| 摘要 |
The manufacture of aluminium fluoride from hexafluorosilicon acid and aluminium hydroxide produces waste silicic acid. From this sodium silicate solution can be made. The acid, which is contaminated with aluminium and fluorine is agitated as an aqueous slurry at 50-100 deg.C, with sodium hydroxide, for 5-10h. Calcium hydroxide is added to the slurry in at least stoichiometric quantities. Calcium fluoride is precipitated during 1-3h at a temperature of 50-100 deg.C, whilst stirring. Sodium hydroxide in sufficient quantity to make Na2OnSIO2 (n is at least 2.5) at 90-110 deg.C over a period of 2-4h. Water glass is formed as a slurry which is filtered. (Provisional Basic previously advised in week 8701) |
