Abstract: The invention relates to a process for the removal of heavy metal ions, particularly chromium, lead and/or zinc ions, from aqueous liquids by precipitation wherein the aqueous liquid containing the heavy metal ions and an aqueous liquid containing a base which precipitates the heavy metal ions in the form of their hydroxide or basic salt are added simultaneously to an amount of water at a pH between 5 and 10 and a temperature between 60.degree. and 100.degree. C. and the pH and the temperature are maintained in the specified ranges during the precipitation.

Abstract: Chromium is selectively precipitated from waste solutions by means of benzoate ion. The resulting chromium benzoate complex is separated, washed and treated with either base or sulfuric acid to recover the benzoate and a chromium hydroxide product.

Abstract: Alloy scrap containing refractory metals such as chromium, molybdenum, tungsten, vanadium, niobium and tantalum and base metals such as nickel, cobalt, copper and iron are treated to partition the refractory metal values from the base metal values without an energy intensive remelting step. The scrap in finely divided form is calcined in the presence of an oxygen containing gas and a member of a certain group of alkali metal salts at a temperature in the range of 800.degree. C. to 1150.degree. C. for 1/4 hour to four hours. This treatment converts the refractory metals to alkali metal molybdates, tungstates, chromates, vanadates, niobates and tantalates and the base metals to oxides. The calcined product may then be water leached to produce a substantially base metal-free liquor rich in refractory metal values. Both the refractory and the base metal values may be subsequently recovered by conventional hydrometallurgical techniques.

Abstract: In the process of recovering molybdenum from a spent catalyst solution obtained from a crude reaction product of a molybdenum catalyzed epoxidation of an olefin with an organic hydroperoxide from which crude reaction product epoxide and an alcohol corresponding to the hydroperoxide is removed, the improvement comprises removing and recovering dissolved molybdenum as a high molybdenum content solid by subjecting the spent catalyst solution to a liquid-to-liquid extraction with an aqueous extract to form a two phase system, separating the molybdenum-rich aqueous extract and precipitating therefrom a high molybdenum content solid by heating the aqueous extract in the presence of hydrogen sulfide or a water soluble sulfide salt.

Abstract: The process relates to the separation of the molybdenum and/or tungsten, titanium, vanadium, niobium or tantalum present in the form of organometallic compounds in residual effluents.It is applicable, in particular, to the effluents originating from the epoxidation of olefins by hydroperoxides.The process involves treating the effluent with from 1 to 10% by weight of water, at between 150.degree. and 220.degree. C. under pressure, to render the metals listed above insoluble, without forming a distinct aqueous phase. The solid phase containing more than 95% of the metals is separated by filtration. After treatment, the effluents can be used without disadvantage, for example as a fuel, and the metals can be recovered from the solid phase.

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.

Abstract: Disclosed is a process for recovering chromium, vanadium, molybdenum, and tungsten from secondary resources such as alloy scrap comprising a refractory metal and base metals such as cobalt nickel, iron, and copper. The scrap is calcined with sodium carbonate in air to convert the refractory metal values to MoO.sub.4.sup..dbd., VO.sub.4.sup..tbd., WO.sub.4.sup..dbd., CrO.sub.4.sup..dbd., and the base metals to water insoluble oxides. A leach of the calcined materials produces a pregnant liquor rich in refractory metals which, after separation of the vanadium, molybdenum and tungsten values, is treated with CO, CHOO.sup.-, CH.sub.3 OH, or HCHO to reduce Cr.sup.+6 to Cr.sup.+3. The carbonate and bicarbonate salts produced as a byproduct of the reduction are recycled to the calcination stage.As a result of the V, W, and Mo partition, a mixed solid comprising CaO.multidot.nV.sub.2 O.sub.5, CaMoO.sub.4, and CaWO.sub.4 is produced.

Abstract: 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.

