Abstract: The present invention discloses a method for decomposing medium-/low-grade scheelite, specifically comprising steps of: grinding medium-/low-grade scheelite, decomposing in an autoclave by using sodium phosphate and activated magnesium fluoride as leaching agents, and treating by solid-liquid separation to obtain crude sodium tungstate solution and residue. In this way, the medium-/low-grade scheelite is decomposed. Magnesium chloride is added in a sodium fluoride solution to prepare activated magnesium fluoride as a leaching agent. The present invention has the advantage that the high-efficiency decomposition of medium-/low-grade scheelite can be realized with low consumption of leaching agents, and the leaching cost can be greatly reduced in comparison to the existing decomposition processes using sodium hydroxide and sodium carbonate. This process is short in route, simple in operation, readily available and reliable in production equipment, and easy for industrialization.

Abstract: Certain embodiments are directed to method for making and using an alkali promoted transition metal sulfide Fischer Tropsch catalyst. Certain embodiments are directed to alkali promoted transition metal sulfide Fischer Tropsch catalyst synthesized using steps comprising (i) mixing an ammonium tetrathiomolybdate (ATM) precursor compound with an alkali metal compound and molybdenum disulfide in deionized water to form a reaction mixture, (ii) heating the reaction mixture at a temperature of at least 200, 250, 300, 350, 400C at a pressure of at lease 900, 1000, 1100, 1500, 2000 psi for more than 0.5 1, 1.5, 2.0, 3 or more hours to form a reaction product, (iii) filtering, washing, and drying the reaction product.

Abstract: The invention provides a continuous method for extracting transition metal, the method comprising: supplying a spent generator liquor comprising transition metal in highly alkaline solution; mixing the liquor with acid thereby generating a solution, wherein the transition metal resides within the solution; combining the solution with an organic liquid comprising tributyl phosphate or other neutral extractant to extract the transition metal within the organic liquid; washing the extracted transition metal in the organic liquid with acid so as to remove non-transition-metal salts from the organic liquid phase; and stripping the washed transition metal loadedorganic liquid phase with hydroxide, water or complexing agent to remove the transition metal from the organic phase.

Abstract: A method for producing an ammonium tungstate aqueous solution includes the steps of: adding sulfuric acid to a solution containing tungstate ions; bringing the solution having the sulfuric acid added therein, into contact with an anion exchange resin; and bringing the anion exchange resin into contact with an aqueous solution containing ammonium ions.

Abstract: A method for extracting tungsten from scheelite by: 1) adding a mixed acid including H2SO4 and H3PO4 to a decomposition reactor; 2) heating the mixed acid to a temperature of 70-100° C.; adding scheelite while controlling the mixed acid present in an amount of 3-8 L per kg of scheelite; allowing the components in the decomposition reactor to react for 1-6 h, and filtering the resulting mixture to obtain a filtrate; 3) supplementing the filtrate with sulfuric acid consumed in the reaction; 4) crystallizing the filtrate to obtain phosphotungstic acid crystals and mother liquor; 5) dissolving the phosphotungstic acid crystals in water to obtain a phosphotungstic acid solution; 6) transforming the phosphotungstic acid solution into an ammonium tungstate solution for the purpose of preparing ammonium paratungstate; and 7) supplementing the mother liquor with phosphoric acid and water to an initial level and reusing the mother liquor for ore leaching.

Abstract: Molybdic oxide is recovered from molybdenite by a multistep process in which (A) the molybdenite is converted to soluble and insoluble molybdic oxide by pressure oxidation, (B) the insoluble molybdic oxide is converted to soluble molybdic oxide by alkaline digestion and then combined with the soluble molybdic oxide, and (C) the molybdenum values of the combined streams are extracted into an organic phase using a nonprimary amine. The extracted molybdenum values are recovered from the organic phase using aqueous ammonia to form ammonium dimolybdate (ADM) which is recovered as refined crystals from a two-step calcination process.

Abstract: Compositions are provided that include nuclear fuel. Methods for treating nuclear fuel are provided which can include exposing the fuel to a carbonate-peroxide solution. Methods can also include exposing the fuel to an ammonium solution. Methods for acquiring molybdenum from a uranium comprising material are provided.

