Abstract: A method for separating and recovering substantially pure aluminum, iron and silica from fly ash, a by-product of coal combustion, includes reacting the fly ash with aqueous fluosilicic acid and aqueous hydrogen fluoride at temperatures sufficiently high to form aqueous silicon fluoride vapor and fluorides and fluosilicate of aluminum and iron, separating the aluminum and iron fluorides and fluorosilicates from the aqueous silicon fluoride vapor, hydrolizing the silicon fluoride vapor to form silicon dioxide in substantially pure form and hydrogen fluoride, recovering and recycling the hydrogen fluoride for reuse in the process, and separating the aluminum and iron fluorides and fluosilicates from one another, and recovering substantially pure aluminum fluoride, substantially pure iron and other substantially pure metals, by electroplating or otherwise.

Abstract: Particulate alumina-base catalysts are treated to recycle the alumina by a two-step process: the first step involving conversion of the alumina to aluminum sulfate by reaction with gaseous sulfur trioxide, and the second step involving conversion of the aluminum sulfate to an aluminum hydroxide compound by reaction with an aqueous hydroxide. Both reactions are topochemical, and the aluminum hydroxide compound is prepared in particulate form.

Abstract: The invention relates to an improved process for reducing the iron content of iron-, silicon- and aluminium-containing raw materials and for producing ferric oxide, optionally along with an alumina concentrate. According to the invention the iron content of mineral raw materials, e.g. bauxites, clay minerals, colliary rocks, red muds, etc. is eliminated by passing through one or more beds prepared from the unground but preferably prebroaken and sized raw material an aqueous hydrochloric acid solution, the concentration of which exceeds 100 g./lit., at a temperature below 90.degree. C., preferably at room temperature, optionally in the presence of a flocculating agent. By pyrolytic decomposition of the ferric chloride prepared ferric oxide can be produced.

Abstract: The invention relates to a process for the recovery of valuable metals from sulfidic, silicate-containing raw materials by slurrying the raw material in water, by subjecting the slurry to a selective leach under atmospheric conditions and in an acidic milieu, and by separating the valuable-metal containing solution from the solid leach residue.When the leach is carried out by introducing an oxygen-bearing gas into the slurry which contains finely-divided sulfide and carbon, the acidity of the slurry drops in a controlled manner so that a high efficiency of oxygen, and a high selectivity of the leach as regards valuable metals, are obtained. Owing to the presence of carbon the oxygen is reduced very easily and so oxygen efficiency is high and the rate of dissolving of the valuable metals increases in the slurry mixture.

Abstract: A leaching process employing acidic chloride solutions, whereby the iron content of aluminous materials such as lower grade iron-containing bauxite ores is reduced, enabling the obtention of valuable products such as metallurgical grade alumina and refractory grade bauxite, previously obtainable only from higher grade low-iron aluminous materials.

Abstract: A starting solid mixture of AlCl.sub.3 and Nacl, which may have been obtained by acid leaching of an aluminiferous mineral and precipitation of the AlCl.sub.3 and NaCl, is mixed with water in an amount to form an aqueous solution containing NaCl and AlCl.sub.3 in a weight ratio Na.sub.2 O/Al.sub.2 O.sub.3 of about 0.028. This is sparged with HCl to precipitate AlCl.sub.3, but the sparging is stopped before a substantial concentration of NaCl starts to come out of solution. The precipitated AlCl.sub.3 may be calcined to Al.sub.2 O.sub.3 and washed to remove any residual NaCl.

Abstract: An improved method of producing anhydrous aluminum chloride via aluminum chloride hexahydrate is provided. In a preferred embodiment the method is incorporated into a process for producing aluminum from aluminous ores, and particularly from domestic ore sources comprising (1) acid leaching an aluminous ore to produce aluminum chloride hexahydrate (ACH); (2) calcining the ACH to a specific temperature of above about 450.degree. C. to produce highly reactive aluminous particles containing high residual chloride and low residual hydrogen levels; (3) reductively chlorinating the calcined ACH at a low temperature to produce anhydrous aluminum chloride suitable for electrolytic reduction; and (4) electrolytically reducing the anhydrous aluminum chloride in a fused salt to produce aluminum metal and chlorine which is recycled to step (3).

