Process for the manufacture of high purity silicic acid

摘要

A process is herein described for the manufacture of high purity, granular silicic acid from aqueous alkali metal silicate solutions by acidification thereof, freezing and subsequently thawing the reaction mixture, and filtering, washing and drying the insoluble residue formed, in which the alkali metal silicate solutions have a molar ratio of SiO2:Me2O of from about 2:1 to 20:1, Me representing an alkali metal, and before freezing the aqueous alkali metal silicate solutions are adjusted to a pH value in the range of from about 2.5 to 6 and to a SiO2 content of from about 1 to 10 percent by weight by means of one or more aqueous solutions or suspensions of organic acids which complex aluminum, titanium, and iron ions and which form soluble alkali metal salts under the conditions of the process.