Concentration Acidified Sea Water by Ion Exchange Membrane Method
Scale Formation in Concentrating Sea Water with Ion Exchange Membrane Method (Part III)
1972 Volume 26 Issue 1 Pages 21-26
Details
1972 Volume 26 Issue 1 Pages 21-26
The author made a study on the effects of addition of hydrochloric acid to sea water upon the pH and concentration of carbonates (CO2-FHCO3-+CO3- -) in dialysates and upon the other results of sea water concentration by electrodialysis with ion exchange membrane. The results obtained were as follows:
1. In case HCl was added, the pH of sea water showed a rapid decline at pH > 4, but a gradual decline at pH<4.
2. The pH of desalted solution was 0-0.7 over that of acidic raw sea water, and the pH of concentrated solution was 0.3-1.4 lower.
3. The concentration of carbonates indicated an effective decrease by lowering the pH of both the sea water and the desalted solution to about 6 and the pH of concentrated solution to about 5.The further decline of pH was less effective for decreasing the concentration of carbonates.
4. The acidification of sea water to pH 4.5-5.5 seemed preferable for decreasing the concentration of carbonates in the concentrated solution. In this case, about 50-70g-HCl/m3-sea water was necessary, and the concentration of the carbonates in the concetrated solution decreased to 0.4-0.55×10-3 mol/l. This was about one-fifth to one-seventh when the sea water with no acid added was concentrated.
5. When the pH of raw sea water declined, there were observed lower current efficiency of electrodialysis (for total salts), lower permeabilities of divalent cations and higher permeability of sulfate.
