Abstract: A hydrometallurgical process for the treatment of a soluble silicate-bearing material for the recovery of its valuable metal content by leaching the silicate-bearing material at an elevated temperature with an aqueous solution of a mineral acid, precipitating silicic acid during the same stage in an easily settling and filtering form, the silicate-bearing material being added at such a rate that its concentration calculated as SiO.sub.2 corresponds to the simultaneously precipitating silicic acid quantity, and by finally separating the solid material from the valuable-metal-bearing solution.

Abstract: An improved process for preparing a metallic sulphate in a reaction zone from mixing of the corresponding metallic sulphide concentrates with ammonium sulphate and heating. Heating preferably includes directly contacting the mixture with products of combustion of a heating fuel at temperatures between about 150.degree. C and about 480.degree. C. The products of combustion may be diluted with a gas, and the metallic sulphate of the corresponding metallic sulphide may be initially mixed with the mixture to inhibit the development of semi-fluid conditions in the reaction of the metallic sulphide concentrates with ammonium sulphate.

Abstract: An iron oxide based pigment in alpha-Fe.sub.2 O.sub.3 form, which contains the water insoluble part obtained by calcination of basic iron sulfate and/or jarosite based residues, this pigment being prepared by a process comprising calcining at a temperature from 600.degree. to 800.degree. C and during a period from 2 to 240 minutes basic iron sulfate and/or jarosite based residues, so as to decompose in an incomplete manner such basic iron sulfates and/or jarosite and to obtain in the calcined product an iron bonded sulfur content of more than 0.6%, and solubilizing the not decomposed iron sulfates with other soluble sulfated metals, such as zinc sulfate, by lixiviating the calcined product, these water-soluble compounds being then separated by appropriate processes.

Abstract: A process for the treatment of zinc calcine containing zinc oxides, zinc sulfates and zinc ferrites, which comprises neutral leaching, hot acid leaching, jarosite precipitation and recycling of the jarosite containing pulp whereby there is obtained increased zinc extractions, improved settling and filtering characteristics of the leach pulp, simplified operation and process control and increased ammonium removal.

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: A process for treating a residue from the sulfuric acid leaching of roasted zinc blende, comprising(a) leaching the residue in a single stage with sulfuric acid and a metal sulfide supplied in a quantity sufficient for transforming the iron into divalent iron, the temperature being maintained between about 60.degree. C and the boiling point,(b) heating the mass to a temperature above the melting point of sulfur, separating a first fine-grained residue of low zinc and iron contents and high lead content, and separating a coarse-grained residue containing sulfur, compounds of iron and any excess metal sulfide from (a),(c) adjusting the pH of the residual solution to at most about 2, at a temperature between about 80.degree.

Abstract: Gallium and other values are recovered from phosphorus-furnace flue-dust by treating dust with sulfuric acid to form a solution and a residue. The residue may be treated for recovery of values. Zinc is precipitated from the solution as zinc ammonium sulfate hexahydrate and an alkaline material is added to precipitate a gallium concentrate and to form a gallium-free solution, which may be treated for recovery of sulfate and phosphate values. The gallium concentrate may be upgraded by mixing concentrate with lime to precipitate calcium phosphate and by subsequently adding sodium hydroxide to redissolve coprecipitated gallium and aluminum compounds. Residual precipitate is recycled and the solution is neutralized to precipitate an upgraded concentrate. Aluminum may be removed as calcium aluminate. Upgraded concentrate may be dissolved in alkaline solution and the solution electrolyzed for deposition and recovery of gallium.

Abstract: A method is provided for processing raw manganese nodules for the selective recovery of metal values of nickel, copper, cobalt and zinc contained therein by hydrometallurgical means. The raw nodules are suspended in water or dilute wash solution to form a suspension. The suspension and sulfuric acid are charged to a pressure vessel to provide a solid-liquid suspension of nodules and leach solution. The solid-liquid suspension of nodules and leach solution is heated in the pressure vessel to a temperature between about 150.degree. C and about 300.degree. C to cause the nickel, copper, cobalt and zinc to be selectively leached from the nodules into the leach solution to form a metal rich leach solution containing these metals and a residue, with the solid-liquid suspension having a sulfuric acid content of less than 35 g/l upon completion of the leaching. The metal rich leach solution containing nickel, copper, cobalt and zinc is separated from the residue.

Abstract: The improvement in the process for recovering zinc from ferrites which includes treating electrolytic zinc plants residues with a sulfuric acid solution to dissolve the zinc and metals, a solution resulting which contains sulphates of zinc and the other dissolved metals. The undissolved residue is separated in a certain manner from the solution. The solids-free solution is neutralized in a second step with calcine or another neutralizing agent containing zinc until a certain acidity is reached so that the iron remaining in solution separates therefrom in the form of its complex basic sulfate. The solids are settled out and then sent to a neutralization step, which is part of the residue separation scheme, where they are used as seeds of crystals of complex basic sulfate of iron which helps to remove iron in the first neutralization step. This final solution is added to the normal circuit or process flow path of electrolytic zinc plants. Any Fe.sup.+.sup.

Abstract: A dilute aqueous slurry of hydrated zinc oxide is subjected to heat and pressure to obtain solids having improved filtering characteristics. The process is especially useful in the treatment of neutralized waste liquor from the viscose rayon system to provide a more economical method for the recovery of zinc sulfate.

Abstract: The process disclosed is for separation of iron from sulphuric acid acidified sulphate solutions containing zinc to be recovered and iron, the process comprising reacting such a solution at atmospheric pressure and at temperatures of 60 to 100.degree.C., preferably 85.degree.-95.degree.C., with a precipitating agent, in the form of a slurry or solid material containing Fe.sub.2 O.sub.3 or Fe(OH).sub.3 as an essential component. The precipitating agent optionally may be "red mud," a byproduct from the decomposition of bauxite. The precipitating agent may contain or have added thereto Al.sub.2 O.sub.3 and TiO.sub.2 which also contribute to the hydrolysis of the solution. The acid strength of the solution is adjusted to a pH of 1.0 - 2.5, preferably 1.4 - 1.7 by controlling additions of the said precipitating agent to the sulphate solution.

Abstract: Lead is recovered from lead sulfide concentrates or mixed lead-zinc concentrates containing iron sulfide by forming a slurry of such concentrates in an aqueous medium containing ammonium sulfate and free ammonia, and introducing such slurry into a closed reaction vessel at a pressure not exceeding 30 psig. Oxygen also is introduced into such vessel to establish therein a partial oxygen pressure of at least a few psi, while vigorously agitating the slurry. The lead sulfide content of the concentrates thereby is converted to the form of substantially water-insoluble oxidic lead compounds, while any zinc sulfide present is dissolved. The slurry then is withdrawn from the reaction vessel and the insoluble residue is separated from the aqueous solution. The latter is treated for recovery of its zinc and ammonia content, and the residue is subjected to a froth flotation operation to form a concentrate containing substantially all the iron sulfide and a tailing containing the oxidic lead compounds.

Abstract: Process for receovering copper values (and zinc, if present) from copper bearing materials, optionally in admixture with iron. The feed material is leached with a mixture of nitric and sulphuric acids, after which the dissolved copper is cemented from solution by contact with iron. The solution, containing dissolved iron (and zinc, if present in the feed material) salts is reacted with ZnO to precipitate iron as ferric oxide, which is separated, leaving zinc sulfate in solution. Solid zinc sulfate is recovered from the solution by evaporation, and then calcined to produce SO.sub.2, which is recovered and recycled as H.sub.2 SO.sub.4, and ZnO, which is reused in the process, any excess being recovered as a product.