Abstract: An improved process is provided for producing via ACH anhydrous aluminum chloride suitable for electrolytic reduction to aluminum wherein the feed ACH is acid leach derived. In a preferred embodiment the acid leach derived ACH is single stage crystallized.

Abstract: An improved process for recovering and recycling coagulant present in water treatment sludges. The improvement comprises several steps. First, enough acid is added to the sludge to solubilize most, but not all, of the coagulant in the sludge. Next, the acid-treated sludge is filtered on a non-mechanical horizontal filter to produce the recovered coagulant in solution as the filtrate. The recovered coagulant has a greater coagulative effect, when later recycled to treat raw water, than the mole equivalent of commercial coagulant. A portion of the recovered coagulant is discarded to control the increase in concentration of unwanted impurities in the recovered coagulant. Finally, this process permits neutralization and later removal of the filtered sludge on the surface of the non-mechanical horizontal filter.

Abstract: A process is described whereby gadolinium and gallium containing by-products can be reprocessed to yield the oxides of these elements in sufficient purity to be re-used in the process for manufacturing Gd.sub.3 Ga.sub.5 O.sub.12 (GGG) single crystal boules thereby improving the economics of production of GGG wafers significantly. The gadolinium and gallium oxides are recovered and separated from transition metal impurities introduced during fabrication of GGG wafers by precipitating the gadolinium as oxalate which is thereafter pyrolyzed to gadolinium oxide and eluting the gallium containing filtrate over an ion exchange resin and precipitating therefrom as an oxalate the gallium present. The gallium precipitate is also pyrolyzed to the gallium oxide. The process can be extended to include purification and re-use of by-products generated in other grinding and polishing operations which may result in the recycling of the order of 80% of the generated by-products.

Abstract: In a process for recovering refractory metal values from a refractory metal carbide cemented with a metal binder. The coated cemented carbide is treated with sulfuric acid to deteriorate the coating.

Abstract: Alkali and alkaline earth metal chlorides contained in a residue of a chlorination process of a feed material of bauxite or clay associated with coal are removed by the addition of sulfuric acid which causes their conversion to their sulfate form, and the simultaneous production of hydrochloric acid. The residue, which has been rendered environmentally acceptable, can be disposed of readily, for example, to an ash pond or disposal area for flue gas desulfurization sludges. The hydrochloric acid is then recycled to the chlorination process. The hydrochloric acid may be utilized, for example, as a binder of the feed material, to prechloridize the feed material or as a portion of the leach solution when the chlorination process is a hydrochloric acid leach.

Abstract: A process of removing iron impurities from ores, particularly useful for removing stains of iron impurities adhered to silica sand particles, comprises grinding the ore, washing and desliming the ground ore to remove the major part of the clay-type binder, attrition-scrubbing the deslimed particles to release further amounts of binder therefrom, washing and desliming to remove said binder, drying and heating the ore particles, treating the hot particles with a chemical agent suitable to conver the iron impurities into water soluble iron compounds, attrition-scrubbing the hot suspension of chemically treated particles to release the stains of iron impurities, and washing with cold water and desliming to recover the purified ore particles.

Abstract: A process is described whereby the "saw kerf" can be reprocessed in sufficient purity to be re-used in the process, thereby improving the economics of production of GGG wafers significantly. Gadolinium and gallium oxides are recovered and separated from transition metal impurities introduced during fabrication of GGG wafers. The process "saw kerf" produced from slicing the crystal boule is dissolved by refluxing in HNO.sub.3, treated with oxalic acid and the resulting oxalates and nitrates separated. Pyrolysis of these salts at temperatures of at least 850.degree. C. resulted in their conversion to Ga.sub.2 O.sub.3 of purity >99.99%. The process can be extended to include purification and re-use of by-products generated in other grinding and polishing operations which may result in the recycling of the order of 80% of the generated by-products.