Abstract: Compositions are provided that include nuclear fuel. Methods for treating nuclear fuel are provided which can include exposing the fuel to a carbonate-peroxide solution. Methods can also include exposing the fuel to an ammonium solution. Methods for acquiring molybdenum from a uranium comprising material are provided.

Abstract: A method for extracting tungsten from scheelite by: 1) adding a mixed acid including H2SO4 and H3PO4 to a decomposition reactor; 2) heating the mixed acid to a temperature of 70-100° C.; adding scheelite while controlling the liquid-solid ratio at about 3:1-8:1 L/kg; allowing the components in the decomposition reactor to react for 1-6 h, and filtering to obtain a filtrate; 3) supplementing the filtrate with sulfuric acid consumed in the reaction; 4) crystallizing the filtrate to obtain phosphotungstic acid crystals and mother liquor; 5) dissolving the phosphotungstic acid crystals in water to obtain phosphotungstic acid solution; 6) transforming the phosphotungstic acid solution into an ammonium tungstate solution for the purpose of preparing ammonium paratungstate; and 7) supplementing the mother liquor with phosphoric acid and water to an initial level and reusing the mother liquor for ore leaching.

Abstract: A process for preparing ammonium metatungstate using ammonium paratungstate as raw material comprising: (A) leaching wet ammonium paratungstate with nitric acid to obtain a dilute solution of ammonium metatungstate; (B) concentrating the dilute solution of ammonium metatungstate to be a concentrated solution of ammonium metatungstate; and (C) spray-drying the concentrated solution of ammonium metatungstate to obtain powder of ammonium metatungstate.

Abstract: A method for preparing ammonium heptamolybdate with the steps of: i) adding a molybdenum-containing organic phase to a liquid-liquid reextraction apparatus or to a desorption apparatus, and ii) directly cold-crystallization ammonium heptamolybdate by cooling the resulting reextraction or desorption solution.

Abstract: A method of recovering vanadium, nickel and molybdenum from heavy crude oil refinery residues comprises pyrolysis and combustion of the residues at temperatures up to 900° C. to produce an ash, converting the ash to an aqueous slurry comprising sodium hydroxide as leading agent and hydrogen peroxide as oxidizer, and extracting vanadium, nickel and molybdenum salts and oxides from the slurry. Extraction processes for the metals are disclosed.

Abstract: Methods for recovering base metals, including, among other metals, molybdenum and nickel, from metal sulfides containing a Group VIB metal and a Group VIII metal. Generally, the methods comprise: contacting metal sulfides with a leaching solution containing ammonia and air to dissolve the metals into the leaching solution, forming a slurry containing soluble complexes of the metals, ammonium sulphate and solid residue containing ammonium metavanadate and any carbonaceous materials. The solid residue containing ammonium metavanadate and carbonaceous materials is then separated from the slurry and metal complexes are precipitated from the slurry by adjusting the pH. A second slurry may be formed comprising a second solid residue and a primary filtrate comprising ammonium sulfate solution that is substantially free of metals.

Abstract: The invention is directed to a process for the continuous preparation of ammonium paratungstate hydrate by back reextraction of a tungsten-laden organic phase with an ammonia-containing aqueous solution in a mixer-settler apparatus. The reextraction is carried out at an NH3:W molar ratio of from 0.83 to 1.30, and a volume feed ratio of the tungsten-laden organic phase to the ammonia-containing aqueous solution of from 5 to 25. The above crystalline is in high purity and in high yield. The production method can be carried out in a simple and energy-efficient manner.

Abstract: A method is disclosed for separating and recovering base metals from a used hydroprocessing catalyst originating from Group VIB and Group VIII metals and containing at least a Group VB metal. In one embodiment, the used catalyst is contacted with an ammonia leaching solution to dissolve and separate the Group VIB and VIII metals from the Group VB metal complex and coke associated with the used catalyst. The resulting Group VIB and VIII metal containing solution is processed through at least two additional precipitation and liquid/solid separation steps to produce, in separate processing streams, a Group VIB metal product solution (such as ammonium molybdate) and a Group VIII metal product solution (such as nickel sulfate). Additionally, two separate filtrate streams are generated from liquid-solid separation steps, which filtrate streams are combined and subjected to hydrolysis and oxidation (oxydrolysis) to generate a purified ammonium sulfate solution for further processing, such as for fertilizer.

Abstract: A method is disclosed for separating and recovering base metals from a used hydroprocessing catalyst originating from Group VIB and Group VIII metals and containing at least a Group VB metal.

