Chemistry of inorganic compounds – Silicon or compound thereof – Oxygen containing
Patent
1983-08-22
1985-12-10
Brody, Christopher W.
Chemistry of inorganic compounds
Silicon or compound thereof
Oxygen containing
423340, C01F 702, C01F 750
Patent
active
045579180
ABSTRACT:
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.degree.-90.degree. 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.
REFERENCES:
patent: 1858100 (1932-05-01), McAdoo
patent: 2657149 (1953-10-01), Iler
patent: 3175882 (1965-03-01), Derr
patent: 3511605 (1970-05-01), Smith et al.
patent: 3551322 (1970-12-01), Baumann et al.
patent: 4028237 (1977-06-01), Nishimura et al.
patent: 4320012 (1982-03-01), Palm et al.
Philadelphia Quartz Company; P.Q. Silicates of Soda Bulletin No. 172, pp. 1 to 8 (1941).
WO 82/02538, PCT/SE82/00004, International Filing Date 1/11/82.
Berglund Lennart H. A.
Lagerstrom Gosta B.
Boliden Aktiebolag
Brody Christopher W.
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