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: Waste materials containing chromium, such as the sludge resulting from neutralization of chromic acid bleed streams from metal cleaning and plating operations, are (1) rendered innocuous for land fill purposes by heating to temperatures of at least about 700.degree. C. to stabilize the materials for safe disposal and (2) activated by heating to temperatures of about 400.degree. to 500.degree. and the chromium content in the resulting calcine can be recovered by thermite reduction.

Abstract: Sulfate solutions containing nickel and cobalt ions are treated by solvent extraction to provide a nickel raffinate with a high Ni:Co ratio and a cobalt raffinate with a high Co:Ni ratio and with low recycle of cobalt by treating the solution with a cobalt extractant to provide a nickel raffinate of high Ni:Co ratio and a loaded extractant, acid stripping the loaded extractant to provide a cobalt sulfate solution containing some nickel and a regenerated cobalt extractant, treating the cobalt sulfate solution with a nickel extractant to provide a cobalt raffinate with a high Co:Ni ratio and acid stripping the loaded nickel extractant to regenerate the extractant and to provide a recyclable sulfate solution containing only a small proportion of the original cobalt.

Abstract: Hexagonal cadmium sulfide, a bright yellow pigment useful in high temperature processing, is produced by reacting cadmium sulfate solution with a solution of a soluble sulfide under pressure and at a temperature of about 250.degree. C.

Abstract: Fine cobalt or nickel powder is produced by hydrogen reduction of a sulfate solution in the presence of a base and a strong reductant such as a metal borohydride wherein the base is added stagewise to the solution with the initial addition of base being sufficient to insure an essentially neutral pH at the time of reductant addition.

Abstract: A solvent extraction process is provided for transferring metal values from one immiscible liquid phase to another, whereby the two liquid phases are vigorously mixed together in a first mixer under conditions in which one liquid phase is rendered continuous, the mixing being continued to effect complete transfer of metal values, and the mixture then passed to a second mixer and the two phases mixed under conditions in which the other phase is rendered continuous, whereby when the two phases are fed to a settler, the rate of disengagement of the two immiscible liquids is substantially increased.

Abstract: Foaming in the hydrometallurgical treatment of a tungsten-containing aqueous solution due to the presence of carbonaceous organic material impurities, such as flotation reagents, is substantially inhibited by the addition of effective amounts of powdered activated carbon, the carbon with the adsorbed impurities being thereafter separated from the solution by filtering. The activated carbon also protects the solvent extraction circuit from contamination. The method is particularly applicable to slurries of tungsten oxide concentrates during the high temperature, high pressure leaching thereof with sodium carbonate solutions in an autoclave.

Abstract: A process is provided for recovering molybdenum and tungsten separately from a sulfide cake containing the same along with arsenic as an impurity. The process comprises dissolving essentially all of the tungsten and molybdenum values contained in the cake in a caustic solution containing at least about 5 but not more than about 6 moles of sodium hydroxide per mole of tungsten plus molybdenum contained in the cake, separating insoluble material from the resulting leach solution and then precipitating one metal value from the group consisting of molybdenum and tungsten preferentially from the other.

Abstract: A process for stripping tungsten values from a tungsten-bearing acidic liquid organic phase into a basic aqueous ammoniacal stripping solution comprises mixing the organic phase and the stripping solution with a high-shear mixing device to maximize the pH gradient between the organic phase and the aqueous solution whereby growth of any precipitated ammonium paratungstate crystals is minimized and the dissolution thereof is maximized and to strip the tungsten values from the organic phase into the stripping solution.

Abstract: Vanadium and nickel values are selectively recovered from a petroleum coke residue by slurrying the coke in an aqueous solution of sodium carbonate providing an excess of the stoichiometric amount of sodium for formation of sodium vanadate and sodium sulfate, and then digesting the slurry at moderately elevated temperature in a pressurized autoclave under an oxygen overpressure supplying at least the stoichiometric amount of oxygen based on the vanadium and sulfur content of the slurry and advantageously sufficient additional oxygen to provide the thermal requirements of the digestion step by oxidation of carbon. In a continuous embodiment, the feed slurry temperature and feed solids content are adjusted according to a substantially inversely correlated relationship. The digestion temperature for a given total pressure and gas flow rate in the autoclave is adjusted to generate a pregnant liquor containing about 20 gpl to about 100 gpl of vanadate (V.sub.2 O.sub.

Abstract: Synthetic scheelite (calcium tungstate) having a low sulfur content is produced in high yield from an aqueous solution of sodium tungstate, that can be contaminated with sulfate ion dissolved therein, by digesting the solution with solid calcium sulfate whereby low-sulfur calcium tungstate precipitates. The solution remaining after filtration of the calcium tungstate product can be treated with calcium sulfate to precipitate additional purified calcium tungstate or to generate a calcium tungstate-calcium sulfate mixture that can be recycled for digestion with additional sulfate-contaminated sodium tungstate solution.

Abstract: A process for the soda ash digestion of scheelite concentrates is provided, the process comprising forming a slurry of a scheelite concentrate in an aqueous sodium carbonate solution and then digesting the slurry in an autoclave at an elevated temperature of at least about 180.degree. C. The concentration of the Na.sub.2 CO.sub.3 solution is substantially inversely correlated to the digestion temperature and substantially directly correlated to the Na.sub.2 CO.sub.3 /WO.sub.3 weight ratio such as to effect the selective dissolution of at least about 95% of the WO.sub.3 in the concentrate and provide a pregnant liquor containing WO.sub.3 while inhibiting substantial dissolution of gangue minerals.