Abstract: Methods and systems for removing copper minerals from a molybdenite concentrate. One embodiment provides leaching copper from the molybdenite concentrate with a leaching solution comprising ferric chloride, removing molybdenite from the leaching solution, introducing an acid into the leaching solution and introducing O2, O3, or a combination of both, into the leaching solution. A method for regenerating ferric chloride in a leaching solution is also provided. One embodiment provides adding a leaching solution comprising Fe(II) ions, Fe(III) ions, or a combination of both, to a mixture of mineral sulfides, introducing an acid into the leaching solution, and introducing O2, O3, or a combination of both, into the leaching solution.

Abstract: The present invention relates to a process for the removal of metal catalyst degradation products from a bleed stream of a catalytic chemical reaction process, wherein the catalyst is based on a metal selected from those in group VIII of the periodic table, chromium, copper, molybdenum, tungsten, rhenium, vanadium, titanium and zirconium, said process comprising treatment of the bleed stream with an alkali metal carbonate or ammonium carbonate source to form a solid complex or an aqueous solution of said solid complex, and removal of the solid complex or the aqueous solution of said solid complex from the bleed stream.

Abstract: The process of this invention is directed to the removal of metals from an unsupported spent catalyst. The catalyst is subjected to leaching reactions. Vanadium is removed as a precipitate, while a solution comprising molybdenum and nickel is subjected to further extraction steps for the removal of these metals. Molybdenum may alternately be removed through precipitation.

Abstract: A method for recovering metals from a spent dispersed catalyst originating from a Group VIB metal sulfide catalyst containing at least a Group VB and Group VIII metal for hydrocarbon oil hydroprocessing is disclosed.

Abstract: A method is disclosed for separating and recovering base metals from a used hydroprocessing catalyst originating from Group VIB and Group VIII metals and containing at least a Group VB metal.

Abstract: A method for recovering metals from a spent dispersed catalyst originating from a Group VIB metal sulfide catalyst containing at least a Group VB and Group VIII metal for hydrocarbon oil hydroprocessing is disclosed.

Abstract: The process of this invention is directed to the removal of metals from an unsupported spent catalyst. The catalyst is subjected to leaching reactions. Vanadium is removed as a precipitate, while a solution comprising molybdenum and nickel is subjected to further extraction steps for the removal of these metals. Molybdenum may alternately be removed through precipitation.

Abstract: A process for reducing the content of alkali metal impurities (e.g., potassium) in ammonium metallate solutions is described. The process involves subjecting a feed solution containing ammonium metallate and alkali metal impurities to membrane filtration. The membrane filtration results in the formation of a retentate having a reduced level alkali metal relative to the feed solution, and a permeate containing substantially the balance of alkali metal. The permeate may also be further treated, to remove alkali metal there from, by passage through a cation exchange column, thereby forming a cation exchange treated permeate that may be combined with the retentate of the membrane filtration step.

Abstract: A process for economically separating and recovering valuable metal components, with few kinds of chemicals being used, with no waste water that causes environmental pollution being discharged, and also perfectly no by-products being formed by means of simple steps.

Abstract: A novel molybdenum compound, ammonium dodecamolybdomolybdate (AMM), is described which may be used in the manufacture of molybdenum metal and molybdenum carbide powders. The molybdenum compound is a dodecaheteropoly acid salt having a Keggin-type structure wherein molybdenum resides in both the hetero as well as peripheral atomic positions. The novel compound has the general formula (NH4)2Mo12MoO40.6H2O. Because of its low solubility, the compound can be crystallized efficiently and at a high purity from ammonium molybdate solutions.

Abstract: High purity ammonium dimolybdate or molybdenum oxide is produced by the pressure oxidation of low grade molybdenite concentrates or molybdenum intermediates. The process entails nearly complete oxidation of the sulfide minerals while optimizing the process chemistry and autoclave conditions to solubilize as little of the molybdenum values as possible. The autoclave discharge 12 is then subjected to a leaching step, either an alkaline leach 50, 400 or ammonium leach 250 process, before or after a liquid/solid separation step 20, 220, 410. The solution is then subjected to (a) filtration 60, 410, solvent extraction 70, 440, crystallization 90,450, and calcination 120, 480 or (b) filtration 260, 280, crystallization 290, and calcination 320 to produce a product suitable for chemical-grade molybdenum oxide 125, 325, 485.

