| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a silicic acid sol, capable of effectively utilizing water useful as a solvent and a raw material especially in the production of the silicic acid sol, capable of reducing a waste treatment cost and a fear of environmental pollution due to reduction in amount of waste material. SOLUTION: In this method for producing a silicic acid sol by using a first electrodialysis apparatus constituted by alternately arranging cation-exchanger membranes and anion-exchanger membranes between an anode and a cathode and electrodialyzing an aqueous solution of alkali silicate, an aqueous solution of a caustic alkali containing a very small amount of silicic acid is separated into a concentrated caustic alkali solution and a diluted aqueous solution of the alkali silicate by using a second electrodialysis apparatus, and the diluted aqueous solution of alkali silicate is supplied to the first electrodialysis apparatus as the aqueous solution of alkali silicate.
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