1972 Volume 26 Issue 1 Pages 38-48
The authors carried out an experiment to examine what effects those reagents, which were added to feed sea water so as to provide the low- permselectivity of bivalent cations to cation exchange membrane, would exert on concentration characteristics when sea water was concentrated by ion exchange membrane method. For this experiment, an electrodialysis apparatus having an effective area of 5 dm2 was used. Also, larger apparatus (115 dm2) was used to examine its practical use on industrial scale. The results from this experiment were as follows:
1. There was not much difference in effects between the reagent solution α and β.
2. The voltage of the cell showed a decline in line with a rise in the ratio of sodium chloride content to total salt in brine. Accordingly, the consumption of electric energy for electrodialysis indicated a remarkable decrease.
3. The permselectivity coefficient of potassium univalent ion through cation membrane decreased also in proportion to an increase in sodium chloride ratio.
4. Relations between the current density and the concentration characteristics or the permselectivity coefficients were similar to the usual membranes having low-permselectivity for bivalent cations.
5. Under the condition that the current density was 2.6 A/dm2 and the pH value of feed sea water was 6, it was posible to maintain the ratio of sodium chloride in the brine (herein expressed as Cl- Ca-Mg (N) ×100/Cl(N) for convenience) in the range of 93% to 96% by adding successively 0.05-0.5 ppm of the reagent α to the feed sea water. The more the reagent was added to the sea water, the higher the ratio of the sodium chloride in the brine became.
6. The ratio of the sodium chloride increased in proportion to a decrease in the pH value of the feed sea water.