Abstract: Disclosed is a device and method of use for detecting polyvalent analytes such as antibody to the AIDS virus, utilizing an inverse sandwich method. The test device comprises a first substance having an epitope, bound to a label and capable of moving within the test device. The test device further comprises a second substance immobilized to the test device and spatially separated from the first substance. The second substance has an epitope substantially similar to the epitope of the first substance. Upon application to the test device, the polyvalent analyte binds to the first substance and moves within the test device to the location of the second substance with both polyvalent analyte and first substance are immobilized at location of the second substance. Polyvalent analyte is detected by the presence of the label at the location of the second substance. Also disclosed is a control substance for use with the device that can be used to determine completion of the test and viability of the device.

Abstract: A molybdenum-based precipitate is prepared according to a process including the first step of forming a crude precipitate by pH adjustment to 6.5 or less in the presence of an alkali metal compound, and the second step of dissolving the crude precipitate in aqueous ammonia and forming a precipitate by pH adjustment to 6.5 or less. Then, the resulting molybdenum-based precipitate is washed with an acid aqueous solution having a pH of 6.5 or less and containing not less than 0.01 mole/L of ammonium root. Thus, a change in average particle diameter can be suppressed and good workability can be achieved, so that a molybdenum-based precipitate having a high purity and a desired average particle diameter can be obtained.

Abstract: High purity ammonium dimolybdate or molybdenum oxide is produced by the pressure oxidation of low grade molybdenite concentrates or molybdenum intermediates. The process entails nearly complete oxidation of the sulfide minerals while optimizing the process chemistry and autoclave conditions to solubilize as little of the molybdenum values as possible. The autoclave discharge 12 is then subjected to a leaching step, either an alkaline leach 50, 400 or ammonium leach 250 process, before or after a liquid/solid separation step 20, 220, 410. The solution is then subjected to (a) filtration 60, 410, solvent extraction 70, 440, crystallization 90,450, and calcination 120, 480 or (b) filtration 260, 280, crystallization 290, and calcination 320 to produce a product suitable for chemical-grade molybdenum oxide 125, 325, 485.

Abstract: A method of treating metal-contaminated spent foundry sand, or other industrial waste, by combining the sand with a sulfite to produce insoluble metal sulfur oxide complexes that do not leach from the sand. The treated waste may also be processed to reducing “clumping,” thereby rendering the treated waste appropriate for use in another industrial process.

Abstract: There is provided a process to reclaim metals from catalysts, said process comprising collecting one or more catalyst containing at least one metal sulfide; leaching the catalyst in an atmospheric leach step; separating the leached slurry into a first liquid stream and a first solid; leaching the first solid in a pressure leach process; separating the second leached slurry into a second liquid stream and a second solid; collecting the first and second liquid streams; oxidizing the combined liquid stream; cooling the oxidized liquid stream; adjusting the pH of the oxidized liquid stream; contacting the cooled oxidized liquid stream with an organic solvent containing an extractant; stripping the soluble metal species from the organic phase; adjusting the pH of the aqueous phase to selectively precipitate at least one metal as a metal salt; and separating the metal salt from the aqueous phase.

Abstract: Process for the production of pure tungsten and/or molybdenum solutions from sources, such as alkaline decomposition solutions, which are contaminated with tantalum, niobium, titanium, aluminium, tin, arsenic, phosphorus and/or silicon, by application of a three stage purification process of pH reduction, anion exchange and membrane electrolysis.

Abstract: A process for recovering valuable metals from a waste catalyst based on an alumina carrier includes (a) roasting the waste catalyst at a temperature range of 400.degree. to 1,000.degree. C. to obtain a roasted product; (b) preparing a reduction dissolution by dissolving the roasted product with sulfuric acid in the presence of a metal as a dissolution catalyst; (c) separating a large part of the aluminum from the reduction dissolution solution and recovering aluminum as ammonium aluminum sulfate from the solution, optionally after subjecting the reduction dissolution solution to a treatment of removing iron; (d) extracting molybdenum as a molybdate by solvent extraction from the solution after separating and recovering aluminum from the solution; (e) extracting vanadium as a vanadate by solvent extraction from the solution obtained as a residue after extracting molybdenum; and (f) recovering nickel and cobalt each as a hydroxide from the extraction residue after recovering vanadium.