Abstract: A process is disclosed for recovering tungsten and molybdenum values from tungsten concentrates containing molybdenum in an amount at least about one-twentieth of the amount of contained WO.sub.3. The concentrate, generally a wolframite concentrate, is subjected to dissolution in hot NaOH solution to provide a pregnant liquor or solution containing tungsten and molybdenum values. The solution, after purification, is treated with a sulfide precipitation agent to precipitate MoS.sub.3 and some WS.sub.3 using a stoichiometric excess of a sulfide precipitating agent to produce a filtrate containing tungsten substantially free of molybdenum. The sulfide precipitate is dissolved in dilute NaOH solution and again precipitated using a stoichiometric deficient amount of the sulfide precipitating agent to produce a precipitate of MoS.sub.3 low in tungsten. The foregoing sulfide precipitation steps may be reversed.

Abstract: Disclosed is a process for recovering chromium, vanadium, molybdenum, and tungsten from secondary resources such as alloy scrap comprising a refractory metal and base metals such as cobalt, nickel, iron, and copper. The scrap is calcined with sodium carbonate in air to convert the refractory metal values to MoO.sub.4.sup.=, VO.sub.4.sup..ident., WO.sub.4.sup.=, and CrO.sub.4.sup.= and the base metals to water insoluble oxides. A leach of the calcined materials produces a pregnant liquor rich in refractory metals which, after separation of the vanadium, molybdenum and tungsten values, is treated with CO, CHOO.sup.- CH.sub.3 OH, or HCHO to reduce Cr.sup.+6 to CR.sup.+3. The carbonate and bicarbonate salts produced as a byproduct of the reduction are recycled to the calcination stage.As a result of the V, W, and Mo partition, a mixed solid comprising CaO.nV.sub.2 O.sub.5, CaMoO.sub.4, and CaWO.sub.4 is produced.

Abstract: Disclosed is a process for recovering chromium, vanadium, molybdenum, and tungsten from secondary resources such as alloy scrap comprising a refractory metal and base metals such as cobalt, nickel, iron, and copper. The scrap is calcined with sodium carbonate in air to convert the refractory metal values to MoO.sub.4.sup.=, VO.sub.4.sup..ident., WO.sub.4.sup.=, and CrO.sub.4.sup.= and the base metals to water insoluble oxides. A leach of the calcined materials produces a pregnant liquor rich in refractory metals which, after separation of the vanadium, molybdenum and tungsten values, is treated with CO, CHOO.sup.-, CH.sub.3 OH, or HCHO to reduce Cr.sup.+6 to Cr.sup.+3. The carbonate and bicarbonate salts produced as a byproduct of the reduction are recycled to the calcination stage.As a result of the V, W, and Mo partition, a mixed solid comprising CaO.nV.sub.2 O.sub.5, CaMoO.sub.4, and CaWO.sub.4 is produced.

Abstract: Disclosed is a process for recovering chromium, vanadium, molybdenum, and tungsten from secondary resources such as alloy scrap comprising a refractory metal and base metals such as cobalt, nickel, iron, and copper. The scrap is calcined with sodium carbonate in air to convert the refractory metal values to MoO.sub.4.sup..dbd., VO.sub.4.sup..tbd., WO.sub.4.sup..dbd., and CrO.sub.4.sup..dbd. and the base metals to water insoluble oxides. A leach of the calcined materials produces a pregnant liquor rich in refractory metals which, after separation of the vanadium, molybdenum and tungsten values, is treated with CO, CHOO.sup.-, CH.sub.3 OH, or HCHO to reduce Cr.sup.+6 to Cr.sup.+3. The carbonate and bicarbonate salts produced as a byproduct of the reduction are recycled to the calcination stage.As a result of the V, W, and Mo partition, a mixed solid comprising CaO.nV.sub.2 O.sub.5, CaMoO.sub.4, and CaWO.sub.4 is produced.

