| 摘要 |
PURPOSE:In a method of forming silica by reacting sodium silicate with a mineral acid, to produce high-purity silica, by forming silica precipitate in an acidic zone in the presence of a chelating agent, and washing the separated and recovered silica with a mineral acid containing hydrogen peroxide. CONSTITUTION:In a method of forming silica by reacting an aqueous solution of sodium silicate with a mineral acid, the amount of a chelating agent contained in the aqueous solution of sodium silicate is 0.01-1wt% based on SiO2, and silica precipitate is formed in an acidic zone. Then, the separated and recovered silica is washed with a mineral acid containing 0.01-1wt% calculated as H2O2 of hydrogen peroxide based on SiO2. Consequently, high-purity silica having impurity content of <=5ppm for each element, <=1ppm U and <=1ppm Tb is obtained.
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