| 摘要 |
PROBLEM TO BE SOLVED: To prevent the transfer of silicate ions to a concn. chamber through an anion exchange membrane, to suppress the generation of scale and to enable long-time continuous operation by adding dipolar ions to an aq. alkali silicate soon. and electrodialyzing the soln. SOLUTION: Dipolar ions of an element such as Al, Zn, Pb or Sn, preferably Al are added to an aq. alkali silicate soln. When Al ions are added, aluminum hydroxide or aluminum oxide may be used as a source of Al. The concn. of the dipolar ions in the aq. alkali silicate soln. is preferably 60-620 ppm. Since it is provable that the dipolar ions and silicate ions in the aq. alkali silicate soln. form a certain complex or clathrate compd., the silicate ions are made less liable to pass an anion exchange membrane. The aq. alkali silicate soln. is then electrodialyzed to obtain the objective dealkalized silica sol.
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