Abstract: Molybdenum is recovered from an ammonium molybdate solution containing phosphate anions by digesting in an ammonium molybdate solution at least one water-soluble compound of at least one metal selected from the group consisting of aluminum, calcium, iron and magnesium in small but effective amounts to precipitate at least about 50% of the phosphate anions for a time sufficient to precipitate the phosphate anion, separating the phosphate precipitate from the ammonium molybdate solution, then acidifying the ammonium molybdate solution with at least one mineral acid selected from the group consisting of sulfuric acid and nitric acid to lower the pH value of the solution to between about 2.5 and about 4.5 to precipitate ammonium polymolybdate, and calcining the ammonium polymolybdate at a temperature below about 750.degree. C. to produce a molybdenum trioxide product.

Abstract: A method has been devised for removing hexavalent chromium from concentrated aqueous alkali metal chlorate solutions by reacting the solution with a hydrazine compound and separating trivalent chromium compound from the solution. Alkali metal hypohalites may be simultaneously removed from the chlorate solution by reaction with excess hydrazine compound.

Abstract: A method has been devised for removing hexavalent chromium from concentrated aqueous alkali metal chlorate solution by reacting the solution with an inorganic sulfur containing compound and separating divalent and trivalent chromium compounds from the solution. Alkali metal hypohalites may be simultaneously removed from the chlorate solution by reaction with excess inorganic sulfur containing compound.

Abstract: In a process for recovering tungsten from cemented tungsten carbide, the tungsten carbide is oxidized to form an oxidized product and the oxidized product is digested in an aqueous solution of alkali metal hydroxide to form a soluble portion containing tungsten values and an insoluble residue portion. According to the improved process of the present invention, tungsten values are recovered from the insoluble residue portion by mixing the insoluble portion with an alkali metal carbonate to form a resulting mixture, roasting the resulting mixture in an atmosphere containing oxygen to oxidize the insoluble portion and form another product which is leached with water to recover soluble tungsten values.

Abstract: Molybdenum is recovered from dilute, ammoniacal, molybdenum containing solutions by adding ferrous ions to the solution to precipitate an iron hydroxide-ammonium molybdate complex. The precipitate is separated from the aqueous raffinate and is treated with acid to resolubilize the molybdenum in the complex. Molybdenum values are recovered from the resulting acid solution by ion exchange. The aqueous raffinate is purged of iron and is reused.

Abstract: Method for the recovery of chrome hydrate or high purity Cr.sub.2 O.sub.3 from chromium ores by roasting the ore with Na.sub.2 CO.sub.3 and CaO, water leaching the roasted mass, precipitating aluminum impurities from the leach liquor as Al(OH).sub.3 and contacting the leach liquor with sulfur and NaOH in order to reduce the chromium values in the leach liquor from valence 6 to 3 to provide a chrome hydrate precipitate. The chrome hydrate precipitate is acid repulped to provide a chrome hydrate from which sodium impurities have been removed. The chrome hydrate is dried and the resulting solids are calcined to provide a high purity Cr.sub.2 O.sub.3.

Abstract: Molybdenum is separated from molybdenum-containing activated charcoal or char also containing small amounts of uranium obtained as a by-product in uranium leaching processes by stripping with an alkaline solution to provide a molybdenum-containing solution containing substantially less than 500 ppm U.sub.3 O.sub.8.

Abstract: An extraction process is described for the selective separation of bivalent metal ions belonging to the group Cu, Co, Ni and Zn in aqueous solution of Cu- and Ni-ions, Cu- and Zn-ions or Cu- and Co-ions, wherein there is used as the extraction medium one or more unsaturated fatty acids, optionally in solution and/or in admixture with saturated fatty acids and an aliphatic oxime.

Abstract: A process for the preparation of a chrome-tanning agent and Glauber's salt from sodium bisulphate contaminated with chromium compounds obtained as by-product from the manufacture of chromic acid from solid sodium dichromate and sulphuric acid, comprising(a) treating an about 20 to 70% aqueous sodium bisulphate solution which contains chromium compounds and is acid with sulphuric acid with sulphur dioxide until all the chromium is present in the form of chromium (III);(b) adding sodium hydroxide to the reduced solution until it has a pH of between about 4 and 5;(c) adding sodium carbonate to the solution to a pH of between approximately 8 and 8.5, thereby precipitating chromium (III) hydroxide;(d) separating off the precipitated chromium (III) hydroxide; and(e) evaporating the filtrate left after removal of the chromium (III) hydroxide to yield solid sodium sulphate.

