REMOVAL OF PHOSPHATE FROM HEXAFLUOROSILICIC ACID SOLUTION

摘要

1278886 Purification of hydrofluorosilicic acid FARBENFABRIKEN BAYER AG 21 Aug 1970 [23 Aug 1969] 40412/70 Heading C1A Phosphate ions are removed from an aqueous solution of H 2 SiF 6 by (a) adding at least sufficient Fe3+ ions to give Fe3+ in the same molar proportion as the phosphate ions, (b) maintaining the solution at 60‹ to 100‹ C. while adding gaseous ammonia until the pH is 2-4 and (c) removing the precipitated iron phosphate formed. Further ammonia may be added until the pH is 8 to 9 whereby SiO Î H 2 O is precipitated and can be separated from the ammonium fluoride.