PROCESS FOR PREPARING CONCENTRATED SILICIC ACID

摘要

The invention relates to a process for preparing concentrated silicic acid of maximum 0.01 % Na 2 O, using silicasol of 3 ... 6 % concentration SiO 2 as starting material, the solution being stabilized with sodium hydroxide, both disolved in water, so as to ensure a SiO 2 : Na 2 O ratio of 62 ... 67. The mixture is boiled at a temperature of 100 degree C for 20 ... 30 minutes and concentrated by evaporation under vacuum of 0.4 ... 0.5 atm, at a temperature of 70 ... 80 degree C. The cooled product is dealkalized on a slightly acid cationite-like resin and the final stabilization is carried out with a saturated aqueous ammonia or amine solution.