Abstract: An improved process is described for the hydrometallurgical liquid phase oxidation of molybdenum disulfide ore concentrates, in which the reactants include in the range of from about 0.12 to about 1.68 mols of an alkali metal hydroxide, preferably sodium hydroxide, per mol of molybdenite, and the time of the reaction, the amount of the alkali metal hydroxide, and the reaction temperature and pressure are coordinated to achieve at least a 95% oxidation conversion of the molybdenum disulfide.

Abstract: A method for treating nonferrous metal hydroxide sludge waste to separate and recover the nonferrous metals therein wherein the waste is first mixed with an alkali hydroxide or carbonate, dried, and then roasted and the water-insoluble residue in the roasted material is treated with sulfuric acid to produce an acid-insoluble residue and a sulfuric acid solution containing copper, aluminum and chromium and thereafter, separating the copper from this solution by liquid-liquid extraction and thereafter, separating the aluminium, chromium, zinc and nickel from the remaining solution by separate liquid-liquid extraction steps.

Abstract: Method for recovering metals from cyanide and hexavalent chromium plating baths comprising immersing plated articles in a reclaiming bath containing an aldehyde or an aldehyde percursor, and optionally an oxidizing agent, to precipitate the excess metal in the residual plating bath in the form of free metal or metal hydroxide and to decompose the cyanide and to reduce the hexavalent chromium to trivalent chromium. The plating bath and reclaiming bath are regenerated. Apparatus is provided to effect this process.

Abstract: The disclosure is of a simple and economical method for recovering the component metals from a sintered metal carbide. The sintered metal carbide is employed as an anode and treated by electrolysis in an acid solution. The metal carbide e.g. WC dissolves and precipitates as a metal hydroxide. At the same time the metal e.g. Co, which is a sintering binder, is electro-deposited on the surface of a cathode. The metal hydroxide may be washed, calcined and reduced in hydrogen gas to obtain a pure metal powder.

Abstract: A method for decontaminating waste materials, wherein the residue of water leaching of the roasted chromium mineral containing water soluble hexavalent chromium compounds is wet ground and classified until obtaining such a granulometrical distribution that not more than 5-10% of the particles have an average size larger than 0.4 mm, and 40-60% of the particles have an average size less than 0.8 mm, and is then subjected to wet treatment under vigorous stirring at about 100.degree. C. with sulphur, in an aqueous emulsion of akaline or alkaline-earth sulphide for 1-4 hours, the percentage of solids in the reactor being in the range of 1-60%, preferably 30-35% by weight; and wherein the reacted slurry is thickened and filtered to provide the restored or decontaminated earth and an effluent, which is partly recycled to grinding or to reaction.

Abstract: To obtain highly purified, lamp grade ammonium paratungstate crystals from any of several different tungsten ores, the ore is reduced to finely divided status and slurried in heated HCl solution to convert tungsten values to WO.sub.3.H.sub.2 O. Recovered tungstic oxide is washed and dissolved in heated aqueous solution of sodium carbonate or sodium hydroxide with the pH maintained at about 8 to 8.5 to form soluble sodium tungstate. Sodium hydroxide is added to raise the pH to about 10.5 to 11.5, and magnesium chloride is added in amount sufficient to somewhat neutralize the solution. Sodium hydroxide is added to raise the pH to about 10.5 to 11.5 to precipitate as hydroxide the magnesium and additional metallic impurities. At least one of ammonium sulfide and thioacetamide is and the heated solution is acidified to a pH in the range from about 2 to 3 to precipitate any molybdenum as MoS.sub.3.

