Kennecott Utah Copper Corporation

Claus Stoiber

Mike Rockandel

Robert E Crossman

Molybdic oxide is recovered from molybdenite by a multistep process in which (A) the molybdenite is converted to soluble and insoluble molybdic oxide by pressure oxidation, (B) the insoluble molybdic oxide is converted to soluble molybdic oxide by alkaline digestion and then combined with the soluble molybdic oxide, and (C) the molybdenum values of the combined streams are extracted into an organic phase using a nonprimary amine. The extracted molybdenum values are recovered from the organic phase using aqueous ammonia to form ammonium dimolybdate (ADM) which is recovered as refined crystals from a two-step calcination process. Hallmarks of the process include one or more of economic ammonia recovery and recycle, use of ferrous sulfate to remove arsenic and/or phosphorus from the Mo-loaded aqueous ammonia strip liquor, two-stage calcination of ADM crystals, recovery of rhenium from a filtrate of the residual molybdenum precipitation stage, selenium removal from the liquid fraction from which rhenium is recovered, and caustic boil of the mother liquor from which the selenium is precipitated.

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West Jordan, UT, United States of America

Claus Stoiber