| 摘要 |
PROBLEM TO BE SOLVED: To provide a purification method by which an aqueous solution of an alkali silicate capable of being used as a raw material of high purity silica, high purity colloidal silica or high purity silica gel can be purified at a low cost. SOLUTION: The purification method of the aqueous solution of an alkali silicate comprises previously controlling the viscosity of the aqueous solution of the alkali silicate to be 1 to 50 mPa.s and then passing the solution through an ultrafiltration membrane whose fractional molecular weight is <=1,500. Thereby, the aqueous solution of the alkali silicate, which contains Cu in an amount of <=200 ppb per silica and is substantially free from particles having particle sizes of >=1 nm, can be obtained.
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