ABSTRACT
Hydrometallurgy is a relatively recent development compared with pyrometallurgy. Leaching is the first prerequisite of any hydrometallurgical process. Hydrometallurgical processing involves leaching with a solution of ammonia. As a rule, the residue from the leaching operation is also treated for molybdenum recovery. The ammoniacal solution resulting from the leaching of the molybdenite calcines and the residue treatment involving either soda ash fusion or acid digestion contains copper, iron, and occasionally zinc and nickel, alkali metals, and sulfate ions, in addition to molybdenum. Alkali leaching has been found advantageous to treat such low-grade molybdenum sources. Application of hydrochloric acid leach has proved to be quite successful for processing molybdenum concentrates consisting of powellite and scheelite as main useful components. The most important applications of hydrometallurgy to primary molybdenum ore treatment are related to those operations to which molybdenite ore that has undergone oxidation changes is subjected.