Abstract: A process for solubilizing uranium and other values in an ore containing the same together with aluminum and phosphorus and effecting regeneration of a mineral acid employed to solubilize the ore. The regeneration is effected by heating the spent acid solution resulting from solubilization of the ore in a reaction zone to a temperature above 100.degree. C. while maintaining at least the autogenic pressure of the heated solution within the reaction zone. The treatment causes aluminum phosphate to precipitate from the solution while simultaneously causing regeneration of at least a portion of the mineral acid in the solution that was consumed to originally solubilize the ore. The dissolved uranium and other elements of value can be recovered from the solution, either before or after acid regeneration, by any known technique. The regenerated mineral acid then can be used to solubilize fresh ore.

Abstract: A process of purifying silica sand comprises grinding sandstone, washing and desliming the ground sandstone to remove the major part of the clay-type binder, attrition-scrubbing the deslimed sand particles to release further amounts of binder therefrom, washing and desliming to remove said binder, drying and heating the sand particles, treating the hot sand with sulfuric acid to convert the iron oxides, ferrosilicates and ferro-aluminous impurities into water soluble compounds, attrition-scrubbing the hot suspension of the chemically treated sand to release the strongly adhering stains of said impurities, washing with cold water and desliming, conditioning the sand suspension with fatty acids or petroleum sulfonate collectors, a polyalcohol frothing agent and, if necessary, a mineral acid to bring the pH to from 1.5 to 7.

Abstract: A process is described whereby the by-products derived from the fabrication of Gd.sub.3 Ga.sub.5 O.sub.12 (GGG) wafers sliced from boules grown from Gd.sub.2 O.sub.3 and Ga.sub.2 O.sub.3 can be reprocessed in sufficient purity to be re-used in the process of growing GGG boules, thereby improving the economics of GGG wafer production. Gadolinium and gallium oxides are recovered and separated from transition metal impurities introduced during fabrication of GGG wafers. The "saw kerf" produced from slicing the crystal boule is dissolved in HCl and filtered to remove residual solids. Gasolinium oxalate is precipitated from the acidic solution by the addition of oxalic acid. Calcination at 850.degree. C. resulted in the isolation of Gd.sub.2 O.sub.3 of >99.99 purity.The pH of the filtrate is adjusted to about 11 with alkali metal hydroxide followed by the addition of sulfide ion. The precipitated transition metal sulfides are removed by filtration. Excess sulfide is removed by treatment with 30% H.sub.2 O.sub.

Abstract: A process for recovery of aluminum from clay comprising treating the crushed clay with water in the form of a fine mist, and in an amount sufficient to form compact surfaces on the particles without agglomeration thereof, and subsequently drying the misted clay to cause the particles to shrink and harden, and calcining and leaching with a mineral acid to extract aluminum from the clay.

Abstract: A high quality iron oxide concentrate, suitable as a feed for blast and electric reduction furnaces is recovered from pulverized coal fly ash. The magnetic portion of the fly ash is separated and treated with a hot strong alkali solution which dissolves most of the silica and alumina in the fly ash, leaving a solid residue and forming a precipitate which is an acid soluble salt of aluminosilicate hydrate. The residue and precipitate are then treated with a strong mineral acid to dissolve the precipitate leaving a solid residue containing at least 90 weight percent iron oxide.

Abstract: Gd.sub.2 O.sub.3 and Ga.sub.2 O.sub.3 are currently used for the fabrication of Gd.sub.3 Ga.sub.5 O.sub.12 (GGG) wafers which are employed as substrates for bubble domain memory devices. In the processing, in the order of 25% of the starting material ends up as process "saw kerf" contaminated with variable amounts of iron, nickel, magnesium, aluminum, zirconium, iridium and silicon. A process is described whereby the "saw kerf" can be reprocessed in sufficient purity to be re-used in the process, thereby improving the economics of production of GGG wafers significantly. Gadolinium and gallium oxides are recovered and separated from transition metal impurities introduced during fabrication of GGG wafers. The process "saw kerf" produced from slicing the crystal boule is dissolved in HCl, treated with H.sub.2 SO.sub.4, and the resulting sulfates separated. Metathesis with (NH.sub.4).sub.2 C.sub.2 O.sub.4 results in conversion of the sulfates to the ammonium oxalates which were calcined at 850.degree. C.