Abstract: A process for recovering tungsten as an ammoniacal tungstate which comprises reacting a tungsten containing material with sodium hydroxide to produce sodium tungstate and forming a first aqueous sodium tungstate solution therefrom, crystallizing sodium tungstate from the first aqueous sodium tungstate solution, dissolving the resulting sodium tungstate crystals in an aqueous medium to form a second aqueous sodium tungstate solution, extracting tungsten from the second aqueous sodium tungstate solution with an organic extracting agent wherein the extracting agent containing tungsten is capable of being stripped of the extracted tungsten by ammonia, and thereafter stripping the extracted tungsten from the organic extracting agent with ammonia to form an ammoniacal tungstate solution, crystallizing a portion of the tungsten contained in the ammoniacal tungstate solution to form a two phase system wherein an ammoniacal tungstate compound comprises the first phase and wherein the resulting mother liquor containing

Abstract: A method for preparing molybdenum and sulfur containing compounds of the general formula X.sub.2 Mo.sub.2 S.sub.12.yH.sub.2 O, where X is a cation selected from the group consisting of Na.sup.+, K.sup.+, R.sub.4 N.sup.+, R.sub.3 NH.sup.+, R.sub.2 NH.sub.2.sup.+, RNH.sub.3.sup.+, NH.sub.4.sup.+, R.sub.4 P.sup.+, R.sub.4 As.sup.+,(R.sub.3 P).sub.2 N.sup.+, R is a C.sub.1 -C.sub.30 alkyl, C.sub.6 -C.sub.30 aryl, C.sub.7 -C.sub.30 aralkyl or C.sub.2 -C.sub.30 alkoxyalkyl group and mixtures thereof, and y is from 0 to 2. The method comprises preparing a sulfide solution that contains from about 9 wt. % to about 13 wt. % sulfide sulfur; contacting the solution with elemental sulfur and a hydroxide; adding a molybdenum compound for a time and at a temperature sufficient to form a reaction mixture and a precipitate; separating the precipitate; and contacting the remaining reaction mixture with additional sulfide solution to form (NH.sub.4 ).sub.2 Mo.sub.2 S.sub.12.yH.sub.2 O.

Abstract: Aluminum is removed from ammonium molybdate solution by the use of Mg.sup.+2 in the solution to precipitate out the aluminum.

Abstract: A quaternary ammonium trihalide, a novel compound, represented by the formula:[A--R'].sup.+ .multidot.X.sub.3.sup.-(wherein A stands for a trialkyl-amino radical or a pyridyl radical, R' for an alkyl radical of 6 to 22 carbon atoms, and X for a halogen atom) and a method for the dissolution of a metal with a liquid consisting essentially of an organic solvent and the quaternary ammonium trihalide.

Abstract: An epoxidation reaction product formed by the molybdenum catalyzed reaction of propylene with tertiary butyl hydroperoxide to provide propylene oxide and tertiary butyl alcohol is separated by distillation into a propylene fraction, a propylene oxide fraction, a tertiary butyl alcohol fraction and a heavy liquid distillation fraction composed primarily of tertiary butyl hydroperoxide, tertiary butyl alcohol, dissolved molybdenum catalyst, and impurities including lower aliphatic C.sub.1 -C.sub.4 carboxylic acids, and the heavy liquid distillation fraction is saturated with ammonia to precipitate the molybdenum therefrom for recovery.

Abstract: An epoxidation reaction product formed by the molybdenum catalyzed reaction of propylene with tertiary butyl hydroperoxide to provide propylene oxide and tertiary butyl alcohol is separated by distillation into a propylene fraction, a propylene oxide fraction, a tertiary butyl alcohol fraction and a heavy liquid distillation fraction composed primarily of tertiary butyl hydroperoxide, tertiary butyl alcohol, dissolved molybdenum catalyst, and impurities including lower aliphatic C.sub.1 -C.sub.4 carboxylic acids, and the dissolved molybdenum content of the heavy distillation fraction is adjusted to about 300 to 500 ppm of dissolved molybdenum, if necessary, by treatment with a precipitating agent and contacted with a solid adsorbent consisting essentially of a synthetic, porous, high surface area amorphous magnesium silicate.

Abstract: A process is disclosed for purifying molybdenum containing arsenic and phosphorus which involves leaching molybdenum trioxide in an acid at a temperature of above about 70.degree. C.