Abstract: A process and a product formed thereby for the recovery of chromium values from aqueous solutions (e.g., waste liquors) comprises contacting an acidic solution containing sulfate ion and trivalent chromium ion with at least about 4 molar equivalents of MgO or Mg(OH).sub.2 per 3 molar equivalents of trivalent chromium in addition to the amount required to neutralize the free acid to a pH of about 4 to form an amorphous, dense solid, grainy, easily settleable, trivalent chromium-containing precipitate in an alkaline solution according to the equation: 3Cr.sub.2 (SO.sub.4) + 8 MgO .fwdarw.Cr.sub.2 (OH).sub.4 SO.sub.4 .multidot. 4Cr(OH).sub.3 .multidot. 4H.sub.2 O + 8 MgSO.sub.4. The trivalent chromium-containing product can be readily separated from the water and is a useful source of chromium for subsequent processing. The water remaining after separation of the precipitate contains less than 0.5 mg/l chromium.

Abstract: Chromates are removed from aqueous alkali metal chlorate solutions by either of two processes. In the first process, a water-soluble sulfide is added to react with the chromate, and then a ferrous salt is added. The soluble sulfate is converted to elemental sulfur and the chromate is converted to an insoluble trivalent Cr-containing material which is removed from solution. In the second process an "iron mud" is prepared by reacting a ferrous salt with sodium hydroxide and added so as to precipitate insoluble trivalent chromium-containing material.

Abstract: Copper, iron, and lead impurities are removed from molybdenum flotation concentrates by mixing the feed concentrates with a nonvolatile chloride salt, heating the mixture to a temperature of from about 200.degree. to 350.degree. C for a time sufficient to activate the lead impurities in the concentrates so that they can be leached therefrom during the subsequent leach step, and leaching copper, iron, and lead impurities from the heat-treated concentrates with a mildly oxidizing leach solution containing chloride ions and having a pH of no more than 4. Preferably, the mixing of the chloride salt and the feed concentrates is achieved by thoroughly mixing an aqueous solution of the salt with the feed concentrates.

Abstract: A process is provided for treating tri (alkaline earth metals) tungstates with an aqueous solution containing cations selected from ammonium, sodium and potassium ions and mixtures thereof, and anions selected from hydroxide, carbonate, bicarbonate, and phosphate ions and mixtures thereof, to form a tungstate salt which is soluble in the solution and an alkaline earth metal compound which is insoluble in the solution. The tri (alkaline earth metal) tungstate can be prepared from iron tungstate, manganese tungstate, and/or an alkaline earth metal tungstate or from ores or concentrates of these tungstates, by a high temperature treatment with an alkaline earth metal donor compound, such as calcium oxide. A preferred soluble tungstate is ammonium tungstate, which can be further processed to yield tungsten trioxide and/or tungsten.

Abstract: A process of recovering molybdenum in the form of molybdic acid from waste products and particularly from spent catalysts containing a support based on gamma-alumina wherein the molybdenum is in the form of molybdenum oxide or molybdenum sulfide comprising treating the waste products with sodium carbonate and heating to convert the molybdenum present to sodium molybdate, and converting the sodium molybdate to molybdic acid by treatment with concentrated nitric acid to produce molybdic acid high in purity that is suitable for the production of molybdenum compounds as well as for the recovery of the pure metal.

Abstract: A process of recovering molybdenum from waste products and particularly from spent catalyst based on active alumina and containing molybdenum compounds comprising mixing the spent catalyst with sodium carbonate powder, adding water and remixing to absorb the water in the catalyst particles, baking the mixture to convert the molybdenum present to sodium molybdate, treating the mixture at ambient temperature with carbon dioxide gas, treating the resultant mixture with hot water to dissolve the sodium molybdate, neutralizing and clarifying with concentrated nitric acid, and precipitating to produce molybdic acid high in purity that is suitable for the production of molybdenum compounds as well as for the recovery of the pure metal.