Abstract: A method of leaching of the metal contents in natural silicates by means of mineral acids to produce a metal-containing leaching liquid and a solid residue is disclosed. The silicate is first crushed but the grain size of substantially all of it is kept above 0.1 mm. It is then leached for a period of time sufficient to form a solid residue consisting chiefly of silica. The process is controlled so that the grains do not change in size or shape in the course of the leaching process. The silicate to be leached may be anorthosite or olivinrich rock and the solid residue from the leaching process may be utilized for building material, as a source for silicon in industrial processes, as a catalyst or carrier of catalysts or as an absorbent.

Abstract: The invention concerns a process for the preparation of alumina and ferric oxide from low-grade aluminium and iron carriers. The processes, in addition to conventional technological steps, comprises the steps of dissolving the iron content of a ground, mineral material in an aqueous hydrochloric acid solution containing 200 to 420 g./lit. of hydrochloric acid at 90.degree. to 130.degree. C., eliminating the iron from the slurry of from a solution obtained by filtration of the slurry, with an anion exchange resin or semipermeable membrane or cloth, continuously or discontinuously, eluting the iron from the ion exchange resin and recycling hydrochloric acid and sulfuric acid in a closed system.

Abstract: Cryolite (Na.sub.3 AlF.sub.6) as a source of aluminum is prepared from coal fly ash by reacting the aluminum oxide (Al.sub.2 O.sub.3) in fly ash with phosphoric acid to form aluminum phosphate, which is then converted to sodium aluminate by reaction with sodium hydroxide, and the sodium aluminate is converted to cryolite by reaction with hydrofluoric acid (HF), or equivalent reagent providing H.sup.+ and F.sup.- ions. Aluminum is thereby obtained from fly ash in a preferred form (as cryolite) for use in producing metallic aluminum.

Abstract: Recovery of fluoride values from carbonaceous waste cathode materials is achieved by reacting the waste materials with oxygen, water, and sulfur dioxide at temperatures between about 600.degree. C. and 1200.degree. C.

Abstract: A process for the recovery of soluble alumina values from alumina-bearing ores comprising simultaneously contacting a stream containing an effective amount of a reducing agent such as SO.sub.2 and a stream containing an effective amount of an oxidizing agent such as Cl.sub.2 with an aqueous slurry of the alumina-bearing ores for a time sufficient to remove at least about 50 weight percent of the soluble alumina values from said ores is disclosed.

Abstract: A process for commercially producing sulfates useful in the water treatment and papermaking industries from by-product aluminum oxides is taught. The process comprises feeding the aluminum oxide by-product and weak process liquor into digester vessel to form a slurry which is then heated. Sulfuric acid and additional oxide feed is added into the slurry mixture allowing the reaction to go to completion. Specific variables such as temperature, pH, reactant concentrations, reaction times and process liquor recycle are controlled to substantially eliminate certain heavy metals in any form whatsoever from contaminating the final sulfate product.

Abstract: A non-evaporative process for the production of drier aluminum sulfate is disclosed. A purified alum liquor containing 6 to 11% alumina as Al.sub.2 O.sub.3 is contacted with aluminum trihydrate and additional sulfuric acid in amounts sufficient to produce drier, low iron aluminum sulfate.

Abstract: Pure alumina (Al.sub.2 O.sub.3) is recovered from alunite (Al.sub.2 (SO.sub.4).sub.3.K.sub.2 SO.sub.4.4 Al (OH).sub.3) which is found mixed with various impurities by first calcinating the alunite in the presence of a chloride to produce impure Al.sub.2 O.sub.3 and other biproducts, and the impure Al.sub.2 O.sub.3 is then contacted with concentrated HCl to produce, after concentration and crystallization, crystals of AlCl.sub.3.6H.sub.2 O. These crystals are then calcinated to yield highly concentrated HCl and pure alumina.

Abstract: A process for treating a rock essentially constituted by calcium aluminophosphate, comprising the treatment of the ground rock with a concentrated sulfuric acid in stoichiometric excess with respect to calcium and aluminum, at a temperature of above about 120.degree. C., for a time between a few minutes and about 5 hours, followed by controlled water take-up. Subsequently, a residue containing substantially all the calcium and the aluminum of the rock and a solution of the acids serving to digest a tricalciumphosphate charge are separated. The process is particularly suitable for the treatment of Thies phosphate ore.

