| 摘要 |
PURPOSE:To produce a high-purity silica gel with simple operation, by mixing an aqueous solution of an alkali metal silicate with a mineral acid keeping the system to an alkaline state, and mixing the produced product with a mineral acid to keep the mixture to a strongly acidic state. CONSTITUTION:An aqueous solution of an alkali metal silicate is mixed with a mineral acid, and the pH of the mixture is maintained at >=7 to obtain the primary silica gel. The aqueous solution of alkali metal silicate is prepared by diluting sodium silicate, etc. with water to a volume about 1.5-5 times the volume of the silicate (SiO2 concentration of about 7-22wt%), and the mineral acid is e.g. about 4-6N sulfuric acid, etc. The produced primary silica gel having the form of a semi-transparent cake is mixed within about 24hr with a mineral acid same to or different from the acid in the above mixture, e.g. about 3- 8N sulfuric acid to keep the pH of the mixture to <=1. The temperature of the system is maintained at about 60-95 deg.C. The produced secondary silica gel is washed with a mineral acid and pure water to obtain a silica gel having a purity of >=99.99wt%.
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