Abstract: Oxide ores or ore concentrates containing organic matter are slurried with water and heated to a temperature of at least about 230.degree. C. under an oxygen partial pressure of at least about 25 psi to oxidize the organic matter. Advantageously, the process in accordance with the present invention can be used in the treatment of tungsten concentrates and can be employed while the tungsten concentrates are being digested with sodium carbonate or sodium hydroxide solutions.

Abstract: A process for conditioning a tungsten concentrate containing tungsten as WO.sub.3, sulfur as sulfide, and calcite to fix at least a portion of the sulfur as calcium sulfate by reaction with the calcite, comprises providing a tungsten concentrate having a calcite content such that less than about 15 wt. % calcium sulfate based on the weight of the WO.sub.3 in the concentrate will be formed and heating the concentrate to a temperature of at least about 500.degree. C. in an oxidizing atmosphere to oxidize substantially all the sulfur in the concentrate to provide a conditioned concentrate having a calcium sulfate content less than about 15% based on the weight of the WO.sub.3, whereby the conditioned concentrate can be efficiently leached with alkali metal carbonates or hydroxides and the resulting alkali metal tungstate solution can be effectively treated to recover an ammonium tungstate solution.

Abstract: A process for extracting tungsten values from an aqueous phase into an organic phase, comprises(a) providing an aqueous phase containing tungsten values dissolved therein, and having an initial pH of about 2.2 to about 4.0,(b) providing an organic phase depleted in tungsten and containing a secondary amine or tertiary amine extractant, a modifier, and the balance a liquid hydrocarbon solvent,(c) extracting tungsten values from said aqueous phase into said organic phase in a plurality of extraction stages operating in countercurrent fashion, and(d) recovering the organic phase enriched in tungsten values and an aqueous raffinate having a pH of about 0.3 to about 4.5.

Abstract: A continuous process with feedback control is disclosed for the soda ash digestion of tungsten concentrates in which a slurry of the concentrate in an aqueous sodium carbonate solution is digested in an autoclave at a temperature of at least about 180.degree. C. to provide a pregnant solution of WO.sub.3. High dissolution efficiency is maintained during digestion by continuously monitoring the pregnant solution which includes determining the specific gravity and the Na.sub.2 CO.sub.3 concentration of the pregnant liquor from which feedback signals are produced which are used to control the amount of Na.sub.2 CO.sub.3 and H.sub.2 O fed to the slurry in accordance with the digestion conditions predetermined to provide the desired dissolution efficiency.

Abstract: A process for the soda ash digestion of refractory tungsten concentrates is provided, the process comprising forming a slurry of the concentrate in an aqueous solution to which sodium carbonate is added in stages while digesting the slurry in an autoclave at a selected elevated temperature of at least about 180.degree. C. to control the concentration of the sodium carbonate during digestion to provide high extraction yields of the contained WO.sub.3. The total amount of the Na.sub.2 CO.sub.3 added stage-wise to complete the digestion is substantially inversely correlated to the digestion temperature and substantially directly correlated to the Na.sub.2 CO.sub.3 /WO.sub.3 weight ratio such as to effect dissolution of at least about 97%, and generally at least about 98%, of the WO.sub.3 in the concentrate and provide a pregnant liquor containing WO.sub.3, the stage-wise addition of the sodium carbonate being such as to inhibit the dissolution of gangue minerals, such as silica, contained in the concentrate.

Abstract: A process for the soda digestion of mixed wolframite and scheelite concentrates is provided, the process comprising forming a slurry of the mixed wolframite and scheelite concentrates in an aqueous sodium carbonate solution and then digesting the slurry in an autoclave at a temperature of at least about 180.degree. C. During digestion a predetermined amount of sodium hydroxide is added calculated stoichiometrically to react with NaHCO.sub.3 formed as a result of the hydrolysis of FeCO.sub.3 or FeCO.sub.3 and MnCO.sub.3 produced during the digestion of the wolframite and convert it to Na.sub.2 CO.sub.3. The concentration of the Na.sub.2 CO.sub.3 solution is substantially inversely correlated to the digestion temperature and substantially directly correlated to the Na.sub.2 CO.sub.3 /WO.sub.3 weight ratio ranging from about 0.9 to 2 such as to effect dissolution of at least about 95% of the WO.sub.3 in the concentrate and provide a pregnant liquor containing said WO.sub.3.

Abstract: A calcium tungstate concentrate is produced by slurrying an aqueous sodium tungstate liquor with calcium carbonate at about 130.degree. C. to about 200.degree. C. while providing sufficient carbon dioxide overpressure to convert sodium carbonate in the slurry to sodium bicarbonate, wherein the conversion of sodium tungstate to solid calcium tungstate in the slurry is promoted. The carbon dioxide is then stripped from the slurry, causing the sodium bicarbonate to convert to sodium carbonate, and a calcium tungstate concentrate is filtered from the slurry. The invention is useful in upgrading impure calcium tungstate concentrates.

Abstract: Basic sodium tungstate leach liquor is treated to reduce the concentration dissolved therein of silica, phosphorus and fluorine impurities in a process which comprises providing a small but effective amount of magnesium in the liquor to maximize removal of silica and phosphorus from solution in the liquor while maintaining the liquor temperature between about 60.degree. C. and about 100.degree. C. and the liquor pH between about 9 and about 11, filtering the liquor, adjusting the liquor pH to between about 6 and about 8 and the liquor temperature to between about 20.degree. C. and about 60.degree. C., and then providing a small but effective amount of aluminum hydroxide in the filtered liquor to maximize removal of fluorine from solution in the liquor while maintaining the liquor temperature between about 20.degree. C. and about 60.degree. C. and the liquor pH between about 6 and about 8.