Abstract: There is disclosed a method for the elimination of the chief impurities in aluminum dross tailings. The method can be used as a pretreatment in the manufacture of aluminum sulfate from aluminum dross tailings in a continuous flow reaction zone in which the dross tailings prior to reaction with sulfuric acid are pretreated to reduce the more objectionable contaminants contained therein to acceptable levels. The most objectionable contaminant in the dross tailings is aluminum metal which, in the invention, is oxidized with water or steam at elevated temperatures. The dross tailings, which are chiefly particles of aluminum oxide, are suspended in an aqueous slurry and the slurry is heated to a temperature from 185.degree.-225.degree. F. and maintained under liquification pressures and sufficient agitation to insure particle-to-particle attrition that removes an aluminum hydroxide coating which would otherwise inhibit the reaction.

Abstract: Method of producing aluminiumchloride with low contents of iron from solutions containing ions of aluminium and iron by precipitation of aluminiumchloride by means of hydrochloric gas where the solution from which the aluminiumchloride is precipitated contains at least 0.1 g Fe/l which solution has been formed by leaching of a natural mineral raw material or artifically produced aluminium-containing raw material by leaching with hydrochloric acid and/or sulphuric acid, respectively a mixture of such acids. The produced aluminiumchloride may be transformed to aluminiumoxide by calcination.

Abstract: Method of producing aluminiumchloride with a low content of magnesium from hydrochloric acid solutions which contain ions of aluminium and magnesium and from which the aluminiumchloride is precipitated by hydrochloric gas and where the precipitation is carried out continuously in cascade so that the major part of the aluminium will be precipitated from solutions in which the ratio between aluminium and magnesium calculated as g Al.sup.+3 /g Mg.sup.+2 is above 0,5. Produced aluminiumchloride may be transformed to aluminiumoxide by calcination.

Abstract: A continuous process for recovering substantially pure aluminum chloride from chlorination products of aluminum ore. The chlorination products are contacted with a first selective solvent to dissolve a substantial portion of the aluminum chloride and some ferric chloride. The solvent is separated from the chlorides which then are treated to produce a ferric chloride-rich stream and an aluminum chloride-rich stream in which the aluminum chloride to ferric chloride ratio is higher than the ratio prior to solvent separation. The aluminum chloride-rich stream is contacted with a second solvent to dissolve any ferric chloride present and saturate the solution with aluminum chloride. Aluminum chloride in excess of that soluble in the second solvent separates as a substantially pure solid phase. The solution is separated from solid phase and recycled in process to recover additional aluminum chloride.

Abstract: A process for preparing manganese nitrate solution by leaching manganese ore containing manganese dioxide in an aqueous slurry containing dissolved nitrogen dioxide gas. The reaction is controlled by monitoring the pH of the aqueous slurry, and adjusting the relative concentration of the manganese ore containing manganese dioxide and/or the rate of addition of nitrogen dioxide containing gas, to establish and maintain the leaching reaction.

Abstract: Aluminum nitrate solutions are subjected to hydrolysis at elevated temperature and pressure, with the pressure being kept relatively low by continual bleeding of reactant gases from the reaction vessel. The resultant product is a noncrystalline alumina that may be readily converted to crystalline alumina by roasting.In addition, the discharged reactant gases are employed for leaching of clay to provide aluminum nitrate feed solution.

Abstract: A method for recovering aluminum values from fly ash comprises sintering the fly ash with a mixture of NaCl and Na.sub.2 CO.sub.3 to a temperature in the range 700.degree.-900.degree. C. for a period of time sufficient to convert greater than 90% of the aluminum content of the fly ash into an acid-soluble fraction and then contacting the thus-treated fraction with an aqueous solution of nitric or sulfuric acid to effect dissolution of aluminum and other metal values in said solution.

Abstract: The invention described herein relates to a method for improving the acid leachability of aluminum and other metal values found in fly ash which comprises sintering the fly ash, prior to acid leaching, with a calcium sulfate-containing composition at a temperature at which the calcium sulfate is retained in said composition during sintering and for a time sufficient to quantitatively convert the aluminum in said fly ash into an acid-leachable form.