Abstract: Metal powders, metal oxide powders, and mixtures thereof of controlled particle size are provided by reacting an aqueous solution containing dissolved metal values with excess urea. Upon heating, urea reacts with water from the solution leaving a molten urea solution containing the metal values. The molten urea solution is heated to above about 180.degree. C. whereupon metal values precipitate homogeneously as a powder. The powder is reduced to metal or calcined to form oxide particles. One or more metal oxides in a mixture can be selectively reduced to produce metal particles or a mixture of metal and metal oxide particles.

Abstract: A flotation process for recovering scheelite from low-grade tungsten ores containing calcium-bearing minerals other than scheelite. Calcium oxide (lime) is added to an ore pulp together with a carbonate alkalizing agent, dispersant and anionic collector. The pulp is subsequently subjected to flotation and the scheelite recovered.

Abstract: A process of recovering and exploiting wastes from chromic anhydride production, wherein the slurry comprising a water suspension of solid waste residue from chromic anhydride processing is subjected to a first reaction stage with sodium chromate solution at a constant flow rate and such a density as to avoid precipitation of sodium sulfate, setting pH to 2-8 by adjusting the slurry flow rate, and finally separating by filtering insoluble chromium chromate formed from the sodium bichromate and sodium sulfate solution.

Abstract: A method for reducing the residual chromate level in effluent waters comprising catalytic reduction of the chromate ion by hydrogen to the trivalent chromium state and removal of the chromium by passage through a cation exchange resin column or by base precipitation in a settling pond.

Abstract: The method comprises the steps of crushing of the ore, neutralization by a mixture of water and sulphuric acid, introduction of a controlled quantity of sulphur dioxide gas at a pH value between 1.5 and 4 for promoting dissolution of nickel, copper and a desired quantity of manganese, leaching of the ore with sulphuric acid at a pH value between 1 and 3 for selectively dissolving the nickel and copper, separation of the solid and liquid phases, and separation of the metals contained in the liquid phase.

Abstract: A process in which copper, nickel, cobalt and molybdenum are recovered by direct leaching of comminuted raw manganese nodules after the nodules are reduced in a reduction circuit with an aqueous ammoniacal leach solution containing cuprous ions. An improvement is disclosed which results from recycling a portion of the metal values recovered back to the reduction circuit as a solid basic metal carbonate. The metal carbonate recycle enables the size of the reactors in the reduction circuit to be reduced. The recycle also increases the efficiency of the process by facilitating the solubilization of copper. Another aspect of the invention resides in the advantages of maintaining solubilized copper in amounts between 10 grams per liter and the solubility limit in the reduction circuit.

Abstract: 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.

Abstract: An improved hydrometallurgical method is provided for producing technical grade molybdic oxide from molybdenite concentrates. According to this method, the molybdenite concentrates are leached in an acid medium having a nitric acid concentration between about 25 gpl and about 50 gpl and an initial sulphuric acid concentration of nil to about 750 gpl, under oxygen pressure of about 100 - 250 psig and at a temperature above 115.degree. C so as to produce technical grade molybdic oxide having not more than 0.1% sulphur. Then a liquid-solid separation of the reaction mixture is effected and the obtained leach liquor is recycled back to the leaching stage optionally after partial neutralization with a basic reagent. The solid is washed and recovered as technical grade molybdic oxide.This invention relates to a novel method of producing hydrometallurgically technical grade molybdic oxide from molybdenite concentrates.

Abstract: A method of treating solid waste material containing minor amounts of water soluble chromium compounds with a reductant, particularly sulfide ions, to convert the soluble chromium to an insoluble state, and produce a solid waste from which substantially no chromium can be leached by water, as by exposure to rain.

Abstract: The present invention provides a method for recovering niobium from a hydrochloric acid solution which contains niobium and vanadium and which may also contain other metals such as, for example, zirconium, titanium, iron, chromium and aluminum. Broadly, the method comprises heating such a solution at a low pH for a period of time sufficient to form a niobium-containing precipitate substantially free of vanadium. Preferably, the solution is heated in the presence of a small amount of sulfuric acid. The precipitate then is recovered from the solution.

