Purification process for technical grade molybdenum oxide

#High purity molybdenum oxide, potassium molybdates, sodium molybdates and ammonium molybdates are of commercial inportance in synthesizing various molybdenum compounds of chemical grade for use in the production of molybdenum catalysts and for reduction to the metallic state, such as by hydrogen reduction, to produce a high purity molybdenum metal.

#A variety of processes and purification techniques have heretofore been used or proposed for use for removing a variety of normally-occurring contaminating metals and/or contaminating metal compounds in technical grade molybdenum oxide concentrates. Such contaminating metals typically include potassium, manganese, lead, tin, calcium, magnesium, iron, copper and aluminum, the concentration of which varies depending on the particular ore body from which the molybdenite (MoS.sub.2) is obtained, and the type and severity of the beneficiation process by which the molybdenite ore is concentrated. Typical of such prior art processes for purifying technical grade molybdenum oxide concentrates are those described in U.S. Pat. Nos. 3,658,464; 3,829,550 and 3,848,049, which are assigned to the same assignee as the present invention. While the foregoing processes have been effective in reducing the concentration of contaminating metals and metallic compounds in technical grade molybdic oxide feed materials, there has been a continuing need for a purification process which is more efficient, which provides for increased yields of the purified molybdenum product, which is more economical to operate, and which reduces the volume of waste streams generated, thereby minimizing waste treatment operations with attendant further cost savings.

#The present invention overcomes many of the shortcomings and disadvantages associated with prior art purification techniques by providing a process which is efficient, economical, simple to control, increases the yield of the purified molybdenum product produced, and wherein the purified product is substantially devoid of any residual contaminating metal or metal compounds therein.

#FIG. 1 comprises a schematic flow diagram of the important process steps for effecting a purification of a molybdenum oxide concentrate in accordance with one of the embodiments of the present invention; and

#FIG. 2 comprises a partial schematic flow diagram in accordance with an alternative embodiment of the invention.

#The concentrations and/or compositions of the various feed materials, substances and solutions, as herein described and as set forth in the subjoined claims, are expressed in terms of percentages by weight unless clearly indicated to the contrary.

#The impure feed material comprises a particulated technical grade concentrate consisting predominantly of molybdenum oxide which contains various contaminating metal constituents and compounds thereof in concentrations depending upon the characteristics of the original ore body and the manner by which the concentrate is produced. Conventionally, such molybdenum oxide concentrates are produced by roasting molybdenite (MoS.sub.2) concentrates at elevated temperature in the presence of excess air to convert the predominant portion of the molybdenum sulfide to molybdenum trioxide.

#The molybdenite concentrate itself can be produced by any one of a variety of ore beneficiation processes in which the molybdenite constituent in the ore body is concentrated so as to reduce the gangue to a level less than about 40%, and more usually to a level of less than about 20%. One of the largest known sources of molybdenite ore is at Climax, Colo., in which the ore body comprises a highly silicified and altered granite through which the molybdenite is distributed in the form of very fine-sized veinlets as relatively soft, hexagonal, black flaky crystals present in a concentration of only about 0.3% to about 0.6% as mined. A preferred method of producing the molybdenite concentrate comprises subjecting the molybdenite containing ore to a grinding operation, whereby the ore is reduced to particles of an average size usually less than about 100 mesh, and whereafter the pulverized ore is subjected to an oil flotation extraction operation employing hydrocarbon oils in combination with various wetting agents, whereby the particles composed predominantly of molybdenum disulfide are retained in the flotation froth, while the gangue constituents composed predominantly of silica remain in the tailing portion of the pulp. The flotation beneficiation process normally involves a series of successive flotation extraction operations, each including an intervening grinding operation, whereby the residual gangue constituents in the concentrate are progressively reduced to the desired level. Technical grade molybdenite concentrates commercially produced by the oil flotation beneficiation process usually contain less than about 10% gangue, and more usually from about 5% to about 6% gangue, with the balance consisting essentially of molybdenum disulfide.