Abstract: A technique for controlling severe chemical reactions which occur when salt containing furnace slags from secondary aluminum melting operations are brought in contact with water is provided. The technique which retards the formation and evolution of hydrogen gas resulting from the reaction of aluminum metal fines with water in the presence of chloride and the formation and evoluation of ammonia gas from the reaction of aluminum nitride with water is accomplished by controlling the pH of the water-solid slurry to be around 8. Consequently, the formation and gaseous evolution of hydrogen is controlled and the evolution of ammonia is eliminated with a concomitant elimination of explosion and fire hazards associated with the uncontrolled chemical reactions.

Abstract: Alumina values are extracted from clay by the steps of pelletizing into spherical particles, calcining the pellets in a fluidized bed reactor, extracting the clay in about 30-40% nitric acid, purifying the basic aluminum nitrate produced, crystallizing aluminum nitrate nonahydrate, decomposing the nonahydrate in at least three steps, calcining the produced alumina and reconstituting the NO.sub.x gases to nitric acid.

Abstract: The invention concerns a process for sulfuric acid treatment of clays or aluminiferous minerals to obtain pure aluminum oxide via a basic intermediate. The process finds application in the production of aluminum through fusion electrolysis and for the production of different types of alumina. The process provides a mass production method which is economically and technically superior over the prior art methods.The mechanically and/or thermally pretreated raw material is subjected to a two-step pressure treatment with sulfuric acid solution. The aluminum sulfate solution is treated to reduce the iron with SO.sub.2 and hydrolytic precipitation of basic aluminum sulfates. After separation of the salts from the mother liquor, which is returned to the process, the aluminum sulfate is thermally decomposed. The SO.sub.2 /SO.sub.3 -containing waste gases from the decomposition are used to renew the treatment acid.

Abstract: A process for preparing a solution of high aluminum content from the combustion residue of a solid carbon-containing fuel having a carbon content of 2% or less by weight and an iron content calculated as Fe.sub.2 O.sub.3 of 4% or less by weight is described. The process consists of (a) pretreating said residue with nitric acid at a temperature lower than the next extraction stage which follows and removing the nitric acid solution from the residue and then (b) extracting said treated residue with nitric acid of strength about 30% to 65% by weight strength at about 100.degree. to 225.degree. C., the amount of nitric acid employed in said pretreatment step and in said extraction step being in excess of the cationic equivalent actually dissolved in each step.

Abstract: Processes for the production of alumina and cement constituents from fly ash, in which the fly ash is subjected to magnetic separation removing magnetic constituents; the remaining non-magnetic fraction of fly ash is then mixed with a calcining agent and water, pelletized, dried and calcined, cooled, and then either acid cured or subjected to a hydrothermic shock treatment in sulfuric acid; the mixture is then diluted with water, filtrated, purified by a solvent extraction process, and evaporated yielding aluminum sulfate, which is then subjected to liquid-solid separation and decomposed at an increased temperature at which the sulfur in the form of sulfur oxide gases and the water vapor is driven off, alumina remains. The leach residue of the alumina extraction yields useful material for cement production.

Abstract: A process for obtaining pure alumina comprising the combination of chlorosulphuric attack of calcined aluminous ores containing impurities, followed by concentration of the liquor obtained after the attack and separation of the sterile material, sulphuric acid treatment of the concentrated liquor followed by chlorination to precipitate almost all the hexahydrated aluminum chloride, separation of the precipitate of hexahydrated aluminum chloride and of the chlorosulphuric mother liquor charged with impurities, pyrohydrolysis of the precipitate to give the desired pure alumina with recycling of released hydrochloric acid, degassing of the chlorosulphuric liquor of impurities with recycling of the gaseous HCl for chlorination, yielding a sulphuric liquor of impurities, finally the elimination of the impurities present in this latter liquor in the form of a sulphuric precipitation by concentration in the presence of potassium ions.

