calculated composition at which NaCl began to deposit coincided completely with that determined experimentally by Harada.
3. The compositions of solutions determined experimentally by Harada after the deposition of NaCl differed greatly from the authors'calculated ones. The authors considered that this phenomenon were due to the supersaturation of sulphates such as löweite (Na₂SO₄·MgSO₄·5/2H₂O), kieserite (MgSO₄·H₂O), etc..
4. The calculated value at which the deposition of löweite began, coincided fairly well with the value determined by Maeda. From this fact, the authors considered that their calculation was highly credible.