Recovery of aluminum fluoride
AssigneeAnaconda Aluminum Co.
InventorThomas F. Payne
Life of this patent
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Abstract
An aqueous solution containing fluorides, for example, hydrofluoric acid, is reacted with commercial grade aluminum oxide comprising predominantly alpha alumina at an elevated temperature to produce a complex aluminum hydroxide fluoride hydrate that precipitates from the solution. The commercial grade aluminum oxide contains an amount of gamma and delta alumina such that the aluminum oxide has a loss of weight on ignition of from about 0.5% to about 2.5%. The resulting aluminum hydroxide fluoride hydrate precipitate is recovered and calcined in a non-oxidizing atmosphere to produce aluminum fluoride suitable for use in the electrolytic production of aluminum.
Claims9
Process for the recovery of aluminum fluoride from a dilute fluoride-containing aqueous solution the fluoride content of which consists essentially of hydrofluoric acid which comprises:
- introducing commercial grade (Bayer process) aluminum oxide into said solution, said aluminum oxide comprising predominantly alpha alumina admixed with a minor amount of less highly calcined forms of alumina such that the aluminum oxide has a loss of weight on ignition of from about 0.5% to about 2.5%,
- reacting the fluoride content of said solution with said less highly calcined forms of alumina for at least about 1 hour with stirring at an elevated temperature of between about 140.degree. F. and the boiling point of the solution to produce a complex aluminum hydroxide fluoride hydrate (16Al(OH,F).sub.3.sup., 6H.sub.2 O) that precipitates from said solution,
- recovering said aluminum hydroxide fluoride hydrate precipitate from said solution, and
- calcining said precipitate to produce aluminum fluoride, combined in a mixture with unreacted aluminum oxide.
Dependencies are inferred from the claim text.