Abstract: This invention relates to a process for recovering tungsten from an alkaline leaching solution of tungsten ores. This invention comprises adjusting the pH of an alkaline leaching solution which is obtained by lixiviating ore containing tungsten with an alkaline solution to 7-8 with acid to oxidize molybdic acid ions in the solution, adding a sulfide donor, then precipitating molybdenum sulfide compounds by adjusting the pH value of the solution to 2-3, and recovering tungstic acid ions as calcium tungstate by the addition of a calcium ion donor after the molybdenum sulfide compounds are separated.

Abstract: Metal can be recovered from metal-containing waste by means of liquid extraction processes. The waste is leached with sulphuric acid. The resulting metal sulphate solution is contacted with an organic solution of a reagent, so as to extract iron and zinc to the organic solution. The organic solution is washed with sulphuric acid in two steps, viz. with weaker acid in the first step, so as to transfer zinc to the washing solution, and with stronger acid in the second step, so as to transfer iron to the washing solution. Zinc and iron have now been separated, and are recovered from the washing solutions in known ways, for example by crystallization. If the waste contains other metals, in addition to iron and zinc, additional selective liquid extraction processes are added, before or after the iron-zinc-extraction.

Abstract: A hydrometallurgical process for treating iron containing metal sulfides for rendering iron and non-ferrous metal values active and amenable for selective extraction and separate recovery. Sulfur values can be controllably produced as elemental sulfur or as sulfuric acid to supply acid requirements of the process, while substantially obviating the discharge of sulfur-containing gases to the atmosphere. Ores and concentrates of the sulfides are thermally activated by sequentially heating and reducing said sulfides in a countercurrent flow of heating and reducing gases respectively in a reactor whereby the reaction products of the reducing gas and sulfides, together with liberated labile sulfur, are controllably combusted with oxygen to satisfy heat requirements of the thermal activation process and to convert sulfur values to SO.sub.2 gas. The activated sulfides are subjected to an acid leach in aqueous sulfuric acid for production of ferrous sulfate and evolution of H.sub.

Abstract: Uranium values are obtained from phosphate rock by acidifying phosphate rock containing uranium values and at least one other heavy metal with a mineral acid so as to obtain a crude acid, solvent extracting the crude acid with an organic solvent so as to separate a raffinate from a relatively pure, wet process phosphoric acid and treating said raffinate with a base so as to raise the pH to 1-2 whereby uranium hydroxide or phosphate and other heavy metal hydroxides or phosphates are coprecipitated. The uranium content of the coprecipitate after drying is at least as high as 0.3% which is comparable to that of uranium ores of the highest quality.

Abstract: From a chromate ion-containing aqueous waste liquor the chromate ion can be advantageously recovered in the form of chromic acid by the process comprising the steps of adding a reducing agent to the chromate ion-containing aqueous waste liquor to precipitate the chromate ion in the form of chromium (III) hydroxide; adding an alkali and aqueous hydrogen peroxide to the precipitated chromium (III) hydroxide to produce a chromate ion-containing aqueous solution; and passing the resultant chromate ion-containing aqueous solution through an H form acidic cation-exchange resin.

Abstract: A continuous method is provided for reclaiming chromium compounds which heretofore were discharged as industrial waste from chrome liquor tanneries. The method includes continuous agitation of chrome sludge along with continuous filtration and movement through successive filtering zones. This method is both economically attractive and vital from an ecological standpoint. The reclaimed chromium values are in condition for reconstitution into fresh chrome-tanning liquors.

Abstract: The known process of separating molybdenum from a tungsten-molybdenum containing alkaline solution has been improved by carrying out the chemical reaction between the solution treated with sulphuric acid and an added sodium bisulphide solution in a continuous process within a multi-stage stirred-tank reactor system, whereby the freed hydrogen sulphide is recycled for absorption by the alkaline solution thus reducing substantially the amount of additional sulphuric acid required for the reaction.