Abstract: Directed to a process for producing a tungsten product of enhanced purity from ammonium paratungstate (APT) with a minimum number of processing steps which comprises mixing the APT with an ammonium solution, autoclaving the mixture at a temperature above the boiling point thereof to dissolve the APT and recrystallizing APT from the solution to yield an APT product of enhanced marketability.

Abstract: Aqueous effluent solutions containing metal cations may be treated with an extractant comprising an organophosphinic acid, a di-2-ethylhexyl phosphoric acid and/or an aliphatic amine to selectively separate chromium, nickel, cobalt, copper and lead cations from the aqueous solution. Typical extraction techniques include liquid-liquid extraction employing either mixer settlers or columns, liquid membrane extraction and selective supported membrane extraction.

Abstract: Refining of either niobium hydroxide or tantalum hydroxide containing transition metals as impurities is accomplished easily and economically by dissolving the metal hydroxide in an aqueous solution of either hydrofluoric acid or oxalic acid, adjusting the pH of the solution to 1 to 4 and adding ammonium pyrrolidinedithiocarbamate (APDC) to the solution while maintaining the temperature of the solution below 60.degree. C. The addition of APDC causes the transition metals to simultaneously precipitate as coordination compounds. The minimum amount of APDC is 0.05 wt % of Nb.sub.2 O.sub.5 or Ta.sub.2 O.sub.5 that can be formed from Nb or Ta contained in the solution. After the treatment with APDC the pH of the solution is raised to 6 or above to precipitate the refined metal hydroxide.

Abstract: A process for purifying molybdenum, which comprises first leaching impure molybdenum trioxide containing potassium in a liquid medium of nitric acid, and an ammoniacal liquor, wherein the nitric acid concentration is about 3.5 to 4.0 moles per liter and the ammonium nitrate concentration is about 0.5 to 1.0 moles per liter, at greater than 50.degree. C. to solubilize the major portion of the potassium and produce a once-leached molybdenum trioxide and a first liquor, removing the once-leached molybdenum oxide from the first liquor, re-leaching the once-leached molybdenum trioxide in nitric acid having a concentration of about 3.5 to 4.0 moles per liter, at greater than 50.degree. C. to produce a twice-leached molybdenum trioxide and a second liquor, removing the twice-leached molybdenum oxide from the second liquor, water washing the twice-leached molybdenum trioxide, digesting the molybdenum trioxide in ammonium hydroxide at greater than 50.degree. C. at a pH of greater than 9.

Abstract: A metal is dissolved by being brought into contact with at least one halogenated hydrocarbon in the presence of a cationic surfactant.

Abstract: A method of extracting tungsten values from tungsten containing ores comprising step (i) forming a mixture of a tungsten containing ore and a first mineral acid adapted to consume acid consuming substances in the ore and step (ii) thereafter adding organic anions to produce a solution containing dissolved tungsten values.

Abstract: A process is disclosed for purifying molybdenum which involves adding to an acidic slurry of molybdenum trioxide, a source of magnesium ions in a solid form, with the amount of magnesium and the magnesium ion concentration in the subsequently formed ammonium molybdate solution being sufficient to subsequently form insoluble compounds containing greater than about 80% by weight of the arsenic and greater than about 80% by weight of the phosphorus, and ammonia in an amount sufficient to subsequently dissolve the molybdenum and subsequently form the insoluble compounds, digesting the resulting ammoniated slurry at a temperature sufficient to dissolve the molybdenum and form an ammonium molybdate solution while the pH is maintained at from about 9 to about 10 to form a solid containing the insoluble compounds, and separating the solid from the ammonium molybdate solution.

Abstract: A method of processing manganese ore by adding the ore to an aqueous solution of acid and H.sub.2 O.sub.2 to form a leach pulp. The leach pulp is agitated for a predetermined time period at predetermined temperatures. The leach pulp is then separated into a solid fraction and a liquid fraction containing solubilized metals. The solubilized metals are then recovered from the liquid fraction.

Abstract: The present invention is a process for selectively precipitating molybdenum in a form that is substantially free from vanadium impurities. The molybdenum is precipitated in the form of ammonium octamolybdate which has a molybdenum to vanadium ratio of about 400:1 in an initial crystallization and a ratio of about 1300:1 in a subsequent recrystallization.