The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 28, 1989
Filed:
Sep. 13, 1985
Gordon Lever, Kingston, CA;
Alcan International Limited, Montreal, CA;
Abstract
Fluoride-containing wastes, arising in the aluminium industry, particularly spent cell linings from reduction cells, are digested with caustic soda for conversion of sodium cryolite to NaF. By use of very strong caustic soda NaF may be left in the solid residues after removal of the residual liquor and recovered from such residues by water leaching. As an alternative weaker caustic soda may be used in the digestion stage and subsequently be crystallised out from the residual liquor, after separation from the solid residues, by evaporating and/or cooling the liquor. The precipitated NaF is then conventiently redissolved in water. The NaF solution prepared by either route is then preferably subjected to electrodialysis to recover a solution of HF from it. Such HF is conveniently converted to AlF.sub.3 by reaction with alumina.