C - Chemistry – Metallurgy – 01 – B
Patent
C - Chemistry, Metallurgy
01
B
23/189, 23/192
C01B 33/187 (2006.01) C01B 33/18 (2006.01) C01B 33/32 (2006.01) C01F 7/54 (2006.01)
Patent
CA 1216135
ABSTRACT OF THE DISCLOSURE The present invention relates to a method for purifying silica waste obtained in the manufacture of aluminium fluoride from hexafluosilicic acid and aluminium hydroxide, whereby the silica, is subjected to an acidic leaching at a pH below 3 to leach out part of the fluorine and substantially all the aluminium present in said waste, and is thereafter subjected to an alkaline leaching at pH 8.5-11.5 to leach out remaining fluorine present in said waste. The leachings are preferably carried out at elevated temperatures, normally 60-90°C, and for a time sufficient to considerably reduce the contents of aluminium and fluorine, normally 1-3 hrs. The silica obtained is highly reactive and can be used as such or transformed into sodium silicate by a reaction with sodium hydroxide. The contents of fluorine and aluminium can be transferred to a process for the production of cryolite or similar compounds.
438849
Berglund Hans A.l.
Lagerstrom Gosta B.
Boliden Aktiebolag
Fetherstonhaugh & Co.
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