Abstract: A method for producing substantially pure alumina from kaolin clay by removing in a soluble form impurities which contaminate the alumina while the aluminum is maintained in an insoluble form. This is accomplished by leaching calcined kaolin clay with at least 36 weight percent hydrochloric acid to dissolve the impurities and convert the aluminum to insoluble aluminum chloride and maintaining the hydrochloric acid concentration in the leach liquor at at least 36 weight percent by the injection of hydrochloric acid gas. The insoluble aluminum chloride is then separated from the dissolved impurities and subjected to a second leaching step to solubilize and separate it from the silica gangue. Substantially pure AlCl.sub.3.sup.. 6H.sub.2 O crystals are recovered from solution and converted to alumina by conventional means. In an alternate embodiment, the process may be practiced on uncalcined clay and includes the addition of a source of fluoride ions, such as H.sub.2 SiF.sub.

Abstract: A cyclic process for obtaining very pure alumina by the hydrochloric acid attack of a silico-aluminous material, the said process comprising, in a first stage, the precipitation of at most 75% of the alumina present in the liquor originating from the attack in the form of hexahydrated aluminum chloride which is subsequently decomposed by heating, then, in a second stage, the treatment of the liquor leaving the first stage with HCl gas in order to precipitate dissolved Al.sub.2 O.sub.3 in the form of hexahydrated aluminum chloride which is recycled into the liquor leaving the attack, while the hydrochloric liquor leaving the second stage and impoverished in Al.sub.2 O.sub.3 but rich in impurities, is treated with a recycled sulphuric liquor in order to precipitate impurities as their corresponding sulphates.

Abstract: In the process for the preparation of pure aluminum oxide by the steps of hydrochloric acid decomposition of mechanically or thermally activated clay or alumina containing minerals, separating the insoluble residue, removing the iron from the solution, crystallizing the aluminum chloride in the iron-free solution, thermally decomposing the crystallizate to aluminum oxide and recovering the hydrochloric acid from the decomposition gases, the improvement comprising effecting the process by the steps of mechanically pretreating the clay, drying the pretreated clay, thermally or mechanically activating the clay, subjecting the activated clay to circulating leaching, separating the leached material into an SiO.sub.2 containing residue and an AlCl.sub.3 solution, extracting the AlCl.sub.3 solution to an evaporating crystallization and thermally decomposing the crystals to produce .alpha.-Al.sub.2 O.sub.3.

Abstract: A process for obtaining pure aluminum oxide (Al.sub.2 O.sub.3) from siliceous aluminum ore is disclosed. The aluminum ore is digested in a hydrochloric acid solution to obtain aluminum chloride, the aluminum chloride is crystallized as the hexahydrate, the aluminum chloride hexahydrate is purified and, subsequently, decomposed to give pure aluminum oxide and secondary products. The mother liquor of the crystallization step and the secondary products of the decomposition step are recycled.

Abstract: The invention provides a process for recovering gallium from calcined clay leached with hydrochloric acid. The leach solution containing aluminum, ferric and gallium chlorides is treated by ion exchange to first remove aluminum ions, following which the solution containing ferric and gallium chlorides is treated to reduce the ferric ions to ferrous ions. The reduced solution is acidified with hydrochloric acid sufficiently to insure that the gallium is present in the form GaCl.sub.4 - ions, and is then again treated by ion exchange to separate the ferrous ions from the gallium for ultimate recovery of the latter.

Abstract: A process for the production of trialuminum nickelide fibers which involves the utilization of an oxalic acid-hydrogen chloride mixture for separating the fibers from a solid, two-phase, composite matrix of aluminum and trialuminum nickelide fibers.

Abstract: A method of obtaining alumina of high purity from aluminous mineral containing impurities by attacking the mineral with a sulphuric acid liquor and separating the resulting liquor from a residue which remains after the attack, the steps of(a) mixing the resulting liquor with a liquor containing HCl and H.sub.2 SO.sub.4,(b) introducing HCl gas into the mixture,(c) cooling the mixture from step (b) to precipitate hydrated aluminum chlorosulphate crystals having the formula AlSO.sub.4 Cl.6-7H.sub.2 O,(d) separating the hydrated crystals of hydrated aluminum chlorosulphate from the mother liquor,(e) heating the separated crystals to a temperature that does not exceed 600.degree. C.