An improved hydrometallurgical method is provided for producing technical grade molybdic oxide from molybdenite concentrates. According to this method, the molybdenite concentrates are leached in an acid medium having a nitric acid concentration between about 25 gpl and about 50 gpl and an initial sulphuric acid concentration of nil to about 750 gpl, under oxygen pressure of about 100 - 250 psig and at a temperature above 115 DEG C so as to produce technical grade molybdic oxide having not more than 0.1% sulphur. Then a liquid-solid separation of the reaction mixture is effected and the obtained leach liquor is recycled back to the leaching stage optionally after partial neutralization with a basic reagent. The solid is washed and recovered as technical grade molybdic oxide.
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