Abstract
In order to prevent deposition of calcium carbonate in concentrating sea water by ion-exchange membrane method, the authors studied effects by of addition of acid to feed sea-water or circulated brine. In this study, electrodialytical tests were carried out within the desalting range of 17-75% by adding hydrochloric acid so the feed sea-water or the circulated brine to adjust the pH value of the brine to be 4-5. Thus, the effects addition of acid on concentration characteristics and prevention of calcium-carbonate deposition were examined.
The results of these experiments revealed that there was little effect on concentration characteristics, but no deposition of calcium-carbonate scale was observed when the pH of brine was kept under 5.
Under ordinary electrdialytical condition, the cost of added acid was estimated at 10 yen per ton of sodium chloride when sulfuric acid was added to the circulated brine.
