Experimental Studies on the Isothermal Evaporation of the Ion-Exchange Membrane Brines at 25°C (II)
Studies on the Concentration of Ion-Exchange Membrane Brine (part 4)
1969 Volume 23 Issue 2 Pages 68-74
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1969 Volume 23 Issue 2 Pages 68-74
In their previous paper (This Journal 20, 254-263 (1967)), the authors reported on the graphical calculations of the process of isothermal evaporation at 25°C of ion-exchange membrane brines by means of equilibrium diagrams of the five-component system.
In the present paper, it was studied on the concentration of the brine belonging to NaCl-KCl-MgCl2-MgSO4-CaSO4-H2O type at 25°C. Two kinds of synthetic brines without calcium sulphate were prepared and evaporated to various concentrations. The compositions of the solutions were chemically analyzed and those crystals deposited were identified by X-ray diffraction.
The authors tried to verify the validity of the graphical calcuations experimentally, and concluded as follows;
1) The compositions of the solutions were found to be fairly good coincidence with the calculated values, and the kinds of deposited crystals also were found to be in complete coincidence with that of crystals on the diagram.
2) For the simplicity's sake, all points on the diagram were combined with straight lines and all surfaces were assumed to be planes. But in fact, it was found that the surfaces to be curved one, and to be convex toward the origin, and the deviation to be the more marked at the higher concentration.
3) In the calculation of the evaporation of the brine, the presence of calcium sulphate may be neglected, as in the case of sea-water concentration.
4) It was found that the specific gravity (d254=1.21-1.33) of the solutions to increase linearly with the chloride ion conceatration, and under the simple conditions as the case of this experiment, chloride ion concentration or specific gravity etc. may be used as the degree of concentration.
