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Expired Canadian patentCanada

Hydrometalurgical production of zinc oxide from roasted zinc concentrates

CA 1317088 C · Owner: Robinson, Murry C. · Inventors: Robinson, Murry C.; Spink, Donald R.; Nguyen, Kim D.

CIPO record

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Abstract From the Canadian patent

A process is provided for obtaining high quality high surface area zinc oxide from a roasted zinc sulphide concentrate by leaching with an ammoniacal ammonium carbonate solution. The process utilizes optional preliminary oxidation and water leaching steps to remove soluble impurities and an optional aqueous sulphur dioxide leaching step to selectively remove readily soluble zinc oxide. The process also includes an optional reduced pressure calcining step to produce zinc oxide with further increased surface area.

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Listed from its CIPO record in Patent Yard's archive of Canadian patents past their term. Its claims, description and drawings are in the CIPO record and on Google Patents, and the Claude kit works from them.

Why it's free to use

  • Granted May 4, 1993. A Canadian patent filed before October 1, 1989 lasted 17 years from grant, so its term ended May 4, 2010.
  • We check Canadian rights only. A patent in its family in another country could still be in force: check its family on Google Patents.
FiledAugust 6, 1987
GrantedMay 4, 1993
Term endedMay 4, 2010
Patent numberCA 1317088 C
Classification (IPC)C01G9/02 +2 more

Timeline

Timeline From CIPO dates

19881991199419972000200320062009Application filedAug 6, 1987Patent grantedMay 4, 1993Term endedMay 4, 2010

Sources & verification

Everything on this page comes from the CIPO record linked above. Contains information licensed under the Open Government Licence – Canada.