Amax Incorporated

Robert C Ziegler

Richard A Ronzio

Paul B Queneau

Leo W Beckstead

Dale K Huggins

Robert F Hogsett

Phillip K Davis

Joseph G Brown

Fred N Oberg

R Stanley Rickard

Dissolved molybdenum is removed from sodium tungstate solutions by adding sulfuric acid to lower the pH value of the solution to between about 8 and about 5, adding to the sodium tungstate solution a water-soluble sulfide in an amount of at least 0.5 gram per liter (gpl) in excess of that required to precipitate as sulfides molybdenum and certain other metals, then lowering the pH value of the sodium tungstate solution to between about 4.0 and about 1.5 as rapidly as possible with sulfuric acid in such a way as to precipitate molybdenum trisulfide while minimizing co-precipitation of tungsten.

Separation of trace molybdenum from tungstate solutions

A process for producing a high purity ammonium heptamolybdate and/or ammonium dimolybdate product by which a particulated molybdenum oxide concentrate is purified to remove contaminating metal cations, whereafter it is leached with an ammoniacal leach solution to extract the molybdenum trioxide constituent therein as soluble ammonium molybdate compounds. The resultant ammoniacal leach solution is thereafter concentrated at an elevated temperature, whereafter at least a portion thereof is adjusted to provide an ammonia-to-molybdenum trioxide mol ratio ranging from about 0.86:1 to about 1.25:1, and the adjusted solution thereafter is cooled to effect a precipitation of ammonium heptamolybdate crystals which are separated and recovered, and the balance of the cooled solution is recirculated for admixture with additional ammoniacal leach solution. A portion of the concentrated ammoniacal leach solution can be further concentrated by evaporation to effect crystallization of ammonium dimolybdate which is separated and recovered.

Process for producing ammonium heptamolybdate and/or ammonium dimolybdate

A simple, efficient and economical process for purifying molybdenum disulfide concentrates by contacting and digesting the molybdenum disulfide feed material with an aqueous acid solution containing a controlled combination of hydrofluoric acid and sulfuric acid in a manner to convert substantially all of the contaminating silica bearing minerals therein to aqueous soluble fluoride and sulfate compounds and any contaminating lead sulfide compounds to lead sulfate compounds, and thereafter washing, neutralizing and drying the purified molybdenum disulfide powder product. In accordance with a preferred practice, when the molybdenum disulfide feed material contains in excess of about 0.1% iron as an indication of pyrite concentration, the concentrate is calcined at an elevated temperature in a nonoxidizing atmosphere prior to the digestion step to effect a conversion of the pyrites to synthetic pyrrhotites, which are softer and less abrasive and are more acid soluble. The product thus derived is eminently suitable for use in the formulation of lubricants and as an intermediate in the synthesis of high purity molybdenum compounds.

Process for treating molybdenite concentrates to produce a lubricant

A process for purifying concentrates of molybdenum oxide containing a variety of naturally-occurring contaminating metals, such as potassium, copper, calcium, magnesium, iron, aluminum, lead, zinc, bismuth, and the like, as well as compounds thereof, by roasting the impure concentrate at an elevated temperature in an oxygen atmosphere to convert sub-oxides of molybdenum to molybdenum trioxide and contaminating metal molybdites to corresponding metal molybdates, which are extracted by a hot aqueous leaching of the concentrate and the solubilized molybdate ions are recovered. The aqueous leached concentrate, after separation from the aqueous leach solution, is leached with an ammoniacal leach solution for converting the molybdenum trioxide constituent therein into soluble ammonium molybdate compounds, and the resultant leach solution is removed from the remaining insoluble residue, which is discarded. The ammoniacal leach solution containing only minimal quantities of remaining contaminating metal ions can be further purified by passage through a chelating cation exchange resin, whereafter the ammonium molybdate compounds are recovered, such as by evaporative crystallization, to produce a high purity ammonium dimolybdate (ADM) product, or alternatively, can be calcined at an elevated temperature to produce a high purity molybdenum trioxide product.

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Lakewood, CO, United States of America

Robert C Ziegler