Hydrometallurgical recovery of molybdenum from the Questa mine

Abstract

The dissolution of molybdenite (MoS 2 ) was studied leaching with acid solution or decomposing with using various oxidizing agents including hypochlorite, carbonate solution. If acid leaching is used, provisions ozone, oxygen-alkali, acid-permanganate, persulfate, should be made to prevent complexing of molybdenum acid-ferric chloride, nitric acid, chlorine dioxide, acid-with iron, calcium, and aluminum ions. chlorate, managanese dioxide-sulfuric acid, and bac-The extraction of molybdenum from leach soluterial oxidation. Hypochlorite in basic solution offers tions was studied employing anion exchange resins, a fast and selective method for dissolving molybdenite. organic solvents, and activated carbon. The adsorption It has the disadvantage of being an expensive and un-characteristics shown by all three for Mo (VI) are alike, stable reagent, difficult to handle, and troublesome to with highest D values obtained at pH 1.5 to 2.5 for the regenerate. Acid-chlorate leaching is not so rapid nor processes. The observed similarities indicate that the so selective as hypochlorite but presents less of a ionic species adsorbed may be the same for the prochandling problem, provides for easy extraction of esses. Efforts are made to explain the irregular variamolybdenum from solution, and is more efficiently re-tion of D with pH and to establish optimum condigenerated. The manganese dioxide-sulfuric acid oxida-tions for loading and elution. tion of molybdenite was studied in detail and was also Studies of the recovery of molybdenum as a marketfound effective. Its only application, however, appears able product were directed toward its precipitation as to be in dissolving molybdenum from high-grade ores the ferric-molybdenum complexes. Stable dehydrated or concentrates. Preliminary tests on bacterial oxida-compounds containing 70 to 80 per cent MoO 3 and 20 tion of molybdenite indicate a favorable response of to 30 per cent Fe 2 O 3 were produced under optimum the specific species Thiobacillus thiooxidans and concentration and pH conditions. Efforts have been Thiobacillus ferrooxidans, which have been tentatively made to elucidate the scheme of precipitation and identified in the Questa mine water.composition of the precipitated iron-molybdenum com-The molybdenum from the primary oxide-molyb-pound and to compare it with the naturally occurring denum minerals such as ferrimolybdite and molyb-mineral, ferrimolybdite, in the oxidized zones of the denum-bearing limonite may be extracted either by molybdenum deposits.