| 摘要 |
PURPOSE:To obtain high-purity silica with low U and Th contents, by adding an acid to an aqueous solution of an alkali silicate, adjusting the pH and bringing the adjusted solution into contact with a strong basic anion exchange polymer. CONSTITUTION:Sulfuric acid or nitric acid is added to an aqueous solution of an alkali silicate (e.g. sodium silicate) in 2-10wt.% concentration to adjust the pH to 1-2. The adjusted aqueous solution of alkali silicate is then heated at 10-60 deg.C, brought into contact with an SO4<2-> or NO3<-> type strong basic anion exchange polymer and then concentrated while being heated. Alternatively an alkali is added to adjust the pH to 6-8 and gelatinize the aqueous solution to afford a silica hydrogel, which is then treated with an acid, washed with deionized water and dried to afford the aimed high-purity silica with respective <=0.1ppb U and Th contents.
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